CN115216574A

CN115216574A - Direct reduction process and direct reduction device for iron-containing composite pellets

Info

Publication number: CN115216574A
Application number: CN202210086538.3A
Authority: CN
Inventors: 叶恒棣; 胡兵; 魏进超; 郑富强; 刘臣; 储太山; 王兆才; 师本敬
Original assignee: Zhongye Changtian International Engineering Co Ltd
Current assignee: Zhongye Changtian International Engineering Co Ltd
Priority date: 2022-01-25
Filing date: 2022-01-25
Publication date: 2022-10-21
Anticipated expiration: 2042-01-25
Also published as: WO2023142481A1; CN115216574B

Abstract

The invention provides a direct reduction process and a direct reduction device for iron-containing composite pellets, which adopt a method of rotary kiln prereduction-melting furnace deep reduction to divide a coal-based rotary kiln into a drying section, a preheating section, a plasma reduction section, a reduction roasting section and a cooling section in sequence for carrying out Fe ₂ O ₃ →Fe ₃ O ₄ →Fe _x A pre-reduction step of O stage, wherein the pre-reduction product reaching a certain reduction degree and residual coal are hot-charged into a melting furnace together for Fe _x Deep reduction reaction at the stage of O → Fe. Meanwhile, the design of the iron-containing composite pellets with special structures is cooperated with the rotary kiln air flow internal circulation system and the reformed gas air flow external circulation system, so that the strength is greatly enhancedThe reducing atmosphere of the material layer is enhanced, the diffusion of the reducing agent in iron ore pellet particles is enhanced, the reduction reaction of the reducing agent at a low-temperature section on the interface of the iron ore pellet particles is enhanced, and the high efficiency of the iron oxide reduction process is finally realized.

Description

Direct reduction process and direct reduction device for iron-containing composite pellets

Technical Field

The invention relates to reduction of iron-containing composite pellets, in particular to a direct reduction process and a direct reduction device of the iron-containing composite pellets, and belongs to the technical field of iron-making production.

Background

The process for extracting metallic iron from iron-containing minerals (mainly iron oxides) mainly comprises a blast furnace method, a direct reduction method, a smelting reduction method and the like. From the metallurgical point of view, iron making is the reverse of iron rusting and gradual mineralization, and simply speaking, pure iron is reduced from iron-containing compounds. A process for producing pig iron by reducing iron ore with a reducing agent at elevated temperature. The main raw materials for iron making are iron ore and coke; the function of the coke is to provide heat and produce the reductant carbon monoxide.

Blast furnace smelting is a continuous process for reducing iron ore to pig iron. Solid raw materials such as iron ore, coke, flux and the like are fed into a blast furnace in batches by a furnace top charging device according to a specified mixing ratio, and the furnace throat charge level is kept at a certain height. The coke and ore form an alternating layered structure within the furnace. The blast furnace method for iron making has the technical problems of long production period, low production efficiency, large energy consumption, large pollutant production amount and the like.

Direct Reduced Iron (DRI) is a supplement to scrap steel in short-run steelmaking processes and an ideal feedstock for the smelting of high quality specialty steels. In recent years, the production of direct reduced iron has rapidly progressed worldwide. Because of the shortage of iron ore resources and natural gas, the development of the direct reduction process in China is slow, and research and practice hotspots are also focused on the coal-based direct reduction process to produce direct reduced iron or metallic iron by adopting non-coking coal. In the existing coal-based direct reduction process, oxidized pellets or cold-bonded pellets are generally used as raw materials to react in a rotary kiln to produce DRI. In the direct reduction process of the coal-based rotary kiln, the charging is required to be 6-8 hours from the charging to the discharging of the product, the production period is longer, and the production efficiency is low. The productivity of the direct reduction process of the rotary kiln, i.e. the amount of products produced by the rotary kiln per unit time, is generally related to the size and structure of the kiln, the conditions of raw materials and fuel, the temperature and temperature distribution in the kiln, the atmosphere and the charging amount, etc., and the reduction speed of the pellets is a fundamental factor affecting the production cycle and the production efficiency of the direct reduction.

At present, in the direct reduction process of the coal-based rotary kiln, the time required by the furnace charge from the charging into the kiln to the discharging of the product can reach 8 hours, the production period is longer, and the production efficiency is low. The low pellet reduction speed and the long heat preservation reduction time in the rotary kiln are the root causes of low production efficiency and long production period of the direct reduction process of the coal-based rotary kiln. In order to improve the reduction speed of direct reduction, researchers and practitioners propose some technical measures, and some measures are proposed in the aspects of kiln body design (CN 110229939A, a two-section rotary kiln method non-coke iron-making device), pellet batching (CN 106591572A, a method for enhancing preparation and reduction of iron ore internal carbon-matched pellets) and the like, but the practicability of industrial application is poor, so far, the method is still mostly stopped at the experimental stage, and the method is not popularized and applied.

The reducing agent in the coal-based rotary kiln direct reduction process is anthracite, and brief introduction reduction reaction of iron oxide and gasification reaction of coal are mainly involved in the reduction process, namely:

Fe _x O _y +C＝Fe _x O _y-1 +CO (1)

Fe _x O _y +CO＝Fe _x O _y-1 +CO ₂ (2)

C+CO ₂ ＝2CO (3)

the reaction activation energy of the formula (1) is 140-400kJ/mol, the reaction activation energy of the formula (2) is 60-80kJ/mol, and the reaction activation energy of the formula (3) is 170-200kJ/mol. In practice, equation (1) proceeds negligibly slowly relative to equations (2) and (3). At present, researchers mostly consider that the solid carbon and the iron oxide react with each other to generate CO through the Boolean reaction (formula (3)) generally, namely, the solid carbon mainly reacts CO with the iron oxide ₂ The reduction to CO is generally less direct with iron oxides. The reduction reaction is carried out from the outside of the pellets to the pellets, and the gasification speed of carbon and the diffusion speed of gas in the pellets have great influence on the progress degree of the reduction reaction. During the reduction process, the reduction reaction of the pellets is controlled by the interfacial chemical reaction and the internal diffusion mixing. As the reduction reaction proceeds, the chemical reaction resistance is constantly decreasing and the internal diffusion resistance is constantly increasing. Therefore, the reducing gas in the middle and later periods of reduction is difficult to enter the inner cores of the pellets, and the reduction degree is increased more slowly, which is an important reason for influencing the overall reduction speed.

In order to improve the reduction speed of direct reduction, researchers and practitioners propose some technical measures, and some measures are proposed in the aspects of kiln body design (such as CN110229939A, a two-section rotary kiln method non-coke iron-making device), pellet batching (such as CN106591572A, a method for enhancing preparation and reduction of iron ore internal carbon-added pellets) and the like, but the practicability of industrial application is poor, so far, the method still mostly stays in the experimental stage and is not popularized and applied.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides an iron-containing composite pellet capable of being rapidly reduced, a process for rapidly and directly reducing the iron-containing composite pellet and a direct reduction device. The composite pellet contains three material layers, the inner core pellet layer (reducing pellet core) is a mixture of reducing agent and binder with high volatile content, and the middle pellet layer is calcium carbonate (CaCO) ₃ ) The material layer and the outer pellet material layer (iron-containing material layer) are a mixture of iron ore concentrate and a binder. During the reduction roasting process of the pellet, the inner core is firstlyThe pelletizing material layer can decompose a large amount of reducing gas (H) ₂ CO and CH ₄ Etc.) for participating in the reduction of iron oxides; then the middle pellet bed is decomposed to release CO ₂ ，CO ₂ The carbon dioxide reacts with C in the inner core pellet material layer to generate more CO, and iron oxide in the outer pellet material layer is reduced when the CO diffuses outwards. Thereby leading the iron oxides on the outer layer and the inner layer of the pellet to simultaneously carry out reduction reaction, and having higher reduction speed and higher reduction pellet strength compared with the common pellet or the internally-matched carbon pellet.

Secondly, aiming at the problems of low diffusion speed of reducing gas in the middle and later stages of reduction and low pellet reduction speed in the prior direct reduction process of the coal-based rotary kiln, low pellet reduction speed in the whole process and long pellet heat preservation reduction time in a kiln body, the invention adopts a rotary kiln prereduction-melting separation furnace deep reduction method to reduce iron oxide in the iron-containing composite pellets into Fe which is easy to generate in the process of reducing the iron oxide into metallic iron ₂ O ₃ →Fe ₃ O ₄ →FeO→Fe _x The reduction reaction in the O stage is completed in a rotary kiln, the pre-reduction product reaching a certain reduction degree and residual coal are hot-charged into a melting furnace together, and Fe is generated in the melting furnace _x Deep reduction reaction at the stage of O → Fe. The technology of the invention completes the reaction of iron oxide from trivalent to divalent easy reduction stage in a rotary kiln, and obtains partial iron crystal in the rotary kiln; then the reaction from most of ferrous iron to metallic iron in the difficult reduction stage is completed in a melting and separating furnace, the reduction conditions provided by the rotary kiln and the deep reduction device are fully utilized, and the characteristics of the iron oxide reduction process are combined, so that the high efficiency of the iron oxide reduction process is realized.

Thirdly, the coal-based rotary kiln is sequentially divided into a drying section, a preheating section, a plasma reduction section, a reduction roasting section and a slow cooling section, and a coal gas reforming vertical shaft and an ash separation device are arranged between the rotary kiln and the melting furnace. According to the properties of hot air in each of a drying section, a preheating section, a plasma reduction section, a reduction roasting section and a slow cooling section, the hot air in each section is subjected to internal circulation treatment of reasonable redistribution in each section, so that the utilization potential of waste heat and waste energy of the hot air is fully exerted, the reaction temperature required by the reduction reaction is reduced, the temperature of the preheating section is increased, the deep proceeding of the reduction reaction in the preheating section is promoted, and the purposes of saving energy, reducing emission and improving the production efficiency are achieved.

Further, high-temperature coal gas overflowing from the top of the melting furnace is reformed through a vertical shaft, and tail gas of the rotary kiln is circulated to the vertical shaft or an ash separation section, so that part of sensible heat of the tail gas is converted into CO and H ₂ Chemical energy potential, then CO and H ₂ Activation to plasma state CO ⁺ Or H ⁺ Then the reducing atmosphere of the material layer is enhanced, the diffusion of the reducing agent in the iron-containing composite pellet ore particles is enhanced, and the reduction reaction of the reducing agent at the low-temperature section on the pellet particle interface is enhanced.

In order to achieve the above object, the technical solution adopted by the present invention is specifically as follows:

according to a first embodiment of the present invention, there is provided a direct reduction process of iron-containing composite pellets.

A direct reduction process of iron-containing composite pellets, the process comprising:

1) And (3) feeding the iron-containing composite pellets into a rotary kiln from the kiln tail according to the trend of the materials, and sequentially carrying out pre-reduction treatment through a drying section, a preheating section, a plasma reduction section, a reduction roasting section and a slow cooling section to obtain a pre-reduction product. And then, conveying the pre-reduction product to a melting furnace for deep reduction treatment to obtain molten iron.

2) And according to the properties of hot air in each section of the rotary kiln, internally circulating the hot air generated in each section among the sections.

3) Reforming high-temperature coal gas generated in the melting furnace to obtain reformed gas, and then conveying the reformed gas to the rotary kiln to participate in the pre-reduction treatment of the iron-containing composite pellets.

Preferably, the iron-containing composite pellet comprises a reduction sphere core positioned at the inner layer, a calcium carbonate layer coated outside the reduction sphere core, and an iron-containing material layer coated outside the calcium carbonate layer. The iron-containing composite pellet is prepared by the following steps: mixing the reducing agent and the binder, and granulating to obtain the reducing spherical core. Then reducing the ballMixing the core with lime milk (prepared by mixing and digesting quicklime and water according to the mass ratio of 1.2-1.8) and granulating to obtain the mother ball coated with the lime milk layer. And then mixing the iron-containing raw material and the binder to form an iron-containing mixture, and mixing and granulating the iron-containing mixture and the mother balls coated with the lime milk layer to obtain the green pellets. Finally adopting a catalyst containing CO ₂ The green pellets are dried by the drying medium to obtain the iron-containing composite pellets.

Preferably, the reducing agent is selected from one or more of bituminous coal, lignite, biomass and organic solid waste. The binder is selected from one or more of bentonite, humic acid and humate. The content of the volatile component of the reducing agent is more than or equal to 25wt%, and the content of the volatile component of the reducing agent is preferably more than or equal to 30wt%.

Preferably, the binder is contained in the reducing sphere core in an amount of 0.05 to 0.3%, preferably 0.08 to 0.2%, based on the total mass of the reducing agent. In the iron-containing mixture, the content of the binder is 0.8 to 3%, preferably 1 to 2% of the total mass of the iron-containing raw material.

Preferably, the diameter of the reduction sphere core is 2 to 6mm, preferably 3 to 5mm. The thickness of the calcium carbonate layer is 1 to 3mm, preferably 1.5 to 2mm. The thickness of the iron-containing material layer is 3-7 mm, and preferably 4-6 mm.

Said CO-containing ₂ Is selected from the group consisting of the addition of CO ₂ The hot air, the hot tail gas of each process of blast furnace steel smelting and the hot tail gas of the direct reduction process. Containing CO ₂ Of the drying medium of ₂ The content of (B) is 5 to 20wt%, preferably 8 to 15wt%. Containing CO ₂ The temperature of the drying medium of (2) is 150 to 300 ℃, preferably 180 to 260 ℃.

Preferably, the iron oxide in the iron-containing composite pellets reacts in the rotary kiln by:

xFe ₂ O ₃ (s)+(3x-2)CO(g)＝2FexO(s)+(3x-2)CO ₂ (g)，

xFe ₂ O ₃ (s)+(3x-2)H ₂ (g)＝2FexO(s)+(3x-2)H ₂ O(g)，

Fe ₂ O ₃ (s)+3CO(g)＝2Fe(s)+3CO ₂ (g)，

Fe ₂ O ₃ (s)+3H ₂ (g)＝2Fe(s)+3H ₂ O(g)。

preferably, the iron oxide is reduced in the rotary kiln to a degree η of 40-80%, preferably 50-70%, more preferably 60-65%. Wherein:

x∈[2/3，+∞)。

preferably, the reduction condition of the iron oxide in the rotary kiln is monitored by detecting the conductivity of the material in the rotary kiln in real time and analyzing the state of the material in the rotary kiln through the conductivity.

Preferably, the electric conductivity of the pre-reduction product obtained by controlling the reduction of the iron oxide through a rotary kiln is 1 x 10 ⁵ ～1*10 ⁷ Ω ^-1 ·m ^-1 Preferably 3 to 10 ⁵ ～7*10 ⁶ Ω ^-1 ·m ^-1 More preferably 5 x 10 ⁵ ～5*1*10 ⁶ Ω ^-1 ·m ^-1 。

Preferably, the reduction degree of the iron oxide in the rotary kiln is controlled by controlling one or more of the carbon distribution amount in the iron oxide, the heat preservation reduction time of the iron oxide in the rotary kiln, and the reduction temperature in the rotary kiln. And the reduction degree of the iron oxide in the rotary kiln is in direct proportion to the carbon distribution amount of the iron oxide, the heat preservation reduction time of the iron oxide in the rotary kiln and the reduction temperature in the rotary kiln.

Preferably, the amount of carbon coordinated in the iron oxide is controlled to be 10 to 40wt%, preferably 15 to 30wt%, more preferably 20 to 25wt%. Further preferably 20 to 25%; for example 20%,21%,22%,23%,24%,25%. The carbon blending amount is the weight ratio of the coal amount in the iron oxide entering the rotary kiln to the whole iron oxide.

Preferably, the heat preservation and reduction time of the iron oxide in the rotary kiln is controlled to be 60-180min, preferably 70-140min, and more preferably 90-120min; for example: 80min,90min,100min,110min,120min. The heat preservation and reduction time of the iron oxide in the rotary kiln refers to the residence time of the iron oxide in the section with the highest temperature in the rotary kiln.

Preferably, the reduction temperature in the rotary kiln is controlled to be 800-1400 ℃, preferably 850-1300 ℃, and more preferably 900-1200 ℃; for example: 900 deg.C, 1000 deg.C, 1050 deg.C, 1100 deg.C, 1150 deg.C, 1200 deg.C, 1300 deg.C, 1400 deg.C. The reduction temperature in the rotary kiln refers to the highest temperature zone in the rotary kiln.

Preferably, the real-time conductivity sigma of the material in the rotary kiln is detected in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} The method specifically comprises the following steps:

establishing a relation between the conductivity and the state and the reduction degree of the materials in the rotary kiln:

if σ _{Time of flight} ≤0.1Ω ^-1 ·m ^-1 Indicating that the material in the rotary kiln is mainly Fe ₂ O ₃ The real-time reduction degree of the iron oxide in the rotary kiln is [0,1%]。

If 0.1 < sigma _{Time of flight} ≤1000Ω ^-1 ·m ^-1 Indicating that the material in the rotary kiln is mainly Fe ₃ O ₄ Is present in such a form that the real-time reduction degree of iron oxide in the rotary kiln is (1%, 11.1%)]。

If 1000 < sigma _{Time of flight} ≤1*10 ⁵ Ω ^-1 ·m ^-1 It shows that the main FeO form of the material in the rotary kiln exists, and the real-time reduction degree of the iron oxide in the rotary kiln is (11.1 percent, 33.3 percent)]。

If 1 x 10 ⁵ ＜σ _Time-piece ≤1*10 ⁷ Ω ^-1 ·m ^-1 It shows that the main FeO and Fe exist in the rotary kiln, and the real-time reduction degree of the iron oxide in the rotary kiln is (33.3 percent, 80 percent)]。

If σ _Time-piece ＞1*10 ⁷ Ω ^-1 ·m ^-1 It shows that the material in the rotary kiln mainly exists in the form of Fe, and the real-time reduction degree of the iron oxide in the rotary kiln is (80%, 1%]。

Preferably, the iron oxide is reduced in real time in the rotary kiln according to the degree eta of reduction of the iron oxide _{Fruit of Chinese wolfberry} Adjusting the process conditions for reducing the iron oxide in the rotary kiln; the method comprises the following steps:

if eta _{Fruit of Chinese wolfberry} Keeping the carbon distribution amount in the existing iron oxide, the heat preservation and reduction time of the iron oxide in the rotary kiln and the reduction temperature in the rotary kiln to continuously operate by =1 +/-10%;

if eta _{Fruit of Chinese wolfberry} > (1 + 10%) η, mediated by any one or more of the following means: reducing the carbon content in the iron oxide, reducing the reduction temperature in the rotary kiln, shortening the heat preservation reduction time of the iron oxide in the rotary kiln and controlling the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η；

If eta _{Fruit of Chinese wolfberry} < (1-10%) η, mediated by any one or more of: increasing the carbon content in the iron oxide, raising the reduction temperature in the rotary kiln, prolonging the heat preservation reduction time of the iron oxide in the rotary kiln, and controlling the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

In the invention, the reduction temperature in the rotary kiln is reduced by the following means: the coal injection quantity in the rotary kiln is reduced and/or the secondary air intake quantity of the rotary kiln is reduced.

In the present invention, the raising of the reduction temperature in the rotary kiln is achieved by: increasing the coal injection quantity in the rotary kiln and/or increasing the secondary air intake quantity of the rotary kiln.

In the invention, the shortening of the heat preservation and reduction time of the iron oxide in the rotary kiln is realized by increasing the rotating speed of the rotary kiln.

In the invention, the prolonging of the heat preservation and reduction time of the iron oxide in the rotary kiln is realized by reducing the rotating speed of the rotary kiln.

Preferably, the reducing of the carbon content in the iron oxide is specifically as follows: each decrease of carbon addition Δ m =10% ₁ Wherein m is ₁ The original carbon content in the iron oxide; i.e. if eta _{Fruit of Chinese wolfberry} > (1 + 10%) eta, controlling carbon distribution m in iron oxide of next batch _i ＝m _i-1 -. DELTA.m; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} To obtain iron oxides in a rotary kilnDegree of reduction eta in real time _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still greater than (1 + 10%) eta, the carbon distribution quantity delta m in the next batch of iron oxide is reduced again until the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

Preferably, the step of increasing the carbon content in the iron oxide specifically comprises the following steps: each increment of carbon addition amount Delta m ₀ ＝10％m ₁ Wherein m is ₁ The original carbon content in the iron oxide is obtained; i.e. if eta _{Fruit of Chinese wolfberry} < (1 + 10%) eta, controlling carbon distribution m in iron oxide of next batch _i ＝m _i-1 +. DELTA m; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still less than (1 + 10%) eta, the carbon distribution quantity delta m in the iron oxide of the next batch is increased again until the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

Preferably, the reducing the coal injection amount in the rotary kiln specifically comprises: each decrease Δ p =10% of coal injection amount ₁ Wherein p is ₁ The original coal injection quantity in the rotary kiln is obtained; i.e. if eta _{Fruit of Chinese wolfberry} Eta (1 + 10%), controlling coal injection amount p in rotary kiln _j ＝p _j-1 -. DELTA.p; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still greater than (1 + 10%) eta, then the coal injection quantity delta p is reduced again until the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

Preferably, the increasing the coal injection amount in the rotary kiln specifically comprises: each increase Δ p =10% of coal injection amount ₁ Wherein p is ₁ The original coal injection quantity in the rotary kiln is obtained; i.e. if eta _{Fruit of Chinese wolfberry} Eta < (1+10%), coal injection amount p in rotary kiln _j ＝p _j-1 B, plus delta p; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _Time-piece Obtaining the iron oxide in the rotationReal-time degree of reduction eta in kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still less than (1 + 10%) eta, the coal injection quantity delta p is increased again until the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

Preferably, the method for reducing the secondary air intake of the rotary kiln specifically comprises the following steps: each time reduction amount of the secondary intake air Δ f =10% ₁ Wherein f is ₁ The primary secondary air intake of the rotary kiln; i.e. if eta _{Fruit of Chinese wolfberry} Eta (1 + 10%), controlling secondary air intake f of rotary kiln _k ＝f _k-1 -. DELTA.f; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still greater than (1 + 10%) eta, the secondary air intake quantity delta f is reduced again until the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

Preferably, the increasing of the secondary air intake of the rotary kiln specifically comprises: Δ f =10% of each increase in the amount of secondarily supplied air ₁ Wherein f is ₁ The primary secondary air intake of the rotary kiln; i.e. if eta _{Fruit of Chinese wolfberry} < (1 + 10%) eta, and controlling secondary air intake f of rotary kiln _k ＝f _k-1 +. Δ f; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still less than (1 + 10%) eta, the secondary air intake quantity delta f is increased again until the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

Preferably, the increasing the rotation speed of the rotary kiln specifically comprises: Δ s =10% per increment of the rotation speed ₁ Wherein s is ₁ The original rotation speed of the rotary kiln; i.e. if eta _{Fruit of Chinese wolfberry} Is greater than (1 + 10%) eta, and the rotating speed s of rotary kiln is controlled _r ＝s _r-1 +. DELTA s; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If it is in real timeEta of state _{Fruit of Chinese wolfberry} Still greater than (1 + 10%) eta, the rotating speed deltas is increased again until the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

Preferably, the reducing the rotation speed of the rotary kiln is specifically as follows: Δ s =10% per reduction of the rotational speed ₁ Wherein s is ₁ The original rotation speed of the rotary kiln; i.e. if eta _{Fruit of Chinese wolfberry} 1+ 10%) eta, controlling the rotation speed s of the rotary kiln _r ＝s _r-1 -. DELTA.s; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still less than (1 + 10%) eta, reducing the rotating speed deltas again until the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

Preferably, step 2) comprises:

201 The hot air at the tail part (close to the kiln tail) of the drying section is conveyed to the reduction roasting section to participate in the reduction roasting treatment. According to the real-time temperature change of the materials in the reduction roasting section, the extraction amount of hot air in the drying section is adjusted and/or the air amount of an air burner in the reduction roasting section is adjusted. And/or

202 The hot air at the tail part of the slow cooling section (close to the reduction roasting section) is conveyed to the preheating section to participate in the preheating treatment of the pellets. And adjusting the hot air extraction amount in the slow cooling section according to the real-time concentration change of CO in the hot air in the slow cooling section.

Alternatively, step 2) comprises:

203 Mixing the hot air output by the drying section with the hot air output by the reduction roasting section to obtain mixed hot air, and then conveying the mixed hot air to the preheating section to participate in preheating treatment of the pellets. And adjusting the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air in the drying section according to the real-time temperature change of the materials in the reduction roasting section.

204 The hot air in the preheating section is conveyed to the drying section to participate in the drying treatment of the pellets. And adjusting the extraction amount of hot air in the preheating section according to the real-time temperature change of the materials in the preheating section.

Alternatively, step 2) comprises:

205 Mixing hot air output from the kiln tail of the rotary kiln with hot air output from the reduction roasting section to obtain mixed wet hot air, and then conveying the mixed wet hot air to the drying section to participate in the drying treatment of the pellets at the initial stage. And adjusting the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air at the tail of the rotary kiln according to the real-time temperature change of the materials in the reduction roasting section.

206 Mixing the hot air output from the later stage of the drying section with the hot air output from the reduction roasting section to obtain mixed dry hot air, and then conveying the mixed dry hot air to the drying section to participate in the drying treatment of the pellets at the initial stage. And adjusting the extraction amount of hot air in the later stage of the drying section and the extraction amount of hot air in the reduction roasting section according to the real-time temperature change of the material in the later stage of the drying section.

Preferably, in step 201), according to the real-time temperature change of the material in the reduction roasting section, the adjusting of the extraction amount of hot air in the drying section and/or the adjusting of the air amount of the air burner in the reduction roasting section specifically comprises: the set temperature of the material in the reduction roasting section is set to be T1 +/-C1 (the range of C1 is 0-50) and DEG C. Detecting the real-time temperature of the material in the reduction roasting section in real time as T2 and DEG C.

Then:

and when T2 is greater than (T1 +/-C1), increasing the extraction amount of hot air in the drying section and/or reducing the air amount of an air burner at the upper part of the material layer in the reduction roasting section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T1 +/-C1).

When T2 epsilon (T1 +/-C1), the current process condition is maintained unchanged.

And when the T2 is less than (T1 +/-C1), reducing the extraction amount of hot air in the drying section and/or increasing the air amount of an air burner at the upper part of the material layer in the reduction roasting section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T1 +/-C1).

Preferably, in step 202), according to the real-time concentration change of CO in the hot air in the slow cooling section, the adjusting of the hot air extraction amount in the slow cooling section specifically comprises: the set concentration of CO in the hot air in the slow cooling section is set to W1 + -D (the range of D is 0-20)%. And detecting the real-time concentration of CO in the hot air in the slow cooling section in real time to be W2 percent. Then:

and when W2 is > (W1 +/-D), increasing the extraction amount of the hot air in the slow cooling section until the real-time concentration of CO in the hot air in the slow cooling section returns to the preset concentration (W1 +/-D).

When W2 epsilon (W1 + -D), the current process conditions are maintained unchanged.

And when W2 is less than (W1 +/-D), reducing the extraction amount of the hot air in the slow cooling section until the real-time concentration of CO in the hot air in the slow cooling section returns to the preset concentration (W1 +/-D).

Preferably, in step 203), the adjusting of the extraction amount of the hot air in the reduction roasting section and the extraction amount of the hot air in the drying section according to the real-time temperature change of the material in the reduction roasting section is specifically as follows: the set temperature of the material in the reduction roasting section is set to be T3 +/-C2 (the range of C2 is 0-50) and DEG C. Detecting the real-time temperature of the material in the reduction roasting section in real time as T4 and DEG C. Then:

and when T4 > (T3 +/-C2), increasing the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air in the drying section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T3 +/-C2).

When T4 epsilon (T3 +/-C2), the current process conditions are maintained unchanged.

And when T4 < (T3 +/-C2), reducing the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air in the drying section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T3 +/-C2).

Preferably, in step 204), according to the real-time temperature change of the material in the preheating section, the adjusting of the extraction amount of the hot air in the preheating section specifically comprises: the set temperature of the material in the preheating section is set to be T5 +/-C3 (the range of C3 is 0-50) and DEG C. And detecting the real-time temperature of the material in the preheating section at T6 and DEG C in real time. Then:

and when T6 is greater than (T5 +/-C3), increasing the extraction amount of the hot air in the preheating section until the real-time temperature of the material in the preheating section returns to the preset temperature (T5 +/-C3).

When T6 epsilon (T5 +/-C3), the current process conditions are maintained unchanged.

And when T6 < (T5 +/-C3), reducing the extraction amount of the hot air in the preheating section until the real-time temperature of the material in the preheating section returns to the preset temperature (T5 +/-C3).

Preferably, in step 205), adjusting the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air at the kiln tail of the rotary kiln according to the real-time temperature change of the material in the reduction roasting section specifically include: the set temperature of the material in the reduction roasting section is set to be T7 +/-C4 (the range of C4 is 0-50) and DEG C. And detecting the real-time temperature of the material in the reduction roasting section at T8 and DEG C in real time. Then:

and when T8 is greater than (T7 +/-C4), increasing the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air at the tail of the rotary kiln until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T7 +/-C4).

When T8 epsilon (T7 +/-C4), the current process conditions are maintained unchanged.

And when T8 is less than (T7 +/-C4), reducing the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air at the tail of the rotary kiln until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T7 +/-C4).

Preferably, in step 206), the adjusting of the extraction amount of the hot air in the later stage of the drying section and the extraction amount of the hot air in the reduction roasting section according to the real-time temperature change of the material in the later stage of the drying section is specifically as follows: the set temperature of the material at the later stage of the drying section is set to be T9 +/-C5 (the range of C5 is 0-50) and DEG C. And detecting the real-time temperature of the material at the later stage of the drying section as T10 and DEG C in real time. Then:

and when T10 > (T9 +/-C5), increasing the extraction amount of hot air in the later stage of the drying section and the extraction amount of hot air in the reduction roasting section until the real-time temperature of the material in the later stage of the drying section returns to the preset temperature (T9 +/-C5).

When T10 epsilon (T9 + -C5), the current process conditions are maintained.

And when T10 is less than (T9 +/-C5), reducing the extraction amount of hot air in the later stage of the drying section and the extraction amount of hot air in the reduction roasting section until the real-time temperature of the material in the later stage of the drying section returns to the preset temperature (T9 +/-C5).

Preferably, step 3) is specifically:

301 The high-temperature coal gas at the top of the melting furnace is conveyed into a vertical shaft for reforming to obtain reformed gas, and then the reformed gas is subjected to plasma activation and conveyed to a plasma reduction section for participating in the pre-reduction treatment of the iron-containing composite pellets. And simultaneously pumping the tail gas of the rotary kiln into the vertical shaft, and adjusting the pumping amount of the tail gas of the rotary kiln according to the real-time temperature change of the materials in the vertical shaft.

Or, the step 3) is specifically:

302 The high-temperature coal gas at the top of the melting furnace is conveyed into a vertical shaft for reforming to obtain reformed gas, and then the reformed gas is subjected to plasma activation and conveyed to a plasma reduction section for participating in the pre-reduction treatment of the iron-containing composite pellets. Meanwhile, tail gas of the rotary kiln is pumped into the ash separation device, and the extraction amount of the tail gas of the rotary kiln is adjusted according to the real-time temperature change of smoke dust in the ash separation device. And finally, carrying out plasma activation on tail gas discharged by the ash separation device, and conveying the tail gas to a plasma reduction section to participate in the pre-reduction treatment of the iron-containing composite pellets.

Preferably, in step 301), the adjusting of the extraction amount of the tail gas of the rotary kiln according to the real-time temperature change of the material in the shaft specifically comprises: the set temperature of the materials in the shaft is set to be T11 +/-C6 (the range of C6 is 0-50) and DEG C. And detecting the real-time temperature of the material in the shaft at T12 and DEG C in real time. Then:

and when T12 > (T11 +/-C6), increasing the extraction amount of the tail gas of the rotary kiln until the real-time temperature of the material in the shaft returns to the preset temperature (T11 +/-C6).

When T12 epsilon (T11 +/-C6), the current process conditions are maintained unchanged.

And when T12 < (T11 +/-C6), reducing the extraction amount of the tail gas of the rotary kiln until the real-time temperature of the material in the shaft returns to the preset temperature (T11 +/-C6).

Preferably, in step 302), the adjusting of the extraction amount of the tail gas of the rotary kiln according to the real-time temperature change of the smoke dust in the ash separation device is as follows: the set temperature of the soot in the ash separator is set to T13 + -C7 (the range of C7 is 0-50) and DEG C.

Real-time temperature of the smoke dust in the ash content separation device is detected to be T14 and DEG C in real time. Then:

and when T14 > (T13 +/-C7), increasing the extraction amount of the tail gas of the rotary kiln until the real-time temperature of the smoke dust in the ash separation device returns to the preset temperature (T13 +/-C7).

When T14 epsilon (T13 +/-C7), the current process conditions are maintained unchanged.

And when T14 < (T13 +/-C7), reducing the extraction amount of the tail gas of the rotary kiln until the real-time temperature of the smoke dust in the ash separation device is returned to be within the preset temperature (T13 +/-C7).

Preferably, the temperature of the high-temperature coal gas discharged from the top of the melting furnace is more than 1400 ℃, preferably more than 1500 ℃, and more preferably more than 1600 ℃; for example: 1400 ℃,1450 ℃,1500 ℃,1550 ℃,1600 ℃,1650 ℃,1700 ℃ and 1800 ℃.

Preferably, the content of CO in the reformed gas is higher than 30vol%, preferably the content of CO is higher than 35vol%, more preferably the content of CO is higher than 40vol%. H ₂ Is higher than 2vol%, preferably H ₂ Is higher than 3vol%, more preferably H ₂ Is higher than 5vol%.

According to a second embodiment of the present invention, there is provided a direct reduction apparatus for iron-containing composite pellets.

An apparatus for direct reduction of iron-containing composite pellets or for use in the process of the first embodiment comprises a rotary kiln, a melting furnace and a microwave plasma exciter. According to the trend of the materials, the rotary kiln is sequentially provided with a drying section, a preheating section, a plasma reduction section, a reduction roasting section and a slow cooling section. The discharge hole of the slow cooling section is directly communicated with the feed inlet of the melting furnace through a vertical shaft. Or the discharge hole of the slow cooling section is communicated with the feed inlet of the ash separation device through a vertical shaft, and the discharge hole of the ash separation device is communicated with the feed inlet of the melting furnace. The microwave plasma exciter is arranged outside the plasma reduction section, and an exhaust port of the microwave plasma exciter is communicated with an air inlet at the bottom of the plasma reduction section. An air flow external circulation system is arranged between the melting furnace and the rotary kiln. And an air flow internal circulation system is arranged between each section of the rotary kiln. Preferably, the ash separation device comprises a shell and a vibrating screen ash conveying mechanism. The vibrating screen ash conveying mechanism is arranged in the shell and communicated with a feeding hole and a discharging hole of the shell.

Preferably, the wind current external circulation system comprises: and communicating a top exhaust port of the melting furnace with a bottom air inlet of the vertical shaft through a first pipeline, and communicating a top exhaust port of the vertical shaft with an air inlet of the microwave plasma exciter through a second pipeline.

Preferably, the kiln tail of the rotary kiln is communicated with a bottom air inlet of the vertical shaft through a third pipeline or is communicated with a bottom air inlet of the ash separating device, and then a top air outlet of the ash separating device is communicated with an air inlet of the microwave plasma exciter through a fourth pipeline.

Preferably, the wind current internal circulation system comprises:

and communicating the top air outlet of the drying section with the bottom air inlet of the reduction roasting section through a fifth pipeline.

Preferably, the top air outlet of the slow cooling section is communicated with the bottom air inlet of the preheating section through a sixth pipeline:

or, the wind current internal circulation system comprises:

and communicating a top air outlet of the drying section with an air inlet of the first air mixing chamber through a seventh pipeline, and communicating a top air outlet of the reduction roasting section with an air inlet of the first air mixing chamber through an eighth pipeline. And then the air outlet of the first air mixing chamber is communicated with the bottom air inlet of the preheating section through a ninth pipeline.

Preferably, the top air outlet of the preheating section is communicated with the bottom air inlet of the drying section through a tenth pipeline.

Or, the wind current internal circulation system comprises:

and communicating an air outlet at the kiln tail of the rotary kiln with an air inlet of a second air mixing chamber through an eleventh pipeline, and communicating an air outlet at the top of the reduction roasting section with an air inlet of the second air mixing chamber through a twelfth pipeline. And then the air outlet of the second air mixing chamber is communicated with the air inlet at the bottom of the drying section at the initial stage through a thirteenth pipeline.

Preferably, the top air outlet at the later stage of the drying section is communicated with the air inlet of the third air mixing chamber through a fourteenth pipeline, and the top air outlet of the reduction roasting section is communicated with the air inlet of the third air mixing chamber through a fifteenth pipeline. And then the air outlet of the third air mixing chamber is communicated with the bottom air inlet at the middle and later stages of the drying section through a sixteenth pipeline.

Preferably, the circulating pipeline of the wind flow external circulating system and the circulating pipeline of the wind flow internal circulating system are respectively and independently provided with a multi-pipe dust remover, a flow regulating valve and a draught fan.

Preferably, the system further comprises a temperature detection device. The temperature detection devices are independently arranged in the drying section, the preheating section, the reduction roasting section, the vertical shaft and the ash separation device.

Preferably, the system further comprises a CO concentration detection device. The CO concentration detection device is arranged in the slow cooling section.

Preferably, the system further comprises a metallization ratio detection device. The metallization ratio detection devices are independently arranged in the preheating section, the plasma reduction section and the reduction roasting section.

Preferably, the device also comprises a burner and a fuel conveying pipeline. The burner is arranged in the reduction roasting section and communicated with the fuel conveying pipeline. And a combustion-supporting air pipe is communicated with the fuel conveying pipeline outside the rotary kiln.

Preferably, a plurality of burners are arranged in the reduction roasting section, and the burners are all communicated with the fuel conveying pipeline.

Preferably, the rotary kiln further comprises a kiln body air duct mechanism, an annular rotary slide rail and a rotary slide mechanism. The annular rotary slide rail is sleeved outside the rotary kiln and supported by the support. The wheel end of the rotary sliding mechanism is connected with the annular rotary sliding rail, the other end of the rotary sliding mechanism is connected with the outer end of the kiln body air duct mechanism, and the inner end of the kiln body air duct mechanism is connected to the kiln wall. Namely, the rotary kiln and the kiln body air duct mechanism can simultaneously rotate on the annular rotary slide rail through the rotary slide mechanism.

Preferably, a plurality of annular rotary sliding rails are arranged outside the rotary kiln. Any one annular rotary slide rail is connected with the rotary kiln through a plurality of rotary slide mechanisms and a plurality of kiln body air duct mechanisms.

Preferably, the kiln body air duct mechanism comprises an air inlet connecting piece, a stop valve, a pull rod and an air inlet. An air inlet channel is formed in the kiln body of the rotary kiln. One end of the baffle valve extends into the air inlet channel, and the other end of the baffle valve is communicated with the air inlet connecting piece. The air inlet is arranged on the air inlet connecting piece. The one end that the rotary kiln was kept away from to the air inlet connecting piece is connected with the one end of pull rod, and the other end of pull rod is connected with rotary sliding mechanism.

Preferably, the rotary sliding mechanism comprises a rotary wheel seat, a lateral rotary wheel and a vertical rotary wheel. The rotary wheel seat is of a concave groove type structure and is meshed with the two side edge parts of the annular rotary sliding rail. And lateral rotating wheels are arranged on the rotating wheel seats on the side surfaces of the annular rotating slide rails. Vertical rotating wheels are arranged on the rotating wheel seats on the outer bottom surfaces of the annular rotating slide rails. The rotary wheel seat can rotate and slide on the annular rotary sliding rail through the lateral rotary wheel and the vertical rotary wheel.

Preferably, the rotary kiln further comprises a horizontal sliding mechanism. The horizontal sliding mechanism comprises a horizontal wheel seat, a horizontal pulley and a horizontal rail. The horizontal rail is a groove-shaped rail arranged at the upper end of the bracket. The bottom end of the horizontal wheel seat is arranged in the horizontal track through the horizontal pulley. The top end of the horizontal wheel seat is connected with the annular rotary sliding rail.

Preferably, the device further comprises a slewing mechanism. The slewing mechanism comprises a slewing motor and a large gear ring. The inner ring of the large gear ring is fixed on the outer wall of the rotary kiln, and the outer ring of the large gear ring is meshed and connected with a transmission gear of the rotary motor.

Preferably, the device further comprises conductivity detection means. The conductivity detection device comprises a detection coil and a magnetic core. The detection coil is connected with a magnetic core, and the magnetic core is arranged on a kiln body of the rotary kiln.

Preferably, the magnetic conducting core is arranged in the side wall of the rotary kiln body, and the distance between the tail end of the magnetic conducting core and the inner wall of the rotary kiln is 0.5-20mm, preferably 1-15mm, and more preferably 2-10mm.

In the prior art, in the direct reduction process of the coal-based rotary kiln, the time from the feeding of the pellet material into the kiln to the discharging of the product from the kiln is 6-8 hours, the production period is longer, and the production efficiency is low. General rotary kilnThe productivity of the original process is generally related to the size and structure of the kiln, the conditions of raw materials and fuel, the temperature and temperature distribution in the kiln, the atmosphere and the charge amount, etc., and is also related to the structure of the pellets themselves, such as the carbon distribution amount, the carbon distribution form, the particle size, etc. The diffusion direction of the reducing agent inside the pellets is one of the key factors influencing the progress of the reduction reaction. Generally, the reducing agent needs to diffuse from the outside of the pellet to the inside of the pellet, and CO generated after reduction ₂ Or H ₂ The O diffuses outward from the inside of the pellet, and the product gas diffusing outward increases the difficulty of the reducing agent diffusing into the inside of the pellet, thereby resulting in slow reduction efficiency. Secondly, in the process of reducing the iron oxide, the iron element is gradually reduced from high valence to low valence. When the temperature is more than 570 ℃, the reduction sequence of the iron oxide is Fe ₂ O ₃ →Fe ₃ O ₄ →FeO→Fe _x O → Fe. Wherein, fe ₂ O ₃ →Fe ₃ O ₄ →FeO→Fe _x The process of O takes a long time because the crystal structure of the iron oxide needs to be changed for many times. And Fe _x The process of O → Fe is the process from iron oxide to simple substance iron, the difficulty is the greatest, and the required process conditions are higher.

In the invention, the iron-containing composite pellet has a multilayer structure, and the diameter of the pellet is 10-25 mm (preferably 12-20 mm). The iron-containing composite pellet comprises three material layers, namely a kernel pellet material layer Q _T -1 is a mixture of a reducing agent with a high content of volatile components and a binder, and an intermediate pelletizing layer Q _T -2 is a calcium carbonate layer (CaCO) ₃ ) Outer layer pelletizing material layer Q _T -3 is a mixture of iron concentrate and binder. Wherein, the kernel pellet Q _T 1 layer with a diameter of 2 to 6mm (preferably 3 to 5 mm) and an intermediate layer Q _T -2 layers having a thickness of 1 to 3mm (preferably 1.5 to 2 mm), Q _T The thickness of the-3 layers is 3 to 7mm (preferably 4 to 6 mm). Q _T The reducing agent in the layer-1 can be one or more of bituminous coal, lignite, biomass and organic solid waste, and Q is _T -1 layer and Q _T The binder in the-3 layers can be organic or inorganic binders such as bentonite, humic acid, humate and the like. The three-layer structure contains ironThe composite pellets can be simultaneously reduced and roasted from an iron-containing material layer Q _T The inside and outside of the 3 layers are simultaneously reduced with iron oxide, and compared with common pellets or internally-matched carbon pellets, the iron oxide reduction pellet has faster reduction speed and higher reduction pellet strength.

In the invention, when the iron-containing composite pellets are subjected to high-temperature reduction in the furnace kiln, the outer layer Q of the pellets _T And 3, carrying out reduction reaction on the iron oxide and the reducing agent in the kiln from outside to inside. When the temperature of the pellets reaches above 810 ℃, the middle Q of the composite pellets _T -2 layers of CaCO ₃ Decomposition reaction occurs to release CO ₂ (CaCO ₃ ＝CaO+CO ₂

)，CO ₂ And Q _T The reducing agent (e.g. C) in layer-1 undergoes a Boolean reaction (CO) _2(g) +C _(s) ＝2CO ⁺ _(g) +2e ^- ) Formation of CO, diffusion of CO out of Q _T -iron oxide reduction in 3 layers. CO produced ₂ The boolean reaction takes place again, so that the reduction cycle of the iron oxides is repeated. Therefore, when the iron-containing composite pellets having a multi-layered structure proposed by the present invention are reduced in a reducing furnace, Q is _T CO liberated by decomposition of calcium carbonate in 2 layers ₂ The iron oxide in the pellet is used as a starter for the reduction reaction of the iron oxide in the pellet, so that the iron oxide on the outer layer and the iron oxide on the inner layer of the pellet are subjected to the reduction reaction simultaneously, and the reduction speed is improved.

In the invention, one or more of bituminous coal, lignite, biomass, organic solid waste and the like which are rich in volatile matters are used as reducing agents and are pre-granulated and pelletized with binders (namely Q) _T -1) as a core placed in the core of the composite pellet. When the iron-containing composite pellets are reduced in a reducing furnace, the pellet core begins to decompose to contain a large amount of H when the temperature reaches over 500 DEG C ₂ CO and CH ₄ Etc. of reducing gas. At this time, due to Q _T -2 calcium carbonate shells surrounding a core layer Q _T -1, the reducing gas cannot diffuse out immediately, thus avoiding the evolution of reducing gas before the iron oxide starts to be significantly reduced. When the temperature reaches above 810 ℃, Q _T The 2 layers begin to decompose, the reducing gas diffuses out in large quantities, Q _T -iron oxide reduction in 3 layers. Due to H ₂ The reducing power of the pellet is far higher than that of CO, and the pellet core Q _T The reduction gas released from the layer-1 greatly promotes the reduction of iron oxides in the composite pellets, thereby improving the overall reduction speed of the pellets.

In the present invention, CO-rich is used ₂ The green pellets are dried by the drying medium of (1), in the drying process, due to lime milk (Ca (OH) ₂ ) The carbonation reaction of (Ca (OH) is very easy to carry out ₂ +CO ₂ ＝CaCO ₃ +H ₂ O，

) The lime milk layer in the middle layer of the green ball is subjected to carbonation reaction to generate CaCO ₃ Thereby forming a calcium carbonate layer and obtaining the fast reduction composite pellet after drying. Wherein, it is rich in CO ₂ The drying medium of (2) may be the addition of CO ₂ Hot air, hot tail gas in various processes of blast furnace steel smelting and direct reduction processes, and the like. Generally, rich in CO ₂ Of the drying medium of ₂ The content of (B) is 5 to 15wt%, preferably 8 to 12wt%.

In the invention, the method of deep reduction by adopting a rotary kiln prereduction-deep reduction device (namely a melting furnace, the same applies below) is also adopted to reduce the iron oxide into the Fe which is easy to generate but takes longer time in the process of reducing the iron oxide into the metallic iron ₂ O ₃ →Fe ₃ O ₄ →FeO→Fe _x The reduction reaction of the O stage is completed in a rotary kiln, the reducing agent in the rotary kiln mainly comprises a coal-based reducing agent and furnace top gas of a deep reduction device, and the main effective components are CO and H ₂ In the rotary kiln pre-reduction stage, some metallic iron may also be formed. Thus, the following reactions mainly occur in the rotary kiln:

3Fe ₂ O ₃ (s)+CO(g)＝2Fe ₃ O ₄ (s)+CO2(g)。

xFe ₃ O ₄ (s)+(4x-3)CO(g ₎ ＝3Fe _x O(s)+(4x-3)CO ₂ (g)。

Fe _x O(s)+CO(g)＝xFe(s)+CO ₂ (g)。

3Fe ₂ O ₃ (s)+H ₂ (g)＝2Fe ₃ O ₄ (s)+H ₂ O(g)。

xFe ₃ O ₄ (s)+(4x-3)H ₂ (g)＝3Fe _x O(s)+(4x-3)H ₂ O(g)。

Fe _x O(s)+H ₂ (g)＝xFe(s)+H ₂ O(g)。

in a rotary kiln, fe ₂ O ₃ Is first reduced to Fe ₃ O ₄ The crystal structure of the iron oxide is changed for the first time, and the reduction degree of the iron oxide is improved from 0 to 11.1 percent. Then from Fe ₃ O ₄ Is reduced into FeO, the crystal structure of the iron oxide is changed for the second time, and the reduction degree of the iron oxide is improved from 11.1 percent to 33.3 percent. Then reduced from FeO to Fe _x O, the crystal structure of the iron oxide is changed for the third time, and the reduction degree of the iron oxide is improved from 33.3 percent to about 80 percent; in the process, partial elementary iron crystals appear, the elementary iron crystals and other iron oxides enter the deep reduction device, and the partial elementary iron crystals serve as 'nuclei', so that the reduction of the iron oxides of the other iron oxides in the deep reduction device is accelerated, and the iron crystals grow. That is to say the reaction taking place in the rotary kiln is: most of Fe ₂ O ₃ Is reduced to FeO, part of Fe ₂ O ₃ Is reduced to Fe; the substances reduced to FeO and reduced to Fe constitute pre-reduction products reaching a certain degree of reduction.

The pre-reduction product reaching a certain reduction degree and residual coal are hot-charged into a deep reduction device together, and Fe is generated in the deep reduction device _x The deep reduction reaction of the O → Fe stage, the reducing agent is mainly C dissolved in molten slag iron, and the following reactions mainly occur:

Fe _x O(s)+[C]＝xFe(s)+CO(g)。

in the deep reduction device, the pre-reduction product reaching a certain reduction degree and carbon are changed into a molten state, and the iron oxide in the pre-reduction product reaching a certain reduction degree is further reduced into simple substance iron by taking the iron in the pre-reduction product reaching a certain reduction degree as a core, so that the reduction of the whole iron oxide is realized. Because the + 2-valent iron is reduced into the simple substance iron, the required process conditions are harsh, and the requirements on kinetic energy and thermodynamic energy are high, the deep reduction device is adopted, so that the iron oxide and the reducing agent enter a liquid state (the gas-solid state reaction in the rotary kiln), and the reduction of the iron oxide is accelerated by the liquid state reaction.

The invention has the technical characteristics that:

(1) The high efficiency of the iron oxide reduction process is realized by controlling the reduction degree of the pre-reduction-deep reduction device and the deep reduction device of the rotary kiln. The reduction process of the rotary kiln mainly comprises coal vaporization and gas-solid reduction reaction of iron oxide and carbon monoxide or hydrogen, the mass transfer efficiency and the heat transfer efficiency are low due to the fact that a material layer is arranged below and gas flows on the material layer, the reduction temperature of the rotary kiln is generally not more than 1250 ℃, and the reduction reaction speed in the rotary kiln is low, so that a long time is needed for completely reducing the iron oxide into the metallic iron in the rotary kiln, but the reaction time is greatly shortened only when the iron oxide is reduced to a ferrous stage (including partial elemental iron). The reduction reaction of the deep reduction device mainly occurs in molten slag iron at the temperature of more than 1400 ℃, and reactants are all in a molten state (liquid state), so the reduction reaction has extremely high occurrence rate. However, the materials in the deep reduction device need to be melted into a molten state, and the melting temperature of the ferric trioxide and the ferroferric oxide is higher, so if the high-valence iron oxide is directly reduced in the deep reduction device, the energy consumption is greatly increased.

The technology completes the reaction of ferric oxide from trivalent to divalent easy reduction stage in a rotary kiln, and completes the reaction of ferrous iron to metallic iron in difficult reduction stage in a deep reduction device. Fully utilizes the reduction conditions provided by the rotary kiln and the deep reduction device and combines the characteristics of the iron oxide reduction process, and realizes the high efficiency of the iron oxide reduction process.

(2) The energy consumption is minimized through reasonable cascade utilization of energy. The technology introduces the part of high-temperature coal gas into a coal-based rotary kiln, realizes the pre-reduction of the iron oxide in the rotary kiln by utilizing the sensible heat and the latent heat of the part of high-temperature coal gas and the reducing gas in the part of high-temperature coal gas, and can effectively reduce the energy consumption of the rotary kiln.

In order to optimize the reduction process of the iron oxide, if the iron oxide is completely reduced in the rotary kiln, the reduction time of the iron oxide is greatly prolonged on one hand, the reduction of the iron oxide is incomplete on the other hand, and the materials are easy to ring in the rotary kiln. If the iron oxide is completely reduced in the deep reduction device, the reduction energy consumption of the iron oxide is greatly increased and the reduction efficiency of the iron oxide is reduced due to the higher melting temperature of the ferric trioxide and the ferroferric oxide. Therefore, the iron oxide reduction process is reasonably distributed in the rotary kiln and the deep reduction device, and the method is of great importance for the technical problems of iron oxide reduction efficiency, energy consumption, ring formation prevention and the like.

In the present invention, the degree of reduction of iron oxide in the rotary kiln is controlled to be eta, which is 40 to 80%, preferably 50 to 70%, more preferably 60 to 65%. That is, in the rotary kiln, it is most reasonable to control the state in which most of the ferric trioxide is reduced to ferrous oxide and the state in which part of the ferric trioxide is reduced to elemental iron. It is found through experiments that if all ferric trioxide is only reduced into the pre-reduction product of ferrous oxide, the pre-reduction product is then subjected to deep reduction in a deep reduction device. The reduction efficiency of the pre-reduction product in the deep reduction device is still low, and the energy consumption is still large. If the pre-reduction product contains part of elemental iron, the reduction efficiency of the pre-reduction product in the deep reduction device is greatly improved.

Through experimental research, the reduction degree of the iron oxide in the rotary kiln is controlled to be eta, and the eta is 40-80%, preferably 50-70%, and more preferably 60-65%. The method is a reasonable technical scheme, which can improve the whole reduction efficiency of the iron oxide and reduce the energy consumption of the iron oxide reduced by the simple substance iron.

The invention controls the reduction degree of iron oxide in the rotary kiln based on the following theory:

iron ore raw materials corresponding to 1 ton of molten iron are generated, the Fe content wFe in the molten iron MFe and the FeO content wFeO in the slag M are set, 97 percent of the sum of the two is from the iron ore raw material, and the iron ore raw material is hematite (assuming that all Fe is used as the iron ore raw material) ₂ O ₃ ) Mass MFe ₂ O ₃ Content wFe ₂ O ₃ ，

1) In a rotary kiln, when Fe ₂ O ₃ Reduction to Fe only ₃ O ₄ In this case, the deoxidation was 1/9, the degree of prereduction was 11.1%, the amount of carbon consumed (energy consumption):

3Fe ₂ O ₃ +CO＝2Fe ₃ O ₄ +CO ₂

C+CO ₂ ＝2CO

obtaining:

in the deep reduction unit, the remaining reduction reaction is carried out, converting to direct reduction of C:

Fe ₃ O ₄ +C＝3FeO+CO

obtaining:

FeO+C＝Fe+CO

obtaining:

2) In a rotary kiln, when Fe ₂ O ₃ Reduction to Fe ₃ O ₄ When the alloy is reduced to FeO, the alloy is deoxidized by 1/3, the pre-reduction degree is 33.3 percent, and the consumed carbon amount (energy consumption) is as follows:

3Fe ₂ O ₃ +CO＝2Fe ₃ O ₄ +CO ₂

C+CO ₂ ＝2CO

obtaining:

Fe ₃ O ₄ +CO＝3FeO+CO ₂

C+CO ₂ ＝2CO

obtaining:

FeO+C＝Fe+CO

obtaining:

3) In a rotary kiln, when Fe ₂ O ₃ Reduction to Fe ₃ O ₄ And when FeO is reduced to Fe, removing the residual 2/3 of oxygen, and setting the pre-reduction degree as eta (more than 33.3%), the consumed carbon amount (energy consumption):

3Fe ₂ O ₃ +CO＝2Fe ₃ O ₄ +CO ₂

C+CO ₂ ＝2CO

obtaining:

Fe ₃ O ₄ +CO＝3FeO+CO ₂

C+CO ₂ ＝2CO

obtaining:

FeO+CO＝Fe+CO ₂

C+CO ₂ ＝2CO

obtaining:

in the deep reduction unit, the remaining reduction reaction is carried out, converting to direct reduction of C: feO + C = Fe + CO

Obtaining:

the invention provides a technical scheme of adopting a rotary kiln for prereduction and a deep reduction device for deep reduction, aiming at the technical problems of high energy consumption, longer production period, low production efficiency and the like of adopting a rotary kiln to reduce iron oxide in the process of adopting a direct reduction method to treat iron oxide; the preliminary reduction (pre-reduction) of iron oxide is carried out by a rotary kiln, and the Fe which is easy to generate in the process of reducing the iron oxide into metallic iron ₂ O ₃ →Fe ₃ O ₄ →FeO→Fe _x The reduction reaction of the O stage is finished in the rotary kiln, the reaction period of the process is long, and the working procedures of drying, preheating and the like of the iron oxide are needed firstly; mixing Fe _x The deep reduction reaction in the O → Fe stage is completed in a deep reduction device, and the stage needs a high-temperature environment to realize high reduction of iron. Through the technical scheme of the rotary kiln prereduction and the deep reduction of the deep reduction device, the efficiency of the direct reduction of the iron oxide is greatly improved, and the energy consumption in the direct reduction process is saved through reasonable process adjustment.

In the preferred scheme of the invention, the reduction condition of the iron oxide in the rotary kiln is monitored by detecting the conductivity of the material in the rotary kiln in real time and analyzing the state of the material in the rotary kiln through the conductivity.

Basic principle of conductivity detection:

in the rotary kiln, the iron-containing raw material for reduction contains Fe as the main component ₂ O ₃ 、Fe ₃ O ₄ And in the process of transferring from the kiln tail to the kiln head, the iron oxide is reduced into FeO and Fe step by step under different temperature and atmosphere conditions, and the change of the iron oxide components causes the change of the electric permeability and the magnetic permeability. When the temperature in the kiln exceeds the Curie temperature of the material, the ferromagnetic material is converted into a paramagnetic material, namely the relative magnetic conductivity is about 1, and the change of the components of the material only changes the self conductivity, so that the reduction degree of the iron oxide at the detection point, the components of the material and the temperature can be judged according to the change of the conductivity of the iron-containing raw material in the rotary kiln.

The non-contact temperature measurement and material component detection device based on the conductivity, the non-contact temperature measurement and material component detection method based on the conductivity, the detection device and the detection method can accurately detect the temperature and the material components without being influenced by the complex environment in the container and interfering the characteristics of the material, prevent the ring formation problem caused by the higher temperature of the material layer, and effectively control the pre-reduction degree or the metallization rate of the furnace burden in the pre-reduction-melting reduction process and the direct reduced iron-electric furnace process.

The detection of the conductivity of the material mainly adopts an eddy current detection method, a detection coil is arranged above a test piece made of a metal material, an alternating excitation signal is added into a coil, an alternating magnetic field is generated around the coil, a metal conductor arranged in the magnetic field generates an eddy current, the eddy current also generates a magnetic field, the directions of the magnetic field and the alternating magnetic field are opposite, the effective impedance of the electrified coil is changed due to the reaction of the magnetic field, and the change of the impedance of the coil completely and uniquely reflects the eddy current effect of an object to be detected.

The detection environment is kept unchanged, and when materials with different conductivities are detected, the eddy current generated on the surface layer has different sizes, so that the influences on the impedance of the detection coil are different, and the conductivity of the metal material can be measured by measuring the change condition of the impedance of the coil.

The design of the detection device:

the steel plate on the outer wall of the rotary kiln is provided with holes for reducing the interference of the eddy effect of the steel plate on the impedance of the coil and transmitting the magnetic field generated by the coil to the surface of the material in the kiln.

The fire-resistant lining is provided with the holes, the lining is not punched, a certain thickness of heat insulation is reserved, the magnetic cores are embedded for conducting magnetism, the magnetic field reaching the material is enhanced, the blocking magnetic field generated by material eddy current is conducted, only one magnetic core is used for conducting magnetism, and attenuation of the magnetic field in an air gap is reduced.

And (3) detection process:

(1) The conventional rotary kiln is divided into four sections, and Fe generally occurs in a preheating section ₂ O ₃ →Fe ₃ O ₄ → FeO, feO → Fe in the baking stage _x O; upon inquiry of data, fe ₂ O ₃ 、Fe ₃ O ₄ Resistivity rho and conductivity of FeO and Fe

The following were used:

substance(s)	Resistivity/Ω · m	Conductivity/omega ^-1 ·m ^-1
			Fe ₂ O ₃	10 ²	10 ^-2
Fe ₃ O ₄	10 ^-2	10 ²
			FeO	10 ^-4	10 ⁴
Fe	10 ^-7	10 ⁷

(2) Since the reduction of iron oxide is carried out stepwise, it is considered that the iron oxide composition of the reduced material is single or two, such as Fe ₂ O ₃ With Fe ₃ O ₄ 、Fe ₃ O ₄ Mixing the pure substances of the two iron oxides with FeO, feO and Fe according to different proportions, measuring the sigma of the mixture, and establishing an equation of the content ratio of the sigma to the iron oxides; then, carrying out reduction roasting on the known sigma mixture under the conditions of reduction temperature T and reduction time T, detecting the chemical composition and sigma of a roasting product, and continuously correcting the relation to obtain:

meanwhile, establishing a relational expression between the reduction degree of the material delta eta and the conductivity delta sigma, delta sigma and the reduction temperature T and the reduction time T:

Δη＝κΔσ＝f(T,t)

(3) In actual production, a material of known chemical composition (i.e. known sigma) ₁ 、η ₁ ) Entering from the tail of a rotary kiln, drying, preheating and roasting to convert into a pre-reduced material with unknown chemical composition, wherein the process conditions are respectively the carbon distribution amount M _c Reduction temperature T, reduction time T; a plurality of (3-4) conductivity detection devices are arranged at the end positions of the preheating section and the roasting section of the rotary kiln, so that the conductivity sigma of the pre-reduced material is measured in time ₂ To obtain

Δη＝κΔσ＝κ(σ ₂ -σ ₁ )

η ₂ ＝η ₁ +Δη

(4) When eta ₂ When the value is the pre-reduction degree eta (1 +/-10%) of the furnace charge required by the deep reduction device, the existing process condition is kept; when eta ₂ When the value exceeds the pre-reduction degree eta (1 + 10%) of furnace charge required by the deep reduction device, the reduction temperature T (such as reducing the coal injection quantity and reducing the secondary air quantity) is properly reduced in time, and the reduction time T (such as accelerating the rotating speed) is reduced; when eta ₂ When the value is lower than the pre-reduction degree eta (1-10%) of the furnace charge required by the deep reduction device, the reduction temperature T should be properly raised in time (such as increasing the coal injection quantity, injecting gas fuel through multiple injection holes), the reduction time T should be increased (such as increasing the rotating speed), and the coal blending quantity M should be increased _c 。

Through experimental research, the electric conductivity of the pre-reduction product obtained by controlling the reduction of the iron oxide through a rotary kiln is 1 x 10 ⁵ ～1*10 ⁷ Ω ^-1 ·m ^-1 Preferably 3 to 10 ⁵ ～7*10 ⁶ Ω ^-1 ·m ^-1 More preferably 5 x 10 ⁵ ～5*1*10 ⁶ Ω ^-1 ·m ^-1 . And calculating the reduction degree of the iron oxide in the rotary kiln by detecting the conductivity and then writing the component content of the corresponding substance. Conductivity 1 x 10 ⁵ ～1*10 ⁷ Ω ^-1 ·m ^-1 When the iron oxide is reduced, the reduction degree of the iron oxide is 40-80%. Conductivity of 3 x 10 ⁵ ～7*10 ⁶ Ω ^-1 ·m ^-1 When the reduction degree of the iron oxide is 50 to 70 percent. Conductivity 5X 10 ⁵ ～5*1*10 ⁶ Ω ^-1 ·m ^-1 When the reduction degree of the iron oxide is 60 to 65 percent. Therefore, the inventor of the present invention found through experiments that the degree of reduction of the material by reduction can be obtained by detecting the conductivity of the material.

Researches find that the reduction degree of the iron oxide in the rotary kiln has a direct relation with the carbon content in the iron oxide, the heat preservation reduction time of the iron oxide in the rotary kiln and the reduction temperature in the rotary kiln; and the reduction degree of the iron oxide in the rotary kiln is in direct proportion to the carbon distribution amount of the iron oxide, the heat preservation reduction time of the iron oxide in the rotary kiln and the reduction temperature in the rotary kiln.

The experimental study shows that:

in order to control the reduction degree of the iron oxide to be 40-80%, the carbon content in the iron oxide should be controlled to be 10-40wt%, the heat preservation and reduction time of the iron oxide in the rotary kiln is controlled to be 60-180min, and the reduction temperature in the rotary kiln is controlled to be 800-1400 ℃.

In order to control the reduction degree of the iron oxide to be 50-60%, the carbon content in the iron oxide should be controlled to be 15-30wt%, the heat preservation and reduction time of the iron oxide in the rotary kiln is controlled to be 70-140min, and the reduction temperature in the rotary kiln is controlled to be 850-1300 ℃.

In order to control the reduction degree of the iron oxide to be 60-65%, the carbon content in the iron oxide should be controlled to be 20-25wt%, the heat preservation and reduction time of the iron oxide in the rotary kiln is controlled to be 90-120min, and the reduction temperature in the rotary kiln is controlled to be 900-1200 ℃.

Therefore, the carbon distribution amount of the iron oxide and the reduction process condition of the iron oxide in the rotary kiln can be controlled, so that the reduction degree of the iron oxide in the rotary kiln can be controlled. And then detecting the reduction degree by detecting the conductivity of the pre-reduction product, and realizing the real-time control of the reduction degree by adjusting the carbon distribution amount of the iron oxide and the reduction process conditions of the iron oxide in the rotary kiln.

In the invention, the carbon distribution amount in the iron oxide refers to the weight ratio of the coal amount in the iron oxide entering the rotary kiln to the whole iron oxide. The holding reduction time of the iron oxide in the rotary kiln refers to the retention time of the iron oxide in the highest temperature section (for example, 1000-1250 ℃) in the rotary kiln. The reduction temperature in the rotary kiln refers to the highest temperature zone (e.g., 1000-1250 ℃) in the rotary kiln.

Since the reduction process of iron oxide exists in the following state, fe ₂ O ₃ 、Fe ₃ O ₄ 、FeO、Fe _x O (i.e., feO coexists with Fe) and Fe; by detecting the electric conductivity of the iron oxides with different reduction degrees and analyzing the components of the iron oxides in the pre-reduction product under the reduction degree, the relationship between the electric conductivity and the states of the materials in the rotary kiln and the reduction degree of the materials can be established as follows:

if σ _{Time of flight} ≤0.1Ω ^-1 ·m ^-1 Indicates thatThe material in the rotary kiln is mainly Fe ₂ O ₃ The real-time reduction degree of the iron oxide in the rotary kiln is [0,1%](ii) a Indicating that iron oxide has not begun to be reduced or that there is little portion reduced;

if 0.1 < sigma _Time-piece ≤1000Ω ^-1 ·m ^-1 Indicating that the material in the rotary kiln is mainly Fe ₃ O ₄ Is present in such a form that the real-time reduction degree of iron oxide in the rotary kiln is (1%, 11.1%)](ii) a Indicating that iron oxide is initially reduced or has been reduced to Fe ₃ O ₄ But has not been reduced to FeO.

If 1000 < sigma _{Time of flight} ≤1*10 ⁵ Ω ^-1 ·m ^-1 It shows that the main FeO form of the material in the rotary kiln exists, and the real-time reduction degree of the iron oxide in the rotary kiln is (11.1 percent, 33.3 percent)](ii) a Indicating that iron oxide has been reduced beyond Fe ₃ O ₄ Is initially reduced or has been reduced to FeO, but has not yet been reduced to Fe.

If 1 x 10 ⁵ ＜σ _{Time of flight} ≤1*10 ⁷ Ω ^-1 ·m ^-1 It shows that the main FeO and Fe exist in the rotary kiln, and the real-time reduction degree of the iron oxide in the rotary kiln is (33.3 percent, 80 percent)](ii) a Indicating that the iron oxide has been reduced beyond the FeO state and that a portion begins to be reduced or has been reduced to Fe, but not all.

If σ _{Time of flight} ＞1*10 ⁷ Ω ^-1 ·m ^-1 It shows that the main Fe form of the material in the rotary kiln exists, and the real-time reduction degree of the iron oxide in the rotary kiln is (80%, 1%)]. Indicating that the iron oxide has been fully reduced to Fe.

Through experimental research, the components of the pre-reduction product can be detected by detecting the conductivity of the pre-reduction product, so as to obtain the reduction degree of the iron oxide. According to the process conditions of the invention, under different reduction conditions, the real-time reduction degree eta of the iron oxide in the rotary kiln is determined _{Fruit of Chinese wolfberry} Timely adjusting the process conditions for reducing the iron oxide in the rotary kiln to ensure that the iron oxide is reduced in the rotary kilnDegree of real-time reduction eta _{Fruit of Chinese wolfberry} ＝(1±10％)η。

The invention provides a detection, judgment and control method, which specifically comprises the following steps:

if eta _{Fruit of Chinese wolfberry} Keeping the carbon distribution amount in the existing iron oxide, the heat preservation and reduction time of the iron oxide in the rotary kiln and the reduction temperature in the rotary kiln to continuously operate by =1 +/-10%; that is, the process conditions of the rotary kiln adopted at present are just the state conditions of the invention which need to obtain the pre-reduction product.

If eta _{Fruit of Chinese wolfberry} > (1 + 10%) η, mediated by any one or more of the following means: reducing the carbon content in the iron oxide, reducing the reduction temperature in the rotary kiln, shortening the heat preservation reduction time of the iron oxide in the rotary kiln and controlling the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} = (1 ± 10%) η; that is, the reduction degree of the pre-reduced product obtained by the current rotary kiln process conditions exceeds the reduction degree required by the invention, which indicates that the reduction degree of the iron oxide in the rotary kiln is excessive, and also indicates that the process conditions cause the overlong reduction time of the iron oxide in the rotary kiln, reduce the reduction efficiency of the whole iron oxide and possibly cause the generation of the ring formation phenomenon.

If eta _{Fruit of Chinese wolfberry} < (1-10%) η, mediated by any one or more of: increasing the carbon content in the iron oxide, raising the reduction temperature in the rotary kiln, prolonging the heat preservation reduction time of the iron oxide in the rotary kiln, and controlling the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} = (1 ± 10%) η. That is, the reduction degree of the pre-reduced product obtained under the currently adopted rotary kiln process conditions does not reach the reduction degree required by the invention, which indicates that the reduction degree of the iron oxide in the rotary kiln is insufficient, and also indicates that the process conditions cause that the pre-reduced product enters the deep reduction device for deep reduction, so that the load of the deep reduction device is increased, the energy consumption of the deep reduction device is increased, and the reduction efficiency of the whole iron oxide is reduced.

In the invention, the reduction of the carbon coordination amount in the iron oxide is specificallyComprises the following steps: each decrease Δ m =10% of carbon addition ₁ (alternatively 2%m ₁ 、30％m ₁ 、4％m ₁ 、5％m ₁ 、6％m ₁ 、7％m ₁ 、8％m ₁ 、9％m ₁ 、12％m ₁ 、15％m ₁ 、18％m ₁ 、20％m ₁ 、25％m ₁ 、30％m ₁ 、35％m ₁ 、40％m ₁ 、45％m ₁ 、50％m ₁ Etc.) where m is ₁ The original carbon content in the iron oxide. I.e. if eta _{Fruit of Chinese wolfberry} > (1 + 10%) eta, controlling carbon distribution m in iron oxide of next batch _i ＝m _i-1 -. DELTA.m; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still greater than (1 + 10%) eta, the carbon-added quantity Δ m (that is to say, m) in the iron oxide of the next batch is reduced again _i+1 ＝m _i-1 -2 x Δ m) until the real-time reduction η of iron oxides in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

In the invention, the specific steps for improving the carbon content in the iron oxide are as follows: each increment of carbon addition amount Delta m ₀ ＝10％m ₁ (alternatively 2%m ₁ 、30％m ₁ 、4％m ₁ 、5％m ₁ 、6％m ₁ 、7％m ₁ 、8％m ₁ 、9％m ₁ 、12％m ₁ 、15％m ₁ 、18％m ₁ 、20％m ₁ 、25％m ₁ 、30％m ₁ 、35％m ₁ 、40％m ₁ 、45％m ₁ 、50％m ₁ Etc.) where m is ₁ The original carbon content in the iron oxide; i.e. if eta _{Fruit of Chinese wolfberry} < (1 + 10%) eta, controlling carbon distribution m in iron oxide of next batch _i ＝m _i-1 B, plus delta m; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still less than (1 + 10%) eta, the formulation in the iron oxide of the next batch is increased againAmount of carbon Δ m (that is, m) _i+1 ＝m _i-1 +2 × Δ m) until the real-time reduction η of iron oxides in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

In the invention, the reducing of the coal injection amount in the rotary kiln specifically comprises the following steps: each decrease Δ p =10% of coal injection amount ₁ (alternatively 2%p ₁ 、30％p ₁ 、4％p ₁ 、5％p ₁ 、6％p ₁ 、7％p ₁ 、8％p ₁ 、9％p ₁ 、12％p ₁ 、15％p ₁ 、18％p ₁ 、20％p ₁ 、25％p ₁ 、30％p ₁ 、35％p ₁ 、40％p ₁ 、45％p ₁ 、50％p ₁ Etc.) wherein p is ₁ The original coal injection quantity in the rotary kiln is obtained; i.e. if eta _{Fruit of Chinese wolfberry} Eta (1 + 10%), controlling coal injection amount p in rotary kiln _j ＝p _j-1 -. DELTA.p; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still greater than (1 + 10%) eta, then the coal injection quantity delta p (that is to say p) is reduced again _i+1 ＝p _i-1 -2 × Δ p) until the real-time reduction η of iron oxides in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

In the invention, the increasing of the coal injection amount in the rotary kiln specifically comprises the following steps: each increase Δ p =10% of coal injection amount ₁ (alternatively 2%p ₁ 、30％p ₁ 、4％p ₁ 、5％p ₁ 、6％p ₁ 、7％p ₁ 、8％p ₁ 、9％p ₁ 、12％p ₁ 、15％p ₁ 、18％p ₁ 、20％p ₁ 、25％p ₁ 、30％p ₁ 、35％p ₁ 、40％p ₁ 、45％p ₁ 、50％p ₁ Etc.) wherein p is ₁ The original coal injection quantity in the rotary kiln is obtained; i.e. if eta _{Fruit of Chinese wolfberry} Eta < (1+10%), coal injection amount p in rotary kiln _j ＝p _j-1 B, plus delta p; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} To obtain iron oxide in the rotationReal-time degree of reduction eta in kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still less than (1 + 10%) eta, then increase coal injection quantity delta p (that is to say p) _i+1 ＝p _i-1 +2 × Δ p) until the real-time reduction η of iron oxides in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

In the invention, the reduction of the secondary air intake of the rotary kiln specifically comprises the following steps: each time reduction amount of the secondary intake air Δ f =10% ₁ (alternatively 2%f ₁ 、30％f ₁ 、4％f ₁ 、5％f ₁ 、6％f ₁ 、7％f ₁ 、8％f ₁ 、9％f ₁ 、12％f ₁ 、15％f ₁ 、18％f ₁ 、20％f ₁ 、25％f ₁ 、30％f ₁ 、35％f ₁ 、40％f ₁ 、45％f ₁ 、50％f ₁ Etc.) wherein f ₁ The primary secondary air intake of the rotary kiln; i.e. if eta _{Fruit of Chinese wolfberry} Eta (1 + 10%), controlling secondary air intake f of rotary kiln _k ＝f _k-1 -. DELTA.f; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still greater than (1 + 10%) eta, then the secondary air intake quantity delta f is reduced again (that is to say f _i+1 ＝f _i-1 -2 x Δ f) until the real-time reduction η of iron oxides in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

In the invention, the increasing of the secondary air intake of the rotary kiln specifically comprises the following steps: Δ f =10% of each increase in the amount of secondarily supplied air ₁ (alternatively 2%f ₁ 、30％f ₁ 、4％f ₁ 、5％f ₁ 、6％f ₁ 、7％f ₁ 、8％f ₁ 、9％f ₁ 、12％f ₁ 、15％f ₁ 、18％f ₁ 、20％f ₁ 、25％f ₁ 、30％f ₁ 、35％f ₁ 、40％f ₁ 、45％f ₁ 、50％f ₁ Etc.) wherein f ₁ The primary secondary air intake of the rotary kiln; i.e. if eta _{Fruit of Chinese wolfberry} Eta < (1 + 10%), controlSecondary air intake f of rotary kiln _k ＝f _k-1 +. DELTA.f; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still less than (1 + 10%) eta, the secondary air intake quantity delta f is increased again (that is to say f _i+1 ＝f _i-1 +2 × Δ f) until the real-time reduction η of iron oxides in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

In the invention, the increasing of the rotating speed of the rotary kiln specifically comprises the following steps: Δ s =10% per increment of the rotation speed ₁ (alternatively 2%s ₁ 、30％s ₁ 、4％s ₁ 、5％s ₁ 、6％s ₁ 、7％s ₁ 、8％s ₁ 、9％s ₁ 、12％s ₁ 、15％s ₁ 、18％s ₁ 、20％s ₁ 、25％s ₁ 、30％s ₁ 、35％s ₁ 、40％s ₁ 、45％s ₁ 、50％s ₁ Etc.) wherein s ₁ The original rotation speed of the rotary kiln; i.e. if eta _{Fruit of Chinese wolfberry} Eta (1 + 10%), controlling rotation speed s of rotary kiln _r ＝s _r-1 +. DELTA s; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still greater than (1 + 10%) eta, then increase the rotation speed deltas (i.e. s) _i+1 ＝s _i-1 +2 × Δ s) until the real-time reduction η of iron oxides in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

In the invention, the reducing the rotating speed of the rotary kiln specifically comprises the following steps: Δ s =10% per reduction of the rotational speed ₁ (alternatively 2%s ₁ 、30％s ₁ 、4％s ₁ 、5％s ₁ 、6％s ₁ 、7％s ₁ 、8％s ₁ 、9％s ₁ 、12％s ₁ 、15％s ₁ 、18％s ₁ 、20％s ₁ 、25％s ₁ 、30％s ₁ 、35％s ₁ 、40％s ₁ 、45％s ₁ 、50％s ₁ Etc.) wherein s ₁ The original rotation speed of the rotary kiln; i.e. if eta _{Fruit of Chinese wolfberry} 1+ 10%) eta, controlling the rotation speed s of the rotary kiln _r ＝s _r-1 -. DELTA.s; then continuously detecting the real-time conductivity sigma of the material in the rotary kiln in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} (ii) a If η of the real-time state _{Fruit of Chinese wolfberry} Still less than (1 + 10%) eta, then the rotation speed deltas is reduced again (that is to say s _i+1 ＝s _i-1 -2 Δ s) until the real-time reduction η of iron oxides in the rotary kiln _{Fruit of Chinese wolfberry} ＝(1±10％)η。

In the invention, iron oxide is subjected to two-step reduction procedures to obtain molten iron, namely rotary kiln pre-reduction and deep reduction (smelting reduction) by a deep reduction device; because the reduction of the iron oxide requires management of a plurality of iron states, the invention provides that according to the stages and characteristics of the reduction of the iron oxide, the time consumption and energy consumption conditions of the iron oxide in each reduction stage are analyzed by combining the process characteristics of the rotary kiln and the deep reduction device, the stage most suitable for the pre-reduction of the iron oxide in the rotary kiln is placed in the rotary kiln, and the stage suitable for the deep reduction in the deep reduction device is placed in the deep reduction device for completion; the reduction degree of the iron oxide in the rotary kiln is controlled, so that the iron oxide is reasonably distributed in the rotary kiln and the deep reduction device in the whole reduction process; the minimum consumption of fuel is realized through the distribution of the reduction stage while the high-efficiency reduction of the iron oxide is ensured; meanwhile, the consumption of fuel is reduced, and the generation of pollution gas and waste residue is further reduced. Through the research and continuous experiments of the inventor, the total fuel consumption of the unit mass of the iron oxide in the whole reduction process is the most economical under the condition of controlling the reduction degree of the iron oxide in the rotary kiln to be eta, wherein the eta is 40-80%, preferably 50-70%, and more preferably 60-65%. Therefore, the reduction of iron oxide can be realized in an energy-saving manner by accurately controlling the stages of the respective reduction of iron oxide in the two reduction processes, i.e., controlling the degree of reduction of iron oxide in the rotary kiln (the reduction stages of the rest are completed in the deep reduction device).

In the invention, the control of the reduction degree of the iron oxide in the rotary kiln can be realized by controlling the carbon mixing amount in the iron oxide, the heat preservation and reduction time of the iron oxide in the rotary kiln, the reduction temperature in the rotary kiln and the like. Under the condition that other conditions are not changed, the higher the carbon distribution amount in the iron oxide is, the higher the reduction degree of the oxide in the rotary kiln is; the longer the heat preservation reduction time of the iron oxide in the rotary kiln is, the larger the reduction degree of the oxide in the rotary kiln is; the higher the reduction temperature in the rotary kiln, the greater the degree of reduction of the iron oxides in the rotary kiln.

Through the continuous research of the inventor of the technical scheme, on the premise of realizing that the degree of reduction eta is 40-80%, preferably 50-70%, and more preferably 60-65%, the optimal process conditions of the carbon distribution amount in the oxide, the heat preservation reduction time of the iron oxide in the rotary kiln and the reduction temperature in the rotary kiln are obtained, the energy of the rotary kiln can be maximally utilized, and the process conditions for saving the fuel most are obtained. Controlling the carbon content in the iron oxide to be 10-40wt%, preferably 15-30wt%, and more preferably 20-25wt%; further preferably 20 to 25%; for example 20%,21%,22%,23%,24%,25%. Controlling the heat preservation reduction time of the iron oxide in the rotary kiln for 60-180min, preferably 70-140min, and more preferably 90-120min; for example: 80min,90min,100min,110min,120min. The reduction temperature in the rotary kiln is controlled between 800 and 1400 ℃, preferably between 850 and 1300 ℃, and more preferably between 900 and 1200 ℃. For example: 900 deg.C, 1000 deg.C, 1050 deg.C, 1100 deg.C, 1150 deg.C, 1200 deg.C, 1300 deg.C, 1400 deg.C. The reduction degree of the iron oxide in the rotary kiln is realized by controlling the process conditions in the rotation and the carbon distribution amount in the iron oxide; but also can reduce the fuel consumption of the iron oxide reduction in the rotary kiln.

Preferably, the rotary kiln pre-reduction product is discharged from the kiln head and then enters the gas reforming vertical shaft, the material in the reforming vertical shaft moves towards the lower part until the material is discharged out of the vertical shaft through a discharge port, the top gas of the deep reduction device is dedusted by a plurality of pipes and then is introduced into the gas reforming vertical shaft through a plurality of branch pipes, and openings are formed below the branch pipes to ensure that the material cannot fall into the branch pipes to cause blockage. The gas moves upwards in the vertical shaft material bed and forms countercurrent movement with the descending pre-reduction material.

In the present invention, the process conditions within the deep reduction apparatus can be controlled, for example: and controlling technological parameters such as coal injection quantity in the deep reduction device, gas input quantity in the deep reduction device and the like, so as to adjust the temperature of high-temperature coal gas discharged by the deep reduction device. In order to realize the reforming of the high-temperature gas in the reforming shaft and the further reduction of the pre-reduction product by the high-temperature gas in the reforming shaft, the temperature of the high-temperature gas discharged from the deep reduction device is preferably controlled to be more than 1400 ℃, preferably more than 1500 ℃, and more preferably more than 1600 ℃. For example: 1400 ℃,1450 ℃,1500 ℃,1550 ℃,1600 ℃,1650 ℃,1700 ℃ and 1800 ℃.

In the invention, the reformed high-temperature coal gas is conveyed to the rotary kiln, and mainly plays the role of a reducing agent while providing heat. The content of the reducing gas in the reformed high-temperature coal gas obtained after passing through the reforming vertical shaft can be controlled by controlling the process parameters such as the flow speed of the high-temperature coal gas discharged by the deep reduction device in the reforming vertical shaft, the temperature of the high-temperature coal gas entering the reforming vertical shaft and the like. In order to ensure the reduction of the reformed high-temperature coal gas in the rotary kiln and the pre-reduction degree of the iron oxide in the rotary kiln, the content of CO in the reformed high-temperature coal gas is controlled to be higher than 30vol%, and the content of CO is preferably higher than 35vol%. H ₂ Is higher than 2vol%, preferably H ₂ Is higher than 3vol%, more preferably H ₂ Is higher than 5vol%.

In the invention, the rotary kiln is a pre-reduction device for iron oxide, and the melting furnace is a deep reduction device for pre-reduction products. The melting furnace can be a smelting reduction furnace, a converter, an electric furnace or a blast furnace.

According to the invention, the condition of the material reduction reaction in the rotary kiln can be judged by monitoring the material temperature, the material surface gas component and the material metallization rate on line, and the material reduction reaction and the temperature can be controlled by adjusting the distribution of the temperature field in the kiln and the flow of the circulating gas introduced into the material layer. The gas components of the charge level can be measured by an online smoke component detection device, and the material metallization rate can be monitored online by a material metallization rate measurement technology based on conductivity. In general: firstly, establishing a reference relation between a thermal regulation system for quickly reducing the material at a low temperature, material layer atmosphere and material metallization rate according to the characteristics of the material and a reducing agent, and determining a necessary heating rate, a temperature interval and a duration range of each main reduction reaction section, a material layer atmosphere and a material surface gas composition range of each reduction reaction section, and a relation between the conductivity and the metallization rate of the material of each reduction reaction section in the material reduction process as a reference requirement for subsequently regulating and controlling the material reduction process in the rotary kiln. Secondly, in the running process of the rotary kiln, the temperature, the material surface waste gas component and the material metallization rate of different sections in the rotary kiln are monitored in real time through temperature monitoring devices, material surface gas component content monitoring devices and material metallization rate monitoring devices which are distributed on the rotary kiln, and then the redistribution amount of the internal circulation gas is adjusted according to data information monitored in real time.

In the invention, because the drying section of the rotary kiln mainly realizes the dehydration process of the raw pellet materials, the temperature is about 300 ℃, and the main components of the drying section are water vapor and CO in the airflow at the tail part (close to the tail part of the rotary kiln) of the drying section ₂ And a small amount of CO, etc. in the conventional condition, the tail gas is discharged out of the rotary kiln and then is subjected to reburning and dust removal treatment, and the CO is discharged out of the rotary kiln ₂ The main outlet for discharge. The positions of the reduction roasting section and the slow cooling section of the rotary kiln are the highest temperature positions generated by a flame nozzle at the kiln head, and a large amount of high-temperature burning coal is contained in the materials at the positions, generally the temperature is over 1200 ℃, and the high-temperature burning coal is an overheated part of the materials. In order to realize that the temperature in the whole rotary kiln reaches the temperature required by reduction, the temperature at the position is generally higher than the temperature required by reduction, namely the heat is surplus; because the materials, the coal ash and the like are easy to melt under the high-temperature condition, the position is also the main position of the ring formation of the rotary kiln, and how to reduce the temperature of the materials at the position plays a key role in relieving the ring formation of the rotary kiln. By mixing water vapor and CO at about 300 deg.C at the tail of drying section ₂ And a small amount of CO hot air tail gas is pumped into the highest temperature part of the reduction roasting section, and the hot air tail gas is pumped from the material of the reduction roasting section and the lower part of the high-temperature combustion coal, so that on one hand, the temperature of the overheated part of the reduction roasting section can be properly reducedThe ring formation can be effectively prevented; on the other hand, water vapor and CO in the hot-blast off-gas ₂ Reacting with unreacted carbon at high temperature to obtain water gas and Boolean reaction to obtain H ₂ And CO, the reaction formula is as follows:

water gas reaction: h ₂ O _(g) +C _(s) ＝H _2(g) +CO _(g)

A Boolean reaction: CO 2 _2(g) +C _(s) ＝2CO _(g)

The water gas reaction and the Boolean reaction are endothermic reactions, can also reduce the temperature of overheated materials in a reduction roasting section, and can also generate reducing gas H ₂ And CO, improving the reducing atmosphere in the material and promoting the reduction reaction.

In a preferred rotary kiln hot air internal circulation scheme of the invention, hot air at the tail part (close to the kiln tail) of the drying section is conveyed into the reduction roasting section to participate in the reduction roasting treatment. According to the real-time temperature change of the materials in the reduction roasting section, the extraction amount of hot air in the drying section is adjusted and/or the air amount of an air burner in the reduction roasting section is adjusted. The specific control mode is as follows: the set temperature of the material in the reduction roasting section is set to be T1 +/-C1 (the range of C1 is 0-50) and DEG C. Detecting the real-time temperature of the material in the reduction roasting section in real time as T2 and DEG C. Then:

and when T2 > (T1 +/-C1), increasing the extraction amount of hot air in the drying section and/or reducing the air amount of an air burner at the upper part of the material layer in the reduction roasting section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T1 +/-C1).

Furthermore, the temperature of the preheating section in the existing coal-based rotary kiln is mainly below 900 ℃, the reaction of CO reducing materials mainly occurs in the coal-based reduction, and the reduction reaction occurs slowly in the preheating section. How to improve the reduction in the preheating sectionThe reaction rate is critical to achieving a low temperature rapid reduction. And H ₂ In contrast, the reducibility of CO is weaker than that of H below 830 DEG C ₂ Thus, H can be introduced into the preheating section ₂ And raising the temperature of the preheating section to enable the preheating section to generate H ₂ The reduction reaction with the materials achieves the purpose of improving the reduction reaction rate of the preheating section. Reducing gas (mainly comprising H) escaping from the upper part of a material layer at the tail part (close to the reduction roasting section) of the slow cooling section ₂ And CO), dedusting by a multi-tube deduster, properly cooling, and sending to a low-temperature part at the tail part (close to the drying section) of the preheating section by a high-temperature exhaust fan through the lower part of the material layer of the preheating section. According to the scheme, on one hand, high-temperature gas at the tail of the slow cooling section can pass through the low-temperature material layer at the preheating section, so that the temperature of the material layer is increased; on the other hand, H in the high-temperature gas ₂ And CO can effectively promote the reduction reaction in the preheating section after entering the material layer, thereby further realizing the purpose of low-temperature rapid reduction.

In a preferred rotary kiln hot air internal circulation scheme of the invention, hot air at the tail of the slow cooling section (close to the reduction roasting section) is conveyed to the preheating section to participate in preheating treatment of the pellets. And adjusting the hot air extraction amount in the slow cooling section according to the real-time concentration change of CO in the hot air in the slow cooling section. The specific control mode is as follows: the set concentration of CO in the hot air in the slow cooling section is set to W1 + -D (the range of D is 0-20)%. And detecting the real-time concentration of CO in the hot air in the slow cooling section in real time to be W2 percent. Then:

In the invention, high-temperature reducing gas (CO) escaping from a material layer at a reduction roasting stage is pumped out, is mixed with tail gas of a rotary kiln in a gas mixing device to about 700 ℃, is pumped to a preheating stage by a high-temperature fan and is fed through the lower part of the material layer at the preheating stage. On the one hand, about 1200 DEG CThe high-temperature CO gas and the rotary kiln tail gas containing water vapor at about 300 ℃ are subjected to temperature neutralization in a gas mixing device, so that the temperature of the mixed gas is about 700 ℃ and is not higher than the heat-resistant temperature of a high-temperature fan; at the same time, part of high-temperature CO gas and water vapor can generate water gas reaction (H) ₂ O _(g) +CO _(s) ＝H _2(g) +CO _2(g) ) Generating H ₂ And CO ₂ The reaction is endothermic and can also play a role in reducing the mixed hot air; secondly, CO and CO are mainly contained in the mixed hot air gas after being uniformly mixed ₂ Water vapor and H ₂ The mixed hot air is fed into the bed of the preheating section, where the remaining steam and the burning coal undergo a water gas reaction (H) ₂ O _(g) +C _(s) ＝H _2(g) +CO _(g) ) The generated reducing gas can make the preheating section generate H ₂ Reducing the material, and strengthening the low-temperature reduction process; further CO ₂ Also, a Boolean reaction (CO) occurs with the burning carbon _2(g) +C _(s) ＝2CO _(g) ) Generating a reducing atmosphere of the CO strengthening preheating section material layer; the mixed hot air is fed from the lower part of the material layer of the preheating section, the heat transmission of the temperature of the preheating section is enhanced through convection heat transfer, and the temperature of the preheating section can be raised.

In a preferred rotary kiln hot air internal circulation scheme, hot air output by the drying section and hot air output by the reduction roasting section are mixed to obtain mixed hot air, and then the mixed hot air is conveyed to the preheating section to participate in preheating treatment of the pellets. And adjusting the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air in the drying section according to the real-time temperature change of the materials in the reduction roasting section. The specific control mode is as follows: the set temperature of the material in the reduction roasting section is set to be T3 +/-C2 (the range of C2 is 0-50) and DEG C. Detecting the real-time temperature of the material in the reduction roasting section in real time as T4 and DEG C. Then:

Furthermore, by raising the temperature of the drying section, speeding up the drying process is also one of the key methods for realizing low-temperature rapid reduction. By feeding the mixed hot air to the preheating section, the temperature of the preheating section is increased and correspondingly the temperature of the gas at the upper part of the preheating section is also increased. The preferred technical scheme of the invention is that gas at the upper part of the preheating section with the raised temperature is pumped out and then is fed into the lower part of the material layer of the drying section, the material temperature of the drying section is raised in a convection heat transfer mode, the drying of the material is accelerated, and meanwhile, the upward flowing gas quickly carries the water vapor dried from the material away from the material layer, so that the quick drying is realized.

In a preferred rotary kiln hot air internal circulation scheme, hot air in the preheating section is conveyed to the drying section to participate in the drying treatment of the pellets. And adjusting the extraction amount of hot air in the preheating section according to the real-time temperature change of the material in the preheating section. The specific control mode is as follows: the set temperature of the material in the preheating section is set to be T5 +/-C3 (the range of C3 is 0-50) and DEG C. And detecting the real-time temperature of the material in the preheating section as T6 and DEG C in real time. Then:

And when the T6 is less than (T5 +/-C3), reducing the extraction amount of the hot air in the preheating section until the real-time temperature of the material in the preheating section returns to the preset temperature (T5 +/-C3).

In the invention, the material contains a large amount of moisture when being added from the tail of the rotary kiln, and the moisture-containing material is gradually dehydrated and dried in the drying section in the kiln in the process that the material continuously moves to the high-temperature area at the head of the kiln along with the rotation of the kiln body. When the pellets run to the kiln head, water in the pellets forms steam under the action of temperature, the external vapor pressure of the pellets is small, the internal vapor pressure is large, and the water is diffused and removed from the inside of the pellets to the outside. The burst temperature of the general iron ore green pellets is about 250-500 ℃, and the tail temperature of a rotary kiln is about 300 ℃, so that once the green pellets containing a large amount of moisture enter the kiln in the drying process, the moisture in the green pellets is quickly changed into water vapor, the external vapor pressure of the green pellets is small, the steam in the pellets quickly escapes, the pellets are easy to burst when the pellet strength is insufficient, a large amount of powder is generated, and the ring formation risk in the kiln is increased. The invention slows down the moisture removal rate in green pellets by increasing the external vapor pressure of the pellets at the initial stage of moisture removal of the pellets. Furthermore, the drying temperature is increased in the middle and later periods of moisture removal in the green pellets, so that the green pellets can be quickly dried, the pellets are prevented from bursting, and the aim of improving the drying efficiency of the rotary kiln is fulfilled. For the materials of which the powder is put into the kiln, the moisture removal is enhanced by high-temperature steam in the early drying stage, and the drying temperature is increased in the later drying stage, so that the rapid drying of the materials can be realized.

Meanwhile, the temperature of the kiln tail waste gas of the rotary kiln is about 300 ℃ generally, and a large amount of water vapor is contained, so that the temperature of the gas in the reduction roasting section kiln is as high as about 1200 ℃. High-temperature gas at about 1200 ℃ in a reduction roasting section is subjected to dust reduction through a multi-tube dust remover, and then is uniformly mixed with waste gas containing water vapor at about 300 ℃ in a kiln tail in a gas mixing device to obtain mixed wet hot air, so that the temperature of the mixed wet hot air is lower than 500 ℃, and then the mixed wet hot air is fed from the lower part of a material layer in the initial drying stage through an exhaust fan, and the material is dried by the high-temperature water vapor. The technical scheme mainly has the following functions: firstly, high-temperature gas in a reduction roasting section is utilized to increase the temperature of the drying initial stage; secondly, utilizing the tail gas of the rotary kiln with lower temperature to neutralize the temperature of high-temperature gas at the roasting section; thirdly, returning water vapor in tail gas of the rotary kiln to a material layer at the initial drying stage to increase the vapor pressure of the material layer and prevent the pellets from bursting; fourthly, the mixed hot air is fed from the lower part of the material layer at the initial drying stage to strengthen the convection heat transfer. The vapor pressure outside the pellets is increased at the initial stage of the drying section, the rapid escape of moisture inside the pellets is effectively inhibited, the pellets are prevented from bursting, and the ring formation risk of the rotary kiln is greatly reduced.

In a preferred rotary kiln hot air internal circulation scheme, hot air output from the kiln tail of the rotary kiln and hot air output from the reduction roasting section are mixed to obtain mixed wet hot air, and then the mixed wet hot air is conveyed to the drying section to participate in the drying treatment of the pellets at the initial stage. And adjusting the extraction amount of hot air in the reduction roasting section and/or the extraction amount of hot air at the kiln tail of the rotary kiln according to the real-time temperature change of the materials in the reduction roasting section. The specific control mode is as follows: the set temperature of the material in the reduction roasting section is set to be T7 +/-C4 (the range of C4 is 0-50) and DEG C. And detecting the real-time temperature of the material in the reduction roasting section at T8 and DEG C in real time. Then:

Further, moisture is removed from the pellets after the initial treatment in the drying section, and the drying temperature is increased in the middle and later stages of the drying section to increase the drying rate without fear of pellet bursting. The content of water vapor in the gas at the later stage of the drying section of the rotary kiln is low, so that the high-temperature gas at about 1200 ℃ of the reduction roasting section is subjected to dust reduction through a multi-tube dust remover, and then is uniformly mixed with the hot air gas at the later stage of the drying section in a gas mixing device to obtain mixed dry hot air, the temperature of the mixed dry hot air is lower than 500 ℃, and then the mixed dry hot air is fed from the lower part of a material layer at the middle and later stages of the drying section through an exhaust fan, and the material is dried by the high-temperature gas without steam. The technical scheme has the main effects that firstly, the high-temperature gas in the roasting section is utilized to increase the drying temperature in the middle and later periods of the drying section and increase the drying speed; secondly, the high-temperature gas temperature of the reduction roasting section is neutralized by the gas at the later stage of the low-temperature drying section; thirdly, mixed gas is fed from the lower part of the material layer in the middle and later drying stages, and convection heat transfer is enhanced. The water vapor dried from the materials is quickly brought away from the material layer by the upward flowing gas, so that the quick drying is realized.

In a preferred rotary kiln hot air internal circulation scheme, hot air output at the later stage of a drying section and hot air output from a reduction roasting section are mixed to obtain mixed dry hot air, and then the mixed dry hot air is conveyed to the drying section to participate in the drying treatment of the pellets at the initial stage. And adjusting the extraction amount of hot air in the later stage of the drying section and the extraction amount of hot air in the reduction roasting section according to the real-time temperature change of the material in the later stage of the drying section. The specific control mode is as follows: the set temperature of the material at the later stage of the drying section is set to be T9 +/-C5 (the range of C5 is 0-50) and DEG C. And detecting the real-time temperature of the material at the later stage of the drying section as T10 and DEG C in real time. Then:

When T10 epsilon (T9 +/-C5), the current process conditions are maintained unchanged.

In a preferred embodiment of the present invention, the deep reduction process of the melting furnace generates a reaction of iron oxide and carbon to generate iron, carbon monoxide and part of carbon dioxide, and the reaction comprises: fe _x O(s)+C＝xFe(s)+CO(g)+CO ₂ (g) .1. The The reaction step produces high-temperature carbon monoxide and carbon dioxide gases, collectively referred to as "high-temperature gas". The temperature of the high-temperature coal gas generated in the melting furnace is more than 1400 ℃, the highest temperature can reach more than 1700 ℃, and the high-temperature coal gas has certain pressure. In the technical scheme of the invention, the heat and the calorific value of the high-temperature coal gas are fully utilized, the rotary kiln needs a high-temperature environment and simultaneously needs reducing gas, the high-temperature coal gas generated by the deep reduction device is conveyed into the rotary kiln and serves as a reducing agent, and meanwhile, the heat of the part of gas is fully utilized, so that the maximum utilization of resources is realized.

In the invention, a large amount of high-temperature coal gas with the temperature of more than 1500 ℃ produced at the top of the melting and separating furnace is removedContains a large amount of unreacted CO and H ₂ In addition, it also contains a large amount of CO ₂ And water vapor, the main components of which are CO (about 21%), CO ₂ (about 25%), H ₂ (about 4%), N ₂ (about 48%), H ₂ O (about 2%). The products after the prereduction of the coal-based rotary kiln mainly comprise high-temperature prereduction materials and high-temperature residual coal. The technology carries out counter-current reaction on the high-temperature pre-reduction product of the coal-based rotary kiln and the deep reduction device, and CO and H in high-temperature coal gas ₂ CO and H while passing through the high temperature pre-reduction product bed ₂ Can perform reduction reaction with unreacted iron oxide to promote the further reduction of the pre-reduced material. CO produced by reduction reaction in deep reduction device ₂ And H ₂ O and CO in high-temperature coal gas ₂ And H ₂ When the O passes through the hot residual coal of the high-temperature pre-reduction product, a Boolean reaction and a water gas reaction occur, and the reforming of the high-temperature coal gas is realized.

Further, high-temperature coal gas generated by the melting furnace is excited by a microwave plasma reactor to lead CO and H ₂ Activation to plasma state CO ⁺ Or H ⁺ And then conveyed to the rotary kiln. CO and H in reformed coal gas ₂ The content is increased, the mixture is introduced into a plasma reduction section of the rotary kiln from the lower part of the material layer, and CO and H are excited by a microwave plasma reactor ₂ Activation to plasma state CO ⁺ Or H ⁺ ：

CO _(g) ＝CO ⁺ _(g) +e ^-

H _2(g) ＝2H ⁺ _(g) +2e ^-

CO in plasma state ⁺ Or H ⁺ Has extremely high activity and far higher oxygen-taking capacity than CO or H in gaseous form ₂ The iron oxide is easy to generate reduction reaction with the iron oxide, and oxygen in the iron oxide is captured, so that the efficient implementation of the reduction reaction is realized:

Fe ₂ O _3(s) +3CO ⁺ _(g) +3e ^- ＝2Fe _(s) +3CO _2(g)

Fe ₂ O _3(s) +6H ⁺ _(g) +6e ^- ＝2Fe _(s) +3H ₂ O _(g)

preferably, because the high-temperature coal gas generated by the deep reduction device contains a part of carbon dioxide, the pre-reduction product discharged by the rotary kiln also contains a part of residual carbon, and the rotary kiln also has a high-temperature environment; in a preferred embodiment of the invention, a coal gas reforming process is added, and carbon dioxide in high-temperature coal gas can generate a Boolean reaction (C + CO) with residual carbon in a pre-reduction product ₂ =2 CO), carbon monoxide is produced; water in the high-temperature coal gas and residual carbon in the pre-reduction product are subjected to water gas reaction (H) ₂ O(g)+C(s)＝CO(g)+H ₂ (g) Hydrogen and carbon monoxide are produced). In the process of the gas reforming procedure, the high-temperature gas generated by the deep reduction device utilizes carbon in the pre-reduction product and a high-temperature environment to react carbon dioxide and water in the high-temperature gas to form gases with reducibility, such as carbon monoxide, hydrogen and the like, so that the content of the reducibility gas in the gas conveyed to the rotary kiln is further improved, the reformed high-temperature gas is activated into a plasma state and then conveyed to the rotary kiln, and the high-temperature plasma state reducibility gas enters the pre-reduction procedure in the rotary kiln for reducing iron oxide. By the technical means, the effective components and product environments in the pre-reduction product and the deep reduction device product are fully utilized, the optimization of the technical scheme is realized, the content of reducing gas in high-temperature coal gas is further improved while resources are fully utilized, and the reduction efficiency in the rotary kiln is further improved; the high-temperature coal gas generated by the deep reduction device is utilized, so that the using amount of fuel in the rotary kiln is saved; by adopting the technical scheme of the invention, the carbon blending amount in the raw materials entering the rotary kiln can be reduced, and compared with the prior art, the fuel consumption can be saved by 20-30%.

The invention carries out reforming treatment on the high-temperature coal gas through the reforming vertical shaft to realize the further reduction of the pre-reduction product. The sensible heat of the pre-reduction product of the rotary kiln, the sensible heat of the high-temperature coal gas and the reduction gas in the rotary kiln are fully utilized to realize the further pre-reduction of the iron oxide. In the pre-reduction process of the coal-based rotary kiln, partial iron oxide still remains to finish the reduction reaction process, and CO in high-temperature coal gas are mixed in a coal gas reforming high-temperature reaction material layerH ₂ And further carrying out pre-reduction reaction on the unreduced iron oxide, improving the reduction degree of the raw materials entering the furnace of the deep reduction device, and reducing the energy consumption of the deep reduction device.

In addition, the CO in the high-temperature residual coal and the high-temperature coal gas in the pre-reduction product of the rotary kiln is fully utilized ₂ And H ₂ O and CO generated by reduction of iron oxide in material layer ₂ And H ₂ O, gas reforming reaction is carried out, and the sensible heat of the materials and the gas flow is converted into high-quality reducing gases of CO and H ₂ Converts the sensible heat into chemical energy of reducing gas, and the reformed gas contains a large amount of CO and H ₂ The heat can be provided for the direct reduction reaction of the rotary kiln through oxidation heat release subsequently, and the heat can also be used as a reducing agent for the direct reduction reaction of the rotary kiln, so that the energy loss caused by temperature reduction in the transmission process of high-temperature coal gas can be reduced, and the reduction gases CO and H in the coal gas introduced into the rotary kiln can be enhanced ₂ And (4) content, strengthening the reduction reaction of the iron oxide in the rotary kiln.

And moreover, the temperature of the rotary kiln prereduced product is about 1200 ℃, the temperature of high-temperature coal gas generated by the deep reduction device is more than 1500 ℃, the highest temperature can reach more than 1700 ℃, when the prereduced product and the high-temperature coal gas perform a reforming reaction in a counter-current manner, the prereduced product at 1200 ℃ moves from the upper part to the lower part, the high-temperature coal gas moves from the lower part of the material layer to the upper part, the reforming reaction can convert part of heat into chemical energy, the temperature of the coal gas can be gradually reduced, but in the process that the prereduced product gradually descends, the temperature of the high-temperature coal gas is higher and higher as the temperature of the high-temperature coal gas is higher, the temperature drop of the prereduced product in the process that the prereduced product is discharged from the head of the rotary kiln to the deep reduction device is added is reduced, and the energy consumption of the deep reduction device is reduced.

In the invention, the reformed high-temperature coal gas is conveyed to the rotary kiln after being plasmatized, and mainly plays a role of a reducing agent while providing heat. The content of reducing gas in the reformed high-temperature coal gas obtained after passing through the reforming vertical shaft can be controlled by controlling the process parameters such as the flow speed of the high-temperature coal gas discharged from the melting furnace in the reforming vertical shaft, the temperature of the high-temperature coal gas entering the reforming vertical shaft and the like. In order to ensure after reformingReducing the high temperature coal gas in the rotary kiln, and in order to ensure the pre-reduction degree of the iron oxide in the rotary kiln, in the invention, the content of CO in the reformed high temperature coal gas is controlled to be higher than 35vol%, and H is controlled ₂ Is higher than 5vol%.

In the invention, the condition of the coal gas reforming reaction is generally judged by monitoring the material temperature of the gas reforming shaft and the gas composition of the charge level on line, and the control of the coal gas reforming reaction and the temperature is further realized by the distribution of the temperature field in the gas reforming shaft and the flow of the circulating gas introduced into the charge level. Generally, a reference relation among the temperature of the gas at the top of the smelting reduction furnace, the tail gas flow of the rotary kiln, the temperature distribution of a vertical shaft and the gas reforming efficiency is established, and the temperature distribution interval range in the gas reforming vertical shaft is determined and used as a reference requirement for the subsequent regulation and control of the reduction process of materials in the rotary kiln and the smelting reduction furnace. And then monitoring the distribution of material temperature fields in the shaft in real time through temperature monitoring and charge level gas component content monitoring devices distributed in the gas reforming shaft.

In a preferred rotary kiln-melting furnace hot air external circulation scheme, a part of rotary kiln tail gas is guided to enter a gas reforming vertical shaft to be used as a main means for adjusting the temperature of the vertical shaft, so that the high-efficiency and rapid gas reforming is ensured. The method comprises the following steps of adjusting the extraction amount of tail gas of the rotary kiln according to the real-time temperature change of materials in the shaft: the set temperature of the materials in the shaft is set to be T11 +/-C6 (the range of C6 is 0-50) and DEG C. And detecting the real-time temperature of the material in the shaft at T12 and DEG C in real time. Then:

In the invention, a proper gas flow range required by ash separation is determined by establishing a reference relation among gas flow, ash separation effect in a rotary kiln reduction product and separated smoke temperature, and the gas flow range is used as a reference requirement for subsequent regulation and control of ash separation. The temperature distribution of the ash separation smoke dust is monitored in real time through the temperature monitoring device for distributing the ash separation smoke dust. Furthermore, the invention also leads a part of the tail gas of the rotary kiln to enter the ash separation section behind the gas reforming vertical shaft as a main means for adjusting the temperature of the ash separation section, thereby ensuring good ash separation effect, simultaneously utilizing more tail gas of the rotary kiln, reducing the energy consumption of the system, improving the production efficiency and achieving the purpose of low-temperature rapid reduction. The method specifically comprises the following steps of adjusting the extraction amount of the tail gas of the rotary kiln according to the real-time temperature change of the smoke dust in the ash separation device: the set temperature of the soot in the ash separator is set to T13 + -C7 (the range of C7 is 0-50) and DEG C. Real-time temperature of the smoke dust in the ash content separation device is detected to be T14 and DEG C in real time. Then:

When T14 ∈ (T13. + -. C7), the current process conditions are maintained unchanged.

In the present invention, the pre-reduction apparatus may be one of a rotary kiln, a rotary hearth furnace, a tunnel kiln, a fluidized bed, or a shaft furnace. The deep reduction device (melting furnace) can be one of a smelting reduction furnace, a converter, an electric furnace or a blast furnace.

Compared with the prior art, the invention has the following beneficial technical effects:

1: the technology adopts a deep reduction method of a rotary kiln prereduction-deep reduction device to reduce iron oxide into Fe which is easy to generate in the process of reducing iron oxide into metallic iron ₂ O ₃ →Fe ₃ O ₄ →Fe _x The reduction reaction in the O stage is completed in a rotary kiln, and the pre-reduction product reaching a certain reduction degree and residual coal are heated together and enter a deep reduction device for deep reduction. By controlling the reduction degree of the iron oxide in the rotary kilnThe iron oxide is reasonably distributed in the rotary kiln and the deep reduction device in the whole reduction process; the minimum consumption of fuel is realized through the distribution of the reduction stage while the high-efficiency reduction of the iron oxide is ensured; meanwhile, the consumption of fuel is reduced, and the generation of pollution gas and waste residue is further reduced.

2: the iron-containing composite pellet provided by the invention has a multilayer structure, a reducing agent core, a calcium carbonate shell layer and an iron-containing material layer are sequentially arranged from the center of the pellet to the outside, and the iron-containing material layer does not need to be internally carbon-blended. When the composite pellet is reduced at high temperature, CO released by decomposition of calcium carbonate in the layer of the pellet ₂ The carbon-containing pellet is used as a starter of the reduction reaction of iron oxide in the pellet, the carbon-containing pellet reacts with a reducing agent of a pellet core layer to generate CO, and the iron oxide is reduced from inside to outside when the CO diffuses outwards, so that the inner and outer areas of the iron oxide in the pellet are reduced simultaneously, the reduction efficiency is improved, the reduction speed is higher than that of a common pellet, and the reduction strength is higher than that of an internally-carbon-mixed pellet.

3: the intermediate material layer of the iron-containing composite pellet is a calcium carbonate shell layer, and in the process of reducing and heating the composite pellet, the H-containing reducing agent decomposed from the pellet core is ₂ The reducing gas is sealed to prevent immediate outward diffusion, and the reducing gas is prevented from escaping before the iron oxide on the outer layer of the pellets starts to be obviously reduced. When the reduction temperature rises to above 810 ℃, the calcium carbonate shell layer of the intermediate material layer begins to decompose to release H ₂ And the reducing gas makes the iron oxide on the outer layer reduced by a large amount of outward diffusion. Due to H ₂ Has a reduction power much higher than that of CO and contains H ₂ The reducing gas greatly promotes the reduction of iron oxides inside the composite pellets.

4: according to the properties of hot air in each section of the rotary kiln, the hot air in each section is subjected to internal circulation treatment among the sections, and the ingredients (water vapor and CO) in the hot air are fully utilized ₂ 、H ₂ CO, etc.) and heat, both realizing CO ₂ The emission reduction is realized, the reducing atmosphere is enhanced, and the H content in the rotary kiln material layer is increased ₂ And the concentration of CO promotes the rapid reduction of the iron oxide, and the low-temperature rapid reduction is realized under the multi-section synergistic effect.

5: the invention is highAnd the warm gas is reformed through a reforming vertical shaft to realize the further reduction of the pre-reduction product. The sensible heat of the pre-reduction product of the rotary kiln, the sensible heat of the high-temperature coal gas and the reduction gas in the rotary kiln are fully utilized to realize the further pre-reduction of the iron oxide. In addition, in the reforming vertical shaft, CO in high-temperature residual coal and high-temperature coal gas in the pre-reduction product of the rotary kiln is fully utilized ₂ And H ₂ O and CO generated by reduction of iron oxide in material layer ₂ And H ₂ O, gas reforming reaction to obtain CO and H ₂ . Further mixing CO with H ₂ Exciting CO and H by microwave plasma reactor ₂ Activation to plasma state CO ⁺ Or H ⁺ . And the reducing atmosphere of the material layer is enhanced, the diffusion of the reducing agent in iron ore particles is enhanced, and the reduction reaction of the reducing agent in a low-temperature section at the interface of the iron ore particles is enhanced.

6: according to the invention, tail gas of the rotary kiln is circularly used in the ash separation section, and the separation of ash in the pre-reduced product is realized by using the tail gas of the rotary kiln, so that an additional inert gas loop is not required to be established, the gas quantity of a system is not increased, the content of useless solids entering a melting reduction furnace is effectively reduced, and the energy consumption of the melting reduction furnace is reduced; the heat of the material layer of the pre-reduction product is used for heating the tail gas to supplement heat for the material at the plasma section; further, part of CO in tail gas of the rotary kiln ₂ And H ₂ Conversion of O to CO and H ₂ The reducing atmosphere in the plasma sub-material layer is improved; CO and H ₂ And then activated into a plasma state by a plasma exciter, so that the reduction reaction is enhanced.

Drawings

FIG. 1 is a flow chart of the direct reduction process of the iron-containing composite pellets of the present invention.

Fig. 2 is a structural view of the iron-containing composite pellet of the present invention.

FIG. 3 is a graph showing the effect of the amount of carbon added to iron oxide in the rotary kiln on the metallization ratio (pre-reduction degree) in the process of the present invention.

FIG. 4 is a graph showing the effect of reduction time in the rotary kiln on metallization ratio (pre-reduction degree) in the process of the present invention.

FIG. 5 is a graph showing the effect of reduction temperature in the rotary kiln on metallization rate (pre-reduction degree) in the process of the present invention.

FIG. 6 is a control flow chart of the internal circulation of the rotary kiln air flow according to the present invention.

FIG. 7 is a flow chart of the second control of the air flow internal circulation of the rotary kiln of the present invention.

FIG. 8 is a flow chart of the three control processes of the air flow internal circulation of the rotary kiln of the present invention.

FIG. 9 is a flow chart of the four control processes of the air flow internal circulation of the rotary kiln of the present invention.

FIG. 10 is a flow chart of the five control processes of the air flow internal circulation of the rotary kiln of the present invention.

FIG. 11 is a flow chart of six control processes of the rotary kiln air flow internal circulation.

FIG. 12 is a control flow chart of the external circulation of the air flow of the rotary kiln-melting furnace according to the present invention.

FIG. 13 is a flow chart of the present invention for controlling the air flow external circulation of the rotary kiln and the melting furnace.

FIG. 14 is a schematic structural diagram of a direct reduction apparatus according to the present invention having a temporary external circulation of the air flow.

FIG. 15 is a schematic structural view of the direct reduction apparatus of the present invention having a second air flow external circulation.

FIG. 16 is a schematic structural diagram of a rotary kiln according to the present invention with a first air flow internal circulation and/or a second air flow internal circulation.

FIG. 17 is a schematic structural diagram of a rotary kiln according to the present invention having three and/or four air-flow internal circulations.

FIG. 18 is a schematic structural diagram of a rotary kiln according to the present invention with five internal circulations of air flow and/or six internal circulations of air flow.

Fig. 19 is a schematic view of the structure of the rotary kiln of the present invention.

FIG. 20 isbase:Sub>A cross-sectional view ofbase:Sub>A rotary kiln A-A according to the present invention.

FIG. 21 isbase:Sub>A perspective view ofbase:Sub>A rotary kiln A-A according to the present invention.

Fig. 22 is a schematic structural view of the rotary kiln of the present invention in which a conductivity detection device is provided.

Figure 23 is a flow chart illustrating the control of pre-reduction of iron oxide in a rotary kiln according to the present invention.

Reference numerals: 1: a rotary kiln; 101: a drying section; 102: a preheating section; 103: a plasma reduction section; 104: a reduction roasting section; 105: a slow cooling section; 106: burning the nozzle; 107: a fuel delivery conduit; 108: a combustion-supporting air duct; 109: a first air mixing chamber; 110: a second air mixing chamber; 111: a third air mixing chamber; 2: melting and separating furnace; 201: a vertical shaft; 202: an ash separation device; 2021: a shell; 2022: a vibration ash screening and conveying mechanism; 3: a microwave plasma exciter; 4: a temperature detection device; 5: a CO concentration detection device; 6: metallization ratio detection means; 7: a kiln body air duct mechanism; 701: an air inlet connecting piece; 702: a stop valve; 703: a pull rod; 704: an air inlet; 705: an air inlet channel; 8: an annular rotary slide rail; 801: a support; 9: a rotary slide mechanism; 901: rotating the wheel seat; 902: a lateral rotating wheel; 903: a vertical rotating wheel; 10: a horizontal sliding mechanism; 1001: a horizontal wheel seat; 1002: a horizontal pulley; 1003: a horizontal rail; 11: a swing mechanism; 1101: a rotary motor; 1102: a large gear ring; 12: a conductivity detection means; 1201: a detection coil; 1202: a magnetically conductive core; l1: a first pipe; l2: a second conduit; l3: a third pipeline; l4: a fourth conduit; l5: a fifth pipeline; l6: a sixth pipeline; l7: a seventh pipe; l8: an eighth conduit; l9: a ninth conduit; l10: a tenth conduit; l11: an eleventh pipe; l12: a twelfth pipeline; l13: a thirteenth pipe; l14: a fourteenth pipe; l15: a fifteenth conduit; l16: a sixteenth conduit.

Detailed Description

The technical solution of the present invention is illustrated below, and the claimed scope of the present invention includes, but is not limited to, the following examples.

A direct reduction device for iron-containing composite pellets comprises a rotary kiln 1, a melting furnace 2 and a microwave plasma exciter 3. According to the trend of materials, the rotary kiln 1 is sequentially provided with a drying section 101, a preheating section 102, a plasma reduction section 103, a reduction roasting section 104 and a slow cooling section 105. The discharge port of the slow cooling section 105 is directly communicated with the feed port of the melting furnace 2 through a vertical shaft 201. Or the discharge hole of the slow cooling section 105 is firstly communicated with the feed inlet of the ash separating device 202 through the vertical shaft 201, and the discharge hole of the ash separating device 202 is then communicated with the feed inlet of the melting furnace 2. The microwave plasma exciter 3 is arranged outside the plasma reduction section 103, and an exhaust port of the microwave plasma exciter 3 is communicated with an air inlet at the bottom of the plasma reduction section 103. An air flow external circulation system is arranged between the melting furnace 2 and the rotary kiln 1. And an air flow internal circulation system is arranged between each section of the rotary kiln 1. Preferably, the ash separator 202 includes a housing 2021 and a vibrating screen ash feeding mechanism 2022. The vibrating screen ash conveying mechanism 2022 is arranged in the shell 2021 and is communicated with a feeding hole and a discharging hole of the shell 2021.

Preferably, the wind current external circulation system comprises: the top exhaust port of the melting furnace 2 is communicated with the bottom air inlet of the vertical shaft 201 through a first pipeline L1, and the top exhaust port of the vertical shaft 201 is communicated with the air inlet of the microwave plasma exciter 3 through a second pipeline L2.

Preferably, the kiln tail of the rotary kiln 1 is communicated with the bottom gas inlet of the shaft 201 or the bottom gas inlet of the ash separating device 202 through a third pipeline L3, and the top gas outlet of the ash separating device 202 is communicated with the gas inlet of the microwave plasma exciter 3 through a fourth pipeline L4.

Preferably, the wind current internal circulation system comprises:

the top air outlet of the drying section 101 is communicated with the bottom air inlet of the reduction roasting section 104 through a fifth pipeline L5.

Preferably, the top air outlet of the slow cooling section 105 is communicated with the bottom air inlet of the preheating section 102 through a sixth pipeline L6:

or, the wind current inner circulation system comprises:

the top air outlet of the drying section 101 is communicated with the air inlet of the first air mixing chamber 109 through a seventh pipeline L7, and the top air outlet of the reduction roasting section 104 is communicated with the air inlet of the first air mixing chamber 109 through an eighth pipeline L8. The air outlet of the first air mixing chamber 109 is communicated with the bottom air inlet of the preheating section 102 through a ninth pipeline L9.

Preferably, the top air outlet of the preheating section 102 is communicated with the bottom air inlet of the drying section 101 through a tenth pipeline L10.

Or, the wind current internal circulation system comprises:

an air outlet at the tail of the rotary kiln 1 is communicated with an air inlet of the second air mixing chamber 110 through an eleventh pipeline L11, and an air outlet at the top of the reduction roasting section 104 is communicated with an air inlet of the second air mixing chamber 110 through a twelfth pipeline L12. The air outlet of the second air mixing chamber 110 is communicated with the air inlet at the bottom of the drying section 101 at the initial stage through a thirteenth pipeline L13.

Preferably, the top air outlet of the later stage of the drying section 101 is communicated with the air inlet of the third air-mixing chamber 111 through a fourteenth pipeline L14, and the top air outlet of the reduction roasting section 104 is communicated with the air inlet of the third air-mixing chamber 111 through a fifteenth pipeline L15. The air outlet of the third air mixing chamber 111 is communicated with the bottom air inlet at the middle and later stages of the drying section 101 through a sixteenth pipeline L16.

Preferably, the circulating pipeline of the air flow external circulating system and the circulating pipeline of the air flow internal circulating system are respectively and independently provided with a multi-pipe dust remover, a flow regulating valve and an induced draft fan.

Preferably, the system further comprises a temperature detection device 4. The temperature detection devices 4 are independently arranged in the drying section 101, the preheating section 102, the reduction roasting section 104, the shaft 201 and the ash separation device 202.

Preferably, the system further comprises a CO concentration detection device 5. The CO concentration detection device 5 is provided in the slow cooling section 105.

Preferably, the system further comprises a metallization ratio detection device 6. The metallization ratio detection devices 6 are independently arranged in the preheating section 102, the plasma reduction section 103 and the reduction roasting section 104.

Preferably, the apparatus further comprises a burner 106 and a fuel delivery conduit 107. The burner 106 is disposed in the reduction roasting section 104 and is in communication with a fuel delivery conduit 107. Outside the rotary kiln 1, a combustion-supporting air duct 108 is also communicated with the fuel conveying pipeline 107.

Preferably, a plurality of burners 106 are arranged in the reduction roasting section 104, and the burners 106 are all communicated with a fuel conveying pipeline 107.

Preferably, the rotary kiln 1 further comprises a kiln body air duct mechanism 7, an annular rotary slide rail 8 and a rotary slide mechanism 9. The annular rotary slide rail 8 is sleeved outside the rotary kiln 1 and supported by a support 801. The wheel end of the rotary sliding mechanism 9 is connected with the annular rotary sliding rail 8, the other end of the rotary sliding mechanism is connected with the outer end of the kiln body air duct mechanism 7, and the inner end of the kiln body air duct mechanism 7 is connected to the kiln wall. Namely, the rotary kiln 1 and the kiln body air duct mechanism 7 can simultaneously rotate on the annular rotary slide rail 8 through the rotary slide mechanism 9.

Preferably, a plurality of annular rotary slide rails 8 are arranged outside the rotary kiln 1. Any one annular rotary slide rail 8 is connected with the rotary kiln 1 through a plurality of rotary slide mechanisms 9 and a plurality of kiln body air duct mechanisms 7.

Preferably, the kiln body air duct mechanism 7 comprises an air inlet connector 701, a stop valve 702, a pull rod 703 and an air inlet 704. An air inlet channel 705 is arranged on the kiln body of the rotary kiln 1. One end of the baffle valve 702 extends into the air inlet channel 705, and the other end thereof is communicated with the air inlet connector 701. The air inlet 704 is formed in the air inlet connector 701. One end of the air inlet connecting piece 701 far away from the rotary kiln 1 is connected with one end of a pull rod 703, and the other end of the pull rod 703 is connected with a rotary sliding mechanism 9.

Preferably, the rotary sliding mechanism 9 includes a rotary wheel base 901, a lateral rotary wheel 902, and a vertical rotary wheel 903. The rotary wheel seat 901 is of a concave groove-shaped structure and is engaged with two side edge portions of the annular rotary slide rail 8. The rotating wheel seats 901 on the side surfaces of the annular rotating slide rail 8 are all provided with lateral rotating wheels 902. Vertical rotating wheels 903 are arranged on the rotating wheel seats 901 on the outer bottom surfaces of the annular rotating slide rails 8. The rotary wheel seat 901 can slide on the annular rotary slide rail 8 in a rotating way through a lateral rotary wheel 902 and a vertical rotary wheel 903.

Preferably, the rotary kiln 1 further includes a horizontal sliding mechanism 10. The horizontal sliding mechanism 10 includes a horizontal wheel base 1001, a horizontal pulley 1002, and a horizontal rail 1003. The horizontal rail 1003 is a groove-shaped rail arranged at the upper end of the bracket 801. The bottom end of the horizontal wheel base 1001 is mounted in a horizontal rail 1003 by a horizontal pulley 1002. The top end of the horizontal wheel seat 1001 is connected with the annular rotary slide rail 8.

Preferably, the apparatus further comprises a swing mechanism 11. The swing mechanism 11 includes a swing motor 1101 and a ring gear 1102. The inner ring of the large gear ring 1102 is fixed on the outer wall of the rotary kiln 1, and the outer ring of the large gear ring 1102 is meshed with a transmission gear of the rotary motor 1101.

Preferably, the device further comprises a conductivity detection means 12. The conductivity detection means 12 comprises a detection coil 1201 and a magnetically permeable core 1202. The detection coil 1201 is connected with a magnetic core 1202, and the magnetic core 1202 is arranged on the kiln body of the rotary kiln 1.

Preferably, the magnetic core 1202 is disposed in the side wall of the rotary kiln 1, and the distance between the end of the magnetic core 1202 and the inner wall of the rotary kiln 1 is 0.5-20mm, preferably 1-15mm, and more preferably 2-10mm.

Experiment for controlling total energy consumption of iron oxide reduction by reduction degree in rotary kiln

According to the reduction process of iron oxide, combining the reduction degree theory of iron oxide in the rotary kiln and the specific process of direct reduction of iron oxide, controlling different pre-reduction degrees of iron oxide in the rotary kiln, calculating pre-reduction products of iron oxide obtained by different pre-reduction degrees in the rotary kiln, and then respectively carrying out deep reduction through a deep reduction device to obtain the total energy consumption for reducing iron oxide into molten iron.

Experiment 1: 14 tons of the same batch of hematite were divided into 14 batches each weighing 1 ton. Respectively placing each batch in a rotary kiln for pre-reduction, and controlling the pre-reduction degrees of the rotary kiln for pre-reduction to be different; then respectively conveying the pre-reduction products discharged from the rotary kiln into a deep reduction device for deep reduction (melting reduction), and controlling the same technological conditions for deep reduction in the deep reduction device to obtain molten iron; calculating the energy consumption of each batch of iron oxide for pre-reduction in the rotary kiln, the energy consumption of the batch of pre-reduction products for deep reduction in a deep reduction device, and calculating the total energy consumption of the batch of iron oxide in the whole reduction process. The results are specifically as follows:

experiments prove that under the condition of controlling the reduction degree of the iron oxide in the rotary kiln to be eta, wherein eta is 40-80%, preferably 50-70%, and more preferably 60-65%, the total energy consumption is the least, namely the most energy-saving.

Experiment 2: experiment for influence of carbon distribution amount in iron oxide in rotary kiln on reduction degree of iron oxide

The same batch of hematite was divided into 5 batches each weighing 1 tonne. Mixing each batch of hematite into coal powder with different weight ratios; and then respectively placing each batch in a rotary kiln for pre-reduction, controlling other process conditions (except carbon blending amount) of the rotary kiln for pre-reduction to be the same, and detecting the reduction degree of the pre-reduced product of each batch after the rotary kiln is pre-reduced.

The method for detecting the reduction degree comprises the following steps: a low-temperature rapid reduction detection method-a non-contact temperature measurement and material component detection device and method based on conductivity. The detection of the conductivity of the material mainly adopts an eddy current detection method, a detection coil is arranged above a test piece made of a metal material, an alternating excitation signal is added into a coil, an alternating magnetic field is generated around the coil, a metal conductor arranged in the magnetic field generates an eddy current, the eddy current also generates a magnetic field, the directions of the magnetic field and the alternating magnetic field are opposite, the effective impedance of the electrified coil is changed due to the reaction of the magnetic field, and the change of the impedance of the coil completely and uniquely reflects the eddy current effect of an object to be detected. The detection environment is kept unchanged, and when materials with different conductivities are detected, the eddy current generated on the surface layer has different sizes, so that the influences on the impedance of the detection coil are different, and the conductivity of the metal material can be measured by measuring the change condition of the impedance of the coil. And calculating the reduction degree of the iron oxide through the conductivity.

The specific results are as follows:

combining the experimental data, the carbon distribution amount in the iron oxide and the reduction degree of the iron oxide are shown in figure 3.

Experiment 3: experiment of influence of heat preservation reduction time of iron oxide in rotary kiln on iron oxide reduction degree

The same batch of hematite was divided into 5 batches each weighing 1 ton. And respectively placing each batch in a rotary kiln for pre-reduction, controlling the heat preservation reduction time of iron oxide in the rotary kiln to be different, controlling other process conditions (except the heat preservation reduction time) of the rotary kiln for pre-reduction to be the same, and detecting the reduction degree of the pre-reduced product of each batch after the rotary kiln is pre-reduced. The method is the same as the above method.

The specific results are as follows:

the heat preservation reduction time and the reduction degree of the iron oxide in the rotary kiln are shown in figure 4 by combining the experimental data.

Experiment 4: experiment of influence of heat preservation reduction time of iron oxide in rotary kiln on iron oxide reduction degree

The same batch of hematite was divided into 5 batches each weighing 1 tonne. And respectively placing each batch in a rotary kiln for pre-reduction, controlling the reduction temperature of the iron oxide in a reduction roasting section in the rotary kiln to be different, controlling other process conditions (except the temperature in the rotary kiln) for pre-reduction in the rotary kiln to be the same, and detecting the reduction degree of the pre-reduced product of each batch after pre-reduction in the rotary kiln. The method is the same as the above method.

The specific results are as follows:

the reduction temperature of the iron oxide in the reduction roasting section of the rotary kiln and the reduction degree of the iron oxide are shown in figure 5 by combining the experimental data.

Example 1

As shown in fig. 1, a direct reduction process of iron-containing composite pellets, the process comprising:

1) And (3) according to the trend of the materials, sending the iron-containing composite pellets into a rotary kiln from the kiln tail, and carrying out pre-reduction treatment on the iron-containing composite pellets sequentially through a drying section, a preheating section, a plasma reduction section, a reduction roasting section and a slow cooling section to obtain a pre-reduction product. And then, conveying the pre-reduction product to a melting furnace for deep reduction treatment to obtain molten iron.

Example 2

Example 1 was repeated except that the iron-containing composite pellet included a reducing core at the inner layer, a calcium carbonate layer coated outside the reducing core, and an iron-containing material layer coated outside the calcium carbonate layer, as shown in fig. 2. The iron-containing composite pellet is prepared by the following steps: mixing the reducing agent and the binder, and granulating to obtain the reducing spherical core. And then mixing the reduction ball core with lime milk (prepared by mixing and digesting quicklime and water according to the mass ratio of 1. And then mixing the iron-containing raw material with a binder to form an iron-containing mixture, and mixing and granulating the iron-containing mixture and the mother balls coated with the lime milk layer to obtain the green pellets. Finally adopting a catalyst containing CO ₂ The green pellets are dried by the drying medium to obtain the iron-containing composite pellets.

Example 3

Example 2 is repeated, except that the volatile content of the reducing agentThe ratio is more than or equal to 25wt%. In the reducing sphere core, the content of the binder is 0.12% of the total mass of the reducing agent. In the iron-containing mixture, the content of the binder is 1.2% of the total mass of the iron-containing raw material. The diameter of the reduction sphere core is 3mm, and the thickness of the calcium carbonate layer is 2mm. The thickness of the iron-containing material layer is 5mm. Containing CO ₂ Of the drying medium of ₂ Is 10wt% and contains CO ₂ The temperature of the drying medium of (3) is 180 ℃.

Example 4

Example 2 is repeated, except that the volatile content of the reducing agent is ≥ 30% by weight. In the reducing sphere core, the content of the binder is 0.10% of the total mass of the reducing agent. In the iron-containing mixture, the content of the binder is 1.0% of the total mass of the iron-containing raw material. The diameter of the reduction sphere core is 3mm, and the thickness of the calcium carbonate layer is 1.8mm. The thickness of the iron-containing material layer is 6mm. Containing CO ₂ Of the drying medium of ₂ Is 8wt% and contains CO ₂ The temperature of the drying medium of (2) is 200 ℃.

Example 5

Example 3 was repeated, the reaction of iron oxide in the rotary kiln being:

xFe ₂ O _3(s) +(3x-2)CO _(g) ＝2Fe _x O _(s) +(3x-2)CO _2(g) ，

xFe ₂ O _3(s) +(3x-2)H _2(g) ＝2Fe _x O _(s) +(3x-2)H ₂ O _(g) ，

Fe ₂ O _3(s) +3CO _(g) ＝2Fe _(s) +3CO _2(g) ，

Fe ₂ O _3(s) +3H _2(g) ＝2Fe _(s) +3H ₂ O _(g) ；

the reduction degree eta of the iron oxide in the rotary kiln is controlled to be 60 percent.

Example 6

Example 5 was repeated except that the degree of reduction of iron oxide in the rotary kiln was controlled to 65%.

Example 7

Example 5 was repeated except that the degree of reduction of iron oxide in the rotary kiln was controlled to 55%.

Example 8

Example 5 was repeated except that the degree of reduction of the iron oxide in the rotary kiln was controlled to 70%.

Example 9

Example 5 is repeated, but the electric conductivity of the material in the rotary kiln is detected in real time, and the state of the material in the rotary kiln is analyzed through the electric conductivity, so that the reduction condition of the iron oxide in the rotary kiln is monitored; controlling the conductivity of the pre-reduced product obtained by reducing the iron oxide through a rotary kiln to be 8 x 10 ⁶ Ω ^-1 ·m ^-1 。

Example 10

Repeating the example 3, namely detecting the conductivity of the materials in the rotary kiln in real time, and analyzing the state of the materials in the rotary kiln through the conductivity so as to monitor the reduction condition of the iron oxide in the rotary kiln; controlling the conductivity of pre-reduced product obtained by reducing iron oxide in a rotary kiln to be 2 x 10 ⁵ Ω ^-1 ·m ^-1 。

Example 11

Repeating the example 3, namely detecting the conductivity of the materials in the rotary kiln in real time, and analyzing the state of the materials in the rotary kiln through the conductivity so as to monitor the reduction condition of the iron oxide in the rotary kiln; controlling the conductivity of the pre-reduced product obtained by reducing the iron oxide through a rotary kiln to be 9 x 10 ⁶ Ω ^-1 ·m ^-1 。

Example 12

Repeating the example 3, and analyzing the state of the material in the rotary kiln through the conductivity by detecting the conductivity of the material in the rotary kiln in real time so as to monitor the reduction condition of the iron oxide in the rotary kiln; controlling the conductivity of the pre-reduced product obtained by reducing the iron oxide through a rotary kiln to be 4 x 10 ⁶ Ω ^-1 ·m ^-1 。

Example 13

Example 3 was repeated except that the amount of carbon added in the iron oxide was controlled to 22wt%, the heat-preservation reduction time of the iron oxide in the rotary kiln was controlled to 100min, and the reduction temperature in the rotary kiln was controlled to 1100 ℃.

Example 14

Example 3 was repeated except that the amount of carbon added in the iron oxide was controlled to 18wt%, the heat-retaining reduction time of the iron oxide in the rotary kiln was controlled to 130min, and the reduction temperature in the rotary kiln was controlled to 1250 ℃.

Example 15

Example 3 was repeated except that the amount of carbon added in the iron oxide was controlled to 30wt%, the heat-preservation reduction time of the iron oxide in the rotary kiln was controlled to 750min, and the reduction temperature in the rotary kiln was controlled to 850 ℃.

Example 16

In detection example 3, the pre-reduction is performed in the rotary kiln to obtain a pre-reduction product, and the real-time conductivity σ of the material in the rotary kiln is detected in real time _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} The method specifically comprises the following steps:

if σ _{Time of flight} ≤0.1Ω ^-1 ·m ^-1 Indicating that the material in the rotary kiln is mainly Fe ₂ O ₃ The real-time reduction degree of the iron oxide in the rotary kiln is [0,1%]；

If 0.1 < sigma _{Time of flight} ≤1000Ω ^-1 ·m ^-1 Indicating that the material in the rotary kiln is mainly Fe ₃ O ₄ Is present in such a form that the real-time reduction degree of iron oxide in the rotary kiln is (1%, 11.1%)]；

If 1000 < sigma _Time-piece ≤1*10 ⁵ Ω ^-1 ·m ^-1 It shows that the main FeO form of the material in the rotary kiln exists, and the real-time reduction degree of the iron oxide in the rotary kiln is (11.1 percent, 33.3 percent)]；

If 1 x 10 ⁵ ＜σ _{Time of flight} ≤1*10 ⁷ Ω ^-1 ·m ^-1 It shows that the main FeO and Fe exist in the rotary kiln, and the real-time reduction degree of the iron oxide in the rotary kiln is (33.3 percent, 80 percent)]；

If σ _Time-piece ＞1*10 ⁷ Ω ^-1 ·m ^-1 Showing the form of main Fe in the material in the rotary kilnThe real-time reduction degree of the iron oxide in the rotary kiln is (80%, 1)]。

Example 17

Example 16 was repeated, and step 2) specifically was:

201 The hot air at the tail part (close to the kiln tail) of the drying section is conveyed to the reduction roasting section to participate in the reduction roasting treatment. And adjusting the extraction amount of hot air in the drying section and adjusting the air amount of an air burner in the reduction roasting section according to the real-time temperature change of the materials in the reduction roasting section.

As shown in fig. 6, in step 201), according to the real-time temperature change of the material in the reduction roasting section, the adjusting of the extraction amount of hot air in the drying section and the adjusting of the air amount of the air burner in the reduction roasting section specifically include: the set temperature of the material in the reduction roasting section is set to be T1 +/-C1 (the range of C1 is 0-50) and DEG C. Detecting the real-time temperature of the material in the reduction roasting section in real time as T2 and DEG C.

Then:

and when T2 > (T1 +/-C1), increasing the extraction amount of hot air in the drying section and reducing the air amount of an air burner at the upper part of the material layer in the reduction roasting section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T1 +/-C1).

And when T2 < (T1 +/-C1), reducing the extraction amount of hot air in the drying section and increasing the air amount of an air burner at the upper part of the material layer in the reduction roasting section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T1 +/-C1).

As shown in fig. 7, in step 202), according to the real-time concentration change of CO in the hot air in the slow cooling section, the amount of hot air extracted in the slow cooling section is specifically adjusted as follows: the set concentration of CO in the hot air in the slow cooling section is set to W1 + -D (the range of D is 0-20)%. And detecting the real-time concentration of CO in the hot air in the slow cooling section in real time to be W2 percent. Then:

When W2 epsilon (W1 + -D), the current process conditions are maintained.

Example 18

Example 16 was repeated, and step 2) specifically was:

As shown in fig. 8, in step 203), according to the real-time temperature change of the material in the reduction roasting section, the extraction amount of the hot air in the reduction roasting section and the extraction amount of the hot air in the drying section are adjusted to be specifically: the set temperature of the material in the reduction roasting section is set to be T3 +/-C2 (the range of C2 is 0-50) and DEG C. Detecting the real-time temperature of the material in the reduction roasting section in real time as T4 and DEG C. Then:

When T4 epsilon (T3 + -C2), the current process conditions are maintained.

As shown in fig. 9, in step 204), according to the real-time temperature change of the material in the preheating section, the extraction amount of the hot air in the preheating section is adjusted as follows: the set temperature of the material in the preheating section is set to be T5 +/-C3 (the range of C3 is 0-50) and DEG C. And detecting the real-time temperature of the material in the preheating section at T6 and DEG C in real time. Then:

Example 19

Example 16 was repeated, and step 2) specifically was:

As shown in fig. 10, in step 205), according to the real-time temperature change of the material in the reduction roasting section, the adjusting of the extraction amount of the hot air in the reduction roasting section and the extraction amount of the kiln tail hot air of the rotary kiln specifically comprises: the set temperature of the material in the reduction roasting section is set to be T7 +/-C4 (the range of C4 is 0-50) and DEG C. And detecting the real-time temperature of the material in the reduction roasting section at T8 and DEG C in real time. Then:

When T8 epsilon (T7 +/-C4), the current process condition is kept unchanged.

As shown in fig. 11, in step 206), according to the real-time temperature change of the material in the later stage of the drying section, the amount of hot air extracted in the later stage of the drying section and the amount of hot air extracted in the reduction roasting section are specifically adjusted as follows: the set temperature of the material at the later stage of the drying section is set to be T9 +/-C5 (the range of C5 is 0-50) and DEG C. And detecting the real-time temperature of the material at the later stage of the drying section as T10 and DEG C in real time. Then:

Example 20

Example 19 was repeated, step 3) specifically being:

301 The high-temperature gas at the top of the melting and separating furnace is conveyed into a vertical shaft for reforming to obtain reformed gas, and then the reformed gas is subjected to plasma activation and conveyed to a plasma reduction section for participating in the pre-reduction treatment of the iron-containing composite pellets. And simultaneously pumping the tail gas of the rotary kiln into the vertical shaft, and adjusting the pumping amount of the tail gas of the rotary kiln according to the real-time temperature change of the materials in the vertical shaft.

As shown in fig. 12, in step 301), adjusting the extraction amount of the tail gas of the rotary kiln according to the real-time temperature change of the material in the shaft specifically comprises: the set temperature of the materials in the shaft is set to be T11 +/-C6 (the range of C6 is 0-50) and DEG C. And detecting the real-time temperature of the material in the shaft at T12 and DEG C in real time. Then:

And when T12 is less than (T11 +/-C6), reducing the extraction amount of the tail gas of the rotary kiln until the real-time temperature of the materials in the shaft returns to the preset temperature (T11 +/-C6).

Example 21

Example 19 was repeated, step 3) specifically being:

302 The high-temperature coal gas at the top of the melting furnace is conveyed into a vertical shaft for reforming to obtain reformed gas, and then the reformed gas is subjected to plasma activation and conveyed to a plasma reduction section for participating in the pre-reduction treatment of the iron-containing composite pellets. Meanwhile, tail gas of the rotary kiln is pumped into the ash separation device, and the pumping amount of the tail gas of the rotary kiln is adjusted according to the real-time temperature change of smoke dust in the ash separation device. And finally, carrying out plasma activation on tail gas discharged by the ash separation device, and conveying the tail gas to a plasma reduction section to participate in the pre-reduction treatment of the iron-containing composite pellets.

As shown in fig. 13, in step 302), the adjusting of the extraction amount of the tail gas of the rotary kiln according to the real-time temperature change of the soot in the ash separation device specifically includes: the set temperature of the soot in the ash separator is set to T13 + -C7 (the range of C7 is 0-50) and DEG C. Real-time temperature of smoke dust in the real-time detection ash content separating device is T14 and DEG C. Then:

Example 22

Example 21 was repeated except that the temperature of the high-temperature gas discharged from the top of the melting furnace was more than 1400 ℃.

Example 23

Example 22 was repeated except that the temperature of the high-temperature gas discharged from the top of the melter-separator was more than 1500 ℃.

Example 23

Example 22 was repeated except that the CO content in the reformed gas was higher than 35vol%. H ₂ Is higher than 3vol%.

Example 24

Example 22 is repeated, except that the CO content in the reformate gas is higher than 35vol%. H ₂ Is higher than 5vol%.

Example 25

As shown in fig. 14, the direct reduction apparatus for iron-containing composite pellets comprises a rotary kiln 1, a melting furnace 2 and a microwave plasma exciter 3. According to the trend of materials, the rotary kiln 1 is sequentially provided with a drying section 101, a preheating section 102, a plasma reduction section 103, a reduction roasting section 104 and a slow cooling section 105. The discharge hole of the slow cooling section 105 is directly communicated with the feed hole of the melting furnace 2 through a vertical shaft 201. The microwave plasma exciter 3 is arranged outside the plasma reduction section 103, and an exhaust port of the microwave plasma exciter 3 is communicated with an air inlet at the bottom of the plasma reduction section 103. An air flow external circulation system is arranged between the melting furnace 2 and the rotary kiln 1. And an air flow internal circulation system is arranged between each section of the rotary kiln 1.

Example 26

Example 25 was repeated, as shown in FIG. 15, except that the discharge port of the slow cooling section 105 was first communicated with the feed port of the ash separator 202 via the shaft 201, and the discharge port of the ash separator 202 was further communicated with the feed port of the melting furnace 2.

Example 27

Example 26 is repeated except that the ash separator 202 includes a housing 2021 and a vibrating screen ash delivery mechanism 2022. The vibrating screen ash conveying mechanism 2022 is arranged in the shell 2021 and communicated with a feeding hole and a discharging hole of the shell 2021.

Example 28

Example 25 was repeated, as shown in fig. 14, except that the wind current external circulation system included: the top exhaust port of the melting furnace 2 is communicated with the bottom air inlet of the vertical shaft 201 through a first pipeline L1, and the top exhaust port of the vertical shaft 201 is communicated with the air inlet of the microwave plasma exciter 3 through a second pipeline L2. The kiln tail of the rotary kiln 1 is communicated with the bottom air inlet of the vertical shaft 201 through a third pipeline L3.

Example 29

Example 27 was repeated, as shown in fig. 15, except that the wind current external circulation system included: the top exhaust port of the melting furnace 2 is communicated with the bottom air inlet of the vertical shaft 201 through a first pipeline L1, and the top exhaust port of the vertical shaft 201 is communicated with the air inlet of the microwave plasma exciter 3 through a second pipeline L2. The kiln tail of the rotary kiln 1 is communicated with the bottom air inlet of the ash separating device 202 through a third pipeline L3, and then the top air outlet of the ash separating device 202 is communicated with the air inlet of the microwave plasma exciter 3 through a fourth pipeline L4.

Example 30

Example 29 is repeated with the wind flow internal circulation system including:

as shown in fig. 16, the top air outlet of the drying section 101 is connected to the bottom air inlet of the reduction roasting section 104 through a fifth pipe L5.

Example 31

Repeating embodiment 30, the wind flow internal circulation system further comprises: the top air outlet of the slow cooling section 105 is communicated with the bottom air inlet of the preheating section 102 through a sixth pipeline L6:

example 32

Example 29 is repeated with the wind stream internal circulation system including:

as shown in fig. 17, the top air outlet of the drying section 101 is connected to the air inlet of the first air-mixing chamber 109 through a seventh pipe L7, and the top air outlet of the reduction roasting section 104 is connected to the air inlet of the first air-mixing chamber 109 through an eighth pipe L8. The air outlet of the first air mixing chamber 109 is communicated with the bottom air inlet of the preheating section 102 through a ninth pipeline L9.

Example 33

Repeating embodiment 32, the wind flow internal circulation system further comprises:

as shown in fig. 17, the top outlet of the preheating section 102 is connected to the bottom inlet of the drying section 101 through a tenth pipe L10.

Example 34

as shown in fig. 18, the kiln tail air outlet of the rotary kiln 1 is communicated with the air inlet of the second air mixing chamber 110 through an eleventh pipeline L11, and the top air outlet of the reduction roasting section 104 is communicated with the air inlet of the second air mixing chamber 110 through a twelfth pipeline L12. The air outlet of the second air mixing chamber 110 is communicated with the bottom air inlet at the initial stage of the drying section 101 through a thirteenth pipeline L13.

Example 35

Repeating embodiment 34, the wind flow internal circulation system further comprises:

as shown in fig. 18, only the top outlet of the later stage of the drying section 101 is communicated with the air inlet of the third air-mixing chamber 111 through a fourteenth pipeline L14, and the top outlet of the reduction roasting section 104 is communicated with the air inlet of the third air-mixing chamber 111 through a fifteenth pipeline L15. The air outlet of the third air mixing chamber 111 is communicated with the bottom air inlet of the middle and later periods of the drying section 101 through a sixteenth pipeline L16.

Example 36

In the example 35, only the circulation pipes of the air flow external circulation system and the air flow internal circulation system are respectively and independently provided with the multi-pipe dust remover, the flow regulating valve and the induced draft fan.

Example 37

Embodiment 36 is repeated as shown in fig. 14-15, except that the system further comprises a temperature sensing device 4. The temperature detection devices 4 are independently arranged in the drying section 101, the preheating section 102, the reduction roasting section 104, the shaft 201 and the ash separation device 202.

Example 38

Example 37 was repeated except that the system further included a CO concentration detection device 5. The CO concentration detection device 5 is provided in the slow cooling section 105.

Example 39

Example 38 is repeated except that the system further comprises metallization ratio detecting means 6. The metallization ratio detection devices 6 are independently arranged in the preheating section 102, the plasma reduction section 103 and the reduction roasting section 104.

Example 40

Example 39 is repeated except that the apparatus further comprises a burner 106 and a fuel delivery conduit 107. The burner 106 is disposed in the reduction roasting section 104 and is in communication with a fuel delivery conduit 107. Outside the rotary kiln 1, a combustion-supporting air duct 108 is also communicated with the fuel conveying pipeline 107.

EXAMPLE 41

The embodiment 40 is repeated except that a plurality of burners 106 are arranged in the reduction roasting section 104, and the plurality of burners 106 are all communicated with a fuel conveying pipeline 107.

Example 42

Embodiment 41 is repeated, as shown in fig. 19, except that the rotary kiln 1 further comprises a kiln body air duct mechanism 7, an annular rotary slide rail 8 and a rotary slide mechanism 9. The annular rotary slide rail 8 is sleeved outside the rotary kiln 1 and supported by a support 801. The wheel end of the rotary sliding mechanism 9 is connected with the annular rotary sliding rail 8, the other end of the rotary sliding mechanism is connected with the outer end of the kiln body air duct mechanism 7, and the inner end of the kiln body air duct mechanism 7 is connected to the kiln wall. Namely, the rotary kiln 1 and the kiln body air duct mechanism 7 can simultaneously rotate on the annular rotary slide rail 8 through the rotary slide mechanism 9.

Example 43

Example 42 is repeated except that the exterior of the rotary kiln 1 is provided with a plurality of endless rotary slide tracks 8. Any one of the annular rotary slide rails 8 is connected with the rotary kiln 1 through a plurality of rotary slide mechanisms 9 and a plurality of kiln body air duct mechanisms 7.

Example 44

Embodiment 43 is repeated as shown in fig. 20-21 except that the kiln body air duct mechanism 7 comprises an air inlet connector 701, a stop valve 702, a pull rod 703 and an air inlet 704. An air inlet channel 705 is arranged on the kiln body of the rotary kiln 1. One end of the baffle valve 702 extends into the air inlet channel 705, and the other end thereof is communicated with the air inlet connector 701. The air inlet 704 is formed in the air inlet connector 701. One end of the air inlet connecting piece 701 far away from the rotary kiln 1 is connected with one end of a pull rod 703, and the other end of the pull rod 703 is connected with a rotary sliding mechanism 9.

Example 45

Embodiment 44 is repeated except that the rotary slide mechanism 9 comprises a rotary wheel base 901, a lateral rotary wheel 902 and a vertical rotary wheel 903. The rotating wheel seat 901 is of a concave groove-shaped structure and is engaged with two side edge portions of the annular rotating slide rail 8. The rotating wheel seats 901 on the side surfaces of the annular rotating slide rail 8 are all provided with lateral rotating wheels 902. Vertical rotating wheels 903 are arranged on the rotating wheel seats 901 on the outer bottom surfaces of the annular rotating slide rails 8. The rotary wheel seat 901 can slide on the annular rotary slide rail 8 in a rotating way through a lateral rotary wheel 902 and a vertical rotary wheel 903.

Example 46

Example 45 is repeated except that the rotary kiln 1 further includes a horizontal sliding mechanism 10. The horizontal sliding mechanism 10 includes a horizontal roller mount 1001, a horizontal pulley 1002, and a horizontal rail 1003. The horizontal rail 1003 is a groove-shaped rail arranged at the upper end of the bracket 801. The bottom end of the horizontal wheel base 1001 is mounted in a horizontal rail 1003 by a horizontal pulley 1002. The top end of the horizontal wheel seat 1001 is connected with the annular rotary slide rail 8.

Example 47

Embodiment 46 is repeated except that the apparatus further comprises a tumbler 11. The swing mechanism 11 includes a swing motor 1101 and a ring gear 1102. The inner ring of the large gear ring 1102 is fixed on the outer wall of the rotary kiln 1, and the outer ring of the large gear ring 1102 is meshed with a transmission gear of the rotary motor 1101.

Example 48

Example 47 is repeated as shown in fig. 22, except that the apparatus further comprises a conductivity detection means 12. The conductivity detection means 12 comprises a detection coil 1201 and a magnetically permeable core 1202. The detection coil 1201 is connected with a magnetic core 1202, and the magnetic core 1202 is arranged on the kiln body of the rotary kiln 1.

Example 49

Example 48 was repeated except that the magnetically permeable core 1202 was disposed in the side wall of the rotary kiln 1 and the distance between the end of the magnetically permeable core 1202 and the inner wall of the rotary kiln 1 was 4mm.

Example 50

Example 49 was repeated except that the magnetically permeable core 1202 was disposed in the side wall of the rotary kiln 1 and the distance between the end of the magnetically permeable core 1202 and the inner wall of the rotary kiln 1 was 8mm.

Claims

1. A direct reduction process of iron-containing composite pellets is characterized by comprising the following steps: the process comprises the following steps:

1) According to the trend of materials, sending the iron-containing composite pellets into a rotary kiln from the kiln tail, and carrying out pre-reduction treatment on the iron-containing composite pellets sequentially through a drying section, a preheating section, a plasma reduction section, a reduction roasting section and a slow cooling section to obtain a pre-reduction product; then sending the pre-reduction product into a melting furnace for deep reduction treatment to obtain molten iron;

2) According to the properties of hot air in each section of the rotary kiln, carrying out internal circulation treatment on the hot air generated in each section among the sections;

2. The process according to claim 1, characterized in that: the iron-containing composite pellet comprises a reducing spherical core positioned at the inner layer, a calcium carbonate layer coated outside the reducing spherical core and an iron-containing material layer coated outside the calcium carbonate layer; the iron-containing composite pellet is prepared by the following steps: mixing a reducing agent and a binder, and granulating to obtain a reducing spherical core; then mixing and granulating the reducing ball cores and lime milk (prepared by mixing and digesting quicklime and water according to the mass ratio of 1.2-1.8) to obtain mother balls coated with lime milk layers; then mixing the iron-containing raw material and a binder to form an iron-containing mixture, and mixing and granulating the iron-containing mixture and the mother balls coated with the lime milk layer to obtain green pellets; finally adopting a catalyst containing CO ₂ The green pellets are dried by the drying medium to obtain the iron-containing composite pellets.

3. The process according to claim 2, characterized in that: the reducing agent is selected from one or more of bituminous coal, lignite, biomass and organic solid waste; the binder is selected from one or more of bentonite, humic acid and humate; the content of the volatile component of the reducing agent is more than or equal to 25wt%, and preferably the content of the volatile component of the reducing agent is more than or equal to 30wt%;

in the reducing spherical core, the content of the binder is 0.05-0.3 percent of the total mass of the reducing agent, and preferably 0.08-0.2 percent; in the iron-containing mixture, the content of the binder is 0.8-3%, preferably 1-2% of the total mass of the iron-containing raw material;

preferably, the diameter of the reduction spherical core is 2-6 mm, preferably 3-5 mm; the thickness of the calcium carbonate layer is 1-3 mm, preferably 1.5-2 mm; the thickness of the iron-containing material layer is 3-7 mm, and preferably 4-6 mm; and/or

Said CO-containing ₂ Is selected from the group consisting of the addition of CO ₂ One or more of hot air, hot tail gas of various processes of blast furnace steel smelting and hot tail gas of a direct reduction process; containing CO ₂ In the drying medium of (2) ₂ The content of (B) is 5 to 20wt%, preferably 8 to 15wt%; containing CO ₂ The temperature of the drying medium of (2) is 150 to 300 ℃, preferably 180 to 260 ℃.

4. The process according to any one of claims 1 to 3, characterized in that: the reaction of the iron oxide in the iron-containing composite pellets in the rotary kiln is as follows:

xFe ₂ O ₃ (s)+(3x-2)CO(g)＝2FexO(s)+(3x-2)CO ₂ (g)，

xFe ₂ O ₃ (s)+(3x-2)H ₂ (g)＝2FexO(s)+(3x-2)H ₂ O(g)，

Fe ₂ O ₃ (s)+3CO(g)＝2Fe(s)+3CO ₂ (g)，

Fe ₂ O ₃ (s)+3H ₂ (g)＝2Fe(s)+3H ₂ O(g)；

controlling the reduction degree of the iron oxide in the rotary kiln to be eta, wherein eta is 40-80%, preferably 50-70%, and more preferably 60-65%; wherein:

5. the process according to claim 4, characterized in that: detecting the conductivity of the materials in the rotary kiln in real time, and analyzing the state of the materials in the rotary kiln through the conductivity so as to monitor the reduction condition of the iron oxide in the rotary kiln;

preferably, the electric conductivity of the pre-reduced product obtained by controlling the reduction of the iron oxide through a rotary kiln is 1 x 10 ⁵ ～1*10 ⁷ Ω ^-1 ·m ^-1 Preferably 3 to 10 ⁵ ～7*10 ⁶ Ω ^-1 ·m ^-1 More preferably 5 x 10 ⁵ ～5*1*10 ⁶ Ω ^-1 ·m ^-1 。

6. The method of direct reduction of iron oxide according to claim 4 or 5, characterized in that: controlling the reduction degree of the iron oxide in the rotary kiln by controlling one or more of the carbon distribution amount in the iron oxide, the heat preservation reduction time of the iron oxide in the rotary kiln and the reduction temperature in the rotary kiln; the reduction degree of the iron oxide in the rotary kiln is in direct proportion to the carbon distribution amount of the iron oxide, the heat preservation reduction time of the iron oxide in the rotary kiln and the reduction temperature in the rotary kiln;

preferably, the carbon distribution in the iron oxide is controlled to be 10-40wt%, preferably 15-30wt%, and more preferably 20-25wt%; the carbon blending amount is the weight ratio of the coal amount in the iron oxide entering the rotary kiln to the whole iron oxide; and/or

Controlling the heat preservation reduction time of the iron oxide in the rotary kiln for 60-180min, preferably 70-140min, and more preferably 90-120min; the heat preservation and reduction time of the iron oxide in the rotary kiln refers to the residence time of the iron oxide in the highest temperature section in the rotary kiln; and/or

Controlling the reduction temperature in the rotary kiln to be 800-1400 ℃, preferably 850-1300 ℃, and more preferably 900-1200 ℃; the reduction temperature in the rotary kiln refers to the highest temperature zone in the rotary kiln.

7. The direct reduction of iron oxide of claim 6The method is characterized in that: real-time detection of real-time conductivity sigma of materials in rotary kiln _{Time of flight} Obtaining the real-time reduction degree eta of the iron oxide in the rotary kiln _{Fruit of Chinese wolfberry} The method specifically comprises the following steps:

if σ _{Time of flight} ≤0.1Ω ^-1 ·m ^-1 Indicating that the material in the rotary kiln is mainly Fe ₂ O ₃ The real-time reduction degree of the iron oxide in the rotary kiln is 0,1%]；

If 1000 < sigma _{Time of flight} ≤1*10 ⁵ Ω ^-1 ·m ^-1 It shows that the main FeO form of the material in the rotary kiln exists, and the real-time reduction degree of the iron oxide in the rotary kiln is (11.1 percent, 33.3 percent)]；

If 1 x 10 ⁵ ＜σ _{Time of flight} ≤1*10 ⁷ Ω ^-1 ·m ^-1 The results show that the main forms of FeO and Fe exist in the rotary kiln, and the real-time reduction degree of the iron oxide in the rotary kiln is (33.3 percent, 80 percent)]；

If σ _{Time of flight} ＞1*10 ⁷ Ω ^-1 ·m ^-1 It shows that the material in the rotary kiln mainly exists in the form of Fe, and the real-time reduction degree of the iron oxide in the rotary kiln is (80%, 1%]。

8. The process according to any one of claims 1 to 7, characterized in that: the step 2) comprises the following steps:

201 Hot air at the tail part (close to the kiln tail) of the drying section is conveyed to the reduction roasting section to participate in reduction roasting treatment; according to the real-time temperature change of the materials in the reduction roasting section, the extraction amount of hot air in the drying section is adjusted and/or the air amount of an air burner in the reduction roasting section is adjusted; and/or

202 The hot air at the tail part of the slow cooling section (close to the reduction roasting section) is conveyed to the preheating section to participate in the preheating treatment of the pellets; according to the real-time concentration change of CO in the hot air in the slow cooling section, adjusting the hot air extraction amount in the slow cooling section;

alternatively, step 2) comprises:

203 Mixing the hot air output by the drying section with the hot air output by the reduction roasting section to obtain mixed hot air, and then conveying the mixed hot air to a preheating section to participate in preheating treatment of the pellets; according to the real-time temperature change of the materials in the reduction roasting section, the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air in the drying section are adjusted; and/or

204 Conveying the hot air in the preheating section to a drying section to participate in the drying treatment of the pellets; according to the real-time temperature change of the materials in the preheating section, the extraction amount of hot air in the preheating section is adjusted;

alternatively, step 2) comprises:

205 Mixing hot air output by the kiln tail of the rotary kiln with hot air output by the reduction roasting section to obtain mixed wet hot air, and then conveying the mixed wet hot air to the drying section to participate in the drying treatment of the pellets at the initial stage; according to the real-time temperature change of the materials in the reduction roasting section, adjusting the extraction amount of hot air in the reduction roasting section and the extraction amount of kiln tail hot air of the rotary kiln; and/or

206 Mixing hot air output at the later stage of the drying section with hot air output from the reduction roasting section to obtain mixed dry hot air, and then conveying the mixed dry hot air to the drying section to participate in the drying treatment of the pellets at the initial stage; and adjusting the extraction amount of hot air in the later stage of the drying section and the extraction amount of hot air in the reduction roasting section according to the real-time temperature change of the material in the later stage of the drying section.

9. The process according to claim 8, characterized in that: in step 201), according to the real-time temperature change of the material in the reduction roasting section, the adjustment of the extraction amount of hot air in the drying section and/or the adjustment of the air amount of an air burner in the reduction roasting section specifically comprises: setting the set temperature of the material in the reduction roasting section as T1 +/-C1 (the range of C1 is 0-50) and DEG C; detecting the real-time temperature of the material in the reduction roasting section in real time as T2 and DEG C; then:

when T2 is greater than (T1 +/-C1), increasing the extraction amount of hot air in the drying section and/or reducing the air amount of an air burner at the upper part of a material layer in the reduction roasting section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T1 +/-C1);

when T2 belongs to (T1 +/-C1), maintaining the current process condition unchanged;

when T2 is less than (T1 +/-C1), reducing the extraction amount of hot air in the drying section and/or increasing the air amount of an air burner at the upper part of the material layer in the reduction roasting section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T1 +/-C1); and/or

In step 202), according to the real-time concentration change of CO in the hot air in the slow cooling section, the adjustment of the hot air extraction amount in the slow cooling section is specifically as follows: setting the set concentration of CO in the hot air in the slow cooling section as W1 +/-D (the range of D is 0-20)%; detecting the real-time concentration of CO in hot air in the slow cooling section in real time to be W2 percent; then:

when W2 is > (W1 +/-D), increasing the extraction amount of the hot air in the slow cooling section until the real-time concentration of CO in the hot air in the slow cooling section returns to the preset concentration (W1 +/-D);

when W2 belongs to (W1 +/-D), maintaining the current process condition unchanged;

10. The process according to claim 8, characterized in that: in step 203), adjusting the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air in the drying section according to the real-time temperature change of the material in the reduction roasting section specifically comprises: setting the set temperature of the material in the reduction roasting section to be T3 +/-C2 (the range of C2 is 0-50) and DEG C; detecting the real-time temperature of the material in the reduction roasting section to be T4 and DEG C in real time; then:

when T4 > (T3 +/-C2), increasing the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air in the drying section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T3 +/-C2);

when T4 belongs to (T3 +/-C2), the current process condition is maintained unchanged;

when T4 is less than (T3 +/-C2), reducing the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air in the drying section until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T3 +/-C2); and/or

In step 204), according to the real-time temperature change of the material in the preheating section, the extraction amount of the hot air in the preheating section is adjusted as follows: setting the set temperature of the material in the preheating section to be T5 +/-C3 (the range of C3 is 0-50) and DEG C; detecting the real-time temperature of the material in the preheating section at T6 and DEG C in real time; then:

when T6 is larger than (T5 +/-C3), increasing the extraction amount of hot air in the preheating section until the real-time temperature of the material in the preheating section returns to the preset temperature (T5 +/-C3);

when T6 belongs to (T5 +/-C3), maintaining the current process condition unchanged;

11. The process according to claim 8, characterized in that: in step 205), adjusting the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air at the tail of the rotary kiln according to the real-time temperature change of the material in the reduction roasting section specifically comprises: setting the set temperature of the material in the reduction roasting section to be T7 +/-C4 (the range of C4 is 0-50) and DEG C; detecting the real-time temperature of the material in the reduction roasting section in real time to be T8 and DEG C; then:

when T8 > (T7 +/-C4), increasing the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air at the tail of the rotary kiln until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T7 +/-C4);

when T8 belongs to (T7 +/-C4), maintaining the current process condition unchanged;

when T8 is less than (T7 +/-C4), reducing the extraction amount of hot air in the reduction roasting section and the extraction amount of hot air at the tail of the rotary kiln until the real-time temperature of the material in the reduction roasting section returns to the preset temperature (T7 +/-C4); and/or

In step 206), the adjusting of the extraction amount of the hot air in the later stage of the drying section and the extraction amount of the hot air in the reduction roasting section according to the real-time temperature change of the material in the later stage of the drying section is specifically as follows: setting the set temperature of the material at the later stage of the drying section as T9 +/-C5 (the range of C5 is 0-50) and DEG C; detecting the real-time temperature of the material at the later stage of the drying section in real time to be T10℃; then:

when T10 > (T9 +/-C5), increasing the extraction amount of hot air in the later stage of the drying section and the extraction amount of hot air in the reduction roasting section until the real-time temperature of the material in the later stage of the drying section returns to the preset temperature (T9 +/-C5);

when T10 belongs to (T9 +/-C5), the current process condition is maintained unchanged;

12. The process according to any one of claims 1 to 11, characterized in that: the step 3) is specifically as follows:

301 Conveying the furnace top high-temperature gas of the melting furnace into a vertical shaft for reforming to obtain reformed gas, then conveying the reformed gas to a plasma reduction section for participating in the pre-reduction treatment of the iron-containing composite pellets after carrying out plasma activation on the reformed gas; simultaneously pumping the tail gas of the rotary kiln into the vertical shaft, and adjusting the pumping amount of the tail gas of the rotary kiln according to the real-time temperature change of materials in the vertical shaft;

or, the step 3) is specifically:

302 Conveying the furnace top high-temperature gas of the melting furnace into a vertical shaft for reforming to obtain reformed gas, then conveying the reformed gas to a plasma reduction section for participating in the pre-reduction treatment of the iron-containing composite pellets after carrying out plasma activation on the reformed gas; simultaneously pumping the tail gas of the rotary kiln into an ash separation device, and adjusting the extraction amount of the tail gas of the rotary kiln according to the real-time temperature change of smoke dust in the ash separation device; and finally, carrying out plasma activation on tail gas discharged by the ash separation device, and conveying the tail gas to a plasma reduction section to participate in the pre-reduction treatment of the iron-containing composite pellets.

13. The process according to claim 12, characterized in that: in step 301), adjusting the extraction amount of the tail gas of the rotary kiln according to the real-time temperature change of the material in the shaft specifically comprises: setting the set temperature of the materials in the shaft to be T11 +/-C6 (the range of C6 is 0-50) and DEG C; detecting the real-time temperature of the materials in the shaft at T12 and DEG C in real time; then:

when T12 > (T11 +/-C6), increasing the extraction amount of tail gas of the rotary kiln until the real-time temperature of the material in the shaft returns to the preset temperature (T11 +/-C6);

when T12 belongs to (T11 +/-C6), maintaining the current process condition unchanged;

when T12 is less than (T11 +/-C6), reducing the extraction amount of tail gas of the rotary kiln until the real-time temperature of the material in the shaft returns to the preset temperature (T11 +/-C6);

or, in step 302), adjusting the extraction amount of the tail gas of the rotary kiln according to the real-time temperature change of the smoke dust in the ash separation device specifically comprises: setting the set temperature of the smoke dust in the ash separation device to be T13 +/-C7 (the range of C7 is 0-50) and DEG C; detecting the real-time temperature of the smoke dust in the ash separation device in real time to be T14 and DEG C; then:

when T14 is > (T13 +/-C7), increasing the extraction amount of the tail gas of the rotary kiln until the real-time temperature of the smoke dust in the ash content separation device returns to the preset temperature (T13 +/-C7);

when T14 belongs to (T13 +/-C7), maintaining the current process condition unchanged;

and when T14 < (T13 +/-C7), reducing the extraction amount of the tail gas of the rotary kiln until the real-time temperature of the smoke dust in the ash content separation device returns to the preset temperature (T13 +/-C7).

14. The process according to claim 12 or 13, characterized in that: the temperature of high-temperature coal gas discharged from the top of the melting furnace is more than 1400 ℃, preferably more than 1500 ℃, and more preferably more than 1600 ℃; and/or

In the reformed gas, the content of CO is more than 30vol%, preferably the content of CO is more than 35vol%, more preferably the content of CO is more than 40vol%; h ₂ Is higher than 2vol%, preferably H ₂ More preferably H, in an amount of more than 3vol% ₂ Is higher than 5vol%.

15. A direct reduction plant of iron-bearing composite pellets or a plant for use in the process of any one of claims 1-14, characterized in that: the device comprises a rotary kiln (1), a melting furnace (2) and a microwave plasma exciter (3); according to the trend of materials, the rotary kiln (1) is sequentially provided with a drying section (101), a preheating section (102), a plasma reduction section (103), a reduction roasting section (104) and a slow cooling section (105); the discharge hole of the slow cooling section (105) is directly communicated with the feed inlet of the melting and separating furnace (2) through a vertical shaft (201); or the discharge hole of the slow cooling section (105) is firstly communicated with the feed inlet of the ash separating device (202) through the vertical shaft (201), and the discharge hole of the ash separating device (202) is then communicated with the feed inlet of the melting furnace (2); the microwave plasma exciter (3) is arranged outside the plasma reduction section (103), and an exhaust port of the microwave plasma exciter (3) is communicated with an air inlet at the bottom of the plasma reduction section (103); an air flow external circulation system is arranged between the melting furnace (2) and the rotary kiln (1); an air flow internal circulation system is arranged between each section of the rotary kiln (1); preferably, the ash separating device (202) comprises a shell cylinder (2021) and a vibrating screen ash conveying mechanism (2022); the vibrating screen ash conveying mechanism (2022) is arranged in the shell cylinder (2021) and communicated with a feeding hole and a discharging hole of the shell cylinder (2021).

16. The system of claim 15, wherein: the wind current extrinsic cycle system includes: communicating a top exhaust port of the melting furnace (2) with a bottom air inlet of a vertical shaft (201) through a first pipeline (L1), and communicating a top exhaust port of the vertical shaft (201) with an air inlet of a microwave plasma exciter (3) through a second pipeline (L2); and/or

The kiln tail of the rotary kiln (1) is communicated with the bottom air inlet of the vertical shaft (201) or the bottom air inlet of the ash separating device (202) through a third pipeline (L3), and then the top air outlet of the ash separating device (202) is communicated with the air inlet of the microwave plasma exciter (3) through a fourth pipeline (L4).

17. The apparatus of claim 15 or 16, wherein: the wind current inner circulation system comprises: the top air outlet of the drying section (101) is communicated with the bottom air inlet of the reduction roasting section (104) through a fifth pipeline (L5); and/or

The top air outlet of the slow cooling section (105) is communicated with the bottom air inlet of the preheating section (102) through a sixth pipeline (L6):

or, the wind current internal circulation system comprises: a top air outlet of the drying section (101) is communicated with an air inlet of the first air mixing chamber (109) through a seventh pipeline (L7), and a top air outlet of the reduction roasting section (104) is communicated with an air inlet of the first air mixing chamber (109) through an eighth pipeline (L8); then, an air outlet of the first air mixing chamber (109) is communicated with an air inlet at the bottom of the preheating section (102) through a ninth pipeline (L9); and/or

The air outlet at the top of the preheating section (102) is communicated with the air inlet at the bottom of the drying section (101) through a tenth pipeline (L10);

or, the wind current internal circulation system comprises: a kiln tail air outlet of the rotary kiln (1) is communicated with an air inlet of a second air mixing chamber (110) through an eleventh pipeline (L11), and meanwhile, a top air outlet of the reduction roasting section (104) is communicated with an air inlet of the second air mixing chamber (110) through a twelfth pipeline (L12); then, an air outlet of the second air mixing chamber (110) is communicated with an air inlet at the bottom of the drying section (101) at the initial stage through a thirteenth pipeline (L13); and/or

A top air outlet at the later stage of the drying section (101) is communicated with an air inlet of a third air mixing chamber (111) through a fourteenth pipeline (L14), and a top air outlet of the reduction roasting section (104) is communicated with an air inlet of the third air mixing chamber (111) through a fifteenth pipeline (L15); then, an air outlet of the third air mixing chamber (111) is communicated with a bottom air inlet at the middle and later stages of the drying section (101) through a sixteenth pipeline (L16);

18. The apparatus according to any one of claims 15-17, wherein: the system also comprises a temperature detection device (4); the temperature detection devices (4) are independently arranged in the drying section (101), the preheating section (102), the reduction roasting section (104), the vertical shaft (201) and the ash separation device (202); and/or

The system also comprises a CO concentration detection device (5); the CO concentration detection device (5) is arranged in the slow cooling section (105); and/or

The system also comprises a metallization ratio detection device (6); the metallization ratio detection devices (6) are independently arranged in the preheating section (102), the plasma reduction section (103) and the reduction roasting section (104).

19. The apparatus of claim 18, wherein: the device also comprises a burner (106) and a fuel delivery pipeline (107); the burner (106) is arranged in the reduction roasting section (104) and is communicated with a fuel conveying pipeline (107); a combustion-supporting air pipe (108) is also communicated with the fuel conveying pipeline (107) outside the rotary kiln (1);

preferably, a plurality of burners (106) are arranged in the reduction roasting section (104), and the burners (106) are all communicated with a fuel conveying pipeline (107).

20. The apparatus according to any one of claims 15-19, wherein: the rotary kiln (1) also comprises a kiln body air duct mechanism (7), an annular rotary slide rail (8) and a rotary sliding mechanism (9); the annular rotary slide rail (8) is sleeved outside the rotary kiln (1) and is supported by a support (801); the wheel end of the rotary sliding mechanism (9) is connected with the annular rotary slide rail (8), the other end of the rotary sliding mechanism is connected with the outer end of the kiln body air duct mechanism (7), and the inner end of the kiln body air duct mechanism (7) is connected to the kiln wall; namely, the rotary kiln (1) and the kiln body air duct mechanism (7) can simultaneously rotate on the annular rotary slide rail (8) through the rotary sliding mechanism (9);

preferably, a plurality of annular rotary sliding rails (8) are arranged outside the rotary kiln (1); any one annular rotary slide rail (8) is connected with the rotary kiln (1) through a plurality of rotary slide mechanisms (9) and a plurality of kiln body air duct mechanisms (7).

21. The apparatus of claim 20, wherein: the kiln body air duct mechanism (7) comprises an air inlet connecting piece (701), a stop valve (702), a pull rod (703) and an air inlet (704); an air inlet channel (705) is formed in the kiln body of the rotary kiln (1); one end of the baffle valve (702) extends into the air inlet channel (705), and the other end of the baffle valve is communicated with the air inlet connecting piece (701); the air inlet (704) is arranged on the air inlet connecting piece (701); one end of the air inlet connecting piece (701) far away from the rotary kiln (1) is connected with one end of a pull rod (703), and the other end of the pull rod (703) is connected with a rotary sliding mechanism (9); and/or

The rotary sliding mechanism (9) comprises a rotary wheel seat (901), a lateral rotary wheel (902) and a vertical rotary wheel (903); the rotary wheel seat (901) is of a concave groove-shaped structure and is occluded at the two side edge parts of the annular rotary slide rail (8); lateral rotating wheels (902) are arranged on rotating wheel seats (901) on the side surfaces of the annular rotating slide rails (8); vertical rotating wheels (903) are arranged on the rotating wheel seats (901) on the outer bottom surface of the annular rotating slide rail (8); the rotary wheel seat (901) can rotate and slide on the annular rotary slide rail (8) through a lateral rotary wheel (902) and a vertical rotary wheel (903).

22. The apparatus of claim 21, wherein: the rotary kiln (1) also comprises a horizontal sliding mechanism (10); the horizontal sliding mechanism (10) comprises a horizontal wheel seat (1001), a horizontal pulley (1002) and a horizontal rail (1003); the horizontal rail (1003) is a groove-shaped rail arranged at the upper end of the bracket (801); the bottom end of the horizontal wheel seat (1001) is installed in a horizontal rail (1003) through a horizontal pulley (1002); the top end of the horizontal wheel seat (1001) is connected with an annular rotary slide rail (8); and/or

The device also comprises a slewing mechanism (11); the slewing mechanism (11) comprises a slewing motor (1101) and a large gear ring (1102); the inner ring of the large gear ring (1102) is fixed on the outer wall of the rotary kiln (1), and the outer ring of the large gear ring (1102) is meshed and connected with a transmission gear of the rotary motor (1101).

23. The apparatus of claim 22, wherein: the device further comprises a conductivity detection means (12); the conductivity detection device (12) comprises a detection coil (1201) and a magnetic core (1202); the detection coil (1201) is connected with a magnetic conduction core (1202), and the magnetic conduction core (1202) is arranged on the kiln body of the rotary kiln (1);

preferably, the magnetic conduction core (1202) is arranged in the side wall of the rotary kiln body of the rotary kiln (1), and the distance between the tail end of the magnetic conduction core (1202) and the inner wall of the rotary kiln (1) is 0.5-20mm, preferably 1-15mm, and more preferably 2-10mm.