CN100519768C - Shaft furnace for production of ferrochromium and smelting method thereof - Google Patents

Abstract

A shaft furnace for ferrochrome smelting and a smelting method thereof. The shaft furnace for ferrochrome smelting comprises a shaft furnace body, which forms a smelting space by a furnace shell and refractory materials, and is divided into upper, middle and lower sections; the upper section of the furnace is the furnace body of the heating zone The middle part of the furnace is the bosh, and its side wall has an inclination angle α; the lower part of the furnace is the hearth; the big bell and funnel are set on the top of the furnace body; the hot air surrounding pipe is set on the side of the middle part of the furnace; the tuyere is set under the middle part of the furnace Along; the cooling device is set in the furnace shell of the main body; the slag outlet and the taphole are respectively opened on the hearth side of the lower part of the furnace. Raw materials such as ore and coke are loaded into the furnace through the big bell and funnel, and the hot air is blown into the shaft furnace from the lower part through the hot air surrounding pipe and the tuyere, and the coke is ignited in front of the tuyere; , the ore is heated, melted and reduced. The invention adopts the heat-solidified ferrochrome agglomerate after the shaft furnace type smelting reduction pre-reduction treatment, and the obtained chromium-containing hot metal directly prepares the stainless steel mother liquor.

Description

Shaft furnace for ferrochrome smelting and smelting method

technical field

The invention belongs to ferroalloy smelting technology and equipment, and relates to a melting-reduction ferrochromium smelting device and a smelting technology, which are used for smelting chromium-containing molten iron (stainless steel mother liquor) for stainless steel.

Background technique

The production of stainless steel has developed from a single smelting, refining and alloying in an electric arc furnace to an electric arc furnace-AOD-two-step method (double process). In the 1980s, a new "three-step" stainless steel production process was developed, that is, primary smelting furnace (electric arc furnace or converter)-converter-vacuum refining furnace. The primary refining furnace only plays the role of melting (providing mother liquor), and the vacuum refining furnace is mainly VOD or AOD, and there are also RH OB and RH KTB. At present, the proportion of three-step method is close to 20%.

From the perspective of chromium, there are four main sources of stainless steel mother liquor: (1) scrap steel; (2) solid high-carbon ferrochrome; (3) liquid high-carbon ferrochrome; (4) liquid stainless steel mother liquor.

At present, the vast majority of stainless steel production processes in the world use the method of adding carbon ferrochrome to scrap steel (or molten iron) to obtain stainless steel mother liquor (ie, chromium-containing molten iron). Scrap steel resources are scarce in developing countries, and the stainless steel mother liquor mostly adopts the electric arc furnace mixing method of solid high-carbon ferrochromium + common molten iron (or some scrap steel). This method requires electric energy to re-melt solid high-carbon ferrochrome, which increases production costs. Since high-carbon ferrochrome is produced in a submerged thermal electric furnace, it has problems such as high power consumption, low productivity, and high requirements for chromium ore, and the kinetic conditions for chromium ore reduction are poor, and the recovery rate of chromium is only 78%~ 93.7%. According to statistics, smelting one ton of carbon ferrochrome requires about 1880-2250kg of chrome lump ore, 410-520kg of coke, 85-95kg of silica and 75-85kg of steel shavings, power consumption of 3100-3300kwh, and chromium recovery rate of 92-95%.

The fatal disadvantages of the above process are high energy consumption, high cost, inability to use fine ore resources, and serious environmental pollution.

The practice of smelting chromium-containing pig iron with blast furnaces began in 1880 in the world. However, due to the limited conditions at that time, especially the insufficient hearth temperature, the furnace equipment was seriously damaged, and the fluidity of chromium-containing pig iron and slag was poor, so normal production could not be carried out. .

In this context, it is imminent to study a new ferrochrome production device with low cost and wide use of various resources. The melting-reduction shaft furnace is expected to be one of the ideal methods to solve the above problems. The principle is to combine the smelting reduction of the blast furnace hearth and the rapid heating of the iron furnace, adopt the oxygen-coal intensified smelting technology to achieve high combustion temperature, and send the thermally consolidated ferrochromium agglomerates after pre-reduction treatment into the vertical Furnace smelting treatment, providing ferrochrome alloy mother liquor for short-process steelmaking, thereby improving the competitiveness of steel products.

Chinese patent CN218952Y "metallized pellet reduction shaft furnace" discloses a reduction shaft furnace in which water gas is used as reducing agent and oxidized pellets are used as raw material to smelt metallized pellets. The furnace is in the shape of a "wine urn", and the furnace body is divided into a preheating section, a reduction section, and a cooling section. The furnace body is equipped with a reduction gas inlet, a cooling gas inlet, and an outlet. The furnace body adopts a mechanical stepless variable speed solid iron product discharge mechanism . The shaft furnace is simple in design and convenient in operation, and can obtain solid metal iron products with a high metallization rate. From the technical process and equipment analysis, the shaft furnace is not suitable for smelting chromium-containing molten iron.

The technology disclosed in the Chinese patent CN2273712Y "reduced iron shaft furnace" is also a special shaft furnace for producing sponge iron (solid product) with coal as a reducing agent. It is mainly composed of a combustion chamber, a reduction chamber and a gas circulation system. The reduction chamber is located in the center of the furnace body. There is a combustion chamber on the periphery of the reduction chamber, which is located at the lower part of the flue and is equipped with a fall-off wall in the combustion chamber. The fall-off wall and the combustion chamber are provided with a gas heater. The heater is connected to the gas input pipe entering the reduction chamber. The reduction chamber The output gas is purified and enters the heater for recycling. The shaft furnace can only be used for the production of solid sponge iron.

Contents of the invention

The object of the present invention is to provide a melting-reduction ferrochrome smelting device using pre-reduced ferrochrome pellets as raw material, which is used to smelt chromium-containing hot metal (stainless steel mother liquor) for the production of stainless steel, replacing the traditional submerged electric furnace chromium The iron smelting process reduces the dependence of ferrochrome alloy production on large amounts of electric energy and expensive ferrochrome concentrate resources.

In order to achieve the above object, the technical scheme of the utility model

The main contents of the present invention are a melting-reduction shaft furnace for ferrochrome smelting and a method for using pre-reduced ferrochrome pellets as raw materials to produce chromium-containing hot metal for stainless steel.

In order to overcome the shortage that the traditional submerged arc furnace must use lump ore and electric energy, the technology adopted in the present invention is to use a rotary hearth furnace to make non-lump ore (powder ore or concentrate) into agglomerates and pre-reduction treatment and then send it to the shaft furnace for smelting. The smelting-reduction shaft furnace smelting must meet the qualified requirements for the use of pre-reduction pellets, oxide reduction and chromium-containing hot metal products.

The shaft furnace for ferrochrome smelting of the present invention comprises: the shaft furnace body, which forms a smelting space by the furnace shell and refractory materials, and is divided into upper, middle and lower sections; Similarly, its function is to rapidly heat the charge to 1000-1300°C; pre-reduced ore or mineral agglomerates containing alloying elements are only heated in this area, without reduction, so there is no requirement for the reduction potential of the furnace gas; the middle section of the furnace is for melting —The bosh of the reduction zone has an inclination angle α on the side wall; the lower section of the furnace is the hearth, which is used to hold molten iron, slag and some unreduced minerals to continue reduction here, and some chemical reactions such as desulfurization are also carried out here, and finally Generate qualified alloy hot metal or alloy mother liquor; the big bell and funnel are set on the top of the upper furnace body of the shaft furnace body; the hot air surrounding pipe is set on the side of the middle section of the furnace; the tuyere is set on the lower edge of the middle section of the furnace; the cooling device, It is installed in the furnace shell of the main body; the slag outlet is opened on the hearth side of the lower part of the shaft furnace body, because the amount of ferrochrome smelting slag is very large; the tap hole is opened on the hearth side of the lower part of the shaft furnace body.

Further, the upper furnace shaft of the shaft furnace body is an inverted cone structure.

The inclination angle α of the bosh side wall in the middle section of the shaft furnace body is less than 70°.

The cooling device is a water cooling structure.

The furnace shell of the shaft furnace body is also provided with an insulating and refractory material layer.

The shaft furnace for smelting ferrochrome and the method for smelting ferrochrome of the present invention comprise,

a. Raw materials such as ore and coke are loaded into the upper section of the ferrochrome smelting shaft furnace through the big bell and funnel, and are rapidly heated to 1000-1300 °C by the rising gas;

b. Hot air with a temperature above 1250°C (1250-1350°C) blows into the shaft furnace from the lower part and ignites coke in front of the tuyere; sends oxygen and coal powder into the middle section of the furnace through the tuyere, and injects coal at 300-400kg/t, and the tuyere Oxygen-coal spray gun can blow 5-20% oxygen to ensure rapid and efficient combustion of coal powder; in this area, oxygen, coal powder and coke are burned to produce a temperature as high as 2300-2500 °C, and the pre-reduced ore is rapidly melted, and most of the minerals are in the This reduction results in the formation of primary slag;

c. The lower part of the furnace is a hearth containing molten iron and slag, where some unreduced minerals continue to be reduced, and some chemical reactions such as desulfurization are also carried out here, and finally qualified molten iron or alloy mother liquor is generated;

d. Using pre-reduced thermally consolidated ferrochrome agglomerates, the coke load is low, the direct reduction rate of ferrochrome is higher than 60%, the gas generation is 4000-6000m ³ /t, and the furnace top temperature is as high as 500-700℃.

Raw materials such as ore and coke are loaded into the furnace through the big bell and funnel, and the hot air with a temperature above 1250°C is blown into the shaft furnace from the lower part through the hot air surrounding pipe and the tuyere, and the coke is ignited in front of the tuyere; As the gas rises, the ore is heated, melted and reduced. As a shaft furnace smelting product, the upper slag is discharged from the slag mouth device, the lower slag and alloy molten iron are discharged from the iron hole device, and the shaft furnace gas is discharged from the gas outlet pipe. The cooling device, refractory material and furnace shell can ensure the formation of a fixed smelting space, so that the smelting process can continue.

The advantage of the present invention is that, compared with scrap steel (or molten iron) plus carbon ferrochrome process, under the conditions of the same raw material, energy medium price and the same molten iron quality, the production cost per ton of stainless steel mother liquor in shaft furnace smelting can be reduced by about three At the same time, it saves a large amount of ferrochrome concentrate lump ore resources; and using the gas produced by the shaft furnace and a small amount of coke (or pulverized coal) as the energy medium of the rotary hearth furnace and the shaft furnace can greatly reduce the consumption of electric energy. The melting-reduction shaft furnace can also provide clean gas, which is beneficial to alleviate the contradiction of gas shortage in short-process steelmaking enterprises.

In order to adapt to the use of pre-reduced pellets in ferrochromium smelting, the edge airflow is relatively developed; the coke load is low, the gas generation is large, and the furnace top temperature is high; the height of the refractory zone is reduced, and the root position is moved downward. Properly increase the diameter of the furnace throat, reduce the height of the furnace throat, furnace body and hearth, and appropriately increase the height of the furnace waist and bosh. In addition, a series of measures such as intensive tuyere spacing, enlarging the cooling area of the shaft furnace, and increasing the cooling intensity of the furnace body; and adopting high-grade refractory materials for the furnace bottom and hearth are adopted to adapt to the differences between pig iron blast furnaces and ferrochrome shaft furnaces. .

Table 1. The difference between the blast furnace producing molten iron and the shaft furnace structure and process parameters of the present invention

Structural part Ferrochrome Smelting Shaft Furnace blast furnace for producing molten iron Hot stove The blast temperature at the tuyere is 1250～1350℃ The blast temperature at the tuyere is 1000～1250℃ Gas dust removal device Dry gas dedusting plant with gas cooling equipment Generally wet gas dedusting device Coal injection / oxygen enrichment equipment Due to the high air temperature and blast oxygen enrichment rate, it has a coal injection capacity of 300-400kg/t. Using the tuyere oxygen coal injection gun, it can enrich oxygen by 5-20%. To ensure fast and efficient combustion of pulverized coal Coal injection capacity per ton of iron is generally less than 230kg/t. Generally, oxygen is enriched before and after the blower, and the oxygen enrichment rate is less than 8%. Furnace design Using pre-reduced thermally consolidated ferrochrome agglomerates, the coke load is low, the direct reduction rate of ferrochrome is higher than 60%, and the amount of gas generated is up to Using sinter\oxidized pellets for smelting, the coke load is low, the direct reduction rate is less than 30%, and the gas generation is only

4000-6000m³/t, the furnace top temperature is as high as 500-700℃, and the edge air flow is relatively developed; the height of the reflow zone is low; The bosh height is higher, the bosh angle is less than 68 degrees, and the furnace body angle is greater than 90 degrees, and the furnace body is funnel-shaped. 1000-1500m³/t, the furnace top temperature is only 200-300℃, the diameter of the furnace throat is small, the height of the reflow zone is high, and the furnace shaft is relatively high; the furnace waist and bosh are short, and the furnace bosh The angle is greater than 80 degrees, the angle of the furnace body is less than 82 degrees, and the furnace body is vertical. Furnace Cooling System The furnace bottom and hearth are built with non-carbon high-grade refractory materials, and an insulation layer is provided to expand the cooling area of the shaft furnace and improve the cooling intensity of the furnace body The whole furnace body can be cooled, and the furnace hearth is made of carbonaceous materials and equipped with a water cooling wall Hearth design The hearth is relatively short, and the depth of the dead material layer in the hearth is only designed to be 0.3-0.5 meters to keep the chromium-containing hot metal above 1530°C The hearth is high; the depth of the dead material layer is designed to be 20% of the diameter of the hearth

Beneficial effects of the present invention

Utilize the shaft furnace smelting reduction of the present invention to directly prepare stainless steel mother liquor and have the following advantages:

(1) The production cost is greatly reduced;

(2) High productivity, suitable for large-scale production of chromium-containing hot metal;

(3) The use of chromite raw materials is flexible, especially the cheap chromite powder ore can be processed to make pre-reduced thermally consolidated chromite agglomerates or used after sintering;

(4) The chromium content in the mother liquor is lower than that of the national standard high-carbon ferrochrome, the reduction of chromite ore is easier and the energy consumption is lower;

(5) The comprehensive recovery rate of chromium is high;

(6) It can save a lot of electricity and reduce the cost of stainless steel.

Description of drawings

Fig. 1 is the structural representation of ferrochromium smelting shaft furnace of the present invention;

Fig. 2 is a schematic diagram of the ferrochromium smelting shaft furnace smelting process and its supporting equipment of the present invention.

Detailed ways

Referring to Fig. 1, the shaft furnace for ferrochromium smelting of the present invention comprises, the shaft furnace body 1, which forms a smelting space by the furnace shell and refractory materials, and is divided into upper, middle and lower sections; the upper section 101 of the furnace is the furnace body of the heating zone , the furnace body is an inverted conical structure, the diameter of the furnace throat 104 is large, and the height of the furnace throat and the furnace body is relatively short; the middle section 102 of the furnace is the bosh of the melting-reduction zone, and its side wall has an inclination angle α, which is less than 70°; the lower section 103 of the furnace is the hearth, and the height of the hearth and the bosh is relatively high; the big bell and funnel 2 are arranged on the top of the upper section 101 of the furnace body of the shaft furnace body; the hot air surrounding pipe 3 is arranged on the side of the middle section 12 of the furnace The tuyere 4 is arranged on the lower edge of the furnace middle section 102; the cooling device 5 is arranged in the furnace shell of the shaft furnace body 1, and the cooling device is a water-cooled structure; Side; Taphole 7 is opened on the 103 hearth side of the lower section of the shaft furnace body stove.

After the pre-reduction treatment, heat-consolidated ferrochrome agglomerate ore, coke and other raw materials (see Table 2, Table 3, and Table 4 for composition) are loaded into the furnace through the big bell and funnel 1, and the hot air with a temperature above 1250°C passes through the hot air The surrounding pipe 3 and the tuyeres 4 are blown into the shaft furnace from the lower part and coke is ignited in front of the tuyeres; during the process of the furnace charge falling, the molten droplets falling and the gas rising, the above-mentioned ores are heated, melted and reduced, and the main chemical reaction of the chromium ore is as follows:

Carbothermal reduction of chromium trioxide: Cr ₂ O ₃ +3C=2Cr+3CO;

Reduction of chromium spinel: MgO·Cr ₂ O ₃ +3C=2Cr+MgO+3CO;

The formation of chromium carbide: Cr ₂ O ₃ +13/3C＝2/3Cr ₂ C ₂ +3CO;

Reduction of chromite: 3FeO·Cr ₂ O ₃ +3C=3Fe+Cr ₂ O ₃ +3CO.

As a shaft furnace smelting product, the upper slag is discharged from the slag outlet 6, the lower slag and alloy molten iron are discharged from the iron outlet 7, and the shaft furnace gas is discharged from the gas outlet pipe 8.

Referring to Fig. 2, raw materials and fuels for smelting are sieved and measured through the ore tank facility 11; they are fed into the shaft furnace 14 by the feeding facility 12 in a prescribed order; The ore is heated, melted and reduced; and transported by the hot metal tank car 21 . Among them, the pulverized coal injection device 13 has a coal injection capacity of 400 kg per ton of iron, and uses an oxygen coal spray gun to ensure rapid and efficient combustion of pulverized coal; dust removal facilities 15, gas cooling device 16, cyclone dust removal device 17 and bag dust removal device 18 can reduce the dust content of the final gas to less than 15mg/Nm ³ , which not only protects the atmospheric environment but also improves the quality of the gas; the hot blast stove 19 adopts a spherical structure and a waste heat recovery device, and uses self-produced shaft furnace gas (low heat generation Value 6000～8000KJ/Nm ³ ) can heat the blast temperature to 1250～1300°C; the blast device 20 is equipped with a BBD dehumidification unit, which can reduce the blast humidity to below 10g/Nm ³ .

All the above-mentioned facilities and devices provide the conditions required for the normal production of the shaft furnace through their respective functions, so that the production process of the shaft furnace for smelting 1530°C chromium-containing hot metal (see Table 5 for product composition) can continue.

Table 2. Chemical composition of pre-reduced thermally consolidated ferrochrome pellets (raw material for ferrochrome smelting shaft furnace), %

Stoves temperature/℃ TF TCr P S 1^# 1350 34.90 17.14 0.020 0.230 2^# 1350 31.53 15.49 0.020 0.170 3^# 1350 32.33 15.90 0.018 0.184 4^# 1350 30.62 15.13 0.017 0.172 5^# 1350 35.68 17.29 0.026 0.191

Production conditions: reduction in rotary hearth furnace at 1350°C for 30 minutes.

Table 3. Composition of PCI coal for ferrochromium smelting shaft furnace (industrial analysis), %

coal type H₂O Ash VM C P S Yongcheng 1.78 11.14 9.12 77.96 0.0063 0.205 shrine 6.77 6.18 30.15 56.90 0.0098 0.266 0.4 Shenfu + 0.6 Yongcheng 3.78 9.16 17.53 69.54 0.0089 0.258

Table 4. Industrial analysis of coke for ferrochromium smelting shaft furnace, %

H₂O Ash VM C P S 4.96 10.71 1.01 83.32 0.025 0.525 0 11.27 1.06 87.71 0.026 0.553

Table 5. Composition of chromium-containing hot metal products

Stoves TFe(%) TCr(%) Si(%) P(%) S(%) C(%) Cr/(Cr+Fe) 1^# 64.4 26.5 0.2 <0.03 0.1 7.4 29.15 2^# 65.8 25.4 0.1 <0.01 0.062 7.3 27.85 3^# 61.0 26.5 1.1 <0.02 0.12 7.9 30.29 4^# 62.8 26.3 0.9 <0.02 0.065 7.2 29.52 5^# 68.0 23.8 <0.1 <0.01 0.21 7.1 25.93

The present invention can use shaft furnace type smelting reduction pre-reduction heat-solidified ferrochrome agglomerate for large-scale stainless steel production bases in my country, and the obtained chromium-containing hot metal can directly prepare stainless steel mother liquor, and then go through high-speed converter decarburization→VOD or AOD The establishment of a new stainless steel production process of refining→continuous casting→continuous rolling is of great significance.

Claims (4)

1. a ferrochrome smelting shaft furnace is characterized in that, it comprises,

The shaft furnace body, it forms one by furnace shell, refractory materials and smelts the space, is divided into the upper, middle and lower section; The stove epimere is the shaft of heating zone; The stove stage casing is the bosh of fusing-reduction zone, and its sidewall has a leaning angle α; The stove hypomere is a cupola well;

Great bell and funnel are arranged at the top of shaft furnace body stove top shaft;

Bustle pipe is arranged at stove stage casing one side;

The air port is arranged at lower edge, stove stage casing;

Refrigerating unit is arranged in the body furnace shell;

Slag notch is opened in shaft furnace body stove hypomere cupola well one side;

Iron notch is opened in shaft furnace body stove hypomere cupola well one side;

Described shaft furnace body stove epimere shaft is an inverted cone-shaped structure.

2. ferrochrome smelting shaft furnace as claimed in claim 1 is characterized in that, the leaning angle α of described shaft furnace body stove stage casing bosh sidewall is less than 70 °.

3. ferrochrome smelting shaft furnace as claimed in claim 1 is characterized in that, described refrigerating unit is a water-cooling structure.

4. ferrochrome smelting shaft furnace as claimed in claim 1 is characterized in that, also is provided with the insulation layer of anti-the material in the described shaft furnace body furnace shell.

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