CN114107582A

CN114107582A - Modified steel slag, preparation method and application in non-blast furnace direct reduction process

Info

Publication number: CN114107582A
Application number: CN202111405811.6A
Authority: CN
Inventors: 梁晓杰; 常景彩; 王鹏; 王勇; 刘衍卉; 马春元; 李蜀生
Original assignee: Qingdao Xiangtai Caineng Technology Co ltd; Shandong University
Current assignee: Qingdao Xiangtai Caineng Technology Co ltd; Shandong University
Priority date: 2021-11-24
Filing date: 2021-11-24
Publication date: 2022-03-01
Anticipated expiration: 2041-11-24
Also published as: CN114107582B

Abstract

The invention belongs to the technical field of metallurgical solid waste resource utilization, and particularly relates to modified steel slag, a preparation method and application thereof in a non-blast furnace direct reduction process. On the basis of the existing air-quenched steel slag treatment process, the invention introduces oxygen-enriched atmosphere adjustment and indirect carbonation technology to realize mineral transformation of iron phase components in the steel slag and effective separation of Ca, P and Fe. The price of the steel slag is 350 yuan/ton if the iron in the steel slag is enriched to 35% according to the ton price of the low-grade iron ore of 10 yuan, the price of the steel slag is 40 yuan/ton (including transportation cost), the yield of each ton of the steel slag is 350 multiplied by 0.68-40 to 198 yuan/ton if 0.68 ton of low-grade iron-rich material is produced according to 1 ton of steel slag, and the created benefit can reach 198 yuan/year if the steel slag is produced according to 1 hundred million tons per year in China.

Description

Modified steel slag, preparation method and application in non-blast furnace direct reduction process

Technical Field

The invention belongs to the technical field of metallurgical solid waste resource utilization, and particularly relates to modified steel slag, a preparation method and application in a non-blast furnace direct reduction process.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

At present, the utilization rate of the steel slag is less than 30 percent, the main utilization direction is in the field of building materials, and the utilization rate is limited by f-CaO and f-MgO in the steel slag. The steel slag has TFe content of about 25%, FeO content of about 20% and CaO content of 41%, so that it has certain iron recovering, carbon fixing and desulfurizing performance, but the steel slag has harmful element P in 3-5% dissolved and FeO reducing difficulty higher than that of Fe₂O₃The silicate phase formed by CaO is generated at high temperature, the crystal growth is complete, the reaction activity is low and the like, thereby limiting the application of the silicate phase in the metallurgical or environmental protection field. For example, the prior art provides a method for preparing a low-cost cementing material from oxygen bubbling liquid steel slag and a method for obtaining the low-cost cementing material, which can utilize the steel slag, but needs to add a siliceous regulator and an aluminum regulator to increase the gelling property of the steel slag, has complex treatment process and higher cost, and cannot solve the problems that the content of P in the steel slag is high and the steel slag cannot be recycled in a metallurgical process.

Therefore, there is a need for a technique for effectively separating Ca, P and Fe elements from steel slag and fully utilizing the separated steel slag product.

Disclosure of Invention

Aiming at the problems in the prior art, the invention aims to provide a modified steel slag, a preparation method and application in a non-blast furnace direct reduction process, on the basis of the existing air quenching steel slag treatment process, oxygen-enriched atmosphere regulation and indirect carbonation technology are introduced to realize mineral transformation of iron phase components in the steel slag and effective separation of Ca, P and Fe, and the modified steel slag can be directly applied to the non-blast furnace direct reduction process, has good reaction activity and realizes recovery of high-value iron.

In order to solve the technical problems, the technical scheme of the invention is as follows:

the first aspect of the invention provides a preparation method of modified steel slag, which comprises the following steps: the steel slag is granulated by air quenching in the oxygen-rich atmosphere to convert FeO into Fe₂O₃And then, Ca and P in the steel slag are separated out by adopting a carbonation technology to obtain the modified steel slag.

The second aspect of the invention provides a modified steel slag obtained by the method.

The third aspect of the invention provides an application of the modified steel slag in a non-blast furnace direct reduction process, and the specific application is a reduction ingredient.

One or more embodiments of the present invention have at least the following advantageous effects:

around the difficulty of restricting the comprehensive utilization of a large amount of steel slag and the national aim of 'double carbon', after the steel slag is treated by the process technology, the effective separation of Ca, P and Fe elements in the steel slag can be realized, Ca is used for carbon fixation and desulfurization in tail gas and reducing carbon emission, and Fe is purified and enriched and then used for non-blast furnace direct reduction, so that the maximum utilization of the value of the steel slag is realized, and the process accords with the circular economy development concept of carbon reduction and emission reduction in China, the dependence on foreign iron ores is reduced, and waste is changed into wealth.

The price of the steel slag is 350 yuan/ton if the iron in the steel slag is enriched to 35% according to the ton price of the low-grade iron ore of 10 yuan, the price of the steel slag is 40 yuan/ton (including transportation cost), the yield of each ton of the steel slag is 350 multiplied by 0.68-40 to 198 yuan/ton if 0.68 ton of low-grade iron-rich material is produced according to 1 ton of steel slag, and the created benefit can reach 198 yuan/year if the steel slag is produced according to 1 hundred million tons per year in China.

The whole process of the process technology has no wastewater, solid waste and the like, and the application of the steel slag in the non-blast furnace direct reduction process is realized.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a schematic flow chart of a preparation method and application of the modified steel slag provided by the invention;

the device comprises an air source 1, an air source 2, high-pressure wind power 3, an oxygen-enriched adjusting valve 4, an oxygen-enriched quick-cutting valve 5, an oxygen-enriched pipeline air source 6, a wind quenching reaction chamber 7, steel slag with the average particle size of 2mm, a separation chamber 8, Ca and Fe, a 9, a plate-and-frame filter press 10, solid particles with the TFe of more than or equal to 35 percent, 11, a batching scale 12, a mixer 13, a disk pelletizer or high-pressure ball pelletizer 14, a dryer 15, a distributor 16, a rotary hearth furnace or rotary kiln 17, a metallized pellet 18, a dust settling chamber 19, a waste heat recovery system 20, a dust removal system 21, and Ca-enriched air ²⁺22, chimney, 23, vacuum filter, 24, CaCO₃Etc., 25, acetic acid-rich solution, 26, extraction reaction system, 27, extractant (tributyl phosphate), 28, distillation separation system, 29, acetic acid, 30, water.

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

As described in the background art, about 3-5% of harmful element P is dissolved in steel slag, and the reduction of FeO is more difficult than that of Fe₂O₃The silicate phase formed by CaO is generated at high temperature, the crystal growth is complete, the reaction activity is low and the like, and the use of the silicate phase in the field of metallurgy or environmental protection is limited.

In order to solve the above technical problems, a first aspect of the present invention provides a method for preparing modified steel slag, which specifically comprises: the steel slag is granulated by air quenching in the oxygen-rich atmosphere to convert FeO into Fe₂O₃And then, Ca and P in the steel slag are separated out by adopting a carbonation technology to obtain the modified steel slag.

In the wind quenching granulation process, oxygen enrichment is introduced, the transformation of iron oxide mineral phases in the steel slag in the wind quenching process is adjusted, and a large amount of FeO is transformed into Fe₂O₃Is beneficial to the direct reduction reaction of the steel slag and a non-blast furnace.

Extracting Ca from the steel slag after being modified by wind quenching by acetic acid²⁺After the Fe element is concentrated and purified, the Fe element is used in the non-blast furnace direct reduction process ingredients to play a role of a skeleton, so that the green ball strength is improved, and the metallization rate is favorably improved. Simultaneously extracted Ca-rich²⁺The solution P is used as a carbon fixing agent and a desulfurizing agent of a non-blast furnace direct reduction process, and the emission of carbon and sulfur in the production process is reduced.

In one or more embodiments of the invention, the air quenching is mainly performed by using air, and meanwhile, an oxygen-enriched pipeline is connected to a main air pipeline, and is provided with an oxygen-enriched regulating valve and an oxygen-enriched quick-cutting valve for regulating the safety in the oxygen-enriched quantity and oxygen-enriched process;

furthermore, the oxygen enrichment rate is 1% -3%, namely O in the air quenching atmosphere is controlled₂The concentration of (A) is 22-24%;

further, O₂After being mixed with air, the mixture is pressurized to 0.5 to 0.6MPa by a high pressure fan and is used as an air source for air quenching of the steel slag.

In the inventionIn one or more embodiments, the steel slag is air-quenched in the air-quenching reaction chamber, and the safety interlock is arranged in the air-quenching reaction chamber and used for monitoring and ensuring the safe operation of the oxygen-enriched air quenching. Wherein the temperature, O, in the reaction chamber is mainly monitored₂Content and pressure, etc.

Is rich in O₂After the air quenching, the FeO content in the steel slag is converted into Fe with the content of more than 90 percent₂O₃And is beneficial to the reduction of iron oxide in the subsequent direct reduction process.

The reaction equation is:

4FeO+O₂→2Fe₂O₃

further, the carbonation process specifically comprises: placing the steel slag after air quenching modification in a Ca and Fe separation chamber, adjusting the concentration of acetic acid to be 15%, controlling the pH value of liquid to be 5.5-6, and controlling the liquid-solid ratio to be 15: 1-25: 1, controlling the reaction temperature at 25-100 ℃, and continuously stirring for 60-90 min to realize the separation of Ca, P and Fe in the steel slag to obtain the steel slag rich in Ca²⁺P solution and Fe-rich modified steel slag.

The reaction equation is as follows:

CaSiO₃+2CH₃COOH→Ca²⁺+2CH₃COO^-1+SiO₂+H₂O (1)

ca and P in steel slag are mainly concentrated in silicic acid phase (CaSiO)₃) And Fe is mainly concentrated in RO phase solid solution which is difficult to dissolve in weak acid, therefore, by the technology, more than 80% of Ca and P elements mainly enter the solution, namely 32% of Ca and P elements enter the solution in the steel slag, Fe elements are left in undissolved solid, the TFe content in the undissolved solid can be enriched to more than 35% through calculation, P elements are also separated, and the remained solid can be used in the metallurgical process through the solid-liquid separation of a plate-and-frame filter press.

Because Ca elements are corroded on the surface and inside of the steel slag in a large amount, the surface and inside of the residual steel slag are rough, and an RO phase with higher strength is reserved, so the steel slag can be used in non-blast furnace direct reduction ingredients and can be used as a skeleton material of a green ball, the 'bond strength' between raw materials is increased through a mixer, a disk pelletizer or a ball press, after a dryer is dried, the strength of the green ball is improved, the damage rate of the green ball in the furnace is reduced, the contact area of the raw materials in the green ball with C and CO can be increased, the reaction efficiency of direct reduction is increased, the metallization rate index of a final product metallized pellet is improved, and the produced metallized pellet is mainly used as a cooling agent for converter steelmaking or for blast furnace ironmaking.

The non-blast furnace direct reduction process mainly comprises the following ingredients:

TABLE 1

Proportioning

Modified steel slag

Bag ash of blast furnace

Dust-removing ash for steelmaking

Sintering machine head ash

Gravitational dust removal ash

Bentonite clay

Percentage of

20～35％

15～25％

10～20％

5～15％

5～10％

Table 2 the control indexes are:

index (I)	Green strength of ball	Amount of C to be added	C/O ratio	Metallization rate	Removing rate of harmful elements such as Zn
						Standard of merit	The number of 0.5m dropping times is more than or equal to 10	12％-14％	0.8-0.9	≥70％	≥85％

Further, the carbonation process is rich in Ca²⁺The solution of P is used as a carbon-fixing and desulfurizing agent for treating the flue gas of the non-blast furnace direct reduction process, and is used for treating the flue gas of the non-blast furnace direct reduction process.

Wherein, Ca is mainly contained²⁺With CO in the flue gas₂And SO₂Reaction to form CaCO₃And CaSO₄·2H₂And separating solid and liquid from the O slurry through a vacuum suction filter, wherein the solid is used as a raw material for producing cement, and the liquid is rich in acetic acid components according to the ratio of acetic acid: molar amount of tributyl phosphate 1:1, adding and extracting, separating mixed liquor of acetic acid and tributyl phosphate from the wastewater, and recycling the wastewater in a Ca and Fe separation chamber. And (3) introducing the mixed solution of acetic acid and tributyl phosphate into a distillation separation system, wherein according to different boiling points, the boiling point of acetic acid is 117.9 ℃, the boiling point of tributyl phosphate is 288.28 ℃, and distilling and separating the acetic acid and the tributyl phosphate for recycling.

Wherein, the extraction and distillation process of the organic solvent tributyl phosphate is used to realize the recycling of acetic acid and water and effectively reduce the treatment cost of the process.

By using the treatment method, smoke plume possibly appears in the discharged smoke, so that the system independently leads out the smoke with the temperature of about 150-180 ℃ from the dedusted smoke, and the smoke is mixed with the carbon-fixing and desulfurized smoke to be heated, thereby eliminating the smoke plume.

The reaction formula is as follows to produce CaCO₃And CaSO₄·2H₂O precipitates, promoting the reaction to the right:

Ca²⁺+2CH₃COO^-1+CO₂+H₂O→CaCO₃↓+2CH₃COOH (2)

Ca²⁺+2CH₃COO^-1+SO₂+O₂+2H₂O→CaSO₄·2H₂O↓+2CH₃COOH (3)

in order to make the technical solutions of the present invention more clearly understood by those skilled in the art, the technical solutions of the present invention will be described in detail below with reference to specific embodiments.

Example 1

A preparation method of modified steel slag comprises the following steps: air is used as a main gas source, 1 to 3 percent of rich oxygen is doped outside a pipeline, and the O-containing gas used in the gas source of the air-quenched liquid steel slag₂The amount reaches 22 to 24 percent, the pressure of an air source for air quenching is 0.5 to 1MPa according to the technological parameters of the air-quenched steel slag, and the outlet of the nozzleThe wind speed is more than or equal to 400m/s, and the slag gas consumption per ton is 1500m³～3000m³The liquid steel slag is made into steel slag particles with the average particle size of 2mm in a wind quenching reaction chamber, the steel slag particles enter a Ca and Fe separation chamber, Ca and Fe in the steel slag are separated after treatment, and the mixture is subjected to solid-liquid separation by a plate-and-frame filter press to obtain the mixture rich in Ca²⁺The solution of P and solid particles with TFe more than or equal to 35 percent, and the part of the solid particles rich in iron is the modified steel slag.

Example 2

The application of the modified steel slag in the non-blast furnace direct reduction process in the embodiment 1 is as follows:

after being measured by a batching scale, the modified steel slag and other raw materials are conveyed into a mixer together according to the proportion (25 percent of modified steel slag, 30 percent of blast furnace cloth bag ash, 20 percent of steelmaking dust removal ash, 10 percent of sintering machine head ash, 10 percent of gravity dust removal ash and 5 percent of bentonite) in table 1 to realize the uniform mixing of the raw materials, and then the mixture enters a disc pelletizer or a high-pressure pellet press to prepare various mixtures into spherical particles with uniform components, and then the spherical particles are dried to remove moisture, conveyed by a distributing machine to enter a rotary hearth furnace or a rotary kiln to produce metallized pellets, flue gas enters a dust settling chamber to be subjected to primary gravity dust removal, then enters a waste heat recovery system to produce steam, and after being further cooled, the flue gas enters a dust removal system to collect particulate matters in the flue gas, the flue gas enters the prepared Ca-rich pellet mill²⁺In the solution of P, the carbon fixation and the desulfurization are carried out, and the reduction of CO in the flue gas is realized₂And SO₂And (4) discharging. Rich in Ca²⁺After the solution of P reacts with the flue gas, the reaction product enters a vacuum suction filter to separate CaCO₃And (3) adding the liquid rich in acetic acid into an extraction system, adding tributyl phosphate into the extraction system for extraction, then adding the extracted liquid into a distillation separation system, heating and separating the acetic acid and the tributyl phosphate by using steam according to the boiling point of the acetic acid of 117.9 ℃ and the boiling point of the tributyl phosphate of 288.28 ℃, and continuously recycling the separated water.

Example 3

after being measured by a batching scale, the modified steel slag and other raw materials are conveyed into a mixer together according to the proportion (35 percent of modified steel slag, 25 percent of blast furnace cloth bag ash, 15 percent of steelmaking dedusting ash, 10 percent of sintering machine head ash, 10 percent of gravity dedusting ash and 5 percent of bentonite) in table 1 to realize the uniform mixing of the raw materials, and then the mixture enters a disc pelletizer or a high-pressure pellet press to prepare various mixtures into spherical particles with uniform components, and then the spherical particles are dried to remove moisture, conveyed by a distributing machine to enter a rotary hearth furnace or a rotary kiln to produce metallized pellets, flue gas enters a dust settling chamber to be subjected to primary gravity dedusting, then enters a waste heat recovery system to produce steam, enters a dedusting system after being further cooled to collect the particulate matters in the flue gas, and then enters the prepared Ca-rich pellet mill²⁺In the solution of P, the carbon fixation and the desulfurization are carried out, and the reduction of CO in the flue gas is realized₂And SO₂And (4) discharging. Rich in Ca²⁺After the solution of P reacts with the flue gas, the reaction product enters a vacuum suction filter to separate CaCO₃And (3) adding the liquid rich in acetic acid into an extraction system, adding tributyl phosphate into the extraction system for extraction, then adding the extracted liquid into a distillation separation system, heating and separating the acetic acid and the tributyl phosphate by using steam according to the boiling point of the acetic acid of 117.9 ℃ and the boiling point of the tributyl phosphate of 288.28 ℃, and continuously recycling the separated water.

The following detailed description of the preparation method and the application of the modified steel slag is made with reference to fig. 1:

(1) the liquid steel slag enters a wind quenching reaction chamber 6, and the air after oxygen enrichment and pressurization is used as an air source 2 to prepare steel slag particles 7 with the average particle size of 2 mm.

(2) Steel slag particles 7 with the average particle size of 2mm enter a Ca and Fe separation chamber 8 through conveying equipment such as a conveying belt, circulating water and acetic acid are added into the separation chamber, the concentration of the acetic acid required by the reaction is adjusted, a stirrer in the separation chamber is started, and the reaction is carried out according to the set reaction time, so that a solid-liquid mixture is obtained.

(3) The solid-liquid mixture is sent into a plate-and-frame filter press 9 by conveying equipment such as a slurry pump and the like to realize the separation of solid and liquid and obtain the Ca-rich mixture²⁺Solution 21 and solid particles with TFe more than or equal to 35 percent10。

(4) Solid particles 10 with TFe more than or equal to 35 percent are metered by a batching scale 11, are sent into a mixer 12 with various raw materials to be uniformly mixed, are sent into a disc pelletizer or a high-pressure ball press 13 to be pelletized and then are molded, are sent into a dryer 14 to remove moisture, enter a distributing machine 15, are sent into a rotary hearth furnace or a rotary kiln 16 after being uniformly fed, are subjected to high-temperature direct reduction reaction in the furnace kiln to produce metallized pellet products 17, and the produced high-temperature flue gas is subjected to waste heat recovery and dust removal through 18, 19 and 20, and is introduced with Ca-rich gas²⁺And the P solution is subjected to carbon fixation and desulfurization reactions, and high-temperature flue gas discharged by a dust removal system needs to be introduced into an external chimney to heat the mixed flue gas and avoid the generation of smoke plume.

(5) Rich in Ca²⁺After the P solution is subjected to carbon fixation and desulfurization reactions, a suspension containing solids is generated and sent into a vacuum suction filter 23 to realize solid-liquid separation, and 24 solid CaCO is obtained₃And 25 acetic acid-rich liquid, which portion enters extraction system 26, and tributyl phosphate: the acetic acid 1:1 is subjected to extraction reaction, the extracted mixed solvent enters a distillation separation system 28, distillation separation is carried out according to the different boiling points of the acetic acid and the tributyl phosphate, and the separated acetic acid 29, the tributyl phosphate 27 and the water 30 are recycled.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of modified steel slag is characterized in thatIn the following steps: the steel slag is granulated by air quenching in the oxygen-rich atmosphere to convert FeO into Fe₂O₃And then, Ca and P in the steel slag are separated out by adopting a carbonation technology to obtain the modified steel slag.

2. The method of claim 1, wherein: the air source of the air quenching is mainly air, and meanwhile, an oxygen-enriched pipeline is connected to the main air pipeline and is provided with an oxygen-enriched adjusting valve and an oxygen-enriched quick-cutting valve for adjusting the oxygen-enriched amount and the safety in the oxygen-enriched process;

preferably, the oxygen enrichment rate is 1% -3%, namely O in the air quenching atmosphere is controlled₂The concentration of (A) is 22-24%.

3. The method of claim 2, wherein: after mixing oxygen and air, pressurizing to 0.5-0.6MPa by a high-pressure fan, and using the mixture as an air source for air quenching the steel slag.

4. The method of claim 1, wherein: the steel slag is air quenched in the air quenching reaction chamber, and the safety interlock is arranged in the air quenching reaction chamber and used for monitoring and ensuring the safe operation of oxygen-enriched air quenching.

5. The method of claim 1, wherein: the carbonation process specifically comprises the following steps: placing the steel slag after air quenching modification in a Ca and Fe separation chamber, adjusting the concentration of acetic acid to be 15%, controlling the pH value of liquid to be 5.5-6, and controlling the liquid-solid ratio to be 15: 1-25: 1, controlling the reaction temperature at 25-100 ℃, and continuously stirring for 60-90 min to realize the separation of Ca, P and Fe in the steel slag to obtain the steel slag rich in Ca²⁺P solution and Fe-rich modified steel slag.

6. Modified steel slag obtained by the process according to any one of claims 1 to 6.

7. The use of the modified steel slag of claim 6 in a non-blast furnace direct reduction process, wherein: the concrete application is reducing ingredients.

8. The use of claim 7, wherein: the carbonation process is rich in Ca²⁺The solution of P is used as a carbon-fixing and desulfurizing agent for treating the flue gas of the non-blast furnace direct reduction process, and is used for treating the flue gas of the non-blast furnace direct reduction process.

After the flue gas is treated, solid and liquid are separated through a vacuum suction filter, wherein the solid is used as a raw material for producing cement, and the liquid is rich in acetic acid components according to the ratio of acetic acid: molar amount of tributyl phosphate 1:1, adding and extracting, separating mixed liquor of acetic acid and tributyl phosphate from the wastewater, and recycling the wastewater in a Ca and Fe separation chamber.

9. The use of claim 8, wherein: and (3) the mixed solution of acetic acid and tributyl phosphate enters a distillation separation system, and acetic acid and tributyl phosphate are separated by distillation and recycled.

10. The use of claim 9, wherein: the flue gas with the temperature of about 150-180 ℃ is led out from the flue gas after dust removal, and is mixed with the flue gas after carbon fixation and desulfurization to be heated, so that the smoke plume is eliminated.