Method for comprehensively treating zinc-containing sulfuric acid slag and blast furnace cloth bag ash

Abstract

The invention discloses a method for comprehensively treating zinc-containing sulfuric acid slag and blast furnace cloth bag ash, which comprises the following steps of: uniformly mixing the zinc-containing sulfuric acid slag, the blast furnace cloth bag ash, a calcium additive and a carbonaceous reducing agent according to the weight ratio of 10: (3-5): (2.5-4): (1.5-3); smoke dust generated by roasting is subjected to oxidation dust removal, cooling separation and desulfurization treatment, and zinc-containing oxide, sulfuric acid and sulfite are obtained; and cooling the roasted material with water, crushing and grinding, and sequentially carrying out high-intensity magnetic separation and low-intensity magnetic separation to obtain high-valued reduced iron powder. The final iron grade can reach 95% or above, and the content of sulfur and zinc is lower than 0.1%. According to the method, the industrial solid waste sulfuric acid slag and the blast furnace cloth bag ash can be converted into the high-valued reduced iron powder, comprehensive recycling of resources is achieved, and environmental and soil pollution caused by stacking is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of comprehensive utilization of solid wastes, and in particular to a method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash. Background Art

[0002] Sulfuric acid slag is an industrial solid waste generated when sulfuric acid is produced using pyrite as raw material, in which the TFe content reaches more than 50%. At present, the main methods for disposing sulphuric acid slag include sorting iron concentrate, making cement admixtures, bricklaying and iron-based pigments, etc. In addition, most of the sulphuric acid slag is not treated and is stored or landfilled, which not only occupies land, but also pollutes and damages the soil and environment.

[0003] The iron grade in sulfuric acid slag is relatively high. Most steel companies in my country often use 5-10% sulfuric acid slag instead of iron ore powder for ironmaking. In addition, sulfuric acid slag can also be prepared into iron concentrate for pelletizing and sintering through mineral processing. However, due to the mutual wrapping and embedding of various minerals in sulfuric acid slag, it is difficult to achieve the ideal index of iron recovered by traditional mineral processing methods such as magnetic separation and flotation. At the same time, the iron loss is large and the sulfur content in the product is high, which limits its use in the ironmaking process. For zinc-containing sulfuric acid slag, due to the high zinc and sulfur content, it is difficult to remove the zinc and sulfur elements by conventional mineral processing and acid leaching and alkali leaching methods.

[0004] At present, the most researched method is to use pyrometallurgical process to recover iron from sulphuric acid slag. Patent application CN113122703A discloses "device and method for integrated treatment of sulphuric acid slag dearsenicization, dezincification and reduction roasting". It uses a microwave reduction roasting furnace to reduce and roast sulphuric acid slag, which has obvious dearsenic and zinc removal effects, but the final iron grade is only about 80%, which is relatively low; Patent application CN111809041A discloses "a method for preparing high-grade iron concentrate using sulphuric acid slag". It uses calcination and magnetic separation to treat sulphuric acid slag, and the final iron grade is relatively low, only more than 60%; Patent application CN102796839A discloses "a process for simultaneous desulfurization of direct reduced iron produced by reduction roasting of sulphuric acid slag". By adding sodium carbonate and calcium carbonate mixed desulfurizer and reducing agent, high-grade direct reduced iron powder is obtained through high-temperature roasting and magnetic separation. The iron grade reaches 90%, and the sulfur removal rate reaches more than 96%, among which the use of The cost of sodium carbonate is high and alkali metal will be introduced into the final product, affecting the quality of the final product; Patent application CN112080635A discloses "a method for preparing iron concentrate from biomass-based self-reduction of sulfate slag", in which sulfate slag, biomass carbon and binder are mixed and pressed into blocks, and directly reduced under nitrogen protection to finally obtain high-purity direct-reduced iron powder. This process requires a protective gas atmosphere, has high requirements on equipment and process, and is difficult to achieve industrial application; Patent application CN102925612A discloses "a method for extracting sponge iron from sulfate slag using tunnel kiln reduction roasting", in which sulfate slag raw material, reducing agent and desulfurizer are mixed, and the mixed raw material is pressed into hollow bricks and placed in a tunnel kiln for reduction roasting. This process adds excessive reducing agent, which significantly increases the processing cost. At the same time, this process does not treat the smoke generated during the roasting process, and the smoke generated during the roasting process will cause secondary pollution to the environment.

[0005] In addition to the above patents, patent application CN103088203B discloses a "method for producing iron concentrate using sulfuric acid slag"; patent application CN118127317A discloses a "method for preparing iron-rich pellets using sulfuric acid slag"; patent application CN106435171A discloses a "method for producing iron concentrate using sulfuric acid slag"; patent application CN106755949A discloses a "method for producing high-purity iron concentrate using sulfuric acid slag" etc. are all based on the recovery and utilization of iron in sulfuric acid slag. Although these patent applications can achieve the recovery of iron, they are prone to cause large iron losses during the processing process, and the final iron grade is not high, and the high-value utilization of the product cannot be achieved. In addition, the equipment and operation requirements are high, making it difficult to achieve industrial application.

[0006] Blast furnace ash is a high-temperature mixture of iron ore powder, coke, limestone and other iron-making raw materials. It is obtained by collecting dry ash from blast furnace gas. The main components are carbon and iron oxide, accounting for 60-70% in total. In addition, it also contains some harmful elements to blast furnace smelting, including 5-10% zinc and 2-5% chlorine. At present, the main treatment methods of blast furnace ash are refining zinc oxide, separating carbon, iron and zinc, direct roasting and landfilling. Among them, the energy consumption in the process of refining zinc oxide is large and the iron in the blast furnace ash is not effectively utilized; the product obtained by separating carbon, iron and zinc is of low value, and the high-value utilization of blast furnace ash cannot be realized; direct roasting is only for obtaining building materials and the effective utilization of blast furnace ash cannot be realized; direct landfilling will pollute the environment and soil and occupy a large amount of land. Therefore, combining the characteristics of slag roasting and blast furnace ash, relevant processes are formulated to treat zinc-containing slag and blast furnace ash, effectively separate the harmful elements therein, recycle the valuable element iron, and prepare high value-added reduced iron powder, thereby achieving the purpose of comprehensive recovery of slag and blast furnace ash, which has important economic and environmental value. Summary of the invention

[0007] The purpose of the present invention is to solve the problems that the current treatment effect of zinc-containing sulfate slag and blast furnace bag ash is poor, the product added value is low, and large-scale utilization cannot be achieved. The method can achieve the purpose of efficiently removing zinc and sulfur from sulfate slag and blast furnace bag ash, and can recycle the iron element in the zinc-containing sulfate slag and blast furnace bag ash to obtain high-value reduced iron powder, thereby achieving high-value utilization of zinc-containing sulfate slag and blast furnace bag ash, reducing environmental pollution, and being able to process zinc-containing sulfate slag and blast furnace bag ash on a large scale.

[0008] In order to achieve the above object, the present invention provides a method for comprehensively treating zinc-containing sulfate slag and blast furnace bag ash, the method comprising the following steps: (1) mixing zinc-containing sulfate slag, blast furnace bag ash, calcium additive, and carbonaceous reducing agent in a weight ratio of 10:3-5:2.5-4:1.5-3; (2) subjecting the fully mixed materials of step (1) to high temperature roasting, and subjecting the smoke generated during the roasting process to oxidation dust removal, cooling separation and desulfurization processes to obtain zinc oxide, sulfuric acid and sulfite; The high temperature environment during the roasting process volatilizes the zinc and sulfur in the zinc-containing sulfate slag and blast furnace bag ash into smoke, and forms zinc oxides and sulfur oxides through oxidation. In the subsequent cooling process, the zinc oxides condense and solidify to form particle deposits, and the sulfur oxides form sulfuric acid and sulfites through the desulfurization process. The carbon powder in the blast furnace bag ash acts as a carbonaceous reducing agent, and reduces the iron oxides in the sulfate slag and blast furnace bag ash to metallic iron during the high-temperature roasting process, thereby reducing the addition of carbonaceous reducing agents.

[0009] (3) introducing the material calcined in step (2) into a cooling pool for water cooling, and crushing and grinding the slag after water cooling; (4) The slag material after crushing and grinding in step (3) is subjected to strong magnetic separation to separate the iron-containing phase, and then the separated iron-containing phase is subjected to a weak magnetic separation process to obtain high-value reduced iron powder.

[0010] Preferably, the calcium additive is limestone or dolomite; The carbonaceous reducing agent is coke powder, lignite or blue charcoal; The calcination temperature is 1200-1300°C, and the calcination time is 0.5-3 h; The zinc-containing sulfate slag, blast furnace bag ash, calcium additive, and carbonaceous reducing agent are in a weight ratio of 10:4:3:2.5; The oxidation dust removal in step (2) is to oxidize the zinc in the high-temperature smoke into zinc oxide and zinc suboxide, and at the same time remove dust to reduce the dust content in the flue gas; The cooling separation is to condense the zinc oxide and zinc suboxide in the flue gas and separate them from the sulfur oxides, and the cooling temperature is below 850°C; The desulfurization is to remove sulfur oxides in the tail gas by desulfurization equipment to form sulfuric acid and sulfite.

[0011] In the step (3), the slag is ground to a particle size of 95 to 98% below 75 μm; The magnetic field strength of the strong magnetic separation is 160~210KA / m, and the magnetic field strength of the weak magnetic separation is 80~120KA / m; The sulfuric acid slag is the waste residue discharged from the pyrite acid production process; The blast furnace bag ash is dust removal ash generated during the blast furnace production process of a steel enterprise.

[0012] More preferably, the chemical composition of the sulfate slag contains 55~65% TFe, 8~12% SiO2, 1~7% Al2O3, 1~5% MgO, 0.2~1.5% Zn, 0.5~1.5% S; the chemical composition of the blast furnace bag ash contains 30~40% TFe, 5~8%SiO2, 4~6% CaO, 2~5% Al2O3, 3~5% Zn, 18~25% C.

[0013] In the step (2), the fuel used in the roasting process is natural gas, blast furnace gas or heavy oil.

[0014] In the step (2) and the step (4), the dust ash obtained by the oxidation dust removal and the tailings obtained by the strong magnetic separation and the weak magnetic separation can be used as roadbed and building materials.

[0015] The present invention provides a method for comprehensively treating zinc-containing sulfate slag and blast furnace bag ash, and the beneficial effects of the present invention include: The method for comprehensively treating zinc-containing sulfate slag and blast furnace ash provided by the present invention includes adding blast furnace ash. As solid waste generated in the blast furnace ironmaking process, blast furnace ash contains a large amount of coke powder, which can be used as a reducing agent to reduce iron oxides in the sulfate slag, while other components in the blast furnace ash will not have other effects on the sulfate slag roasting process. By adding blast furnace ash, the use of carbonaceous reducing agents can be reduced, saving energy consumption. In addition, adding blast furnace ash can increase the zinc content in the smoke during the roasting process, thereby increasing the final zinc oxide and secondary zinc oxide grades. Therefore, the method achieves the purpose of converting the two industrial solid wastes, sulfate slag and blast furnace ash, into high-value-added products, and solves the problem of large-scale stacking of sulfate slag and blast furnace ash and waste of resources.

[0016] The present invention performs oxidation dust removal, cooling separation and desulfurization treatment on the smoke generated during the roasting process to achieve the separation of zinc and sulfur during the roasting process, and obtains roasting byproducts containing zinc oxide, sulfuric acid and sulfite; separates the elemental iron in the roasting slag through strong magnetic separation and weak magnetic separation processes to obtain a grade of more than 95%, wherein the sulfur and zinc content is reduced to less than 0.1%. The treatment method is simple, the byproduct products are stable, and high-purity, high-grade, high-value-added reduced iron powder can be obtained, while the iron recovery rate is high and the zinc and sulfur contents are low. The method not only consumes industrial solid waste but also improves economic benefits, but also reduces the pressure of solid waste treatment for enterprises, and has good economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The present invention provides a process flow chart of the method for comprehensively treating zinc-containing sulfate slag and blast furnace bag ash. DETAILED DESCRIPTION

[0018] The present invention is further illustrated and described below in conjunction with embodiments, but the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the present invention and embodiments, all other inventions and embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0020] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0021] Example 1: A method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash The sulfuric acid slag used in this embodiment is the slag discharged after pyrite acid production, and the blast furnace bag ash used is the dust ash produced in the blast furnace production process, and the chemical composition is shown in Table 1; in this embodiment, coke powder (with a fixed carbon content of >85% and a volatile matter of 10%) is selected as the carbonaceous reducing agent, and the calcium additive used is limestone.

[0022] Table 1 Main chemical components of sulfuric acid slag and blast furnace bag ash used in Example 1 (wt.%)

[0023] like Figure 1 As shown, the specific implementation steps of the method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash are as follows: (1) fully mix zinc-containing sulfate slag, blast furnace bag ash, limestone and coke powder in a weight ratio of 10:4:3:2.5; (2) The mixed material in step (1) is subjected to high temperature roasting at a temperature of 1250° C. for a roasting time of 1 hour, and the smoke generated during the roasting process is subjected to oxidation and dust removal, and the zinc in the high-temperature smoke is oxidized into zinc oxide and zinc suboxide, and the dust content in the flue gas is reduced by dust removal equipment; the zinc oxide and zinc suboxide in the flue gas are then condensed at 750° C. to separate them from sulfur oxides; and the sulfur oxides in the tail gas are removed by a desulfurization absorption tower to form sulfuric acid and sulfite; (3) The material calcined in step (2) is directly poured into a cooling pool for cooling, the water-cooled material is introduced into a crusher for crushing, and the crushed material is ground until the particle size is less than 75 μm, accounting for 96%; (4) The slag after crushing and grinding in step (3) is magnetically separated from the iron-containing phase on a magnetic separator with a magnetic field strength of 210KA / m, and then the separated iron-containing phase is magnetically separated on a weak magnetic separator with a magnetic field strength of 100kA / m to obtain high-value reduced iron powder.

[0024] The final reduced iron powder after treatment by this process has an iron grade of 97%, a mesh size of less than 200 meshes, a S content of 0.06%, a Zn content of 0.09%, a sulfur removal rate of 92%, and a zinc removal rate of 80%, and has a high economic value.

[0025] Example 2: A method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash The sulfuric acid slag used in this embodiment is the slag discharged after the pyrite acid is made, and the blast furnace bag ash used is the dust ash produced in the blast furnace production process, and the chemical composition is shown in Table 2; in this embodiment, blue charcoal (wherein the fixed carbon content is> 80%) is selected as the carbonaceous reducing agent, and dolomite is the calcium additive (CaO:MgO=3:2); Table 2 Main chemical components of sulfuric acid slag and blast furnace bag ash used in Example 2 (wt.%)

[0026] like Figure 1 As shown, the specific implementation steps of the method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash are as follows: (1) fully mixing zinc-containing sulfate slag, blast furnace ash, dolomite and semi-coke in a weight ratio of 10:3:2.5:2; (2) The mixed material in step (1) is subjected to high temperature roasting at a roasting temperature of 1300° C. for a roasting time of 0.5 h, and the smoke generated during the roasting process is subjected to oxidation and dust removal, and the zinc in the high-temperature smoke is oxidized into zinc oxide and zinc suboxide, and the dust content in the flue gas is reduced by dust removal equipment; the zinc oxide and zinc suboxide in the flue gas are then condensed at 750° C. to separate them from sulfur oxides; and the sulfur oxides in the tail gas are removed by a desulfurization absorption tower to form sulfuric acid and sulfite; (3) The material calcined in step (2) is directly poured into a cooling pool for cooling, the water-cooled material is introduced into a crusher for crushing, and the crushed material is ground until the particle size is less than 75 μm, accounting for 97%; (4) The slag after crushing and grinding in step (3) is magnetically separated from the iron-containing phase on a magnetic separator with a magnetic field strength of 180kA / m, and then the separated iron-containing phase is magnetically separated on a weak magnetic separator with a magnetic field strength of 90kA / m to obtain high-value reduced iron powder.

[0027] The final reduced iron powder after treatment by this process has an iron grade of 95%, a mesh size of less than 200 meshes, a S content of 0.09%, a Zn content of 0.05%, a sulfur removal rate of 90%, and a zinc removal rate of 78%, which has a high economic value.

Claims

1. A method for comprehensively treating zinc-containing sulfate slag and blast furnace bag ash, characterized in that: The method comprises the following steps: (1) mixing zinc-containing sulfate slag, blast furnace bag ash, calcium additive, and carbonaceous reducing agent in a weight ratio of 10:3-5:2.5-4:1.5-3; (2) subjecting the fully mixed materials of step (1) to high temperature roasting, and subjecting the smoke generated during the roasting process to oxidation dust removal, cooling separation and desulfurization processes to obtain zinc oxide, sulfuric acid and sulfite; (3) water cooling the material after roasting in step (2), and crushing and grinding the slag after water cooling; (4) The slag material after crushing and grinding in step (3) is subjected to strong magnetic separation to separate the iron-containing phase, and then the separated iron-containing phase is subjected to a weak magnetic separation process to obtain high-value reduced iron powder.

2. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: The calcium additive is limestone or dolomite; the carbonaceous reducing agent is coke powder, lignite or blue charcoal.

3. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: The calcination temperature is 1200-1300°C, and the calcination time is 0.5-3 h.

4. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: The zinc-containing sulfate slag, blast furnace bag ash, calcium additive and carbonaceous reducing agent are in a weight ratio of 10:4:3:2.

5.

5. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: Includes one or more of the following (1)-(3): (1) The oxidation dust removal in step (2) is to oxidize the zinc in the high-temperature smoke into zinc oxide and zinc suboxide, and at the same time reduce the dust content in the flue gas by dust removal; (2) The cooling separation is to condense the zinc oxide and zinc suboxide in the flue gas and separate them from the sulfur oxides, and the temperature of the cooling separation is below 850°C; (3) The desulfurization process is to remove sulfur oxides in the tail gas by using a desulfurization device to form sulfuric acid and sulfite.

6. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: In the step (3), the slag is ground to a particle size of 95-98% below 75 μm.

7. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 1, characterized in that: The strong magnetic separation magnetic field strength is 160~210KA / m, and / or the weak magnetic separation magnetic field strength is 80~120KA / m.

8. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to any one of claims 1 to 7, characterized in that: The sulfuric acid slag is waste slag discharged from the pyrite acid production process; and / or, the blast furnace bag ash is dust removal ash generated in the blast furnace production process of a steel enterprise.

9. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to claim 8, characterized in that: The chemical composition of the sulfate slag contains 55~65% TFe, 8~12% SiO2, 1~7% Al2O3, 1~5% MgO, 0.2~1.5% Zn, 0.5~1.5% S; and / or, the chemical composition of the blast furnace bag ash contains 30~40% TFe, 5~8% SiO2, 4~6% CaO, 2~5% Al2O3, 3~5% Zn, 18~25% C.

10. The method for comprehensive treatment of zinc-containing sulfate slag and blast furnace bag ash according to any one of claims 1 to 7, characterized in that: In the step (2), the fuel used in the roasting process is natural gas, blast furnace gas or heavy oil.

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