A method for selectively and deeply extracting zinc from bag dust / screening powder in the iron and steel smelting industry based on enhanced biological leaching

Abstract

The present invention provides a method for selectively and deeply extracting zinc from cloth bag ash / screening powder in the iron and steel smelting industry based on enhanced biological leaching. By adding concentrated sulfuric acid and enhancing the biological leaching technology, selective and deep extraction of valuable metal zinc in cloth bag ash and screening powder under high solid-liquid ratio conditions can be achieved, realizing both high-yield utilization of zinc and low zinc residue in the leaching residue and recycling for ironmaking, providing technical guarantee for the high-value resource utilization of zinc and iron elements.

Description

Technical Field

[0001] The present invention relates to the technical field of resource utilization of solid waste, and particularly to a method for selectively and deeply extracting zinc from bag dust / screen powder in the iron and steel smelting industry based on enhanced biological leaching. Background Art

[0002] Iron and steel smelting is one of the most important basic industries in China. Currently, China's annual iron and steel output exceeds 1 billion tons, accounting for more than 55% of the global total output. A large amount of primary industrial solid waste is generated during the iron and steel smelting process, including steel slag, blast furnace slag, iron and steel dust sludge, and desulfurization ash, etc. In addition, the treatment and disposal of iron and steel smelting solid waste will also generate secondary solid waste, such as secondary ash (screen powder) produced by zinc extraction from the waste of rotary hearth furnace / rotary kiln for steelmaking.

[0003] Among the iron and steel smelting solid waste, there is a large category with zinc and iron valuable metals as its important components and structural characteristics, mainly including blast furnace bag dust in primary solid waste and screen powder in secondary solid waste from rotary hearth furnace / rotary kiln. Blast furnace bag dust is the dust collected by bag dust removal after the flue gas discharged from the top of the blast furnace is subjected to gravity dust removal during the blast furnace smelting process; screen powder is the secondary ash produced by zinc extraction from the waste steel smelting in rotary hearth furnace / rotary kiln.

[0004] Bag dust contains iron (20 - 40%), zinc (2.5 - 10%), potassium (0.5 - 3.0%), sodium (0.5 - 2.0%), chlorine (2 - 10%), etc., and belongs to medium iron-containing dust sludge.

[0005] Extracting and recovering the valuable metal zinc from bag dust and screen powder represents the development direction of the treatment, disposal and resource utilization of this type of solid waste.

[0006] Biological leaching technology refers to the behavior of microorganisms using various functions such as acidolysis, oxidation, reduction, and complexation of themselves and their metabolites to dissolve and release target metal ions in solid-phase materials into the liquid phase, and has the characteristics of mild reaction, simple equipment, convenient operation, economic efficiency, environmental friendliness, and green and low-carbon. Summary of the Invention

[0007] In order to solve the above technical problems, the present invention provides a method for selectively and deeply extracting zinc from bag dust / screen powder in the iron and steel smelting industry based on enhanced biological leaching, which uses biological leaching technology for the green extraction of zinc in bag dust and screen powder, and realizes the selective and deep extraction of zinc under a high solid-liquid ratio through enhanced biological leaching, synchronously completing the high leaching of zinc and the low loss of iron, laying a foundation for the high-yield and high-value utilization of zinc and the recycling of iron-rich leached residue for ironmaking.

[0008] To achieve this technical purpose, the present invention adopts the following scheme:

[0009] A method for selectively and deeply extracting zinc from cloth bag ash / screening powder in the iron and steel smelting industry based on enhanced biological leaching, comprising the following steps:

[0010] S1. Preparation of biologically active leachate: Add a basic inorganic salt medium and a sulfur-containing ore inorganic energy substrate to a membrane bioreactor, inoculate a sulfur-oxidizing bacterium, an iron-oxidizing bacterium, or a complex microbial community of sulfur-oxidizing bacteria and iron-oxidizing bacteria, regulate the culture temperature, stirring speed, and aeration volume, extract the active leachate and supplement inorganic salts to achieve the balance between influent and effluent, and after the concentration of the active substance reaches the designed value, extract the culture solution through the membrane to obtain the biologically active leachate;

[0011] S2. Enhanced biological leaching of zinc in cloth bag ash / screening powder: Add cloth bag ash / screening powder to a leaching tank, input the biologically active leachate obtained in step S1, add concentrated sulfuric acid and an auxiliary agent, and heat and stir for reaction;

[0012] S3. Impurity removal from the zinc-containing leachate: After the enhanced biological leaching is completed, perform solid-liquid separation on the mud-water mixture, collect the leached residue and the leachate, add hydrogen peroxide and sodium carbonate or sodium hydroxide to the leachate until the pH of the solution rises to 3.0 - 3.5 to form ferric hydroxide precipitation, then perform solid-liquid separation, collect the iron-based precipitate and the leached residue and directly send them back to the furnace for ironmaking, and the zinc-rich purified leachate after iron removal is used for the preparation of zinc carbonate;

[0013] S4. Preparation and refinement of zinc carbonate: Slowly add 1.0 - 2.0 M sodium carbonate mother liquor to the zinc-rich purified leachate at room temperature and continuously stir until the pH of the solution rises to 8.0 - 8.5 for precipitation reaction, transfer the mud-water mixture to a thickener for static settlement, and then perform deep dehydration on the precipitate by suction filtration, pressure filtration, or centrifugation and perform deep washing and refinement with distilled water;

[0014] S5. Reuse of washing water: Collect the washing water in step S4 for the preparation of the medium and the preparation of the active leachate in step S1.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] Through the enhanced biological leaching technology, the present invention can selectively and deeply extract the valuable metal zinc in cloth bag ash and screening powder under the condition of a high solid-liquid ratio, realizing both the high-yield utilization of zinc and the low zinc residue in the leached residue and its recycling for ironmaking, providing technical support for the high-value resource utilization of zinc and iron elements.

[0017] Furthermore, the membrane pore size of the membrane bioreactor is 0.1 - 0.6 microns, and the membrane material is a ceramic membrane, an inorganic membrane, an organic membrane, or a composite membrane.

[0018] Further, the sulfur-containing inorganic energy substrates include sulfur, 0.5% - 2%; waste sulfur paste, 0.5% - 2%; thiosulfate, 0.5% - 2%; ferrous sulfate, 1.0% - 5%; pyrite, 1.0% - 5% or one or more of other sulfur-containing ores.

[0019] Further, the inoculation amount of the bacterial agent is 5% - 20%, the culture temperature is 20 - 40 °C, the stirring speed is 30 - 150 revolutions per minute, the aeration rate is 0.10 - 1.0 reactor volume per minute, and 0.5 - 2.0 reactor volumes of active leachate are extracted through the membrane every day and inorganic salt culture solution is supplemented synchronously to achieve the balance of influent and effluent.

[0020] Further, the characteristics of the active leachate are pH value 0.5 - 2.0, Fe 2+ concentration 200 - 1000 mg / L, Fe 3+ concentration 500 - 2500 mg / L, total concentration of small molecular organic acids 100 - 500 mg / L, total concentration of extracellular polymeric substances 200 - 1000 mg / L.

[0021] Further, concentrated sulfuric acid is 2% - 10%, and the additives are one or more of ammonium sulfate 1.5% - 5.0%, ammonium nitrate 1.5% - 5.0%, sodium nitrate 1.5% - 5.0%, potassium nitrate 1.5% - 5.0%, urea 1.5% - 5.0%, oxalic acid 0.2% - 1.0%, citric acid 0.2% - 1.0%, EDTA 0.2% - 1.0%, ammonium acetate 0.1% - 0.5%, sodium alginate 0.1% - 0.5%, sodium tartrate 0.1% - 0.5%.

[0022] Further, the solid-liquid ratio is 10% - 30%, the reaction temperature is 60 - 95 °C, the reaction pressure is normal pressure, the stirring speed is 60 - 300 revolutions per minute, and the reaction time is 1.0 - 3.0 hours; the leaching concentration of zinc is 5 - 20 g / L, the leaching rate of zinc is 75 - 95%, the dissolution concentration of iron is 0.5 - 2.5 g / L, and the dissolution rate of iron is ≤ 5.0%.

[0023] Further, the solid-liquid ratio is 10% - 30%, the reaction temperature is 140 - 210 °C, the reaction pressure is 4 - 20 atmospheres, the stirring speed is 60 - 300 revolutions per minute, and the reaction time is 1.0 - 3.0 hours; the leaching concentration of zinc is 5 - 20 g / L, the leaching rate of zinc is 75 - 95%, the dissolution concentration of iron is 0.5 - 2.5 g / L, and the dissolution rate of iron is ≤ 5.0%.

[0024] Further, the residual zinc concentration in the leaching residue is ≤ 0.3%, hydrogen peroxide is added to the leaching solution at 80 - 85 °C, hydrogen peroxide is 0.5 - 2%, and the total iron concentration of the zinc-rich purification solution is ≤ 100 mg / L.

[0025] Furthermore, the concentration of sodium carbonate mother liquor is 1.0 - 2.0 M, the stirring rate is 100 - 200 revolutions per minute, the reaction lasts for 30 minutes, and after standing for 30 - 60 minutes, the yield of zinc carbonate is ≥90%, and the purity of zinc carbonate is ≥95%. Detailed implementation manners

[0026] To fully understand the purpose, features, and effects of the present invention, the present invention will be described in detail through the following specific implementation manners, but the present invention is not limited thereto only.

[0027] Description of the substance content in the present invention:

[0028] For solid n%, the mass ratio of the solid added to the liquid to the liquid volume is n%. For example, for sulfur 2%, it means adding 2 g of sulfur to 100 ml of liquid, and the unit is g / ml;

[0029] For liquid n%, the volume ratio of the added liquid to the total liquid volume is n%. For example, when the inoculation amount of the strain is 5%, it means adding 5 ml of the strain to 95 ml of the culture medium, the total volume is 100 ml, and the volume ratio is 5%. Example 1

[0030] S1. Preparation of biologically active leachate. Add a basic inorganic salt medium and waste sulfur paste (2%), thiosulfate (2%), and pyrite (1.0%, 50 mesh) to a membrane bioreactor (MBR, membrane pore size 0.2 microns, membrane material organic membrane), and inoculate a complex microbial community of sulfur-iron oxidizing bacteria (inoculation amount 5%). The culture temperature is 40°C, the stirring speed is 150 revolutions per minute, the aeration rate is 0.10 reactor volume per minute, and 1.0 reactor volume of active leachate is extracted through the membrane every day and inorganic salt culture solution is synchronously supplemented to achieve the balance of influent and effluent. Characteristics of the active leachate: pH value 0.8, Fe 2+ concentration 600 mg / L, Fe 3+ concentration 1000 mg / L, total concentration of small molecule organic acids 250 mg / L, total concentration of extracellular polymeric substances 200 mg / L.

[0031] S2. Enhanced biological leaching of zinc in cloth bag ash. Input the active leachate into a leaching tank and add concentrated sulfuric acid (2%), ammonium acetate (0.1%), and sodium alginate (0.1%). At a solid-liquid ratio of 20%, 85°C, normal pressure, stirring speed 120 revolutions per minute, reaction time 2.0 hours, the leaching concentration of zinc is 12 g / L, the leaching rate of zinc is 90%, the dissolution concentration of iron is 1.0 g / L, and the dissolution rate of iron is 3.0%.

[0032] S3. Impurity removal from zinc-containing leaching solution. After the enhanced bioleaching is completed, the mud-water mixture is subjected to solid-liquid separation by suction filtration to collect the leaching residue and the leaching solution. The residual zinc concentration in the leaching residue is 0.28%, meeting the zinc content requirement for recycling in iron smelting. After adding hydrogen peroxide (1%) and sodium hydroxide mother liquor (2M) to the leaching solution at 85°C until the solution pH rises to 3.5 to form iron hydroxide precipitate, solid-liquid separation is carried out by centrifugation. The iron-based precipitate is directly recycled for iron smelting, and the zinc-rich purified solution after iron removal (total iron concentration 90 mg / L) is used for the preparation of zinc carbonate.

[0033] S4. Preparation and purification of zinc carbonate. At room temperature, sodium carbonate mother liquor (1.0M) is slowly added to the zinc-rich purified solution with continuous stirring (100 revolutions per minute) until the solution pH rises to 8.5. After 30 minutes of precipitation reaction, the mud-water mixture is transferred to a thickener and left to stand for 60 minutes, and then the precipitate is subjected to deep dehydration by suction filtration and deeply washed and refined with distilled water. The yield of zinc carbonate is 96%, and the purity of zinc carbonate is 98%, which is a qualified product. Example 2

[0034] S1. Preparation of bioactive leachate. In a membrane bioreactor (MBR, membrane pore size 0.4 microns, membrane material is ceramic membrane), basic inorganic salt medium and sulfur (1%), waste sulfur paste (1%), pyrite (2.0%, 100 mesh) are added, and a complex microbial community of sulfur-iron oxidizing bacteria is inoculated (inoculation amount 10%). The culture temperature is 35°C, the stirring speed is 150 revolutions per minute, the aeration rate is 0.5 reactor volumes per minute, and 0.5 reactor volumes of active leachate are extracted through the membrane every day and inorganic salt culture solution is synchronously supplemented to achieve the balance of influent and effluent. Characteristics of the active leachate: pH value 0.6, Fe 2+ concentration 900 mg / L, Fe 3+ concentration 1500 mg / L, total concentration of small molecular organic acids 300 mg / L, total concentration of extracellular polymeric substances 500 mg / L.

[0035] S2. Enhanced bioleaching of zinc in the undersize powder. Active leachate is input into the leaching tank and concentrated sulfuric acid (5%), urea (2.0%), ammonium acetate (0.1%) and sodium tartrate (0.1%) are added. At a solid-liquid ratio of 15%, under high pressure and high temperature (12 atmospheres, 180°C), the stirring speed is 200 revolutions per minute, and the reaction time is 3.0 hours. The leaching concentration of zinc is 5.5 g / L, the leaching rate of zinc is 80%, the dissolution concentration of iron is 2.1 g / L, and the dissolution rate of iron is 4.5%.

[0036] S3. Impurity removal from zinc-containing leaching solution. After the enhanced biological leaching is completed, the mud-water mixture is subjected to solid-liquid separation by pressure filtration. The leaching residue and leaching solution are collected. The residual zinc concentration in the leaching residue is 0.3%, meeting the zinc content requirement for recycling in iron smelting. After adding hydrogen peroxide (2%) and sodium carbonate solution (2.0 M) to the leaching solution at 85 °C until the solution pH rises to 3.5 to form iron hydroxide precipitate, solid-liquid separation is carried out by suction filtration. The iron-based precipitate is directly recycled for iron smelting, and the zinc-rich purification solution with iron removed (total iron concentration 100 mg / L) is used for the preparation of zinc carbonate.

[0037] S4. Preparation and refinement of zinc carbonate. At room temperature, sodium carbonate mother liquor (1.0 M) is slowly added to the zinc-rich purification solution with continuous stirring (150 revolutions per minute) until the solution pH rises to 8.5. After 30 minutes of precipitation reaction, the mud-water mixture is transferred to a thickener and left standing for 60 minutes, and then the precipitate is deeply dehydrated by centrifugation and deeply washed and refined with distilled water. The yield of zinc carbonate is 92%, and the purity of zinc carbonate is 97%, which belongs to qualified products. Example 3

[0038] S1. Preparation of biologically active leachate. In a membrane bioreactor (MBR, membrane pore size 0.6 microns, membrane material is composite membrane), basic inorganic salt medium and sulfur (1%), ferrous sulfate (1%), pyrite (2.0%, 100 mesh) are added, and sulfur-oxidizing bacteria are inoculated (inoculation amount 15%). The culture temperature is 35 °C, the stirring speed is 150 revolutions per minute, the aeration rate is 0.5 reactor volumes per minute, and 0.7 reactor volumes of active leachate are extracted through the membrane every day and inorganic salt culture solution is synchronously supplemented to achieve the balance of influent and effluent. Characteristics of the active leachate: pH value 0.7, Fe 2+ concentration 950 mg / L, Fe 3+ concentration 1400 mg / L, total concentration of small molecular organic acids 300 mg / L, total concentration of extracellular polymeric substances 500 mg / L.

[0039] S2. Enhanced biological leaching of zinc in the screenings. Active leachate is input into the leaching tank and concentrated sulfuric acid (10%), ammonium nitrate (2.0%), EDTA (0.1%) and citric acid (0.1%) are added. At a solid-liquid ratio of 30%, under pressurized high temperature (15 atmospheres, 200 °C), stirring speed of 300 revolutions per minute, reaction time of 2 hours, the leaching concentration of zinc is 10.5 g / L, the leaching rate of zinc is 82%, the dissolution concentration of iron is 3.5 g / L, and the dissolution rate of iron is 5%.

[0040] S3. Impurity removal from zinc-containing leaching solution. After the enhanced biological leaching is completed, the mud-water mixture is subjected to solid-liquid separation by pressure filtration. The leaching residue and leaching solution are collected. The residual zinc concentration in the leaching residue is 0.3%, meeting the zinc content requirement for recycling in iron smelting. After adding hydrogen peroxide (5%) and sodium carbonate solution (2.0 M) to the leaching solution at 85 °C until the solution pH rises to 3.5 to form iron hydroxide precipitate, solid-liquid separation is carried out by suction filtration. The iron-based precipitate is directly recycled in iron smelting, and the zinc-rich purified solution (total iron concentration 50 mg / L) after iron removal is used for the preparation of zinc carbonate.

[0041] S4. Preparation and purification of zinc carbonate. At room temperature, sodium carbonate mother liquor (2.0 M) is slowly added to the zinc-rich purified solution with continuous stirring (150 revolutions per minute) until the solution pH rises to 8.0. After the precipitation reaction for 30 minutes, the mud-water mixture is transferred to a thickener and left standing for 60 minutes, and then the precipitate is deeply dehydrated by centrifugation and deeply washed and refined with distilled water. The yield of zinc carbonate is 91%, and the purity of zinc carbonate is 96%, which belongs to qualified products. Comparative Example 1

[0042] Compared with Example 1, concentrated sulfuric acid was not added in step S2.

[0043] The leaching concentration of zinc is 5.3 g / L, and the leaching rate of zinc is 40%. Comparative Example 2

[0044] Compared with Example 2, the pressure in step S2 was normal pressure, and concentrated sulfuric acid was not added.

[0045] The leaching concentration of zinc is 0.75 g / L, and the leaching rate of zinc is 11%. Comparative Example 3

[0046] Compared with Example 3, the pressure in step S2 was normal pressure, and concentrated sulfuric acid was not added.

[0047] The leaching concentration of zinc is 1.15 g / L, and the leaching rate of zinc is 9%.

[0048] Finally, it should be noted that the above-listed are only the preferred embodiments of the present invention. Of course, those skilled in the art can make changes and modifications to the present invention. If these modifications and variations fall within the scope of the claims of the present invention and its equivalent technologies, they should be considered as the protection scope of the present invention.

Claims

1. A method for selective deep zinc extraction from bag ash / undersize powder in the steel smelting industry based on enhanced bioleaching, characterized in that: The following steps are involved: S1. Preparation of biologically active leachate: adding basic inorganic salt culture medium and sulfur-containing mineral inorganic energy substrate to a membrane bioreactor, accessing sulfur oxidizing bacteria, iron oxidizing bacteria or a composite bacterial community of sulfur oxidizing bacteria and iron oxidizing bacteria, regulating the culture temperature, stirring speed and aeration volume, the aeration volume is 0.10-1.0 reactor volume / minute, extracting active leachate and supplementing inorganic salts to achieve influent and effluent balance, and after the active substance concentration reaches the designed value, extracting the culture solution through the membrane to obtain biologically active leachate; The active leachate is characterized by a pH value of 0.5-2.0, Fe 2+ Concentration 200~1000mg / L, Fe 3+ Concentration 500~2500mg / L, total concentration of small molecule organic acids 100~500mg / L, total concentration of extracellular polymers 200~1000mg / L; S2, enhanced bioleaching of zinc in bag ash / screen underpowder, add bag ash / screen underpowder into the leaching tank, input the bioactive leachate obtained in step S1, the solid-liquid ratio is 30%, add concentrated sulfuric acid and auxiliary agent, heat and stir to react, the reaction time is 2.0 hours; The concentrated sulfuric acid is 2%~10%, and the auxiliary agent is one or more of ammonium sulfate 1.5%~5.0%, ammonium nitrate 1.5%~5.0%, sodium nitrate 1.5%~5.0%, potassium nitrate 1.5%~5.0%, urea 1.5%~5.0%, oxalic acid 0.2%~1.0%, citric acid 0.2%~1.0%, EDTA 0.2%~1.0%, ammonium acetate 0.1%~0.5%, sodium alginate 0.1%~0.5%, sodium tartrate 0.1%~0.5%; S3. Impurity removal of zinc-containing leachate. After enhanced bioleaching, the mud-water mixture is subjected to solid-liquid separation, and the leaching residue and leachate are collected. Hydrogen peroxide and sodium carbonate or sodium hydroxide are added to the leachate until the pH of the solution rises to 3.0-3.5 to generate iron hydroxide precipitation. After solid-liquid separation, the iron-based precipitate and the leaching residue are collected and directly returned to the furnace for ironmaking. The iron-rich purified liquid after iron removal is used for the preparation of zinc carbonate; the zinc leaching concentration is 5-20g / L, the zinc leaching rate is 75-95%, the iron dissolution concentration is 0.5-2.5g / L, and the iron dissolution rate is ≤5.0%; the zinc residual concentration in the leaching residue is ≤0.3%, hydrogen peroxide is added to the leachate at 80-85°C, the hydrogen peroxide is 0.5-2%, and the total iron concentration of the zinc-rich purified liquid is ≤100mg / L; S4, preparation and purification of zinc carbonate, slowly add 1.0-2.0M sodium carbonate mother liquor to the zinc-rich purified liquid at room temperature and stir continuously until the pH value of the solution rises to 8.0-8.5, the stirring rate is 100-200 rpm, the precipitation reaction is carried out for 30 minutes, the mud-water mixture is transferred to a thickener and allowed to stand for 30-60 minutes, and then the precipitate is deeply dehydrated by suction filtration, filter pressing or centrifugation and deeply washed and refined with distilled water; the zinc carbonate yield is ≥90%, and the zinc carbonate purity is ≥95%; S5. Reuse of washing water: collecting the washing water in step S4 for use in the preparation of the culture medium and active leachate in step S1.

2. The method for selective deep zinc extraction from bag ash / undersize powder in the steel smelting industry based on enhanced bioleaching according to claim 1, characterized in that: The membrane pore size of the membrane bioreactor is 0.1~0.6 microns, and the membrane material is inorganic membrane, organic membrane or composite membrane.

3. The method for selective deep zinc extraction from bag ash / undersize powder in the steel smelting industry based on enhanced bioleaching according to claim 1, characterized in that: Sulfur-containing mineral inorganic energy substrates include sulfur, 0.5%~2%; waste sulfur paste, 0.5%~2%; thiosulfate, 0.5%~2%; ferrous sulfate, 1.0%~5%; pyrite, 1.0%~5% or one or more of other sulfur-containing minerals.

4. The method for selective deep zinc extraction from bag ash / undersize powder in the steel smelting industry based on enhanced bioleaching according to claim 1, characterized in that: The inoculation amount of the bacterial agent is 5%~20%, the culture temperature is 20~40℃, the stirring speed is 30~150 rpm, 0.5~2.0 reactor volumes of active leachate are extracted through the membrane every day and inorganic salt culture solution is supplemented simultaneously to achieve a balance between influent and effluent.

5. The method for selective deep zinc extraction from bag ash / undersize powder in the steel smelting industry based on enhanced bioleaching according to claim 1, characterized in that: In step S2, the reaction temperature is 60-95° C., the reaction pressure is normal pressure, and the stirring speed is 60-300 rpm.

6. The method for selective deep zinc extraction from bag ash / undersize powder in the steel smelting industry based on enhanced bioleaching according to claim 1, characterized in that: In step S2, the reaction temperature is 140-210° C., the reaction pressure is 4-20 atmospheres, and the stirring speed is 60-300 rpm.