Method for removing elemental sulfur in zinc sulfate leachate

Abstract

The invention relates to the technical field of lead and zinc smelting, in particular to a method for removing elemental sulfur in zinc sulfate leachate. Comprising the following steps: (1) adding copper sulfate into zinc sulfate leaching liquid or leaching slurry to form first mixed slurry, adding iron powder into the first mixed slurry to form second mixed slurry, and reacting the second mixed slurry to obtain third mixed slurry without elemental sulfur; and (2) carrying out liquid-solid separation on the third mixed slurry to obtain a zinc sulfate solution and leaching residues. According to the method, the copper sulfate and the iron powder are added into the zinc sulfate leaching solution or the leaching slurry, and the elemental sulfur in the zinc sulfate leaching solution or the leaching slurry is removed, so that the influence of the elemental sulfur is eliminated.

Description

Technical Field

[0001] This invention relates to the field of lead and zinc smelting technology, and specifically to a method for removing elemental sulfur from zinc sulfate leachate. Background Technology

[0002] Currently, metallic zinc is mostly obtained through a smelting process of "roasting / reduction-leaching-purification-electrowinning". Specifically, zinc roasted ore is leached with dilute sulfuric acid (electrowinning waste liquid) to obtain zinc sulfate solution. After purification, zinc is extracted from the solution by electrowinning. However, zinc sulfate solution often contains harmful impurities, making purification and impurity removal a crucial process step. For example, patent publication number CN105755296A, entitled "Method for Removing Calcium from Zinc Sulfate Solution Produced by Hydrometallurgical Zinc Refining", includes the following steps: cooling the zinc sulfate solution; adding a thickener to the zinc sulfate solution and adjusting the pH of the zinc sulfate solution to 4.0~4.5; adding the zinc sulfate solution to a thickener and allowing it to remain in the thickener for 5 to 30 hours to obtain a calcium-containing underflow and a calcium-removed overflow, reducing labor costs for cleaning calcium scale and improving production efficiency. Currently, there are no reports on the removal of elemental sulfur from zinc sulfate leachate. Therefore, this invention provides a method for removing elemental sulfur from zinc sulfate leachate. Summary of the Invention

[0003] The technical problem to be solved by this invention is to provide a method for removing elemental sulfur from zinc sulfate leaching solution. The aim is to remove elemental sulfur from the zinc sulfate leaching solution or leaching slurry by adding copper sulfate and iron powder, thereby eliminating the influence of elemental sulfur.

[0004] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: A method for removing elemental sulfur from zinc sulfate leachate includes the following steps: (1) Add copper sulfate to zinc sulfate leaching solution or leaching slurry to form a first mixed slurry, then add iron powder to the first mixed slurry to form a second mixed slurry, and then react the second mixed slurry to obtain a third mixed slurry after removing elemental sulfur; the pH of the zinc sulfate leaching solution is 4.6~5.4; (2) The third mixed slurry is subjected to liquid-solid separation to obtain zinc sulfate solution and leaching residue.

[0005] Among them, zinc sulfate leachate or leachate slurry is the leachate or slurry after liquid-solid separation of acidic flue gas leachate (pH<2) neutralized to pH=4.6~5.4 by flue gas or zinc calcined sand at 60~95℃.

[0006] The soot is zinc oxide-containing soot formed during the reduction and volatilization roasting of raw ore or zinc leaching residue in the zinc smelting process. For example, the soot formation process can be as follows: zinc leaching residue is mixed with reducing agents such as coke and coal powder in a certain proportion and then reduced and smelted in a kiln. The furnace temperature generally reaches 1100℃~1300℃. At this time, metals such as Zn, Pb, and Fe in zinc leaching residue are reduced to elemental form, and Zn and Pb volatilize into the flue gas and are subsequently oxidized to form soot. The soot is then recovered after being collected by electrostatic precipitator or bag filter.

[0007] The zinc calcined sand is a product obtained by roasting zinc concentrate, and mainly contains zinc oxide, zinc sulfate, zinc sulfide, etc.

[0008] Based on the above technical solution, the present invention can be further improved as follows.

[0009] Furthermore, the zinc content in the zinc sulfate leaching solution is below 170 g / L, and the elemental sulfur content is below 2 g / L.

[0010] Furthermore, the iron powder has a particle size of less than 100 μm and a weight percentage of 70% to 100%, and the effective metallic iron has a weight percentage of 80% to 100%.

[0011] Furthermore, the iron powder includes at least one of atomized iron powder, reduced iron powder, electrolytic iron powder, and mechanically pulverized iron powder.

[0012] Furthermore, the copper sulfate includes industrial-grade or higher copper sulfate reagents with or without water of crystallization; for example, industrial-grade or analytical-grade, etc.; the copper content is above 16%, and it can be added as a copper sulfate solution dissolved in water or as solid copper sulfate that has not been dissolved in water.

[0013] Furthermore, the molar ratio of copper in the copper sulfate to elemental sulfur in the zinc sulfate leaching solution is 0.5~1.2:1.

[0014] Furthermore, the molar ratio of effective metallic iron in the iron powder to copper in the copper sulfate is 1~1.5:1.

[0015] Furthermore, the reaction conditions for the second mixed slurry are: reaction at 55℃~95℃ for 10 min~120 min with stirring.

[0016] The rotation speed is greatly affected by the size of the stirrer. For example, the speed of an industrial stirrer is 20 to 40 rpm, while the speed of a stirrer developed in the laboratory is 250 to 400 rpm.

[0017] The removal of elemental sulfur is related to the amount of copper sulfate added, the amount of iron powder added, the particle size of the iron powder, and the effective iron content in the iron powder, as well as the removal temperature and time.

[0018] Furthermore, the elemental sulfur content in the desulfurized zinc sulfate solution is less than 10 mg / L.

[0019] This invention addresses the issue that during the reduction and volatilization roasting of raw ore or leaching residue, if the oxygen potential is not properly controlled, high-valence sulfur in the raw material will be reduced to elemental sulfur. When the elemental sulfur is above 450°C, it enters the flue gas in the form of vapor. This flue gas is captured by electrostatic precipitators or bag filters, and then subjected to acid leaching. The flue gas is formed in the gas phase and has extremely fine particles (micron-level). During acid leaching, the elemental sulfur in the flue gas (generally less than 5%) will enter the leachate in a molten or semi-molten state. Because the elemental sulfur in the flue gas is extremely fine, and under leaching conditions, the elemental sulfur is mostly in a semi-molten or even molten state, resulting in the elemental sulfur and the leachate being miscible. The presence of elemental sulfur increases the viscosity of the leaching slurry, slowing down liquid-solid separation. After separation, the solution turns black during subsequent purification to remove impurities such as copper, cadmium, and cobalt, making impurity removal difficult. This invention addresses the presence of elemental sulfur and its impact on the smelting system. For the first time, it proposes a method to remove elemental sulfur from zinc sulfate solution by adding copper sulfate and iron powder, thus eliminating the influence of elemental sulfur. The zinc sulfate solution after elemental sulfur removal enters the purification process, while the corresponding leaching residue enters the subsequent original leaching process to recover valuable elements (such as Zn, Pb, Cd, and Cu) from the residue.

[0020] The beneficial effects of this invention are: (1) This invention proposes for the first time to add copper sulfate to zinc sulfate leaching solution or leaching slurry as a precursor for removing elemental sulfur from zinc sulfate leaching solution; iron powder is added to zinc sulfate leaching solution or leaching slurry as an inducer, and the effective metallic iron in the iron powder and the precursor copper sulfate undergo an in-situ displacement reaction to form highly active metallic copper, which serves as a highly efficient remover of elemental sulfur; the highly efficient remover copper reacts with elemental sulfur in the solution at 55℃~95℃ to generate inactive compound copper sulfide, while excess iron powder acts as a scavenger to remove residual elemental sulfur in the solution, forming ferrous sulfide precipitate, and copper sulfide and ferrous sulfide enter the leaching residue during liquid-solid separation, thereby achieving the purpose of removing elemental sulfur.

[0021] (2) The present invention uses copper sulfate as a precursor and iron powder as an inducer to remove elemental sulfur effectively. The elemental sulfur content in the zinc sulfate solution after removing elemental sulfur is less than 8 mg / L, and the removal rate reaches more than 98%.

[0022] (3) The method of the present invention is simple, easy to operate and does not affect the original production process. Attached Figure Description

[0023] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0024] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they should be performed according to the techniques or conditions described in the literature in this field, or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0025] Description of the source of materials and reagents: The atomized iron powder is a product prepared by the Shanghai Alloy Powder Scientific Research Center; the reduced iron powder is a product sold by Tianjin Kemei Chemical Reagent Co., Ltd. and reduced pig iron powder from a steel plant in Xinjiang; the electrolytic iron powder is a product prepared by Kepule (Shenyang) Technology Co., Ltd.; and the mechanically pulverized iron powder is a self-made iron powder from a factory in Xinjiang.

[0026] Example 1: This embodiment uses a batch of neutral leachate (zinc sulfate leachate) from a factory in Xinjiang as raw material, and its main components are shown in Table 1: Table 1. Composition of a neutral leachate from Xinjiang (g / L) A method for removing elemental sulfur from zinc sulfate leachate includes the following steps ( Figure 1 ): Add a solution prepared with pure reagent containing 24% copper (60 g / L elemental copper) to the leachate with the composition shown in Table 1, and add copper sulfate at a concentration of 8.86 kg / m³. 3 Add (the molar ratio of elemental copper to elemental sulfur in the solution is 1.05:1), followed by reducing iron powder. 97% of the iron powder has a particle size below 100 μm, and the effective metallic iron content in the iron powder is 98.2%. The amount of iron powder added is 2.18 kg / m³. 3 The effective metallic iron in the solution was added in a molar ratio of 1.2:1 (iron powder:copper in solution). The slurry containing the added reduced iron powder was kept at 60℃ for 120 min, followed by liquid-solid separation. Testing revealed a rapid decrease in elemental sulfur content during the holding period; after 120 min, the elemental sulfur content was 3 mg / L, achieving a removal rate of 99.71%. The slag after liquid-solid separation mainly consisted of CuS, Cd, and FeS. The separated solution then entered a solution purification system, and the purification process proceeded smoothly.

[0027] Example 2: This embodiment uses a batch of neutral leaching slurry from a factory in Xinjiang as raw material, and its main components are shown in Table 2: Table 2. Composition of a neutral leaching pulp from Xinjiang A method for removing elemental sulfur from zinc sulfate leachate includes the following steps ( Figure 1 ): Add industrial-grade copper sulfate solid with a Cu content of 23% to the slurry with the composition shown in Table 2, at a rate of 3.13 kg / m³. 3 (The molar ratio of elemental copper to elemental sulfur in the solution is 1.1:1), followed by the addition of atomized iron powder. 100% of the iron powder has a particle size below 100 μm, and the effective metallic iron content in the atomized iron powder is 99.99%. The amount of iron powder added is 0.87 kg / m³. 3 Add (the weight ratio of iron powder to Cu in the solution is 1.5:1).

[0028] The slurry containing atomized iron powder was kept at 90℃ for 30 minutes, followed by liquid-solid separation. Testing revealed that the elemental sulfur content in the solution gradually decreased during the holding period, reaching 2 mg / L after 30 minutes, with a removal rate of 99.39%. The solution after liquid-solid separation then entered the solution purification system, and the purification process proceeded smoothly.

[0029] Example 3: This embodiment uses a batch of neutral leachate from flue dust from a factory in Liaoning Province as raw material. Its main components are shown in Table 3. Table 3. Composition of a neutral leachate from Liaoning Province (g / L) A method for removing elemental sulfur from zinc sulfate leachate includes the following steps ( Figure 1 ): Industrial-grade copper sulfate solid with a copper content of 22% was added to the leachate with the composition shown in Table 3. The amount of copper sulfate added was 4.74 kg / m³. 3 Add (the molar ratio of elemental copper to elemental sulfur in the solution is 1.5:1), followed by reducing iron powder. 100% of the iron powder must be less than 100 μm in size, and the effective metallic iron content must be 99.0%. The amount of iron powder added is 1.39 kg / m³. 3 Add (the molar ratio of effective metallic iron powder to copper in the solution is 1.5:1).

[0030] The slurry containing added iron powder was kept at 80℃ for 70 min, followed by liquid-solid separation. Testing revealed a rapid decrease in elemental sulfur content during the holding period, reaching 2 mg / L after 70 min, representing a sulfur removal rate of 99.43%. The slag after liquid-solid separation primarily consisted of CuS, FeS, and Cd. The separated solution then entered a solution purification system, with the purification process proceeding smoothly.

[0031] Example 4: This embodiment uses a batch of neutral leaching slurry from a factory in Inner Mongolia as raw material. Its main components are shown in Table 4. Table 4. Composition of a neutral leaching pulp from Inner Mongolia A method for removing elemental sulfur from zinc sulfate leachate includes the following steps ( Figure 1 ): Add industrial copper sulfate solid with a copper content of 20% to the slurry with the composition shown in Table 4, at a rate of 2.07 kg / m³. 3 Add (the molar ratio of elemental copper to elemental sulfur in the solution is 1.1:1), followed by electrolytic iron powder. The iron powder must be 100% smaller than 100 μm, and contain 99.99% effective metallic iron. The amount of iron powder added is 0.46 kg / m³. 3 Add (the molar ratio of effective metallic iron powder to Cu in the solution is 1.4:1).

[0032] The slurry containing added iron powder was kept at 85℃ for 60 minutes, followed by liquid-solid separation. Testing revealed that the elemental sulfur content in the solution gradually decreased during the holding period, reaching 2 mg / L after 60 minutes, with a removal rate of 98.95%. The solution after liquid-solid separation entered the solution purification system, and the purification process proceeded smoothly.

[0033] Example 5: This embodiment uses a batch of neutral leachate from flue dust from a factory in Sichuan as raw material, and its main components are shown in Table 5: Table 5. Composition of a neutral leaching pulp in Sichuan (g / L) A method for removing elemental sulfur from zinc sulfate leachate includes the following steps ( Figure 1 ): Add 2.80 kg / m³ of leachate with the composition shown in Table 5. 3Industrial-grade copper sulfate solid with a copper content of 22% (molar ratio of elemental copper to elemental sulfur in the solution is 0.5:1) was added, followed by atomized iron powder. 100% of the iron powder had a particle size below 100 μm, and the effective metallic iron content in the atomized iron powder was 99.99%. The amount of iron powder added was 1.63 kg / m³. 3 Add (the weight ratio of iron powder to Cu in the solution is 1.5:1).

[0034] The slurry containing added iron powder was kept at 95℃ for 20 minutes, followed by liquid-solid separation. Testing revealed that the elemental sulfur content in the solution gradually decreased during the holding period, reaching 2 mg / L after 20 minutes, with a removal rate of 99.68%. The solution after liquid-solid separation entered the solution purification system, and the purification process proceeded smoothly.

[0035] Comparative Example 1 Unlike Example 1, in this comparative example, reducing iron powder was added to the leachate with the composition shown in Table 1. 97% of the iron powder had a particle size below 100 μm, and the effective metallic iron content in the iron powder was 95%. The amount of iron powder added was 2.68 kg / m³. 3 The effective metallic iron in the iron powder was added at a molar ratio of 1.5:1 to sulfur in the solution. The slurry containing the added reducing iron powder was then kept at 60℃ for 120 min, followed by liquid-solid separation. Analysis revealed a rapid decrease in elemental sulfur content during the holding period. After 120 min, the elemental sulfur content was 163 mg / L, representing a removal rate of 84.02%. The slag after liquid-solid separation primarily consisted of Fe and FeS.

[0036] It can be seen that when Fe powder is added at only 1.5 times the theoretical amount, the removal rate of elemental sulfur in the solution is 84.02%. Compared with Example 1, when copper sulfate is used as a precursor, highly active fine-particle elemental Cu will be generated under the action of Fe powder, and it will react quickly with elemental sulfur to remove elemental sulfur, with a removal rate of 99.71%.

[0037] Comparative Example 2 Compared to Example 1, the reduced iron powder was replaced with 10% reduced uncrushed pig iron powder from a steel plant with a particle size of 100 μm; the rest remained the same as in Example 1. Testing showed that the elemental sulfur content in the desulfurized solution was 0.61 g / L, and the elemental sulfur removal rate reached 40.20%. The main phases of the slag after liquid-solid separation were Fe, FeS, CuS, and Cd.

[0038] In summary, this invention is the first to propose adding copper sulfate to the neutral leaching solution or leaching slurry of flue dust as a precursor for removing elemental sulfur from the solution. Iron powder is added to the neutral leaching solution or leaching slurry as an inducing agent. The effective metallic iron in the iron powder undergoes an in-situ displacement reaction with the precursor copper sulfate to form highly active metallic copper, which serves as a highly efficient remover of elemental sulfur. The highly efficient remover copper reacts with elemental sulfur in the solution at 55℃~95℃ to form the inactive compound copper sulfide. Simultaneously, excess iron powder acts as a reaction medium to remove residual elemental sulfur in the solution, forming ferrous sulfide precipitate. Copper sulfide and ferrous sulfide enter the leaching residue during liquid-solid separation, achieving the purpose of removing elemental sulfur.

[0039] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method for removing elemental sulfur from zinc sulfate leachate, characterized in that, Includes the following steps: (1) Add copper sulfate to zinc sulfate leaching solution or leaching slurry to form a first mixed slurry, then add iron powder to the first mixed slurry to form a second mixed slurry, and then react the second mixed slurry to obtain a third mixed slurry after removing elemental sulfur; the pH of the zinc sulfate leaching solution is 4.6~5.4; (2) The third mixed slurry is subjected to liquid-solid separation to obtain zinc sulfate solution and leaching residue.

2. The method for removing elemental sulfur from zinc sulfate leachate according to claim 1, characterized in that, The zinc sulfate leaching solution or leaching slurry is the leaching solution or slurry obtained after liquid-solid separation of flue gas acidic leaching solution and flue gas or zinc calcined sand; the zinc content in the zinc sulfate leaching solution or leaching slurry is below 170 g / L and the elemental sulfur content is below 2 g / L.

3. The method for removing elemental sulfur from zinc sulfate leachate according to claim 1, characterized in that, The iron powder has a particle size of less than 100 μm and a weight percentage of 70% to 100%, and the effective metallic iron has a weight percentage of 80% to 100%.

4. The method for removing elemental sulfur from zinc sulfate leachate according to claim 3, characterized in that, The iron powder includes at least one of atomized iron powder, reduced iron powder, electrolytic iron powder, and mechanically pulverized iron powder.

5. The method for removing elemental sulfur from zinc sulfate leachate according to claim 1, characterized in that, The copper sulfate mentioned includes industrial-grade or higher copper sulfate reagents with or without water of crystallization.

6. The method for removing elemental sulfur from zinc sulfate leachate according to claim 1, characterized in that, The molar ratio of elemental sulfur in the copper sulfate to that in the zinc sulfate leaching solution is 0.5~1.2:

1.

7. The method for removing elemental sulfur from zinc sulfate leachate according to claim 1, characterized in that, The molar ratio of effective metallic iron in the iron powder to copper in the copper sulfate is 1~1.5:

1.

8. The method for removing elemental sulfur from zinc sulfate leachate according to claim 1, characterized in that, The reaction conditions for the second mixed slurry are: reaction at 55℃~95℃ with stirring for 10 min~120 min.

9. A method for removing elemental sulfur from zinc sulfate leachate according to any one of claims 1 to 8, characterized in that, The elemental sulfur content in the zinc sulfate solution after desulfurization is less than 8 mg / L.

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