Comprehensive utilization system and method of coarse zinc powder

Abstract

The invention discloses a comprehensive utilization system and method of coarse zinc powder. The system comprises a coarse zinc powder washing system and a mother liquor iodine extraction system, the coarse zinc powder washing system comprises an alkaline leaching unit, a water treatment unit and a filtrate evaporative crystallization unit which are arranged in sequence; the alkaline leaching unit is used for carrying out alkaline leaching and two times of rinsing on the coarse zinc powder to obtain alkaline leaching filtrate and washed zinc powder; the water treatment unit is used for softening, de-weighting and flocculating the alkaline leaching filtrate obtained by the alkaline leaching unit to obtain purified filtrate and water treatment mud cakes; the filtrate evaporative crystallization unit is used for performing evaporative crystallization on the purified filtrate obtained by the water treatment unit; the mother liquor iodine extraction system comprises a liquid storage tank, a reaction tank, a thickener and a mother liquor evaporation and crystallization unit which are connected in sequence; the liquid storage tank is connected with a mother liquid outlet of the filtrate evaporation crystallization unit; a mother liquor outlet of the mother liquor evaporation and crystallization unit is connected with the liquid storage tank. By adopting a pure wet process, the problems of difficulty in direct recycling of the coarse zinc powder, low comprehensive utilization value and the like are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of solid waste, and more specifically, to a comprehensive utilization system and method for crude zinc powder. Background Art

[0002] The zinc-containing dust and sludge generated in steelmaking is an important zinc recycling resource, mainly from processes such as sintering, pelletizing, blast furnace, converter (electric furnace), etc. The dust and sludge with low zinc content (w(Zn) < 1.0%) can be returned to the sintering process for recycling, while using the dust and sludge with high zinc content in sintering will affect the quality of sinter and the operation of the blast furnace. At present, the metallurgical dust and sludge with high zinc content in China are usually treated by processes such as rotary hearth furnace and rotary kiln, so that zinc is further enriched into crude zinc powder and used as raw material for zinc smelting.

[0003] In terms of the electrolytic zinc process, when crude zinc powder is leached, fluorine and chlorine will enter the zinc hydrometallurgical system, which is not conducive to electrolytic zinc and accelerates the corrosion of equipment and facilities. During electrolytic zinc, fluorine and chlorine gradually increase in the electrolytic system. When reaching a certain amount, fluoride ions will corrode the cathode aluminum plate, forming an aluminum oxide film on the surface of the cathode aluminum plate, causing the precipitated zinc to react with the fresh surface of the cathode aluminum plate to form shiny zinc-aluminum alloy, and at the same time greatly increasing the consumption of aluminum plates; in addition, chloride ions will corrode the lead anode plate, resulting in a decline in the quality of zinc ingot products. When the chloride ions in the electrolytic system reach a relatively high content, chlorine gas will be generated on the surface of the anode, causing serious impacts on the on-site environment and safety. Therefore, it is very important to remove fluorine and chlorine from crude zinc powder before it enters the zinc electrolytic system.

[0004] At present, the main methods for removing fluorine and chlorine by pyrometallurgy are multi-hearth furnace roasting and rotary kiln roasting. This method has stable operation and simple process, but it has problems such as high investment cost and high energy consumption. There are also processes for removing fluorine and chlorine by hydrometallurgy. Although the hydrometallurgy process has the advantages of simple operation, low investment cost and low operating cost, there are also many problems in the implementation process.

[0005] Chinese Patent Application No. CN202211263566.2 discloses a method for treating high-chlorine secondary crude zinc powder to produce zinc and lead by a fully wet process, which uses a chloride medium to treat high-chlorine crude zinc powder, including processes such as chloride central leaching, chloride oxidation acid leaching, non-saponification extraction - stripping in chloride medium, neutralization and zinc precipitation in the extraction solution to remove potassium, sodium and chlorine, dissolving lead in chloride solution, and electroplating lead in chloride solution, etc., to achieve the comprehensive recovery of zinc, lead, chlorine, potassium, sodium, etc. from high-chlorine crude zinc powder; however, this method has problems such as high requirements for process control of chloride ion complexation reaction and difficult to guarantee the recovery efficiency, and it is rarely applied industrially.

[0006] Chinese Patent Application No. CN201210275990.0 discloses a method for harmless resource treatment of crude zinc powder alkaline elution chlorine wastewater. The technological process is as follows: The crude zinc powder alkaline elution chlorine wastewater containing Na, Cl, Pb, and Zn is subjected to equal neutralization and coagulation precipitation treatment to obtain sediment containing heavy metals such as Pb and Zn, which is sent to processes such as rotary kiln volatilization for comprehensive recovery. The obtained sodium chloride filtrate is sent to multi-effect evaporation crystallization treatment, and the filtrate is evaporated and concentrated, crystallized, and dehydrated by a centrifuge in the multi-effect evaporation to obtain salt products, realizing the recovery of the above valuable elements. The process technology is mature and the operation is simple, but the key control processes in the process are not clear, it is difficult to ensure the production line efficiency and product quality, and the recovery and utilization of other valuable elements such as K and I are not considered.

[0007] Chinese Patent Application No. CN202410883575.6 discloses a method for efficiently extracting iodine from salt-containing wastewater obtained by a crude zinc powder pretreatment process. After the mixed salt solution is evaporated and concentrated, crystallized, and dehydrated by a centrifuge, potassium salt and sodium salt products are obtained, and then crude iodine is prepared; then potassium iodide products are prepared using the crude iodine as raw materials. The key control processes in the process are not clear, and it is difficult to ensure the production line efficiency and product quality.

[0008] Based on the above characteristics and problems, the present invention provides a comprehensive utilization method and system for crude zinc powder. Through a wet process, the separation, recovery, and utilization of valuable elements such as Zn, K, Na, Cl, and I are realized. The process is flexible and the process control points are clear, solving problems such as the difficulty of directly recycling crude zinc powder and its low comprehensive utilization value, and having practical significance for the development of comprehensive utilization technology of secondary zinc resources. Summary of the Invention

[0009] Aiming at the defects existing in the prior art, the purpose of the present invention is to provide a comprehensive utilization system and method for crude zinc powder, which adopts a pure wet process to realize the comprehensive recovery and utilization of valuable metals in crude zinc powder, and solves problems such as the difficulty of directly recycling crude zinc powder and its low comprehensive utilization value.

[0010] To achieve the above purpose, the present invention adopts the following technical solutions:

[0011] The first aspect of the present invention provides a comprehensive utilization system for crude zinc powder, including a crude zinc powder water washing system and a mother liquor iodine extraction system;

[0012] The crude zinc powder water washing system includes an alkali leaching unit, a water treatment unit, and a filtrate evaporation crystallization unit arranged in sequence;

[0013] The alkali leaching unit is used to perform alkali leaching and two - stage rinsing on the crude zinc powder to obtain alkali leaching filtrate and washed zinc powder; the alkali leaching unit includes a ash bin, an alkali leaching module, and a rinsing module connected in sequence. The alkali leaching module includes an alkali leaching tank connected to the ash bin and a first filter press connected to the alkali leaching tank. The filtrate outlet of the first filter press is connected to the water treatment unit; the rinsing module includes a primary rinsing tank, a second filter press, a secondary rinsing tank, and a third filter press connected in sequence.

[0014] The water treatment unit is used to soften, remove heavy metals, and flocculate the alkali leaching filtrate obtained from the alkali leaching unit to obtain purified filtrate and water treatment sludge cake; the water treatment unit includes a reaction tank connected to the first filter press and a fourth filter press connected to the reaction tank.

[0015] The filtrate evaporation and crystallization unit is used to perform evaporation and crystallization on the purified filtrate obtained from the water treatment unit; the inlet of the filtrate evaporation and crystallization unit is connected to the first filter press.

[0016] The mother liquor iodine extraction system includes a storage tank, a reaction tank, a concentrator, and a mother liquor evaporation and crystallization unit connected in sequence; the storage tank is connected to the mother liquor outlet of the filtrate evaporation and crystallization unit; the mother liquor outlet of the mother liquor evaporation and crystallization unit is connected to the storage tank.

[0017] Preferably, the filtrate outlet of the third filter press is connected to the primary rinsing tank, and the filtrate outlet of the second filter press is connected to the alkali leaching tank.

[0018] Preferably, the first filter press, the second filter press, the third filter press, and the fourth filter press can be plate - and - frame filter presses.

[0019] Preferably, the condensate outlet of the filtrate evaporation and crystallization unit is connected to the water inlet of the alkali leaching tank and / or the primary rinsing tank and / or the secondary rinsing tank.

[0020] Preferably, the mother liquor outlet of the filtrate evaporation and crystallization unit is connected to the storage tank through a mother liquor pipeline. An iodine analyzer and a three - way valve are provided on the mother liquor pipeline. The three - way valve is connected to the alkali leaching tank through a mother liquor branch pipe.

[0021] When the iodine analyzer detects that the iodine content of the remaining salt - extracting mother liquor from the filtrate evaporation and crystallization unit is ≥300 mg / L, the three - way valve opens the mother liquor pipeline, and the remaining salt - extracting mother liquor enters the storage tank; otherwise, the three - way valve opens the mother liquor branch pipe, and the remaining salt - extracting mother liquor enters the alkali leaching tank for circulation.

[0022] The second aspect of the present invention provides a comprehensive utilization method for crude zinc powder. The comprehensive utilization system for crude zinc powder as described in the first aspect of the present invention is used to perform the following steps:

[0023] S1. Mix the crude zinc powder and water evenly in an alkali leaching tank to obtain a mixed ore pulp, add soda ash for alkali leaching, and then perform two rinses to obtain an alkali leaching filtrate and washed zinc powder;

[0024] S2. Soften, remove heavy metals, and flocculate the alkali leaching filtrate in a water treatment unit, and then obtain a purified filtrate and water treatment mud cake through pressure filtration;

[0025] S3. Concentrate and evaporate and crystallize the purified filtrate in a filtrate evaporation and crystallization unit to obtain KCl products and NaCl products;

[0026] S4. Detect the iodine content in the remaining salt extraction mother liquor after evaporation and crystallization. When the iodine content in the remaining salt extraction mother liquor < 300 mg / L, send the remaining salt extraction mother liquor to the primary alkali leaching process in step S1 for recycling until the iodine content in the remaining salt extraction mother liquor ≥ 300 mg / L;

[0027] S5. Send the remaining salt extraction mother liquor with an iodine content ≥ 300 mg / L to the mother liquor iodine extraction system for oxidation treatment, and then obtain potassium iodate products and KCl products by low-temperature crystallization.

[0028] Preferably, step S1 includes the following processes:

[0029] S11. Add the crude zinc powder to an alkali leaching tank and mix it evenly with water to obtain a mixed ore pulp;

[0030] S12. Add soda ash to the mixed ore pulp for alkali leaching, and then perform pressure filtration to obtain an alkali leaching filtrate and an alkali leaching mud cake;

[0031] S13. Send the alkali leaching mud cake to a primary rinsing tank, add water for primary rinsing, and perform pressure filtration after rinsing to obtain a rinsed mud cake;

[0032] S14. Send the rinsed mud cake to a secondary rinsing tank, add water for secondary rinsing, and perform pressure filtration after rinsing to obtain washed zinc powder.

[0033] Preferably, the water used in step S11, step S13, and step S13 is mixed at a solid-liquid ratio of 1:2 - 4.

[0034] Preferably, in step S1:

[0035] In step S11, in the crude zinc powder, the Zn content is 20 - 60%, the Cl content is 2 - 20%, the K content is 1 - 20%, the Na content is 1 - 5%, and the I content is 0.01 - 0.3%;

[0036] In step S12, during the alkali leaching process, the pH of the mixed ore pulp after adding soda ash is 7 - 9, and the time for alkali leaching is 15 - 60 min;

[0037] In step S12, the pH of the alkali leaching filtrate is 7-9;

[0038] In step S13, the time used for the first rinsing is 15-60 min;

[0039] In step S14, the time used for the second rinsing is 15-60 min;

[0040] In step S14, the Zn content of the water-washed zinc powder is ≥40%, the Cl content is <1%, and the I content is <0.01%.

[0041] Preferably, in step S2:

[0042] During the softening process, a pH regulator is added to adjust the pH of the alkali leaching filtrate to 9-11, and then sodium carbonate is added for softening;

[0043] During the weight removal process, a weight removal agent is added to the alkali leaching filtrate, and the weight removal agent is selected as sodium sulfate decahydrate;

[0044] During the flocculation process, a flocculant is added to the alkali leaching filtrate. The flocculant is selected as polyacrylamide, and the addition amount of the flocculant is 0.1-0.5% of the weight of the alkali leaching filtrate;

[0045] In the purified filtrate, the Ca content is <50 mg / L, the Zn content is <10 mg / L, and the Pb content is <10 mg / L.

[0046] Preferably, step S5 includes the following processes:

[0047] S51, after the remaining iodine extraction mother liquor with an iodine content ≥300 mg / L is sent to the storage tank of the mother liquor iodine extraction system, the remaining iodine extraction mother liquor enters the reaction tank, and a pH regulator is added to adjust and maintain the pH of the remaining iodine extraction mother liquor to less than 2;

[0048] S52, excessive chlorine is introduced into the remaining iodine extraction mother liquor for oxidation treatment. After the oxidation reaction ends, potassium hydroxide is continuously added to adjust the pH to 6-7;

[0049] S53, the solution treated in step S52 is sent to a concentrator for concentration and then enters the mother liquor evaporation and crystallization unit for low-temperature crystallization to obtain potassium iodate products and KCl products;

[0050] S54, the iodine extraction mother liquor coming out of the mother liquor evaporation and crystallization unit returns to the storage tank for recycling.

[0051] Preferably, in step S53, during the low-temperature crystallization process, the temperature is controlled at 0-10 °C.

[0052] The effects of the present invention are as follows:

[0053] 1. The comprehensive utilization system of crude zinc powder of the present invention designs an alkali leaching unit, a water treatment unit, a filtrate evaporation and crystallization unit and a mother liquor iodine extraction system. After being treated by this system, the enrichment and recovery of ions such as Zn, Pb, Fe, K, Na, Cl, and I are realized; the Zn grade in zinc powder is greatly improved, and the product value is increased; the recovered potassium salt, sodium salt and iodized salt are sold externally, increasing the project benefits; this system is environmentally friendly and maximizes the resource value.

[0054] 2. The present invention adopts an alkali leaching process for crude zinc powder, realizing the efficient separation of ions such as Zn, Pb, Fe, Ca, and Mg from ions such as K, Na, Cl, I, and F. Compared with the traditional process, the Zn recovery rate and Cl removal rate are improved; the contents of metal ions such as Ca, Zn, and Pb in the alkali leaching filtrate of the present invention are relatively low, greatly reducing the cost of the water treatment process.

[0055] 3. The present invention develops a two-step low-cost process route to recover iodine from iodine-containing waste liquid, proposes clear process control parameters, can effectively stabilize the process cost, improve the productivity of the production line, and produce high-quality potassium iodate products; no other impurity elements are introduced into the mother liquor iodine extraction system, and no secondary solid waste or toxic and harmful gases are generated during the process.

[0056] 4. The present invention can realize the separation of various elements (such as Zn, K, Na, Cl, I, etc.) in crude zinc powder, has a flexible process, is easy to operate, has clear process control, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a schematic structural diagram of the crude zinc powder washing system of the comprehensive utilization system of crude zinc powder of the present invention;

[0058] Figure 2 It is a schematic structural diagram of the mother liquor iodine extraction system of the comprehensive utilization system of crude zinc powder of the present invention;

[0059] Figure 3 It is a schematic flow diagram of the alkali leaching and rinsing processes of the crude zinc powder of the present invention;

[0060] Figure 4 It is a schematic flow diagram of the water treatment of the alkali leaching filtrate and the evaporation and crystallization of the purified filtrate of the present invention;

[0061] Figure 5 It is a schematic flow diagram of the iodine recovery from the remaining salt extraction mother liquor of the present invention;

[0062] In the figure, 1. ash bin; 2. alkali leaching tank; 3. first filter press; 4. primary rinsing tank; 5. second filter press; 6. secondary rinsing tank; 7. third filter press; 8. reaction tank; 9. fourth filter press; 10. filtrate evaporation and crystallization unit; 11. liquid storage tank; 12. reaction tank; 13. thickener; 14. mother liquor evaporation and crystallization unit. Detailed implementation manners

[0063] In order to better understand the above technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0064] Combined with Figure 1 、 Figure 2 As shown, a comprehensive utilization system for crude zinc powder provided by the present invention includes a crude zinc powder water washing system and a mother liquor iodine extraction system. The crude zinc powder water washing system includes an alkali leaching unit, a water treatment unit, and a filtrate evaporation and crystallization unit 10 arranged in sequence. The comprehensive utilization system for crude zinc powder realizes the separation and enrichment of valuable elements through a pure wet process technology according to the content of valuable metals in the crude zinc powder, and finally recovers and utilizes them in this system.

[0065] Combined with Figure 1 As shown, the alkali leaching unit is used to perform alkali leaching and two - stage rinsing on the crude zinc powder to obtain an alkali leaching filtrate and washed zinc powder. The alkali leaching unit includes a ash bin 1, an alkali leaching module, and a rinsing module connected in sequence. The ash bin 1 mainly stores the collected crude zinc powder. The alkali leaching module includes an alkali leaching tank 2 connected to the ash bin 1 and a first filter press 3 connected to the alkali leaching tank 2; the alkali leaching tank 2 is used to mix the crude zinc powder from the ash bin 1 with water (fresh water or the primary filtrate from the second filter press 5 of the rinsing module or the condensed water from the evaporation and crystallization system or the remaining salt - extracting mother liquor, etc.) evenly and perform alkali leaching; the filtrate outlet of the first filter press 3 is connected to the water treatment unit. The rinsing module includes a first - stage rinsing tank 4, a second filter press 5, a second - stage rinsing tank 6, and a third filter press 7 connected in sequence. The first - stage rinsing tank 4 is used to mix the alkali - leached mud cake from the first filter press 3 with water (fresh water or the secondary filtrate from the third filter press 7 or the condensed water from the evaporation and crystallization system, etc.) and perform a first - stage rinsing; the second - stage rinsing tank 6 is used to mix the rinsed mud cake from the second filter press 5 with water (fresh water or the condensed water from the evaporation and crystallization system, etc.) and perform a second - stage rinsing. In a specific embodiment, the filtrate outlet of the third filter press 7 is connected to the first - stage rinsing tank 4, and the filtrate outlet of the second filter press 5 is connected to the alkali leaching tank 2.

[0066] Combined with Figure 1 As shown, the water treatment unit is used to soften, remove heavy metals, and flocculate the alkali leaching filtrate obtained from the alkali leaching unit to obtain a purified filtrate and water treatment mud cake (which can be further utilized in a rotary kiln); the water treatment unit includes a reaction tank 128 connected to the first filter press 3 and a fourth filter press 9 connected to the reaction tank 128.

[0067] The above - mentioned first filter press 3, second filter press 5, third filter press 7, and fourth filter press 9 can be selected as plate - and - frame filter presses.

[0068] Combined with Figure 1As shown, the filtrate evaporation and crystallization unit 10 is used to evaporate and crystallize the purified filtrate obtained from the water treatment unit; the inlet of the filtrate evaporation and crystallization unit 10 is connected to the first filter press 3. In a specific embodiment, the condensate outlet of the evaporation and crystallization system is connected to the water inlet of the alkali leaching tank 2 and / or the first rinsing tank 4 and / or the second rinsing tank 6.

[0069] Combined with Figure 2 As shown, the mother liquor iodine extraction system includes a liquid storage tank 11, a reaction tank 128, a concentrator 13, and a mother liquor evaporation and crystallization unit 14 connected in sequence; the liquid storage tank 11 is connected to the mother liquor outlet of the filtrate evaporation and crystallization unit 10; the reaction tank 128 is used to adjust the pH of the remaining salt extraction mother liquor, perform an oxidation reaction with a certain amount of chlorine gas, and adjust the pH of the oxidized system, etc.; the mother liquor outlet of the mother liquor evaporation and crystallization unit 14 is connected to the liquid storage tank 11. In a specific embodiment, the mother liquor outlet of the filtrate evaporation and crystallization unit 10 is connected to the liquid storage tank 11 through a mother liquor pipeline, and an iodine analyzer and a three-way valve are provided on the mother liquor pipeline. The three-way valve is connected to the alkali leaching tank 2 through a mother liquor branch pipe; when the iodine analyzer detects that the iodine content of the remaining salt extraction mother liquor from the filtrate evaporation and crystallization unit 10 is ≥ 300 mg / L, the three-way valve opens the mother liquor pipeline, and the remaining salt extraction mother liquor enters the liquid storage tank 11; otherwise, the three-way valve opens the mother liquor branch pipe, and the remaining salt extraction mother liquor enters the alkali leaching tank 2 for circulation.

[0070] Combined with Figures 3 to 5 As shown, a comprehensive utilization method of crude zinc powder adopts the above-mentioned comprehensive utilization system of crude zinc powder to perform the following steps:

[0071] S1, Mix the crude zinc powder with water evenly in the alkali leaching tank to obtain a mixed ore pulp, add soda ash for alkali leaching, and then perform two rinsing operations to obtain an alkali leaching filtrate and washed zinc powder;

[0072] This step mainly includes the alkali leaching and rinsing processes. The crude zinc powder is mixed evenly with water in a certain proportion to obtain a mixed ore pulp system, and soda ash is added to adjust the pH of the system to fully leach the crude zinc powder; it specifically includes the following processes:

[0073] S11, Add the crude zinc powder into the alkali leaching tank and mix it evenly with water to obtain a mixed ore pulp;

[0074] In the crude zinc powder used in this step, the Zn content is 20 - 60%, the Cl content is 2 - 20%, the K content is 1 - 20%, the Na content is 1 - 5%, and the I content is 0.01 - 0.3%; among them, the water in this step can be fresh water or the primary filtrate from the second filter press of the rinsing module or the condensate from the evaporation and crystallization system or the remaining salt extraction mother liquor, etc.;

[0075] S12, Add soda ash to the mixed ore pulp for alkali leaching, and then perform pressure filtration to obtain an alkali leaching filtrate and an alkali leaching mud cake;

[0076] In the alkali leaching process of this step, the pH of the mixed pulp after adding soda ash is 7 - 9, and the time for alkali leaching is 15 - 60 min; the pH of the alkali leaching filtrate obtained after alkali leaching is 7 - 9;

[0077] S13. Feed the alkali leaching mud cake into the first - stage rinsing tank, add water for primary rinsing, and perform pressure filtration after rinsing to obtain the rinsed mud cake; the time for primary rinsing is 15 - 60 min; among them, the water used in this step can be fresh water, or the secondary filtrate from the third pressure filter, or the condensate water from the evaporation and crystallization system, etc.;

[0078] S14. Feed the rinsed mud cake into the second - stage rinsing tank, add water for secondary rinsing, and perform pressure filtration after rinsing to obtain the washed zinc powder.

[0079] In this step, the time for secondary rinsing is 15 - 60 min; the Zn content of the washed zinc powder obtained after secondary rinsing is ≥40%, the Cl content is <1%, and the I content is <0.01%. The water used in this step can be fresh water or the condensate water from the evaporation and crystallization system, etc.;

[0080] The water used in the above steps S11, S13, and S13 is mixed at a solid - liquid ratio of 1:2 - 4.

[0081] S2. Soften, remove heavy metals, and flocculate the alkali leaching filtrate in the water treatment unit, and then obtain the purified filtrate and water treatment mud cake through pressure filtration;

[0082] This step is for the water treatment unit to purify and remove impurities, adding agents step by step to reduce the hardness and heavy metal ion content of the alkali leaching filtrate, so that the water quality meets the requirements of the subsequent filtrate evaporation and crystallization unit;

[0083] In the softening process of this step, add a pH regulator to adjust the pH of the alkali leaching filtrate to 9 - 11, and then add sodium carbonate for softening. The addition amount of sodium carbonate is specifically determined according to the content of Ca, Mg and other ions in the system. In the heavy - metal removal process, add a heavy - metal remover to the alkali leaching filtrate. The heavy - metal remover is selected as sodium sulfate nonahydrate, and the addition amount of the heavy - metal remover is specifically determined according to the content of heavy metal ions such as Zn, Pb in the system. In the flocculation process, add a flocculant to the alkali leaching filtrate. The flocculant is selected as polyacrylamide, and the addition amount of the flocculant is 0.1 - 0.5% of the weight of the alkali leaching filtrate.

[0084] In the above - obtained purified filtrate, the Ca content is <50 mg / L, the Zn content is <10 mg / L, and the Pb content is <10 mg / L.

[0085] S3. Concentrate and evaporate and crystallize the purified filtrate in the filtrate evaporation and crystallization unit to obtain KCl products and NaCl products;

[0086] This step is to concentrate, evaporate and crystallize the purified filtrate after purification and impurity removal in step S2 in a filtrate evaporation and crystallization unit to obtain KCl product and NaCl product respectively;

[0087] S4, detecting the iodine content in the remaining salt extraction mother liquor after evaporation and crystallization, and when the iodine content in the remaining salt extraction mother liquor is less than 300 mg / L, sending the remaining salt extraction mother liquor to the primary alkali leaching process of step S1 for circulation until the iodine content in the remaining salt extraction mother liquor is ≥300 mg / L;

[0088] This step is mainly to accumulate iodine in the solution. The remaining salt extraction mother liquor after evaporation and crystallization will be used in the first alkali leaching process of step S1 for circulation until the iodine content in the remaining salt extraction mother liquor is ≥300 mg / L, and then it will enter step S5 for treatment.

[0089] S5, the remaining salt extraction mother liquor with iodine content ≥300 mg / L is sent to the mother liquor iodine extraction system for oxidation treatment, and then low-temperature crystallization is used to obtain potassium iodate products and KCl products.

[0090] This step is the mother liquor iodine extraction system. After the residual mother liquor of the S5 system is circulated, the residual mother liquor of the S5 system with an iodine content of ≥300 mg / L (i.e., high-iodine mother liquor) is obtained. The oxidation process is used to recover the crude iodine and finally prepare potassium iodate products. Specifically, it includes the following steps:

[0091] S51, after the remaining salt extraction mother liquor with an iodine content of ≥300 mg / L is sent to the liquid storage tank of the mother liquor iodine extraction system, the remaining salt extraction mother liquor enters the reaction tank, and a pH regulator is added to adjust and maintain the pH of the remaining salt extraction mother liquor to less than 2;

[0092] S52, passing excess chlorine gas into the remaining salt extraction mother liquor for oxidation treatment, and after the oxidation reaction is completed, continue to add potassium hydroxide to adjust the pH to 6-7;

[0093] In this step, chlorine is used as a reducing agent, and iodine is first reduced to elemental iodine. Excessive chlorine is continuously introduced, and elemental iodine and chlorine work together to generate hydroiodic acid and hydrochloric acid. The reaction equation is shown below. The production process is as follows: As chlorine is introduced, the color of the system changes from light yellow to brown and then to light yellow.

[0094] 2I - +Cl2=I2↓+2Cl -

[0095] 5Cl2+I2+6H2O=2HIO3+10HCl

[0096] After the oxidation reaction is completed, potassium hydroxide is added to adjust the pH of the system to 6-7. The reaction equation is shown below.

[0097] KOH + HIO3 = KIO3 + H2O

[0098] KOH + HCl = KCl + H2O

[0099] S53. Feed the solution processed in step S52 into a concentrator for concentration, and then enter the mother liquor evaporation and crystallization unit for low-temperature crystallization to obtain potassium iodate product and KCl product. During the low-temperature crystallization process, the temperature is controlled at 0 - 10 °C. The crystallization efficiency of the potassium iodate product and KCl product reaches over 90%.

[0100] S54. The iodine-extracted mother liquor from the mother liquor evaporation and crystallization unit is returned to the storage tank for recycling.

[0101] Example 1

[0102] This example uses Figure 1 and Figure 2 the comprehensive utilization system of crude zinc powder shown in

[0103] (1) Alkali leaching unit. Mix the crude zinc powder (Zn 52.77%, Cl 13.39%, K 8.11%, Na 4.16%, I 0.13%) with water (fresh water or filter press water from the rinsing module or condensed water from the evaporation and crystallization system or the remaining mother liquor for salt extraction, etc.) in an alkali leaching tank at a solid-liquid ratio of 1:2 to obtain a mixed pulp system. Add soda ash to adjust the system to pH = 7 for alkali leaching. The alkali leaching time is 20 min to fully leach the crude zinc powder, obtaining an alkali leaching filtrate (pH = 8) and an alkali leaching mud cake. Then, rinse the alkali leaching mud cake twice. The solid-liquid ratio for the first rinse is 1:2 (the water used is fresh water or the secondary filtrate from the third filter press or condensed water from the evaporation and crystallization system, etc.), and the first rinse time is 20 min. The solid-liquid ratio for the second rinse is 1:2 (the water used is fresh water or condensed water from the evaporation and crystallization system, etc.), and the second rinse time is 20 min. Finally, obtain washed zinc powder with Zn 70%, Cl 0.23%, K 0.22%, Na 0.14%, I 0.009%.

[0104] (2) Water treatment unit: Add chemicals such as lye (adjust pH to 11), sodium carbonate (softening agent, dosage is 7 kg / ton of filtrate), and sodium sulfide nonahydrate (heavy metal removal agent, dosage is 0.8 kg / ton of filtrate) step by step to reduce the hardness and heavy metal ion content of the alkali leaching filtrate respectively. After treatment, in the solution system, Ca is 40 mg / L, Zn is 5 mg / L, and Pb is 8 mg / L. Finally, add polyacrylamide (flocculant, dosage is 0.3% of the weight of the alkali leaching filtrate). After pressure filtration, the water treatment mud cake is returned to the rotary kiln process, and the quality of the purified filtrate (Ca content < 50 mg / L, Zn content < 10 mg / L, Pb content < 10 mg / L) meets the requirements of the evaporation crystallization system and is ready for evaporation crystallization.

[0105] (3) Filtrate evaporation crystallization unit: Concentrate, evaporate, and crystallize the purified filtrate after purification and impurity removal in step (2) to obtain NaCl product and KCl product respectively. Among them, the NaCl content in the NaCl product is 99% and is directly sold externally; the K2O content in the KCl product is 58%, meeting the requirements of national standard first-class products and can be sold externally.

[0106] (4) Mother liquor iodine extraction system: The remaining salt extraction mother liquor in the system of step (3) is returned to the alkali leaching process for recycling. After obtaining the remaining salt extraction mother liquor with an I content of 350 mg / L (i.e., high-iodine mother liquor), it enters the mother liquor iodine extraction system. Add hydrochloric acid in the reaction tank to adjust the pH to 2, continuously introduce excessive chlorine for oxidation treatment. Observe that the solution changes from light yellow to brown and then to light yellow to terminate the reaction, and then add flaky sodium hydroxide to adjust the system pH to 7. Then enter the concentrator, concentrate with concentrated salt solution, and finally after low-temperature crystallization (temperature is 0 °C), obtain KIO3 product and KCl product respectively. Among them, the recovery rate of KIO3 is 91%, and after refining, it is sold externally; the K2O content in the KCl product is 58%, meeting the requirements of national standard first-class products and is sold externally.

[0107] Example 2

[0108] This example uses Figure 1 and Figure 2 The comprehensive utilization system of crude zinc powder shown to process the crude zinc powder as follows:

[0109] (1) Alkali leaching unit: Coarsely ground zinc powder (Zn 35.4%, Cl 23.4%, K 12.4%, Na 4%, I 0.20%) and water (fresh water, or filter press water from the rinsing module, or condensed water from the evaporation and crystallization system, or remaining mother liquor for salt extraction, etc.) are mixed evenly in an alkali leaching tank at a solid-liquid ratio of 1:2 to obtain a mixed pulp system. Soda ash is added to adjust the system to pH = 9 for alkali leaching. The alkali leaching time is 45 minutes to fully leach the coarsely ground zinc powder, obtaining alkali leaching filtrate (pH = 9) and alkali leaching mud cake. Then, the alkali leaching mud cake is rinsed twice in sequence. During the first rinse, the solid-liquid ratio is 1:2 (the water used is fresh water, or secondary filtrate from the third filter press, or condensed water from the evaporation and crystallization system, etc.), and the first rinse time is 30 minutes. During the second rinse, the solid-liquid ratio is 1:2 (the water used is fresh water, or condensed water from the evaporation and crystallization system, etc.), and the second rinse time is 30 minutes. Finally, washed zinc powder Zn 46.7%, Cl 0.68%, K 0.36%, Na 0.40%, I 0.015% is obtained.

[0110] (2) Water treatment unit: Chemical agents such as alkali solution (to adjust pH to 11), sodium carbonate (softening agent, dosage 7.6 kg / ton of filtrate), and sodium sulfide nonahydrate (heavy metal removal agent, dosage 0.7 kg / ton of filtrate) are added step by step to reduce the hardness and heavy metal ion content of the alkali leaching filtrate. In the treated solution system, Ca is 45 mg / L, Zn is 6 mg / L, and Pb is 7 mg / L. Finally, polyacrylamide (flocculant, dosage 0.3% of the weight of the alkali leaching filtrate) is added. After pressure filtration, the water treatment mud cake is returned to the rotary kiln process, and the quality of the purified filtrate (Ca content < 50 mg / L, Zn content < 10 mg / L, Pb content < 10 mg / L) meets the requirements of the evaporation and crystallization system and is ready for evaporation and crystallization.

[0111] (3) Filtrate evaporation and crystallization unit: The purified filtrate after purification and impurity removal in step (2) is concentrated, evaporated, and crystallized to obtain NaCl product and KCl product respectively. The NaCl content in the NaCl product is 99% and is directly sold externally. The K2O content in the KCl product is 58%, meeting the requirements of national standard first-class products and can be sold externally.

[0112] (4) Mother liquor iodine extraction system. The remaining salt extraction mother liquor in step (3) is returned to the alkali leaching process for recycling. After obtaining the remaining salt extraction mother liquor with an I content of 480 mg / L (i.e., high-iodine mother liquor), it enters the mother liquor iodine extraction system. Hydrochloric acid is added in the reaction tank to adjust the pH to 2, and excessive chlorine is continuously introduced for oxidation treatment. When the solution changes from light yellow to brown and then back to light yellow, the reaction is terminated. Then, flaky sodium hydroxide is added to adjust the system pH to 6.5. After that, it enters the concentrator and is concentrated using the concentrated salt solution. Finally, after low-temperature crystallization (at a temperature of 5°C), KIO3 product and KCl product are obtained respectively. Among them, the recovery rate of KIO3 is 90%. After refining, it is sold externally. The K2O content in the KCl product is 57%, meeting the requirements of the national standard for first-class products and is sold externally.

[0113] Those of ordinary skill in the art in this technical field should recognize that the above embodiments are only used to illustrate the present invention, rather than to limit the present invention. As long as within the scope of the essential spirit of the present invention, changes and modifications to the above-described embodiments will fall within the scope of the claims of the present invention.

Claims

1. An integrated utilization system for crude zinc powder, characterized in that, It includes a crude zinc powder water washing system and a mother liquor iodine extraction system; The crude zinc powder water washing system includes an alkali leaching unit, a water treatment unit, and a filtrate evaporation and crystallization unit arranged in sequence; The alkali leaching unit is used to perform alkali leaching and two rinses on the crude zinc powder to obtain an alkali leaching filtrate and washed zinc powder; this alkali leaching unit includes a dust bin, an alkali leaching module, and a rinsing module connected in sequence. The alkali leaching module includes an alkali leaching tank connected to the dust bin and a first filter press connected to the alkali leaching tank. The filtrate outlet of the first filter press is connected to the water treatment unit; the rinsing module includes a first-stage rinsing tank, a second filter press, a second-stage rinsing tank, and a third filter press connected in sequence; The water treatment unit is used to soften, remove heavy metals, and flocculate the alkali leaching filtrate obtained from the alkali leaching unit to obtain a purified filtrate and water treatment cake; this water treatment unit includes a reaction tank connected to the first filter press and a fourth filter press connected to the reaction tank; The filtrate evaporation and crystallization unit is used to evaporate and crystallize the purified filtrate obtained from the water treatment unit; the inlet of this filtrate evaporation and crystallization unit is connected to the first filter press; The mother liquor iodine extraction system includes a liquid storage tank, a reaction tank, a concentrator, and a mother liquor evaporation and crystallization unit connected in sequence; the liquid storage tank is connected to the mother liquor outlet of the filtrate evaporation and crystallization unit; the mother liquor outlet of the mother liquor evaporation and crystallization unit is connected to the liquid storage tank.

2. The comprehensive utilization system of crude zinc powder according to claim 1, wherein, The filtrate outlet of the third filter press is connected to the first-stage rinsing tank, and the filtrate outlet of the second filter press is connected to the alkali leaching tank.

3. The comprehensive utilization system of crude zinc powder according to claim 1, characterized in that The first filter press, the second filter press, the third filter press, and the fourth filter press can be selected as plate and frame filter presses.

4. The comprehensive utilization system of crude zinc powder according to claim 1, wherein The condensate outlet of the evaporation and crystallization system is connected to the water inlet of the alkali leaching tank and / or the first-stage rinsing tank and / or the second-stage rinsing tank.

5. The comprehensive utilization system of crude zinc powder according to claim 1, wherein The mother liquor outlet of the filtrate evaporation and crystallization unit is connected to the liquid storage tank through a mother liquor pipeline. An iodine analyzer and a three-way valve are provided on the mother liquor pipeline. This three-way valve is connected to the alkali leaching tank through a mother liquor branch pipe; When the iodine analyzer detects that the iodine content of the remaining salt extraction mother liquor coming out of the filtrate evaporation and crystallization unit is ≥ 300 mg / L, the three-way valve opens the mother liquor pipeline, and the remaining salt extraction mother liquor enters the liquid storage tank; otherwise, the three-way valve opens the mother liquor branch pipe, and the remaining salt extraction mother liquor enters the alkali leaching tank for circulation.

6. A comprehensive utilization method of crude zinc powder, characterized in that, The comprehensive utilization system of crude zinc powder as described in any one of claims 1 to 5 is used to perform the following steps: S1, Mix the crude zinc powder and water evenly in the alkali leaching tank to obtain a mixed ore pulp, add soda ash for alkali leaching, and then perform two rinses to obtain an alkali leaching filtrate and washed zinc powder; S2, Soften, remove heavy metals, and flocculate the alkali leaching filtrate in the water treatment unit, and then obtain a purified filtrate and water treatment cake after pressure filtration; S3, Concentrate and evaporate and crystallize the purified filtrate in the filtrate evaporation and crystallization unit to obtain KCl products and NaCl products; S4, Detect the iodine content in the remaining salt extraction mother liquor after evaporation and crystallization. When the iodine content in the remaining salt extraction mother liquor is < 300 mg / L, send the remaining salt extraction mother liquor to the primary alkali leaching process in step S1 for circulation until the iodine content in the remaining salt extraction mother liquor is ≥ 300 mg / L; S5. Feed the remaining iodine-extracting mother liquor with an iodine content of ≥ 300 mg / L into the mother liquor iodine extraction system for oxidation treatment, and then obtain potassium iodate products and KCl products by low-temperature crystallization.

7. The comprehensive utilization method of crude zinc powder according to claim 6, characterized in that, Step S1 includes the following processes: S11. Add coarse zinc powder into the alkali leaching tank and mix it evenly with water to obtain a mixed ore pulp. S12. Add soda ash to the mixed ore pulp for alkali leaching, and then perform pressure filtration to obtain alkali leaching filtrate and alkali leaching mud cake. S13. Feed the alkali leaching mud cake into the first-stage rinsing tank, add water for the first rinsing, and perform pressure filtration after rinsing to obtain a rinsed mud cake. S14. Feed the rinsed mud cake into the second-stage rinsing tank, add water for the second rinsing, and perform pressure filtration after rinsing to obtain washed zinc powder.

8. The comprehensive utilization method of crude zinc powder according to claim 7, characterized in that, In steps S11, S13, and S13, the water used is mixed at a solid-liquid ratio of 1:2 to 4.

9. The comprehensive utilization method of crude zinc powder according to claim 7, characterized in that, In step S1: In step S11, in the coarse zinc powder, the Zn content is 20 - 60%, the Cl content is 2 - 20%, the K content is 1 - 20%, the Na content is 1 - 5%, and the I content is 0.01 - 0.3%. In step S12, during the alkali leaching process, after adding soda ash, the pH of the mixed ore pulp is 7 - 9, and the alkali leaching time is 15 - 60 min. In step S12, the pH of the alkali leaching filtrate is 7 - 9. In step S13, the time for the first rinsing is 15 - 60 min. In step S14, the time for the second rinsing is 15 - 60 min. In step S14, the Zn content of the washed zinc powder is ≥ 40%, the Cl content is < 1%, and the I content is < 0.01%.

10. The comprehensive utilization method of crude zinc powder according to claim 6, characterized in that, In step S2: During the softening process, add a pH regulator to adjust the pH of the alkali leaching filtrate to 9 - 11, and then add sodium carbonate for softening. During the heavy metal removal process, add a heavy metal remover to the alkali leaching filtrate, and the heavy metal remover is selected as sodium sulfate decahydrate. During the flocculation process, add a flocculant to the alkali leaching filtrate, the flocculant is selected as polyacrylamide, and the addition amount of the flocculant is 0.1 - 0.5% of the weight of the alkali leaching filtrate. In the purified filtrate, the Ca content is < 50 mg / L, the Zn content is < 10 mg / L, and the Pb content is < 10 mg / L.

11. The comprehensive utilization method of crude zinc powder according to claim 6, characterized in that, Step S5 includes the following processes: S51. After feeding the remaining iodine-extracting mother liquor with an iodine content of ≥ 300 mg / L into the storage tank of the mother liquor iodine extraction system, the remaining iodine-extracting mother liquor enters the reaction tank, and a pH regulator is added to adjust and maintain the pH of the remaining iodine-extracting mother liquor to less than 2. S52. Pass excessive chlorine into the remaining iodine-extracting mother liquor for oxidation treatment. After the oxidation reaction ends, continue to add potassium hydroxide to adjust the pH to 6 - 7. S53. Feed the solution treated in step S52 into a concentrator for concentration, and then enter the mother liquor evaporation and crystallization unit for low-temperature crystallization to obtain potassium iodate products and KCl products. S54. The iodine-extracting mother liquor coming out of the mother liquor evaporation and crystallization unit returns to the storage tank for recycling.

12. The comprehensive utilization method of crude zinc powder according to claim 11, characterized in that, In step S53, during the low-temperature crystallization process, the temperature is controlled at 0 - 10°C.

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