Advanced treatment process for copper smelting waste acid

Abstract

The invention discloses a copper smelting waste acid deep treatment process, and belongs to the technical field of copper smelting waste acid treatment. The method comprises the following steps: (1) primary sulfuration copper removal; (2) secondary vulcanization arsenic removal; (3) first-stage deacidification treatment; (4) removing heavy metals by neutralizing ferric salt in a second stage; (5) neutralizing ferric salt in a third section to remove heavy metal; (6) hardness reduction treatment; (7) membrane treatment; and (8) evaporative crystallization. According to the method, the copper smelting waste acid wastewater is subjected to advanced treatment such as pollutant removal and product quality regulation and control, and zero emission of the copper smelting waste acid wastewater is truly realized.

Description

Technical Field

[0001] This invention belongs to the field of copper smelting waste acid treatment technology, and relates to a deep treatment process for copper smelting waste acid. Background Technology

[0002] The acidic wastewater generated during copper smelting contains high levels of pollutants such as arsenic and heavy metals, making direct discharge impossible. Treatment is necessary. However, this wastewater not only has high pollutant content but also exhibits complex pollutant properties. Therefore, the wastewater not only suffers from the toxicity of the pollutants themselves but also fails to meet usage or environmental protection requirements, exhibiting characteristics such as high liquid hardness, high sludge density index, and high turbidity. Consequently, current treatment processes for copper smelting acidic wastewater are inadequate to meet increasingly stringent environmental regulations.

[0003] The "Terminology for Water Conservation in Industrial Water Use" (GB / T21534-2008) states that "zero discharge" of wastewater means that the production water system of an enterprise or main unit achieves zero discharge of industrial wastewater. Therefore, the wastewater such as acidic wastewater generated by the relevant unit needs to be recycled, used as raw materials for other industries, transferred to waste residue, and treated as solid waste to achieve "zero discharge".

[0004] Therefore, it is necessary to provide a deep treatment process for copper smelting acid wastewater to comprehensively treat copper smelting acid wastewater and truly achieve "zero discharge" of copper smelting acid wastewater. Summary of the Invention

[0005] To overcome the problems in the background technology, this invention improves the treatment process of acid wastewater in copper smelting, which not only thoroughly removes pollutants such as arsenic, copper and other heavy metals from the acid wastewater, but also regulates the quality of the acid wastewater. After deep treatment, the copper smelting acid wastewater not only has low pollution or even no pollution, but also improves the usability of the substances generated during the treatment process, laying a solid foundation for zero discharge.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: This invention proposes a deep treatment process for copper smelting waste acid, which includes the following steps: (1) First-stage copper removal by sulfidation: The copper-containing sludge produced in the copper smelting process and the copper-containing sludge produced in the copper electrolysis process are subjected to copper removal by sulfidation to obtain copper removal liquid and copper slag. The copper slag is then transported to the pyrometallurgical copper smelting process for use.

[0007] (2) Secondary sulfidation arsenic removal: The sulfidation arsenic removal liquid after copper removal in step (1) and the arsenic-containing waste acid generated during copper smelting are subjected to sulfidation arsenic removal treatment to obtain sulfidation arsenic removal liquid and sulfidation arsenic slag. The sulfidation arsenic slag is transferred to a specialized treatment facility for solid waste disposal.

[0008] (3) First-stage acid reduction treatment: Add calcium carbonate to the sulfide-treated arsenic-removed liquid in step (2) until the liquid pH is 1-4, and then perform thickening and centrifugation treatments in sequence to obtain the acid-reduced liquid and the by-product gypsum. The by-product gypsum can be used as a raw material in the construction and other industries.

[0009] (4) Two-stage neutralization of iron salts to remove heavy metals: Add calcium hydroxide to the deacidified liquid in step (3) until the liquid pH is 10~11.8, then add polyferric sulfate to the liquid until the liquid pH is 8~10.5, and add hydrogen peroxide at the same time. Then add polyacrylamide to the liquid for flocculation. Finally, the liquid is concentrated and filtered in sequence to obtain the two-stage supernatant and neutralization residue.

[0010] The free radicals or intermediates generated by hydrogen peroxide can enhance the coagulation effect of polyferric sulfate and promote the formation of flocs by heavy metals and polyferric sulfate.

[0011] (5) Three-stage neutralization of iron salt for deep removal of heavy metals: Add calcium hydroxide to the supernatant of the second stage in step (4) until the liquid pH is 10-11.5, then add polyferric sulfate until the liquid pH is 8-10.5, add hydrogen peroxide, then add sodium hydrosulfide, and finally add polyacrylamide to the liquid for flocculation and thickening treatment to obtain the three-stage supernatant and thickened bottom sludge. The thickened bottom sludge is transported to step (4) for recycling treatment.

[0012] (6) Hardness reduction treatment: Carbon dioxide is added to the three supernatants in step (5) until the liquid hardness is below 100 mg / L. Sodium hydroxide is added to adjust the pH of the liquid. Then, polyacrylamide and polyaluminum chloride are added to the liquid for flocculation. Finally, the liquid is subjected to thickening and suspension filtration treatment in sequence to obtain low hardness supernatant, thickened bottom mud, and filtered bottom mud. The thickened bottom mud and filtered bottom mud are all transported to step (3) for recycling treatment.

[0013] (7) Membrane treatment: The low hardness supernatant in step (6) is subjected to membrane treatment to obtain permeate, wastewater and high pressure reverse osmosis concentrate. The permeate is transported to the chemical water treatment station for use, the wastewater is transported to step (6) for recycling treatment, and the high pressure reverse osmosis concentrate is transported to the evaporation crystallization process for use.

[0014] (8) Evaporation and crystallization: The high-pressure reverse osmosis concentrate in step (7) is subjected to evaporation and crystallization treatment to complete the deep treatment of copper smelting waste acid.

[0015] Preferably, in step (1), sodium hydrosulfide is added to the copper-containing sludge and copper-containing sludge to remove copper, and the mass ratio of sodium hydrosulfide added to copper in the copper-containing sludge satisfies sodium hydrosulfide:copper = 1:1.14.

[0016] Preferably, in step (2), sodium hydrosulfide is added to the arsenic-containing waste acid to remove arsenic. Sodium hydrosulfide is added until the arsenic-removed liquid is titrated with a 13.6% sodium hydrosulfide solution and no yellow precipitate appears and a white mist is produced.

[0017] Because the solubility product of copper sulfide is relatively smaller than that of arsenic sulfide, in the primary copper removal process, although the waste acid also contains arsenic, the addition of sodium hydrosulfide will result in preferential copper removal.

[0018] Preferably, in step (3), the concentrated underflow of the thickening treatment is centrifuged, and the filtrate obtained after centrifugation is returned to the thickening treatment for recycling. The deacidified liquid is the supernatant obtained after the thickening treatment.

[0019] Preferably, in step (4), calcium hydroxide is added to a liquid pH of 10.5-11.5, polyferric sulfate is added to a liquid pH of 9.5-10.5, and the mass-to-volume ratio of hydrogen peroxide added is H2O2:liquid = 125g:1m. 3 The mass ratio of polyacrylamide added to liquid volume is polyacrylamide:liquid = 2g:1m 3 The underflow obtained from the thickening process is subjected to pressure filtration. The filtrate produced by pressure filtration is returned to the thickening process for recycling. The supernatant of the second stage is the supernatant obtained from the thickening process, and the neutralization residue is the solid residue produced by pressure filtration.

[0020] Preferably, in step (5), calcium hydroxide is added to control the pH value to 10.5-11.5, polyferric sulfate is added to control the pH value to 9-10.5, and the mass-to-liquid volume ratio of hydrogen peroxide is H2O2:liquid = 125g:1m. 3 The mass ratio of sodium hydrosulfide added to the liquid volume is sodium hydrosulfide:liquid = 91g:1m³. 3 The mass ratio of polyacrylamide added to liquid volume is polyacrylamide:liquid = 2g:1m 3 .

[0021] Preferably, in step (6), sodium hydroxide is added to control the pH value to 10.5-11.5, and the mass ratio of polyacrylamide added to liquid volume is polyacrylamide:liquid = 2g:1m 3The mass ratio of polyaluminum chloride added to liquid volume is polyaluminum chloride: liquid = 35g: 1m³. 3 The supernatant obtained from the concentration process is then subjected to suspension filtration.

[0022] Preferably, in step (7), the membrane treatment process includes the following steps: S1: Add polyaluminum chloride to the low-hardness supernatant, then perform multi-media filtration to obtain multi-media filter residue and multi-media filtrate. The mass ratio of polyaluminum chloride added to liquid volume is polyaluminum chloride:liquid = 30g:1m 3 The multi-media filter residue and the backwash steam washing wastewater generated during the multi-media filtration process are transported to step (6) for recycling.

[0023] S2: Perform self-cleaning filtration on the multi-media filtrate in step S1 to obtain self-cleaning filter residue and self-cleaning filtrate. The self-cleaning filter residue and the backwash water generated during the self-cleaning filtration process are transported to step (6) for circulation treatment.

[0024] S3: The self-cleaning filtrate in step S2 is subjected to ultrafiltration to obtain ultrafiltration permeate and ultrafiltration residue. The ultrafiltration residue, as well as the backwash drainage and overflow of ultrafiltration permeate generated during the ultrafiltration process, are transported to step (6) for recycling.

[0025] S4: The ultrafiltration permeate from step S3 is subjected to resin exchange treatment to obtain resin exchange permeate. The overflow generated during the resin exchange treatment and the overflow of the resin permeate are transported to step (6) for recycling.

[0026] Most ultrafiltration permeate is treated by resin exchange in the resin exchange process. However, depending on specific needs, the ultrafiltration permeate can also be backwashed. Sodium hypochlorite, citric acid, and liquid alkali are added to the backwashed permeate, which is then sent to step S3 for recycling. The mass ratio of sodium hypochlorite to liquid volume is: sodium hypochlorite: liquid = 44g:1m³. 3 The mass ratio of citric acid added to the liquid volume is: citric acid: liquid = 25g: 1m 3 The ratio of liquid alkali to liquid volume is: liquid alkali: liquid = 425g: 1m³ 3 Additionally, depending on specific needs, the ultrafiltration permeate can be transported to step S1 for recycling.

[0027] S5: After adding a non-anaerobic bactericide, a reducing agent, and a membrane scale inhibitor to the resin exchange permeate from step S4, the resin exchange permeate is subjected to primary reverse osmosis treatment. The non-anaerobic bactericide is isothiazolinone, the reducing agent is sodium bisulfite, and the mass ratio of the non-anaerobic bactericide added to the liquid volume is non-anaerobic bactericide: liquid = 5g: 1m³.3 The ratio of reducing agent to liquid volume is reducing agent: liquid = 12g: 1m³. 3 The reaction solution, with the membrane scale inhibitor added at a mass ratio of 23g to 1ml of liquid, is as follows: membrane scale inhibitor: liquid = 23g: 1ml 3 The reaction solution is treated by first-stage reverse osmosis to obtain permeate I and concentrate I. The reverse osmosis membrane cleaning water generated during the first-stage reverse osmosis process is returned to step (6) for recycling. The overflow of concentrate I is transported to step (6) for recycling.

[0028] S6: After adding a non-oxygen bactericide, reducing agent, membrane antiscalant, and concentrated sulfuric acid to the concentrate I from step S5, the concentrate I is subjected to high-pressure reverse osmosis treatment. After high-pressure reverse osmosis treatment, high-pressure reverse osmosis permeate and high-pressure reverse osmosis concentrate are obtained. The high-pressure reverse osmosis concentrate is transported to the evaporation and crystallization process for use. The overflow of the high-pressure reverse osmosis concentrate is transported to step (6) for circulation treatment. The high-pressure reverse osmosis permeate and the permeate I from step S5 are combined to form mixed permeate. The non-oxygen bactericide is isothiazolinone, the reducing agent is sodium bisulfite, and the mass ratio of the non-oxygen bactericide added to the liquid volume is non-oxygen bactericide: liquid = 2g: 1m 3 The ratio of reducing agent to liquid volume is reducing agent: liquid = 5g: 1m³. 3 The ratio of membrane scale inhibitor to liquid volume is: membrane scale inhibitor: liquid = 6g: 1m 3 The concentrated sulfuric acid concentration is 98%, and concentrated sulfuric acid is added until the liquid pH is < 6.5.

[0029] S7: After adding a non-oxygen bactericide, reducing agent, and membrane antiscalant to the mixed permeate in step S6, the mixed permeate is subjected to two-stage reverse osmosis treatment. After the two-stage reverse osmosis treatment, permeate II and concentrate II are obtained. The overflow of the mixed permeate is sent to step (6) for circulation treatment. Permeate II is sent to the chemical water treatment station for use. Concentrate II is sent to step S5 and combined with the resin exchange permeate for circulation treatment. The non-oxygen bactericide is isothiazolinone, and the reducing agent is sodium bisulfite. The mass ratio of the non-oxygen bactericide added to the liquid volume is non-oxygen bactericide: body fluid = 5g: 1m 3 The ratio of reducing agent to liquid volume is reducing agent: liquid = 13g: 1m³. 3 The reaction solution, with the membrane scale inhibitor added at a mass ratio of 25g to 1ml of liquid, is as follows: membrane scale inhibitor: liquid = 25g: 1ml 3 Reaction solution.

[0030] Preferably, in steps S1-S7, the liquid generated during the venting operation is transported to step (6) for recycling.

[0031] Preferably, in step (8), the evaporation crystallization process includes the following steps: Q1: The high-pressure reverse osmosis concentrate is subjected to triple-effect evaporation crystallization, thickening, and centrifugation sequentially to obtain sodium sulfate crystals and triple-effect mother liquor. The sodium sulfate crystals are dried to obtain sodium sulfate product. The saturation temperature difference of the triple-effect evaporation crystallization is controlled between 4.5 and 9.5℃. The liquids produced by thickening and centrifugation are both triple-effect mother liquors.

[0032] Q2: The triple-effect mother liquor is subjected to freeze crystallization and centrifugation sequentially to obtain sodium sulfate decahydrate and freeze mother liquor. The sodium sulfate decahydrate is then melted and sent to step Q1 for recycling. The triple-effect mother liquor mainly enters the single-effect evaporation crystallization process, but according to actual needs, the triple-effect mother liquor can also be returned to step Q1 for triple-effect evaporation crystallization again.

[0033] Q3: The frozen mother liquor from step Q2 is subjected to single-effect evaporation crystallization, thickening, and centrifugation sequentially to obtain sodium chloride crystals and single-effect mother liquor. The sodium chloride crystals are then dried to obtain the sodium chloride product. The saturation temperature difference of the single-effect evaporation crystallization is controlled to be 4.5~9.5℃. The liquids produced by thickening and centrifugation are both single-effect mother liquors.

[0034] Q4: The single-effect mother liquor from step Q3 is dried to obtain mixed salt solid waste, which is then disposed of. The single-effect mother liquor mainly enters the drying process to form mixed salt solid waste. However, depending on actual needs, the single-effect mother liquor can also be returned to step Q3 for single-effect evaporation and crystallization to produce sodium chloride, while preventing pipeline blockage.

[0035] The beneficial effects of this invention are: 1. The treatment process of this invention can not only effectively remove heavy metals, arsenic and other pollutants from copper smelting wastewater, but also effectively control the quality of the products in the treatment process, and realize the recycling of some products, providing a new approach to truly achieve "zero discharge" of wastewater.

[0036] 2. This invention effectively reduces liquid turbidity and sludge density index (SDI) through membrane treatment, enhances the reduction of liquid hardness, removes salt from the liquid, and maintains a high water production rate (the desalination rate of the first-stage reverse osmosis can reach over 98.5%, and the water production rate can reach 74%; the desalination rate of the second-stage reverse osmosis can reach over 98.5%, and the water production rate can reach 85%; the desalination rate of the high-pressure reverse osmosis can reach over 97.5%, and the water production rate can reach 62%). This allows the membrane-treated water to be sent to a water treatment plant for use, avoiding the direct discharge of copper smelting acid wastewater. Specifically, through membrane treatment, the liquid turbidity can be reduced to below 0.5 NTU, the SDI to below 3, and the liquid calcium hardness to 10 mg / L.

[0037] 3. This invention utilizes the concentrated water with high salt content generated by membrane treatment for evaporation and crystallization to prepare sodium sulfate and sodium chloride products. The sodium sulfate product meets the Class III Grade 1 standard of "Industrial Anhydrous Sodium Sulfate" (GB / T6009-2014), and the sodium chloride product meets the Grade 2 standard of solar-dried industrial salt in "Industrial Salt" (GB / T 5462-2015), thus allowing for direct sale and achieving increased economic benefits. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 This is a schematic diagram of the membrane treatment process of the present invention; Figure 3 This is a schematic diagram of the evaporation crystallization process of the present invention. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited to the content described.

[0040] Example 1 This embodiment describes the deep treatment of copper smelting waste acid using the following method: (1) Primary sulfide copper removal: Sodium hydrosulfide is added to the anode mud produced during copper smelting and the copper-containing waste acid produced during copper electrolysis according to the mass ratio of sodium hydrosulfide added to copper in the copper-containing waste acid as sodium hydrosulfide: copper = 1:1.14 for copper removal treatment.

[0041] (2) Secondary sulfide removal of arsenic: After mixing the sulfide removal of copper liquid obtained in step (1) and the arsenic-containing waste acid generated during the copper smelting process, sodium hydrosulfide is added to carry out sulfide removal of arsenic to obtain sulfide removal of arsenic liquid and sulfide arsenic slag. Sodium hydrosulfide is continuously added until no yellow precipitate appears and white fog is generated during the titration of the sulfide removal of arsenic liquid with a concentration of 13.6% sodium hydrosulfide solution.

[0042] (3) Acid reduction treatment: Add calcium carbonate to the sulfide-removed arsenic solution in step (2) until the liquid pH=2, and then perform thickening treatment and centrifugation treatment in sequence to obtain the acid reduction solution and the by-product gypsum.

[0043] (4) Second-stage neutralization of iron salts to remove heavy metals: Add calcium hydroxide to the deacidified solution from step (3) until the liquid pH=11, then add polyferric sulfate and hydrogen peroxide to the liquid until the liquid pH=9.5, wherein the hydrogen peroxide is added at a volume ratio of 125g:1m 3 Add it, then follow the ratio of 2g:1m 3Polyacrylamide was added to the liquid in a certain proportion for flocculation. Finally, the liquid was concentrated and filtered in sequence to obtain two supernatants and neutralization residue.

[0044] (5) Three-stage neutralization of iron salts to remove heavy metals: Add calcium hydroxide to the supernatant from the second stage in step (4) until the liquid pH is 10.5, then add polyferric sulfate and hydrogen peroxide until the liquid pH is 9. The hydrogen peroxide is added at a volume ratio of 125g:1ml to the liquid. 3 Add it, then follow the ratio of 91g:1m 3 Sodium hydrosulfide was added in a ratio of 2g:1m to deeply remove heavy metals from the liquid. 3 Polyacrylamide is added to the liquid in a certain proportion for flocculation and then the liquid is thickened to obtain three supernatants and thickened bottom sludge. The thickened bottom sludge is then transported to step (4) for recycling.

[0045] (6) Hardness reduction treatment: Add carbon dioxide to the three supernatants in step (5) until the liquid hardness is below 100 mg / L, and add sodium hydroxide to maintain the liquid pH=11. Then, add sodium hydroxide at a ratio of 2g:1mg / L. 3 And 35g:1m 3 Polyacrylamide and polyaluminum chloride were added to the liquid in proportions to flocculate. Finally, the liquid was subjected to thickening and suspension filtration treatment in sequence to obtain low-hardness supernatant, thickened bottom sludge, and filtered bottom sludge. The thickened bottom sludge and filtered bottom sludge were transported to step (3) for recycling.

[0046] (7) Membrane treatment: ①According to 30g:1m 3 Polyaluminum chloride is added to the low-hardness supernatant in a certain proportion, and then the liquid is subjected to multi-media filtration to obtain multi-media filter residue and multi-media filtrate. The multi-media filter residue and the backwash steam washing water generated during the multi-media filtration process are transported to step (6) for recycling.

[0047] ② Perform self-cleaning filtration on the multi-media filtrate to obtain self-cleaning filter residue and self-cleaning filtrate. Transport the self-cleaning filter residue and backwash water generated during the self-cleaning filtration process to step (6) for recycling.

[0048] ③ The self-cleaning filtrate is subjected to ultrafiltration to obtain ultrafiltration permeate and ultrafiltration residue. The ultrafiltration residue and the backwash drainage and overflow of ultrafiltration permeate generated during the ultrafiltration process are transported to step (6) for recycling.

[0049] ④ The ultrafiltration permeate is subjected to resin exchange treatment to obtain resin exchange permeate. The overflow generated during the resin exchange treatment and the overflow of the resin permeate are transported to step (6) for recycling.

[0050] ⑤According to 5g:1m 3 12g:1m 3 23g:1m 3 After adding isothiazolinone, sodium bisulfite and membrane antiscalant to the resin exchange permeate in the specified proportions, the resin exchange permeate is subjected to first-stage reverse osmosis treatment to obtain permeate I and concentrate I. The reverse osmosis membrane cleaning water generated during the first-stage reverse osmosis process is returned to step (6) for circulation treatment, and the overflow of concentrate I is transported to step (6) for circulation treatment.

[0051] ⑥According to 2g:1m 3 5g:1m 3 6g:1m 3 Isothiazolinone, sodium bisulfite, and membrane antiscalant were added to concentrate I in the specified proportions. At the same time, concentrated sulfuric acid with a concentration of 98% was added until the liquid pH reached below 6.5. Then, high-pressure reverse osmosis treatment was carried out on concentrate I. After high-pressure reverse osmosis treatment, high-pressure reverse osmosis permeate and high-pressure reverse osmosis concentrate were obtained. The high-pressure reverse osmosis concentrate was transported to the evaporation and crystallization process for use. The overflow of the high-pressure reverse osmosis concentrate was transported to step (6) for circulation treatment. The high-pressure reverse osmosis permeate and the permeate I in step (5) were combined to form mixed permeate.

[0052] ⑦According to 5g:1m 3 13g:1m 3 25g:1m 3 After adding isothiazolinone, sodium bisulfite and membrane antiscalant to the mixed permeate, the mixed permeate is subjected to two-stage reverse osmosis treatment. After the two-stage reverse osmosis treatment, permeate II and concentrate II are obtained. The overflow of the mixed permeate is sent to step (6) for circulation treatment. Permeate II is sent to the chemical water treatment station for use. Concentrate II is sent to step ⑤ and combined with the resin exchange permeate for circulation treatment.

[0053] During the membrane treatment process described above, the liquid generated during the venting operation is transported to step (6) for recycling.

[0054] (8) Evaporation and crystallization: ① The high-pressure reverse osmosis concentrate is subjected to triple-effect evaporation crystallization, then thickened until the liquid concentration reaches 20%-30%, and then centrifuged to obtain sodium sulfate crystals and triple-effect mother liquor. The sodium sulfate crystals are dried at 50~80℃ to obtain sodium sulfate product. The saturation temperature difference of triple-effect evaporation crystallization is controlled at 7℃. ② The triple-effect mother liquor is frozen and crystallized at -5~5℃, and then centrifuged to obtain sodium sulfate decahydrate and frozen mother liquor. The sodium sulfate decahydrate is then melted and transferred to the triple-effect evaporation crystallization process for triple-effect evaporation cycle treatment.

[0055] ③ The frozen mother liquor is subjected to single-effect evaporation crystallization, then thickened to a concentration of 20%~30%, and then centrifuged to obtain sodium chloride crystals and single-effect mother liquor. The sodium chloride crystals are dried at 50~80℃ to obtain sodium chloride product. The saturation temperature difference of single-effect evaporation crystallization is controlled at 7℃. ④ The single-effect mother liquor is dried at 50~90℃ to obtain mixed salt solid waste, which is then disposed of as solid waste.

[0056] Example 2 This embodiment describes the deep treatment of copper smelting waste acid using the following method: (1) Primary sulfide copper removal: Sodium hydrosulfide is added to the anode mud produced during copper smelting and the copper-containing waste acid produced during copper electrolysis according to the mass ratio of sodium hydrosulfide added to copper in the copper-containing waste acid as sodium hydrosulfide: copper = 1:1.14 for copper removal treatment.

[0057] (2) Secondary sulfide removal of arsenic: After mixing the sulfide removal of copper liquid obtained in step (1) and the arsenic-containing waste acid generated during the copper smelting process, sodium hydrosulfide is added to carry out sulfide removal of arsenic to obtain sulfide removal of arsenic liquid and sulfide arsenic slag. Sodium hydrosulfide is continuously added until no yellow precipitate appears and white fog is generated during the titration of the sulfide removal of arsenic liquid with a concentration of 13.6% sodium hydrosulfide solution.

[0058] (3) Acid reduction treatment: Add calcium carbonate to the sulfide-removed arsenic solution in step (2) until the liquid pH=1, and then perform thickening treatment and centrifugation treatment in sequence to obtain the acid reduction solution and the by-product gypsum.

[0059] (4) Two-stage neutralization of iron salts to remove heavy metals: Add calcium hydroxide to the deacidified solution from step (3) until the liquid pH=10, then add polyferric sulfate and hydrogen peroxide to the liquid until the liquid pH=8, wherein the hydrogen peroxide is added at a volume ratio of 125g:1m 3 Add it, then follow the ratio of 2g:1m 3 Polyacrylamide was added to the liquid in a certain proportion for flocculation. Finally, the liquid was concentrated and filtered in sequence to obtain two supernatants and neutralization residue.

[0060] (5) Three-stage neutralization of iron salts to remove heavy metals: Add calcium hydroxide to the supernatant from the second stage in step (4) until the liquid pH=10, then add polyferric sulfate and hydrogen peroxide until the liquid pH=8, wherein the hydrogen peroxide is added at a volume ratio of 125g:1m 3 Add it, then follow the ratio of 91g:1m 3 Sodium hydrosulfide was added in a ratio of 2g:1m to deeply remove heavy metals from the liquid. 3Polyacrylamide is added to the liquid in a certain proportion for flocculation and then the liquid is thickened to obtain three supernatants and thickened bottom sludge. The thickened bottom sludge is then transported to step (4) for recycling.

[0061] (6) Hardness reduction treatment: Add carbon dioxide to the three supernatants in step (5) until the liquid hardness is below 100 mg / L, and add sodium hydroxide to maintain the liquid pH at 10.5. Then, add sodium hydroxide at a ratio of 2 g: 1 mg / L. 3 And 35g:1m 3 Polyacrylamide and polyaluminum chloride were added to the liquid in proportions to flocculate. Finally, the liquid was subjected to thickening and suspension filtration treatment in sequence to obtain low-hardness supernatant, thickened bottom sludge, and filtered bottom sludge. The thickened bottom sludge and filtered bottom sludge were transported to step (3) for recycling.

[0062] (7) Membrane treatment: ①According to 30g:1m 3 Polyaluminum chloride is added to the low-hardness supernatant in a certain proportion, and then the liquid is subjected to multi-media filtration to obtain multi-media filter residue and multi-media filtrate. The multi-media filter residue and the backwash steam washing water generated during the multi-media filtration process are transported to step (6) for recycling.

[0063] ② Perform self-cleaning filtration on the multi-media filtrate to obtain self-cleaning filter residue and self-cleaning filtrate. Transport the self-cleaning filter residue and backwash water generated during the self-cleaning filtration process to step (6) for recycling.

[0064] ③ The self-cleaning filtrate is subjected to ultrafiltration to obtain ultrafiltration permeate and ultrafiltration residue. The ultrafiltration residue and the backwash drainage and overflow of ultrafiltration permeate generated during the ultrafiltration process are transported to step (6) for recycling.

[0065] ④ The ultrafiltration permeate is subjected to resin exchange treatment to obtain resin exchange permeate. The overflow generated during the resin exchange treatment and the overflow of the resin permeate are transported to step (6) for recycling.

[0066] ⑤According to 5g:1m 3 12g:1m 3 23g:1m 3 After adding isothiazolinone, sodium bisulfite and membrane antiscalant to the resin exchange permeate in the specified proportions, the resin exchange permeate is subjected to first-stage reverse osmosis treatment to obtain permeate I and concentrate I. The reverse osmosis membrane cleaning water generated during the first-stage reverse osmosis process is returned to step (6) for circulation treatment, and the overflow of concentrate I is transported to step (6) for circulation treatment.

[0067] ⑥According to 2g:1m 3 5g:1m3 6g:1m 3 Isothiazolinone, sodium bisulfite, and membrane antiscalant were added to concentrate I in the specified proportions. At the same time, concentrated sulfuric acid with a concentration of 98% was added until the liquid pH reached below 6.5. Then, high-pressure reverse osmosis treatment was carried out on concentrate I. After high-pressure reverse osmosis treatment, high-pressure reverse osmosis permeate and high-pressure reverse osmosis concentrate were obtained. The high-pressure reverse osmosis concentrate was transported to the evaporation and crystallization process for use. The overflow of the high-pressure reverse osmosis concentrate was transported to step (6) for circulation treatment. The high-pressure reverse osmosis permeate and the permeate I in step (5) were combined to form mixed permeate.

[0068] ⑦According to 5g:1m 3 13g:1m 3 25g:1m 3 After adding isothiazolinone, sodium bisulfite and membrane antiscalant to the mixed permeate, the mixed permeate is subjected to two-stage reverse osmosis treatment. After the two-stage reverse osmosis treatment, permeate II and concentrate II are obtained. The overflow of the mixed permeate is sent to step (6) for circulation treatment. Permeate II is sent to the chemical water treatment station for use. Concentrate II is sent to step ⑤ and combined with the resin exchange permeate for circulation treatment.

[0069] During the membrane treatment process described above, the liquid generated during the venting operation is transported to step (6) for recycling.

[0070] (8) Evaporation and crystallization: ① The high-pressure reverse osmosis concentrate is subjected to triple-effect evaporation crystallization, then thickened until the liquid concentration reaches 20%-30%, and then centrifuged to obtain sodium sulfate crystals and triple-effect mother liquor. The sodium sulfate crystals are dried at 50~80℃ to obtain sodium sulfate product. The saturation temperature difference of triple-effect evaporation crystallization is controlled at 4.5℃. ② The triple-effect mother liquor is frozen and crystallized at -5~5℃, and then centrifuged to obtain sodium sulfate decahydrate and frozen mother liquor. The sodium sulfate decahydrate is then melted and transferred to the triple-effect evaporation crystallization process for triple-effect evaporation cycle treatment.

[0071] ③ The frozen mother liquor is subjected to single-effect evaporation crystallization, then thickened to a concentration of 20%~30%, and then centrifuged to obtain sodium chloride crystals and single-effect mother liquor. The sodium chloride crystals are dried at 50~80℃ to obtain sodium chloride product. The saturation temperature difference of single-effect evaporation crystallization is controlled at 4.5℃. ④ The single-effect mother liquor is dried at 50~90℃ to obtain mixed salt solid waste, which is then disposed of as solid waste.

[0072] Example 3 This embodiment describes the deep treatment of copper smelting waste acid using the following method: (1) Primary sulfide copper removal: Sodium hydrosulfide is added to the anode mud produced during copper smelting and the copper-containing waste acid produced during copper electrolysis according to the mass ratio of sodium hydrosulfide added to copper in the copper-containing waste acid as sodium hydrosulfide: copper = 1:1.14 for copper removal treatment.

[0073] (2) Secondary sulfide removal of arsenic: After mixing the sulfide removal of copper liquid obtained in step (1) and the arsenic-containing waste acid generated during the copper smelting process, sodium hydrosulfide is added to carry out sulfide removal of arsenic to obtain sulfide removal of arsenic liquid and sulfide arsenic slag. Sodium hydrosulfide is continuously added until no yellow precipitate appears and white fog is generated during the titration of the sulfide removal of arsenic liquid with a concentration of 13.6% sodium hydrosulfide solution.

[0074] (3) Acid reduction treatment: Add calcium carbonate to the sulfide-removed arsenic solution in step (2) until the liquid pH=2, and then perform thickening treatment and centrifugation treatment in sequence to obtain the acid reduction solution and the by-product gypsum.

[0075] (4) Two-stage neutralization of iron salts to remove heavy metals: Add calcium hydroxide to the deacidified solution from step (3) until the liquid pH is 11.8, then add polyferric sulfate and hydrogen peroxide to the liquid until the liquid pH is 10.5, wherein the hydrogen peroxide is added at a volume ratio of 125g:1m 3 Add it, then follow the ratio of 2g:1m 3 Polyacrylamide was added to the liquid in a certain proportion for flocculation. Finally, the liquid was concentrated and filtered in sequence to obtain two supernatants and neutralization residue.

[0076] (5) Three-stage neutralization of iron salts to remove heavy metals: Add calcium hydroxide to the supernatant from the second stage in step (4) until the liquid pH is 11.5, then add polyferric sulfate and hydrogen peroxide until the liquid pH is 10.5, wherein the hydrogen peroxide is added at a volume ratio of 125g:1ml to the liquid. 3 Add it, then follow the ratio of 91g:1m 3 Sodium hydrosulfide was added in a ratio of 2g:1m to deeply remove heavy metals from the liquid. 3 Polyacrylamide is added to the liquid in a certain proportion for flocculation and then the liquid is thickened to obtain three supernatants and thickened bottom sludge. The thickened bottom sludge is then transported to step (4) for recycling.

[0077] (6) Hardness reduction treatment: Add carbon dioxide to the three supernatants in step (5) until the liquid hardness is below 100 mg / L, and add sodium hydroxide to maintain the liquid pH at 11.5. Then, add sodium hydroxide at a ratio of 2 g: 1 mg / L. 3 And 35g:1m 3Polyacrylamide and polyaluminum chloride were added to the liquid in proportions to flocculate. Finally, the liquid was subjected to thickening and suspension filtration treatment in sequence to obtain low-hardness supernatant, thickened bottom sludge, and filtered bottom sludge. The thickened bottom sludge and filtered bottom sludge were transported to step (3) for recycling.

[0078] (7) Membrane treatment: ①According to 30g:1m 3 Polyaluminum chloride is added to the low-hardness supernatant in a certain proportion, and then the liquid is subjected to multi-media filtration to obtain multi-media filter residue and multi-media filtrate. The multi-media filter residue and the backwash steam washing water generated during the multi-media filtration process are transported to step (6) for recycling.

[0079] ② Perform self-cleaning filtration on the multi-media filtrate to obtain self-cleaning filter residue and self-cleaning filtrate. Transport the self-cleaning filter residue and backwash water generated during the self-cleaning filtration process to step (6) for recycling.

[0080] ③ The self-cleaning filtrate is subjected to ultrafiltration to obtain ultrafiltration permeate and ultrafiltration residue. The ultrafiltration residue and the backwash drainage and overflow of ultrafiltration permeate generated during the ultrafiltration process are transported to step (6) for recycling.

[0081] ④ The ultrafiltration permeate is subjected to resin exchange treatment to obtain resin exchange permeate. The overflow generated during the resin exchange treatment and the overflow of the resin permeate are transported to step (6) for recycling.

[0082] ⑤According to 5g:1m 3 12g:1m 3 23g:1m 3 After adding isothiazolinone, sodium bisulfite and membrane antiscalant to the resin exchange permeate in the specified proportions, the resin exchange permeate is subjected to first-stage reverse osmosis treatment to obtain permeate I and concentrate I. The reverse osmosis membrane cleaning water generated during the first-stage reverse osmosis process is returned to step (6) for circulation treatment, and the overflow of concentrate I is transported to step (6) for circulation treatment.

[0083] ⑥According to 2g:1m 3 5g:1m 3 6g:1m 3 Isothiazolinone, sodium bisulfite, and membrane antiscalant were added to concentrate I in the specified proportions. At the same time, concentrated sulfuric acid with a concentration of 98% was added until the liquid pH reached below 6.5. Then, high-pressure reverse osmosis treatment was carried out on concentrate I. After high-pressure reverse osmosis treatment, high-pressure reverse osmosis permeate and high-pressure reverse osmosis concentrate were obtained. The high-pressure reverse osmosis concentrate was transported to the evaporation and crystallization process for use. The overflow of the high-pressure reverse osmosis concentrate was transported to step (6) for circulation treatment. The high-pressure reverse osmosis permeate and the permeate I in step (5) were combined to form mixed permeate.

[0084] ⑦According to 5g:1m 3 13g:1m 3 25g:1m 3 After adding isothiazolinone, sodium bisulfite and membrane antiscalant to the mixed permeate, the mixed permeate is subjected to two-stage reverse osmosis treatment. After the two-stage reverse osmosis treatment, permeate II and concentrate II are obtained. The overflow of the mixed permeate is sent to step (6) for circulation treatment. Permeate II is sent to the chemical water treatment station for use. Concentrate II is sent to step ⑤ and combined with the resin exchange permeate for circulation treatment.

[0085] During the membrane treatment process described above, the liquid generated during the venting operation is transported to step (6) for recycling.

[0086] (8) Evaporation and crystallization: ① The high-pressure reverse osmosis concentrate is subjected to triple-effect evaporation crystallization, then thickened until the liquid concentration reaches 20%-30%, and then centrifuged to obtain sodium sulfate crystals and triple-effect mother liquor. The sodium sulfate crystals are dried at 50~80℃ to obtain sodium sulfate product. The saturation temperature difference of triple-effect evaporation crystallization is controlled at 9.5℃. ② The triple-effect mother liquor is frozen and crystallized at -5~5℃, and then centrifuged to obtain sodium sulfate decahydrate and frozen mother liquor. The sodium sulfate decahydrate is then melted and transferred to the triple-effect evaporation crystallization process for triple-effect evaporation cycle treatment.

[0087] ③ The frozen mother liquor is subjected to single-effect evaporation crystallization, then thickened to a concentration of 20%~30%, and then centrifuged to obtain sodium chloride crystals and single-effect mother liquor. The sodium chloride crystals are dried at 50~80℃ to obtain sodium chloride product. The saturation temperature difference of single-effect evaporation crystallization is controlled at 9.5℃.

[0088] ④ The single-effect mother liquor is dried at 50~90℃ to obtain mixed salt solid waste, which is then disposed of as solid waste.

[0089] In summary, this invention allows all liquids to be recycled throughout the entire treatment process, truly achieving "zero discharge" of copper smelting acid wastewater.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A deep treatment process for waste acid from copper smelting, characterized in that: The deep treatment process for waste acid from copper smelting includes the following steps: (1) First-stage copper removal by sulfidation: copper-containing sludge and copper-containing sludge generated during copper smelting and copper electrolysis are subjected to copper removal by sulfidation to obtain copper removal liquid and copper sludge. The copper sludge is then transported to the pyrometallurgical copper smelting process for use. (2) Secondary sulfidation arsenic removal: The sulfidation arsenic removal liquid after copper removal in step (1) and the arsenic-containing waste acid generated during copper smelting are subjected to sulfidation arsenic removal treatment to obtain sulfidation arsenic removal liquid and sulfidation arsenic slag. (3) Acid reduction treatment: Add calcium carbonate to the sulfide-removed arsenic solution in step (2) until the liquid pH is 1-4, and then perform thickening and centrifugation treatment on the liquid in sequence to obtain the acid reduction solution and the by-product gypsum. (4) Two-stage neutralization of iron salts to remove heavy metals: Add calcium hydroxide to the deacidified liquid in step (3) until the liquid pH is 10~11.8, then add polyferric sulfate to the liquid until the liquid pH is 8~10.5, and add hydrogen peroxide at the same time. Then add polyacrylamide to the liquid for flocculation. Finally, the liquid is concentrated and filtered in sequence to obtain the two-stage supernatant and neutralization residue. (5) Three-stage neutralization of iron salt for deep removal of heavy metals: Add calcium hydroxide to the supernatant of the second stage in step (4) until the liquid pH is 10-11.5, then add polyferric sulfate until the liquid pH is 8-10.5, add hydrogen peroxide, then add sodium hydrosulfide, and finally add polyacrylamide to the liquid for flocculation and then thicken the liquid to obtain the three-stage supernatant and thickened bottom sludge. The thickened bottom sludge is transported to step (4) for recycling. (6) Hardness reduction treatment: Carbon dioxide is added to the three supernatants in step (5) until the liquid hardness is lower than 100 mg / L. Sodium hydroxide is added to adjust the pH of the liquid. Then, polyacrylamide and polyaluminum chloride are added to the liquid for flocculation. Finally, the liquid is subjected to thickening and suspension filtration treatment in sequence to obtain low hardness supernatant, thickened bottom mud, and filtered bottom mud. The thickened bottom mud and filtered bottom mud are all transported to step (3) for recycling treatment. (7) Membrane treatment: The low hardness supernatant in step (6) is subjected to membrane treatment to obtain permeate, wastewater and high pressure reverse osmosis concentrate. The permeate is transported to the chemical water treatment station for use, the wastewater is transported to step (6) for recycling treatment, and the high pressure reverse osmosis concentrate is transported to the evaporation crystallization process for use. (8) Evaporation and crystallization: The high-pressure reverse osmosis concentrate in step (7) is subjected to evaporation and crystallization treatment to complete the deep treatment of copper smelting waste acid.

2. The processing technology according to claim 1, characterized in that: In step (1), sodium hydrosulfide is added to the copper-containing sludge and copper-containing sludge to remove copper. The mass ratio of sodium hydrosulfide added to copper in the copper-containing sludge satisfies sodium hydrosulfide:copper = 1:1.

14.

3. The processing technology according to claim 1, characterized in that: In step (2), sodium hydrosulfide is added to the arsenic-containing waste acid to remove arsenic. Sodium hydrosulfide is added until the arsenic-removed liquid is titrated with a 13.6% sodium hydrosulfide solution and no yellow precipitate appears and a white mist is produced.

4. The processing technology according to claim 1, characterized in that: In step (3), the concentrated underflow of the thickening treatment is centrifuged, and the filtrate obtained after centrifugation is returned to the thickening treatment for recycling. The deacidified liquid is the supernatant obtained after the thickening treatment.

5. The processing technology according to claim 1, characterized in that: In step (4), calcium hydroxide is added to bring the liquid pH to 10.5-11.5, polyferric sulfate is added to bring the liquid pH to 9.5-10.5, and the mass-to-volume ratio of hydrogen peroxide added is H2O2:liquid = 125g:1m. 3 The mass ratio of polyacrylamide added to liquid volume is polyacrylamide:liquid = 2g:1m 3 The underflow obtained from the thickening process is subjected to pressure filtration. The filtrate produced by pressure filtration is returned to the thickening process for recycling. The supernatant of the second stage is the supernatant obtained from the thickening process, and the neutralization residue is the solid residue produced by pressure filtration.

6. The processing technology according to claim 1, characterized in that: In step (5), calcium hydroxide is added to control the pH value at 10.5-11.5, polyferric sulfate is added to control the pH value at 9-10.5, and the mass-to-volume ratio of hydrogen peroxide added is H2O2:liquid = 125g:1m 3 The mass ratio of sodium hydrosulfide added to the liquid volume is sodium hydrosulfide:liquid = 91g:1m³. 3 The mass ratio of polyacrylamide added to liquid volume is polyacrylamide:liquid = 2g:1m 3 .

7. The processing technology according to claim 1, characterized in that: In step (6), sodium hydroxide is added to control the pH value to 10.5-11.5, and the mass ratio of polyacrylamide to liquid volume is polyacrylamide:liquid = 2g:1m 3 The mass ratio of polyaluminum chloride added to liquid volume is polyaluminum chloride: liquid = 35g: 1m³. 3 The supernatant obtained from the concentration process is then subjected to suspension filtration.

8. The processing technology according to claim 1, characterized in that: In step (7), the membrane treatment process specifically includes the following steps: S1: Add polyaluminum chloride to the low-hardness supernatant, then perform multi-media filtration to obtain multi-media filter residue and multi-media filtrate. The mass ratio of polyaluminum chloride added to liquid volume is polyaluminum chloride:liquid = 30g:1m 3 The multi-media filter residue and the backwash steam washing wastewater generated during the multi-media filtration process are transported to step (6) for recycling. S2: Perform self-cleaning filtration on the multi-media filtrate in step S1 to obtain self-cleaning filter residue and self-cleaning filtrate. The self-cleaning filter residue and the backwash water generated during the self-cleaning filtration process are transported to step (6) for circulation treatment. S3: Ultrafiltration is performed on the self-cleaning filtrate in step S2 to obtain ultrafiltration permeate and ultrafiltration residue. The ultrafiltration residue, as well as the backwash drainage and overflow of ultrafiltration permeate generated during the ultrafiltration process, are transported to step (6) for recycling. S4: The ultrafiltration permeate from step S3 is subjected to resin exchange treatment to obtain resin exchange permeate. The overflow generated during the resin exchange treatment and the overflow of the resin permeate are transported to step (6) for recycling. S5: After adding a non-anaerobic bactericide, a reducing agent, and a membrane scale inhibitor to the resin exchange permeate from step S4, the resin exchange permeate is subjected to primary reverse osmosis treatment. The non-anaerobic bactericide is isothiazolinone, the reducing agent is sodium bisulfite, and the mass ratio of the non-anaerobic bactericide added to the liquid volume is non-anaerobic bactericide: liquid = 5g: 1m³. 3 The ratio of reducing agent to liquid volume is reducing agent: liquid = 12g: 1m³. 3 The reaction solution, with the membrane scale inhibitor added at a mass ratio of 23g to 1ml of liquid, is as follows: membrane scale inhibitor: liquid = 23g: 1ml 3 The reaction solution is treated by first-stage reverse osmosis to obtain permeate I and concentrate I. The reverse osmosis membrane cleaning water generated during the first-stage reverse osmosis process is returned to step (6) for recycling. The overflow of concentrate I is transported to step (6) for recycling. S6: After adding a non-oxygen bactericide, reducing agent, membrane antiscalant, and concentrated sulfuric acid to the concentrate I from step S5, the concentrate I is subjected to high-pressure reverse osmosis treatment. After high-pressure reverse osmosis treatment, high-pressure reverse osmosis permeate and high-pressure reverse osmosis concentrate are obtained. The high-pressure reverse osmosis concentrate is transported to the evaporation and crystallization process for use. The overflow of the high-pressure reverse osmosis concentrate is transported to step (6) for circulation treatment. The high-pressure reverse osmosis permeate and the permeate I from step S5 are combined to form mixed permeate. The non-oxygen bactericide is isothiazolinone, the reducing agent is sodium bisulfite, and the mass ratio of the non-oxygen bactericide added to the liquid volume is non-oxygen bactericide: liquid = 2g: 1m 3 The ratio of reducing agent to liquid volume is reducing agent: liquid = 5g: 1m³. 3 The ratio of membrane scale inhibitor to liquid volume is: membrane scale inhibitor: liquid = 6g: 1m 3 The concentrated sulfuric acid concentration is 98%, and concentrated sulfuric acid is added until the liquid pH is < 6.5; S7: After adding a non-oxygen bactericide, reducing agent, and membrane antiscalant to the mixed permeate in step S6, the mixed permeate is subjected to two-stage reverse osmosis treatment. After the two-stage reverse osmosis treatment, permeate II and concentrate II are obtained. The overflow of the mixed permeate is sent to step (6) for circulation treatment. Permeate II is sent to the chemical water treatment station for use. Concentrate II is sent to step S5 and combined with the resin exchange permeate for circulation treatment. The non-oxygen bactericide is isothiazolinone, and the reducing agent is sodium bisulfite. The mass ratio of the non-oxygen bactericide added to the liquid volume is non-oxygen bactericide: body fluid = 5g: 1m 3 The ratio of reducing agent to liquid volume is reducing agent: liquid = 13g: 1m³. 3 The reaction solution, with the membrane scale inhibitor added at a mass ratio of 25g to 1ml of liquid, is as follows: membrane scale inhibitor: liquid = 25g: 1ml 3 Reaction solution.

9. The processing technology according to claim 8, characterized in that: In steps S1-S7, the liquid generated during the venting operation is transported to step (6) for recycling.

10. The processing technology according to claim 1, characterized in that: In step (8), the specific process of evaporation and crystallization is as follows. Includes the following steps: Q1: The high-pressure reverse osmosis concentrate is subjected to triple-effect evaporation crystallization, thickening, and centrifugation in sequence to obtain sodium sulfate crystals and triple-effect mother liquor. The sodium sulfate crystals are dried to obtain sodium sulfate product. The saturation temperature difference of triple-effect evaporation crystallization is controlled at 4.5~9.5℃. Q2: The triple-effect mother liquor is subjected to freeze crystallization and centrifugation in sequence to obtain sodium sulfate decahydrate and freeze mother liquor. The sodium sulfate decahydrate is then melted and transported to step Q1 for recycling. Q3: The frozen mother liquor in step Q2 is subjected to single-effect evaporation crystallization, thickening, and centrifugation in sequence to obtain sodium chloride crystals and single-effect mother liquor. The sodium chloride crystals are dried to obtain sodium chloride product. The saturation temperature difference of single-effect evaporation crystallization is controlled to be 4.5~9.5℃. Q4: The single-effect mother liquor in step Q3 is dried to obtain mixed salt solid waste, and the mixed salt solid waste is disposed of as solid waste.

Images