Zinc smelting waste acid wastewater zero discharge treatment system and treatment method

Abstract

The invention discloses a zero-discharge treatment system and a zero-discharge treatment method for waste acid and wastewater in zinc smelting, and belongs to the technical field of industrial waste acid treatment. The treatment system comprises a vulcanization reaction section, a neutralization reaction section, a weight removal unit, a hardness reduction unit, a multi-medium filter, an ultrafiltration membrane device, a first-stage reverse osmosis device and a high-pressure reverse osmosis device, and the treatment units adopt a stepped series design to form a complete waste acid and wastewater treatment chain, so that the purposes of recycling and zero emission are achieved. Compared with the prior art, the system adopts a multi-stage synergistic treatment process, firstly, arsenic is removed through a vulcanization reaction section, a neutralization reaction is performed, then, heavy metals and fluorides are removed, hardness is reduced by adopting carbon dioxide, and then membrane separation and permeation treatment are performed, so that carbon emission reduction is realized while waste residues are reduced; and gradient utilization of the wastewater is realized through step-by-step treatment, so that the purposes of resource recycling and zero emission of the waste acid wastewater are achieved.

Description

Technical Field

[0001] This invention relates to a method for treating waste acid wastewater generated in the zinc smelting industry, specifically a process for removing arsenic, heavy metals, and reducing hardness from waste acid wastewater, as well as recycling and achieving zero discharge, belonging to the field of industrial waste acid treatment technology. Background Technology

[0002] In the processes of metal smelting and sulfuric acid production, large quantities of industrial waste acid containing heavy metals, arsenic, fluorine, and chlorine are generated. This waste acid not only pollutes the environment and wastes sulfur resources, but also poses significant safety hazards. Considering that waste acid contains abundant sulfuric acid and valuable metals, comprehensive treatment and recycling using appropriate methods can alleviate environmental pressure and achieve secondary resource recovery and comprehensive utilization.

[0003] Currently, the treatment of waste acid widely adopts the traditional sulfide neutralization process, which generates a large amount of hazardous waste annually and produces effluent with high hardness, making direct reuse impossible. With the rise of the "zero-emission" concept in the environmental protection field, traditional waste acid treatment methods are struggling to achieve economical and efficient results. Therefore, optimizing and improving traditional processes to explore a reasonable and effective way to treat waste acid, ensuring effluent meets standards for reuse, recovering valuable components, and avoiding the generation of large amounts of waste residue and wastewater is of great significance to the green and sustainable development of the zinc smelting industry. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a zero-discharge treatment system and method for zinc smelting acid wastewater that is flexible in operation, simple in operation, highly efficient and energy-saving, and environmentally friendly.

[0005] The objective of this invention can be achieved through the following technical solutions: A zero-discharge treatment system for zinc smelting wastewater includes a sulfidation reaction section, a neutralization reaction section, a degravation unit, a hardening unit, a multi-media filter, an ultrafiltration membrane device, a primary reverse osmosis device, and a high-pressure reverse osmosis device. Each treatment unit adopts a stepped series design to form a complete wastewater treatment chain, achieving the purpose of recycling and zero discharge. The system employs a multi-stage synergistic treatment process. First, arsenic is removed and neutralized through a sulfidation reaction stage. Then, heavy metals and fluorides are removed, and carbon dioxide is used to reduce hardness. Finally, membrane separation and osmosis treatment are carried out to achieve the goal of efficient wastewater recycling and true zero discharge.

[0006] Furthermore, the sulfidation reaction section includes two reaction tanks, a primary reaction tank and a secondary reaction tank, as well as a thickening tank. Sodium hydrosulfide is added to the primary reaction tank to carry out a sulfidation reaction to remove arsenic from the wastewater. PAM is added to the secondary reaction tank to carry out flocculation and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation enters the neutralization reaction section.

[0007] Furthermore, the neutralization reaction section includes two neutralization tanks, a primary neutralization tank and a secondary neutralization tank, and a thickening tank. Lime slurry is added to the primary neutralization tank and the secondary neutralization tank respectively to carry out a neutralization reaction, and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation enters the weight removal unit.

[0008] Furthermore, the heavy metal removal unit includes four reaction units: a primary reaction unit, a secondary reaction unit, a tertiary reaction unit, a quaternary reaction unit, and a thickening tank. Lime slurry, polyferric sulfate, a defluorinating agent, and PAM agent are added to the four reaction units respectively to remove heavy metals and fluorides. After the reaction, the wastewater enters the thickening tank to achieve solid-liquid separation. Part of the supernatant after separation is used to prepare lime slurry, and the remainder enters the hardening unit.

[0009] Furthermore, the hardening unit includes, in sequence along the water flow direction, a pH adjustment tank, a softener, and a suspended media filter. The pH is adjusted to 12 by adding liquid alkali in the pH adjustment tank, and CO2 is introduced into the softener to remove calcium from the wastewater. 2+ The slurry generated by the reaction is pumped into a suspended packing filter. The filtered water is clear and transparent. Part of it is used for flue gas scrubbing water in the acid production system purification section, and the remainder is pumped into the multi-media filter of the deep membrane treatment unit.

[0010] Furthermore, the multi-media filter and ultrafiltration membrane device are used to remove residual suspended solids, colloids and some organic matter from the wastewater. The water after ultrafiltration by the ultrafiltration membrane device enters the first-stage reverse osmosis device through a first-stage reverse osmosis booster pump.

[0011] Furthermore, a self-cleaning filter is installed between the multi-media filter and the ultrafiltration membrane device to prevent sand and gravel from entering the ultrafiltration membrane device.

[0012] Furthermore, the primary reverse osmosis unit is for concentration and desalination, with the permeate entering a collection tank and the concentrate entering a high-pressure reverse osmosis unit.

[0013] Furthermore, the high-pressure reverse osmosis unit further concentrates the concentrate from the first-stage reverse osmosis, reducing the amount of concentrate produced and increasing the water production rate of the reverse osmosis system. The water produced by the high-pressure reverse osmosis unit enters the collection tank and is mixed with the water produced by the first-stage reverse osmosis unit for reuse in the cooling system makeup water. The concentrate is sent to the flue gas furnace for slag flushing.

[0014] A method for zero-discharge treatment of zinc smelting acid wastewater, specifically comprising: 1) The wastewater is first collected and enters the wastewater storage tank. It is then pumped into the sulfidation reaction section. Sodium hydrosulfide is added to the primary reaction tank of this section to carry out the sulfidation reaction and remove arsenic from the wastewater. PAM is added to the secondary reaction tank to carry out flocculation and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation enters the neutralization reaction section. 2) Lime slurry is added to the primary neutralization tank and the secondary neutralization tank of the neutralization reaction section to carry out the neutralization reaction, and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation then enters the heavy removal unit. 3) Lime slurry is added to the first-stage reaction unit of the heavy removal unit, polyferric sulfate is added to the second-stage reaction unit, defluorinating agent is added to the third-stage reaction unit, and PAM is added to the fourth-stage reaction unit. After the reaction, the wastewater enters the thickening tank to achieve solid-liquid separation. Part of the supernatant after separation is used to prepare lime slurry, and the remainder enters the hardening unit. 4) Adjust the pH to 12 in the pH adjustment tank of the hardening unit by adding liquid alkali, and then introduce CO2 into the softener to remove calcium from the wastewater. 2+ The slurry generated by the reaction is pumped into a suspended packing filter. The filtered water is clear and transparent. Part of it is used for flue gas scrubbing water in the purification section of the acid production system, and the remainder is pumped into the multi-media filter of the deep membrane treatment unit. 5) After gravity removal and hardening, the incoming water passes through a multi-media filter and an ultrafiltration membrane device in sequence to remove residual suspended solids, colloids and some organic matter in the wastewater. The water after ultrafiltration through the ultrafiltration membrane device enters the first-stage reverse osmosis unit through a first-stage reverse osmosis booster pump. 6) The main function of the first-stage reverse osmosis unit is to concentrate and desalinate the water. The permeate enters the collection tank, and the concentrate enters the high-pressure reverse osmosis unit. 7) The permeate from the high-pressure reverse osmosis unit enters the permeate tank and is mixed with the permeate from the first-stage reverse osmosis unit for reuse as makeup water in the cooling system. The concentrate is sent to the flue gas furnace for slag flushing.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention optimizes and improves traditional wastewater treatment processes by introducing carbon dioxide hardening technology, providing a new solution for high-hardness wastewater generated during wastewater treatment. Compared to traditional hardening methods such as chemical precipitation and ion exchange softening, carbon dioxide hardening technology reduces the generation of waste residue and recycled wastewater, effectively lowering wastewater treatment costs. It also effectively utilizes carbon dioxide from industrial waste gas, achieving both wastewater resource recovery and carbon emission reduction.

[0016] 2. This invention utilizes five stages to treat acid wastewater step-by-step, achieving cascaded utilization of the wastewater. The effluent from the lime-iron salt degravation treatment can be used to prepare lime slurry; the effluent from the carbon dioxide dehardening treatment can be used for flue gas scrubbing in the acid production system's purification stage; and the effluent from the deep membrane system treatment can be used as makeup water for the cooling system. The system can be flexibly operated and switched according to production needs.

[0017] 3. The wastewater treatment system of this invention produces no wastewater throughout the entire process. After final treatment by the deep membrane system, the produced water is reused to replenish the equipment cooling system, and the concentrated water is used for slag flushing in the fuming furnace, achieving zero wastewater discharge. This is of great significance for saving water resources and reducing environmental pollution, and improves both economic and social benefits. Attached Figure Description

[0018] Figure 1 This is a structural diagram of the processing system of the present invention; In the diagram, 1-sulfurization reaction section, 2-neutralization reaction section, 3-weight removal unit, 4-hardening unit, 5-multi-media filter, 6-ultrafiltration membrane device, 7-first-stage reverse osmosis device, and 8-high-pressure reverse osmosis device. Detailed Implementation

[0019] The technical solution and effects of the present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the scope of protection of the present invention is not limited thereto. Example 1

[0020] like Figure 1 As shown, this embodiment provides a zero-discharge treatment system for zinc smelting wastewater, including a sulfidation reaction section 1, a neutralization reaction section 2, a degravation unit 3, a hardening unit 4, a multi-media filter 5, an ultrafiltration membrane device 6, a primary reverse osmosis device 7, and a high-pressure reverse osmosis device 8. Each treatment unit adopts a stepped series design to form a complete wastewater treatment chain, achieving the purpose of recycling and zero discharge.

[0021] The system employs a multi-stage synergistic treatment process. First, arsenic is removed and neutralized through a sulfidation reaction stage. Then, heavy metals and fluorides are removed, and carbon dioxide is used to reduce hardness. Finally, membrane separation and osmosis treatment are carried out to achieve the goal of efficient wastewater recycling and true zero discharge.

[0022] In one specific implementation, the sulfidation reaction section 1 includes two reaction tanks, a primary reaction tank and a secondary reaction tank, and a thickening tank. Sodium hydrosulfide is added to the primary reaction tank to carry out a sulfidation reaction to remove arsenic from the wastewater. PAM is added to the secondary reaction tank to carry out flocculation and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation enters the neutralization reaction section 2, and the sulfidation slag after separation is safely treated.

[0023] In this embodiment, the removal of arsenic from wastewater by adding sodium hydrosulfide to the primary reaction tank is achieved through the following mechanism: In an acidic environment, sodium hydrosulfide first decomposes into sodium hydroxide and hydrogen sulfide. The hydrogen sulfide can react with As in the solution. 3+ The reaction produces a sparingly soluble As2S3 precipitate, which is then separated by sedimentation to remove arsenic.

[0024] Among them, the added sodium hydrosulfide reacts with As in the wastewater. 3+ The molar ratio is 3:2. This sulfidation method has limited effect on trace amounts of arsenic, but for acidic wastewater with high arsenic content, the sulfidation method can remove more than 99% of the arsenic in the wastewater, forming arsenic-containing waste residue with arsenic sulfide as the main component and a high content, which effectively reduces the arsenic content in the solution and is conducive to the recovery and utilization of arsenic.

[0025] In this embodiment, the amount of PAM added to the secondary reaction tank is 3~5 mg / L.

[0026] In one specific implementation, the neutralization reaction section 2 includes two neutralization tanks, a primary neutralization tank and a secondary neutralization tank, and a thickening tank. Lime slurry is added to the primary neutralization tank and the secondary neutralization tank respectively to carry out a neutralization reaction to remove sulfate ions and produce general solid waste gypsum. Then, it enters the thickening tank to achieve solid-liquid separation. The supernatant after separation enters the heavy removal unit 3, and the gypsum residue after separation is safely treated.

[0027] In this embodiment, the concentration of lime slurry added to the primary neutralization tank and the secondary neutralization tank is 10wt%~20wt%, and the mixture is stirred. After the neutralization reaction is complete, the pH value is approximately 7.

[0028] In one specific implementation, the heavy metal removal unit 3 includes four reaction units: a primary reaction unit, a secondary reaction unit, a tertiary reaction unit, a quaternary reaction unit, and a thickening tank. Lime slurry, polyferric sulfate, a defluorinating agent, and PAM reagent are added to the four reaction units to remove heavy metals and fluorides. After the reaction, the wastewater enters the thickening tank to achieve solid-liquid separation. Part of the supernatant after separation is used to prepare lime slurry, and the remainder enters the hardening unit 4. The heavy metal slag after separation can be sold directly or further used as raw material for the recovery of valuable metals such as zinc and copper.

[0029] In this embodiment, lime slurry is added to the primary reaction unit to adjust the pH of the wastewater to 8-11, thereby promoting the formation of insoluble hydroxide precipitates from heavy metal ions.

[0030] When polyferric sulfate is added to the secondary reaction unit, its hydrolysis products neutralize the negative charge on the surface of colloidal particles through positive charge, and capture tiny precipitates by forming a network structure through polymeric iron chains. At the same time, the iron-based flocs have a strong affinity for As, Hg and other heavy metals, which can further remove heavy metals. The dosage of polyferric sulfate is affected by various factors such as pH value, type and concentration of heavy metals.

[0031] In the tertiary reaction unit, a defluorinating agent, such as calcium hydroxide, calcium chloride, or zeolite, is added. These agents have a large specific surface area and can adsorb fluoride ions through physical or chemical action, thereby achieving defluorination. In this embodiment, calcium hydroxide is preferred, and the dosage is 5 to 10 times the fluoride content in the wastewater.

[0032] PAM is added to the fourth-stage reaction unit to promote solid-liquid separation through flocculation. The addition amount is 3~5 mg / L.

[0033] In one specific implementation, the hardness reduction unit 4 includes, in sequence along the water flow direction, a pH adjustment tank, a softener, and a suspended media filter. The pH is adjusted to approximately 12 by adding liquid alkali in the pH adjustment tank. CO2 is introduced into the softener to remove calcium from the wastewater. 2+ The slurry generated by the reaction is pumped into a suspended packing filter. The filtered water is clear and transparent. Part of it is used for flue gas scrubbing water in the acid production system purification section, and the remainder is pumped into the multi-media filter 5 of the deep membrane treatment unit.

[0034] In this embodiment, the packing material in the suspended packing filter is specifically a polymer-modified foamed material (such as polystyrene) with a density of 0.05-0.1 and a particle size of 1.0-2.0 mm. The main component of the underflow from the suspended packing filter is calcium carbonate slurry, which is returned to the waste acid treatment section to neutralize the waste acid, without generating secondary waste residue.

[0035] In this embodiment, the amount and rate of CO2 addition are controlled by the pH values ​​before and after hardening removal. CO2 is introduced into the water to form CO3. 2- H + CO3 2- With Ca 2+ This process forms CaCO3 precipitate and simultaneously lowers the pH value of the wastewater. To ensure sufficient CO3... 2- Sufficient alkalinity needs to be maintained before hardening, i.e., the pH should be adjusted to around 12 before hardening. When introducing CO2 gas, it needs to be introduced slowly and evenly. If the CO2 gas is introduced too quickly or in too much way, it will not only result in low CO2 utilization but also cause calcium carbonate to dissolve. Therefore, the pH should be controlled to around 8.5 after hardening with carbon dioxide.

[0036] In one specific implementation, the multi-media filter 5 and the ultrafiltration membrane device 6 are used to remove residual suspended solids, colloids and some organic matter from the wastewater. The water after ultrafiltration by the ultrafiltration membrane device 6 enters the first-stage reverse osmosis unit 7 through a first-stage reverse osmosis booster pump. The backwash water of the multi-media filter 5 is returned to the front-end hardening unit for treatment, and the backwash water of the ultrafiltration membrane device 6 is returned to the permeate tank of the hardening unit. A self-cleaning filter is installed between the multi-media filter 5 and the ultrafiltration membrane device 6 to prevent sand and gravel from entering the ultrafiltration membrane device 6.

[0037] In this embodiment, the multi-media filter 5 adopts a double-layer filtration. The upper layer is filled with anthracite with a particle size of 1.2-2.5mm and a filling height of 400mm; the lower layer is filled with quartz sand with a particle size of 0.5-1.2mm and a filling height of 800mm.

[0038] The ultrafiltration membrane in the ultrafiltration membrane device 6 is an external pressure type PVDF hollow fiber membrane.

[0039] In one specific implementation, the primary reverse osmosis unit 7 is for concentration and desalination, with the permeate entering the collection tank and the concentrate entering the high-pressure reverse osmosis unit 8.

[0040] In this embodiment, the reverse osmosis membrane in the first-stage reverse osmosis device 7 is selected from DuPont CR series spiral wound polyamide composite film elements, which are highly durable, resistant to pollution, and have low energy consumption.

[0041] In one specific implementation, the high-pressure reverse osmosis device 8 further concentrates the concentrate from the first-stage reverse osmosis, which can reduce the amount of concentrate produced and increase the water production rate of the reverse osmosis system. The water produced by the high-pressure reverse osmosis device 8 enters the collection tank and is mixed with the water produced by the first-stage reverse osmosis device 7 for reuse in the cooling system makeup water. The concentrate is sent to the flue gas furnace for slag flushing.

[0042] In this embodiment, the reverse osmosis membrane in the high-pressure reverse osmosis device 8 is a DuPont XC series spiral wound polyamide composite film element, which can further concentrate the brine to achieve water recovery in a near-zero discharge system.

[0043] In this embodiment, to ensure the effectiveness of the chemical cleaning of the membrane and to ensure the long-term stable operation of the concentrate reverse osmosis system, the first-stage reverse osmosis unit 7 and the high-pressure reverse osmosis unit 8 are equipped with online flushing and offline cleaning devices. Example 2

[0044] This embodiment uses the wastewater of acid produced by a zinc smelter as the treatment object. By treating it, the goal of recycling and zero discharge is achieved.

[0045] The incoming acid wastewater has the following characteristics: H2SO4 concentration 5wt%, Pb concentration 12mg / L, As concentration 1000mg / L, Hg concentration 7mg / L, Cd concentration 1.8mg / L, Ti concentration 0.78mg / L, fluoride concentration 4000mg / L, CODcr concentration 8000mg / L, and total N concentration 1100mg / L.

[0046] The wastewater treatment method using the system of this invention is as follows: 1) The wastewater is first collected and enters the wastewater storage tank. It is then pumped into the sulfidation reaction section. In the primary reaction tank of this section, 1120 mg / L sodium hydrosulfide is added to the sulfidation reaction to remove arsenic from the wastewater. In the secondary reaction tank, 3 mg / L PAM is added to the flocculation tank and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation enters the neutralization reaction section. 2) In the neutralization reaction section, lime slurry with a concentration of 15% is added to the primary and secondary neutralization tanks to carry out the neutralization reaction. The neutralization tanks are equipped with pH meters. When the pH value is close to 7, it indicates that the reaction is complete. Then, it enters the thickening tank to achieve solid-liquid separation. The concentration of each component in the supernatant after separation is reduced. The concentration of As in the effluent is 35 mg / L, which means that the arsenic removal efficiency is 96.5%. Then it enters the heavy gravimetric unit. 3) Lime slurry is added to the primary reaction unit of the heavy metal removal unit to adjust the pH of the wastewater to around 10; polyferric sulfate is added to the secondary reaction unit at approximately 0.3 kg per ton of wastewater; a defluorinating agent is added to the tertiary reaction unit at approximately 20 kg per ton of wastewater; and PAM is added to the quaternary reaction unit at a concentration of 3 mg / L. Due to the addition of lime slurry in the neutralization and heavy metal removal units, the total hardness of the wastewater after the reaction reaches as high as 2500 mg / L (calculated as CaCO3). The wastewater then enters a thickening tank for solid-liquid separation. Part of the supernatant is used to prepare lime slurry, and the remainder enters the hardness reduction unit. 4) Adjust the pH to approximately 12 in the pH adjustment tank of the hardening unit by adding liquid alkali. Slowly and evenly introduce CO2 into the softener to remove calcium from the wastewater. 2+ The pH is controlled at around 8.5 after carbon dioxide removal and hardness control. The slurry generated by the reaction is pumped into a suspended media filter, and the filtered water is clear and transparent. Part of it is used for flue gas scrubbing water in the acid production system purification section, and the remainder is pumped into the multi-media filter of the deep membrane treatment unit. After this step, the effluent has fluoride ≤10mg / L, total hardness ≤100mg / L (calculated as CaCO3), Ti ≤0.017mg / L, and other components meet the wastewater discharge limits for workshops or production facilities in Table 2 of the "Emission Standard of Pollutants for Lead and Zinc Industry" (GB25466-2010), namely Pb ≤0.5mg / L, As ≤0.3mg / L, Hg ≤0.03mg / L, and Cd ≤0.05mg / L.

[0047] 5) After gravity removal and hardening, the incoming water passes through a multi-media filter and an ultrafiltration membrane device in sequence to remove residual suspended solids, colloids and some organic matter in the wastewater. The water after ultrafiltration through the ultrafiltration membrane device enters the first-stage reverse osmosis unit through a first-stage reverse osmosis booster pump. 6) The main function of the first-stage reverse osmosis unit is to concentrate and desalinate the water. The permeate enters the collection tank, and the concentrate enters the high-pressure reverse osmosis unit. 7) The permeate from the high-pressure reverse osmosis unit enters the permeate tank and is mixed with the permeate from the first-stage reverse osmosis unit for reuse as makeup water in the cooling system. The concentrate is sent to the flue gas furnace for slag flushing.

[0048] The final product water has a pH of 6.5-8.5, total hardness ≤50mg / L (calculated as CaCO3), TDS ≤500mg / L, ammonia nitrogen ≤10mg / L, CODcr ≤60mg / L, and conductivity ≤600μS / cm, which fully meets the requirements for indirect cooling water makeup for the plant's equipment.

[0049] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A zero-discharge treatment system for zinc smelting acid wastewater, characterized in that, The treatment system includes a sulfidation reaction section, a neutralization reaction section, a heavy removal unit, a hardening unit, a multi-media filter, an ultrafiltration membrane device, a first-stage reverse osmosis device, and a high-pressure reverse osmosis device. Each treatment unit adopts a stepped series design to form a complete chain for treating acidic wastewater, achieving the goal of recycling and zero discharge. The system employs a multi-stage synergistic treatment process. First, arsenic is removed and neutralized through a sulfidation reaction stage. Then, heavy metals and fluorides are removed, and carbon dioxide is used to reduce hardness. Finally, membrane separation and osmosis treatment are carried out to achieve the goal of efficient wastewater recycling and true zero discharge.

2. The processing system according to claim 1, characterized in that, The sulfidation reaction section includes two reaction tanks, a primary reaction tank and a secondary reaction tank, as well as a thickening tank. Sodium hydrosulfide is added to the primary reaction tank to carry out a sulfidation reaction to remove arsenic from the wastewater. PAM is added to the secondary reaction tank to carry out flocculation and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation enters the neutralization reaction section.

3. The processing system according to claim 1, characterized in that, The neutralization reaction section includes two neutralization tanks, a primary neutralization tank and a secondary neutralization tank, and a thickening tank. Lime slurry is added to the primary neutralization tank and the secondary neutralization tank respectively to carry out a neutralization reaction, and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation enters the weight removal unit.

4. The processing system according to claim 1, characterized in that, The heavy metal removal unit includes four reaction units: a primary reaction unit, a secondary reaction unit, a tertiary reaction unit, a quaternary reaction unit, and a thickening tank. Lime slurry, polyferric sulfate, a defluorinating agent, and PAM agent are added to the four reaction units respectively to remove heavy metals and fluorides. After the reaction, the wastewater enters the thickening tank to achieve solid-liquid separation. Part of the supernatant after separation is used to prepare lime slurry, and the remainder enters the hardening unit.

5. The processing system according to claim 1, characterized in that, The hardness reduction unit, along the water flow direction, includes a pH adjustment tank, a softener, and a suspended media filter. The pH is adjusted to 12 by adding liquid alkali in the pH adjustment tank, and CO2 is introduced into the softener to remove calcium from the wastewater. 2+ The slurry generated by the reaction is pumped into a suspended packing filter. The filtered water is clear and transparent. Part of it is used for flue gas scrubbing water in the acid production system purification section, and the remainder is pumped into the multi-media filter of the deep membrane treatment unit.

6. The processing system according to claim 1, characterized in that, The multi-media filter and ultrafiltration membrane device are used to remove residual suspended solids, colloids and some organic matter from the wastewater. The water after ultrafiltration by the ultrafiltration membrane device enters the first-stage reverse osmosis unit through the first-stage reverse osmosis booster pump.

7. The processing system according to claim 6, characterized in that, A self-cleaning filter is installed between the multi-media filter and the ultrafiltration membrane device to prevent sand and gravel from entering the ultrafiltration membrane device.

8. The processing system according to claim 1, characterized in that, The first-stage reverse osmosis unit is for concentration and desalination. The permeate enters the collection tank, and the concentrate enters the high-pressure reverse osmosis unit.

9. The processing system according to claim 1, characterized in that, The high-pressure reverse osmosis unit further concentrates the concentrate from the first-stage reverse osmosis, reducing the amount of concentrate produced and increasing the water production rate of the reverse osmosis system. The water produced by the high-pressure reverse osmosis unit enters the collection tank and is mixed with the water produced by the first-stage reverse osmosis unit for reuse in the cooling system makeup water. The concentrate is sent to the flue gas furnace for slag flushing.

10. A method for zero-discharge treatment of zinc smelting acid wastewater, characterized in that, The specific processing method is as follows: 1) The wastewater is first collected and enters the wastewater storage tank. It is then pumped into the sulfidation reaction section. Sodium hydrosulfide is added to the primary reaction tank of this section to carry out the sulfidation reaction and remove arsenic from the wastewater. PAM is added to the secondary reaction tank to carry out flocculation and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation enters the neutralization reaction section. 2) Lime slurry is added to the primary neutralization tank and the secondary neutralization tank of the neutralization reaction section to carry out the neutralization reaction, and then enters the thickening tank to achieve solid-liquid separation. The supernatant after separation then enters the heavy removal unit. 3) Lime slurry is added to the first-stage reaction unit of the heavy removal unit, polyferric sulfate is added to the second-stage reaction unit, defluorinating agent is added to the third-stage reaction unit, and PAM is added to the fourth-stage reaction unit. After the reaction, the wastewater enters the thickening tank to achieve solid-liquid separation. Part of the supernatant after separation is used to prepare lime slurry, and the remainder enters the hardening unit. 4) Adjust the pH to 12 in the pH adjustment tank of the hardening unit by adding liquid alkali, and then introduce CO2 into the softener to remove calcium from the wastewater. 2+ The slurry generated by the reaction is pumped into a suspended packing filter. The filtered water is clear and transparent. Part of it is used for flue gas scrubbing water in the purification section of the acid production system, and the remainder is pumped into the multi-media filter of the deep membrane treatment unit. 5) After gravity removal and hardening, the incoming water passes through a multi-media filter and an ultrafiltration membrane device in sequence to remove residual suspended solids, colloids and some organic matter in the wastewater. The water after ultrafiltration through the ultrafiltration membrane device enters the first-stage reverse osmosis unit through a first-stage reverse osmosis booster pump. 6) The main function of the first-stage reverse osmosis unit is to concentrate and desalinate the water. The permeate enters the collection tank, and the concentrate enters the high-pressure reverse osmosis unit. 7) The permeate from the high-pressure reverse osmosis unit enters the permeate tank and is mixed with the permeate from the first-stage reverse osmosis unit for reuse as makeup water in the cooling system. The concentrate is sent to the flue gas furnace for slag flushing.

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