A wet zinc refining alkali washing wastewater resource system

Abstract

This utility model discloses a resource recovery system for wastewater from a wet zinc smelting process. The system includes a pretreatment subsystem, a membrane concentration subsystem, an evaporation crystallization subsystem, and a product water purification subsystem. The pretreatment subsystem includes a sulfidation unit, a sand filtration unit, and an ultrafiltration unit. The membrane concentration subsystem includes a nanofiltration unit, a high-pressure nanofiltration unit, and an electrodialysis unit. The evaporation crystallization subsystem includes a first MVR evaporation crystallization unit and a second MVR evaporation crystallization unit. The product water purification subsystem includes an ozone catalytic oxidation unit and a stripping ammonia removal unit. This application achieves product water reuse and salt recovery through processes such as heavy metal precipitation, membrane concentration and membrane salt separation, MVR evaporation crystallization, ozone catalytic oxidation, and stripping ammonia removal. It solves the problem of direct discharge of highly alkaline, high-salt wastewater containing heavy metal pollutants, which harms the environment.

Description

Technical Field

[0001] This utility model belongs to the field of metallurgical wastewater treatment / wastewater resource utilization, and in particular relates to a resource utilization system for wet zinc smelting alkaline washing wastewater. Background Technology

[0002] Hydrometallurgical zinc smelting is currently the mainstream zinc smelting process. Its core involves leaching zinc calcined ore with sulfuric acid, followed by electrolytic extraction of metallic zinc. However, zinc calcined ore often contains impurity metals such as Fe, Cu, Cd, Co, Ni, As, and Sb. These impurities dissolve along with the zinc during leaching, affecting the efficiency of subsequent electrolysis and the purity of the zinc product. To improve raw material purity, sodium hydroxide alkaline washing pretreatment is widely used in the treatment of zinc-containing ores or intermediate products.

[0003] Washing ore with NaOH solution can dissolve impurities such as silicates and carbonates (e.g., CaCO3, SiO2) in the ore, reducing acid consumption and impurity content in subsequent acid leaching processes. For zinc existing in salt form (e.g., ZnCl2, ZnCO3), NaOH can convert it into insoluble Zn(OH)2 precipitate, preventing zinc loss during washing and thus improving zinc recovery. Furthermore, under alkaline conditions, some heavy metals (e.g., Pb, As) form hydroxide precipitates, while zinc can be selectively retained or precipitated by controlling pH, achieving preliminary separation. However, this process also generates a large amount of saline alkaline washing wastewater.

[0004] Alkaline washing wastewater is generally characterized by high pH values, high levels of heavy metal ions, and high salt content. If left untreated, this type of wastewater not only increases the environmental burden, but the heavy metal ions in the water can also accumulate through the food chain, posing a threat to human health.

[0005] Utilizing alkaline washing wastewater as a resource can not only reduce wastewater treatment costs but also achieve over 90% wastewater reuse and over 80% salt recovery, reducing fresh water consumption and wastewater discharge, and significantly decreasing pollutant emissions, aligning with the trends of wastewater resource utilization and "zero discharge." Therefore, alkaline washing wastewater from hydrometallurgical processes possesses both polluting and resource-related characteristics. Separately recovering salt and water resources is a problem that urgently needs to be solved by those skilled in the art. Utility Model Content

[0006] The purpose of this invention is to overcome the problems of existing technologies by disclosing a resource recovery system for alkaline washing wastewater from a wet zinc smelting process. Through processes such as heavy metal precipitation, membrane concentration and salt separation, MVR evaporation and crystallization, ozone catalytic oxidation, and stripping to remove ammonia, the system achieves wastewater reuse and salt recovery. This solves the problem of direct discharge of highly alkaline, high-salt wastewater containing heavy metal pollutants, which causes environmental harm.

[0007] The objective of this utility model is achieved through the following technical solution:

[0008] A system for the resource recovery of wastewater from a wet zinc smelting process, comprising: a pretreatment subsystem, a membrane concentration subsystem, an evaporation and crystallization subsystem, and a product water purification subsystem;

[0009] The pretreatment subsystem includes: a sulfidation unit, a sand filtration unit, and an ultrafiltration unit; the membrane concentration subsystem includes a nanofiltration unit, a high-pressure nanofiltration unit, and an electrodialysis unit; the evaporation crystallization subsystem includes a first MVR evaporation crystallization unit and a second MVR evaporation crystallization unit; and the product water purification subsystem includes an ozone catalytic oxidation unit and a stripping ammonia removal unit.

[0010] In the treatment of wet zinc smelting alkali washing wastewater, the wastewater is configured to pass sequentially through a sulfidation unit, a sand filtration unit, and an ultrafiltration unit. The permeate from the ultrafiltration unit is then sent to a nanofiltration unit.

[0011] The permeate from the nanofiltration unit is transported to the electrodialysis unit, the concentrate from the nanofiltration unit is transported to the high-pressure nanofiltration unit, the permeate from the high-pressure nanofiltration unit is transported to the electrodialysis unit, and the concentrate from the high-pressure nanofiltration unit is transported to the first MVR evaporation and crystallization unit to generate sodium sulfate.

[0012] The concentrated water from the electrodialysis unit is transported to the second MVR evaporation and crystallization unit to generate sodium chloride; the permeate from the electrodialysis unit, the first MVR evaporation and crystallization unit, and the second MVR evaporation and crystallization unit is transported to the ozone catalytic oxidation unit, and the permeate from the ozone catalytic oxidation unit is transported to the deammoniation unit to generate ammonia water and reused permeate.

[0013] According to a preferred embodiment, the sulfidation unit removes zinc ions, fluoride ions, thallium ions, and other heavy metal ions by adding sodium hydroxide and a heavy metal scavenging agent.

[0014] According to a preferred embodiment, the sand filter unit and the ultrafiltration unit are configured to remove suspended solids and colloids from the water.

[0015] According to a preferred embodiment, the concentrated water produced by the ultrafiltration unit is transported to the upstream side of the sulfidation unit and mixed with the wet zinc smelting alkaline washing wastewater to be treated.

[0016] According to a preferred embodiment, the nanofiltration unit is configured to remove SO4 from the inflowing water. 2- It is trapped on the concentrated water side.

[0017] According to a preferred embodiment, the high-pressure nanofiltration unit is configured to remove SO4 from the inflowing water. 2- Cl - It is trapped on the concentrated water side.

[0018] The aforementioned main solution of this utility model and its various further alternative solutions can be freely combined to form multiple solutions, all of which are solutions that can be adopted by this utility model and for which protection is sought. Those skilled in the art, after understanding the solution of this utility model, will realize, based on existing technology and common knowledge, that there are many combinations, all of which are technical solutions to be protected by this utility model; therefore, they are not exhaustively listed here.

[0019] The beneficial effects of this utility model are:

[0020] 1. In view of the water quality characteristics of the alkaline washing wastewater in wet zinc smelting, a system was invented to convert it into industrial-grade sodium sulfate and sodium chloride crystals with economic value. This system can recover more than 95% of water resources, greatly improve water resource utilization efficiency, and effectively reduce environmental pollution.

[0021] 2. Although the salt content in the raw water is high, it does not meet the economic requirements for direct evaporation crystallization to produce salt, and monovalent Cl- is also present in the water. - and divalent SO4 2- Direct evaporation and crystallization can generate large amounts of mixed salts. Nanofiltration and high-pressure nanofiltration are used to increase the salt concentration in the wastewater and remove Cl- from the water. - and SO4 2- Effective separation to achieve SO4 2- The removal rate reaches over 98%. The TDS of the high-pressure nanofiltration concentrate reaches over 200 g / L, greatly reducing the investment and operating costs of subsequent MVR evaporation and crystallization equipment.

[0022] 3. Considering the high COD and ammonia nitrogen concentrations in the permeate from the sodium sulfate MVR evaporation and crystallization unit, the freshwater from the electrodialysis unit, and the permeate from the sodium chloride MVR evaporation and crystallization unit are used in stages to remove COD and ammonia nitrogen from the water. The final product is reclaimed water with a TDS content ≤200 mg / L, a COD content ≤30 mg / L, and an ammonia nitrogen content ≤5 mg / L, as well as a small amount of ammonia water byproduct with a concentration of approximately 15%.

[0023] 4. Considering the issues of salt resource recovery rate and purity in this wastewater, a combination process of nanofiltration + high-pressure nanofiltration is adopted to achieve a salt resource recovery rate of over 92% in the wastewater, a sodium sulfate crystallization purity of over 96%, which meets the Class III Grade I standard of GB / T6009 "Industrial Anhydrous Sodium Sulfate", and a sodium chloride crystallization purity of up to 92%, which meets the Grade II standard of GB / T5462-2015 "Industrial Salt Standard". Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the principle and structure of the wet zinc smelting alkaline washing wastewater resource utilization system of this utility model. Detailed Implementation

[0025] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0026] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0027] In the description of this utility model, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this utility model is in use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0028] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0029] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0030] Furthermore, it should be noted that unless otherwise specified, the specific structures, connections, positions, power sources, etc. involved in this utility model are all things that a person skilled in the art can know without creative effort based on the prior art.

[0031] refer to Figure 1 As shown, this application discloses a resource recovery system for alkali washing wastewater from wet zinc smelting. The resource recovery system for alkali washing wastewater from wet zinc smelting includes: a pretreatment subsystem, a membrane concentration subsystem, an evaporation and crystallization subsystem, and a product water purification subsystem.

[0032] The pretreatment subsystem includes a sulfidation unit, a sand filtration unit, and an ultrafiltration unit; the membrane concentration subsystem includes a nanofiltration unit, a high-pressure nanofiltration unit, and an electrodialysis unit; the evaporation crystallization subsystem includes a first MVR evaporation crystallization unit and a second MVR evaporation crystallization unit; and the product water purification subsystem includes an ozone catalytic oxidation unit and a stripping ammonia removal unit.

[0033] The sulfidation unit can employ softening and heavy metal ion removal reaction equipment and precipitation equipment; the sand filtration unit can use a quartz sand filter; the ultrafiltration unit can use DuPont SFP2880 ultrafiltration membranes. The nanofiltration unit of the membrane concentration subsystem can use DuPont NF1000 nanofiltration membranes, and the high-pressure nanofiltration unit can use DuPont NF1000HP high-pressure nanofiltration membranes, with a maximum operating pressure of 68 bar. The electrodialysis unit, MVR evaporation crystallization unit, ozone catalytic oxidation unit, and stripping deammoniation unit all use commercially available conventional equipment.

[0034] In the process of treating the wet zinc smelting alkaline washing wastewater, the wet zinc smelting alkaline washing wastewater is configured to pass through a sulfidation unit, a sand filtration unit and an ultrafiltration unit in sequence, and the product water of the ultrafiltration unit is sent to the nanofiltration unit.

[0035] Specifically, the sulfidation unit removes zinc, fluoride, and thallium ions by adding sodium hydroxide and a heavy metal scavenging agent. The sand filtration unit and ultrafiltration unit are configured to remove suspended solids and colloids from the water. The concentrated water produced by the ultrafiltration unit is transported upstream of the sulfidation unit and mixed with the wet zinc smelting alkaline washing wastewater to be treated.

[0036] The permeate from the nanofiltration unit is transported to the electrodialysis unit, the concentrate from the nanofiltration unit is transported to the high-pressure nanofiltration unit, the permeate from the high-pressure nanofiltration unit is transported to the electrodialysis unit, and the concentrate from the high-pressure nanofiltration unit is transported to the first MVR evaporation and crystallization unit to generate sodium sulfate.

[0037] The nanofiltration unit is configured to remove SO4 from the inflow water. 2-It is retained on the concentrate side; specifically, more than 95% of SO4 can be retained on the concentrate side. 2- The high-pressure nanofiltration unit is configured to remove SO4 from the inflowing water. 2- Cl - It is retained on the concentrate side, thus removing most of the SO4. 2- The concentrated water is retained on the concentrate side, and the TDS of the concentrate is concentrated to meet the feed water requirements of the subsequent MVR evaporation and crystallization system.

[0038] The concentrate from the electrodialysis unit is sent to the second MVR evaporation and crystallization unit to generate sodium chloride; the permeate from the electrodialysis unit, the first MVR evaporation and crystallization unit, and the second MVR evaporation and crystallization unit is sent to the ozone catalytic oxidation unit, and the permeate from the ozone catalytic oxidation unit is sent to the deammoniation unit to generate ammonia water and reused permeate.

[0039] The permeate from nanofiltration and high-pressure nanofiltration units contains only trace amounts of SO4. 2- The two permeate streams, containing a large amount of Cl-, are mixed and further concentrated through an electrodialysis unit to increase the TDS concentration to meet the influent requirements of the second MVR evaporation crystallization system. Industrial-grade sodium sulfate and sodium chloride are then produced separately through the two MVR evaporation crystallization units.

[0040] In the entire wastewater treatment system, the distilled water (product water) produced by the first MVR evaporation and crystallization unit, the fresh water produced by the electrodialysis unit, and the distilled water (product water) produced by the second MVR evaporation and crystallization unit all require further removal of impurities such as organic matter and ammonia nitrogen before their water quality meets the requirements for reuse within the plant area. These three product water streams are mixed and first pass through an ozone catalytic oxidation unit to remove COD. The effluent then undergoes a stripping ammonia removal unit to remove ammonia nitrogen, ultimately yielding reusable water and a small amount of ammonia product. Stripping refers to the process of directly contacting wastewater with steam, causing volatile toxic and harmful substances in the wastewater to diffuse into the gas phase in a certain proportion, thereby achieving the purpose of separating pollutants from the wastewater. Stripping ammonia removal is a conventional method for removing ammonia nitrogen from wastewater in existing technologies.

[0041] This application system employs a pretreatment subsystem, a membrane concentration subsystem, an evaporation and crystallization subsystem, and a product water purification subsystem to convert the alkaline washing wastewater generated during the hydrometallurgical zinc smelting process into economically valuable industrial-grade sodium sulfate and sodium chloride crystals, and to recover more than 95% of the water resources. This not only solves the problem of high pH, ​​high heavy metal and salt content in the alkaline washing wastewater of hydrometallurgical zinc smelting, which is difficult to treat, but also enables the recycling of salt and water resources in the wastewater.

[0042] Example 1:

[0043] Taking the alkaline washing wastewater generated by a hydrometallurgical zinc smelting enterprise as an example, the treatment volume is 15m³. 3 / h, water quality parameters: TDS content = 63100 mg / L, Na + Concentration = 23804 mg / L, Zn 2+ Concentration = 26.1 mg / L, Pb 2 +Concentration = 8.53 mg / L, Cd 2+ Concentration = 15.31 mg / L, Cl - Concentration = 28182 mg / L, SO4 2- The concentration is 11572 mg / L, COD content is 160 mg / L, and ammonia nitrogen concentration is 417 mg / L. The treatment should yield industrial-grade sodium chloride and sodium sulfate crystals, with the recovered water having a TDS content ≤200 mg / L, COD content ≤30 mg / L, and ammonia nitrogen concentration ≤5 mg / L. The wastewater should be treated using the wastewater resource recovery system disclosed in this application.

[0044] First, the wastewater passes through a sulfidation unit, where sodium hydroxide and a heavy metal scavenging agent are added to remove Zn from the water. 2+ Pb 2 + and Cd 2+ The concentrations of [specific substances] were reduced to below 2.71 mg / L, 2.36 mg / L, and 3.78 mg / L, respectively. Subsequently, the turbidity of the wastewater was controlled to 0.1 NTU through sand filtration and ultrafiltration units. The permeate from the ultrafiltration unit was concentrated and separated for monovalent and divalent ions by nanofiltration, achieving a concentrated TDS content exceeding 100,000 mg / L. - The content can reach over 20,000 mg / L, SO4 2- The concentration can reach over 40,000 mg / L. Its product water has a TDS concentration of around 50,000 mg / L, and Cl... - The content is around 20,000 mg / L, SO4 2- The content is below 400 mg / L.

[0045] The concentrate from the nanofiltration unit is further concentrated and separated into monovalent and divalent ions using a high-pressure nanofiltration unit, resulting in a TDS content of over 200,000 mg / L and SO42- content of [missing information]. 2 Concentration and - Cl - With a concentration ratio close to 10:1, industrial-grade sodium sulfate crystals were subsequently prepared using the first MVR evaporation and crystallization unit. The nanofiltration unit produced SO4 in the water. 2- The concentration is below 700 mg / L. The permeate from the nanofiltration unit and the high-pressure nanofiltration unit is mixed and then concentrated by the electrodialysis unit to reduce the TDS content in the water to above 150,000 mg / L. Then, the second MVR evaporation and crystallization unit is used to prepare industrial-grade sodium chloride crystals.

[0046] In the aforementioned units, the TDS content in the wastewater obtained by mixing the distilled water from the first MVR evaporation and crystallization unit and the fresh water from the electrodialysis unit can be controlled below 200 mg / L, the COD content below 100 mg / L, and the ammonia nitrogen concentration below 50 mg / L. Using an ozone catalytic oxidation unit and a stripping ammonia removal unit, the COD and ammonia nitrogen content in the water can be reduced to below 30 mg / L and 5 mg / L, respectively, while producing a small amount of ammonia water byproduct with a concentration of approximately 15%.

[0047] The above treatment of wet zinc smelting alkaline washing wastewater can convert over 92% of the salt in the water into sodium sulfate crystals with a purity of up to 96% and sodium chloride crystals with a purity of 92%, and can recover over 95% of the water resources. This system features high efficiency in resource utilization, high recovery rate, simple operation, high cost-effectiveness, and stable product quality.

[0048] The above description is only a preferred embodiment of the present utility model and is not intended to limit the present utility model. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. A resource utilization system for alkali washing wastewater from wet zinc smelting, characterized in that, The wet zinc smelting alkaline washing wastewater resource utilization system includes: a pretreatment subsystem, a membrane concentration subsystem, an evaporation crystallization subsystem, and a product water purification subsystem; The pretreatment subsystem includes: a sulfidation unit, a sand filtration unit, and an ultrafiltration unit; the membrane concentration subsystem includes a nanofiltration unit, a high-pressure nanofiltration unit, and an electrodialysis unit; the evaporation crystallization subsystem includes a first MVR evaporation crystallization unit and a second MVR evaporation crystallization unit; and the product water purification subsystem includes an ozone catalytic oxidation unit and a stripping ammonia removal unit. In the treatment of wet zinc smelting alkali washing wastewater, the wastewater is configured to pass sequentially through a sulfidation unit, a sand filtration unit, and an ultrafiltration unit. The permeate from the ultrafiltration unit is then sent to a nanofiltration unit. The permeate from the nanofiltration unit is transported to the electrodialysis unit, the concentrate from the nanofiltration unit is transported to the high-pressure nanofiltration unit, the permeate from the high-pressure nanofiltration unit is transported to the electrodialysis unit, and the concentrate from the high-pressure nanofiltration unit is transported to the first MVR evaporation and crystallization unit to generate sodium sulfate. The concentrated water from the electrodialysis unit is transported to the second MVR evaporation and crystallization unit to generate sodium chloride; the permeate from the electrodialysis unit, the first MVR evaporation and crystallization unit, and the second MVR evaporation and crystallization unit is transported to the ozone catalytic oxidation unit, and the permeate from the ozone catalytic oxidation unit is transported to the deammoniation unit to generate ammonia water and reused permeate.

2. The wet zinc smelting alkaline washing wastewater resource utilization system as described in claim 1, characterized in that, The sulfidation unit removes zinc ions, fluoride ions, thallium ions, and other heavy metal ions by adding sodium hydroxide and a heavy metal scavenging agent.

3. The wet zinc smelting alkaline washing wastewater resource utilization system as described in claim 2, characterized in that, The sand filtration unit and ultrafiltration unit are configured to remove suspended solids and colloids from the water.

4. The wet zinc smelting alkaline washing wastewater resource utilization system as described in claim 3, characterized in that, The concentrated water produced by the ultrafiltration unit is transported to the upstream side of the sulfidation unit and mixed with the wet zinc smelting alkaline washing wastewater to be treated.

5. The wet zinc smelting alkaline washing wastewater resource utilization system as described in claim 1, characterized in that, The nanofiltration unit is configured to remove SO4 from the inflow water. 2- It is trapped on the concentrated water side.

6. The wet zinc smelting alkaline washing wastewater resource utilization system as described in claim 1, characterized in that, The high-pressure nanofiltration unit is configured to remove SO4 from the inflow water. 2- Cl - It is trapped on the concentrated water side.

Images