WO2024040904A1 - Comprehensive treatment method for wastewater - Google Patents

Abstract

Disclosed in the present invention is a comprehensive treatment method for wastewater. The wastewater comprises phosphorus-containing wastewater, magnesium-containing wastewater and ammonia-containing wastewater. The comprehensive treatment method comprises the following steps: according to the molar ratio of nitrogen, magnesium and phosphorus of (9-11): (1.5-2.5): 1, mixing phosphorus-containing wastewater, magnesium-containing wastewater and ammonia-containing wastewater to obtain a mixed solution, and reacting and aging to obtain a mother solution and struvite. In the comprehensive processing method, phosphorus-containing wastewater, magnesium-containing wastewater and ammonia-nitrogen-containing wastewater generated in different procedures during a lithium battery recycling process are mixed for reaction to serve as a phosphorus source, a magnesium source and a nitrogen source to form struvite; and phosphorus and magnesium resources in wastewater are used to the greatest extent, can be directly used as a high-quality phosphate fertilizer for agriculture and forestry, have relatively high added values, and do not generate solid wastes containing phosphorus or magnesium. In addition, the reaction process do not require process facilities which occupy excessively large area.

Description

A comprehensive treatment method for wastewater Technical field

This application relates to the technical field of wastewater treatment, and in particular to a comprehensive treatment method for wastewater.

Background technique

Ternary lithium batteries, especially lithium nickel cobalt manganate ternary lithium batteries, have attracted much attention due to their high energy density. The increasing demand for lithium batteries is also accompanied by the generation of a large number of used lithium batteries. How to effectively recycle retired lithium batteries and alleviate corresponding resource shortages and environmental problems has gradually become an important issue in the lithium battery industry. At present, there are attempts to directly use the products as raw materials to prepare nickel-cobalt-manganese ternary precursor materials after recycling waste lithium batteries. However, in the above process, various wastewaters are still generated at different stages. For example, in the lithium recovery stage, phosphate is usually used to precipitate and recover lithium ions, which leads to the generation of phosphorus-containing wastewater; other wastewater such as nickel, cobalt and manganese sulfate The refining stage and the synthesis stage of the nickel-cobalt-manganese ternary precursor also generate magnesium-containing wastewater and ammonia-containing wastewater respectively.

For the above-mentioned wastewater, there are currently different treatment methods. For example, the usual treatment method for magnesium-containing wastewater is to undergo liquid alkali adjustment and mixing reaction sedimentation to convert the magnesium element into magnesium hydroxide. After press filtration, solid waste and waste water are formed. liquid, and the waste liquid is returned to the sedimentation tank. The water produced in the sedimentation tank is filtered, adjusted to neutral, and then discharged or evaporated by MVR. The phosphorus-containing wastewater is similar to the calcium hydroxide solution. The phosphorus element in it is converted into Calcium phosphate is formed into solid waste and waste liquid after filtration. The waste liquid is returned to the sedimentation tank. The water produced in the sedimentation tank is filtered, adjusted to neutral, and then discharged or evaporated by MVR. It can be seen that the treatment method of this type of wastewater consumes liquid alkali or calcium hydroxide, which will lead to an increase in the total salt and hardness of the wastewater, and requires a large sedimentation tank to complete the treatment. The resulting magnesium hydroxide solid waste Or calcium phosphate solid waste requires multiple processes before it can be used as an auxiliary material for the preparation of other chemical industrial products, and its natural added value is low.

Therefore, it is necessary to maximize the utilization of phosphorus and magnesium resources in wastewater, achieve reduction or even zero output of phosphorus-containing solid waste and magnesium-containing solid waste, and obtain high value-added by-products. The required facilities occupy an area Comprehensive treatment method for small area wastewater.

Contents of the invention

This application aims to solve at least one of the technical problems existing in the prior art. To this end, this application proposes a comprehensive treatment method for wastewater. The processing method has a simple processing flow, high processing efficiency and low processing cost.

The first aspect of this application provides a comprehensive treatment method for wastewater. The wastewater includes phosphorus-containing wastewater, magnesium-containing wastewater and ammonia-containing wastewater. The comprehensive treatment method includes the following steps:

S1: According to the molar ratio of nitrogen, magnesium and phosphorus (9-11): (1.5-2.5): 1, mix phosphorus-containing wastewater, magnesium-containing wastewater and ammonia-containing wastewater to obtain a mixed liquid;

S2: Wait for the mixed solution to react, age, and separate to obtain mother liquor and struvite.

The comprehensive processing method according to the embodiment of the present application has at least the following beneficial effects:

This comprehensive treatment method uses the mixed reaction of phosphorus-containing wastewater, magnesium-containing wastewater and ammonia nitrogen-containing wastewater produced in different processes during the production of ternary lithium batteries to form struvite as a phosphorus source, magnesium source and nitrogen source respectively, maximizing the degree of By utilizing the phosphorus and magnesium resources in wastewater, it can be directly used in agriculture and forestry as high-quality phosphate fertilizer, which has high added value and does not produce solid waste containing phosphorus or magnesium. In addition, the reaction process does not require excessively large process facilities.

In addition, in this comprehensive treatment method, because the components of the ternary lithium battery wastewater are relatively complex, the characteristics of the element composition are taken into consideration, and at the same time, in order to reduce the total amount of mother liquor generated after the reaction, and avoid excessive amounts of subsequent salt recovery and treatment This leads to prolonged treatment time, so the wastewater generated in the production line is usually used as the reaction material without dilution during the treatment process. Therefore, it is different from the nitrogen, magnesium and phosphorus in struvite MgNH ₄ PO ₄ ·6H ₂ O 1: With a molar ratio of 1:1, a nitrogen-magnesium-phosphorus ratio of (9-11): (1-3):1 is selected for the reaction in this process. On the other hand, according to the principle of chemical equilibrium, the reaction process is controlled through higher ammonia concentration conditions and the aging time required after the reaction is reduced.

In some embodiments of the present application, the molar ratio of nitrogen, magnesium and phosphorus is (9-11): (1.5-2.5):1, and the phosphorus-containing wastewater, magnesium-containing wastewater and ammonia-containing wastewater are mixed to obtain a mixed liquid.

In some embodiments of the present application, S1 includes:

S11: Mix phosphorus-containing wastewater and ammonia-containing wastewater according to the molar ratio of nitrogen to phosphorus (9-11):1 to obtain nitrogen-phosphorus wastewater;

S12: Then add magnesium-containing wastewater to the nitrogen-phosphorus wastewater according to the molar ratio of magnesium to phosphorus (1-3):1, adjust the pH to 8-10, and obtain a mixed liquid.

In this preparation process, we choose to first mix phosphorus-containing wastewater and ammonia-containing wastewater to obtain nitrogen-phosphorus wastewater, and then add magnesium-containing wastewater to adjust the value to promote the reaction to form struvite as much as possible instead of magnesium phosphate, magnesium hydroxide and other products. , reduce the output of magnesium-containing solid waste, and improve the yield and purity of struvite.

In some embodiments of the present application, the ammonia-containing wastewater is filtered to remove insoluble valuable metals and adjust the pH to 5-9.5 before mixing. In ammonia-containing wastewater, there may be a certain amount of insoluble matter (such as hydroxide, etc.) of at least one valuable metal element such as nickel, cobalt and manganese. This insoluble matter may be incorporated into the subsequent crystallization of struvite. into the product thereby affecting the purity of struvite. Therefore, these metal insolubles need to be removed in advance through appropriate methods. Considering the cost of treatment and the simplicity of the process, filtration should be selected for removal. In addition, since the pH of the raw material will affect the pH of the reaction system and thus the occurrence of side reactions, resulting in changes in the recovery efficiency of nitrogen, phosphorus, and magnesium in wastewater and the crystallization of struvite, comprehensive consideration must be given to filtering to remove insoluble valuable metals. After treatment, the nitrogen-containing wastewater was further adjusted.

In some embodiments of the present application, the ammonia-containing wastewater is ammonia-containing sulfate wastewater.

In some embodiments of the present application, the pH value of ammonia-containing wastewater is 12-14, and the ammonia nitrogen concentration is 0.1-3g/L.

In some embodiments of the present application, the solid content of valuable metal insoluble matter in ammonia-containing wastewater is 0.001-0.02g/L, and the particle size distribution D50 of the valuable metal insoluble matter particles is 0.1-10 μm.

In some embodiments of the present application, the insoluble valuable metals in ammonia-containing wastewater mainly include hydroxides of nickel, cobalt and manganese.

In some embodiments of the present application, after the ammonia-containing wastewater is filtered to remove insoluble valuable metals, the filtrate has a nickel concentration of 0.1-2 mg/L, a cobalt concentration of 0.1-2 mg/L, and a manganese concentration of 0.1 -2mg/L. In the filtered filtrate, metal elements such as nickel, cobalt and manganese mainly exist in the form of soluble complexes.

In some embodiments of the present application, a membrane filter is used to filter valuable metal insoluble matter in ammonia-containing wastewater, such as an organic membrane filter or an inorganic membrane filter, preferably an organic membrane filter.

In some embodiments of the present application, the pore size of the filter element of the organic membrane filter used for filtration of valuable metal insoluble matter in ammonia-containing wastewater ranges from 0.3 to 0.5 μm.

In some embodiments of the present application, the material of the organic membrane filter used to filter valuable metal insoluble matter in ammonia-containing wastewater is at least one of 304 stainless steel, 316 stainless steel, 316L stainless steel and other steel materials.

In some embodiments of the present application, the filter element material of the organic membrane filter used to filter valuable metal insoluble matter in ammonia-containing wastewater is PVC or ceramic membrane.

In some embodiments of the present application, after filtering the ammonia-containing wastewater to remove insoluble valuable metals, the method further includes adjusting the pH to weakly acidic, neutral or weakly alkaline, for example, adjusting the pH to about 5-9.5. In this step, the reagent used to adjust the pH may be dilute sulfuric acid, for example, dilute sulfuric acid with a concentration of 0.5-3.0 mol/L. The specific method for adjusting the pH through the reagent may be automatic feeding via pump interlocking.

In some embodiments of the present application, the magnesium-containing wastewater is adsorbed to remove oil before mixing. The oil in magnesium-containing wastewater as organic matter will affect the quality of struvite crystal particles, and will also affect the oil or COD value in the mother liquor generated after the reaction. Therefore, the oil in magnesium-containing wastewater must be removed in advance before mixing as reaction raw materials. In order to improve the quality of struvite crystallization, it will also facilitate the subsequent possible MVR evaporation process.

In some embodiments of the present application, the magnesium-containing wastewater is magnesium-containing sulfate wastewater.

In some embodiments of the present application, the pH value of the magnesium-containing wastewater is 1-3, and the concentration of magnesium element in the magnesium-containing wastewater is 5-25g/L.

In some embodiments of the present application, the nickel element concentration in the magnesium-containing wastewater is 0.1-2mg/L, the cobalt element concentration is 0.1-2mg/L, the manganese element concentration is 0.1-3mg/L, and the chlorine element concentration is 0.1-1g /L, the sodium concentration is 5-10g/L, the calcium concentration is 1-3mg/L, and the oil content is ≤10mg/L.

In some embodiments of the present application, the method of oil removal is adsorption. Optional materials for adsorption materials include but are not limited to activated carbon, porous polymers, porous alumina, porous silica, molecular sieves, kaolin, titanium dioxide, ceria and other porous materials. Material. Preferably, activated carbon is used for adsorption and oil removal. The source of activated carbon can be wood, cotton, peat, coal, coconut shell, asphalt, coke, coal tar, fruit, nuts, carbon black, graphite, etc., and its size can range from 20 to 100 mesh, for example. It can be understood that when using activated carbon for adsorption, it is best to use concentrated water (conductivity 150-350μs/cm), pure water (conductivity 0.5-25μs/cm), tap water (conductivity 150-220μs/cm), etc. At least one of them is subject to backwash pretreatment. During pretreatment, the solid-liquid ratio of activated carbon and water is preferably ≥1:5. The number of washes can be, for example, 2-5 times. Backwashing can be automatically controlled by pressure gauge-valve-pump interlocking. .

In some embodiments of the present application, the phosphorus-containing wastewater is phosphorus-containing sulfate wastewater.

In some embodiments of the present application, the pH value of the phosphorus-containing wastewater is 5-9, and the phosphorus element concentration is 0.5-3g/L.

In some embodiments of the present application, the nickel element concentration in phosphorus-containing wastewater is 0.1-2mg/L, the cobalt element concentration is 0.1-2mg/L, the manganese element concentration is 0.1-1mg/L, and the chlorine element concentration is 0.1-1g /L, the sodium concentration is 0.5-2.0g/L, the calcium concentration is 1-3mg/L, and the oil concentration is ≤3mg/L. It can be understood that when the phosphorus-containing or ammonia-containing wastewater contains a certain concentration of oil, it can also be considered to perform adsorption and oil removal treatment on the phosphorus-containing or ammonia-containing wastewater before mixing.

In some embodiments of the present application, when mixing ammonia-containing wastewater and phosphorus-containing wastewater, the stirring speed of the mixing is controlled to be 50-200 rpm, the temperature is 10-35°C, and the mixing time is 5-30 minutes.

In some embodiments of the present application, at least one of liquid alkali, ion membrane caustic soda, filtered ammonia-containing wastewater, etc. can be used to adjust the solution when adding magnesium-containing wastewater to the nitrogen-phosphorus wastewater and adjusting the pH to 8-10. The pH is adjusted. Further, adjust the pH to 8-9.5. In some embodiments of the present application, when using filtered ammonia-containing wastewater to adjust the pH, a pH meter-pump interlocking automatic feeding can be used.

In some embodiments of the present application, after adding magnesium-containing wastewater to the nitrogen-phosphorus wastewater and adjusting the pH, the rotation speed of the stirring reaction is controlled to be 10-60rpm, the temperature is 15-25°C, and the reaction time is 0.1-5h, and further reaction is carried out. The time is 0.5-1h.

In some embodiments of the present application, magnesium-containing wastewater is added to the nitrogen-phosphorus wastewater to adjust the pH. After the reaction of the mixed solution is completed, it is allowed to stand for aging. The temperature can be kept the same as the reaction temperature, for example, 15-25°C. After aging, the struvite and the aged mother liquor can be separated at least through filter press. Specifically, a membrane filter press or a box filter press can be used for solid-liquid separation. In some of these methods, the moisture in the struvite obtained by solid-liquid separation is removed by drying, for example, by low-temperature drying, and the drying time can be 4-8 hours. Low-temperature drying equipment can choose a disc dryer or paddle dryer with exhaust function.

In some embodiments of the present application, the percentage content of the total mass of nickel, cobalt and manganese in the dried struvite is ≤0.0001%, and the purity of the struvite is relatively high, which can reach 97.5-99.8%.

In some embodiments of the present application, when the concentrations of valuable transition metal elements such as nickel, cobalt, and manganese in the mother liquor are very low, for example, below 5, 2, 1, 0.5, 0.2, and 0.1 mg/L, the mother liquor can be directly Return to the mixture. When the concentration of these valuable transition metal elements is relatively high, for example, higher than 0.1, 0.2, 0.5, 1, 2, or 5 mg/L, they exist in the form of complexes in the mother liquor and are difficult to separate by filtration. Therefore, it is necessary to further reduce the ammonia nitrogen in the mother liquor through deamination and then remove it.

In some embodiments of the present application, when the concentration of valuable heavy metal elements such as nickel, cobalt and manganese in the mother liquor is high, ammonia nitrogen, magnesium, phosphorus, and valuable heavy metals can be removed through breakpoint chlorine addition and aeration stripping. Process it further. Specifically, when its content is high, it is necessary to find an outlet for valuable heavy metals, magnesium and other elements in the reaction system to prevent the increase in the content of nickel, cobalt, manganese and magnesium hydroxide due to the increased number of mother liquor reuses, which ultimately affects the The quality of struvite formed. In addition, it is extremely difficult to backwash magnesium hydroxide and other materials through filters. If the processing and recovery process is directly operated by filtration, the recovery process will be more complicated.

In some embodiments of the present application, the pH value of the mother liquor is 7.0-8.0.

In some embodiments of the present application, the comprehensive treatment method also includes S3: the mother liquor is added with chlorine at the break point and aerated to remove ammonia nitrogen. Since filtered ammonia-containing wastewater is used in the reaction material, there will be a large amount of ammonia nitrogen in the mother liquor. For this reason, the ammonia nitrogen can be removed efficiently and simply through breakpoint chlorine addition and aeration stripping; at the same time, because ammonia nitrogen is removed by After removal, the valuable metal complexes that may be present in the mother liquor will also be converted into precipitates and can be removed, thereby improving the purity of the soluble salt components in the mother liquor.

In some embodiments of the present application, S3 includes:

S31: Pass sodium hypochlorite or chlorine gas into the mother liquor to perform deamination treatment;

S32: Adjust the pH value of the deamination-treated mother liquor to alkaline, heat, aerate, and blow off residual ammonia and residual chlorine.

When using first breakpoint chlorination for primary deamination, since at least one of sodium hypochlorite or chlorine is used, in order to oxidize ammonia into nitrogen, the pH of the mother liquor needs to be controlled to be at least neutral, and during aeration and stripping When the pH of the mother liquor is alkaline, it is necessary to control the pH of the mother liquor to be alkaline. Therefore, if the method of first aeration and stripping and then breakpoint chlorination is adopted, the pH value must be adjusted to alkaline through an alkaline substance before aeration and stripping can be implemented. After the reaction is completed, It is necessary to add acidic substances to adjust the value to neutral and then implement breakpoint chlorination. If you need to continue to remove phosphorus and magnesium later, you still need to adjust the value to alkaline again. In contrast, first chlorination at the breakpoint and then aeration and stripping reduces the number of value adjustments, the process is simpler, and the construction cost of treatment facilities, the cost of auxiliary materials, and the total salt produced by subsequent evaporation are also more.

In some embodiments of the present application, sodium hypochlorite is used for breakpoint chlorination.

In some embodiments of the present application, while the breakpoint chlorination reaction removes ammonia nitrogen, the oil content in the mother liquor can also be reduced by 5-10%.

In some embodiments of the present application, an online ammonia nitrogen detection instrument can be used to automatically sample and detect the ammonia nitrogen concentration in the mother liquor.

In some embodiments of the present application, the molar ratio (chlorine element to nitrogen element) of the sodium hypochlorite or chlorine gas introduced by chlorination at the break point and the ammonia nitrogen in the mother liquor is (4-12):1, for example, it can be 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, and further (6-10):1, 8:1. In some embodiments of the present application, sodium hypochlorite can be added in the form of a solution, and the concentration of the sodium hypochlorite solution can be 10-100kg/m ³ , 20-90kg/m ³ , 30-80kg/m ³ , 40-60kg/m ³ . The amount of sodium hypochlorite solution can be controlled by the DCS or PLC program through the integration of online ammonia nitrogen detector detection data, liquid level meter detection data, feeding time, reaction time and other data.

In some embodiments of the present application, after the mother liquor is denitrified by adding breakpoint chlorine, the escaped nitrogen, ammonia, chlorine and water vapor can be absorbed using an absorption tower. In some embodiments, the absorption liquid in the absorption tower uses at least one of concentrated water (conductivity 150-350 μs/cm), pure water (conductivity 0.5-25 μs/cm), and tap water (conductivity 150-220 μs/cm). A sort of.

In some embodiments of the present application, adjusting the pH of the mother liquor after deamination to alkalinity can specifically adjust the pH to 12-14. The reagents used to adjust the pH can be liquid soda, ion membrane caustic soda, as mentioned above. etc., you can use pH meter-pump interlocking to control the feeding.

In some embodiments of the present application, after adjusting the pH to alkaline, the heating can be done by raising the temperature to 85-95°C. For example, a plate heat exchanger can be used for heating. The temperature control during the heating process can be controlled by thermometer-steam valve interlocking. .

In some embodiments of the present application, compressed air can be used as the aeration gas source during aeration and stripping. The air pressure of the compressed air can be controlled at 0.3-0.7MPa. The processing time of the aeration and stripping can be controlled by a DCS or PLC program. Adjust according to the ammonia concentration in the mother liquor. In some embodiments, when the ammonia concentration is ≤10 mg/L, the aeration stripping reaction ends.

In some embodiments of the present application, the residual ammonia concentration in the mother liquor after aeration and stripping is ≤10 mg/L, and the residual chlorine concentration is ≤0.5 mg/L.

In some embodiments of the present application, the nitrogen, ammonia, chlorine and water vapor escaped from the aeration stripping can be absorbed using an absorption tower. In some embodiments, the absorption liquid in the absorption tower uses at least one of concentrated water (conductivity 150-350 μs/cm), pure water (conductivity 0.5-25 μs/cm), and tap water (conductivity 150-220 μs/cm). A sort of.

In some embodiments of the present application, the absorption liquid in the absorption tower can be used to prepare sodium hypochlorite after absorbing a set concentration of chlorine.

In some embodiments of the present application, the oil content in the mother liquor decreases by 1-5% after aeration and stripping.

In some embodiments of the present application, the comprehensive treatment method also includes: S4: press filtration of the mother liquor to obtain filtrate and filter residue. After removing ammonia nitrogen, the mother liquor still contains a certain amount of phosphorus and magnesium, so the main contents obtained by press filtration include insoluble in the filtrate. Precipitation of magnesium phosphate and magnesium hydroxide.

In some embodiments of the present application, the filtrate obtained by press filtration is filtered again to remove insoluble matter and then undergoes salt recovery treatment. Since it is impossible for all insoluble materials to participate in the formation of filter residue during the filter press process, the filtrate is filtered again after the filter press to remove as many insoluble components as possible, which mainly include hydroxides of nickel, cobalt and manganese, magnesium phosphate and hydrogen. At least one of them, such as magnesium oxide, varies according to the specific composition of the three wastewaters and mother liquor and the specific selection of each parameter in the aforementioned operating steps. In some embodiments, the method of salt recovery processing may be, for example, using an MVR system for evaporation processing.

In some embodiments of the present application, the moisture content of the filter residue is 40.2-45.1%.

In some embodiments of the present application, in S4, the filtrate obtained by press filtration is filtered again to remove insoluble matter. The filtrate has a concentration of nickel, cobalt and manganese ≤ 0.5 mg/L, a magnesium concentration ≤ 3 mg/L, and a phosphorus concentration ≤ 1mg/L, ammonia concentration ≤10mg/L.

In some embodiments of the present application, a membrane filter is used for re-filtration, which may be an organic membrane filter, for example.

In some embodiments of the present application, after filtering again, the organic membrane filter is backwashed, and the washed water participates in the pressure filtration of the mother liquor to remove ammonia nitrogen.

In some embodiments of the present application, the pH of the filter residue obtained by pressure filtration in S4 and the insoluble matter obtained by filtering again are adjusted to obtain a magnesium solution, and the magnesium solution is reused into the mixed solution. In the process of filter press and subsequent filtration, the stored filter residue and other insoluble matter are separated. In order to achieve zero output of magnesium solid waste, it is formed into a solution containing magnesium ions by adjusting the pH, and then reused in the mixed solution to participate again. Struvite formation. As mentioned above, it is understandable that since the insoluble matter may also contain hydroxides of nickel, cobalt and manganese, the magnesium solution may also contain trace amounts of nickel, cobalt and manganese.

In some embodiments of the present application, dilute sulfuric acid can be used to adjust the pH of the filter residue and insoluble matter obtained by medium pressure filtration in S4. For example, the pH can be adjusted to 2.0-3.5. During the adjustment process, a pH meter can be used - Pump interlocking and automatic control of feeding. The concentration of dilute sulfuric acid used for adjustment may be, for example, 0.5-3.0 mol/L.

The second aspect of this application provides a comprehensive wastewater treatment system, including a struvite production unit. The struvite production unit includes:

Wastewater supply device for providing phosphorus-containing wastewater, ammonia-containing wastewater and magnesium-containing wastewater;

A struvite synthesis device is used to mix phosphorus-containing wastewater, ammonia-containing wastewater and magnesium-containing wastewater to obtain a mixed liquid, and react to generate struvite;

A separation device is used to separate struvite from the mixed liquid to form a mother liquid.

In some embodiments of the present application, the wastewater supply device includes:

A phosphorus-containing wastewater supply device is used to provide phosphorus-containing wastewater to the struvite synthesis device;

An ammonia-containing wastewater supply device is used to provide ammonia-containing wastewater to the struvite synthesis device. The ammonia-containing wastewater supply device is also provided with a first filter component. The first filter component is used to filter out valuable metal insoluble matter in the ammonia-containing wastewater. ;

The magnesium-containing wastewater supply device is used to provide magnesium-containing wastewater to the struvite synthesis device. The magnesium-containing wastewater supply device is also equipped with an oil removal component, and the oil removal component is used to remove oil from the magnesium-containing wastewater.

In some embodiments of the present application, the phosphorus-containing wastewater supply device includes a phosphorus-containing wastewater storage tank.

In some embodiments of the present application, the ammonia-containing wastewater supply device includes a first organic membrane filter and a first organic membrane filter production tank, and the filtering component is the first organic membrane filter.

In some embodiments of the present application, the magnesium-containing wastewater supply device includes a magnesium-containing wastewater storage tank and an adsorption column, and the adsorption column is the oil removal component.

In some embodiments of the present application, the struvite synthesis device includes:

Struvite primary reaction tank. The struvite primary reaction tank is used for preliminary mixing of phosphorus-containing wastewater and ammonia-containing wastewater;

The struvite secondary reaction tank is used to receive the initially mixed product and magnesium-containing wastewater in the struvite primary reaction tank, and mix to obtain a mixed liquid;

The aging tank is used for the mixed liquid to react to form struvite and to age and precipitate struvite crystals.

In some embodiments of the present application, the separation device includes:

The first filter press is used to separate struvite crystals from the mixed liquid and form a mother liquor;

Dryer, the dryer is used to dry the separated struvite crystals.

In some embodiments of the present application, the comprehensive treatment system also includes a mother liquor recovery unit, and the mother liquor recovery unit includes:

Ammonia removal device, including breakpoint chlorination equipment and aeration and stripping equipment, is used to sequentially add breakpoint chlorine and aeration and stripping to the mother liquor to remove ammonia nitrogen;

Magnesium removal device, used to separate magnesium-containing precipitates from the mother liquor after ammonia removal;

Salt recovery device is used to separate soluble salts from the mother liquor after magnesium removal.

In some embodiments of the present application, the mother liquor recovery unit further includes a first liquid receiving tank for receiving the mother liquor from the first filter press. The mother liquor received by the first liquid receiving tank is then introduced into the ammonia removal device for subsequent recovery processing.

In some embodiments of the present application, the breakpoint chlorination equipment includes a reaction tank for providing a space for the mother liquor to react with sodium hypochlorite or chlorine gas. In some of these ways, the breakpoint chlorination equipment also includes a sodium hypochlorite or chlorine gas supply component for supplying sodium hypochlorite or chlorine gas to the reaction tank.

In some embodiments of the present application, the aeration and stripping equipment includes an aeration and stripping reaction tank and a heating component. In some of these embodiments, the heating component is a heat exchanger, such as a plate heat exchanger.

In some embodiments of the present application, the magnesium removal device includes a second filter press for separating magnesium-containing precipitates from the mother liquor through filter press.

In some embodiments of the present application, the magnesium removal device also includes a magnesium recovery device for reforming the magnesium-containing precipitate into a magnesium-containing precipitate. magnesium solution and reused in the mixed solution in the struvite synthesis unit.

In some embodiments of the present application, the salt recovery device includes an MVR evaporation system.

In some embodiments of the present application, the salt recovery device further includes a second filtering component, and the second filtering component is used to filter insoluble matter in the mother liquor. In some embodiments, the second filtration component includes a second organic membrane filter and a second organic membrane filter water production tank, and the mother liquor produced by the second organic membrane filter water production tank is used to flow to the MVR evaporation system.

Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the application.

Description of drawings

Figure 1 is a flow chart of a comprehensive treatment method for ternary lithium battery wastewater in an embodiment of the present application.

Figure 2 is a PID diagram of the comprehensive wastewater treatment system in the embodiment of the present application. Among them, A-G respectively represent phosphorus-containing wastewater, ammonia-containing wastewater, high-pressure gas source, magnesium-containing wastewater, liquid alkali, sodium hypochlorite and high-pressure steam.

Reference signs: phosphorus-containing wastewater storage tank 1, ammonia-containing wastewater storage tank 2, first organic membrane filter 3, first organic membrane filter production tank 4, struvite primary reaction tank 5, struvite secondary reaction Tank 6, aging tank 7, first filter press 8, magnesium-containing wastewater storage tank 9, adsorption column 10, reaction tank 11, first liquid receiving tank 12, second filter press 13, aeration and stripping reaction tank 14. Plate heat exchanger 15, disc dryer 16, second liquid tank 17, second organic membrane filter 18, second organic membrane filter water production tank 19, MVR evaporation system 20.

Detailed ways

The concept of the present application and the technical effects produced will be clearly and completely described below in conjunction with the embodiments to fully understand the purpose, features and effects of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all of the embodiments. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without exerting creative efforts are all The scope of protection of this application.

The embodiments of the present application are described in detail below. The described embodiments are exemplary and are only used to explain the present application and cannot be understood as limiting the present application.

In the description of this application, several means one or more, plural means two or more, greater than, less than, exceeding, etc. are understood to exclude the original number, and above, below, within, etc. are understood to include the original number. If there is a description of first and second, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of indicated technical features or implicitly indicating the order of indicated technical features. relation. In the following description, although a logical order is shown in the flowcharts, in some cases, the steps shown or described may be performed in a different order than in the flowcharts.

Unless otherwise defined, all technical and scientific terms used in this application are consistent with the technical terms belonging to the technical field of this application. The meaning is generally understood by technicians to be the same. The terms used herein are only for the purpose of describing the embodiments of the present application and are not intended to limit the present application.

In the description of this application, reference to the description of the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" is intended to be in conjunction with the description of the embodiment. or examples describe specific features, structures, materials, or characteristics that are included in at least one embodiment or example of the present application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The following is explained with specific examples.

Example 1

In this embodiment, it is planned to comprehensively treat ammonia-containing wastewater, phosphorus-containing wastewater, and magnesium-containing wastewater generated during the recycling process of nickel-cobalt-manganese ternary lithium batteries.

Among them, the pH value of the ammonia-containing wastewater is 13, the ammonia nitrogen concentration, P, Mg, Ni, Co, Mn, and oil content are shown in Table 1. The particle size D50 of the nickel-cobalt-manganese insoluble particles is about 1 μm.

The pH value of magnesium-containing wastewater is 2. The contents of P, Mg, Ni, Co, Mn, and oil are shown in Table 1. Cl is 0.1-1g/L, Na is 5-10g/L, and Ca is 1-3mg/ L.

The pH value of phosphorus-containing wastewater is 7. The contents of P, Mg, Ni, Co, Mn, and oil are shown in Table 1. Cl is 0.1-1g/L, Na is 0.5-2g/L, and Ca is 1-3mg/L. L.

This comprehensive processing method, refer to Figure 1, includes the following steps:

(1) The first organic membrane filter is used to filter the ammonia-containing wastewater, and the nickel, cobalt and manganese insoluble matter is filtered out. The filtered ammonia-containing wastewater is produced in the production tank of the first organic membrane filter, and is added at room temperature. 1mol/L dilute sulfuric acid adjusts the pH value of ammonia-containing wastewater to 8.37;

(2) Pour the phosphorus-containing wastewater in the phosphorus-containing wastewater storage tank and the ammonia-containing wastewater adjusted in step (1) into the struvite primary reaction tank to mix. Control the molar ratio of nitrogen to phosphorus to 10.4:1, and rotate at 50 rpm. Stir and mix at a rotating speed for 5 minutes;

(3) Use an activated carbon adsorption column to pretreat the magnesium-containing wastewater, adsorb the oil and then enter the magnesium-containing wastewater storage tank, and then pass it into the struvite secondary reaction tank together with the mixed liquid stirred in step (2). Control the molar ratio of nitrogen, magnesium and phosphorus to 10.4:2:1, stir at a speed of 30 rpm, and add the ammonia-containing wastewater after filtering and before adjusting the pH in step (1) to adjust the pH value of the mixed wastewater in this step to 9.41. When the pH value is stable, stop stirring after stirring for 30 minutes, move it to an aging tank and seal it (to prevent ammonia from escaping and losing) and let it stand for 16 hours for aging treatment. When alum flower-like white struvite crystals appear, check the pH value of the aging solution. 8.13. The first filter press filters the aged liquid. The filter residue is struvite crystals. The struvite crystals are sent to a disc dryer and dried at 30°C for 4 hours.

(4) The mother liquor of the aging liquid after medium pressure filtration in step (3) enters the first liquid receiving tank, and its pH is measured to be 8.13 and the concentration of ammonia, phosphorus, magnesium, nickel, cobalt, manganese, and oil is detected. After transferring to the reaction tank, add sodium hypochlorite solution (effective chlorine concentration 10%), control the molar ratio of chlorine to nitrogen to 8:1, stir and react at 50 rpm for 1.5 hours, after the reaction is completed, the remaining ammonia concentration is detected to be 53.48 mg. /L.

(5) Use liquid caustic soda to adjust the pH of the mother liquor after the reaction in step (4) to 12.87, heat the adjusted mother liquor to 90°C through a plate heat exchanger, and aerate it in an aeration and stripping reaction tank for 1.5 hours. . During the heated aeration process, tap water is used to absorb escaping gases.

(6) The mother liquor after the reaction in step (5) is filtered again using a second filter press. The filtrate after filtering enters the second liquid receiving tank, and is filtered through the second organic membrane filter to remove magnesium phosphate and magnesium hydroxide. , the filtrate output from the second organic membrane filter production tank enters the MVR evaporation system for processing.

(7) Use 1 mol/L dilute sulfuric acid to adjust the pH of the filter residue produced by the pressure filtration in step (6) and the insoluble matter filtered out by the organic membrane filter to obtain a magnesium sulfate solution, which is then reused in the struvite secondary reaction tank to participate in the avianization process. Bezoar crystallization.

The contents of each component in the mother liquor obtained after pressure filtration in step (4) and the filtrate produced by pressure filtration after aeration of the mother liquor in step (6) are as shown in Table 1 below. The composition of the struvite crystal produced in step (3) is as follows As shown in Table 2, the content of each component after drying the filter residue after filtering in step (6) is shown in Table 3. The sodium hypochlorite solution (effective chlorine concentration 10%) in step (4) and the adjusted value in step (5) The amount of liquid caustic soda used (sodium hydroxide mass percentage is 30%) (the mass of NaClO and NaOH added relative to the volume of the mother liquor) is shown in Table 4.

Table 1. Content of each component of the material (mg/L)

Table 2. Content of each component in struvite crystal (%)

Table 3. Contents of each component after drying the filter residue (%)

Table 4. Material unit consumption

The comprehensive treatment system for wastewater involved in the above comprehensive treatment method is further described as follows:

The comprehensive treatment system includes a struvite production unit and a mother liquor recovery unit. Referring to Figure 2, the struvite production unit includes a wastewater supply device, a struvite synthesis device and a separation device.

The wastewater supply device includes a phosphorus-containing wastewater supply device, an ammonia-containing wastewater supply device and a magnesium-containing wastewater supply device. The phosphorus-containing wastewater supply device includes a phosphorus-containing wastewater storage tank 1 with a radar level gauge. The ammonia-containing wastewater supply device includes an ammonia-containing wastewater storage tank 2 with a breathing valve, a first organic membrane filter 3 with a pressure gauge and a backwash function, and a first organic membrane filter with a breathing valve and a radar level gauge. Maternity tank 4. The magnesium-containing wastewater supply device includes a magnesium-containing wastewater storage tank 9 with a radar level gauge and an adsorption column 10 composed of activated carbon with a pressure gauge and backwash function.

The struvite synthesis device includes a struvite primary reaction tank 5 with a radar level gauge, a thermometer and a pH meter, a struvite secondary reaction tank 6 with a radar level gauge, a thermometer and a pH meter, and a struvite secondary reaction tank 6 with a radar level gauge, thermometer and pH meter. Aging tank 7 for liquid level gauge, thermometer and pH meter.

The separation device includes a first filter press 8 with air blowing function and a disc dryer 16.

The mother liquor recovery unit includes a first liquid receiving tank 12 for receiving the mother liquor, an ammonia removal device, a magnesium removal device and a salt recovery device. The first liquid tank 12 is equipped with a radar level gauge.

Ammonia removal equipment includes breakpoint chlorination equipment and aeration and stripping equipment. The breaking point chlorination equipment includes a reaction tank 11 with a radar level gauge, a thermometer and a pH meter. The aeration and stripping equipment includes an aeration and stripping reaction tank 14 with a radar level gauge, a thermometer and a pH meter, and a plate heat exchanger 15 with a thermometer in the heat exchange outlet section.

The magnesium removal device includes a second filter press 13 with air blowing function.

The salt recovery device includes a second liquid receiving tank 17 with a radar level gauge, a second organic membrane filter 18 with a pressure gauge and backwash function, and a second organic membrane filter production tank with a radar level gauge. 19. MVR evaporation system 20.

Among them, the first organic membrane filter and the second organic membrane filter are made of 304 stainless steel, and the filter element is a PVC membrane with a pore size of 0.4 μm.

Example 2

This embodiment provides a comprehensive treatment method for ternary lithium battery wastewater. The difference from Example 1 is that in step (3), the molar ratio of nitrogen, magnesium and phosphorus is controlled to 9:2:1. At the same time, aging is performed after filtering. The concentration of nickel, cobalt, and manganese in the mother liquid of the liquid was tested to be less than 0.5 mg/L. Therefore, the mother liquid was directly reused in the struvite secondary reaction tank for reuse.

Example 3

This embodiment provides a comprehensive treatment method for ternary lithium battery wastewater. The difference from Embodiment 1 is that step (3) The molar ratio of nitrogen, magnesium and phosphorus is controlled to be 11:2:1. During deamination by chlorine addition at breakpoint, equimolar chlorine gas is introduced to replace sodium hypochlorite.

The comprehensive processing effects of Embodiments 2 and 3 are basically the same as those of Embodiment 1, and will not be described again here.

Example 4

This embodiment provides a comprehensive treatment method for ternary lithium battery wastewater. The difference from Example 1 is that the phosphorus-containing wastewater, the filtered ammonia-containing wastewater and the deoiled magnesium-containing wastewater are directly treated with a ratio of 10.4:2:1. The molar ratio of nitrogen, magnesium and phosphorus is stirred and reacted in the reaction tank. The purity of struvite converted to nitrogen in the struvite crystal finally obtained in this example is far lower than 97.7%.

Example 5

This embodiment provides a comprehensive treatment method for ternary lithium battery wastewater. The difference from Embodiment 1 is that step (4) and step (5) are different, specifically as follows:

(4) After medium-pressure filtration in step (3), the mother liquor of the aging liquid enters the liquid receiving tank. Measure its pH to 8.13 and detect the concentrations of ammonia, phosphorus, magnesium, nickel, cobalt, manganese and oil. Add liquid caustic soda to adjust the pH to 12.87, heat the adjusted mother liquor to 90°C through a plate heat exchanger, and aerate it in the aeration and stripping reaction tank for 1.5 hours. During the heated aeration process, tap water is used to absorb escaping gases.

(5) Add 1 mol/L dilute sulfuric acid to the aerated mother liquor to adjust it to neutrality, add sodium hypochlorite solution, control the molar ratio of chlorine to nitrogen to 8:1, stir the reaction at 50 rpm for 1.5 hours, and then add Liquid caustic soda re-adjusts the pH of the mother liquor to 12.

It can be seen that after adjusting the sequence of aeration and breakpoint chlorination, in order to make the reaction proceed smoothly, it is necessary to adjust the pH multiple times. Therefore, the process of this embodiment is more complicated than that of Embodiment 1, and the cost is increased. After MVR evaporation Total salt content rises.

Comparative example 1

This comparative example provides a comprehensive treatment method for ternary lithium battery wastewater. The difference from Example 1 is that in step (3), the molar ratio of nitrogen, magnesium and phosphorus is controlled to 5:2:1.

Comparative example 2

This comparative example provides a comprehensive treatment method for ternary lithium battery wastewater. The difference from Example 1 is that in step (3), the molar ratio of nitrogen, magnesium and phosphorus is controlled to 1:2:1.

Comparative Examples 1 and 2 used a lower ammonia concentration for the mixing reaction. The aging time required for final crystallization was much longer than 16 hours. The size of the struvite crystallized by crystallization was also larger, and the effect of using it as chemical fertilizer was poor. .

Based on the above embodiments and comparative examples, it can be seen that the comprehensive processing method provided by this application has the following effects:

(1) Struvite is prepared using crystallization aging + filtration. The entire process does not use a sedimentation tank, which solves the problem of large area occupied by industrial wastewater treatment facilities for ternary precursors.

(2) Use the breakpoint chlorination method + aeration stripping method to comprehensively treat the residual ammonia and residual chlorine in the mother liquor wastewater prepared from struvite, which solves the problem that the struvite synthesized by the sedimentation tank method cannot be discharged due to excessive residual ammonia. , through the automatic control device, the entire deamination process The amount of sodium hypochlorite added can be reasonably controlled to minimize the aeration time.

(3) Use a combination of press filtration + organic membrane filtration to treat phosphorus, magnesium and heavy metals in the wastewater after secondary deamination of synthetic struvite mother liquor. There is also no need to use a sedimentation tank. The wastewater treatment facility occupies a small area and can control nickel in the filtrate. The concentration of cobalt and manganese is below 0.5 mg/L, the concentration of magnesium is below 3 mg/L, the concentration of phosphorus is below 1 mg/L, and the concentration of ammonia is below 10 mg/L.

(4) This treatment method comprehensively considers the disposal of the mother liquor produced during the preparation process of struvite and the recycling of phosphorus and magnesium resources remaining in the mother liquor, and maximizes the recovery of magnesium and phosphorus produced during the production of nickel-cobalt-manganese ternary cathode materials. resources, and produces high value-added by-product struvite. The materials used are very common in the ternary cathode material production industry and are easy to obtain.

(5) This application solves the problems of large consumption of liquid alkali and increase of total salt in the wastewater during the treatment of magnesium-containing sulfate wastewater in the nickel-cobalt-manganese ternary precursor industrial wastewater. The problem of large area occupied by the treatment facilities, magnesium hydroxide The problem of solid waste generation and the low added value of magnesium hydroxide.

(6) This application solves the problems of large consumption of calcium hydroxide and increase in total hardness of wastewater during the treatment of phosphorus-containing sulfate wastewater in nickel-cobalt-manganese ternary precursor industrial wastewater, as well as the problem of large area occupied by treatment facilities, calcium phosphate The problem of mud and solid waste generation and the low added value of calcium phosphate.

(7) This application is based on the current mainstream ternary battery recycling process, integrates various wastewaters generated by the battery recycling process, achieves comprehensive disposal of wastewater, and resource utilization of waste residues, and can be widely promoted for ternary battery recycling recycling industry.

(8) This application uses nickel-cobalt-manganese ternary precursor industrial wastewater as raw material and relies on the proposed process route to prepare higher-purity struvite. The struvite product does not contain heavy metals such as nickel-cobalt-manganese, and can be promoted to applications containing nickel-cobalt-manganese heavy metals. Recovery and separation of ammonia nitrogen, phosphorus and magnesium in nickel, cobalt and manganese heavy metal wastewater.

(9) This application uses the breakpoint chlorination method and the aeration stripping method to remove ammonia and deamination, which can reduce the oil content in the mother liquor to a certain extent, which is beneficial to the subsequent wastewater filtration of the organic membrane filter and the subsequent MVR evaporation. System wastewater evaporates.

The present application has been described in detail above with reference to the embodiments. However, the present application is not limited to the above-mentioned embodiments. Various changes can be made within the knowledge scope of those of ordinary skill in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments may be combined with each other without conflict.

Claims (10)

A comprehensive treatment method for wastewater, characterized in that the wastewater includes phosphorus-containing wastewater, magnesium-containing wastewater and ammonia-containing wastewater, and the comprehensive treatment method includes the following steps: S1: According to the molar ratio of nitrogen, magnesium and phosphorus to (9-11): (1-3): 1, mix the phosphorus-containing wastewater, the magnesium-containing wastewater and the ammonia-containing wastewater to obtain a mixed liquid; S2: The mixed liquid is reacted, aged, and separated to obtain mother liquid and struvite. The comprehensive processing method according to claim 1, characterized in that said S1 includes: S11: Mix the phosphorus-containing wastewater and the ammonia-containing wastewater according to the molar ratio of nitrogen to phosphorus (9-11):1 to obtain nitrogen-phosphorus wastewater; S12: Then add the magnesium-containing wastewater to the nitrogen-phosphorus wastewater according to the molar ratio of magnesium to phosphorus (1-3):1, adjust the pH to 8-10, and obtain the mixed liquid. The comprehensive treatment method according to claim 1 or 2, characterized in that the ammonia-containing wastewater is filtered to remove insoluble valuable metals and adjust the pH to 5-9.5 before mixing. The comprehensive treatment method according to claim 1 or 2, characterized in that the magnesium-containing wastewater is adsorbed to remove oil before mixing. The comprehensive processing method according to claim 1 or 2, characterized in that the comprehensive processing method further includes: S3: The mother liquor is added with chlorine at the breaking point and aerated to remove ammonia nitrogen; Preferably, the S3 includes: S31: Pass sodium hypochlorite or chlorine gas into the mother liquor to perform deamination treatment; S32: Adjust the pH value of the deamination-treated mother liquor to alkaline, heat, aerate, and blow off residual ammonia and residual chlorine. The comprehensive processing method according to claim 5, characterized in that the comprehensive processing method further includes: S4: Press filter the mother liquor to obtain filtrate and filter residue; Preferably, the filtrate obtained by medium pressure filtration in S4 is filtered again to remove insoluble matter and then subjected to salt recovery treatment; Preferably, the filter residue obtained by pressure filtration in S4 and the insoluble matter obtained by filtering again are adjusted to pH to obtain a magnesium solution, and the magnesium solution is reused in the mixed liquid obtained in S1. A comprehensive wastewater treatment system is characterized by including a struvite production unit, and the struvite production unit includes: A wastewater supply device, the wastewater supply device is used to provide phosphorus-containing wastewater, ammonia-containing wastewater and magnesium-containing wastewater; A struvite synthesis device, which is used to mix the phosphorus-containing wastewater, the ammonia-containing wastewater and the magnesium-containing wastewater to obtain a mixed liquid, and react to generate struvite; A separation device is used to separate the struvite from the mixed liquid to form a mother liquid. The comprehensive treatment system according to claim 7, characterized in that the wastewater supply device includes: A phosphorus-containing wastewater supply device, the phosphorus-containing wastewater supply device is used to provide phosphorus-containing wastewater to the struvite synthesis device; Ammonia-containing wastewater supply device, the ammonia-containing wastewater supply device is used to provide ammonia-containing wastewater to the struvite synthesis device, the ammonia-containing wastewater supply device is also provided with a filter component, the filter component is used to filter out the ammonia-containing wastewater Valuable metal insoluble matter in ammonia-containing wastewater; Magnesium-containing wastewater supply device, the magnesium-containing wastewater supply device is used to provide magnesium-containing wastewater to the struvite synthesis device, the magnesium-containing wastewater supply device is also provided with an oil removal component, and the oil removal component is used to remove The oil content in the magnesium-containing wastewater. The comprehensive treatment system according to claim 7, characterized in that the comprehensive treatment system further includes a mother liquor recovery unit, and the mother liquor recovery unit includes: Ammonia removal device, the ammonia removal device includes breakpoint chlorination equipment and aeration and stripping equipment, used to sequentially perform breakpoint chlorine addition and aeration stripping to the mother liquor to remove ammonia nitrogen; Magnesium removal device, the magnesium removal device is used to separate magnesium-containing precipitates from the mother liquor after ammonia removal; A salt recovery device is used to separate soluble salts from the mother liquor after magnesium removal. The comprehensive treatment system according to claim 9, wherein the salt recovery device includes an MVR evaporation system.