CN116692910A - Recycling process of waste lithium iron phosphate battery - Google Patents

Abstract

The application relates to a recovery process of a waste lithium iron phosphate battery, which comprises the following steps: crushing waste batteries in an electrified way to obtain fragments; pyrolyzing and roasting fragments and sodium chloride; physically screening the fragments to obtain anode and cathode powder; the anode and cathode powder is subjected to alkali dissolution to obtain an intermediate product; performing primary acid leaching on the intermediate product to obtain primary leaching liquid and primary leaching residues; purifying the first-stage leaching solution to obtain a purified solution; separating from the purified liquid to obtain battery grade lithium carbonate; performing secondary acid leaching on the primary leaching residues to obtain secondary leaching residues and secondary leaching solutions, and washing and drying the secondary leaching residues to obtain carbon powder; adding phosphoric acid into the secondary leaching solution, oxidizing, and then introducing a dilute ammonia solution to obtain crude ferric phosphate; adding sulfuric acid into the crude ferric phosphate for aging, and roasting to obtain the battery grade ferric phosphate. The method has the characteristics of safety, reliability, high efficiency, energy conservation, high recovery rate, environment friendliness, simplicity and effectiveness, and is suitable for large-scale industrial production.

Description

Recycling process of waste lithium iron phosphate battery

technical field

The present application relates to the technical field of waste battery recycling, in particular to a recycling process of waste lithium iron phosphate batteries.

Background technique

With the rapid development of the new energy vehicle industry, the power battery market dominated by lithium batteries is showing a blowout trend. Lithium iron phosphate batteries have become the most commonly used power batteries for new energy vehicles due to their high safety performance and good stability. However, the service life of such batteries is usually 5-8 years, and large-scale batteries will face scrapping. There are a large amount of scarce lithium metal and high-value iron phosphate in lithium iron phosphate batteries. Resource recycling has good environmental value, social value and economic value. Therefore, how to effectively treat and utilize resources is a major issue in the field of new energy. topic.

At present, the recycling technology of decommissioned lithium iron phosphate batteries is in its infancy, and no unified and mature industrialization route has been formed. The recycling technologies of lithium iron phosphate cathode materials at home and abroad mainly include high-temperature regeneration technology, biological recycling technology, and wet recycling technology.

High-temperature regeneration technology refers to the use of high-temperature roasting to remove impurities in the positive electrode material disassembled from the retired lithium iron phosphate battery to achieve direct regeneration or to supplement the corresponding elements for repair to achieve regeneration. The high-temperature regeneration technology has simple processes, less environmental pollution, and less consumables. It only needs to add a small amount of lost lithium, iron, phosphorus, etc. to complete the repair, but this process has high requirements on the impurity content in the positive electrode material obtained by dismantling, and the aluminum, copper and other impurities entrained in the positive electrode material during the dismantling process are not easy to remove. , has a great influence on the electrochemical performance of the repaired electrode material.

Bioleaching recovery technology refers to the method of using microorganisms to leaching, converting the metal in the lithium iron phosphate cathode material into a soluble compound and then selectively dissolving it, and gradually recovering the valuable metal in the solution. At present, the bioleaching technology for lithium iron phosphate is still in the research stage. Since the leaching needs to cultivate the corresponding microbial flora, the process of cultivating the corresponding microbial flora is not only complicated and the cultivation time is long, so this method has certain difficulties in realizing industrial production.

Wet recovery technology refers to the use of acid-base solution to dissolve metal ions in lithium iron phosphate batteries, and then extract the dissolved metals in the form of salts and oxides through precipitation and extraction to achieve the purpose of recycling valuable components of waste batteries . Due to the simplicity of the wet recycling process and low equipment requirements, it is especially suitable for industrial production. It is currently the most studied and mainstream recycling route for decommissioned lithium iron phosphate batteries at home and abroad. At present, the most widely used in the industry is to first recover the precious lithium resources in the lithium iron phosphate positive electrode material after acid leaching. The remaining ferrophosphorus is treated as waste after the iron is recovered by precipitation in most companies, and the resource recovery is not thorough. .

Contents of the invention

The purpose of this application is to provide a recycling process for waste lithium iron phosphate batteries, which is safe, reliable, efficient, energy-saving, high recovery rate, green and environmentally friendly, simple and effective, and is suitable for large-scale industrial production.

To this end, the embodiment of the present application provides a recycling process for waste lithium iron phosphate batteries, including the following steps:

Charge and crush waste batteries to obtain fragments;

Pyrolytically roasting the fragments by mixing them with sodium chloride to remove titanium metal;

Physically sieving the fragments after pyrolysis and roasting to obtain positive and negative electrode powders;

removing metal aluminum from the positive and negative electrode powder by alkaline dissolution to obtain an intermediate product;

performing primary acid leaching on the intermediate product to obtain primary leachate and primary leach slag;

Purify the primary leachate to remove fluorine and phosphate to obtain a purified solution;

Separating and obtaining battery-grade lithium carbonate from the purified liquid;

performing secondary acid leaching on the primary leaching slag with sulfuric acid to obtain a secondary leaching solution and a secondary leaching slag, wherein the secondary leaching slag is washed and dried to obtain carbon powder;

adding phosphoric acid to the secondary leaching solution, oxidizing with an oxidizing agent, passing dilute ammonia solution into the oxidized solution to obtain crude iron phosphate;

Sulfuric acid is added to the crude iron phosphate for aging, and then roasted to obtain battery-grade iron phosphate.

In a possible implementation manner, the charging and crushing of the waste battery is carried out to obtain fragments, including:

Nitrogen gas is introduced during the crushing process of the waste battery, and the length of the fragments is less than or equal to 40 mm.

In a possible implementation manner, the pyrolytic roasting of the fragments mixed with sodium chloride to remove titanium metal includes:

Mix the fragments with sodium chloride, the molar ratio of sodium chloride to titanium metal is 6-8:1;

The mixed fragments are pyrolytically roasted with sodium chloride, nitrogen gas is passed through during the pyrolytic roasting process for anaerobic protection, the pyrolytic roasting temperature is 500°C-600°C, and the pyrolytic roasting time is 0.5h-1.5h.

In a possible implementation manner, the fragments after pyrolysis and roasting are physically sieved to obtain positive and negative electrode powders, including:

Through at least one separation method of screening, air separation, magnetic separation, and eddy current separation, the steel shell, copper column head, and positive and negative pole pieces are obtained, and the positive and negative pole pieces are separated by a dry airflow stripping machine to obtain positive and negative pole powder. , copper foil and aluminum foil.

In a possible implementation manner, the positive and negative electrode powders are dissolved in alkali to remove metal aluminum to obtain intermediate products, including:

Add 2%-5% sodium hydroxide solution to the positive and negative electrode powders, wherein the solid-to-liquid ratio of the positive and negative electrode powders to the sodium hydroxide solution is 1:3, and the alkali dissolution time is 1h-2h The filter residue after filtration is the intermediate product, and the intermediate product includes lithium iron phosphate, a conductive agent and a mixture wrapped on the surface of lithium iron phosphate.

In a possible implementation manner, the intermediate product is subjected to primary acid leaching to obtain a primary leachate and a primary leach residue, including:

Slurrying 70%-80% of the intermediate product with pure water;

Add sulfuric acid and hydrogen peroxide solution for one acid leaching, the acid leaching time is 1.5h-2.5h, the acid leaching temperature is 50°C-60°C, two washings are performed after one acid leaching, and one leaching residue and one immersion liquid are obtained;

Add the remaining mixed solution of the intermediate product, sulfuric acid and hydrogen peroxide to the primary immersion solution for secondary acid leaching, the acid leaching time is 1.5h-2.5h, the temperature is 50°C-60°C, after the second acid leaching Carry out two washes, obtain secondary leaching residue and secondary immersion liquid;

The primary leaching solution includes the secondary leaching solution, and the primary leaching residue includes the primary leaching residue and the secondary leaching residue.

In a possible implementation, the primary leach solution is purified by adding aluminum sulfate and sodium hydroxide to remove fluorine and phosphate to obtain a purified solution, including:

adding the aluminum sulfate and the sodium hydroxide to the primary leaching solution for preliminary purification, the pH value of the solution is 8-9, and the reaction time is 0.5h-1h;

Sodium hydroxide will be added to the solution after preliminary purification to adjust the pH value of the solution to 11-12;

Sodium carbonate is added to the solution, the soaking temperature is 55°C-65°C, and the reaction time is 0.5h-1.0h;

Adding a flocculant to carry out precipitation filtration to obtain the purified liquid.

In a possible implementation, the separation of battery-grade lithium carbonate from the purified liquid includes:

Sodium carbonate is added to the purification solution, the reaction temperature is 90°C-95°C, and the reaction time is 1h-2h;

After the reaction, centrifuge filtration, hot water washing, and pure water slurry to obtain lithium iron carbonate slurry;

The lithium iron carbonate slurry is sent into a carbonization tower and carbon dioxide is carbonized at normal temperature;

Filter the carbonized slurry;

Thermally decompose the filtered solution;

The decomposed solution is centrifuged to obtain the battery-grade lithium carbonate.

In a possible implementation, the secondary acidification of the primary leaching residue is carried out to obtain a secondary leaching solution and a secondary leaching residue, and the secondary leaching residue is washed and dried to obtain carbon powder, including:

acid leaching the pulped secondary leaching residue and sulfuric acid solution with a content of 20%-25%, the reaction time is 2h-3h, and performing pressure filtration;

acid leaching the filtered solid and 20%-25% sulfuric acid solution, the reaction time is 2h-3h, to obtain the secondary leaching residue and the secondary leaching liquid, washing the secondary leaching residue, The carbon powder was obtained after filtration and drying.

In a possible implementation, adding phosphoric acid to the secondary leaching solution, oxidizing with an oxidizing agent, passing dilute ammonia solution into the oxidized solution to obtain crude iron phosphate, including:

Add the phosphoric acid to the secondary leaching solution, control the ratio of phosphorus to iron to 1.03-1.07:1, add the oxidant hydrogen peroxide to oxidize, the reaction time is 1h-1.5h, and pass the oxidized solution into 5%-10% dilute Ammonia solution forms a slurry with non-agglomerated precipitates, and the pH value of the final reaction solution is 1.8-2;

Press-filter the slurry to obtain the solid crude iron phosphate.

In a possible implementation, add sulfuric acid to the crude iron phosphate for aging, and then obtain battery-grade iron phosphate by roasting, including:

Aging the solid crude iron phosphate and sulfuric acid solution with a content of 20%-25%, the pH value of the solution is 1.3-1.5, the reaction time is 1.5h-2.5h, and the reaction temperature is 93°C-97°C;

The aged slurry is press-filtered, washed with water twice, then the washed slurry is centrifugally filtered, the solid after centrifugal filtration is dried, and the dried solid is roasted in a rotary kiln at a temperature of 640°C -660°C, the calcination time is 2h-3h, and the battery-grade iron phosphate product is obtained after calcination.

According to the recycling process of waste lithium iron phosphate battery provided by the embodiment of the present application, it includes the following steps: charging and crushing the waste battery to obtain fragments; mixing the fragments with sodium chloride for pyrolysis roasting to remove metal titanium; pyrolysis roasting The final fragments are physically sieved to obtain positive and negative electrode powders; the positive and negative electrode powders are removed from the metal aluminum by alkali dissolution to obtain intermediate products; the intermediate products are subjected to primary acid leaching to obtain primary leaching liquid and primary leaching slag; The primary leachate is purified to remove fluorine and phosphate to obtain a purified liquid; the battery-grade lithium carbonate is obtained by separating from the purified liquid; the primary leach residue is subjected to secondary acid leaching to obtain a secondary leach liquid and a secondary leach residue. The leaching residue is washed and dried to obtain carbon powder; add phosphoric acid to the secondary leaching solution, oxidize it through an oxidant, and pass dilute ammonia solution into the oxidized solution to obtain crude iron phosphate; add sulfuric acid to the crude iron phosphate for aging and then roasted to obtain battery-grade iron phosphate. This application adopts the self-developed recycling process, which has the characteristics of safety, reliability, high efficiency and energy saving, high recovery rate, green environmental protection, simplicity and effectiveness, and is suitable for large-scale industrial production. Compared with the high-temperature regeneration technology, this application can completely remove impurities such as aluminum and copper entrained in the positive electrode material, and this application uses fewer high-temperature scenarios, which reduces the recycling cost. Compared with the biological leaching recovery process, this application does not need to cultivate microbial colonies, reduces the leaching cycle, and the process is relatively simple. Compared with the wet recovery process, this application not only recovers battery-grade lithium carbonate, but also recovers battery-grade iron phosphate and 98% carbon powder, which makes the recovery more thorough and reduces the pollution of waste to the environment.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present application. Those skilled in the art can also obtain other drawings based on these drawings without creative work. In addition, in the drawings, the same reference numerals are used for the same components, and the drawings are not drawn in actual scale.

Fig. 1 shows the process flow chart of a kind of spent phosphoric acid battery recycling process that the embodiment of the application provides;

Fig. 2 shows the relationship diagram of the amount of sodium chloride added to the removal rate of metal titanium provided by the embodiment of the present application.

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments It is a part of the embodiments of this application, but not all of them. Based on the embodiments in the present application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present application.

As shown in FIG. 1 , FIG. 1 shows a process flow diagram of a waste phosphoric acid battery recovery process provided in the embodiment of the present application. The embodiment of the present application provides a recycling process for waste phosphoric acid batteries, comprising the following steps:

S1. Charge and crush waste batteries to obtain fragments;

S2, mixing the fragments with sodium chloride for pyrolytic roasting to remove metallic titanium;

S3. Physically sieving the pyrolyzed and roasted fragments to obtain positive and negative electrode powders;

S4, removing metal aluminum from the positive and negative electrode powders by alkali dissolution to obtain intermediate products;

S5, performing primary acid leaching on the intermediate product to obtain primary leachate and primary leach residue;

S611, purifying the primary leaching solution to remove fluorine and phosphate radicals to obtain a purification solution;

S612, separating and obtaining battery-grade lithium carbonate from the purified liquid;

S621. Perform secondary acid leaching on the primary leaching slag to obtain a secondary leaching solution and a secondary leaching slag, and obtain carbon powder after the secondary leaching slag is washed and dried;

S622, adding phosphoric acid to the secondary leaching solution, oxidizing with an oxidizing agent, passing dilute ammonia solution into the oxidized solution to obtain crude iron phosphate;

S623. Adding sulfuric acid to the crude iron phosphate for aging, and then roasting to obtain battery-grade iron phosphate.

Among them, S611, S612 can be performed simultaneously with S621, S622, and S623 to shorten the recovery processing time.

Waste batteries have completed the step-by-step recovery of all valuable resources of waste batteries through the above process, and prepared high-value products such as battery-grade lithium carbonate, battery-grade iron phosphate and carbon powder, and battery-grade lithium carbonate and battery-grade iron phosphate are used to prepare phosphoric acid Therefore, this recycling technology has effectively promoted the sustainable development of the lithium iron phosphate battery industry and opened up a green, environmentally friendly and economically feasible path for battery development. This application adopts a complete set of recycling technology independently developed, which has the characteristics of safety, reliability, high efficiency and energy saving, high recovery rate, green environmental protection, simplicity and effectiveness, and is suitable for large-scale industrial production.

Compared with the high-temperature regeneration technology, this application can remove impurities such as aluminum and copper entrained in the positive electrode material, so that the removal rate is high, and the application uses fewer high-temperature scenarios, which reduces the recycling cost. Compared with the biological leaching recovery process, this application does not need to cultivate microbial colonies, reduces the leaching cycle, and the process is relatively simple. Compared with the wet recovery process, this application not only recovers battery-grade lithium carbonate, but also recovers battery-grade iron phosphate and 98% carbon powder, which makes the recovery more thorough and reduces the pollution of waste to the environment.

In some optional embodiments, charging and crushing the waste battery to obtain fragments includes: passing nitrogen protection during the crushing process of the waste battery, and the length of the fragments is less than or equal to 40 mm.

In S1, when crushing, the waste battery is sent to the dismantling equipment feeding system, and is conveyed to the crusher through a belt for charged crushing. During the crushing process, nitrogen gas is passed through for anaerobic protection, so as to avoid sparks during the crushing process and improve the crushing efficiency. safety. Through one-time shearing and crushing, the crushed material is fully dispersed. The crushed material is flake-shaped, with a length of ≤40mm, which is convenient for post-processing. When the length is greater than 40mm, the dispersion effect of the crushed material is not good, and post-processing is inconvenient.

In some optional embodiments, mixing the fragments with sodium chloride for pyrolytic roasting to remove metallic titanium includes: mixing the fragments with sodium chloride, the molar ratio of sodium chloride to metallic titanium being 6-8 : 1; The mixed fragments are pyrolytically roasted with sodium chloride, and nitrogen is introduced into the process of pyrolytic roasting for anaerobic protection. The pyrolytic roasting temperature is 500°C-600°C, and the pyrolytic roasting time is 0.5h- 1.5h.

In S2, the crushed fragments contain impurity metal titanium, which needs to be removed. At high temperature, metal titanium, carbon, and sodium chloride react to form titanium tetrachloride. Among them, carbon is mainly composed of oxygen in the air, etc. The oxidizing gas reacts, consumes the oxidizing substances of the air, and creates a reducing atmosphere, which can reduce the reaction potential energy of titanium and chlorine. The boiling point of titanium tetrachloride is 135°C, which can be volatilized directly and enter the waste recovery system to remove metal titanium. Since the crushed fragments also contain carbon black substances, no additional carbon needs to be added during the pyrolysis roasting process.

Before pyrolysis roasting, detect the content of metal titanium, and then add sodium chloride according to the content of metal titanium, in order to remove metal titanium, add excess sodium chloride, the excess coefficient of sodium chloride is 150%-200% , so that the molar ratio of sodium chloride to titanium metal is 6-8:1, and then sent to the pyrolysis furnace for pyrolysis roasting. During pyrolysis and roasting, nitrogen gas is introduced throughout the whole process for protection. The pyrolysis and roasting temperature is 500°C-600°C to facilitate the volatilization of the generated titanium tetrachloride. The pyrolysis roasting time is 0.5h-1.5h.

Referring to FIG. 2 , FIG. 2 shows a relationship diagram of the amount of sodium chloride added to the removal rate of metallic titanium provided in the examples of the present application. Among them, the removal rate of metal titanium changes with the addition of sodium oxide. When the excess coefficient of sodium chloride is more than 140%, the removal rate of metal titanium reaches more than 90%. After that, continue to add sodium chloride, and the removal rate of metal titanium is slow. Increase. Therefore, according to the content of titanium metal, sodium chloride of corresponding quality is added to make the content of metal titanium less than 100ppm, which can ensure that the content of metal titanium in subsequent products does not exceed the standard.

During the pyrolysis and roasting process, organic binders, lithium hexafluorophosphate, organic carbonate solvents, and diaphragms undergo reactions such as bond breakage of macromolecules, isomerization, and polymerization of small molecules to form liquid, gaseous, and solid products, which solves the problem of electrolysis. Then the liquid, gaseous and solid products are passed into the secondary combustion chamber to oxidize and react with natural gas and air, so that various organic substances can be fully oxidized and burned to generate HF, LiOH, H ₂ O and CO ₂ , and the combustion exhaust gas is passed through After being cooled to 110°C-120°C in the quench tower, it enters the lye spray tower for defluorination, and then passes through the bag filter to collect dust and discharge it up to the standard. At the same time, the electrode sheet material after pyrolysis and roasting is relatively loose, which is convenient for subsequent electrode powder peeling.

In some optional embodiments, the fragments after pyrolysis and roasting are physically sieved to obtain positive and negative electrode powders, including: through at least one separation method in the process of sieving, air separation, magnetic separation, and eddy electric separation Obtain the steel shell, copper column head and positive and negative electrode sheets, and separate the positive and negative electrode sheets by a dry air flow stripping machine to obtain positive and negative electrode powder, copper foil and aluminum foil.

In S3, the material after pyrolysis and roasting can be separated by at least one separation method in the process of screening, air separation, magnetic separation, and eddy current separation, or can be separated by all the above separation methods, and the steel shell can be obtained after separation , copper pillars and positive and negative electrodes. Then, the positive and negative electrode sheets are separated by a dry air stripping machine, and the positive and negative electrode powder on the surface of the copper and aluminum foil is peeled off to obtain the positive and negative electrode powder and the copper and aluminum foil. The copper and aluminum foils are then separated by color separation to obtain copper foils and aluminum foils respectively. The disassembled steel shell, copper foil, and aluminum foil are transported to the general solid waste and hazardous waste temporary storage room for sale through ton bag packaging, and the positive and negative electrode powder are packed in ton bags and sent to the next step for recycling.

In some optional embodiments, the positive and negative electrode powders are dissolved in alkali to remove metal aluminum to obtain intermediate products, including: adding 2%-5% sodium hydroxide solution to the positive and negative electrode powders, wherein the positive and negative electrode powders are mixed with The solid-to-liquid ratio of the sodium hydroxide solution is 1:3, and the alkali dissolution time is 1h-2h. The filtered residue is an intermediate product, which includes lithium iron phosphate, a conductive agent, and a mixture wrapped on the surface of lithium iron phosphate.

In S4, the positive and negative electrode powder also contains impurity metal aluminum, aluminum is an amphoteric metal, and can be dissolved into metaaluminate under alkaline conditions, while the lithium iron phosphate in the positive and negative electrode powder is insoluble in alkali, so according to this characteristic Aluminum can be removed by alkali washing. Transport the positive and negative electrode powders containing metal aluminum to the alkali washing tank, add 2%-5% sodium hydroxide solution, the solid-liquid ratio of the positive and negative electrode powder to the sodium hydroxide solution is 1:3, the solid-liquid ratio here It refers to the mass ratio of solid to liquid. The alkali dissolution time is 1h-2h, and then it is filtered, and the alkali-dissolved water is sent to the sewage treatment station for treatment. The positive and negative electrode powder after removing metal aluminum is an intermediate product. The intermediate product includes lithium iron phosphate, A conductive agent and a mixture coated on the surface of lithium iron phosphate. Among them, according to the content of metal aluminum in the positive and negative electrode powder, it can be divided into one-stage or multi-stage alkali dissolution, and the content of metal aluminum after alkali dissolution is less than 500ppm.

In some optional embodiments, the intermediate product is subjected to primary acid leaching to obtain primary leachate and primary leach residue, including: slurrying 70%-80% of the intermediate product with pure water; then adding sulfuric acid and The hydrogen peroxide solution is subjected to one acid leaching, the acid leaching time is 1.5h-2.5h, the acid leaching temperature is 50°C-60°C, two washings are carried out after one acid leaching, and one leaching residue and one immersion liquid are obtained; in one immersion liquid Add the remaining intermediate products, sulfuric acid and hydrogen peroxide for secondary acid leaching. The acid leaching time is 1.5h-2.5h and the temperature is 50°C-60°C. The secondary leaching liquid; the primary leaching liquid includes the secondary leaching liquid, and the primary leaching residue includes the primary leaching residue and the secondary leaching residue.

In S5, the intermediate product is subjected to primary acid leaching treatment, and the primary acid leaching treatment may include one, two acid leaching treatments or multiple acid leaching treatments. Taking two acid leaching treatments as an example here, compared with only one acid leaching treatment, the separation of primary leaching residue and primary leaching solution is more thorough.

First, 70%-80% of the intermediate product is slurried with pure water, and the liquid-solid ratio of liquid and solid is controlled to be 4:1, and the liquid-solid ratio is the mass ratio of liquid to solid, and then sent to the primary leaching tank. In this application Pure water includes distilled water and deionized water, usually deionized water for industrial use. Then add sulfuric acid and hydrogen peroxide to the primary leaching tank for an acid leaching treatment, the acid leaching time is 1.5h-2.5h, and the acid leaching temperature is 50°C-60°C. After the primary acid leaching is completed, separation is carried out to obtain the primary leaching residue and the primary immersion liquid. The primary leaching residue is washed twice, and the washing water is returned to the primary leaching tank for another acid leaching.

The primary immersion liquid is sent to the secondary leaching tank, and the remaining intermediate products, concentrated sulfuric acid and hydrogen peroxide are added for secondary acid leaching to increase the concentration of lithium. The acid leaching time is 1.5h-2.5h, and the acid leaching temperature is 50°C-60°C. °C, the secondary acid leaching is completed and separated to obtain the secondary leaching solution and the secondary leaching residue, the secondary leaching residue is washed twice, and the washing water is returned to the primary leaching tank for acid leaching.

Wherein the content of sulfuric acid and hydrogen peroxide is adjusted according to the content of lithium iron phosphate, and can be set in excess, so that lithium ions in lithium iron phosphate can be leached.

After two times of acid leaching, the secondary leaching liquid, the primary leaching residue and the secondary leaching residue are obtained, the primary leaching liquid includes the secondary leaching liquid, and the primary leaching residue includes the primary leaching residue and the secondary leaching residue. In this application, the intermediate product is divided into two acid leaching treatments, which further improves the leaching rate of lithium.

This application adopts a selective leaching process, and by optimizing the leaching conditions, the leaching rate of lithium can reach more than 98%, while the leaching rate of iron is less than 0.3%, and phosphorus is hardly leached.

In some optional embodiments, the primary leaching solution is purified to remove fluorine and phosphate to obtain the purification solution, including: adding aluminum sulfate and sodium hydroxide to the primary leaching solution for preliminary purification, and the pH of the solution is 8-9, the reaction time is 0.5h-1h; add sodium hydroxide to the solution after preliminary purification, adjust the pH value of the solution to 11-12, then add sodium carbonate, the soaking temperature is 55°C-65°C, the reaction The time is 0.5h-1.0h, adding a flocculant for precipitation and filtration to obtain a purified solution.

In S611, the primary leaching solution is sent to a purification tank, and aluminum sulfate and sodium hydroxide are added to remove fluorine and phosphate in the solution, wherein the amount of aluminum sulfate is 1-1.2% of the total molar amount of fluorine and phosphate in the solution. The pH value of the solution is controlled by sodium hydroxide solution to be 8-9, the reaction time is 0.5h-1h, and the fluorine and phosphate groups are removed by aluminum sulfate.

After preliminary purification, send the liquid to the secondary purification tank for secondary purification, add sodium hydroxide to adjust the pH value of the solution to 11-12, add a small amount of sodium carbonate according to the calcium content, control the reaction temperature at 60 °C, and react Time 0.5h-1.0h, then add flocculant PAM to flocculate, remove a small amount of iron, magnesium, calcium and other metal ions in the solution, and then filter to obtain the purified solution, the content of iron ions in the purified solution is less than 10ppm, and the content of calcium ions is less than 5ppm. Magnesium ions are less than 5ppm.

In some optional embodiments, the separation of battery-grade lithium carbonate from the purification solution includes: adding sodium carbonate to the purification solution, the reaction temperature is 90°C-95°C, and the reaction time is 1h-2h; after the reaction, centrifugal filtration , hot water washing, and pure water slurry to obtain lithium iron carbonate slurry; send the lithium iron carbonate slurry to the carbonization tower and carbon dioxide at room temperature for carbonization; filter the carbonized slurry; heat the filtered solution Decomposition; the decomposed solution is centrifuged to obtain battery grade lithium carbonate.

In S612, the purification solution is sent to the lithium sink tank through precision filtration, and excess sodium carbonate is added, the temperature is controlled at 90°C-95°C, the reaction time is 1h-2h, and then the slurry is centrifugally filtered, and the filtered solid is used Wash in hot water at 90°C-95°C.

In this application, a small amount of impurities contained in the solution can be removed by adding aluminum sulfate and adjusting the PH value to be alkaline, adding sodium carbonate to precipitate lithium to obtain crude lithium carbonate, and further carbonizing and refining to obtain battery-grade lithium carbonate, and the recovery rate of lithium is 93%. above. Moreover, after lithium precipitation, the mother liquor can simply neutralize excess sodium carbonate, evaporate and crystallize to obtain industrial grade sodium sulfate, and the product reaches the (GBT 6009-2014 anhydrous sodium sulfate) standard.

The washed solid is added to pure water for slurrying, and then sent to the carbonization tower for continuous carbonization. The continuous carbonization tower adopts a large length-to-diameter ratio reaction tower, and the material and gas are fully countercurrently operated, which increases the reaction time of the material and gas. The top liquid distribution device disperses the material into the carbonization tower, making the reaction more uniform and the reaction efficiency higher. A special air distribution device is installed at the bottom of the carbonization tower to increase the uniformity of the air intake and make the reaction more complete.

The slurry is transported into the top of the first-stage carbonization tower by the carbonization feed pump. The slurry flows slowly from the top of the equipment to the bottom of the carbonization tower, and reacts with carbon dioxide during the flow process. The discharge pump is transported to the top of the secondary carbonization tower, and the slurry flows slowly from the top of the equipment to the bottom of the carbonization tower. During the flow, it reacts with carbon dioxide. The reacted material is extracted from the bottom of the carbonization tower and transported by the secondary discharge pump. After entering the buffer tank of the carbonized liquid for buffering, it is sent to the precision filter by the buffer discharge pump for filtration. Wherein the carbonization temperature of the slurry in the primary carbonization tower and the secondary carbonization tower is normal temperature.

The filtered supernatant enters the fine filtrate tank, is transported by the decomposition feed pump, passes through the preheater and the mother liquor to heat up, and then enters the decomposition tower, where it is heated and decomposed. The decomposed slurry is transported into the fine filter material slurry tank by the decomposition discharge pump, and then transported into the centrifuge by the centrifugal feed pump for centrifugal separation to obtain battery-grade lithium carbonate.

In some optional embodiments, secondary acidification is performed on the primary leaching slag to obtain the secondary leaching liquid and the secondary leaching slag, and the secondary leaching slag is washed and dried to obtain carbon powder, including: pulping the The secondary leaching residue and sulfuric acid solution with a content of 20%-25% are subjected to acid leaching, and the reaction time is 2h-3h, and pressure filtration is carried out; the solid after pressure filtration is mixed with a sulfuric acid solution with a content of 20%-25%, and the reaction time is 2h -3h, obtain the secondary leaching residue and the secondary leaching solution, wash, filter and dry the secondary leaching residue to obtain carbon powder.

In S621, pure water is added to the primary leaching residue for slurrying. After slurrying, it is sent to the primary FP leaching tank, and sulfuric acid solution with a content of 20%-25% is added to the tank for acidification. The sulfuric acid solution can be passed through concentrated sulfuric acid Diluted with pure water. Among them, the mass ratio of solid to liquid is controlled to be 1:4, and the reaction time is 2h-3h. After the leaching is completed, it is pumped to the filter press for pressure filtration, and the solid is transferred to the secondary FP leaching tank, and 20% -25% sulfuric acid solution, control the mass ratio of solid to liquid to be 1:4, and the reaction time is 2h-3h to obtain the secondary leaching residue and secondary leaching liquid. The secondary leaching residue is washed three times, and the washing water is returned to FP for leaching tank, filter and dry the washed secondary leaching residue to form carbon powder with a purity of more than 98%, and store it for sale.

In some optional embodiments, phosphoric acid is added to the secondary leaching solution, oxidized by an oxidizing agent, and dilute ammonia solution is passed through the oxidized solution to obtain crude iron phosphate, including: adding phosphoric acid to the secondary leaching solution to control phosphorus The iron ratio is 1.03-1.07:1, adding oxidant hydrogen peroxide to oxidize, the reaction time is 1h-1.5h, the oxidized solution is passed into 5%-10% dilute ammonia solution to form a slurry with unagglomerated precipitates, and the final reaction solution The pH value is 1.8-2; the slurry is press-filtered to obtain solid crude iron phosphate.

In S622, pass the secondary leaching solution into the pH adjustment tank, add phosphoric acid to the tank, control the ratio of phosphorus to iron at 1.03 to 1.07, and then send it to the oxidation tank, add excess oxidant hydrogen peroxide, control the reaction time 1h-1.5h, after The oxidized solution is sent to the precision filter, the fine filtrate is sent to the FP synthesis tank, and the configured 5%-10% dilute ammonia solution is passed into the synthesis tank, and the feed rate of ammonia water is properly controlled, as long as the formed precipitate does not form agglomerates. Can. Control the pH value of the final reaction solution to 1.8-2. The synthetic slurry is pumped into a filter press for pressure filtration and washing to obtain solid crude iron phosphate.

In some optional embodiments, sulfuric acid is added to the crude iron phosphate for aging, and then roasted to obtain battery-grade iron phosphate, including: aging solid crude iron phosphate and a sulfuric acid solution with a content of 20%-25%, The pH value of the solution is 1.3-1.5, the reaction time is 1.5h-2.5h, and the reaction temperature is 93°C-97°C; the aged slurry is press-filtered, washed with water twice, and then washed. Centrifugal filtration, drying the solids after centrifugal filtration, and roasting the dried solids in a rotary kiln at a temperature of 640°C-660°C and a roasting time of 2h-3h to obtain battery-grade iron phosphate products.

In S623, solid crude ferric phosphate is added into pure water for slurrying, and the slurried crude ferric phosphate enters the aging tank, and the solid-liquid ratio is controlled to be 1:3-4, where the solid-liquid ratio is the mass ratio, Use sulfuric acid to adjust the pH value of the aging tank solution to 1.3-1.5. For the first synthesis of ferric phosphate, it is necessary to use sulfuric acid to adjust the pH of the aging solution, and then add a small amount of aged ferric phosphate. Aging for 2h-3h, the aging temperature Control at 93°C-97°C. After aging, the slurry is sent to the FP filter press, washed twice with pure water and the mass ratio of solid to liquid is controlled at 1:4-5, and the slurry after washing is pumped to the centrifuge for filtration, and the filtered material is sent to the flash dryer for drying. After the material is flash-dried, the material is collected by the pulse bag filter and then enters the rotary kiln for roasting. The roasting temperature is 640°C-660°C, and the roasting time is 2h- 3h, the battery-grade iron phosphate product can be obtained after roasting.

This application can synthesize ferric phosphate at normal temperature. Adding sulfuric acid to adjust the pH or adding aged ferric phosphate can greatly shorten the aging time during aging. The aged ferric phosphate can be washed twice with water to meet the requirements of battery grade. requirements.

And the filtered mother liquor is ammonium sulfate wastewater, and the impurities are mainly iron, phosphate, and other small amounts of metals, which can be removed by adjusting the alkali and adding a small amount of precipitant, and then evaporate and crystallize to obtain pure ammonium sulfate products, which can be used for Fertilizer etc.

Specific embodiment one

S1, send the waste battery to the dismantling equipment feeding system, and transport it to the crusher through the belt for live crushing. The crushing process is protected by nitrogen anaerobic protection, and the crushed material is flakes with a length of ≤40mm.

S2, carry out pyrolytic roasting on the fragments, before pyrolytic roasting, detect the content of metal titanium, then add sodium chloride according to the content of metal titanium, the molar ratio of sodium chloride to metal titanium is 6:1, and then send into the pyrolysis furnace for pyrolysis roasting. During pyrolysis and roasting, nitrogen gas is introduced throughout the process for protection. The temperature of pyrolysis and roasting is 500°C and the time of pyrolysis and roasting is 0.5 hours.

S3, separating the pyrolysis-roasted materials through screening, air separation, magnetic separation, and eddy electric separation in sequence, and obtaining steel shells, copper column heads, and positive and negative pole pieces after separation. Then, the positive and negative electrode sheets are separated by a dry air stripping machine, and the positive and negative electrode powder on the surface of the copper and aluminum foil is peeled off to obtain the positive and negative electrode powder and the copper and aluminum foil. The copper and aluminum foils are then separated by color separation to obtain copper foils and aluminum foils respectively. The disassembled steel shells, copper foils, and aluminum foils are packed in large bags and transported to the general solid waste and hazardous waste temporary storage room for storage and sale.

S4, transport the positive and negative electrode powder containing metal aluminum to the alkali washing tank, add 2% sodium hydroxide solution, the solid-liquid ratio of the positive and negative electrode powder to the sodium hydroxide solution is 1:3, and the alkali dissolution time is 1h, Then it is filtered, and the alkali-soluble water is sent to the sewage treatment station for treatment. The positive and negative electrode powder after removing the metal aluminum is an intermediate product. The intermediate product includes lithium iron phosphate, a conductive agent, and a mixture wrapped on the surface of lithium iron phosphate.

S5, Slurry 70% of the intermediate product with pure water, control the ratio of liquid and solid to 4:1, and then send it to the primary leaching tank. Add sulfuric acid and hydrogen peroxide to the primary leaching tank for one acid leaching treatment, the acid leaching time is 1.5h, and the acid leaching temperature is 50°C. After the primary acid leaching is completed, separation is carried out to obtain the primary leaching residue and the primary immersion liquid. The primary leaching residue is washed twice, and the washing water is returned to the primary leaching tank for another acid leaching.

The primary immersion liquid is sent to the secondary leaching tank, and the remaining intermediate products, concentrated sulfuric acid and hydrogen peroxide are added for secondary acid leaching to increase the concentration of lithium. The acid leaching time is 1.5h, and the acid leaching temperature is 50°C. After the separation is completed, the secondary leaching solution and the secondary leaching residue are obtained. The secondary leaching residue is washed twice, and the washing water is returned to the primary leaching tank for acid leaching. After two times of acid leaching, the secondary leaching liquid, the primary leaching residue and the secondary leaching residue are obtained, the primary leaching liquid includes the secondary leaching liquid, and the primary leaching residue includes the primary leaching residue and the secondary leaching residue.

S611, send the primary leaching solution into a purification tank, add aluminum sulfate and sodium hydroxide to remove fluorine and phosphate in the solution, the amount of aluminum sulfate is added according to 1 times the total molar amount of fluorine and phosphate in the solution, pass through sodium hydroxide The pH value of the control solution was 8, and the reaction time was 0.5h. After preliminary purification, send the liquid to the secondary purification tank for secondary purification, add sodium hydroxide to adjust the pH value of the solution to 11, and add a small amount of sodium carbonate according to the calcium content, control the reaction temperature at 60°C, and the reaction time 0.5h, Then add the flocculant PAM to flocculate, remove a small amount of metal ions such as iron, magnesium, and calcium in the solution, and then filter to obtain the purified solution.

S612, the purification solution is sent to the lithium sink tank through precision filtration, and excess sodium carbonate is added, the temperature is controlled at 90°C, and the reaction time is 1h, then the slurry is subjected to centrifugal filtration, and the filtered solid is washed with hot water at 90°C.

The washed slurry is transported into the top of the first-stage carbonization tower by the carbonization feed pump. The slurry flows slowly from the top of the equipment to the bottom of the carbonization tower, and reacts with carbon dioxide during the flow process. The reacted material is extracted from the bottom of the carbonization tower. It is transported into the top of the secondary carbonization tower by the primary discharge pump. The slurry flows slowly from the top of the equipment to the bottom of the carbonization tower, and reacts with carbon dioxide during the flow process. The material pump is transported into the carbonized liquid buffer tank for buffering, and then transported by the buffer discharge pump into the precision filter for filtration. Wherein the carbonization temperature of the slurry in the primary carbonization tower and the secondary carbonization tower is normal temperature.

The filtered supernatant enters the fine filtrate tank, is transported by the decomposition feed pump, passes through the preheater and the mother liquor to heat up, and then enters the decomposition tower, where it is heated and decomposed. The decomposed slurry is transported into the fine filter material slurry tank by the decomposition discharge pump, and then transported into the centrifuge by the centrifugal feed pump for centrifugal separation to obtain battery-grade lithium carbonate.

S621, adding pure water to the primary leaching slag for slurrying, after slurrying, send it to the primary FP leaching tank, and add 20% sulfuric acid solution in the tank for acidification. Among them, the mass ratio of solid to liquid is controlled to be 1:4, and the reaction time is 2 hours. After the leaching is completed, it is pumped to the filter press for pressure filtration, and the solid is transferred to the secondary FP leaching tank, and 20% of Sulfuric acid solution, the mass ratio of solid to liquid is controlled to be 1:4, the reaction time is 2h, and the secondary leaching residue and secondary leaching liquid are obtained. The secondary leaching residue is washed three times, and the washing water is returned to the FP leaching tank once. The first-grade leaching residue is filtered and dried to form carbon powder with a purity of more than 98%, which is stored for sale.

S622, pass the secondary leaching solution into the pH adjustment tank, add phosphoric acid into the tank, control the ratio of phosphorus to iron at 1.03, then send it into the oxidation tank, add excess oxidant hydrogen peroxide, control the reaction time for 1 hour, and send the oxidized solution into the precision The filter and fine filtrate are sent to the FP synthesis tank, and the configured 5% dilute ammonia solution is passed into the synthesis tank, and the feed rate of ammonia water is properly controlled, as long as the generated precipitate does not form agglomerates. Control the pH value of the final reaction solution to 1.8. The synthetic slurry is pumped into a filter press for pressure filtration and washing to obtain solid crude iron phosphate.

S623, adding solid crude iron phosphate into pure water for slurrying, putting the slurryed crude iron phosphate into the aging tank, controlling the mass ratio of solid to liquid to be 1:3, and adjusting the pH value of the aging tank solution to 1.3 with sulfuric acid , the first synthesis of ferric phosphate needs to use sulfuric acid to adjust the pH of the aging solution, and then add a small amount of aged ferric phosphate, then age for 2 hours, the aging temperature is controlled at 93°C, and after aging, the slurry is sent to FP filter press Machine, washed twice with pure water and the mass ratio of solid and liquid is controlled at 1:4, the slurry after washing is pumped to a centrifuge for filtration, and the filtered material is sent to a flash dryer for drying, and the material is flash evaporated After drying, the material is collected by the pulse bag filter and then enters the rotary kiln for roasting. The roasting temperature is 640°C and the roasting time is 2 hours. After roasting, the battery-grade iron phosphate product is obtained.

Specific embodiment two

S1, send the waste battery to the dismantling equipment feeding system, and transport it to the crusher through the belt for live crushing. The crushing process is protected by nitrogen anaerobic protection, and the crushed material is flakes with a length of ≤40mm.

S2, carry out pyrolytic roasting on the fragments, before pyrolytic roasting, detect the content of metal titanium, then add sodium chloride according to the content of metal titanium, the molar ratio of sodium chloride to metal titanium is 7:1, and then send into the pyrolysis furnace for pyrolysis roasting. During the pyrolysis roasting, nitrogen gas is introduced throughout the process for protection. The pyrolysis roasting temperature is 550°C, and the pyrolysis roasting time is 1 hour. Titanium tetrachloride produced after the roasting of metal titanium volatilizes to the waste recovery system.

S3, separating the pyrolysis-roasted materials through screening, air separation, magnetic separation, and eddy electric separation in sequence, and obtaining steel shells, copper column heads, and positive and negative pole pieces after separation. Then, the positive and negative electrode sheets are separated by a dry air stripping machine, and the positive and negative electrode powder on the surface of the copper and aluminum foil is peeled off to obtain the positive and negative electrode powder and the copper and aluminum foil. The copper and aluminum foils are then separated by color separation to obtain copper foils and aluminum foils respectively. The disassembled steel shells, copper foils, and aluminum foils are packed in large bags and transported to the general solid waste and hazardous waste temporary storage room for storage and sale.

S4, transport the positive and negative electrode powder containing metal aluminum to the alkali washing tank, add 3% sodium hydroxide solution, the solid-liquid ratio of the positive and negative electrode powder to the sodium hydroxide solution is 1:3, and the alkali dissolution time is 1.5h , and then filtered, the alkali-soluble water is sent to the sewage treatment station for treatment, and the positive and negative electrode powder after removing metal aluminum is an intermediate product, which includes lithium iron phosphate, a conductive agent, and a mixture wrapped on the surface of lithium iron phosphate.

S5, slurry 75% of the intermediate product with pure water, control the ratio of liquid and solid to 4:1, and then send it to the primary leaching tank. Add sulfuric acid and hydrogen peroxide to the primary leaching tank for one acid leaching treatment, the acid leaching time is 2 hours, and the acid leaching temperature is 55°C. After the primary acid leaching is completed, separation is carried out to obtain the primary leaching residue and the primary immersion liquid. The primary leaching residue is washed twice, and the washing water is returned to the primary leaching tank for another acid leaching.

The primary immersion liquid is sent to the secondary leaching tank, and the remaining intermediate products, concentrated sulfuric acid and hydrogen peroxide are added for secondary acid leaching to increase the concentration of lithium. The acid leaching time is 2 hours, and the acid leaching temperature is 55 ° C. The secondary acid leaching is completed Separation is carried out to obtain the secondary leaching liquid and the secondary leaching residue, the secondary leaching residue is washed twice, and the washing water is returned to the primary leaching tank for acid leaching. After two times of acid leaching, the secondary leaching liquid, the primary leaching residue and the secondary leaching residue are obtained, the primary leaching liquid includes the secondary leaching liquid, and the primary leaching residue includes the primary leaching residue and the secondary leaching residue.

S611, send the primary leaching solution into a purification tank, add aluminum sulfate and sodium hydroxide to remove fluorine and phosphate in the solution, the amount of aluminum sulfate is added according to 1 times the total molar amount of fluorine and phosphate in the solution, pass through sodium hydroxide The pH value of the control solution was 9, and the reaction time was 0.75h. After preliminary purification, send the liquid to the secondary purification tank for secondary purification, add sodium hydroxide to adjust the pH value of the solution to 12, and add a small amount of sodium carbonate according to the calcium content, control the reaction temperature at 60°C, and the reaction time 0.75h, Then add the flocculant PAM to flocculate, remove a small amount of metal ions such as iron, magnesium, and calcium in the solution, and then filter to obtain the purified solution.

S612, the purification solution is sent to the lithium sink tank through precision filtration, and excess sodium carbonate is added, the temperature is controlled at 93°C, the reaction time is 1.5h, and then the slurry is subjected to centrifugal filtration, and the filtered solid is washed with hot water at 93°C.

The washed slurry is transported into the top of the first-stage carbonization tower by the carbonization feed pump. The slurry flows slowly from the top of the equipment to the bottom of the carbonization tower, and reacts with carbon dioxide during the flow process. The reacted material is extracted from the bottom of the carbonization tower. It is transported into the top of the secondary carbonization tower by the primary discharge pump. The slurry flows slowly from the top of the equipment to the bottom of the carbonization tower, and reacts with carbon dioxide during the flow process. The material pump is transported into the carbonized liquid buffer tank for buffering, and then transported by the buffer discharge pump into the precision filter for filtration. Wherein the carbonization temperature of the slurry in the primary carbonization tower and the secondary carbonization tower is normal temperature.

The filtered supernatant enters the fine filtrate tank, is transported by the decomposition feed pump, passes through the preheater and the mother liquor to heat up, and then enters the decomposition tower, where it is heated and decomposed. The decomposed slurry is transported into the fine filter material slurry tank by the decomposition discharge pump, and then transported into the centrifuge by the centrifugal feed pump for centrifugal separation to obtain battery-grade lithium carbonate.

S621, adding pure water to the primary leaching slag for slurrying, after slurrying, send it to the primary FP leaching tank, and add 23% sulfuric acid solution in the tank for acidification. Among them, the mass ratio of solid to liquid is controlled to be 1:4, and the reaction time is 2.5h. After the leaching is completed, it is pumped to the filter press for pressure filtration, and the solid is transferred to the secondary FP leaching tank, and 23% of the content is added to the tank. sulfuric acid solution, the mass ratio of solid to liquid is controlled to be 1:4, the reaction time is 2.5h, and the secondary leaching residue and secondary leaching liquid are obtained. The secondary leaching residue is washed three times, and the washing water is returned to the FP leaching tank once, and the washed The second-stage leaching residue is filtered and dried to form carbon powder with a purity of more than 98%, which is stored for sale.

S622, pass the secondary leaching solution into the pH adjustment tank, add phosphoric acid to the tank, control the ratio of phosphorus to iron at 1.05, then send it into the oxidation tank, add excess oxidant hydrogen peroxide, control the reaction time for 1.5h, and send the oxidized solution into Precision filter, the fine filtrate is sent to the FP synthesis tank, and the configured 7% dilute ammonia solution is passed into the synthesis tank, and the feed rate of ammonia water is properly controlled, as long as the formed precipitate does not form agglomerates. Control the pH value of the final reaction solution to 1.9. The synthetic slurry is pumped into a filter press for pressure filtration and washing to obtain solid crude iron phosphate.

S623, adding solid crude iron phosphate into pure water for slurrying, putting the slurryed crude iron phosphate into the aging tank, controlling the mass ratio of solid to liquid to be 1:3.5, and adjusting the pH value of the aging tank solution to 1.4 with sulfuric acid For the first synthesis of ferric phosphate, it is necessary to use sulfuric acid to adjust the pH of the aging solution, and then add a small amount of aged ferric phosphate for subsequent aging for 2.5 hours, and the aging temperature is controlled at 95°C. Filter machine, washed twice with pure water and the mass ratio of solid and liquid is controlled at 1:4.5, the slurry after washing is pumped to the centrifuge for filtration, and the filtered material is sent to the flash dryer for drying, and the material is flashed After steaming and drying, the material is collected by the pulse bag filter and then enters the rotary kiln for roasting. The roasting temperature is 650°C and the roasting time is 2.5 hours. After roasting, the battery-grade iron phosphate product is obtained.

Specific embodiment three

S1, send the waste battery to the dismantling equipment feeding system, and transport it to the crusher through the belt for live crushing. The crushing process is protected by nitrogen anaerobic protection, and the crushed material is flakes with a length of ≤40mm.

S2, carry out pyrolytic roasting on the fragments, before pyrolytic roasting, detect the content of metal titanium, then add sodium chloride according to the content of metal titanium, the molar ratio of sodium chloride to metal titanium is 8:1, and then send into the pyrolysis furnace for pyrolysis roasting. During pyrolysis and roasting, nitrogen is introduced throughout the process for protection. The temperature of pyrolysis and roasting is 600°C, and the time of pyrolysis and roasting is 1.5 hours. The titanium tetrachloride produced by metal titanium after roasting volatilizes to the waste recovery system.

S3, separating the pyrolysis-roasted materials through screening, air separation, magnetic separation, and eddy electric separation in sequence, and obtaining steel shells, copper column heads, and positive and negative pole pieces after separation. Then, the positive and negative electrode sheets are separated by a dry air stripping machine, and the positive and negative electrode powder on the surface of the copper and aluminum foil is peeled off to obtain the positive and negative electrode powder and the copper and aluminum foil. The copper and aluminum foils are then separated by color separation to obtain copper foils and aluminum foils respectively. The disassembled steel shells, copper foils, and aluminum foils are packed in large bags and transported to the general solid waste and hazardous waste temporary storage room for storage and sale.

S4, transport the positive and negative electrode powders containing metal aluminum to the alkali washing tank, add 5% sodium hydroxide solution, the solid-liquid ratio of the positive and negative electrode powders to the sodium hydroxide solution is 1:3, and the alkali dissolution time is 2h, Then it is filtered, and the alkali-soluble water is sent to the sewage treatment station for treatment. The positive and negative electrode powder after removing the metal aluminum is an intermediate product. The intermediate product includes lithium iron phosphate, a conductive agent, and a mixture wrapped on the surface of lithium iron phosphate.

S5, Slurry 80% of the intermediate product with pure water, control the ratio of liquid and solid to 4:1, and then send it to the primary leaching tank. Add sulfuric acid and hydrogen peroxide to the primary leaching tank for an acid leaching treatment, the acid leaching time is 2 hours, and the acid leaching temperature is 60°C. After the primary acid leaching is completed, separation is carried out to obtain the primary leaching residue and the primary immersion liquid. The primary leaching residue is washed twice, and the washing water is returned to the primary leaching tank for another acid leaching.

The primary immersion liquid is sent to the secondary leaching tank, and the remaining intermediate products, concentrated sulfuric acid and hydrogen peroxide are added for secondary acid leaching to increase the concentration of lithium. The acid leaching time is 2.5h, and the acid leaching temperature is 60°C. After the separation is completed, the secondary leaching solution and the secondary leaching residue are obtained. The secondary leaching residue is washed twice, and the washing water is returned to the primary leaching tank for acid leaching. After two times of acid leaching, the secondary leaching liquid, the primary leaching residue and the secondary leaching residue are obtained, the primary leaching liquid includes the secondary leaching liquid, and the primary leaching residue includes the primary leaching residue and the secondary leaching residue.

S611, send the primary leaching solution into a purification tank, add aluminum sulfate and sodium hydroxide to remove fluorine and phosphate in the solution, the amount of aluminum sulfate is added according to 1.2 times the total molar amount of fluorine and phosphate in the solution, pass through sodium hydroxide The pH value of the control solution was 9, and the reaction time was 1 h. After preliminary purification, send the liquid to the secondary purification tank for secondary purification, add sodium hydroxide to adjust the pH value of the solution to 12, and add a small amount of sodium carbonate according to the calcium content, control the reaction temperature at 60°C, and the reaction time for 1h, then Add the flocculant PAM to flocculate, remove a small amount of metal ions such as iron, magnesium, and calcium in the solution, and then filter to obtain the purified solution.

S612, the purification solution is sent to the lithium sink tank through precision filtration, and excess sodium carbonate is added, the temperature is controlled at 95°C, the reaction time is 2h, and then the slurry is subjected to centrifugal filtration, and the filtered solid is washed with hot water at 95°C.

The washed slurry is transported into the top of the first-stage carbonization tower by the carbonization feed pump. The slurry flows slowly from the top of the equipment to the bottom of the carbonization tower, and reacts with carbon dioxide during the flow process. The reacted material is extracted from the bottom of the carbonization tower. It is transported into the top of the secondary carbonization tower by the primary discharge pump. The slurry flows slowly from the top of the equipment to the bottom of the carbonization tower, and reacts with carbon dioxide during the flow process. The material pump is transported into the carbonized liquid buffer tank for buffering, and then transported by the buffer discharge pump into the precision filter for filtration. Wherein the carbonization temperature of the slurry in the primary carbonization tower and the secondary carbonization tower is normal temperature.

The filtered supernatant enters the fine filtrate tank, is transported by the decomposition feed pump, passes through the preheater and the mother liquor to heat up, and then enters the decomposition tower, where it is heated and decomposed. The decomposed slurry is transported into the fine filter material slurry tank by the decomposition discharge pump, and then transported into the centrifuge by the centrifugal feed pump for centrifugal separation to obtain battery-grade lithium carbonate.

S621, adding pure water to the primary leaching slag for slurrying, after slurrying, send it to the primary FP leaching tank, and add 25% sulfuric acid solution in the tank for acidification. Among them, the mass ratio of solid to liquid is controlled to be 1:4, and the reaction time is 3 hours. After the leaching is completed, it is pumped to the filter press for pressure filtration, and the solid is transferred to the secondary FP leaching tank, and 25% of Sulfuric acid solution, the mass ratio of solid to liquid is controlled to be 1:4, the reaction time is 3h, and the secondary leaching residue and secondary leaching liquid are obtained. The secondary leaching residue is washed three times, and the washing water is returned to the FP leaching tank once. The first-grade leaching residue is filtered and dried to form carbon powder with a purity of more than 98%, which is stored for sale.

S622, pass the secondary leaching solution into the pH adjustment tank, add phosphoric acid to the tank, control the ratio of phosphorus to iron at 1.07, then send it into the oxidation tank, add excess oxidant hydrogen peroxide, control the reaction time for 1.5h, and send the oxidized solution into Precision filter, the fine filtrate is sent to the FP synthesis tank, and the configured 10% dilute ammonia solution is passed into the synthesis tank, and the feed rate of ammonia water is properly controlled, as long as the formed precipitate does not form agglomerates. Control the pH value of the final reaction solution to 2. The synthetic slurry is pumped into a filter press for pressure filtration and washing to obtain solid crude iron phosphate.

S623, adding solid crude iron phosphate into pure water for slurrying, putting the slurryed crude iron phosphate into the aging tank, controlling the mass ratio of solid to liquid to be 1:4, and adjusting the pH value of the aging tank solution to 1.5 with sulfuric acid , the first synthesis of ferric phosphate needs to use sulfuric acid to adjust the pH of the aging solution, and then add a small amount of aged ferric phosphate, then age for 3 hours, and the aging temperature is controlled at 97°C. After aging, the slurry is sent to FP filter press Machine, washed twice with pure water and the mass ratio of solid and liquid is controlled at 1:5, the slurry after washing is pumped to the centrifuge for filtration, and the filtered material is sent to the flash dryer for drying, and the material is flash evaporated After drying, the material is collected by the pulse bag filter and then enters the rotary kiln for roasting. The roasting temperature is 660°C and the roasting time is 3 hours. After roasting, the battery-grade iron phosphate product is obtained.

The test results of specific embodiment one, specific embodiment two and specific embodiment three are shown in Table 1.

Table 1

With reference to Table 1, it can be seen that the lithium overall recovery rate of embodiment one, embodiment two and embodiment three is greater than 93%, and the ferrophosphorus leaching rate is greater than 99%; the products obtained are all battery-grade lithium carbonate and battery-grade iron phosphate, And the recovery rate of carbon powder is also greater than 98%.

This application not only recycles battery-grade lithium carbonate, but also recycles battery-grade iron phosphate and 98% carbon powder, which makes the recycling more thorough and reduces the pollution of waste to the environment.

It should be noted that references in the specification to "one embodiment," "an embodiment," "exemplary embodiment," "some embodiments," etc. mean that the described embodiments may include particular features, structures, or characteristics, but not necessarily Each embodiment includes that particular feature, structure or characteristic. Furthermore, such phrases are not necessarily referring to the same embodiment. Furthermore, where a particular feature, structure, or characteristic is described in conjunction with an embodiment, it is within the purview of those skilled in the art to implement such feature, structure, or characteristic in conjunction with other embodiments that are explicitly or not explicitly described.

It should be readily understood that "on", "above" and "over" in this disclosure should be interpreted in the broadest manner such that "on" means not only " directly on something", also includes the meaning of "on something" with intermediate features or layers in between, and "above" or "over" not only includes "on something" or " The meaning of "over" may also include the meaning of "above" or "over" without intervening features or layers (ie, directly on something).

In addition, spatially relative terms, such as "below", "below", "below", "above", "above", etc., may be used herein for convenience of description to describe the position of one element or feature with respect to other elements or features. the relationship shown. Spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.

It should be noted that in this article, relative terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply these No such actual relationship or order exists between entities or operations. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes elements not expressly listed. other elements of or also include elements inherent in such a process, method, article, or device. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, rather than limiting them; although the application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present application. scope.

Claims (11)

1. The recovery process of the waste lithium iron phosphate battery is characterized by comprising the following steps of:

crushing waste batteries in an electrified way to obtain fragments;

mixing the fragments with sodium chloride for pyrolysis roasting to remove metallic titanium;

physically screening the fragments after pyrolysis roasting to obtain anode and cathode powder;

removing metal aluminum from the anode and cathode powder through alkali dissolution to obtain an intermediate product;

performing primary acid leaching on the intermediate product to obtain primary leaching liquid and primary leaching residues;

purifying the primary leaching solution to remove fluorine and phosphate so as to obtain a purified solution;

separating from the purified liquid to obtain battery grade lithium carbonate;

Performing secondary acid leaching on the primary leaching slag to obtain secondary leaching liquid and secondary leaching slag, and washing and drying the secondary leaching slag to obtain carbon powder;

adding phosphoric acid into the secondary leaching solution, oxidizing by an oxidant, and introducing a dilute ammonia solution into the oxidized solution to obtain crude ferric phosphate;

and adding sulfuric acid into the crude ferric phosphate for aging, and roasting to obtain the battery-grade ferric phosphate.

2. The process for recycling waste lithium iron phosphate battery according to claim 1, wherein the step of crushing the waste battery to obtain fragments comprises the steps of:

and introducing nitrogen in the process of crushing the waste batteries, wherein the length of the fragments is less than or equal to 40mm.

3. The process for recycling waste lithium iron phosphate battery according to claim 1, wherein the steps of mixing the fragments with sodium chloride and performing pyrolysis roasting to remove metallic titanium comprise:

mixing the fragments with the sodium chloride, wherein the molar ratio of the sodium chloride to the metallic titanium is 6-8:1, a step of;

and (3) carrying out pyrolysis roasting on the mixed fragments and the sodium chloride, introducing nitrogen in the pyrolysis roasting process for carrying out anaerobic protection, wherein the pyrolysis roasting temperature is 500-600 ℃, and the pyrolysis roasting time is 0.5-1.5 h.

4. The process for recycling waste lithium iron phosphate battery according to claim 1, wherein the step of physically sieving the fragments after pyrolysis and roasting to obtain positive and negative electrode powder comprises the steps of:

the steel shell, the copper column head and the positive and negative plates are obtained through at least one separation mode of screening, winnowing, magnetic separation and vortex electric separation procedures, and the positive and negative plates are separated through a dry airflow stripping machine to obtain the positive and negative powder, the copper foil and the aluminum foil.

5. The process for recycling waste lithium iron phosphate battery according to claim 1, wherein the step of removing metal aluminum from the positive and negative electrode powders by alkali dissolution to obtain an intermediate product comprises the steps of:

adding 2% -5% sodium hydroxide solution into the anode powder and the cathode powder, wherein the solid-to-liquid ratio of the anode powder to the sodium hydroxide solution is 1:3, and the alkali dissolution time is 1h-2h; the filtered filter residue is the intermediate product, and the intermediate product comprises lithium iron phosphate, a conductive agent and a mixture coated on the surface of the lithium iron phosphate.

6. The process for recycling waste lithium iron phosphate batteries according to claim 1, wherein the step of performing primary acid leaching on the intermediate product to obtain primary leachate and primary leaching residues comprises the steps of:

Slurrying 70% -80% of the intermediate product with pure water;

adding sulfuric acid and hydrogen peroxide solution for primary acid leaching for 1.5-2.5 h at 50-60 ℃, and washing twice after primary acid leaching to obtain primary leaching residue and primary leaching liquid;

adding the rest mixed solution of the intermediate product, sulfuric acid and hydrogen peroxide into the primary immersion liquid for secondary acid leaching, wherein the acid leaching time is 1.5-2.5 h, the temperature is 50-60 ℃, and the secondary acid leaching is followed by two washes to obtain secondary leaching residues and secondary immersion liquid;

the primary leaching liquid comprises the secondary leaching liquid, and the primary leaching slag comprises the primary leaching slag and the secondary leaching slag.

7. The process for recycling waste lithium iron phosphate battery according to claim 1, wherein the purifying the primary leachate to remove fluorine and phosphate radical and obtain a purified solution comprises:

adding the aluminum sulfate and the sodium hydroxide into the primary leaching solution for primary purification, wherein the PH value of the solution is 8-9, and the reaction time is 0.5-1 h;

adding sodium hydroxide into the solution after primary purification, and adjusting the PH value of the solution to be 11-12;

adding sodium carbonate into the solution, wherein the purification temperature is 55-65 ℃ and the reaction time is 0.5-1.0 h;

Adding a flocculating agent for precipitation and filtration to obtain the purified liquid.

8. The process for recycling waste lithium iron phosphate batteries according to claim 1, wherein the separation of the purified solution to obtain battery grade lithium carbonate comprises:

adding sodium carbonate into the purifying liquid, wherein the reaction temperature is 90-95 ℃ and the reaction time is 1-2 h;

centrifugal filtration, hot water washing and pure water slurrying are carried out after the reaction to obtain lithium iron carbonate slurry;

delivering the lithium iron carbonate slurry into a carbonization tower to be carbonized with carbon dioxide at normal temperature;

filtering the carbonized slurry;

carrying out thermal decomposition on the filtered solution;

and carrying out centrifugal separation on the decomposed solution to obtain the battery grade lithium carbonate.

9. The process for recycling waste lithium iron phosphate batteries according to claim 1, wherein the secondary acidification is performed on the primary leaching residues to obtain secondary leaching solutions and secondary leaching residues, and the secondary leaching residues are washed and dried to obtain carbon powder, and the process comprises the following steps:

carrying out acid leaching on the pulpified secondary leaching residues and sulfuric acid solution with the content of 20% -25%, wherein the reaction time is 2-3 hours, and carrying out filter pressing;

and (3) carrying out acid leaching on the filter-pressed solid and sulfuric acid solution with the content of 20% -25%, wherein the reaction time is 2-3 hours, obtaining secondary leaching residues and secondary leaching liquid, washing, filtering and drying the secondary leaching residues, and obtaining the carbon powder.

10. The process for recycling waste lithium iron phosphate batteries according to claim 1, wherein adding phosphoric acid into the secondary leaching solution, oxidizing by an oxidant, and introducing a dilute ammonia solution into the oxidized solution to obtain crude ferric phosphate, comprises:

adding the phosphoric acid into the secondary leaching solution, and controlling the phosphorus-iron ratio to be 1.03-1.07:1, adding the oxidant hydrogen peroxide for oxidization for 1h to 1.5h, introducing 5% -10% of diluted ammonia water solution into the oxidized solution to form slurry with non-agglomerated sediment, and finally enabling the pH value of the reaction solution to be 1.8-2;

and carrying out filter pressing on the slurry to obtain the solid crude ferric phosphate.

11. The process for recycling waste lithium iron phosphate battery according to claim 1, wherein adding sulfuric acid into the crude ferric phosphate for aging, and roasting to obtain battery-grade ferric phosphate, comprises:

aging the solid crude ferric phosphate and sulfuric acid solution, wherein the pH value of the solution is 1.3-1.5, the reaction time is 1.5-2.5 h, and the reaction temperature is 93-97 ℃;

and (3) carrying out filter pressing on the aged slurry, washing the slurry twice, carrying out centrifugal filtration on the washed slurry, drying the centrifugally filtered solid, roasting the dried solid in a rotary kiln at 640-660 ℃ for 2-3 hours, and roasting to obtain the battery-grade ferric phosphate product.