Recycling method of lithium iron phosphate waste
By reacting lithium iron phosphate waste with concentrated sulfuric acid and crystallization treatment, efficient recycling of lithium, iron and phosphorus was successfully achieved, solving the problems of resource waste and environmental pollution in the existing technology, and the process is environmentally friendly and efficient.
Patent Information
- Application Number
- CN202411923482.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-25
- Publication Date
- 2025-03-28
AI Technical Summary
The existing lithium iron phosphate waste recycling methods cannot efficiently recycle resources such as lithium, iron and phosphorus, resulting in waste of resources and environmental pollution.
By adding lithium iron phosphate waste to water and mixing slurry, and reacting with concentrated sulfuric acid, lithium iron phosphate solution and carbon slag are obtained. Crystallization treatment was performed in an inert gas to obtain ferrous sulfate heptahydrate, lithium sulfate and crystallization mother liquor. The crystallization mother liquor was then purified to obtain phosphoric acid.
It realizes efficient recycling of lithium, iron and phosphorus, reduces acid consumption and wastewater waste slag emissions, and is environmentally friendly.
Smart Images
Figure CN119706887A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium battery recycling and reuse, and in particular to a method for recycling lithium iron phosphate waste. Background Art
[0002] Lithium iron phosphate batteries are low-priced and highly safe, and are widely used in electric bicycles, electric vehicles, electric buses and other fields. With the rapid development of the new energy industry, the amount of scrapped lithium iron phosphate batteries has increased year by year. The huge occupation of resources and the threat to the environment by waste lithium iron phosphate batteries have attracted great attention from the society. Therefore, how to recycle and reuse waste lithium iron phosphate batteries is a major problem that needs to be solved urgently.
[0003] At present, there are two main methods for recycling lithium iron phosphate waste. One is the direct regeneration of lithium iron phosphate waste, and the other is the step-by-step recycling to prepare lithium carbonate (or lithium hydroxide) and iron phosphate. The regenerated lithium iron phosphate product obtained by the first direct regeneration method has poor electrical properties, harsh regeneration conditions, and a narrow range of applications. The second step-by-step recycling method to prepare lithium carbonate and iron phosphate produces an iron phosphate product with poor quality stability, difficulty in market promotion, and a single product application. At present, many recycling manufacturers only extract lithium from lithium iron phosphate waste. Iron, phosphorus, carbon, etc. still remain in the waste residue after lithium extraction and are treated as general solid waste, resulting in a waste of resources.
[0004] Therefore, it is urgent to develop a new process for simultaneously recovering lithium, iron, phosphorus, etc., to achieve efficient recovery of the three resources of lithium, iron and phosphorus, and to expand the application market of lithium iron phosphate waste recycling products. Summary of the invention
[0005] The purpose of the present invention is to provide a method for recycling lithium iron phosphate waste in view of the shortcomings of the prior art.
[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:
[0007] The present invention provides a method for recycling lithium iron phosphate waste, comprising the following steps:
[0008] 1) adding water to the lithium iron phosphate waste to prepare a slurry to obtain lithium iron phosphate waste slurry;
[0009] 2) reacting the lithium iron phosphate waste slurry with concentrated sulfuric acid to obtain a lithium iron phosphorus solution and carbon slag;
[0010] 3) crystallizing the lithium iron phosphorus solution in an inert gas to obtain ferrous sulfate heptahydrate, lithium sulfate and crystallization mother liquor;
[0011] 4) Purifying the crystallization mother liquor to obtain phosphoric acid.
[0012] Preferably, in step 1), the mass ratio of the lithium iron phosphate waste to water is 1:3-5.
[0013] Preferably, the mass ratio of the concentrated sulfuric acid in step 2) to the lithium iron phosphate waste in step 1) is 0.7-0.9:1, and the mass concentration of the concentrated sulfuric acid is 95-98%;
[0014] Step 2) The reaction temperature is 30-100° C. and the reaction time is 0.5-4 h.
[0015] Preferably, the crystallization treatment in step 3) comprises freeze crystallization and evaporation concentration crystallization performed sequentially, and the freeze crystallization obtains ferrous sulfate heptahydrate.
[0016] Preferably, the freeze-crystallization temperature is -20 to -10°C, and the freeze-crystallization time is 12 to 20 hours.
[0017] Preferably, the evaporation concentration and crystallization is to first perform evaporation concentration and then cool for crystallization; the evaporation concentration temperature is 110-130° C., and the evaporation concentration is stopped when the volume of the solution is 3 / 5-4 / 5 of the initial volume;
[0018] When cooled to a temperature of 55-65°C, lithium sulfate is crystallized;
[0019] When cooled to a temperature of -20 to -10°C, ferrous sulfate heptahydrate is obtained by crystallization.
[0020] Preferably, the evaporation, concentration and crystallization are repeated until the phosphate ion concentration in the crystallization mother liquor reaches 16 to 18 mol / L.
[0021] Preferably, the purification in step 4) comprises mixing the crystallization mother liquor with tributyl phosphate to obtain an oil phase, and then mixing the oil phase with water to obtain phosphoric acid.
[0022] Preferably, the volume ratio of the crystallization mother liquor to tributyl phosphate is 1:0.8-1.2, and the volume ratio of the crystallization mother liquor to water is 1:0.8-1.2.
[0023] The beneficial effects of the present invention include the following:
[0024] The present invention acid-leaches lithium iron phosphate waste to separate carbon residue to obtain a lithium iron phosphorus solution, and then fractionally crystallizes the lithium iron phosphorus solution to obtain ferrous sulfate heptahydrate and lithium sulfate, and the obtained crystallization mother liquor is purified to obtain phosphoric acid. The present invention provides a new idea for recycling lithium iron phosphate waste, extracts valuable elements such as iron, phosphorus, and lithium, and has less acid consumption, no wastewater and waste residue discharge, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] Figure 1 The present invention is a flow chart of the method for recycling lithium iron phosphate waste. DETAILED DESCRIPTION
[0026] The present invention provides a method for recycling lithium iron phosphate waste, comprising the following steps:
[0027] 1) adding water to the lithium iron phosphate waste to prepare a slurry to obtain lithium iron phosphate waste slurry;
[0028] 2) reacting the lithium iron phosphate waste slurry with concentrated sulfuric acid to obtain a lithium iron phosphorus solution and carbon slag;
[0029] 3) crystallizing the lithium iron phosphorus solution in an inert gas to obtain ferrous sulfate heptahydrate, lithium sulfate and crystallization mother liquor;
[0030] 4) Purifying the crystallization mother liquor to obtain phosphoric acid.
[0031] In the present invention, the lithium iron phosphate waste preferably includes waste obtained by dismantling and crushing discarded lithium iron phosphate batteries and / or scraps discarded during the production process of lithium iron phosphate batteries.
[0032] In the present invention, the mass ratio of the lithium iron phosphate waste to water in step 1) is preferably 1:3-5, more preferably 1:3.5-4.5, and more preferably 1:4.
[0033] In the present invention, the mass ratio of the concentrated sulfuric acid in step 2) to the lithium iron phosphate waste in step 1) is preferably 0.7-0.9:1, more preferably 0.75-0.85:1, and more preferably 0.8:1; the mass concentration of the concentrated sulfuric acid is preferably 95-98%, and more preferably 96-97%;
[0034] The reaction temperature in step 2) is preferably 30-100°C, more preferably 40-80°C, and more preferably 60°C; the reaction time is preferably 0.5-4h, more preferably 1-3h, and more preferably 2h.
[0035] In the present invention, the inert gas in step 3) is preferably nitrogen.
[0036] In the present invention, the crystallization treatment in step 3) preferably comprises freeze crystallization and evaporation concentration crystallization performed in sequence, and the freeze crystallization obtains ferrous sulfate heptahydrate.
[0037] In the present invention, after the freeze crystallization is completed, the product of the freeze crystallization is preferably centrifuged to obtain a crude ferrous sulfate heptahydrate product and a crystallization mother liquor, and the crude ferrous sulfate heptahydrate product is recrystallized to obtain ferrous sulfate heptahydrate and a recrystallization mother liquor; the recrystallization is preferably to prepare the crude ferrous sulfate heptahydrate product into a saturated aqueous solution of ferrous sulfate, and the saturated aqueous solution of ferrous sulfate is first evaporated and concentrated in nitrogen, and then cooled for crystallization; the temperature of the evaporation and concentration is preferably 110-130° C., more preferably 120° C., the evaporation and concentration is preferably stopped when the volume of the solution is 1 / 5-2 / 5 of the initial volume (volume of the saturated aqueous solution of ferrous sulfate), and cooling and crystallization are started, and when the temperature is cooled to -20--10° C., the product is centrifuged to obtain ferrous sulfate heptahydrate and a recrystallization mother liquor; the speed of the centrifugation is independently preferably 1000-1500 rpm, more preferably 1200 rpm; the time of the centrifugation is independently preferably 20-40 min, more preferably 30 min; the recrystallization mother liquor is preferably merged into the crystallization mother liquor, and evaporated, concentrated and crystallized.
[0038] In the present invention, the freeze crystallization temperature is preferably -20 to -10°C, more preferably -18 to -12°C, and more preferably -15°C; the freeze crystallization time is preferably 12 to 20 hours, more preferably 14 to 18 hours, and more preferably 16 hours.
[0039] In the present invention, the evaporation concentration crystallization is preferably performed by first evaporation concentration and then cooling for crystallization; the evaporation concentration temperature is preferably 110-130°C, more preferably 115-125°C, and more preferably 120°C; the evaporation concentration is stopped when the volume of the solution is preferably 3 / 5-4 / 5 of the initial volume, and more preferably 2 / 3;
[0040] Preferably, when the temperature is cooled to 55-65°C, lithium sulfate is crystallized, more preferably 58-62°C, and more preferably 60°C;
[0041] Preferably, when the temperature is cooled to -20 to -10°C, ferrous sulfate heptahydrate is crystallized, more preferably -18 to -12°C, and even more preferably -15°C.
[0042] In the present invention, it is preferred to repeat evaporation concentration and crystallization until the phosphate ion concentration in the crystallization mother liquor is preferably 16 to 18 mol / L, more preferably 16.5 to 17.5 mol / L, and even more preferably 17 mol / L.
[0043] In the present invention, during the evaporation, concentration and crystallization process, when the temperature is cooled to 55-65°C, the cooled product is preferably centrifuged to obtain lithium sulfate and crystallization mother liquor I, and the crystallization mother liquor I is further cooled and crystallized; the centrifugal speed is preferably 1000-1500rpm, more preferably 1200rpm; the centrifugal time is preferably 20-40min, more preferably 30min.
[0044] In the present invention, during the evaporation, concentration and crystallization process, when the temperature is cooled to -20 to -10°C, the cooled product is preferably centrifuged to obtain a crude ferrous sulfate heptahydrate product and a crystallization mother liquor II, and the crude ferrous sulfate heptahydrate product is recrystallized to obtain ferrous sulfate heptahydrate and a recrystallization mother liquor; the recrystallization is preferably to prepare the crude ferrous sulfate heptahydrate product into a saturated aqueous solution of ferrous sulfate, to evaporate and concentrate the saturated aqueous solution of ferrous sulfate in nitrogen, and then to cool and crystallize; the temperature of the evaporation and concentration is preferably 110 to 130°C, and more preferably 120°C. The evaporation concentration is preferably stopped when the volume of the solution is 1 / 5 to 2 / 5 of the initial volume (saturated aqueous solution of ferrous sulfate), and cooling and crystallization are started. When the temperature is cooled to -20 to -10°C, the product is centrifuged to obtain ferrous sulfate heptahydrate and a recrystallization mother liquor; the speed of the centrifugation is independently preferably 1000 to 1500 rpm, and more preferably 1200 rpm; the time of the centrifugation is independently preferably 20 to 40 min, and more preferably 30 min; the recrystallization mother liquor is preferably combined with the crystallization mother liquor II, and the evaporation concentration and crystallization are repeated;
[0045] In the present invention, the purification in step 4) preferably comprises mixing the crystallization mother liquor with tributyl phosphate to obtain an oil phase, and then mixing the oil phase with water to obtain phosphoric acid.
[0046] In the present invention, the volume ratio of the crystallization mother liquor to tributyl phosphate is preferably 1:0.8-1.2, more preferably 1:0.9-1.1, and more preferably 1:1; the volume ratio of the crystallization mother liquor to water is preferably 1:0.8-1.2, more preferably 1:0.9-1.1, and more preferably 1:1.
[0047] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.
[0048] Example 1
[0049] 800g of lithium iron phosphate waste material and 4000g of water were mixed and slurried to obtain lithium iron phosphate waste slurry. The lithium iron phosphate waste slurry was mixed with 597g of concentrated sulfuric acid (the mass concentration of concentrated sulfuric acid was 98%), and placed at 60°C for reaction for 2h to obtain lithium iron phosphorus solution and carbon slag. Under a nitrogen atmosphere, the lithium iron phosphorus solution was placed at -20°C for freezing for 16h, and then the resulting product was centrifuged at a speed of 1200rpm for 30min to obtain a crude product of ferrous sulfate heptahydrate and a crystallization mother liquor. Under a nitrogen atmosphere, the crystallization mother liquor was placed at 120°C, and the heating was stopped when the solution volume was evaporated to 2 / 3 of the volume of the crystallization mother liquor, and natural cooling was performed. When cooled to 60°C, the resulting product was centrifuged at a speed of 1200rpm for 30min to obtain lithium sulfate and crystallization mother liquor I. The crystallization mother liquor I was further cooled to -20°C, and the resulting product was centrifuged at a speed of 1200rpm for 30min to obtain a crude product of ferrous sulfate heptahydrate and a crystallization mother liquor II. The crystallization mother liquor II was repeatedly evaporated and naturally cooled until the final phosphate ion concentration in the crystallization mother liquor reached 16 mol / L.
[0050] Mix 1L of the final crystallization mother liquor with 1L of tributyl phosphate, shake manually for 10 minutes, let stand for phase separation, remove the raffinate to obtain an oil phase, add 1L of water to the oil phase, shake manually for 10 minutes, let stand for phase separation, remove the water phase, and obtain phosphoric acid.
[0051] The crude ferrous sulfate heptahydrate product is made into a saturated aqueous solution of ferrous sulfate. Under a nitrogen atmosphere, the saturated aqueous solution of ferrous sulfate is placed at 120° C., and the heating is stopped when the volume of the solution is evaporated to 1 / 3 of the volume of the saturated aqueous solution of ferrous sulfate, and the solution is naturally cooled to -20° C. The obtained product is centrifuged at a speed of 1200 rpm for 30 minutes to obtain ferrous sulfate heptahydrate and a recrystallization mother liquor. The recrystallization mother liquor can be mixed with the crystallization mother liquor II for repeated evaporation and natural cooling.
[0052] The compositions of the raw material lithium iron phosphate waste and the products ferrous sulfate heptahydrate, carbon slag, lithium sulfate and phosphoric acid in this embodiment are shown in Table 1.
[0053] Table 1 Elemental contents of iron, phosphorus, lithium and sulfur in the raw materials and products of Example 1
[0054]
[0055] Example 2
[0056] 1000g of lithium iron phosphate waste material and 3000g of water were mixed and slurried to obtain lithium iron phosphate waste slurry. The lithium iron phosphate waste slurry was mixed with 747g of concentrated sulfuric acid (the mass concentration of concentrated sulfuric acid was 95%), and placed at 100°C for reaction for 0.5h to obtain lithium iron phosphorus solution and carbon slag. Under a nitrogen atmosphere, the lithium iron phosphorus solution was placed at -15°C for 16h, and then the resulting product was centrifuged at a speed of 1500rpm for 20min to obtain a crude product of ferrous sulfate heptahydrate and a crystallization mother liquor. Under a nitrogen atmosphere, the crystallization mother liquor was placed at 120°C, and the heating was stopped when the solution volume was evaporated to 2 / 3 of the volume of the crystallization mother liquor, and natural cooling was performed. When cooled to 55°C, the resulting product was centrifuged at a speed of 1000rpm for 40min to obtain lithium sulfate and crystallization mother liquor I. The crystallization mother liquor I was further cooled to -15°C, and the resulting product was centrifuged at a speed of 1500rpm for 20min to obtain a crude product of ferrous sulfate heptahydrate and a crystallization mother liquor II. The crystallization mother liquor II was repeatedly evaporated and naturally cooled until the final phosphate ion concentration in the crystallization mother liquor reached 16.5 mol / L.
[0057] Mix 1L of the final crystallization mother liquor with 1L of tributyl phosphate, shake manually for 10 minutes, let stand for phase separation, remove the raffinate to obtain an oil phase, add 1L of water to the oil phase, shake manually for 10 minutes, let stand for phase separation, remove the water phase, and obtain phosphoric acid.
[0058] The crude ferrous sulfate heptahydrate product is made into a saturated aqueous solution of ferrous sulfate. Under a nitrogen atmosphere, the saturated aqueous solution of ferrous sulfate is placed at 120° C., and the heating is stopped when the volume of the solution is evaporated to 1 / 3 of the volume of the saturated aqueous solution of ferrous sulfate, and the solution is naturally cooled to -15° C. The obtained product is centrifuged at a speed of 1500 rpm for 20 minutes to obtain ferrous sulfate heptahydrate and a recrystallization mother liquor. The recrystallization mother liquor can be mixed with the crystallization mother liquor II for repeated evaporation and natural cooling.
[0059] The compositions of the raw material lithium iron phosphate waste and the products ferrous sulfate heptahydrate, carbon slag, lithium sulfate and phosphoric acid in this embodiment are shown in Table 2.
[0060] Table 2 Elemental contents of iron, phosphorus, lithium and sulfur in the raw materials and products of Example 2
[0061]
[0062] Example 3
[0063] 1000g of lithium iron phosphate waste material and 4000g of water were mixed and slurried to obtain lithium iron phosphate waste slurry. The lithium iron phosphate waste slurry was mixed with 896g of concentrated sulfuric acid (the mass concentration of concentrated sulfuric acid was 96%), and placed at 30°C for 4h to react to obtain lithium iron phosphorus solution and carbon slag. Under a nitrogen atmosphere, the lithium iron phosphorus solution was placed at -10°C for 16h, and then the resulting product was centrifuged at a speed of 1000rpm for 40min to obtain a crude product of ferrous sulfate heptahydrate and a crystallization mother liquor. Under a nitrogen atmosphere, the crystallization mother liquor was placed at 120°C, and the heating was stopped when the solution volume was evaporated to 2 / 3 of the volume of the crystallization mother liquor, and natural cooling was performed. When cooled to 65°C, the resulting product was centrifuged at a speed of 1500rpm for 20min to obtain lithium sulfate and crystallization mother liquor I. The crystallization mother liquor I was further cooled to -10°C, and the resulting product was centrifuged at a speed of 1000rpm for 40min to obtain a crude product of ferrous sulfate heptahydrate and a crystallization mother liquor II. The crystallization mother liquor II was repeatedly evaporated and naturally cooled until the final phosphate ion concentration in the crystallization mother liquor reached 17 mol / L.
[0064] Mix 1L of the final crystallization mother liquor with 1L of tributyl phosphate, shake manually for 10 minutes, let stand for phase separation, remove the raffinate to obtain an oil phase, add 1L of water to the oil phase, shake manually for 10 minutes, let stand for phase separation, remove the water phase, and obtain phosphoric acid.
[0065] The crude ferrous sulfate heptahydrate product is made into a saturated aqueous solution of ferrous sulfate. Under a nitrogen atmosphere, the saturated aqueous solution of ferrous sulfate is placed at 120° C., and the heating is stopped when the volume of the solution is evaporated to 1 / 3 of the volume of the saturated aqueous solution of ferrous sulfate, and the solution is naturally cooled to -10° C. The obtained product is centrifuged at a speed of 1000 rpm for 40 minutes to obtain ferrous sulfate heptahydrate and a recrystallization mother liquor. The recrystallization mother liquor can be mixed with the crystallization mother liquor II for repeated evaporation and natural cooling.
[0066] The compositions of the raw material lithium iron phosphate waste and the products ferrous sulfate heptahydrate, carbon slag, lithium sulfate and phosphoric acid of this embodiment are shown in Table 3.
[0067] Table 3 Elemental contents of iron, phosphorus, lithium and sulfur in the raw materials and products of Example 3
[0068]
[0069] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.
Claims
1. A method for recycling lithium iron phosphate waste, characterized in that: The following steps are included: 1) adding water to the lithium iron phosphate waste to prepare a slurry to obtain lithium iron phosphate waste slurry; 2) reacting the lithium iron phosphate waste slurry with concentrated sulfuric acid to obtain a lithium iron phosphorus solution and carbon slag; 3) crystallizing the lithium iron phosphorus solution in an inert gas to obtain ferrous sulfate heptahydrate, lithium sulfate and crystallization mother liquor; 4) Purifying the crystallization mother liquor to obtain phosphoric acid.
2. The recycling method according to claim 1, characterized in that: In step 1), the mass ratio of the lithium iron phosphate waste to water is 1:3-5.
3. The recovery method according to claim 1 or 2, characterized in that: The mass ratio of the concentrated sulfuric acid in step 2) to the lithium iron phosphate waste in step 1) is 0.7-0.9:1, and the mass concentration of the concentrated sulfuric acid is 95-98%; Step 2) The reaction temperature is 30-100° C. and the reaction time is 0.5-4 h.
4. The recycling method according to claim 3, characterized in that: Step 3) The crystallization treatment comprises freezing crystallization and evaporation concentration crystallization performed in sequence, and the freezing crystallization obtains ferrous sulfate heptahydrate.
5. The recycling method according to claim 4, characterized in that: The temperature of the freeze crystallization is -20 to -10°C, and the time of the freeze crystallization is 12 to 20 hours.
6. The recycling method according to claim 4 or 5, characterized in that: The evaporation concentration and crystallization is to first perform evaporation concentration and then cool for crystallization; the evaporation concentration temperature is 110-130° C., and the evaporation concentration is stopped when the volume of the solution is 3 / 5-4 / 5 of the initial volume; When cooled to a temperature of 55-65°C, lithium sulfate is crystallized; When cooled to a temperature of -20 to -10°C, ferrous sulfate heptahydrate is obtained by crystallization.
7. The recycling method according to claim 6, characterized in that: Repeat the evaporation, concentration and crystallization until the phosphate ion concentration in the crystallization mother liquor reaches 16 to 18 mol / L.
8. The recycling method according to claim 7, characterized in that: Step 4) The purification comprises mixing the crystallization mother liquor with tributyl phosphate to obtain an oil phase, and then mixing the oil phase with water to obtain phosphoric acid.
9. The recycling method according to claim 8, characterized in that: The volume ratio of the crystallization mother liquor to tributyl phosphate is 1:0.8-1.2, and the volume ratio of the crystallization mother liquor to water is 1:0.8-1.2.