CN114835099A

CN114835099A - Recycling method and recycling system device of waste lithium iron phosphate

Info

Publication number: CN114835099A
Application number: CN202210425570.XA
Authority: CN
Inventors: 王云山; 杨刚; 安学斌
Original assignee: Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS
Priority date: 2022-04-21
Filing date: 2022-04-21
Publication date: 2022-08-02

Abstract

The invention provides a regeneration and utilization method and a regeneration and utilization system device of waste lithium iron phosphate, wherein the regeneration and utilization method comprises the following steps: crushing and screening the waste lithium iron phosphate anode to obtain impurity-containing metal aluminum and waste lithium iron phosphate black ash; extracting phosphorus, iron and lithium in the obtained waste lithium iron phosphate black ash by a wet method, and performing solid-liquid separation to obtain a silicon-carbon material and an extracting solution; oxidizing to convert ferrous iron in the obtained extracting solution into ferric iron to obtain an oxidized extracting solution; mixing phosphoric acid with the obtained oxidation extract, and carrying out solid-liquid separation to obtain a lithium chloride solution and iron phosphate; mixing a sodium carbonate solution with the obtained lithium chloride solution, and carrying out solid-liquid separation to obtain a sodium chloride solution and lithium carbonate; and mixing the reducing agent, the obtained iron phosphate and the obtained lithium carbonate, and calcining to obtain the lithium iron phosphate. The recycling method realizes resource utilization of phosphorus, iron and lithium in the waste lithium iron phosphate, realizes recycling of hydrochloric acid, realizes recycling preparation of the lithium iron phosphate, and is a green and clean process.

Description

Recycling method and recycling system device of waste lithium iron phosphate

Technical Field

The invention belongs to the technical field of waste lithium battery recycling, relates to a recycling method of waste lithium iron phosphate, and particularly relates to a recycling method and a recycling system device of waste lithium iron phosphate.

Background

Because the lithium iron phosphate has the advantages of safety, good cycle performance and the like, the lithium iron phosphate can be widely applied to automobiles as a power battery. In actual life, a large number of lithium iron phosphate batteries are scrapped, and the percentage of the waste lithium batteries reaches about 65%. The waste lithium iron phosphate contains phosphorus, iron and lithium resources, and the recycling of the waste lithium iron phosphate greatly relieves the difficulty of relevant resource shortage. The treatment of the waste lithium iron phosphate battery comprises physical and chemical means, wherein the chemical treatment comprises a pyrogenic method and a wet method, the pyro method and the wet method are used for obtaining a lithium iron phosphate material by high-temperature calcination and screening, and a proper amount of lithium, iron and phosphorus are added into the lithium iron phosphate material to regenerate and synthesize the lithium iron phosphate; the latter is mainly directed at lithium iron phosphate anode materials, is a mainstream mode, but has relatively long flow, strict equipment requirements and secondary pollution hidden trouble.

CN102583297A discloses a method for recovering and regenerating lithium iron phosphate as a positive electrode material of a lithium ion battery. The invention belongs to the technical field of lithium ion batteries. A recovery and regeneration method of lithium iron phosphate as a positive material of a lithium ion battery comprises the following steps; (1) leaching iron ions, sodium ions and other impurity ions in the lithium iron phosphate serving as the positive electrode material of the lithium ion battery by using an acid solution with the pH value of 1-2; (2) filtering, washing the lithium iron phosphate with distilled water, and adding ethanol and/or an acetone wetting agent into the washed lithium iron phosphate to prepare suspension; (3) mixing soluble ferric salt, lithium salt, phosphate and a carbon source in a solution of ethanol according to a proportion, adding the mixture into the suspension, mixing, and drying at 80-150 ℃ in vacuum or protective atmosphere; (4) and baking the lithium iron phosphate anode material for 3 to 6 hours at the temperature of 600 to 800 ℃ in an inert gas atmosphere to obtain the lithium iron phosphate anode material.

CN111403837A discloses a regeneration method of lithium iron phosphate in retired lithium battery. The method comprises the following steps: pretreating a positive electrode material obtained by decomposing the waste lithium iron phosphate battery to obtain a lithium iron phosphate semi-finished product; mixing the lithium iron phosphate semi-finished product with aluminum powder and carbon fibers, then placing the mixture into a dispersing agent for wet ball milling, pre-drying the obtained mixed slurry to obtain pre-dried powder, and placing the pre-dried powder into an argon atmosphere for blowing and drying to obtain dried powder; continuously blowing and heating the dried powder in the mixed atmosphere of hydrogen and argon, and keeping the temperature for a period of time to obtain a precursor; and (4) continuously purging the precursor at constant temperature in a mixed atmosphere of carbon source gas and hydrogen, and then cooling in an argon atmosphere to finish regeneration.

CN113501510A discloses a method for recycling a waste lithium iron phosphate battery positive electrode material, which comprises the steps of firstly stripping a current collector of a waste lithium iron phosphate positive plate or leftover material from an active material by using an organic solvent to obtain lithium iron phosphate powder; adding the obtained lithium iron phosphate powder into a mixed solution of a leaching agent and hydrogen peroxide for liquid-phase leaching, and filtering to obtain a lithium-containing filtrate and iron phosphate filter residues; removing impurities from the lithium-containing filtrate, evaporating and concentrating the lithium-containing filtrate, and adding a sodium carbonate solution to precipitate lithium element in the form of lithium carbonate to obtain battery-grade lithium carbonate; and (3) reversely washing the iron phosphate filter residue by using hydrochloric acid, and drying and crushing to obtain the battery-grade iron phosphate. The lithium iron phosphate positive electrode material is prepared by using the battery-grade lithium carbonate and the battery-grade iron phosphate as raw materials.

The currently disclosed method and system for recycling waste lithium iron phosphate have certain defects, and have the problems of poor performance of the obtained lithium iron phosphate, long recycling process, secondary pollution to the environment, high requirement on equipment and high recycling cost. Therefore, it is important to develop a novel method and a system for recycling waste lithium iron phosphate.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a regeneration method and a regeneration system device for waste lithium iron phosphate, and the regeneration method for waste lithium iron phosphate realizes resource utilization of phosphorus, iron and lithium in the waste lithium iron phosphate, realizes regeneration cyclic utilization of hydrochloric acid, and realizes regeneration preparation of the lithium iron phosphate; the recycling method has no discharge of waste water, waste gas and solid waste in the process of recycling the waste lithium iron phosphate, has no pollution to the environment, and is a green and clean process; the recycling method has the advantages of short recycling process of the waste lithium iron phosphate, low requirement on equipment and low recycling cost.

In order to achieve the purpose, the invention adopts the following technical scheme:

in a first aspect, the invention provides a recycling method of waste lithium iron phosphate, which comprises the following steps:

(1) crushing and screening the waste lithium iron phosphate anode to obtain impurity-containing metal aluminum and waste lithium iron phosphate black ash;

(2) extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash obtained in the step (1) by a wet method, and performing solid-liquid separation to obtain a silicon-carbon material and an extracting solution;

(3) oxidizing to convert ferrous iron in the extracting solution obtained in the step (2) into ferric iron to obtain an oxidized extracting solution;

(4) mixing phosphoric acid with the oxidation extracting solution obtained in the step (3), and carrying out solid-liquid separation to obtain a lithium chloride solution and ferric phosphate;

(5) mixing a sodium carbonate solution with the lithium chloride solution obtained in the step (4), and carrying out solid-liquid separation to obtain a sodium chloride solution and lithium carbonate;

(6) and (4) mixing a reducing agent, the iron phosphate obtained in the step (4) and the lithium carbonate obtained in the step (5), and calcining to obtain the lithium iron phosphate.

According to the method for recycling the waste lithium iron phosphate, the waste lithium iron phosphate is crushed, sieved and purified, and then metal aluminum and other impurities in the waste lithium iron phosphate are separated from the waste lithium iron phosphate black ash to obtain the waste lithium iron phosphate black ash; then extracting the waste lithium iron phosphate black ash by a wet method by using an extracting agent, and leaching phosphorus, iron and lithium in the waste lithium iron phosphate black ash to obtain a solution containing phosphoric acid, ferrous chloride and lithium chloride; oxidizing to convert ferrous iron into ferric iron to obtain oxidized extract containing phosphoric acid, ferric chloride and lithium chloride; mixing phosphoric acid and the oxidation extracting solution and carrying out a synthesis reaction to prepare iron phosphate, generating hydrogen chloride in the reaction process, and absorbing the generated hydrogen chloride to obtain regenerated hydrochloric acid for recycling; separating the synthesized ferric phosphate to obtain a lithium chloride solution, mixing a sodium carbonate solution with the lithium chloride solution, filtering after reaction to obtain solid lithium carbonate, and evaporating and crystallizing the filtered mother liquor to obtain solid sodium chloride; and mixing the prepared iron phosphate and lithium carbonate with a reducing agent, and calcining to obtain the lithium iron phosphate.

The method for recycling the waste lithium iron phosphate realizes resource utilization of phosphorus, iron and lithium in the waste lithium iron phosphate, realizes regeneration and cyclic utilization of hydrochloric acid, and realizes regeneration and preparation of the lithium iron phosphate; the recycling method has no discharge of waste water, waste gas and solid wastes in the process of recycling the waste lithium iron phosphate, has no pollution to the environment, and is a green and clean process; the recycling method has the advantages of short recycling process of the waste lithium iron phosphate, low requirement on equipment and low recycling cost.

As a preferable technical scheme of the invention, the crushing and screening in the step (1) comprises mechanical crushing and vibratory screening which are sequentially carried out.

Preferably, the mesh number of the waste lithium iron phosphate black ash in the step (1) is 150 to 200 meshes, for example, 150 meshes, 155 meshes, 160 meshes, 165 meshes, 170 meshes, 175 meshes, 180 meshes, 185 meshes, 190 meshes, 195 meshes or 200 meshes, but the waste lithium iron phosphate black ash is not limited to the listed values, and other values not listed in the numerical value range are also applicable.

Preferably, the mechanical disruption comprises jaw crushing and/or ball milling.

Preferably, the temperature of the wet extraction in step (2) is 85-95 ℃, for example, 85 ℃, 86 ℃, 87 ℃, 88 ℃, 89 ℃, 90 ℃, 91 ℃, 92 ℃, 93 ℃, 94 ℃ or 95 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the time of the wet extraction in step (2) is 90-150 min, such as 90min, 95min, 100min, 105min, 110min, 115min, 120min, 125min, 130min, 135min, 140min, 145min or 150min, but not limited to the enumerated values, and other non-enumerated values in the range of the enumerated values are also applicable.

Preferably, the extractant for the wet extraction in step (2) comprises hydrochloric acid.

Preferably, the hydrochloric acid is used in an amount of 5 to 9% excess of the theoretical amount, for example, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5% or 9% based on the total extraction of phosphorus, iron and lithium from the waste lithium iron phosphate black ash, but the hydrochloric acid is not limited to the listed values, and other non-listed values in the range of the values are also applicable.

Preferably, the hydrochloric acid has a concentration of 18 to 21 wt%, and may be, for example, 18 wt%, 18.5 wt%, 19 wt%, 19.5 wt%, 20 wt%, 20.5 wt%, or 21 wt%, but is not limited to the recited values, and other values not recited within the range are also applicable.

As a preferable technical scheme of the invention, the oxidation in the step (3) comprises electrolytic oxidation and/or chemical oxidation.

Preferably, the chemically oxidizing agent comprises hydrogen peroxide and/or oxygen.

Preferably, the amount of oxidant is in theoretical excess of 3 to 9%, for example 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5% or 9% based on complete oxidation of ferrous iron to ferric iron in the extract, but is not limited to the recited values, and other values not recited in this range are equally applicable.

In a preferred embodiment of the present invention, the molar ratio of phosphorus in the phosphoric acid to iron in the oxidation extract in step (4) is (1 to 1.2):1, and may be, for example, 1:1, 1.02:1, 1.05:1, 1.07:1, 1.1:1, 1.12:1, 1.15:1, 1.17:1 or 1.2:1, but not limited to the above-mentioned values, and other values not listed in the above-mentioned range are also applicable.

Preferably, the concentration of the phosphoric acid in step (4) is 30 to 35 wt%, for example 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt% or 35 wt%, but not limited to the recited values, and other values not recited in the range of the recited values are also applicable.

Preferably, the temperature of the mixing in step (4) is 130 to 160 ℃, for example 130 ℃, 135 ℃, 140 ℃, 145 ℃, 150 ℃, 155 ℃ or 160 ℃, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the mixing time in step (4) is 4-6 h, such as 4h, 4.2h, 4.5h, 4.7h, 5h, 5.2h, 5.5h, 5.7h or 6h, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the mixing in step (4) comprises stirring and/or ultrasound.

Preferably, hydrogen chloride is generated during the mixing in the step (4), and the hydrogen chloride is absorbed by an absorbent to obtain regenerated hydrochloric acid which is used as an extractant in the wet extraction in the step (2).

Preferably, the concentration of the regenerated hydrochloric acid is 18 to 21 wt%, and may be, for example, 18 wt%, 18.2 wt%, 18.5 wt%, 18.7 wt%, 19 wt%, 19.2 wt%, 19.5 wt%, 19.7 wt%, 20 wt%, 20.2 wt%, 20.5 wt%, 20.7 wt%, or 21 wt%, but is not limited to the recited values, and other values not recited in the range of the recited values are also applicable.

Preferably, the absorbent comprises water or hydrochloric acid at a concentration of less than 5 wt%, for example 4.5 wt%, 4 wt%, 3.5 wt%, 3 wt%, 2.5 wt%, 2 wt%, 1.5 wt%, 1 wt%, 0.5 wt% or 0.1 wt%, but is not limited to the recited values, and other non-recited values within the range are equally applicable.

The absorbent is an initial absorbent adopted by a hydrochloric acid absorption tower, and the absorbent adopts a circular absorption mode in the process of absorbing hydrogen chloride, namely water or low-concentration hydrochloric acid (the concentration is less than 5 wt%) is initially adopted as the absorbent, and then the absorbent circularly absorbs the hydrochloric acid until the concentration reaches the concentration required by circular utilization, so that the absorbent is used for wet extraction.

The absorption process of the hydrogen chloride adopts a step absorption mode, namely, the tail gas purification tower firstly adopts water to absorb the hydrogen chloride, the concentration is increased after multiple cycles to obtain low-concentration hydrochloric acid (the concentration is less than 5 wt%), and then the low-concentration hydrochloric acid is used as an absorbent of the hydrochloric acid absorption tower to finally obtain high-concentration hydrochloric acid, so that the cyclic utilization of the regenerated hydrochloric acid is realized.

In a preferred embodiment of the present invention, the molar ratio of sodium carbonate in the sodium carbonate solution in step (5) to lithium chloride in the lithium chloride solution is 1 (1.6-2.4), and may be, for example, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, 1:2.3 or 1:2.4, but not limited to the values listed, and other values not listed in the range of the values are also applicable.

Preferably, the concentration of the sodium carbonate solution in step (5) is 20 to 25 wt%, for example 20 wt%, 20.5 wt%, 21 wt%, 21.5 wt%, 22 wt%, 22.5 wt%, 23 wt%, 23.5 wt%, 24 wt%, 24.5 wt% or 25 wt%, but is not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the temperature of the mixing in step (5) is 75 to 85 ℃, and may be, for example, 75 ℃, 76 ℃, 77 ℃, 78 ℃, 79 ℃, 80 ℃, 81 ℃, 82 ℃, 83 ℃, 84 ℃ or 85 ℃, but is not limited to the recited values, and other values not recited within the range of the values are also applicable.

Preferably, the mixing time in step (5) is 2-4 h, such as 2h, 2.2h, 2.5h, 2.7h, 3h, 3.2h, 3.5h, 3.7h or 4h, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, the sodium chloride solution obtained in the step (5) is evaporated and crystallized to obtain sodium chloride.

Preferably, the evaporative crystallization comprises evaporation and crystallization which are sequentially carried out, wherein the evaporation temperature is 130-150 ℃, and the crystallization temperature is 20-30 ℃.

The temperature of evaporation is limited to 130 to 150 ℃ in the present invention, and may be 130 ℃, 132 ℃, 135 ℃, 137 ℃, 140 ℃, 142 ℃, 145 ℃, 147 ℃ or 150 ℃, for example, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

In a preferred embodiment of the present invention, the reducing agent in step (6) includes any one or a combination of at least two of oxalic acid, sucrose or glucose, and typical but non-limiting combinations include a combination of oxalic acid and sucrose, a combination of sucrose and glucose, or a combination of oxalic acid, sucrose and glucose.

Preferably, the reducing agent in step (6) is used in a theoretical excess of 10 to 20%, for example, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20% based on the total reduction of ferric iron in the iron phosphate to ferrous iron, but is not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, in the step (6), the molar ratio of the iron phosphate to the lithium carbonate is (0.8-1.2): 1, and may be, for example, 0.8:1, 0.85:1, 0.9:1, 0.95:1, 1:1, 1.05:1, 1.1:1, 1.15:1 or 1.2:1, but is not limited to the enumerated values, and other non-enumerated values within the numerical range are also applicable.

Preferably, the temperature of the calcination in step (6) is 550 to 650 ℃, and may be, for example, 550 ℃, 560 ℃, 570 ℃, 580 ℃, 590 ℃, 600 ℃, 610 ℃, 620 ℃, 630 ℃, 640 ℃ or 650 ℃, but is not limited to the recited values, and other values not recited in the range of the recited values are also applicable.

Preferably, the calcination time in step (6) is 3 to 6 hours, such as 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

As a preferable aspect of the present invention, the recycling method includes the steps of:

(1) sequentially carrying out mechanical crushing and vibration screening on the waste lithium iron phosphate anode to obtain waste lithium iron phosphate black ash containing impurity metal aluminum and with the mesh number of 150-200 meshes;

(2) extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash obtained in the step (1) by using hydrochloric acid with the concentration of 18-21 wt% as an extracting agent through a wet method at the temperature of 85-95 ℃ for 90-150 min; completely extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash as a reference, wherein the amount of hydrochloric acid is 5-9% of theoretical excess; performing solid-liquid separation to obtain a silicon-carbon material and an extracting solution;

(3) converting ferrous iron in the extracting solution obtained in the step (2) into ferric iron by electrolytic oxidation and/or chemical oxidation, wherein the ferrous iron in the extracting solution is completely oxidized into the ferric iron as a reference, and the amount of the oxidant is 3-9% of theoretical excess amount, so as to obtain an oxidized extracting solution;

(4) mixing 30-35 wt% phosphoric acid and the oxidation extracting solution obtained in the step (3) at 130-160 ℃ for 4-6 h by stirring and/or ultrasonic, wherein the molar ratio of phosphorus in the phosphoric acid to iron in the oxidation extracting solution is (1-1.2): 1; generating hydrogen chloride during mixing, absorbing the hydrogen chloride by water or hydrochloric acid with the concentration lower than 5 wt% to obtain regenerated hydrochloric acid with the concentration of 18-21 wt%, and using the regenerated hydrochloric acid as an extracting agent in the wet extraction in the step (2); performing solid-liquid separation to obtain a lithium chloride solution and iron phosphate;

(5) mixing a 20-25 wt% sodium carbonate solution with the lithium chloride solution obtained in the step (4) at 75-85 ℃ for 2-4 h, wherein the molar ratio of sodium carbonate in the sodium carbonate solution to lithium chloride in the lithium chloride solution is 1 (1.6-2.4); performing solid-liquid separation to obtain a sodium chloride solution and lithium carbonate; evaporating the sodium chloride solution at 130-150 ℃, and crystallizing at 20-30 ℃ to obtain sodium chloride;

(6) mixing a reducing agent, the iron phosphate obtained in the step (4) and the lithium carbonate obtained in the step (5), wherein on the basis of completely reducing ferric iron in the iron phosphate into ferrous iron, the amount of the reducing agent is 10-20% of theoretical excess, and the molar ratio of the iron phosphate to the lithium carbonate is (0.8-1.2): 1; calcining at 550-650 ℃ for 3-6 h to obtain the lithium iron phosphate.

In a second aspect, the invention provides a recycling system device based on the recycling method in the first aspect, and the recycling system device comprises a crushing and screening device, a wet extraction device, an oxidation device, an iron phosphate preparation device and a lithium carbonate preparation device which are sequentially connected;

the recycling system device also comprises a lithium iron phosphate preparation device which is respectively connected with the iron phosphate preparation device and the lithium carbonate preparation device.

The crushing and screening device in the recycling system device is used for crushing and grinding the waste lithium iron phosphate anode and removing impurities to obtain waste lithium iron phosphate black ash; adding the lithium iron phosphate black ash into a wet extraction device, performing wet extraction by using an extractant, and performing liquid-solid separation to obtain an extracting solution containing phosphoric acid, ferrous chloride and lithium chloride; adding the extracting solution into an oxidizing device, adding an oxidizing agent for oxidation, and converting all ferrous iron in the extracting solution into ferric iron to obtain an oxidized extracting solution; mixing the oxidized extracting solution and phosphoric acid in an iron phosphate preparation device, reacting the phosphoric acid and ferric chloride to synthesize iron phosphate, performing liquid-solid separation to obtain iron phosphate and a lithium chloride solution, feeding the iron phosphate into a lithium iron phosphate preparation device, and feeding the lithium chloride solution into a lithium carbonate preparation device; mixing a lithium chloride solution and a sodium carbonate solution in a lithium carbonate preparation device, and performing liquid-solid separation to obtain a lithium carbonate solution and a sodium chloride solution, wherein the lithium carbonate enters a lithium iron phosphate preparation device; and mixing the iron phosphate, the lithium carbonate and the reducing agent in the lithium iron phosphate preparation device, and calcining to obtain the lithium iron phosphate.

The recycling system device provided by the invention has the advantages of simple structure and convenience in use, can realize recycling of all components in the waste lithium iron phosphate, realizes recycling of hydrochloric acid, does not discharge three wastes, and does not cause environmental pollution.

As a preferable technical scheme of the present invention, the crushing and screening device includes a crusher and a screening machine, an inlet of the crusher is a feeding port of the waste lithium iron phosphate, an outlet of the crusher is connected to an inlet of the screening machine, and an outlet of the screening machine is connected to the wet extraction device.

The crusher is used for crushing and grinding the waste lithium iron phosphate, and the screening machine is used for removing impurities to obtain the waste lithium iron phosphate black ash.

Preferably, the wet extraction device comprises a wet extraction kettle and a wet extraction filter press, an inlet of the wet extraction kettle is connected with an outlet of the sieving machine, an outlet of the wet extraction kettle is connected with an inlet of the wet extraction filter press, and a liquid outlet of the wet extraction filter press is connected with the oxidation device.

The lithium iron phosphate black ash is added into a wet extraction kettle, an extracting agent is adopted for wet extraction, and liquid-solid separation is carried out by a wet extraction filter press to obtain an extracting solution containing phosphoric acid, ferrous chloride and lithium chloride.

Preferably, a discharge pump of the wet extraction kettle is arranged between the outlet of the wet extraction kettle and the inlet of the wet extraction filter press.

The discharge pump of the wet extraction kettle is used for pumping the materials in the wet extraction kettle into a wet extraction filter press for liquid-solid separation.

Preferably, the oxidation device comprises an oxidation tank, an inlet of the oxidation tank is connected with a liquid outlet of the wet extraction filter press, and an outlet of the oxidation tank is connected with the iron phosphate preparation device.

Preferably, the iron phosphate preparation facilities include synthetic cauldron of iron phosphate and iron phosphate pressure filter, the entry of the synthetic cauldron of iron phosphate and the exit linkage of oxidation groove, the liquid outlet of the synthetic cauldron of iron phosphate and the entry linkage of iron phosphate pressure filter, the liquid outlet of iron phosphate pressure filter is connected with lithium carbonate preparation facilities, the solid export of iron phosphate pressure filter is connected with lithium iron phosphate preparation facilities.

The phosphoric acid and ferric chloride are mixed in a ferric phosphate synthesis kettle, and the ferric phosphate is synthesized after reaction.

Preferably, an iron phosphate discharge pump is arranged between the liquid outlet of the iron phosphate synthesis kettle and the inlet of the iron phosphate filter press.

The iron phosphate discharge pump is used for pumping materials in the iron phosphate synthesis kettle into an iron phosphate filter press for liquid-solid separation.

Preferably, the recycling system device further comprises a gas treatment device, and the gas treatment device is connected with the iron phosphate preparation device.

Preferably, the gas treatment device comprises a hydrochloric acid absorption tower and a tail gas purification tower, a gas inlet of the hydrochloric acid absorption tower is connected with a gas outlet of the iron phosphate synthesis kettle, and a gas outlet of the hydrochloric acid absorption tower is connected with a gas inlet of the tail gas purification tower.

The hydrogen chloride generated in the mixing process of phosphoric acid and ferric chloride in the iron phosphate synthesis kettle is absorbed by a hydrochloric acid absorption tower to obtain regenerated hydrochloric acid, and the tail gas is purified by a tail gas purification tower and then is discharged after reaching the standard.

Preferably, a tail gas induced draft fan is arranged between the gas outlet of the hydrochloric acid absorption tower and the gas inlet of the tail gas purification tower.

The tail gas induced draft fan is used for sending gas obtained after hydrogen chloride is absorbed in the hydrochloric acid absorption tower into the tail gas purification tower for tail gas purification.

Preferably, the recycling system device further comprises an absorption tower circulating pump, an inlet of the absorption tower circulating pump is connected with a liquid outlet of the hydrochloric acid absorption tower, and an outlet of the absorption tower circulating pump is respectively connected with a hydrochloric acid inlet of the wet extraction kettle and a liquid inlet of the hydrochloric acid absorption tower.

The absorption tower circulating pump of the invention has the function of circularly absorbing the gas-phase hydrogen chloride entering the hydrochloric acid absorption tower by the dilute hydrochloric acid, and conveying the generated regenerated hydrochloric acid to the wet extraction kettle to be used in the wet extraction process together with the supplemented hydrochloric acid.

Preferably, the recycling system device further comprises a purification tower circulating pump, an inlet of the purification tower circulating pump is connected with a liquid outlet of the tail gas purification tower, and an outlet of the purification tower circulating pump is respectively connected with a liquid inlet of the hydrochloric acid absorption tower and a liquid inlet of the tail gas purification tower.

The purification tower circulating pump has the functions of circularly purifying gas entering the tail gas purification tower by water or dilute hydrochloric acid, and conveying circulating liquid reaching a certain concentration to the hydrochloric acid absorption tower for absorbing gas-phase hydrogen chloride.

The solvent adopted by the tail gas purification tower is water, the water is input from a liquid inlet at the top of the tail gas purification tower, the gas is input from a gas inlet at the bottom of the tail gas purification tower, after absorption is completed, the gas is discharged from the top of the tower, the liquid is discharged from the bottom of the tower, part of the liquid flows back through a circulation pump of the purification tower and is used as an absorbent, and the other part of the liquid is used as an absorbent of a hydrochloric acid absorption tower and is input from a liquid inlet at the top of the hydrochloric acid absorption tower.

The absorption process of the hydrogen chloride adopts step absorption, namely, the tail gas purification tower firstly adopts water to absorb the hydrogen chloride, the concentration is increased after multiple cycles to obtain low-concentration hydrochloric acid (the concentration is lower than 5 wt%), then the low-concentration hydrochloric acid is used as an absorbent of the hydrochloric acid absorption tower, and finally high-concentration hydrochloric acid (18-21 wt%) is obtained, so that the regeneration and cyclic utilization of the hydrochloric acid are realized.

Preferably, the lithium carbonate preparation facilities include lithium carbonate synthesis cauldron and lithium carbonate pressure filter, the liquid export of the entry linkage iron phosphate pressure filter of the synthetic cauldron of lithium carbonate, the export of the synthetic cauldron of lithium carbonate and the entry linkage of lithium carbonate pressure filter, the solid export of lithium carbonate pressure filter is connected with lithium iron phosphate preparation facilities.

Preferably, the recycling system device further comprises an evaporative crystallizer, and an inlet of the evaporative crystallizer is connected with a liquid outlet of the lithium carbonate filter press.

The sodium chloride solution obtained in the lithium carbonate preparation device enters an evaporation crystallizer, and the sodium chloride solution is evaporated and crystallized in the evaporation crystallizer to obtain sodium chloride solid.

Preferably, a lithium carbonate discharge pump is arranged between the outlet of the lithium carbonate synthesis kettle and the inlet of the lithium carbonate filter press.

The lithium carbonate discharge pump is used for pumping materials in the lithium carbonate synthesis kettle into the lithium carbonate filter press for liquid-solid separation.

Preferably, the lithium iron phosphate preparation device comprises a mixing stirrer and a high-temperature calcinator, wherein the inlet of the mixing stirrer is connected with the solid outlet of the iron phosphate filter press and the solid outlet of the lithium carbonate filter press, and the outlet of the mixing stirrer is connected with the inlet of the high-temperature calcinator.

The heating mode of the high-temperature calcinator is indirect heating, and the high-temperature calcinator takes natural gas as fuel.

Preferably, an iron phosphate conveyor is arranged between the inlet of the mixing stirrer and the solid outlet of the iron phosphate filter press.

Preferably, a lithium carbonate conveyor is arranged between the inlet of the mixing stirrer and the solid outlet of the lithium carbonate filter press.

The iron phosphate conveyor and the lithium carbonate conveyor are used for conveying solid materials in the iron phosphate filter press and the lithium carbonate filter press to the mixing stirrer.

As a preferable technical scheme, a stirrer is arranged in the wet extraction kettle, and a graphite coating is arranged on the inner wall of the wet extraction kettle.

The wet extraction kettle is made of hydrochloric acid resistant and phosphoric acid resistant materials, the heating mode of the wet extraction kettle is indirect heating, and the heating source of the wet extraction kettle is low-pressure steam.

Preferably, a stirrer is arranged in the oxidation tank, and the oxidation tank comprises a steel-lined tetrafluoro tank.

Preferably, a stirrer is arranged in the iron phosphate synthesis kettle, and a graphite coating is arranged on the inner wall of the iron phosphate synthesis kettle.

The heating mode of the iron phosphate synthesis kettle is indirect heating, and the heating source of the iron phosphate synthesis kettle is low-pressure steam.

Preferably, a stirrer is arranged in the lithium carbonate synthesis kettle, and the material of the lithium carbonate synthesis kettle comprises an alloy.

The heating mode of the lithium carbonate synthesis kettle is indirect heating, and the heating source of the lithium carbonate synthesis kettle is low-pressure steam.

Preferably, the material of the evaporative crystallizer comprises an alloy.

Compared with the prior art, the invention has the beneficial effects that:

(1) the method for recycling the waste lithium iron phosphate realizes resource utilization of phosphorus, iron and lithium in the waste lithium iron phosphate, realizes regeneration and cyclic utilization of hydrochloric acid, and realizes regeneration and preparation of the lithium iron phosphate;

(2) the method for recycling the waste lithium iron phosphate has the advantages that no waste water, waste gas and solid waste are discharged in the process of recycling the waste lithium iron phosphate, no pollution is caused to the environment, and the method is a green and clean process;

(3) the method for recycling the waste lithium iron phosphate has the advantages of short recovery flow of the waste lithium iron phosphate, low requirement on equipment and low recovery cost;

(4) the recycling system device is simple in structure and convenient to use.

Drawings

FIG. 1 is a schematic structural diagram of a recycling system apparatus according to an embodiment of the present invention.

Fig. 2 is a flowchart of a method for recycling waste lithium iron phosphate provided in embodiments 1 to 5 of the present invention.

The device comprises a crusher 1, a sieving machine 2, a wet extraction kettle 3, a wet extraction kettle 4, a wet extraction kettle discharge pump 5, a wet extraction filter press 5, an oxidation tank 6, a ferric phosphate synthesis kettle 7, a hydrochloric acid absorption tower 8, an absorption tower circulating pump 9, a tail gas induced draft fan 10, a tail gas purification tower 11, a purification tower circulating pump 12, a ferric phosphate discharge pump 13, a ferric phosphate filter press 14, a lithium carbonate synthesis kettle 15, a lithium carbonate discharge pump 16, a lithium carbonate filter press 17, an evaporation filter press 18, a ferric phosphate crystallizer 19, a lithium carbonate conveyor 20, a mixing stirrer 21 and a high-temperature calcinator 22.

Detailed Description

It should be noted that, in the description of the present invention, unless otherwise explicitly specified or limited, the terms "disposed," "connected" and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art through specific situations.

The technical solution of the present invention is further explained by the following embodiments.

In a specific embodiment, the invention provides a recycling system device, which comprises a crushing and screening device, a wet extraction device, an oxidation device, an iron phosphate preparation device and a lithium carbonate preparation device which are sequentially connected;

The crushing and screening device in the recycling system device is used for crushing and grinding the waste lithium iron phosphate anode and removing impurities to obtain waste lithium iron phosphate black ash; adding the lithium iron phosphate black ash into a wet extraction device, carrying out wet extraction by using an extractant, and then carrying out liquid-solid separation to obtain an extracting solution containing phosphoric acid, ferrous chloride and lithium chloride; adding the extracting solution into an oxidizing device, adding an oxidizing agent for oxidation, and converting all ferrous iron in the extracting solution into ferric iron to obtain an oxidized extracting solution; mixing the oxidized extracting solution and phosphoric acid in an iron phosphate preparation device, reacting the phosphoric acid and ferric chloride to synthesize iron phosphate, performing liquid-solid separation to obtain iron phosphate and a lithium chloride solution, feeding the iron phosphate into a lithium iron phosphate preparation device, and feeding the lithium chloride solution into a lithium carbonate preparation device; mixing a lithium chloride solution and a sodium carbonate solution in a lithium carbonate preparation device, and performing liquid-solid separation to obtain a lithium carbonate solution and a sodium chloride solution, wherein the lithium carbonate enters a lithium iron phosphate preparation device; and mixing the iron phosphate, the lithium carbonate and a reducing agent in a lithium iron phosphate preparation device, and calcining to obtain the lithium iron phosphate.

Further, as shown in fig. 1, the crushing and screening device includes a crusher 1 and a screening machine 2, an inlet of the crusher 1 is a feeding port of waste lithium iron phosphate, an outlet of the crusher 1 is connected with an inlet of the screening machine 2, and an outlet of the screening machine 2 is connected with the wet extraction device.

The crusher 1 is used for crushing and grinding waste lithium iron phosphate, and the screening machine 2 is used for removing impurities to obtain waste lithium iron phosphate black ash.

Further, the wet extraction device comprises a wet extraction kettle 3 and a wet extraction filter press 5, wherein an inlet of the wet extraction kettle 3 is connected with an outlet of the sieving machine 2, an outlet of the wet extraction kettle 3 is connected with an inlet of the wet extraction filter press 5, and a liquid outlet of the wet extraction filter press 5 is connected with the oxidation device.

The lithium iron phosphate black ash is added into a wet extraction kettle 3, an extracting agent is adopted for wet extraction, and liquid-solid separation is carried out by a wet extraction filter press 5 to obtain an extracting solution containing phosphoric acid, ferrous chloride and lithium chloride.

Further, a wet extraction kettle discharge pump 4 is arranged between the outlet of the wet extraction kettle 3 and the inlet of the wet extraction filter press 5.

The discharge pump 4 of the wet extraction kettle is used for pumping the materials in the wet extraction kettle 3 into the wet extraction filter press 5 for liquid-solid separation.

Further, the oxidation device comprises an oxidation tank 6, an inlet of the oxidation tank 6 is connected with a liquid outlet of the wet extraction filter press 5, and an outlet of the oxidation tank 6 is connected with the iron phosphate preparation device.

Further, the iron phosphate preparation facilities include synthetic cauldron 7 of iron phosphate and iron phosphate pressure filter 14, the entry of the synthetic cauldron 7 of iron phosphate and the exit linkage of oxidation groove 6, the liquid outlet of the synthetic cauldron 7 of iron phosphate and the entry linkage of iron phosphate pressure filter 14, the liquid outlet of iron phosphate pressure filter 14 is connected with lithium carbonate preparation facilities, the solid export of iron phosphate pressure filter 14 is connected with lithium iron phosphate preparation facilities.

Phosphoric acid and ferric chloride are mixed in a ferric phosphate synthesis kettle 7, and ferric phosphate is synthesized after reaction.

Further, an iron phosphate discharging pump 13 is arranged between the liquid outlet of the iron phosphate synthesis kettle 7 and the inlet of the iron phosphate filter press 14.

The iron phosphate discharge pump 13 is used for pumping the materials in the iron phosphate synthesis kettle 7 into the iron phosphate filter press 14 for liquid-solid separation.

Further, the recycling system device also comprises a gas treatment device, and the gas treatment device is connected with the iron phosphate preparation device.

Further, the gas treatment device comprises a hydrochloric acid absorption tower 8 and a tail gas purification tower 11, wherein a gas inlet of the hydrochloric acid absorption tower 8 is connected with a gas outlet of the iron phosphate synthesis kettle 7, and a gas outlet of the hydrochloric acid absorption tower 8 is connected with a gas inlet of the tail gas purification tower 11.

The hydrogen chloride generated in the mixing process of phosphoric acid and ferric chloride in the iron phosphate synthesis kettle 7 is absorbed by the hydrochloric acid absorption tower 8 to obtain regenerated hydrochloric acid, and the tail gas is purified by the tail gas purification tower 11 and then is discharged after reaching the standard.

Further, a tail gas induced draft fan 10 is arranged between a gas outlet of the hydrochloric acid absorption tower 8 and a gas inlet of the tail gas purification tower 11.

The tail gas induced draft fan 10 is used for sending the gas after the hydrochloric acid absorption tower 8 absorbs the hydrogen chloride into the tail gas purification tower 11 for tail gas purification.

Further, the recycling system device further comprises an absorption tower circulating pump 9, an inlet of the absorption tower circulating pump 9 is connected with a liquid outlet of the hydrochloric acid absorption tower 8, and an outlet of the absorption tower circulating pump 9 is respectively connected with a hydrochloric acid inlet of the wet extraction kettle 3 and a liquid inlet of the hydrochloric acid absorption tower 8.

The absorption tower circulating pump 9 of the present invention is used for circulating and absorbing the gas phase hydrogen chloride entering the hydrochloric acid absorption tower 8 by the dilute hydrochloric acid, and conveying the generated regenerated hydrochloric acid to the wet extraction kettle 3, and using the regenerated hydrochloric acid and the supplemented hydrochloric acid in the wet extraction process.

Further, the recycling system device further comprises a purification tower circulating pump 12, an inlet of the purification tower circulating pump 12 is connected with a liquid outlet of the tail gas purification tower 11, and an outlet of the purification tower circulating pump 12 is respectively connected with a liquid inlet of the hydrochloric acid absorption tower 8 and a liquid inlet of the tail gas purification tower 11.

The purification tower circulation pump 12 of the present invention is used to circulate water or dilute hydrochloric acid for purifying the gas entering the tail gas purification tower 11, and to transport the circulating liquid reaching a certain concentration to the hydrochloric acid absorption tower 8 for absorbing the gas phase hydrogen chloride.

The solvent adopted by the tail gas purification tower 11 is water, the water is input from a liquid inlet at the top of the tail gas purification tower 11, the gas is input from a gas inlet at the bottom of the tail gas purification tower 11, after absorption is completed, the gas is discharged from the top of the tower, the liquid is discharged from the bottom of the tower, part of the liquid reflows through a circulation pump 12 of the purification tower and is used as an absorbent, the other part of the liquid is used as the absorbent of the hydrochloric acid absorption tower 8 and is input from a liquid inlet at the top of the hydrochloric acid absorption tower 8.

The absorption process of the hydrogen chloride adopts step absorption, namely, the tail gas purification tower 11 firstly adopts water to absorb the hydrogen chloride, the concentration is increased after multiple cycles to obtain low-concentration hydrochloric acid (the concentration is lower than 5 wt%), then the low-concentration hydrochloric acid is used as an absorbent of the hydrochloric acid absorption tower 8, and finally high-concentration hydrochloric acid (18-21 wt%) is obtained, so that the regeneration and cyclic utilization of the hydrochloric acid are realized.

Further, the lithium carbonate preparation device includes that the cauldron 15 is synthesized to lithium carbonate and lithium carbonate pressure filter 17, the liquid export of the entry linkage ferric phosphate pressure filter 14 of the cauldron 15 is synthesized to lithium carbonate, the export of the cauldron 15 is synthesized to lithium carbonate and the entry linkage of lithium carbonate pressure filter 17, the solid export of lithium carbonate pressure filter 17 is connected with lithium iron phosphate preparation device.

Further, the recycling system device further comprises an evaporative crystallizer 18, and an inlet of the evaporative crystallizer 18 is connected with a liquid outlet of the lithium carbonate filter press 17.

The sodium chloride solution obtained in the lithium carbonate preparation device enters the evaporative crystallizer 18, and the sodium chloride solution is evaporated and crystallized in the evaporative crystallizer 18 to obtain sodium chloride solid.

Further, a lithium carbonate discharge pump 16 is arranged between the outlet of the lithium carbonate synthesis kettle 15 and the inlet of the lithium carbonate filter press 17.

The lithium carbonate discharge pump 16 is used for pumping the material in the lithium carbonate synthesis kettle 15 into the lithium carbonate filter press 17 for liquid-solid separation.

Further, the lithium iron phosphate preparation device comprises a mixing stirrer 21 and a high-temperature calcinator 22, wherein the inlet of the mixing stirrer 21 is connected with the solid outlet of the iron phosphate filter press 14 and the solid outlet of the lithium carbonate filter press 17, and the outlet of the mixing stirrer 21 is connected with the inlet of the high-temperature calcinator 22.

The heating mode of the high-temperature calciner 22 is indirect heating, and the high-temperature calciner 22 takes natural gas as fuel.

Further, an iron phosphate conveyor 19 is provided between an inlet of the mixer 21 and a solid outlet of the iron phosphate filter press 14.

Further, a lithium carbonate conveyor 20 is provided between an inlet of the mixer 21 and a solid outlet of the lithium carbonate filter press 17.

The iron phosphate conveyor 19 and the lithium carbonate conveyor 20 according to the present invention are used for conveying the solid materials in the iron phosphate filter press 14 and the lithium carbonate filter press 17 to the mixing and stirring machine 21.

As a preferred technical scheme of the present invention, a stirrer is disposed in the wet extraction kettle 3, and a graphite coating is disposed on an inner wall of the wet extraction kettle 3.

The wet extraction kettle 3 has the performances of hydrochloric acid resistance and phosphoric acid resistance, the heating mode of the wet extraction kettle 3 is indirect heating, and the heating source of the wet extraction kettle 3 is low-pressure steam.

Further, a stirrer is arranged in the oxidation tank 6, and the oxidation tank 6 comprises a steel-lined tetrafluoro tank.

Further, a stirrer is arranged in the iron phosphate synthesis kettle 7, and a graphite coating is arranged on the inner wall of the iron phosphate synthesis kettle 7.

The heating mode of the iron phosphate synthesis kettle 7 is indirect heating, and the heating source of the iron phosphate synthesis kettle 7 is low-pressure steam.

Further, a stirrer is arranged in the lithium carbonate synthesis kettle 15, and the material of the lithium carbonate synthesis kettle 15 includes an alloy.

The heating mode of the lithium carbonate synthesis kettle 15 is indirect heating, and the heating source of the lithium carbonate synthesis kettle 15 is low-pressure steam.

Further, the material of the evaporative crystallizer 18 includes an alloy.

Example 1

The embodiment provides a recycling method of waste lithium iron phosphate, as shown in fig. 2, the recycling method includes the following steps:

(1) ball milling and vibration screening are sequentially carried out on the waste lithium iron phosphate positive electrode to obtain waste lithium iron phosphate black ash containing aluminum impurity and 175 meshes;

(2) extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash obtained in the step (1) by a wet method at 87 ℃ for 120min by using hydrochloric acid with the concentration of 20.5 wt% as an extracting agent; completely extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash as a reference, wherein the use amount of the hydrochloric acid is 8% of theoretical use amount excess; performing solid-liquid separation to obtain a silicon-carbon material and an extracting solution;

(3) oxidizing with hydrogen peroxide to convert ferrous iron in the extracting solution obtained in the step (2) into ferric iron, wherein the ferrous iron in the extracting solution is completely oxidized into ferric iron as a reference, and the amount of the oxidant is 6% of theoretical excess amount, so as to obtain an oxidized extracting solution;

(4) mixing 35 wt% phosphoric acid and the oxidation extracting solution obtained in the step (3) at 155 ℃ for 5 hours by stirring, wherein the molar ratio of phosphorus in the phosphoric acid to iron in the oxidation extracting solution is 1.15: 1; hydrogen chloride is generated during mixing, and is absorbed by hydrochloric acid with the concentration of 4 wt% to obtain regenerated hydrochloric acid with the concentration of 20 wt%, wherein the regenerated hydrochloric acid is used as an extracting agent in the wet extraction in the step (2); performing solid-liquid separation to obtain a lithium chloride solution and iron phosphate;

(5) mixing a 24 wt% sodium carbonate solution with the lithium chloride solution obtained in the step (4) at 78 ℃ for 3h, wherein the molar ratio of sodium carbonate in the sodium carbonate solution to lithium chloride in the lithium chloride solution is 1: 2.2; performing solid-liquid separation to obtain a sodium chloride solution and lithium carbonate; evaporating the sodium chloride solution at 140 ℃, and crystallizing at 28 ℃ to obtain sodium chloride;

(6) mixing oxalic acid, the iron phosphate obtained in the step (4) and the lithium carbonate obtained in the step (5), wherein on the basis of completely reducing ferric iron in the iron phosphate into ferrous iron, the use amount of the oxalic acid is 15% of theoretical excess, and the molar ratio of the iron phosphate to the lithium carbonate is 1.1: 1; calcining the mixture for 5 hours at the temperature of 580 ℃ to obtain the lithium iron phosphate.

Example 2

(1) ball milling and vibrating screening are sequentially carried out on the waste lithium iron phosphate positive electrode to obtain waste lithium iron phosphate black ash containing impurity metal aluminum and having the mesh number of 165;

(2) extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash obtained in the step (1) by a wet method at 90 ℃ for 135min by using hydrochloric acid with the concentration of 20 wt% as an extracting agent; completely extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash as a reference, wherein the use amount of the hydrochloric acid is 7% of theoretical use amount excess; performing solid-liquid separation to obtain a silicon-carbon material and an extracting solution;

(3) converting ferrous iron in the extracting solution obtained in the step (2) into ferric iron by oxygen oxidation, wherein the ferrous iron in the extracting solution is completely oxidized into the ferric iron as a reference, and the amount of the oxidant is 4% of theoretical excess amount, so as to obtain an oxidized extracting solution;

(4) mixing 34 wt% phosphoric acid and the oxidation extracting solution obtained in the step (3) at 145 ℃ for 5.5 hours of ultrasound, wherein the molar ratio of phosphorus in the phosphoric acid to iron in the oxidation extracting solution is 1.1: 1; hydrogen chloride is generated during mixing, and is absorbed by hydrochloric acid with the concentration of 3 wt% to obtain regenerated hydrochloric acid with the concentration of 20.5 wt%, and the regenerated hydrochloric acid is used as an extracting agent in the wet extraction in the step (2); performing solid-liquid separation to obtain a lithium chloride solution and iron phosphate;

(5) mixing a sodium carbonate solution with the concentration of 21 wt% with the lithium chloride solution obtained in the step (4) at 80 ℃ for 3.5h, wherein the molar ratio of sodium carbonate in the sodium carbonate solution to lithium chloride in the lithium chloride solution is 1: 2; performing solid-liquid separation to obtain a sodium chloride solution and lithium carbonate; evaporating the sodium chloride solution at 135 ℃, and crystallizing at 25 ℃ to obtain sodium chloride;

(6) mixing sucrose, the iron phosphate obtained in the step (4) and the lithium carbonate obtained in the step (5), wherein on the basis of completely reducing ferric iron in the iron phosphate into ferrous iron, the theoretical excess amount of the sucrose is 12%, and the molar ratio of the iron phosphate to the lithium carbonate is 1: 1; calcining the mixture for 5.5 hours at the temperature of 600 ℃ to obtain the lithium iron phosphate.

Example 3

(1) jaw crushing and vibration screening are sequentially carried out on the waste lithium iron phosphate anode to obtain waste lithium iron phosphate black ash containing impurity metal aluminum and 185 meshes;

(2) extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash obtained in the step (1) by a wet method at 92 ℃ for 90min by using hydrochloric acid with the concentration of 21 wt% as an extracting agent; completely extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash as a reference, wherein the amount of the hydrochloric acid is 6% of theoretical excess amount; performing solid-liquid separation to obtain a silicon-carbon material and an extracting solution;

(3) converting ferrous iron in the extracting solution obtained in the step (2) into ferric iron through electrolytic oxidation, wherein the ferrous iron in the extracting solution is completely oxidized into the ferric iron as a reference, and the amount of the oxidant is 8% of theoretical excess amount, so as to obtain an oxidized extracting solution;

(4) mixing 33 wt% phosphoric acid and the oxidation extracting solution obtained in the step (3) at 130 ℃ for 4.5 hours by stirring, wherein the molar ratio of phosphorus in the phosphoric acid to iron in the oxidation extracting solution is 1.05: 1; hydrogen chloride is generated during mixing, and is absorbed by hydrochloric acid with the concentration of 4.5 wt% to obtain regenerated hydrochloric acid with the concentration of 21 wt%, wherein the regenerated hydrochloric acid is used as an extracting agent in the wet extraction in the step (2); performing solid-liquid separation to obtain a lithium chloride solution and iron phosphate;

(5) mixing a 22 wt% sodium carbonate solution with the lithium chloride solution obtained in the step (4) at 82 ℃ for 4h, wherein the molar ratio of sodium carbonate in the sodium carbonate solution to lithium chloride in the lithium chloride solution is 1: 1.8; performing solid-liquid separation to obtain a sodium chloride solution and lithium carbonate; evaporating the sodium chloride solution at 145 ℃ and crystallizing at 30 ℃ to obtain sodium chloride;

(6) mixing glucose, the iron phosphate obtained in the step (4) and the lithium carbonate obtained in the step (5), wherein on the basis of completely reducing ferric iron in the iron phosphate into ferrous iron, the dosage of the glucose is 10% of theoretical excess, and the molar ratio of the iron phosphate to the lithium carbonate is 0.9: 1; calcining the mixture for 3 hours at the temperature of 620 ℃ to obtain the lithium iron phosphate.

Example 4

(1) jaw crushing and vibration screening are sequentially carried out on the waste lithium iron phosphate anode to obtain waste lithium iron phosphate black ash containing aluminum impurity and with the mesh number of 150 meshes;

(2) extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash obtained in the step (1) by a wet method at 85 ℃ for 150min by using hydrochloric acid with the concentration of 19 wt% as an extracting agent; completely extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash as a reference, wherein the amount of the hydrochloric acid is 5% of theoretical excess amount; performing solid-liquid separation to obtain a silicon-carbon material and an extracting solution;

(3) oxidizing with hydrogen peroxide to convert ferrous iron in the extracting solution obtained in the step (2) into ferric iron, wherein the ferrous iron in the extracting solution is completely oxidized into ferric iron as a reference, and the amount of the oxidant is 9% of theoretical excess amount, so as to obtain an oxidized extracting solution;

(4) mixing 32 wt% phosphoric acid and the oxidation extracting solution obtained in the step (3) at 140 ℃ for 6 hours by stirring, wherein the molar ratio of phosphorus in the phosphoric acid to iron in the oxidation extracting solution is 1: 1; hydrogen chloride is generated during mixing, and is absorbed by hydrochloric acid with the concentration of 1.5 wt% to obtain regenerated hydrochloric acid with the concentration of 19 wt%, and the regenerated hydrochloric acid is used as an extracting agent in the wet extraction in the step (2); performing solid-liquid separation to obtain a lithium chloride solution and iron phosphate;

(5) mixing a 20 wt% sodium carbonate solution with the lithium chloride solution obtained in the step (4) at 85 ℃ for 2h, wherein the molar ratio of sodium carbonate in the sodium carbonate solution to lithium chloride in the lithium chloride solution is 1: 1.6; performing solid-liquid separation to obtain a sodium chloride solution and lithium carbonate; evaporating the sodium chloride solution at 150 ℃, and crystallizing at 20 ℃ to obtain sodium chloride;

(6) mixing oxalic acid, the iron phosphate obtained in the step (4) and the lithium carbonate obtained in the step (5), wherein on the basis of completely reducing ferric iron in the iron phosphate into ferrous iron, the dosage of the oxalic acid is 18% of theoretical excess, and the molar ratio of the iron phosphate to the lithium carbonate is 1.2: 1; calcining at 550 ℃ for 6h to obtain the lithium iron phosphate.

Example 5

(1) ball milling and vibration screening are sequentially carried out on the waste lithium iron phosphate positive electrode to obtain waste lithium iron phosphate black ash containing aluminum impurity and 200 meshes;

(2) extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash obtained in the step (1) by a wet method at 95 ℃ for 105min by using hydrochloric acid with the concentration of 18 wt% as an extracting agent; completely extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash as a reference, wherein the amount of the hydrochloric acid is 9% of theoretical excess amount; performing solid-liquid separation to obtain a silicon-carbon material and an extracting solution;

(3) converting ferrous iron in the extracting solution obtained in the step (2) into ferric iron by oxygen oxidation, wherein the ferrous iron in the extracting solution is completely oxidized into the ferric iron as a reference, and the amount of the oxidant is 3% of theoretical excess amount, so as to obtain an oxidized extracting solution;

(4) mixing 30 wt% phosphoric acid and the oxidation extracting solution obtained in the step (3) at 160 ℃ for 4 hours of stirring, wherein the molar ratio of phosphorus in the phosphoric acid to iron in the oxidation extracting solution is 1.2: 1; hydrogen chloride is generated during mixing, regenerated hydrochloric acid with the concentration of 18 wt% is obtained after the hydrogen chloride is absorbed by water, and the regenerated hydrochloric acid is used as an extracting agent in the wet extraction in the step (2); performing solid-liquid separation to obtain a lithium chloride solution and iron phosphate;

(5) mixing a 25 wt% sodium carbonate solution with the lithium chloride solution obtained in the step (4) at 75 ℃ for 2.5h, wherein the molar ratio of sodium carbonate in the sodium carbonate solution to lithium chloride in the lithium chloride solution is 1: 2.4; performing solid-liquid separation to obtain a sodium chloride solution and lithium carbonate; evaporating the sodium chloride solution at 130 ℃, and crystallizing at 22 ℃ to obtain sodium chloride;

(6) mixing glucose, the iron phosphate obtained in the step (4) and the lithium carbonate obtained in the step (5), wherein on the basis of completely reducing ferric iron in the iron phosphate into ferrous iron, the dosage of the glucose is 20% of theoretical excess, and the molar ratio of the iron phosphate to the lithium carbonate is 0.8: 1; calcining at 650 ℃ for 4h to obtain the lithium iron phosphate.

The main element composition of the waste lithium iron phosphate used in examples 1 to 5 is shown in table 1.

TABLE 1

Make up of	Fe	P	Al	Li
					Content (wt%)	28.27	15.86	3.19	3.67

The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are within the scope and disclosure of the present invention.

Claims

1. The method for recycling waste lithium iron phosphate is characterized by comprising the following steps of:

2. The recycling method of claim 1, wherein the crushing and screening of step (1) comprises mechanical crushing and vibratory screening in sequence;

preferably, the mesh number of the waste lithium iron phosphate black ash in the step (1) is 150-200 meshes;

preferably, the temperature of the wet extraction in the step (2) is 85-95 ℃;

preferably, the time for the wet extraction in the step (2) is 90-150 min;

preferably, the extractant for the wet extraction in step (2) comprises hydrochloric acid;

preferably, on the basis of completely extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash, the amount of the hydrochloric acid is 5-9% of theoretical excess amount;

preferably, the concentration of the hydrochloric acid is 18-21 wt%.

3. The recycling method according to claim 1 or 2, wherein the oxidation of step (3) comprises electrolytic oxidation and/or chemical oxidation;

preferably, the chemically oxidizing agent comprises hydrogen peroxide and/or oxygen;

preferably, on the basis of completely oxidizing ferrous iron in the extracting solution into ferric iron, the amount of the oxidant is 3-9% of the theoretical amount of excess.

4. The recycling method according to any one of claims 1 to 3, wherein the molar ratio of phosphorus in the phosphoric acid to iron in the oxidation extract in the step (4) is (1-1.2): 1;

preferably, the concentration of the phosphoric acid in the step (4) is 30-35 wt%;

preferably, the temperature of the mixing in the step (4) is 130-160 ℃;

preferably, the mixing time in the step (4) is 4-6 h;

preferably, the mixing in step (4) comprises stirring and/or ultrasound;

preferably, hydrogen chloride is generated during the mixing in the step (4), and the hydrogen chloride is absorbed by an absorbent to obtain regenerated hydrochloric acid which is used as an extractant in the wet extraction in the step (2);

preferably, the concentration of the regenerated hydrochloric acid is 18-21 wt%;

preferably, the absorbent comprises water or hydrochloric acid at a concentration of less than 5 wt%.

5. The recycling method according to any one of claims 1 to 4, wherein the molar ratio of sodium carbonate in the sodium carbonate solution to lithium chloride in the lithium chloride solution in step (5) is 1 (1.6 to 2.4);

preferably, the concentration of the sodium carbonate solution in the step (5) is 20-25 wt%;

preferably, the temperature of the mixing in the step (5) is 75-85 ℃;

preferably, the mixing time in the step (5) is 2-4 h;

preferably, sodium chloride is obtained after the sodium chloride solution in the step (5) is evaporated and crystallized;

6. The recycling method according to any one of claims 1 to 5, wherein the reducing agent in step (6) comprises any one or a combination of at least two of oxalic acid, sucrose or glucose;

preferably, on the basis of completely reducing ferric iron in the iron phosphate into ferrous iron, the amount of the reducing agent in the step (6) is 10-20% of theoretical excess;

preferably, the molar ratio of the ferric phosphate to the lithium carbonate in the step (6) is (0.8-1.2): 1;

preferably, the calcining temperature in the step (6) is 550-650 ℃;

preferably, the calcining time in the step (6) is 3-6 h.

7. The recycling method according to any one of claims 1 to 6, characterized by comprising the steps of:

(2) extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash obtained in the step (1) by using hydrochloric acid with the concentration of 18-21 wt% as an extracting agent through a wet method at the temperature of 85-95 ℃ for 90-150 min; completely extracting phosphorus, iron and lithium in the waste lithium iron phosphate black ash as a reference, wherein the amount of the hydrochloric acid is 5-9% of theoretical excess amount; performing solid-liquid separation to obtain a silicon-carbon material and an extracting solution;

(4) mixing 30-35 wt% phosphoric acid and the oxidation extracting solution obtained in the step (3) at 130-160 ℃ for 4-6 h by stirring and/or ultrasonic mixing, wherein the molar ratio of phosphorus in the phosphoric acid to iron in the oxidation extracting solution is (1-1.2): 1; generating hydrogen chloride during mixing, absorbing the hydrogen chloride by water or hydrochloric acid with the concentration lower than 5 wt% to obtain regenerated hydrochloric acid with the concentration of 18-21 wt%, and using the regenerated hydrochloric acid as an extracting agent in the wet extraction in the step (2); performing solid-liquid separation to obtain a lithium chloride solution and iron phosphate;

8. A recycling system device based on the recycling method of any one of claims 1 to 7, wherein the recycling system device comprises a crushing and screening device, a wet extraction device, an oxidation device, an iron phosphate preparation device and a lithium carbonate preparation device which are connected in sequence;

9. The recycling system device of claim 8, wherein the crushing and screening device comprises a crusher and a screening machine, an inlet of the crusher is a feeding port of the waste lithium iron phosphate, an outlet of the crusher is connected with an inlet of the screening machine, and an outlet of the screening machine is connected with the wet extraction device;

preferably, the wet extraction device comprises a wet extraction kettle and a wet extraction filter press, an inlet of the wet extraction kettle is connected with an outlet of the sieving machine, an outlet of the wet extraction kettle is connected with an inlet of the wet extraction filter press, and a liquid outlet of the wet extraction filter press is connected with the oxidation device;

preferably, a discharge pump of the wet extraction kettle is arranged between the outlet of the wet extraction kettle and the inlet of the wet extraction filter press;

preferably, the oxidation device comprises an oxidation tank, an inlet of the oxidation tank is connected with a liquid outlet of the wet extraction filter press, and an outlet of the oxidation tank is connected with the iron phosphate preparation device;

preferably, the iron phosphate preparation device comprises an iron phosphate synthesis kettle and an iron phosphate filter press, an inlet of the iron phosphate synthesis kettle is connected with an outlet of the oxidation tank, a liquid outlet of the iron phosphate synthesis kettle is connected with an inlet of the iron phosphate filter press, a liquid outlet of the iron phosphate filter press is connected with the lithium carbonate preparation device, and a solid outlet of the iron phosphate filter press is connected with the lithium iron phosphate preparation device;

preferably, an iron phosphate discharge pump is arranged between the liquid outlet of the iron phosphate synthesis kettle and the inlet of the iron phosphate filter press;

preferably, the recycling system device further comprises a gas treatment device, and the gas treatment device is connected with the iron phosphate preparation device;

preferably, the gas treatment device comprises a hydrochloric acid absorption tower and a tail gas purification tower, a gas inlet of the hydrochloric acid absorption tower is connected with a gas outlet of the iron phosphate synthesis kettle, and a gas outlet of the hydrochloric acid absorption tower is connected with a gas inlet of the tail gas purification tower;

preferably, a tail gas induced draft fan is arranged between the gas outlet of the hydrochloric acid absorption tower and the gas inlet of the tail gas purification tower;

preferably, the recycling system device further comprises an absorption tower circulating pump, an inlet of the absorption tower circulating pump is connected with a liquid outlet of the hydrochloric acid absorption tower, and an outlet of the absorption tower circulating pump is respectively connected with a hydrochloric acid inlet of the wet extraction kettle and a liquid inlet of the hydrochloric acid absorption tower;

preferably, the recycling system device further comprises a purification tower circulating pump, an inlet of the purification tower circulating pump is connected with a liquid outlet of the tail gas purification tower, and an outlet of the purification tower circulating pump is respectively connected with a liquid inlet of the hydrochloric acid absorption tower and a liquid inlet of the tail gas purification tower;

preferably, the lithium carbonate preparation device comprises a lithium carbonate synthesis kettle and a lithium carbonate filter press, an inlet of the lithium carbonate synthesis kettle is connected with a liquid outlet of the iron phosphate filter press, an outlet of the lithium carbonate synthesis kettle is connected with an inlet of the lithium carbonate filter press, and a solid outlet of the lithium carbonate filter press is connected with the lithium iron phosphate preparation device;

preferably, the recycling system device further comprises an evaporative crystallizer, and an inlet of the evaporative crystallizer is connected with a liquid outlet of the lithium carbonate filter press;

preferably, a lithium carbonate discharging pump is arranged between the outlet of the lithium carbonate synthesis kettle and the inlet of the lithium carbonate filter press;

preferably, the lithium iron phosphate preparation device comprises a mixing stirrer and a high-temperature calcinator, wherein an inlet of the mixing stirrer is connected with a solid outlet of an iron phosphate filter press and a solid outlet of a lithium carbonate filter press, and an outlet of the mixing stirrer is connected with an inlet of the high-temperature calcinator;

preferably, an iron phosphate conveyor is arranged between the inlet of the mixing stirrer and the solid outlet of the iron phosphate filter press;

10. The recycling system apparatus according to claim 9, wherein a stirrer is disposed in the wet extraction kettle, and a graphite coating is disposed on the inner wall of the wet extraction kettle;

preferably, a stirrer is arranged in the oxidation tank, and the oxidation tank comprises a steel lining tetrafluoro tank;

preferably, a stirrer is arranged in the iron phosphate synthesis kettle, and a graphite coating is arranged on the inner wall of the iron phosphate synthesis kettle;

preferably, a stirrer is arranged in the lithium carbonate synthesis kettle, and the material of the lithium carbonate synthesis kettle comprises an alloy;

preferably, the material of the evaporative crystallizer comprises an alloy.