CN109913652B

CN109913652B - Comprehensive treatment method for waste refractory material in preparation process of ternary cathode material

Info

Publication number: CN109913652B
Application number: CN201711328413.2A
Authority: CN
Inventors: 孙振华; 李少鹏; 李会泉; 高奥雷
Original assignee: Institute of Process Engineering of CAS
Current assignee: Institute of Process Engineering of CAS
Priority date: 2017-12-13
Filing date: 2017-12-13
Publication date: 2021-02-09
Anticipated expiration: 2037-12-13
Also published as: CN109913652A

Abstract

The invention provides a comprehensive treatment method of a waste refractory material in a preparation process of a ternary cathode material. The waste refractory material comprises silicon, aluminum and magnesium impurities, and the method comprises the following steps: 1) mixing the waste refractory, acid and an additive, carrying out leaching reaction, and then separating to obtain a purified refractory and a leaching solution; 2) adjusting the pH value of the leaching solution to 2-4, and performing solid-liquid separation to obtain solid residues and a separation solution; 3) adjusting the pH value of the separation liquid to 4.5-5.5, and carrying out solid-liquid separation to obtain solid slag and a molten aluminum removal liquid; 4) adjusting the pH value of the aluminum-removing liquid to be more than or equal to 9, and carrying out solid-liquid separation to obtain a ternary mixture and a coprecipitation separation liquid; 5) magnesium removal: adjusting the pH value of the coprecipitation separation liquid to be more than or equal to 11, and carrying out solid-liquid separation to obtain solid slag and magnesium removal liquid; 6) and (3) lithium deposition: adding a precipitator into the magnesium removal liquid, and carrying out solid-liquid separation to obtain a lithium-containing substance and a lithium precipitation liquid. The method realizes the recycling of nickel, cobalt, manganese and lithium in the waste refractory materials, purifies the waste refractory materials, and is easy for industrial production.

Description

Comprehensive treatment method for waste refractory material in preparation process of ternary cathode material

Technical Field

The invention relates to a method for recycling and treating solid wastes in new energy industry, in particular to a comprehensive treatment method of waste refractory materials in a preparation process of a ternary cathode material.

Background

In recent years, with the vigorous support of national policies and the rapid advance of current energy and information industries, new energy industries represented by electric vehicles are rapidly developed, and the lithium battery industry is rapidly developed, and the rapid development of upstream and downstream industries is greatly driven.

The ternary nickel-cobalt-manganese cathode material is widely applied to the field of new energy as an important battery cathode material, and the demand and the yield of the ternary cathode material are increased year by year due to the research and development upgrading of the cathode material. In the firing process of the ternary nickel-cobalt-manganese anode material powder, refractory materials such as mullite cordierite sagger, cover plate push plate and the like are generally used for high-temperature synthesis in a roller kiln. In the roasting process, the nickel cobalt lithium manganate raw material reacts with the surface of the refractory material, so that the performance of the refractory material is reduced, the anode material is difficult to further roast, meanwhile, the surface of the waste refractory material is corroded, and the waste refractory material is difficult to directly return to the refractory material preparation process.

At present, the comprehensive utilization method aiming at the waste refractory materials is less, and the application mode is mainly focused on the production process of refractory materials or ceramic materials. CN 101284723a discloses a "method for preparing a seventh hollow clay brick by using waste sagger material", which is to perform water sealing and cleaning on waste saggers in the firing process of ceramsite proppant, and then further crush and grade coarse and fine materials, and respectively use the crushed and graded coarse and fine materials as a raw material to be added into the firing process of low-porosity clay bricks, so that the waste saggers can be utilized, the environmental pollution is reduced, and natural resources are saved. CN103383192A discloses a method for producing sagger products by using waste saggers, wherein the saggers discarded in the production process of domestic ceramics are crushed, ball-milled and screened to be used as clinker, and then the clinker is mixed with raw materials, kneaded, molded, roasted and the like to prepare the saggers made of aluminum, silicon and magnesium, the adding amount of the waste saggers can reach 50% of the raw materials, and the sagger products have stable quality and meet related standards. However, in the production process of the nickel cobalt lithium manganate positive electrode material, due to the alkali metal reaction on the surface of the refractory material, the nickel cobalt lithium manganate positive electrode material is difficult to directly return to be utilized, and no relevant literature report related to comprehensive utilization of waste refractory materials in the new energy industry exists at present. With the rapid development of the new energy industry, the requirement of comprehensive utilization of waste refractory materials in the new energy industry is more and more urgent.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a method for comprehensively treating waste refractory materials in the preparation process of a ternary cathode material. The method provided by the invention has the advantages of simple process, mild conditions, low equipment requirement, low energy consumption, wide raw material source and low price, can effectively realize the recovery of valuable metal elements such as nickel, cobalt, manganese, lithium and the like in the waste refractory materials, ensures the purification of the sagger body, can return to the preparation process of the refractory materials, realizes the comprehensive recycling of the waste refractory materials for the ternary anode materials in the whole process, and has better industrial application prospect and economic benefit.

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

the invention provides a comprehensive treatment method of a waste refractory material in a ternary cathode material preparation process, wherein the waste refractory material contains silicon, aluminum and magnesium impurities, and the method comprises the following steps:

(1) acid leaching reaction: mixing the waste refractory material, an acid solution and an additive, carrying out leaching reaction, and separating after the reaction to obtain a purified refractory material and a leaching solution;

(2) silicon removal: adjusting the pH value of the leachate obtained in the step (1) to 2-4, reacting, and performing solid-liquid separation after reaction to obtain solid residues and a separation solution;

(3) aluminum removal: adjusting the pH value of the separation liquid obtained in the step (2) to 4.5-5.5 for reaction, and carrying out solid-liquid separation after the reaction to obtain solid slag and an aluminum-removing liquid;

(4) triple coprecipitation: adjusting the pH value of the molten aluminum removed in the step (3) to be more than or equal to 9 for reaction, and performing solid-liquid separation after the reaction to obtain a ternary mixture and a coprecipitation separation liquid;

(5) magnesium removal: adjusting the pH value of the coprecipitation separation liquid in the step (4) to be more than or equal to 11 for reaction, and carrying out solid-liquid separation after the reaction to obtain solid slag and magnesium removal liquid;

(6) and (3) lithium deposition: and (5) adding a precipitator into the magnesium removal solution in the step (5) for reaction, and performing solid-liquid separation after the reaction to obtain a lithium-containing substance and a lithium precipitation solution.

In the present invention, the pH of the leachate obtained in step (1) is adjusted to 2 to 4, for example, 2, 3 or 4 in step (2), but the pH is not limited to the values listed, and other values not listed in the range of the values are also applicable.

In the present invention, the pH of the separated liquid in the step (2) is adjusted to 4.5 to 5.5, for example, 4.5, 5 or 5.5 in the step (3), but the pH is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable. This pH range allows aluminum, an impurity, to precipitate out as aluminum hydroxide.

In the invention, the pH value of the aluminum removing liquid obtained in the step (3) is adjusted to be not less than 9, such as 9, 9.5, 10, 11 or 12 in the step (4).

In the present invention, step (5) adjusts the pH to 11 or more, for example, 11, 12, 13 or 13.5.

The technical scheme of the invention effectively realizes the comprehensive recycling of the waste refractory materials in the preparation process of the ternary battery material, has high recycling rate of valuable elements such as lithium, cobalt, nickel and manganese, ensures that the waste saggars can be used as raw materials for producing the saggars or the refractory materials after being purified, and has the advantages of mild conditions, simple operation, low cost of raw materials, simple equipment and better industrial application prospect.

In the step (1) of the invention, the additive has the function of promoting the dissolution of nickel, cobalt, manganese, lithium and the like in an acid system. And (2) adjusting the pH value of the leachate obtained in the step (1) to 2-4, and then precipitating silicon, so that silicon is removed by a solid-liquid separation method without independently adding a precipitator. And (3) increasing the pH value to 4.5-5.5 in the step (3) to enable aluminum to form aluminum hydroxide precipitate, and continuously increasing the pH value to be more than or equal to 9 in the step (4) to obtain a precipitated ternary mixture without independently adding a precipitator. The ternary mixture obtained in step (4) is a ternary crude mixture which contains some impurities and can be further refined to improve the quality of the ternary crude mixture.

According to the invention, the waste refractory materials in the preparation process of the ternary battery anode material are recycled according to the sequence of acid leaching, silicon removal, aluminum removal, ternary product precipitation, magnesium removal and lithium precipitation, so that the pH value is gradually increased, the impurity removal efficiency can be ensured, the recycling rate of valuable elements such as lithium, nickel, cobalt and manganese is increased, the raw material consumption in the recycling process is reduced, and the cost is saved.

The following is a preferred technical solution of the present invention, but not a limitation to the technical solution provided by the present invention, and the technical objects and advantageous effects of the present invention can be better achieved and achieved by the following preferred technical solution.

In a preferred embodiment of the present invention, the silicon element is present in a mass fraction of 18 to 23 wt%, for example, 18, 19, 20, 21, 22 or 23 wt%, based on 100% by mass of the total mass of the waste refractory, but the silicon element is not limited to the above-mentioned values, and other values not shown in the above-mentioned range are also applicable, and preferably 21.32 wt%.

Preferably, the aluminum element is present in a mass fraction of 20 to 25 wt%, such as 20, 21, 22, 23, 24 or 25 wt%, based on 100% by mass of the total mass of the waste refractory, but not limited to the recited values, and other unrecited values within the range are equally applicable, preferably 22.43 wt%.

Preferably, the magnesium element is present in a mass fraction of 3 wt% to 5 wt%, such as 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, or 5 wt%, based on 100% by mass of the total mass of the waste refractory, but not limited to the recited values, and other values not recited within the range are equally applicable, preferably 4.598 wt%.

Preferably, the spent refractory material comprises a spent sagger.

Preferably, the ternary positive electrode material is a lithium nickel cobalt manganese oxide material.

In a preferred embodiment of the present invention, in the step (1), the acid solution is a sulfuric acid solution.

Preferably, the concentration of the sulfuric acid solution is 0.5mol/L to 5mol/L, such as 0.5mol/L, 1mol/L, 2mol/L, 3mol/L, 4mol/L, or 5mol/L, but not limited to the recited values, and other values not recited in the range of values are also applicable, preferably 2mol/L to 3 mol/L;

preferably, in step (1), the additive comprises any one or a combination of at least two of hydrogen peroxide, sodium sulfite or sodium thiosulfate, and typical but non-limiting combinations are as follows: a combination of hydrogen peroxide and sodium sulfite, a combination of hydrogen peroxide and sodium thiosulfate, a combination of sodium sulfite and sodium thiosulfate, and the like. In the present invention, the above-mentioned additives are preferred because they have a good reduction performance for nickel cobalt in a sulfuric acid solution, and can reduce nickel cobalt manganese more favorably.

Preferably, in the step (1), the waste refractory is subjected to bulk leaching or crushing leaching in the leaching reaction.

Preferably, in step (1), the temperature of the leaching reaction is 10 ℃ to 90 ℃, for example, 10 ℃, 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃ or 90 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, in step (1), the leaching reaction time is 6h to 12h, such as 6h, 7h, 8h, 9h, 10h, 11h or 12h, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, step (1) further comprises washing the clean refractory material and then recovering the washed clean refractory material for preparing a new refractory material.

Preferably, in the step (1), the waste refractory is added to the leachate again to perform the leaching reaction, and the leaching process is repeated.

Preferably, in the step (2), the pH of the leachate obtained in the step (1) is adjusted by using a neutralizing agent.

Preferably, the neutralising agent comprises any one or a combination of at least two of calcium oxide, calcium hydroxide or calcium carbonate, typically but not limited to a combination of: combinations of calcium oxide and calcium hydroxide, calcium oxide and calcium carbonate, calcium hydroxide and calcium carbonate, and the like, but are not limited to the above-listed neutralizing agents, and other neutralizing agents commonly used in the art to achieve the same effect may also be used in the present invention. The calcium-containing neutralizer can not only adjust the pH, but also form calcium silicate with silicon, thereby improving the silicon removal effect. When the calcium-containing neutralizing agent is used, the solid slag obtained in the step (2) is calcium slag.

Preferably, in step (2), the pH of the solution is adjusted to 2 to 3, such as 2, 2.5 or 3, but not limited to the values recited, and other values not recited within the range of values are also applicable.

Preferably, in step (2), the reaction time of the reaction is 0.5h to 2h, for example 0.5h, 1h, 1.5h or 2h, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, in the step (2), the solid-liquid separation mode is filtration separation.

Preferably, step (2) further comprises washing and filtering the solid slag.

Preferably, the washed wash solution is mixed into the separation liquid of step (2).

Preferably, step (2) further comprises: and filtering and separating the leachate to remove solids in the leachate before adding the neutralizing agent.

In a preferred embodiment of the present invention, in the step (3), the pH of the separated liquid in the step (2) is adjusted with an alkaline substance.

Preferably, the alkaline substance is sodium hydroxide.

Preferably, the alkaline substance is an alkaline solution.

Preferably, the concentration of the alkaline solution is 10% to 40% by mass, for example 10%, 20%, 30% or 40%, but not limited to the recited values, and other values not recited within the range of values are also applicable.

Preferably, the alkaline substance is added in a stirring state.

Preferably, in the step (3), the solid-liquid separation mode is filtration.

Preferably, step (3) further comprises washing the solid slag.

Preferably, the washed washing liquid is mixed into the aluminum removing liquid in the step (3).

Preferably, in the step (3), the solid slag is aluminum hydroxide.

Preferably, in step (3), the reaction time of the reaction is 0.5h to 2h, for example 0.5h, 1h, 1.5h or 2h, but is not limited to the recited values, and other values not recited within the range of the values are also applicable.

As a preferable technical scheme of the invention, in the step (4), the pH value of the aluminum-removing liquid obtained in the step (3) is adjusted by using alkaline substances.

Preferably, the alkaline substance is sodium hydroxide.

Preferably, the alkaline substance is an alkaline solution.

Preferably, the alkaline substance is added in a stirring state.

Preferably, in the step (4), the pH of the aluminum-removing liquid obtained in the step (3) is adjusted to 9.5-10.5, such as 9.5, 10 or 10.5, but not limited to the recited values, and other values in the range of the recited values are also applicable.

Preferably, in step (4), the reaction time of the reaction is 0.5h to 5h, for example 0.5h, 1h, 2h, 3h, 4h or 5h, but is not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, in the step (4), the solid-liquid separation mode is filtration separation.

Preferably, step (4) further comprises washing the ternary mixture.

Preferably, the washed washing solution is mixed into the coprecipitation separation solution of step (4). By this step, the washing liquid can be recovered and reused.

Preferably, in the step (4), the ternary mixture refining step (4') is further included: and adding the ternary mixture into an acid solution for re-dissolving to obtain a dissolved solution, adding a neutralizing agent and an impurity removing agent into the dissolved solution, carrying out first solid-liquid separation after reaction, adding a supplement and a precipitating agent into the liquid obtained by solid-liquid separation, mixing, carrying out precipitation reaction, carrying out second solid-liquid separation after the precipitation reaction is finished, and taking out solids to obtain a ternary precursor.

Preferably, in step (4'), the acid solution is a sulfuric acid solution.

Preferably, in step (4'), the acid solution has a concentration of 10% to 40% by mass, for example, 10%, 20%, 30%, or 40%, but not limited to the recited values, and other values not recited in the above range are also applicable.

Preferably, in step (4'), the neutralizing agent is any one of sodium hydroxide, calcium oxide or calcium carbonate or a combination of at least two thereof.

Preferably, in step (4'), the impurity removal agent contains fluorine. The fluorine-containing impurity-removing agent is used here because the fluorine-containing impurity-removing agent can remove calcium and magnesium impurities by producing precipitates such as calcium fluoride and magnesium fluoride.

Preferably, in the step (4'), the impurity removing agent is any one of sodium fluoride, potassium fluoride or ammonium fluoride or a combination of at least two of the above.

Preferably, the dosage of the impurity removing agent is such that the molar ratio of the total amount of calcium and magnesium in the solution after the neutralizing agent is added to the fluoride ions is 1: 2.

Preferably, in the step (4'), the first solid-liquid separation mode is filtration separation.

Preferably, in step (4'), the mixing is stirring mixing.

Preferably, in step (4'), the extender comprises any one or a combination of at least two of cobalt, nickel or manganese salts, typically but not limited to: a combination of cobalt and nickel salts, a combination of nickel and manganese salts, a combination of cobalt, nickel and manganese salts, preferably any one or a combination of at least two of cobalt, nickel or manganese sulphate, typically but not limited to: a combination of cobalt sulfate and nickel sulfate, a combination of cobalt sulfate and manganese sulfate, a combination of nickel sulfate and manganese sulfate, and a combination of cobalt sulfate, nickel sulfate and manganese sulfate. But are not limited to the listed supplements, and other supplements commonly used in the art to achieve the same effect may be used in the present invention.

Preferably, in step (4'), the precipitating agent is sodium carbonate or sodium hydroxide.

Preferably, in the step (4'), the amount of the precipitant is such that the total charge of the precipitant is not less than the total charge of the nickel ions, the cobalt ions and the manganese ions in the liquid obtained by the second solid-liquid separation.

Preferably, in the step (4'), the second solid-liquid separation mode is filtration separation.

Preferably, step (4') further comprises washing and drying the ternary precursor to obtain a ternary precursor product.

In the preferred embodiment of the present invention, in the step (5), the pH of the coprecipitated separation liquid in the step (4) is adjusted using an alkaline substance.

Preferably, the alkaline substance is sodium hydroxide.

Preferably, the alkaline substance is an alkaline solution.

Preferably, the concentration of the alkaline solution is 10% to 40% by mass, for example, 10%, 20%, 30%, or 40%, but is not limited to the recited values, and other values not recited within the range of the recited values are also applicable, preferably 20% to 30%.

Preferably, in step (5), the pH is adjusted to 11 to 13, such as 11, 1.5, 12, 12.5 or 13, but not limited to the values recited, and other values not recited within this range are equally applicable, preferably 11.5 to 12.5.

Preferably, in step (5), the reaction is carried out under stirring conditions.

Preferably, in the step (5), the aging is performed before the solid-liquid separation after the completion of the reaction.

Preferably, in step (5), the solid-liquid separation is filtration separation.

Preferably, step (5) further comprises washing and drying the solid slag.

Preferably, the washing solution is mixed into the magnesium removing solution in the step (5).

Preferably, in the step (5), the solid slag is magnesium slag.

Preferably, step (5) further comprises the step (5') of concentrating: and (4) concentrating the magnesium-removed liquid obtained in the step (5) to obtain a concentrated solution, adding an impurity removing agent to carry out impurity removing reaction, and carrying out solid-liquid separation to obtain a refined concentrated solution.

Preferably, in step (5'), the concentration is performed by evaporative concentration.

Preferably, in step (5'), the Li concentration in the finally obtained concentrate is set to 20g/L to 30g/L, for example, 20g/L, 24g/L, 26g/L, 28g/L or 30g/L, but not limited to the recited values, and other values not recited in the numerical range are also applicable.

Preferably, in step (5'), the impurity removing agent is any one or a combination of at least two of sodium fluoride, ammonium fluoride or potassium fluoride, preferably sodium fluoride.

Preferably, in step (5'), the solid-liquid separation is a filtration separation.

Preferably, in the step (5'), condensed water obtained in the concentration process is returned to the washing or acid-preparing process for reuse.

In a preferred embodiment of the present invention, in the step (6), the precipitant is a soluble carbonate solution.

Preferably, the soluble carbonate solution is a sodium carbonate solution.

Preferably, the soluble carbonate solution is a saturated solution.

Preferably, in step (6), the reaction temperature is 85 ℃ to 95 ℃, for example 85 ℃, 90 ℃ or 95 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, in step (6), the reaction time is 0.5h to 5h, such as 0.5h, 1h, 2h, 3h, 4h or 5h, but not limited to the recited values, and other values not recited in the range of the values are also applicable.

Preferably, in the step (6), the solid-liquid separation mode is filtration separation.

Preferably, step (6) further comprises washing and drying the lithium-containing material to obtain a lithium-containing product.

Preferably, the washing solution is mixed into the lithium precipitating solution of step (6). This operation can realize the recycling of the washing liquid.

Preferably, in the step (6), the lithium-containing substance is lithium carbonate.

As a preferred technical scheme of the invention, the method further comprises the step (7) of crystallizing: crystallizing the precipitated lithium solution obtained in the step (6), and then carrying out solid-liquid separation to obtain a solid and a separation solution.

Preferably, the crystallization is a cooling crystallization.

Preferably, the crystallization temperature is from-10 ℃ to 10 ℃, such as-10 ℃, -5 ℃, 0 ℃, 5 ℃ or 10 ℃, but not limited to the recited values, and other values not recited in this range of values are equally applicable.

Preferably, the crystallization is carried out in a crystallizer.

Preferably, the solid-liquid separation mode is centrifugal separation.

Preferably, the solid obtained by solid separation is sodium sulfate decahydrate.

Preferably, the separated liquid is returned to the step (5) for preparation of the alkaline substance for adjusting the pH. This operation can realize the recycling of the separated liquid.

As a preferred technical solution of the present invention, when the lithium precipitation solution obtained in step (6) contains sodium sulfate, the method further comprises step (7) of a sodium sulfate causticization conversion cycle: adding oxalic acid into the lithium precipitation solution obtained in the step (6) for conversion reaction, and performing first solid-liquid separation to obtain sodium hydrogen oxalate solid and conversion solution; mixing the sodium hydrogen oxalate with calcium hydroxide for reaction, and performing secondary solid-liquid separation after the reaction is finished to obtain calcium oxalate solid and sodium hydroxide solution; and mixing the calcium oxalate solid with the conversion solution, adding sulfuric acid, carrying out heating reaction, carrying out solid-liquid separation for the third time to obtain calcium sulfate solid and separation solution, and crystallizing the separation solution to obtain oxalic acid crystals.

In the invention, the steps can realize the recycling of the sodium element and reduce the consumption of the sodium hydroxide, but the pH needs to be adjusted by using alkaline substances containing the sodium element, such as the sodium hydroxide, and the like, and the steps can be not feasible if other alkali metal elements are introduced.

Preferably, the conversion reaction is carried out under stirring conditions.

Preferably, the temperature of the conversion reaction is from 0 ℃ to 40 ℃, for example, 0 ℃, 10 ℃, 20 ℃, 25 ℃, 30 ℃ or 40 ℃, but is not limited to the recited values, and other values not recited within this range are equally applicable, preferably from 10 ℃ to 25 ℃.

Preferably, in the conversion reaction, the molar ratio of oxalic acid to sodium ions is 0.8 to 1.2, for example, 0.8, 0.9, 1.0, 1.1, or 1.2, but not limited to the recited values, and other values not recited within the range of the recited values are also applicable, preferably 0.9 to 1.1.

Preferably, the first solid-liquid separation is a filtration separation.

Preferably, the solid sodium hydrogen oxalate obtained by the first solid-liquid separation is sodium hydrogen oxalate hydrate.

Preferably, the reaction of the sodium hydrogen oxalate with the calcium hydroxide is carried out under stirring conditions.

Preferably, the reaction temperature in the reaction of sodium hydrogen oxalate with calcium hydroxide is 40 ℃ to 100 ℃, for example 40 ℃, 60 ℃, 80 ℃, 90 ℃ or 100 ℃, but not limited to the recited values, and other values not recited in the range of the values are also applicable, preferably 60 ℃ to 90 ℃.

Preferably, in the reaction of sodium hydrogen oxalate and calcium hydroxide, the molar ratio of sodium hydrogen oxalate to calcium hydroxide is 0.8 to 1.2, for example, 0.8, 1.0 or 1.2, but not limited to the recited values, and other values not recited within the range of the recited values are also applicable.

Preferably, the second solid-liquid separation is a filtration separation.

Preferably, the sodium hydroxide solution obtained by the second solid-liquid separation is used for preparing an alkaline substance for adjusting the pH in the step (5).

Preferably, the amount of sulfuric acid added is such that the molar ratio of calcium oxalate to sulfuric acid is from 0.8 to 1, for example 0.8, 0.9 or 1, but is not limited to the recited values, and other values not recited within this range are equally applicable.

Preferably, the calcium oxalate solid is mixed with the conversion solution, and the reaction by adding sulfuric acid is carried out under stirring.

Preferably, the heating temperature is 80 ℃ to 100 ℃, such as 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃, but not limited to the recited values, and other values not recited in the range of values are also applicable.

Preferably, the third solid-liquid separation is a filtration separation.

Preferably, the filtration separation is a hot filtration.

Preferably, the crystallization is a cooling crystallization.

Preferably, the oxalic acid crystals are returned to the conversion reaction process.

As a further preferred technical solution of the method of the present invention, the method comprises the steps of:

(1) acid leaching reaction: mixing waste refractory materials containing silicon, aluminum and magnesium impurities, sulfuric acid solution with the concentration of 2-3 mol/L and additives, carrying out leaching reaction at the temperature of 10-90 ℃ for 6-12 h, wherein the waste refractory materials are subjected to integral leaching or crushing leaching in the leaching reaction, separating after the reaction to obtain purified refractory materials and leachate, washing and recovering the purified refractory materials for preparing new refractory materials, adding the waste refractory materials into the leachate again for leaching reaction, and repeating the leaching process; based on the total mass of the waste refractory material as 100%, the mass fraction of silicon is 18-23 wt%, the mass fraction of aluminum is 20-25 wt%, and the mass fraction of magnesium is 3-5 wt%;

(2) silicon removal: filtering and separating the leachate obtained in the step (1) to remove solids, adding a neutralizing agent, adjusting the pH value of the solution to 2-3, reacting for 0.5-2 h, filtering and separating after the reaction to obtain solid slag and a separation solution, washing and filtering the solid slag, and mixing the washed washing solution into the separation solution obtained in the step (2);

(3) aluminum removal: adding a sodium hydroxide solution with the mass percentage concentration of 10% -40% into the separation liquid obtained in the step (2) under the stirring condition, adjusting the pH of the separation liquid obtained in the step (2) to 4.5-5.5, reacting for 0.5-2 h, filtering and separating to obtain solid slag and an aluminum removing liquid, washing the solid slag, wherein the solid slag is aluminum hydroxide, and mixing the washed washing liquid into the aluminum removing liquid obtained in the step (3);

(4) triple coprecipitation: adding a sodium hydroxide solution with the mass percentage concentration of 10% -40% into the aluminum-removing liquid obtained in the step (3), adjusting the pH to 9.5-10.5, reacting for 0.5-5 h, filtering and separating after the reaction to obtain a ternary mixture and a coprecipitation separation liquid, washing and drying the ternary mixture, and mixing a washing liquid obtained by washing into the coprecipitation separation liquid;

(4') ternary mixture refining: adding the ternary mixture into a sulfuric acid solution with the mass percentage concentration of 10% -40% for re-dissolving to obtain a dissolved solution, adding a neutralizing agent into the dissolved solution for neutralization reaction, adding a fluorine-containing impurity removing agent, wherein the amount of the impurity removing agent meets the molar ratio of the total amount of calcium and magnesium in the dissolved solution after the aluminum removing agent is added to fluoride ions of 1:2, performing first filtration and separation after the reaction, adding a supplement into the liquid obtained by solid-liquid separation, adding a precipitating agent after the supplement is completely dissolved, stirring and performing precipitation reaction, performing second filtration and separation after the precipitation reaction is finished to obtain a solid, obtaining a ternary precursor, and washing and drying the ternary precursor to obtain a ternary precursor product; the precipitator is sodium carbonate or sodium hydroxide; the supplement comprises any one or a combination of at least two of cobalt sulfate, nickel sulfate or manganese sulfate;

(5) magnesium removal: adding a sodium hydroxide solution with the mass percentage concentration of 20-30% into the coprecipitation separation liquid obtained in the step (4), adjusting the pH to 11.5-12.5, reacting and aging, and filtering and separating after the reaction to obtain solid slag and a magnesium removal liquid;

(5') concentrating: evaporating and concentrating the magnesium-removed liquid obtained in the step (5) to obtain a concentrated solution with the concentration of Li being 20 g/L-30 g/L, returning condensed water obtained in the concentration process to the washing or acid preparation process for reuse, adding sodium fluoride into the concentrated solution according to the molar ratio of the total amount of calcium and magnesium to fluoride ions of 1:2, stirring for reaction, and filtering to remove solids in the concentrated solution to obtain a refined concentrated solution;

(6) and (3) lithium deposition: adding a saturated sodium carbonate solution into the refined concentrated solution obtained in the step (5') to react at the temperature of 85-95 ℃ for 0.5-5 h, filtering and separating after the reaction to obtain lithium carbonate and a lithium deposition solution, and washing and drying the lithium carbonate to obtain a lithium carbonate product;

(7) and (3) crystallization: and (4) cooling and crystallizing the lithium precipitation liquid obtained in the step (6) in a crystallizer at the temperature of-10 ℃, then performing centrifugal separation to obtain sodium sulfate decahydrate solid and separation liquid, and returning the separation liquid to the step (5) to prepare an alkaline substance for adjusting the pH value.

As another further preferable technical solution of the method of the present invention, the method comprises the steps of:

(7) sodium sulfate causticization conversion cycle: adding oxalic acid into the lithium precipitation solution obtained in the step (6), wherein the molar ratio of oxalate ions to sodium ions is 0.8-1.2, carrying out conversion reaction at the temperature of 10-25 ℃ while stirring, and filtering and separating for the first time to obtain sodium hydrogen oxalate solid and conversion solution; mixing the sodium hydrogen oxalate with calcium hydroxide, reacting at the temperature of 60-90 ℃ under stirring, and after the reaction is finished, performing secondary filtration and separation to obtain a calcium oxalate solid and a sodium hydroxide solution, wherein the sodium hydroxide solution is used for preparing an alkaline substance for adjusting the pH in the step (5); mixing the calcium oxalate solid with the conversion solution, adding sulfuric acid, wherein the molar ratio of the calcium oxalate to the sulfuric acid is 0.8-1, stirring and reacting at 80-100 ℃, filtering and separating for the third time to obtain calcium sulfate solid and separation solution, crystallizing the separation solution to obtain oxalic acid crystals, and returning the oxalic acid crystals to the conversion reaction process.

According to the further optimized technical scheme, the processes of acid leaching, step-by-step pH adjustment for precipitation, filtering separation, concentration, carbonation precipitation, crystallization separation or oxalic acid conversion and the like are adopted, comprehensive recycling of the waste refractory materials in the preparation process of the ternary battery materials is effectively achieved, the recovery rate of lithium, cobalt, nickel and manganese valuable elements is high, and meanwhile, the waste saggars can be used for producing saggars or raw materials of the refractory materials after being purified.

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

(1) the invention provides a whole set of method for comprehensively utilizing waste heat-resistant materials in the preparation process of the ternary cathode material, effectively realizes the recycling of valuable metals of nickel, cobalt, manganese and lithium in the waste refractory materials in the production process of the ternary cathode material, and has the leaching rate of nickel, cobalt and manganese up to 81 percent and the leaching rate of lithium up to 85 percent. Meanwhile, the waste refractory materials are purified, the reaction condition is mild, the process is simple, the equipment requirement is low, the raw material source is wide, the price is low, and the industrial production is easy to realize.

(2) In the method provided by the invention, the ternary mixture obtained in the step (4) is refined, so that the purity of the finally obtained ternary precursor product can be obviously improved, the impurity content is reduced, and meanwhile, the proportion of each metal element in the ternary precursor product can be adjusted through a supplement.

(3) In the method provided by the invention, the wastes generated in multiple steps can be recycled, so that the cost is saved and the waste discharge is reduced.

Drawings

Fig. 1 is a schematic flow chart of a comprehensive treatment method of a waste refractory material in a ternary cathode material preparation process provided in embodiment 1 of the present invention, wherein the direction of an arrow in the schematic flow chart is the process flow direction of the method provided in embodiment 1 of the present invention;

fig. 2 is a schematic flow chart of a comprehensive treatment method of the waste refractory material in the preparation process of the ternary cathode material provided in embodiment 3 of the present invention, and the arrow direction in the schematic flow chart is the process flow direction of the method provided in embodiment 3 of the present invention.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

Example 1

The embodiment provides a comprehensive treatment method of a waste refractory material in a ternary cathode material preparation process, which comprises the following specific steps:

(1) the preparation method comprises the steps of immersing the waste sagger (ternary waste refractory) shown in the table 1 into a leaching tank of 10L sulfuric acid with the molar concentration of 2mol/L for reaction, adding 100mL of hydrogen peroxide (additive) for normal-temperature leaching reaction, taking out the sagger after leaching for 10h, immersing the purified sagger in clean water, and washing the sagger with the clean water after immersing for 5h to prepare the refractory powder by crushing and screening.

(2) And (3) after 20 waste saggers are repeatedly leached, filtering and separating the leachate, returning filter residues to a leaching tank for deep leaching, discharging the filter residues as solid wastes after washing is finished, adding calcium hydroxide (neutralizing agent) into the filtered filtrate for neutralization, controlling the pH end point to be 2.0, reacting for 30min, filtering and separating, and washing the separated solid by 1:1 water to obtain calcium sulfate and calcium silicate products (calcium slag).

(3) And (3) slowly adding 30% sodium hydroxide solution (alkali) into the filtrate obtained in the last step under the condition of continuous stirring, controlling the pH end point to be 4.5, carrying out filtration separation after reacting for 1h, and washing a filter cake to obtain an aluminum hydroxide product.

(4) And (3) mixing the filtrate obtained in the last step with washing liquor, slowly adding 40% sodium hydroxide solution (alkali) into the mixed washing liquor, stirring and neutralizing the mixed washing liquor, controlling the pH of the solution to be 10.5, reacting for 1 hour, filtering and separating, and washing and filtering a filter cake to obtain a ternary coprecipitation crude product.

(4') re-dissolving the ternary coprecipitation crude product by using 30% sulfuric acid, firstly adding calcium hydroxide (neutralizer) into the solution for neutralization after dissolution, then adding sodium fluoride (impurity removal agent) according to the molar ratio of the total amount of calcium and magnesium to fluoride ions of 1:2, stirring for reaction, filtering and separating to filter out impurities after the reaction is finished, supplementing cobalt sulfate and manganese sulfate (supplement) into refined solution according to the molar ratio of nickel, cobalt and manganese of 1:1:1, blending, adding 40% sodium hydroxide solution (precipitant) according to the molar ratio of nickel, cobalt and manganese to sodium hydroxide of 1:2 for precipitation reaction, filtering and separating after the reaction is finished, washing a filter cake, drying to obtain a ternary precursor, and returning the filtrate to the leaching process of the step (1).

(5) Mixing the ternary coprecipitation filtering filtrate with washing liquor, adding 40% sodium hydroxide solution while stirring, adjusting the pH value to 12.5, stirring for reaction for 30min, aging for 30min after reaction, filtering and separating, and washing the filtered filter cake with water to obtain the magnesium hydroxide product.

(5') the filtrate mixed washing liquor obtained at the last step enters an evaporation concentration process, water in the solution is evaporated until the concentration of lithium in the solution is 25g/L, and the evaporated water is condensed and then returns to a complex acid or washing process. Adding 1.8g of sodium fluoride into the evaporation mother liquor according to the molar ratio of the total amount of calcium and magnesium to the fluorine ions of 1:2, stirring for reaction (deeply removing impurities), and filtering and separating to remove impurities after the reaction is finished.

(6) And (3) adding 35% of sodium carbonate saturated solution into the filtrate obtained in the last step, carrying out precipitation reaction at the reaction temperature of 95 ℃, carrying out centrifugal separation when the solution is hot after the reaction time is 2 hours, and washing, separating and drying the solid obtained after the centrifugal separation to obtain a lithium carbonate product.

(7) And (3) carrying out condensation, filtration and separation on the separated mother liquor, wherein the condensation temperature is-5 ℃, adding a small amount of seed crystals for crystallization, carrying out centrifugal separation, washing the separated solid cold water, drying to obtain a sodium sulfate decahydrate solid, and returning the separated liquid to the alkali preparation process.

In this example, the chemical composition of the waste refractory raw material is shown in table 1, which is a waste sagger from a cathode material manufacturing plant.

TABLE 1 ternary discarded sagger element composition table (wt%)

In the embodiment, the extraction rate of nickel, cobalt and manganese elements is 75%, the leaching rate of lithium is 82%, a 333 type nickel, cobalt and manganese ternary precursor product is obtained, and the waste sagger is effectively purified.

The flow chart of this embodiment is schematically shown in fig. 1, and the arrow direction in the flow chart is the process flow direction of the method provided in embodiment 1 of the present invention.

Example 2

(1) the waste sagger used in example 1 is immersed into a leaching tank of 10L sulfuric acid with the molar concentration of 3mol/L for reaction, 600mL of hydrogen peroxide is added for leaching reaction at 25 ℃, the sagger is taken out after leaching for 10h, the purified sagger is immersed in clear water, and the sagger is washed by clear water after being immersed for 6h and then is used for crushing and screening to prepare refractory powder.

(2) And after 25 waste saggers are repeatedly leached, filtering and separating the leachate, returning filter residues to a leaching tank for deep leaching, washing the filter residues to be discharged as solid waste, slowly adding calcium oxide into the filtered filtrate for neutralization, controlling the pH end point to be 3.0, reacting for 30min, filtering and separating, and washing the separated solid by 1:1 water to be used as calcium sulfate and calcium silicate products.

(3) And (3) slowly adding 30% sodium hydroxide solution into the filtrate obtained in the last step under the condition of continuous stirring, controlling the pH end point to be 5.0, carrying out first filtration and separation after reacting for 2 hours, washing a filter cake, and carrying out second filtration to obtain an aluminum hydroxide product.

(4) And (3) slowly adding 30% sodium hydroxide solution into the filtrate mixed washing liquid obtained by the first filtration and separation in the last step for stirring and neutralization reaction, controlling the pH of the solution to be 10, carrying out filtration and separation after reacting for 2 hours, and washing and filtering a filter cake to obtain a ternary coprecipitation crude product.

(4') re-dissolving the ternary coprecipitation crude product by using 30% sulfuric acid, firstly adding calcium hydroxide into the solution for neutralization after dissolution, then adding ammonium fluoride according to the molar ratio of the total amount of calcium and magnesium to fluoride ions of 1:2, stirring for reaction, filtering and separating after the reaction is finished, supplementing nickel sulfate and manganese sulfate into the refined solution according to the molar ratio of nickel, cobalt and manganese in the solution of 6:2:2, adding a saturated solution of sodium carbonate according to the molar ratio of nickel, cobalt and manganese to sodium carbonate of 1:1 for precipitation reaction, filtering and separating after the reaction is finished, washing and drying a filter cake to obtain a ternary precursor.

(5) Mixing the ternary precursor coarse precipitation filtration filtrate with washing liquor, adding 40% sodium hydroxide solution under stirring, adjusting the pH value to 13, stirring and reacting for 30min, aging for 30min after reaction, filtering and separating, and washing the filtered filter cake to obtain the magnesium hydroxide product.

(5') the filtrate mixed washing liquor obtained at the last step enters an evaporation concentration process, water in the solution is evaporated until the concentration of lithium in the solution is 22g/L, the evaporated water is condensed and then returns to an acid preparation process or a washing process, sodium fluoride is added into the evaporation mother liquor according to the molar ratio of the total amount of calcium and magnesium to fluorine ions of 1:2, the mixture is stirred and reacted, and the mixture is filtered and separated after the reaction is finished.

(6) And adding 35% of sodium carbonate saturated solution into the filtrate obtained in the last step, carrying out precipitation reaction at the reaction temperature of 95 ℃, filtering and separating the filtrate while the filtrate is hot after the reaction is carried out for 2 hours, and washing and separating the filtered filter cake to obtain a lithium carbonate product.

(7) And (3) carrying out condensation, filtration and separation on the separated mother liquor, wherein the condensation temperature is 5 ℃, adding a small amount of seed crystals for crystallization, carrying out filtration and separation, separating filter cakes, washing with cold water, drying to obtain sodium sulfate decahydrate solid, and returning the filtrate to the processes of alkali preparation or neutralization and magnesium precipitation.

In the embodiment, the extraction rate of nickel, cobalt and manganese elements is 81%, the leaching rate of lithium is 85%, a 622-type nickel, cobalt and manganese ternary precursor product is obtained, and the waste sagger is effectively purified.

Example 3

(1) the waste sagger (ternary waste refractory) used in example 1 is immersed into a leaching tank of 10L sulfuric acid (obtained by acid preparation) with the molar concentration of 2.5mol/L for reaction, 500mL hydrogen peroxide (additive) is added for normal-temperature leaching reaction, the sagger is taken out after leaching for 10h, the purified sagger is immersed into clear water, and the sagger is washed by clear water after being immersed for 6h and then is used for crushing and screening to prepare purified refractory powder.

(2) After 15 waste saggers are repeatedly leached, filtering and separating leachate, returning filter residues to a leaching tank for deep leaching, washing the filter residues to be discharged as solid waste, slowly adding digested/size-mixed calcium carbonate (neutralizer) into the filtered filtrate for neutralization, controlling the pH end point to be 2.0, reacting for 30min, performing first filtering and separating, washing the separated solid by 1:1, performing second filtering to be used as calcium sulfate and calcium silicate products (calcium slag), and returning the filtered filtrate for the second filtering to the digesting/size-mixing step.

(3) Slowly adding 30% sodium hydroxide solution (obtained by alkali preparation) into the filtrate obtained in the first filtration in the last step under continuous stirring, controlling the pH end point to be 4.5, carrying out first filtration separation after reacting for 2h, and washing and filtering a filter cake and carrying out secondary filtration to obtain an aluminum hydroxide product;

(4) mixing the filtrates obtained in the first and second filtration, slowly adding 30% sodium hydroxide solution (obtained by adding alkali) to perform stirring neutralization reaction, controlling the pH of the solution to be 10.5, reacting for 3h, filtering, separating, washing and filtering the filter cake to obtain a ternary coprecipitation crude product,

(4') re-dissolving the ternary coprecipitation crude product by using 30% sulfuric acid, firstly adding calcium oxide (neutralizer) into the solution for neutralization after dissolution, then adding potassium fluoride (impurity removal agent) according to the molar ratio of the total amount of calcium and magnesium to fluorine ions of 1:2, stirring for reaction, filtering and separating after the reaction is finished, filtering out impurities, supplementing nickel sulfate and manganese sulfate (supplement) into refined liquid according to the molar ratio of nickel, cobalt and manganese in the solution of 5:2:3, blending, adding 40% sodium hydroxide solution (precipitant) according to the molar ratio of nickel, cobalt and manganese to sodium hydroxide of 1:2 for precipitation reaction, filtering and separating after the reaction is finished, and drying a filter cake to obtain a ternary precursor.

(5) Mixing the ternary precursor coarse precipitation filtration filtrate with washing liquor, adding 40% sodium hydroxide solution (obtained by alkali preparation) while stirring, adjusting the pH value to 13, stirring for reaction for 30min, aging for 30min after reaction, carrying out primary filtration separation, washing the filtered filter cake with water, and carrying out secondary filtration to obtain the magnesium hydroxide product.

(5') mixing the filtrate obtained by the primary filtration and the secondary filtration in the previous step with washing liquid, entering an evaporation concentration process, evaporating water in the solution until the concentration of lithium in the solution is 22g/L, condensing the evaporated water, returning to an acid preparation process or a washing process, adding sodium fluoride (impurity removing agent) into the evaporation mother liquor according to the molar ratio of the total amount of calcium and magnesium to fluorine ions of 1:2, reacting under the condition of stirring for deep impurity removal, and filtering and separating to remove impurities after the reaction is finished.

(6) And (3) adding 35% of sodium carbonate saturated solution (obtained by alkali preparation) into the filtrate obtained in the last step, carrying out precipitation reaction at the reaction temperature of 95 ℃, carrying out centrifugal separation when the solution is hot after the reaction time is 2 hours, and washing, separating and drying the solid obtained after separation to obtain a lithium carbonate product.

(7) Mixing the separated precipitation mother liquor with the ternary coprecipitation mother liquor, adding oxalic acid according to the molar ratio of 1.1:1 of oxalic acid to sodium ions to perform stirring conversion reaction, controlling the reaction temperature at 20 ℃, performing reaction for 2 hours, filtering and separating to obtain hydrated sodium hydrogen oxalate crystals and conversion filtrate, adding calcium hydroxide into the hydrated sodium hydrogen oxalate according to the molar ratio of 1.2:1 to perform stirring full reaction to perform conversion, controlling the reaction temperature at 85 ℃, performing stirring reaction for 3 hours, filtering and separating to obtain calcium oxalate solids and a sodium hydroxide solution, and returning the sodium hydroxide solution to the alkali liquor preparation step; adding the obtained calcium oxalate solid into conversion filtrate, supplementing 30% sulfuric acid, stirring at 80 ℃ for full reaction for conversion, filtering and separating after reacting for 2 hours to obtain calcium sulfate solid and filtrate, cooling the filtrate to 5 ℃, crystallizing, filtering to obtain oxalic acid crystals, and returning the filtered filtrate to the sodium oxalate conversion reaction process.

In the embodiment, the extraction rate of nickel, cobalt and manganese elements is 74%, the leaching rate of lithium is 75%, a 622 type nickel, cobalt and manganese ternary precursor product is obtained, and the waste sagger is effectively purified.

The flow chart of this embodiment is schematically shown in fig. 2, and the arrow direction in the flow chart is the process flow direction of the method provided in embodiment 3 of the present invention.

Example 4

(1) the waste sagger used in example 1 is immersed into a leaching tank of 15L sulfuric acid with the molar concentration of 2mol/L for reaction, 500mL hydrogen peroxide is added for normal-temperature leaching reaction, the sagger is taken out after leaching for 10h, the purified sagger is immersed in clear water, and the sagger is washed by the clear water after being immersed for 12h and then is used for crushing and screening to prepare the refractory powder.

(2) And (3) repeatedly leaching 20 waste sagger, filtering and separating the leachate, returning filter residues to a leaching tank for deep leaching, washing the filter residues to be discharged as solid waste, slowly adding calcium carbonate into the filtered filtrate for neutralization, controlling the pH end point to be 2.0-3.0, reacting for 30min, filtering and separating, and washing the separated solid by 1:1 water to be used as calcium sulfate and calcium silicate products.

(3) And (3) slowly adding 30% sodium hydroxide solution into the filtrate obtained in the last step under the condition of continuous stirring, controlling the pH end point to be 4.5-5.0, carrying out first filtration and separation after reacting for 2 hours, washing a filter cake, and carrying out second filtration to obtain an aluminum hydroxide product.

(4) And (3) slowly adding 30% sodium hydroxide solution into the filtrate mixed washing liquid obtained by the first filtration and separation in the last step for stirring and neutralization reaction, controlling the pH of the solution to be 10.5, carrying out filtration and separation after reacting for 3 hours, and washing and filtering a filter cake to obtain a ternary coprecipitation crude product.

(4') re-dissolving the ternary coprecipitation crude product by using 30% sulfuric acid, firstly adding calcium oxide into the solution for neutralization after dissolution, then adding sodium fluoride according to the molar ratio of the total amount of calcium and magnesium to fluoride ions of 1:2, stirring for reaction, filtering and separating after the reaction is finished, supplementing nickel sulfate into the refined solution according to the molar ratio of nickel, cobalt and manganese in the solution of 8:1:1, adding 40% sodium hydroxide solution according to the molar ratio of nickel, cobalt and manganese to sodium hydroxide of 1:2 for precipitation reaction, filtering and separating after the reaction is finished, washing and drying a filter cake to obtain a ternary precursor.

(5') the filtrate mixed washing liquor obtained at the last step enters an evaporation concentration process, water in the solution is evaporated until the concentration of lithium in the solution is 27g/L, the evaporated water is condensed and then returns to an acid preparation process or a washing process, sodium fluoride is added into the evaporation mother liquor according to the molar ratio of the total amount of calcium and magnesium to fluorine ions of 1:2, the mixture is stirred and reacted, and the mixture is filtered and separated after the reaction is finished.

(7) Adding oxalic acid into the separated precipitation mother liquor according to the molar ratio of the oxalic acid to sodium ions being 1.1:1, stirring and converting, controlling the reaction temperature at 20 ℃, filtering and separating after reacting for 2 hours to obtain hydrated sodium oxalate crystals and conversion filtrate, adding calcium hydroxide into the hydrated sodium oxalate according to the molar ratio of 1.2:1, stirring and fully reacting at 85 ℃, filtering and separating after stirring and reacting for 3 hours to obtain calcium oxalate solids and a sodium hydroxide solution, and returning the sodium hydroxide solution to the alkali liquor preparation step; adding the obtained calcium oxalate solid into conversion filtrate, supplementing 30% sulfuric acid, stirring at 80 ℃ for full reaction, filtering and separating after 2h reaction to obtain calcium sulfate solid and filtrate, cooling the filtrate to 5 ℃ for crystallization to obtain oxalic acid crystals, and returning to the sodium hydrogen oxalate conversion reaction process.

In the embodiment, the extraction rate of nickel, cobalt and manganese elements is 72%, the leaching rate of lithium is 80%, a 811 type nickel, cobalt and manganese ternary precursor product is obtained, and the waste sagger is effectively purified.

Example 5

(1) the waste sagger used in example 1 is immersed into a leaching tank of 10L sulfuric acid with the molar concentration of 0.5mol/L for reaction, 600mL of hydrogen peroxide is added for leaching reaction at 90 ℃, the sagger is taken out after leaching for 6h, the sagger after purification is immersed in clear water, and the sagger is washed by clear water after immersion for 6h and is used for crushing and screening to prepare refractory powder.

(2) And after 25 waste saggers are repeatedly leached, filtering and separating the leachate, returning filter residues to a leaching tank for deep leaching, washing the filter residues to be discharged as solid waste, slowly adding calcium oxide into the filtered filtrate for neutralization, controlling the pH end point to be 4.0, reacting for 1 hour, filtering and separating, and washing the separated solid in a ratio of 1:1 to obtain calcium sulfate and calcium silicate products.

(3) And (3) slowly adding 30% sodium hydroxide solution into the filtrate obtained in the last step under the condition of continuous stirring, controlling the pH end point to be 5.5, carrying out first filtration and separation after reacting for 0.5h, washing a filter cake, and carrying out second filtration to obtain an aluminum hydroxide product.

(4) And (3) slowly adding 30% sodium hydroxide solution into the filtrate mixed washing liquid obtained by the first filtration and separation in the last step for stirring and neutralization reaction, controlling the pH of the solution to be 9, carrying out filtration and separation after reacting for 0.5h, and washing and filtering a filter cake to obtain a ternary coprecipitation crude product.

(5) Mixing the ternary precursor coarse precipitation filtration filtrate with washing liquor, adding 40% sodium hydroxide solution under stirring, adjusting the pH value to 11.5, stirring for reaction for 30min, aging for 30min after reaction, filtering and separating, and washing the filtered filter cake to obtain the magnesium hydroxide product.

(5') the filtrate mixed washing liquor obtained finally in the last step enters an evaporation concentration process, water in the solution is evaporated until the concentration of lithium in the solution is 20g/L, the evaporated water is condensed and then returns to an acid preparation process or a washing process, sodium fluoride is added into the evaporation mother liquor according to the molar ratio of the total amount of calcium and magnesium to fluorine ions of 1:2, the mixture is stirred and reacted, and the mixture is filtered and separated after the reaction is finished.

(6) And adding 35% of sodium carbonate saturated solution into the filtrate obtained in the last step, carrying out precipitation reaction at the reaction temperature of 85 ℃ for 0.5h, filtering and separating while the solution is hot, and washing and separating the filtered filter cake to obtain a lithium carbonate product.

(7) And (3) carrying out condensation, filtration and separation on the separated mother liquor, wherein the condensation temperature is 10 ℃, adding a small amount of seed crystals for crystallization, carrying out filtration and separation, separating filter cakes, washing with cold water, drying to obtain sodium sulfate decahydrate solid, and returning the filtrate to the processes of alkali preparation or neutralization and magnesium precipitation.

In the embodiment, the extraction rate of nickel, cobalt and manganese elements is 88%, the leaching rate of lithium is 95%, a 622-type nickel, cobalt and manganese ternary precursor product is obtained, and the waste sagger is effectively purified.

Example 6

(1) the waste sagger used in example 1 is immersed into a leaching tank of 10L sulfuric acid with the molar concentration of 0.5mol/L for reaction, 600mL of hydrogen peroxide is added for leaching reaction at 10 ℃, the sagger is taken out after leaching for 12h, the sagger after purification is immersed in clear water, and the sagger is washed by clear water after being immersed for 6h and then is used for crushing and screening to prepare refractory powder.

(2) And after 25 waste saggers are repeatedly leached, filtering and separating the leachate, returning filter residues to a leaching tank for deep leaching, washing the filter residues to be discharged as solid waste, slowly adding calcium oxide into the filtered filtrate for neutralization, controlling the pH end point to be 3.0, reacting for 2 hours, filtering and separating, and washing the separated solid by 1:1 to obtain calcium sulfate and calcium silicate products.

(4) And (3) slowly adding 30% sodium hydroxide solution into the mixed washing liquid of the filtrate obtained by the first filtration and separation in the last step, stirring and neutralizing the mixed washing liquid, controlling the pH of the solution to be 9.5, reacting for 5 hours, then filtering and separating, and washing and filtering a filter cake to obtain a ternary coprecipitation crude product.

(5) Mixing the ternary precursor coarse precipitation filtration filtrate with washing liquor, adding 40% sodium hydroxide solution under stirring, adjusting the pH value to 11, stirring and reacting for 30min, aging for 30min after reaction, filtering and separating, and washing the filtered filter cake to obtain the magnesium hydroxide product.

(5') the filtrate mixed washing liquor obtained finally in the last step enters an evaporation concentration process, water in the solution is evaporated until the concentration of lithium in the solution is 30g/L, the evaporated water is condensed and then returns to an acid preparation process or a washing process, sodium fluoride is added into the evaporation mother liquor according to the molar ratio of the total amount of calcium and magnesium to fluorine ions of 1:2, the mixture is stirred and reacted, and the mixture is filtered and separated after the reaction is finished.

(6) And (3) adding 35% of sodium carbonate saturated solution into the filtrate obtained in the last step, carrying out precipitation reaction at the reaction temperature of 90 ℃, filtering and separating the filtrate while the filtrate is hot after the reaction time of 5 hours, and washing and separating the filtered filter cake to obtain a lithium carbonate product.

(7) And (3) carrying out condensation, filtration and separation on the separated mother liquor, wherein the condensation temperature is-10 ℃, adding a small amount of seed crystals for crystallization, carrying out filtration and separation, separating filter cakes, washing with cold water, drying to obtain sodium sulfate decahydrate solid, and returning the filtrate to the processes of alkali preparation or neutralization and magnesium precipitation.

In the embodiment, the extraction rate of nickel, cobalt and manganese elements is 61%, the leaching rate of lithium is 65%, a 622-type nickel, cobalt and manganese ternary precursor product is obtained, and the waste sagger is effectively purified.

Example 7

Referring to example 4, the specific method of this embodiment is characterized in that oxalic acid is added to the separated precipitation mother liquor of step (7) according to a molar ratio of oxalic acid to sodium ions of 0.9:1 to perform a stirring conversion reaction, the reaction temperature is controlled at 0 ℃, sodium oxalate hydrate crystals and conversion filtrate are obtained after 2 hours of reaction and filtration separation, calcium hydroxide is added to the sodium oxalate hydrate according to a molar ratio of 1:1 to perform a sufficient reaction with stirring, the reaction temperature is 90 ℃, calcium oxalate solids and sodium hydroxide solution are obtained after 3 hours of stirring reaction and filtration separation, and the sodium hydroxide solution is returned to the alkali liquor preparation step; adding the obtained calcium oxalate solid into conversion filtrate, supplementing 30% of sulfuric acid, stirring at 100 ℃ for full reaction, wherein the molar ratio of calcium oxalate to sulfuric acid is 0.8, filtering and separating after reacting for 2 hours to obtain calcium sulfate solid and filtrate, cooling the filtrate to 5 ℃, crystallizing to obtain oxalic acid crystals, and returning to the sodium hydrogen oxalate conversion reaction process.

Example 8

Referring to example 4, the specific method of this example is different in that oxalic acid is added to the separated precipitation mother liquor in the step (7) according to a molar ratio of 0.8:1 of oxalic acid to sodium ions to perform a stirring conversion reaction, the reaction temperature is controlled at 40 ℃, after the reaction for 2 hours, sodium hydrogen oxalate hydrate crystals and conversion filtrate are obtained after filtration and separation, calcium hydroxide is added to the sodium hydrogen oxalate hydrate according to a molar ratio of 0.8:1 to perform a sufficient reaction with stirring, the reaction temperature is 100 ℃, after the stirring reaction for 3 hours, calcium oxalate solids and sodium hydroxide solution are obtained by filtration and separation, and the sodium hydroxide solution returns to the alkali liquor preparation step; adding the obtained calcium oxalate solid into conversion filtrate, supplementing 30% of sulfuric acid, stirring at 90 ℃ for full reaction, wherein the molar ratio of calcium oxalate to sulfuric acid is 0.9, reacting for 2 hours, filtering and separating to obtain calcium sulfate solid and filtrate, cooling the filtrate to 5 ℃, crystallizing to obtain oxalic acid crystals, and returning to the sodium hydrogen oxalate conversion reaction process.

Example 9

Referring to example 4, the specific method of this example is different in that oxalic acid is added to the separated precipitation mother liquor in the step (7) according to a molar ratio of oxalic acid to sodium ions of 1.2:1 to perform a stirring conversion reaction, the reaction temperature is controlled at 10 ℃, after the reaction for 2 hours, sodium hydrogen oxalate hydrate crystals and conversion filtrate are obtained after filtration and separation, calcium hydroxide is added to the sodium hydrogen oxalate hydrate according to a molar ratio of 1.2:1 to perform a sufficient reaction with stirring, the reaction temperature is 40 ℃, after the stirring reaction for 3 hours, calcium oxalate solids and sodium hydroxide solution are obtained by filtration and separation, and the sodium hydroxide solution returns to the alkali liquor preparation step; adding the obtained calcium oxalate solid into conversion filtrate, supplementing 30% of sulfuric acid, stirring at 80 ℃ for full reaction, wherein the molar ratio of calcium oxalate to sulfuric acid is 1, filtering and separating after reacting for 2 hours to obtain calcium sulfate solid and filtrate, cooling the filtrate to 5 ℃, crystallizing to obtain oxalic acid crystals, and returning to the sodium hydrogen oxalate conversion reaction process.

Example 10

Referring to example 4, the specific method of this embodiment is characterized in that oxalic acid is added to the separated precipitation mother liquor of step (7) according to a molar ratio of oxalic acid to sodium ions of 1.2:1 to perform a stirring conversion reaction, the reaction temperature is controlled at 25 ℃, sodium oxalate hydrate crystals and conversion filtrate are obtained after 2 hours of reaction and filtration separation, calcium hydroxide is added to the sodium oxalate hydrate according to a molar ratio of 1.2:1 to perform a sufficient reaction with stirring, the reaction temperature is 60 ℃, calcium oxalate solids and sodium hydroxide solution are obtained after 3 hours of reaction with stirring, and the sodium hydroxide solution is returned to the alkali liquor preparation step; adding the obtained calcium oxalate solid into conversion filtrate, supplementing 30% of sulfuric acid, stirring at 80 ℃ for full reaction, wherein the molar ratio of calcium oxalate to sulfuric acid is 1, filtering and separating after reacting for 2 hours to obtain calcium sulfate solid and filtrate, cooling the filtrate to 5 ℃, crystallizing to obtain oxalic acid crystals, and returning to the sodium hydrogen oxalate conversion reaction process.

Comparative example 1

This comparative example was the same as example 1 except that the aluminum-removing step (3)) and the triple co-precipitation and the refining steps thereof (step (4) and step (4')) were reversed in order.

The result is that most of aluminum and the ternary coprecipitate are precipitated simultaneously, part of aluminum is dissolved again and enters a liquid phase, the aluminum is difficult to separate, aluminum influences the product in the subsequent magnesium and lithium precipitation process, and the acid consumption in the redissolution treatment process is increased due to the large amount of aluminum in the coarse precipitate.

The results of the embodiment and the comparative example are combined, so that the method provided by the invention effectively realizes the recycling of valuable nickel, cobalt, manganese and lithium in the waste refractory material in the production process of the ternary cathode material, and meanwhile, the waste refractory material is purified, the reaction condition is mild, the process is simple, the equipment requirement is low, the raw material source is wide, the price is low, and the industrial production is easy to realize. The comparative example did not adopt the scheme of the present invention, and thus the excellent effects of the present invention could not be obtained.

The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. A comprehensive treatment method for waste refractory materials in the preparation process of a ternary cathode material, wherein the waste refractory materials contain silicon, aluminum and magnesium impurities, and is characterized by comprising the following steps:

(6) and (3) lithium deposition: adding a precipitator into the magnesium removal solution obtained in the step (5) for reaction, and performing solid-liquid separation after the reaction to obtain a lithium-containing substance and a lithium precipitation solution;

the mass fraction of the silicon element is 18-23 wt% based on the total mass of the waste refractory material as 100%; the mass fraction of the aluminum element is 20 wt% -25 wt%; the mass fraction of the magnesium element is 3 wt% -5 wt%.

2. The method according to claim 1, wherein the mass fraction of the elemental silicon is 21.32 wt% based on 100% of the total mass of the waste refractory.

3. The method of claim 1, wherein the mass fraction of the aluminum element is 22.43 wt% based on 100% of the total mass of the spent refractory.

4. The method according to claim 1, wherein the mass fraction of the magnesium element is 4.598 wt% based on 100% of the total mass of the waste refractory.

5. The method of claim 1, wherein the waste refractory material comprises a waste sagger.

6. The method of claim 1, wherein the ternary positive electrode material is a lithium nickel cobalt manganese oxide material.

7. The method according to claim 1 or 2, wherein in step (1), the acid solution is a sulfuric acid solution.

8. The method according to claim 7, wherein the concentration of the sulfuric acid solution is 0.5 to 5 mol/L.

9. The method according to claim 8, wherein the concentration of the sulfuric acid solution is 2 to 3 mol/L.

10. The method of claim 1 or 2, wherein in step (1), the additive comprises any one of hydrogen peroxide, sodium sulfite or sodium thiosulfate or a combination of at least two of the above.

11. The method according to claim 1 or 2, wherein in step (1), the waste refractory is subjected to bulk leaching or crushing leaching in the leaching reaction.

12. The method according to claim 1 or 2, wherein the temperature of the leaching reaction in step (1) is 10 ℃ to 90 ℃.

13. The method according to claim 1 or 2, wherein the leaching reaction time in step (1) is 6 to 12 hours.

14. The method of claim 1 or 2, wherein step (1) further comprises washing the cleaned refractory material and recovering the washed refractory material for use in preparing a new refractory material.

15. The method according to claim 1 or 2, wherein in step (1), the waste refractory material is added to the leachate again to carry out the leaching reaction, and the leaching process is repeated.

16. A process according to claim 1 or 2, wherein in step (2) the pH of the leachate obtained in step (1) is adjusted using a neutralising agent.

17. The method of claim 16, wherein the neutralizing agent comprises any one of calcium oxide, calcium hydroxide, or calcium carbonate, or a combination of at least two thereof.

18. The method according to claim 16, wherein in the step (2), the pH of the solution is adjusted to 2 to 3.

19. The method according to claim 1 or 2, wherein in the step (2), the reaction time of the reaction is 0.5h to 2 h.

20. The method according to claim 1 or 2, wherein in the step (2), the solid-liquid separation mode is filtration separation.

21. The method of claim 1 or 2, wherein step (2) further comprises washing and filtering the solid slag.

22. The method of claim 21, wherein the washed wash solution is mixed into the separation liquid of step (2).

23. The method of claim 16, wherein step (2) further comprises: and filtering and separating the leachate to remove solids in the leachate before adding the neutralizing agent.

24. The method according to claim 1 or 2, wherein in the step (3), the pH of the separated liquid in the step (2) is adjusted with an alkaline substance.

25. The method of claim 24, wherein the alkaline substance is sodium hydroxide.

26. The method of claim 24, wherein the alkaline substance is an alkaline solution.

27. The method of claim 26, wherein the alkaline solution is present at a concentration of 10% to 40% by weight.

28. The method of claim 24, wherein the alkaline substance is added while stirring.

29. The method according to claim 1 or 2, wherein in the step (3), the solid-liquid separation mode is filtration.

30. The method of claim 1 or 2, wherein step (3) further comprises washing the solid slag.

31. The method as claimed in claim 30, wherein the washing liquid is mixed into the depoling liquid of step (3).

32. The method according to claim 1 or 2, wherein in the step (3), the solid slag is aluminum hydroxide.

33. The method according to claim 1 or 2, wherein in the step (3), the reaction time of the reaction is 0.5h to 2 h.

34. The method according to claim 1 or 2, characterized in that in step (4), the pH of the depoling liquid obtained in step (3) is adjusted by an alkaline substance.

35. The method of claim 34, wherein the alkaline material is sodium hydroxide.

36. The method of claim 34, wherein the alkaline substance is an alkaline solution.

37. The method of claim 36, wherein the alkaline solution is present at a concentration of 10% to 40% by weight.

38. The method of claim 34, wherein the alkaline substance is added while stirring.

39. The method as claimed in claim 34, wherein in the step (4), the pH of the aluminum-removing liquid obtained in the step (3) is adjusted to 9.5-10.5.

40. The method according to claim 1 or 2, wherein in the step (4), the reaction time of the reaction is 0.5h to 5 h.

41. The method according to claim 1 or 2, wherein in the step (4), the solid-liquid separation mode is filtration separation.

42. The method of claim 1 or 2, wherein step (4) further comprises washing the ternary mixture.

43. The method of claim 42, wherein the washed wash solution is mixed into the co-precipitated separation solution of step (4).

44. The method according to claim 1 or 2, wherein in step (4), further comprising step (4') of refining the ternary mixture: and adding the ternary mixture into an acid solution for re-dissolving to obtain a dissolved solution, adding a neutralizing agent and an impurity removing agent into the dissolved solution, carrying out first solid-liquid separation after reaction, adding a supplement and a precipitating agent into the liquid obtained by solid-liquid separation, mixing, carrying out precipitation reaction, carrying out second solid-liquid separation after the precipitation reaction is finished, and taking out solids to obtain a ternary precursor.

45. The method according to claim 44, wherein in step (4'), the acid solution is a sulfuric acid solution.

46. The method according to claim 44, wherein in the step (4'), the acid solution has a concentration of 10-40% by mass.

47. The method according to claim 44, wherein in step (4'), the neutralizing agent is any one of sodium hydroxide, calcium oxide or calcium carbonate or a combination of at least two of them.

48. The method of claim 44, wherein in step (4'), the scavenger comprises fluorine.

49. The method according to claim 44, wherein in the step (4'), the impurity removing agent is any one of sodium fluoride, potassium fluoride or ammonium fluoride or a combination of at least two of the above.

50. The method as claimed in claim 44, wherein the amount of the impurity removing agent is such that the molar ratio of the total amount of calcium and magnesium to fluoride ions in the solution after the neutralizing agent is added is 1: 2.

51. The method according to claim 44, wherein in the step (4'), the first solid-liquid separation mode is filtration separation.

52. The method according to claim 44, wherein in step (4'), the mixing is stirring mixing.

53. The method as claimed in claim 44, wherein in step (4'), the extender comprises any one or a combination of at least two of cobalt, nickel or manganese salts.

54. The method according to claim 53, wherein in step (4'), the extender is any one of cobalt sulfate, nickel sulfate or manganese sulfate or a combination of at least two thereof.

55. The method according to claim 44, wherein in step (4'), the precipitating agent is sodium carbonate or sodium hydroxide.

56. The method as claimed in claim 44, wherein in the step (4'), the amount of the precipitant is such that the total anionic charge of the precipitant is not less than the total charge of nickel ions, cobalt ions and manganese ions in the liquid obtained by the second solid-liquid separation.

57. The method according to claim 44, wherein in the step (4'), the second solid-liquid separation mode is filtration separation.

58. The method according to claim 44, wherein step (4') further comprises washing and drying the ternary precursor to obtain a ternary precursor product.

59. The method according to claim 1 or 2, wherein in step (5), the pH of the coprecipitated separation solution of step (4) is adjusted by using a basic substance.

60. The method of claim 59, wherein said alkaline substance is sodium hydroxide.

61. The method of claim 59, wherein said alkaline substance is an alkaline solution.

62. The method as claimed in claim 61, wherein the alkaline solution is present in an amount of 10 to 40% by weight.

63. The method as claimed in claim 62, wherein the alkaline solution is at a concentration of 20-30% by mass.

64. The method according to claim 1 or 2, wherein in the step (5), the pH is adjusted to 11 to 13.

65. The method as claimed in claim 64, wherein in the step (5), the pH value is adjusted to 11.5-12.5.

66. The process according to claim 1 or 2, wherein in step (5), the reaction is carried out under stirring conditions.

67. The process according to claim 1 or 2, wherein in step (5), the aging is carried out after the completion of the reaction before the solid-liquid separation.

68. The method according to claim 1 or 2, wherein in step (5), the solid-liquid separation is a filtration separation.

69. The method of claim 1 or 2, wherein step (5) further comprises washing and drying the solid slag.

70. The method according to claim 69, wherein the washed washing solution is mixed into the magnesium removal solution of step (5).

71. The method according to claim 1 or 2, wherein in the step (5), the solid slag is magnesium slag.

72. The method according to claim 1 or 2, wherein step (5) further comprises step (5') of concentrating: and (4) concentrating the magnesium-removed liquid obtained in the step (5) to obtain a concentrated solution, adding an impurity removing agent to carry out impurity removing reaction, and carrying out solid-liquid separation to obtain a refined concentrated solution.

73. The method according to claim 72, wherein in step (5'), the concentration is carried out by evaporation.

74. The method according to claim 72, wherein in the step (5'), the concentration of Li in the finally obtained concentrated solution is set to 20 to 30 g/L.

75. The method as claimed in claim 72, wherein in the step (5'), the impurity removing agent is any one or a combination of at least two of sodium fluoride, ammonium fluoride or potassium fluoride.

76. The method of claim 75, wherein in step (5'), the impurity removal agent is sodium fluoride.

77. The process of claim 72, wherein in step (5'), said solid-liquid separation is a filtration separation.

78. The method according to claim 72, wherein in step (5'), the condensed water obtained from the concentration process is returned to the washing or acid-complexing process for reuse.

79. The method according to claim 1 or 2, wherein in step (6), the precipitant is a soluble carbonate solution.

80. The method as claimed in claim 79 wherein the soluble carbonate solution is a sodium carbonate solution.

81. The method of claim 79, wherein the soluble carbonate solution is a saturated solution.

82. The method according to claim 1 or 2, wherein the temperature of the reaction in step (6) is 85 to 95 ℃.

83. The method according to claim 1 or 2, wherein in the step (6), the reaction time is 0.5h to 5 h.

84. The method according to claim 1 or 2, wherein in the step (6), the solid-liquid separation mode is filtration separation.

85. The method of claim 1 or 2, wherein step (6) further comprises washing and drying the lithium-containing material to obtain a lithium-containing product.

86. The method of claim 85, wherein the washed wash solution is mixed into the lithium precipitation solution of step (6).

87. The method according to claim 1 or 2, wherein in step (6), the lithium-containing substance is lithium carbonate.

88. The process according to claim 1 or 2, characterized in that it further comprises a step (7) of crystallization: crystallizing the precipitated lithium solution obtained in the step (6), and then carrying out solid-liquid separation to obtain a solid and a separation solution.

89. The method as claimed in claim 88, wherein the crystallization is a cooling crystallization.

90. The method as claimed in claim 88, wherein the temperature of the crystallization is from-10 ℃ to 10 ℃.

91. The method as claimed in claim 88, wherein the crystallization is carried out in a crystallizer.

92. The method of claim 88, wherein the solid-liquid separation is by centrifugation.

93. The process of claim 88, wherein the solid separated is sodium sulfate decahydrate.

94. The method of claim 88, wherein the separated liquid is returned to step (5) for the preparation of a basic substance for adjusting pH.

95. The method according to claim 1 or 2, wherein when the lithium precipitation solution obtained in step (6) contains sodium sulfate, the method further comprises step (7) of sodium sulfate causticization conversion cycle: adding oxalic acid into the lithium precipitation solution obtained in the step (6) for conversion reaction, and performing first solid-liquid separation to obtain sodium hydrogen oxalate solid and conversion solution; mixing the sodium hydrogen oxalate with calcium hydroxide for reaction, and performing secondary solid-liquid separation after the reaction is finished to obtain calcium oxalate solid and sodium hydroxide solution; and mixing the calcium oxalate solid with the conversion solution, adding sulfuric acid, carrying out heating reaction, carrying out solid-liquid separation for the third time to obtain calcium sulfate solid and separation solution, and crystallizing the separation solution to obtain oxalic acid crystals.

96. The method as recited in claim 95 wherein the conversion reaction is conducted under agitation conditions.

97. The method as recited in claim 95 wherein the temperature of the conversion reaction is between 0 ℃ and 40 ℃.

98. The process as claimed in claim 97, wherein the temperature of the conversion reaction is 10 ℃ to 25 ℃.

99. The method as claimed in claim 95, wherein the molar ratio of oxalic acid to sodium ions in the conversion reaction is 0.8-1.2.

100. The method as claimed in claim 99, wherein the molar ratio of oxalic acid to sodium ions in the conversion reaction is 0.9-1.1.

101. The method as recited in claim 95 wherein the first solid-liquid separation is a filtration separation.

102. The process of claim 95, wherein said solid sodium oxalate resulting from said first solid-liquid separation is sodium hydrogen oxalate hydrate.

103. The method as recited in claim 95 wherein the reaction of the sodium hydrogen oxalate with the calcium hydroxide is conducted with agitation.

104. The method as claimed in claim 95, wherein the reaction temperature of the sodium hydrogen oxalate and the calcium hydroxide is 40-100 ℃.

105. The method as claimed in claim 104, wherein the reaction temperature of the sodium hydrogen oxalate and the calcium hydroxide is 60-90 ℃.

106. The method as claimed in claim 95, wherein the molar ratio of sodium hydrogen oxalate to calcium hydroxide in the reaction of sodium hydrogen oxalate and calcium hydroxide is 0.8-1.2.

107. The method as recited in claim 95 wherein the second solid-liquid separation is a filtration separation.

108. The method as claimed in claim 95, wherein the sodium hydroxide solution obtained by the second solid-liquid separation is used for preparing the alkaline substance for adjusting pH in the step (5).

109. The method as claimed in claim 95, wherein the sulfuric acid is added in an amount such that the molar ratio of calcium oxalate to sulfuric acid is 0.8-1.

110. The process of claim 95, wherein the calcium oxalate solid is mixed with the conversion solution and the reaction with the addition of sulfuric acid is carried out with stirring.

111. The method of claim 95, wherein the heating is at a temperature of 80 ℃ to 100 ℃.

112. The method as recited in claim 95 wherein the third solid-liquid separation is a filtration separation.

113. The method of claim 112, wherein said filtering separation is a hot filtration.

114. The method of claim 95, wherein said crystallization is a cooling crystallization.

115. The method as claimed in claim 95, wherein the oxalic acid crystals are returned to the conversion reaction process.

116. Method according to claim 1, characterized in that it comprises the following steps: