阅读说明：本技术 废旧锂离子电池正极材料的回收利用方法 (Recycling method of waste lithium ion battery anode material ) 是由 郑铁江 蒋国强 曹圣平 陈电华 李国� 唐义 马俊华 于 2020-05-12 设计创作，主要内容包括：本发明涉及一种废旧锂离子电池正极材料的回收利用方法,将电池粉料在真空气氛中加热煅烧,利用负极碳作为还原剂,使得金属离子被还原。然后向还原粉料中加入水并通入CO<Sub>2</Sub>进行氢化、过滤。水浸液经蒸发、洗涤、烘干得到高纯碳酸锂。水浸渣经过酸浸得到酸浸液,酸浸液经除铜及铁铝后再加入P<Sub>2</Sub>0<Sub>4</Sub>萃取得到镍钴锰净化液。向净化液中加入可溶盐调整配比,然后进行共沉淀反应,过滤得到Ni<Sub>x</Sub>Co<Sub>y</Sub>Mn<Sub>1-x-y</Sub>(OH)<Sub>2</Sub>。利用本方法处理锂离子电池,镍钴锰的回收率均大于98％,锂的回收率大于95％且得到碳酸锂纯度高,可直接用于三元电池正极材料的制备,实现资源循环利用。该方法工艺简单,优先提取高纯碳酸锂,提高了锂回收率,不需使用还原剂浸出,提高了有价金属元素的回收率。(The invention relates to a recycling method of a waste lithium ion battery anode material, which heats and calcines battery powder in a vacuum atmosphere, and reduces metal ions by using cathode carbon as a reducing agent. Then adding water into the reduced powder and introducing CO 2 Hydrogenation and filtration are carried out. And evaporating, washing and drying the water leaching solution to obtain the high-purity lithium carbonate. The water leaching slag is subjected to acid leaching to obtain acid leaching solution, the acid leaching solution is subjected to copper and iron-aluminum removal, and then P is added 2 0 4 Extract and obtainTo obtain the nickel-cobalt-manganese purifying liquid. Adding soluble salt into the purified solution to adjust the ratio, then carrying out coprecipitation reaction, and filtering to obtain Ni x Co y Mn 1‑x‑y (OH) 2 . When the method is used for treating the lithium ion battery, the recovery rates of nickel, cobalt and manganese are all more than 98%, the recovery rate of lithium is more than 95%, the purity of the obtained lithium carbonate is high, and the lithium carbonate can be directly used for preparing the anode material of the ternary battery, so that the resource recycling is realized. The method has simple process, preferentially extracts high-purity lithium carbonate, improves the recovery rate of lithium, does not need to use a reducing agent for leaching, and improves the recovery rate of valuable metal elements.)

1. A method for recycling a waste lithium ion battery anode material is characterized by comprising the following steps:

(1) calcining and reducing: heating, calcining and reducing battery powder containing the lithium ion battery anode material in a vacuum atmosphere, and crushing and sieving the battery powder to obtain reduced powder;

(2) and (3) extracting lithium: adding water into the reduced powder obtained in the step (1), uniformly mixing, and then introducing CO₂Hydrogenating and filtering to obtain a lithium bicarbonate solution and water-soaked slag;

(3) preparing high-purity lithium carbonate: heating, evaporating and concentrating the lithium bicarbonate solution obtained in the step (2), and washing and drying to obtain high-purity lithium carbonate;

(4) acid leaching: adding the water leaching residue obtained in the step (2) into an acid solution, and stirring and leaching to obtain a pickle liquor containing nickel, cobalt, manganese, aluminum, copper and iron;

(5) copper removal: adding iron powder into the pickle liquor obtained in the step (4), and filtering to obtain copper-removed liquor after the reaction is completed;

(6) removing iron and aluminum: adding sodium sulfate into the copper-removed solution obtained in the step (5), stirring, slowly dropwise adding industrial hydrogen peroxide, adding an alkali solution to adjust the pH value to 1.5-2.0, heating to react, cooling after the reaction is finished, adding an alkali solution to adjust the pH value to 3.0-4.0, and filtering to obtain an iron and aluminum-removed solution;

(7) and (3) extraction and impurity removal: adding an acid solution into the liquid obtained in the step (6) except for the iron and the aluminum to adjust the pH value to 1.5-2.5, extracting by using an organic extractant to enable nickel, cobalt and manganese in the pickle liquor to be retained in a water phase, enabling all impurities except the nickel, the cobalt and the manganese to enter an organic phase, and separating and collecting the water phase to obtain a purified solution;

(8) preparing a ternary precursor: detecting the concentration of nickel, cobalt and manganese in the purified liquid obtained in the step (7), adding soluble nickel salt, cobalt salt or manganese salt into the purified liquid to adjust the proportion, so that the molar ratio of the nickel, the cobalt and the manganese in the purified liquid reaches the required molar ratio of the ternary anode material precursor, then adding ammonia water and alkali liquor to carry out coprecipitation reaction, and filtering to obtain the ternary anode precursor precipitated Ni_xCo_yMn_1-x-y(OH)₂。

2. The recycling method of the anode material of the waste lithium ion battery according to claim 1, wherein the battery powder in the step (1) includes the anode material and the cathode material of the lithium ion battery and elements such as copper, aluminum and iron, and the anode material of the lithium ion battery includes one or more of lithium cobaltate, lithium manganate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate; the calcining temperature in the step (1) is 700-1000 ℃, the calcining time is 1-6 h, and the vacuum degree is-0.1 MPa to-0.01 MPa.

3. The recycling method of the anode material of the waste lithium ion battery according to claim 1, wherein the solid-liquid mass ratio in the step (2) is battery powder: water 1: (10 to 15) introducing CO₂The flow rate of (A) is 20ml/min, the hydrogenation temperature is room temperature, and the hydrogenation time is 2-3 h.

4. The recycling method of the anode material of the waste lithium ion battery according to claim 1, wherein the evaporation and concentration temperature in the step (3) is 85-95 ℃.

5. The recycling method of the anode material of the waste lithium ion battery according to claim 1, wherein the acid in the step (4) is one or a mixture of sulfuric acid, hydrochloric acid and nitric acid, and the concentration of the acid solution is 0.1-1 mol/L; the solid-liquid mass ratio is water immersion slag: acid solution 1: (3-5), the leaching temperature is 40-80 ℃, the leaching time is 1-3 h, and the stirring speed is 200-500 r/min.

6. The recycling method of the anode material of the waste lithium ion battery according to claim 1, wherein the molar weight of the added iron powder in the step (5) is 1-3 times of the copper content in the solution, the reaction temperature is 30-80 ℃, and the reaction time is 10-60 min.

7. The method for recycling the anode material of the waste lithium ion battery according to claim 1, wherein the adding amount of the sodium sulfate and the hydrogen peroxide in the step (6) is as follows: sodium sulfate: hydrogen peroxide (100 mL): (1-3) g: (2-10) calculating the volume of the solution, wherein the dropping time of hydrogen peroxide is 1-2 hours, and the dropping temperature is 40-50 ℃; heating to 85-95 ℃ for reaction for 1-2 h, and adding an alkali solution to adjust the pH after the temperature is reduced to 55-65 ℃.

8. The method for recycling the anode material of the waste lithium ion battery according to claim 1, wherein the alkali in the step (6) is one or more mixed solution of sodium hydroxide, ammonia water, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate and ammonium bicarbonate.

9. The recycling method of the anode material of the waste lithium ion battery according to claim 1, wherein the extractant used in the step (7) is P204, the saponification rate of the P204 is 60-75%, the volume fraction of the P204 is 15-25%, the PH value of the aqueous phase solution is controlled to 2-3, and the volume ratio of the organic phase to the aqueous phase is organic phase: water phase (0.2-1): 1, the extraction stage is 3-5 stages of countercurrent extraction.

10. The recycling method of the anode material of the waste lithium ion battery according to claim 1, wherein one or more of nickel sulfate, nickel nitrate, nickel chloride, cobalt sulfate, cobalt nitrate, cobalt chloride, manganese nitrate or manganese sulfate is added during the adjustment of the mixture ratio in the step (8), the alkali liquor added during the coprecipitation is one or more of sodium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, ammonium carbonate solution and ammonium bicarbonate solution, the concentration of the alkali liquor is 1-2 mol/L, the concentration of ammonia water is 10-15%, the reaction pH is 10.5-12.5, the reaction temperature is 40-90 ℃, and the stirring speed is 800-1500 r/min.

Technical Field

The invention relates to the technical field of battery recovery, in particular to a method for recycling a waste lithium ion battery anode material.

Background

With the rapid growth of the electric automobile industry, the scrappage of the power battery of the electric automobile also rapidly increases, and according to prediction, the annual accumulated scrappage of the power battery of the electric automobile in China reaches the scale of 32.3 million tons by 2020.

The power battery does not contain heavy metal elements with high toxicity such as mercury, cadmium, lead and the like, but also can bring various pollutions to the environment, such as: heavy metals in the battery anode material can raise the pH value of the environment, and toxic gas can be generated when the heavy metals are not properly treated; the power battery contains various metals and electrolyte, which can harm human health. In addition, the power battery contains a large amount of recyclable valuable metals, such as Co, Ni, Mn, Cu, Li, Al, Fe and the like. Wherein, part of the metal resources belong to elements which are relatively lacked in the nature and are relatively expensive. Therefore, if the power battery cannot be effectively recycled, precious metal loss and heavy metal pollution are inevitably caused, and the recycling of the power battery not only has economic value, but also has environmental protection significance.

At present, two methods for recycling waste ternary batteries mainly comprise a high-temperature solid phase repair method and a wet element extraction method. Wherein: the high-temperature solid phase repairing method is that the nickel cobalt lithium manganate is separated from other impurity elements by methods of sorting, chemical impurity removal and the like, and the obtained nickel cobalt lithium manganate is subjected to lithium supplement and high-temperature calcination to obtain the nickel cobalt lithium manganate ternary battery anode material with restored performance; the wet element extraction method is to carry out acid leaching, chemical impurity removal, deep impurity removal by extraction or nickel, cobalt and manganese separation on the nickel cobalt lithium manganate ternary powder to obtain sulfate, and add sodium carbonate into a lithium-containing solution to carry out evaporation concentration to obtain lithium carbonate. The method synchronously reduces and leaches valuable metals such as nickel, cobalt, manganese, lithium and the like, and a large amount of reducing agents such as hydrogen peroxide or sodium hypochlorite and the like are consumed; lithium loss occurs in each step in the subsequent working procedures, so that the final recovery rate of lithium can only reach about 65-70%; the obtained lithium carbonate is industrial-grade lithium carbonate, and high-purity lithium carbonate can be obtained by adding hydrogenation and purification; meanwhile, a large amount of water leaching slag containing cathode carbon is generated, and the disposal cost is increased; and a sodium precipitation process is required to be added before lithium precipitation, and a washing procedure is added after lithium precipitation, so that the production cost is increased.

In summary, the prior art for recycling and preparing the anode material of the waste lithium ion battery mainly has the following defects: the process is complex, and a large amount of chemical reagents are used; the lithium recovery rate is low, the lithium loss is serious, and the production cost of the lithium ion battery is undoubtedly increased when the price of the lithium raw material rises; the valuable metal elements are recovered by leaching with a large amount of reducing agents, and the recovery rate of the valuable metal elements is low.

Disclosure of Invention

The invention aims to solve the technical problem of providing a method for recycling the anode material of the waste lithium ion battery, simplifying the recycling process of the anode material of the lithium ion battery, preferentially extracting high-purity lithium carbonate, improving the lithium recovery rate, not using a reducing agent for leaching and improving the recovery rate of valuable metal elements.

The invention provides a method for recycling a waste lithium ion battery anode material, which comprises the following steps:

(1) calcining and reducing: heating, calcining and reducing battery powder containing the lithium ion battery anode material in a vacuum atmosphere, and crushing and sieving the battery powder to obtain reduced powder;

(2) and (3) extracting lithium: adding water into the reduced powder obtained in the step (1) and mixing uniformlyHomogenizing, then introducing CO₂Carrying out hydrogenation reaction, and filtering to obtain a lithium bicarbonate solution and water-soaked slag;

(3) preparing high-purity lithium carbonate: heating, evaporating and concentrating the lithium bicarbonate solution obtained in the step (2), and washing and drying to obtain high-purity lithium carbonate;

(4) acid leaching: adding the water leaching residue obtained in the step (2) into an acid solution, and stirring and leaching to obtain a pickle liquor containing nickel, cobalt, manganese, aluminum, copper and iron;

(5) copper removal: adding iron powder into the pickle liquor obtained in the step (4), and filtering to obtain copper-removed liquor after the reaction is completed;

(6) removing iron and aluminum: adding sodium sulfate into the copper-removed solution obtained in the step (5), stirring, slowly dropwise adding industrial hydrogen peroxide, adding an alkali solution to adjust the pH value to 1.5-2.0, heating to react, cooling after the reaction is finished, adding an alkali solution to adjust the pH value to 3.0-4.0, and filtering to obtain an iron and aluminum-removed solution;

(7) and (3) extraction and impurity removal: adding an acid solution into the liquid obtained in the step (6) except for the iron and the aluminum to adjust the pH value to 1.5-2.5, extracting by using an organic extractant to enable nickel, cobalt and manganese in the pickle liquor to be retained in a water phase, enabling all impurities except the nickel, the cobalt and the manganese to enter an organic phase, and separating and collecting the water phase to obtain a purified solution;

(8) preparing a ternary precursor: detecting the concentration of nickel, cobalt and manganese in the purified liquid obtained in the step (7), adding soluble nickel salt, cobalt salt or manganese salt into the purified liquid to adjust the proportion, so that the molar ratio of the nickel, the cobalt and the manganese in the purified liquid reaches the required molar ratio of the ternary anode material precursor, then adding ammonia water and alkali liquor to carry out coprecipitation reaction, and filtering to obtain the ternary anode precursor precipitated Ni_xCo_yMn_1-x-y(OH)₂；

Preferably, the battery powder in the step (1) comprises a lithium ion battery anode material, a cathode material and elements such as copper, aluminum and iron, wherein the lithium ion battery anode material comprises one or more of lithium cobaltate, lithium manganate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate; the calcining temperature in the step (1) is 700-1000 ℃, the calcining time is 1-6 h, and the vacuum degree is-0.1 MPa to-0.01 MPa.

Preferably, the solid-liquid mass ratio in the step (2) is that of the battery powder: water 1: (10 to 15) introducing CO₂The flow rate of the soaking solution is 20ml/min, the soaking temperature is room temperature, and the soaking time is 2-3 h.

Preferably, the evaporation concentration temperature in the step (3) is 85-95 ℃.

Preferably, the acid in the step (4) is one or a mixture of sulfuric acid, hydrochloric acid and nitric acid, and the concentration of the acid solution is 0.1-1 mol/L; the solid-liquid mass ratio is water immersion slag: acid solution 1: (3-5), the leaching temperature is 40-80 ℃, the leaching time is 1-3 h, and the stirring speed is 200-500 r/min.

Preferably, in the step (5), the molar weight of the added iron powder is 1-3 times of the copper content in the solution, the reaction temperature is 30-80 ℃, and the reaction time is 10-60 min.

Preferably, the adding amount of the sodium sulfate and the hydrogen peroxide in the step (6) is as follows: sodium sulfate: hydrogen peroxide (100 mL): (1-3) g: (2-10) calculating the volume of the solution, wherein the dropping time of hydrogen peroxide is 1-2 hours, and the dropping temperature is 40-50 ℃; heating to 85-95 ℃ for reaction for 1-2 h, and adding an alkali solution to adjust the pH after the temperature is reduced to 55-65 ℃.

Preferably, the alkali in the step (6) is one or a mixture of sodium hydroxide, ammonia water, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate and ammonium bicarbonate.

Preferably, the extractant used in the step (7) is P204, the saponification rate of P204 is 60-75%, the pH value of the aqueous phase solution is controlled to be 2-3, and the volume ratio of the organic phase to the aqueous phase is that of the organic phase: water phase (0.2-1): 1, the extraction stage is 3-5 stages of countercurrent extraction.

Preferably, one or more of nickel sulfate, nickel nitrate, nickel chloride, cobalt sulfate, cobalt nitrate, cobalt chloride, manganese nitrate or manganese sulfate is/are added when the mixture ratio is adjusted in the step (8), alkali liquor added during coprecipitation is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate and ammonium bicarbonate solution, the concentration of the alkali liquor is 1-2 mol/L, the concentration of ammonia water is 10-15%, the reaction pH is 10.5-12.5, the reaction temperature is 40-90 ℃, and the stirring speed is 800-1500 r/min.

The principle of the invention is as follows: firstly, heating and calcining battery powder containing a lithium ion battery anode material in a vacuum atmosphere, and reducing metal ions in the mixed battery powder by using cathode carbon as a reducing agent. Then adding water into the reduction powder and mixing evenly, and then introducing CO₂Carrying out a hydrogenation reaction, Li⁺Is leached with HCO₃ ⁺And reacting to obtain a lithium bicarbonate solution, filtering to obtain the lithium bicarbonate solution, heating, evaporating and concentrating, washing and drying to obtain the high-purity lithium carbonate. Adding the filtered water leaching residue into an acid solution, stirring and leaching to obtain a pickling solution containing nickel, cobalt, manganese, aluminum, copper and iron, adding iron powder into the obtained pickling solution, and replacing Cu in the solution by iron²⁺Filtering to remove copper, adding sodium sulfate into the copper-removed solution, stirring, slowly adding industrial hydrogen peroxide dropwise, adjusting pH and temperature to separate out iron and aluminum in a precipitation form, filtering to remove iron and aluminum, adding an organic extractant P204 for extraction to keep nickel, cobalt and manganese in the pickle liquor in a water phase, allowing impurities except nickel, cobalt and manganese to enter an organic phase, separating and collecting the water phase to obtain a purified solution to obtain a pure nickel, cobalt and manganese solution, namely a purified solution. Detecting the concentration of nickel, cobalt and manganese in the purified solution, adding soluble nickel salt, cobalt salt or manganese salt into the purified solution to adjust the proportion, so that the molar ratio of nickel, cobalt and manganese in the purified solution reaches the required molar ratio of the ternary anode material precursor, then adding ammonia water and alkali liquor to carry out coprecipitation reaction, and filtering to obtain the ternary anode precursor precipitate Ni_xCo_yMn_1-x-y(OH)₂。

The invention has the beneficial effects that:

1. the lithium is preferentially extracted to prepare the high-purity lithium carbonate, the recovery rate of the lithium is as high as 95 percent, the recovery rate is high, and the product purity is high;

2. the lithium carbonate obtained by recycling does not need to be washed by pure water for many times, so that the generation amount of waste water is greatly reduced, and water resources are saved;

3. the cathode carbon is fully utilized as a reducing agent, so that the generation amount of solid waste is greatly reduced;

4. the nickel-cobalt separation process is omitted, the components of the purified liquid are adjusted according to the proportion and then directly precipitated to obtain the ternary positive precursor materials with different proportions, and the production cost is greatly reduced;

5. the obtained ternary precursor and lithium carbonate have high purity, can be directly used for preparing the ternary battery anode material, and really realizes the cyclic utilization of resources.

In conclusion, according to the method for recycling the waste lithium ion battery anode material, the recovery rates of nickel, cobalt and manganese are all larger than 98%, the recovery rate of lithium is larger than 95%, the purity of the obtained lithium carbonate is high, the method can be directly used for preparing the ternary battery anode material, and the resource recycling is really realized. The method has simple process, preferentially extracts high-purity lithium carbonate, greatly improves the recovery rate of lithium, does not need to use a reducing agent for leaching, and greatly improves the recovery rate of valuable metal elements.

Drawings

Fig. 1 is a process flow chart of the method for recycling the anode material of the waste lithium ion battery.

Detailed Description

The invention provides a method for recycling a waste lithium ion battery anode material, which comprises the following steps:

(1) calcining and reducing: heating, calcining and reducing battery powder containing the lithium ion battery anode material in a vacuum atmosphere, and crushing and sieving the battery powder to obtain reduced powder; the battery powder comprises a lithium ion battery anode material, a lithium ion battery cathode material and elements such as copper, aluminum, iron and the like, wherein the lithium ion battery anode material comprises one or more of lithium cobaltate, lithium manganate, lithium nickel cobalt aluminate and lithium nickel cobalt manganate; the calcination temperature is 700-1000 ℃, the calcination time is 1-6 h, and the vacuum degree is-0.1 MPa to-0.01 MPa;

(2) and (3) extracting lithium: adding water into the reduced powder obtained in the step (1), uniformly mixing, and then introducing CO₂Hydrogenating and filtering to obtain a lithium bicarbonate solution and water-soaked slag; the solid-liquid mass ratio is battery powder: water 1: (10 to 15) introducing CO₂The flow rate of the catalyst is 20ml/min, the immersion temperature is room temperature, and the hydrogenation time is 2-3 h;

(3) preparing high-purity lithium carbonate: heating, evaporating and concentrating the lithium bicarbonate solution obtained in the step (2), and washing and drying to obtain high-purity lithium carbonate; the evaporation concentration temperature is 85-95 ℃;

(4) acid leaching: adding the water leaching residue obtained in the step (2) into an acid solution, and stirring and leaching to obtain a pickle liquor containing nickel, cobalt, manganese, aluminum, copper and iron; the acid is one or a mixture of more of sulfuric acid, hydrochloric acid and nitric acid, and the concentration of the acid solution is 0.1-1 mol/L; the solid-liquid mass ratio is water immersion slag: acid solution 1: (3-5), leaching at the temperature of 40-80 ℃, for 1-3 h, and stirring at the speed of 200-500 r/min;

(5) copper removal: adding iron powder into the pickle liquor obtained in the step (4), and filtering to obtain copper-removed liquor after the reaction is completed; adding iron powder into the solution, wherein the molar weight of the added iron powder is 1-3 times of the content of copper in the solution, the reaction temperature is 30-80 ℃, and the reaction time is 10-60 min.

(6) Removing iron and aluminum: according to the solution after copper removal: sodium sulfate: hydrogen peroxide (100 mL): (1-3) g: (2-10) mL, adding sodium sulfate into the copper-removed liquid obtained in the step (5), stirring, slowly dropwise adding industrial hydrogen peroxide, dropwise adding the hydrogen peroxide for 1-2 hours at the dropwise adding temperature of 40-50 ℃, adding an alkali solution to adjust the pH value to 1.5-2.0, heating to 85-95 ℃, reacting for 1-2 hours, adding the alkali solution to adjust the pH value to 3.0-4.0 after the temperature is reduced to 55-65 ℃, and filtering to obtain an iron and aluminum-removed liquid; the alkali is one or a mixture of sodium hydroxide, ammonia water, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate, ammonium carbonate, sodium bicarbonate, potassium bicarbonate and ammonium bicarbonate;

(7) and (3) extraction and impurity removal: adding an acid solution into the liquid obtained in the step (6) after iron and aluminum removal to adjust the pH value to 1.5-2.5, wherein the volume ratio of an organic phase to a water phase is as follows: water phase (0.2-1): 1, adding an organic extractant P204 with the saponification rate of 60-75% into the mixed solution, controlling the pH value of the aqueous phase solution to be 2-3, carrying out countercurrent extraction with the extraction stages of 3-5, retaining nickel, cobalt and manganese in the pickle liquor in the aqueous phase through the extraction of the organic extractant P204, allowing all impurities except the nickel, cobalt and manganese to enter an organic phase, and separating and collecting the aqueous phase to obtain a purified solution;

(8) preparing a ternary precursor: detecting the concentration of nickel, cobalt and manganese in the purified liquid obtained in the step (7), adding soluble nickel salt, cobalt salt or manganese salt into the purified liquid to adjust the proportion, so that the molar ratio of the nickel, the cobalt and the manganese in the purified liquid reaches the required molar ratio of the ternary anode material precursor, then adding ammonia water and alkali liquor to carry out coprecipitation reaction, and filtering to obtain the ternary anode precursor precipitated Ni_xCo_yMn_1-x-y(OH)₂(ii) a And one or more of nickel sulfate, cobalt sulfate or manganese sulfate is/are added during the adjustment of the mixture ratio, the alkali liquor added during the coprecipitation is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate and ammonium bicarbonate solution, the concentration of the alkali liquor is 1-2 mol/L, the concentration of ammonia water is 10-15%, the reaction pH is 10.5-12.5, the reaction temperature is 40-90 ℃, and the stirring speed is 800-1500 r/min.