阅读说明：本技术 一种以锂辉石为原料硫酸—气氨联合制备碳酸锂的方法 (Method for preparing lithium carbonate by taking spodumene as raw material through combination of sulfuric acid and gas ammonia ) 是由 周堃 程籽毅 曾英 魏卓 何智妍 肖淑云 王彦旭 于 2020-11-11 设计创作，主要内容包括：本发明公开了一种以锂辉石为原料硫酸—气氨联合制备碳酸锂的方法,具体包括矿样的制备、两段焙烧、浸出、气氨中和除杂和碳酸铵沉淀锂等工艺,本发明工艺简明有序,工艺流程中某些原料可以循环使用,沉淀锂温度较低,降低了能耗,采用氨气对浸出液进行中和除杂,大幅度减少了废固的产生,避免了钠盐中和引入的钠离子对碳酸锂产品品质影响,部分氨气可以回收使用,并可以回收中和热量,提高了工艺的环保性和经济性,改用碳酸铵为沉锂剂,在氨气中和除杂、净化浓缩后,剩余母液可得到比硫酸钠附加值更高的产品硫酸铵,大大提高了原料和药品的利用率,此方法对锂辉石制备碳酸锂工艺有很好的指导意义,对锂辉石矿工业化生产碳酸锂有很好的的前景。(The invention discloses a method for preparing lithium carbonate by taking spodumene as raw material and combining sulfuric acid with gas ammonia, which comprises the processes of ore sample preparation, two-stage roasting, leaching, gas ammonia neutralization and impurity removal, lithium precipitation by ammonium carbonate and the like, the process is simple and orderly, certain raw materials in the process flow can be recycled, the temperature of lithium precipitation is lower, the energy consumption is reduced, the leachate is neutralized and impurity removed by ammonia gas, the generation of waste solids is greatly reduced, the influence of sodium ions introduced by sodium salt neutralization on the quality of lithium carbonate products is avoided, part of ammonia gas can be recycled, the neutralization heat can be recovered, the environmental protection and the economical efficiency of the process are improved, ammonium carbonate is used as a lithium precipitation agent, after the ammonia gas neutralization and impurity removal, purification and concentration, the residual mother liquor can obtain products with higher added value than sodium sulfate, the utilization rate of the raw materials and the medicine is greatly improved, and the method has good guiding significance for the spodumene preparation process of lithium carbonate, has good prospect for the industrial production of lithium carbonate in spodumene mines.)

1. A method for preparing lithium carbonate by taking spodumene as a raw material through combination of sulfuric acid and gas ammonia is characterized by comprising the following steps:

a) pretreating spodumene ore, namely crushing the spodumene ore, and uniformly mixing the crushed spodumene ore and the crushed spodumene ore after ball milling;

b) roasting the crushed and ball-milled spodumene ore sample at high temperature for a certain time, and crushing and ball-milling the spodumene ore sample again after cooling; adding concentrated sulfuric acid, mixing uniformly, compacting, and reacting at a certain temperature to obtain acidified slag; cooling the acidified slag, adding water, stirring for a certain time at normal temperature, and filtering after the leaching reaction is finished to obtain a lithium leaching solution;

c) adding a small amount of calcium carbonate into the obtained lithium leachate to neutralize part of free acid, then introducing ammonia gas, neutralizing the lithium leachate to remove impurities, and stopping reaction; adding a polyacrylamide flocculant into the neutralized impurity-removed liquid, controlling the flocculation time, slowly and uniformly stirring, then filtering to obtain impurity-removed liquid, carrying out primary concentration, introducing ammonia gas, adding an ammonium carbonate solution, and stirring for reaction for a certain time to obtain a primary purified liquid;

d) carrying out secondary concentration on the first-stage purified liquid, slowly adding an ammonium carbonate solution, and stirring for reacting for a certain time to obtain lithium carbonate precipitate; washing the lithium carbonate precipitate in boiling water and drying to obtain solid lithium carbonate; and returning the mother liquor after lithium carbonate precipitation to the previous stage for continuous concentration, returning the residual mother liquor for a certain number of times, and performing evaporation crystallization to prepare ammonium sulfate.

2. The method for preparing lithium carbonate by using spodumene as a raw material through combination of sulfuric acid and gaseous ammonia as claimed in claim 1, wherein the spodumene ore is crushed in the step a) and is ball-milled until the ore powder passes through a 100-200-mesh standard sample sieve.

3. The method for preparing lithium carbonate by combining sulfuric acid and gaseous ammonia with spodumene as a raw material according to claim 1, wherein the roasting temperature of the spodumene ore powder in the step b) is 1000-1100 ℃, the roasting time is 25-40 min, and the spodumene ore powder is crushed and ball-milled to pass through a 150-200-mesh target standard sample sieve after being cooled.

4. The method for preparing lithium carbonate by combining sulfuric acid and gaseous ammonia using spodumene as a raw material according to claim 1, wherein the addition amount of concentrated sulfuric acid in the step b) is 0.8 to 1.2 times of the theoretical amount, the sulfation reaction temperature is 230 ℃ to 260 ℃, and the reaction time is 25 to 40min, so that acidified slag is obtained; and b), cooling the acidified slag, adding water in an amount which is 1.5-2.5 times of the mass of the mineral powder, controlling the reaction time to be 15-30 min at normal temperature, and stirring at a speed of 80-150 r/min to perform leaching reaction.

5. The method for preparing lithium carbonate by using spodumene as a raw material through combination of sulfuric acid and gaseous ammonia, according to claim 1, wherein in the step c), the stirring rate of the lithium leachate is controlled to be 80-150 r/min, a small amount of calcium carbonate is added to neutralize the free acid of the leachate until the pH value is 0.5-1.5, the stirring rate after filtration is controlled to be 80-150 r/min, the ammonia gas introduction rate is 0.1-0.3L/min, and the reaction is stopped when the neutralization and impurity removal are carried out on the lithium leachate until the pH value is 6.0-7.0; the concentration of the polyacrylamide flocculant is 10g/L, the mass of the flocculant is 0.1-0.5% of the mass of the neutralization impurity-removing liquid, the flocculation time is controlled to be 10-20min, the mixture is slowly stirred, and then the mixture is filtered to obtain the impurity-removing liquid.

6. The method for preparing lithium carbonate by using spodumene as a raw material through combination of sulfuric acid and gaseous ammonia as claimed in claim 1, wherein the impurity-removed liquid in the step c) is subjected to primary concentration until the lithium ion concentration is: 10-15 g/L, controlling the ammonia gas introduction rate of the first-stage concentrated solution to be 0.05-0.15L/min, adding 100g/L ammonium carbonate solution, controlling the mass of the ammonium carbonate solution to be 3-8% of the mass of the impurity-removed solution, controlling the reaction time to be 15-30 min, and controlling the stirring rate to be 80-120 r/min to obtain the first-stage purified solution.

7. The method for preparing lithium carbonate by using spodumene as a raw material through the combination of sulfuric acid and gaseous ammonia, as claimed in claim 1, wherein the primary purified liquid in the step d) is subjected to secondary concentration until the lithium ion concentration is: 25-35 g/L.

8. The method for preparing lithium carbonate by using spodumene as a raw material through combination of sulfuric acid and gaseous ammonia as claimed in claim 1, wherein the concentration of the ammonium carbonate solution used for preparing the lithium carbonate precipitate in the step d) is 500g/L, the mass of the ammonium carbonate solution is 1.1 to 1.3 times of the theoretical amount, the stirring rate for preparing the lithium carbonate precipitate is 80 to 120r/min, the reaction temperature is 50 ℃ to 75 ℃, and the reaction time is 60 to 80 min.

9. The method for preparing lithium carbonate from spodumene by combining sulfuric acid and gaseous ammonia as a raw material according to claim 1, wherein the lithium carbonate precipitate is washed with boiling water in the step d) for 1 to 3 times.

10. The method for preparing lithium carbonate by using spodumene as a raw material through combination of sulfuric acid and gaseous ammonia as claimed in claim 1, wherein the mother liquor after lithium carbonate precipitation in the step d) can be returned for a certain number of times, and then is subjected to evaporation crystallization to prepare ammonium sulfate.

Technical Field

The invention belongs to the field of metal hydrometallurgy and comprehensive utilization of mineral resources, and particularly relates to a method for preparing lithium carbonate by combining sulfuric acid and ammonia gas which take spodumene as a raw material.

Background

Lithium is mainly applied to the directions of lubricating grease, medicines, aluminum smelting, ceramics, glass, lithium batteries and the like, and in nearly ten years, lithium is also more widely applied to the fields of air conditioners, catalysts and the like. Because the nation pays more attention to energy and environmental protection problems, the demand for green energy is increased, and the intensity of environmental protection treatment is increased, so that the development and utilization of clean energy becomes very important, wherein the lithium ion battery technology is the model of clean new energy, most obviously, the demand of a clean new energy lithium battery automobile is increased rapidly, the demand for lithium is also increased continuously, and the demand for lithium is kept 5% -15% of the annual demand for lithium. In China, lithium resources mainly exist in salt lake brine, deep underground brine and lithium-containing ores. For the front-end material lithium carbonate of lithium ion batteries produced by extracting lithium from brine and extracting lithium from ores, more companies can adopt battery-grade lithium carbonate produced by extracting lithium from spodumene, because many other impurity metal ions cannot be carried in the process of preparing lithium carbonate by extracting lithium from ores, and various metal elements in the process of extracting lithium from brine have some uncontrollable influence on the rear-end batteries. In the existing process for preparing lithium carbonate from spodumene, the lime sintering method has high energy consumption and low recovery rate of lithium; the chlorination roasting method has simple flow and higher recovery rate, but has strong corrosion of furnace gas and higher requirement on equipment, and is mainly applied to the generation process of lepidolite; the existing sulfuric acid method always has the condition that the carrying-out amount of lithium after acid leaching is too high, the recovery rate of lithium is influenced, the resource waste is serious, the waste solid amount of the generated calcium sulfate is large, the additional value of the sodium sulfate as a byproduct is low, and meanwhile, the introduced sodium ions can influence the quality of a rear-end battery-grade lithium carbonate product, so that the method does not accord with the national green and environment-friendly production concept and policy. Therefore, a method for preparing lithium carbonate from spodumene with high efficiency and green color needs to be developed.

Disclosure of Invention

Aiming at the defects, the invention provides a method for preparing lithium carbonate by combining sulfuric acid and gas ammonia, a small amount of calcium sulfate by-products, no sodium ion introduction, no sodium sulfate by-product with low added value and ammonium sulfate fertilizer by-product are generated, the overall energy consumption of the process is reduced, and the method for preparing lithium carbonate by spodumene is environment-friendly.

In order to achieve the purpose, the technical scheme of the invention is as follows:

a method for preparing lithium carbonate by taking spodumene as a raw material through sulfuric acid-gas ammonia combination comprises the following steps:

a) pretreating spodumene ore, namely crushing the spodumene ore, and uniformly mixing the crushed spodumene ore and the crushed spodumene ore after ball milling;

b) roasting the crushed and ball-milled spodumene ore sample at high temperature for a certain time, and crushing and ball-milling the spodumene ore sample again after cooling; adding concentrated sulfuric acid, mixing uniformly, compacting, and reacting at a certain temperature to obtain acidified slag; cooling the acidified slag, adding water, stirring for a certain time at normal temperature, and filtering after the leaching reaction is finished to obtain a lithium leaching solution;

c) adding a small amount of calcium carbonate into the obtained lithium leachate to neutralize part of free acid, then introducing ammonia gas, neutralizing the lithium leachate to remove impurities, and stopping reaction; adding a polyacrylamide flocculant into the neutralized impurity-removed liquid, controlling the flocculation time, slowly and uniformly stirring, then filtering to obtain impurity-removed liquid, carrying out primary concentration, introducing ammonia gas, adding an ammonium carbonate solution, and stirring for reaction for a certain time to obtain a primary purified liquid;

d) carrying out secondary concentration on the first-stage purified liquid, slowly adding an ammonium carbonate solution, and stirring for reacting for a certain time to obtain lithium carbonate precipitate; washing the lithium carbonate precipitate in boiling water and drying to obtain solid lithium carbonate; and returning the mother liquor after lithium carbonate precipitation to the previous stage for continuous concentration, returning the residual mother liquor for a certain number of times, and performing evaporation crystallization to prepare ammonium sulfate.

Preferably, the spodumene ore in the step a) is crushed and ball-milled until the ore powder passes through a 100-200-target standard sample sieve.

Preferably, in the step b), the roasting temperature of the spodumene ore powder is 1000-1100 ℃, the roasting time is 25-40 min, and the spodumene ore powder is crushed and ball-milled until the spodumene ore powder passes through a 150-200-mesh standard sample sieve after being cooled.

Preferably, the adding amount of the concentrated sulfuric acid in the step b) is 0.8-1.2 times of the theoretical dosage, the sulfation reaction temperature is 230-260 ℃, and the reaction time is 25-40 min, so that acidified slag is obtained; and b), cooling the acidified slag, adding water in an amount which is 1.5-2.5 times of the mass of the mineral powder, controlling the reaction time to be 15-30 min at normal temperature, and stirring at a speed of 80-150 r/min to perform leaching reaction.

Preferably, in the step c), when calcium carbonate is added into the lithium leachate to neutralize free acid, the stirring rate is controlled to be 80-150 r/min, the lithium leachate is neutralized to have a pH value of 0.5-1.5, the calcium carbonate is filtered, the filtrate is controlled to have a stirring rate of 80-150 r/min, the ammonia gas is introduced at a rate of 0.1-0.3L/min, and the reaction is stopped when the lithium leachate is neutralized and impurity-removed to have a pH value of 6.0-7.0; the concentration of the polyacrylamide flocculant is 10g/L, the mass of the flocculant is 0.1-0.5% of the mass of the neutralization impurity-removing liquid, the flocculation time is controlled to be 10-20min, the mixture is slowly stirred, and then the mixture is filtered to obtain the impurity-removing liquid, the concentration of sulfate radicals in the impurity-removing liquid is reduced, the condition that lithium ammonium sulfate double salt is not generated in the subsequent concentration process can be ensured, namely a large amount of metal cation impurities in the leachate are removed, such as: fe³⁺，Al³⁺Etc., without affecting the lithium concentration.

Preferably, the impurity-removed solution in the step c) is subjected to first-stage concentration until the lithium ion concentration is: 10-15 g/L, controlling the ammonia gas introduction rate of the first-stage concentrated solution to be 0.05-0.15L/min, adding 100g/L ammonium carbonate solution, controlling the mass of the ammonium carbonate solution to be 3-8% of the mass of the impurity-removing solution, controlling the reaction time to be 15-30 min, controlling the stirring rate to be 80-120 r/min, and removing calcium, magnesium and other ions remained in the impurity-removing solution to obtain a first-stage purified solution.

Preferably, the first-stage purified liquid in the step d) is secondarily concentrated to a lithium ion concentration of: 25-35 g/L.

Preferably, the concentration of the ammonium carbonate solution used for preparing the lithium carbonate precipitate in the step d) is 500g/L, the adding mass is 1.1-1.3 times of the theoretical dosage, the stirring rate for preparing the lithium carbonate precipitate is 80-120 r/min, the reaction temperature is 50-75 ℃, and the reaction time is 60-80 min.

Preferably, in said step d), the lithium carbonate precipitate is washed with boiling water for 1 to 3 times.

Preferably, after the mother liquor obtained by precipitating the lithium carbonate in the step d) is returned for a certain number of times, evaporation crystallization is performed to prepare the ammonium sulfate.

Has the advantages that:

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

1) the method has simple and orderly process, all the used chemical medicines are conventional medicines, the lithium deposition temperature in the process flow is lower, and the energy consumption is reduced;

2) in the invention, the dosage of solid medicines used in neutralization and impurity removal is small, such as: calcium carbonate is adopted to neutralize and remove impurities from the leachate, so that the generation of waste solids of calcium sulfate dihydrate is greatly reduced, part of ammonia can be recycled, the neutralization heat can be recovered, and the environmental protection and the economical efficiency of the process are improved;

3) in the invention, the lithium precipitating agent sodium carbonate used for precipitating lithium used in the existing lithium carbonate preparation process is changed into ammonium carbonate, and after neutralization, impurity removal, purification and concentration are carried out on ammonia gas, the residual mother liquor can obtain the product ammonium sulfate with higher added value than sodium sulfate, so that the utilization rate of raw materials and medicines is greatly improved.

Drawings

Fig. 1 is a process flow diagram of a method for preparing lithium carbonate by taking spodumene as a raw material through combination of sulfuric acid and gaseous ammonia.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The technical scheme of the invention is as follows: the raw material for preparing the lithium carbonate is spodumene concentrate after flotation, and the general formula is Li₂O·Al₂O₃·4SiO₂Pretreating the ore sample until the ore sample passes through a 150-200-target standard sample sieve, wherein the particle size of the ore sample is about 0.075mm, the content of lithium oxide is about 6.21%, and impurity ions mainly comprise Fe, Al, Ca and the like;

the invention provides a method for preparing lithium carbonate by taking spodumene as a raw material through sulfuric acid-gas ammonia combination, which comprises the following steps:

example 1

a. 20.83g of pretreated spodumene ore powder with the particle size of 150 meshes is taken and placed in an alumina crucible.

b. And (2) putting the crucible into a muffle furnace, heating to 1030 ℃ at the speed of 5 ℃/min, keeping the temperature for 35min, crushing after cooling until the temperature is 180-target standard sample sieve, adding 20g of concentrated sulfuric acid (1.0 time of the theoretical dosage), keeping the temperature at 250 ℃ for 25min, adding 40g of water (the liquid-solid ratio is 2:1) after cooling, keeping the reaction time at 15min, stirring at the speed of 100r/min, and filtering to obtain a lithium leachate with the leaching rate of 95.79%.

c. Adding a small amount of calcium carbonate into the lithium leachate, controlling the stirring rate at 80r/min to neutralize the pH of the lithium leachate until the pH is 0.8, filtering, controlling the stirring rate at 80r/min, introducing ammonia gas at 0.1L/min, neutralizing the lithium leachate until the pH is 6.0, adding a polyacrylamide solution with the concentration of 10g/L, uniformly stirring the mixture, controlling the flocculation time to be 10min, filtering the mixture to obtain an impurity-removed solution, and filtering the impurity-removed solution to obtain the lithium neutralization impurity-removed solution, wherein the lithium content is 95.12%, the lithium loss is 0.67%, the iron removal rate is 98.34%, and the aluminum removal rate is 98.71%. And (3) carrying out primary concentration on the neutralized impurity-removed liquid until the concentration of lithium ions is 10g/L, controlling the introduction rate of ammonia gas to be 0.05L/min, adding an ammonium carbonate solution with the concentration of 100g/L, wherein the mass of the ammonium carbonate solution is 3% of the mass of the impurity-removed liquid, controlling the reaction time to be 15min, controlling the stirring rate to be 80r/min, and removing calcium ions, magnesium ions and the like which are residual in the impurity-removed liquid to obtain a primary purified liquid.

d. And (3) carrying out secondary concentration on the first-stage purified liquid until the lithium ion concentration is 25g/L, adding 1.2 times of the theoretical dosage of an ammonium carbonate solution as a lithium precipitation agent with the concentration of 500g/L, and stirring at the reaction temperature of 60 ℃ for 60min to prepare lithium carbonate precipitate, wherein the stirring speed of the lithium carbonate precipitate is 100 r/min. And after the reaction is finished, washing the lithium carbonate precipitate in boiling water for 2 times to obtain the lithium carbonate precipitate, drying the lithium carbonate precipitate, and analyzing the lithium carbonate precipitate by ICP (inductively coupled plasma) to obtain the lithium carbonate precipitate with the purity of over 94.6 percent.

Example 2

a. Taking 50g of the pretreated spodumene ore powder, wherein the particle size of the spodumene ore powder is larger than a 150-target standard sample sieve, and placing the spodumene ore powder in an alumina crucible.

b. And (2) putting the crucible into a muffle furnace, heating to 1040 ℃ at the speed of 5 ℃/min, keeping the temperature for 35min, cooling, crushing to 180-mesh standard sample sieve, adding 55g of concentrated sulfuric acid (1.1 times of the theoretical dosage), keeping the temperature at 260 ℃ for 30min, cooling, adding 100g of water (liquid-solid ratio is 2:1), keeping the reaction time at 15min, and stirring at the speed of 120r/min to obtain the leaching rate of lithium of 96.53%.

c. Adding a small amount of calcium carbonate into the lithium leachate, controlling the stirring rate at 120r/min to neutralize the pH of the lithium leachate until the pH is 1.0, filtering, controlling the stirring rate at 120r/min, controlling the ammonia gas introduction rate at 0.15L/min, neutralizing the lithium leachate until the pH is 6.5, adding a polyacrylamide solution with the concentration of 10g/L, uniformly stirring, controlling the flocculation time at 15min, and filtering to obtain an impurity-removed solution, wherein the mass of a flocculating agent is 0.3% of that of the impurity-removed solution, the flocculation time is controlled at 96.10%, the lithium loss is 0.43%, the iron removal rate is 99.82%, and the aluminum removal rate is 99.67%. And (3) carrying out primary concentration on the neutralized impurity-removed liquid until the concentration of lithium ions is 10g/L, controlling the introduction rate of ammonia gas to be 0.1L/min, adding an ammonium carbonate solution with the concentration of 100g/L, wherein the mass of the ammonium carbonate solution is 5% of the mass of the impurity-removed liquid, controlling the reaction time to be 20min, controlling the stirring rate to be 120r/min, and removing calcium ions, magnesium ions and the like which are residual in the impurity-removed liquid to obtain a primary purified liquid.

d. And (3) carrying out secondary concentration on the first-stage purified liquid until the lithium ion concentration is as follows: 30g/L, adding 1.3 times of the theoretical dosage of an ammonium carbonate solution with the concentration of 500g/L as a lithium precipitation agent, wherein the stirring speed for preparing lithium carbonate precipitate is 120r/min, the reaction temperature is 60 ℃, and the reaction time is 60 min. And after the reaction is finished, washing the lithium carbonate precipitate in boiling water for 3 times to obtain the lithium carbonate precipitate, drying the lithium carbonate precipitate, and analyzing the lithium carbonate precipitate by ICP (inductively coupled plasma) to obtain the lithium carbonate precipitate with the purity of more than 96.3%.

Example 3

a. 100g of pretreated spodumene ore powder with the particle size of 150-target standard sample sieve is taken and placed in an alumina crucible.

b. And (2) putting the crucible into a muffle furnace, heating to 1050 ℃ at the speed of 5 ℃/min, keeping the temperature for 30min, crushing after cooling until the temperature is 150-target standard sample sieve, adding 100g of concentrated sulfuric acid (1.0 time of the theoretical dosage), keeping the temperature for 30min at 250 ℃, adding 200g of water (liquid-solid ratio is 2:1) after cooling, keeping the reaction time for 15min, and stirring at the speed of 110r/min to obtain the leaching rate of lithium of 98.53%.

c, adding a small amount of calcium carbonate into the lithium leachate, controlling the stirring rate at 110r/min to neutralize the pH value of the lithium leachate until the pH value is 1.5, filtering, controlling the stirring rate at 110r/min in the leachate, stopping the reaction when the ammonia gas introduction rate is 0.1L/min to the pH value of 7.0, adding 10g/L of polyacrylamide solution, (0.5% of the quality of the leachate), controlling the flocculation time at 20min, and filtering to obtain a neutralized impurity removal solution, wherein the lithium yield is 97.97%, the lithium loss is 0.56%, the iron removal rate is 99.91% and the aluminum removal rate is 98.51%. And (3) carrying out primary concentration on the neutralized impurity-removed liquid until the concentration of lithium ions is 15g/L, controlling the introduction rate of ammonia gas to be 0.15L/min, adding an ammonium carbonate solution with the concentration of 100g/L, wherein the mass of the ammonium carbonate solution is 7% of the mass of the impurity-removed liquid, controlling the reaction time to be 30min, controlling the stirring rate to be 110r/min, and removing calcium ions, magnesium ions and the like which are residual in the impurity-removed liquid to obtain a primary purified liquid.

d. And (3) carrying out secondary concentration on the first-stage purified liquid until the lithium ion concentration is as follows: 35g/L, adding 1.5 times of the theoretical dosage of an ammonium carbonate solution with the concentration of 500g/L as a lithium precipitation agent, wherein the stirring speed for preparing lithium carbonate precipitate is 110r/min, the reaction temperature is 65 ℃, and the reaction time is 80 min. And after the reaction is finished, washing the lithium carbonate precipitate in boiling water for 3 times to obtain the lithium carbonate precipitate, drying the lithium carbonate precipitate, and analyzing the lithium carbonate precipitate by ICP (inductively coupled plasma) to obtain the lithium carbonate precipitate with the purity of more than 95.9%.

Example 4: comparison process of sulfuric acid-ammonia gas combination method and existing sulfuric acid method

100.00g of each pretreated spodumene ore sample is respectively named as A (100.00 g; the existing sulfuric acid method) and B (100.00 g; the sulfuric acid-gas ammonia combined method). Heating the group A to 1100 deg.C with the existing sulfuric acid process, and maintaining the temperature for 30 min; cooling, crushing to 150 meshes, adding 1.5 times of sulfuric acid, roasting at 250 ℃ for 35min, adding the roasted clinker into water with a liquid-solid ratio of 2.5, and soaking in lithium by water; adding calcium carbonate into the leachate to neutralize excessive sulfuric acid until the pH value is 7.0, filtering, concentrating the leachate, adding sodium carbonate and soda ash to remove impurities, concentrating the obtained purified solution to reach the lithium ion concentration of 30g/L, heating the purified solution to 98 ℃, adding a sodium carbonate solution to perform carbonization lithium precipitation reaction, filtering, washing with hot water, and drying to obtain lithium carbonate powder. Heating the group B to 1050 ℃ at the speed of 5 ℃/min, then preserving heat for 30min, cooling, then adding 1.3 times of sulfuric acid, preserving heat for 30min at the temperature of 250 ℃, cooling, then adding water with the liquid-solid ratio of 2.0 times to the acidified and roasted ore sample, and leaching for 15min at the rotating speed of 120 r/min; adding a small amount of calcium carbonate into the leachate to neutralize the pH value to 1.0, filtering, introducing ammonia gas at the speed of 0.1L/min to neutralize and remove impurities, adding 0.5 percent and 10g/L polyacrylamide solution, settling for 15min, filtering, performing primary concentration, controlling the ammonia gas introduction speed to be 0.05L/min, adding 10ml and 100g/L ammonium carbonate solution, controlling the reaction time to be 15min, controlling the stirring speed to be 100r/min, filtering to obtain a primary purified solution (the lithium ion concentration is 10g/L), concentrating the primary purified solution to the lithium ion concentration of 30g/L, controlling the ammonia gas introduction speed to be 0.05L/min, adding 20ml and 500g/L ammonium carbonate solution, controlling the reaction time to be 60min, controlling the reaction temperature to be 65 ℃, controlling the stirring speed to be 120r/min, washing the lithium carbonate solid in boiling water for 3 times, filtering, drying to obtain solid lithium carbonate. The process comparison results are shown in table 1:

TABLE 1A, B comparison of two sets of Processes

Therefore, after the concentrate after spodumene flotation is pretreated, the lithium in the spodumene is converted into a lithium sulfate solution by adopting preferential roasting conversion and sulfuric acid leaching, a small amount of calcium carbonate is used for neutralizing free acid, ammonia gas is introduced for neutralizing and removing impurities, excessive sulfuric acid is neutralized, a large amount of calcium sulfate waste solids are not generated, the carrying amount of lithium is small, the impurity removal rate is extremely high, two-stage concentration is adopted for controlling the generation of ammonium sulfate lithium double salt, so that the loss of lithium is reduced, the lithium yield is improved by mother liquor circulation when lithium carbonate is precipitated, the purity of lithium carbonate is improved by washing with boiling water, part of medicines can be recycled, the generated waste solids are small, a high-added-value ammonium sulfate fertilizer is produced as a byproduct, sodium ions are not introduced, the influence on a rear-end lithium battery is avoided, the feasibility is improved, the environment friendliness is improved, and the economy is improved.

Although the present invention has been described with reference to the above embodiments, it should be understood that the present invention is not limited to the above embodiments, and those skilled in the art can make various changes and modifications without departing from the scope of the present invention.