A method for extracting lithium from face shell materials and overhaul slag and co-producing steel plant slag agents

Abstract

The present invention provides a method for extracting lithium from casing materials and overhaul slag and co-producing steel plant slag melting agents, which includes mixing and finely grinding the casing materials and overhaul slag, followed by acid leaching. The leaching residue is obtained after secondary leaching and scrubbing, and the residue is pelletized with limestone and a binder and dried to produce slag melting agents; the leaching solution is purified and enriched with lithium by an adsorption material, and the lithium-rich slag is desorbed at high temperature and high pressure - cooled - membrane concentrated, and finally an industrial-grade lithium carbonate product is synthesized; this method highly utilizes the tail slag by producing it into slag melting agents for steel plants while efficiently recovering metallic lithium, and no waste water or waste residue is generated.

Description

Technical Field

[0001] The present invention relates to the field of comprehensive utilization of industrial waste in the electrolytic aluminum industry, and particularly to a method for extracting lithium from cell shells and overhaul slag and co-producing steel-making slag agents. Background Art

[0002] With the wide application of electronic products such as electric vehicles and smart phones, lithium, as an important battery material, has become increasingly popular. With the decline in the price of lithium carbonate, the recovery of lithium from battery waste is in a loss-making state, while various waste slags generated during the aluminum smelting process contain a large amount of lithium, which is an important source for obtaining lithium and has attracted more and more attention from practitioners.

[0003] When aluminum is produced industrially by the cryolite-aluminum oxide molten salt electrolysis method, the waste aluminum electrolyte usually contains a relatively high content of lithium. The reason is that the raw material aluminum oxide for electrolytic aluminum contains Li2O to varying degrees. During the electrolysis process, lithium elements enter the electrolyte in the form of ions. As the age of the electrolytic cell increases, lithium elements continuously accumulate. When the lithium element in the aluminum electrolyte reaches 2-3% by mass in terms of LiF, it helps to lower the primary crystallization temperature of the electrolyte and reduce energy consumption. However, when the lithium element content in the aluminum electrolyte is too high, the electrolyte system will not only reduce the solubility of aluminum oxide in the electrolyte, but also cause an increase in the superheat of the electrolyte, resulting in increased energy consumption, shortened service life of the electrolytic cell, and affecting the economic benefits of electrolytic aluminum. Therefore, when the lithium element content in the aluminum electrolyte is too high, the aluminum electrolyte needs to be replaced regularly, and the replaced aluminum electrolyte is the waste aluminum electrolyte.

[0004] The cell shell material is the alumina crust on the upper part of the anode of the electrolytic cell. The cell shell material has functions such as heat preservation and anti-oxidation, and can be repeatedly used in the electrolysis production process after being crushed. During the anode electrolysis process, some electrolytes will cover the anode residue, so the cell shell material is a physical mixture of alumina and electrolyte, which contains impurity elements such as carbon, calcium, silicon, and iron in addition to elements such as sodium, aluminum, fluorine, and lithium.

[0005] The service life of the electrolytic cell used in aluminum electrolysis is generally 3-5 years. The waste materials formed by the replaced electrolytic cells during equipment maintenance are collectively referred to as the overhaul slag of the aluminum electrolytic cell. Usually, 20-30 kg of overhaul slag is generated for every 1 ton of aluminum produced. The overhaul slag can generally be divided into waste refractory materials, waste cathode carbon materials, and mixtures, which not only contain valuable elements such as Li and Al, but also are rich in fluorides and cyanides with strong toxicity. According to the standard, the amounts of fluorides and cyanides in the leachate of the overhaul slag can reach about 2500 and 5 mg / L respectively, far exceeding the safety values specified in the standard. Effectively recovering the lithium resources therein can not only turn waste into treasure and alleviate the shortage of lithium resources, but also reduce the environmental pollution caused by the waste slag.

[0006] Data shows that China's aluminum electrolysis industry produces more than one million tons of surplus waste aluminum electrolyte and overhaul slag every year. After lithium extraction from relatively pure electrolyte, it is processed into recycled cryolite or aluminum fluoride and then reused in the aluminum smelting industry. For example, CN114438329A discloses a comprehensive recovery method for waste lithium-containing aluminum electrolyte. First, the lithium-containing aluminum electrolyte is crushed and finely ground into electrolyte powder with a mesh size of 100-400; an acid solution is prepared and a leaching intensifier is added, and then the electrolyte powder is added to the acid solution for leaching and filtration. The obtained filter residue is washed and dried to obtain a cryolite product. However, due to the complex composition, many impurities, high carbon content, low available fluorine content, and lower lithium content than the electrolyte in the face shell material and overhaul slag, the lithium concentration in the solution after leaching is low, so it has not been efficiently utilized. Some are landfilled after harmless treatment, resulting in waste of resources, or there are problems such as long process routes and high production costs. Because when removing impurities from a solution with low lithium and high impurities, a large amount of auxiliary materials will be consumed and the lithium entrainment loss is large. Secondly, the lithium-containing solution after impurity removal often has a concentration of only about 2 g / L or even lower, and a large amount of crystalline salt will precipitate during evaporation and concentration, and the lithium entrainment loss in the salt is very large. Finally, when synthesizing the concentrated solution, only crude lithium carbonate can be obtained due to high impurities.

[0007] CN 115846377 A discloses a harmless electrolytic aluminum overhaul slag, its application, and an electrolytic aluminum overhaul slag harmless method. After treatment, it meets the standards and reaches the entry conditions for a flexible landfill. This method does not recover lithium and does not highly utilize the overhaul slag.

[0008] CN 118125481 A discloses a treatment method for electrolytic aluminum carbon slag. First, the electrolytic aluminum carbon slag is calcined at 1200 °C to burn off the carbon in the electrolytic aluminum carbon slag, obtaining lithium-rich soot and lithium-rich electrolyte; then sulfuric acid is used to activate the lithium-rich electrolyte to obtain a defluorinated lithium-rich electrolyte slurry and hydrogen fluoride gas; after solid-liquid separation of the defluorinated lithium-rich electrolyte slurry, a lithium-rich electrolyte filtrate and a lithium-rich electrolyte filter cake are obtained, and the lithium-rich electrolyte filter cake is heated and leached and solid-liquid separated to obtain an aluminum fluoride filter cake. This route has high energy consumption during high-temperature calcination, and lithium entrainment loss is bound to occur when synthesizing aluminum fluoride first and then extracting lithium.

[0009] Therefore, there is an urgent need to develop a method with a short process, high yield, and high added value of tailings, which can simultaneously treat the face shell material and overhaul slag without generating waste water and waste residue. Summary of the Invention

[0010] The purpose of the present invention is to provide a method for extracting lithium from the face shell material and overhaul slag and co-producing steel plant slag agent in view of the above deficiencies of the existing technology.

[0011] To achieve the above purpose, the present invention adopts the following technical solutions:

[0012] The present invention provides a method for extracting lithium from face shell material and overhaul slag and co-producing steel plant slag-making agent, including N consecutive cycles and the following steps:

[0013] S1. Grind the overhaul slag into powder with a particle size of 100 mesh to 200 mesh, add a flotation agent to float and separate carbon powder; grind the face shell material into powder with a particle size of 100 mesh to 200 mesh, mix it with the flotated overhaul slag, and perform acid leaching. The doping ratio of the face shell material to the overhaul slag is 1:(0 - 2);

[0014] S2. Mix the mixed raw materials with a second solution to adjust the pulp density. The mass - volume ratio of the raw materials to the second solution is 1:(1 - 3). Then, by mass, add 4% - 10% of a leaching aid, add a cyanide - breaking agent and a leaching agent, maintain the system pH at 0.5 - 1.5, and stir and react at 70°C - 100°C for 1 - 4 hours;

[0015] S3. After the end of S2, pump in a fourth solid material. By mass, the ratio of the fourth solid material to the mixture of the face shell material and the overhaul slag is (0.1 - 0.3):1. Adjust the pH to 2 - 4, stabilize for 30 - 60 min, and then press - filter the slurry to obtain a first filtrate and a first filter residue;

[0016] If the lithium content of the first filter residue is less than 0.1%, then S4 is omitted;

[0017] S4. The first filter residue is subjected to secondary leaching with a third solution. By mass, the liquid - solid ratio is controlled at 1.5 - 3:1, adjust the pH to 1 - 2 with industrial hydrochloric acid or sulfuric acid, react at 50°C - 80°C for 1 h - 2 h, and press - filter to obtain a second filtrate and a second filter residue;

[0018] S5. The second filter residue is adjusted and washed with a fifth solution. By mass, the liquid - solid ratio is controlled at 1.5 - 3:1, wash at room temperature for 30 - 60 min, and after press - filtering, obtain a third filtrate and a third filter residue;

[0019] S6. Mix the third filter residue with aggregate and binder. By mass, the mixing ratio is 100:5 - 20:1 - 5. After pelletizing and drying, a slag - making agent product is obtained.

[0020] Furthermore, it also includes:

[0021] S7. Add the first filtrate and alkali solution to an impurity - removal tank, control the pH value at 5 - 8, and the temperature at 40°C - 80°C, so that the impurity elements in the solution precipitate out. After stirring and reacting for 1 h and filtering, a fourth filtrate and a fourth filter residue are obtained;

[0022] S8. Use liquid caustic soda to completely dissolve the sixth solid material and / or aluminum hydroxide to obtain a sodium aluminate solution, and use hydrochloric acid or sulfuric acid and / or aluminum hydroxide to completely dissolve to obtain an aluminum chloride solution or an aluminum sulfate solution; add the sodium aluminate solution and the aluminum chloride solution or the aluminum sulfate solution to the fourth filtrate, control the pH during the process to be 9 - 10, control the end-point pH to be 6 - 8, the temperature to be 80°C - 100°C, stabilize for 1 h - 3 h and then filter press to obtain a fifth filtrate and a fifth filter residue; the fifth filter residue is a lithium-rich residue with a lithium content greater than 4%.

[0023] Further, it also includes:

[0024] S9. Slurry the fifth filter residue with pure water, with a liquid-solid ratio of 10 - 30:1, perform high-temperature and high-pressure decomposition at 200°C - 250°C for 1 h - 3 h, filter to obtain a sixth filtrate and a sixth filter residue, cool the sixth filter residue and pure water through a multi-stage plate heat exchanger and circulating water, obtain a lithium-rich concentrated solution after membrane concentration, and then synthesize industrial-grade lithium carbonate.

[0025] Further, in S1, the mixing ratio of the ground face shell material and the flotation-treated overhaul slag is, by mass ratio, the fluorine is greater than 26% - 36% and the carbon is 5% - 15% after mixing;

[0026] When the carbon in the ground face shell material and the flotation-treated overhaul slag is less than 15%, the overhaul slag does not need to be separated by flotation to remove carbon powder.

[0027] Further, the flotation agent is a general term for a foaming agent, an inhibitor, and a collector; the foaming agent is No. 2 oil or ether alcohol; the inhibitor is water glass; the collector is kerosene.

[0028] Further, in S2,

[0029] The leaching aid is alumina or aluminum hydroxide. After adding the leaching aid, the molar ratio of fluorine to aluminum in the mixture slurry is controlled between 2 - 3:1;

[0030] The leaching agent is industrial hydrochloric acid or sulfuric acid;

[0031] If the cyanide-breaking agent is for a hydrochloric acid system, sodium chlorate or sodium hypochlorite is selected, and if the cyanide-breaking agent is for a sulfuric acid system, hydrogen peroxide is selected,

[0032] The addition ratio is 0 - 2% of the weight of the face shell material and the overhaul slag, and the cyanide radical is converted into non-toxic nitrogen and carbon dioxide.

[0033] Further, it is characterized in that:

[0034] When N is 1,

[0035] The second solution and the third solution are tap water; the fifth solution is tap water;

[0036] The fourth solid material is not added; the sixth solid material is aluminum hydroxide;

[0037] When N is greater than 1,

[0038] The second solution is the second filtrate; the third solution is the third filtrate; the fifth solution is the fifth filtrate;

[0039] The fourth solid material is the fourth filter residue; the sixth solid material is the sixth filter residue.

[0040] The beneficial effects of the present invention are as follows: The present invention combines the treatment of hazardous waste residues such as face shell materials and overhaul slag. For the problem of low lithium content and high impurities in the leaching solution, adsorption and enrichment of lithium are used instead of the traditional impurity removal idea. After the lithium-rich material is analyzed, industrial-grade lithium carbonate is prepared, and the leaching residue is made into a slag melting agent used in steel mills. China's annual steel output reaches 1 billion tons, and the dosage of slag melting agent per ton of steel is about 2‰, so the market is huge and the production cost of steel enterprises can be effectively reduced. The entire treatment process is short, the lithium recovery rate is high, and no waste liquid or waste residue is generated throughout the process. Description of the Drawings

[0041] Figure 1 is a flow chart of a method for extracting lithium from face shell materials and overhaul slag and co-producing a slag melting agent for steel mills. Detailed Embodiments

[0042] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0043] Please refer to Figure 1 , a method for extracting lithium from face shell materials and overhaul slag and co-producing a slag melting agent for steel mills, including N consecutive cycles, and the following steps:

[0044] S1. Grind the overhaul slag into a powder with a particle size of 100 mesh to 200 mesh, add a flotation agent to float and separate carbon powder; grind the face shell material into a powder with a particle size of 100 mesh to 200 mesh, mix it with the flotation-treated overhaul slag, and perform acid leaching. The doping ratio of the face shell material to the overhaul slag is 1:(0 - 2);

[0045] S2. Mix the mixed raw materials with the second solution to adjust the pulp. The mass-volume ratio of the raw materials to the second solution is 1:(1 - 3). Then, by mass, add 4% - 10% of a leaching aid, add a cyanide-breaking agent and a leaching agent, maintain the pH of the system at 0.5 - 1.5, and stir and react at 70°C - 100°C for 1 - 4 hours;

[0046] S3. After the completion of S2, pump in the fourth solid material. By mass ratio, the ratio of the fourth solid material to the mixture of the face shell material and the overhaul slag is (0.1 - 0.3):1. Adjust the pH to 2 - 4. After stabilizing for 30 - 60 min, press-filter the slurry to obtain the first filtrate and the first filter residue.

[0047] If the lithium content of the first filter residue is less than 0.1%, then S4 is omitted.

[0048] S4. The first filter residue is secondarily leached with the third solution. By mass ratio, the liquid-solid ratio is controlled to be 1.5 - 3:1. Add industrial hydrochloric acid or sulfuric acid to adjust the pH to 1 - 2. React at 50°C - 80°C for 1 h - 2 h, and then press-filter to obtain the second filtrate and the second filter residue.

[0049] S5. Adjust and wash the second filter residue with the fifth solution. By mass ratio, the liquid-solid ratio is controlled to be 1.5 - 3:1. Wash at room temperature for 30 - 60 min, and then press-filter to obtain the third filtrate and the third filter residue.

[0050] S6. Mix the third filter residue with the aggregate and the binder. By mass ratio, the mixing ratio is 100:5 - 20:1 - 5. After briquetting and drying, a slag melting agent product is obtained.

[0051] Also included:

[0052] S7. Add the first filtrate and the alkali solution to the impurity removal tank, control the pH value to be 5 - 8, and the temperature to be 40°C - 80°C to precipitate the impurity elements in the solution. After stirring and reacting for 1 h and then filtering, obtain the fourth filtrate and the fourth filter residue.

[0053] S8. Use liquid caustic soda to completely dissolve the sixth solid material and / or aluminum hydroxide to obtain a sodium aluminate solution, and use hydrochloric acid or sulfuric acid and / or aluminum hydroxide to completely dissolve to obtain an aluminum chloride solution or an aluminum sulfate solution; add the sodium aluminate solution and the aluminum chloride solution or the aluminum sulfate solution to the fourth filtrate, control the pH during the process to be 9 - 10, and the end-point pH to be 6 - 8, and the temperature to be 80°C - 100°C. After stabilizing for 1 h - 3 h, press-filter to obtain the fifth filtrate and the fifth filter residue; the fifth filter residue is a lithium-rich slag with a lithium content greater than 4%.

[0054] Also included:

[0055] S9. Adjust the slurry of the fifth filter residue with pure water, with a liquid-solid ratio of 10 - 30:1. Perform high-temperature and high-pressure decomposition at 200°C - 250°C for 1 h - 3 h, and then filter to obtain the sixth filtrate and the sixth filter residue. The sixth filter residue and pure water are cooled through a multi-stage plate heat exchanger and circulating water, and after membrane concentration, a lithium-rich concentrated solution is obtained, and then industrial-grade lithium carbonate is synthesized.

[0056] In S1, the mixing ratio of the ground face shell material and the overhaul slag after flotation is such that, by mass ratio, the fluorine content after mixing is greater than 26% to 36%, and the carbon content is 5% to 15%.

[0057] When the carbon content in the ground face shell material and the overhaul slag after flotation is less than 15%, the overhaul slag does not need to be separated by flotation to remove carbon powder.

[0058] The flotation agent is a general term for a foaming agent, an inhibitor, and a collector; the foaming agent is No. 2 oil or ether alcohol; the inhibitor is water glass; the collector is kerosene.

[0059] In S2,

[0060] The leaching aid is alumina or aluminum hydroxide. After the addition of the leaching aid, the molar ratio of fluorine to aluminum in the mixture slurry is controlled between 2 and 3:1.

[0061] The leaching agent is industrial hydrochloric acid or sulfuric acid.

[0062] If the cyanide breaker is for a hydrochloric acid system, sodium chlorate or sodium hypochlorite is selected; if the cyanide breaker is for a sulfuric acid system, hydrogen peroxide is selected. The addition ratio is 0 - 2% of the weight of the face shell material and the overhaul slag, and the cyanide radical is converted into non-toxic nitrogen and carbon dioxide.

[0063] When N is 1,

[0064] The second solution and the third solution are tap water; the fifth solution is tap water.

[0065] The fourth solid material is not added; the sixth solid material is aluminum hydroxide.

[0066] When N is greater than 1,

[0067] The second solution is the second filtrate; the third solution is the third filtrate; the fifth solution is the fifth filtrate.

[0068] The fourth solid material is the fourth filter residue; the sixth solid material is the sixth filter residue.

[0069] Example 1

[0070] S1. Grind the overhaul slag to less than 150 mesh, then add a flotation agent composed of No. 2 oil, water glass, and kerosene to float and separate the carbon powder. After drying, the carbon powder is sold outside. Grind the face shell material to less than 150 mesh, then mix the face shell material and the overhaul slag after flotation for acid leaching. The doping ratio of the face shell material to the overhaul slag is 1:2; after mixing, the fluorine content is 28.8% and the carbon content is 6.5%.

[0071] Face shell material: lithium 1.2%, silicon dioxide 0.65%, calcium oxide 3.2%, aluminum oxide 18.5%, sodium oxide 24.8%, fluorine 33.5%, carbon 3.5%.

[0072] Overhaul slag: lithium 0.85%, fluoride 26.8%, cyanide 0.22%, aluminum nitride 2.5%, aluminum carbide 3.8%, carbon 22.5%;

[0073] S2. Mix 10 tons of mixed raw materials with 20 cubic meters of the second filtrate to form a slurry, then add 1 ton of aluminum hydroxide, add 10 kg of sodium chlorate solid powder, and then add 5.3 tons of industrial hydrochloric acid to adjust the pH to 1.1, and stir and react at 90 °C for 3 hours;

[0074] S3. After S2 is completed, pump in 5 cubic meters of the fourth filter residue, adjust the pH of the slurry to 3.2, keep it stable for 30 min, and then press-filter the slurry to obtain the first filtrate and the first filter residue. The lithium content in the first filtrate is 4.1 g / L, and the lithium content in the first filter residue is 0.36%;

[0075] S4. The first filter residue is subjected to secondary leaching with the third filtrate. By mass, the liquid-solid ratio is 2:1. Add industrial hydrochloric acid to adjust the pH to 1.2, react at 80 °C for 1 h, and then press-filter to obtain the second filtrate and the second filter residue. The lithium content in the second filter residue is 0.22%; The secondary leaching adopts high-acid leaching, and the leaching solution is used as the bottom liquid for the first leaching. A higher pH in the first leaching can reduce the impurity content in the leaching solution and effectively reduce the consumption of lye in the impurity removal process;

[0076] S5. Adjust and wash the second filter residue with the fifth filtrate. By mass, the liquid-solid ratio is controlled at 2:1, wash at room temperature for 60 min, and then press-filter to obtain the third filtrate and the third filter residue. The third filter residue contains 0.03% lithium;

[0077] S6. Mix the third filter residue with 5% limestone particles and 1% organic lignin paste binder, mix well, press into 10×25 mm elliptical balls by a briquetting machine, and then dry and package the slag remover product after drying by a dryer, with a moisture content of 0.2%;

[0078] S7. Synchronously add the first filtrate and 32% liquid caustic soda to the impurity removal tank, control the pH value during the process to be 5 - 8, the end-point pH to be 6.5, stir and react at 80 °C for 1 h, and then filter to obtain the fourth filtrate and the fourth filter residue. The lithium content in the fourth filter residue is 0.8%, and the lithium content in the third filtrate is 3.1 g / L;

[0079] S8. The sodium aluminate solution is obtained by completely dissolving the liquid caustic soda and the sixth filter residue, and the aluminum chloride solution is obtained by completely dissolving hydrochloric acid and aluminum hydroxide. The fourth filtrate is heated to 90 °C, and then the sodium aluminate solution and the aluminum chloride solution are added to the fourth filtrate in a concurrent flow manner. The pH of the process is controlled to be 9 - 10, and the addition ends after 30 min. The end-point pH is controlled to be 7.5, and after stabilizing for 1 h at 90 °C, filtration is carried out to obtain the fifth filtrate and the fifth filter residue. The residual lithium content in the fifth filtrate is 15 mg / L, and the fifth filter residue is a lithium-rich residue with a lithium content of 4.2%. Instead of the traditional process route of removing impurities first and then concentrating, lithium is adsorbed and enriched. The post-adsorption liquid is used for adjusting the slurry of the impurity removal residue and then returned to the first leaching process. When the impurities are enriched to a certain extent, the leaching of impurities will be inhibited, and there is no need to concentrate the lithium-containing solution to produce crystalline salts.

[0080] S9. The fifth filter residue is slurried with pure water at a liquid-solid ratio of 20:1, heated to 200 °C and resolved for 1 h. After filtration, the sixth filtrate and the sixth filter residue are obtained. The lithium content in the sixth filtrate is 1.75 g / L. After heat exchange with pure water through a multi-stage plate exchanger and cooling with circulating water to 50 °C, a lithium-rich concentrated solution with a lithium content of 20.5 g / L is obtained after three-stage membrane concentration. Then, sodium carbonate solution is added for synthesis to obtain industrial-grade lithium carbonate, and the main content of lithium carbonate is above 99.2%.

[0081] Example 2

[0082] S1. The face shell material and the overhaul slag are mixed and ground in a mill to obtain a mixed raw material with a particle size ground to less than 150 mesh. The mixing ratio of the two is 1:0.2, and after mixing, the fluorine content is 32.5% and the carbon content is 6.8%.

[0083] S2. 10 tons of the mixed raw material is mixed and slurried with 25 cubic meters of the second filtrate, then 0.8 tons of alumina is added, then 20 kg of industrial hydrogen peroxide solution is added, and then 3.4 tons of industrial sulfuric acid is added to adjust the pH to 1.0, and the mixture is stirred and reacted at 90 °C for 4 hours.

[0084] S3. After S2 is completed, 5 cubic meters of the fourth filter residue is pumped in, the pH of the slurry is adjusted to 3.5, and after stabilizing for 30 min, the slurry is filtered to obtain the first filtrate and the first filter residue. The lithium content in the first filter residue is 0.36%.

[0085] S4. The first filter residue is subjected to secondary leaching with the third filtrate, the pH is adjusted to 1.5 with industrial sulfuric acid, and the reaction is carried out at 80 °C for 1 h. After filtration, the second filtrate and the second filter residue are obtained. The lithium content in the second filter residue is 0.12%.

[0086] S5. The second filter residue is adjusted and washed with the fifth filtrate. In terms of mass ratio, the liquid-solid ratio is controlled to be 2:1, and the washing is carried out at room temperature for 45 min. After filtration, the third filtrate and the third filter residue are obtained. The lithium content in the third filter residue is 0.06%.

[0087] S6. Mix the third filter residue with 8% calcite particles and 2% heavy oil, and after mixing evenly, press them into 10×25 mm elliptical balls by a briquetting machine, then dry them in a dryer and package them to obtain the slag melting agent product with a moisture content of 0.25%.

[0088] S7. Synchronously add the first filtrate and 32% liquid caustic soda to the impurity removal tank, control the pH value of the process at 5 - 8, with the end-point pH being 7.0, stir and react at 80 °C for 1 h and then filter to obtain the fourth filtrate and the fourth filter residue, and the lithium content in the filter residue is 0.68%.

[0089] S8. Completely dissolve the sixth filter residue with liquid caustic soda to obtain a sodium aluminate solution, and completely dissolve industrial sulfuric acid and aluminum hydroxide to obtain an aluminum sulfate solution; heat the fourth filtrate to 90 °C, then add the sodium aluminate solution and the aluminum sulfate solution to the fourth filtrate in a parallel flow manner, control the pH value of the process at 9 - 10, finish adding in 40 min, control the end-point pH at 8.0, continue to stabilize at 90 °C for 1 h and then filter press to obtain the fifth filtrate and the fifth filter residue; the residual lithium content in the fifth filtrate is 20.0 mg / L, the fifth filter residue is a lithium-rich residue with a lithium content of 4.45%.

[0090] S9. Slurry the fifth filter residue with pure water at a liquid-solid ratio of 25:1, heat it to 220 °C for desorption for 2 h, filter to obtain the sixth filtrate and the sixth filter residue, the lithium content in the sixth filtrate is 1.55 g / L, heat exchange with pure water through a multi-stage plate heat exchanger and cool it to 55 °C with circulating water, obtain a lithium-rich concentrated solution with a lithium content of 22.0 g / L after three-stage membrane concentration, then add sodium carbonate solution for synthesis to obtain industrial-grade lithium carbonate, and the main content of lithium carbonate is above 99.2%, which can be directly used as raw materials for low-end battery products without further carbonization and purification.

[0091] Example 3

[0092] S1. Grind the overhaul slag to less than 150 mesh, then add a flotation agent composed of ether alcohol, water glass and kerosene to float and separate the carbon powder, and the carbon powder is dried and sold outside; grind the shell material to less than 150 mesh, then mix the shell material with the overhaul slag after flotation for acid leaching, and the mixing ratio of the two is 1:1; after mixing, the fluorine content is 32.5 and the carbon content is 5.8%.

[0093] S2. Mix 10 tons of mixed raw materials with 25 cubic meters of the second filtrate to make a slurry, then add 0.8 tons of aluminum hydroxide, then add 15 kg of sodium hypochlorite solution, and then add 4.8 tons of industrial hydrochloric acid to adjust the pH to 1.3, and stir and react at 95 °C for 4 hours.

[0094] S3. After S2 is completed, pump in 2 cubic meters of the fourth filter residue, adjust the pH of the slurry to 2.5, stabilize for 30 min and then filter press the slurry to obtain the first filtrate and the first filter residue, and the lithium content in the first filter residue is 0.08%; there is no secondary leaching step.

[0095] S4. Adjust and wash the first filter residue with the fifth filtrate. In terms of mass ratio, the liquid-solid ratio is controlled at 2:1, and it is washed at room temperature for 60 minutes. After pressure filtration, the third filtrate and the third filter residue are obtained, and the lithium content in the third filter residue is 0.04%.

[0096] S6. Mix the third filter residue with 5% dolomite particles and 4% boron soil. After mixing evenly, press it into 10×25 mm elliptical balls by a briquetting machine, and then dry it by a dryer and package it to produce a slag melting agent product with a moisture content of 0.2%.

[0097] S7. Synchronously add the first filtrate and 32% liquid caustic soda to the impurity removal tank, control the pH value of the process to be 5-8, the end point pH to be 8.0, stir and react at 80 °C for 1 hour and then filter to obtain the fourth filtrate and the fourth filter residue, and the lithium content in the filter residue is 0.76%.

[0098] S8. Completely dissolve sodium aluminate solution by using liquid caustic soda and aluminum hydroxide, and completely dissolve aluminum chloride solution by using hydrochloric acid and the sixth filter residue; heat the fourth filtrate to 92 °C, and then add the sodium aluminate solution and the aluminum chloride solution into the fourth filtrate in a parallel flow manner, control the pH value of the process to be 9-10, and finish adding in 30 minutes. Control the end point pH to be 8.0, continue to stabilize at 92 °C for 1 hour and then carry out pressure filtration to obtain the fifth filtrate and the fifth filter residue; the residual lithium content in the fifth filtrate is 12 mg / L, the fifth filter residue is a lithium-rich residue, and the lithium content is greater than 4.25%.

[0099] S9. Adjust the slurry of the fifth filter residue with pure water, with a liquid-solid ratio of 22:1, heat it to 250 °C and carry out desorption for 1.5 hours. After filtration, the sixth filtrate and the sixth filter residue are obtained. The lithium content in the sixth filtrate is 1.66 g / L. After heat exchange through a multi-stage plate heat exchanger with pure water and cooling with circulating water to 60 °C, a lithium-rich concentrated solution with a lithium content of 21.6 g / L is obtained after three-stage membrane concentration, and then industrial-grade lithium carbonate is synthesized by adding sodium carbonate solution, and the main content of lithium carbonate is above 99.2%.

[0100] The above embodiments only express the implementation modes of the present invention, and the description is relatively specific and detailed, but it cannot be understood as a limitation to the scope of the patent of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention should be based on the appended claims.

Claims

1. A method for extracting lithium from flour shell material and overhaul slag and co-producing slag-removing agent for steel mills, characterized in that: It includes N consecutive loops and the following steps: S1. Grind the overhaul slag into powder of 100-200 mesh, add flotation agent to float and separate carbon powder; Grind the shell material into powder of 100-200 mesh, mix it with the overhaul slag after flotation, and acid leaching. The mixing ratio of shell material to overhaul slag is 1: (0-2); S2, mixing the mixed raw material and the second filtrate to prepare a slurry, wherein the mass volume ratio of the raw material to the second filtrate is 1:(1-3), then adding 4%-10% of a leaching aid, a cyanide destroying agent and a leaching agent by mass ratio, maintaining the system pH at 0.5-1.5, and stirring the reaction at 70°C-100°C for 1-4 hours; S3, after the end of S2, the fourth filter residue is pumped in, and the ratio of the fourth filter residue to the mixture of the shell material and the overhaul residue is (0.1-0.3) by mass ratio: 1, the pH is adjusted to 2-4, and after stabilization for 30-60 minutes, the slurry is filtered to obtain the first filtrate and the first filter residue; If the lithium content of the first filter residue is less than 0.1%, S4 is omitted; S4, the first filter residue is subjected to secondary leaching with the third filtrate, the liquid-to-solid ratio is controlled to be 1.5-3:1 by mass ratio, the pH is adjusted to 1-2 by industrial hydrochloric acid or sulfuric acid, the reaction is carried out at 50°C-80°C for 1h-2h, and the second filtrate and the second filter residue are obtained by filter pressing; S5, adjusting and stirring the second filter residue with the fifth filtrate, controlling the liquid-to-solid ratio to be 1.5-3:1 by mass ratio, washing at room temperature for 30-60 minutes, and obtaining a third filtrate and a third filter residue after filter pressing; S6, mixing the third filter residue, aggregate and adhesive in a mass ratio of 100:5-20:1-5, and preparing a slag dissolving agent product after ball pressing and drying; Also includes: S7, adding the first filtrate and alkali solution into a decontamination tank, controlling the pH value to 5-8 and the temperature to 40°C-80°C, so that the impurity elements in the solution are precipitated, stirring the reaction for 1h and filtering to obtain a fourth filtrate and a fourth filter residue; S8, using liquid alkali to completely dissolve the sixth filter residue and / or aluminum hydroxide to obtain a sodium aluminate solution, and using hydrochloric acid or sulfuric acid to completely dissolve aluminum hydroxide to obtain an aluminum chloride solution or an aluminum sulfate solution; adding the sodium aluminate solution and the aluminum chloride solution or the aluminum sulfate solution to the fourth filtrate, controlling the pH during the process to 9-10, the endpoint pH to 6-8, the temperature to 80°C-100°C, stabilizing for 1h-3h and then filtering by pressure to obtain a fifth filtrate and a fifth filter residue; the fifth filter residue is a lithium-rich residue with a lithium content greater than 4%; Also includes: S9, slurrying the fifth filter residue with pure water, with a liquid-to-solid ratio of 10-30:1, analyzing at high temperature and high pressure at 200°C-250°C for 1h-3h, filtering to obtain a sixth filtrate and a sixth filter residue, and subjecting the sixth filter residue and pure water to multi-stage plate exchange and circulating water cooling, membrane concentration to obtain a lithium-rich concentrate, and then synthesizing to obtain industrial-grade lithium carbonate; The leaching aid is aluminum oxide or aluminum hydroxide. After the leaching aid is added, the molar ratio of fluorine to aluminum in the mixed slurry is controlled between 2 and 3:1; The leaching agent is industrial hydrochloric acid or sulfuric acid.

2. The method for extracting lithium from flour shell material and overhaul slag and co-producing slag-removing agent for steel plant according to claim 1, characterized in that: In S1, the mixing ratio of the ground flour shell material and the overhaul slag after flotation is, by mass ratio, fluorine is greater than 26% to 36% and carbon is 5% to 15% after mixing; When the carbon content in the ground flour shell material and the overhaul slag after flotation is less than 15%, the overhaul slag does not need to be flotated to separate the carbon powder.

3. The method for extracting lithium from flour shell material and overhaul slag and co-producing slag-removing agent for steel plant according to claim 2, characterized in that: The flotation agent is a general term for foaming agent, inhibitor and collector; the foaming agent is No. 2 oil or ether alcohol; the inhibitor is water glass; and the collector is kerosene.

4. The method for extracting lithium from flour shell material and overhaul slag and co-producing slag-removing agent for steel mill according to claim 1, characterized in that: In S2, If the cyanide-breaking agent is a hydrochloric acid system, sodium chlorate or sodium hypochlorite is selected; if the cyanide-breaking agent is a sulfuric acid system, hydrogen peroxide is selected. The addition ratio is 0-2% of the weight of the shell material and overhaul slag, and cyanide is converted into non-toxic nitrogen and carbon dioxide.

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