CN118651875A - Method for removing impurities from slag in lithium carbonate production and method for producing lithium carbonate - Google Patents

Abstract

The invention discloses a method for treating impurity-removing slag in lithium carbonate production and a method for producing lithium carbonate, which solve the technical problems of lithium loss and insufficient utilization of colloid precipitates such as Fe (OH) ₃、Al(OH)₃ and the like in the prior art. The impurity removal slag treatment method in the lithium carbonate production comprises the following steps: (1) roasting the impurity-removed slag to obtain a roasted material; (2) Adding water into the roasting material, pulping, and filtering to obtain filter residues and filtrate, wherein the filtrate is used as lithium leaching solution.

Description

Method for removing impurities from slag in lithium carbonate production and method for producing lithium carbonate

Technical Field

The invention relates to the technical field of lithium carbonate production, and in particular to a method for removing impurities and slag in lithium carbonate production and a method for producing lithium carbonate.

Background Art

At present, the main process of preparing lithium carbonate from lepidolite raw materials by the acid method is: roasting the lepidolite raw materials to obtain lepidolite clinker → acidifying the lepidolite clinker to obtain lepidolite acidified material → adding water to prepare the slurry → purification → lithium extraction.

In the roasting section:

First, the chemical composition of lepidolite is K{Li _2-x Al _1+x [Al _2x Si _4-2x O ₁₀ ](OH, F) ₂ }(x＝0～0.5), which generally contains 2～7% of fluorine. The main function of roasting is to remove the fluorine in the lepidolite raw material. Steam defluorination utilizes the reaction of lepidolite raw material and water vapor in a roasting kiln under high temperature conditions to produce high-temperature hydrogen fluoride gas, and removes the fluorine from the lepidolite raw material in the form of hydrogen fluoride gas. The defluorination flue gas generated in the steam defluorination process contains hydrogen fluoride gas and water vapor. Therefore, the defluorination flue gas has the dual characteristics of high temperature and high corrosion, which makes the design of the hydrogen fluoride recovery system used when the defluorination flue gas is directly used in hydrogen fluoride production complex and costly.

Secondly, the traditional roasting process is to directly burn and heat the roasting kiln by introducing natural gas. Since the heating elements in the kiln are affected by various factors such as airflow and material position, it is usually difficult to achieve accurate temperature control, which not only leads to uneven temperature distribution in the kiln, but also hot spots and cold spots may exist at the same time, thus affecting product quality and consistency, and easily causes a large amount of heat energy loss, increasing energy consumption. In addition, the combustion of natural gas leads to an increase in the content of pollutants such as HF, NO _x , and SO ₂ in the defluorinated flue gas output by the roasting kiln, and the flue gas volume is large. In order to meet the environmental emission standards, the defluorinated flue gas needs to be dusted, denitrated, and desulfurized for environmental protection, which increases the difficulty of pollution control, project investment, and operating costs at the treatment end.

In the acidification section:

First, the lithium in the lithium mica clinker is converted into soluble lithium through acidification roasting, and then the soluble lithium can be leached out by adding water to adjust the slurry. The traditional acidification section is to directly burn and heat the acidification kiln by introducing natural gas. Since the heating elements in the kiln are affected by many factors such as airflow and material position, it is usually difficult to achieve accurate temperature control, which not only leads to uneven temperature distribution in the kiln, but also hot spots and cold spots may exist at the same time, thus affecting product quality and consistency, and easily causing a large amount of heat energy loss, increasing energy consumption. At the same time, the combustion of natural gas causes the acidification kiln to output a large amount of acidification flue gas, which contains acid mist, and the subsequent treatment equipment is large, with high investment and large land occupation.

Secondly, during the acidification and roasting process, because other elements are leached out with the lithium element at the same time, the amount of acid added will far exceed the theoretical amount of acid required for leaching lithium. The large amount of acid used will increase production costs, is not friendly to environmental protection, and increase the subsequent treatment pressure of the acidic liquid.

In the water adding and slurry mixing section:

In order to improve the lithium leaching rate, the traditional process requires the lepidolite raw material or lepidolite clinker to be ground to a finer particle size (usually less than 200 meshes) in order to obtain a higher lithium leaching rate in the acidification stage, so that it can be dissolved into the liquid phase in the water addition and slurry mixing stage. However, the grinding process not only increases the complexity of the process, but also increases the energy consumption of the entire process, and also increases the difficulty of subsequent filtration.

In the purification section:

The traditional purification process is to use a pump to transport the slurry into the neutralization tank after adding water and adjusting the slurry, and add calcium oxide or calcium hydroxide into the neutralization tank to neutralize the residual acid in the lithium mica acidified material to adjust the pH to about 6.5. After the neutralization and pH adjustment are completed, the slurry is transported to the pressing system by a pump for solid-liquid separation. The liquid phase is the leachate and the solid phase is the impurity removal residue.

First, the use of calcium oxide or calcium hydroxide alone cannot achieve deep purification. The resulting purified liquid still contains a large amount of impurity metal ions, especially calcium ions. The leaching liquid must be further purified later, which is complex, energy-intensive, and requires a large amount of reagents. In order to precipitate Fe and Al as much as possible, excessive calcium ions are usually added, which will generate more calcium sulfate precipitation in the sulfuric acid method, increase the amount of slag, and thus increase the cost of subsequent waste slag disposal.

Secondly, during the neutralization and pH adjustment process, colloidal precipitates such as Fe(OH) ₃ and Al(OH) ₃ will be produced. These precipitates have an adsorption capacity for lithium ions. They will not only directly entrain lithium salts, but also easily clog the filter pores, making it difficult to squeeze and dehydrate, increasing the moisture content of the dewatered slag, and increasing the amount of lithium salts taken away, further increasing the loss of lithium. For this reason, the dewatered slag needs to be washed repeatedly to reduce the loss of lithium, but this will not only increase the water and energy consumption of the system, but also make it difficult to wash out some of the lithium salts entrained by the dewatered slag, resulting in a high lithium loss. In addition, the colloidal precipitates such as Fe(OH) ₃ and Al(OH) ₃ in the dewatered slag have not been fully utilized.

Summary of the invention

In the first aspect, the main purpose of the present invention is to provide a first lepidolite raw material roasting system to solve the technical problem of high cost of defluorination flue gas treatment in the prior art. The technical solution is as follows:

The first lepidolite raw material roasting system includes: a condensation component, which is used to condense the defluorinated flue gas generated by the roasting kiln and output a gas-liquid-solid mixture; the condensation component includes a condensation pipe and a cooling jacket connected to the flue gas outlet of the roasting kiln; a buffer component, which is used to temporarily store the gas-liquid-solid mixture; the buffer component includes a buffer tank connected to the condensation pipe; an absorption component, which is used to absorb non-condensables in the buffer tank; the absorption component includes an absorption device connected to the non-condensables in the buffer tank; a reflux component, which is used to reflux the tail gas to the buffer tank when the hydrogen fluoride in the tail gas discharged by the absorption component exceeds a preset value; the reflux component includes a hydrogen fluoride detection device arranged at the tail gas outlet of the absorption device and a reflux pipe connecting the buffer tank and the downstream pipeline of the hydrogen fluoride detection device.

As a further improvement of the above-mentioned lepidolite raw material roasting system: the condenser is a pipe made of polytetrafluoroethylene, or the inner wall of the condenser has a polytetrafluoroethylene coating.

As a further improvement of the above-mentioned lithium mica raw material roasting system: the condenser is arranged obliquely, and the connection between the condenser and the smoke outlet of the roasting kiln is higher than the connection between the condenser and the buffer tank.

As a further improvement of the above-mentioned lepidolite raw material roasting system: the absorption component includes at least two absorption devices arranged in series.

As a further improvement of the above-mentioned lepidolite raw material roasting system: the processing system also includes a neutralization reaction component for reacting the condensate in the buffer tank with the alkali solution, and the neutralization reaction component includes a neutralization reaction tank.

As a further improvement of the above-mentioned lithium mica raw material roasting system: the processing system also includes a solid-liquid separation component for performing solid-liquid separation on the solid-liquid mixture output from the buffer tank and the absorption component or on the solid-liquid mixture output from the neutralization reaction tank and the absorption component.

As a further improvement of the above-mentioned lithium mica raw material roasting system: a liquid level meter is provided on the buffer tank, and a first valve interlocked with the liquid level meter is provided on the connecting pipe between the buffer tank and the neutralization reaction component or on the connecting pipe between the buffer tank and the solid-liquid separation component.

As a further improvement of the above-mentioned lepidolite raw material roasting system: the solid-liquid separation component is a filtering device or a centrifugal device.

As a further improvement of the above-mentioned lepidolite raw material roasting system: a second valve and a third valve interlocked with a hydrogen fluoride detection device are respectively provided on the downstream pipeline and the reflux pipe.

In the second aspect, the main purpose of the present invention is to provide a second lepidolite raw material roasting system to solve the technical problems caused by direct heating of natural gas in the prior art. The technical solution is as follows:

The second lithium mica raw material roasting system includes a roasting kiln for roasting the lithium mica raw material. The lithium mica raw material roasting system also includes: a roasting kiln heating jacket, which is used to heat the roasting kiln; a first heat exchanger, which is used to perform heat exchange between the lithium mica dry material to be entered into the roasting kiln and the first defluorination flue gas output from the roasting kiln; a second heat exchanger, which is used to perform heat exchange between the second defluorination flue gas output from the first heat exchanger and the defluorination agent to be entered into the roasting kiln; and a third heat exchanger, which is used to perform heat exchange between the primary cold air output from the roasting kiln heating jacket and the cold wind.

As a further improvement of the above-mentioned lepidolite raw material roasting system: the first heat exchanger is a cyclone preheater.

As a further improvement of the above-mentioned lepidolite raw material roasting system: the lepidolite raw material roasting system also includes a first dust collector, an arsenic recovery unit and a hydrogen fluoride recovery unit for sequentially treating the third defluorination flue gas output from the second heat exchanger.

As a further improvement of the above-mentioned lithium mica raw material roasting system: the lithium mica raw material roasting system also includes a lithium mica dry material buffer bin, the particulate matter intercepted by the first dust collector flows into the lithium mica dry material buffer bin, and the lithium mica dry material buffer bin outputs the lithium mica dry material to the first heat exchanger to perform heat exchange with the first defluorination flue gas output from the roasting kiln.

As a further improvement of the above-mentioned lithium mica raw material roasting system: the lithium mica raw material roasting system also includes a lithium mica raw material warehouse for storing lithium mica raw materials and a drying kiln for drying the lithium mica raw materials, the hot air obtained after the third heat exchanger processes the cold air flows into the drying kiln as a heat source, and the lithium mica dry material dried in the drying kiln flows into the lithium mica buffer warehouse.

As a further improvement of the above-mentioned lepidolite raw material roasting system: the lepidolite raw material roasting system also includes a second dust collector for removing dust from the lepidolite dust gas output by the drying kiln, and the particles intercepted by the second dust collector flow into the lepidolite raw material bin.

As a further improvement of the above-mentioned lithium mica raw material roasting system: the lithium mica raw material roasting system also includes a roasting kiln hot air furnace that heats the energy gas and outputs the jacket gas for heating the roasting kiln to the roasting kiln heating jacket, and the secondary cold air obtained after the third heat exchanger processes the primary cold air flows into the roasting kiln hot air furnace as energy gas.

As a further improvement of the above-mentioned lepidolite raw material roasting system: the lepidolite raw material roasting system also includes a roasting kiln cooler for cooling the lepidolite clinker outputted from the roasting kiln and a lepidolite clinker storage tank for storing the lepidolite clinker.

In the third aspect, the main purpose of the present invention is to provide a lithium mica clinker acidification system to solve the technical problems caused by direct heating of natural gas in the prior art. The technical solution is as follows:

The lepidolite clinker acidification system comprises an acidification kiln for acidification of the lepidolite clinker, wherein the lepidolite clinker is obtained by roasting a lepidolite raw material. The lepidolite clinker acidification system further comprises: a filter for filtering the acidification flue gas outputted from the acidification kiln and outputting dust and low-dust gas; an acidification kiln heating jacket for heating the acidification kiln; and an acidification kiln hot blast furnace for inputting jacket gas for heating the acidification kiln into the acidification kiln heating jacket; wherein the cold air outputted from the acidification kiln heating jacket partially flows into the acidification kiln hot blast furnace as energy gas.

As a further improvement of the above-mentioned lepidolite clinker acidification system: the lepidolite clinker acidification system also includes an acid storage tank, a lepidolite clinker storage tank and an acid mixing machine for mixing the lepidolite clinker and the acid.

As a further improvement of the above-mentioned lepidolite clinker acidification system: the lepidolite clinker acidification system also includes a salt storage tank, and the acid mixer is used to mix the lepidolite clinker, acid and salt.

As a further improvement of the above-mentioned lepidolite clinker acidification system: the dust output by the filter flows into the acid mixing machine.

As a further improvement of the above-mentioned lepidolite clinker acidification system: the lepidolite clinker acidification system also includes a deacidification device for deacidifying the low-dust gas output by the filter.

As a further improvement of the above-mentioned lepidolite clinker acidification system: the deacidification device is a spray tower.

As a further improvement of the above-mentioned lepidolite clinker acidification system: the lepidolite clinker acidification system also includes an acidification kiln cooler for cooling the lepidolite acidified material output from the acidification kiln and a lepidolite acidified material storage tank for storing the lepidolite acidified material.

In a fourth aspect, the main purpose of the present invention is to provide a method for pretreating a lepidolite raw material to solve the technical problems caused by high acid dosage in the prior art. The technical solution is as follows:

The invention discloses a pretreatment method for a lepidolite raw material, which is used for leaching lithium element in the lepidolite raw material. The pretreatment method comprises the steps of: roasting the lepidolite raw material to obtain lepidolite clinker; roasting the lepidolite clinker, salt and acid to obtain lepidolite acidified material.

As a further improvement of the above-mentioned pretreatment method of lepidolite raw materials: the mixture of lepidolite clinker, salt and acid is roasted at 200-320° C. for 0.5-1.5 h, and the lepidolite acidified material is obtained after cooling.

As a further improvement of the above-mentioned pretreatment method of lepidolite raw materials: firstly, a mixture of lepidolite clinker and salt is calcined at 800-900°C for 0.5-1.5h, then acid is added when the temperature is lowered to 200-320°C and the temperature is kept at this temperature for 0.5-1.5h, and then the lepidolite acidified material is obtained after cooling.

As a further improvement of the above-mentioned pretreatment method of lepidolite raw material: the acid is sulfuric acid; the salt is any one of potassium sulfate, sodium sulfate and calcium sulfate.

As a further improvement of the above-mentioned pretreatment method of lepidolite raw materials: the mass ratio of sulfate to lepidolite clinker is (0.03-0.15):1.

As a further improvement of the above-mentioned pretreatment method of lepidolite raw materials: the mass ratio of sulfuric acid to lepidolite clinker is (0.2-0.45):1.

As a further improvement of the above-mentioned pretreatment method of lepidolite raw material: the pretreatment method further comprises the step of: mixing the lepidolite clinker and the salt by ball milling.

As a further improvement of the above-mentioned pretreatment method of the lepidolite raw material: the lepidolite raw material is calcined at 800-1000°C.

As a further improvement of the above-mentioned pretreatment method of lepidolite raw material, the method further comprises the steps of:

Adding water to the lepidolite acidified material to form a slurry, and then stirring at a high speed to obtain a slurry;

After solid-liquid separation of the slurry, leachate and leach residue are obtained.

In a fifth aspect, the main purpose of the present invention is to provide a system for pre-treating lepidolite raw materials to solve the technical problems caused by grinding lepidolite raw materials or lepidolite clinker in the prior art. The technical solution is as follows:

The lepidolite raw material pretreatment system comprises: a lepidolite raw material roasting system for roasting the lepidolite raw material and outputting lepidolite clinker; the lepidolite raw material roasting system comprises a roasting kiln; a lepidolite clinker acidification system for acidifying the lepidolite clinker and outputting lepidolite acidified material; the lepidolite clinker acidification system comprises an acidification kiln; a lepidolite acidified material slurry mixing system for adding water to the lepidolite acidified material to slurry mix and output lithium leaching solution; the lepidolite acidified material slurry mixing system comprises a high-speed dispersing device for high-speed dispersing treatment of the lithium leaching solution. Among them, the lepidolite raw material roasting system is preferably the lepidolite raw material roasting system described in the second aspect above, and the lepidolite clinker acidification system is preferably the lepidolite clinker acidification system described in the third aspect above.

In a sixth aspect, the main purpose of the present invention is to provide a lithium mica acidified material leaching system to solve the technical problems of lithium loss and filter pore blockage caused by neutralization and pH adjustment before filtration in the prior art. The technical solution is as follows:

The lepidolite acidified material leaching system comprises: a lepidolite acidified material slurry mixing system for mixing the lepidolite acidified material with water and outputting turbid lithium leaching solution; a primary filtering component for filtering the turbid lithium leaching solution and outputting clear lithium leaching solution and leaching residue; and a washing filtering component for washing the leaching residue and outputting lithium washing solution and lithium washing residue, wherein the lithium washing solution is used as the lithium leaching solution.

As a further improvement of the above-mentioned lepidolite acidification material leaching system: the lepidolite acidification material slurry mixing system includes a lepidolite acidification material slurry mixing tank and/or includes a high-speed dispersing device for high-speed dispersing treatment of turbid lithium leaching solution.

As a further improvement of the above-mentioned lithium mica acidified material leaching system: the primary filtration component includes a primary plate and frame filter press.

As a further improvement of the above-mentioned lithium mica acidified material leaching system: the washing and filtering assembly comprises:

The first-stage slurry tank is used to add water to the leached residue to slurry and output the first-stage slurry;

The primary filtering equipment is used to filter the primary slurry and output primary filter residue and primary filtrate.

As a further improvement of the above-mentioned lithium mica acidified material leaching system: the washing and filtering component also includes:

The secondary slurry tank is used to add water to the primary filter residue to prepare the slurry and output the secondary slurry;

The secondary filtering equipment is used to filter the secondary slurry and output the secondary filter residue and the secondary filtrate.

As a further improvement of the above-mentioned lithium mica acidified material leaching system: it also includes an intermediate tank for storing clear lithium leaching solution, and the primary filtrate and the secondary filtrate are both used as lithium washing solution to flow into the intermediate tank and used as lithium leaching solution.

In the seventh aspect, the main purpose of the present invention is to provide a method and system for treating impurities in the production of lithium carbonate to solve the technical problems of lithium loss and insufficient utilization of colloidal precipitates such as Fe(OH) ₃ and Al(OH) ₃ in the prior art. The technical solution is as follows:

The method for removing impurities from slag in lithium carbonate production comprises the following steps:

(1) roasting the impurity-removed slag to obtain a roasting material;

(2) The roasted material is slurried with water and then filtered to obtain a filter residue and a filtrate, and the filtrate is used as a lithium leaching solution.

As a further improvement of the above-mentioned method for treating impurity-removing slag in lithium carbonate production, it also includes drying the impurity-removing slag before roasting.

As a further improvement of the above-mentioned slag removal treatment method in lithium carbonate production: the roasting temperature is 200-400°C and the roasting time is 20-80 minutes.

As a further improvement of the above-mentioned slag removal treatment method in lithium carbonate production: add water to adjust the liquid-to-solid ratio in the slurry to (1-3):1, stir at 30-80°C for 20-60 minutes and then filter.

As a further improvement of the above-mentioned slag treatment method for removing impurities in lithium carbonate production: the step (2) comprises: adding water to the roasted material to adjust the slurry and then filtering to obtain a first filter residue and a first filtrate; adding water to the first filter residue to adjust the slurry and then filtering to obtain a second filter residue and a second filtrate.

As a further improvement of the above-mentioned slag treatment method for removing impurities in lithium carbonate production: the step (2) also includes: adding water to the second filter residue to prepare a slurry and filtering to obtain a third filter residue and a third filtrate; and combining the first filtrate, the second filtrate and the second filtrate into a filtrate and using it as a lithium leaching solution.

As a further improvement of the above-mentioned method for treating impurity-removing slag in lithium carbonate production: the preparation of the impurity-removing slag comprises the steps of:

(1) adding alkaline solution to the lithium leaching solution until the pH value is 2 to 3;

(2) continuing to add seed crystals to the lithium leaching solution, wherein the seed crystals include Al ₂ O ₃ and/or Fe ₂ O ₃ ;

(3) continuing to add alkali solution to the lithium leaching solution until the pH value is 6 to 8 to obtain a solid-liquid mixture;

(4) filtering the solid-liquid mixture to obtain impurity-free residue and purified liquid.

As a further improvement of the above-mentioned slag removal treatment method in lithium carbonate production: the seed crystal adopts the third filter residue.

As a further improvement of the above-mentioned method for treating impurity-removing slag in lithium carbonate production: the preparation of the impurity-removing slag comprises the steps of:

(1) adding hydrogen peroxide to a lithium leaching solution to obtain an oxidation solution;

(2) adding alkaline solution to the oxidizing solution until the pH value is 6 to 8 to obtain a first solid-liquid mixture;

(3) filtering the first solid-liquid mixture to obtain a first impurity-removed residue and a filtrate;

(4) adding alkali solution to the filtrate until the pH value is 10 to 12, and then adding a soluble carbonate to obtain a second solid-liquid mixture;

(5) filtering the second solid-liquid mixture to obtain a second impurity-removed slag and a purified liquid; the impurity-removed slag at least includes the first impurity-removed slag, for example, it may contain only the first impurity-removed slag, or it may be a mixture of the first impurity-removed slag and the second impurity-removed slag.

The impurity removal slag treatment system in lithium carbonate production includes: a roasting furnace for roasting the impurity removal slag and outputting the roasted material; a first slurry mixing tank for adding water to the roasted material for slurry mixing and outputting the first slurry; a first filtering device for filtering the first slurry and outputting the first filter residue and the first filtrate.

As a further improvement of the above-mentioned impurity removal slag treatment system in lithium carbonate production: it also includes a drying device for drying the impurity removal slag.

As a further improvement of the above-mentioned impurity removal slag treatment system in lithium carbonate production: it also includes:

The second slurry mixing tank is used to mix the first filter residue with water to output the second slurry;

The second filtering device is used to filter the second slurry and output a second filter residue and a second filtrate.

As a further improvement of the above-mentioned impurity removal slag treatment system in lithium carbonate production: it also includes:

The third slurry mixing tank is used to mix the second filter residue with water and output the third slurry;

The third filtering device is used to filter the third slurry and output a third filter residue and a third filtrate.

As a further improvement of the above-mentioned impurity removal slag treatment system in lithium carbonate production: it also includes an intermediate tank, and the first filtrate, the second filtrate and the third filtrate flow into the intermediate tank and are used as lithium leaching solution.

As a further improvement of the above-mentioned impurity removal slag processing system in lithium carbonate production: it also includes a filter residue storage tank for storing the third filter residue.

As a further improvement of the above-mentioned slag removal system in lithium carbonate production: the roasting furnace is an externally heated roasting furnace.

In the eighth aspect, the main purpose of the present invention is to provide a first lithium leachate purification method and a lithium leachate purification system to solve the technical problem that the purification is not thorough due to the simple use of calcium oxide or calcium hydroxide in the prior art. The technical solution is as follows:

The first method is a lithium leaching solution purification method, comprising the following steps:

(1) adding hydrogen peroxide to a lithium leaching solution to obtain an oxidation solution;

(2) adding alkaline solution to the oxidizing solution until the pH value is 6 to 8 to obtain a first solid-liquid mixture;

(3) filtering the first solid-liquid mixture to obtain a first impurity-removed residue and a filtrate;

(4) adding alkali solution to the filtrate until the pH value is 10 to 12, and then adding a soluble carbonate to obtain a second solid-liquid mixture;

(5) filtering the second solid-liquid mixture to obtain a second impurity-removed residue and a purified liquid.

As a further improvement of the above-mentioned lithium leaching solution purification method: in step (1): the amount of hydrogen peroxide used is 1.1 to 1.4 times the mass of Fe2 ⁺ in the lithium leaching solution, the hydrogen peroxide is prepared into a solution with a mass fraction of 22% to 30%, and the oxidation solution is obtained after reacting for 10 to 30 minutes.

As a further improvement of the above lithium leaching solution purification method: in step (2): the alkaline solution is potassium hydroxide and/or sodium hydroxide, and the pH is adjusted to 6 to 8 and then reacted for 10 to 30 minutes to obtain a first solid-liquid mixture.

As a further improvement of the above-mentioned lithium leaching solution purification method: in step (4): the alkaline solution is potassium hydroxide and/or sodium hydroxide, and after adding a soluble carbonate and reacting for 10 to 30 minutes, a second solid-liquid mixture is obtained.

As a further improvement of the above-mentioned lithium leaching solution purification method: step (2) and step (4) are carried out at 40-60° C.; and a flocculant is also used in step (2) and step (4).

As a further improvement of the above-mentioned lithium leaching solution purification method: in step (4): the carbonate is potassium carbonate and/or sodium carbonate, and its amount is 1.05 to 1.1 times the molar amount of Ca2 ⁺ in the filtrate calculated as carbonate ions.

As a further improvement of the above-mentioned lithium leaching solution purification method: it also includes step (6): subjecting the purified solution to resin adsorption treatment.

As a further improvement of the above-mentioned lithium leaching solution purification method: in step (6), the resin is first swelled with water, then washed with a hydrochloric acid solution with a mass fraction of 4 to 5%, and finally washed with a potassium hydroxide and/or sodium hydroxide solution with a mass fraction of 2 to 4% to neutralize the resin.

As a further improvement of the above-mentioned lithium leaching solution purification method: the purification method also includes the step of filtering the lithium leaching solution obtained by slurrying the lithium mica acidified material with water.

The first type is a lithium leaching solution purification system, comprising: a first reaction component, used to react lithium leaching solution, hydrogen peroxide and alkali solution to generate a first solid-liquid mixture; the first reaction component comprises a first reaction tank, a hydrogen peroxide dosing device for adding hydrogen peroxide to the first reaction tank, a first alkali solution dosing device for adding alkali solution to the first reaction tank, a first pH detector for detecting the pH of the material in the first reaction tank, and a first agitator for stirring the material in the first reaction tank; a first filtering component, used to filter the first solid-liquid mixture and output a first impurity removal residue and impurity removal liquid; a second reaction component, used to react filtrate, alkali solution and carbonate to generate a second solid-liquid mixture; the second reaction component comprises a second reaction tank, a second alkali solution dosing device for adding alkali solution to the second reaction tank, a carbonate dosing device for adding carbonate to the second reaction tank, a second pH detector for detecting the pH of the material in the second reaction tank, and a second agitator for stirring the material in the second reaction tank; a second filtering component, used to filter the second solid-liquid mixture and output a second impurity removal residue and a purified liquid.

As a further improvement of the above lithium leaching solution purification system: the first reaction component also includes a first flocculant adding device for adding flocculant into the first reaction tank.

As a further improvement of the above lithium leaching solution purification system: the second reaction component also includes a second flocculant adding device for adding flocculant into the second reaction tank.

As a further improvement of the above-mentioned lithium leaching solution purification system: the first filter component includes a first plate and frame filter press.

As a further improvement of the above-mentioned lithium leaching solution purification system: the second filter assembly includes a second plate and frame filter press and a precision filter connected in sequence.

As a further improvement of the above lithium leaching solution purification system: the purification system also includes a resin adsorption device for performing resin adsorption treatment on the purified solution.

As a further improvement of the lithium leaching solution purification system, the purification system further comprises a primary filtering component for filtering the lithium leaching solution obtained by slurrying the lepidolite acidified material with water.

As a further improvement of the above-mentioned lithium leaching solution purification system: the primary filtration component includes a primary plate and frame filter press.

In the ninth aspect, the main purpose of the present invention is to provide a second lithium leachate purification method and a lithium leachate purification system to solve the technical problem that the purification is not thorough due to the simple use of calcium oxide or calcium hydroxide in the prior art. The technical solution is as follows:

The second method is a lithium leaching solution purification method, comprising the following steps:

(1) adding alkaline solution to the lithium leaching solution until the pH value is 2 to 3;

(2) continuing to add seed crystals to the lithium leaching solution, wherein the seed crystals include any of Al ₂ O ₃ , Fe ₂ O ₃ , Fe(OH) ₃ , and Al(OH) ₃ ;

(3) continuing to add alkali solution to the lithium leaching solution until the pH value is 6 to 8 to obtain a solid-liquid mixture;

(4) filtering the solid-liquid mixture to obtain impurity-free residue and purified liquid.

As a further improvement of the above-mentioned lithium leaching solution purification method: the alkali solution in step (1) is potassium hydroxide and/or sodium hydroxide; step (1) is carried out at a rotation speed of 200 to 400 rpm.

As a further improvement of the above lithium leaching solution purification method: in step (2), the mass of the seed crystals added to every 1L of lithium leaching solution is 0.05% to 0.5% of the liquid volume.

As a further improvement of the above lithium leaching solution purification method: the preparation method of the seed crystal includes the steps of: adding alkaline solution to the lithium leaching solution to a pH of 6-8, collecting the generated precipitated residue, and roasting the precipitated residue to obtain the seed crystal.

As a further improvement of the above lithium leaching solution purification method: when pH ≤ 3, the stirring rate is 200 to 400 rpm, and when pH > 3, the stirring rate is ≤ 100 rpm; after pH adjustment, the reaction is carried out for 20 to 40 minutes for liquid-solid separation.

As a further improvement of the above lithium leaching solution purification method: the preparation method of the seed crystal includes the steps of: roasting the impurity-removed slag, then adding water to adjust the slurry and filtering, and the obtained filter residue is the seed crystal.

As a further improvement of the above lithium leaching solution purification method: the roasting temperature is 200-400° C. and the roasting time is 20-80 minutes.

As a further improvement of the above-mentioned lithium leaching solution purification method: step (3) is carried out at a rotation speed of 50 to 150 rpm; the reaction time in step (3) is 30 to 120 minutes; and a flocculant is also used in step (3).

As a further improvement of the above-mentioned lithium leaching solution purification method: it also includes step (5): subjecting the purified solution to resin adsorption treatment.

The second type is a lithium leaching solution purification system, comprising: a reaction component for reacting lithium leaching solution, alkali solution and seed crystals to generate a solid-liquid mixture; the reaction component comprises a reaction tank, an alkali solution adding device for adding alkali solution to the reaction tank, a seed crystal adding device for adding seed crystals to the reaction tank, a pH detector for detecting the pH of the material in the reaction tank, and a stirrer for stirring the material in the reaction tank; a filtering component for filtering the solid-liquid mixture and outputting impurity-removing residue and purified liquid.

As a further improvement of the above lithium leaching solution purification system: the reaction component also includes a flocculant adding device for adding flocculant into the reaction tank.

As a further improvement of the above-mentioned lithium leaching solution purification system: the filtering component includes a plate and frame filter press and a precision filter connected in sequence.

As a further improvement of the above lithium leaching solution purification system: the purification system also includes a resin adsorption device for performing resin adsorption treatment on the purified solution.

As a further improvement of the above lithium leaching solution purification system: the purification system also includes a primary filtering component for filtering the lithium leaching solution obtained by adding water to the slurry.

As a further improvement of the above-mentioned lithium leaching solution purification system: the primary filtration component includes a primary plate and frame filter press.

In the tenth aspect, the main purpose of the present invention is to provide a lithium carbonate production method and a lithium carbonate production system with simple process, low energy consumption, high lithium recovery rate and good product quality. The technical scheme is as follows:

A lithium carbonate production system, comprising any of the systems described in the above nine aspects.

A lithium carbonate production method adopts the above-mentioned lithium carbonate production system.

The present invention is further described below in conjunction with the accompanying drawings and specific embodiments. Additional aspects and advantages of the present invention will be partially given in the following description, partially become apparent from the following description, or be learned through the practice of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings constituting a part of the present invention are used to assist in understanding the present invention. The contents provided in the drawings and their related descriptions in the present invention can be used to explain the present invention, but do not constitute improper limitations on the present invention. In the drawings:

FIG1 is a schematic structural diagram of a first embodiment of a system for roasting lepidolite raw materials according to the present invention.

FIG. 2 is a schematic structural diagram of a second embodiment of a system for roasting lepidolite raw materials according to the present invention.

FIG3 is a schematic structural diagram of a third embodiment of a system for roasting lepidolite raw materials according to the present invention.

FIG. 4 is a schematic structural diagram of a first embodiment of a lepidolite clinker acidification system according to the present invention.

FIG5 is a schematic structural diagram of a second embodiment of a lepidolite clinker acidification system according to the present invention.

FIG6 is a schematic structural diagram of an embodiment of a system for pretreating lepidolite raw materials according to the present invention.

FIG. 7 is a schematic structural diagram of an embodiment of a lithium mica acidification material leaching system of the present invention.

FIG8 is a schematic structural diagram of an embodiment of a slag removal treatment system for lithium carbonate production according to the present invention.

FIG. 9 is a schematic structural diagram of a first embodiment of a lithium leaching solution purification system according to the present invention.

FIG. 10 is a schematic structural diagram of a second embodiment of a lithium leaching solution purification system according to the present invention.

FIG. 11 is a schematic structural diagram of the optimal embodiment of the lithium carbonate production system of the present invention.

The relevant marks in the above-mentioned drawings are:

1111-condenser, 1112-cooling jacket, 112-buffer tank, 1121-liquid level gauge, 1122-first valve, 113-absorption device, 1141-hydrogen fluoride detection device, 1142-reflux pipe, 1143-second valve, 1144-third valve, 115-neutralization reaction component, 116-solid-liquid separation component, 1210-roasting kiln heating jacket, 1211-first heat exchanger, 1212-second heat exchanger, 1213-third heat exchanger, 1221-first dust collector, 1222-second dust collector, 123-arsenic recovery unit, 124-hydrogen fluoride recovery unit, 1251-lithium Mica dry material buffer bin, 1252-lepidolite raw material bin, 126-drying kiln, 127-roasting kiln hot air furnace, 128-roasting kiln cooler, 129-lepidolite clinker storage tank, 131-filter, 132-acidification kiln heating jacket, 133-acidification kiln hot air furnace, 1341-acid storage tank, 1342-salt storage tank, 135-acid mixing machine, 136-deacidification device, 137-acidification kiln cooler, 138-lepidolite acidification material storage tank, 200-lepidolite raw material roasting system, 300-lepidolite clinker acidification system, 400-lepidolite acidification material slurry mixing system, 510-primary filtration component, 520-washing filtration component , 521-first slurry mixing tank, 522-first filtering equipment, 523-secondary slurry mixing tank, 524-secondary filtering equipment, 600-intermediate tank, 700-residue removal system, 800-lithium leaching solution purification system, 900-lithium extraction system, 710-drying equipment, 720-roasting furnace, 731-first slurry mixing tank, 732-first filtering equipment, 741-second slurry mixing tank, 742-second filtering equipment, 751-third slurry mixing tank, 752-third filtering equipment, 760-filter residue storage tank, 810-first reaction tank, 811-first alkali solution dosing device, 812-hydrogen peroxide dosing device, 813-first pH detector, 814-first agitator, 815-first flocculant dosing device, 820-first plate and frame filter press, 830-second reaction tank, 831-second alkali solution dosing device, 832-carbonate dosing device, 833-second pH detector, 834-second agitator, 835-second flocculant dosing device, 841-second plate and frame filter press, 842-precision filter, 843-plate and frame filter press, 850-resin adsorption device, 860-reaction tank, 861-alkali solution dosing device, 862-seed dosing device, 863-pH detector, 864-agitator, 865-flocculant dosing device.

DETAILED DESCRIPTION

The present invention is described clearly and completely below in conjunction with the accompanying drawings. A person skilled in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

The technical solutions and technical features provided in each part of the present invention, including the following description, may be combined with each other if there is no conflict.

In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

About the terms and units in the present invention: The terms "include", "have" and any variations thereof in the description and claims of the present invention and related parts are intended to cover non-exclusive inclusions.

FIG1 is a schematic structural diagram of a first embodiment of a system for roasting lepidolite raw materials according to the present invention.

As shown in FIG. 1 , the lithium mica raw material roasting system includes a condensation component, a buffer component, an absorption component, a reflux component, a neutralization reaction component 115 and a solid-liquid separation component 116 .

The condensation component is used to condense the defluorinated flue gas and output a gas-liquid-solid mixture; the condensation component includes a condenser pipe 1111 and a cooling jacket 1112 connected to the flue gas outlet of the roasting kiln; the condenser pipe 1111 is a pipe made of polytetrafluoroethylene, or the inner wall of the condenser pipe 1111 has a polytetrafluoroethylene coating, thereby preventing the high-temperature hydrogen fluoride gas and water vapor from causing softening or corrosion of the pipe.

The buffer assembly is used to temporarily store the gas-liquid-solid mixture; the buffer assembly includes a buffer tank 112 connected to the condenser 1111; thereby, on the one hand, it prevents the alkali solution in the absorption assembly from being sucked back into the roasting kiln due to the pressure in the roasting kiln becoming smaller, and on the other hand, it allows part of the slag that enters the buffer assembly along with the defluorination flue gas to settle in the buffer tank 112. The buffer tank 112 is provided with a liquid level gauge 1121, and a first valve 1122 interlocked with the liquid level gauge 1121 is provided on the connecting pipe between the buffer tank 112 and the neutralization reaction assembly 115. The condenser 1111 is arranged at an angle, and the connection between the condenser 1111 and the roasting kiln flue gas outlet is higher than the connection between the condenser 1111 and the buffer tank 112, thereby allowing the defluorination flue gas to enter the buffer tank 112 by utilizing the gas pressure and height difference after being cooled in the cooling jacket 1112.

The absorption assembly is used to absorb the non-condensable matter in the buffer tank 112, mainly including uncondensed hydrogen fluoride gas and water vapor and a small amount of dust; the absorption assembly includes an absorption device 113 connected to the non-condensable matter in the buffer tank 112; the absorption assembly includes at least two absorption devices 113 arranged in series to achieve the purpose of completely absorbing hydrogen fluoride. The absorption device 113 uses an alkaline absorbent, which can be any of but not limited to sodium hydroxide solution, calcium hydroxide solution, and potassium hydroxide solution. The absorption device 113 can be but not limited to a spray tower.

The reflux component is used to reflux the tail gas to the buffer tank 112 when the hydrogen fluoride in the tail gas discharged by the absorption component exceeds a preset value, thereby further maintaining the pressure stability of the system. The reflux component includes a hydrogen fluoride detection device 1141 provided at the tail gas outlet of the absorption device 113 and a reflux pipe 1142 connecting the buffer tank 112 and the downstream pipeline of the hydrogen fluoride detection device 1141; a second valve 1143 and a third valve 1144 interlocked with the hydrogen fluoride detection device 1141 are respectively provided on the downstream pipeline and the reflux pipe 1142.

The neutralization reaction component 115 is used to react the condensate in the buffer tank 112 with the alkaline solution. The neutralization reaction component 115 includes a neutralization reaction tank. The alkaline absorbent in the neutralization reaction tank can be, but is not limited to, any of sodium hydroxide solution, calcium hydroxide solution, and potassium hydroxide solution.

The solid-liquid separation component 116 is used for performing solid-liquid separation on the solid-liquid mixture outputted from the neutralization reaction tank and the absorption component. The solid-liquid separation component 116 is a filtering device or a centrifugal device.

In addition to the condenser 1111, the equipment and pipelines through which the material containing hydrogen fluoride flows are also preferably made of polytetrafluoroethylene, or the inner wall has a polytetrafluoroethylene coating.

FIG. 2 is a schematic structural diagram of a second embodiment of a system for roasting lepidolite raw materials according to the present invention.

Compared with the first embodiment, the lithium mica raw material roasting system of this embodiment has the following differences: as shown in FIG2 , the neutralization reaction component 115 is not provided. Among them, the absorption device 113 uses water as an absorbent, the solid-liquid separation component 116 is used to perform solid-liquid separation on the solid-liquid mixture output from the buffer tank 112 and the absorption component, and a first valve 1122 interlocked with a liquid level meter 1121 is provided on the connecting pipe between the buffer tank 112 and the solid-liquid separation component 116. As a result, the obtained clear liquid is enriched with more hydrogen fluoride, which can be used for the recovery and utilization of hydrogen fluoride.

The first and second embodiments of the lithium mica raw material roasting system of the present invention fully consider the characteristics of the defluorination flue gas, and through multi-stage treatment such as condensation, buffering, and absorption, the emission of pollutants is effectively reduced, and the recycling efficiency of resources is also improved, which is of positive significance for improving the environmental protection and economy of the entire process. Compared with the system design of directly utilizing defluorination flue gas to produce hydrogen fluoride in the prior art, the first and second embodiments of the lithium mica raw material roasting system of the present invention have a simpler structure, low investment cost, and different implementation methods can be selected according to the hydrogen fluoride content, which has stronger practicality. The object of action of the treatment system of the above-mentioned embodiment of the present invention is universal, and can be the defluorination flue gas produced by an internal heating roasting kiln (i.e., directly introducing natural gas into the roasting kiln), or the defluorination flue gas produced by an external heating roasting kiln (using jacket heating or electric heating).

FIG3 is a schematic structural diagram of a third embodiment of a system for roasting lepidolite raw materials according to the present invention.

As shown in Figure 3, the lithium mica raw material roasting system includes a roasting kiln for roasting the lithium mica raw material, a roasting kiln heating jacket 1210, a first heat exchanger 1211, a second heat exchanger 1212, a third heat exchanger 1213, a first dust collector 1221, an arsenic recovery unit 123, a hydrogen fluoride recovery unit 124, a lithium mica dry material buffer bin 1251, a lithium mica raw material bin 1252, a drying kiln 126, a second dust collector 1222, a roasting kiln hot air furnace 127, a roasting kiln cooler 128 and a lithium mica clinker storage tank 129.

The roasting kiln heating jacket 1210 is used to heat the roasting kiln.

The first heat exchanger 1211 is used to exchange heat between the lepidolite dry material to be introduced into the roasting kiln and the first defluorinated flue gas outputted from the roasting kiln; the first heat exchanger 1211 is a cyclone preheater. The particles intercepted by the first dust collector 1221 flow into the lepidolite dry material buffer bin 1251, and the lepidolite dry material buffer bin 1251 outputs the lepidolite dry material to the first heat exchanger 1211 for heat exchange with the first defluorinated flue gas outputted from the roasting kiln.

The second heat exchanger 1212 is used to perform heat exchange between the second defluorination flue gas output by the first heat exchanger 1211 and the defluorination agent to be introduced into the roasting kiln.

The third heat exchanger 1213 is used to exchange heat between the primary cold air and the cold air outputted from the roasting kiln heating jacket 1210. The roasting kiln hot air furnace 127 is used to heat the energy gas and output the jacket gas for heating the roasting kiln to the roasting kiln hot air furnace 127 in the roasting kiln heating jacket 1210. The secondary cold air obtained after the third heat exchanger 1213 processes the primary cold air flows into the roasting kiln hot air furnace 127 as the energy gas (except for the refluxed secondary cold air, the main component is natural gas).

The first dust collector 1221, the arsenic recovery unit 123 and the hydrogen fluoride recovery unit 124 sequentially process the third defluorinated flue gas output by the second heat exchanger 1212. Among them, the first dust collector 1221 can not only recover the lithium mica dust, but also improve the purity of the arsenic oxide and hydrogen fluoride recovered subsequently. The arsenic recovery unit 123 preferably, but not limited to, recovers the arsenic oxide by condensation. The hydrogen fluoride recovery unit 124 preferably, but not limited to, recovers hydrogen fluoride by condensation and/or absorption.

The lepidolite raw material warehouse 1252 is used to store lepidolite raw materials, the drying kiln 126 is used to dry the lepidolite raw materials, the hot air obtained after the third heat exchanger 1213 processes the cold air flows into the drying kiln 126 as a heat source, and the lepidolite dry material dried in the drying kiln 126 flows into the lepidolite buffer warehouse. The second dust collector 1222 is used to remove dust from the lepidolite dust gas output by the drying kiln 126, and the particles intercepted by the second dust collector 1222 flow into the lepidolite raw material warehouse 1252.

The roasting kiln cooler 128 is used to cool the lepidolite clinker output from the roasting kiln, and the lepidolite clinker storage tank 129 is used to store the cooled lepidolite clinker.

It can be seen that the lithium mica raw material roasting system of the third embodiment of the present invention has the following advantages:

1. The closed roasting kiln is used, and the lithium mica raw materials are indirectly heated in the roasting kiln without direct contact with flames or flue gas. Therefore, it can reduce safety risks such as fire and explosion, reduce pollution to the lithium mica raw materials, and reduce the emission of harmful substances in the defluorination flue gas, which is more in line with environmental protection requirements.

2. The jacket structure makes the heat distribution in the roasting kiln more uniform. On the one hand, the lithium mica raw material is heated evenly, reducing the thermal stress of the lithium mica raw material during the heating process and reducing the risk of explosion of the lithium mica raw material. On the other hand, it reduces the high-temperature area inside the roasting kiln and reduces the safety risk of operators. By controlling the heating temperature and heating rate of the roasting kiln heating jacket 1210, precise temperature control can be achieved, and the temperature and reaction rate inside the roasting kiln can be more easily controlled. Therefore, the roasting process can be better controlled, which helps to reduce the consumption of defluorination agents, achieve efficient defluorination, improve the quality and stability of lithium mica clinker, and has a wider range of uses and flexibility. It can reduce the temperature difference stress inside the roasting kiln, reduce the damage to the roasting kiln caused by thermal shock and thermal fatigue, and thus extend the service life of the roasting kiln. The jacket structure can reduce the loss of heat to the external environment, help reduce energy consumption, and improve energy efficiency.

3. The primary cold air output from the roasting kiln heating jacket 1210 is used to preheat the cold air entering the roasting kiln hot air furnace 127 and is used as a heat source for the drying kiln 126 to dry the lithium mica raw material, thereby realizing the recovery and utilization of waste heat.

4. The high-temperature first defluorination flue gas is used to preheat the defluorination agent to be fed into the kiln, thereby increasing the temperature of the defluorination agent entering the kiln, reducing the heat demand of the roasting kiln, and achieving energy saving and consumption reduction.

5. Only defluorination agent is introduced into the roasting kiln without the introduction of natural gas combustion flue gas, so that the defluorination tail gas has a single component, which is conducive to the recovery and utilization of arsenic oxides and hydrogen fluoride, and reduces the land occupation and investment of the tail gas treatment device.

FIG. 4 is a schematic structural diagram of a first embodiment of a lepidolite clinker acidification system according to the present invention.

As shown in FIG4 , the lepidolite clinker acidification system includes an acidification kiln for acidifying the lepidolite clinker, a filter 131, an acidification kiln heating jacket 132, an acidification kiln hot air furnace 133, an acid storage tank 1341, a lepidolite clinker storage tank 129, an acid mixing machine 135, a deacidification device 136, an acidification kiln cooler 137 and a lepidolite acidified material storage tank 138, wherein the lepidolite clinker is obtained by roasting a lepidolite raw material.

The acidification kiln heating jacket 132 is used to heat the acidification kiln.

The acidizing kiln hot blast furnace 133 is used to input jacket gas for heating the acidizing kiln into the acidizing kiln heating jacket 132. Part of the cold air output by the acidizing kiln heating jacket 132 flows into the acidizing kiln hot blast furnace 133 as energy gas (mainly natural gas), and part is directly discharged.

The acid mixer 135 is used to mix the lepidolite clinker and acid.

The filter 131 is used to filter the acidification fume outputted from the acidification kiln and output dust and low-dust gas. The dust outputted from the filter 131 flows into the acid mixer 135 .

The deacidification device 136 is used to deacidify the low-dust gas output by the filter 131 , and the deacidification device 136 is a spray tower.

The acidification kiln cooler 137 is used to cool the lepidolite acidified material output from the acidification kiln, and the lepidolite acidified material storage tank 138 is used to store the cooled lepidolite acidified material.

FIG5 is a schematic structural diagram of a second embodiment of a lepidolite clinker acidification system according to the present invention.

Compared with the first embodiment, the lithium mica clinker acidification system of this embodiment has the following differences: as shown in FIG5 , it further includes a salt storage tank 1342, and the acid mixer 135 is used to mix the lithium mica clinker, acid and salt. The acid storage tank 1341 preferably stores sulfuric acid, and the salt storage tank 1342 preferably stores any of potassium sulfate, sodium sulfate and calcium sulfate. Thus, the lithium mica clinker is acidified by sulfuric acid and sulfate at the same time, which can save acid aging time, significantly reduce the amount of sulfuric acid used, and improve the lithium leaching rate.

It can be seen that the lithium mica clinker acidification system of the above embodiment of the present invention has the following advantages:

1. The closed acidification kiln is used, and the lithium mica clinker is indirectly heated in the acidification kiln without direct contact with flames or flue gas. Therefore, it can reduce safety risks such as fire and explosion, reduce pollution to the lithium mica clinker, and reduce the emission of harmful substances in the acidification flue gas, which is more in line with environmental protection requirements.

2. The jacket structure makes the heat distribution in the acidizing kiln more uniform. On the one hand, the lithium mica clinker is heated evenly, reducing the thermal stress of the lithium mica clinker during the heating process and reducing the risk of lithium mica clinker explosion. On the other hand, the high-temperature area inside the acidizing kiln is reduced, reducing the safety risk of operators. By controlling the heating temperature and heating rate of the acidizing kiln heating jacket 132, precise temperature control can be achieved, and the temperature and reaction rate inside the acidizing kiln can be more easily controlled. Therefore, the roasting process can be better controlled, the quality and stability of the lithium mica acidizing material can be improved, and the lithium leaching rate can be improved, which has a wider range of uses and flexibility. The temperature difference stress inside the acidizing kiln can be reduced, and the damage to the acidizing kiln caused by thermal shock and thermal fatigue can be reduced, thereby extending the service life of the acidizing kiln. The jacket structure can reduce the loss of heat to the external environment, which helps to reduce energy consumption and improve energy efficiency.

3. There is no natural gas combustion flue gas introduced into the acidification kiln, which makes the gas volume of the acidification flue gas small and the composition single, reducing the land occupation and investment of the tail gas treatment device.

4. The cold air output from the acidification kiln heating jacket 132 is circulated back to the acidification kiln hot air furnace 133, so that the heat energy is fully utilized and the energy consumption is low.

The first embodiment of the pretreatment method of the lepidolite raw material of the present invention is used to leach lithium from the lepidolite raw material, comprising the steps of:

The lepidolite raw material is subjected to roasting treatment at 800-1000° C. for 0.5-1.5 h to obtain lepidolite clinker;

The mixture of lepidolite clinker, salt and acid is subjected to roasting treatment at 200-320° C. for 0.5-1.5 h to obtain lepidolite acidified material;

Adding water to the lepidolite acidified material to form a slurry to obtain a slurry;

After solid-liquid separation of the slurry, leachate and leach residue are obtained.

The traditional calcination process of preparing lithium carbonate by the lithium mica salt method is to mix the lithium mica raw material with salt and then calcine it at high temperature. The cations in the salt can replace the lithium in the lithium mica raw material, so that the lithium and the acid ions can be combined to form a soluble lithium salt, and then water is directly added to adjust the slurry and filter to obtain the leachate. However, if this method wants to achieve a higher lithium leaching rate, it is necessary to increase the amount of salt. The large amount of salt used leads to a significant increase in the amount of slag, which in turn leads to an increase in the amount of water for slurry adjustment, which further leads to a significant increase in the processing pressure of the filtered leachate and leached slag. Similarly, in the acidification and calcination process of preparing lithium carbonate by the lithium mica acid method, because other elements are leached out by acid at the same time as lithium, the amount of acid added will far exceed the amount of acid required for theoretical lithium leaching. The large amount of acid used will increase production costs, is not friendly to environmental protection, and increase the subsequent processing pressure on acidic liquids.

The pretreatment method of the lithium mica raw material of the above embodiment of the present invention first realizes defluorination and crystallization through high-temperature roasting, which is conducive to the leaching of lithium, and then through the synergistic effect of salt and acid, not only the lithium leaching rate is improved, but also the amount of leaching agent (i.e. acid and salt) is effectively reduced compared with the traditional salt method and acid method, and the amount of slurry water and acidic liquid is less, thereby reducing the raw material cost and subsequent processing cost. It has been verified that the pretreatment method of the lithium mica raw material of the above embodiment of the present invention can ensure a lithium leaching rate of more than 75%, and the amount of acid can be reduced by more than 30% compared with the traditional method.

The second embodiment of the pretreatment method of the lepidolite raw material of the present invention is used to leach the lithium element in the lepidolite raw material, comprising the steps of:

The lepidolite raw material is subjected to roasting treatment at 800-1000° C. for 0.5-1.5 h to obtain lepidolite clinker;

Firstly, a mixture of lithium mica clinker and salt is roasted at 800-900°C for 0.5-1.5h, then acid is added when the temperature is lowered to 200-320°C and the temperature is kept at this temperature for 0.5-1.5h to obtain lithium mica acidified material;

Adding water to the lepidolite acidified material to form a slurry to obtain a slurry;

After solid-liquid separation of the slurry, leachate and leach residue are obtained.

Compared with the first embodiment, the second embodiment of the method for pretreating lithium mica raw materials uses salt and acid separately, firstly allowing the salt and lithium mica clinker to fully react at a higher temperature, and then injecting acid for secondary leaching when the kiln temperature automatically drops to a lower temperature, thereby finally achieving deep leaching of lithium.

The third embodiment of the pretreatment method of the lepidolite raw material of the present invention is used to leach lithium from the lepidolite raw material, comprising the steps of:

The lepidolite raw material is subjected to roasting treatment at 800-1000° C. for 0.5-1.5 h to obtain lepidolite clinker;

The lithium mica clinker and the salt are ball-milled and mixed, and then an acid is added, and the mixture of the lithium mica clinker, the salt and the acid is roasted at 200 to 320° C. for 0.5 to 1.5 hours to obtain a lithium mica acidified material;

Add water to the lepidolite acidified material to form a slurry, and then stir at a high speed of 800 to 2000 rpm for 50 minutes to obtain a slurry;

After solid-liquid separation of the slurry, leachate and leach residue are obtained.

Compared with the first embodiment, the third embodiment of the pretreatment method of lithium mica raw materials firstly fully mixes the lithium mica clinker and the salt by ball milling, which helps the salt to leach the lithium in the lithium mica clinker at low temperature and reduces the heat consumption of the acidification kiln. Secondly, by high-speed stirring the slurry after adding water to the slurry, high-speed stirring can provide greater kinetic energy, which is not only conducive to the rapid dissolution of soluble lithium, but also makes the collision between the lithium mica acidification material particles more intense and frequent, and also plays a grinding role on the lithium mica acidification material to a certain extent, so that the particle size of the lithium mica acidification material is reduced and the dissolution rate is increased.

In the three embodiments of the pretreatment method of the lepidolite raw material, the acid and the salt preferably have the same acid radical ions to avoid introducing too many impurity ions. Preferably, the acid is sulfuric acid, and the salt is any of potassium sulfate, sodium sulfate, and calcium sulfate. When the mass ratio of sulfate to lepidolite clinker is (0.03-0.15):1, and the mass ratio of sulfuric acid (using concentrated sulfuric acid with a mass fraction of 98%) to lepidolite clinker is (0.2-0.45):1, the best lithium leaching rate can be obtained.

In the three embodiments of the above-mentioned lithium mica raw material pretreatment method, the roasting treatment of the lithium mica raw material preferably adopts the lithium mica raw material roasting system 200 shown in any one of Figures 1-3, and the roasting treatment of the lithium mica clinker, salt and acid preferably adopts the lithium mica clinker acidification system 300 shown in Figure 4 or Figure 5.

FIG6 is a schematic structural diagram of an embodiment of a system for pretreating lepidolite raw materials according to the present invention.

As shown in FIG. 6 , the lepidolite raw material pretreatment system includes a lepidolite raw material roasting system 200 , a lepidolite clinker acidification system 300 and a lepidolite acidified material slurry mixing system 400 .

The lepidolite raw material roasting system 200 is used to roast the lepidolite raw material and output lepidolite clinker; the lepidolite raw material roasting system 200 is preferably the lepidolite raw material roasting system 200 shown in any one of FIGS. 1-3 .

The lepidolite clinker acidification system 300 is used to perform acidification treatment on the lepidolite clinker and output the lepidolite acidified material; the lepidolite clinker acidification system 300 is preferably the lepidolite clinker acidification system 300 shown in FIG. 4 or FIG. 5 .

The lithium mica acidified material slurry mixing system 400 is used to add water to the lithium mica acidified material for slurry mixing and output lithium leaching solution; the lithium mica acidified material slurry mixing system 400 includes a high-speed dispersing device for high-speed dispersing of the lithium leaching solution; the high-speed dispersing device refers to a stirring device with a stirring speed of more than 800 rpm, which can be used but is not limited to any one of a double-axis high-speed disperser, a concentric double-axis high-speed disperser, a disc-type double-axis stirring disperser, and a disc-type three-axis stirring disperser.

The lithium mica raw material pretreatment system of the above embodiment of the present invention no longer uses the traditional low-speed anchor stirring (stirring for 3 to 5 hours), but adopts a high-speed dispersing device to stir the slurry after adding water and slurrying at high speed. High-speed stirring can provide greater kinetic energy, which is not only conducive to the rapid dissolution of soluble lithium, but also can make the collision between the lithium mica acidified material particles more intense and frequent, and to a certain extent also plays a grinding role on the lithium mica acidified material, so that the particle size of the lithium mica acidified material is reduced and the dissolution rate is increased. It has been verified that the lithium mica raw material pretreatment system of the above embodiment of the present invention can not only reduce the leaching stirring time to less than 60 minutes, but also no longer need to finely grind the lithium mica raw material or lithium mica clinker, and the particle size of about 100 to 200 mesh can be directly acidified, which reduces the leaching time and greatly increases the leaching efficiency.

FIG. 7 is a schematic structural diagram of an embodiment of a lithium mica acidification material leaching system of the present invention.

As shown in FIG. 7 , the lepidolite acidified material leaching system includes a lepidolite acidified material slurry mixing system 400 , a primary filtering component 510 and a washing filtering component 520 which are sequentially connected.

The lepidolite acidified material slurry mixing system 400 is used to add water to the lepidolite acidified material for slurry mixing and output turbid lithium leaching solution; the lepidolite acidified material slurry mixing system 400 includes a lepidolite acidified material slurry mixing tank and/or includes a high-speed dispersing device for high-speed dispersing treatment of turbid lithium leaching solution.

The primary filter assembly 510 is used to filter the turbid lithium leaching solution and output clear lithium leaching solution and leaching residue; the primary filter assembly 510 includes a primary plate and frame filter press.

The washing and filtering component 520 is used to wash the leached residue and output lithium washing solution and lithium washing residue. The lithium washing solution is used as lithium leaching solution. The washing and filtering component 520 includes a primary slurry mixing tank 521, a primary filtering device 522, a secondary slurry mixing tank 523 and a secondary filtering device 524; the primary slurry mixing tank 521 is used to add water to the leached residue to mix the slurry and output the primary slurry; the primary filtering device 522 is used to filter the primary slurry and output the primary filter residue and the primary filtrate; the secondary slurry mixing tank 523 is used to add water to the primary filter residue to mix the slurry and output the secondary slurry; the secondary filtering device 524 is used to filter the secondary slurry and output the secondary filter residue and the secondary filtrate. The primary filtrate and the secondary filtrate flow into the intermediate tank 600 and are combined with the clear lithium leaching solution to be used as the lithium leaching solution.

The lithium mica acidified material leaching system of the above embodiment of the present invention directly performs filtration and washing under acidic conditions after adding water to slurry, which has the following advantages: First, the leached residue does not contain colloidal substances, and solid-liquid separation can be performed efficiently, minimizing the water content of the leached residue. The water content of the leached residue is reduced, that is, the lithium salt carried away by the leached residue is reduced, which not only reduces the lithium loss, but also the leached residue only needs to be washed 1 to 2 times to wash out the lithium salt entrained in the leached residue, which reduces the number of washings compared with the traditional process, and reduces water consumption and energy consumption. Secondly, since there is no colloidal substance, the liquid phase is easier to pass through the filter hole, the filtering effect is better, and the filter medium is cleaner after the slag cake is unloaded, and the cleaning frequency is lower, which is conducive to improving the filtering effect and stability of the primary filter assembly 510. It has been verified that the lithium mica acidified material leaching system of the above embodiment of the present invention can increase the lithium recovery rate by at least 3% compared with the lithium recovery rate of the traditional process, and the number of washing times of the leached residue can be reduced by at least 2 times.

An embodiment of the method for treating impurity-removing slag in lithium carbonate production of the present invention is to recycle the impurity-removing slag, which can be obtained by adding water to a lepidolite acidified material to make a slurry-purification, or by adding water to a lepidolite acidified material to make a slurry-filtration-purification, wherein the purification process is preferably the lithium leaching solution purification method and purification system shown in FIG. 9 or FIG. 10 below; the impurity-removing slag treatment method comprises the following steps:

(1) The impurity-removed slag is roasted to obtain a roasted material; the roasting temperature is 200-400° C., and the roasting time is 20-80 minutes; the impurity-removed slag is dried before roasting.

(2) Add water to the roasted material to prepare a slurry, and then filter to obtain a first filter residue and a first filtrate.

(3) Add water to the first filter residue to prepare a slurry and then filter to obtain a second filter residue and a second filtrate.

(4) adding water to the second filter residue to prepare a slurry and then filtering to obtain a third filter residue and a third filtrate; the first filtrate, the second filtrate and the third filtrate are combined into a filtrate and used as a lithium leaching solution.

Among them, in steps (2)-(4), the liquid-to-solid ratio of water added in the slurry adjustment is (1-3):1, and the mixture is stirred at 30-80°C for 20-60 minutes and then filtered. This method uses less water and has a better washing effect.

FIG8 is a schematic structural diagram of an embodiment of a slag removal treatment system for lithium carbonate production according to the present invention.

As shown in FIG8 , the treatment system used in the embodiment of the above-mentioned method for treating impurity-removing slag includes a drying device 710, a roasting furnace 720, a first slurry mixing tank 731, a first filtering device 732, a second slurry mixing tank 741, a second filtering device 742, a third slurry mixing tank 751, and a third filtering device 752. The drying device 710 performs drying treatment on the impurity-removing slag. The roasting furnace 720 is used to roast the impurity-removing slag and output the roasted material; the roasting furnace 720 is an external heating roasting furnace 720, such as electric heating or jacket heating. The first slurry mixing tank 731 is used to add water to the roasted material for slurry mixing and output the first slurry; the first filtering device 732 is used to filter the first slurry and output the first filter residue and the first filtrate. The second slurry mixing tank 741 is used to add water to the first filter residue for slurry mixing and output the second slurry; the second filtering device 742 is used to filter the second slurry and output the second filter residue and the second filtrate. The third slurry mixing tank 751 is used to add water to the second filter residue to mix the slurry and output the third slurry; the third filtering device 752 is used to filter the third slurry and output the third filter residue and the third filtrate. The first filtrate, the second filtrate and the third filtrate flow into the intermediate tank 600 and are used as lithium leaching solution. The third filter residue is stored in the filter residue storage tank 760.

In the traditional process, only about 30% of lithium is washed out of the impurity slag in the background technology after washing, and the lithium loss is relatively high. In comparison, the impurity slag treatment method and impurity slag treatment system 700 of the above embodiment of the present invention have the advantages of: aluminum hydroxide is converted into aluminum oxide by roasting. Aluminum oxide is non-colloidal in nature and has poor adsorption to lithium salts, so that the adsorbed lithium salts are easily washed out by water, and at least 60% of lithium can be washed out, and the lithium recovery rate can be greatly improved. The obtained lithium washing solution can be directly sent to the lithium extraction system 900, or can be sent to the lithium leaching solution purification system 800. The main components of the modified impurity removal slag (i.e., the third filter residue) are mainly aluminum oxide and iron oxide. In particular, when the impurity removal slag is obtained by slurrying, filtering, and purification of lithium mica acidified material with water (i.e., the lithium leaching solution outputted from the above-mentioned lithium mica acidified material leaching system is obtained after purification), the slag content in the modified impurity removal slag is small and mainly composed of metal oxides. Therefore, it is convenient for subsequent use, for example, it is used as a seed in the second embodiment of the lithium leaching solution purification method and purification system below, thereby realizing the deep recycling of impurity removal slag resources.

The first embodiment of the lithium leachate purification method of the present invention is to purify the lithium leachate, and the lithium leachate can be obtained by adding water to the lithium mica acidified material to make a slurry, or by adding water to the lithium mica acidified material to make a slurry-filtering, and the most preferred one is from the above-mentioned intermediate tank 600 (i.e., the lithium leachate output from the lithium mica acidified material leaching system shown in Figure 7); the lithium leachate purification method comprises the following steps:

(1) adding hydrogen peroxide to the lithium leaching solution to obtain an oxidation solution; the amount of the hydrogen peroxide used is 1.1 to 1.4 times the mass of Fe2 ⁺ in the lithium leaching solution, and the hydrogen peroxide is prepared into a solution with a mass fraction of 22% to 30%. After reacting for 10 to 30 minutes, the oxidation solution is obtained.

(2) adding an alkali solution to the oxidizing solution until the pH value is 6 to 8 to obtain a first solid-liquid mixture; the alkali solution is potassium hydroxide and/or sodium hydroxide, and after the pH value is adjusted to 6 to 8, reacting at 40 to 60° C. for 10 to 30 minutes to obtain the first solid-liquid mixture.

(3) filtering the first solid-liquid mixture to obtain a first impurity-removed residue and a filtrate.

(4) adding alkali solution to the filtrate until the pH value is 10 to 12, and then adding a soluble carbonate to obtain a second solid-liquid mixture; the alkali solution is potassium hydroxide and/or sodium hydroxide; the carbonate is potassium carbonate and/or sodium carbonate; wherein, in order to avoid lithium loss caused by the conversion of lithium element to lithium carbonate precipitation as much as possible, the process is carried out at 40 to 60° C., and the amount of carbonate used is 1.05 to 1.1 times the molar amount of Ca2 ⁺ in the filtrate in terms of carbonate ions; after adding the soluble carbonate, reacting for 10 to 30 minutes to obtain the second solid-liquid mixture.

(5) filtering the second solid-liquid mixture to obtain a second impurity-removed residue and a purified liquid.

(6) The purified liquid is subjected to resin adsorption treatment. Prior to adsorption, the resin is first swelled with water, then washed with a 4-5% by mass hydrochloric acid solution to remove inorganic impurities, and finally washed with a 2-4% by mass potassium hydroxide and/or sodium hydroxide solution to neutralize the resin to remove organic impurities.

Preferably, flocculants are also used in step (2) and step (4), which can improve the reaction efficiency and facilitate filtration.

FIG. 9 is a schematic structural diagram of a first embodiment of a lithium leaching solution purification system according to the present invention.

As shown in FIG. 9 , the lithium leachate purification system 800 used in the first embodiment of the lithium leachate purification method includes a first reaction component, a first filtering component, a second reaction component, a second filtering component and a resin adsorption device 850 .

The first reaction component is used to react the lithium leaching solution, hydrogen peroxide and alkali solution to generate a first solid-liquid mixture; the first reaction component includes a first reaction tank 810, a hydrogen peroxide dosing device 812 for adding hydrogen peroxide to the first reaction tank 810, a first alkali solution dosing device 811 for adding alkali solution to the first reaction tank 810, a first pH detector 813 for detecting the pH of the material in the first reaction tank 810, a first agitator 814 for stirring the material in the first reaction tank 810, and a first flocculant dosing device 815 for adding flocculant to the first reaction tank 810.

The first filtering component is used to filter the first solid-liquid mixture and output first impurity-removed residue and impurity-removed liquid; the first filtering component includes a first plate and frame filter press 820.

The second reaction component is used to react the filtrate, alkali solution and carbonate to generate a second solid-liquid mixture; the second reaction component includes a second reaction tank 830, a second alkali solution adding device 831 for adding alkali solution to the second reaction tank 830, a carbonate adding device 832 for adding carbonate to the second reaction tank 830, a second pH detector 833 for detecting the pH of the material in the second reaction tank 830, a second agitator 834 for stirring the material in the second reaction tank 830, and a second flocculant adding device 835 for adding flocculant to the second reaction tank 830.

The second filtering component is used to filter the second solid-liquid mixture and output a second impurity-removed residue and a purified liquid; the second filtering component includes a second plate-frame filter press 841 and a precision filter 842 connected in sequence.

The resin adsorption device 850 is used to perform resin adsorption treatment on the purification liquid.

The first embodiment of the lithium leachate purification method and lithium leachate purification system 800 of the present invention has the following advantages:

1. First, by using hydrogen peroxide, divalent iron ions can be oxidized to trivalent iron ions, and finally converted into iron hydroxide precipitation, so that iron impurities are deeply removed. Secondly, first neutralize to a pH of 6-8 to remove most impurities such as Fe and Al, and then adjust to a pH of 10-12 to allow impurities such as Ca, Mg, and Mn to react with hydroxide and precipitate, and then use potassium carbonate and/or sodium carbonate to deeply remove impurity ions that are not precipitated in the form of carbonates. Finally, adding resin adsorption can further improve the recovery rate of lithium.

The above-mentioned step-by-step operation is conducive to the selective precipitation of impurities and reduces the loss of lithium. In addition, the combination of hydroxide and carbonate not only reduces the cost of the reagent, but also allows the impurities to be removed thoroughly. The Al, Fe, Ca, Mg, Mn, Ni, Cu, and Zn in the obtained purified solution meet the electrical grade standards. By controlling the carbonate dosage and the reaction temperature, most impurities can be precipitated and the co-precipitation of lithium can be avoided as much as possible, which is conducive to improving the reaction speed and selectivity.

2. Lepidolite itself has a lot of potassium. Using potassium hydroxide and/or sodium hydroxide instead of traditional calcium oxide or calcium hydroxide can reduce the introduction of impurity ions, and the generated byproduct _K2SO4 or _Na2SO4 (acidification using _sulfuric acid) has good solubility, which not only reduces the amount of precipitation ( _calcium sulfate precipitation generated when there is no sulfuric acid method), but also can be further purified by evaporation and crystallization before lithium extraction to prepare high-purity _K2SO4 or _Na2SO4 products, thereby realizing the _resource utilization of high-potassium _lepidolite raw materials. In the traditional process, too many calcium ions will be introduced, and the excess calcium ions need to be removed by adding carbonate, which increases the amount of carbonate, prolongs the process, and increases the cost of reagents.

The second embodiment of the lithium leachate purification method of the present invention is to purify the lithium leachate, and the lithium leachate can be obtained by adding water to the lithium mica acidified material to make a slurry, or by adding water to the lithium mica acidified material to make a slurry-filtering, and the most preferred one is from the above-mentioned intermediate tank 600 (i.e., the lithium leachate output from the lithium mica acidified material leaching system shown in Figure 7); the lithium leachate purification method comprises the following steps:

(1) adding alkaline solution to the lithium leaching solution until the pH value is 2-3; the alkaline solution is potassium hydroxide and/or sodium hydroxide; and the process is carried out at a rotation speed of 200-400 rpm.

(2) Continue to add _seed crystals to the lithium leaching solution, wherein the seed crystals include any of _Al2O3 , _Fe2O3 , Fe(OH) ₃ , and Al(OH) ₃ ; the mass of the seed crystals added to each liter of lithium leaching solution _is 0.05% to 0.5% of the liquid volume.

(3) Continue to add alkali solution to the lithium leaching solution until the pH value is 6 to 8 to obtain a solid-liquid mixture.

(4) filtering the solid-liquid mixture to obtain impurity-free residue and purified liquid.

(5) The purified liquid is subjected to resin adsorption treatment. Prior to adsorption, the resin is first swelled with water, then washed with a 4-5% by mass hydrochloric acid solution to remove inorganic impurities, and finally washed with a 2-4% by mass potassium hydroxide and/or sodium hydroxide solution to neutralize the resin to remove organic impurities.

The seed crystals can be purchased from outside or prepared from intermediate products in the production of lithium carbonate.

When the seed crystals include Fe(OH) ₃ and Al(OH) ₃ , they can be prepared by the following preparation method: adding alkali solution to the lithium leaching solution until the pH is 6-8, and collecting the generated precipitated residue to obtain the seed crystals.

In the above-mentioned lithium leaching solution purification method and seed preparation method, the pH and stirring speed are preferably controlled as follows: when pH≤3, the stirring rate is 200-400 rpm, and when pH＞3, the stirring rate is ≤100 rpm; after pH adjustment, react for 20-40 minutes for liquid-solid separation. The reason for such control is that when pH<3, Fe ³⁺ and Al ³⁺ are in a dissolved state, and a higher stirring rate (200-400 rpm) is required at this time to improve the reaction kinetics, accelerate the contact between metal ions and ^OH- in the solution, and promote the precipitation reaction. When pH≥3, Fe(OH) ₃ and Al(OH) ₃ begin to precipitate in large quantities, and a lower stirring rate (≤100 rpm) is required at this time to reduce the mechanical crushing of the precipitated particles and avoid the production of too small colloidal particles. Because larger particles are easy to precipitate and filter, it is beneficial to improve the efficiency of subsequent solid-liquid separation and reduce the adsorption of lithium ions in the solution, thereby reducing the co-precipitation loss of lithium. In summary, through the combined control of pH and stirring rate, the precipitation kinetics and crystal growth behavior of Fe(OH) ₃ and Al(OH) ₃ can be regulated to obtain larger particle precipitation products, which is of great significance for subsequent solid-liquid separation and lithium recovery.

When the seed crystals include Al ₂ O ₃ and Fe ₂ O ₃ , the third filter residue in the above-mentioned slag removal treatment method and slag removal treatment system 700 can be adopted, or the seed crystals can be obtained by calcining the above-mentioned precipitated residue.

Preferably, step (3) is carried out at a rotation speed of 50 to 150 rpm, the reaction time is 30 to 120 minutes, and a flocculant is also used, which can improve the reaction efficiency and facilitate filtration.

FIG. 10 is a schematic structural diagram of a second embodiment of a lithium leaching solution purification system according to the present invention.

As shown in FIG. 10 , the lithium leachate purification system used in the second embodiment of the lithium leachate purification method includes a reaction component, a filtering component and a resin adsorption device 850 .

The reaction component is used to react lithium leaching solution, alkali solution and seed crystals to generate a solid-liquid mixture; the reaction component includes a reaction tank 860, an alkali solution adding device 861 for adding alkali solution to the reaction tank 860, a seed crystal adding device 862 for adding seed crystals to the reaction tank 860, a pH detector 863 for detecting the pH of the material in the reaction tank 860, an agitator 864 for stirring the material in the reaction tank 860, and a flocculant adding device 865 for adding flocculant to the reaction tank 860.

The filtering component is used to filter the solid-liquid mixture and output the impurity-removed residue and purified liquid; the filtering component includes a plate and frame filter press 843 and a precision filter 842 connected in sequence.

The resin adsorption device 850 is used to perform resin adsorption treatment on the purification liquid.

The second embodiment of the lithium leachate purification method and lithium leachate purification system 800 of the present invention has the following advantages:

1. By adding a small amount of seed crystals as the precipitate growth site, it is helpful for the rapid growth of the precipitate and the increase of the size of the precipitate, thereby improving the purification reaction rate and filtration efficiency. When the _seed crystals include _{Al2O3 and Fe2O3} , the adsorption effect on lithium salts is small, which can reduce lithium loss. In particular, the seed crystals used can directly adopt the third filter residue in the above-mentioned impurity removal slag treatment method and impurity removal slag treatment system 700, or can be directly prepared from lithium leaching solution using a simple method, so as to achieve internal circulation, reduce solid waste generation, and significantly save the production cost of lithium carbonate.

2. Lepidolite itself has a lot of potassium elements. Using potassium hydroxide and/or sodium hydroxide instead of traditional calcium oxide or calcium hydroxide can reduce the introduction of impurity ions, and the generated byproduct _K2SO4 or _Na2SO4 (acidification using _sulfuric acid) has good solubility _, which not only reduces the amount of precipitation (calcium sulfate precipitation generated when there is no sulfuric acid method), but also can be further purified by evaporation and crystallization before the lithium extraction system 900 to prepare high-purity _K2SO4 or _Na2SO4 products, thereby realizing the resource utilization of high-potassium _lepidolite raw materials. In the traditional process _, too many calcium ions will be introduced, and the excess calcium ions need to be removed by adding carbonate, which increases the amount of carbonate, prolongs the process, and increases the cost of reagents.

The best embodiment of the lithium carbonate production method and production system of the present invention is obtained by combining the method and system shown in Figures 1-9, which are as follows:

FIG. 11 is a schematic structural diagram of the optimal embodiment of the lithium carbonate production system of the present invention.

As shown in FIG11, the lithium carbonate production system includes a lithium mica raw material pretreatment system shown in FIG6, a lithium mica acidification material leaching system shown in FIG7, and a lithium extraction system 900, specifically, including a lithium mica raw material roasting system 200 shown in any one of FIG1-3, a lithium mica clinker acidification system 300 shown in FIG4 or FIG5, a slag removal treatment system 700 shown in FIG8, and a lithium leaching solution purification system 800 shown in FIG9 or FIG10. The lithium extraction system 900 is used to extract lithium from the purified liquid and output lithium carbonate, and conventional methods can be used, such as using an evaporation concentration system, a lithium precipitation system, and a lithium washing system. First, most of the water is removed by evaporation concentration to greatly increase the concentration of lithium in the solution. Then, the concentrated lithium solution is added with alkaline raw materials such as potassium carbonate and/or sodium carbonate to react the lithium ions in the solution with carbonate ions to precipitate lithium carbonate. The amount of carbonate added needs to be controlled at 1.05 to 1.1 times the theoretical value to minimize the loss of lithium. Finally, the precipitated lithium carbonate is filtered and separated, and the lithium carbonate is washed multiple times to remove the residual impurity ions therein.

The lithium carbonate production method and production system of the present invention have the advantages possessed by the above-mentioned various process sections, especially when the above-mentioned method and system are organically combined into one, the advantages of minimum energy consumption, minimum solid waste, maximum resource utilization, minimum lithium loss, maximum product purity and minimum production cost can be achieved.

The above is a description of the relevant contents of the present invention. A person skilled in the art will be able to implement the present invention based on these descriptions. Based on the above contents of the present invention, all other embodiments obtained by a person skilled in the art without creative work shall fall within the scope of protection of the present invention.

Claims (10)

1. A method for treating impurity-free slag in lithium carbonate production, wherein the preparation of the impurity-free slag comprises the steps of treating lithium leaching solution with alkali solution and then performing solid-liquid separation, wherein the method comprises the following steps: (1) roasting the impurity-removed slag to obtain a roasting material; (2) The roasted material is slurried with water and then filtered to obtain a filter residue and a filtrate, and the filtrate is used as a lithium leaching solution. 2. The impurity-removing slag treatment method in lithium carbonate production as claimed in claim 1, characterized in that: it also includes drying the impurity-removing slag before roasting. 3. The method for removing impurities from slag in lithium carbonate production as claimed in claim 1, characterized in that the roasting temperature is 200-400°C and the roasting time is 20-80 minutes. 4. The method for removing impurities and residues in lithium carbonate production as claimed in claim 1, characterized in that the liquid-to-solid ratio in the slurry preparation with water is (1-3):1, and the mixture is stirred at 30-80°C for 20-60 minutes and then filtered. 5. The method for removing impurities from slag in lithium carbonate production according to claim 1, characterized in that: the step (2) comprises: adding water to the roasted material for slurry adjustment and then filtering to obtain a first filter residue and a first filtrate; adding water to the first filter residue for slurry adjustment and then filtering to obtain a second filter residue and a second filtrate. 6. The method for removing impurities from slag in lithium carbonate production according to claim 5, characterized in that: the step (2) further comprises: adding water to the second filter residue for slurry preparation and filtering to obtain a third filter residue and a third filtrate; and combining the first filtrate, the second filtrate and the second filtrate into a filtrate for use as a lithium leaching solution. 7. The method for treating impurity-removing slag in lithium carbonate production according to claim 6, wherein the preparation of the impurity-removing slag comprises the steps of: (1) adding alkaline solution to the lithium leaching solution until the pH value is 2 to 3; (2) continuing to add seed crystals to the lithium leaching solution, wherein the seed crystals include Al ₂ O ₃ and/or Fe ₂ O ₃ ; (3) continuing to add alkali solution to the lithium leaching solution until the pH value is 6 to 8 to obtain a solid-liquid mixture; (4) filtering the solid-liquid mixture to obtain impurity-free residue and purified liquid. 8. The method for removing impurities from slag in lithium carbonate production according to claim 7, wherein the seed crystals are the third filter residue. 9. The method for treating impurity-removing slag in lithium carbonate production according to claim 1, wherein the preparation of the impurity-removing slag comprises the steps of: (1) adding hydrogen peroxide to a lithium leaching solution to obtain an oxidation solution; (2) adding alkaline solution to the oxidizing solution until the pH value is 6 to 8 to obtain a first solid-liquid mixture; (3) filtering the first solid-liquid mixture to obtain a first impurity-removed residue and a filtrate; (4) adding alkali solution to the filtrate until the pH value is 10 to 12, and then adding a soluble carbonate to obtain a second solid-liquid mixture; (5) filtering the second solid-liquid mixture to obtain a second impurity-removed slag and a purified liquid; the impurity-removed slag at least includes the first impurity-removed slag. 10. A method for producing lithium carbonate, characterized in that it comprises the steps of: The lepidolite raw material is subjected to roasting treatment to obtain lepidolite clinker; Acidifying the lepidolite clinker to obtain lepidolite acidified material; Adding water to the lepidolite acidified material to prepare a slurry to obtain a lithium leaching solution; Purifying the lithium leaching solution to obtain impurity-removed slag and purified solution; The impurity removal residue is treated by the impurity removal residue treatment method according to any one of claims 1 to 9 to obtain a filtrate; The purified liquid is subjected to lithium extraction treatment to obtain lithium carbonate.