CN113003590A - Method for preparing lithium carbonate by thermal reduction of spodumene - Google Patents

Method for preparing lithium carbonate by thermal reduction of spodumene Download PDF

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CN113003590A
CN113003590A CN202110470971.2A CN202110470971A CN113003590A CN 113003590 A CN113003590 A CN 113003590A CN 202110470971 A CN202110470971 A CN 202110470971A CN 113003590 A CN113003590 A CN 113003590A
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lithium
spodumene
lithium carbonate
thermal reduction
carbonate
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钟辉
干勇
杨培
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Sichuan Wanbang Shenghui New Energy Technology Co ltd
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Sichuan Wanbang Shenghui New Energy Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D15/00—Lithium compounds
    • C01D15/08—Carbonates; Bicarbonates
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B7/00—Hydraulic cements
    • C04B7/14—Cements containing slag
    • C04B7/147—Metallurgical slag
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
    • C01P2006/00—Physical properties of inorganic compounds
    • C01P2006/80—Compositional purity
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P40/00—Technologies relating to the processing of minerals
    • Y02P40/10—Production of cement, e.g. improving or optimising the production methods; Cement grinding

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  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Organic Chemistry (AREA)
  • Ceramic Engineering (AREA)
  • Inorganic Chemistry (AREA)
  • Structural Engineering (AREA)
  • Manufacture And Refinement Of Metals (AREA)

Abstract

The invention relates to the technical field of lithium carbonate production, in particular to a method for preparing lithium carbonate by using alpha-type spodumene as a raw material through thermal reduction. The method comprises the following steps: mixing alpha type spodumene concentrate powder with a reducing agent and a blocking agent, reducing in a reducing furnace under the conditions of vacuum and high temperature to reduce lithium in the spodumene into metal lithium steam, and condensing to obtain metal lithium and reduced spodumene slag containing metal lithium and lithium oxide; leaching spodumene slag containing metal lithium and lithium oxide with water to obtain leaching slag and slurry; and precipitating the leaching residue and the slurry to remove calcium and filter, wherein the filtrate is a lithium carbonate raw material solution, and then concentrating and precipitating lithium to produce a battery-grade or high-purity lithium carbonate product. The new method is a green and environment-friendly technology, avoids the production of high-risk chemicals chlorine and the use of sulfuric acid in the prior art, and has small environmental load; no environmental pollution and solid waste discharge, good environmental benefit and good safety.

Description

Method for preparing lithium carbonate by thermal reduction of spodumene
Technical Field
The invention relates to the technical field of lithium carbonate production, in particular to a method for preparing lithium carbonate by using alpha-type spodumene as a raw material through thermal reduction.
Background
With the rapid development of new energy sources, lithium ion batteries, the global demand for lithium products has increased at an average rate of 15-20% per year. Lithium carbonate is used as the most main lithium source of lithium batteries, and the production technology of lithium carbonate becomes one of the key technologies for the development of the field and also becomes the research and development hot spot of the current global technology.
At present, the global lithium carbonate production technology generally adopts a sulfuric acid acidification roasting method for production, namely spodumene is used as a raw material and is produced through the technical processes of calcination transformation, crushing, concentrated sulfuric acid mixing, acidification roasting, leaching, purification, filtration, evaporation concentration, lithium precipitation, filtration, evaporative crystallization, recycling of a byproduct sodium sulfate and the like. The main disadvantages of this method are:
(1) the production process is complex, the material consumption is high, the lithium utilization rate is low (82-86%), and the production cost is high (reaching 4-4.5 ten thousand yuan/ton, while the market price of the current industrial-grade lithium carbonate product is 4.0-4.3 ten thousand yuan/ton).
(2) A large amount of sulfuric acid mist is generated in the high-temperature roasting process, and the environmental pollution is great.
(3) The slag and the by-product sodium sulfate are more (about 8 tons of slag and 2 tons of sodium sulfate are generated by 1 ton of lithium carbonate), the value of the slag and the by-product sodium sulfate is low, the recycling and processing cost is high, and the environmental load is large. Therefore, the traditional method for preparing lithium carbonate from spodumene has high cost and poor market competitiveness.
Disclosure of Invention
According to the defects in the prior art, the invention provides the method for preparing the lithium carbonate by the thermal reduction of the spodumene, which has the advantages of simple production process, low production cost, no environmental pollution and solid waste discharge and small environmental load. The method can be used for producing lithium carbonate and metal lithium, and the produced product has good quality and high value and can be used for directly producing high-purity lithium carbonate of a grade higher than that of a battery grade.
In order to achieve the above purpose, the specific technical scheme of the invention is as follows:
a method for preparing lithium carbonate by thermal reduction of spodumene comprises the following steps: alpha type spodumene is used as a raw material, alpha type spodumene, a reducing agent and a blocking agent are mixed to prepare a mass under the conditions of vacuum and high temperature, thermal reduction is carried out in a reducing furnace to reduce lithium in the spodumene into metal lithium steam, and then condensation is carried out to obtain metal lithium and reduced lithium-containing materialSpodumene slag of lithium metal, lithium oxide; extracting spodumene slag containing metal lithium and lithium oxide, leaching with water, filtering the leached slag and slurry to obtain filtrate as lithium hydroxide solution, evaporating and concentrating, and introducing CO2Carbonating the gas, filtering the slurry, drying the filter cake to obtain a lithium carbonate product, and returning the mother liquor to the concentration section for circulation.
As a better embodiment in the application, the spodumene is alpha-type spodumene concentrate, the grade of the spodumene concentrate is more than or equal to 5 percent, and the granularity of the spodumene concentrate is 150-mesh and 200-mesh.
As a preferred embodiment in the present application, the reducing agent is a composite reducing agent, and is prepared from high-silicon ferrosilicon, aluminum powder and aluminum-silicon powder in a mass ratio of 1: 0.1-0.5: 0.1-0.5, and is high-silicon ferrosilicon; aluminum powder with Al content more than or equal to 99 wt%; aluminum powder with activity accounting for 70 wt% and granularity of 6-10 um; aluminum silicon powder or carbon powder with the aluminum silicon content of more than or equal to 98 percent.
As a better embodiment in the application, the high-silicon ferrosilicon has the silicon content of more than or equal to 75 wt% and the grain size of 6-8 um; the aluminum powder has an aluminum content of more than or equal to 99 wt%, an activity of 70 wt% and a particle size of 6-8 um; the aluminum silicon powder has the aluminum silicon content of more than or equal to 98 wt% and the granularity of 6-8 um.
As a preferred embodiment herein, the fluxing agent is CaO, and the CaO content is 90-98% (wt%).
As a preferred embodiment of the present application, the addition amounts of the α type spodumene concentrate, the reducing agent, and the flux inhibitor are, by mass, 1: 0.1-0.5: 0.3-2.5.
As a preferred embodiment of the present invention, the pellets are pressed into a spherical or flaky product having a particle size of 10 to 100mm by a briquetting machine at the time of briquetting.
In a preferred embodiment of the present invention, the lithium metal is crude lithium, and is refined under protection of Ar gas and stirring to obtain lithium metal with a purity of greater than 99%.
As a better implementation mode in the application, the leached slag and slurry are precipitated, calcium is removed, and a filter cake obtained by filtering is dried and used for producing cement.
The method for preparing lithium carbonate by the thermal reduction of spodumene comprises the following specific steps:
first-step thermal reduction: mixing a certain amount of alpha spodumene concentrate with a reducing agent and a solid resisting agent, pressing the mixture into balls or sheets with the particle size of 10-100mm by using a briquetting machine, putting the balls or sheets into a crucible, and carrying out thermal reduction under the conditions of high temperature and vacuum of a reduction furnace; after the reduction reaction is finished, when the furnace temperature is reduced to be less than or equal to 40 ℃, taking out the metallic lithium in a condensing chamber in the furnace, and taking the metallic lithium as a metallic lithium refining raw material to refine the lithium; and taking out the spodumene slag containing the metal lithium and the lithium oxide left after reduction in the crucible, and carrying out the next leaching.
The second step is leaching and calcium removal: and leaching the obtained spodumene slag containing metal lithium and lithium oxide by using pure water, adding soda ash according to the total amount of calcium ions in a system after leaching is finished, stirring for 20-50min, stopping stirring, drying and crushing a filter cake obtained by filtering, and selling the filter cake as cement clinker. And filtering the mother liquor I to obtain a lithium carbonate raw material solution.
The third step is CO absorption2Carbonating to prepare lithium carbonate: concentrating the filtered mother liquor 1 to Li+Filtering at a concentration of 15-30g/l to remove the very small amount of CaCO formed during evaporation3Then introducing carbon dioxide gas, absorbing under alkaline condition and making carbonation reaction, making the above-mentioned absorption and carbonation reaction be implemented under the conditions of normal temp. and normal pressure and stirring so as to make Li be+With CO2And (3) forming lithium carbonate precipitate, filtering the formed slurry to obtain a filter cake, drying the filter cake to obtain a lithium carbonate product, and returning the filtered mother liquor II to the concentration working section for circulation.
As a preferred embodiment in the present application, the thermal reduction conditions are: the temperature is 850 ℃ and 1300 ℃, the absolute pressure is 2-50Pa, and the time is 5-25 hours, preferably 10-20 hours.
As a preferred embodiment in this application, the leaching conditions in the second step are: the temperature is 20-90 ℃, and the solid-to-liquid ratio is 1: 1-7, and the leaching time is 30-300 min.
As a preferred embodiment in the present application, the second step is conducted by mass percentageThe addition of two-step soda ash is formed into CaCO according to precipitation3105-110% of the theoretical amount of (A).
As a preferred embodiment in this application, CO is used in the third step2The gas introduction amount is 400 percent of 100-.
Compared with the prior art, the positive effects of the invention are as follows:
the novel method is a green and environment-friendly technology, avoids the production of high-risk chemicals chlorine and the use of sulfuric acid in the existing technology for producing metal lithium, and has small environmental load; no environmental pollution and solid waste discharge, good environmental benefit and good safety.
And (II) the alpha type spodumene is directly produced by taking the alpha type spodumene as a raw material, and the working procedures of high-temperature calcination transformation, sulfuric acid acidification roasting and the like in the prior art are omitted. Simple process, easy operation, low energy consumption, good product quality and high value, can directly produce high-purity lithium hydroxide with higher grade than battery grade, and the value of the high-purity lithium hydroxide is 200 percent of that of the existing lithium hydroxide product.
The method can produce lithium hydroxide and metal (accounting for 40-60% of the total lithium), and has high lithium utilization rate (the total lithium utilization rate is more than or equal to 95%, and the lithium utilization rate in the prior art is 80-86%).
Fourthly, the production cost is low, and the production cost of each ton of lithium carbonate is 10 to 20 percent lower than that of the existing spodumene hydrogen and lithium oxide technology; the production cost of the metallic lithium is 50-60% lower than that of the prior art.
And fifthly, the by-product is spodumene slag which is mainly silicate and is an ideal key raw material (clinker) for cement production, so that the utilization value is high, and the recovery process of low-value by-product sodium sulfate in the traditional technology is omitted.
Description of the drawings:
fig. 1 is a schematic diagram of a process flow for preparing lithium carbonate by the thermal reduction of spodumene.
Detailed Description
A method for preparing lithium carbonate and metallic lithium by a spodumene thermal reduction method is based on the following principle: alpha-type spodumene is taken as a raw material, alpha-type spodumene concentrate powder, reducing agent powder and a fluxing agent are mixed under the conditions of vacuum and high temperature, reduction is carried out in a reduction furnace, lithium in the spodumene is reduced into metal lithium steam, metal lithium (abbreviated as 'crude lithium') and reduced spodumene slag containing metal lithium and lithium oxide are obtained after condensation, the obtained metal 'crude lithium' is refined under the protection of Ar gas and stirring, metal lithium with the purity of more than 99 percent can be produced, the spodumene slag containing the metal lithium and the lithium oxide is taken out and leached by water, and the following reactions are carried out:
metallic lithium Li + H in slag2O ＝LiOH+0.5H2 (1)
Lithium oxide Li in slag2O+H2O＝2LiOH (2)
Precipitating the above leaching residue and slurry with soda ash, purifying to remove calcium, filtering to obtain filtrate, evaporating and concentrating, and introducing CO2Gas, or sodium carbonate is added to carbonate and precipitate lithium, and the reaction is as follows:
carbonation: 2LiOH + CO2＝Li2CO3↓+H2O (3)
Or precipitated lithium: 2LiOH + Na2CO3＝Li2CO3↓+2NaOH (4)
And filtering the slurry, drying the filter cake to obtain a lithium carbonate product, and returning the mother liquor to the concentration section for circulation. The leached slag is sold as a building raw material. The method comprises the following specific steps:
first-step thermal reduction: mixing a certain amount of alpha-type spodumene concentrate with a reducing agent and a dissolution inhibitor, wherein the spodumene is the alpha-type spodumene concentrate, and the grade of the alpha-type spodumene concentrate is generally more than or equal to 5 percent (namely the grade of the alpha-type spodumene concentrate is Li)2O is more than or equal to 5.0 percent), preferably more than or equal to 6 percent, and the granularity is between-150 and-200 meshes.
As a preferred embodiment in the present application, the reducing agent is a composite reducing agent, and is prepared from high-silicon ferrosilicon, aluminum powder and aluminum-silicon powder in a mass ratio of 1: 0.1-0.5: 0.1-0.5, mixing; the silicon content of the high-silicon ferrosilicon is more than or equal to 75 percent (wt percent), and the granularity is 6-8 um; the aluminum powder has an aluminum content of more than or equal to 99 percent (wt%), an activity of 70 percent (wt%) and a particle size of 6-8 um; the aluminumSilicon powder, wherein the aluminum-silicon content is more than or equal to 98 percent (wt percent), and the granularity is 6-8 um; the fluxing agent is lime, and the CaO content of the fluxing agent is 90-98% (wt%). The composite oxidant of the present invention must be used because of the low lithium content in the raw material spodumene (general grade Li)2O of 5 to 6%) and exists in a dense spodumene structure, which is extremely difficult to oxidize to metallic lithium.
As a preferred embodiment in this application, the spodumene concentrate, reducing agent and fluxing agent are added in the following amounts: spodumene: reducing agent: the fusing inhibitor is 1: 0.1-0.5: 0.3-2.5 (mass ratio),
the method for preparing lithium carbonate by the thermal reduction of spodumene specifically comprises the following steps:
first-step thermal reduction: mixing alpha type spodumene concentrate, a reducing agent and a flux-resisting solid, pressing the mixture into balls or sheets with the particle size of 10-100mm by using a briquetting machine, putting the balls or sheets into a crucible, and carrying out vacuum reduction in a reduction furnace; after the reduction reaction is finished, when the furnace temperature is reduced to be less than or equal to 40 ℃, taking out the metallic lithium in a condensing chamber in the furnace (called as crude lithium) and refining the lithium as a metallic lithium refining raw material; then, taking out the remaining spodumene slag containing the metal lithium and the lithium oxide after reduction in the crucible, and carrying out the next leaching;
the second step is leaching and calcium removal: and (3) stirring and leaching the obtained spodumene slag containing metal lithium and lithium oxide by using pure water at the temperature of 20-90 ℃, wherein the solid-liquid mass ratio is 1: 1-7, and the leaching time is 30-300 min; after leaching, adding a precipitator soda ash according to the total amount of calcium ions in the system, stirring for 20-50min, stopping stirring, filtering, washing to obtain a filter cake, drying and crushing the filter cake to obtain a cement clinker, and selling the filter cake as a hydrogen-producing lithium oxide raw material solution;
the third step is lithium carbonate: concentrating the filtered mother liquor to Li+The content is 18-20g/l, then filtration is carried out, calcium carbonate newly generated in the evaporation process is removed by filtration, and then CO is introduced2Carbonating to precipitate lithium or adding sodium carbonate as precipitant to precipitate lithium, filtering (vacuum filtering, centrifugal filtering or pressure filtering), drying the obtained filter cake to obtain lithium carbonate product, and returning the filtered mother liquor toAnd (4) circulating the leachate.
The first step thermal reduction conditions are as follows: the temperature is 850-1300 ℃, the absolute pressure is 2-50Pa, and the time is 5-25 hours.
The leaching conditions in the second step are as follows: the temperature is 20-80 ℃, and the solid-liquid mass ratio is 1: 2-5, and the leaching time is 40-180 min. In the second step, the amount of soda ash added is determined according to the amount of CaCO formed by precipitation3105-110% of the theoretical mass.
The method can simultaneously produce lithium carbonate and metallic lithium.
Concentration may be by forced evaporation, or reverse osmosis, or electrodialysis, or a combination thereof.
The present invention will be described in further detail with reference to specific embodiments for the purpose of making the objects, technical solutions and advantages of the present invention more apparent, but it should not be construed that the scope of the above-described subject matter of the present invention is limited to the following examples.
In the present application,%, unless otherwise specified, means% by mass, i.e., wt%.
Example 1:
taking alpha-spodumene concentrate (containing Li) with the granularity of about-200 meshes and the grade of 6.0 percent2O6%) 1.0kg, lime (containing 90% CaO and having a particle size of 60-100um), and a composite reducing agent (consisting of high-silicon ferrosilicon, aluminum powder and aluminum-silicon powder in a mass ratio of 1: 0.1-0.5: 0.1-0.5) in a mass ratio of 1: 0.12: 1.0, adding 2.12kg of solid, uniformly mixing the solid, pressing into a briquette, wherein the briquette is a cylindrical flaky object with the diameter of 2.0cm and the thickness of 1.0cm, filling the cylindrical flaky object into a graphite crucible sprayed with a ceramic anti-corrosion layer, and then putting the graphite crucible into a special electric heating reduction furnace. Vacuumizing the reduction furnace, controlling the absolute pressure of the reduction furnace to be 15.0Pa, electrifying, heating at the temperature of 900 ℃ in the furnace for 10 hours, stopping heating, releasing pressure, and naturally cooling to normal temperature and normal pressure. And opening the furnace door, taking out the crude lithium metal in the condensing chamber in the furnace, and taking the crude lithium metal as a raw material for smelting and refining the lithium metal by a lithium metal flux. Then the remaining spodumene slag containing metallic lithium and lithium oxide after reduction in the crucible is taken out and put into an electric heater with the volume of 12.0LAdding 8.0L of pure water into a stainless steel reaction kettle, heating to 60 ℃, stirring and leaching for 90min, stopping stirring, preparing 18mL of sodium carbonate solution (saturated) solution with the concentration of 450g/L by using analytically pure sodium carbonate, adding the sodium carbonate solution into the leachate for precipitation and calcium removal, keeping the temperature and stirring for 30min, filtering while hot (filtering by using a centrifugal machine), washing by using 2.0L of hot pure water to obtain a filter cake and a filtering mother solution 1 (containing washing water), heating the filtering mother solution 1 to boiling for evaporation and concentration, concentrating until the mother solution contains 20.58g/L of lithium, filtering the solution, and filtering to remove a very small amount of CaCO formed in the evaporation process3Obtaining filtered mother liquor 2, then introducing industrial grade 1 carbon dioxide gas into the filtered mother liquor 2 in a bubbling mode through a porous gas distributor, carrying out absorption and carbonation reactions at normal temperature and normal pressure under stirring, wherein the introduction amount of the carbon dioxide gas is 5.87mol, the introduction time is 90min, then filtering, washing and drying the obtained filter cake to obtain the high-purity lithium carbonate product, and returning filtered mother liquor 3 to the concentration section for circulation. The results are shown in Table 1.
Example 2:
taking spodumene concentrate (containing Li) with granularity of-200 meshes and grade of 6.0%2O6%) 1.0kg, lime (containing 95% CaO and having a particle size of 60-100um), and a composite reducing agent (consisting of high-silicon iron, aluminum powder and aluminum-silicon powder in a mass ratio of 1: 0.1-0.5: 0.1-0.5) by mixing ═ 1: 0.3: 1.0 (mass ratio), the total amount of solids added was 2.3kg, the solids were mixed well, pressed into pellets, the size of which was 2.0cm in diameter and 1.0cm in thickness, and loaded into a graphite crucible sprayed with a ceramic anti-corrosion layer, and the graphite crucible was then placed in a special reduction furnace (electrical heating). Vacuumizing the reduction furnace, controlling the absolute pressure to be 8.0Pa, electrifying, heating at 1000 ℃ for 10 hours, stopping heating, releasing pressure, and naturally cooling to normal temperature and normal pressure. Opening furnace door, taking out crude lithium metal in condensing chamber in furnace, using it as melting agent of lithium metal to smelt and refine raw material, taking out residual spodumene slag containing lithium metal and lithium oxide after reduction in crucible, placing it into electric heating stainless steel reaction kettle whose volume is 12.0L, adding 8.0L of pure water, heating to 60 deg.C, stirringThe leaching was carried out for 90min, followed by filtration while hot (centrifuge filtration) and washing with 2.0L of hot purified water to give a cake and filtration mother liquor 1 (containing washing water). Heating the filtered mother liquor 1 to boil for evaporation concentration until the mother liquor contains 21.11g/L lithium, filtering the solution to remove the very small amount of CaCO formed in the evaporation process3Obtaining filtered mother liquor 2, then introducing industrial grade 1 carbon dioxide gas into the filtered mother liquor 2 in a bubbling mode through a porous gas distributor, carrying out absorption and carbonation reactions at normal temperature and normal pressure under stirring, wherein the introduction amount of the carbon dioxide gas is 6.15mol, the introduction time is 90min, then filtering, washing and drying the obtained filter cake to obtain the high-purity lithium carbonate product, and returning filtered mother liquor 3 to the concentration section for circulation. The results are shown in Table 1. The liquid returns to the circulation. The results are shown in Table 1.
Example 3:
taking spodumene concentrate (containing Li) with granularity of-200 meshes and grade of 6.0%2O6%) 1.0kg, lime (containing 95% CaO and having a particle size of 60-100um), and a composite reducing agent (consisting of high-silicon iron, aluminum powder and aluminum-silicon powder in a mass ratio of 1: 0.1-0.5: 0.1-0.5) by mixing ═ 1: 0.5: 1.0 (mass ratio), the total amount of solid added is 2.5kg, the solid is pressed into a briquette after being evenly mixed, the briquette is a cylindrical sheet-shaped object with the diameter of 2.0cm and the thickness of 1.0cm, the cylindrical sheet-shaped object is put into a graphite crucible which is sprayed with a ceramic anti-corrosion layer, and the graphite crucible is put into a special reducing furnace (electric heating). Vacuumizing the reduction furnace, controlling the absolute pressure to be 5.0Pa, electrifying, heating at 1100 ℃ for 10 hours, stopping heating, releasing pressure, and naturally cooling to normal temperature and normal pressure. And opening the furnace door, taking out the crude lithium metal in the condensing chamber in the furnace, and taking the crude lithium metal as a raw material for smelting and refining the lithium metal by a lithium metal flux. Then, the spodumene slag containing metallic lithium and lithium oxide remaining after reduction in the crucible was taken out, placed in an electrically heated stainless steel reaction kettle having a volume of 12.0L, added with 8.0L of pure water, heated to 60 ℃, stirred and leached for 90min, then filtered while hot (centrifuge filtration), and washed with 2.0L of hot pure water to obtain a filter cake and a filtration mother liquor 1 (containing washing water). Heating the filtered mother liquor 1 to boil, evaporating and concentrating to obtain mother liquorThen filtering the solution to remove the very small amount of CaCO formed in the evaporation process3Obtaining filtered mother liquor 2, then introducing industrial grade 1 carbon dioxide gas into the filtered mother liquor 2 in a bubbling mode through a porous gas distributor, carrying out absorption and carbonation reactions at normal temperature and normal pressure under stirring, wherein the introduction amount of the carbon dioxide gas is 5.37mol, the introduction time is 90min, then filtering, washing and drying the obtained filter cake to obtain the high-purity lithium carbonate product, and returning filtered mother liquor 3 to the concentration section for circulation. The results are shown in Table 1.
Example 4:
taking spodumene concentrate (containing Li) with granularity of-200 meshes and grade of 6.0%2O6%) 1.0kg, lime (containing 95% CaO and having a particle size of 60-100um), and a composite reducing agent (consisting of high-silicon iron, aluminum powder and aluminum-silicon powder in a mass ratio of 1: 0.1-0.5: 0.1-0.5) by mixing ═ 1: 0.5: 2.0 (mass ratio), 3.5kg of solid, the solid is uniformly mixed, pressed into a briquette, the briquette is a cylindrical sheet-shaped object with the diameter of 2.0cm and the thickness of 1.0cm, the cylindrical sheet-shaped object is put into a graphite crucible which is sprayed with a ceramic anti-corrosion layer, and the graphite crucible is put into a special reducing furnace (electric heating). Vacuumizing the reduction furnace, controlling the absolute pressure to be 5.0Pa, electrifying, heating at 1150 ℃ for 15 hours, stopping heating, releasing pressure, and naturally cooling to normal temperature and normal pressure. Opening a furnace door, taking out the crude metal lithium in a condensation chamber in the furnace, taking the crude metal lithium as a metal lithium flux for smelting and refining raw materials, taking out the spodumene slag containing the metal lithium and the lithium oxide left after reduction in a crucible, putting the slag into an electric heating stainless steel reaction kettle with the volume of 25.0L, adding 14L of pure water, heating to 60 ℃, stirring and leaching for 90min, then filtering while hot (filtering by a centrifugal machine), and washing by using 2.0L of hot pure water to obtain a filter cake and a filtering mother liquor 1 (containing washing water). Heating the filtered mother liquor 1 to boil for evaporation concentration until lithium content in the mother liquor is 23.6g/L, filtering the solution, and filtering to remove the extremely small amount of CaCO formed in the evaporation process3Obtaining filtered mother liquor 2, then introducing industrial grade 1 carbon dioxide gas into the filtered mother liquor 2 in a bubbling mode through a porous gas distributor,the absorption and carbonation reactions are carried out at normal temperature and normal pressure under stirring, the introduction amount of carbon dioxide gas is 5.13mol, the introduction time is 90min, then the filtration is carried out, the obtained filter cake is washed and dried to obtain the high-purity lithium carbonate product, and the filtered mother liquor 3 is returned to the concentration section for circulation. The results are shown in Table 1.
Example 5:
taking spodumene concentrate (containing Li) with granularity of-200 meshes and grade of 6.0%2O6%) 1.0kg, lime (containing 95% CaO and having a particle size of 60-100um), and a composite reducing agent (consisting of high-silicon iron, aluminum powder and aluminum-silicon powder in a mass ratio of 1: 0.1-0.5: 0.1-0.5) by mixing ═ 1: 0.5: 2.5 (mass ratio), the solid addition amount is 4.0kg, the solid is pressed into a briquette after being evenly mixed, the briquette is a cylindrical sheet-shaped object with the diameter of 2.0cm and the thickness of 1.0cm, the cylindrical sheet-shaped object is put into a graphite crucible which is sprayed with a ceramic anti-corrosion layer, and the graphite crucible is put into a special reducing furnace (electric heating). Vacuumizing the reduction furnace, controlling the absolute pressure to be 3.0Pa, electrifying, heating at 1300 ℃ for 20 hours, stopping heating, releasing pressure, and naturally cooling to normal temperature and normal pressure. And opening the furnace door, taking out the crude lithium metal in the condensing chamber in the furnace, and taking the crude lithium metal as a raw material for smelting and refining the lithium metal by a lithium metal flux. Then, the spodumene slag containing metallic lithium and lithium oxide remaining after reduction in the crucible was taken out, placed in an electrically heated stainless steel reaction kettle having a volume of 25.0L, added with 16.0L of pure water, heated to 60 ℃, stirred and leached for 90min, then filtered while hot (centrifuge filtration), and washed with 4.0L of hot pure water to obtain a filter cake and a filtration mother liquor 1 (containing washing water). Heating the filtered mother liquor 1 to boil for evaporation concentration until lithium content in the mother liquor is 23.9g/L, filtering the solution, and filtering to remove the extremely small amount of CaCO formed in the evaporation process3Obtaining filtered mother liquor 2, adding precipitator industrial grade 1 sodium carbonate into the filtered mother liquor 2, adding the sodium carbonate according to 110% of the theoretical amount of lithium carbonate in the completely precipitated mother liquor 2, stirring for 90min at normal temperature and normal pressure, filtering, washing and drying the obtained filter cake to obtain the high-purity lithium carbonate product, and returning the filtered mother liquor 3 to the concentration section for circulation. The results are shown in Table 1.
TABLE 1
Figure BDA0003045314340000111
Figure BDA0003045314340000121
Note:
(1) the spodumene yield was 1.0kg and the grade was 6.0% for all examples (Li)2O6%) and a total amount of 27.9 g of lithium
(2) The lithium primary precipitation rate refers to the precipitation rate of lithium during carbonation, and the filtrate 3 also contains about 10-20% of Li+And the lithium is returned to the circulation, so that the lithium loss is not caused.
(3) In Table 1, ICP plasma spectrometry was used for the measurement of elements such as lithium and calcium, as in Table 2 below.
Comparative example 1:
the other conditions were the same as in example 5 except that the thermal reduction temperature was lowered from 1300 ℃ to 800 ℃, the reduced spodumene slag was leached and decalcified to give a concentrate of 20g/L lithium in the solution, the solution was filtered to remove the very small amount of CaCO formed during evaporation3Obtaining filtered mother liquor 2, adding precipitator industrial grade 1 sodium carbonate into the filtered mother liquor 2, adding the sodium carbonate according to 110% of the theoretical amount of lithium carbonate in the completely precipitated mother liquor 2, stirring for 90min at normal temperature and normal pressure, filtering, washing and drying the obtained filter cake to obtain the high-purity lithium carbonate product, and returning the filtered mother liquor 3 to the concentration section for circulation. The results are shown in Table 2.
Comparative example 2
The other conditions were the same as in example 5 except that spodumene, the composite reducing agent and the lime solid powder were uniformly mixed and then reduced in a reducing furnace without agglomeration. Leaching and decalcifying the reduced spodumene slag, concentrating the leaching solution until the content of lithium in the solution is 204g/L, filtering the solution, and filtering to remove the extremely small amount of CaCO formed in the evaporation process3To obtainFiltering the mother liquor 2, adding precipitator industrial grade 1 sodium carbonate into the filtered mother liquor 2, adding the sodium carbonate according to 110% of the theoretical amount of lithium carbonate in the completely precipitated mother liquor 2, stirring for 90min at normal temperature and normal pressure, filtering, washing and drying the obtained filter cake to obtain the high-purity lithium carbonate product, and returning the filtered mother liquor 3 to the concentration section for circulation. The results are shown in Table 2.
Comparative example 3
The other conditions were the same as in example 5 except that the Si content in the Si-Fe component of the composite reducing agent was 50% (wt%), the other components and proportions in the composite reducing agent were unchanged, the reduced spodumene slag was leached and decalcified, the concentrate of the leach solution was concentrated to a solution with a Li content of 20g/L, and the solution was filtered to remove the very small amount of CaCO formed during evaporation3Obtaining filtered mother liquor 2, adding precipitator industrial grade 1 sodium carbonate into the filtered mother liquor 2, adding the sodium carbonate according to 110% of the theoretical amount of lithium carbonate in the completely precipitated mother liquor 2, stirring for 90min at normal temperature and normal pressure, filtering, washing and drying the obtained filter cake to obtain the high-purity lithium carbonate product, and returning the filtered mother liquor 3 to the concentration section for circulation. The results are shown in Table 2.
Comparative example 4
The other conditions were the same as in example 5 except that the reducing agent used was a single high-silicon ferrosilicon having a silicon content of 75% (wt%) as the reducing agent, the reduced spodumene slag was leached and decalcified, the concentrate of the leachate was concentrated to a lithium content of 20g/L in the solution, and the solution was filtered to remove a very small amount of CaCO formed during evaporation3Obtaining filtered mother liquor 2, adding precipitator industrial grade 1 sodium carbonate into the filtered mother liquor 2, adding the sodium carbonate according to 110% of the theoretical amount of lithium carbonate in the completely precipitated mother liquor 2, stirring for 90min at normal temperature and normal pressure, filtering, washing and drying the obtained filter cake to obtain the high-purity lithium carbonate product, and returning the filtered mother liquor 3 to the concentration section for circulation. The results are shown in Table 2.
TABLE 2
Item Comparative example 1 Comparative example 2 Comparative example 3 Comparative example 4
Total amount of reducing slag (kg) 3.97 3.95 3.90 3.95
Lithium content in reducing slag (%) 0.66 0.645 0.532 0.697
Lithium yield in crude lithium/% 5.31 7.44 23.7 1.35
Lithium yield in the leachate/% 8.66 14.53 16.35 0.57
Total yield of lithium/% 13.97 21.97 40.05 1.92
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (10)

1. A method for preparing lithium carbonate by the thermal reduction of spodumene is characterized by comprising the following steps: alpha type spodumene is used as a raw material, under the conditions of vacuum and high temperature, the alpha type spodumene, a reducing agent and a blocking agent are mixed to prepare a mass, thermal reduction is carried out in a reducing furnace, lithium in the spodumene is reduced into metal lithium steam, and then condensation is carried out to obtain metal lithium and reduced spodumene slag containing the metal lithium and lithium oxide; extracting spodumene slag containing metal lithium and lithium oxide, leaching with water, precipitating the obtained leaching residue and slurry by precipitation method to remove calcium, filtering the leaching residue and slurry to obtain filtrate as lithium hydroxide solution, evaporating and concentrating, and introducing CO2And (3) carrying out carbonation on the gas to precipitate lithium, filtering the slurry, drying the filter cake to obtain a lithium carbonate product, and returning the mother liquor to the concentration working section for circulation.
2. The method for preparing lithium carbonate by the thermal reduction of spodumene as claimed in claim 1, wherein said spodumene is alpha-type spodumene concentrate, the grade of which is not less than 5%, and the particle size of which is 150-mesh and 200-mesh.
3. The method for preparing lithium carbonate by the thermal reduction of spodumene according to claim 1, wherein: the reducing agent is a composite reducing agent, and is prepared from high-silicon ferrosilicon, aluminum powder and aluminum-silicon powder in a mass ratio of 1: 0.1-0.5: 0.1-0.5 by mixing.
4. The method for preparing lithium carbonate by the thermal reduction of spodumene according to claim 1, wherein: the dissolution inhibitor is lime, and the CaO content of the dissolution inhibitor is 90-98% (wt%).
5. The method for preparing lithium carbonate by the thermal reduction of spodumene according to claim 1, wherein: the addition amounts of the alpha type spodumene concentrate, the reducing agent and the blocking agent are 1: 0.1-0.5: 0.3-2.5.
6. The method for preparing lithium carbonate by the thermal reduction of spodumene according to claim 1, wherein: when in briquetting, the mixture is pressed into balls or tablets with the grain diameter of 10-100mm by a briquetting machine.
7. The method for preparing lithium carbonate by the thermal reduction of spodumene according to claim 1, wherein said thermal reduction conditions are: the temperature is 850-1300 ℃, the absolute pressure is 2-50Pa, and the time is 5-25 hours.
8. The method for preparing lithium carbonate by the thermal reduction of spodumene according to claim 3, wherein: the silicon content of the high-silicon ferrosilicon is more than or equal to 75 wt%, and the granularity is 6-8 um; the aluminum powder has an aluminum content of more than or equal to 99 wt%, an activity of 70 wt% and a particle size of 6-8 um; the aluminum silicon powder has the aluminum silicon content of more than or equal to 98 wt% and the granularity of 6-8 um.
9. The method for producing lithium carbonate by the thermal reduction of spodumene according to any one of claims 1 to 8, wherein: the metal lithium is crude lithium, and is refined under the protection of Ar gas and stirring state to obtain the metal lithium with the purity of more than 99%.
10. The method for producing lithium carbonate by the thermal reduction of spodumene according to any one of claims 1 to 8, wherein: and (4) precipitating and decalcifying the leaching slag and the slurry, and drying a filter cake obtained by filtering to produce cement.
CN202110470971.2A 2021-04-29 2021-04-29 Method for preparing lithium carbonate by thermal reduction of spodumene Withdrawn CN113003590A (en)

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