CN113149039B - Method for preparing lithium oxide by thermal reduction of spodumene - Google Patents
Method for preparing lithium oxide by thermal reduction of spodumene Download PDFInfo
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- CN113149039B CN113149039B CN202110481642.8A CN202110481642A CN113149039B CN 113149039 B CN113149039 B CN 113149039B CN 202110481642 A CN202110481642 A CN 202110481642A CN 113149039 B CN113149039 B CN 113149039B
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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
- C01D15/02—Oxides; Hydroxides
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- 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
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
- C22B26/10—Obtaining alkali metals
- C22B26/12—Obtaining lithium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B5/00—General methods of reducing to metals
- C22B5/02—Dry methods smelting of sulfides or formation of mattes
- C22B5/04—Dry methods smelting of sulfides or formation of mattes by aluminium, other metals or silicon
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- 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
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- 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
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- 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
Abstract
The invention relates to the technical field of lithium hydroxide production, in particular to a method for preparing lithium oxide through thermal reduction of spodumene. The method comprises the following steps: alpha type spodumene is used as a raw material, spodumene concentrate powder is mixed with a reducing agent and a dissolution inhibitor, reduction is carried out in a reduction furnace under the conditions of vacuum and high temperature, 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 metal lithium and lithium oxide;leaching spodumene slag containing metal lithium and lithium oxide with water to obtain leaching slag and slurry; filtering and washing the leached slag and slurry to obtain filtrate, evaporating and crystallizing the lithium hydroxide solution to produce battery-grade or high-purity LiOH.H 2 And (4) O products. The method has simple production process, and can produce the lithium hydroxide mainly through reduction, leaching and evaporation; not only can produce lithium hydroxide, but also can produce metal (accounting for about 40-60% of the total amount of lithium), and the utilization rate of lithium is high.
Description
Technical Field
The invention relates to the technical field of lithium hydroxide production, in particular to a method for preparing lithium oxide by thermally reducing spodumene.
Background
With the rapid development of new energy, the lithium ion battery is increasingly demanded in the market. Lithium hydroxide is used as a key raw material of a ternary cathode material with high specific energy, and the market demand is increased at an average speed of 15-20% in recent 5 years, so that the development and improvement of the existing lithium hydroxide production technology become the research focus of the lithium hydroxide industry at present. At present, the global lithium hydroxide 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 (more than or equal to 1050 ℃), crushing, concentrated sulfuric acid mixing, acidification roasting, leaching, purification, filtration, sodium hydroxide causticization, freezing, 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 large, the lithium utilization rate is low (80-86%), and the production cost is high (4.5-5.3 ten thousand yuan/ton, while the market price of the current industrial lithium hydroxide product is 4.5-5.5 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 byproduct sodium sulfate have high yield (about 8 tons of slag and 2 tons of sodium sulfate are generated by 1 ton of lithium hydroxide), the value of the slag and the byproduct sodium sulfate is low, the recycling cost is high, and the environmental load is large. Therefore, the traditional method for producing the spodumene hydrogen and lithium oxide has high cost and poor market competitiveness.
Disclosure of Invention
The invention provides a brand-new method for preparing lithium hydroxide from spodumene according to the defects in the prior art, and the specific technical scheme of the invention is as follows:
a method for preparing lithium oxide by the thermal reduction of spodumene comprises the following steps: alpha type spodumene is used as a raw material, alpha type spodumene concentrate powder, reducing agent powder and a blocking agent are mixed to prepare a dough, thermal reduction is carried out in a reducing furnace under the conditions of vacuum and high temperature, lithium in the spodumene is reduced into metal lithium steam, then condensation is carried out, metal lithium (referred to as 'crude lithium') and reduced spodumene slag containing metal lithium and lithium oxide are obtained, the obtained metal lithium is referred to as 'crude lithium', and refining is carried out under the protection of Ar gas and stirring, so that metal lithium with the purity of more than 99% can be produced; then the spodumene slag containing the metal lithium and the lithium oxide is taken out and leached by water, so that the following reactions are carried out:
metallic lithium Li + H in slag 2 O→Li + +OH - +0.5H 2
Lithium oxide Li in slag 2 O+H 2 O→Li + +OH -
Removing calcium from the leached residue and slurry with sodium carbonate, filtering, washing to obtain filtrate as lithium hydroxide solution, evaporating, crystallizing, and producing cell-grade or high-purity LiOH 2 The O product, filter cake (i.e. slag) is dried and can be sold as clinker for producing cement, which can be used for directly producing cement.
As a preferred embodiment in this application, the grade of the alpha spodumene concentrate should be 5% or more (i.e., li) 2 O is more than or equal to 5.0wt percent), the grade is preferably more than or equal to 6 percent, and the granularity is 150-200 meshes.
As a better implementation mode in the application, the reducing agent is a composite reducing agent and is prepared by mixing high-silicon ferrosilicon, aluminum powder and aluminum-silicon powder according to the mass ratio of 1:0.1-0.5:0.1-0.5 by mixing. The silicon content of the high-silicon ferrosilicon is more than or equal to 75wt%, and the granularity is 6-8um; the aluminum powder has an aluminum content of more than or equal to 99wt%, an activity of 70wt% and a particle size of 6-8um; the aluminum silicon powder has the aluminum silicon content of more than or equal to 98wt% and the particle size of 6-8um.
As a preferred embodiment herein, the retarder agent is lime having a CaO content of 90-98% (wt%).
As a preferred embodiment in this application, the spodumene concentrate, reducing agent and fluxing agent are added in the following amounts: α type spodumene: reducing agent: flux barrier =1:0.1-0.5:0.3-2.5 (mass ratio),
the method for preparing the lithium oxide by the thermal reduction of the spodumene specifically comprises the following steps
First-step thermal reduction: mixing a certain amount of alpha type spodumene concentrate with a reducing agent and a solid of a flux inhibitor, pressing the mixture into balls or sheets with the particle size of 10-100mm by a briquetting machine, putting the balls or sheets into a crucible, reducing the balls or sheets in a reducing furnace at high temperature under vacuum, opening a furnace door after the reduction reaction is finished, and taking out metal lithium (namely crude lithium) in a condensing chamber in the furnace to be used as a metal lithium refining raw material for refining 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.
As a preferred embodiment in the present application, the thermal reduction conditions are: the temperature is 850-1300 deg.C, the absolute pressure is 2-50Pa, and the time is 5-25 hr, preferably 10-20 hr.
Leaching and calcium removal in the second step: and (2) leaching the obtained spodumene slag containing metal lithium and lithium oxide by stirring with pure water at the temperature of 20-90 ℃, wherein the solid-liquid ratio is =1:1-7 (mass ratio), and the leaching time is 30-300min. After leaching time is reached, adding soda ash according to the total amount of calcium ions in the system, stirring for 20-50min, stopping stirring, and filtering. The obtained filter cake is dried and crushed to be sold as cement clinker. And filtering the mother liquor to obtain the hydrogen and lithium oxide raw material liquor.
As a preferred embodiment in this application, the leaching conditions are: the temperature is 40-80 ℃, and the solid-liquid ratio is =1:2-5 (mass ratio), and the leaching time is 40-180min.
As a preferred embodiment in this application, soda ash is added in an amount to precipitate CaCO 3 105 to 110% by mass of the theoretical amount of (A).
The filtration may be vacuum filtration, centrifugal filtration, or pressure filtration.
Step three, hydrogen and lithium oxide production: the filtration mother liquor (Li thereof) + With a content of 0.2-1.5 g/l) is concentrated to Li + The content is 25-60g/l, and then coolingCrystallizing at 20-50 deg.C, filtering (vacuum filtering, centrifugal filtering or pressure filtering), drying the obtained filter cake to obtain lithium hydroxide product, and returning the filtered mother liquor to the leachate for circulation.
Concentration may be by forced evaporation, or reverse osmosis, or electrodialysis, or a combination thereof.
Compared with the prior art, the positive effects of the invention are as follows:
the production process is simple and easy to operate, lithium hydroxide can be produced mainly through reduction, leaching and evaporation, the product quality is good, the value is high, high-purity lithium hydroxide with a grade higher than that of a battery grade can be directly produced, and the selling price can reach 8-10 ten thousand yuan/ton.
The method can not only produce lithium hydroxide, but also produce metal (accounting for about 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 (III) the production cost is low, and the production cost of each ton of lithium hydroxide is 2-3 ten thousand yuan/ton.
(IV) the by-product is spodumene slag which is mainly silicate, is an ideal key raw material (clinker) for cement production, and has higher utilization value and small environmental load; no environmental pollution and solid waste discharge, and good environmental benefit.
Description of the drawings:
FIG. 1 is a flow chart of the process for preparing lithium oxide by the thermal reduction of spodumene according to the present invention.
Detailed Description
A method for preparing lithium oxide by thermally reducing spodumene, which comprises the following steps: alpha type spodumene is used as a raw material, alpha type spodumene concentrate powder is mixed with a reducing agent and a blocking agent to prepare a dough, reduction is carried out in a reduction furnace under the conditions of vacuum and high temperature, lithium in the spodumene is reduced into metal lithium steam, and then condensation is carried out, so that metal lithium and reduced spodumene slag containing metal lithium and lithium oxide are obtained; leaching spodumene slag containing metal lithium and lithium oxide with water to obtain leaching slag and slurry; filtering the leached slag and slurry to obtain filtrate, evaporating and crystallizing the lithium hydroxide solution to produce cell-level or high-purity LiOH 2 And (4) O products.
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%.
And drying filter cakes obtained by filtering the leaching residues and the slurry, and using the filter cakes to produce cement.
The grade of the alpha-type spodumene concentrate is more than or equal to 5 percent, namely Li 2 O is more than or equal to 5.0 percent, and the granularity is 150-200 meshes; the mass ratio of the adding amounts of the spodumene concentrate, the reducing agent and the fusing inhibitor is 1:0.1-0.5:0.3-2.5.
The reducing agent is high-silicon ferrosilicon, wherein Al is aluminum powder with the content of more than or equal to 99wt%, the activity accounts for 70wt%, the aluminum powder with the granularity of 6-10um, and aluminum silicon powder or carbon powder with the aluminum silicon composite content of more than or equal to 98%; the fusing inhibitor is CaO and Al 2 O 3 Or CaO and Al 2 O 3 Mixture of (2), al 2 O 3 Is industrial grade 1 alumina.
The method for preparing the lithium oxide by the thermal reduction of the 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, and taking the metallic lithium as a metallic lithium refining raw material to refine 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.
Leaching and calcium removal in the second step: and (3) leaching the obtained spodumene slag containing metal lithium and lithium oxide by stirring with pure water at the temperature of 20-90 ℃, wherein the solid-liquid ratio is =1:1-7, and the leaching time is 30-300min; and after leaching, adding soda ash according to the total amount of calcium ions in the system, stirring for 20-50min, stopping stirring, filtering, drying and crushing the obtained filter cake, selling the filter cake as cement clinker, and using the filtered mother liquor as a lithium hydroxide raw material solution.
Step three, hydrogen and lithium oxide production: concentrating the filtered mother liquor to Li + In an amount of 25-60g/l, cooling and crystallizing at the crystallization temperature of 20-50 ℃, drying a filter cake obtained by filtering to obtain a lithium hydroxide product, and returning a filtering mother liquor to the leaching solution for circulation.
The first-step thermal reduction conditions are as follows: the temperature is 850-1300 deg.C, the absolute pressure is 2-50Pa, and the time is 5-25 hr.
The leaching conditions in the second step are as follows: the temperature is 40-80 ℃, and the solid-liquid mass ratio is 1:2-5, and the leaching time is 40-180min. In the second step, the amount of soda ash added is determined according to the amount of CaCO formed by precipitation 3 105-110% of the theoretical mass.
The method can simultaneously produce lithium hydroxide and metal lithium, and the total utilization rate of lithium is more than or equal to 95 percent in the process of producing the lithium hydroxide.
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 type spodumene concentrate (containing Li) with the granularity of 200 meshes and the grade of 6.0 percent 2 O = 6%) 1.0kg, lime (which contains CaO content)>85 percent of the grain size is 60-100 um) and solid reducing agent are evenly mixed and pressed into lumps to prepare cylindrical flaky objects with the diameter of 2.0cm and the thickness of 1.0 cm; 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 1:0.3:0.3, the silicon content of the high-silicon iron is more than or equal to 75wt percent, and the granularity is 6-8um; the Al content in the aluminum powder is more than or equal to 99wt%; the activity accounts for 70wt%, and the granularity is 6-10um; the aluminum-silicon content in the aluminum-silicon powder is more than or equal to 98 percent, and the granularity is 6-8um. 1:0.12:1.0 (mass ratio), putting the graphite crucible sprayed with the ceramic anti-corrosion layer into the furnace, and then putting the graphite crucible into an electric heating reduction furnace for thermal reduction. Vacuumizing the reduction furnace, controlling absolute pressure at 15.0Pa, electrifying, heating at 900 deg.C for 10 hr, stopping heating, releasing pressure, and naturally cooling to room temperatureAnd normal pressure. The furnace door is opened, the crude lithium metal in the condensing chamber in the furnace is taken out and is used as the raw material for refining the lithium metal, the total weight of the raw material is tested to be 11.88g, and the lithium content is 94.3 percent (wt percent).
Taking out reduced spodumene slag containing metal lithium and lithium oxide in a crucible, weighing 1.97kg, placing into an electrically-heated stainless steel reaction kettle with a volume of 12.0L, adding 8.0L of pure water, heating to 60 deg.C, stirring for leaching for 90min, stopping stirring, sampling to assay Ca in the solution 2+ 0.24g/L, then preparing a sodium carbonate solution (saturated) with analytically pure sodium carbonate to a concentration of 450g/L, taking 18mL of the solution, adding the solution into the leachate to precipitate and remove calcium, then keeping the temperature and stirring for 30min, then filtering while hot (filtering by a centrifuge), and washing with 2.0L of hot pure water to obtain 1.91kg (dry weight) of filter cake and 9.6L of filtering mother liquor (containing washing water). The mother liquid Li is tested + Heating the filtered mother liquor to boil, evaporating and concentrating until the volume of the mother liquor is 500mL, testing the concentrated solution until the lithium content is 27.26g/L, cooling, crystallizing, and filtering to obtain LiOH 2 And O, returning the crystallization filtering mother liquor to circulation. The results are shown in Table 1.
Example 2:
taking alpha type spodumene concentrate (containing Li) with the granularity of 200 meshes and the grade of 6.0% 2 O = 6%) 1.0kg of lime (which contains CaO in a proportion of 1.0kg of lime>85 percent, the granularity is 60-100 um) and a composite reducing agent (same as the example 1), after the solids are uniformly mixed, the mixture is pressed into a briquette to be made into 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 then the graphite crucible is put into a reducing furnace for thermal reduction (electric heating); the addition amount of the alpha type spodumene, the composite reducing agent and the lime is 1:0.3:1.0 (mass ratio). 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. The furnace door is opened, the crude lithium metal in the condensing chamber in the furnace is taken out and is used as the raw material for refining the lithium metal, the total weight of the raw material is 12.23g through test, and the lithium content is 95.7 percent. Then the reduced lithium containing metal in the crucibleAnd spodumene slag of lithium oxide was taken out, weighed to 2.25kg in total, and placed in an electrically heated stainless steel reaction vessel having a volume of 12.0L, and 8.0L of pure water was added, heated to 60 ℃, stirred and leached for 90min, and then filtered while hot (centrifuge filtration), and washed with 2.0L of hot pure water to obtain 2.23kg (dry weight) of a filter cake and 9.7L of a filtration mother liquor (containing washing water). The mother liquid Li is tested + Heating the filtered mother liquor to boil, evaporating and concentrating until the volume of the mother liquor is 500mL, testing 29.96g/L lithium in the concentrated solution, cooling, crystallizing, and filtering to obtain LiOH 2 And the crystallization filtering mother liquor returns to circulation. The results are shown in Table 1.
Example 3:
taking alpha type spodumene concentrate (containing Li) with the granularity of 200 meshes and the grade of 6.0 percent 2 O = 6%) 1.0kg, and lime (which contains CaO content)>85 percent, the granularity is 60-100 um) and a composite reducing agent (same as the embodiment 1), after the solids are uniformly mixed, the mixture is pressed into a briquette, a cylindrical flake with the diameter of 2.0cm and the thickness of 1.0cm is prepared, the cylindrical flake is put into a graphite crucible which is sprayed with a ceramic anti-corrosion layer, and then the graphite crucible is put into a reducing furnace (electrically heated); the adding amount of spodumene, the composite reducing agent and lime is 1:0.5:1.0 (mass ratio). 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. The furnace door is opened, the crude lithium metal in the condensing chamber in the furnace is taken out and is used as the raw material for refining the lithium metal, the total weight is 13.63g by test, and the lithium content is 96.1 percent. Then, the reduced spodumene slag containing metallic lithium and lithium oxide in the crucible was taken out, weighed, and totally 2.46kg, put into an electrically heated stainless steel reaction kettle with a volume of 12.0L, added with 8.0L of pure water, heated to 60 ℃, stirred and leached for 90min, then filtered while hot (by a centrifuge), and washed with 2.0L of hot pure water, to obtain 1.9kg (dry weight) of filter cake and 9.55L of filtered mother liquor (containing washing water). The mother liquid Li is tested + Heating the filtered mother liquor to boil, concentrating by evaporation until the volume of the mother liquor is 450mL, testing the concentrated solution containing 29.07g/L lithium, cooling, crystallizing, and passing throughFiltering to obtain LiOH.H 2 And O, returning the crystallization filtering mother liquor to circulation. The results are shown in Table 1.
Example 4:
taking alpha type spodumene concentrate (containing Li) with the granularity of 200 meshes and the grade of 6.0 percent 2 O = 6%) 1.0kg, and lime (which contains CaO content)>85%, particle size of 60-100 um), composite reducing agent (same as example 1), solid is mixed evenly, pressed into pellets, made into cylindrical sheet-like objects with diameter of 2.0cm and thickness of 1.0cm, put into a graphite crucible sprayed with ceramic anti-corrosion layer, and put into a reducing furnace (electric heating), the adding amount of spodumene, composite reducing agent and lime is 1:0.5:2.0 (mass ratio). 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. The furnace door is opened, the crude lithium metal in the condensing chamber in the furnace is taken out and is used as the raw material for refining the lithium metal, the total weight is 14.88g by test, and the lithium content is 96.8 percent. Then, the reduced spodumene slag containing metallic lithium and lithium oxide in the crucible is taken out, the weight is calculated, 3.47kg in total, the slag is placed into an electrically heated stainless steel reaction kettle with the volume of 25.0L, 14L of pure water is added, the temperature is heated to 60 ℃, the slag is stirred and leached for 90min, then the slag is filtered while hot (the slag is filtered by a centrifugal machine), and the slag is washed by 2.0L of hot pure water, so that 3.46kg (dry weight) of filter cake and 13.2L of filtered mother liquor (containing washing water) are obtained. The mother liquid Li is tested + Heating the filtered mother liquor to boil, evaporating and concentrating until the volume of the mother liquor is 400mL, testing the concentrated liquor to contain 31.5g/L lithium, cooling, crystallizing, and filtering to obtain LiOH.H 2 And O, returning the crystallization filtering mother liquor to circulation. The results are shown in Table 1.
Example 5:
taking alpha type spodumene concentrate (containing Li) with the granularity of 200 meshes and the grade of 6.0 percent 2 O = 6%) 1.0kg, and lime (which contains CaO content)>85%, granularity of 60-100 um), composite reducing agent (same as example 1), pressing into balls after solid mixing, making into cylindrical sheet with diameter of 2.0cm and thickness of 1.0cm, and filling into stone sprayed with ceramic anti-corrosion layerAn ink crucible, and then the graphite crucible is put into a reduction furnace (electrical heating); the mass ratio of spodumene to the composite reducing agent to lime =1:0.5: 2.5). 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. The furnace door is opened, the crude lithium metal in the condensing chamber in the furnace is taken out and is used as the raw material for refining the lithium metal, the total weight is 15.67g through test, and the lithium content is 97.0 percent. Then, the reduced spodumene slag containing metallic lithium and lithium oxide in the crucible was taken out, weighed, and 3.97kg in total, and placed in an electrically heated stainless steel reaction kettle with a volume of 25.0L, 16.0L of pure water was added, heated to 60 ℃, stirred and leached for 90min, and then filtered while hot (filtered by a centrifuge), and washed with 4.0L of hot pure water, to obtain 3.97kg (dry weight) of a filter cake and 16L of a filtration mother liquor (containing washing water). The mother liquid Li is tested + Heating the filtered mother liquor to boil and evaporating for concentration until the volume of the mother liquor is 350mL, testing 34.06g/L of lithium in the concentrated solution, cooling, crystallizing, and filtering to obtain LiOH.H 2 And O, returning the crystallization filtering mother liquor to circulation. The results are shown in Table 1.
Example 6:
taking alpha type spodumene concentrate (containing Li) with the granularity of 200 meshes and the grade of 6.0 percent 2 O = 6%) 1.0kg, and lime (which contains CaO content)>85%, the granularity is 60-100 um), and a composite reducing agent (same as the example 1), after the solids are uniformly mixed, the mixture is pressed into a briquette, a cylindrical sheet-shaped object with the diameter of 2.0cm and the thickness of 1.0cm is prepared, the cylindrical sheet-shaped object is put into a graphite crucible which is sprayed with a ceramic anti-corrosion layer, the graphite crucible is put into a reducing furnace (electric heating), and the mass ratio of the alpha-spodumene, the composite reducing agent and the lime is 1:0.5:2.0. vacuumizing the reduction furnace, controlling the absolute pressure to be 3.0Pa, electrifying, heating at 1300 ℃ for 25 hours, stopping heating, releasing pressure, and naturally cooling to normal temperature and normal pressure. The furnace door is opened, the crude lithium metal in the condensing chamber in the furnace is taken out and is used as the raw material for refining the lithium metal, the total weight of the raw material is 14.06g through test, and the lithium content is 94.6 percent. Then returning the crucibleThe original spodumene slag containing metallic lithium and lithium oxide was taken out, 3.45kg in total by weight, placed in an electrically heated stainless steel reaction vessel having a volume of 25.0L, added with 14.0L 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 3.45kg (dry weight) of filter cake and 12.9L of filtered mother liquor (containing washing water). The mother liquid Li is tested + Heating the filtered mother liquor to boil, evaporating and concentrating until the volume of the mother liquor is 400mL, testing 32.73g/L of lithium in the concentrated solution, cooling, crystallizing, and filtering to obtain LiOH.H 2 And O, returning the crystallization filtering mother liquor to circulation. The results are shown in Table 1.
Table 1 example test results
Note: the spodumene yield was 1.0kg and the grade was 6.0% for all examples (Li) 2 O = 6%) with a total lithium content of 27.9 g
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, the concentrate of the leachate was brought to a lithium content of 34g/L in the solution, and then cooled, crystallized and filtered to obtain LiOH 2 And O, returning the crystallization filtering mother liquor to circulation, wherein the experimental result is shown in the table 2.
Comparative example 2
The other conditions were the same as in example 5 except that the spodumene, ferrosilicon and lime solid powder were uniformly mixed and then reduced in a reducing furnace without agglomeration. Leaching the reduced spodumene slag, removing calcium, concentrating the leaching solution until the content of lithium in the solution is 34g/L, cooling, crystallizing and filtering to obtain LiOH.H 2 And O, returning the crystallization and filtration mother liquor to circulation, wherein the experimental result is shown in a table 2.
Comparative example 3
The other conditions were the same as in example 5 except that the reducing agent used was a single reducing agent, namely ferrosilicon having a silicon content of 60% (wt.%)) Leaching and decalcifying the reduced spodumene slag, concentrating the leaching solution until the content of lithium in the solution is 34g/L, cooling, crystallizing and filtering to obtain LiOH.H 2 And O, returning the crystallization and filtration mother liquor to circulation, wherein the experimental result is shown in a table 2.
Comparative example 4
The other conditions were the same as in example 5 except that the spodumene concentrate grade used was 4.5 (which contained Li) 2 O = 4.5%), granularity of 200 meshes, leaching and decalcifying the reduced spodumene slag, concentrating the leaching solution until the content of lithium in the solution is 34g/L, cooling, crystallizing and filtering to obtain LiOH 2 And O, returning the crystallization filtering mother liquor to circulation, wherein the experimental result is shown in the table 2.
TABLE 2
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 (8)
1. A method for preparing lithium oxide by thermally reducing spodumene is characterized by comprising the following steps: alpha type spodumene is used as a raw material, the alpha type spodumene is mixed with a reducing agent and a blocking agent to prepare a dough, the prepared dough is reduced in a reducing furnace under the conditions of vacuum and high temperature, lithium in the spodumene is reduced to metal lithium vapor, and then the metal lithium and the reduced spodumene slag containing the metal lithium and lithium oxide are obtained through condensation; leaching spodumene slag containing metal lithium and lithium oxide with water to obtain leaching slag and slurry; removing calcium from the leached residue and slurry, filtering, and washing to obtain filtrate which is lithium hydroxide solutionEvaporating and crystallizing the solution and the lithium hydroxide solution to produce battery grade or high-purity LiOH 2 O products; the spodumene is alpha-type spodumene concentrate, the grade of the spodumene concentrate is more than or equal to 5 percent, namely Li 2 O is more than or equal to 5.0 percent, and the granularity is 150-200 meshes; 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 percent; the flux inhibitor is lime, and the CaO content of the flux inhibitor is 90-98wt%; the mass ratio of the alpha type spodumene concentrate to the reducing agent to the blocking agent is 1:0.1-0.5:0.3-2.5.
2. A method for producing lithiated lithium hydroxide by the thermal reduction of spodumene according to claim 1, wherein: condensing the metal lithium vapor to obtain crude lithium, and refining under the protection of Ar gas and stirring to obtain metal lithium with purity of more than 99%; and filtering and washing the leached slag and the slurry to obtain a filter cake, and drying the filter cake to produce cement.
3. A method for producing lithiated lithium hydroxide by the thermal reduction of spodumene according to claim 1, wherein: the silicon content of the high-silicon ferrosilicon is more than or equal to 75wt%, and the granularity is 6-8um; the aluminum powder has an aluminum content of more than or equal to 99wt%, an activity of 70wt% and a particle size of 6-8um; the aluminum silicon powder has the aluminum silicon content of more than or equal to 98wt% and the particle size of 6-8um.
4. A method for producing lithium oxide by the thermal reduction of spodumene as claimed in any one of claims 1 to 3, comprising the steps of:
first-step thermal reduction: mixing spodumene concentrate, reducing agent and solid of dissolution inhibitor, pressing into spherical or sheet with particle size of 10-100mm by briquetting machine, placing into crucible, and vacuum reducing in reducing 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 lithium; 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 (2) leaching the obtained spodumene slag containing metal lithium and lithium oxide by stirring with pure water at the temperature of 20-90 ℃, wherein the solid-liquid ratio is =1:1-7, and the leaching time is 30-300min; after leaching, adding soda ash according to the total amount of calcium ions in the system, stirring for 20-50min, filtering after stopping stirring, washing to obtain a filter cake, drying and crushing the filter cake to obtain a cement clinker, and selling the cement clinker, wherein a filtering mother solution is used as a hydrogen-producing lithium oxide raw material solution;
step three, hydrogen and lithium oxide production: concentrating the filtered mother liquor to Li + The content is 25-60g/l, then cooling and crystallizing are carried out, the crystallization temperature is 20-50 ℃, a filter cake obtained by filtering is dried to obtain a lithium hydroxide product, and a filtering mother liquor is returned to the leaching liquid for circulation.
5. The method for producing lithiated spodumene by thermal reduction of spodumene as recited in claim 4, wherein the first thermal reduction step is carried out under the following conditions: the temperature is 850-1300 deg.C, the absolute pressure is 2-50Pa, and the time is 5-25 hr.
6. A method for producing lithiated spodumene by thermal reduction of spodumene as claimed in claim 4, wherein the leaching conditions in the second step are: the temperature is 40-80 ℃, and the solid-liquid mass ratio is 1:2-5, and the leaching time is 40-180min.
7. The method for producing lithiated spodumene by thermal reduction of spodumene as claimed in claim 4, wherein the amount of soda ash added in the second step is such that CaCO is formed by precipitation 3 105-110% of the theoretical mass of (A).
8. The method for producing lithiated spodumene by thermal reduction of spodumene as recited in claim 4, wherein: the method can produce lithium hydroxide and metallic lithium simultaneously; the total utilization rate of lithium is more than or equal to 95 percent.
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