Efficient transformation roasting method for spodumene

Abstract

The invention discloses an efficient transformation roasting method of spodumene, which comprises the following steps: according to the physical and chemical characteristics of spodumene, before microwave heating, carrying out modification preheating roasting to strengthen the microwave absorption capacity of spodumene, and then transferring hot-state preheated roasted sand into a high-temperature microwave roasting furnace, so that the transformation roasting efficiency of spodumene is improved in a microwave heating manner; the comprehensive recovery rate of lithium is improved. Besides, on the basis of the wave-absorbing characteristic of spodumene, graphite and biomass charcoal with the wave-absorbing performance similar to that of preheated spodumene are selected as a wave-absorbing auxiliary heating medium, the microwave power density is controlled, and the proportion, the granularity and the adding amount of the wave-absorbing auxiliary heating medium are designed, so that most microwaves directly act on spodumene minerals; according to the method, the transformation efficiency of spodumene is remarkably improved, meanwhile, the temperature of a part of areas in ore is suddenly changed under microwave radiation, crystals in a high-temperature area are subjected to brittle fracture, produced transformed calcine is extremely easy to grind, and the grinding cost of the transformed calcine in the acidification roasting procedure is greatly reduced.

Description

Technical Field

[0001] The invention relates to the field of metallurgy, and in particular to a high-efficiency transition roasting method for spodumene. Background Art

[0002] Lithium is a metal element, known as green energy metal and "white oil". Before the development of power batteries, lithium was mainly used in traditional industries. With the vigorous development of consumer electronics and electric vehicle industries, it has become the most important application field. In the consumption structure in 2021, the battery field has occupied more than 78% of the market share. Now, lithium batteries have been widely used in electric vehicles, energy storage batteries, laptops, mobile phones, digital cameras, small electronic equipment, aerospace, electromechanical and military communications.

[0003] In terms of lithium resources, lithium is mainly found in salt lake brine and granite pegmatite deposits. Spodumene (LiAl Si2O6) has become one of the main commercial lithium ores due to its large reserves and high lithium content. In terms of spodumene lithium extraction technology, natural spodumene (α type) is a single-chain silicate mineral with a stable structure. Except for hydrofluoric acid and some fluorides, which can destroy its structure under medium and low temperature conditions, other conventional chemical reagents need to react with spodumene under high temperature and high pressure conditions. The current spodumene lithium extraction technology requires pretreatment of natural lithium ore to change its chemical activity. The sulfuric acid method has been widely used due to its simple process and high metal recovery rate. This method first roasts natural spodumene at 950-1100℃ to transform it from monoclinic α spodumene to tetragonal β spodumene. Due to the crystal transformation, the physical and chemical properties of the mineral also change significantly with the change of the crystal structure, the chemical activity increases, and it can react with acids and alkalis. Then the transition roasted sand is finely ground, mixed with sulfuric acid and then acid-roasted at 200-300°C to generate soluble lithium sulfate and insoluble gangue, and finally the two-phase separation of lithium metal and gangue minerals is completed by water leaching. Therefore, in the spodumene sulfuric acid process for lithium extraction, roasting and converting the dense crystal structure of α-spodumene is the key to spodumene lithium extraction technology.

[0004] At present, the industrial spodumene transition roasting mainly adopts internal heat type rotary kiln equipment, with pulverized coal, natural gas etc. as heat source, but due to the lack of fuels such as coal and natural gas in some countries or regions, and the logistics foundation is relatively weak, the traditional method fuel cost is high. To solve this problem, researchers have proposed different energy combination roasting schemes, such as patent document CN117450778A discloses a two-stage spodumene transition roasting system and method, using combined energy "electricity+sulfur" to carry out transition roasting of spodumene, by the first section electromagnetic induction low temperature roasting heating+second section sulfur oxidation self-heating high temperature roasting mode, the focus is on solving the defect that electromagnetic heating cannot run for a long time at high temperature, but the high temperature roasting process is still a traditional heating method, just replace traditional energy with sulfur, the manufacturing cost of sulfur is still high, in addition, when directly using sulfur as roasting energy, sulfur combustion will produce a large amount of acidic gas (sulfur oxide) and toxic gas (hydrogen sulfide), which is harmful to human and environmental health, and needs to match and build an environmental protection treatment system, and the economic cost is high.

[0005] Microwave heating is an emerging low-carbon green heating method. It mainly relies on the high-frequency reciprocating motion of dipole molecules inside the heated body to generate "internal friction heat" to increase the temperature of the heated material. It does not require any heat conduction process and has the advantages of fast heating speed and uniform heating. However, the feasibility of this method depends on the dielectric properties (wave absorption ability) of the heated material. The relevant patent technologies of microwave heating in the lithium extraction process of spodumene are as follows:

[0006] Patent document CN102433430A discloses a method for producing β-spodumene concentrate by applying microwave to spodumene ore, wherein microwave is used to transform and roast spodumene, and the spodumene ore has a particle size of 0.2 to 30 mm, and microwave heating is performed for 30 to 50 minutes at a temperature of 930 to 1050° C., followed by cooling and sieving to obtain β-spodumene concentrate. The effects of impurity elements in spodumene, microwave power density, and microwave absorption performance of spodumene on the transformation effect of spodumene are not considered, and the crystal form transformation is poor, and the lithium recovery rate is less than 85%.

[0007] Patent document CN108165767A discloses a method for leaching spodumene based on microwave and pressure field, using microwave to pre-treat spodumene, then carrying out sulfuric acid leaching process to spodumene after microwave irradiation, under the condition of heating and pressurization, valuable metals such as lithium are leached as lithium sulfate. However, its microwave heating process uses a rotary kiln lined with silicon carbide for roasting, but the influence of impurity elements and microwave power density on the transition roasting effect in spodumene is not considered. During the microwave heating process, most of the microwaves are absorbed by the silicon carbide lining, and the main heating method becomes the radiation heating of spodumene by silicon carbide, which is difficult to realize the effective roasting and modification of spodumene by microwave. And in industrial production, the kiln lined with silicon carbide is difficult to withstand impact, has high requirements for process equipment, is difficult to operate, and is difficult to realize large-scale production.

[0008] Patent document CN114107674A discloses a method for extracting rubidium from spodumene tailings by volatilization based on a microwave field. The spodumene tailings containing rubidium are mixed with inorganic fibers, water glass, coal powder, etc. to form balls, which are then roasted under a microwave field to volatilize and concentrate rubidium in the smoke. Silicon carbide is still used as the lining during the high-temperature heating process. The process also has problems such as high requirements for process equipment and difficult operation.

[0009] Patent document CN1994874A discloses a solid phase-microwave synthesis method of polycrystalline LiFePO4 powder, which uses microwave-assisted synthesis of polycrystalline LiFePO4 powder, and microwave roasting of a graphite-coated precursor. The reducing atmosphere provided by the graphite during the roasting process is used to focus on solving the problem of the oxidation of divalent iron ions affecting the purity of the product during the precursor roasting process. The precursor synthesis process is mainly radiation heating after graphite absorbs microwaves. However, most of the microwaves are absorbed by graphite, and the surface precursor in direct contact with the graphite may overheat, thereby affecting the product quality. Summary of the invention

[0010] In view of the deficiencies in the prior art, the present invention aims to provide a high-efficiency transition roasting method for spodumene.

[0011] In order to achieve the above object, the present invention adopts the following technical solution:

[0012] A spodumene efficient transformation roasting method comprises the following steps:

[0013] Step S1, sample preparation: uniformly mixing the wave absorbing auxiliary heat medium and the spodumene concentrate to obtain a furnace mixed material;

[0014] Step S2, preheating, reforming and roasting: sending the mixed material obtained in step S1 into a preheating roasting furnace, preheating and roasting the mixed material to 450-600° C., and obtaining a fired material 1;

[0015] Step S3, transition roasting: the sintered material 1 obtained in step S2 is sent into a microwave roasting furnace in a hot state, the microwave frequency and microwave power density are controlled, the sintered material 1 is heated to 1000-1100° C., and then kept warm for 10-30 minutes to obtain transition roasted sand;

[0016] Step S4, waste heat recovery: The transition roasted sand produced in step S3 is air-cooled to recover waste heat, and high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and medium- and low-temperature hot air below 600°C is used for dehydration and drying of the mixed material entering the furnace.

[0017] Furthermore, in step S1, the particle size of the spodumene concentrate is 50-200 mesh, and the particle size of the wave-absorbing auxiliary heat medium is 100-200 mesh.

[0018] Furthermore, in step S1, the mass of the wave-absorbing auxiliary heat medium is 1-5% of the mass of the spodumene concentrate.

[0019] Furthermore, in step S1, the wave-absorbing auxiliary heat medium includes graphite and biochar, the mass percentage of graphite is 20%-70%, and the mass percentage of biochar is 30%-80%.

[0020] Furthermore, in step S1, the graphite comes from waste electrodes of the aluminum industry, and the biomass charcoal is prepared from straw and / or dead leaves.

[0021] Furthermore, in step S3, a double helical auger is provided at the center of the microwave roasting furnace to assist in turning the materials, and the material of the double helical auger is a high temperature heat-resistant alloy.

[0022] Furthermore, in step S3, the microwave frequency is 2450 Hz or 915 Hz, and the microwave power density is 10 kW / m 3 -25kW / m 3 .

[0023] Furthermore, in step S3, the microwave power density is modified according to the impurity components and the particle size of the spodumene concentrate; when the particle size of the spodumene concentrate is 50-100 mesh, if the total content of Mn and Fe in the spodumene concentrate is ≤2%, the microwave power density is controlled at 15 kW / m 3 -25kW / m 3 If the total content of Mn and Fe in spodumene concentrate is greater than 2%, the microwave power density is controlled at 13kW / m 3 -20kW / m 3 When the particle size of spodumene concentrate is 100-200 mesh, if the total content of Mn and Fe in the spodumene concentrate is ≤2%, the microwave power density is controlled at 15kW / m 3 -20kW / m 3If the total content of Mn and Fe in spodumene concentrate is greater than 2%, the microwave power density is controlled at 10 kW / m 3 -15kW / m 3 .

[0024] Furthermore, the method further comprises step S5, carbon selection: performing carbon selection on the transition roasted sand after the waste heat recovery by air cooling, enriching and recovering the residual graphite therein, and the obtained graphite is returned to be used as the auxiliary heat absorbing medium after drying.

[0025] The beneficial effects of the present invention are:

[0026] (1) The present invention proposes a two-stage transformation roasting process for spodumene based on the physical and chemical characteristics of spodumene itself. Before microwave heating, the process is firstly carried out for modification and preheating roasting to enhance the microwave absorption capacity of spodumene, and then the hot preheated roasted sand is transferred into a high-temperature microwave roasting furnace. This operation mode can not only significantly reduce the energy consumption of transformation roasting, but also greatly improve the transformation rate of spodumene and the comprehensive recovery rate of lithium.

[0027] (2) Based on the wave-absorbing properties of spodumene, the present invention selects "graphite + biomass charcoal" with similar wave-absorbing properties to that of preheated spodumene as a wave-absorbing auxiliary heat medium, designs the ratio, particle size and addition amount of the wave-absorbing auxiliary heat medium, so that most of the microwaves act directly on the spodumene mineral itself, significantly improving the transformation efficiency of spodumene. At the same time, the temperature of some areas in the ore changes suddenly under microwave radiation, and the crystals in the high-temperature area undergo brittle fracture. The resulting transformation roasted sand is very easy to grind, which greatly reduces the crushing cost of the transformation roasted sand in the acidification roasting process.

[0028] (3) The present invention uses "graphite + biochar" as the auxiliary heat absorbing medium, and utilizes the characteristics of biochar that is fluffy, porous, flammable, and has stronger absorbing ability (compared to graphite). On the one hand, it can quickly absorb and heat combustion under the microwave field, thereby improving the temperature stability of the preheating, reforming, and roasting products. On the other hand, it can utilize the flammable characteristics of biochar to drive graphite oxidation and heating, thereby improving energy utilization. In addition, after high-temperature roasting, the residual graphite in the roasted sand can be enriched and recovered through the mineral processing process for recycling.

[0029] (4) Based on the characteristics of spodumene raw materials, the present invention combines different mineral particle sizes, utilizes the selective heating characteristics of microwaves, and matches the microwave power density to avoid the influence of overheating and melting of strong absorbing phases in the mine on the transformation effect of spodumene. It solves the problems of agglomeration and scarring in the kiln caused by microwave high-temperature roasting of fine-grained spodumene and highly impure spodumene, reduces the difficulty of process operation, and improves the lithium recovery rate.

[0030] (5) The present invention uses "graphite + biomass carbon" as the wave-absorbing auxiliary heat medium, which improves the energy utilization efficiency of waste electrode materials and low-carbon biomass materials and promotes resource recycling and low-carbon emission reduction.

[0031] (6) The present invention utilizes the selective heating characteristics of microwaves to directly heat the materials, thereby reducing the heating temperature of the kiln and solving the problem of steel softening faced by existing externally heated electric high-temperature roasting furnaces when heating materials.

[0032] (7) The present invention can reduce the energy consumption per ton of ore roasting by recovering the waste heat of high-temperature transition roasted sand through air cooling. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart for implementing the methods of Examples 1-9 of the present invention. DETAILED DESCRIPTION

[0034] The present invention will be further described below in conjunction with the accompanying drawings. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0035] Example 1

[0036] This embodiment provides a spodumene efficient transformation roasting method, and the specific process is as follows:

[0037] Spodumene (Li2O 6%, Fe 0.12%, Mn 0.12%) was ground to 100 meshes, and 1% of microwave-absorbing auxiliary heat medium was added, the particle size of the microwave-absorbing auxiliary heat medium was 200 meshes, and the composition of the microwave-absorbing auxiliary heat medium was 50% of waste graphite and 50% of biomass carbon. After the spodumene concentrate and the microwave-absorbing auxiliary heat medium were mixed evenly, they were preheated and roasted in an electric furnace to 450°C to obtain a calcined material 1 to enhance the microwave absorption capacity of the spodumene concentrate. The calcined material 1 was then transferred to a microwave roasting furnace in a hot state, and the microwave frequency was 2450Hz and the microwave power density was 23kw / m 3 Under the conditions of , the calcined material is heated to 1050°C and then kept warm for 30 minutes to obtain transition roasted sand.

[0038] In this embodiment, the spodumene concentrate and the wave-absorbing auxiliary heat medium are first dehydrated and dried in a dehydration drying furnace before entering the electric furnace. After the transition roasted sand is obtained, the waste heat is first recovered by air cooling, and the high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and the medium-low temperature hot air below 600°C is sent to the dehydration drying furnace for dehydration and drying of the mixed material entering the furnace. The transition roasted sand after air cooling waste heat recovery is subjected to carbon selection operation to enrich and recover the residual graphite therein, and the obtained graphite is returned to be used as the wave-absorbing auxiliary heat medium after drying.

[0039] The transition roasted sand after carbon selection was successively ground (-200 mesh accounted for 90%), sulphate roasted (250 ℃ insulation for 30 minutes), and leached (liquid-solid ratio 1.7 room temperature water immersion for 30 minutes). The obtained leached slag contained about 0.05% Li2O and the lithium leaching rate was about 99.2%.

[0040] Example 2

[0041] This embodiment provides a spodumene efficient transformation roasting method, and the specific process is as follows:

[0042] Spodumene (Li2O 6%, Fe 1.48%, Mn 0.61%) was ground to 100 mesh, and 3% of microwave-absorbing auxiliary heat medium was added, the particle size of the microwave-absorbing auxiliary heat medium was 200 mesh, and the composition of the microwave-absorbing auxiliary heat medium was 50% waste graphite + 50% biomass carbon. After the spodumene concentrate and the microwave-absorbing auxiliary heat medium were mixed evenly, they were preheated and roasted in an electric furnace to 450°C to obtain a fired material 1, and then the fired material 1 was transferred to a microwave roasting furnace in a hot state, and the microwave frequency was 2450Hz and the microwave power density was 16kw / m 3 Under the conditions of , the calcined material is heated to 1050°C and then kept warm for 30 minutes to obtain transition roasted sand.

[0043] In this embodiment, the spodumene concentrate and the wave-absorbing auxiliary heat medium are first dehydrated and dried in a dehydration drying furnace before entering the electric furnace. After the transition roasted sand is obtained, the waste heat is first recovered by air cooling, and the high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and the medium-low temperature hot air below 600°C is sent to the dehydration drying furnace for dehydration and drying of the mixed material entering the furnace. The transition roasted sand after air cooling waste heat recovery is subjected to carbon selection operation to enrich and recover the residual graphite therein, and the obtained graphite is returned to be used as the wave-absorbing auxiliary heat medium after drying.

[0044] The transition roasted sand was successively ground (-200 mesh accounted for 90%), sulphate roasted (250 ℃ heat preservation for 30 min), and leached (liquid-solid ratio 1.7 room temperature water immersion for 30 min). The obtained leached slag contained about 0.10% Li2O and the lithium leaching rate was about 98.4%.

[0045] Example 3

[0046] This embodiment provides a spodumene efficient transformation roasting method, and the specific process is as follows:

[0047] Spodumene (Li2O 6%, Fe 0.56%, Mn 0.13%) was ground into 50 meshes, and 3% of microwave-absorbing auxiliary heat medium was added. The particle size of the microwave-absorbing auxiliary heat medium was 200 meshes, and the composition of the microwave-absorbing auxiliary heat medium was 50% of waste graphite + 50% of biomass carbon. After the spodumene concentrate and the microwave-absorbing auxiliary heat medium were evenly mixed, they were preheated and roasted in an electric furnace to 450°C to obtain a fired material 1, and then the fired material 1 was hot transferred into a microwave roasting furnace at a microwave frequency of 2450 Hz and a microwave power density of 25 kw / m 3 Under the conditions of , the calcined material is heated to 1050°C and then kept warm for 30 minutes to obtain transition roasted sand.

[0048] In this embodiment, the spodumene concentrate and the wave-absorbing auxiliary heat medium are first dehydrated and dried in a dehydration drying furnace before entering the electric furnace. After the transition roasted sand is obtained, the waste heat is first recovered by air cooling, and the high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and the medium-low temperature hot air below 600°C is sent to the dehydration drying furnace for dehydration and drying of the mixed material entering the furnace. The transition roasted sand after air cooling waste heat recovery is subjected to carbon selection operation to enrich and recover the residual graphite therein, and the obtained graphite is returned to be used as the wave-absorbing auxiliary heat medium after drying.

[0049] The transition roasted sand after carbon selection was successively ground (-200 mesh accounted for 90%), sulphate roasted (250 ℃ insulation for 30 minutes), and leached (liquid-solid ratio 1.7 room temperature water immersion for 30 minutes). The obtained leached slag contained about 0.09% Li2O and the lithium leaching rate was about 98.5%.

[0050] Example 4

[0051] This embodiment provides a spodumene efficient transformation roasting method, and the specific process is as follows:

[0052] Spodumene (Li2O 6%, Fe 0.56%, Mn 0.13%) was ground into 50 meshes, and 1% of microwave-absorbing auxiliary heat medium was added. The particle size of the microwave-absorbing auxiliary heat medium was 200 meshes, and the composition of the microwave-absorbing auxiliary heat medium was 50% waste graphite + 50% biomass carbon. After the spodumene concentrate and the microwave-absorbing auxiliary heat medium were mixed evenly, they were preheated and roasted in an electric furnace to 450°C to obtain a fired material 1, and then the fired material 1 was transferred to a microwave roasting furnace in a hot state at a microwave frequency of 2450 Hz and a microwave power density of 20 kw / m 3 Under the conditions of 1 to 1050 ℃ heat preservation 30min, to obtain the transformation roasted sand.

[0053] In this embodiment, the spodumene concentrate and the wave-absorbing auxiliary heat medium are first dehydrated and dried in a dehydration drying furnace before entering the electric furnace. After the transition roasted sand is obtained, the waste heat is first recovered by air cooling, and the high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and the medium-low temperature hot air below 600°C is sent to the dehydration drying furnace for dehydration and drying of the mixed material entering the furnace. The transition roasted sand after air cooling waste heat recovery is subjected to carbon selection operation to enrich and recover the residual graphite therein, and the obtained graphite is returned to be used as the wave-absorbing auxiliary heat medium after drying.

[0054] The transition roasted sand after carbon selection was successively ground (-200 mesh accounted for 90%), sulfated roasted (250℃ insulation for 30 min), and leached (liquid-solid ratio 1.7 room temperature water immersion for 30 min). The obtained leached residue contained about 0.07% Li2O and the lithium leaching rate was about 98.9%.

[0055] Example 5

[0056] This embodiment provides a spodumene efficient transformation roasting method, and the specific process is as follows:

[0057] Spodumene (Li2O 6%, Fe 0.56%, Mn 0.13%) was ground into 50 meshes, and 5% of microwave-absorbing auxiliary heat medium was added. The microwave-absorbing auxiliary heat medium had a particle size of 200 meshes and a composition of 70% of waste graphite + 30% of biomass carbon. After the spodumene concentrate and the microwave-absorbing auxiliary heat medium were evenly mixed, they were preheated and roasted in an electric furnace to 450°C to obtain a fired material 1. The fired material 1 was then transferred to a microwave roasting furnace in a hot state and roasted at a microwave frequency of 2450 Hz and a microwave power density of 23 kw / m 3 Under the conditions of , the calcined material is heated to 1050°C and then kept warm for 30 minutes to obtain transition roasted sand.

[0058] In this embodiment, the spodumene concentrate and the wave-absorbing auxiliary heat medium are first dehydrated and dried in a dehydration drying furnace before entering the electric furnace. After the transition roasted sand is obtained, the waste heat is first recovered by air cooling, and the high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and the medium-low temperature hot air below 600°C is sent to the dehydration drying furnace for dehydration and drying of the mixed material entering the furnace. The transition roasted sand after air cooling waste heat recovery is subjected to carbon selection operation to enrich and recover the residual graphite therein, and the obtained graphite is returned to be used as the wave-absorbing auxiliary heat medium after drying.

[0059] The transition roasted sand after carbon selection was successively ground (-200 mesh accounted for 90%), sulfated roasted (250℃ insulation for 30 min), and leached (liquid-solid ratio 1.7 room temperature water immersion for 30 min). The obtained leached residue contained about 0.15% Li2O and the lithium leaching rate was about 97.6%.

[0060] Example 6

[0061] This embodiment provides a spodumene efficient transformation roasting method, and the specific process is as follows:

[0062] Spodumene (Li2O 6%, Fe 0.56%, Mn 0.13%) was ground into 50 meshes, and 5% of microwave-absorbing auxiliary heat medium was added. The microwave-absorbing auxiliary heat medium had a particle size of 200 meshes and a composition of 70% of waste graphite + 30% of biomass carbon. After the spodumene concentrate and the microwave-absorbing auxiliary heat medium were evenly mixed, they were preheated and roasted in an electric furnace to 450°C to obtain a fired material 1. The fired material 1 was then transferred to a microwave roasting furnace in a hot state and roasted at a microwave frequency of 915 Hz and a microwave power density of 20 kw / m 3 Under the conditions of , the calcined material is heated to 1050°C and then kept warm for 30 minutes to obtain transition roasted sand.

[0063] In this embodiment, the spodumene concentrate and the wave-absorbing auxiliary heat medium are first dehydrated and dried in a dehydration drying furnace before entering the electric furnace. After the transition roasted sand is obtained, the waste heat is first recovered by air cooling, and the high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and the medium-low temperature hot air below 600°C is sent to the dehydration drying furnace for dehydration and drying of the mixed material entering the furnace. The transition roasted sand after air cooling waste heat recovery is subjected to carbon selection operation to enrich and recover the residual graphite therein, and the obtained graphite is returned to be used as the wave-absorbing auxiliary heat medium after drying.

[0064] The transition roasted sand after carbon selection was successively ground (-200 mesh accounted for 90%), sulfated roasted (250℃ insulation for 30 min), and leached (liquid-solid ratio 1.7 room temperature water immersion for 30 min). The obtained leached residue contained about 0.12% Li2O and the lithium leaching rate was about 98%.

[0065] Example 7

[0066] This embodiment provides a spodumene efficient transformation roasting method, and the specific process is as follows:

[0067] Spodumene (Li2O 6%, Fe 0.56%, Mn 0.13%) was ground into 50 meshes, and 2% of microwave-absorbing auxiliary heat medium was added, the particle size of the microwave-absorbing auxiliary heat medium was 200 meshes, and the composition of the microwave-absorbing auxiliary heat medium was 70% waste graphite + 30% biomass carbon. After the spodumene concentrate and the microwave-absorbing auxiliary heat medium were mixed evenly, they were preheated and roasted in an electric furnace to 450°C to obtain a fired material 1, and then the fired material 1 was transferred to a microwave roasting furnace in a hot state, and the microwave frequency was 2450Hz and the microwave power density was 20kw / m 3 Under the conditions of 1 to 1100 ℃ heat to keep warm for 30min, to obtain transition roasted sand.

[0068] In this embodiment, the spodumene concentrate and the wave-absorbing auxiliary heat medium are first dehydrated and dried in a dehydration drying furnace before entering the electric furnace. After the transition roasted sand is obtained, the waste heat is first recovered by air cooling, and the high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and the medium-low temperature hot air below 600°C is sent to the dehydration drying furnace for dehydration and drying of the mixed material entering the furnace. The transition roasted sand after air cooling waste heat recovery is subjected to carbon selection operation to enrich and recover the residual graphite therein, and the obtained graphite is returned to be used as the wave-absorbing auxiliary heat medium after drying.

[0069] The transition roasted sand after carbon selection was successively ground (-200 mesh accounted for 90%), sulfated roasted (250℃ insulation for 30 min), and leached (liquid-solid ratio 1.7 room temperature water immersion for 30 min). The obtained leached residue contained about 0.05% Li2O and the lithium leaching rate was about 99.2%.

[0070] Example 8

[0071] This embodiment provides a spodumene efficient transformation roasting method, and the specific process is as follows:

[0072] Spodumene (Li2O 6%, Fe 0.56%, Mn 0.13%) was ground into 50 meshes, and 3% of microwave-absorbing auxiliary heat medium was added. The particle size of the microwave-absorbing auxiliary heat medium was 200 meshes, and the composition of the microwave-absorbing auxiliary heat medium was 70% of waste graphite + 30% of biomass carbon. After the spodumene concentrate and the microwave-absorbing auxiliary heat medium were evenly mixed, they were preheated and roasted in an electric furnace to 600°C to obtain a fired material 1, and then the fired material 1 was transferred to a microwave roasting furnace in a hot state at a microwave frequency of 2450 Hz and a microwave power density of 20 kw / m 3 Under the conditions of 1 to 1100 ℃, the sintered material is heated and kept warm for 30 minutes to obtain transition roasted sand.

[0073] In this embodiment, the spodumene concentrate and the wave-absorbing auxiliary heat medium are first dehydrated and dried in a dehydration drying furnace before entering the electric furnace. After the transition roasted sand is obtained, the waste heat is first recovered by air cooling, and the high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and the medium-low temperature hot air below 600°C is sent to the dehydration drying furnace for dehydration and drying of the mixed material entering the furnace. The transition roasted sand after air cooling waste heat recovery is subjected to carbon selection operation to enrich and recover the residual graphite therein, and the obtained graphite is returned to be used as the wave-absorbing auxiliary heat medium after drying.

[0074] The transition roasted sand after carbon selection was successively ground (-200 mesh accounted for 90%), sulfated roasted (250℃ insulation for 30min), and leached (liquid-solid ratio 1.7 room temperature water immersion for 30min). The obtained leached residue contained about 0.06% Li2O and the lithium leaching rate was about 99%.

[0075] Example 9

[0076] This embodiment provides a spodumene efficient transformation roasting method, and the specific process is as follows:

[0077] Spodumene (Li2O 6%, Fe 0.12%, Mn 0.12%) was ground to 100 meshes, and 1% of microwave-absorbing auxiliary heat medium was added, the particle size of the microwave-absorbing auxiliary heat medium was 200 meshes, and the composition of the microwave-absorbing auxiliary heat medium was 50% of waste graphite and 50% of biomass carbon. After the spodumene concentrate and the microwave-absorbing auxiliary heat medium were mixed evenly, they were preheated and roasted in an electric furnace to 450°C to obtain a calcined material 1 to enhance the microwave absorption capacity of the spodumene concentrate. The calcined material 1 was then transferred to a microwave roasting furnace in a hot state, and the microwave frequency was 2450Hz and the microwave power density was 10kw / m 3 Under the conditions of , the calcined material is heated from 1 to 1000°C and then kept warm for 10 minutes to obtain transition roasted sand.

[0078] In this embodiment, the spodumene concentrate and the wave-absorbing auxiliary heat medium are first dehydrated and dried in a dehydration drying furnace before entering the electric furnace. After the transition roasted sand is obtained, the waste heat is first recovered by air cooling, and the high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and the medium-low temperature hot air below 600°C is sent to the dehydration drying furnace for dehydration and drying of the mixed material entering the furnace. The transition roasted sand after air cooling waste heat recovery is subjected to carbon selection operation to enrich and recover the residual graphite therein, and the obtained graphite is returned to be used as the wave-absorbing auxiliary heat medium after drying.

[0079] The transition roasted sand after carbon selection was successively ground (-200 mesh accounted for 90%), sulfated roasted (250℃ insulation for 30 min), and leached (liquid-solid ratio 1.7 room temperature water immersion for 30 min). The obtained leached residue contained about 0.1% Li2O and the lithium leaching rate was about 98.4%.

[0080] Comparative Example 1

[0081] Spodumene (Li2O 6%, Fe 0.56%, Mn 0.13%) is ground to 50 meshes, accounting for 60%, and is subjected to transformation roasting using traditional energy sources such as pulverized coal and natural gas to obtain transformation roasting. The transformation roasted sand is successively ground (200 meshes, accounting for 90%), sulphate roasted (250°C for 30 min), leached (liquid-solid ratio 1.7, room temperature water immersion for 30 min), and the obtained leached slag contains about 0.2% Li2O, and the lithium leaching rate is about 96.7%. Compared with the spodumene transformation roasting method proposed in Examples 1-9, the comparative process (traditional process) needs to consume a large amount of energy, and problems such as overburning and roasted sand agglomeration often occur in the production operation process. The transformation rate of spodumene roasted sand is low, and before the roasted sand enters the acidification roasting process, due to the large hardness of the transformation roasted sand, it is necessary to rely on a large mill to carefully grind, consuming a large amount of grinding energy.

[0082] For those skilled in the art, various corresponding changes and modifications can be made according to the above technical solutions and concepts, and all of these changes and modifications should be included in the protection scope of the claims of the present invention.

Claims

1. A spodumene efficient transformation roasting method, characterized in that, The following steps are involved: Step S1, sample preparation: uniformly mixing the wave absorbing auxiliary heat medium and the spodumene concentrate to obtain a furnace mixed material; Step S2, preheating, reforming and roasting: sending the mixed material obtained in step S1 into a preheating roasting furnace, preheating and roasting the mixed material to 450-600° C., and obtaining a fired material 1; Step S3, transition roasting: the sintered material 1 obtained in step S2 is sent into a microwave roasting furnace in a hot state, the microwave frequency and microwave power density are controlled, the sintered material 1 is heated to 1000-1100° C., and then kept warm for 10-30 minutes to obtain transition roasted sand; Step S4, waste heat recovery: The transition roasted sand produced in step S3 is air-cooled to recover waste heat, and high-temperature hot air above 600°C is sent to the preheating roasting furnace for auxiliary heating, and medium- and low-temperature hot air below 600°C is used for dehydration and drying of the mixed material entering the furnace.

2. The method according to claim 1, characterized in that In step S1, the particle size of the spodumene concentrate is 50-200 mesh, and the particle size of the wave-absorbing auxiliary heat medium is 100-200 mesh.

3. The method according to claim 1, characterized in that In step S1, the mass of the wave-absorbing auxiliary heat medium is 1-5% of the mass of the spodumene concentrate.

4. The method according to claim 1, characterized in that In step S1, the wave-absorbing auxiliary heat medium includes graphite and biochar, the mass percentage of graphite is 20%-70%, and the mass percentage of biochar is 30%-80%.

5. The method according to claim 1, characterized in that In step S1, the graphite comes from waste electrodes of the aluminum industry, and the biomass charcoal is prepared from straw and / or dead leaves.

6. The method according to claim 1, characterized in that In step S3, a double helical auger is provided at the center of the microwave roasting furnace to assist in turning the materials, and the double helical auger is made of a high temperature heat-resistant alloy.

7. The method according to claim 1, characterized in that In step S3, the microwave frequency is 2450 Hz or 915 Hz, and the microwave power density is 10 kW / m 3 -25kW / m 3 .

8. The method according to claim 7, characterized in that In step S3, the microwave power density is modified according to the impurity components and the particle size of the spodumene concentrate; when the particle size of the spodumene concentrate is 50-100 mesh, if the total content of Mn and Fe in the spodumene concentrate is ≤2%, the microwave power density is controlled at 15 kW / m 3 -25kW / m 3 If the total content of Mn and Fe in spodumene concentrate is greater than 2%, the microwave power density is controlled at 13kW / m 3 -20kW / m 3 When the particle size of spodumene concentrate is 100-200 mesh, if the total content of Mn and Fe in the spodumene concentrate is ≤2%, the microwave power density is controlled at 15kW / m 3 -20kW / m 3 If the total content of Mn and Fe in spodumene concentrate is greater than 2%, the microwave power density is controlled at 10 kW / m 3 -15kW / m 3 .

9. The method according to claim 4, characterized in that The method further comprises step S5, carbon selection: performing carbon selection on the transition roasted sand after the waste heat recovery by air cooling, enriching and recovering the residual graphite therein, and returning the obtained graphite to be used as the auxiliary heat absorbing medium after drying.

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