Method and system for preparing lithium hydroxide from spodumene acidified material

Abstract

The invention discloses a method and a system for preparing lithium hydroxide from a spodumene acidified material. The method comprises the following steps: sequentially carrying out transformation roasting, acidifying roasting and adsorption, eluting and extracting lithium, adding water to dilute the acidified material, stirring to fully dissolve lithium ions in the acidified material, and adsorbing and enriching the lithium ions by utilizing a lithium adsorbent. And eluting lithium ions adsorbed and enriched by the lithium adsorbent through a dilute sulfuric acid solution to obtain a lithium sulfate feed liquid. And then sequentially passing through a pre-concentration membrane distillation unit, an ion exchange device, a bipolar membrane electrodialysis unit and an alkali liquor membrane distillation unit to prepare lithium hydroxide. Compared with the prior art, the method has the advantages that the acidified clinker does not need to be leached and filtered, so that a large amount of Na < + > and Ca < 2 + > ions introduced by adding caustic soda, soda ash or lime milk during leaching treatment are avoided, and the impurity removal difficulty and cost are reduced; and secondly, the lithium which is not adsorbed and eluted is continuously circulated in the adsorption lithium removal mechanism, so that the loss amount of the lithium element is reduced, meanwhile, an additional process for recovering the lithium element in the filter-pressed lithium slag is not needed, the process cost is reduced, and relatively good practicability is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium hydroxide production, and specifically relates to a method and a system for preparing lithium hydroxide from spodumene acidified material. Background Art

[0002] At present, the main methods for preparing lithium hydroxide from spodumene are the lithium sulfate finished liquid caustic soda conversion method and the lithium carbonate lime milk causticization method. The two methods have the same pre-process, that is, spodumene undergoes transformation roasting, cooling fine grinding, acid roasting, leaching filtration, purification, evaporation and other processes to obtain lithium sulfate finished liquid. For the subsequent process, the lithium sulfate finished liquid caustic soda conversion method is to prepare frozen denitrification mother liquor by subjecting the lithium sulfate finished liquid to the caustic soda conversion-freezing denitrification process, and then to prepare lithium hydroxide monohydrate by evaporation and crystallization; the lithium carbonate lime milk causticization method first prepares lithium carbonate by lithium precipitation reaction under heating conditions, and uses an automatic centrifuge to separate the lithium precipitation slurry into liquid and solid, and prepares causticized liquid by lime milk causticization of lithium carbonate, and prepares causticized finished liquid after clarification and fine filtration, and then prepares lithium hydroxide monohydrate by evaporation and crystallization process.

[0003] However, in the leaching and filtration process, the above two methods generally use caustic soda, soda ash or lime milk to neutralize the excess acid and adjust the pH, which will introduce a large amount of Na + , Ca 2+ ions, further impurities need to be removed; then the leachate is filtered, washed, cleaned, and slag unloaded through a filter press. The investment cost of a filter press (such as a plate and frame filter) is high, and the lithium slag produced by the filter press loses some lithium elements and needs to be recovered, further increasing the production cost. In the subsequent process, whether it is the caustic soda conversion method or the lime milk causticization method, a large amount of Na + , Ca 2+ The newly introduced large amount of Na + , Ca 2+ ions plus other ions in the leachate itself (mainly Na + , K + , Ca 2+ Mg 2+ , Fe) need to be removed, resulting in high impurity removal costs.

[0004] Chinese patent CN116332208A discloses a method for preparing battery-grade lithium hydroxide from spodumene acid leaching solution, wherein the acid leaching solution is separated from high-valent ions by nanofiltration membrane, evaporated and concentrated, two-stage chemical impurity removal, resin deep impurity removal, and bipolar membrane separation to obtain alkaline solution, and the alkaline solution is then concentrated, crystallized, and recrystallized to obtain battery-grade lithium hydroxide monohydrate. Compared with the traditional caustic soda conversion method and lithium carbonate lime milk causticization method, the above patent reduces the introduction of Na in the subsequent process. + , Ca 2+However, it is still impossible to avoid the introduction of a large amount of Na in the leaching process. + , Ca 2+ , multiple stages of impurity removal processes are required to meet product requirements. Secondly, in the evaporation concentration and crystallization process, the existing technology often uses multi-effect evaporation or mechanical steam recompression evaporation to concentrate and crystallize the concentrated liquid. The evaporation equipment used in these two methods has the disadvantages of large footprint, high steam consumption or high compressor cost, and chloride ions are corrosive to equipment steel. The equipment construction, production operation and subsequent maintenance costs are high. Summary of the invention

[0005] The object of the present invention is to provide a method and system for preparing lithium hydroxide from spodumene acidification material, aiming to solve the above-mentioned problems.

[0006] The present invention is mainly achieved through the following technical solutions: A method for preparing lithium hydroxide from spodumene acidified material comprises the following steps: Step S1. Transformation roasting: placing the spodumene material in a rotary kiln and calcining it to generate a roasted material, so that the spodumene crystal form is converted from α-type to β-type; then, the roasted material temperature is cooled to 110~120°C by a grate cooler, and sent to a ball mill to be crushed to obtain a fine powder roasted material with a particle size of less than 200 mesh; Step S2. Acidification and roasting: The fine powder roasted material and concentrated sulfuric acid are respectively put into an acid mixing machine for mixing to obtain a mixed acid material, wherein the concentrated sulfuric acid is in excess of 20wt% to 40wt%; the mixed acid material is then put into an acidification rotary kiln for roasting to generate an acidified material, and then sent to a cooling kiln for cooling to 90 to 100°C; Step S3. adsorption and elution to extract lithium: adding water to dilute the acidified material and stirring to fully dissolve the lithium ions in the acidified material, using the lithium adsorbent to adsorb and enrich the lithium ions, and then eluting the lithium ions adsorbed and enriched by the lithium adsorbent with a dilute sulfuric acid solution to obtain a lithium sulfate solution; Step S4. Pre-concentration treatment: evaporating and concentrating the lithium sulfate feed solution through a pre-concentration membrane distillation unit to obtain a pre-concentrated solution; Step S5. Ion exchange treatment: introducing the pre-concentrated solution into an ion exchange device, and treating it with a cation exchange resin in the ion exchange device to obtain a pre-electrolyte; Step S6. Bipolar membrane electrodialysis separation: subjecting the pre-electrolyte to bipolar membrane electrodialysis to obtain alkaline solution and dilute sulfuric acid; Step S7. Preparation of lithium hydroxide: The alkali solution is transported to an alkali solution membrane distillation unit for evaporation, concentration and crystallization, and lithium hydroxide and mother liquor are separated by a centrifuge.

[0007] In order to better realize the present invention, further, in the step S3, the cooled acidified material is added to an adsorption box with a built-in lithium adsorbent, a dilution liquid is supplied to the adsorption box through a water tank, and a blade agitator inside the adsorption box is started to stir and dilute the acidified material, and then, the stirring and adding of the dilution liquid are stopped, and all the liquid inside the adsorption box is introduced into the water tank; then, dilute sulfuric acid is provided to the adsorption box through an acid supply tank to rinse the lithium adsorbent, and the eluted lithium ions are filtered and introduced into a pre-concentration membrane distillation unit.

[0008] In order to better implement the present invention, further, in step S6, the dilute sulfuric acid is transported to the acid liquid membrane distillation unit for evaporation and concentration to obtain dilute sulfuric acid with a concentration of 40 wt % and transported to the acid supply tank.

[0009] The present invention is mainly achieved through the following technical solutions: A system for preparing lithium hydroxide from spodumene acidified material is used to realize the above-mentioned method for preparing lithium hydroxide from spodumene acidified material, comprising a transformation roasting mechanism, a ball mill, an acidification roasting mechanism, an adsorption and delithiation mechanism, a pre-concentration membrane distillation unit, an ion exchange device, a bipolar membrane electrodialyzer, an alkaline liquid membrane distillation unit and a centrifuge, which are arranged in sequence from front to back; the heat sources of the pre-concentration membrane distillation unit and the alkaline liquid membrane distillation unit are from the hot flue gas generated by the transformation roasting mechanism, the ion exchange device is provided with a cation exchange resin, and the adsorption and delithiation mechanism is provided with a lithium adsorbent.

[0010] In order to better realize the present invention, further, the adsorption and delithiation mechanism includes an adsorption box, a water tank, an acid supply box, a lithium liquid recovery component and a drainage filter component, and a feed port is arranged on one side of the adsorption box; a stirring mechanism is installed in the middle part of the adsorption box, and a lithium adsorbent is installed on the side wall inside the adsorption box, and a plurality of acid inlet channels are arranged on the top of the adsorption box corresponding to the lithium adsorbent, and the acid supply box is connected to the acid inlet channel through an acid inlet pump; the water tank is connected to the water inlet channel at the top of the adsorption box through a water pump, one end of the lithium liquid recovery component and the drainage filter component are respectively connected to the drainage hole and the drainage hole at the bottom of the adsorption box, and the other ends of the lithium liquid recovery component and the drainage filter component are respectively connected to the water tank and the pre-concentration membrane distillation unit.

[0011] In order to better realize the present invention, further, the lithium liquid recovery component includes a first ball valve and a circulating water pump arranged in sequence from front to back, and the drainage filter component includes a second ball valve, a filter and a drainage pump arranged in sequence from front to back, the first ball valve and the second ball valve are respectively connected to the drain hole and the drainage hole, and the circulating water pump and the drainage pump are respectively connected to the water tank and the pre-concentration membrane distillation unit.

[0012] In order to better realize the present invention, it further includes an acid liquid membrane distillation unit, which is used to evaporate and concentrate the dilute sulfuric acid obtained after treatment by the bipolar membrane electrodialysis instrument to obtain dilute sulfuric acid with a concentration of 40wt% and transport it to the acid supply box.

[0013] In order to better realize the present invention, further, the pre-concentration membrane distillation unit, the alkali liquid membrane distillation unit and the acid liquid membrane distillation unit respectively include a heating component arranged in sequence from front to back, a plurality of membrane distillation components connected in series through pipelines, and a cooling component, and the heat source of the heating component comes from the hot flue gas generated by the transformation roasting mechanism.

[0014] In order to better realize the present invention, further, the membrane distillation component includes a flow-through component, a hydrophobic membrane, a condensation component and a condensation sheet arranged in sequence from front to back, and the condensation component of the membrane distillation component at the tail end is connected to the vacuum pump; the flow-through component and the condensation component are made of non-metallic materials, and the hydrophobic membrane and the condensation sheet are made of polytetrafluoroethylene and polypropylene, respectively.

[0015] In order to better realize the present invention, further, the transition roasting mechanism includes a roasting rotary kiln and a grate cooler arranged in sequence from front to back, and the acidification roasting mechanism includes an acid mixing machine, an acidification rotary kiln and a cooling kiln arranged in sequence from front to back.

[0016] The beneficial effects of the present invention are as follows: (1) The present invention dilutes and stirs the acidified material through the adsorption and delithiation mechanism to fully dissolve the lithium ions therein, then uses the lithium adsorbent to enrich the lithium ions, and elutes the lithium ions on the lithium adsorbent through a dilute sulfuric acid solution to prepare a lithium sulfate liquid, without the need for leaching and filtering the acidified clinker. Compared with the conventional leaching and filtration process, the present invention avoids the introduction of a large amount of Na+ by adding caustic soda, soda ash or lime milk during the leaching process. + , Ca 2+ On the other hand, the present invention does not use a filter press, which reduces the equipment investment cost, and further allows the unadsorbed lithium to continue to circulate in the adsorption and delithiation mechanism through the lithium liquid recovery component and filter in the adsorption and delithiation mechanism, thereby reducing the loss of lithium elements. At the same time, no additional process is required to recover the lithium elements in the filter press lithium slag, thereby reducing the process cost and having good practicality.

[0017] (2) The present invention evaporates and concentrates lithium sulfate liquid, alkali liquid containing lithium hydroxide and dilute sulfuric acid through a pre-concentration membrane distillation unit, an alkali liquid membrane distillation unit and an acid liquid membrane distillation unit, respectively. The present invention effectively reduces the load of subsequent equipment by pre-concentrating the lithium sulfate liquid. The membrane distillation unit equipment itself is small in size and is skid-mounted, with a compact structure, small footprint and low civil engineering cost. Compared with multiple-effect evaporation or mechanical steam recompression evaporation, the flow-through parts and condensation parts of the membrane distillation component are supported by non-metallic materials, which effectively avoids the corrosion of chloride ions to metals. It can operate under acidic or alkaline conditions and is more suitable for concentrating liquid, lithium hydroxide and dilute sulfuric acid. The membrane distillation component utilizes the waste heat of the transition roasting process, which effectively reduces the operating cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The present invention is a flow chart of a method for preparing lithium hydroxide from spodumene acidified material; Figure 2 It is a structural schematic diagram of the lithium adsorption and delithiation mechanism; Figure 3 It is a schematic diagram of the structure of the lithium liquid recovery component and the drainage filter component; Figure 4 It is a structural schematic diagram of a pre-concentration membrane distillation unit; Figure 5 It is a structural schematic diagram of an alkali liquid membrane distillation unit; Figure 6 It is a structural schematic diagram of the acid liquid membrane distillation unit; Figure 7 Schematic diagram of the structure of the membrane distillation component.

[0019] Wherein: 11-water supply pipe, 12-water supply pump, 13-acid inlet pump, 14-adsorption box, 141-box cover, 1411-water inlet channel, 1412-acid inlet channel, 142-driving motor, 143-blade agitator, 144-box body, 1441-feed port, 145-lithium adsorbent, 15-lithium liquid recovery component, 151-circulating water pump, 153-first ball valve, 16-drainage filter component, 161-second ball valve, 162-filter, 163-drainage pump, 21-heating component, 22-membrane distillation component, 23-cooling component, A1-flow component, A2-hydrophobic membrane, A3-condensation sheet, A4-condensation component, A5-vacuum pump. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention clearer, the embodiments of the present invention will be further described below in conjunction with the accompanying drawings. The following is a preferred embodiment of the present invention, which is intended to provide a basic understanding of the present invention, but is not intended to confirm the key or decisive elements of the present invention or to limit the scope of protection.

[0021] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0022] Embodiment 1: A method for preparing lithium hydroxide from spodumene acidified material. The contents of the main components of the spodumene used in this embodiment are shown in Table 1.

[0023] Table 1 like Figure 1 As shown, this embodiment includes the following steps: Step S1. Transformation roasting The spodumene material is placed in a rotary kiln and calcined at a temperature of 1050-1100°C, and the spodumene crystal form is converted from α-type to β-type to generate roasted material; the roasted material temperature is cooled to 110-120°C by a grate cooler; the roasted material is sent to a ball mill and crushed to a particle size of less than 200 meshes to obtain a fine powder roasted material; Step S2. Acidification and Calcination The fine powder roasted material and concentrated sulfuric acid are put into the acid mixing machine for mixing, with the excess of concentrated sulfuric acid being 20%~40%; the mixed acid material is then put into the acidification rotary kiln, roasted at 200~320℃ to generate acidified material, and sent to the cooling kiln to be cooled to 90~100℃; Step S3. Adsorption and elution of lithium First, water is added to dilute the acidified material and stirred to fully dissolve the lithium ions in the acidified material, and the lithium ions are adsorbed and enriched by the lithium adsorbent 145. The lithium ions of the lithium adsorbent 145 are then washed away by a dilute sulfuric acid solution to obtain a lithium sulfate feed solution; the feed solution is transported to a pre-concentration membrane distillation unit.

[0024] Step S4. Pre-concentration of feed liquid The feed liquid is evaporated and concentrated by a pre-concentration membrane distillation unit to obtain a pre-concentrated liquid, thereby reducing the load on subsequent equipment; the heat source of the pre-concentration membrane distillation unit comes from the hot flue gas generated in the transformation roasting process; the pre-concentration membrane distillation unit is connected to an ion exchange device.

[0025] Step S5. Removal of small amounts of calcium, magnesium, aluminum, and iron ions The pre-concentrated liquid enters the ion exchange device, which is equipped with a cation exchange resin. The pre-concentrated liquid passes through the cation exchange resin, which uses the ion exchange selectivity of the cation exchange resin to adsorb a small amount of calcium, magnesium, aluminum, and iron ions in the pre-concentrated liquid to obtain a pre-electrolyte.

[0026] Step S6. Bipolar membrane electrodialysis separation The pre-electrolyte is subjected to bipolar membrane electrodialysis to obtain alkaline solution and dilute sulfuric acid. The alkaline solution is mainly lithium hydroxide and contains a small amount of sodium hydroxide and potassium hydroxide.

[0027] Step S7. Preparation of lithium hydroxide The alkali solution is transported to an alkali solution membrane distillation unit, where the alkali solution is evaporated, concentrated and crystallized to separate lithium from sodium and potassium, and then separated by a centrifuge to obtain lithium hydroxide and mother liquor.

[0028] Step S8. Concentrating dilute sulfuric acid The dilute sulfuric acid obtained in step S6 is transported to the acid liquid membrane distillation unit, and the dilute sulfuric acid is evaporated and concentrated by the acid liquid membrane distillation unit to obtain sulfuric acid with a concentration of 40%, and is supplied to step S3 to elute the lithium ions of the lithium adsorbent 145.

[0029] Embodiment 2: A system for preparing lithium hydroxide from spodumene acidified material comprises a transformation roasting mechanism, a ball mill, an acidification roasting mechanism, an adsorption and delithiation mechanism, a pre-concentration membrane distillation unit, an ion exchange device, a bipolar membrane electrodialyzer, an alkali liquid membrane distillation unit and a centrifuge, which are arranged in sequence from front to back; the heat sources of the pre-concentration membrane distillation unit and the alkali liquid membrane distillation unit are from hot flue gas generated by the transformation roasting mechanism, and the ion exchange device is provided with a cation exchange resin.

[0030] Preferably, if Figure 2 and Figure 3 As shown, the adsorption and de-lithium mechanism includes a water tank, an adsorption box 14, an acid supply box, a lithium liquid recovery component 15 and a drainage filter component 16; the lithium liquid recovery component 15 includes a circulating water pump 151 and a first ball valve 153; the drainage filter component 16 includes a drainage pump 163, a filter 162 and a second ball valve 161. The inner side wall of the adsorption box 14 is installed with a lithium adsorbent 145, and the middle part of the adsorption box 14 is installed with a stirring mechanism.

[0031] Specifically, the adsorption box 14 includes a box body 144 and a box cover 141. The box cover 141 is provided with a water inlet channel 1411 and two acid inlet channels 1412. Two lithium adsorbents 145 are provided at the bottom of the box body 144. The lithium adsorbents 145 are against the side wall of the box body 144, and the acid inlet channels 1412 are provided corresponding to the lithium adsorbents 145. A drainage hole and a liquid drainage hole are provided in the middle of the bottom surface of the box body 144, and a feed port 1441 is provided on the side wall of the box body 144.

[0032] The water inlet channel 1411, the water supply pump 12, and the water tank are connected in sequence through pipelines; the acid inlet channel 1412, the acid inlet pump 13, and the acid supply tank are connected in sequence through pipelines; the drain hole, the first ball valve 153, the circulating water pump 151, and the water tank are connected in sequence through pipelines; the liquid discharge hole, the second ball valve 161, the filter 162, the liquid discharge pump 163, and the pre-concentration membrane distillation unit are connected in sequence through pipelines.

[0033] Preferably, the stirring mechanism includes a driving motor 142 and a blade stirrer 143 . The driving motor 142 is fixedly mounted above the box cover 141 , and the blade stirrer 143 is rotatably mounted at the bottom of the box body 144 , passes through the axial hole in the middle of the box cover 141 and cooperates with the driving motor 142 for transmission.

[0034] During the operation of the adsorption and delithiation mechanism, the cooled acidified material enters the adsorption box 14 through the feed port 1441, the water supply pipe 11 provides and replenishes water for diluting the acidified material, and the water in the water tank enters the box body 144 through the water inlet channel 1411 through the water supply pump 12, and the water level is added to the bottom of the feed port 1441 to prevent the solution from overflowing from the feed port 1441; the blade stirrer 143 is started and stirred for about 1 hour to fully dissolve the lithium ions in the acidified material and fully absorb the lithium ions dissolved in the water; the blade stirrer 143 is closed, and the circulating water pump 151 and the first ball valve 15 are opened. 3. The solution in the box 144 enters the water tank along the pipeline, and water can be recycled to dissolve the acidified material, reduce water consumption, and ensure that the unadsorbed lithium continues to circulate in the adsorption and de-lithium mechanism, and the loss of lithium element is very small; after the solution in the box 144 is drained, the circulating water pump 151 and the first ball valve 153 are closed; the acid inlet pump 13 is turned on, and the dilute sulfuric acid in the acid supply box enters the box 144 through the acid inlet channel 1412, and the dilute sulfuric acid washes the lithium adsorbent 145 to elute the lithium ions on the lithium adsorbent 145; the drainage pump 163 and the second ball valve 161 are turned on to transport the feed liquid to the pre-concentration membrane distillation unit. Preferably, the filter residue in the filter 162 is cleaned regularly, and the filter residue is poured from the feed port 1441, and adsorption and elution are performed again to extract lithium, which also ensures that the unadsorbed lithium continues to circulate in the adsorption and de-lithium mechanism, and the loss of lithium element is very small, and no additional lithium residue treatment equipment is required, reducing investment costs.

[0035] Preferably, if Figure 4 , Figure 5 and Figure 6 As shown, the pre-concentration membrane distillation unit, the alkali liquid membrane distillation unit and the acid liquid membrane distillation unit respectively include a heating component 21 connected in sequence, a plurality of membrane distillation components 22 connected in series through pipelines and a cooling component 23, and the heat source of the heating component 21 comes from the hot flue gas generated in the transition roasting process.

[0036] Specifically, Figure 4 As shown, in the pre-concentration membrane distillation unit, the membrane distillation component 22 that directly contacts the heating component 21 is connected to the adsorption and delithiation mechanism, and the feed liquid first enters the membrane distillation component 22 and then enters other membrane distillation components 22 in sequence through the pipeline for evaporation and concentration to obtain a pre-concentrated liquid. The pre-concentrated liquid is discharged from the last membrane distillation component 22 and enters the ion exchange device.

[0037] Specifically, Figure 5 As shown, in the alkali liquid membrane distillation unit, the alkali liquid is sequentially evaporated, concentrated and crystallized through each membrane distillation component 22 to separate lithium hydroxide from sodium hydroxide and potassium hydroxide, and then separated by a centrifuge to obtain lithium hydroxide and mother liquor.

[0038] Specifically, Figure 6 As shown, in the acid liquid membrane distillation unit, the dilute sulfuric acid is evaporated and concentrated through each membrane distillation module 22 in turn to obtain dilute sulfuric acid with a concentration of 40wt%. Preferably, the generated 40wt% dilute sulfuric acid is connected to the acid supply box of the adsorption and de-lithium mechanism through a pipeline to replenish the acid supply box with acid liquid for eluting the lithium ions on the lithium adsorbent 145.

[0039] Preferably, the pre-concentration membrane distillation unit, the alkali liquid membrane distillation unit and the acid liquid membrane distillation unit are skid-mounted, with a compact structure and small footprint.

[0040] Preferably, if Figure 7 As shown, the membrane distillation assembly 22 of the pre-concentration membrane distillation unit, the alkali liquid membrane distillation unit and the acid liquid membrane distillation unit includes a flow component, a hydrophobic membrane A2, a condensation component A4 and a condensation sheet A3 which are arranged in sequence; the flow component A1 and the condensation component A4 are made of non-metallic materials, the hydrophobic membrane A2 is made of polytetrafluoroethylene, and the condensation sheet A3 is made of polypropylene.

[0041] Preferably, the membrane distillation assembly 22 at the tail end is also connected to a vacuum pump A5, and the vacuum pump A5 is connected to a condensation component A4 of the membrane distillation assembly 22 at the tail end, so that a certain negative pressure is generated in the membrane distillation assembly 22 to improve the evaporation efficiency.

[0042] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for preparing lithium hydroxide from spodumene acidified material, characterized in that: The following steps are involved: Step S1. Transformation roasting: placing the spodumene material in a rotary kiln and calcining it to generate a roasted material, so that the spodumene crystal form is converted from α-type to β-type; then, the roasted material temperature is cooled to 110~120°C by a grate cooler, and sent to a ball mill to be crushed to obtain a fine powder roasted material with a particle size of less than 200 mesh; Step S2. Acidification and roasting: The fine powder roasted material and concentrated sulfuric acid are respectively put into an acid mixing machine for mixing to obtain a mixed acid material, wherein the concentrated sulfuric acid is in excess of 20wt% to 40wt%; the mixed acid material is then put into an acidification rotary kiln for roasting to generate an acidified material, and then sent to a cooling kiln for cooling to 90 to 100°C; Step S3. adsorption and elution to extract lithium: adding water to dilute the acidified material and stirring to fully dissolve the lithium ions in the acidified material, using the lithium adsorbent (145) to adsorb and enrich the lithium ions, and then eluting the lithium ions adsorbed and enriched by the lithium adsorbent (145) with a dilute sulfuric acid solution to obtain a lithium sulfate solution; Step S4. Pre-concentration treatment: evaporating and concentrating the lithium sulfate feed solution through a pre-concentration membrane distillation unit to obtain a pre-concentrated solution; Step S5. Ion exchange treatment: introducing the pre-concentrated solution into an ion exchange device, and treating it with a cation exchange resin in the ion exchange device to obtain a pre-electrolyte; Step S6. Bipolar membrane electrodialysis separation: subjecting the pre-electrolyte to bipolar membrane electrodialysis to obtain alkaline solution and dilute sulfuric acid; Step S7. Preparation of lithium hydroxide: The alkali solution is transported to an alkali solution membrane distillation unit for evaporation, concentration and crystallization, and lithium hydroxide and mother liquor are separated by a centrifuge.

2. A method for preparing lithium hydroxide from a spodumene acidifying material according to claim 1, characterized in that, In the step S3, the cooled acidified material is added to an adsorption box (14) having a built-in lithium adsorbent (145), a dilution liquid is supplied to the adsorption box (14) through a water tank, and a blade stirrer (143) inside the adsorption box (14) is started to stir and dilute the acidified material. Then, the stirring and the addition of the dilution liquid are stopped, and all the liquid inside the adsorption box (14) is introduced into the water tank. Then, dilute sulfuric acid is supplied to the adsorption box (14) through an acid supply tank to rinse the lithium adsorbent (145), and the eluted lithium ions are filtered and introduced into a pre-concentration membrane distillation unit.

3. A method for preparing lithium hydroxide from a spodumene acidifying material according to claim 2, characterized in that, In the step S6, the dilute sulfuric acid is transported to the acid liquid membrane distillation unit for evaporation and concentration to obtain dilute sulfuric acid with a concentration of 40 wt % and transported to the acid supply tank.

4. A system for preparing lithium hydroxide from spodumene acidified material, used to implement the method for preparing lithium hydroxide from spodumene acidified material according to any one of claims 1 to 3, characterized in that: The invention comprises a transformation roasting mechanism, a ball mill, an acidification roasting mechanism, an adsorption and delithiation mechanism, a pre-concentration membrane distillation unit, an ion exchange device, a bipolar membrane electrodialyzer, an alkaline liquid membrane distillation unit and a centrifuge, which are arranged in sequence from front to back; the heat source of the pre-concentration membrane distillation unit and the alkaline liquid membrane distillation unit comes from the hot flue gas generated by the transformation roasting mechanism, the ion exchange device is provided with a cation exchange resin, and the adsorption and delithiation mechanism is provided with a lithium adsorbent (145) inside.

5. A system for preparing lithium hydroxide from a spodumene acidifying material according to claim 4, characterized in that, The adsorption and delithiation mechanism comprises an adsorption box (14), a water tank, an acid supply box, a lithium liquid recovery component (15) and a drainage filter component (16); a feed port (1441) is arranged on one side of the adsorption box (14); a stirring mechanism is arranged in the middle of the adsorption box (14), and a lithium adsorbent (145) is arranged on the side wall of the adsorption box (14); a plurality of acid inlet channels (1412) are arranged at the top of the adsorption box (14) corresponding to the lithium adsorbent (145); the acid supply box is connected to the acid inlet channels (1412) via an acid inlet pump (13); the water tank is connected to the water inlet channel (1411) at the top of the adsorption box (14) via a water pump; one end of the lithium liquid recovery component (15) and the drainage filter component (16) are respectively connected to the drainage hole and the drainage hole at the bottom of the adsorption box (14); and the other ends of the lithium liquid recovery component (15) and the drainage filter component (16) are respectively connected to the water tank and the pre-concentration membrane distillation unit.

6. A system for preparing lithium hydroxide from a spodumene acidifying material according to claim 5, characterized in that, The lithium liquid recovery component (15) comprises a first ball valve (153) and a circulating water pump (151) which are arranged in sequence from front to back, and the drainage filter component (16) comprises a second ball valve (161), a filter (162) and a drainage pump (163) which are arranged in sequence from front to back, the first ball valve (153) and the second ball valve (161) are connected to the drainage hole and the drainage hole respectively, and the circulating water pump (151) and the drainage pump (163) are connected to the water tank and the pre-concentration membrane distillation unit respectively.

7. A system for preparing lithium hydroxide from a spodumene acidifying material according to claim 5 or 6, characterized in that, It also includes an acid liquid membrane distillation unit, which is used to evaporate and concentrate the dilute sulfuric acid obtained after treatment by the bipolar membrane electrodialysis instrument to obtain dilute sulfuric acid with a concentration of 40wt% and transport it to the acid supply box.

8. A system for preparing lithium hydroxide from a spodumene acidifying material according to claim 7, characterized in that, The pre-concentration membrane distillation unit, the alkali liquid membrane distillation unit and the acid liquid membrane distillation unit respectively comprise a heating component (21) arranged in sequence from front to back, a plurality of membrane distillation components (22) connected in series via pipelines, and a cooling component (23), wherein the heat source of the heating component (21) comes from the hot flue gas generated by the transition roasting mechanism.

9. A system for preparing lithium hydroxide from a spodumene acidifying material according to claim 8, characterized in that, The membrane distillation assembly (22) comprises a flow-through component (A1), a hydrophobic membrane (A2), a condensation component (A4) and a condensation sheet (A3) which are arranged in sequence from front to back, and the condensation component (A4) of the membrane distillation assembly (22) at the rear end is connected to a vacuum pump (A5); the flow-through component (A1) and the condensation component (A4) are made of non-metallic materials, and the hydrophobic membrane (A2) and the condensation sheet (A3) are made of polytetrafluoroethylene and polypropylene, respectively.

10. A system for preparing lithium hydroxide from a spodumene acidifying material according to claim 4, characterized in that, The transition roasting mechanism comprises a roasting rotary kiln and a grate cooler which are arranged in sequence from front to back, and the acidification roasting mechanism comprises an acid mixing machine, an acidification rotary kiln and a cooling kiln which are arranged in sequence from front to back.

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