Lithium phosphate solid phase fluorine removal system and method
By using a lithium phosphate solid-phase defluorination system, which employs a microwave tunnel kiln and a multi-stage spray absorption tower to treat the tail gas, the problem of difficult removal of fluorine impurities in lithium phosphate has been solved, achieving efficient and low-cost defluorination.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-20
- Publication Date
- 2026-03-10
AI Technical Summary
Existing technologies are ineffective at removing fluorine impurities from lithium phosphate. Liquid-phase treatment is inefficient and costly, and may have adverse effects on equipment and the environment.
A lithium phosphate solid-phase defluorination system is adopted, which uses microwave tunnel kiln heating and concentrated sulfuric acid treatment, combined with multi-stage spray absorption tower to treat the tail gas, to achieve solid-phase defluorination, generate calcium fluoride slag and recycle dilute sulfuric acid.
It achieves efficient removal of fluorine impurities from lithium phosphate, reduces production costs, minimizes equipment corrosion and environmental impact, and improves energy utilization efficiency.
Smart Images
Figure CN121623713A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium phosphate production technology, and more specifically to a solid-phase defluorination system and method for lithium phosphate. Background Technology
[0002] With the rapid development of the lithium battery industry, the recycling and utilization of various lithium-containing waste liquids has gradually gained attention. The product obtained through recycling processes is usually lithium phosphate. However, due to the unavoidable inclusion of impurities during the recycling process, the resulting lithium phosphate often contains a high concentration of fluorine. The presence of fluorine impurities not only seriously affects the purity of lithium phosphate but also limits its application in high-value-added fields.
[0003] Existing defluorination methods mainly employ liquid-phase treatments such as water washing and acid washing. However, because lithium phosphate itself is a poorly soluble compound with extremely low solubility in aqueous or acidic phases, liquid-phase defluorination efficiency is poor, making it difficult to completely remove fluorine impurities. Furthermore, some chemical treatments require the use of highly corrosive media or high-energy-consuming conditions, which not only increases treatment costs but may also have adverse effects on equipment and the environment.
[0004] Therefore, there is currently a lack of an economical, efficient, simple, and industrially applicable lithium phosphate defluorination technology, and there is an urgent need to develop new defluorination methods to improve the quality and application value of recovered lithium phosphate. Summary of the Invention
[0005] The purpose of this invention is to overcome the above-mentioned problems and provide a lithium phosphate solid-phase defluorination system and method. This invention is simple to operate and easy to implement. The lithium phosphate reaction occurs at medium to low temperatures in the process, and concentrated sulfuric acid is used directly, resulting in minimal corrosion to equipment, low equipment requirements, and easy absorption and treatment of the exhaust gas, making it environmentally friendly.
[0006] To achieve the above objectives, the present invention provides a lithium phosphate solid-phase defluorination system, including a reaction tower, a mixer, a microwave tunnel kiln, and a tunnel kiln tail gas treatment device. The reaction tower is used to mix sulfuric acid solution with lithium phosphate to obtain a mixture; The mixer is used to stir the mixture from the reaction tower to obtain the reaction mixture; The microwave tunnel kiln is used to heat the reaction material from the mixer to obtain fluorine-containing gas and defluorinated lithium phosphate; The tunnel kiln tail gas treatment equipment is used to absorb and treat fluorine-containing gases from the microwave tunnel kiln to obtain a dilute sulfuric acid solution. The dilute sulfuric acid solution obtained from the tunnel kiln tail gas treatment equipment is then returned to the reaction tower for recycling.
[0007] The lithium phosphate solid-phase defluorination system also includes a ball mill, which is used to ball mill lithium phosphate to obtain lithium phosphate powder.
[0008] Furthermore, a feed inlet is provided in the middle of the reaction tower, and the ball mill is connected to the feed inlet to transport lithium phosphate powder from the ball mill into the reaction tower to mix with sulfuric acid solution.
[0009] In a specific implementation, lithium phosphate powder can be transported to the reaction tower by means of airflow.
[0010] Preferably, the reaction tower is equipped with a spraying device for spraying sulfuric acid solution.
[0011] More preferably, the top of the reaction tower is equipped with a spraying device to spray the sulfuric acid solution in a mist, which falls under the action of gravity and mixes with the lithium phosphate powder fed in the middle to obtain a mixture. Then, under the action of gravity, the mixture falls to the bottom of the reaction tower.
[0012] In a specific implementation, the spraying device is a high-pressure polytetrafluoroethylene spray head.
[0013] The lithium phosphate solid-phase defluorination system of the present invention also includes a first transport vehicle.
[0014] In a specific embodiment of the present invention, the bottom of the reaction tower is provided with a discharge port, and the first conveyor is located below the discharge port of the reaction tower. Under the action of gravity, the mixture passes through the discharge port of the reaction tower and falls into the first conveyor. The mixture is then transported to the mixer through the inlet of the mixer by the first conveyor. After being stirred and mixed evenly, the reaction mixture is obtained.
[0015] Furthermore, the lithium phosphate solid-phase defluorination system of the present invention also includes a second conveyor. The reactants in the mixer pass through the mixer outlet and are transported by the second conveyor to a microwave tunnel kiln for heating to obtain fluorine-containing gas and defluorinated lithium phosphate.
[0016] More preferably, the microwave tunnel kiln is equipped with an energy-saving microwave heating tube, which is used to microwave heat the reaction material.
[0017] In a specific implementation, both the first and second transport aircraft described in this invention are belt transport aircraft.
[0018] In a preferred embodiment, the tunnel kiln tail gas treatment equipment includes a primary spray absorption tower, a secondary spray absorption tower, a tertiary spray absorption tower, and a solid fluorine reactor; wherein the primary spray absorption tower, the secondary spray absorption tower, and the tertiary spray absorption tower are connected in sequence; the solid fluorine reactor is connected to the primary spray absorption tower; and the solid fluorine reactor is also connected to the top of the reaction tower.
[0019] Furthermore, the lithium phosphate solid-phase defluorination system of the present invention also includes a gas absorption tower. The microwave tunnel kiln and the primary spray absorption tower are connected through the gas absorption tower. The fluorine-containing gas from the microwave tunnel kiln enters the primary spray absorption tower through the gas absorption tower for the first absorption treatment, resulting in a mixed solution containing hydrogen fluoride and sulfuric acid and primary tail gas. The mixed solution containing hydrogen fluoride and sulfuric acid then enters the solid fluoride reactor for solid fluoride treatment, resulting in a dilute sulfuric acid solution. The dilute sulfuric acid solution in the solid fluoride reactor is returned to the reaction tower for recycling. The primary tail gas then enters the secondary spray absorption tower for the second absorption treatment, resulting in secondary tail gas. The secondary tail gas then enters the tertiary spray absorption tower for the second absorption treatment, resulting in exhaust tail gas.
[0020] A second aspect of the present invention provides a lithium phosphate solid-phase defluorination method, which is implemented in the above-mentioned lithium phosphate solid-phase defluorination system and includes: (1) Lithium phosphate is ball-milled in a ball mill to obtain lithium phosphate powder. The ball-milled lithium phosphate powder is then transported to a reaction tower by an airflow and mixed with sulfuric acid solution in the reaction tower to obtain a mixture. (2) The mixture is stirred in a mixer to obtain a reaction mixture; (3) The reactants are conveyed to a microwave tunnel kiln for heating to obtain fluorine-containing gas and defluorinated lithium phosphate; (4) The fluorine-containing gas enters the tunnel kiln tail gas treatment equipment through the gas absorption tower for absorption treatment to obtain a dilute sulfuric acid solution. The dilute sulfuric acid solution obtained from the tunnel kiln tail gas treatment equipment is returned to the reaction tower for recycling.
[0021] In this invention, the particle size of the lithium phosphate powder in step (1) is 100-300 mesh.
[0022] In this invention, the concentration of the sulfuric acid solution sprayed by the spraying device is 95-98 wt% (the effect of sulfuric acid solution with this concentration is better than that of other low concentrations); the mass ratio of lithium phosphate powder to the sprayed sulfuric acid solution in the reaction tower is controlled to be 1:0.1-0.5, and more preferably 1:0.3-0.5.
[0023] Further, in step (3), the heating conditions include: a temperature of 300-400℃ and a time of 1-2h; more preferably, the heating conditions include: a temperature of 380-400℃ and a time of 1-2h.
[0024] In step (3), during the heating process, the fluorine in the material is combined with the hydrogen in the sulfuric acid to form hydrogen fluoride molecules. After heating, the hydrogen fluoride molecules leave the material in gaseous form and enter the tunnel kiln tail gas treatment equipment to achieve the purpose of removing fluorine impurities in the solid state. Furthermore, due to the excessive use of sulfuric acid solution, at this heating temperature, the excess sulfuric acid will evaporate and decompose simultaneously, producing sulfuric acid gas and sulfur trioxide gas.
[0025] The principle of heating to remove fluoride in step (3) is as follows: 2F - + 2H + + SO4 2- → 2HF + SO4 2- HF (heated) → HF (gas) ↑ Preferably, the primary absorbent sprayed in the primary spray absorption tower is pure water; the secondary absorbent sprayed in the secondary spray absorption tower is a suspension containing calcium hydroxide and calcium sulfate; and the tertiary absorbent sprayed in the tertiary spray absorption tower is liquid alkali.
[0026] The fluorine-containing gas in this invention mainly contains HF gas, excess sulfuric acid gas, and sulfur trioxide gas.
[0027] In a specific implementation, the fluorine-containing gas enters the primary spray absorption tower through a gas absorption tower, where it comes into contact with the primary absorbent for the first absorption treatment. The primary absorbent absorbs the HF gas, excess sulfuric acid gas, and sulfur trioxide gas from the fluorine-containing gas (after absorption with pure water, the sulfur trioxide gas will revert back to sulfuric acid), forming a mixed solution containing hydrogen fluoride and sulfuric acid. This removes a portion of the HF gas, excess sulfuric acid gas, and sulfur trioxide gas, resulting in primary tail gas (the first absorption treatment cannot completely absorb all the HF gas, sulfuric acid gas, and sulfur trioxide gas, so some unabsorbed HF gas, sulfuric acid gas, and sulfur trioxide gas will still remain in the primary tail gas). The primary tail gas then enters the secondary spray absorption tower, where it comes into contact with the secondary absorbent for the second absorption treatment. At this time, the hydrogen fluoride in the primary tail gas reacts with calcium ions to form calcium fluoride precipitate (calcium fluoride slag is obtained through periodic filtration), removing the unabsorbed portion from the primary tail gas. The HF gas absorbed by the agent yields secondary tail gas (which still contains acidic gases such as sulfuric acid and sulfur trioxide). This secondary tail gas then enters a tertiary spray absorption tower, where it undergoes a third absorption treatment with alkaline solution to completely remove acidic substances (ensuring emissions meet standards), resulting in exhaust tail gas. The mixed solution containing hydrogen fluoride and sulfuric acid obtained in the first absorption treatment enters a solid fluoride reactor, where calcium sulfate is added to solidify the fluoride, yielding calcium fluoride slag and a dilute sulfuric acid solution. The dilute sulfuric acid solution from the solid fluoride reactor is returned to the reaction tower for recycling (under continuous acid gas absorption, the concentration of the dilute sulfuric acid solution obtained by the tunnel kiln tail gas treatment equipment can reach 30-50 wt%, which is then reused. The amount of reused dilute sulfuric acid is relatively small; the reaction tower mainly uses the newly added 95-98 wt% sulfuric acid solution from the spray, with the reuse of the dilute sulfuric acid solution only slightly reducing the amount of sprayed sulfuric acid solution), thus improving utilization efficiency.
[0028] The amount of the primary, secondary, and tertiary absorbents used should be sufficient to absorb the corresponding gases.
[0029] After exiting the microwave tunnel kiln, the defluorinated lithium phosphate obtained in step (3) is crushed and sieved to obtain a qualified product with low fluorine content. Experimental data show that this method can reduce the fluorine content in lithium phosphate from 5000 ppm to below 50 ppm, with a fluorine impurity removal rate as high as 99%.
[0030] Compared with the prior art, the present invention has the following advantages: (1) The present invention is simple to operate and easy to implement. The lithium phosphate reaction is a medium-low temperature solid-phase reaction, and concentrated sulfuric acid is used directly, which has little corrosion to equipment and low requirements. The tail gas is easy to absorb and treat, which is environmentally friendly.
[0031] (2) Using sulfuric acid as a defluorinating agent, the cost is only one-tenth of that of other defluorinating agents (the market price of sulfuric acid is 600 yuan / ton, and the price of various special defluorinating agents ranges from 3,000 to 20,000 yuan). This method has a clear cost advantage.
[0032] (3) Fluorine is eventually converted into calcium fluoride solid slag, which is harmless and has low treatment costs. Sulfuric acid is converted into dilute sulfuric acid in the tail gas treatment, which can be used for production without waste of raw materials and can further reduce production costs.
[0033] (4) The heating method has been improved from traditional steam and heat transfer oil heating to energy-saving microwave direct heating, which increases energy utilization efficiency by 20%-40%, further reduces defluorination costs, and has significant energy-saving effect. Attached Figure Description
[0034] Figure 1 This is a schematic diagram of the lithium phosphate solid-phase defluorination system of the present invention; Figure 2 This is a schematic flowchart of the lithium phosphate solid-phase defluorination method of the present invention.
[0035] Explanation of reference numerals in the attached figures 1. Reaction tower; 2. Mixer; 3. Microwave tunnel kiln; 4. Tunnel kiln tail gas treatment equipment; 5. Ball mill equipment; 6. First conveyor; 7. Gas absorption tower; 8. Second conveyor; 1-1 Spraying device; 3-1 Microwave heating tube; 4-1 Primary spray absorption tower; 4-2 Secondary spray absorption tower; 4-3 Tertiary spray absorption tower; 4-4 Solid fluorine reactor. Detailed Implementation
[0036] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.
[0037] The endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0038] Furthermore, if the embodiments of this invention involve descriptions such as "first" or "second," these descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions provided in the various embodiments of this invention can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.
[0039] The lithium phosphate solid-phase defluorination method in the following examples is as follows: Figure 1 The lithium phosphate solid-phase defluorination system shown includes: a reaction tower 1, a mixer 2, a microwave tunnel kiln 3, a tunnel kiln tail gas treatment device 4, a ball mill 5, a first conveyor 6, a gas absorption tower 7, and a second conveyor 8. A feed inlet is provided in the middle of the reaction tower 1, and the ball mill 5 is connected to the feed inlet of the reaction tower 1; a spray device 1-1 is provided at the top of the reaction tower 1, and the spray device 1-1 is a high-pressure polytetrafluoroethylene spray head; a discharge outlet is provided at the bottom of the reaction tower 1, and the first conveyor 6 is located below the discharge outlet of the reaction tower 1. The microwave tunnel kiln 3 is equipped with an energy-saving microwave heating tube 3-1; The tunnel kiln tail gas treatment equipment 4 includes a primary spray absorption tower 4-1, a secondary spray absorption tower 4-2, a tertiary spray absorption tower 4-3, and a solid fluorine reactor 4-4; wherein the primary spray absorption tower 4-1, the secondary spray absorption tower 4-2, and the tertiary spray absorption tower 4-3 are connected in sequence; the solid fluorine reactor 4-4 is connected to the primary spray absorption tower 4-1; the solid fluorine reactor 4-4 is also connected to the top of the reaction tower 1; The microwave tunnel kiln 3 and the primary spray absorption tower 4-1 are connected through the gas absorption tower 7; Both the first transport aircraft 6 and the second transport aircraft 8 are belt transport aircraft; The primary absorbent sprayed in the primary spray absorption tower 4-1 is pure water; the secondary absorbent sprayed in the secondary spray absorption tower 4-2 is a suspension containing calcium hydroxide and calcium sulfate; and the tertiary absorbent sprayed in the tertiary spray absorption tower 4-3 is liquid alkali.
[0040] The flowchart of the lithium phosphate solid-phase defluorination method in the embodiments is as follows: Figure 2 As shown.
[0041] Example 1 (1) Lithium phosphate is ball-milled in ball milling equipment 5 to obtain lithium phosphate powder (fluorine content 5000ppm). The particle size of lithium phosphate powder is 100-300 mesh. The ball-milled lithium phosphate powder is transported to the feed port of reaction tower 1 by airflow and enters reaction tower 1. Spraying device 1-1 is turned on to spray sulfuric acid solution with a concentration of 98wt% into reaction tower 1 and mixes with the lithium phosphate powder fed in the middle. The mass ratio of lithium phosphate powder to sprayed sulfuric acid solution in reaction tower 1 is controlled to be 1:0.35 to obtain a mixture. (2) The mixture falls to the bottom of the reaction tower 1 under the action of gravity, and falls into the first conveyor 6 through the outlet of the reaction tower 1. It is then transported to the mixer 2 through the inlet of the mixer 2 via the first conveyor 6. After being stirred and mixed evenly in the mixer 2, the reaction material is obtained. (3) The reactant is transported to the microwave tunnel kiln 3 through the outlet of the mixer 2 via the second conveyor 8. The reactant is microwave heated by the microwave heating tube 3-1. The microwave heating conditions include a temperature of 380℃ and a time of 1h to obtain fluorine-containing gas and defluorinated lithium phosphate. After the defluorinated lithium phosphate comes out of the microwave tunnel kiln 3, it is cooled to room temperature (25℃), crushed, and sieved to obtain a qualified lithium phosphate product with low fluorine content (the fluorine content is detected to be 27ppm). (4) Fluorine-containing gas enters the first-stage spray absorption tower 4-1 through the gas absorption tower 7, and undergoes the first absorption treatment by contacting the first-stage absorbent to obtain a mixed solution containing hydrogen fluoride and sulfuric acid and the first-stage tail gas. The mixed solution containing hydrogen fluoride and sulfuric acid then enters the solid fluoride reactor 4-4, where calcium sulfate is added to react and solidify fluoride to obtain calcium fluoride slag and dilute sulfuric acid solution. The dilute sulfuric acid solution in the solid fluoride reactor 4-4 is returned to the reaction tower 1 for recycling. The first-stage tail gas then enters the second-stage spray absorption tower 4-2, and undergoes the second absorption treatment by contacting the second-stage absorbent to obtain calcium fluoride precipitate (which is periodically filtered to obtain calcium fluoride slag) and the second-stage tail gas. The second-stage tail gas then enters the third-stage spray absorption tower 4-3, and undergoes the third absorption treatment by contacting the alkaline solution to obtain the exhaust tail gas.
[0042] Example 2 The method was implemented according to Example 1, except that in step (1), the mass ratio of lithium phosphate powder to sprayed sulfuric acid solution was 1:0.1; in step (3), the microwave heating temperature was 300°C; and after the defluorinated lithium phosphate came out of the microwave tunnel kiln 3, the fluorine content was detected to be 4000ppm.
[0043] Example 3 The method was implemented according to Example 1, except that in step (1), the mass ratio of lithium phosphate powder to sprayed sulfuric acid solution was 1:0.2; in step (3), the microwave heating temperature was 350°C; and after the defluorinated lithium phosphate came out of the microwave tunnel kiln 3, the fluorine content was detected to be 2700 ppm.
[0044] Example 4 The method was implemented according to Example 1, except that in step (1), the mass ratio of lithium phosphate powder to sprayed sulfuric acid solution was 1:0.5; in step (3), the microwave heating temperature was 400°C; and after the defluorinated lithium phosphate came out of the microwave tunnel kiln 3, the fluorine content was detected to be 35 ppm.
[0045] Comparative Example 1 This comparative example uses a wet defluorination process, and the specific operation is as follows: (1) Prepare a slurry of lithium phosphate with a fluorine content of 5000ppm and pure water. The mass ratio of pure water to lithium phosphate is 3:1. Add concentrated sulfuric acid. The mass ratio of concentrated sulfuric acid to lithium phosphate is 10:100. Then add calcium oxide. The molar amount of calcium oxide added is the same as the molar amount of fluorine in lithium phosphate. Stir the mixture thoroughly for 2 hours. (2) After the reaction, the calcium in the material reacts with phosphate and fluoride ions to form insoluble calcium phosphate and calcium fluoride precipitates, which mix with insoluble lithium phosphate and cannot be separated. This method has no effect on defluorination.
[0046] The defluorination effects of the above embodiments and comparative examples are shown in Table 1.
[0047] Table 1 As shown in Table 1, when using traditional liquid-phase defluorination methods, lithium phosphate and solid fluoride residue both precipitate and cannot be separated. The solid-phase defluorination method of this invention achieves better defluorination results. Based on the examples, the defluorination effect is relatively poor when the amount of sulfuric acid is too small or the temperature is below 380°C. Examples 1 and 4 show the best defluorination effects, with defluorination rates both >99%.
[0048] It should be understood that any parts not described in detail in this specification belong to the prior art.
[0049] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.
Claims
1. A lithium phosphate solid phase fluorine removal system, characterized by, The system comprises a reaction tower (1), a mixer (2), a microwave tunnel kiln (3), and a tunnel kiln tail gas treatment device (4). The reaction tower (1) is used for mixing sulfuric acid solution and lithium phosphate to obtain a mixture. The mixer (2) is used for stirring the mixture from the reaction tower (1) to obtain a reaction material. The microwave tunnel kiln (3) is used for heating the reaction material from the mixer (2) to obtain fluorine-containing gas and fluorine-removed lithium phosphate. The tunnel kiln tail gas treatment device (4) is used for absorbing the fluorine-containing gas from the microwave tunnel kiln (3) to obtain a dilute sulfuric acid solution, and the dilute sulfuric acid solution obtained by the tunnel kiln tail gas treatment device (4) is returned to the reaction tower (1) for recycling.
2. The lithium phosphate solid-phase defluorination system according to claim 1, characterized in that, The lithium phosphate solid-phase fluorine removal system further comprises a ball milling device (5) for ball milling lithium phosphate to obtain lithium phosphate powder. The lithium phosphate powder from the ball milling device (5) is transported into the reaction tower (1) to be mixed with the sulfuric acid solution.
3. The lithium phosphate solid-phase fluorine removal system according to claim 1 or 2, characterized by, The reaction tower (1) is provided with a spraying device (1-1) for spraying the sulfuric acid solution.
4. The lithium phosphate solid-phase defluoridation system according to claim 1, wherein, The tunnel kiln tail gas treatment device (4) comprises a first-stage spraying absorption tower (4-1), a second-stage spraying absorption tower (4-2), a third-stage spraying absorption tower (4-3), and a fluorine fixation reactor (4-4). The first-stage spraying absorption tower (4-1) is used for first-stage absorption treatment of the fluorine-containing gas from the microwave tunnel kiln (3) to obtain a mixed solution containing hydrogen fluoride and sulfuric acid and first-stage tail gas. The fluorine fixation reactor (4-4) is used for fluorine fixation of the mixed solution containing hydrogen fluoride and sulfuric acid from the first-stage spraying absorption tower (4-1) to obtain a dilute sulfuric acid solution. The second-stage spraying absorption tower (4-2) is used for second-stage absorption treatment of the first-stage tail gas from the first-stage spraying absorption tower (4-1) to obtain second-stage tail gas. The third-stage spraying absorption tower (4-3) is used for third-stage absorption treatment of the second-stage tail gas from the second-stage spraying absorption tower (4-2) to obtain exhaust tail gas.
5. A lithium phosphate solid phase fluorine removal method characterized by, The system comprises: lithium phosphate is ball milled in the ball milling device (5) to obtain lithium phosphate powder, and the ball-milled lithium phosphate powder is transported by airflow into the reaction tower (1) to be mixed with the sulfuric acid solution, thereby obtaining a mixture; the mixture is stirred in the mixer (2) to obtain a reaction material; the reaction material is sent by a conveyor (6) into the microwave tunnel kiln (3) for heating to obtain fluorine-containing gas and fluorine-removed lithium phosphate; the fluorine-containing gas is absorbed by a gas absorption tower (7) into the tunnel kiln tail gas treatment device (4) for absorption treatment to obtain a dilute sulfuric acid solution, and the dilute sulfuric acid solution obtained by the tunnel kiln tail gas treatment device (4) is returned to the reaction tower (1) for recycling.
6. The lithium phosphate solid phase fluorine removal method according to claim 5, characterized by, The particle size of the lithium phosphate powder is 100-300 mesh.
7. The lithium phosphate solid phase defluorination method according to claim 5, characterized by, The mass ratio of the feeding amount of lithium phosphate powder to the sulfuric acid solution in the reaction tower (1) is 1:0.1-0.
5.
8. The lithium phosphate solid phase fluorine removal method according to claim 5 or 7, characterized by, The concentration of the sulfuric acid solution is 95-98 wt%.
9. The lithium phosphate solid phase fluorine removal method according to claim 5, characterized by, The heating conditions include a temperature of 300-400℃ and a time of 1-2h.
10. The lithium phosphate solid phase defluorination method according to claim 5, characterized by, The first-stage absorbent in the first-stage spray absorption tower (4-1) of the tunnel kiln tail gas treatment equipment (4) is pure water; the second-stage absorbent in the second-stage spray absorption tower (4-2) is a suspension containing calcium hydroxide and calcium sulfate; and the third-stage absorbent in the third-stage spray absorption tower (4-3) is liquid alkali.