Production system for precipitating lithium carbonate from lithium hydroxide mother liquor

Abstract

The utility model discloses a lithium hydroxide mother liquor precipitated lithium carbonate production system which comprises a front-stage impurity removal system, a reaction kettle, a centrifugal machine, a first-stage size mixing tank, a first-stage size washing kettle, a first-stage centrifugal machine, a second-stage size mixing tank, a second-stage size washing kettle, a second-stage centrifugal machine and a drying machine, a flowmeter and a regulating valve are arranged on the carbon dioxide inlet pipe, and an inlet pipe disc is arranged in the reaction kettle and is communicated with the carbon dioxide inlet pipe. Compared with the prior art, the pre-stage impurity removal system is used for removing impurities from the lithium hydroxide mother liquor, the proportion of carbon dioxide is reasonably controlled, excessive generation of lithium bicarbonate is avoided, and proper feeding amount, temperature and stirring speed are adopted, so that the reaction speed is controlled, a target lithium carbonate crystal form is obtained, impurity carrying is reduced, and the lithium carbonate quality is improved. The two-stage process operation of normal-temperature reaction and high-temperature pyrolysis is adopted, so that complete pyrolysis of lithium bicarbonate is ensured, the solubility of lithium carbonate is reduced, and the yield of lithium carbonate is increased.

Description

Technical Field

[0001] The utility model relates to the field of chemical industry, in particular to a lithium hydroxide mother liquor precipitation lithium carbonate production system. Background Art

[0002] At present, the high-impurity mother liquor (the main component is 11% saturated concentration lithium hydroxide) produced by the lithium hydroxide process in the lithium chemical industry is usually recovered by carbon dioxide neutralization precipitation. However, due to the high impurity content in the mother liquor, which contains impurities such as calcium, magnesium, sodium, potassium, and iron, the process is not thoroughly impurity-removing, and the product has high impurities; the crystal formation in the reaction link is easy to carry impurities, affecting the product quality; and lithium carbonate has a certain solubility, and the operating parameters of the rinsing link are not appropriate, which will also lead to an increase in the system's liquid holding capacity or poor rinsing effect. When lithium hydroxide and carbon dioxide react, when carbon dioxide is excessive, lithium bicarbonate is generated, resulting in a significant reduction in yield; when carbon dioxide is insufficient, the reaction is incomplete, the yield is low, and lithium hydroxide is carried, and the product quality is low. The process of generating lithium carbonate reaction is very easy to cause pipe blockage and wall attachment due to the characteristics of the material, which often leads to poor system operation and system shutdown and cleaning.

[0003] In view of the above situation, the process parameters of each operating link of the lithium hydroxide mother liquor precipitation lithium carbonate process were studied, and a series of reasonable process production systems were explored to improve product quality and reduce project energy consumption. Utility Model Content

[0004] The purpose of the utility model is to provide a lithium hydroxide mother liquor precipitation lithium carbonate production system that solves the above-mentioned problems.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the utility model is: a lithium hydroxide mother liquor precipitation lithium carbonate production system, comprising a front-stage impurity removal system, a reactor, a centrifuge, a first-level slurry mixing tank, a first-level slurry washing tank, a first-level centrifuge, a second-level slurry mixing tank, a second-level slurry washing tank, a second-level centrifuge and a dryer, the front-stage impurity removal system, the reactor, the centrifuge, the first-level slurry mixing tank, the first-level slurry washing tank, the first-level centrifuge, the second-level slurry mixing tank, the second-level slurry washing tank, the second-level centrifuge and the dryer are sequentially connected through a lithium hydroxide delivery pipeline, the reactor is provided with a carbon dioxide inlet pipe, the carbon dioxide inlet pipe is provided with a flow meter and a regulating valve, the reactor is provided with an inlet pipe disc, the inlet pipe disc is provided with a plurality of exhaust holes, and the inlet pipe disc is connected with the carbon dioxide inlet pipe.

[0006] Preferably, a secondary wash water recovery pipe is provided between the secondary centrifuge and the primary slurry mixing tank, and a transfer tank and a solution pump are provided on the secondary wash water recovery pipe.

[0007] Preferably, the reactor, the first-stage pulp washing reactor and the second-stage pulp washing reactor are provided with a jacket, the jacket is provided with a steam inlet pipe and a condensate outlet pipe, and the jacket on the reactor.

[0008] Preferably, the jacket of the reactor is also provided with a circulating cooling water inlet pipe and a circulating cooling water outlet pipe, both of which are connected to the interior of the jacket, the circulating cooling water inlet pipe is located at the bottom of the jacket, and the circulating cooling water outlet pipe is located at the upper part of the jacket.

[0009] Preferably, an inert gas vent valve is also provided on the top of the reactor.

[0010] Preferably, a variable frequency stirring device is provided in the reactor.

[0011] Preferably, the impurity removal system consists of an impurity removal kettle, a microporous filter element filter, a nanofiltration device and a resin adsorption filter. The impurity removal kettle, the microporous filter element filter, the nanofiltration device and the resin adsorption filter are connected in sequence through a lithium hydroxide delivery pipeline. The resin adsorption filter is connected to the inside of the reactor through a lithium hydroxide delivery pipeline. A drug adding box is provided on the impurity removal kettle.

[0012] Preferably, transfer tanks are provided on the lithium hydroxide delivery pipelines between the microporous filter element filter and the nanofiltration device and between the resin adsorption filter and the secondary evaporation crystallization system.

[0013] Compared with the prior art, the utility model has the following advantages:

[0014] 1. The combination of chemical impurity removal, nanofiltration and resin adsorption impurity removal is used to remove impurities from lithium hydroxide mother liquor efficiently and reliably.

[0015] 2. Based on the reaction molar ratio and combined with engineering experiments, adopt a reasonable ratio of carbon dioxide to avoid excessive production of lithium bicarbonate.

[0016] 3. Use appropriate feed amount, temperature and stirring rate to control the reaction rate to obtain the target lithium carbonate crystal form and reduce impurity carryover.

[0017] 4. In the reactor stage, a two-stage process of normal temperature reaction and high temperature pyrolysis is adopted to ensure complete pyrolysis of lithium bicarbonate.

[0018] 5. Carry out scientific theoretical calculation and material balance, use the secondary washing water as part of the primary rinsing water, reduce the use of system water, and thus reduce the load of subsequent solution concentration. The water and energy consumption in the rinsing process is 20% better than the industry.

[0019] 6. Use a reasonable rinsing temperature to reduce the solubility of lithium carbonate and increase the yield of lithium carbonate.

[0020] 7. The product meets the standards of "YS / T 582-2013 Battery Grade Lithium Carbonate", LiCO 3 ≥99.5. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is the system principle diagram of the utility model;

[0022] Figure 2 It is the structural principle diagram of the reactor of the utility model.

[0023] In the figure, 1. dosing box; 2. impurity removal kettle; 3. microporous filter element filter; 4. nanofiltration equipment; 5. resin adsorption filter; 6. reactor; 7. centrifuge; 8. primary pulp mixing tank; 9. primary pulp washing kettle; 10. primary centrifuge; 11. secondary pulp mixing tank; 12. secondary pulp washing kettle; 13. secondary centrifuge; 14. dryer; 15. lithium hydroxide delivery pipeline; 16. transfer tank; 17. carbon dioxide inlet pipe; 18. secondary washing water recovery pipe; 19. flow meter; 20. regulating valve; 21. inlet pipe disc; 22. jacket; 23. steam inlet pipe; 24. condensate outlet pipe; 25. circulating cooling water inlet pipe; 26. circulating cooling water outlet pipe; 27. inert gas vent valve. DETAILED DESCRIPTION

[0024] The utility model will be further described below.

[0025] A lithium hydroxide mother liquor precipitation lithium carbonate production system, see Figure 1 to Figure 2 , including a front-stage impurity removal system, a reactor 6, a centrifuge 7, a primary slurry mixing tank 8, a primary slurry washing tank 9, a primary centrifuge 10, a secondary slurry mixing tank 11, a secondary slurry washing tank 12, a secondary centrifuge 13 and a dryer 14. The front-stage impurity removal system, the reactor 6, the centrifuge 7, the primary slurry mixing tank 8, the primary slurry washing tank 9, the primary centrifuge 10, the secondary slurry mixing tank 11, the secondary slurry washing tank 12, the secondary centrifuge 13 and the dryer 14 are sequentially connected through a lithium hydroxide conveying pipeline 15. The utility model uses high-impurity lithium hydroxide mother liquor as a raw material, and obtains battery-grade lithium carbonate through a series of processes such as chemical impurity removal, physical impurity removal, nanofiltration, resin adsorption, reaction, centrifugal separation, two-stage rinsing, and drying.

[0026] In the reactor 6, carbon dioxide (gas) is introduced into the lithium hydroxide solution for reaction to generate lithium carbonate precipitation. Circulating water is introduced during the reaction to control the formation rate of the crystal form. After the reaction is completed, the temperature is raised to 90° C. to completely decompose the excess lithium bicarbonate generated by the side reaction into lithium carbonate.

[0027] Reaction equation: 2LiOH+CO 2 =Li 2CO 3 ↓+H 2 0

[0028] Side reaction: Li 2 CO 3 (poorly soluble)+H 2 0+CO 2 =2LiHCO 3 (soluble)

[0029] Pyrolysis reaction: 2LiHCO 3 =Li 2 CO 3 ↓+H 2 0+CO 2 ↑

[0030] When lithium hydroxide reacts with carbon dioxide, if there is an excess of carbon dioxide, lithium bicarbonate will be generated, resulting in a significant reduction in yield; if there is insufficient carbon dioxide, the reaction will be incomplete, the yield will be low, and lithium hydroxide will be entrained, resulting in low product quality; if the reaction is too fast, the crystals will be unevenly formed and impurities will be entrained. The stirring rate and temperature also have a direct impact on the shape of the crystals.

[0031] The reactor 6 is provided with a carbon dioxide inlet pipe 17, and the carbon dioxide inlet pipe 17 is provided with a flow meter 19 and a regulating valve 20. The rate and total amount of carbon dioxide addition can be controlled by the carbon dioxide flow meter 19 and the regulating valve 20 to avoid excessive generation of lithium bicarbonate and too fast reaction; the reactor 6 is provided with a variable frequency stirring device, and the size of the lithium carbonate crystals can be controlled by variable frequency stirring.

[0032] The reactor 6, the primary pulp washing reactor 9 and the secondary pulp washing reactor 12 are provided with a jacket 22, and the jacket 22 is provided with a steam inlet pipe 23 and a condensed water outlet pipe 24. The jacket 22 on the reactor 6 can be temperature-controlled to ensure complete decomposition of lithium bicarbonate.

[0033] The jacket 22 of the reactor 6 is also provided with a circulating cooling water inlet pipe 25 and a circulating cooling water outlet pipe 26, both of which are connected to the inside of the jacket 22, the circulating cooling water inlet pipe 25 is located at the bottom of the jacket 22, and the circulating cooling water outlet pipe 26 is located at the upper part of the jacket 22. The circulating cooling water inlet pipe 25 and the circulating cooling water outlet pipe 26 are added to the jacket 22, and the circulating cooling water is introduced, and the jacket 22 can be used to timely control the temperature of the reactor 6 to ensure the stability of the lithium carbonate crystals in the reactor 6.

[0034] Through actual production test experience, controlling the carbon dioxide: lithium hydroxide = 1.4:1 can not only make the reaction more thorough but also avoid excessive hydrogenation, which is an ideal balance point.

[0035] Regarding the pyrolysis temperature. Lithium bicarbonate begins to decompose at 60°C, and complete decomposition requires 85°C. Choosing pyrolysis at 90°C without boiling can effectively prevent the current situation of incomplete decomposition of lithium bicarbonate and blockage of the pipe, and also ensure the yield, and will not waste excessive steam consumption.

[0036] The reactor 6 is provided with an air intake pipe disc 21, on which a plurality of exhaust holes are provided. The air intake pipe disc 21 is connected to the carbon dioxide intake pipe 17. The air intake pipe disc 21 can realize uniform intake of carbon dioxide and fully react with lithium hydroxide.

[0037] The centrifuge 7 separates the lithium carbonate slurry after the reaction. The lithium carbonate solid is sent to the next link for slurry adjustment, and the liquid (containing lithium) is returned to the system for use.

[0038] The lithium carbonate solid separated by centrifuge 7 is sent to the pulping tank, slurried with secondary washing water, and sent to the pulp washing kettle for stirring and washing at a temperature of 80°C. Because the separated lithium carbonate solid will carry certain soluble impurities, such as Na + , K + ,cl - 、SO 4 2- , slurry washing is required. The higher the solution temperature, the lower the solubility of lithium carbonate. High-temperature rinsing can increase product yield.

[0039] After the primary pulp washing kettle is stirred and washed once, it is separated by a primary centrifuge 10, and the primary washing liquid (containing lithium) is returned to the system for use. The lithium carbonate solid from the primary washing is sent to the secondary pulp mixing tank 11 for pulping. The pulp is mixed with pure water and sent to the secondary pulp washing kettle for stirring and washing. The stirring and washing temperature is 80°C.

[0040] After the secondary washing, the secondary centrifuge 13 is used for separation, and the lithium carbonate solid is sent down for drying. The secondary washing liquid has few impurities and can be used as the slurry for the primary washing. Therefore, a secondary washing water recovery pipe 18 is provided between the secondary centrifuge 13 and the primary slurry mixing tank 8. The secondary washing water recovery pipe 18 is provided with a transfer tank 16 and a solution pump to realize the recycling of the secondary washing water.

[0041] The secondary centrifuge 13 sends the wet lithium carbonate crystals to the dryer 14, where they are dried to a water content of ≤0.25% and packaged for sale. The product meets the standards of "YS / T 582-2013 Battery Grade Lithium Carbonate", LiCO3≥99.5

[0042] The top of the reactor 6 is also provided with an inert gas vent valve 27 , which can be used to discharge the inert gas in the reactor 6 .

[0043] The impurity removal system consists of an impurity removal kettle 2, a microporous filter element filter 3, a nanofiltration device 4 and a resin adsorption filter 5. The impurity removal kettle 2, the microporous filter element filter 3, the nanofiltration device 4 and the resin adsorption filter 5 are connected in sequence through a lithium hydroxide delivery pipeline 15. The resin adsorption filter 5 is connected to the inside of the reaction kettle 6 through the lithium hydroxide delivery pipeline 15. A drug adding box 1 is provided on the impurity removal kettle 2.

[0044] The impurity removal system is used to remove chemical impurities, physical impurities, nanofiltration and resin adsorption from the lithium hydroxide mother liquor raw material with high impurities.

[0045] Chemical impurity removal: Lithium hydroxide mother liquor is the liquid that is circulated in the system during the concentration process of the lithium hydroxide device. As time goes by, various impurities in the mother liquor are gradually enriched and eventually fail to meet the product quality requirements and need to be discharged from the system for recovery.

[0046] Lithium hydroxide mother liquor contains more Ca 2+ Mg 2+ 、Na + , K + , Fe 3+ Soluble impurities and some insoluble impurities are removed. First, add impurity removers such as sodium carbonate and oxalic acid to the impurity removal kettle 2 through the dosing box 1, and then add impurity removers such as sodium carbonate and oxalic acid to the impurity removal kettle 2. 2+ Mg 2+ , Fe 3+ reaction to precipitate high-valent metal ions.

[0047] Physical impurity removal: The carbonate / oxalate precipitate produced by chemical impurity removal is pumped into the microporous filter element filter 3 along with the slurry, and filtered in a 0.5μm high-precision filter to remove the precipitate and insoluble particles in the solution.

[0048] Nanofiltration: The lithium hydroxide solution filtered by the microporous filter is sent to the nanofiltration device 4. The pore size of the nanofiltration membrane is a few nanometers, so it is called nanofiltration. It can intercept organic matter and multivalent soluble ions, and allow small molecular organic matter and monovalent ions to pass through. This equipment can deeply remove impurities from the part where oxalic acid is not thoroughly removed. The test effect feedback is for Ca 2+ Mg 2+ , Fe 3 + , Mn 4+ 、Al 3+ 、SI 4+ 、SO 4 2- It has excellent removal effect on high-valent ions.

[0049] Resin adsorption: Finally, the resin adsorption filter 5 is used to absorb the adsorption groups on the surface of the resin (such as -COOH, -NH 2The resin can combine with certain molecules in the solution to form specific organic chemicals, so that certain substances in the solution are adsorbed on the resin surface instead of being dissolved.

[0050] A transfer tank 16 is provided on the lithium hydroxide delivery pipeline 15 between the microporous filter element filter 3 and the nanofiltration device 4 and between the resin adsorption filter 5 and the secondary evaporation crystallization system. The filtered lithium hydroxide solution is transferred and cached through the transfer tank 16 to control the filtration time and the filtration effect.

[0051] The utility model uses "high-impurity lithium hydroxide mother liquor" as raw material, and obtains "battery-grade lithium carbonate" through a series of impurity removal, reaction, rinsing and other means. The product meets the indicators of "YS / T 582-2013 Battery-grade lithium carbonate". LiCO 3 ≥99.5. Compared with traditional production methods, it improves production efficiency, improves product quality and reduces production energy consumption.

[0052] The above is a detailed introduction to a lithium hydroxide mother liquor precipitation lithium carbonate production system provided by the utility model. This article uses specific examples to illustrate the principles and implementation methods of the utility model. The description of the above embodiments is only used to help understand the method of the utility model and its core idea; at the same time, for general technical personnel in this field, according to the idea of ​​the utility model, there will be changes in the specific implementation method and application scope, and changes and improvements to the utility model will be possible without exceeding the concept and scope specified in the attached claims. In summary, the content of this specification should not be understood as a limitation on the utility model.

Claims

1. A lithium hydroxide mother liquor precipitation lithium carbonate production system, characterized in that: The invention comprises a front-stage impurity removal system, a reactor, a centrifuge, a primary slurry mixing tank, a primary slurry washing tank, a primary centrifuge, a secondary slurry mixing tank, a secondary slurry washing tank, a secondary centrifuge and a dryer. The front-stage impurity removal system, the reactor, the centrifuge, the primary slurry mixing tank, the primary slurry washing tank, the primary centrifuge, the secondary slurry mixing tank, the secondary slurry washing tank, the secondary centrifuge and the dryer are sequentially connected via a lithium hydroxide delivery pipeline. The reactor is provided with a carbon dioxide inlet pipe, a flow meter and a regulating valve are provided on the carbon dioxide inlet pipe, an inlet pipe disc is provided in the reactor, a plurality of exhaust holes are opened on the inlet pipe disc, and the inlet pipe disc is connected with the carbon dioxide inlet pipe.

2. A lithium hydroxide mother liquor precipitation lithium carbonate production system according to claim 1, characterized in that: A secondary washing water recovery pipe is arranged between the secondary centrifuge and the primary slurry mixing tank, and a transfer tank and a solution pump are arranged on the secondary washing water recovery pipe.

3. A lithium hydroxide mother liquor precipitation lithium carbonate production system according to claim 1, characterized in that: The reaction kettle, the first-stage pulp washing kettle and the second-stage pulp washing kettle are provided with jackets, and the jackets are provided with a steam inlet pipe and a condensed water outlet pipe.

4. A lithium hydroxide mother liquor precipitation lithium carbonate production system according to claim 3, characterized in that: The jacket of the reactor is also provided with a circulating cooling water inlet pipe and a circulating cooling water outlet pipe, both of which are connected to the inside of the jacket, the circulating cooling water inlet pipe is located at the bottom of the jacket, and the circulating cooling water outlet pipe is located at the upper part of the jacket.

5. A lithium hydroxide mother liquor precipitation lithium carbonate production system according to claim 1, characterized in that: An inert gas vent valve is also provided on the top of the reactor.

6. A lithium hydroxide mother liquor precipitation lithium carbonate production system according to claim 1, characterized in that: The reactor is provided with a variable frequency stirring device.

7. A lithium hydroxide mother liquor precipitation lithium carbonate production system according to claim 1, characterized in that: The impurity removal system consists of an impurity removal kettle, a microporous filter element filter, a nanofiltration device and a resin adsorption filter. The impurity removal kettle, the microporous filter element filter, the nanofiltration device and the resin adsorption filter are connected in sequence through a lithium hydroxide delivery pipeline. The resin adsorption filter is connected to the inside of the reaction kettle through the lithium hydroxide delivery pipeline. A drug adding box is provided on the impurity removal kettle.

8. A lithium hydroxide mother liquor precipitation lithium carbonate production system according to claim 7, characterized in that: Transfer tanks are respectively arranged on the lithium hydroxide delivery pipelines between the microporous filter element filter and the nanofiltration device and between the resin adsorption filter and the secondary evaporation crystallization system.

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