System for recovering sodium-lithium concentrated solution from lithium precipitation mother solution

Abstract

The utility model relates to the field of lithium precipitation mother liquor byproduct recovery, in particular to a system for recovering sodium-lithium concentrated liquor from lithium precipitation mother liquor, which comprises a feed preheating system, an evaporation and concentration system and an extraction, separation and recovery system which are communicated with one another, the extraction, separation and recovery system comprises a double-body cyclone, a thickener, a centrifugal machine, a mother liquid tank and a concentrated liquid tank, the double-body cyclone is formed by connecting two coaxially arranged cyclone units in parallel, the two cyclone units are communicated with the evaporation and concentration system through a feeding pipeline, an underflow port of each cyclone unit is connected with a liquid inlet of the thickener, and an underflow port of each centrifugal machine is connected with a liquid outlet of the centrifugal machine; the top of the cyclone unit is provided with an overflow port and is connected with the concentrated solution tank through an overflow pipe, the overflow pipe of the thickener is connected with the mother solution tank, an underflow port of the thickener is connected with a feed port of the centrifugal machine, a discharge port of the centrifugal machine is connected with the blanking barrel, and a liquid outlet of the centrifugal machine is connected with the concentrated solution tank. The system for recovering the sodium-lithium concentrated solution from the lithium precipitation mother solution is high in recovery efficiency.

Description

Technical Field

[0001] This utility model relates to the field of lithium precipitation mother liquor by-product recovery, specifically to a system for recovering sodium lithium concentrate from lithium precipitation mother liquor. Background Technology

[0002] Lithium precipitation mother liquor is the solution remaining after the lithium precipitation step in the lithium salt production process. In the production of lithium carbonate using the carbonate precipitation method, approximately 20% of the lithium is lost in the mother liquor due to process limitations. This mother liquor not only contains a high concentration of lithium but also other elements such as sodium and sulfate. Therefore, lithium precipitation mother liquor is a saturated salt solution primarily composed of sodium sulfate, with sodium and lithium coexisting.

[0003] CN118576991A discloses an MVR evaporation crystallization system, comprising: a crystallization separator for boiling and evaporating lithium precipitation mother liquor to obtain sodium sulfate slurry and secondary steam; a heater for heating the lithium precipitation mother liquor, the heater being connected to the crystallization separator; a steam compressor, one end of which is connected to the crystallization separator for recovering and increasing the thermal energy of the secondary steam generated by the crystallization separator, and the other end of which is connected to the heater for recycling the secondary steam; a preheater for recovering the waste heat of the evaporation condensate and non-condensable gas generated by the MVR evaporation crystallization system to preheat the lithium precipitation mother liquor, the preheater being connected to the crystallization separator, and the preheated lithium precipitation mother liquor entering the crystallization separator; and a forced circulation pump connected to both the crystallization separator and the heater, the forced circulation pump being used to drive the lithium precipitation mother liquor to circulate in the crystallization separator, the forced circulation pump, and the heater.

[0004] The existing recovery system suffers from low lithium recovery rates due to crystallization and tank blockage caused by the high salt content in the sodium-lithium concentrate. Utility Model Content

[0005] The technical problem to be solved by this utility model is to overcome the deficiencies and defects mentioned in the background art above, and to provide a system for recovering sodium lithium concentrate from lithium precipitation mother liquor with high recovery efficiency.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this utility model is: a system for recovering sodium lithium concentrate from lithium precipitation mother liquor, comprising: a feeding preheating system, an evaporation concentration system and an extraction separation and recovery system connected in sequence;

[0007] The extraction, separation, and recovery system includes a twin-body hydrocyclone, a thickener, a centrifuge, a mother liquor tank, and a concentrate tank. The twin-body hydrocyclone consists of two coaxially arranged hydrocyclone units connected in parallel. The two hydrocyclone units are connected to the evaporation and concentration system through a feed pipe. The underflow port of the hydrocyclone unit is connected to the liquid inlet of the thickener. The top of the hydrocyclone unit is provided with an overflow port, which is connected to the concentrate tank through an overflow pipe. The overflow pipe of the thickener is connected to the mother liquor tank. The underflow port of the thickener is connected to the feed port of the centrifuge. The discharge port of the centrifuge is connected to the discharge cylinder. The liquid outlet of the centrifuge is connected to the concentrate tank.

[0008] In one embodiment, each hydrocyclone unit includes a cylindrical body and a conical tube disposed at the bottom of the cylindrical body; the top of the cylindrical body is provided with an overflow port, and the bottom of the conical tube is provided with an underflow port; the inner wall of the conical tube is provided with helical guide vanes.

[0009] In one embodiment, the feed inlet of the twin-body hydrocyclone is connected to the side wall cuts on the cylindrical bodies of the two hydrocyclone units.

[0010] In one embodiment, the overflow port of the hydrocyclone unit extends downward along the cylindrical body to below the horizontal line of the feed inlet.

[0011] In one embodiment, a sight glass for observing the color and state of the material is installed at the underflow port of the hydrocyclone unit.

[0012] In one embodiment, the feed preheating system includes a feed pump connected to a mother liquor tank, a condensate heat exchanger, a non-condensable steam heat exchanger, and a steam heat exchanger connected to the feed pump.

[0013] In one embodiment, the inlet of the raw material pump is connected to the mother liquor tank via a siphon tank, the outlet of the raw material pump is connected to the inlet of the condensate heat exchanger, one outlet of the condensate heat exchanger is connected to one inlet of the non-condensable steam heat exchanger, and one outlet of the non-condensable steam heat exchanger is connected to one inlet of the steam heat exchanger.

[0014] In one embodiment, the evaporation and concentration system includes a forced evaporator, a forced evaporator, a crystallizer, a gas scrubbing tower, and a centrifugal compressor. A non-condensable heat exchanger is connected to the forced evaporator and the forced evaporator, and a steam heat exchanger is connected to the forced evaporator and the forced evaporator via a condensate tank. The forced evaporator and the forced evaporator are connected to the crystallizer, and the crystallizer is connected to the centrifugal compressor via the gas scrubbing tower.

[0015] In one embodiment, the bottom ceramic column of the crystallizer is connected to the crystal slurry pump, and the outlet of the crystal slurry pump is connected to the twin-body hydrocyclone through a feed pipe.

[0016] In one embodiment, a stirrer is installed inside the thickener.

[0017] Compared with existing technologies, the beneficial effects of this utility model are as follows: This utility model uses a dual-body hydrocyclone and a centrifuge to separate and recover sodium-lithium concentrate to a sodium-lithium concentrate tank, which can be directly reused in the lithium precipitation workshop; the distilled water obtained by evaporation can be reused in production, and the sodium sulfate obtained by evaporation can be used as a by-product industrial salt. The hydrocyclone mainly separates based on centrifugal force and eddy current effect. The dual-body hydrocyclone of this application consists of two hydrocyclone units connected coaxially in parallel, sharing the same feed pipe to evenly distribute the slurry to the two hydrocyclone units. The hydrocyclone units rotate and form a strong vortex flow. In this way, the mixture inside the hydrocyclone is subjected to the combined action of centrifugal force and gravity. Due to centrifugal sedimentation, larger particles, which are heavier, are discharged from the bottom outlet of the hydrocyclone and enter the thickener, while smaller particles, which are lighter, are discharged from the overflow pipe of the hydrocyclone and stored in the concentrate tank. This prevents clogging and achieves good solid-liquid separation. In this application, the dual-body hydrocyclone generates a more intense swirling flow through two cylinders rotating in opposite directions, which can more efficiently separate impurities in the liquid and more finely separate tiny particles and harmful substances, thereby improving the overall lithium recovery efficiency. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a system structure for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to one embodiment.

[0020] Figure 2 This is a schematic diagram of the structure of a twin-body cyclone separator according to one embodiment.

[0021] Attached reference numerals: 1. Main steam valve; 2. Steam heat exchanger control valve; 3. Steam control valve; 4. Condensate heat exchanger; 5. Non-condensable steam heat exchanger; 6. Steam heat exchanger; 7. Ceramic column; 8. Twin-body hydrocyclone; 9. Crystallizer reflux valve; 10. Mother liquor tank; 11. Raw material pump; 12. Condensate pump; 13. Condensate tank; 14. Forced circulation pump; 15. Forced evaporator one; 16. Forced evaporator two; 17. Crystallization section 18. Scrubber; 19. Centrifugal compressor; 20. Thickener; 210. Thickener overflow port; 21. Mother liquor tank; 22. Concentrate tank; 23. Mother liquor pump; 24. Crystal slurry pump; 25. Centrifuge; 26. Centrifuge filtrate outlet; 81. Hydrocyclone inlet; 82. Hydrocyclone overflow port; 83. Cylindrical body; 84. Conical cylinder; 85. Spiral guide vane; 86. Sight glass; 87. Side wall cut. Detailed Implementation

[0022] To facilitate understanding of this utility model, the following description will be provided in more comprehensive and detailed manner with reference to the accompanying drawings and preferred embodiments. However, the scope of protection of this utility model is not limited to the following specific embodiments.

[0023] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of protection of this invention.

[0024] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0025] Please see Figure 1-2 A system for recovering sodium-lithium concentrate from lithium precipitation mother liquor includes a feed preheating system, an evaporation concentration system, and an extraction separation and recovery system connected in series. Specifically, the system for recovering sodium-lithium concentrate from lithium precipitation mother liquor mainly includes a raw material pump 10, a condensate heat exchanger 4, a non-condensable steam heat exchanger 5, a steam heat exchanger 6, a condensate tank 13, a forced evaporator I 15, a forced evaporator II 16, a crystallizer 17, a crystal slurry pump 24, a twin-body hydrocyclone 8, a thickener 20, a centrifuge 25, a mother liquor tank 21, a gas scrubbing tower 18, a centrifugal compressor 19, a concentrate tank 22, and connecting pipes and control valves.

[0026] Specifically, in one embodiment, the feed preheating system includes a raw material pump 11 connected to a mother liquor tank 10, a condensate heat exchanger 4, a non-condensable steam heat exchanger 5, and a steam heat exchanger 6 all connected to the raw material pump 11. The inlet of the raw material pump 11 and the mother liquor tank 10 are connected via a siphon tank, which is installed on the suction pipe before the pump. The siphon tank helps the raw material pump 11 establish negative pressure during startup, achieving self-priming. The outlet of the raw material pump 11 is connected to one of the inlets of the condensate heat exchanger 4, one of the outlets of the condensate heat exchanger 4 is connected to one of the inlets of the non-condensable steam heat exchanger 5, one of the outlets of the non-condensable steam heat exchanger 5 is connected to one of the inlets of the steam heat exchanger 6, and one of the outlets of the steam heat exchanger 6 is connected to the bottom inlet of the forced evaporator 15 via a pipe.

[0027] Preferably, one inlet of the condensate heat exchanger 4 is connected to the outlet of the condensate tank 13 via a condensate pump 12, and one outlet of the condensate heat exchanger 4 is connected to an external drainage pipe or a reuse pipe. One inlet of the non-condensable steam heat exchanger 5 is connected to the non-condensable steam outlet of forced evaporator 15 and forced evaporator 2 16, and the outlet of the non-condensable steam heat exchanger 5 is connected to a non-condensable steam discharge pipe. One inlet of the steam heat exchanger 6 is connected to the main steam pipeline (live steam pipeline) via a steam heat exchanger control valve 2 on a connecting branch pipeline. The main steam pipeline is equipped with a main steam valve 1 and a steam heat exchanger control valve 3. One outlet of the steam heat exchanger 6 is connected to the top inlet of the condensate tank 13. The top inlet of the condensate tank 13 is connected to the condensate outlet of forced evaporator 15 and forced evaporator 2 16.

[0028] The evaporation and concentration system includes a forced evaporator 15, a forced evaporator 16, a crystallizer 17, a scrubbing tower 18, and a centrifugal compressor 19. Forced evaporators 15 and 16 are connected to the crystallizer 17, which in turn is connected to the centrifugal compressor 19 via the scrubbing tower 18. The top circulation outlet of forced evaporator 15 is connected to the circulation inlet of crystallizer 17; one of the circulation outlets of crystallizer 17 is connected to the circulation inlet of forced evaporator 16; the bottom circulation outlet of forced evaporator 16 is connected to the inlet of forced circulation pump 14; and the outlet of forced circulation pump 14 is connected to the circulation inlet of forced evaporators. The top secondary steam outlet of crystallizer 17 is connected to the inlet of scrubbing tower 18; the secondary steam outlet of scrubbing tower 18 is connected to the secondary steam inlet of centrifugal compressor 19; and the secondary steam outlet of centrifugal compressor 19 is connected to the inlets of forced evaporators 15 and 16. The air inlets of forced evaporators 15 and 16 are connected to the main steam pipeline via steam control valve 3. The bottom outlet and side outlet of the bottom crystalline column 7 of the crystallizer 17 are connected to the liquid inlet of the crystal slurry pump 24, and the liquid outlet of the crystal slurry pump 24 is connected to the feed inlet of the twin-body hydrocyclone 8 via a feed pipe.

[0029] The twin-body hydrocyclone 8 consists of two coaxially arranged hydrocyclone units connected in parallel. The hydrocyclone inlets 81 of the two units are connected to the evaporation and concentration system via a feed pipe. The underflow outlet of each hydrocyclone unit is connected to the liquid inlet of the thickener 20. An overflow outlet 82 is located at the top of each hydrocyclone unit, and this overflow outlet 82 is connected to the concentrate tank 22 via an overflow pipe. The overflow pipe is connected to a liquid inlet at the top of the crystallizer 17 via a reflux valve 9. The thickener 20 is equipped with a stirrer. Its overflow outlet 210 is connected to the mother liquor tank 21 via an overflow pipe. The underflow outlet of the thickener 20 is connected to the feed inlet of the centrifuge 25. The discharge outlet of the centrifuge 25 is connected to the discharge cylinder. After discharge, the material enters the drying process. The liquid outlet of the centrifuge 25 is connected to the concentrate tank 22.

[0030] Specifically, each hydrocyclone unit includes a cylindrical body 83 and a conical cylinder 84 located at the bottom of the cylindrical body 83. The top of the cylindrical body 83 has a hydrocyclone overflow port 82, and the bottom of the conical cylinder 84 has a bottom outlet; preferably, the inner wall of the conical cylinder 84 is provided with spiral guide vanes 85. Preferably, the feed inlet 81 of the dual-body hydrocyclone 8 is connected to the side wall cutouts 87 on the cylindrical bodies 83 of the two hydrocyclone units. With the above-described structure, the hydrocyclone unit allows a solid-liquid mixture to enter the hydrocyclone body through the inlet pipe, forming a vortex. Solid particles move towards the outer wall due to centrifugal force and deposit, forming a solid-phase sedimentation zone, while the liquid moves upward along the central axis of the vortex, forming a liquid-phase discharge zone, thus achieving solid-liquid separation. Preferably, the overflow port of the hydrocyclone unit extends downward along the cylindrical body to below the horizontal line of the feed inlet. Therefore, the liquid separated by the hydrocyclone unit will not mix with the raw material at the feed inlet, resulting in better separation. Preferably, a sight glass 86 for observing the color and state of the material is installed at the underflow port of the hydrocyclone unit.

[0031] The working principle of this invention is as follows: When the mother liquor containing sodium sulfate and lithium sulfate is stored in the crystal slurry pump 10, dilute sulfuric acid is added to adjust the pH of the lithium precipitation mother liquor in the crystal slurry pump 10 to 6-8. The lithium precipitation mother liquor in the crystal slurry pump 10 is then fed into the condensate heat exchanger 4, the non-condensable steam heat exchanger 5, and the steam heat exchanger 6 in sequence for preheating. After the temperature of the lithium precipitation mother liquor is increased, it enters the forced evaporator 15 for heat exchange. Under the action of the forced circulation pump 14, the lithium precipitation mother liquor rises to the crystallization separator 17. In the crystallization separator 17, the static pressure of the lithium precipitation mother liquor decreases, causing the lithium precipitation mother liquor to evaporate. The evaporation produces secondary steam that overflows from the lithium precipitation mother liquor. The lithium precipitation mother liquor is concentrated to supersaturation, causing crystal growth. The large crystal particles after growth precipitate into the ceramic column 7 under the action of gravity. The desaturated lithium precipitation mother liquor enters the forced evaporator 16. The lithium precipitation mother liquor is continuously evaporated and concentrated or concentrated and crystallized under the action of the forced circulation pump 14. Sodium sulfate slurry obtained in the Taoxi column 7 is pumped by the slurry pump 24 into the twin-body hydrocyclone 8. Secondary steam in the crystallizer 17 enters the scrubbing tower 18 through the top of the crystallizer 17. After purification by the separation and defoaming device, it enters the centrifugal compressor 19 to compress the secondary steam and then sends it to the shell side of forced evaporators 15 and 16 as heating steam, achieving continuous evaporation through thermal energy circulation. Non-condensable steam in the forced evaporator 6 enters the non-condensable steam heat exchanger along the non-condensable steam pipe outlet and is then discharged. The steam entering forced evaporators 15 and 16 condenses and enters the condensate tank 13. Under the action of the condensate pump 12, it enters the condensate heat exchanger for heat exchange and is then reused or discharged.

[0032] The sodium sulfate slurry obtained in column 7 is pumped to a twin-cell hydrocyclone 8 by pump 24. The twin-cell hydrocyclone 8 consists of two parallel hydrocyclone units sharing the same inlet 81 for even slurry distribution. The slurry is forced tangentially into the two hydrocyclone units under pressure. Under the action of the circular barrel wall, the mixture rotates and forms a strong vortex. The mixture inside the twin-cell hydrocyclone 8 is subjected to the combined effects of centrifugal force and gravity. Larger particles, being heavier, are discharged from the bottom outlet of the twin-cell hydrocyclone 8 into the thickener 20, while smaller particles, being lighter, are discharged from the overflow pipe 82 of the twin-cell hydrocyclone 8 into the concentrate tank 22 for storage. Simultaneously, a portion of the sodium-lithium concentrate can enter the crystallizer 17 for further concentration via the reflux valve 9. The lithium mother liquor entering the thickener 20 is separated from the sodium sulfate crystal slurry by gravity sedimentation. The solids are then introduced into the centrifuge 25 through the underflow port to achieve solid-liquid separation. The centrifuge 25 ejects the concentrate into the sodium-lithium concentrate tank 22 for storage and recovery. The supernatant in the thickener 20 overflows into the mother liquor tank 21. The sodium sulfate concentrate in the mother liquor tank 21 is discharged into the crystallizer 17 by the mother liquor pump 23 for further evaporation and concentration.

[0033] This invention employs a dual-body hydrocyclone and centrifuge 25 to separate and recover sodium-lithium concentrate into a sodium-lithium concentrate tank 22, which can be directly reused in the lithium precipitation workshop. The distilled water obtained from evaporation can be reused in production, and the sodium sulfate obtained from evaporation can be used as a by-product industrial salt. The hydrocyclone unit mainly relies on centrifugal force and eddy current effect for separation. The dual-body hydrocyclone of this application consists of two hydrocyclone units connected in parallel, sharing the same feed pipe to evenly distribute the slurry into the two hydrocyclone units. The hydrocyclone units rotate and form a strong vortex flow. Thus, the mixture inside the hydrocyclone is subjected to the combined action of centrifugal force and gravity. Due to centrifugal sedimentation, larger particles, which are heavier, are discharged from the bottom outlet of the hydrocyclone and enter the thickener 20, while smaller particles, which are lighter, are discharged from the overflow pipe of the hydrocyclone and stored in the concentrate tank 22. This process is less prone to clogging and results in good solid-liquid separation. In this application, the dual-body hydrocyclone generates a more intense swirling flow through two cylinders rotating in opposite directions, which can more efficiently separate impurities in the liquid and more finely separate tiny particles and harmful substances, thereby improving the overall lithium recovery efficiency.

Claims

1. A system for recovering sodium-lithium concentrate from lithium precipitation mother liquor, characterized in that, include: The feed preheating system, evaporation and concentration system, and extraction, separation and recovery system are connected in sequence. The extraction, separation and recovery system includes a twin hydrocyclone (8), a thickener (20), a centrifuge (25), a mother liquor tank (21), and a concentrate tank (22). The twin hydrocyclone (8) is composed of two coaxially arranged hydrocyclone units connected in parallel. The two hydrocyclone units are connected to the evaporation and concentration system through a feed pipe. The bottom outlet of the hydrocyclone unit is connected to the liquid inlet of the thickener (20). The top of the hydrocyclone unit is provided with an overflow port (82) and is connected to the concentrate tank (22) through an overflow pipe. The overflow pipe of the thickener (20) is connected to the mother liquor tank (21). The bottom outlet of the thickener (20) is connected to the feed inlet of the centrifuge (25). The discharge port of the centrifuge (25) is connected to the discharge cylinder. The liquid outlet of the centrifuge (25) is connected to the concentrate tank (22).

2. The system for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to claim 1, characterized in that, Each hydrocyclone unit includes a cylindrical body (83) and a conical tube (84) disposed at the bottom of the cylindrical body (83); the top of the cylindrical body (83) is provided with an overflow port, and the bottom of the conical tube (84) is provided with an underflow port; the inner wall of the conical tube (84) is provided with spiral guide vanes (85).

3. The system for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to claim 2, characterized in that, The feed inlet (81) of the twin hydrocyclone (8) is connected to the side wall cutouts (87) on the cylindrical bodies (83) of the two hydrocyclone units.

4. The system for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to claim 1, characterized in that, The overflow port of the hydrocyclone unit extends downward along the cylindrical body (83) to below the horizontal line of the feed inlet.

5. The system for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to claim 1, characterized in that, The hydrocyclone unit is equipped with a sight glass (86) at the underflow outlet for observing the color and state of the material.

6. The system for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to claim 5, characterized in that, The feed preheating system includes a feed pump (11) connected to the mother liquor tank (10), a condensate heat exchanger (4), a non-condensable steam heat exchanger (5), and a steam heat exchanger (6) connected to the feed pump (11).

7. The system for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to claim 6, characterized in that, The inlet of the raw material pump (11) is connected to the mother liquor tank (10) via a siphon tank. The outlet of the raw material pump (11) is connected to the inlet of the condensate heat exchanger (4). One of the outlets of the condensate heat exchanger (4) is connected to one of the inlets of the non-condensable steam heat exchanger (5). One of the outlets of the non-condensable steam heat exchanger (5) is connected to one of the inlets of the steam heat exchanger (6).

8. The system for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to claim 7, characterized in that, The evaporation and concentration system includes a forced evaporator (15), a forced evaporator (16), a crystallizer (9), a scrubbing tower (18), and a centrifugal compressor (19). A non-condensable heat exchanger (5) is connected to the forced evaporator (15) and the forced evaporator (16). A steam heat exchanger (6) is connected to the forced evaporator (15) and the forced evaporator (16) via a condensate tank (13). The forced evaporator (15) and the forced evaporator (16) are connected to the crystallizer (9). The crystallizer (9) is connected to the centrifugal compressor (19) via the scrubbing tower (18).

9. The system for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to claim 7, characterized in that, The bottom ceramic column (7) of the crystallizer (9) is connected to the crystal slurry pump (24), and the outlet of the crystal slurry pump (24) is connected to the double-body hydrocyclone through the feed pipe.

10. The system for recovering sodium-lithium concentrate from lithium precipitation mother liquor according to claim 1, characterized in that, The thickener (20) is equipped with a stirrer.

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