Method and System for Quickly Extracting Lithium Carbonate from Saline Lake Water

Abstract

The present invention discloses a method for quickly extracting lithium carbonate from saline lake water and a system for the same. The method comprises: first quick-freezing the saline lake water to obtain lithium-rich brine, then evaporating under reduced pressure to enable lithium carbonate to be rapidly precipitated out. The method has advantages of short process flow and less labor consumption, thereby enabling continuous automatic operation, high energy utilization and environment-friendly. Further, the crystallization rate is several times faster than that of the salt-pan process and the grade of lithium carbonate salt mine obtained can reach 95% or more, therefore the method of the present invention is particularly suitable for industrial production in the remote saline lake region. The system comprises a reduced-pressure evaporation crystallizer, a vacuum-pumping apparatus, a brine preheating apparatus and a brine cooling apparatus, which concentrates the brine by quick-evaporation of the water, promotes lithium carbonate to form non-uniform nucleus, and improves the crystallization efficiency.

Claims

1.-10. (canceled)

11. A method for quickly extracting lithium carbonate from saline lake water, the method comprising: introducing a lithium-rich brine into a reduced-pressure evaporation crystallizer to oversaturate and precipitate out lithium carbonate from the lithium-rich brine by a reduced-pressure evaporation process, while leaving a residual liquid; discharging the residual liquid; collecting the precipitate in the crystallizer; and drying the precipitate to obtain lithium carbonate crystals.

12. The method according to claim 11, wherein during the reduced-pressure evaporation process, the pressure of the reduced-pressure evaporation crystallizer is maintained between 25 kPa and 45 kPa.

13. The method according to claim 11, wherein the temperature for the reduced-pressure evaporation process ranges from 60 C. to 80 C.

14. The method according to claim 11, wherein the lithium-rich brine is preheated before being introduced into the reduced-pressure evaporation crystallizer.

15. The method according to claim 11, wherein the lithium-rich brine is prepared by a process comprising: cooling saline lake water to a temperature ranging from 40 C. to 20 C. to precipitate sodium and potassium salts present in the water; and separating the precipitated sodium and potassium salts from the water to obtain the lithium-rich brine.

16. The method according to claim 11, wherein the system for implementing the method comprises: a reduced-pressure evaporation crystallizer; a vacuum-pumping apparatus; a brine preheating apparatus; and a brine cooling apparatus, wherein the reduced-pressure evaporation crystallizer comprises an outer wall, an inner container and an upper cover, a heater equipped between the outer wall and the inner container, wherein the upper cover comprises a top and a bottom, wherein the top of the upper cover is equipped with a steam outlet and a brine inlet and the bottom of the upper cover is equipped with several detachable fins, wherein the steam outlet is connected with the vacuum-pumping apparatus via pipes, wherein the vacuum-pumping apparatus is connected with the brine preheating apparatus via pipes, and wherein the brine preheating apparatus is connected with the brine cooling apparatus via pipes.

17. The method according to claim 16, wherein the fins are configured to have cannelures.

18. The method according to claim 16, wherein the heater is equipped outside of the inner container.

19. The method according to claim 16, wherein a heat exchanger used for pre-cooling the saline lake water is equipped between the brine preheating apparatus and the brine cooling apparatus.

20. The method according to claim 16, wherein the heater is an electric heater.

21. The method according to claim 12, wherein the temperature for the reduced-pressure evaporation process ranges from 60 C. to 80 C.

22. The method according to claim 12, wherein the lithium-rich brine is preheated before being introduced into the reduced-pressure evaporation crystallizer.

23. The method according to claim 12, wherein the lithium-rich brine is prepared by a process comprising: cooling saline lake water to a temperature ranging from 40 C. to 20 C. to precipitate sodium and potassium salts present in the water; and separating the precipitated sodium and potassium salts from the water to obtain the lithium-rich brine.

24. The method according to claim 17, wherein the heater is equipped outside of the inner container.

25. The method according to claim 17, wherein a heat exchanger used for pre-cooling the saline lake water is equipped between the brine preheating apparatus and the brine cooling apparatus.

26. The method according to claim 17, wherein the heater is an electric heater.

Description

DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a structural schematic diagram of the device of the present invention;

[0036] FIG. 2 is a structural schematic diagram of the fins of the device of the present invention.

DETAILED DESCRIPTION

[0037] The present invention will be further illustrated below with reference to the accompanying drawings and embodiments.

[0038] Referring to FIGS. 12, a system for quickly extracting lithium carbonate from saline lake water, comprising a reduced-pressure evaporation crystallizer, a vacuum-pumping apparatus 5, a brine preheating apparatus 6 and a brine cooling apparatus 7. The reduced-pressure evaporation crystallizer has an outer wall 1, an inner container 2 and an upper cover 3. Heater 4 is equipped between the outer wall 1 and the inner container 2. The top of the upper cover 3 is equipped with a steam outlet 31 and a brine inlet 32, the bottom of which is equipped with several detachable fins 33. The steam outlet 31 is connected with the vacuum-pumping apparatus 5 which connected with the brine preheating apparatus 6, and the brine preheating apparatus 6 is connected with the brine cooling apparatus 7 via pipes.

[0039] As a further improvement of the present invention, the fins 33 are configured to have cannelures.

[0040] As a further improvement of the present invention, the heater 4 is equipped around outside the inner container 2. In particular, the heater is an electric heater.

[0041] As a further improvement of the present invention, a heat exchanger used for pre-cooling saline lake brine is equipped between the brine preheating apparatus and the brine cooling apparatus.

[0042] The electric energy used in the system of the present invention comes from solar power station. In the remote plateau area, the abundant solar energy resource can be used effectively, which is green and environment-friendly.

[0043] The fins are configured to have cannelures which further increase the non-uniformly nucleation area of Li.sub.2CO.sub.3, promote the nucleation and crystallization of Li.sub.2CO.sub.3, thereby increase the crystallization efficiency of Li.sub.2CO.sub.3.

[0044] After the vacuum-pumping apparatus is connected, the vapor pressure of the brine surface can be further decreased which accelerates the crystallization. The recycled steam enters into the brine preheating apparatus, making more efficient use of the energy.

[0045] The heater is equipped around the outside of the inner container which makes the saline lake brine self-circulate and develop a countercurrent flow after being heated, causing more uniform heating, while lithium carbonate fouling on the wall of the inner container, which adversely affects heating efficiency, can be avoided.

[0046] During operation, the saline lake brine is cooled in brine cooling apparatus 7. Preferably, filtrated lithium-rich brine is pre-cooled as it passes through the heat exchanger, which increases the temperature of the lithium-rich brine at the same time. Subsequently, the lithium-rich brine enters into the brine preheating apparatus 6 to be pre-heated, and then enters into the inner container 2 of the reduced-pressure evaporation crystallizer via the brine inlet 32. Then vacuum-pumping apparatus 5 is switched on to reduce the vapor pressure of the inner container 2, so as to accelerate evaporation and crystallization. Pumped-out steam enters into the brine preheating apparatus 6, and is collected by the via pipe 8.

Embodiment 1

[0047] 1) The brine of North lake of Zhabuye saline lake taken in summer (the concentration of lithium ion is 0.78 g/L, and the initial temperature of the brine is 5 C. is cooled to 40 C. by industrial freezing system. After the precipitation of sodium chloride, potassium chloride, and aphthitalite, a solid-liquid separation is carried out to obtain the lithium-rich brine;

[0048] 2) The obtained lithium-rich brine is transferred into the reduced-pressure evaporation crystallizers after being pre-heated by the preheating apparatus, wherein each crystallizer contains 30 L brine;

[0049] 3) The brine is quickly heated to 60 C., evaporated at a reduced-pressure for 5 min, and the pressure of the crystallizer is balanced at 26 kPa. After 2 hours, a lithium-rich salt mixture having a thickness of about 2 mm has been deposited on the bottom of the crystallizer, and the residual brine is discharged.

[0050] The grade of obtained lithium carbonate in the mixture is 95.2%, and the precipitation rate of the lithium salt is 99.0%.

[0051] The operation is run continuously for seven days following the above procedure. The grade of lithium carbonate obtained from the salt crystallized in the reduced-pressure evaporation crystallizer is 95.2% and the mixture is of 3.55 tons. The time required for producing lithium carbonate is 1.97 days per ton on average.

Embodiment 2

[0052] 1) The brine of North lake of Zhabuye saline lake taken in summer (the concentration of lithium ion is 0.54 g/L, and the initial temperature of the brine is 8 C.) is cooled to 30 C. using an industrial freezing system. After precipitation of sodium chloride, potassium chloride, and aphthitalite, a solid-liquid separation is carried out to obtain the lithium-rich brine;

[0053] 2) The obtained lithium-rich brine is transferred into the reduced-pressure evaporation crystallizers after being pre-heated by the preheating apparatus, wherein each crystallizer contains 30 L brine;

[0054] 3) The brine is quickly heated to 70 C., evaporated at a reduced-pressure for 5 min, and the pressure of the crystallizer is balanced at 36 kPa. After 2 hours, a lithium-rich salt mixture having a thickness of about 2 mm has been deposited on the bottom of the crystallizer, and the residual brine is discharged.

[0055] The grade of obtained lithium carbonate in the mixture is 95.8%, and the precipitation rate of the lithium salt is 99.6%.

[0056] The operation is run continuously for seven days following the above procedure. The grade of lithium carbonate obtained from the salt precipitated in the reduced-pressure evaporation crystallizer is 95.8% and the mixture is of 3.80 tons. The time required for producing lithium carbonate is 1.84 days per ton on average.

Embodiment 3

[0057] 1) The brine of salt-span of Zhabuye saline lake which has been dried in the sun for 10 days (the concentration of lithium ion is 1.2 g/L, and the initial temperature of the brine is 5 C.) is cooled to 20 C. by industrial freezing system. After precipitation of sodium chloride, potassium chloride, and aphthitalite, a solid-liquid separation is carried out to obtain the lithium-rich brine;

[0058] 2) The obtained lithium-rich brine is transferred into the reduced-pressure evaporation crystallizers after being pre-heated by the preheating apparatus, wherein each crystallizer contains 30 L brine;

[0059] 3) The brine is quickly heated to 75 C., evaporated at a reduced-pressure for 5 min, and the pressure of the crystallizer is balanced at 40 kPa. After 2 hours, a lithium-rich salt mixture having a thickness of about 4 mm has been deposited on the bottom of the crystallizer, and the residual brine is discharged.

[0060] The grade of obtained lithium carbonate in the mixture is 96.6%, and the precipitation rate of the lithium salt is 99.0%. The operation is run continuously for seven days following the above procedure.

[0061] The grade of lithium carbonate obtained from the salt precipitated in the reduced-pressure evaporation crystallizer is 96.6% and the mixture is of 4.01 tons. The time required for producing lithium carbonate is 1.75 days per ton on average.

Embodiment 4

[0062] 1) The brine of salt-span of Zhabuye saline lake which has been dried in the sun for 60 days (the concentration of lithium ion is 2.1 g/L, and the initial temperature of the brine is 12 C.) is cooled to 20 C. by industrial freezing system. After precipitation of sodium chloride, potassium chloride, and aphthitalite, a solid-liquid separation is carried out to obtain the lithium-rich brine;

[0063] 2) The obtained lithium-rich brine is transferred into the reduced-pressure evaporation crystallizers after being pre-heated by the preheating apparatus, wherein each crystallizer contains 30L brine;

[0064] 3) The brine is quickly heated to 80 C., evaporated at a reduced-pressure for 5 min, and the pressure of the crystallizer is balanced at 45 kPa. After 2 hours, a lithium-rich salt mixture having a thickness of about 5 mm has been deposited on the bottom of the crystallizer, then the residual brine is discharged.

[0065] The grade of obtained lithium carbonate in the mixture is 97.3%, and the precipitation rate of the lithium salt is 99.8%.

[0066] The operation is run continuously for seven days following the above procedure. The grade of lithium carbonate obtained from the salt precipitated in the reduced-pressure evaporation crystallizer is 97.3% and the mixture is of 4.28 tons. The time required for producing lithium carbonate is 1.63 days per ton on average.

[0067] As can be seen from the data of the above embodiments, lithium carbonate can be quickly and effectively extracted from the saline lake brine. The grade of lithium carbonate obtained by the method of the present invention is especially high, even can reach 95% or more, and the total recovery can reach 99%.

[0068] The device of the present invention can significantly promote moisture evaporation and make full use of the heat, therefore has advantages of good acceleration effect and high crystallization efficiency. The acceleration process is a purely physical process, which is environment-friendly and green. Most of lithium carbonate obtained by crystallization adhere to the fins and are easy to be collected. When the crystallization process of lithium carbonate is accelerated, the fresh water can also be produced, which is particularly suitable for remote saline lake mining area.