Method and system for preparing lithium carbonate from lithium ore

Abstract

Disclosed by the invention is a method for preparing lithium carbonate from lithium ore, comprising the steps of: preparing lithium sulfate leachate from lithium ore concentrate, removing Fe.sup.2+ and Al.sup.3+ from the lithium sulfate leachate by adding alkali, removing Ca.sup.2+ and Mg.sup.2+ from the lithium sulfate leachate by an ion exchange method, adding a saturated solution of soda ash into the obtained concentrated solution of lithium sulfate leachate, precipitating lithium carbonate, filtering and separating the lithium carbonate precipitate, washing with hot water and drying to obtain a finished lithium carbonate product. The invention saves the production cost, and obviously improves the purity of lithium carbonate as a final product. In addition, disclosed by the invention is also a system for realizing the method for preparing lithium carbonate from lithium ore.

Claims

1. A system for preparing concentrated Li.sub.2SO.sub.4 leachate from lithium ore, comprising: a leachate production system to produce Li.sub.2SO.sub.4 leachate from lithium ore; a precision filtration device to remove Fe.sup.2+ and Al.sup.3+ from the Li.sub.2SO.sub.4 leachate and produce a filtered Li.sub.2SO.sub.4 leachate; an ion exchange device to remove Ca.sup.2+ and Mg.sup.2+ from the filtered Li.sub.2SO.sub.4 leachate and produce a deionized Li.sub.2SO.sub.4 leachate; and a membrane concentrator to produce the concentrated Li.sub.2SO.sub.4 leachate from the deionized Li.sub.2SO.sub.4 leachate wherein the membrane concentrator comprises an ultrafiltration membrane filtration device followed by a disk-tube reverse osmosis membrane filtration device.

2. The system of claim 1, further comprising: a pretreatment device to ensure a quality of the deionized Li.sub.2SO.sub.4 leachate entering the membrane concentrator; wherein the pretreatment device comprises: a primary filtration device to control an impurity concentration of the deionized Li.sub.2SO.sub.4 leachate entering the membrane concentrator; and a pH adjustment device to control a pH of the deionized Li.sub.2SO.sub.4 leachate entering the membrane concentrator.

3. The system of claim 1 wherein the disk-tube reverse osmosis membrane filtration device is a single stage device.

4. The system of claim 1 wherein the ion exchange device removes Ca.sup.2+ and Mg.sup.2+ from the filtered Li.sub.2SO.sub.4 leachate by a process comprising: exposing the filtered Li.sub.2SO.sub.4 leachate to an ion exchange resin.

5. The system of claim 1 wherein the filtered Li.sub.2SO.sub.4 leachate has a concentration of Fe.sup.2+ of less than 0.005% and a concentration of Al.sup.3+ of less than 0.005%.

6. The system of claim 1 wherein the deionized Li.sub.2SO.sub.4 leachate has a concentration of Ca.sup.2+ of less than 0.0024% and a concentration of Mg.sup.2+ of less than 0.0040%.

7. The system of claim 1 wherein the disk-tube reverse osmosis membrane filtration device is a multi-stage device.

8. The system of claim 1 wherein the ultrafiltration membrane filtration device is operative to intercept substances with molecular weight greater than 2000 and diameter of 0.005-0.05 m.

9. The system of claim 1 wherein the disk-tube reverse osmosis membrane filtration device is operative to intercept substances with molecular weight 50-150 and diameter of 0.0001-0.001 m.

10. The system of claim 1, wherein the membrane concentrator emits concentrated Li.sub.2SO.sub.4 leachate having a concentration of at least 15%.

11. The system of claim 1, wherein the membrane concentrator emits concentrated Li.sub.2SO.sub.4 leachate having a concentration between 15% and 20%.

12. The system of claim 1 wherein the precision filtration device removes Fe.sup.2+ and Al.sup.3+ from the Li.sub.2SO.sub.4 leachate by a process comprising: adding alkali to adjust a pH of the Li.sub.2SO.sub.4 leachate and cause precipitation of the Fe.sup.2+ and Al.sup.3+; and filtering the Fe.sup.2+ and Al.sup.3+ precipitates to produce the filtered Li.sub.2SO.sub.4 leachate.

13. The system of claim 12 wherein adding alkali to adjust the pH of the Li.sub.2SO.sub.4 leachate is adding alkali to adjust the pH of the Li.sub.2SO.sub.4 leachate to between 9 and 10.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) The drawings described here are used for further understanding of the invention, and form a part thereof. The contents provided in the drawings and their related descriptions in the invention are used to explain the invention, but not improperly limit thereto. In the drawings:

(2) FIG. 1 is a flow diagram of the devices relating to the method and system for preparing lithium carbonate from lithium ore of the invention.

(3) Relevant marks in the above drawings are as follows: 1: Precision filtration device; 2: Ion exchange device; 3: Pretreatment device; 4: Ultrafiltration membrane filtration device; 5: Disk-tube reverse osmosis membrane filtration device; 6: Li.sub.2SO.sub.4 leachate production system; 7: Lithium precipitation system; 8: Drying system.

DETAILED DESCRIPTION

(4) The invention will be clearly and completely described in combination with drawings. Those skilled in the art will be able to implement the invention based on these descriptions. Before the invention is described with reference to the drawings, it should be particularly noted that:

(5) In the invention, the technical solutions and technical features provided in various parts, including the following description, can be combined with each other without conflict.

(6) In addition, the embodiments of the invention referred to in the following description are generally only part of embodiments of the invention, but not all embodiments. Therefore, based on the embodiments of the invention, all other embodiments obtained by those skilled in the art without creative work shall fall within the protection scope of the invention.

(7) With respect to terms and units in the invention, the terms comprising, having and any variations thereof in the specification, claims and related parts of the invention are intended to cover non-exclusive inclusion.

(8) The invention provides a method for preparing lithium carbonate from lithium ore, comprising the steps of: 1) preparing lithium sulfate leachate from lithium ore concentrate, wherein the specific preparation process of lithium sulfate leachate is based on the prior art, and the preparation process of lithium sulfate leachate in this specific embodiment is as follows: roasting and cooling lithium ore concentrate to obtain lithium ore calcine; grinding lithium ore calcine to obtain lithium ore powder; adding sulfuric acid into lithium ore powder, and roasting to obtain acid clinker; adding calcium carbonate into acid clinker to obtain a mixture, adding water into the mixture, and filtering when the pH value of the mixture is 5.5-6.0 to obtain lithium sulfate leachate; 2) adjusting the pH value of the lithium sulfate leachate to 9-10 by adding alkali, and precipitating Fe.sup.2+ and Al.sup.3+ in the lithium sulfate leachate; 3) filtering the lithium sulfate leachate obtained in 2) and removing Fe.sup.2+ and Al.sup.3+ precipitates therefrom; 4) treating the filtered lithium sulfate leachate by an ion exchange method and removing Ca.sup.2+ and Mg.sup.2+ therefrom; 5) performing membrane concentration on the lithium sulfate leachate obtained by the ion exchange treatment to produce a concentrated solution of lithium sulfate leachate, wherein the concentration of Fe.sup.2+, Al.sup.3+, Ca.sup.2+ and Mg.sup.2+ in the concentrated solution is less than 0.0005%, 0.0005%, 0.0024% and 0.0040% respectively, and the concentration of lithium sulfate in the concentrated solution is 15-20%; and 6) adding a saturated solution of soda ash into the concentrated solution of lithium sulfate leachate obtained in 5), precipitating lithium carbonate, filtering and separating the lithium carbonate precipitate, washing with hot water and drying to obtain a finished lithium carbonate product.

(9) The suspended matter in the lithium sulfate leachate is removed and the pH value thereof is adjusted before the lithium sulfate leachate is concentrated in 5).

(10) The membrane concentration process in 5) comprises ultrafiltration membrane filtration and reverse osmosis filtration.

(11) The invention is described in detail below by comparing several groups of methods for preparing lithium carbonate from lithium ore and the method for preparing lithium carbonate from lithium ore in the invention: Comparative experiment 1: Lithium sulfate leachate was prepared from lithium ore concentrate, and then only a large amount of alkali was added to the lithium sulfate leachate to remove impurities therefrom; Comparative experiment 2: Lithium sulfate leachate was prepared from lithium ore concentrate, and then lithium carbonate leachate was purified by the ion exchange method. Example 1: The method for preparing lithium carbonate from lithium ore of the invention was used.

(12) Table 1 compares the experimental effects of the above three groups of experimental methods:

(13) TABLE-US-00001 Ion concentration of lithium sulfate leachate Experimental after impurity method Experimental effect Production cost removal (%) Comparative The experiment could The reagent cost was a factor c.sub.(Fe.sup.2+.sub.) < 0.0005 experiment 1 not guarantee the impurity that must be considered. The c.sub.(Al.sup.3+.sub.) < 0.0005 removal effect due to treatment cost of this method c.sub.(Ca.sup.2+.sub.) < 0.0027 complex system equipment was the highest among the three c.sub.(Mg.sup.2+.sub.) < 0.0045 and many process steps. methods, which was about 240-340 yuan/ton of water. Comparative Ionic resin was prone to The recycling rate of resin was c.sub.(Fe.sup.2+.sub.) < 0.0005 experiment 2 iron poisoning due to low, which indirectly increased c.sub.(Al.sup.3+.sub.) < 0.0005 the existence of iron ions. the treatment cost, about c.sub.(Ca.sup.2+.sub.) < 0.0026 Thus, resin was deactivated 150-270 yuan/ton of water. c.sub.(Mg.sup.2+.sub.) < 0.0043 and could not be recycled, which increased the treatment cost. The resin should be treated as solid waste. Example 1 Less process steps; This method could reduce the c.sub.(Fe.sup.2+.sub.) < 0.0005 Ensure recycling rate of treatment cost and ensure the c.sub.(Al.sup.3+.sub.) < 0.0005 the resin; ion removal rate, with low risk c.sub.(Ca.sup.2+.sub.) < 0.0024 Impurity removal effect of resin poisoning and high c.sub.(Mg.sup.2+.sub.) < 0.0040 superior to the previous recycling rate. Its treatment two methods. cost was the lowest among the three methods, about 120-200 yuan per ton of water.

(14) According to Table 1, Example 1 of the invention as the best experimental effect, the lowest production cost, and the highest quality of lithium carbonate products produced from lithium sulfate leachate. The above ion concentration refers to the mass ratio of ion to lithium sulfate leachate.

(15) In Example 1, the concentration of lithium sulfate in the concentrated solution in 5) was changed to 15%, 18% and 20% as three groups of examples, and the final experimental effect was the same as that in Example 1.

(16) The term precision filtration refers to a filtration treatment process for removing fine suspended matters or colloidal particles from water that cannot be filtered by sand filtration. It is often used for water treatment as a pretreatment device for preparing ultrapure water.

(17) The embodiment of the invention further provides a system for preparing lithium carbonate from lithium ore. As shown in FIG. 1, the system for preparing lithium carbonate from lithium ore in this specific embodiment comprises a Li.sub.2SO.sub.4 leachate production system 6, a precision filtration device 1, an ion exchange device 2, a pretreatment device 3, an ultrafiltration membrane filtration device 4, a disk-tube reverse osmosis membrane filtration device 5, a lithium precipitation system 7 and a drying system 8 that are sequentially connected.

(18) Further, the pretreatment device 3 comprises a primary filtration device and a pH adjustment device. The precision filtration device 1 is a filtration device with filtering temperature being controlled at 50-70 C.

(19) Preferably, the precision filtration device 1 is capable of intercepting substances with diameter greater than 0.1 m; the ultrafiltration membrane filtration device 4 is capable of intercepting substances with molecular weight greater than 2000 and diameter of 0.005-0.05 m; and the disk-tube reverse osmosis membrane filtration device 5 is capable of intercepting substances with molecular weight of 50-150 and diameter of 0.0001-0.001 m.

(20) The Li.sub.2SO.sub.4 leachate production system 6 is mainly used to obtain Li.sub.2SO.sub.4 leachate after finely grinding lithium ore concentrate, roasting, adding sulfuric acid and CaCO.sub.3.

(21) The lithium precipitation system 7 is mainly used to obtain a liquid containing lithium carbonate solid by controlling the temperature of Li.sub.2SO.sub.4 concentrated solution produced by the disk-tube reverse osmosis membrane filtration device 5 at 85-95 C. and adding saturated Na.sub.2CO.sub.3 solution. The liquid containing lithium carbonate solid is subject to solid-liquid separation and dried by the drying system 8 to obtain a Li.sub.2CO.sub.3 finished product.

(22) Based on the system for preparing lithium carbonate from lithium ore in this specific embodiment, Li.sub.2SO.sub.4 leachate is filtered by a precision filtration device 1 for precision filtration, which showed a better filtration effect compared with the plate and frame filter in the prior art. The ion exchange resin in the ion exchange device 2 can remove Ca.sup.2+ and Mg.sup.2+ with simple process and better removal effect. Then, the primary filtration device and pH adjustment device as the pretreatment devices are used to control impurity concentration and pH of Li.sub.2SO.sub.4 leachate entering the membrane concentration and filtration system. Finally, the ultrafiltration membrane filter device 4 and disk-tube reverse osmosis membrane filtration device 5 replace the original evaporation concentration system, thus reducing the production energy consumption and improving the product quality.

(23) The system for preparing lithium carbonate from lithium ore in this embodiment requires the use of ion exchange resin in the ion exchange device, which can remove Ca.sup.2+ and Mg.sup.2+ more thoroughly compared with the prior art. Instead of the evaporation process, the membrane concentration filtration system can reduce energy consumption and save cost, and allow the produced water to be reused in the production system. The system can be widely applied to purification and concentration treatment in the lithium salt production industry by the sulfuric acid process, reveal low operation cost and simple control, and avoid secondary pollution to the environment.

(24) The relevant contents of the invention are as described above. Those skilled in the art will be able to implement the invention based on these descriptions. Based on the above contents of the invention, all other examples obtained by those skilled in the art without creative work shall fall within the protection scope of the invention.

(25) The above mentioned embodiments are only preferred embodiments of the invention and not used to limit the invention. Any modification, equivalent replacement and improvement made according to the spirit and rule of the invention can be incorporated in the protection scope of the invention.

(26) The relevant contents of the invention are as described above. Those skilled in the art are able to implement the invention based on these descriptions. The above contents of the invention can be obtained by those skilled in the art without making creative work.