Method for recycling calcium sulfate in production of lithium carbonate from lepidolite

Abstract

The application provides a method for recycling calcium sulfate in lithium mica production of lithium carbonate, and belongs to the technical field of smelting.The lithium mica is calcined with the calcium sulfate clinker, the pressure filtration residue after the lithium ion is leached by water is put into an aqueous sulfamate solution and is stirred again, the calcium sulfate in the residue is reacted with the sulfamate and is dissolved, ion exchange is carried out through a sodium type ion exchange resin, backwashing and precipitation processes are carried out, the calcium sulfate is generated again, and the calcium sulfate is returned as a lithium mica auxiliary material, so that the recycling of the calcium sulfate is realized, and the treated filter residue is used as a mixed material and does not affect the performance of the prepared cement.The process can significantly improve the consumption amount of the lithium mica residue in the cement industry, saves the land resources occupied by the stacking or landfill of the lithium mica residue, reduces the environmental protection pressure, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of smelting, and particularly relates to a method for recycling calcium sulfate in production of lithium mica into lithium carbonate. BACKGROUND

[0002] In the process of producing lithium carbonate from lithium mica, lithium mica needs to be mixed with auxiliary materials, and then roasted at a high temperature of 950-1000 degrees, and then the roasted material is crushed to about 80 meshes, and then lithium ions are leached out by water, and then lithium carbonate is precipitated by adding sodium carbonate solution under certain pH conditions. In the production of lithium carbonate from lithium mica, the auxiliary materials used in the mixing of lithium mica are first potassium-sodium chloride (sodium chloride and potassium chloride), but due to the serious corrosion of chlorine ions on equipment, the production of lithium carbonate currently generally uses sulfates (potassium sulfate, sodium sulfate and calcium sulfate) instead of potassium-sodium chloride as auxiliary materials.

[0003] When calcium sulfate is used as an auxiliary material for producing lithium carbonate from lithium mica, a large amount of calcium sulfate (total proportion of 20%-25%) is added, so that a large amount of calcium sulfate is contained in the obtained lithium mica residue. At present, the treatment of lithium mica residue is mainly to prepare cement as a mixed material. Due to the large amount of calcium sulfate brought in by lithium mica residue, the sulfur trioxide content of the prepared cement is too high, which causes the setting time of the cement mixed with a small amount of lithium mica residue to be significantly prolonged, and the performance of the cement is reduced to different degrees, and the higher the mixing amount, the more obvious the reduction. SUMMARY

[0004] In view of the problems in the background art, the purpose of the present application is to provide a method for recycling calcium sulfate in the production of lithium carbonate from lithium mica: the lithium mica and the roasted material after roasting with calcium sulfate, and the pressure filtration residue after leaching out lithium ions by water, are placed in an aqueous sulfamate solution and stirred again to react, so that the calcium sulfate in the residue reacts with the sulfamate to dissolve, and then ion exchange, backwashing and precipitation procedures are carried out by using sodium-type ion exchange resin, and then the calcium sulfate is converted to return as an auxiliary material for lithium mica, so that the recycling of calcium sulfate is realized, and the treated filtration residue as a mixed material does not affect the performance of the prepared cement.

[0005] The present application provides a method for recycling calcium sulfate in the production of lithium carbonate from lithium mica, comprising the following steps:

[0006] Step one: calcium sulfate is used as an auxiliary material to mix and roast with lithium mica to obtain a roasted material, and the roasted material is leached out of lithium ions by water to obtain lithium mica pressure filtration residue;

[0007] Step two: the obtained lithium mica pressure filtration residue is placed in an aqueous sulfamate solution and stirred to react, and then filtered to obtain filtrate A and residue, and solid sodium sulfate is separated from filtrate B by freezing crystallization of filtrate A;

[0008] Step three: ion exchange of the filtrate B with sodium type ion exchange resin to obtain filtrate C, which is concentrated and heated to obtain sulfamate aqueous solution and returned to step two for reuse;

[0009] Step four: backwashing of the ion exchanged resin with sodium chloride solution to obtain backwashing liquid D, which is reacted with solid sodium sulfate to obtain precipitate E and filtrate F, precipitate E is calcium sulfate, which is dried and returned to step one for reuse as auxiliary material, and filtrate F is sodium chloride solution, which is adjusted in concentration and returned to step four for reuse as resin backwashing liquid.

[0010] As preferred, the sulfamate in step two is sodium sulfamate, which is fully dissolved in hot water at 60-90°C to prepare an aqueous solution with a concentration of 10%-20%.

[0011] As preferred, the addition amount ratio of the lithium mica filter cake to the sulfamate aqueous solution in step two is 1:(2.01-2.3) according to the molar ratio of sulfate in the lithium mica filter cake to sulfamate in the sulfamate aqueous solution, and more preferably 1:(2.05-2.2).

[0012] As preferred, the stirring reaction in step two is carried out at room temperature for 10-30 min.

[0013] As preferred, the concentrated and heated filtrate C in step three is concentrated to a concentration of 10%-30% at a heating temperature of 60-90°C.

[0014] As preferred, the concentration of the sodium chloride solution in step four is 5%-10%.

[0015] As preferred, the addition amount ratio of the backwashing liquid D to the solid sodium sulfate in step four is 1:1 according to the molar ratio of Ca 2+ in the backwashing liquid D to SO4 2- in the solid sodium sulfate.

[0016] The process reaction process of the present application is as follows:

[0017] 1) 2NaNH2O3S + CaSO4 = Ca(NH2O3S)2 + Na2SO4

[0018] 2) Ca(NH2O3S)2 + 2NaCl = 2NaNH2O3S + CaCl2

[0019] 3) CaCl2 + Na2SO4 = CaSO4 + 2NaCl

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] The application provides a method for recycling calcium sulfate in lithium mica production of lithium carbonate, which has simple technical process, all process products can be reused, greatly reduces the process cost, and can greatly reduce the calcium sulfate content in lithium mica slag, so that the calcium sulfate content in the treated lithium mica slag fully meets the requirements of the cement industry. The process can significantly improve the consumption of lithium mica slag in the cement industry, save the land resources occupied by the stacking or landfill of lithium mica slag, reduce the environmental protection pressure, and has a wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The process flow chart of the application is shown. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the application clearer, the technical scheme of the application will be clearly and completely described below in combination with examples. If the specific conditions are not indicated in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments are not indicated by the manufacturer, they are all conventional products that can be purchased in the market.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application only for the purpose of describing specific embodiments and is not intended to limit the application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0025] Example 1

[0026] 1. 1000g of lithium mica slag (the measured sulfate content in the slag is 10.5%, which is equivalent to 1.09mol) is weighed; 279.52g of sodium sulfamic acid with a content of 95% (2.23mol) is weighed, and dissolved with 1400g of hot water (75℃) for standby.

[0027] 2. 1000g of lithium mica slag is added to the sodium sulfamic acid aqueous solution, stirred at room temperature for 30 minutes, filtered to obtain filtrate A and filter residue. The filter residue is dried, and the sulfate content is detected.

[0028] 3. The filtrate A is frozen, and the solid sodium sulfate and filtrate B are obtained by filtration; the filtrate B is passed through a sodium type ion exchange resin to obtain filtrate C, and the filtrate C is concentrated to a concentration of 15%-30% for recycling leaching of lithium mica slag.

[0029] 4. The used sodium type ion exchange resin is backwashed with 5% sodium chloride solution to obtain backwash liquid D; solid sodium sulfate is added to the backwash liquid D, stirred, and filtered after the reaction is completed to obtain precipitate E and filtrate F. The precipitate E is washed and dried to obtain calcium sulfate product, which can be returned to the previous process as an auxiliary material for lepidolite batching; the filtrate F is adjusted to a concentration of 5% and can be returned for washing the sodium type ion exchange resin.

[0030] Example 2

[0031] 1. 1000g of lepidolite residue (the measured sulfate content of the residue is 9.5%, which is equivalent to 0.99 mol) is weighed; 267.93g of 95% sodium sulfamate (2.13 mol) is weighed and dissolved in 1410g of hot water (75°C) for use.

[0032] 2. The 1000g of lepidolite residue is added to the sodium sulfamate aqueous solution, stirred at room temperature for 30 minutes, filtered to obtain filtrate A and filter residue. The filter residue is dried and the sulfate content is detected.

[0033] 3. The filtrate A is frozen and filtered to obtain solid sodium sulfate and filtrate B; the filtrate B is passed through a sodium type ion exchange resin to obtain filtrate C, and the filtrate C is concentrated to a concentration of 15%-30% for cyclic leaching of lepidolite residue.

[0034] 4. The used sodium type ion exchange resin is backwashed with 5% sodium chloride solution to obtain backwash liquid D; solid sodium sulfate is added to the backwash liquid D, stirred, and filtered after the reaction is completed to obtain precipitate E and filtrate F. The precipitate E is washed and dried to obtain calcium sulfate product, which can be returned to the previous process as an auxiliary material for lepidolite batching; the filtrate F is adjusted to a concentration of 5% and can be returned for washing the sodium type ion exchange resin.

[0035] Examples 3-10

[0036] The same as example 1, 1000g of lepidolite residue from different sources is weighed, and according to the amount of sulfate contained, the corresponding proportion of sodium sulfamate is added. (The amount of sodium sulfamate is shown in Table 1)

[0037] The residual amount of sulfate in the lepidolite residue after washing in the above examples is detected, and the results are as follows.

[0038] Table 1

[0039]

[0040] As can be seen from the test results of Examples 1-10, the lithium mica slag initially contains a high content of sulfur trioxide, the lowest of which is 6.8%, far exceeding the requirement of the cement standard that the content of sulfur trioxide is less than 3.5%. After the re-washing according to the present application, the content of sulfur trioxide in the slag is greatly reduced to less than 3.5%; even if a larger proportion is used in the mixed cement, the sulfur trioxide index and the use performance of the obtained cement product will not be affected.

[0041] The above described embodiments only express several preferred embodiments of the present application, which are described in a more specific and detailed manner, but are not used to limit the present application. It should be noted that for those skilled in the art, the present application can also have various changes and modifications, and any modification, equivalent replacement, improvement, etc. made within the concept and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for recycling calcium sulfate in the production of lithium carbonate from lepidolite, characterized in that, Includes the following steps: Step 1: Using calcium sulfate as an auxiliary material, calcining it with lepidolite to obtain clinker, and then leaching lithium ions from the clinker with water to obtain lepidolite filter residue. Step 2: Place the obtained lithium mica filter residue into an aqueous solution of aminosulfonate and stir to react. Then filter to obtain filtrate A and filter residue. Freeze and crystallize filtrate A to separate solid sodium sulfate and filtrate B. Step 3: Ion exchange filtrate B with sodium-type ion exchange resin to obtain filtrate C. Concentrate filtrate C and heat it to obtain an aminosulfonate aqueous solution, which is then returned to Step 2 for reuse. Step 4: Backwash the ion-exchange resin with sodium chloride solution to obtain backwash solution D. React backwash solution D with solid sodium sulfate to generate precipitate E and filtrate F. Precipitate E is calcium sulfate, which is dried and returned to step 1 as an auxiliary material for reuse. Filtrate F is sodium chloride solution, which is adjusted in concentration and returned to step 4 as resin backwash solution for reuse.

2. The method for recycling calcium sulfate in the production of lithium carbonate from lepidolite according to claim 1, characterized in that, The aminosulfonate mentioned in step two is sodium aminosulfonate, which is fully dissolved in hot water at 60-90℃ to prepare an aqueous solution with a concentration of 10%-20%.

3. The method for recycling calcium sulfate in the production of lithium carbonate from lepidolite according to claim 1, characterized in that, Step 2: The ratio of the amount of lithium mica filter residue to the aminosulfonate aqueous solution is 1:(2.01-2.3) based on the molar ratio of sulfate in the lithium mica filter residue to aminosulfonate in the aminosulfonate aqueous solution.

4. The method for recycling calcium sulfate in the production of lithium carbonate from lepidolite according to claim 1, characterized in that, The stirring reaction described in step two is carried out at room temperature for 10-30 minutes.

5. The method for recycling calcium sulfate in the production of lithium carbonate from lepidolite according to claim 1, characterized in that, Step 3: Concentrate filtrate C by heating to a concentration of 10%-30% at a temperature of 60-90℃.

6. The method for recycling calcium sulfate in the production of lithium carbonate from lepidolite according to claim 1, characterized in that, The sodium chloride solution concentration in step four is 5%-10%.

7. The method for recycling calcium sulfate in the production of lithium carbonate from lepidolite according to claim 1, characterized in that, Step 4: The ratio of backwash solution D to solid sodium sulfate added is based on the Ca content in backwash solution D. 2+ SO4 in solid sodium sulfate 2- Molar ratio 1:1.

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