阅读说明：本技术 一种氟化钙的制备方法 (Preparation method of calcium fluoride ) 是由 吕天宝 冯祥义 武文焕 冯怡利 王军堂 刘尧 马荣刚 卢实凯 于 2019-09-27 设计创作，主要内容包括：本发明涉及氟化钙方法,具体涉及一种采用石灰法、综合利用锂云母制备氟化钙的方法,本发明提供的氟化钙的制备方法,包括制备锂盐窑灰,后按稀碱液与锂盐窑灰的液固比,在稀碱液中加入锂盐窑灰,形成料浆Ⅰ,将料浆Ⅰ加热溶解,形成料浆Ⅱ,过滤,加入石灰乳,反应、过滤,得到滤饼,滤饼经过洗涤、烘干,得到氟化钙产品；本发明中氟化钙的制备方法,采用锂盐生产过程中的锂云母焙烧窑灰与稀碱液按比例混合,得到不饱和的氟化钠溶液,然后将石灰乳缓慢加入氟化钠溶液中,通过特定温度和反应时间,制得含量大于95％的氟化钙产品,其中在生产氟化钙过程中产生的滤液,可以重复循环使用,代替稀碱液溶解窑灰中的氟化钠,节约生产成本,降低劳动消耗。(The invention relates to a calcium fluoride method, in particular to a method for preparing calcium fluoride by comprehensively utilizing lepidolite by a lime method, which comprises the steps of preparing lithium salt kiln ash, adding the lithium salt kiln ash into dilute alkali liquor according to the liquid-solid ratio of the dilute alkali liquor to the lithium salt kiln ash to form slurry I, heating and dissolving the slurry I to form slurry II, filtering, adding lime cream, reacting and filtering to obtain a filter cake, washing and drying the filter cake to obtain a calcium fluoride product; according to the preparation method of calcium fluoride, lepidolite roasting kiln dust in a lithium salt production process is mixed with dilute alkali liquor in proportion to obtain an unsaturated sodium fluoride solution, then lime milk is slowly added into the sodium fluoride solution, and a calcium fluoride product with the content of more than 95% is prepared through specific temperature and reaction time, wherein filtrate generated in the calcium fluoride production process can be recycled, the dilute alkali liquor is replaced for dissolving sodium fluoride in the kiln dust, the production cost is saved, and the labor consumption is reduced.)

1. A preparation method of calcium fluoride is characterized in that: the preparation method comprises the following steps:

1) preparing lithium salt kiln dust:

adding 1 part of kiln dust and 0.3 part of sulfuric acid into a reaction kettle according to the weight part ratio, stirring for 50-100 minutes, and filtering through a filter screen with the mesh number of 300 to obtain the lithium fluoride salt-containing ash kiln dust for later use;

2) adding lithium salt kiln dust containing fluoride salt into dilute alkali liquor according to the liquid-solid ratio of the dilute alkali liquor to the lithium salt kiln dust, and mixing to form slurry I;

3) heating and stirring the slurry I until fluoride salt in the lithium salt kiln dust is completely dissolved to form slurry II;

4) filtering the slurry II to obtain an unsaturated sodium fluoride solution;

5) adding lime milk according to the concentration of sodium fluoride in an unsaturated sodium fluoride solution, firstly, adding the lime milk according to the ratio of sodium fluoride: adding lime milk into an unsaturated sodium fluoride solution at a CaO molar ratio of 2-3:1, reacting for 0.5-2 hours at 80-90 ℃, filtering again to obtain a filter cake and a filtrate, washing and drying the filter cake to obtain a calcium fluoride product with the purity content of more than 95.5%, and returning the filtrate for recycling.

2. The method for preparing calcium fluoride according to claim 1, wherein: the sulfuric acid in the step 1) is 98% concentrated sulfuric acid.

3. The method for preparing calcium fluoride according to claim 1, wherein: the dilute alkali solution in the step 2) is sodium hydroxide solution and Na₂The concentration of O is 10-50g/L, wherein the liquid-solid ratio of the dilute alkali liquor to the lithium salt kiln dust is 2-10: 1.

4. the method for preparing calcium fluoride according to claim 1, wherein: the heating and dissolving temperature in the step 3) is 30-90 ℃, and the stirring time is 0.5-3 hours.

5. The method for preparing calcium fluoride according to claim 1, wherein: the mass concentration of the sodium fluoride in the unsaturated sodium fluoride solution in the step 4) is 20-50 g/L.

6. The method for preparing calcium fluoride according to claim 1, wherein: the lime milk in the step 5) is an aqueous solution of calcium oxide, wherein CaO refers to effective CaO.

7. The method for preparing calcium fluoride according to claim 1, wherein: and (3) replacing the dilute alkali liquor in the step 2) with the recovered sodium hydroxide solution in the step 5), and returning the filtrate to the process for dissolving the sodium fluoride in the lithium salt kiln dust again.

8. The method for preparing calcium fluoride according to claim 1 or 2, wherein: the content of fluorine element in the lithium salt kiln dust in the step 1) is 18-22%.

Technical Field

The invention relates to a calcium fluoride method, in particular to a method for preparing calcium fluoride by comprehensively utilizing lepidolite by a lime method.

Background

The calcium fluoride has wide application range, and has wider and wider application prospect with the progress of science and technology. At present, the method is mainly used in three industries of metallurgy, chemical industry and building materials, and is secondly used in light industry, optics, carving and national defense industry. The fluorite has the characteristics of reducing the melting point of refractory substances, promoting the flow of furnace slag, well separating slag from metal, desulfurizing and dephosphorizing in the smelting process, enhancing the malleability and tensile strength of the metal and the like. Therefore, it is widely used as a fluxing agent in iron and steel smelting, iron alloy production, iron melting process and non-ferrous metal smelting. In the glass industry, fluorite is added as a fluxing agent and an opacifier, and can promote the melting of glass raw materials; in cement production, fluorite is added as a mineralizer. The fluorite can reduce the sintering temperature of furnace burden, reduce fuel consumption, enhance the liquid phase viscosity of clinker during sintering and promote the formation of tricalcium silicate; in the ceramic industry, fluorite is mainly used as an enamel, which can play a role in color promotion and fluxing in the production process of the enamel; fluorite is also used in the enamel industry and cast stone production. Another important use of fluorite is in the production of hydrofluoric acid. Hydrofluoric acid is produced by the reaction of acid grade fluorite (concentrate of fluorite) with sulfuric acid in a furnace or tank, and is divided into anhydrous hydrofluoric acid and aqueous hydrofluoric acid, both of which are colorless liquids that are volatile, have strong pungent odor and strong corrosivity. It is a key raw material for producing various organic and inorganic fluorides and fluorine elements.

However, the storage amount of fluorite ore in China is small, and the fluorite ore is listed as strategic resource by the nation to protect and prohibit exploitation, so that a new fluorine raw material route is inevitably developed. For many years, researchers have conducted extensive research into the preparation of calcium fluoride. The methods for producing calcium fluoride, which have been studied so far, are largely classified into those using industrial products as raw materials and those using industrial wastes and by-products as raw materials, from the viewpoint of raw materials for production. The preparation method of the industrial finished product is divided into a direct precipitation method, a micro-emulsion method, a hydrothermal method and other methods; the method comprises the steps of taking industrial waste and byproducts as raw materials, taking fluorine-containing waste acid of lithium hexafluorophosphate byproduct as a raw material, reacting with calcium chloride under certain conditions to prepare calcium fluoride, taking fluorine-containing bottom mud as a raw material, settling and acidifying, adding alkali liquor to remove silicon, finally calcining to obtain a calcium fluoride product, taking a phosphate fertilizer byproduct, namely fluosilicic acid as a raw material, ammoniating to obtain ammonium fluoride, and reacting with calcium hydroxide to obtain calcium fluoride.

With the rapid development of the lithium battery industry, the consumption of battery-grade lithium salt in China is greatly increased, the lithium salt is produced mainly by an ore method and a brine method, a mine method comprises two methods of spodumene and lepidolite, the storage capacity of the spodumene in China is little and mainly lepidolite ore, and the lepidolite ore contains about 2.5 percent of fluorine elements and even exceeds the fluorine content in phosphorite. During production, during the roasting process of the lepidolite, a large amount of fluorine is enriched in kiln dust, and the fluorine in the kiln dust can exceed 20 percent. Due to the special roasting process of the lepidolite, phase analysis of kiln dust shows that fluorine in the kiln dust mainly exists in a sodium fluoride form, and meanwhile, a small amount of sodium fluosilicate and calcium fluoride exist. The existence of fluorine is unfavorable for lithium carbonate production, kiln dust can cause the waste of a large amount of lithium if abandoning, if directly return the flow, can produce certain influence to lithium carbonate production. Therefore, the research on the process method which can eliminate the influence of fluorine on the production of lithium salt and can also utilize the fluorine in the lithium salt to prepare the calcium fluoride product has great significance for not only opening up a new raw material route in the fluorine chemical industry but also realizing the comprehensive utilization of waste residues.

Disclosure of Invention

The invention provides a preparation method of calcium fluoride, aiming at the problems that the existing preparation process of calcium fluoride is complex, the required raw material reserves are small and in short supply, three wastes are discharged in the production process of calcium fluoride, the required raw materials are more, the energy consumption is high, the production cost is increased, and the purity of the prepared calcium fluoride is low.

In order to solve the above problems, the present invention provides a preparation method of calcium fluoride, comprising:

1) preparing lithium salt kiln dust:

adding 1 part of kiln dust and 0.3 part of sulfuric acid into a reaction kettle according to the weight part ratio, stirring for 50-100 minutes, and filtering through a filter screen with the mesh number of 300 to obtain the lithium fluoride salt-containing ash kiln dust for later use;

2) adding lithium salt kiln dust containing fluoride salt into dilute alkali liquor according to the liquid-solid ratio of the dilute alkali liquor to the lithium salt kiln dust, and mixing to form slurry I;

3) heating and stirring the slurry I until fluoride salt in the lithium salt kiln dust is completely dissolved to form slurry II;

4) filtering the slurry II to obtain an unsaturated sodium fluoride solution;

5) adding lime milk according to the concentration of sodium fluoride in an unsaturated sodium fluoride solution, firstly, adding the lime milk according to the ratio of sodium fluoride: adding lime milk into an unsaturated sodium fluoride solution at a CaO molar ratio of 2-3:1, reacting for 0.5-2 hours at 80-90 ℃, filtering again to obtain a filter cake and a filtrate, and washing and drying the filter cake to obtain a calcium fluoride product with the purity content of more than 95.5%.

Further, the sulfuric acid in the step 1) is 98% concentrated sulfuric acid.

Further, the dilute alkali solution in the step 2) is sodium hydroxide solution, and Na is contained in the sodium hydroxide solution₂The concentration of O is 10-50g/L, wherein the liquid-solid ratio of the dilute alkali liquor to the lithium salt kiln dust is 2-10: 1, the dilute alkali solution contains Na₂O can effectively improve the purity of the calcium fluoride.

Further, the heating and dissolving temperature in the step 3) is 30-90 ℃, and the stirring time is 0.5-3 hours.

Further, the mass concentration of the sodium fluoride in the unsaturated sodium fluoride solution in the step 4) is 20-50 g/L.

Further, the lime milk in the step 5) is an aqueous solution of calcium oxide, and CaO of the lime milk refers to effective CaO.

Further, the filtrate obtained in the step 5) is the sodium hydroxide solution after being recovered, the dilute alkali solution obtained in the step 2) is replaced, and the filtrate is returned to the flow and is reused for dissolving the sodium fluoride in the lithium salt kiln dust, so that the production cost can be saved, and the labor consumption can be reduced.

Further, the content of fluorine element in the lithium salt kiln dust is 18-22%.

Further, the temperature and the stirring time of the slurry I both influence the recovery rate of fluorine, when the temperature is lower than 30 ℃ and the stirring time is less than 0.5, the recovery rate of fluorine is less than 40%, when the temperature is higher than 90 ℃ and the stirring time is less than 0.5 hour, the recovery rate of fluorine is less than 60%, and when the temperature reaches 90 ℃ and the stirring time is more than 3 hours, the recovery rate of fluorine can reach 85%.

Further, the temperature of the unsaturated sodium fluoride solution and the lime milk during reaction is 80-90 ℃, and the reaction time is 0.5-2 hours. The reaction time and temperature of the unsaturated sodium fluoride solution and the lime milk also influence the recovery rate of fluorine, when the temperature is lower than 80 ℃ and the stirring time is less than 0.5, the recovery rate of fluorine is less than 50%, when the temperature is higher than 80 ℃ and the stirring time is higher than 2 hours, the recovery rate of fluorine is less than 70%, and when the temperature reaches 90 ℃ and the stirring time is higher than 2 hours, the recovery rate of fluorine can reach 85%.

The invention has the beneficial effects that:

1. according to the preparation method of calcium fluoride, lepidolite roasting kiln dust in a lithium salt production process is mixed with dilute alkali liquor in proportion to obtain an unsaturated sodium fluoride solution, then lime milk is slowly added into the sodium fluoride solution, and a calcium fluoride product with the content of more than 95% is prepared through specific temperature and reaction time, wherein filtrate generated in the calcium fluoride production process can be recycled, the dilute alkali liquor is replaced for dissolving sodium fluoride in the kiln dust, the production cost is saved, and the labor consumption is reduced.

2. The preparation method of calcium fluoride not only effectively utilizes fluorine in calcined lepidolite kiln dust in lithium salt production to convert most of the fluorine into calcium fluoride products, but also has simple process and low energy consumption, and the filtrate after reaction can be recycled, thereby conforming to the national environmental protection policy.

3. The method is different from the traditional calcium fluoride preparation method, and breaks through the limitation of raw materials required by the existing calcium fluoride preparation. Compared with the existing calcium fluoride preparation technology, the raw materials are easy to obtain, the process is simple, and the prepared calcium fluoride product has higher quality. The process has the advantages of simple process, low energy consumption, no three-waste discharge, and great elimination of the influence of fluorine on the production of lithium salt.

4. The preparation method of calcium fluoride, which is disclosed by the invention, has a profound significance for protecting limited fluorite resources in China, fully utilizing fluorine resources in lithium carbonate production and bringing a profound significance to domestic fluorine chemical industry.

Detailed Description

For better understanding of the present invention, the technical solution of the present invention will be described in detail with specific examples, but the present invention is not limited thereto.