阅读说明：本技术 一种以氟硅酸为原料制备低硅氟化氢铵的生产工艺 (Production process for preparing low-silicon ammonium bifluoride by taking fluosilicic acid as raw material ) 是由 宁延生 林玉果 朱建平 郭西凤 张福 刘兰波 杨玉田 杨贤 王阔 于 2019-12-31 设计创作，主要内容包括：本发明公开了一种以氟硅酸为原料制备低硅氟化氢铵的生产工艺,其是利用氟硅酸溶液为原料,通过氨化脱硅,过滤后得到氟化铵初级溶液；然后在氟化铵初级溶液中加入脱硅剂进行二次脱硅,然后过滤、浓缩、结晶,得到氟化氢铵产品。本发明的氟化氢铵产品中氟硅酸根含量低于0.2％,极大提高了副产氟硅酸的应用价值。(The invention discloses a production process for preparing low-silicon ammonium bifluoride by taking fluosilicic acid as a raw material, which is characterized in that fluosilicic acid solution is taken as a raw material, ammoniation desilication is carried out, and ammonium fluoride primary solution is obtained after filtration; and then adding a desiliconization agent into the primary ammonium fluoride solution for secondary desiliconization, and then filtering, concentrating and crystallizing to obtain an ammonium bifluoride product. The content of fluosilicic acid radicals in the ammonium bifluoride product is lower than 0.2 percent, and the application value of the by-product fluosilicic acid is greatly improved.)

1. A production process for preparing low-silicon ammonium bifluoride by taking fluosilicic acid as a raw material is characterized by comprising the following steps:

firstly, taking fluorosilicic acid solution as a raw material, carrying out ammoniation desiliconization, and filtering to obtain ammonium fluoride primary solution;

secondly, adding a desiliconization agent into the primary ammonium fluoride solution for secondary desiliconization, and then filtering, concentrating and crystallizing to obtain an ammonium bifluoride product.

2. The process for preparing low-silicon ammonium bifluoride from fluosilicic acid as a raw material according to claim 1, wherein the fluosilicic acid solution is an industrial byproduct fluosilicic acid solution, which is a by-product containing fluosilicic acid in the process of producing anhydrous hydrogen fluoride or phosphate fertilizer, and a by-product of fluosilicic acid solution produced in other industries.

3. The production process for preparing low-silicon ammonium bifluoride from fluosilicic acid as a raw material according to claim 1, wherein the ammoniation desilication is carried out by charging ammonia gas or ammonia water into a fluosilicic acid solution.

4. The process for preparing low-silicon ammonium bifluoride from fluosilicic acid as a raw material according to claim 1, wherein the desiliconizing agent used in the secondary desiliconization is a fluoride salt.

5. The process for preparing low-silicon ammonium bifluoride from fluosilicic acid as a raw material according to claim 4, wherein the fluoride salt is at least one of potassium fluoride and sodium fluoride.

6. A process for preparing low-silicon ammonium bifluoride from fluorosilicic acid as raw material as claimed in claim 5, wherein the amount of said desiliconizing agent added is 1.0-2.0 times of the theoretical amount of fluorosilicate generated from fluorosilicate in the primary solution of ammonium fluoride.

7. The process for preparing low-silicon ammonium bifluoride from fluosilicic acid as a raw material according to claim 6, wherein the reaction temperature of the secondary desiliconization treatment is 25-65 ℃, and the stirring time is 30-120 min.

8. The process for preparing low-silicon ammonium bifluoride from fluosilicic acid as a raw material according to claim 1, wherein the content of fluosilicic acid radicals in the ammonium bifluoride product is less than 0.2%.

Technical Field

The invention relates to the technical field of ammonium bifluoride production, in particular to a production process for preparing low-silicon ammonium bifluoride by using fluosilicic acid as a raw material.

Background

The ammonium bifluoride is white or colorless transparent orthorhombic crystal, the product is flaky, slightly sour, the relative density is 1.52, the melting point is 125.6 ℃, and the boiling point is 240 ℃. It has wide application prospect, including the following inventions:

(1) the composite material is used as a glass etching agent, a disinfectant, an antiseptic, a solvent of metal beryllium, a surface treatment agent of a silicon steel plate, and is also used for manufacturing ceramics and magnesium alloy. Can be used as chemical agent, glass etchant (often used together with hydrofluoric acid), disinfectant and antiseptic for fermentation industry, solvent for preparing metallic beryllium from beryllium oxide, and surface treating agent for silicon steel plate. It is also used for cleaning and descaling ceramic and magnesium alloy, boiler water supply system and steam generation system, and acidifying treatment of oil field sandstone. Also as alkylation, isomerization catalyst components;

(2) it is used for acidifying treatment in oil field and preparing magnesium and magnesium alloy. It can be used as the delustering, frosting and etching agent of glass, as the protecting agent of wood and the brightening agent of aluminum, as the rust remover in textile industry, and also as the analyzing agent in electroplating and electronic industry. Used as analytical reagents and as bacterial inhibitors.

(3) Can corrode glass and is corrosive to skin. Can be used as chemical reagent, glass etching agent (used together with hydrofluoric acid), disinfectant and antiseptic in fermentation industry, solvent for preparing beryllium metal from beryllium oxide, surface treating agent for silicon steel plate, cleaning and descaling for manufacturing ceramics and magnesium alloy, boiler water supply system and steam generation system, acid treatment for oil field sandstone, and alkylation and isomerization catalyst component. It is used for beryllium smelting, welding electrode making, cast steel, wood preservative, etc.

(4) Used as a sequestering agent for ferric ions.

A great amount of fluorosilicic acid solutions with different concentrations are produced in the production process of anhydrous hydrogen fluoride and phosphate fertilizer. In order to reduce the production cost, many enterprises produce ammonium bifluoride by using the by-product fluosilicic acid as a raw material. And (3) treating the fluorosilicic acid solution by using industrial ammonia water to remove silicon dioxide, and concentrating, deaminating, crystallizing and drying the obtained ammonium fluoride solution to obtain the ammonium bifluoride. By adopting the process method, first-class products and qualified products with the fluosilicic acid root content of 1.5 percent and 3.0 percent can be prepared. But it has been very difficult to prepare a superior product having a fluosilicic acid root content of 0.5%. And the content of fluosilicic acid radical in ammonium bifluoride used for producing electronic grade nitrogen trifluoride is required to be less than 0.2 percent. Ammonium bifluoride produced by using hydrofluoric acid as a raw material is usually adopted, so that the production cost is greatly increased.

The preparation process of ammonium bifluoride mostly uses hydrofluoric acid as basic raw material, and ammonia gas is introduced for neutralization to prepare the ammonium bifluoride. In recent years, in order to reduce the production cost, the preparation method turns to the utilization of anhydrous hydrogen fluoride or hydrofluosilicic acid which is a byproduct in the phosphate fertilizer production process as a raw material, and the specific process comprises the steps of reacting a hydrofluosilicic acid solution with industrial ammonia water or gaseous ammonia to generate a silicon dioxide and ammonium fluoride solution, and filtering to remove the silicon dioxide to obtain the ammonium fluoride solution. Concentrating the ammonium fluoride solution after silica removal, adding anhydrous hydrogen fluoride or hydrofluoric acid into the concentrated solution, and cooling, crystallizing and separating to obtain an ammonium bifluoride product. The reaction process is as follows:

H₂SiF₆+6NH₃2H₂O＝6NH₄F+SiO₂(1)

the following problems exist in the production of ammonium bifluoride products by using the by-product fluosilicic acid: because the fluosilicic acid ammonification reaction (1) is a reversible reaction, the reaction is difficult to be carried out completely, and even under the condition of excessive ammonia, part of ammonium fluosilicate still remains in the reaction liquid. After the precipitated silica is removed by filtration, a small amount of the filtered silica is inevitably present. The part of silicon dioxide fine particles are brought into a concentration system along with the ammonium bifluoride solution, concentration is a process of high-temperature evaporation and continuous ammonia overflow, and silicon dioxide and ammonium bifluoride are easy to dissolve and react to generate ammonium fluosilicate. The ammonium fluosilicate is cooled, crystallized and separated along with the concentrated solution, and part of the ammonium fluosilicate is brought into an ammonium bifluoride product, so that the quality of the final product is influenced. The content of fluorine silicate in the qualified products of the national standard of ammonium bifluoride reaches up to 3 percent. If the content of the fluosilicate in the product needs to be further reduced, the most effective method is to increase the amount of the ammonia water added in the reaction (1).

The excessive use of ammonia water in the reaction (1) has the disadvantages that on one hand, the field ammonia smell is very large when the precipitated silica is separated by a filter press, so that not only is the environment polluted, but also the loss of ammonia is caused; on the other hand, the excess ammonia must be distilled off and recovered during the concentration of the ammonium fluoride solution, thereby increasing the load on the subsequent ammonia recovery process. This is very disadvantageous for the industrial production of the process.

In order to solve the problems, the document mentions that a certain amount of solid KOH is added into a silicon removal tank to refine and remove silicon by ammonolysis of fluosilicic acid, the solution is filtered after full reaction, the filtrate is refined ammonium fluoride solution, a filter cake is washed and dried to obtain a potassium fluosilicate finished product, the pH value of the reaction end point is about 7-8, and the temperature is controlled to be about 90 ℃ after the reaction is finished. When the method is used for desiliconization, the added potassium hydroxide has more amount and good effect, but the potassium hydroxide is used as strong alkali, so that fluosilicic acid radical ions are easily decomposed and react with precipitated silicon dioxide to form potassium water glass. The effect of silicon removal is limited. In patent No. CN101898769A, "a method for producing high-purity ammonium bifluoride" mentioned that anhydrous hydrogen fluoride is introduced into ammonium fluoride reaction liquid to prepare high-purity ammonium bifluoride, the raw material ammonium fluoride is prepared by aminolysis of fluosilicic acid which is a byproduct in phosphate fertilizer industry. However, the patent does not mention how to desiliconize the ammonium fluoride raw material, and the content of fluosilicic acid radical in the target product of the patent is 0.6%, and the content of fluosilicic acid radical in the example is 0.3% at the minimum, which can not meet the requirement of ammonium bifluoride reagent grade products.

Therefore, how to produce high-purity ammonium bifluoride by using the byproduct fluosilicic acid as a raw material is a technical problem to be solved urgently in the industry.

Disclosure of Invention

Based on the above, the invention aims to provide a production process for preparing low-silicon ammonium bifluoride by using by-product fluosilicic acid as a raw material. The content of fluosilicic acid radicals in the ammonium bifluoride product prepared by the method is lower than 0.2 percent, hydrofluoric acid does not need to be added, the production cost is reduced, and the feasibility of industrial production is high.

In order to achieve the purpose, the invention provides the following scheme:

a production process for preparing low-silicon ammonium bifluoride by taking fluosilicic acid as a raw material comprises the following steps:

firstly, taking fluorosilicic acid solution as a raw material, carrying out ammoniation desiliconization, and filtering to obtain ammonium fluoride primary solution;

secondly, adding a desiliconization agent into the primary ammonium fluoride solution for secondary desiliconization, and then filtering, concentrating and crystallizing to obtain an ammonium bifluoride product.

Preferably, the fluorosilicic acid solution is an industrial byproduct fluorosilicic acid solution, which is a byproduct containing fluorosilicic acid in the process of producing anhydrous hydrogen fluoride or phosphate fertilizer, and is a byproduct of fluorosilicic acid solution produced in other industries.

Preferably, the ammoniation desiliconization is carried out by charging ammonia gas or ammonia water into the fluorosilicic acid solution.

Further preferably, the desiliconization agent used in the secondary desiliconization is a fluoride salt. The fluoride salt is at least one of potassium fluoride and sodium fluoride.

Specifically, in some embodiments, the desiliconization agent is added in an amount of 1.0 to 2.0 times the theoretical amount of fluorosilicate formation from fluorosilicate in the ammonium fluoride primary solution.

Specifically, the reaction temperature of the secondary desiliconization treatment is 25-65 ℃, and the stirring time is 30-120 min.

The content of fluosilicic acid radicals in the ammonium bifluoride product is lower than 0.2 percent.

The reaction mechanism of the present invention is as follows:

in the invention, when the reaction (1) is carried out, the ammonia water is added into the precipitated silica slurry in a theoretical amount or a slight excess amount, and after the reaction is finished, the ammonium fluoride can be directly filtered without cooling the precipitated silica slurry. Obviously, this still fails to qualify the fluorosilicate content of the ammonium acid fluoride product. The method adopts a mode of adding a silicon removing agent to deeply remove silicon from the ammonium fluoride solution, and the selected silicon removing agent is soluble fluoride, such as potassium fluoride, sodium fluoride and the like.

Soluble fluorides are added into the ammonium fluoride solution according to the content of the fluosilicate in a calculated amount, and the soluble fluorides are subjected to precipitation reaction with the fluosilicate to form corresponding fluosilicate to be separated out from the ammonium fluoride solution. The reaction formula is as follows:

(NH₄)₂SiF₆+2MF＝NH₄F+M₂SiF₆(2)

after the silicon removing agent is added into the ammonium fluoride solution, the mixture is stirred to complete the reaction (2). Then, ammonium fluoride solution with low fluorosilicate content is obtained through precise filtration and separation, and the fluorosilicate content of the ammonium hydrogen fluoride product obtained through subsequent process treatment can be reduced to within 0.2 percent of the index. The insoluble fluosilicate obtained after filtration can be used as a raw material for producing corresponding fluoride.

Compared with the prior art, the invention discloses the following technical effects: the method does not need to add excessive ammonia water in the reaction process, and avoids the escape of the excessive ammonia water in the separation process. Not only protects the environment, but also reduces the loss of ammonia, can ensure that the content of fluosilicate in the ammonium hydrogen fluoride product produced by taking fluosilicic acid as a raw material reaches the standard requirements of various levels, and particularly can meet the index requirements of fluosilicic acid radicals in the reagent-level ammonium hydrogen fluoride standard. The product can be applied to producing electronic-grade nitrogen trifluoride, obviously improves the production environment in the ammonolysis process and reduces the loss of ammonia. The invention also obviously increases the economic benefit of the product and has good popularization value.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to specific embodiments, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The invention aims to provide a production process for preparing low-silicon ammonium bifluoride by using a byproduct fluosilicic acid as a raw material.

The present invention will be described in further detail with reference to specific embodiments in order to make the above objects, features and advantages more apparent and understandable.