Comprehensive utilization method of fluosilicic acid containing hydrogen fluoride

Abstract

The invention relates to a comprehensive utilization method of fluosilicic acid containing hydrogen fluoride, which comprises the following steps: 1) reacting a stock solution containing fluosilicic acid with a potassium fluoride raw material, and carrying out solid-liquid separation to obtain potassium fluosilicate and a hydrofluoric acid solution; 2) reacting potassium fluosilicate with a sodium hydroxide raw material, and carrying out solid-liquid separation to obtain a mixture of a potassium fluoride solution, sodium fluoride and silicon dioxide; and returning the potassium fluoride solution to the step 1) to be recycled as a potassium fluoride raw material. According to the scheme, hydrofluoric acid is prepared from fluosilicic acid containing hydrogen fluoride, sodium fluoride and water glass products are produced at the same time, no other byproduct waste is produced, and the raw material utilization rate is high. And meanwhile, the method has the advantages of low raw material cost, low equipment cost and low energy consumption cost, can generate remarkable economic benefits, and is suitable for popularization and application.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and particularly relates to a comprehensive utilization method of fluosilicic acid containing hydrogen fluoride. Background Art

[0002] In the fluorine chemical and phosphorus chemical industries, fluorosilicic acid containing hydrogen fluoride is produced as a by-product, such as the fluorosilicic acid produced by Jinshi Resources in Inner Mongolia, which contains 10-15% hydrogen fluoride and 30-35% fluorosilicic acid. Some of the processes for preparing hydrogen fluoride from fluorosilicic acid disclosed in the prior art have high costs and poor economic benefits. Patent 201710216329.5 discloses a cyclic production process for preparing hydrogen fluoride from fluorosilicic acid. It does not actually consume alkaline earth metal fluorides or alkali metal fluorides. The fluorides can be recycled and only fluorosilicic acid raw materials and water are consumed. Therefore, the raw material cost of this process is low. However, this process requires high-temperature heating of the fluorosilicate solid, which consumes a large amount of heat, has high energy consumption costs, and also limits its economic benefits. Summary of the Invention

[0003] In response to the above technical problems, the present invention provides a comprehensive utilization method of hydrofluorosilicic acid containing hydrogen fluoride, which has low raw material and energy consumption costs and can produce significant economic benefits. The specific scheme is: A comprehensive utilization method of fluosilicic acid comprises the following steps: 1) reacting a stock solution containing fluorosilicic acid with a potassium fluoride raw material, and obtaining potassium fluorosilicate and hydrofluoric acid solution after solid-liquid separation; 2) Potassium fluorosilicate reacts with sodium hydroxide raw material, and after solid-liquid separation, a mixture of potassium fluoride solution, sodium fluoride and silicon dioxide is obtained; the potassium fluoride solution is returned to step 1) and recycled as potassium fluoride raw material.

[0004] Wherein, step 1) carries out the following reaction: H2SiF6+2KF=K2SiF6↓+2HF Step 2) Carry out the following reaction: K2SiF6+4NaOH=2KF+4NaF↓+SiO2↓+2H2O Potassium fluoride is for recycling, and its main raw materials are fluorosilicic acid and sodium hydroxide, and output is low-concentration hydrofluoric acid and sodium fluoride. This scheme selects potassium fluoride as raw material, and the potassium fluorosilicate generated in the first step is substantially insoluble in water and is easily separated from hydrofluoric acid. The potassium fluoride generated in the second step is soluble in water, and sodium fluoride and silicon dioxide are insoluble in water, and are also easy to isolate potassium fluoride solution, and technological operation is simple. In this scheme, the reaction of fluorosilicic acid and potassium fluoride can be carried out in a stirred tank, and the separation of potassium fluorosilicate and the separation of sodium fluoride and silicon dioxide can all be filtered using a plate and frame filter press, and the alkali-soluble nature of potassium fluorosilicate can be carried out in a common reactor, so equipment cost is low.

[0005] Furthermore, the mixture in step 2) is subjected to coarse separation by gravity separation to obtain crude sodium fluoride and silicon dioxide, and the crude sodium fluoride is subjected to alkali washing to remove silicon to obtain sodium fluoride.

[0006] Furthermore, the washing liquid produced by alkali washing and the silicon dioxide separated by gravity separation are used to make water glass.

[0007] Furthermore, the potassium fluoride raw material is a 40% potassium fluoride solution. The concentration of the potassium fluoride solution affects the concentration of the produced hydrofluoric acid.

[0008] Furthermore, the sodium hydroxide raw material is a sodium hydroxide solution with a concentration of 30wt%. The concentration of the sodium hydroxide solution affects the concentration of the potassium fluoride solution after alkali dissolution separation.

[0009] Furthermore, in step 2), the potassium fluoride solution is first concentrated and then returned to step 1) for recycling as potassium fluoride raw material.

[0010] In the above scheme, when the hydrogen fluoride content in the fluorosilicic acid stock solution is 10%, the resulting hydrofluoric acid concentration is approximately 18%, which still falls short of the 30% required for industrial-grade hydrofluoric acid. Furthermore, the production of high-concentration hydrofluoric acid from low-concentration hydrofluoric acid requires distillation. Due to the highly corrosive and toxic nature of hydrogen fluoride, the distillation equipment must exhibit very high corrosion resistance and sealing properties. Therefore, due to equipment limitations, low-concentration hydrofluoric acid can only be sold as a raw material for the production of high-concentration hydrofluoric acid.

[0011] To address these technical issues, we proposed an improved solution based on the original proposal, aiming to produce high-concentration hydrofluoric acid without increasing equipment costs. Specifically, in step 2), the potassium fluoride solution is first concentrated, then diluted with the hydrofluoric acid solution produced in step 1), and then returned to step 1 for recycling.

[0012] After the potassium fluoride solution is concentrated, it is diluted to a suitable concentration with the low-concentration hydrofluoric acid produced in step 1), and then reacted with the fluosilicic acid solution to prepare hydrofluoric acid, which can increase the concentration of the hydrofluoric acid to 30%.

[0013] In addition, in the solution of the present invention, since sodium fluoride is slightly soluble in water, a small amount of sodium fluoride will enter the solution when the potassium fluoride solution is filtered and separated in step 2), and eventually enter the hydrofluoric acid through recycling, resulting in a decrease in the sodium fluoride yield. This loss will result in a decrease in the sodium fluoride yield of approximately 10%.

[0014] Although some dissolved sodium fluoride crystallizes and forms a precipitate during the concentration stage, direct filtration of this precipitate requires additional steps, and the small amount of precipitate makes filtration difficult. With this improved solution, the total amount of sodium fluoride gradually accumulates as the hydrofluoric acid concentration increases. When potassium fluoride reacts with fluorosilicic acid, the accumulated sodium fluoride exceeds its solubility, forming a precipitate. This is ultimately separated during filtration of the potassium fluorosilicate in step 1) and recovered in the alkaline hydrolysis step. Therefore, this solution can also increase the yield of sodium fluoride.

[0015] Specifically, in step 2), the potassium fluoride solution is concentrated to a concentration of 45 wt% or higher and then diluted with the hydrofluoric acid solution produced in step 1) to a concentration of 30-40 wt%. This increases the hydrofluoric acid concentration to 30%, meeting industrial-grade hydrofluoric acid requirements, and improves the sodium fluoride yield by 5%.

[0016] Furthermore, in step 1), the potassium fluoride raw material is a potassium fluoride solution that has been recycled more than once. By using the recycled potassium fluoride solution as the raw material to react with fluorosilicic acid, the sodium fluoride carried over from the potassium fluoride solution will be incorporated into the produced hydrofluoric acid. This hydrofluoric acid can then be used to dilute the potassium fluoride solution after alkaline dissolution and concentration in the next step, thereby achieving cumulative recovery of sodium fluoride from the hydrofluoric acid and improving the yield of sodium fluoride.

[0017] The present invention utilizes hydrofluoric acid containing hydrofluoric acid to produce hydrofluoric acid, simultaneously producing sodium fluoride and water glass products, without any other by-product waste, and achieving high raw material utilization. Furthermore, the invention has the advantages of low raw material costs, equipment costs, and energy consumption costs, can generate significant economic benefits, and is suitable for widespread application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0019] The present invention is described below in detail with reference to specific embodiments of the present invention. The description herein is intended only to explain the present invention and is not intended to limit the present invention. Based on the embodiments of the present invention, any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art without creative work in all other embodiments obtained by them should be included within the scope of protection of the present invention.

[0020] according to Figure 1 The process flow chart shown is for treating the fluosilicic acid containing about 10-15% hydrogen fluoride produced as a by-product of Jinshi Resources in Inner Mongolia: The first step is to use caustic soda to alkaline hydrolyze potassium fluorosilicate to generate potassium fluoride, silicon dioxide and sodium fluoride, and filter to obtain potassium fluoride solution: K2SiF6+4NaOH=2KF+4NaF+SiO2+2H2O The second step is to react potassium fluoride solution with HF-containing fluorosilicic acid to generate potassium fluorosilicate and hydrofluoric acid, which are then filtered to obtain a potassium fluorosilicate and hydrofluoric acid solution (acidity 17-20%): H2SiF6+2KF=K2SiF6+2HF Step 3: The sodium fluoride and silicon dioxide mixture obtained in the first step is separated from most of the silicon dioxide by a hydrocyclone. The remaining small amount of silicon dioxide in the sodium fluoride is dissolved with hot caustic soda solution. The sodium fluoride is filtered and washed to obtain qualified sodium fluoride. The by-product, dilute low modulus water glass, can be recycled to a certain concentration, and then the modulus can be increased and sold as a commodity. SiO2+2NaOH=Na2SiO3+H2O All reactions in the project are divided into three steps. Now add the two chemical reaction equations in the first and second steps above: K2SiF6+4NaOH+H2SiF6+2KF=2KF+K2SiF6+4NaF+2HF+SiO2+2H2O Eliminating the same values ​​on both sides of the equal sign, we can obtain the following formula: H2SiF6+4NaOH=2HF+4NaF+SiO2+2H2O The above equation represents the raw materials and products of this process. The substances eliminated on both sides of the equation are intermediate circulating substances, which are theoretically not consumed. Qualified sodium fluoride can be obtained after the third step.

[0021] The following are some specific embodiments: Example 1 1. React 40wt% potassium fluoride solution with 10wt% HF-containing fluorosilicic acid to generate potassium fluorosilicate and hydrofluoric acid, and filter to obtain potassium fluorosilicate and 18wt% hydrofluoric acid solution.

[0022] 2. Potassium fluorosilicate is dissolved in 30wt% sodium hydroxide solution and filtered to obtain 24wt% potassium fluoride solution. The filter cake is a mixed paste of sodium fluoride and silicon dioxide.

[0023] A 3.24 wt% potassium fluoride solution is concentrated to 40 wt% by triple-effect evaporation and then reacted with HF-containing fluorosilicic acid to produce an 18 wt% hydrofluoric acid solution.

[0024] 4. The sodium fluoride and silicon dioxide mixture is re-selected in a hydrocyclone to separate the majority of the silicon dioxide, which is used to make water glass. The remaining silicon dioxide in the sodium fluoride is dissolved in a hot caustic soda solution, filtered, and washed to obtain qualified sodium fluoride. The solution after washing the sodium fluoride with the caustic soda solution is a dilute sodium silicate solution with a low modulus. This solution is heated in a reactor and a certain amount of silicon dioxide is added while stirring to react and produce water glass with a modulus greater than 3. After filtration and concentration to a specific gravity of 1.4, it can be sold as a finished product or directly used to make molecular sieves.

[0025] This embodiment can obtain 18wt% hydrofluoric acid solution, sodium fluoride and water glass. The yield of sodium fluoride is about 80%.

[0026] Example 2 1. React 40wt% potassium fluoride solution with 10wt% HF-containing fluorosilicic acid to generate potassium fluorosilicate and hydrofluoric acid, and filter to obtain potassium fluorosilicate and 18wt% hydrofluoric acid solution.

[0027] 2. Potassium fluorosilicate is dissolved in 30wt% sodium hydroxide solution and filtered to obtain 24% potassium fluoride solution. The filter cake is a mixed paste of sodium fluoride and silicon dioxide.

[0028] The 3.24% potassium fluoride solution was concentrated to 48% by weight by triple-effect evaporation and then diluted with the 18% by weight hydrofluoric acid from step 1 at a ratio of 1:5 to obtain a 40% by weight potassium fluoride solution. The 40% by weight potassium fluoride solution was then reacted with 10% by weight HF in fluorosilicic acid to prepare a 30% by weight hydrofluoric acid solution.

[0029] 4. The sodium fluoride and silicon dioxide mixture is re-selected in a hydrocyclone to separate the majority of the silicon dioxide, which is used to make water glass. The remaining silicon dioxide in the sodium fluoride is dissolved in a hot caustic soda solution, filtered, and washed to obtain qualified sodium fluoride. The solution after washing the sodium fluoride with the caustic soda solution is a dilute sodium silicate solution with a low modulus. This solution is heated in a reactor and a certain amount of silicon dioxide is added while stirring to react and produce water glass with a modulus greater than 3. After filtration and concentration to a specific gravity of 1.4, it can be sold as a finished product or directly used to make molecular sieves.

[0030] This embodiment can obtain 30wt% hydrofluoric acid solution, sodium fluoride and water glass. The yield of sodium fluoride is about 80%.

[0031] Example 3 1. React 40wt% potassium fluoride solution with 10wt% HF-containing fluorosilicic acid to generate potassium fluorosilicate and hydrofluoric acid, and filter to obtain potassium fluorosilicate and 18wt% hydrofluoric acid solution.

[0032] 2. Potassium fluorosilicate is dissolved in a 30wt% sodium hydroxide solution and filtered to obtain a 24wt% potassium fluoride solution. The filter cake is a mixed paste of sodium fluoride and silicon dioxide. The potassium fluoride solution obtained in this step contains approximately 4wt% sodium fluoride (the solubility of sodium fluoride at 20°C is 4.17g / 100ml).

[0033] The 3.24% potassium fluoride solution is concentrated to 48% by weight via triple-effect evaporation and then diluted with the 18% by weight hydrofluoric acid from step 1 at a ratio of 1:5 to obtain a 40% by weight potassium fluoride solution. The 40% by weight potassium fluoride solution is then reacted with 10% HF-containing fluorosilicic acid to prepare a 30% by weight hydrofluoric acid solution. The sodium fluoride introduced into the potassium fluoride solution enters the 30% by weight hydrofluoric acid solution.

[0034] 4. The potassium fluorosilicate separated in step 3 is dissolved in 30wt% sodium hydroxide solution and filtered to obtain a 24% potassium fluoride solution. The filter cake is a mixed paste of sodium fluoride and silicon dioxide.

[0035] 5. the 24wt% potassium fluoride solution of step 4 is concentrated to 48wt% through triple-effect evaporation, then added in a ratio of 1:5 with 30% hydrofluoric acid of step 3, and diluted to obtain 40wt% potassium fluoride solution. 40wt% potassium fluoride solution is reacted with the hydrofluoric acid solution of 50wt% containing 10wt%HF. When potassium fluoride solution concentrates, part of sodium fluoride forms crystallization, and the 30wt% hydrofluoric acid solution for dilution is also dissolved with sodium fluoride, and then reacts with the hydrofluoric acid solution. Due to accumulation of concentration, total sodium fluoride amount exceeds solubility, and part of sodium fluoride is separated by filtration with potassium silicofluoride in the form of precipitation. Finally, this part of sodium fluoride is filtered and recovered in the potassium silicofluoride alkaline hydrolysis process. The yield of sodium fluoride can be increased to 85%.

[0036] 6. The sodium fluoride and silicon dioxide mixture from steps 2 and 4 is subjected to gravity separation in a hydrocyclone to separate the majority of the silicon dioxide, which is used to produce water glass. The remaining small amount of silicon dioxide in the sodium fluoride is dissolved with a hot caustic soda solution, and the solution is filtered and washed to obtain qualified sodium fluoride. The solution obtained by washing the sodium fluoride with the caustic soda solution is a dilute sodium silicate solution with a low modulus. This solution is heated in a reactor and a certain amount of silicon dioxide is added with stirring to react and produce water glass with a modulus greater than 3. After filtration and concentration to a specific gravity of 1.4, it can be sold as a finished product or directly used to produce molecular sieves.

[0037] This embodiment can obtain 50wt% hydrofluoric acid solution, sodium fluoride and water glass. The yield of sodium fluoride is about 85%.

Claims

1. A comprehensive utilization method of hydrofluoric acid containing hydrofluoric acid, characterized in that: The following steps are involved: 1) reacting a stock solution containing fluorosilicic acid with a potassium fluoride raw material, and obtaining potassium fluorosilicate and hydrofluoric acid solution after solid-liquid separation; 2) Potassium fluorosilicate reacts with sodium hydroxide raw material, and after solid-liquid separation, a mixture of potassium fluoride solution, sodium fluoride and silicon dioxide is obtained; the potassium fluoride solution is returned to step 1) and recycled as potassium fluoride raw material.

2. The comprehensive utilization method of hydrofluoric acid containing hydrogen fluoride according to claim 1, characterized in that: The mixture in step 2) is subjected to coarse separation by gravity separation to obtain crude sodium fluoride and silicon dioxide. The crude sodium fluoride is subjected to alkali washing to remove silicon to obtain sodium fluoride.

3. The comprehensive utilization method of hydrofluoric acid containing hydrogen fluoride according to claim 2, characterized in that: The washing liquid produced by alkali washing and the silicon dioxide separated by gravity are used to make water glass.

4. The comprehensive utilization method of hydrofluoric acid containing hydrogen fluoride according to claim 2, characterized in that: The sodium hydroxide raw material is a sodium hydroxide solution with a concentration of 30wt%.

5. The comprehensive utilization method of hydrofluoric acid containing hydrogen fluoride according to claim 2, characterized in that: In step 1), the potassium fluoride raw material is a potassium fluoride solution with a concentration of 40 wt%.

6. The comprehensive utilization method of hydrofluoric acid containing hydrogen fluoride according to claim 2, characterized in that: In step 2), the potassium fluoride solution is first concentrated and then returned to step 1) for recycling as potassium fluoride raw material.

7. The comprehensive utilization method of hydrofluoric acid containing hydrogen fluoride according to claim 2, characterized in that: In step 2), the potassium fluoride solution is concentrated and then diluted with the hydrofluoric acid solution produced in step 1), and then returned to step 1) for recycling as a potassium fluoride raw material.

8. The comprehensive utilization method of hydrofluoric acid containing hydrogen fluoride according to claim 7, characterized in that: In step 2), the potassium fluoride solution is concentrated to a concentration of more than 45 wt%, and then diluted with the hydrofluoric acid solution produced in step 1) to a concentration of 30-40 wt%.

9. The comprehensive utilization method of hydrofluoric acid containing hydrogen fluoride according to claim 7, characterized in that: In step 1), the potassium fluoride raw material is a potassium fluoride solution that is recycled more than once.

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