TWI733103B - Low-temperature wet process for manufacturing hydrofluoric acid - Google Patents

Abstract

The present invention relates to a low-temperature wet process for manufacturing hydrofluoric acid, in which the solubility of sulfuric acid in water is utilized to separate hydrogen fluoride vapor from sulfuric acid and water in a low-temperature and wet environment, so that the separated hydrogen fluoride vapor can then be condensed into hydrofluoric acid. Moreover, the hydrofluoric acid can be further purified by distillation/fractionation.

Description

Low-temperature wet hydrofluoric acid manufacturing method

The present invention relates to a manufacturing method of hydrofluoric acid, especially a manufacturing method completed in a low-temperature and wet environment.

The traditional method of producing hydrofluoric acid is to use fluorite (the main component is calcium fluoride) to react with sulfuric acid to produce hydrogen fluoride gas, and then distill and cool it to obtain liquid hydrofluoric acid. In all the processes that are often inconsistent with traditional processes, all processes are operated at low temperatures. Most of the traditional processes require a high temperature of at least 600 degrees Celsius, which easily leads to excessive energy loss and prolonged production time.

Although the current patent case is similar to the case filed in the Chinese Mainland of Announcement No. CN101913565A, it mentions a method of producing hydrogen fluoride from fluorite powder and sulfuric acid. The specific steps are as follows: add sulfuric acid solution and fluorite powder into a stirred reactor, and add The ratio is that the molar ratio of calcium fluoride to sulfuric acid is 1:3~1:30; and the fineness of fluorite powder is 280 mesh to 1220 mesh; the reaction temperature is controlled at 90°C to 300°C; hydrogen fluoride gas and sulfuric acid are produced after the reaction Calcium solid; hydrogen fluoride gas is purified, condensed, and rectified to obtain anhydrous hydrogen fluoride; or purified and absorbed to obtain hydrofluoric acid; calcium sulfate solid and sulfuric acid are transferred from the reactor to the filtration system for solid-liquid separation, and the separated sulfuric acid The solution returns to the reactor; after the calcium sulfate solid is separated from the sulfuric acid, it is washed and dried to become a by-product. The invention has the advantages of simple equipment, high reaction efficiency, low cost and easy formation of industrialized production.

And, the patent case CN85104494A mentions a method for producing hydrofluoric acid by reacting sulfuric acid and fluorspar, including: a) sending sulfuric acid and fluorspar into a pre-reactor or pre-mixer, and operating to produce 40- at its outlet. 50% converted powdered product; b) Send the powdered product at 20°-120°C into a rotary furnace with an operating temperature of 80°C-350°C to generate hydrofluoric acid and calcium sulfate; c) The reaction product is circulated into the furnace, so that the molar ratio of calcium fluoride to calcium sulfate in the powdery product entering the furnace is 1:3-1:3.5. The method of the present invention can continuously produce high-yield and continuous production with a purity of 98 -99% hydrofluoric acid, and can greatly reduce the agglomeration and furnace wall corrosion problems often encountered in the prior art methods.

Although some of the above cases mentioned that the production temperature is below 120 degrees Celsius, the largest range is still high temperature, which may still lead to the lack of high energy consumption.

Furthermore, most of the current traditional techniques are still using fluorite powder, which is due to the limited consumption of natural resources, which still cannot effectively solve this problem.

Furthermore, the current traditional technologies are all high-temperature types, which are prone to high corrosive defects.

In view of the above-mentioned deficiencies of the prior art, the present invention has developed a low-temperature wet hydrofluoric acid manufacturing method, including the following steps: mixing a calcium fluoride and a reaction space in a reaction space of 60 degrees to 120 degrees Celsius A sulfuric acid solution is subjected to a pre-reaction, wherein the molar number of the sulfuric acid solution is higher than the molar number of the calcium fluoride, and the concentration of the sulfuric acid solution is between 40% and 80%; after the pre-reaction is completed, a Perform an acidic scrubbing on the calcium fluoride and the sulfuric acid solution in the scrubbing environment to obtain a water-containing hydrofluoric acid gas; distill or fractionate the water-containing hydrofluoric acid gas, and the temperature during the process is controlled at 30°C to 40°C; A condensation procedure is performed on the water-containing hydrofluoric acid gas, the working temperature of the condensation procedure is controlled at 18°C to 19°C, and water or hydrofluoric acid is used as an absorbent to condense an aqueous hydrofluoric acid solution of any purity.

Wherein, the calcium fluoride can be obtained from waste gas or wastewater containing fluorine compounds.

Further, the calcium fluoride is filtered, dried, and then ground into powder.

Furthermore, a rotary kiln or a vertical reaction tank with a built-in stirrer performs stirring in the reaction space.

The acidic washing is performed with acid washing water, wherein the pH of the washing water is 5.5 to 6.7. In addition, the washing water is formed by dissolving a sulfuric acid in water, and the sulfuric acid is a product of the acid washing process.

Compared with the prior art, the manufacturing method of the present invention has the following effects:

1. The process temperature of the present invention is kept within 120 degrees Celsius, which can effectively prevent high energy loss caused by high temperature.

2. Since the process temperature of the present invention is controlled at a low temperature, the subsequent condensation collection effect is better.

3. Since the process temperature of the present invention is controlled at a low temperature, the corrosiveness caused by the acidic process is greatly reduced.

4. Both calcium fluoride and sulfuric acid used in the present invention can be obtained from waste gas or wastewater discharged from factories, which can effectively carry out waste recovery operations, and is not limited to fluorite or pure sulfuric acid.

5. The invention uses a rotary kiln and a vertical reaction tank with a built-in stirrer to increase the mixing capacity in the furnace, and at the same time increase the contact of the reaction. At the same time, the non-traditional high temperature can also reduce unnecessary corrosive gas generation and reduce condensed liquid In particular, the reactor can adopt electric heating or direct heating.

[The first figure] is the process flow chart of the present invention.

Please refer to the first figure, the low-temperature wet hydrofluoric acid manufacturing method of the present invention can be clearly presented in the flowchart, which is described in detail below:

Generally, fluorite and pure sulfuric acid are used to manufacture hydrofluoric acid. However, in order to effectively reduce the consumption of natural resources, the present invention can use fluorine-containing hydrofluoric acid wastewater to neutralize stabilized calcium fluoride sludge and use The high-purity sulfuric acid produced in the process of the electronics factory is used for the process operation. Among them, the calcium fluoride content in the calcium fluoride sludge is more than 60% can be used.

As mentioned in the previous paragraph, since the calcium fluoride we obtain is a mixture of hydrofluoric acid wastewater and calcium fluoride sludge, it must be filtered and dried to remove unnecessary impurities, and the dried fluoride Calcium is ground into powder and mixed with sulfuric acid solution in a pre-reactor, where the molar number of the sulfuric acid solution is higher than the molar number of the calcium fluoride, and then it is sent to a reaction space. In this embodiment, the reaction space is A reaction furnace, and the temperature is controlled at 60-120 degrees Celsius, to assist the fluorine-containing hydrofluoric acid waste water to produce steam and hydrogen fluoride gas into the subsequent condensation step, and will not participate in impurities such as calcium fluoride or calcium sulfate powder.

Or, through a rotary kiln and a vertical reaction tank with a built-in stirrer, the mixing capacity in the furnace can be increased, while the contact of the reaction can be increased, and unnecessary tail gas and condensation can be reduced. In particular, the reactor can use electric heating. Type or direct heating method.

After the reaction of the reaction furnace is completed, an acid washing is performed on the calcium fluoride and the sulfuric acid solution in a washing environment. In this embodiment, the washing environment is a washing tower.

Sulfuric acid, water-containing hydrofluoric acid gas or other impurities are separated by acid washing (in this example, water is introduced). The boiling point of sulfuric acid is relatively high. Whether it is gas or liquid droplets, it has high solubility in water and is easy to remove. The solubility of acid gas in water is relatively small. In addition to the separation of sulfuric acid, water and hydrofluoric acid gas by lowering the temperature by washing with water, it can also be adjusted to acidity by washing water or the pH value of the acid gas will be changed to acid after dissolving sulfuric acid gas. The PH value is 5.5 to 6.7 to reduce the solubility of hydrofluoric acid and improve the purity of recovered hydrofluoric acid.

A condenser is connected after the washing tower, and the water-containing hydrofluoric acid gas separated from the washing is condensed to obtain an aqueous hydrofluoric acid solution under the condition of controlling the temperature at 18°C to 22°C.

In order to increase the concentration of the obtained hydrofluoric acid aqueous solution, we can further connect distillation or fractionation equipment, the distillation or fractionation temperature is controlled at 30 to 40 degrees Celsius, and the condensation temperature after distillation is controlled below 19 degrees (that is, less than The condensation point of hydrogen fluoride), and finally pure water or hydrofluoric acid as the absorbent, it is possible to obtain an aqueous solution of hydrofluoric acid of any purity.

The mechanism of hydrofluoric acid production of the present invention includes two reactions:

1. Calcium fluoride and sulfuric acid contact to form hydrogen fluoride (gaseous state), the reaction rate depends on the surface area of unit weight of calcium fluoride, and the technology of overcoming activation energy

2. On the other hand, a second liquid dissolution reaction to generate hydrofluoric acid will occur, and the concentration of sulfuric acid will play an important role at this time.

The present invention produces hydrofluoric acid in a low temperature and wet (with water) manner, and another feature is that a higher concentration (40-80%) of sulfuric acid is stored in the reactor, which will change the boiling point of the solution (e.g. 40wt% sulfuric acid solution is 113.6℃), and low temperature operation in the reactor is conducive to the sub-boiling distillation/evaporation of the hydrofluoric acid aqueous solution. In this low temperature state, the impurities in the reactant will not easily become gaseous (that is, there is less water Steam generation), so in the subsequent distillation or fractionation purification process, the use of energy can be reduced and the quality of hydrofluoric acid can be improved.

Based on the description of the above embodiments, when one can fully understand the operation and use of the present invention and the effects of the present invention, but the above embodiments are only the preferred embodiments of the present invention, and the implementation of the present invention cannot be limited by this. The scope, that is, simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the content of the description of the invention, are all within the scope of the present invention.

Claims (6)

A method for producing low-temperature wet hydrofluoric acid, comprising the following steps: mixing a calcium fluoride and a sulfuric acid solution in a reaction space of 60°C to 120°C to perform a pre-reaction, wherein the molar number of the sulfuric acid solution It is higher than the molar number of the calcium fluoride, and the concentration of the sulfuric acid solution is between 40% and 80%; after the pre-reaction is completed, an acid wash is performed on the calcium fluoride and the sulfuric acid solution in a washing environment, To obtain a water-containing hydrofluoric acid gas; to distill or fractionate the water-containing hydrofluoric acid gas, and the temperature in the process is controlled at 30 to 40 degrees Celsius; to perform a condensation procedure on the water-containing hydrofluoric acid gas, and the work of the condensation procedure The temperature is controlled at 18 to 19 degrees Celsius, and water or hydrofluoric acid is used as an absorbent to condense an aqueous solution of hydrofluoric acid of any purity. The method for producing low-temperature wet hydrofluoric acid according to claim 1, wherein the calcium fluoride is obtained from waste gas or wastewater containing fluorine compounds. According to the method for producing low-temperature wet hydrofluoric acid according to claim 2, the calcium fluoride is filtered, dried, and then ground into powder. According to the method for producing low-temperature wet hydrofluoric acid according to claim 1, furthermore, stirring is performed in the reaction space by a rotary kiln or a vertical reaction tank with a built-in stirrer. The method for producing low-temperature wet hydrofluoric acid according to claim 1, wherein the acidic washing is performed with acid washing water, wherein the pH of the washing water is 5.5 to 6.7. According to the method for producing low-temperature wet hydrofluoric acid according to claim 5, the washing water system is formed by dissolving a sulfuric acid in water, and the sulfuric acid is a product of the acid washing process.

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