Abstract
The present invention discloses a method of producing high-purity magnesium fluoride crystals, comprising the following steps: (1) mixing magnesium carbonate with water, stirring, and preparing a magnesium carbonate suspension, passing CO2 gas into the magnesium carbonate suspension for carbonization to obtain a reaction solution A; (2) ammoniacal decomposition of fluorosilicic acid to produce ammonium fluoride solution or ammonium hydrofluoric acid solution; (3) mixing the reaction solution A with ammonium fluoride solution or ammonium hydrofluoric acid solution to Reaction to obtain high-purity magnesium fluoride slurry, the CO2 gas generated in the reaction process is collected and returned to be used in the carbonization reaction, and the ammonia gas generated in the reaction process is collected and used; (4) high-purity magnesium fluoride slurry is filtered, the filtrate is returned to be used in the preparation of magnesium carbonate suspension, and the filtrate cake is a high-purity magnesium fluoride ointment, and the filtrate cake is washed, dried, and sintered, obtaining high-purity magnesium fluoride crystals. The present invention has good economic, social and environmental benefits, and is suitable for popularization and application.
Description
A method for producing high purity magnesium fluoride crystals
Technical Field
The present invention relates to the technical field of magnesium fluoride production, and specifically relates to a production method of high purity magnesium fluoride crystals.
Background Technology
Magnesium fluoride is an important inorganic chemical raw material, which is widely used in the fields of hot pressing crystals, vacuum coating and preparation of optical glass. Most of the magnesium fluoride produced at present is colloidal precipitate, which condenses into hard lumps difficult to be used directly in the drying process, and must be crushed and sifted before it can be used. However, fluoride on most materials have strong corrosive, so the crushing equipment is more difficult to select materials, if the choice of material is not appropriate, the magnesium fluoride products will cause contamination and affect its quality. Therefore, the direct production of powdered or crystalline magnesium fluoride is imperative.
At present, the main source of fluorine is fluorite and phosphate rock, with the development of circular economy and low carbon economy, saving fluorite resources, make full use of phosphorus ore fluorine resources will be the inevitable trend of the development of fluorine chemical industry in the future. Fluorosilicic acid is the by-product of anhydrous hydrofluoric acid and phosphate fertilizer industry, the current use of fluorine in fluorosilicic acid is still in the production of low value-added sodium fluorosilicate and other fluoride, and will also be a large number of by-products of waste liquids, resulting in low recycling efficiency and environmental pressure.
Contents of the invention
An object of the present invention is to provide a production method of high-purity magnesium fluoride crystals.
In order to realize the above purpose, the technical solution adopted in the present invention is: a production method of high-purity magnesium fluoride crystals, including the following steps:
(1) mixing magnesium carbonate with water, stirring, and formulating into a magnesium carbonate suspension with a weight percentage concentration of 1% to 10%, passing CO2 gas into the magnesium carbonate suspension, with a partial pressure of CO2 gas of 0.2 to 10 atmospheres, and carbonization reaction for 2 to 40 hours, controlling the reaction temperature of 1 ℃ to 30 ℃, and after that obtaining a reaction solution A, which is a mixed solution of magnesium carbonate and magnesium bicarbonate. Standby;
(2) Ammoniate fluorosilicic acid to produce ammonium fluoride solution or ammonium hydrofluoride solution with a weight percentage concentration of 5 to 50%;
(3) will step (1) obtained reaction solution A and step (2) obtained ammonium fluoride solution or ammonium hydrofluoric acid solution, mixed solution B, mixed solution B contains magnesium, fluorine elements in the molar ratio of: Mg elements: F elements = 1: (1 ~ 3), mixed solution B at 5 ~ 80 ℃ reaction 0.5 ~ 7 hours to obtain high-purity magnesium fluoride slurry, the CO2 gas generated in the process of the reaction after collection returned to step (1) and used in the carbonization reaction, and the ammonia gas generated in the reaction process was collected and returned to step (2) for use;
(4) The high-purity magnesium fluoride slurry described in step (3) is filtered, and the filtrate is returned to step (1) for preparing magnesium carbonate suspension, and the filter cake is a high-purity magnesium fluoride ointment, and the filter cake is washed, dried, and sintered thereafter for 5-18 hours at 450-600°C, which results in high-purity magnesium fluoride crystals.
Further, the magnesium carbonate described in step (1) is industrial grade magnesium carbonate or high purity magnesium carbonate.
The fluorosilicic acid described in step (2) is a by-product of the phosphate fertilizer industry or a by-product of the anhydrous hydrofluoric acid production process.
The drying process in step (4) is vacuum drying, and the drying temperature is controlled at 50 to 150°C for 12 to 24 hours.
The advantages of the production method of high-purity magnesium fluoride crystals provided by the present invention are as follows: (1) the present invention adopts the technology of carbonization under pressure, which ensures the conversion rate of fluorine and magnesium, and improves the quality of magnesium fluoride products; (2) the process of the present invention is short, with simple and easy-to-operate equipment; (3) there is no “three wastes” emission in the whole process, and all the wastewater is recycled. The ammonia and carbon dioxide gases released during the reaction process are collected and reused; ④ The fluorosilicic acid by-produced from phosphate fertilizer or anhydrous hydrofluoric acid is used as raw material, which saves the strategic resource fluorite, opens up new fluorine resources or realizes the reuse of fluorine resources, solves the bottleneck restricting the development of phosphorus fertilizer and fluoride salt industries, reduces the pressure on environmental protection, lowers the production cost and realizes the comprehensive utilization of fluorine resources; ⑤ The whole reaction is carried out under alkaline conditions, and the process is simple and easy to operate; ⑤ The whole reaction is carried out under alkaline conditions, and the process is simple and easy to operate. The whole reaction is carried out under alkaline conditions, the reaction is mild, the corrosion rate of the equipment is low, and the cost is low; ⑥ The high-purity magnesium fluoride produced by the present invention is a crystalline precipitate, and the product has a better infrared transmittance, which is practical and meets the requirements for the use of optical and other industries.
The production method of high purity magnesium fluoride crystals provided by the present invention makes use of fluorosilicic acid, which is a fluorine-containing waste in the production process of phosphorus fertilizer industry and fluorine chemical industry, to produce fluoride salt products with high value-added, and realizes the reduction, reuse and recycling of fluorine resources, which conforms to the principle of “3R” proposed by the state, and it is the direction of the development of the fluorine chemical industry in the future; The high-purity magnesium fluoride crystals obtained from the production can be used directly without crushing and sieving, which is not only convenient to use, but also will not cause secondary pollution due to crushing and sieving, and the quality is more guaranteed. This invention has good economic, social and environmental benefits, suitable for popularization and application.