Method for efficiently producing sodium fluoride, aluminum fluoride and silicon tetrachloride by comprehensively utilizing sodium fluorosilicate

Abstract

The invention discloses a method for efficiently producing sodium fluoride, aluminum fluoride and silicon tetrachloride by comprehensively utilizing sodium fluorosilicate. The method includes a fluidized drying process, a fluidized decomposition process, a vapor deposition process, a vaporization process and a condensation process. The method includes the steps that sodium fluorosilicate is driedby fluidization to obtain anhydrous sodium fluorosilicate; then anhydrous sodium fluorosilicate enters the fluidized decomposition process to obtain a sodium fluoride product and a silicon tetrafluoride-rich gas mixture; in the vapor deposition process, the silicon tetrafluoride-rich gas mixture reacts with vaporized aluminum trichloride to obtain an aluminum fluoride product and a silicon tetrachloride-rich gas mixture; and the silicon tetrachloride-rich gas mixture is subjected to the condensation process to obtain a silicon tetrachloride product, and tail gas in the condensation process issent to an alkaline washing tower for treatment. The method has the advantages of short process, low energy consumption, environmental friendliness, high product added value and the like.

Description

technical field [0001] The invention belongs to the fields of chemical industry and materials, and in particular relates to a method for comprehensively utilizing sodium fluorosilicate to efficiently produce various chemical products (sodium fluoride, aluminum fluoride and silicon tetrachloride). Background technique [0002] my country is a big producer of phosphate fertilizers, and the production is accompanied by a large amount of fluosilicic acid output. At present, fluosilicic acid is mainly used to produce sodium fluosilicate. The product value of sodium fluorosilicate is low, the production capacity is excess, and the economic benefit is poor. Therefore, through technological innovation, the development and utilization of sodium fluorosilicate to produce high value-added fluorine salt chemicals has great economic and social benefits. Sodium fluorosilicate can be thermally decomposed to prepare sodium fluoride and silicon tetrafluoride. Sodium fluoride is an importa...

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Problems solved by technology

[0003] However, sodium fluorosilicate is prone to melting and agglomeration during the decomposition process of the fixed bed, resulting in incomplete decomposition and increased energy consumption.

Although silicon tetrafluoride is an indispensable chemical reagent in the electronics industry, its market capacity is small, and it is difficult to effectively match it compared with the huge amount of sodium fluorosilicate

However, the process is still fixed-bed decomposition, which has small processing capacity and complicated operation, which is not conducive to large-scale continuous production, and needs to add decomposition aids, which increases the cost.

Chinese patent 201710216329.5 discloses a cyclic production process for preparing hydrogen fluoride from fluorosilicic acid, which involves thermal decomposition of sodium fluorosilicate to prepare sodium fluoride solid and silicon tetrafluoride gas, but does not give an actual operation plan

However, the process of preparing white carbon black by gas-phase hydrolysis of silicon tetrafluoride requires high temperature due to thermodynamic limitations, and the reaction conversion rate is low, so it is difficult to implement industrially.

[0006] In summary, the existing technologies for comprehensive utilization of sodium fluorosilicate have problems such as melting agglomeration, incomplete decomposition, need to add additives, and long process

The obtained silicon tetrafluoride has a small market capacity, and it is difficult to match a large amount of sodium fluorosilicate

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