Method for efficiently producing silicon tetrafluoride and sodium fluoride by using sodium fluorosilicate

Abstract

The invention discloses a method for efficiently producing silicon tetrafluoride and sodium fluoride by using sodium fluorosilicate. The method includes a dehydration and drying process, a decomposition process, a desiliconization process and an absorption process. The method specifically includes the steps that sodium fluorosilicate is subjected to the dehydration and drying process to obtain anhydrous sodium fluorosilicate; then anhydrous sodium fluorosilicate enters the decomposition process to obtain silicon tetrafluoride and semi-finished sodium fluoride; a part of silicon tetrafluoride is returned to the decomposition process to be used as fluidizing gas, and the other part of silicon tetrafluoride is used as a silicon tetrafluoride product; a part of the semi-finished sodium fluoride directly enters the desiliconization process to obtain a sodium fluoride product, and silicon tetrafluoride tail gas is generated; and the other part of the semi-finished sodium fluoride is used forabsorbing silicon tetrafluoride in the desiliconized tail gas to obtain semi-finished sodium fluorosilicate, the semi-finished sodium fluorosilicate is returned to the decomposition process, and thetail gas in the absorption process is sent to an alkaline washing tower for treatment. The method is suitable for the decomposition of sodium fluorosilicate to prepare silicon tetrafluoride and sodiumfluoride, and has the advantages of short process, low energy consumption, environmental friendliness, high added value of products and the like.

Description

technical field [0001] The invention belongs to the fields of chemical industry and materials, in particular to a method for efficiently producing silicon tetrafluoride and sodium fluoride by using sodium fluorosilicate. 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 silicon tetrafluoride and sodium fluoride. Silicon tetrafluoride is an important chemical raw material in the electronics and semiconductor industrie...

AI Technical Summary

Problems solved by technology

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, this process regenerates incompletely decomposed sodium fluorosilicate through a wet process, which has the disadvantages of long process, repeated drying, and high energy consumption.

[0004] In summary, the existing technology for preparing silicon tetrafluoride and sodium fluoride by pyrolysis of sodium fluorosilicate has problems such as melting agglomeration, incomplete decomposition, need to add additives, and long process

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