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

A technology of silicon tetrafluoride and sodium fluorosilicate, which is applied in the fields of materials and chemicals, can solve the problems of silicon tetrafluoride and sodium fluoride fusion agglomeration, long process, complicated operation, etc., and achieve economic and social benefits , reduce production costs, and have strong environmental friendliness

Active Publication Date: 2020-01-14
INST OF PROCESS ENG CHINESE ACAD OF SCI
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  • Abstract
  • Description
  • Claims
  • Application Information

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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

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

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Embodiment 1

[0028] figure 1 It is a schematic flow chart of the method for efficiently producing silicon tetrafluoride and sodium fluoride by utilizing sodium fluorosilicate described in the present invention.

[0029] combine figure 1 , a method for the efficient production of silicon tetrafluoride and sodium fluoride from sodium fluorosilicate used in this example, including dehydration and drying process 1, decomposition process 2, desiliconization process 3 and absorption process 4 four processes, specifically according to Follow these steps:

[0030] 1) The sodium fluorosilicate raw material is firstly dehydrated and dried to obtain anhydrous sodium fluorosilicate, and the dry tail gas is sent to an alkali washing tower for treatment;

[0031] 2) Anhydrous sodium fluorosilicate is sent to the decomposition process to obtain silicon tetrafluoride gas and semi-finished sodium fluoride, part of the silicon tetrafluoride gas is returned to the decomposition process as fluidizing gas, a...

Embodiment 2

[0035] This embodiment adopts the method for producing silicon tetrafluoride and sodium fluoride as described in Example 1. The dehydration and drying process 1 adopts vacuum drying, the drying and dehydration temperature is 0 ° C, and the drying time is 36 hours; A fluidized bed reactor with a decomposition temperature of 400°C and a residence time of 180 minutes, and the fluidization gas is silicon tetrafluoride gas; the desiliconization process 3 uses a fluidized bed reactor with a reaction temperature of 700°C and a residence time of 15 minutes. The gas is purified air; the absorption step 4 adopts a fluidized bed reactor with a reaction temperature of 25° C. and a residence time of 180 minutes. The fluidization gas is silicon tetrafluoride tail gas produced in the desiliconization step. The impurity silicon content of sodium fluoride product is 0.3wt% (as SiO 2 meter), the recovery rate of silicon in the raw material is 93% (to enter SiF 4 product count).

Embodiment 3

[0037]This embodiment adopts the method for producing silicon tetrafluoride and sodium fluoride as described in Example 1. The dehydration and drying process 1 adopts fluidized bed drying, the drying and dehydration temperature is 200 ° C, and the drying time is 0.1 h; the decomposition process 2 A fluidized bed reactor is used in the process, the decomposition temperature is 700°C, the residence time is 15min, and the fluidization gas is silicon tetrafluoride; the desiliconization process 3 adopts a fluidized bed reactor, the reaction temperature is 400°C, and the residence time is 180min. The fluidization gas is purified nitrogen; the absorption process 4 adopts a fluidized bed reactor with a reaction temperature of 300° C. and a residence time of 15 minutes. The fluidization gas is silicon tetrafluoride tail gas produced in the desiliconization process. The impurity silicon content of sodium fluoride product is 0.35wt% (as SiO 2 meter), the recovery rate of silicon in the r...

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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...

Claims

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Application Information

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IPC IPC(8): C01B33/107C01D3/02
CPCC01B33/10705C01D3/02C01P2006/80
Inventor 朱庆山杨海涛范川林
Owner INST OF PROCESS ENG CHINESE ACAD OF SCI
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