Method for purifying silicon tetrachloride by double-effect distillation

Abstract

The invention discloses a method for purifying silicon tetrachloride by double-effect distillation, which comprises the following steps: (1) the rough silicon tetrachloride obtained in the previous process firstly enters a spray column, the gas phase extracted by a cold fractional condenser at the top of the spray column is a non-condensable gas, and the non-condensable gas is condensed by the fractional condenser to obtain liquid phase rough silicon tetrachloride, wherein part of the liquid phase rough silicon tetrachloride flows back, and part of the liquid phase rough silicon tetrachlorideis discharged to enter a lightness-removing column; part of a material discharged from the kettle of the spray column enters a reboiler of the kettle of the spray column, and part of the material discharged from the kettle of the spray column is extracted; (2) the gas phase at the top of the lightness-removing column is extracted as a heat source to enter a condensing reboiler of the kettle of a weight-removing column for carrying out heat exchange, then part of the liquid phase heat source is taken as a backflow liquid at the top of the lightness-removing column to flow back, and part of theliquid phase heat source is extracted; part of rough silicon tetrachloride in the kettle of the lightness-removing column enters the reboiler of the kettle of the lightness-removing column, and part of the rough silicon tetrachloride is discharged to enter the weight-removing column; and (3) the gas phase extracted at the top of the weight-removing column enters a complete condenser at the top ofthe weight-removing column, part of a liquid phase obtained by condensing of the complete condenser flows back, and part of the liquid phase is discharged to obtain silicon tetrachloride products. Byadopting the method of the invention, the energy consumption can be saved by 30%-50%.

Description

technical field [0001] The invention belongs to the technical field of rectification, and in particular relates to a method for purifying silicon tetrachloride by double-effect rectification. Background technique [0002] Silicon tetrachloride is an important chemical raw material, mainly used in the manufacture of organosilicon compounds, such as silicate, silicone oil, high-temperature insulating paint, silicone resin, silicone rubber and heat-resistant gasket materials; high-purity tetrachloride Silicon can be used as a material for the manufacture of polycrystalline silicon, high-purity silicon dioxide, inorganic silicon compounds, and quartz fibers; it is used in the military industry to manufacture smoke agents; it is used in the metallurgical industry to manufacture corrosion-resistant ferrosilicon; it is used in the foundry industry as a Release agent. Crude silicon tetrachloride is mainly obtained by distilling ferrosilicon and chlorine gas at a temperature above 2...

AI Technical Summary

Problems solved by technology

The adsorption method is a process of separating the components by using the difference in binding force between the components in the mixture and the adsorbent. Generally, the adsorption method is only good for one or one type of impurities. For example, US Patent No. 5,723,644 introduces a SiO 2 Supported Cu or Cu compounds as adsorbents to remove SiCl 4 However, this method only has a good effect on the removal of P impurities and does not remove other impurities well, which limits the application of adsorption methods in the purification of silicon tetrachloride.

The reaction method is to add a component to react with some components in the mixture. After the reaction, each component is easy to separate to achieve the separation effect. The reaction method is generally coupled with other methods to achieve a good separation effect, such as the Japanese patent JP2005-067979 introduced a method of using ethers with the general formula R1-O-R2 (R1, R2=C4~8 alkyl) as a complexing agent to rectify and separate impurities such as B and P in chlorosilanes, but the separation The coupling of method and rectification, and the use of complexing agents increase the cost of separation, which limits the application of reaction methods

The rectification method is to use the difference in volatility of each component in the solution to separate the components through partial vaporization and partial condensation. For example, the Chinese patent application number 200310122893.9 introduces a method to produce high-purity silicon tetrachloride through two rectifications. method, but this method adopts batch operation, which is not conducive to large-scale industrial production

In addition, the conventional distillation process has low thermodynamic efficiency and high energy consumption, which is not conducive to reducing production costs. The application of double-effect distillation with energy coupling can reduce energy consumption

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