CN101823718A

CN101823718A - Method for producing silica by hydrolyzing and precipitating silicon tetrachloride at low temperature

Info

Publication number: CN101823718A
Application number: CN 201010164963
Authority: CN
Inventors: 李平
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-05-07
Filing date: 2010-05-07
Publication date: 2010-09-08

Abstract

The invention discloses a method for producing silica by hydrolyzing and precipitating silicon tetrachloride at low temperature, belonging to the technical field of compounds of silicon. The method comprises the following steps: adding prepared sodium salt solution in a closed reaction kettle, adding silicon tetrachloride, and regulating pH value to be 8-9 after reaction; vehiclerying out solid-liquid separation, drying the separated salt water for concentration to obtain sodium chloride product, and cleaning the solid silica to remove residual sodium chloride; preparing the used water into salt water for cyclic utilization; and drying the cleaned silica to obtain silica product. The invention can be vehicleried out in closed conditions and has the advantages of simple technology, high safety and reliability, low power consumption, big handling capacity, no pollution and low investment.

Description

Utilize hydrolyzing and precipitating silicon tetrachloride at low temperature to produce the method for silicon-dioxide

(1) technical field: the present invention relates to a kind of by product that produces in the polysilicon production process that utilizes---silicon tetrachloride is produced the method for silicon-dioxide, belongs to the compound technical of silicon.

(2) background technology: polysilicon is the critical materials of unicircuit and photovoltaic generation, and along with the rapid growth of the domestic and international polysilicon market requirement, China's production of polysilicon scale enlarges rapidly.Produce a large amount of by product---silicon tetrachlorides in the polysilicon production process.Silicon tetrachloride is a kind of poisonous and harmful liquid with severe corrosive, can bring huge pollution to environment, and human life security in serious threat.The harmless treatment silicon tetrachloride is the important step that China's polysilicon industry energy-saving reduced discharging, keeps the safety in production, protected environment, is the sector key of healthy development.Since 2008, all parts of the country have tens polysilicon projects to announce to start building or go into operation, and China's polysilicon ultimate production progressively increases, and expecting silicon tetrachloride generation in 2010 will be above 100,000 ton.For numerous production of polysilicon enterprises, the pollution problem of silicon tetrachloride becomes the bottleneck of restriction enterprise development.How safe and harmlessization processing and recycle silicon tetrachloride and become the task of top priority.

At present, domestic enterprise mainly contains two kinds of method processing silicon chloride.A kind of method is: utilize hydrogen that it is reduced to the main raw material trichlorosilane of polysilicon under High Temperature High Pressure, reprocessing synthesizes polysilicon.This treatment process exists invests big, shortcomings such as energy consumption is high, transformation efficiency is low, complex procedures, restricts its application of enterprise at home greatly.Another kind method is to utilize the thermal silica of silicon tetrachloride production high added value, but shortcoming that this method exists also that investment is huge, technical process is complicated, energy consumption is high, production equipment is little, treatment capacity is little etc. can not satisfy requirement of enterprise far away to the digestion process amount of silicon tetrachloride.

Therefore, the silicon tetrachloride treatment process that research is fit to China's national situation turns waste into wealth this harmful waste, and China's polysilicon industry cleaner production and Sustainable development are had significant meaning.

(3) summary of the invention:

1, goal of the invention: the objective of the invention is to deficiency at the prior art scheme, a kind of simple and reliable process is provided, energy consumption is low, treatment capacity is big, the free of contamination method of utilizing hydrolyzing and precipitating silicon tetrachloride at low temperature to produce silicon-dioxide, to solve the problem of safe and harmlessization of silicon tetrachloride as by-product of polysilicon recycling.

2, a kind of method of utilizing hydrolyzing and precipitating silicon tetrachloride at low temperature to produce silicon-dioxide of technical scheme in turn includes the following steps:

A, preparation dispersion agent: sodium salt is added in the entry, be mixed with the solution of 30%-40% proportion concentration, sodium salt as dispersion agent, makes precipitation of silica keep the fine particle shape in the low temperature hydrolysis precipitin reaction;

B, low temperature hydrolysis: add the above-mentioned dispersion agent for preparing in closed reactor, add silicon tetrachloride again, the silicon tetrachloride hydrolysis generates poly-silicic acid and hydrochloric acid under normal temperature condition;

C, precipitin reaction: add sodium hydroxide in poly-silicic acid and the hydrochloric acid soln, and regulate pH value in 8-9; Poly-silicic acid and sodium hydroxide reaction generate precipitation of silica and water; Hydrochloric acid and sodium hydroxide reaction generate sodium-chlor and water;

D, solid-liquid separation: will carry out solid-liquid separation in precipitation of silica and the salt solution adding whizzer, after the salt solution partial concentration drying after the separation, metering packing is the sodium-chlor finished product;

E, washing drying: the precipitation of silica of solid part washes with water again, and it is residual to remove sodium-chlor; The water of washing is mixed with salt solution again, recycles as dispersion agent; Washing silicon-dioxide well is through the centrifuge dewatering after drying, and metering packing is the silicon-dioxide finished product.

Salt among the present invention can be sodium salt such as sodium-chlor, also can be that ammonium salts such as ammonium chloride, bicarbonate of ammonia are made dispersion agent.

3, beneficial effect: silicon tetrachloride carries out the low temperature hydrolysis reaction in closed reactor, reaction process is safe and reliable, and deleterious hydrogen chloride gas can't overflow harmful to human, also can not cause hydrogen chloride gas polluted air and environment; Hydrolysis reaction carries out under cryogenic air tight condition, need not consume fuel, meets the requirement of energy-saving and emission-reduction; Low temperature hydrolysis precipitator method speed of response is fast, transformation efficiency height, digestion process silicon tetrachloride on a large scale; In reaction, add dispersion agent, the fineness and the quality of high silicon dioxide can be provided greatly, increase added value of product; The whole production processing method has that principle is simple, safe and reliable, energy consumption is low, treatment capacity is big, pollution-free, advantage such as investment is little, meet China's energy, environmental protection policy fully, solve the innoxious recycling problem of silicon tetrachloride of production of polysilicon enterprise well, had huge economic benefit and social benefit.Can reach goal of the invention fully.

(4) embodiment:

1, preparation dispersion agent: sodium-chlor adds in the entry, is mixed with salt solution, and salt solution is the sodium chloride solution of 35% proportion concentration, and sodium-chlor as dispersion agent, makes precipitation of silica keep the fine particle shape in the low temperature hydrolysis precipitin reaction.

2), low temperature hydrolysis: add the salt solution for preparing in closed reactor, silicon tetrachloride is added closed reactor again and carry out the low temperature hydrolysis reaction, temperature is at normal temperature, and silicon tetrachloride hydrolysis under the condition of closed reactor generates poly-silicic acid and hydrochloric acid.

3), precipitin reaction: add sodium hydroxide in poly-silicic acid and the hydrochloric acid soln, and regulate pH value in 8-9; Poly-silicic acid and sodium hydroxide reaction generate precipitation of silica and water, and hydrochloric acid and sodium hydroxide reaction generate sodium-chlor and water.Obtain precipitation of silica and salt solution after this step reaction.

4), solid-liquid separation: will carry out solid-liquid separation in precipitation of silica and the salt solution adding horizontal helical type whizzer, after the salt solution partial concentration drying after the separation, metering packing is the sodium-chlor finished product.

5), washing is dry: the precipitation of silica of solid part is washed with water to sodium-chlor again less than 1.5%.The water of washing is mixed with salt solution again, recycles as dispersion agent.Washing silicon-dioxide well is through horizontal helical type centrifuge dewatering after drying, and metering packing is the silicon-dioxide finished product.

Claims

1. method of utilizing hydrolyzing and precipitating silicon tetrachloride at low temperature to produce silicon-dioxide in turn includes the following steps:

A, preparation dispersion agent: sodium salt is added in the entry, be mixed with the solution of 30%-40% proportion concentration;

B, low temperature hydrolysis: add the above-mentioned dispersion agent for preparing in closed reactor, add the silicon tetrachloride reaction that is hydrolyzed again, the silicon tetrachloride hydrolysis generates and gathers silicic acid and hydrochloric acid under normal temperature condition;

D, solid-liquid separation: precipitation of silica and salt solution are carried out solid-liquid separation in whizzer, after the salt solution partial concentration drying after the separation, metering packing is the sodium-chlor finished product;

2. the method for utilizing hydrolyzing and precipitating silicon tetrachloride at low temperature to produce silicon-dioxide according to claim 1 is characterized in that described sodium salt can replace with ammonium salt.