SU833290A1 - Method of cleaning gas from silicon tetrachloride - Google Patents

Description

(54) METHOD FOR CLEANING GAS FROM SILICON TETRACHLORIDE

one

The invention relates to the purification of gases from silicon tetrachloride by absorption and can be used in the technology for purifying waste gases from the production of silicon tetrachloride.

A known method of purification of waste gases containing silicon tetrachloride by absorbing it with a solution of milk of lime, allows to effectively capture silicon tetrachloride and its hydrolysis products. Acidic water resulting from absorption is sent to settling neutralizers and discarded and j.

The disadvantages of the method are the high consumption of milk of lime and the irretrievable loss of silicon tetrachloride.

The purpose of the invention is to reduce the consumption of milk of lime and the possibility of recovery of silicon tetrachloride.

The goal is achieved by the fact that the gas to be purified is previously worked up with the bottom residue of the distillation stage of crude tetrachloride. cream with (-10) - (followed by EH1 alkaline silicon tetrachloride from the vat residue by heating.

The method is carried out as follows.

Gases containing silicon tetrachloride, after cooling the subshots in the jass-exchange apparatus, are irrigated in) the 1st vat residue of the silicon trachloride at (-10) - (- 30/3. The gases leaving the apparatus in order to remove the residual amounts of silicon tetrachloride send on A. absorption lime 4 milk.

The absorbed residue of cortical tetrachloride is distilled at 70-80 ° C, condensed into a collection of technical bluestone, and at rest, the absorption returns.

Claims (3)

Example A gas mixture containing 6.3 o6.%. SICt4 for 5 hours at a speed of 6.6 l / h is passed through a packed column filled with 70 g of bottom distillation of silicon tetrachloride of the following composition, wt.%: SiCl40.3 -0.7 48.0-61.0 SigCU 26.3-44.3 The gas leaving the packed column contains 0.1 bb.% SiCb at a degree absorption of 84% and is sent for final purification by absorption with lime milk. The SiCl gas thus purified does not contain. PRI me R 2. A gas mixture containing 2.1 00.% SlCl for 6 hours at a rate of 7 l / h is passed at -23 ° C through a packed column filled with 70 g of bottoms having a composition similar to that shown in Example 1. Exit from the packed column, the gas contains 0.018% by volume of SiCI at an absorption level of 99.09% and is directed to absorption by lime milk. PRI me R 3. A gas mixture containing 20.3% by volume of SiCK, for 2 hours at a rate of 3.5 g / h, is passed through a packed column filled with 70 g of bottoms having a composition similar to that shown in Example 1. Exit The gas from the packed column contains 0.006 bytes. SiCl at a rate of absorption of 99.6% and is directed to absorption by lime milk. EXAMPLE 4 50 g of the SICK solution in the bottoms obtained under the conditions described in example 3, containing 12.3% by weight of silicon tetrachloride, is placed in the cube of the distillation unit and when the SiCl4 obtained from SiCl46 is stripped,} g which is 0% 98% of the absorbed amount of product. The given examples show that the pretreatment of the gas to be purified with the bottom residue of the raw material rectification phase of silicon tetrachloride at (-10) - (- 30) C makes it possible to isolate the main amount of the product and drastically reduce the amount of milk of lime supplied to the aftertreatment gas. Carrying out the pretreatment process at a temperature above drastically reduces the degree of absorption of StCl, and the decrease in temperature is less impractical because of a slight increase in the degree of absorption. Using the proposed method allows to reduce the loss of silicon tetrachloride with exhaust gases and reduce the consumption of milk of lime. Claims The method of purifying gas from silicon tetrachloride by absorbing it with lime milk, which is different) that, in order to reduce the consumption of milk of lime and the possibility of silicon tetrachloride recuperation, the gas to be purified is pretreated with the bottom residue of the distillation of silicon tetrachloride at (-10) - (- 30G C followed by separation of silicon tetrachloride from the vat residue by heating Sources of information taken into account during the examination 1. Furman Af.ft .. Rabovsky BG Basics of chemistry and technology ezvodnyh chlorides, M .. Chemistry, 1970, pp. 169-170 (prototype).