JPS61178027A - Treatment of exhaust gas containing halogenated hydrocarbon - Google Patents

Abstract

PURPOSE:To make halogenated hydrocarbon innoxious by perfectly decomposing the same, by a method wherein exhaust gas containing halogenated hydrocarbon is mixed with air and the resulting gaseous mixture is passed through a heat treatment pipe heated to 600 deg.C or more so as to be held for 3sec or more and subsequently passed through a solid alkali packed tank. CONSTITUTION:Exhaust gas containing halogenated hydrocarbon is introduced into a reactor 10 evacuated by a vacuum pump 8 and receives the contact reaction with the base material 2 directly heated by a high frequency induction coil 3 to adhere a precipitated substance B. The exhaust gas passed through the reaction chamber is mixed with air C in a mixing chamber 11 and the resulting gaseous mixture is decomposed to carbon and hydrogen halide in a process for passing said gaseous mixture through the spiral tube 4 heated to 600 deg.C or more by an electric furnace 5 so as to require 3sec or more and carbon is converted to carbon dioxide while hydrogen halide is removed by the solid alkali tank 15 of the post-stage and the treated gas is exhausted as exhaust gas G by a vacuum pump.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for treating gases containing toxic gas-phase 10-genated hydrocarbons.

(Prior art and its problems) In recent years, groups such as graphite and metals have been produced by gas phase reactions at high temperatures, such as thermal decomposition of volatile metal halides, metal organic compounds, hydrocarbon compounds, hydrogen reduction, and substitution reactions. Chemical vapor deposition methods are widely used to deposit carbon, carbide, silicide, etc. on the surface of materials.

Among these, halogenated hydrocarbons are widely used as a carbon source for generating pyrolytic carbon and depositing silicon carbide.

Halogenated hydrocarbons are toxic, and unlike metal halides such as S i C1a, many of them are stable in air and water at room temperature. For example dichloroethane.

Examples include dichloroethylene, trichloroethane, t')/loloethylene, tetrachloroethylene, or derivatives thereof.

However, although unreacted halogenated hydrocarbons are contained in the exhaust gas after a gas-phase reaction using halogenated hydrocarbons, there are few effective ways to treat them. The current situation is that there is no such thing. For example, a method is known in which the exhaust gas discharged from a vacuum evacuation device such as a rotary pump to maintain a reduced pressure in the reaction chamber is treated with water or an alkaline solution, but this method is effective against hydrogen chloride gas (s). Hydrocarbons have no effect. Moreover, considering that the emission regulations for organic chlorides are strict, ranging from P, P, B, orders of magnitude, it is desirable that these halogenated hydrocarbons be completely decomposed or separated and stored.

On the other hand, there is also the problem that halogenated hydrocarbons deteriorate the vacuum evacuation equipment.

(Object of the invention) The present invention relates to a method for treating halogenated hydrocarbon-containing exhaust gas that eliminates the above-mentioned problems.

(Means for Solving the Problems) The present invention involves mixing exhaust gas containing halogenated hydrocarbons with air, passing it through a heat treatment tube heated to 600°C or higher for 3 seconds or more, and then passing it through a solid alkali filling tank. The present invention relates to a method for treating halogenated hydrocarbon-containing exhaust gas that is passed through.

In the present invention, it is preferable to set the heating temperature to 900° C. or higher because decomposition of the halogenated hydrocarbon is promoted. There are no particular restrictions on the size and shape of the material 9 of the heat treatment tube, but it is preferable to use a serpentine tube or a spiral tube because the heat treatment section through which the gas passes can be lengthened in a small space and the exhaust gas can be sufficiently decomposed. In the heat treatment, the halogenated hydrocarbon is decomposed into carbon and hydrogen halide. In order to oxidize the carbon in the heat treatment tube, gasify it, and discharge it, the exhaust gas is mixed with air before being sent to the heat treatment tube. For mixing, exhaust gas is sent to, for example, a mixing chamber, and an appropriate amount of air is introduced and mixed through an air inlet provided in the mixing chamber using a buried control valve. There are no restrictions on the mixing method, structure, etc., as long as the exhaust gas and air can be mixed uniformly.

For uniform mixing, it is preferable to extend the mixing process to some extent or to stir. The amount of air added is in excess of the amount required for reaction with carbon.

In the present invention, if the heating temperature of the heat treatment tube is less than 600°C and the time for passing the exhaust gas is less than 3 seconds, the halogenated hydrocarbon will be decomposed, but it will not be enough to oxidize the carbon fine powder produced by decomposition. be.

The exhaust gas from the heat treatment tube passes through the solid alkali-filled tank to remove the hydrogen halide contained therein. Obi-zukuri of alkaline filling tank, 01! There are no particular limitations on the alkali used, as long as it can sufficiently remove hydrogen halides.

Preferably, the method of the present invention is used in combination with a chemical vapor deposition method. Gas-phase reactions in chemical vapor deposition are generally carried out by sending the raw material gas together with a carrier gas while reducing the pressure. Just add. If not used together, it is preferable to add an air supply (exhaust) pump, an aspirator, etc. to improve the gas flow.

(Example) FIG. 1 shows a process diagram when the chemical vapor deposition method and the method of the present invention are used together. Operate vacuum pump 8.

After opening the pressure reduction control valve 7 and reducing the pressure in the reaction chamber 10.

The flow is introduced into the At-reaction chamber 10 by opening the control valve 1 and introducing a mixture of gas containing halogenated hydrocarbon and carrier gas.

The base material 2 is directly heated by the high frequency induction coil 3, and the gas containing the halogenated hydrocarbon in the mixed gas contacts the heated base material and reacts, and is heated on the base material 2. A precipitate of Bi is deposited. Thereafter, the flow rate control valve 1 and the pressure reduction control valve 7tl are appropriately operated to maintain the reaction chamber 10 at a reduced pressure to continue the above reaction. The exhaust gas that has passed through the reaction chamber 10 is led to a mixing chamber 11, where it is mixed with air C that flows in from an air inlet 13 through a flow rate control valve 12, and is heated in an electric furnace 5 using a tube with an inner diameter of 10 mm and a number of turns of 20. During the process of passing through the spiral tube 4, the carbon is decomposed into carbon and hydrogen halide, and the carbon is immediately converted into carbon dioxide by oxygen in the air in the spiral tube. The exhaust gas that has passed through the spiral tube passes through a solid alkali filling tank 15 to remove halogenated hydrocarbons, and is discharged as exhaust gas G by a vacuum pump 8. 9 is a gas detector, and 14 is a check valve.

In the above method, 1,111-t! 20 volumes of J chloroethane (grade 1 reagent manufactured by Wako Pure Chemical Industries, Ltd.) and 80 volumes of argon as a carrier gas.

9 reaction chambers 10 using pitch coke-based artificial graphite as the base material 2
The pressure inside is 40mmHg, and the flow rate of mixed gas A is 20mmHg/min.
0mt! The temperature of the substrate 2 was set to 800° C. to carry out the reaction, and pyrolytic carbon was deposited on the substrate 2. The flow rate of introduced air C mixed with exhaust gas is 600 m1 per minute! , the temperature of the spiral tube 4 that decomposes the exhaust gas is set to 1000°C.
passed in 3 seconds.

The gas that has passed through the spiral tube 4 is passed through a solid alkali-filled tank 15 filled with granular caustic soda (special grade reagent manufactured by Wako Tsumugi Co., Ltd.) 2009 with a diameter of 5 mm to absorb hydrogen chloride (HCI). As a result of analysis using a gas chromatograph (Model 023), no unreacted halogenated hydrocarbons were found, and HC1! showed only slight o, oos and oxidation.

(Effects of the Invention) According to the present invention, halogenated hydrocarbons are completely decomposed and only harmless decomposition products can be discharged, and deterioration of the vacuum evacuation device can also be prevented.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing exhaust gas treatment in an embodiment of the present invention. Explanation of symbols 1...Flow control valve 2...Base material 3...^Frequency induction coil 4...Spiral tube 5...Electric furnace
7... Pressure reduction control valve 8... Vacuum pump 9
...Gas detector 10...Reaction chamber 11.
...Mixing chamber 12...Flow rate control valve 13...Air inlet 14...Backflow prevention valve 15...Solid alkali filling tank control...

Claims (1)

[Claims] 1. Halogenated hydrocarbon, which is characterized by mixing the exhaust gas containing the halogenated hydrocarbon with air, passing it through a heat treatment tube heated to 600°C or more for 3 seconds or more, and then passing it through a solid alkali-filled tank. A method of treating contained exhaust gas.