Experimental Study of Organic Waste Gas Treatment by Microwave Plasma Generated at Atmospheric Pressure

Tri-benzene organic emission is a kind of toxic exhaust commonly produced in petrochemical industry. There are some characteristics, such as large emissions, low concentration, difficult centralized processing and decontamination. So, we set up a device to generate a large volume and stable microwave plasma at atmospheric pressure. The working gas could be nitrogen, oxygen or air with the gas flow rate of 0.3~10 L/min to generate the plasma. By experiments, we studied the effect of microwave propagation on the plasma characteristics under different working gas. Then p-Xylene exhaust gas was treated with three kinds of plasma. The results show that removal efficiency of p-Xylene is higher than 95% in different microwave power and gas flow rate, and the lowest treatment microwave power can be achieved by 1 000 W with a great performance. In the air plasma treatment condition, the p-Xylene concentration can be up to 2 400 mg/m³ with little incomplete oxidized production. However, the nitrogen oxides are generated as by-products during the reaction, which have to be passed to the alkali solution to be removed. The results show that atmospheric microwave plasma can efficiently and completely reduce the p-Xylene content of exhausts, and other similar organic compounds in the exhaust gas also have apparent removal efficiency. The method has great potential environmental protection industry.