Effect of Nitrogen/Oxygen Substances on the Pyrolysis of Alkane-Rich Gases to Acetylene by Thermal Plasma

Abstract

It is important to convert alkane-rich gases, such as coke oven gas, to value-added chemicals rather than direct emission or combustion. Abundant nitrogen/oxygen substances are present in the actual alkane-rich gases. However, the research about how they influence the conversion in the pyrolysis process is missing. In this work, a systematic investigation on the effect of various nitrogen/oxygen-containing substances, including N2, CO, and CO2,on the pyrolysis of CH4 to C2H2 was performed by a self-made 50 kW rotating arc thermal plasma reactor, and the pyrolysis of a simulated coke oven gas as a model of alkane-rich mixing gas was conducted as well. It was found that the presence of N2 and CO2 was not conducive to the main reaction of alkane pyrolysis for C2H2, while CO, as a stable equilibrium product, had little effect on the cracking reaction. Consequently, it is suggested that a pretreatment process of removing N2 and CO2 should be present before pyrolysis. Both input power and feed rate had considerable effect on the pyrolysis of the simulated coke oven gas, and a C2H2 selectivity of 91.2% and a yield of 68.3% could be obtained at an input power of 17.9 kW.

Keywords

• thermal plasma
• pyrolysis
• alkane-rich gas
• acetylene
• coke oven gas