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

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 CH4to C2H2was 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 N2and CO2was 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 N2and CO2should be present before pyrolysis. Both input power and feed rate had considerable effect on the pyrolysis of the simulated coke oven gas, and a C2H2selectivity 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