Experimental Comparison of Methane Pyrolysis in Thermal Plasma

Abstract

Methane pyrolysis via thermal plasma was investigated experimentally on a 2 kW DC arc plasma setup in argon atmosphere. Two widely applied methane pyrolysis profiles, i.e., pre-mixing methane and argon before fed into plasma torch, and injecting methane into pure argon plasma jet at torch outlet, were compared. Performances of methane pyrolysis regarding to methane conversion, acetylene selectivity, acetylene specific energy requirement (SER), and plasma stability were concluded. Results showed that pre-mixing methane and argon before fed into plasma torch would be efficient in converting methane and acetylene production, with higher conversion of methane and lower SER to acetylene at a given specific energy. Also, methane in arc zone would cause periodic fluctuations of plasma voltage and power, which could be reduced by controlling methane fraction in feed. On the other hand, when methane was injected into argon plasma jet at torch outlet, the energy efficiency in converting methane and producing acetylene would be lower. And the plasma would barely participate in the reaction other than providing heat, but the erosion of electrode was much slower and slighter. It was also validated that the SER of acetylene was limited by the thermal loss of the setup due to size-effect of reactor.