Experimental and theoretical evaluation on triple thermal plasma pyrolysis of methane to hydrogen and solid carbon

The plasma pyrolysis of methane is notable technology to produce hydrogen because the thermal plasma is a flexible energy source and appropriate for the endothermic process [1]. Among various thermal plasma sources, direct current (DC) thermal plasma has a strong turbulent flow allowing starting materials to enhance mixing with plasma. The triple thermal plasma process has been applied for nanomaterial synthesis and exhibited the advantages notably [2]. Y. H. Lee et al. [3] applied the triple thermal plasma to the pyrolysis of methane and indicated the remarkable performance by comparing it with other DC thermal plasma processes. Nevertheless, it was insufficient to analyze the methane conversion mechanism. In addition, a large amount of acetylene was produced, causing the efficiency of hydrogen production to be reduced. For this reason, the process must be evaluated and optimized using various analysis methods. Therefore, this work evaluated the triple thermal plasma pyrolysis of methane to hydrogen and solid carbon by employing experimental and theoretical works. The conversion rate of methane and selectivities of each product were analyzed by varying the methane flow rate at a fixed power supply of approximately 30 kW, and the specific energy requirement (SER) per 1 kg of hydrogen was estimated to find the optimized condition. Furthermore, the thermal flow in the reactor with plasma was estimated using the computational fluid dynamics (CFD) software, Fluent (Ver. 2019 R2) by ANSYS Inc. The calculated temperature and velocity distributions were employed to theoretically understand the methane conversion mechanism. In addition, the energy balance was analyzed to find the optimized condition.