(70g) Simulation of Hydrogen and Acetylene Production By Methane Pyrolysis in Thermal Plasma

Rehmet, C. - Presenter, Tsinghua University
With the recent shale gas disposal and increase of biogas production, acetylene production from methane could play an important role in near future. Indeed, gas pyrolysis by thermal plasma can produce competitive hydrogen and acetylene for PVC production. Besides, acetylene could be converted to ethylene and ethylene to synfuel which can be an attractive gas to liquid solution to produce transportable fuel [1]. A closer process has been already massively set-up and used in Germany before and after Second World War to produce synthetic rubber and hydrogen for coal hydrogenation process [2]. Recently, we have done many experiments converting coal or liquid hydrocarbons to acetylene by thermal plasma with satisfied performances [3]. However, acetylene is unstable at medium temperature and can convert to tar and oil in about 2 ms and then, the pyrolysis products should be cooled rapidly. Cold gas/liquid hydrocarbons can be used as quenching media to increase the yield of ethylene, i.e. a desired by-product. In order to improve the process efficiency, a deep study has been carried out based on experimental and numerical simulation with methane used as feedstock.

The experimental results show that the methane conversion through both plasma devices is higher than 90% and leads mainly to acetylene and hydrogen with high yields. Also, few-layers graphene have been obtained in most of the cases. This investigation suggests that such a simple technique is easy to operate and suitable for mass production of acetylene and few-layer GNs in a scalable process. To improve and have a better understanding of our lab experimental set-up, a numerical model has been established. The plasma is considered using a MHD model. The reaction kinetics and carbon nanoparticle formation have been considered in a sophisticated model. A parametric study has been made on plasma power and hydrogen/methane ratio. The plasma parameters and the hydrogen ratio could be adjusted to improve the acetylene formation and the graphite nanosheets formation