Hydrogen Evolution from Hydrocarbon Pyrolysis in a Simulated Liquid Metal Bubble Reactor

Abstract

The evolution of hydrogen from methane decomposition in a liquid metal bubble reactor (LMBR) has become a recent subject of interest; this study examines a novel approach to hydrogen production from pyrolysis of complex hydrocarbon fuels. Modeling hydrocarbon fuel decomposition in an LMBR is executed in two stages of pyrolysis: First, primary pyrolysis intermediates are simulated using a functional-group-based kinetic model (FGMech). Then, a detailed high temperature mechanism (AramcoMech 1.3 + KAUST PAH + 5 solid carbon chemistry) is applied to simulate secondary pyrolysis of intermediates. The quantities of major products of the secondary pyrolysis simulation (CH4, H2, Cs, C6H6) are approximated by simplified regression equations. Further decomposition of smaller hydrocarbons (until exiting the reactor) is simulated using a coupled kinetic and hydrodynamics model that has been reported in the literature. The mixing effects of bubble coalescence and breakup are investigated in a comparative study on homogeneous and non-homogeneous reactors. Finally, a qualitative relationship between H2 yield per mass of fuel, functional group, and other factors such as temperature, pressure, and residence time is analyzed. In general, the H/C ratio and cyclic/aromatic content are the main features influencing total conversion to H2.