Kinetic modelling of methane decomposition in a tubular solar reactor

Solar methane cracking is a promising pathway to produce hydrogen and carbon black with the bonus of zero CO2 emission. A kinetic simulation of the methane decomposition in a tubular solar chemical reactor prototype is presented. This reactor is composed of four independent tubular reaction zones inserted in a graphite cavity receiver. Chemical reaction modelling is carried out thanks to the Dsmoke software, using a detailed kinetic scheme for the wide range modelling of alkane transformation. First, a kinetic analysis of the chemical system is presented to determine the sequence of methane cracking and a sensitivity analysis of the results on temperature (in the range 1500–2300 K) and on natural gas composition is performed. Then, a kinetic simulation of the solar reactor is proposed and implemented, in which each tubular reaction zone is modelled by three plug-flow reactors in series representing the pre-heating, isothermal, and cooling zones of the reactor. It predicts the evolution of gas species concentrations as a function of residence time. Comparisons with experimental results between 1670 K and 1770 K show good agreement for CH4 conversion, and CH4 and H2 off-gas compositions.