Kinetics and heat transfer analysis of carbon catalyzed solar cracking process

Abstract

Solar thermochemical processing offers production of many fuels and commodities via reduced emission footprint. Although solar reactor design and flow configuration play a key role in process efficiency, use of the right catalyst further enhances the overall efficiency. Solar cracking of methane provides an excellent example of the direct effect of carbon catalyst on the heat transfer which in turn affects the feedstock decomposition rate. In this paper, a compilation of our research results on the testing of carbon catalyst using thermogravimetry, and its impact on the heat transfer are summarized along with a thorough kinetics analysis of methane decomposition. It is seen that carbon seeding uniforms the reactor temperature and the volumetric heating caused by the suspended carbon particles substantially improves the reactor performance. 37 chemical gas-phase reactions and rate constants were considered to simulate the non-catalyzed methane cracking, whereas 8 chemical surface reactions and rate constants were considered for methane cracking with carbon catalyst. As for the heat transfer analysis, thermal interaction of gas-particle flow and the thermal hydraulics between gas flow and particle were studied by two way coupled Euler-Lagrange approach. Discrete ordinate model was used to solve radiative transport between reactor walls and entrained particles. The results show that when carbon loading is increased from 0.2 g/min to 0.6 g/min, the product gas temperature reduces from 1121 K to 1010 K, whereas mass fractions of methane shows 30% increase in efficiency.