A drop-tube particle-entrained flow solar reactor applied to thermal methane splitting for hydrogen production

A solar chemical reactor with continuous particle feeding in a tubular absorber has been designed and tested for CO2-free hydrogen production from thermal methane decomposition. The entrained-flow reactor was operated on sun with carbon black particle injection in a stream of methane diluted in argon. The carbon particles are expected to act as a catalyst for the dissociation reaction and the indirect irradiation via an intermediate opaque tubular absorber results in a more uniform heating of the reactor volume and thus an easier reaction temperature control and determination. The effect of particle injection on the reactor performance was investigated as a function of the type of carbon black catalyst and characteristics, reaction temperature (1150-1400 degrees C), total volumetric gas flow rate and methane content in the feed gas (10-40%). Key measured performance outputs were CH4 conversion and H-2 yield, C2H2 outlet concentration, and solar-to-chemical reactor efficiency. The particle feeding did not drastically improve the methane decomposition rate and hydrogen yield, which can presumably be attributed to kinetic limitation due to short particle residence time in the high-temperature region. Likewise, the inlet methane mole fraction was not a primary influencing parameter. In contrast, the temperature and the gas flow rate strongly affected the methane decomposition rate. (C) 2015 Elsevier Ltd. All rights reserved.