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 C), total volumetric gas flow rate and methane content in the feed
gas (10–40%). Key measured performance outputs were CH4 conversion and H2 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.