Solar thermal cracking of methane in a particle-flow reactor for the co-production of hydrogen and carbon

An experimental investigation on the thermal decomposition of CH4 into C and H2 was carried out using a 5 kW particle-flow solar chemical reactor tested in a solar furnace in the 1300–1600 K range. The reactor features a continuous flow of CH4 laden with μm-sized carbon black particles, confined to a cavity receiver and directly exposed to concentrated solar irradiation of up to 1720 suns. The reactor performance was examined for varying operational parameters, namely the solar power input, seed particle volume fraction, gas volume flow rate, and CH4 molar concentration. Methane conversion and hydrogen yield exceeding 95% were obtained at residence times of less than 2.0 s. A solar-to-chemical energy conversion efficiency of 16% was experimentally reached, and a maximum value of 31% was numerically predicted for a pure methane flow. SEM images revealed the formation filamentous agglomerations on the surface of the seed particles, reducing their active specific surface area.