Hydrogen-rich syngas production through coal and charcoal gasification using microwave steam and air plasma torch

In the present study, microwave plasma gasification of two kinds of coal and one kind of charcoal was performed with various O2/fuel ratios of 0–0.544. Plasma-forming gases used under 5 kW microwave plasma power were steam and air. The changes in the syngas composition and gasification efficiency in relation to the location of the coal supply to the reactor were also compared. As the O2/fuel ratio was increased, the H2 and CH4 contents in the syngas decreased, and CO and CO2 increased. When steam plasma was used to gasify the fuel with the O2/fuel ratio being zero, it was possible to produce syngas with a high content of hydrogen in excess of 60% with an H2/CO ratio greater than 3. Depending on the O2/fuel ratio, the composition of the syngas varied widely, and the H2/CO ratio necessary for using the syngas to produce synthetic fuel could be adjusted by changing the O2/fuel ratio alone. Carbon conversion increased as the O2/fuel ratio was increased, and cold gas efficiency was maximized when the O2/fuel ratio was 0.272. Charcoal with high carbon and fixed carbon content had a lower carbon conversion and cold gas efficiency than the coals used in this study.

► Microwave plasma gasification of coals and charcoal was performed. ► The hydrogen and methane contents in the syngas increased with the O2/fuel ratio decreased. ► Syngas with high hydrogen content exceeding 60% was produced by using steam plasma torch. ► H2/CO ratio in the syngas can be easily adjusted by changing the O2/fuel ratio. ► The maximum cold gas efficiency was shown when the O2/fuel ratio was 0.272.