Combined steam and CO2 reforming of CH4 for syngas production in a gliding arc discharge plasma

To reduce soot formation during the CO2 reforming of CH4 and to optimize the H-2/CO ratio of produced syngas, the combination of steam and CO2 reforming of CH4 (SDMR) in a gliding arc discharge (GAD) plasma reactor is investigated. The effect of the addition of steam on gliding arc discharge characteristics, methane reforming performance, and SDMR at varying CH4 /CO2 molar ratios are discussed. When the steam-to-carbon (S/C) molar ratio increases from 0 to 2.3, the CH4 conversion and energy conversion efficiency of syngas production (ECEsyngas) increase initially and then decrease, reaching their maximum values (55.6 % and 36 %, respectively) at an S/C ratio of 0.58. The increased number of OH radicals and H atoms generated from H2O in the plasma promotes CH4 dissociation, H-2 selectivity and H-2 yield. The H-2/CO molar ratio increases from 0.76 to 1.1. The addition of steam significantly suppresses the soot formation, allowing the CH4/CO2 molar ratio to range between 1/3 and 3/1 with a carbon balance of > 82 % and a broadly adjustable H-2/CO ratio (ranging between 0.4 and 3.0). The ECEsygas decreases while the energy conversion efficiency for fuel production (ECEfuel) increases alongside increasing CH4/CO2 molar ratios. The ECEfuel peaks at 49.3 % at a CH4/CO2 molar ratio of 3/1. Acetic acid is the primary constituent of the resulting liquid product. A possible reaction mechanism of SDMR is also proposed.