The formation mechanism of CO2 and its conversion in the process of coal gasification under arc plasma conditions

The carbon dioxide (CO2) formation mechanism and co-conversion of CO2 with coal was investigated in the process of coal gasification in a steam medium at atmospheric pressure under arc plasma conditions in a tube-type setup. The arc plasma was diagnosed in situ by optical emission spectroscopy and the gas products were analysed by gas chromatography. CO2 yields are correlated with the quantitative emission peak intensity of the active species in plasma when the operating parameter is changed. The results show that the greater the emission peak intensity of the CH radicals, C-2 radicals, OH radicals or O atoms, the smaller the CO2 yield is, which means that the CO2 formation process is inhibited by increasing the concentration of the mentioned active species under arc plasma conditions. On the basis of the diagnosis results, co-conversion of CO2 and coal in a steam medium under plasma conditions was carried out in the same setup and the results show that CO2 conversion reaches 88.6% while the concentration of CO + H-2 reaches 87.4%; at the same time, coal conversion is in the range 54.7 - 68.7%, which proves that co-conversion of CO2 and coal in a steam medium under plasma conditions might be a prospective way to utilize CO2 and the production of synthesis gas.