Plasma-Augmented Fluidized Bed Gasification of Sub-bituminous Coal in CO 2 –O 2 Atmospheres

Abstract The gasification of a sub-bituminous coal using CO 2 –O 2 gas mixtures was studied in a plasma-augmented fluidized bed gasifier. Firstly, the coal was chemically characterized and the gasification process was examined using Thermogravimetric and Differential Thermal Analysis (TGA/DTA) in CO 2 , O 2 and at a CO 2 to O 2 ratio of 3 to 1. Secondly, the equilibrium gas compositions were obtained using the Gibbs free energy minimization method (HSC Chemistry®7). Thirdly, gasification tests were performed in a plasma-augmented fluidized bed and the off-gas temperatures and compositions were determined. Finally, for comparison purposes, control tests were conducted using a conventional fluidized bed coal gasifier and these results were compared to those achieved in the plasma-augmented fluidized bed gasifier. The effects of bed temperature and CO 2 to O 2 ratio were studied. For both gasifiers, at a given bed temperature, the off-gas compositions were in general agreement with the equilibrium values. Also, for both gasifiers, an experimental CO 2 to O 2 ratio of about 3 to 1 resulted in the highest syngas grade (%CO + %H 2 ). Both higher off-gas temperatures and syngas grades could be achieved in the plasma-augmented gasifier, in comparison to the conventional gasifier. These differences were attributed to the higher bed temperatures in the plasma-augmented fluidized bed gasifier.