Simulation of catalytic coal gasification in a pressurized jetting fluidized bed: Effects of operating conditions

• Hydrodynamic behaviors in grid zone change less at steam/coal ratio above 1.
• Methane concentration reaches the maximum at steam/coal ratio of 0.5.
• Carbon conversion increases significantly at low catalyst loading and moderately at higher one.
• Catalyst loading 10 wt.%, steam/coal ratio 1 and oxygen/coal ratio 0.3 are suitable.
• The order for methane yield is: O2/H2O/syngas > O2/H2O/N2 > O2/H2O/CO2.

A one-dimensional steady-state model of catalytic coal gasification, which was previously established in a pressurized jetting fluidized bed, is extended to investigate the effects of different operating conditions (catalyst loading, steam/coal ratio and oxygen/coal ratio) on hydrodynamic parameters, particle temperature, gas temperature, gas composition, carbon conversion and methane yield. The results indicate that the steam/coal ratio has significantly associated with hydrodynamic parameters. The maximum particle temperature changes obviously with steam/coal ratio and oxygen/coal ratio. Methane concentration goes up slowly when catalyst loading is above 10 wt.% and reaches maximum point when steam/coal ratio is about 0.5 by weight. Both the total carbon conversion and carbon conversion due to char gasification rise sharply as steam/coal ratio increases, while there are slow increase for both of them as catalyst loading and oxygen/coal ratio increase. The carbon conversion due to char combustion maintains at low level, and the methane yield decreases with the increase of catalyst loading, steam/coal ratio and oxygen/coal ratio. In conclusion, the suitable operating conditions for catalytic coal gasification are as follows: catalyst loading of 10 wt.%, steam/coal ratio of 1 and oxygen/coal ratio of 0.3. The maximum methane yield can be obtained by using the scheme of O2/H2O/syngas.