Kinetics of pinewood sawdust pellets gasification by carbon dioxide and steam at excess pressure.

The paper presents the results of pinewood sawdust pellets gasification in atmosphere of carbon dioxide and steam at pressure varied in range 1-5 bar. The initial sawdust was dried at atmospheric air and pressurized into cylindrical pellets by cold pressing method. The dependences of sample mass on time at different temperatures and pressures were obtained as well as apparent kinetic parameters of heterogeneous gasification reactions in isothermal conditions. The activation energy and frequency factor for carbon dioxide was found to decrease with pressure from 108.6 kJ/mole at 1 bar to 83.1 kJ/mole at 5 bar. This could indicate non-zero order of reaction by gaseous reactant and more developed porous structure of char formed at high pressure. Opposite results were obtained for steam – activation energy was found to increase with pressure from 32.4 kJ/mole at 1 bar to 49.0 kJ/mole at 5 bar. This could be attributed to diffusional resistance of gasification products formed in the vicinity of the sample. [ABSTRACT FROM AUTHOR]