Behavior of alkaline species in coal combustion and gasification

To understand better the gas-vapor-particle system behavior in combustion and gasification, the aerosol dynamics during flue gas cooling have been modeled. The aerosol General Dynamic Equation is solved numerically by combining the methods introduced by Gelbard, Bunz and Ahluwalia et al. Particles are divided into n size classes each of which having different chemical composition. Basic physical interactions, i.e., nucleation, vapor condensation, coagulation and deposition are considered. The gas phase chemical composition is solved by assuming that at high temperatures the characteristic times for chemical reactions are short compared to the characteristic times for nucleation and condensation. The gas phase chemical equilibrium model is coupled to the overall aerosol model so that the changes in the local gas phase species concentration due to temperature decrease, vapor condensation, nucleation and deposition are recalculated after every time step. The governing number balance equation for a closed system of aerosol is solved numerically along with the gas phase and condensed phase conservation equations.