Effectiveness factors and instability in non-catalytic gas-solid reactions: the effect of solid heat capacity

Non-isothermal non-catalytic gas-solid reactions of the general type aA_gas + B_solid ? gG_gas + sS_solid are discussed, the theoretical treatment being based on the well-known pseudo-steady-state 'sharp interface' or 'shell progressive' mechanism. Reaction rates and rates of mass and heat transfer are developed in terms of the rate of production of product gas at the reaction interface in a sphere of reaction solid. Solution of the dimensionless equations is achieved by finite difference computation. Corresponding equations for the infinite cylinder and the slab are presented. White steady-state mass balances are assumed, a simple transient term is introduced into the energy balance to avoid instantaneous temperature changes, and to rationalise the analysis of instability. The importance of this transient term is illustrated. © 1968.