Steady-state kinetic model for solid-fluid reactions

Abstract

The model assumes (i) the reacting solid becomes covered by a coherent coating of solid products and (ii) the reaction may be poisoned by a sufficiently high concentration of outward diffusing material. The three kinetic regimes and their rate controlling processes are linear (surface decomposition of reacting solid), parabolic (inflow of fluid reactant), and joint (dual control by outflow of material and surface decomposition). For a large plane surface the model gives classical tarnishing kinetics plus the possibility of joint kinetics between the linear and parabolic regimes. For a discrete particle the reaction must start and finish linear, but otherwise, may be almost entirely parabolic or joint. For testing experimental data it may be convenient to use the approximation dF/d(tz)= kz(1−F)N/R, where z depends on both regime and particle shape.