Extension of the linear driving force-dusty gas model approximation to include surface or micropore diffusion

This paper presents linear driving force approximations for the dusty gas model in a bisolute system obeying linear or Langmuir isotherms, in two situations: when there is a nonnegligible surface flux in parallel with the diffusive and convective fluxes; and when there is a micropore resistance to mass transfer in series. The approximations were developed using a semi-empirical procedure that starts with the particle response to a square wave perturbation considering a simple diffusion/convection mechanism, and proceeds by consecutive corrections to this basic result. These corrections are obtained using superposition, similarity and pattern recognition. The approximations are good (average quadratic error ⩽10%) when representing the system cyclic steady state, whether the perturbations are sharp or smooth.