Industrial scale fixed bed processes are largely conducted at modest to high values of the particle Reynolds number. Laboratory fluid-solid fixed bed studies, including catalyst rate measurements, are carried out often at Re-p<0.1, a flow regime largely devoid of fluid-particle transport data and correlations. From a study of methyl iodide adsorption over charcoal it is shown that it is possible to use the transient breakthrough behaviour of a well-mixed recycle absorber to analyse gas-particle film coefficients where standard experimental models are not effective.