Non-catalytic fluid-solid reactions are of common occurrence in chemical and metallurgical industries, pollution abatement, manufacture of "skeletal" catalysts like Raney nickel, to name a few applications. A new version of the grain model for analyzing the kinetics of this category of reactions has been presented in this paper. The model allows variation with conversion in the size distribution of the grains constituting the reactant solid particulates. This methodology has built in automatic variation of porosity, specific surface area and other pertinent structural parameters characterizing the porous particle and does not require a priori assumption of any relationship between porosity and conversion, thus widening the scope of model applications. The model was tested successfully by applying it to predict accurately the conversion-time behavior for well-known examples of gas-solid reactions wherein, given the density difference between the product and the reactant, grains grow and the reactions are known to "die-off' prematurely. The model also predicted remarkably well the final structural properties of Raney Ni catalyst particles in a laboratory process of its preparation from Raney Ni-Al alloy by selective leaching of Al with alkali. (C) 2004 Elsevier B.V. All rights reserved.