Abstract: A process whereby particulate materials with a polymeric coating of controlled thickness are obtained by passing gas at a pre-determined temperature and flow rate substantially symmetrically through a bed of particles to create a coherent symmetrical spouting zone of fully-spouted, suspended particles is disclosed. The suspended particles are contacted with an atomized spray of polymer solution. The spray has a controlled flow rate and is confined to the spouting zone. As the process proceeds, the solvent evaporates from the fine droplets of the polymer solvent solution on contact or very quickly after contact of the polymer solvent solution with the particles. Structurally sensitive particulate material such as biomass is therefore only fleetingly contacted with solvent, on its outer shell only, and no substantial damage to the material can be effected by the solvent. Also, the coating solidifies quickly so that the little or no particle agglomeration or attrition occurs.