Adhesion of solid particles to gas bubbles. Part 1: Modelling

Abstract

Particle-to-bubble adhesion is important in the areas of anti-foaming, in flotation processes and in multiphase slurry reactors. In the present work we particularly address the latter. The behaviour of fine catalyst particles adhering to gas bubbles in aqueous media is governed by the surface hydrophobicity. This adhesion on its turn influences the G–L mass transfer, bubble coalescence and the particle agglomeration. Existing models for the quantitative description of adhesion of particle to a G–L interface usually assume nonporous, spherical particles with a smooth surface and a well-defined contact angle. As catalyst particles are normally highly porous, have a rough surface, and an irregular shape, we developed a generalised model describing the adhesion of particles to a gas bubble based on maximum adhesive and cohesive forces as the main parameters. This model describes adhesion of: (i) a single spherical particle, (ii) a monolayer of particles, and (iii) a particle agglomerate. The cohesive forces between particles play a key role. For small cohesive forces, the particles can either adhere as a single particle or as a monolayer, while stronger cohesive forces allow multilayer adhesion or adhesion of particle clusters via one or few particles.