Spouted bed, as one of the typical fluidization reactors, has been widely used in agriculture, food, pharmacy, energy, environment, chemical, nuclear technology and many other fields, with showing the commercial successes in a variety of physical operations such as drying, blending, granulation, cooling, coating, as well as the attractive prospect in the thermochemical processes including coal gasification, resourced utilization of biomass, oil shale pyrolysis, iron ore reduction, petroleum catalytic cracking, etc. Nevertheless, up to today, our knowledge on spouted bed is still very limited, especially in the aspects on the gas-solid dynamics of non-spherical particles and the scaleup, leading to numerous difficulties in scaling design and configuration optimization. The present work is devoted to revealing complex gas-solid flow characteristics and scaling relationships by experimental and simulated approaches.
Spouted bed experimental system was established and the spouting behaviors of the mixtures of cylindroid particles and spherical bed materials were investigated. Results found in the spouted bed with two particles, the spouting and mixing usually synchronously develop, and when the spouting is well established, two particles in the bed are easy to achieve fulling mixing. The detailed relationships between spouting characteristics and the operating conditions were also obtained. Based on relationships, two different non-spherical particle spouting systems, i.e., the spouting system functioned by non-spherical particle and the spouting functioned by bed materials were proposed.
The CFD-DEM modelling for spouting cylindroid particles was significantly improved in the current dissertation. The perfectly cylindroid particle was represented with the combined geometric elements method and by fully analyzing the various contact criterions between cylindroid surface, flats and edges and improving the syamlal-Obrien drag model, and thus calculating the contact forces between cylinders and interaction force between cylinders and gas more accurately, the CFD-DEM simulation on “turbulent gas phase + real cylinders + spouting” was first achieved. Based on the CFD-DEM simulations, the effects of particle shape on the spouting characteristics were investigated in the particle scale.
The numerical scaleup and design method were developed. By directly predicting the gas-solid flow behaviors in large-scale spouted bed, the relationship between the minimum spouting velocity and the particle properties, bed structures and operating conditions were systematically studied and a new correlation was proposed. Lastly, the numerical scaleup and design method was used to design an industrial scale biomass-carrier mixer.