Simulations on mixing behaivors of superheated steam, heat-carrier and biomass particles

A three-dimensional Eulerian-Eulerian multiphase model (two-fluid model, TFM) was developed to simulate the three-phase mixing behaviors of superheated steam, heat-carrier and biomass particles in an industrial-scale spout-fluid bed mixer. The superheated steam was treated as continuous primary phase simulated by the k-ε two-equation turbulent model, while the heat-carrier and biomass were treated as two different secondary phases, and their viscosities and pressures were provided by the Kinetic theory of granular flow. The interactions between gas phase and each solid phase are described by Symbol-O'Brein drag model, while the interaction between two solid phases is described by morsi-alexander model. Heat transfers between gas phase and solid phases were calculated by Gunn model. Based on above models, the mixing effectiveness of the mixer was valuated and the effects of material properties on the heat transfer between phases were numerically investigated. Results show that the mixing effectivenss of spout-fluid mixer can reach over 70% and the final temperature of biomass is most sensitive to the size of biomass particle.