Movement and Mixing of Biomass or Coal Particles in a Fluidized Bed Combustor Under High Temperatures

The combustion characteristics of a single fuel particle in fluidized beds are widely studied. However, in most simulation of the single particle combustion in fluidized beds, the particle is always assumed to be staying in the emulsion phase, which is quite different from the real motion characteristics. Monitoring the motion characteristics of fuel particles at different positions in the furnace is of great significance for understanding the conversion process of fuel in the fluidized bed. In this work, the motion characteristics of a single fuel particle (coal or biomass) at different locations (the emulsion phase and the splash zone) were investigated in a 2D visualized fluidized bed combustor. The movement during its real combustion process, including devolatilization and char combustion, was recorded with a high-resolution video camera. It is found that the motion characteristics of different fuel particles are significantly different. Residence time in the emulsion phase of coal char particles was longer than that of biomass char particles. In the devolatilization process, the particles stay most of the time in the emulsion phase. As the char combustion continued, the particle density decreased and the char appeared more in the splash zone or floated on the surface of the bed. With increasing the fluidizing velocity, the time share of the char particle in splash zone increased. The residence time of the particles in the emulsion phase was increased with the particle size improved.