The external or internal fluidized bed of large circulating fluidized bed(CFB) boiler is in fact a fine particle bubbling fluidized bed

and its gas-solid flow characteristics are different from those of the main combustion chamber. In this work

the distributions of the solids holdup

the velocities of the particles and the thicknesses of the particle boundary layers in the fine particle bubbling fluidized beds with different reflux structures and different layouts of the heating surfaces were studied by Eulerian-Eulerian approach incorporating the kinetic theory of granular flow. Some numerical results were compared with the experimental data to verify the accuracy of the numerical simulation model. The numerical results show that

when the inlet and the outlet of the particles were located on the opposite side of the fine particle bubbling fluidized bed

the movement of the particles in the fine particle bubbling fluidized bed was more intense. At the same time

when the layout direction of the heat exchange tubes was perpendicular to the direction of the particles flowing out of the fluidized bed from the reflux port

the heat exchange tubes could enhance the disturbance of the particle flow in the fine particle bubbling fluidized bed and inhibit the formation of the particle boundary layers on the side walls.