Gas Velocity Range of Stable Operation in a Gas-Solid Multistage Fluidized Bed with Overflow Standpipes
溢流管式多层气固流化床稳定操作气速范围的影响因素

The variation of gas velocity range of stable operation with major configuration and operating parameters in a gas-solid four-stage fluidized bed with overflow standpipes was studied.The tested parameters included the particle feeding rate,opening ratio and orifice size of gas distributor,inner diameter of overflow standpipe,and type and size of particles.The results showed that the minimal gas velocity(Umin) for stable operation increased with increase in the particle feeding rate,opening ratio of gas distributor and size of the treated particles,while it decreased with increase of the inner diameter of overflow standpipes and was independent of the orifices size of gas distributor.The maximal gas velocity(Umax) of stable operation increased with increase of the particle size and opening ratio and orifices size of gas distributor but decreased with increase of the inner diameter of overflow standpipes.For the tested silica sand and coal particles,Umax increased with increase of the particle feeding rate,but it was almost a constant when the superficial particle velocity was over 1.0×10-4 m/s.The threshold gas velocity ratio(Umax/Umin) of silica sand was about 3 times of that of coal,indicating that the operation flexibility of gas velocity for silica sand was higher than that of coal probably due to the poor particle fluidity of coal with high moisture.