Investigation on The Hydrodynamic Properties in The External Loop of Circulating Fluidized Bed With a Loop Seal

The pressure balance and mass balance are influenced by the characteristics of different components in the loop of a circulating fluidized bed (CFB). Experiments were conducted in a 4.3 m high cold laboratory CFB test rig with a loop seal. With a fixed bed inventory and superficial gas velocity, the pressure drop of the loop seal decreased with increasing aeration, thus causing an increase in the solid circulation flux (Gs). Correspondingly, the pressure drop in the riser became higher with increasing Gs; the pressure drop of the cyclone had a non-linear relationship with Gs, and the transition point was determined in the experiment. Using the laser fiber and gas tracer method, hydrodynamic characteristics in the standpipe were directly measured. It was found that the pressure gradient, voidage, and solid height in the standpipe were affected by the pressure balance in the whole loop. By adjusting the gas flow rate and direction in the standpipe, the gas-solid slip velocity and pressure gradient changed correspondingly. Therefore, the standpipe could maintain the pressure balance and realize self-equilibrium of the loop by absorbing the pressure drop variations of other parts in the system