The investigation of U-type nonmechanical recycling valve is carried out on a cold-circulating fluidized bed (CFB) test facility. The size of the cross section of the valve is used to study the influence of the structural characteristics of the cross section on the return characteristics of the U-type valve. The influence of horizontal opening of U-valve on solids circulating rate are also studied. When the fluidizing gas velocity is constant
the solid circulating rate increases linearly first and then reaches constant. At a given loosing gas rate
the maximal circulating rate of system depends mainly on the fluidizing gas velocity. The optimized opening ratio of the horizontal section is about 25% cross section area of the standpipe.
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