A cold test model study of the staged cascade fluidized bed coal combustion process is described. Proper cascade flow of solids through the system was found to be sensitive to bed and downcomer distributor plate pressure drops. Control of bed depth by weir level was also complicated at high fluidization velocities by the process of entrained particles falling back into the downcomer. Bed to tube heat transfer coefficients ranging from 142 to 256W/m2•K were measured at the top surface of a simulated boiler tube in shallow beds, 0.15 to 0.23m deep.

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