The differential pressure of combustion chamber reflects the amount of the materials concentration of the suspending section at the bottom of the fluidized bed, namely the dilute phase zone. A certain differential pressure of combustion chamber is corresponding to a certain boiler output. The higher the differential pressure of combustion chamber is, the bigger the boiler output is, and vice versa.  The differential pressure of combustion chamber during normal operation is about 300-800Pa. When the differential pressure of the combustion chamber rises, the circulating ash increases and the burden of the returns feeder is increased, therefore during normal operation, the differential pressure of the combustion chamber must be reasonably controlled. If the differential pressure is too high, the returns feeder will be blocked by ash; if the differential pressure is too low, the boiler output will be insufficient.