The characteristics of pressure fluctuation in a standpipe at negative pressure gradient were investigated based on measurement in the gas-solid two-phase circulating fluidized bed(CFB).When the solid particles flowed downward from low pressure part to high pressure part in the standpipe, the particles compressed the gas entrained by them, which resulted in the instability of gas-solid two-phase flow.This instability was shown as pressure fluctuation, undulating particle velocity and uneven concentration.The range of pressure fluctuation was related to the negative pressure gradient in the standpipe.
