The unstable problem of dropping pulverized coal flow from impeller type feeder has been analysis.Results show that the unstable dropping pulverized coal flow from the feeder is related to large fluectuation of positive pressure in the outlet pipe of pulverized coal

and the fluctuation can't be effectively conducted to the upper gap of pulverized coal deposited in the measuring impeller.The main factors affecting the dropping pulverized coal flow are the static pressure in the outlet pipe

and the viscosity of pulverized coal.Reducing the static pressure in the outlet pipe

decreasing the viscosity of pulverized coal or increasing the acting force from the outside

can enhance the stability of dropping pulverized coal flow from the impeller type feeder.