Abstract: As the upstream system of coal gasification process,the dense phase conveying of pulverized coal at high pressures directly affects the stabilization,reliability and safe operation of gasifier. The conveying characteristics of pulverized coal may be accordingly changed when the coal type of gasification is changed or blended with other types,which has a certain impact on the smooth operation of the pulverized coal conveying process. To study the operating characteristics of coal-providing system for a coal gasification unit,based on the mixed raw materials of a coal gasification unit,the characterization experiments were conducted on the powder fluidity through HR index and FF function. Then,the dense phase conveying experiments were done in the pipeline with inner diameter of 25 mm and 15 mm pipeline under the back pressure of 2,4 and 5 MPa.The influence law of the superficial gas velocity,and back pressure on the pulverized coal flow was discussed. Finally,the average fluctuation and maximum fluctuation of mass flow rate of the pulverized coal were used as evaluation index of stability for the pulverized coal conveying process and the fluctuation correlation between the various process parameters was compared and analyzed. The results show that the HR index of the raw coal is 1.42 and the FF function is 2-4. Combined with the fluidity classification table,the fluidity of the pulverized coal is located in the bonding area,but close to the easy fluidity area. With the increasing of superficial gas velocity,the mass flow rate of the pulverized coal first increases and then decreases,reaching the largest flow at the critical gas velocity. The pressure drop of particle phase decreases because the gas-phase pressure drop occupies the main body and the mass flow rate of pulverized coal starts to decrease after the apparent gas velocity exceeding the critical gas velocity. The back pressure has certain influence on the mass flow rate and flow-pattern transformation of pulverized coal. At the same superficial gas velocity,the back pressure increases and the pulverized coal flow has a downward trend,which is more obvious in the small pipeline with inner diameter of 15 mm. The higher the conveying pressure is,the more rapid the transition from dense phase to dilute phase is. According to the conveying phase diagrams of back pressure 2 and 4 MPa,the curvature of the phase diagram curve under 25 mm pipe diameter is about 2 times of that of the curve under 15 mm pipe diameter at the critical gas velocity. The average fluctuation and maximum fluctuation of mass flow rate of the pulverized coal can be used as evaluation criteria for transportation stability. Within the experimental range,the average fluctuation range of mass flow rate is less than 3%,and the maximum fluctuation range is less than 10%; the maximum fluctuation range of pulverized coal flow is about 3.4 times of the average fluctuation range,and the correlation coefficient between the two is 0.948.