Experimental study on dense-phase pneumatic conveying of coal powder at high pressures

Clean utilization and conversion of coal resources is significant to China’s energy sustainable development. Entrained-flow coal gasification technology is an important method used for clean and efficient conversion of coal. The characteristics and stability of high-pressure dense-phase pneumatic conveying of pulverized coal is crucial to the safe and stable operation of dry-feed entrained-flow coal gasifiers. Dense-phase pneumatic conveying experiments were carried out using a high-volatile bituminous coal in pipes with diameters of 25, 15 and 10 mm, respectively, and at back pressures of 1.0–4.0 MPag. The conveying characteristics and effects of operating and structure parameters were studied. Pressure drop models were established for horizontal and vertical upward conveying. The prediction uncertainty was within ±30% for the horizontal conveying and ±20% for the vertical upward conveying. The relative standard deviation of solid flow rate was proposed to explain conveying stability. The effect of operating parameters on conveying stability was systematically analyzed. The gas velocity-related criterion was proposed for stable conveying.