The conveying characteristics of powder material transport are investigated for a pilot-scale pneumatic conveyor. The experimental system is a closed-loop, dense-phase pneumatic transport system, incorporating an auxiliary air-assisted conveying line. Powder materials, such as cement, fly ash, pulverized coal and rawmeal have been conveyed and their suitability to conveyed in the dense phase is investigated. The air supply is achieved through axial and annular nozzles, in addition to an air supply through the solids feeding device, namely the blowtank. From a secondary pipeline, which runs parallel to the main conveying line, air is injected into the conveying pipeline at regular intervals. The power consumed in supplying compressed air through the different nozzles is evaluated and the effect of the phase density on the air supply through these nozzles is also estimated. A large number of experiments are carried out to identify the optimum combinations, such that the air mass flow rates and supply line pressures of air are low, resulting in less power consumption. Useful conclusions are drawn for design and layout of the auxiliary air-assisted pneumatic conveying system. © 1993.