A new design approach for the acceleration region of vertical, dilute-phase pneumatic conveyors

An analysis has been completed for a comprehensive set of pressure drop data from the acceleration region of seven vertical, dilute-phase pneumatic conveyors. The data provided are for materials with terminal velocities from 2.05 to 22.4 m/s conveyed in risers with heights from 3 to 11.2 m and internal diameters from 0.028 to 0.083 m. Particle velocities derived from the pressure drop data were used to develop an equation of motion that includes terms for terminal velocity, and the distance traveled from the feed point. Despite covering a range of conditions, no effect of other variables was identified. Particle velocities were predicted by the equation of motion and used to calculate total pressure gradients that are within 97 Pa/m (95% confidence limits) of the measured values. The voidage correction of gas and terminal velocities recommended by other studies did not improve the pressure drop predictions. The spreadsheet model developed is simpler than the available complex numerical models and provides more accurate results. Acceleration lengths are longer than allowed for in many studies, and erstwhile established-flow data and correlations likely contain acceleration effects.