Vertical pneumatic conveying in dilute and dense-phase flows: Experimentalstudy of the influence of particle density and diameter on fluid dynamic behavior

In this work, the effects of particle size and density on the fluid dynamic behavior of vertical gas-solid transport of Group D particles in a 53.4 mm diameter transport tube were studied. For the conditions tested, the exper imental curves of pressure gradient versus air velocity presented a minimum pressure gradient point, which is associated with a change in the flow reg ime from dense to dilute phase. The increases in particle size from 1.00 to 3.68 mm and in density from 935 to 2500 kg/m(3) caused an increase in pres sure gradient for the dense-phase transport region, but were not relevant i n dilute transport. The transition velocity between dense and dilute flow ( U-min) also increased with increasing particle density and diameter. An emp irical equation was fitted for predicting transition air velocity for the t ransport of glass spheres. Additional experiments, covering a wider range o f conditions and particles properties, are still needed to allow the fittin g of a generalized equation for prediction of U-min.