Prediction of hopper discharge rates of binary granular mixtures

Measured flowing densities of binary mixtures of equal-solids density near-spherical granules discharging from a hopper are correlated with static densities calculated using the linear-mixture packing model developed by Yu and Standish. This correlation is used in a modified form of the Beverloo equation to predict the rate of discharge of solid materials through a hopper orifice. The so-called 'empty annulus' effect in the modified Beverloo equation is related to statistical mean particle sizes representing binary mixtures. A general equation is developed in two forms, the first is universal, encompassing both segregating and non-segregating systems, and the second is specific to non-segregating systems. They can be used to calculate hopper discharge rates for binary mixtures without need for experimental data. Both are found to correlate closely with experimentally measured discharge rates. (C) 1998 Elsevier Science Ltd.