Axial transport of granular solids in rotating cylinders. Part 2: Experiments in a non-flow system

Abstract

Experiments are reported here on the axial mixing of sodium carbonate and sodium bicarbonate in a batch, horizontal, rotating cylinder. The results show the effect of hold-up, particle size and speed of rotation on the axial dispersion coefficient and are interpreted in terms of the stochastic transport model recently proposed by the authors. A complementary approach invoking a surface diffusion coefficient in the thin cascade layer is also presented and applied to the data. This surface diffusivity forms a more fundamental transport parameter than the axial dispersion coefficient, and collisional theories of rapid flows of solids should provide a suitable route for its prediction. Correlations are developed here which relate the maximum angular deviation (defined in Part I), and the surface diffusion coefficient, with the characteristic translational kinetic energy and describe well the effect of variations in particle size, hold-up and speed of rotation.