Theoretical and experimental investigation on angle of repose of biomass–coal blends

The angle of repose of granular materials has been extensively studied, for it is a very important macroscopic parameter in characterizing the flowability of granular materials. The primary objective of the work is to develop a linear model, and to propose a quantitative expression about the angle of repose (ΦR) of mixed granular system, which gives a qualitative understanding of the influence of physical parameters on mixed granular flow behavior. The results show that the variation amplitude of tangent ΦR is linear with the related particle physical properties (density, particle size and secondary particle mass fraction). It is shown that the most important parameters determining the mixed granular system angle of repose are density variation and surface roughness for the similar particle size. In addition, whether the particle size of base particle material or secondary particle varies or not, the linear relationship always exists. And the slope k is determined primarily by particle shape and surface friction coefficient.