Numerical modeling of grinding rate in granular flow of brittle materials

In an iron-making blast furnace, an operation with pulverized coal injection (PCI) causes an accumulation of powder by crushing between coke particles and decreases permeability through the coke bed. It is so difficult to measure a mount of coke powders, so we developed a model to simulate a grinding rate with movements of particles of brittle material such as coke using Discrete Element Method (DEM). In order to estimate the performance of our simulation model, we carried out the mutual friction of grinding test with two gypsum areas, and derived the grinding rate equation for the simulation model from the experimental results. The grinding rate of gypsum particles in a rotational drum was measured and calculated with various porosities of gypsum and the rotational speed of the drum. As a result, the difference between predicted and measured grinding rate was larger in the case that the particle porosity was small (i.e. particle is hard) and a rotational speed of drum is high because we ignored the body breakage at contact between particles. On the other hand, the calculated grinding rate was the same as experimental one when the particle porosity was large (i.e. particle is soft.). It is concluded that DEM is useful tool for the prediction of grinding rate of particles. We expect the developed model to predict the grinding rate of coke particles in a raceway. However we might consider not only friction but also the body breakage in the simulation model to determine the correct grinding rate.