Modeling of coke particle breakage in blast furnace considering pore structure by discrete element method

Cokes play an important role in the blast furnace as a spacer for maintaining gas permeability. Since blast furnaces with large inner volumes exceeding 5 000 m3 are now common in Japan, use of high strength coke has become a crucial issue for modern blast furnaces. However, general methods for evaluating coke strength, for example, the drum test, are insufficient for understanding the breakage behavior of coke in detail. In order to evaluate the coke breakage behavior in blast furnaces, a coke breakage model based on the discrete element method (DEM) with cluster particles and parallel bonds was developed. According to experiments using the indirect tensile test, the tensile strength of cokes shows a wide distribution because of the randomness of the pore arrangement. Therefore, a DEM simulation model for coke breakage was developed considering pores with random positions. DEM simulations of the indirect tensile test were conducted for 10 cases of random pore arrangements for each of Coke A (small porosity) and Coke B (large porosity). The tensile strength obtained from the experiments and DEM simulations was compared by a Weibull analysis. The simulation results were in agreement with the experimental results including the distribution of coke strength. Finally, the probability distributions of coke breakage obtained from the Weibull analysis were applied to the DEM simulation result of the material flow in a 5 000 m3 blast furnace, and the percentage of coke breakage in the deadman region of the blast furnace was evaluated for Coke A and Coke B.