Abstract
Cokes in a blast furnace play an important role as a spacer for keeping gas permeability. Currently blast furnaces with large inner volume, exceeding 5000 m3, become common in Japan. Consequently, use of high strength coke is a crucial issue for modern blast furnaces. However, general methods for evaluating coke strength, for example drum test, are not enough for understanding the breakage behavior of cokes in detail. In order to evaluate the coke breakage behavior in blast furnaces, coke breakage model based on discrete element method (DEM) with cluster particles and bonds was developed.
According to the experiments of indirect tensile test, the tensile strength of cokes shows wide distribution because of the randomness of the coke pore arrangement. Then, the DEM simulation model for coke breakage was developed by considering pores with random position. DEM simulations of indirect tensile test condition, with 10 cases of random pore arrangement for each Coke A (small porosity) and Coke B (large porosity), were carried out. The tensile strength obtained from experiments and DEM simulations were compared by using Weibull analysis. The simulation results show an agreement with the experimental results including distribution of coke strength. Finally, the probability distributions of coke breakage obtained from Weibull analysis was applied to a DEM simulation result of material flow in 5000 m3 blast furnace and percentages of coke breakage at deadman region were evaluated for Coke A and B.
