Numerical Analysis of Reaction Degradation for Three-dimensional Coke Pore Structure

Abstract

In order to investigate coke degradation behavior due to CO 2 gasification reaction in the blast furnace, mass transfer analyses with the reaction and stress analyses for coke considering its structure after the reaction were performed. Using the finite element method, CO 2 gas diffusion in a coke lump and consumption of coke matrices owing to the gasification reaction were considered for the coke model in which the actual coke structure was reproduced. The rate-controlling step was also evaluated calculating the Thiele modulus and the effectiveness factor of catalyst obtained from CO 2 concentration distribution in a coke lump. Further, stress analyses assuming a uniaxial tensile test were carried out for the coke model after CO 2 gasification reaction, and the effect of the gasification reaction on a stress state in a coke lump was investigated. As a result, the reaction progressed mainly in the vicinity of the external surface with reaction temperature of 1 673 K while it did uniformly in the whole coke lump with 1 273 and 1 473 K. Thus, the rate-controlling step shifted from the reaction-controlling step to the diffusion-controlling step with an increase in a reaction temperature, and the Thiele modulus and the effectiveness factor of catalyst also showed the same trend. From the stress analysis, coke strength decreased uniformly in the whole coke lump in case of the reaction-controlling step whereas it did mainly in the vicinity of the external surface in case of diffusion-controlling step.

Development of Analytical Method of Predicting Fissures Formation for Carbonization Process of Coke

“…Shohei MATSUO, 1) * Yasuhiro SAITO, 2) Yohsuke MATSUSHITA, 3) Hideyuki AOKI 3) and Hideyuki HAYASHIZAKI 3,4) distribution and thermal stress caused by the temperature gradient in the coke oven is necessary for the prediction of the formation of fissures during the carbonization of coke. Numerical analysis through models such as the finite element method (FEM) have been widely used to simulate the mechanical response of the coke, 6,[11][12][13] and for thermal stress analyses. 8,[14][15][16][17][18] Sato et al, 16) Goto et al 17) and Jenkins et al 8) performed the thermal stress analyses of coke models with major fissures using FEM and investigated the mechanism for the formation of fissures and factors that influence their spacing.…”

Three-dimensional Rapid Imaging and Shape Evaluation of Multiple Coke Particles

“…This imaging method is mainly used for non-destructive observation of the internal structure of materials. Microfocus X-ray CT has been used to observe the pore structure of coke, to investigate the effect of pore structure on strength or reactivity of coke, [16][17][18] and to observe the carbonization process. 19) Microfocus X-ray CT provides a resolution of several microns.…”

Hot Strength of Coke Prepared by Briquetting and Carbonization of Lignite

“…However, it was believed that the gasification of Coke D also occurred in a reaction-controlled regime. Numazawa et al 22,23) investigated reaction mechanisms of coke degradation by CO 2 , and they found that the rate-determining step changed from reaction rate to gas diffusion at 1100 ºC. Ono et al 16) showed that pore structure inside a coke after CO 2 gasification at 1100 ºC was uniform.…”