Reaction Kinetics of Coke and some Carbonaceous Materials with CO₂ and Coke Strength after Reaction

Abstract

The reaction rate per unit mass of wood char was an order of magnitude larger than that of coke and graphite and that of glassy carbon was an order of magnitude smaller than the latter. However, the reaction rate per unit surface area of wood char was smaller than that of graphite. The reaction of coke proceeded homogeneously at temperatures lower than 1373 K, while the reaction was restricted to the surface layer at higher temperatures. The tensile strength of coke after reaction decreased with the reaction degree at 1273 K, but was not changed or even increased at 1573 K. This is due to the fact that at 1573 K the core of the sample was not attacked by CO2 but strengthened by further crystallization.

Micro Pore Structure and Reaction Rate of Coke, Wood Charcoal and Graphite with CO2

“…Kashiwaya et al 12) suggested that the reaction should not occur on the surface of smaller pores than 10 Ϫ5 m which are found in the highly graphitized area. The area becomes inactive because of the graphitization by heated up to higher temperature than 1 773 K. On the other hand, one of the present authors reported in the previous work 2) that the reaction of coke occurred just in the surface layer and no reaction occurred in the bulk at higher temperature than 1 373 K. In this case, the CO 2 molecules are consumed in the surface layer and cannot penetrate into the bulk. Thus, apparently, the small pores in the bulk cannot contribute to the reaction.…”

“…For that purpose, the reaction kinetics of various carbonaceous materials should be clarified. In the previous work, 1,2) wide variety of materials from the activated carbon to glassy carbon were examined with respect to the reaction with CO 2 in the low temperature range between 823 and 1 173 K. The reaction rates were two orders of magnitude different from each other. In order to explain the difference, the new reaction rate was defined by the reaction rate per unit surface area using the data of specific surface area.…”

Structure Analysis of Coke, Wood Charcoal and Bamboo Charcoal by Raman Spectroscopy and Their Reaction Rate with CO2

“…For that purpose, the reaction mechanism of various carbonaceous materials should be clarified. In the previous works, 1,2) wide variety of materials from the activated carbon to glassy carbon were examined with respect to the reaction with CO 2 in the low temperature range between 823 and 1 173 K. The reaction rates were two orders of magnitude different from each other. In order to examine the difference, the effect of pore structure on the reaction kinetics was examined by following the change in reaction rate, specific surface area and pore structure with the reaction degree.…”

Effects of Stefan Flow on Metallurgical Coke Gasification with CO2

“…Therefore, if Stefan flow is ignored, a significant effect results on the non-equimolar mass transfer process. Stefan flow has not been considered in previous studies of the coke gasification reaction. − If Stefan flow is considered, a different understanding will emerge on the behavior and mechanism of the coke gasification reaction.…”