The effect of pore structure on the char‐steam reaction

Abstract

The kinetics of the char-steam gasification reaction and the accompanying pore structure changes have been investigated experimentally and interpreted through the use of the random pore model of Bhatia and Perlmutter (1980) and its extensions developed in this study. To allow model evaluations, surface areas and pore-size distributions were obtained for various partially-reacted char samples. Surface areas follow the reaction rates as a function of conversion, supporting the interpretation that the reaction of porous char with steam is governed by the structural changes that occur as conversion proceeds. Reaction rate constants were obtained from the kinetic data.A pyrolytic change of char mass was observed during the heatup period from room temperature to reaction temperature for each of the two char samples tested. This results in a significant increase in surface area and a decrease in pore structure parameter. It is shown that this pore structure parameter is very sensitive to changes in conversion when the initial parameter is large and the conversion is small.

Reactivity of chars and carbons: New insights through molecular modeling

“…Under these conditions structural effects will dominate. This is indeed supported by the observations of surface area and rate maximima at about the same conversion in several cases (Su and Perlmutter, 1985;Chi and Perlmutter, 1989). Consequently, in the present work wc have focused on the structural issues, with the addition of chemisorption and surface dynamics to be considered subsequently.…”

“…Models considering internal reaction include the volume and grain reaction models (Szekely et al, 19761, and those that focus on the pore struc-ture (Petersen, 1957;Bhatia and Perlmutter, 1980;Gavalas, 1980). The volume and grain reaction models have the deficiency that they cannot predict a rate maximum with increase in conversion in the chemically controlled regime, a5 is commonly observed (Su and Perlmutter, 1985;Chi and Perlmutter, 1989). This feature can be predicted by the random pore models (Petersen, 1957;Bhatia and Perlmutter, 1980;Gavalas, 1980), which consider the competing mechanisms of pore growth and overlap.…”

A Modified Quantize Model for Depicting Coal Char Combustion under O2/CO2 Atmosphere

“…As the particle and char reaction processes, the relationship between the internal surface area and porosity of the char can be given by [25] …”

The combustion reactivity of coal chars in oxyfuel atmosphere: Comparison of different random pore models

“…According to the symmetry of normal distribution L(r) and the pore characteristics of solid [26,27], the structure parameter may be expressed as:…”