Evolution of pore structure and fractal characteristics of coal char during coal gasification

Abstract

This study classifies the evolutionary properties of coal char pore structure which occur during coal gasification. CO2 gasification of various coal samples was carried out in a fixed bed reactor. The resulting chars were analysed using N2 isothermal adsorption/desorption and scanning electron microscopy (SEM), coupled with fractal theory. Analytical results indicate that the pore structure of coal char underwent micropore evolving, enlarging and overlapping, while more mesopores and macropores developed with continued gasification. The surface area of coal char increased to its maximum value when carbon conversion reached approximately 50%. Fractal calculation results showed that two types of fractal structures associated with the coal char surface and pore structure underwent stereome development and elapsing. However, the evolutionary properties were unique for different coal samples. High rank coal had a complex spatial structure with more micro-pores, whereas lower rank coal had a much flatter spatial structure.