Effects of Retorting Factors on Combustion Properties of Shale Char. 2. Pore Structure

Abstract

The devolatilization of solid fuels will cause remarkable changes to the pore structures of the resulting char particles, which has a significant influence on successive reactions, such as the combustion of the char particles and the formation of ash. In the present work, the pore structures of shale chars prepared under different retorting conditions were measured by employing a N2 adsorption−desorption method. On the basis of the measured results and thermal degradation mechanisms of the kerogen within oil shale, the effects of four retorting parameters on the pore structures of shale char were discussed. An elevating retorting temperature will notably increase the pore volume and specific surface area in shale char. However, at the higher retorting temperatures, the cracking and carbonization of residual organic matter within shale char become more intensive. Subsequently, the pores are easily blocked (especially small pores), and the specific surface area of the char particles decreases slightly. In terms of the residence time of retorting at a low temperature of 430 °C, sufficient residence time is required for forming more extensive porosity within shale char particles. The particle size and low heating rate were found to have little effect on the surface area and pore volume of shale char.