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.

Experimental Study of High Temperature Combustion for Enhanced Shale Gas Recovery

“…The SEM images demonstrate that combustion not only resulted in increasing of pore diameter but also resulted in thermal cracking on the surface of shale. This phenomena is consistent with oil shale combustion . During the combustion, volatile matters were heated up first and broken into gaseous hydrocarbon.…”

Influence of pyrolysis condition and transition metal salt on the product yield and characterization via Huadian oil shale pyrolysis

“…At high pyrolysis temperature, most of the organic matters could be cracked and released from the shale, but there were still a portion of organic matters would be carbonized before they escaped the shale [11,14]. Meanwhile, some organic matters would combine with metal element to form intermediate products, and then these formed intermediate products and coke would adhere to the inner walls of small pores of the shale, resulting in the blockage of the pore [15]. Besides, metal Co was easy to cause the low efficiency of carbon dioxide reforming of methane [16].…”

Influence of In Situ Pyrolysis on the Evolution of Pore Structure of Oil Shale

“…Yang et al [41] quantitatively characterized the pore structure during pyrolysis by mercury intrusion porosimetry (MIP). On a smaller scale, using low-pressure nitrogen adsorption (LPNA), Han and Sun et al [42,43] concluded that heating softens or carbonizes organic matter and causes pore blockage, which affects pore structure parameters. Wang et al [44] considered that pore connectivity caused by the generation and migration of pyrolysis products is an important factor for the increase of porosity.…”