Pore Structure of Oil Shale Heated by Using Conduction and Microwave Radiation: A Case Study of Oil Shale from the Fushun in China

Abstract

To examine the evolution of the internal pore structure of and the law of changes in oil shale under different heating modes but at the same temperature, this study subjected $\phi 20\text{mm}\times 20\text{mm}$ specimens of oil shale to temperatures in the range of 20°C ~500°C by using a muffle furnace and a microwave pyrolysis device. We carried out experiments on the pyrolysis reaction under different temperatures and used scanning electron microscopy, backscattering, the mercury intrusion test, and MATLAB for a refined characterization of the specimens. The results showed that the microwave pyrolysis of oil shale was much shorter than its conduction-induced heating. As the microwave power increased, the time required to reach the target temperature decreased. The phenomenon of “hole blocking” was observed at 400°C ~500°C during conduction-based heating but did not occur in the microwave pyrolysis of oil shale. The porosity of oil shale heated by conduction was 3.4 times higher than its original porosity, whereas that of oil shale heated by microwave radiation was 4.9 times higher than its original value. It can be seen that compared with conduction heating, radiant heating makes the pyrolysis of organic matter in oil shale more complete. During the pyrolysis process of oil shale, the complete reaction of organic matter causes the thermal fracture of the oil shale to produce a large number of pores and interconnected cracks. Thereby, a seepage channel for pyrolysis gas and oil is formed, and the recovery rate of oil and gas is increased.