Behavior and kinetics of the conversion/combustion of oil shale and its components under air condition

In this work, the conversion/combustion behavior and kinetics of oil shale and its components (bitumen, kerogen, and bitumen-free oil shale) were investigated under air condition using thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FT-IR) to have a deeper understanding of the combustion/conversion mechanism of oil shale for its potential development using in-situ combustion (ISC) technology. The results show that the reaction stages were very different amongst bitumen, kerogen, and oil shale. For bitumen, three reaction stages were observed, i.e., low-temperature oxidation (LTO), fuel deposition (FD), and high-temperature oxidation (HTO). For kerogen, one broad reaction peak was identified as the thermal-oxidative decomposition of kerogen, where two main stages occurred, which can be considered as FD and HTO. But the FD and HTO are different from that of bitumen, and they are more overlapped with each other and cannot be separated as two regions. The thermal-oxidative decomposition of kerogen is very complicated and may include an autocatalytic mechanism. The mineral matrix in oil shale showed an obvious catalytic influence on the thermal-oxidative decomposition of kerogen. The additivity prediction shows that the LTO of bitumen and thermal-oxidative decomposition of kerogen interacted with each other before 400 °C, and they did not comply with their own reaction pathways. The findings in this work provide some fundamental and significant knowledge of oil shale conversion for its potential development by ISC technique.