The heating performance and kinetic behaviour of oil shale during microwave pyrolysis

In this study, the microwave pyrolysis of oil shales (MPOS) from Estonian Kukersite, Moroccan Tarfaya, Chinese Longkou, and Chinese Barkol were investigated. The heating performance of MPOS was also examined. A comparison study between MPOS and conventional oil shale pyrolysis (CPOS) was conducted, which included comparing the temperature profile, heating rate, weight loss at the same temperature, and the organic decomposition kinetic parameters. Results indicate that, under MPOS, both the maximum temperature (T-m) and average heating rate (gamma) were influenced by the organic matter content in oil shale, and the effects were more significant at higher microwave powers (400-700 W) than at lower powers (200-400 W). Furthermore, both T-m or gamma were linearly and/or exponentially correlated with microwave power with a breakpoint of 400 W in each correlation. Compared with CPOS, MPOS provided higher gamma based on the same input powers and higher weight loss at the same temperatures. This demonstrates that MPOS requires much less processing time and a lower input energy than CPOS. Additionally, the kinetics of oil shale pyrolysis were modelled using the Kissinger method. For organic matter decomposition, MPOS decreased the activation energy by 13-39% and increased the reaction rate constant by at least 65%, compared to CPOS. This implies that under MPOS, higher powers are necessary to establish oil shale thermal reactivity and higher reaction rates can be obtained, thereby causing greater weight loss than with CPOS. (C) 2021 Published by Elsevier Ltd.

Automated summary

In this study, the microwave pyrolysis of oil shales from different regions was investigated, and a comparison with conventional oil shale pyrolysis was conducted. The results showed that the microwave power and organic matter content in oil shale had significant effects on the temperature profile and heating rate. Microwave pyrolysis achieved higher weight loss and required less processing time and energy input compared to conventional pyrolysis. Additionally, the activation energy decreased and the reaction rate constant increased under microwave pyrolysis, indicating higher thermal reactivity and reaction rates.