The autothermic pyrolysis in-situ conversion process for oil shale recovery: Effect of gas injection parameters

Abstract

The scale benefit exploitation of oil shale is of great significance to alleviate the current world energy shortage. The autothermic pyrolysis in-situ conversion process (ATS) method shows the feasibility and broad prospects of in-situ efficient utilization of oil shale resources (Guo et al., 2022) [29]. This study conducts in-situ pyrolysis of oil shale by ATS method with oxygen content and injection gas flow as experimental parameters, further clarifying the energy efficiency mechanism and influence characteristics of oxygen injection amount on the in-situ autothermic pyrolysis. The results showed that the in-situ self-pyrolysis reaction can be successfully triggered at 300 °C under the injection parameters of 12,16,21% oxygen content and 3,5,7 L/min injection gas flow rate. However, neither too low nor too high oxygen injection amount can achieve a good in-situ conversion effect. Within the range of parameters considered in this study, the optimal combination of oxygen injection parameters for in-situ pyrolysis of oil shale by the ATS method is 16% oxygen content and 5 L/min injection gas flow. The recovery rate of its cracked oil is 67.1%, and its energy efficiency is as high as 3.46, which is 6.78 times the energy efficiency of in-situ high-temperature nitrogen pyrolysis, realizing the benefits of the transformation of oil shale resources. Meanwhile, according to the apparent optical characteristics of the sample after the experiment and the evolution of the material components in each reaction region, the in-situ autothermic pyrolysis has a significant regional fingering feature. It is hoped that this study will provide reliable data support for the large-scale application of the ATS method.