Optimal parameter adjustment of catalytic combustion heaters for oil shale in-situ conversion of low calorific value gases

Oil shale resources are huge, and in order to develop and utilize them rationally, it is crucial to research heaters suitable for downhole in-situ conversion mining. Compared with the problems of short life and multi-stage energy utilization of downhole electric heaters, combustion heaters have advantages such as high thermal efficiency and low cost. The heater uses low calorific value industrial waste gas as the fuel for gas injection, which reduces carbon emissions and environmental pollution and saves gas injection costs. In this paper, we propose to apply catalytic combustion of low calorific value industrial waste gas to generate high temperature exhaust gas suitable for mining, and establish the relationship between gas injection flow rate, combustion chamber parameters and gas injection duration by mathematical methods. The effect of the downhole high-pressure environment on the catalytic combustion characteristics of low calorific gas was simulated and the formula for calculating the content of low calorific gas in the exhaust gas was modified. The results show that the determination of the relational equation solves the problem of excessive axial volume in the design process of downhole heaters. Under high pressure conditions downhole, the exhaust gas temperature and low calorific gas conversion rate are significantly improved. The catalyst ignition temperature ranged from 973 K to 1073 K. Increasing the downhole pressure to 5 MPa increased the conversion of low calorific value gas from 74.56% to 88.22%. The gas injection rate and calorific value range can be calculated by correcting the equation for the content of low calorific gas in the exhaust gas. The conclusion of the study provides a reference basis for the selection of catalytic combustion process parameters for low calorific industrial waste gas, and also provides an important theoretical basis for the construction of the downhole test prototype.