Dynamic modelling and characteristics analysis of a novel in situ tar-rich coal pyrolysis mining system driven by solar energy

As a strategic alternative to conventional oil and gas resources, tar-rich coal, coupled with its low-carbon in-situ extraction technologies, is rapidly emerging as a pivotal focus for sustainable energy development. This study presents an innovative tower type solar in-situ pyrolysis system for tar-rich coal (TS-IPS/TRC) to significantly reduce energy consumption in tar-rich coal extraction. A transient multiphysics model, integrating solar thermal conversion, nitrogen mediated heat transfer, and pyrolysis reaction kinetics, was constructed to investigate the influence of two critical operating parameters, nitrogen temperature and flow rate, on the dynamic behavior of the system. The results demonstrate that the heating rate during the initial pyrolysis stage is more responsive to variations in flow rate. Spatially, increasing the flow rate significantly enhance the heating effect near the injection well, while the effect gradually diminish in the regions farther away from the injection well. In accordance with system operational requirements, the optimal pyrolysis temperature was ascertained to be 983.15 K under a 24–hour cyclic operation strategy. In light of the temporal variations in solar energy, three operational approaches were subjected to rigorous evaluation. The results reveal that intermittent operation coupled with an elevated inlet temperature and a reduced flow rate of the heat transfer medium significantly enhances techno–economic performance. The intermittent heating mode effectively improves temperature uniformity within the pyrolysis zone. A 12–hour cyclic operation strategy is recommended. Increasing the inlet temperature from 933.15 K to 1033.15 K and decreasing the inlet flow velocity from 5 m/s to 2 m/s substantially increases the gas production rate by 61 %. The TS-IPS/TRC system can reduce power consumption by 61 % and decrease carbon emissions by 2.52 × 10⁸ kg under the pyrolysis condition of 80 % of tar-rich coal. The proposed system demonstrates great potential in terms of energy conservation and emission reduction by pioneering a novel method for sustainable extraction of tar-rich coal in a low-carbon way.