A numerical study on the multi-physics coupling mechanisms and spatiotemporal evolution of the in-situ coal-to-hydrogen process

As the global energy transition accelerates, in-situ coal-to-hydrogen (ISCH) is emerging as a vital technology for the clean utilization of deep coal resources. This study employs a custom-developed numerical model to systematically analyze the spatiotemporal evolution of coupled multi-physics fields during the ISCH process. The research reveals, for the first time, a complete “energy accumulation-release” cycle governing the process, characterized by a unique dynamic mode wherein the high-temperature reaction front transitions from “heating and expansion” to “core cooling with edge propagation.” Building upon this finding, the study further elucidates a profound “imprint effect” from the reaction history, where local carbon depletion forms “combustion dead zones,” and downstream steam accumulation creates internal “reservoirs” for secondary supply. Product transport, in turn, is governed by a switching mechanism between dominant physical fields: hydrogen transport exhibits a full life cycle, evolving from initial diffusion-dominated “radial dispersion” to subsequent pressure-gradient-driven “unidirectional displacement.” These innovative findings not only reveal the complex coupling mechanisms among reaction kinetics, multiphase flow, and heat transfer but also provide a solid theoretical basis for optimizing injection strategies, controlling front stability, and maximizing product recovery. This work offers significant guidance for advancing the industrialization of coal-based clean hydrogen energy technology.