Reaction behavior and kinetic characteristics of carbon monoxide in the in-situ supercritical water - coal gasification system

Carbon monoxide (CO), as an inevitable byproduct in the in-situ supercritical water–coal gasification process coupled with oxygen injection for temperature elevation and hydrogen production, becomes a critical component that must be suppressed and converted due to its low calorific value and toxicity. Based on a self-developed in-situ supercritical water-coal gasification cyclic continuous reaction system, cyclic continuous reaction experiments of CO under supercritical water-coal gasification conditions at different temperatures were conducted. In combination with reaction kinetics, the reaction behavior and kinetic characteristics of CO in the in-situ supercritical water-coal gasification system were systematically analyzed. The main research findings are as follows: Firstly, 450 °C is the threshold temperature that triggers the rapid consumption of CO and promotes the formation of H 2 , CO 2 , and CH 4 through the water-gas shift reaction and other related reactions. With increasing temperature, CO consumption increasingly favors the formation of H 2 . Secondly, the rates of the water-gas shift reaction and the methanation reaction at different supercritical water-coal gasification temperatures directly determine the conversion rate and conversion pathway of CO. Thirdly, the supercritical water-coal gasification environment intrinsically promotes CO consumption and H 2 formation, providing an advantageous medium for hydrogen production. Enhancing the forward rate of the water-gas shift reaction is essential not only for accelerating CO consumption but also for elevating H 2 concentration, while accelerating the forward methanation reaction is critical for further reducing CO levels. Finally, after CO injection, the steady-state concentration of H 2 is essentially unaffected by reaction temperature, whereas higher temperatures favor the overall reaction pathway toward the formation of high-calorific-value gases such as H 2 and CH 4 . This study fills the existing gap regarding the reaction behavior and kinetic characteristics of CO in the in-situ supercritical water-coal gasification system. It provides essential theoretical guidance for effectively suppressing and converting CO, optimizing product composition, and enhancing hydrogenation efficiency within in-situ supercritical water-coal gasification processes. • A self-developed in-situ cyclic continuous supercritical water-coal gasification system was established. • The reaction behavior and kinetic characteristics of CO in the supercritical water-coal gasification system were elucidated. • Revealed the critical temperature and key reaction pathways for rapid CO consumption and hydrogen-rich product formation.