On explosion limits of H₂/CO/O₂ mixtures

The pressure–temperature explosion limits of H₂/CO/O₂ mixtures were analyzed computationally and theoretically. It is shown that, with the addition of even a minute quantity of H₂, the mixture explosion limits evolve from being monotonic to the non-monotonic Z-shaped response characteristic of H₂/O₂ mixtures. It is further shown that the explosion limit at various conditions can be reproduced well with a reduced mechanism of 12 elementary steps and 10 species. Eigenvalue analysis of this mechanism leads to an analytic solution for the explosion limits, yielding explicit expressions for the degenerate high- and low-pressure explosion peninsulas as well as the individual first, second and third limits. The separate and coupled roles of H₂ and CO oxidation are identified, leading to enhanced insight of this foundational component in the mechanisms of hydrocarbon oxidation, as well as useful information in the utilization of syngas.