Thermal reactivity and gas–solid product evolution during coal catalytic combustion: An experimental study

To achieve efficient and clean coal combustion, catalytic combustion technology has received widespread attention. This paper systematically studied the influence of calcium-based compounds on the thermal reactivity and gas–solid two-phase product evolution behavior of different coal using TG-MS and FTIR analysis, combining kinetics and thermodynamics methods, the catalytic coal mechanism was discussed. Results demonstrated that both catalysts improved the combustion reactivity, the burnout temperatures of lignite, bituminous coal and anthracite were reduced by 30.75 °C, 53 °C and 25.5 °C respectively with CaO, as well as decreased by 24.75 °C, 55.5 °C and 29 °C respectively with CaCl₂. Meanwhile, it was worth noting that the activation energy of three coals was also reduced. CaCl₂ was more likely to bind with the C = O functional group on the surface of coal, forming CO-Ca²⁺ complexes, resulting in a decrease in the content of C = O and C-O. While CaO tended to absorb volatile matter, causing local overheating and promoting the breakage of side chains and bridge bonds. Besides, the calcium-based compounds advanced the gas evolution peak of combustion and the emissions of CO₂, NO₂ and SO₂ were effectively controlled. These results aimed at providing a new reference direction for further industrial development of clean coal combustion technology.