Thermogravimetric analysis of the effects of four ionic liquids on the combustion characteristics and kinetics of weak caking coal.

Abstract This study examined the combustion characteristics and kinetics of coal samples treated with imidazole-based ionic liquids (ILs), namely, [Emim][BF 4 ], [Bmim][BF 4 ], [Bmim][NO 3 ], and [Bmim][I], under oxidation. The oxidation of the coal samples was investigated using thermogravimetry (TG) at heating rates of 4.0, 6.0, 8.0, and 10.0 °C·min−1. The results for the IL-treated samples revealed that the composite index S (representing the ignition, combustion, and burnout properties) decreased and H f (representing the rate and intensity of the combustion process) increased with high correlation coefficients. The characteristic temperatures of the maximum oxidization mass gain (T 2), ignition point (T 3), maximum mass loss rate (T 4), and burnout point (T 5) increased by 13.1 ± 0.5, 9.2 ± 0.5, 21.5 ± 0.5, and 35.9 ± 0.5 °C, respectively. At T 3 and the maximum mass loss rate, the release of CO and CO 2 was further altered, suggesting that the C O functional groups were damaged or oxidized. The results of the Ozawa-Flynn-Wall kinetic equation used to determine the apparent activation energy (E a) of coal samples revealed that the E a of the treated samples increased. The reaction rate constant characterizes the effect of E a and pre-exponential factors (A), and the results showed that ILs can weaken the reaction process at low temperatures (<130 °C). Highlights • Changes in the combustion performance occurred in samples treated with ILs. • The S decreased and H f increased with an increase in the amount of ash. • The reaction process of the treated sample is accelerated above 130 °C determined by k. • The difference in gas reveals that C O was destroyed by ILs. [ABSTRACT FROM AUTHOR]