The Production of Active Free Radicals During Thermal Decomposition and Its Influence on Subsequent Oxidation Behavior

To deeply analyze the production of active free radicals during thermal decomposition and its influence on subsequent oxidation behavior. In the study, experiments on low-temperature thermal decomposition, low-temperature oxidation, and room-temperature oxidation were conducted on four coal samples. Gas generation products, coal core temperature, functional groups (FTIR), and free radicals (In-suit ESR) testing were adopted. The evolution laws of various free radical concentration were analyzed via peak fitting of free radical spectra. The main active free radicals were identified and their impact on subsequent oxidation process was analyzed. In-suit ESR experiments show that the free radicals generated by thermal decomposition can accumulate under inert conditions. Alkyl radicals play an important role in oxidation process. The room-temperature oxidation of thermal decomposition coal demonstrated that alkyl radicals are active free radicals. Alkyl radicals can undergo free radical-chain reactions with oxygen at normal-temperature, resulting in free radical concentration increased, gas production, and heat production. Alkyl radicals significantly enhance the oxidation of coal, and the extent of enhancement is directly proportional to their quantity. This research is effectively promoted the exploration of the coal spontaneous combustion mechanism and the development of flame retardants.