Mechanistic Study Of The Inhibition Of Coal Spontaneous Combustion By Catechin

The coal industry is a key energy pillar industry in China and has an important strategic position in the energy field.The stable development of the coal industry is of great significance to economic development of China,but it faces the danger of spontaneous combustion of coal during coal mining,storage,and transportation,which will cause energy waste,property loss,environmental pollution,and even casualties.Adding an inhibitor is a common method for controlling spontaneous combustion of coal.However,general inhibitors exist problems such as low efficiency and short life.Therefore,the research on environmentally-friendly and high-efficiency inhibitors and their inhibition mechanisms is of great theoretical and practical significance for the prevention and control of coal spontaneous combustion.This paper proposes natural antioxidant catechin as an inhibitor against coal spontaneous combustion.The mechanism of catechin inhibition of coal spontaneous combustion is analyzed by using quantum chemistry.The molecular structure models of C₇H₇·,C₇H₅O·,C₇H₇O·,C₇H₇O₂·and OH active radicals in coal are constructed.The activity of the hydroxyl groups on the catechin can be analyzed by the bond dissociation energy,and the meta-hydroxy group of the B ring is obtained as the optimal active site,thereby constructing H·and EC·free radicals of catechin.The enthalpy change and Gibbs free energy change of the reaction process of H·and EC·with five kinds of active free radicals in coal are calculated,and the thermal stability of the reaction process is analyzed.The results showed that catechin can convert the active free radicals in coal to inert compounds or relatively stable free radicals;H.has higher reactivity than EC·,which is the main factor for inhibiting spontaneous combustion of coal.The characteristic changes of free radicals in the oxidation process of coal samples before and after inhibition are analyzed by electron paramagnetic resonance.It is found that the free radical concentration of the two coal samples gradually increased with the temperature rise,and the g-factor and line width?H also gradually increased.At the same temperature,the free radical content of the inhibited coal sample is less than that of the raw coal,and the g-factor and the line width?H are smaller.The change of functional groups in the oxidation process of coal is analyzed by infrared experiments.In the low-temperature oxidation stage,the content of reactive functional groups such as alkyl-CH₃/-CH₂-,aromatic hydrocarbon C-H and hydroxyl-OH in coal increase with the temperature rise,and they react with oxygen to produce oxygen-containing functional groups such as carbonyl C=O and ether bond C-O-C.The addition of catechin reduces the reaction rate between the groups in the coal.The reaction of hydrocarbons is weakened,and the production of oxygen-containing functional groups is also reduced.The thermogravimetry-infrared-gas phase-mass spectrometry is used to compare and analyze the changes in coal samples before and after the inhibition.The thermal analysis experiments show that the mass gain stage of the coal samples with catechins disappeared compared with the raw coal samples.The maximum exothermic rate is decreased,indicating that catechin can hinder the reaction between coal and oxygen.Infrared and gas phase mass spectrometry experiments detect the gas change in the low-temperature oxidation stage of coal.The results show that the release of water from the coal sample is more than that of the raw coal,and the amount of CO and CO₂ released is reduced.Through the above methods,the results show that catechin has a good effect on inhibiting spontaneous combustion of coal.