Study On The Micro-characteristics Of Ionic Liquids Inhibit Oxidation For Lignite At Low Temperature

Lignite plays an important role in China’s energy economy and is mainly used as a fuel for power plants,chemical raw materials,and catalyst carriers,et.al.However,it has many characteristics,such as strong chemical reactivity,easy weathering in the air,hardly to store and transport.It not only causes coal spontaneous combustion,fire and explosion,but also causes serious accident consequences.In recent years,the hot topic of suppression of coal spontaneous combustion has been studied by many scholars.Among them,ionic liquid（ILs）chemical inhibitors have been widely discussed and developed.In this paper,9 common ILs and lignite from Da Nanhu mine in Shenhua Guoneng Hami Coal&Electricity Limited Company at Xinjiang Province were studyed as study object.The following three parts were studied:（1）X-ray diffraction（XRD）and scanning electron microscopy（SEM）tests showed that ILs can dissolve minerals,the crystallite structure is more stable,the degree of extension（L_a）has undergone major changes,and the interlayer spacing（d_m）does not change significantly.The number of aromatic tablets（M_c）decreased,the stacking height（L_c）decreased significantly,the degree of coalification（P）decreased,the angle of the particle surface became dull,the surface of the coal particles became smoother,and the coal structure was loose,indicating that the ILs caused damage to the physical and chemical characteristics of the coal.（2）Conducting the infrared spectrum（FTIR）test,the functional groups were attributed.The proportional content method was used to qualitatively and quantitatively compare the destruction of four functional groups by ILs.The results show that the ILs can destroy the content of functional groups in the surface molecules of coal,but it hardly solve and destroy the species of functional groups.The order of destruction of the hydroxyl,aliphatic hydrocarbon,and oxygen-containing functional groups was the strongest:6#[BMIM][NTf₂],5#[BMIM][AcO],6#[BMIM][NTf₂].The lowest levels of damage are:2#[BMIM][NO₃],6#[BMIM][NTf₂],7#[EMIM][NTf₂].The degree of destruction is closely related to the type of anion or cation contained and the chain length in the ILs.（3）Employing the TG-DSC-FTIR system test,based on multiple heating rates,selecting the combination of universal differential and integral,Ozawa method to determine the apparent activation energy（E_a）of the coal sample at the low temperature oxidation stage,and the most optimum kinetic mechanism function were determined by Bagchi method.The results show that the physical adsorption of coal samples increases during the low temperature oxidation process.The ILs can effectively inhibit the reaction of coal samples in water evaporation and desorption weightlessness process,but it does not play a significant role in the combustion stage.The characteristic temperature also has a corresponding effect.The starting temperature and the ending temperature of CO₂ and CO are delayed during the release process.Appropriate increase in apparent activation energy（E_a）is obtained by selecting the two methods at different stages,the stability is improved,and the optimum kinetic mechanism functions are also changed.Summarizing the aboves,it can be concluded that the ILs can cause damage to the physical and chemical properties,functional groups and other micro-structures of lignite,and the oxidation kinetics also changes,and the stability also increases accordingly.The oxidation activity of lignite is inhibited by ILs.Moreover,the variability of cation and anion in ILs has a significant effect on the micro-structure and oxidation characteristics of coal.