Study On Effect Of Aromaticity Of Coal And Hydrogen Bond To Calcium Retardant’s Inhibition For Coal Spontaneous Combustion

Coal spontaneous combustion cause energy dissipation and environmental pollution, as well as serious problems on production security of coal mine. The use of retardant has been an effective method in preventing coal spontaneous combustion. Due to the complexity of coal structure and component, thoroughly research on mechanism of inhibition of coal spontaneous combustion is needed. Theory of coordinate inhibition in preventing coal spontaneous combustion means that in the presence of retardant, the active groups of coal forms complex with metal ions in retardant so as to prevent their reaction with oxygen. This thesis based on theory of coordinate inhibition, utilized quantum chemistry theory, studied coal aromaticity, hydrogen bond and sovation effect which affected the complex properties. The geometrical characteristics, frontier molecular orbital, net charge population, spectrum characteristics and binding energy of the complex between N containing active structures in coal and calcium based retardant were investigated. The research achievements are creation and improvement on theory of coordinate inhibition.Affects on forming complex according to the increasing aromaticity of N containing characteristic structures in coal were studied. An increase of N-Ca-O bond angel, a decrese of Ca-N coordination bond legth and an increase of Ca-O coordination bond legth were noticed along with the increase of aromaticity during calculation on B3LYP/6-311G* level adoping density functional theory. Ca-N-C-O four member ring structure was formed when the number of benzene ring rose to four. The energy gap of complex between Ca²⁺ and active structure of coal increase gradually, the total energy of complex system decrease gradually, and the stability of complex so formed increase gradually. There was no noticeable shift of stretching vibration peak of the coordination bond Ca-O, on the contrary large blue shift was observed of stretching vibration peak of the coordination bond Ca-N. This indicated that large effect on coordination bond Ca-N by the aromaticity of the active group of coal, and more stability of the complex. It is found that the larger the aromaticity of the charictristic sturcture of coal, the more efficent of retardant’s inhibition effect.Effect of hydrogen bond on forming complex was studied. Optimized calculation of the process of coordination in the presence of H₂O was carried on B3LYP/6-311G* level adoping density functional theory. Result showed that H₂O first react with the ligand–OH of Ca²⁺ through molecular recognition and molecular guide of hydrogen bond, and further react with Ca²⁺ to form complex. Hydrogen bond always maintained and helped to form intramolecular Ca-O-H-O four member ring structure, which largely increased the stability of complex. The enegy level of frontier molecular orbital and system energy of complex decreased which result in more stability. Ca still diverge its apparent charge after one H₂O molecule coordinated so as it can keep on forming more coordination bond. The intramolecular Ca-O-H-O four member ring structure formed in the presence of H₂O, and the effect of aromaticity of coal on coordination bond Ca-N decresed. The inhibition effect largely increased when solvent coordinated through hydrogen bond.Affect on Ca²⁺ retardant complex forming by effect of salvation was sturdied. Affect on complex forming by effect of salvation was sturdied by polarizable continuum model（PCM）. Result showed that molecular conformation changed on liquid phase, the composition of HOMO orbital of complex in solution shifted to benzene ring and C of side chain from Ca and N, result in enhancement of Ca-N coordination bond as well as less activity of N. Energy difference frontier molecular orbital and net charge population indicated that more stability of complex. It suggested that complex more stable in aqueoue solution and better inhibition effect of retardant.Extreme effect of solvent on inhibition effect of retardant was showed on microcosmic, the necessarity in the need for solvent selection during the configuration retardant process was illustrated, and creation and improvement on theory of coordinate inhibition were achieved in this thesis.