Construction Of Superfine Pulverized Coal Macromolecular Model And Mechanism Analysis Of Light Hydrocarbon Release During Rapid Pyrolysis

With the environmental pollution becoming more and more serious,and the energy structure continuously adjusting,the clean burning of coal is getting more and more attention in our country.Superfine pulverized coal reburning is proposed as a new clean coal combustion technology because of its clean and efficient characteristics.Therefore,the in-depth study on the molecular structure and reaction mechanism of superfine pulverized coal has a profound impact on the rational and effective utilization of superfine pulverized coal.Simulation and experiment are combined in this dissertation.Based on the analysis of traditional characterization experiments(Fourier transform infrared spectroscopy,X-ray photoelectron spectroscopy and ¹³C nuclear magnetic resonance spectroscopy)and the hand-drawn extraction results of aromatic lattice of high-resolution transmission electron microscope,a relatively reasonable structure model of HN coal macromolecules?particle size of 23.9?m?C₂₅₈H₁₇₂N₄O₁₂S was constructed.After the geometric optimization and dynamic simulation of the molecular model based on Materials studio software,it was found that the bond angle energy and torsion energy of molecules were significantly increased,and the three-dimensional structure of molecules was more obvious.We add periodic boundary conditions to the macromolecule model in amorphous cell module to simulate and calculate a more reasonable coal density of1.45g/cm³.In VAMP module,based on the semi-empirical quantum mechanics theory,chemical parameters such as bond order and bond length of some typical fragments were calculated and analyzed.Ether bond?—O—?is easily broken to form free oxygen atoms;Functional groups have a greater impact on the stability of surrounding chemical bonds:thiophene has a greater effect on C-C bond strengthening than pyrrole has on C-C bond;Carbonyl group?C=O?can weaken adjacent C-C bond,making carbonyl group content in high order coal lower.In the experiment part,Gasmet DX-4000 was used to determine the composition of light hydrocarbon rapidly pyrolyzed by superfine pulverized coal in a high temperature fixed bed.The results showed that the total emission of CH₄,C₂?C₂H₂,C₂H₄,C₂H₆?and C₃H₈ increased with the decrease of pulverized coal particle size.Among different types of coal,C₁?C₂ and C₃ yields of low-order coal are significantly higher than those of high-order coal.In CO₂ atmosphere,the release amount of light hydrocarbon is lower than that in N₂ atmosphere.Finally,based on the above simulation results and a large number of experimental data,it provides a relatively complete explanation for the experimental phenomenon of light hydrocarbon rapidly pyrolyzed by superfine pulverized coal in high temperature fixed bed.The results show that the experimental phenomena are consistent with the simulation results of macromolecular structure.