Molecular Modelling And Microwave Pyrolysis Studies Of ZaoQuan Coal

Coal plays a crucial role in China's energy structure.The efficient and comprehensive utilization of coal is a vital measure to achieve energy conservation and emission reduction.Pyrolysis,a important research object,is a basic step of coal conversion process,which affects liquefaction,gasification and other processes.Compared with conventional pyrolysis,microwave heating is rapid,efficient,easy to operate and has a good prospect in the field of coal pyrolysis.In this thesis,the macromolecular structure model of ZQ coal in ningdong zaoquan coal-mine was constructed by means of various characterizations such as elemental analysis,X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),combined with computer-aided techniques.After annealing dynamics simulation and structural optimizations,reactive force field molecular dynamics simulation was conducted to investigate the influence of pyrolysis temperature and heating rate on pyrolysis behavior,and to predict the pyrolysis reaction properties of coal.In terms of the experiment part,the microwave assisted pyrolysis of coal was adopted to discuss the influence of the pyrolysis temperature,heating rate,residence time and microwave power on the pyrolysis process of ZQ coal,and also summarized the generation rules of gas,liquid and solid products.Using pyrrole and pyridine as nitrogen model to study the combustion reaction mechanism by means of ReaxFF MD in order to find out the formation and transformation mechanism of nitrogen-oxides.The variation of molecular numbers of reactants,products and main intermediates at different combustion temperatures was investigated.In this work,the theoretical research and pyrolysis experiment were combined to explore the relationship between the microstructure and the chemical reaction properties of macroscopic substances from multiple perspectives,aiming at a deeper understanding of the phenomenon and nature in the pyrolysis process of coal.The research shows:The spatial configuration of the model is changed significantly after annealing dynamics simulation and structural optimizations.Vibration analysis and density functional calculation further confirmed the rationality of the coal model.It was found that heating rate had significalt influence on the generation of gas in the pyrolysis simulation process of ZQ coal.Most of the pyrolysis products were gaseous hydrocarbons and light tar,while the macromolecules(C40+)were the minority.In addition,the formation paths of CO2,CO and H2O in the pyrolysis process were visually tracked,and the generation mechanism was obtained.The pyrolysis of ZQ coal was studied by microwave assisted technology,and it was shown that different factors had different effects on the product distribution in the process of microwave pyrolysis.However,in general,the yield of pyrolysis gas was increased.By comparing with the simulation results,it was found that the amounts of CO2 and H2 had a good correlation with the experimental conclusion.The yield of semi-coke decreased and the degree of graphitization increased gradually.The amounts of tar increased firstly,but then decreased.There was a highest tar yield in the case of 20?/min,510?,600 W and 10 min.The components of tar was analyzed by means of GC-MS,and it was found that there were considerable difference between the components of tar in different factors during pyrolysis.But the tar components contained more acids,esters and ketones as a whole,which might be related to the higher oxygen content in ZQ coal.In the study of the combustion mechanism about pyrrole and pyridine,the result showed that temperature was an important factor.In the combustion process,the amounts of CO2 and H2O increased significantly and then tended to be stable with the progress of the reaction.And the time to reach equilibrium would be accelerated with the increase of temperature.In addition,it was shown that the combustion mechanism of pyrrole and pyridine was different.The decomposition rate of them increased as temperature increased.However,the decomosition time of pyridine was longer than that of pyrrole at the same temperature,since the deeomposition rate was slower.The combustion products and nitrogen-containing intermediates of them were nearly same,but the way of ring-cracking and hydrocarbon free radical cleavage path during pyrolysis were obviously distinct.