Study On Co-gasification Mechanism Of Coal And Alkaline Organic Wastewater

In view of the lack of reaction mechanism of co-gasification of coal and organic wastewater,this research applied molecular dynamics simulation and quantum chemical calculations to conduct investigation on the co-gasification mechanism of coal and Na+-containing organic wastewater,which are a part of the preliminary work for the development of the reactive force field of the above-mentioned system.After establishing a model of co-gasification of coal and organic wastewater in Material Studio,the results of molecular dynamics simulation under universal force field(UFF)showed that as the temperature increases,the load of Na+growed uniform,and the optimal Na+loading in the system will also be larger.The simulation results under different pressures showed that as the pressure rises,the kinetic energy was not the predominant factor affecting the reaction rate,but because water molecules formed water clusters and the generated hydrogen radicals and hydroxide radicals produced huge amount of hydrogen and accelerated the reaction rates under supercritical conditions.Furthermore,the molecular dynamics simulation results of the two ensembles of NPT and NVT were consistent,which was suitable for the subsequent development of reactive force field.Aiming at the Na+-catalyzed coke-steam gasification process,which was the key step in the development of the reaction force field of the aforementioned system and also the rate control step in the coal gasification process,Gaussian09 software was applied and M06-2X functionals were adopted to analyze the quantum chemical calculations of coke-steam gasification in two forms,i.e.Na+loaded as phenolic group and Na+in the graphite interlayer while original coal coke model was applied as blank controls.The loading form of phenolic groups had a stronger catalytic effect than the graphite interlayer structure.The former reduced the reaction energy barrier by about 200kJ/mol,while the latter only reduced the reaction energy barrier by 11.6kJ/mol.The sodium-oxygen seven-membered heterocyclic ring formed by the former has a catalytic effect both on promoting desorption of hydrogen and carbon monoxide,but the Na-O-H group formed by the latter only has a certain catalytic effect on hydrogen desorption.Since the loading form of Na has a certain correlation with the metamorphic degree of coal,explained the selection of coal type also affects the catalytic effect of Na.This quantum chemical calculation involved the energy and structure transformation of the three following functional groups,i.e.O-Na,C-O-Na and O-Na-O,providing part of the training parameters for the development of the subsequent reaction force field.