Study On Conversion Of Tar From Coal Gasification Under CO₂ Atmosphere By Non-equilibrium Plasma

The new generation of coal chemical technology and the development of cleaning coal technology are of great significance to China's energy use and environmental problems,coal gasification is one of the most important coal technologies.When tar is not the desired product of coal gasification,it will do great harm to the gasification system and equipments using syngas.Therefore,it is important to study on tar cleaning technology in the process of coal gasification.In addition,non-equilibrium plasma has a unique advantage in the field of chemical reaction transformation and is becoming a new research hotspot.So this paper wants to use non-equilibrium plasma technology to convert tar for establishing the cleaning gasification system and studies on the characteristics of tar conversion by non-equilibrium plasma.At first,this paper does some research on coal gasification reactor and designs a two-stage moving bed rector using driving wall type heating under CO2 atmosphere.Numerical simulation is used to study the moving bed reactor heating effect and coal pyrolysis characteristics.The results show that the moving bed reactor can achieve good heating result and the pyrolysis reaction can also finish smoothly.For the research on tar conversion using non-equilibrium plasma technology,this paper wants to own conversion characteristics and mechanism of benzene,one of tar main compounds,under CO2 atmosphere by non-equilibrium plasma.Experiment and numerical simulation are the main study methods.The experiment includes the determination of product components and the plasma emission spectrum diagnosis.Because of the importance of the reaction atmosphere to tar conversion,CO2 non-equilibrium plasma characteristics are studied by experiment and numerical simulation firtly and the non-equilibrium plasma reaction model of CO2 is established,which is the preparaty study.Then,the gaseous products and plasma spectral properties of benzene conversion are studied under CO2 atmosphere by non-equilibrium plasma.The non-equilibrium plasma transformation mechanism model of benzene under CO2 atmosphere is established and the transformation process and mechanism are analyzed and discussed by comparing the thermodynamic transformation at high temperature with the non-equilibrium plasma transformation of benzene under CO2 atmosphere.The results are as follows:CO and O2 will be generated by CO2 non-equilibrium plasma reaction and the generation of O radicals is one of the main sources of CO2 non-equilibrium plasma activity based on the CO2 non-equilibrium plasma emission spectrum.Benzene can be transformed under CO2 atmosphere using non-equilibrium.CO is the main gaseous product and carbon deposition found in the experiment.The non-equilibrium plasma emission spectra of CO2,pure benzene gas and mixed simulated gas show that CO2 non-equilibrium plasma dominates in the reaction compared to benzene's,so O radicals play an important role in the conversion reaction.Finally,the study of benzene conversion mechanism shows that O radicals from CO2 plasma dissociation are one of main reasons for triggering benzene non-equilibrium plasma conversion and the free radicals are not appear in benzene thermodynamic transformation of at high temperature.Under the triggering of O radicals,the gaseous products in the kinetic simulation results are consistent with the experiment.In addition,the analysis of the formation mechanism of carbon deposition shows that the carbon deposition is mainly elemental carbon,which is closely related to the series of electronic collision dissociation reactions occurring under the discharge condition of benzene.