The Interactional Study Of Soot Formation With Flame Radiation And NO_X Emission In Natural Gas Diffusion Combustion

Along with the advance of"transfer natural gas from the west to the east"project and the attention of environmental protection , the exploitation and utilization of natural gas has been developed rapidly as one of the clean energies in our country.Even now,there lies two urgent problems in the combustion process of power plant boiler.One is that the superheater and reheater overheat because the quantity of heat in flame doesn't be absorbed fully by the waterwall as the result of the poor total radiation of natural gas flame.The other is the emission of NOX produced in burning.The most effective way solving the two problems is the study of its formation mechanism,so we should analyze the influence of different combustion conditions on flame radiation and NOX emission,provide the theory support for the reasonable choice of combustion mode.In this paper,research shows that when premixed degree is low and environmental temperature is high,the soot produced in flame will enhance the total radiation of flame consumedly,consequently decrease the flame temperature and thermal NOX emission.Besides the soot also can deoxidize the NOX produced in flame.In this paper a perfect and flexible measurement system of NOX emission had been established firstly.The NOX emission characteristics of CH4-air and LPG-air flames were investigated experimentally under different premixed degrees,environmental temperatures and gas flows.It was found that there is a critical environmental temperature,the rule of NOX emission and premixed degree is classified into three phrases according to the NOX formation mechanism below the temperature.As the premixed degree increases,prompt NOX functions first,then prompt NOX and thermal NOX both function and thermal NOX functions last.Above the temperature,thermal NOX functions all along.In addition,with the environmental temperature varying in a certain scope,the rule of NOX emission and environmental temperature is a quadratic function for diffusion and low premixed flames,while the NOX emission is stable as to the environmental temperature for fully premixed and high premixed flames.The NOX emission can be expressed as a uniform quintic function of premixed degree when gas flow varies.The development of a subminiature natural gas combustion apparatus and the on-line debugging of it with Fourier Transform Infrared spectroscopy(FTIR) are also completed in this paper.We use FTIR E-T technology to investigate the influence of different premixed degrees and different environmental temperatures on total radiation and temperature of CH4-air flame on line via FTIR.It was found that when premixed degree varies in atmosphere,the position of soot formation in flame changes,the temperature and total radiation in flame upside change and the whole radiation of flame changes,but the whole temperature of flame is stable.Furthermore,in close space,flame temperature decreases because of higher environmental temperature . The influence of environmental temperature on flame temperature is obvious at lower premixed degree,while the influence of environmental temperature on total radiation is clear at higher premixed degree.In conclusion,on the basis of the integration of NOX measuring test and FTIR measurement experimentation,this paper analyses the influence of different combustion conditions on soot formation,NOX emission and total radiation in CH4-air flame roundly and interprets the correlation among them with reason.