Ignition And Combustion Characteristics Of Pulverized Coal Based On OH-PLIF Diagnostic Techniques

A flat flame burner of pulverized coal reactor system simulating the combustion conditions of industrial pulverized coal boiler was designed,to study ignition and combustion characteristics of pulverized coal(PC)under high temperature gas atmosphere.Through devolatilization,ignition,and volatile combustion processes of PC was studied by OH-PLIF,the distribution of OH* around the particles and the distribution of OH* around particle group are analyzed,to analyze the ignition mechanism of pulverized coal.The normalized distribution curve of the total light intensity signal,the normalized distribution curve of the OH* spontaneous emission signal and the normalized distribution curve of the OH-PLIF fluorescence signal of the powder jet flame were obtained by three different measurement methods,and the ignition points and the ignition delay time obtained by the three method to determine the merits of the three measurement means.To inv estigate the influence of ambient oxygen concentration on the ignition delay time of PC with the ignition delay time of the total light intensity signal,the OH* spontaneous emission signal and the OH-PLIF fluorescence signal,the combustion characteristics of jet flame were analyzed.Finally,through industry analysis,proximate analysis and pore analysis of the char sample,we can study the burnout characteristics of PC,while the degree of burnout of coal should verify the accuracy of the previous optical measurement results.The results show that: The ignition delay time of bituminous coal and lignite coal decrease with the increase of ambient oxygen concentration(10%-30% O2)by three different measurement methods;The OH * distribution of bituminous PC group is stable,and the ignition of particle group is that volatiles are burned first and then heat char particles,so the particles group is dominated by the homogeneous ignition mechanism;The OH* distribution of the well-dispersed PC particles group is wrapped on the outer surface of the char particles,with the increase of the oxygen concentration,the combustion reaction zone is expanding and the combustion reaction is more intense;and at the same time,the osmotic ability of the oxygen molecules is stronger,and the combustion reaction inside the PC flow is exacerbated.After analyzing the trend of curve of the normalized distribution curve of the total light intensity signal,the normalized distribution curve of the OH* spontaneous emission signal and the normalized distribution curve of the OH-PLIF fluorescence signal of the powder jet flame,it can found that OH-PLIF fluorescence signal has the best response to combustion reaction,therefore OH-PLIF measurement method is an important tool for measuring combustion zone of PC volatile.Particle group undergoes prolonged heating and burning,leading to the char surface softening,melting,hole collapse and ash melting phenomenon,therefore the pore structure of the char will be increased sharply after less;The decrease of the pore structure of the char can verify the above analysis of the burnout characteristics of coal char;and also confirm accuracy of optical measuring methods.