| Low biomass combustion temperature has restricted the application of pure biomass power generation technology. Oxy-fuel combustion can improve the boiler combustion temperature and control and recover CO2. NO conversion and flame characteristics on biomass pellet are completely different between oxy-fuel combustion and air combustion. Its phenomenon and mechanism need more research.In this paper, the independent design of biomass pellet combustion test rig, flame measurement hardware and flame measurement software were used to research NO conversion and flame image characteristics of typical biomass pellet. Three kinds of ambient temperature(800℃、900℃、1000℃)、four kinds of O2volume fraction(25%、30%.35%.40%) and two kinds of atmosphere (O2/CO2and O2/N2) were designed.First, the impacts of biomass fuel type, ambient temperature, oxygen and atmosphere on NO conversion were investigated. Results show that because of high volatile content of biomass, NO conversion is mainly in the volatile combustion. This phase of the total amount of NO generation is60%-70%. When using oxy-fuel combustion, high concentration of CO2makes the combustion process generate a lot of CO which has a significant inhibitory effect on NO generation. When the amount of fuel-N is higher, NO emissions are also higher but the conversion ratio of fuel-N to NO is declining. When the temperature is higher, the total NO release is also higher but different biomass particles have different increasing proportion. The total conversion of NO increase with the increase of the volume fraction of O2. Under the O2/N2atmosphere, high concentration of oxygen makes the combustion process generate almost no CO. The whole reaction process is carried out in an oxidizing atmosphere. The total amount of NO conversion is much higher than O2/CO2atmosphere. The effects of fuel-N, temperature, and oxygen volume fraction on the total amount of NO show similar law between O2/N2atmosphere and O2/CO2atmosphere. But under O2/N2atmosphere, fuel-N to NO conversion ratio is higher. Second, the effects of ambient temperature, oxygen volume fraction and atmosphere on the flame image of biomass combustion were researched. Results show that the higher oxygen volume fraction is, the brighter biomass combustion flame is. It means the combustion temperature is higher. At the same volume fraction of oxygen, when ambient temperature was increased from800℃to900℃, the flame temperature increased more obviously. The flame temperature of rice husk particles improves about80℃and the flame temperature of wood pellets improves about110℃. When ambient temperature is increased from900℃to1000℃, the flame temperature of rice husk particles improves about50℃and the flame temperature of wood pellets improves about40℃. O2/CO2atmosphere has an impact on the formation of flame. On900℃,25%O2, the maximum combustion temperature of wood pellets reaches990℃in the O2/N2atmosphere and970℃in the O2/CO2atmosphere. |
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