Research On Vaporization Behavior Of Selenium In Oxy-fuel Combustion Process

Trace elements from coal combustion significantly threaten people's health and global environment, so it is imperative to remove trace elements from coal combustion. Research about trace elements and their compounds has been a new and front field of combustion pollution and has been paid more attention than before. Oxy-fuel combustion is now a new technology which can achieve integrative control of pollutants emissions. This technology uses O2 and recycled flue gas(mainly CO2) as medium to replace air in combustion process. The previous results showed that this technology can prevent CO2/SO2/NO emissions simultaneously, but more researches must be carried out on trace elements emissions in oxy-fuel combustion.In this study, experiments have been done to investigate the coal combustion characteristic and the vaporization behavior of Se in oxy-fuel combustion process on the basis of previous study. The study on the coal combustion characteristic in oxy-fuel combustion has been carried out using three typical western coals. The influence of some factors, such as heating rate, combustion atmosphere and Ca:Se has been studied. After adding SeO2 into the typical western coals, the influence of CaO and different combustion atmosphere on the vaporization behavior of Se has been studied. The results showed that in static experiments the pulverized coal had better ignition characteristic and higher combustible rate in oxy-fuel combustion, and the combustion characteristic had been improved. In the pure mineral of SeO2 and CaO combustion experiments, the vaporization rate and total emission amount in oxy-fuel combustion differed from that in air combustion. In oxy-fuel combustion, the total vaporization amount was less. In the same atmosphere, Se vaporized more with Ca:Se growing. The heating rate hardly affected SeO2 vaporization, mainly accelerating or deferring its vaporization. After adding SeO2/CaO into the pulverized coal, the experiments showed that Calcium-based compound can prevent the vaporization of Se. The volatile in coal released in advance at lower temperature, and the pulverized coal burnt better and released less Se in oxy-combustion process.The above research results gave the basis of further researches and applications.