Experimental Study On The Particle Emissions Of Recycled Flue Gas Combustion Of Coal

Flue gas recycled (FGR) combustion technology is seen as an effective way to reduce CO2 emission of boiler in power plant. Study on the characteristics of pollutants emission is significant for developing the corresponding pollution control technology and improving flue gas recycled combustion system. In this work, based on 15 KW one-dimensional download furnace, experiments of flue gas recycled and air combustion were developed and pollutants emission under these two conditions were compared.It was found that, because the primary air was completely recycled flue gas, burnout rate of coal particle in FGR condition decreased 4.6% and CO concentration in flue gas increased a little. Because of the accumulation effect and less flue gas flux in FGR combustion, NOX and SO2 concentration in flue gas significantly increased. The conversion rate of fuel-N decreased, due to that NOX reacts with coal during FGR process. The conversion rate of fuel-S also decreased because some fuel-S retents in the deposited ash along the combustion system.ELPI was used to measure emission concentration and size distribution of the particulate matter PM10. The results showed that amount of PM10 in FGR condition was more than that in air conditon and there were two peaks in size distributions of PM10 mass concentration of both combustion conditions. Peak in submicron zone in FGR combustion moved to larger particle size because of high O2, CO2 and CO concentration.Observations of SEM and EDX showed that PM10 in both experiments had the same morphology and components. There were much more soot in PM10 from FGR condition for its lower burnout rate and coal particle burning temperature.ICP was used to analyze element distribution in the particles. It was found that most minor elements and trace elements distribution in PM10 from both combustion conditions changed a lillte except Se. Se content in PM10 from FGR condition was significantly higher than that in air combustion. This may because that the reaction between CaO and SeO2 was promoted by high H2O vapor concentration in FGR combustion. So is the reaction between SO2 and ash sticked on the bag.The study on pollutant, especially particulate matter emission from FGR combustion showed that the PM control technology for FGR combustion can be similar as regular air combustion, but different SO2 control technology must be considered. High SO2 concentration in recycled flue gas will cause severe erosion. High temperature FGD technology should be taken for high sulfur coal. Research in this work will give important support for further research and improvement of FGR combustion technology.