| O2/CO2 combustion is one of the promising technologies to control the CO2 emission from coal-fired power plants.At present,the technology has many key problems to be solved urgently.Compared with conventional air combustion,high concentration of CO2 and H2 O in wet flue gas of O2/CO2 combustion will have a certain effect on combustion.The effect of CO2 and H2 O in flue gas on the O2/CO2 combustion characteristics of Datong bituminous coal firstly studied using TG-DTG method of heat balance.The results show that CO2 and H2 O mainly affect the burning rate of pulverized coal through physical and gasification reactions,and the gasification reactions of CO2 and H2 O begin at about 900? and 800? respectively.H2 O plays a leading role in the co-gasification of CO2/H2 O.The kinetics calculation shows that in 5% oxygen concentration,char activation energy O2/N2<O2/CO2< O2/CO2/H2 O.Reduce the oxygen concentration,the DTG curve move to the high-temperature zone,char activation in different reaction atmosphere can decrease.In order to further clarify the mechanism of the CO2/H2 O gasification influence of coal O2/CO2 combustion,the isothermal temperature combustion behavior of Datong bituminous coal and Yangquan anthracite coal in O2/N2,O2/CO2 and O2/H2O/CO2 atmosphere were studied in the temperature of 800-1200? and oxygen concentration in the range of 2-21% using self-made analysis system.The results show that the burning rate of pulverized coal is O2/N2>O2/CO2/H2O>O2/CO2,because of the difference of specific heat and oxygen diffusion capacity of N2,H2 O and CO2 at 800?.At 1000?,H2 O and CO2 were reacted with pulverized coal to promote the consumption of coal powder,so that the overall reaction rate of the pulverized coal in O2/CO2/H2 O was gradually close to and exceeded the burning rate in O2/N2.The increase of temperature can enhance the effect of CO2/H2 O,so as to improve the overall reaction rate of coal.But increasing oxygen concentration will weaken the gasification effect,so that the reaction process of pulverized coal in 21% oxygen concentration is close to.Gasification was more significant in the process of high coal gasification reaction.Study of Datong bituminous coal and Yangquan anthracite coal O2/CO2/H2 O isothermal combustion NO release and ash characteristics.The results show that the Datong bituminous coal combustion in O2/CO2 and O2/N2 only have one NO concentration peak,but in O2/CO2/H2 O because the H2 O gasification,with the increase of temperature NO release gradually into two concentration peaks.Yangquan anthracite coal NO release process is similar to Datong bituminous coal.NO emissions of Datong bituminous coal in O2/CO2 is lower than O2/N2.In 5% oxygen concentration,due to the strong influence of H2 O gasification,so that the NO emissions of Datong Coal in O2/CO2/H2 O with the increase of temperature gradually close to and more than O2/CO2.The increase of oxygen concentration reduced the gasification effect,and the NO emission of Datong Coal in O2/CO2/H2 O was lower than that in O2/CO2.NO emissions of Yangquan anthracite coal is higher than that of Datong bituminous coal,but the trend of different atmosphere were basically the same with Datong coal.Under the 5% oxygen concentration,the NO emission increases with the increase of the concentration of water vapor,and the NO emission decreases with the increase of the concentration of water vapor at 21% oxygen concentration.The effect of CO2/H2 O gasification on the transformation of fly ash in different atmosphere is not obvious. |
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