| The increasing severity of the greenhouse effect has accelerated the development of oxygen-enriched combustion technology.O2/H2O is considered as a new type of oxygen-rich combustion,in which the tissue fuel is burned in oxygen and water vapor.CO2 capture is achieved by condensing and removing H2O from the flue gas.O2/H2O combustion mode has the advantages of compact system structure and low cost of CO2 purification,which has attracted widespread attention from researchers.In this paper,a self-designed thermostatic thermogravimetric and on-line monitoring experiment system for pollutants is adopted to study in detail the effect law of component concentration,temperature,coal species and other factors on coal combustion and NO release in O2/H2O atmosphere,providing further reference for the cognition of this combustion mode.The main research contents and results are as follows:（1）The effects of O2,H2O,and oxygen-water ratio on coal combustion characteristics in O2/H2O atmosphere were investigated.It was found that under the same O2 concentration,the burnout time is shortened with the increase of H2O concentration and the promoting effect is gradually weakened.At some one H2O concentration,increasing the O2 concentration can strengthen the burning rate of pulverized coal but weaken the intensity of the gasification reaction.When O2 and H2O cooperate,O2 has a significant promoting effect on coal combustion compared with H2O.With the increase of oxygen to water ratio,both the burnout time of pulverized coal and the maximum combustion rate of coke appear earlier,but the maximum combustion rate of coke decreases first and then increases.With the increasing of temperature,the gasification reaction is enhanced.High concentration（80%）of steam can raise the burning rate of different coal,and the higher the coal rank,the effect of steam is more obvious.（2）Comparing the pulverized coal combustion in O2/H2O and O2/N2atmospheres and calculating the kinetic parameters of the combustion reaction.The results show that in the range of 1:9,2:8,3:7 oxygen water/nitrogen ratio,the burnout time of coal in the O2/H2O atmosphere is earlier than that in the O2/N2atmosphere,the oxygen water/nitrogen ratio is increased,and the difference in burnout time is reduced.With the increasing of temperature,the comprehensive effect of H2O on coal combustion behaves differently:900～1100°C,H2O has a significant effect on accelerating the ignition of pulverized coal;1200～1400°C,the role of H2O is mainly reflected in the gasification reaction with coke.The calculation results of the kinetic parameters further show that the apparent activation energy of coal combustion in the O2/H2O atmosphere is smaller than the apparent activation energy in the O2/N2 atmosphere with the range of 900～1400°C.（3）The effects of O2,H2O,and oxygen-water ratio on NO release from coal combustion in O2/H2O atmosphere were investigated and compared with the release of NO in O2/N2 atmosphere.The study found that constant O2（or H2O）concentration,increasing H2O（or O2）concentration,exacerbated the instantaneous NO concentration peaks of volatile nitrogen and coke nitrogen combustion,and increased the total NO release.When O2 and H2O are synergistic,H2O has a greater effect on promoting NO release from coal combustion than O2.Increasing the oxygen-water ratio is an effective measure to reduce NO emissions.With the increase of temperature,the total amount of NO released by O2/H2O is lower than that of O2/N2atmosphere,which may be related to the content of CO in the O2/H2O atmosphere and its reduction strength to NO at different temperatures. |
PDF Full Text Request