Experimental And Numerical Simulation Studies Of Pulverized Coal Combustion In O₂/CO₂/H₂O Atmosphere

CO₂ emission of coal-fired power plants is the main source of CO₂ emission in China.Oxygen-enriched combustion technology is a new combustion technology with high carbon capture rate and can reduce low NOx emissions.Due to the effect of circulating flue gas,the water vapor concentration in oxygen-enriched combustion atmosphere can be as high as 30%?40%.To obtain the combustion characteristics of pulverized coal closer to the oxygen-enriched atmosphere of the boiler,the ignition and burnout characteristics of pulverized coal and the physical and chemical structure characteristics of coal were studied by experiments in O₂/CO₂/H₂O atmosphere.It provides a theoretical basis for the application of oxygen-enriched coal combustion technology in practical boilers.First,the combustion characteristics of four typical dynamic coal in china under O₂/CO₂/H₂O atmosphere?40% O₂,0?50% H₂O?were studied on thermogravimetric analyzer.The main results showed that :?1?The water vapor concentration increased,the ignition and burnout of Shenmu bituminous coal increased by 66.2? and 26.12?,Xingyi anthracite,Jincheng poor coal,Hailar lignite fire delayed 15.4?,15.53?,44.79?.The water vapor concentration increases,the weight loss rate and the comprehensive combustion index of the four kinds of coal increase,and the comprehensive combustion index of high volatile coal is more affected by water vapor.?2?The kinetic solution shows that the combustion of all four kinds of coal can be considered as a first-order reaction,and the activation energy is E related to the ignition temperature of coal.Secondly,the coal chars of Shenmu bituminous coal and Xingyi anthracite were prepared under O₂/CO₂/H₂O atmosphere?5% O₂,10%?30% H₂O?by using SHEFR.the main results show that :?1?In the process of pyrolysis of shenmu bituminous coal to produce coal char,the pore structure becomes abundant and the pore size distribution is wide.The increase of water vapor concentration greatly promotes the micropore and mesopore formation of 1?10 nm.?2?In the process of coal coke formation,the unstable carbon-containing functional groups are condensed,the sp2 C content increases,and the oxygen-containing functional groups are decomposed into small molecular gases at high temperature.The oxygen-containing functional groups of soot char are removed more thoroughly.With the increase of water vapor concentration from 10% to 30%,the sp2 C content of Shenmu bituminous coal and Xingyi anthracite coke decreased by 19.7% and20.35% due to the gasification reaction of C_?s?-H2 O.Finally,CFD software was used to study the effects of atmosphere,excess oxygen coefficient,wall temperature and average pulverized coal particle size on temperature field,component concentration,C_?s?consumption type,and NO emissions using EFCM.The main results show that :?1?the increase of water vapor concentration and O₂ concentration will increase the temperature in the reactor,reduce the NO emission,and increase the temperature peak after replacing the diluted gas CO₂ with the N2.Under N2 atmosphere,increasing O₂ concentration will significantly increase the amount of thermodynamic NO,and increasing water vapor concentration will reduce the generation of thermodynamic NO;?2?C_?s?diffusion competition is the main mechanism of heterotropic reaction competition,and increasing the concentration of gas corresponding to coal coke surface will increase the proportion of C_?s?consumed by the corresponding heterotropic reaction.