Experimental Study On Ignition And Combustion Of Single Biomass Particle And Combustion Characteristics Of Ethanol Spray Under Oxyfuel Conditions

As a kind of renewable energy,biomass has a wide utilization prospect,which is considered as a CO₂-neutral fuel.Oxyfuel combustion is one of the most promising technologies for CO₂ capture and storage.The utilization of biomass coupled with oxyfuel combustion technology could be a 'carbon negative' technology.Biomass combustion for power generation and bio-ethanol technology are two important methods of biomass utilization.In this paper,two aspects of research work are carried out on the single biomass particle ignition combustion and the ethanol spray combustion under oxyfuel conditions.First,a single particle ignition combustion test bench was built based on the McKenna flat flame burner.Taking pine wood particle as the material,the whole combustion process of single particle was recorded by a CCD high speed camera.The ignition and combustion characteristics of the millimeter-grade pine particles under oxyfuel conditions were studied.The results show that the primary pine wood particles show a homogeneous ignition model under all the experimental conditions.The effect of O₂ concentration on the ignition delay time of pine wood particles is relatively weak.In the O₂ concentration range of 21%to 55%,the volatile combustion duration time and residual char combustion duration time both decrease with the increase of O₂ concentration.The ignition delay time is prolonged by the increase of the size of spherical pine wood particles.Under the same volume condition,the ignition delay time of cylinder particles is significantly smaller than that of spherical particles,and the ignition delay time decreases with the increase of length diameter ratio?l/d?.The torrefaction treatment reduce the ignition delay time of the particles and promote the ignition.The volatile combustion duration and residual char combustion duration of pinewood particles show the opposite tendency with the increase of torrefaction degree,and the total burnout time of particles decreases with the increase of torrefaction degree.Secondly,the combustion characteristics of ethanol spray under oxyfuel conditions were investigated in the spray combustion test rig conducted using a McKenna flat flame burner.The flame feature parameters and CH*radical distribution feature parameters were extracted based on image processing technology.The flame height,flame area,and flame average brightness were proposed to characterize the flame features.The study focused on the effects of O₂ concentration,CO₂ concentration and ethanol/N₂ mass flow rate ratio?ME/MN₂?on spray flame and CH*radical distribution characteristics.The results show that,in the O₂ concentration range of 21%to 55%,the flame height and the flame area both decrease with the increase of O₂ concentration while the flame average brightness shows the opposite tendency.A higher O₂ concentration leads to smaller reaction distribution region and higher combustion intensity according to the CH*radical distribution characteristics.The effect of CO₂ concentration on flame size and flame average brightness is opposite to that of O₂ concentration,and the effect of CO₂ concentration on flame average brightness is more remarkable than that on flame size.In addition,the increasing trends of flame size and combustion intensity are observed with increasing ME/MN₂ ratio.