The Effects Of Biomass Fiber Components On The Combustion Characteristics Of Biomass And Biomass-Coal Mixtures Under High Heating Rate Conditions

Energy crisis and environmental problems are common challenges for human society.Biomass energy is an important energy to deal with global warming due to the advantages of wide distribution,rich reserves,renewability,and carbon neutrality.Oxy-fuel combustion of biomass and co-combustion of biomass and coal can effectively realize "carbon emission reduction".At present,multiple researches have been conducted on the combustion characteristics of biomass,oxy-fuel combustion characteristics of biomass,and cocombustion characteristics of biomass and coal mixtures under low heating rate conditions.Many of them have analyzed these combustion characteristics from biomass fiber components(lignin,hemicellulose,and cellulose).The heating rate will significantly affect the combustion characteristics of biomass and its influencing mechanism,and the actual biomass combustion is carried out under high heating rate conditions.Hence,it is meaningful to study the effects of biomass fiber components on the combustion characteristics of biomass and biomass-coal mixtures under high heating rate conditions.In this paper,the effects of biomass fiber components on the combustion characteristics of biomasss and biomass-coal mixtures under high heating rate conditions will be studied in the following four aspects.The influence of biomass fiber components on the combustion characteristics of biomass under a high heating rate condition was studied by a drop tube furnace and radiant energy analysis technology.The results indicated that the lignin content in biomass determines the ignition mechanism,the rate of increase in the flame temperature after ignition,the char ignition time,and the maximum combustion temperature of biomass.The ignition temperature of biomass mainly depends on the cellulose component.Biomass with moderate and high lignin content ignites homogeneously,and biomass with very low lignin content ignites hetero-homogeneously.After homogeneous ignition,the rate of increase in the flame temperature of biomass increases approximately linearly with the increase of lignin content,while the char ignition time of biomass decreases approximately linearly with the increase of lignin content.The effects of biomass fiber components on the ignition mechanism of biomass under a high heating rate condition and different oxygen concentrations were studied in a drop tube furnace.The results showed that the effects of the oxygen concentration on the ignition mechanism of biomass are closely related to the lignin content.Only when the lignin content is very low(less than 5%),it is related to the cellulose content.Meanwhile,the change of ignition mechanism of biomass leads to the doubling of the rate of increase in the flame temperature after ignition.The biomass fiber components,peanut shell,and their mixtures with bituminous coal were pressed into pellets.The influence of the synergistic effects between biomass fiber components and coal on the volatiles and char ignition of biomass-coal mixtures under a high heating rate condition were studied using a Hencken burner and radiant energy analysis technology.The results indicated that the synergistic effects between peanut shell and bituminous coal promote the homogeneous ignition and char ignition of the mixtures,which mainly stems from the synergistic effects between cellulose in biomass and bituminous coal.Five types of biomass and their mixtures with bituminous coal were pressed into pellets.The influence of synergistic effects and alkali metal on the volatiles and char ignition of biomass and biomass-coal mixtures under a high heating rate condition was studied in a Hencken burner.The results showed that the catalytic effects of potassium on the synergistic effects between cellulose and lignin need to meet two conditions for the promotion of biomass ignition.First,the mass proportion of cellulose in the total mass of cellulose and lignin in biomass should be in the range of 50%～75%.Secend,the cellulose content in biomass should be greater than 40%.The synergistic effects between biomass and bituminous coal at 25% biomass blending ratio mainly come from the synergistic effects between cellulose and bituminous coal,while the catalytic effects of potassium is not obvious.