Co-combustion Behavior And Ash Fusion Characteristics Of Biomass/Lignite Based On Two-stage Scheme

The combustion performance, kinetics and ash fusin characteristics of two biomass species (Eucalyptus bark and cornstalk) and lignite under air atmosphere are evaluated using thermal analysis techniques. The effects of sample kinds, blending ratio and heating rates on the combustion are revealed based on the two-stage scheme, which refers to the combustion period of volatile matters and the combustion period ofcoke. The influance of biomass kind, blending ratio and heating rates on ash fusion characteristics are obtaind. Ash fusion kinetics of samples are determined.Based on TG and DTG curves of samples, two biomasses show better volatile matter release performance and comprehensive combustion performance than those of the lignite. By increasing biomass blending ratio and heating rate, those performances of biomassed/lignite get improved. When blending ratios of biomass are over20%, the combustion performances of blends are improved obviously. Blending ratio and heating rate gets significant influence on volatile matter release index and comprehensive combustion index of Eucalyptus bark/lignite. The volatile matter release index is mainly affected by blending ratio, while comprehensive combustion index affected by heating rate.From the mass spectrometry curves, with increasing the blending ratio, the releasing strength of CO2and NO2decreased first, then incresed again,40%Eucalyptus bark/60%Lignite shows the optimal releasing performance. H2O shows the maximum releasing strength. The releasing strength of SO2was determined by the content of sulfur for each sample. When increasing the heating rate, the releasing of CO2and NO2for Eucalyptus bark/lignite decreased gradually, while cornstalk/lignite shows completely opposite conclusions.In the combustion period of volatile matters, except for60%Eucalyptus bark/40%Lignite, the dominant mechanisms of combustion for biomass/lignite during the pre-peak period are described by the three dimensional diffusion. The dominant mechanisms during the post-peak period are described by Mampel Power rule and the three dimensional diffusion. The apparent activation energy of biomss/lignite is in the range of49.28kJ/mol to113.98kJ/mol at pre-peak, while50.23kJ/mol to131.26kJ/mol at post-peak. In the combustion period of coke, the dominant mechanisms of combustion for biomass/lignite during the pre-peak and post-peak period are described by Mampel Power rule and the three dimensional diffusion. The apparent activation energy of biomsses/lignite is in the range of25.20kJ/mol to76.13kJ/mol at pre-peak, while24.18kJ/mol to100.64kJ/mol at post-peak. For the20%Eucalyptus bark/80%Lignite, there is a strong synergistic effect in its parent samples at10℃/min heating rate.Lignite shows higher ash fusion temperature than that of biomasses/lignite, which is from1320℃to1458℃, and from1173℃to1420℃, respectively. The ash fusion temperature decreases with the increase of biomass blending ratio. The blending ratio should be less than40%in order to prevent depositing and slaggingThe dominant mechanisms of ash fusion for biomass/lignite during the pre-peak and post-peak period are described by Mampel Power rule, the three dimensional diffusion and random nuclear producing and growing process. The apparent activation energy of biomsses/lignite is in the range of294.37kJ/mol to814.38kJ/mol at pre-peak, while311.48kJ/mol to701.64kJ/mol at post-peak. There is a strong synergistic effect in its parent samples for the20%Eucalyptus bark/80%Lignite at15℃/min heating rate. The study can be used as basic reference for the furtherresearch of co-combustion of biomass/coal...