THE STUDY OF SAWDUST COMBUSTION IN A VORTEXING FLUIDIZED BED COMBUSTOR

摘要

In order to understand the combustion phenomena of woody material in a vortexing fluidized bed combustor (VFBC), a series sawdust combustion tests were carried out in a pilot scale VFBC. The sawdust is from the residuals of timber industry. The pilot VFBC consists of a 0.4m×0.8m×0.75m (W×L×H) of rectangular combustion chamber and a cylindrical freeboard with 0.75m I.D. The secondary air is injected at the position of 1.75m above distributor. The effects of operating parameters on the combustion efficiency, temperature distribution, and combustion proportion are investigated in this present work. The results of this study indicate that as primary air increasing, more heat released in the splashing zone; however, more unburned carbon particles reduce combustion efficiency. Higher secondary air flow prolonged the residence time of the unburned carbon particles to make the heating release ratio rise on the second air zone and freeboard zone. The combustion efficiency and heating release ratio increase with excess air, because of more oxygen reacted with combustibles. The features of the performance of sawdust combustion in VFBC reflect the specific fuel properties of high volatile biomass. The results of this study will help us to design a VFBC which can extract the biomass energy of woody biomass.