Combustion characteristics of pelletized-biomass fuels: a thermogravimetric analysis and combustion study in a fluidized-bed combustor

摘要

This work aimed to investigate the combustion characteristics of rubberwood sawdust pellet (RSP), teak sawdust pellet (TSP), eucalyptus bark pellet (EBP), cassava rhizomes pellet (CRP), and their corresponding raw biomass. The experiments were performed in a thermogravimetric (TG) analyzer and a fluidized-bed combustor (FBC). Thermogravimetric analysis (TGA) was conducted in the temperature range of 30-1000 & DEG;C at a heating rate of 10 & DEG;C/min in a dry air atmosphere. The combustion experiments were conducted in a twin-cyclone FBC at 120 kilowatts (kW(th)) heat input with three values of excess air (EA): 40, 50, and 60%. The combustion reactivity of the pellets was lower than raw biomasses, as indicated by higher values of peak, ignition, and burnout temperatures, as well as a lower comprehensive performance index value. The activation energies of the biomass pellets were greater than the as-received biomasses, indicating that the biomass pellets required higher energy and temperature and a longer time for complete combustion. The pellet fuels had a higher residence time and better mixing of the fuel and bed particles, leading to higher combustion intensity in a fluidized bed. Carbon monoxide (CO), hydrocarbon (CxHy), and nitric oxide (NO) emissions of the combustor when firing the pellets were lower compared to the burning of as-received biomasses. When firing the pellets at optimal EA (about 40%), the combustor operated at high combustion efficiency of 99.0-99.8%. This study indicated that the biomass pellets have desirable combustion characteristics that could be used as alternative fuels for sustainable energy production.