In stoker-firing furnaces, possible conditions created by adverse characteristics are excess fuel size and rapid changes in fuel moisture. The excess fuel size may lead to reduced suspension burning and grate piling, while the moisture content of the fuel leads to fuel slugging to the furnace, piling and clinkering, and heat damage to grates. Bagasse is one such biomass fuel, a renewable energy source used in stoker-fired furnaces in the sugar industry for power generation. The fuel has various particles sizes. The particle sizes have their own influence on the combustion in the furnace. This paper explains the simulation and experimental work conducted on the combustion of bagasse on a grate and the thermal decomposition of different size bagasse particles with sophisticated tests. The experimental results obtained validate the simulation work carried out on bagasse combustion. The distribution of temperature fields and their locations inside the furnace are well predicted.