SIMULATION OF A SMALL SCALE PELLET BOILER

A Computational Fluid Dynamics model, implemented in the FLUENT code, has been used to describe with detail the combustion inside the furnace of a 15 kW pellet boiler. The solid biomass is modeled by the reaction of the volatile mater. The air supply is split into two regions with varying AF ratios. It was also observed that the NO formation in the combustion chamber is essentially due to the fuel-NO path and therefore the variations of excess air did not affect the concentration levels of NO at the exit of the combustion chamber. However by increasing the air supply in the vicinity of the grate (by moving the secondary air supply closer to the primary air supply) the NO levels increased. The emissions of the flue gases were measured and compared with the computed results. The results enable the optimization of the combustion chamber design and the efficient fine tuning of a pellet boiler for a wide range of power levels.