Evaluating the feasibility of biomass pyrolysis oil for spray combustion applications

Current fuel conversion technology is a result of decades of experience with fossil fuels. The liquid fuels derived from the pyrolysis of biomass are significantly different from fossil fuel oils. The chemical and physical properties of typical pyrolysis oils were investigated and compared to fossil fuels. Special fuel handling requirements for the bio-oil were incorporated into a fuel delivery system design and a laboratory scale spray combustor system was constructed. The implications of the viscosity and surface tension on the atomization were analyzed, leading to an experimental combustion chamber and air swirler design. Hot-gas filtered pyrolysis oil made from poplar wood at NREL was used in the combustion experiments. Emissions were monitored and CFR 40 part 60 methods were used to sample stack gas. These results were used to determine optimal operating conditions. It was concluded that, within specific constraints, an industrial size boiler or furnace could be constructed and operated to reliably burn pyrolysis oil. The boiler, when operating at optimal combustion conditions, would not violate the US Clean Air Act emissions standards (as currently proposed).