The effects of nozzle design on the combustion of wood-derived fast pyrolysis oil

Highlights: • Better atomization was achieved by reducing the total area of the nozzle air cap outlets and by increasing the air/liquid relative velocity within the nozzle's mixing chamber. • Particulate emissions were reduced with better atomization, dispersal of the spray and sufficient hot-zone residence time. • Nozzle coking was reduced with better atomization and reduced recirculation at the base of the nozzle. • Flame seating and stability were improved with better atomization and strengthened recirculation. • Better nozzle design made possible combustion without blending, cold-starts and no pilot flame during steady-state operation. - Abstract: Researchers examined how nozzle design influences the combustion and emissions of a 10 kW, pure fast pyrolysis oil (FPO) flame from a swirl burner within an insulated combustor using an internally mixed air-blast nozzle. No other studies are known that conducted a detailed investigation of the effect of nozzle design on the combustion and emissions of a pure FPO spray flame. FPO (also called bio-oil or pyrolysis liquid biofuel) is a biofuel made from waste wood, but its properties, especially its high water content, make efficient combustion challenging. Combustion experiments showed how carbon monoxide (CO) emissions, nitric oxide (NO) emissions, carbonaceous residue, flame stability and nozzle coking were influenced by the nozzle's mixing chamber diameter and outlet number/diameter, angle and total area. Ultimately, an optimized nozzle was designed that achieved a self-sustaining FPO flame with excellent stability, low emissions and low coking; it also operated under ^cold-start conditions and at steady-state conditions, did not require a pilot flame to maintain a stable, seated flame. The results show that with careful nozzle design, FPO is able to perform very effectively in burners and can therefore help to facilitate the replacement of fossil fuels.