Browsing by Author "Boateng, Akwasi A."

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    Pyrolysis Oil Combustion in a Horizontal Box Furnace with an Externally Mixed Nozzle
    (2016-04) Lujaji, Frank C.; Boateng, Akwasi A.; Schaffer, Mark A.; Mullen, Charles A.; Mkilaha, Iddi; Mtui, Peter L.
    Combustion characteristics of neat biomass fast-pyrolysis oil were studied in a horizontal combustion chamber with a rectangular cross-section. An air-assisted externally mixed nozzle known to successfully atomize heavy fuel oils was installed in a modified 100 kW (350"000 BTU/h nominal capacity) burner to explore full utility for pyrolysis oil (bio-oil) combustion in a furnace. Combustion experiments were conducted at air/fuel equivalence ratios of 0.46, 0.53, and 0.68 (116, 88, and 47% excess air, respectively) and compared to diesel fuel flames (control) at the two higher air/fuel equivalence ratios. In these experiments, the fuel flow rate was maintained at a constant energy input (equivalent of 24 kWth). The results revealed that, while the externally mixed nozzle could effectively atomize and ensure stable combustion of neat bio-oil at the set heat rate, this comes with a penalty associated with a lower peak flame temperature and, hence, heat flux. The formation of carbon monoxide (CO) decreases with an increasing air/fuel equivalence ratio for bio-oil combustion. The levels of carbon dioxide (CO2) and nitrogen oxides (NOx) increase with an increasing air/fuel equivalence ratio for bio-oil combustion and were slightly higher than that generated by diesel. Hydrocarbon emissions do not follow any defined trend with an increasing air/fuel equivalence ratio for bio-oil, as typically observed for diesel fuels as a result of the oxygenated nature of bio-oil.
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    Spray Atomization of Bio-Oil/Ethanol Blends with Externally Mixed Nozzles
    (2015-09) Lujaji, Frank; Boateng, Akwasi A.; Schaffer, Mark A .; Mtui, Peter L.; Mkilaha, Iddi
    Experiments were conducted to investigate the properties of sprays of pyrolysis oil (bio-oil) blends with ethanol using an air assisted atomization nozzle operated without combustion. This was done in order to explore the potential for pyrolysis oil combustion in industrial and residential furnaces. The liquid samples investigated were bio-oil blends with ethanol (EtOH), neat ethanol and diesel. The bio-oil:EtOH blends were prepared in concentrations of 20:80 and 40:60vol%. Twin-fluid externally mixed nozzles SU2, SU4, and SU5 with liquid orifice areas of 0.40, 1.82 and 5.07mm2, respectively, were used in the spray experiments. The liquid and atomizing air flow rates as well as temperature were controlled to maintain constant liquid flow rates (cc/s) equivalent to 30 and 50kW energy input. Images of atomized spray droplets were measured to determine their size and velocity. Results show that it is possible to spray bio-oil/ethanol mixtures containing up to 40% bio-oil that has a low water content (12.60%). High viscosity and a tendency to coagulate were the main drawbacks; however, the 20:80 bio-oil:EtOH blend and neat ethanol in all three nozzles exhibited spray characteristics similar to that of diesel over atomization air flow rates of 15-30SLPM.