Abstract
Research and/or Engineering Questions/Objective
Wood pyrolysis oil (WPO) derived from wood has been regarded as an alternative fuel to be used in diesel engines. However, the direct use of WPO in a diesel engine is not possible due to the low energy density, high acidity, high viscosity, high water content, and low cetane number of PO. In this study, we would like to apply WPO in a diesel generator through the mixing with alcohol fuel and cetane enhancements. WPO-alcohol blended fuel which has an enough auto-ignitability can be produced via simple mixing of PO, alcohol fuel, and cetane enhancements.
Methodology
The most widely used approach to improve the fuel qualities of WPO are blending of WPO with other hydrocarbon fuels which have higher cetane number. However, WPO and fossil fuels are not usually blended because of its different polarity. Hence, a cumbersome process called emulsification is needed to mix WPO and fossil fuels with appropriate surfactants. However, the emulsification process needs additional time and costs, and clogging and polymerization problems in fuel supply system are still occurred. Polymerization of WPO can be prevented by diluting WPO in alcohol fuels. Early mixing with alcohol fuels has an added benefit of significantly improving the storage and handling properties of WPO. However, WPO-alcohol blended fuel still does not produce the self-ignition; hence additional cetane enhancements should be added in the blended fuel. In this study, we would like to use WPO through the mixing with n-butanol and cetane enhancements (PEG 400 and 2-EHN).
Results
By selecting the proper portion of WPO-butanol-cetane enhancements, the fuel properties were improved for the energy density, viscosity, and auto-ignitability. Experimental results showed that highly stable engine operation was obtained for WPO-blended fuels with a maximum WPO content of 15 wt%. The combustion of WPO-butanol blended fuels produced more hydrocarbon (HC) and carbon monoxide (CO) emissions than diesel fuel combustion over most of the generator load range due to the incomplete combustion of the blended fuels. And nitrogen oxides (NOx) emissions for the blended fuel were higher than those of diesel fuel under the generator load range of 3 kWe due to the high fuel NOx of the blended fuels. PM generation from the blended fuels was reduced up to 90% due to the high oxygen content of the blended fuels.
Limitations of this study
An important limitation of the current study is that the durability of fuel injection system (injector, high pressure pump, low pressure pump) is not guaranteed. Long-term operation of the generator fueled with the blended fuels should be conducted.
What does the paper offer that is new in the field including in comparison to other work by the authors?
The experiment in this study was conducted in a diesel generator system with mechanical injector and pump. This system is not sensitive for the fuel quality especially for the lubricity, viscosity, and impurities. Therefore, this study could commercially apply in a real-world diesel generator.
Conclusions
The blended fuel of wood pyrolysis oil and n-butanol was examined as an alternative fuel that might be able to replace conventional diesel fuel. The performance and emission characteristics of the generator fueled with the blended fuels were comparable to the diesel generator.
KEYWORDS : Fast pyrolysis, Wood pyrolysis oil (WPO), Biomass, Butanol, Diesel generator