| Summary: | 博士 === 國立成功大學 === 環境工程學系 === 102 === The interest in developing clean and sustainable energy sources has grown considerably due to the finite supply of fossil fuels and the environmental and health concerns related to pollutant emissions. In this study, the emission of persistent organic pollutants (POPs) from diesel engine were investigated, including polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated Biphenyls (PCBs), polychlorined diphenyl ethers (PCDEs), polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs), polybrominated biphenyls (PBBs), and polybrominated diphenyl ethers (PBDEs). In addition, the waste cooking oil (WCO)-base biodiesel and water-containing alcohol (butanol and acetone-butanol-ethanol (ABE)), which simulate the products of biomass fermentation without dehydration and no addition of surfactants, were tested as alternative fuels to enhance the energy efficiency and lower pollutant emissions from diesel engines.
Results indicated that the emission of PAHs, PCDD/Fs, PCBs, PCDEs, PBDD/Fs, PBB, and PBDEs from diesel engine fueled with commercial diesel (B2) were 0.596-0.617 g BaPeq g/Nm3, 4.48-9.72 pg I-TEQ pg/Nm3, 0.0775-1.15 pg WHO-TEQ /Nm3, ND, 0.566-2.40 pg TEQ /Nm3, 9.66 pg/Nm3, and 39.4-41.3 ng/Nm3, demonstrating that the diesel engines are responsible source of the environment POPs. The addition of WCO-based biodiesel not only reduced the precursors of the aforesaid pollutants, but promoted more complete combustion in the diesel engine. Although the chlorine content of the WCO-based biodiesel was about five times higher than that of the commercial diesel, using B10 and B20 as fuels can decrease these emission factors of POP, and the reduction increased along with the percentage of biodiesel added to the blends.
For the water-containing butanol, it was found that can also reduce the emissions of persistent organic pollutants (POPs) from diesel engines, after using blends of B2 with 10% and 20% water-containing butanol, the POP emission factors were decreased by amounts in the range of 22.6%-42.3% and 38.0%-65.5% on a mass basis, as well as 18.7%-78.1% and 51.0%-84.9% on a toxicity basis. This POP reductions of water-containing butanol were similar to that of WCO-based biodiesel. However, the small amount of water content may lower the in-cylinder temperature (cooling effect), thus, solves the problem of greater nitrogen oxide (NOx) emissions from biodiesel fueled diesel engine.
For the other water-containing ABE, the diesel blend with 20 vol% water-containing ABE enhanced the break thermal efficiencies (BTE) by 3.26-8.56%., and reduce the emissions of particulate matter (PM) and NOx by 5.82-61.6%, 3.69-16.4%, respectively, when compared to regular diesel. In order to produce more preferable properties for diesel engine, addition of biodiesel in water-containing ABE diesel blends are consider. Although biodiesel had greater NOx emissions, the blends that contained 25% of the water-containing ABE had significantly lower NOx (4.30-30.7%), PM (10.9-63.1%), and PAH emissions (26.7-67.6 %) than the biodiesel-diesel blends and regular diesel, respectively. In addition, the energy efficiency of this new blend was 0.372-7.88% higher with respect to both the biodiesel-diesel blends and regular diesel. These benefits resulted from higher oxygen content of ABE which promote more complete combustion, and the cooling effect that is caused by the high vaporization heat of water-containing ABE.
Consensually, the bio-fuels content in the ABE-biodiesel-diesel blend is up to 75% (50% biodiesel and 25% water-containing ABE solution) and can be used in unmodified diesel engines without higher NOx emissions, one that also has the advantages of greater energy efficiency, trade off, and lower PM and POP emissions. In addition, blend with the water-containing alcohol and WCO-based biodiesel not only solves the problem of waste oil disposal, but also improve the fuel properties. On the other hand, the acceptance of a small amount of water in the fuel blends can simplify the fuel production process by eliminating the need for dehydration and surfactant addition. In summary, this research identified an innovating and simple way to utilize the bio-produced water-containing alcohol and biodiesel as a cleaner fuel.
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