Ultrasonic Preparation of Emulsions Derived from Aqueous Bio-oil Fraction and 0# Diesel and Combustion Characteristics in Diesel Generator

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• 作者：Yuping Li ; Tiejun Wang ; Wei Liang ; Chuangzhi Wu ; Longlong Ma ; Qi Zhang ; Xinghua Zhang ; Ting Jiang
• 刊名：Energy & Fuels
• 出版年：2010
• 出版时间：March 18, 2010
• 年：2010
• 卷：24
• 期：3
• 页码：1987-1995
• 全文大小：843K
• 年卷期：v.24,no.3(March 18, 2010)
• ISSN：1520-5029

文摘

Preparation of emulsions from aqueous fractions of biomass pyrolysis liquid (bio-oil) and 0# diesel was studied under ultrasonic power. The thermogravimetric analysis and combustion characteristics of the optimized emulsions in a particular diesel generator were also investigated. The results show that the mass ratio of aqueous bio-oil fraction to 0# diesel affected the emulsion stability greatly, by factor analysis method, and the optimized emulsion was not stratified for 30 days when the ratio was 1:9 under the following conditions: water:bio-oil mass ratio, 2:1; ultrasonic time, 120 min; formula emulsifier addition (Span-80:Tween-80:Tween-20:n-octanol ratio = 72:9:9:10, wt%), 3 wt% (which was longer than that prepared by mechanical agitation). The density and heat value of the nonstratified emulsions (after 30 days) were similar with those of 0# diesel, because of the low aqueous bio-oil fraction content and 0# diesel dilution; however, an increase of more than 38.4% in the dynamic viscosity and a decrease in pH from 5.26 to <3 may result from the concentrated polar oxygenates and carbohydrates in aqueous bio-oil fraction, which were further solubilized in water-in-oil (W/O) emulsion droplets. In addition, ultrasonic emulsification resulted in entropy augmentation and equilibrium tendencies (by thermodynamic analysis). Thermogravimetric analysis of the emulsion shows that there is a weight loss peak that is attributed to residual carbon combustion above 400 °C, in addition to a similar hydrocarbon vaporization peak at 180 °C with diesel. The existence of residual carbon and the high viscosity of the emulsion might have caused inefficient combustion when the output power of diesel generator was above 1400 W with high feeding amount, which also resulted in higher exhaust gas temperature than diesel feedstock, although microexplosion may have occurred. Moreover, when the output power increased to 1600 W with the emulsion used, the O₂ and NO_X emissions decreased 21% and 87.2%, respectively, the CO₂ emission increased 13.3%, and the CO and SO₂ emissions increased quickly to 5124 ppm and 59 ppm, respectively, compared with pure diesel. The corrosion and blockage caused by coking of the injector were obvious.