Optimum reaction time, performance and exhaust emissions of biodiesel produced by microwave irradiation

Abstract

While transesterification is well established, there remain considerable inefficiencies in existing transesterification processes. In this study an alternative energy stimulant, ''microwave irradiation'' was used for the production of the alternative energy source, biodiesel. The optimum parametric conditions obtained from the conventional technique were applied using microwave irradiation in order to compare both systems. The results showed that application of radio frequency microwave energy offers a fast, easy route to this valuable biofuel with advantages of enhancing the reaction rate and improving the separation process. The methodology allows for the use of high free fatty acid content feedstock, including used cooking oil; hence it helps to reduce the cost of production which constitutes a major hurdle towards widespread commercialization of biodiesel. The study also showed that the optimum reaction time for microwave-enhanced biodiesel production should be highly respected. Exceeding the optimum reaction time will lead to deterioration of both biodiesel yield and purity. This paper also reported the performance and exhaust emissions from a diesel engine when fuelled with a petroleum diesel fuel and two different biodiesel fuels; one obtained by the conventional technique and the other by microwave irradiation. It was concluded that microwave-enhanced biodiesel is not, at least, inferior to that produced by the conventional technique.

Different techniques for the production of biodiesel from waste vegetable oil

“…This increase is proportional to the decrease in the heating value of biodiesel. Refaat et al (2008b) found that the difference in performance between microwave-enhanced biodiesel and petroleum diesel was not statistically significant; a slight increase in SFC was detected with biodiesel, no significant differences were observed in brake thermal efficiency and the combustion efficiency remained constant using either microwave-enhanced biodiesel or Diesel fuel. Najafi et al (2007) noticed that by adding 20 % of waste vegetable oil methyl ester to petrodiesel fuel the maximum power and torque increased by 2.7 % and 2.9 %, respectively (Najafi et al, 2007).…”

“…Most of the studies on the base-catalyzed transesterification of WVO reported that maximum conversion to the ester occurred with a molar ratio of 6:1 (Tomasevic and Siler-Marinkovic, 2003;Saifuddin and Chua, 2004;Encinar et al, 2005;Gupta et al, 2007;Meng et al, 2008;Refaat et al, 2008b). Transesterification of pretreated waste rapeseed oil carried out by Yuan et al (2008) showed a maximum conversion at 6.5:1 of methanol to oil ratio, whereas an earlier study by Leung and Guo (2006) found a maximum conversion at a ratio of 7:1.…”

“…(Barnard et al, 2007). In a study by Refaat et al (2008b) the optimum parametric conditions obtained from the conventional technique were applied using microwave irradiation in order to compare both systems for the production of biodiesel from neat and waste vegetable oils. The results showed that application of radio frequency microwave energy offers a fast, easy route to this valuable biofuel with advantages of enhancing the reaction rate and improving the separation process.…”

“…The performance of engines fueled with biodiesel produced from waste vegetable oil was extensively covered in the literature (Dorado, 2003a;Tashtoush et al, 2003;Volmajer and Kegl, 2003;Najafi et al, 2007;Lapuerta et al, 2008;Meng et al, 2008;Refaat et al, 2008b;Utlu and Kocak, 2008;Ghobadian et al, 2009) Lapuerta et al (2008 tested two different biodiesel fuels, obtained from waste cooking oils with different previous uses in a diesel commercial engine either pure or in 30 % and 70 % v/v blends with a reference diesel fuel. The main objective of their work was to study the effect of biodiesel blends on particulate emissions, measured in terms of mass, optical effect (smoke opacity) and size distributions.…”

“…Kegl (2008Kegl ( , 2006 indicated that, using biodiesel, harmful emissions (NO x , CO, smoke and HC) can be reduced to some extent by adjusting the injection pump timing properly. Numerous reports in the literature deal with the study of exhaust emissions from engines fueled with biodiesel produced from waste vegetable (Dorado, 2003a;Tashtoush et al, 2003;Sudhir et al, 2007;Lapuerta et al, 2008;Meng et al, 2008;Refaat et al, 2008b;Utlu and Kocak, 2008;Ghobadian et al, 2009). Lapuerta et al (2008) found that by using biodiesel the soot and particulate matter emissions, as well as the particle number concentration, decreased sharply, mainly due to the oxygen content of the biodiesel, which improve the oxygen availability in rich-zone flames in the combustion chamber.…”