A study on the fuel properties and engine performance of biodiesel refined from used cooking oil

• Main Authors: Min-Shiu Wu, 吳明修
• Other Authors: Cherng-Yuan Lin
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/49404209407779663619

碩士 === 國立臺灣海洋大學 === 輪機工程系 === 92 === Abstract Air pollutants which are produced from burning fossil fuel in diesel engines would result in damage to environment. Diesel engines have been considered as one of major pollution sources in metropolitan regions. Biodiesel is a clean alternative fuel for fossil diesel. The burning of biodiesel generally produces lower concentrations of CO, HC, and PM, and almost zeros SO2 emission which would reduce corrosion rate of metallic parts of a power plant. Biodiesel can not only be used as fuel but also as lubricant for moving parts. The higher flash point of biodiesel would also promote safety of its usage, storage and transportation. Hence, the study of biodisel is one of emphases for the development of alternative clean fuel. The use of recycled used cooking oil to refine biodiesel may reduce the cost of biodiesel production. An ultrasonic vibration method can be used instead of a method of heating and stirring for enhancing a transesterification reaction. The transesterification reaction time may therefore be shortened. The cavitation phenomenon which occurs during ultrasonic vibration is able to curtail the thickness of liquid film of the reactant mixture. The mixture between methanol and triglyceride can then be accelerated, which will prevent the loss of biodiesel from being mixing with the soap during long reaction time. Moreover, the use of transesterification reaction accompanied with ultrasonic vibration may reduce the required amount of catalyst, proceed at a room temperature, and omit the installation of a heater. The higher the vibration frequency of an ultrasonic vibrator is, the larger biodiesel yield would be obtained. This study applied ultrasonic vibration method to proceed transesterification reaction for biodiesel production. At the first stage of the experiment, the sample No.1 biodiesel was refined from the used cooking oil by employing the method of transesterification reaction together with ultrasonic vibration. A peroxidation process was further employed to refine the sample No.1 biodiesel to produce the sample No.2 biodiesel in order to improve the fuel properties and oxygen content. The experimental results show that the acid value of the sample No. 2 biodiesel was slightly larger than the sample No. 1 biodiesel while the oxygen content and cetane index increased considerably. Higher oxygen of biodiesel can facilitate combustion reaction. The burning of the sample No.2 biodiesel in the diesel engine was also observed to form lower NOx, CO and CO2 concentrations in the exhaust gas. Larger cetane index of the sample No. 2 biodiesel than the commercialized biodiesel and diesel caused decrease of ignition delay and thus improvement of the combustion efficiency. At the second stage of the experiment, the sample No. 3 biodiesel was further refined from the sample No. 2 biodiesel. The n-hexadecane which is a cetane improver was added in the refining process for biodiesel production. The n-hexadecane agent and methanol was mixed prior to the transesterification reaction. The sample No. 3 biodiesel was found to produce lower CO, CO2 and smoke opacity than the diesel. In addition, the NOx emission from burning the sample No. 3 biodiesel was lower than from burning the sample No. 2 biodiesel by about 8% at the engine torque of 15 kgf-m.