Process optimization for biodiesel production from Tung (Aleurites fordii.) oil and its emissions characteristics

Abstract

Biodiesel is receiving increased attention as an alternative, non-toxic, biodegradable, and renewable diesel fuel. It is derived from oils and fats by transesterification with alcohols. The present glut of energy crises due to continuous depletion of scarce fossil fuels has resulted in hike of global prices of crude petroleum which is bound to affect the economy of many countries. In a country like India, where edible oils are still imported, it would be worthwhile to explore the possibility of using such non edible oils in CI engines which are not in practice as cooking oil. Therefore, the study on Tung oil as fuel for CI engine was undertaken. Tung oil was transesterified with methyl alcohol to obtain methyl ester of Tung oil to reduce its kinematic viscosity in the range of diesel fuel. The process parameters such as molar ratio, kaOH concentration and settling time were standardized to obtain higher recovery of esters. About 94 percent ester can be recovered if the Tung oil-methyl alcohol mixture of 5:1 molar ratio is preheated for 30 min at 600C and then reacted with 1.5 percent KOH for 1 h at 600C and then allowed to settle for 24 h in order to get methyl ester of 4.6 cS kinematic viscosity. Different blends of Tung biodiesel with diesel in proportion of 10:90, 15:85and 20:80 were prepared. The characteristic fuel properties such as kinematic viscosity, relative density, gross heat of combustion, cloud and pour point, flash and fire point, carbon and ash content and total acidity of refined Tung oil, its methyl esters and their blends with diesel were compared. The results of different fuel properties of blends of methyl ester of Tung oil with diesel were almost similar to diesel. A 3.73 kW, constant speed compression ignition engine was tested on diesel, blends of methyl ester of Tung oil of 4.6. cS kinematic viscosity with diesel (10:90, 15:85, and 20:80). The study of engine exhaust emission reported lower emission compared to diesel . The CO emission on all fuel types was found to be lower. The emission of NOx from the engine was found slightly higher on each fuel types under entire range of brake load conditions than that on diesel. The best performance in terms of various parameters of the engine was observed when a blend of 30 percent methyl ester of Tung oil with 70 percent diesel was used which enables 30 percent diesel replacement.