BIODIESEL PRODUCTION USING CAVITATION TECHNIQUES

Abstract

The increasing industrialization and motorization of the world has lead to steep rise in the demand of petroleum based fuels. Moreover the finite reserves of crude oil are concentrated in certain regions of the world and most of the developing countries are net importer of the crude oil. Large outflow of foreign exchange and uncertainty in its availability is a matter of major concern for the developing countries like India. Excessive use of fossil fuels also resulted in global environmental degradation effects such as smog, greenhouse effect, acid rain, ozone layer depletion, climate change, etc. The main reason for increased pollution level inspite of stringent emission norms that have been enforced, is the increased demand for energy in all sectors and most significantly in the transport sector. Depleting reserves of crude petroleum, uncertainty in availability, environmental degradation and the rapid hike in petroleum prices have lead to search for the alternate fuels, with particular emphasis on the biofuels, that possess the advantage of being renewable and showing an ad-hoc advantage in reducing CO2 emissions. Biofuels made from agricultural products (oxygenated by nature) reduce the dependence on oil imports, support local agricultural industries and enhances farming incomes. Moreover, they also benefit in terms of reduced smokiness or particulate matter in engine exhausts. There are several factors that need to be taken care before recommending any alternate fuel to be used with existing technologies on a large scale. The main factors are stated below:-  Extent of modification required in existing hardwares, i.e., if any alternate fuel needs extensive modification in the existing hardware involving huge capital investment, then it may be difficult to implement. iii

 The investment cost for developing infrastructure to manufacture and supply of these alternate fuels. The excessive infrastructure cost may act as a deterrent to the development of the alternate energy resources.  Environmental compatibility as compared to conventional fuels.  Additional cost to the user in terms of routine maintenance, equipment wear and lubricating oil life. The excessive additional cost will have an adverse effect on the widespread acceptance of alternate fuels. Biodiesel is an alternate fuel, which has a high potential to gradually replace petro-diesel as it satisfies most of the parameters mentioned above. This research work primarily focus on conversion of non-edible oils into their methylesters. Oil extracted from Jatropha seeds forms the background of the experiments, however new oils such as Deodar oil and Semal oil were also explored and investigated for the first time. The present work highlights the advantages of using cavitation techniques for biodiesel production. A framework for optimization of various process parameters such as Molar ratio, Catalyst concenteration, Reaction time and Power supplied to ultrasonic transducers has been presented for biodiesel production from various types ultrasonic cavitation reactors. The optimization of these process parameters were also performed on a closed loop ultrasonic reactor. The set up of closed loop ultrasonic reactor was made for large scale batch type biodiesel production. Moreover the biodiesel production was carried out at different pressures. Ultrasonic irradiation in reaction mixture flowing under pressurized conditions resulted in significant reduction in reaction time. The closed loop ultrasonic reactor was then converted into a combined process reactor in order to increase the efficiency and reliability of the system. The set iv

up consist of a closed-loop circuit comprising a feed tank connected with a mechanical stirrer, a reciprocating pump and an ultrasonic reactor. Optimization of process parameters were also carried out for closed loop ultrasonic reactor. The economic viability of the power required for transesterification of vegetable oil into biodiesel is than carried out in terms of energy efficiency and energy use index. Energy requirements of biodiesel production under optimized conditions are then compared for various ultrasonic reactors for small scale and large scale biodiesel production. Overall energy balance is then carried out for various ultrasonic reactors. Double and Triple frequency flow cells showed improved reaction yield, reduced reaction time, reduced catalyst requirement and molar ratio, lower Specific Energy consumption and higher Energy Use Index. Power requirement increases whereas considerable reduction in optimal reaction time was observed in case of ultrasonic irradiation at pressurized condition as compared to ultrasonic irradiation in unpressurised flow of reaction mixture. The latter effect dominates and overall reduction in energy requirement was noticed in case of pressurised ultrasonics. The requirement of molar ratio and catalyst concenteration also reduces under pressurised ultrasonic conditions. Combined process reactor performed better on most of the parameters as compared to closed loop ultrasonic reactors, however the major advantage was improved reliability of biodiesel production system. Property testing of biodiesel so produced was carried out and most of the properties of the biodiesel were within the acceptable limits of Bureau of Indian Standards. Oxidative stability of Jatropha oil methyl esters was not lying within acceptable limits. The oxidative stability can be increased by use of suitable antioxidants.