Abstract
Biodiesel has been proven to be the best reliable alternative for petroleum diesel. Besides, being renewable, it is biodegradable and non-toxic fuel. This paper aimed to study the production of this green fuel using industrial, competitive techniques; base-catalysed transesterification and supercritical methanol transesterification. The research involved techniques for reaction parameters optimisation and thus embedded optimum values into a simulation-based design procedure for overall energy optimisation/integration and emissions reduction.
Literature experimental reaction data for the two technologies conduct an optimisation for biodiesel production. The state-of-the-art process flowsheets for the two processes were used for the study. This optimisation was done for the most affecting parameters on the production processes. The experimental results from the literature for the two techniques were optimally analysed using parameters analyse carried out using Pareto chart, contour plot methodology, and surface plot methodology. The research study revealed that the key process variable for the base-catalysed process was the catalyst loading. On the other hand, for the supercritical methanol process, the most prominent variable was the methanol to oil ratio. The optimal process conditions were used to build an ASPEN HYSYS rigorous simulation model for the previous techniques. The supercritical based-process was chosen for further studies for its better economic performance.
Pinch Analysis principles through ASPEN Energy Analyser software were employed to analyse the energy performance of the overall optimum model obtained from ASPEN HYSYS. The energy targets were calculated for biodiesel production using supercritical methanol approach. Composite curves resulted in 3.4 and 3.7 MW for heating and cooling requirements, respectively compared with 4.4 and 4.7 MW for the original process. Finally, a heat exchanger network was developed to accomplish the energy targets proposed by the composite curves. The resulting integrated process flowsheet has better energy saving opportunities. The energy consumption of the optimum case has been reduced by 25 %, and thus substantial cut in the CO2 emissions. Utility curves were also generated to determine the loads of hot utilities to be produced by the proposed energy integration.
