Steady-state optimization for biodiesel production in a reactive distillation column

Biodiesel is a notable alternative to the widely used petroleum-derived diesel fuel since it can be generated by domestic natural sources such as soybeans, rapeseeds, coconuts, and even recycled cooking oil, and thus reduces dependence on diminishing petroleum fuel from foreign sources. The advantages of biodiesel as diesel fuel are its portability, ready availability, renewability, higher combustion efficiency, lower sulfur and aromatic content, higher cetane number, and higher biodegradability. The main disadvantages of biodiesel as diesel fuel are its higher viscosity, lower energy content, higher cloud point and pour point, higher nitrogen oxide emission, lower engine speed and power, injector coking, engine compatibility, high price, and higher engine wear. Therefore, biodiesel production is confronted with two main tasks: cost reduction and ecological restrictions. Also, beside these objectives, the social involvements of biodiesel production and use must not be neglected. The best decisions regarding all these aspects imply solving optimization problems. Biodiesel is defined as a mixture of fatty acid alkyl esters which are commonly produced from triglycerides and alcohol through trans-esterification reaction in the presence of alkali catalysts. In this work, canola oil and methanol were used in this research as the feedstocks, and potassium hydroxide and potassium methoxide were used as different formulations of catalysts. A laboratory-scale continuous-flow reactive distillation column system was simulated at optimum conditions by Aspen HYSYS Software. The homogeneous alkali and acid catalyzed were applied to the system. The non-catalytic reaction, where the absence of catalyst simplifies the purification procedures and the products can be easily separated. The critical operating conditions and high consumption of methanol and energy make it uneconomical. Based on the optimization of energy integration and methanol recovery strategies, optimization strategies were assessed for saving energy and recovery methanol.