Enhanced methanol recovery and glycerol separation in biodiesel production – DWC makes it happen

Biodiesel is a renewable fuel that consists of fatty acids methyl esters – currently produced by trans-esterification of glycerides with methanol. After the biodiesel synthesis, the downstream processing steps involve the purification of crude glycerol, as well as the separation of excess methanol (recyclable), glycerol by-product and water (from washing and pre-treatment steps). The separation of the ternary mixture methanol–water–glycerol is carried out in a conventional direct sequence that requires two distillation columns and rather high amounts of energy. tudy proposes an efficient process intensification method for this ternary separation, namely the use of a dividing-wall column (DWC) that is able to separate all products at high purity, in only one equipment unit. AspenTech Aspen Plus and Aspen Dynamics were used as computer aided process engineering tools to perform the rigorous steady-state and dynamic simulations, as well as the optimization of the new DWC separation alternative. In order to allow a fair comparison, all designs analyzed here were optimized using the sequential quadratic programming (SQP) method. Remarkable, the results show that the proposed DWC system requires 27% less energy and 12% lower investment costs, thus having a significant contribution towards inexpensive biodiesel production.