Optimizing algal biodiesel production from a novel reactive distillation based unit: Reducing CO2 emission and cost

Abstract

The algal biodiesel as a potential alternative to conventional petroleum fuel and first-generation biofuel has been explored extensively but the efficacy of its production in a reactive distillation (RD) unit is yet to be analyzed thoroughly. In this contribution, the performance of the RD column is enhanced by process intensification and optimization. A multi-objective optimization (MOO) strategy is framed for optimizing the RD column for three conflicting objectives. For this MOO, the elitist non-dominated sorting genetic algorithm (NSGA-II) is employed. From the obtained Pareto-optimal front, one optimal solution for RD design is selected using the technique for order of preference by similarity to ideal solution (TOPSIS) with entropy information for weighting of objectives. To further reduce the environmental impact and optimal usage of internal energy, a novel thermally coupled reactive distillation (TCRD) column is suggested. Finally, a biodiesel production unit is developed by integrating a decanter with the TCRD column, to produce biodiesel product of 99.45 wt.% purity. Performance of the TCRD column is better than the conventional RD column, in terms of CO2 emission reduction (14.49%) and total annual cost savings (3.72%). Energetic sustainability of the proposed biodiesel process is determined by net energy ratio (NER) of 1.79, net energy value (NEV) of 18.2 and net renewable energy value (NREV) of 41.4 MJ/kg.