Nano-catalytic heterogeneous reactive distillation for algal biodiesel production: Multi-objective optimization and heat integration

Abstract

This work proposes a novel reactive distillation (RD) column for the production of algal biodiesel by the use of a heterogeneous nano-catalyst, Ca(OCH3)2. The elitist non-dominated sorting genetic algorithm (NSGA-II) is employed to optimize the design of this RD column to maximize biodiesel purity while minimizing total annual cost and CO2 emissions. The optimal point is recommended by a Pareto ranking method, namely, technique for order of preference by similarity to ideal solution (TOPSIS) with entropy information for the weighting of objectives. To improve biodiesel purity, a decanter is proposed to couple with the RD column at the bottom. Subsequently, performance of the optimal RD column is further improved by retrofitting it with the vapor recompression arrangement. In this proposed intensified configuration, a reactive stage is thermally integrated with the reboiler to constitute a side vapor recompressed RD (SVRRD) column. Finally, a comparative study is performed to quantify the performance improvement of the proposed SVRRD column over the conventional RD column. It is found that there is a 34.6% reduction in CO2 emissions with a payback period of 4.54 years for the vapor recompressor. Hence, the proposed SVRRD is attractive with better performance in terms of energetic, environmental and economic perspectives.