Design and retrofitting of ultrasound intensified and ionic liquid catalyzed in situ algal biodiesel production

Abstract

Although biodiesel synthesis has been widely studied, the use of wet microalgal feedstock for biodiesel synthesis using ionic liquid catalyst and ultrasonication is scarce to find, especially pertaining to economic viability and environmental impact. In this study, new processes are designed based on the experimental results for ultrasound assisted in situ algal biodiesel production using an ionic liquid catalyst. Process retrofitting is then conducted using a divided-wall column (DWC) and multistage vapor recompression (MVR). Later, comparative analyses in terms of capital cost, cost of manufacturing (COM), cost of biodiesel, specific energy consumption (SEC) and carbon emission is presented. The process with DWC and MVR resulted in a significant saving in COM (13.84%), biodiesel cost (18.24%), utility cost (45.44%), SEC (29.15%) and carbon emissions (38.15%) than those in its counterpart. This study shows that the biodiesel cost is linearly dependent on the cost of feedstock and process economics can be improved by converting glycerol to triacetin. Major contributions of this work are (1) experimental and process design for a novel ultrasound assisted and ionic liquid catalyzed algal biodiesel production, (2) retrofitting using DWC and MVR and (3) investigation of the uncertainty in the thermodynamic property. This study is significant as it designs processes based on the experimental outcomes and investigates designs for their economic as well as environmental merits.