Design and operation of extractive distillation systems using different class of entrainers for the production of fuel grade tert-butyl Alcohol:A techno-economic assessment

The 21st century beholds interest in biofuels, leading to a key challenge being the production of fuel grade 'tert butyl alcohol' (TBA) with reduced economics. As a consequent step in the investigation with a different class of entrainers for TBA dehydration (Aniya et al. 2015, 2016) through extractive distillation (ED), the present study explores the utilization of ionic liquid [emim][Cl] and inorganic salt [MgCl2] as a potent entrainer. A comprehensive approach is proposed with phase-equilibrium measurements, thermodynamic modeling, design and process optimization using Aspen Plus. A techno-economic assessment of all the investigated processes (conventional solvents: CSED, solvent + salt: SEED, designer solvents or ionic liquids: DEED and ionic liquid + salt: DSEED) concluded SEED process to be the most promising with 6%, 18% and 37% savings in TAC and 9%, 23% and 41% savings in SEC as compared to the DSEED, DEED and CSED processes respectively. Further, retrofits (heat integration and thermally coupled schemes) demonstrated 13% and 6% reduction in specific energy consumption respectively thus improving the energy efficiency of ED systems. Heat integration brought in 12% savings in TAC over SEED process. However, thermally coupled schemes resulted in marginal benefit (2% savings) in terms of TAC over SEED process.