Process synthesis and simulation-based optimization of ethylbenzene/styrene separation using double-effect heat integration and self-heat recuperation technology: A techno-economic analysis

Ethylbenzene/styrene separation is a typical example of the most costly processes in the chemical industry due to their close-boiling points of these two species. To reduce the cost of their separation, the concepts of double-effect distillation (DED) and self-heat recuperation technology (SHRT) have been implemented to produce three energy-efficient distillation configurations in either an individual or synergistic manner. To obtain a fair comparison, all the candidate processes were optimized to a minimum in total annual cost (TAC), using a simulation-based optimization framework on a simulator Aspen Plus and an optimizer programmed in MATLAB with a metaheuristic algorithm. For a small treatment capacity (100 kmol/h) and a short payback period (PBP, 3 years), the DED and SHRT configurations were found to reduce the TAC by ~8% compared to the conventional process design. The TAC reduction can be improved to as much as ~28% with a larger capacity (1000 kmol/h). The synergistic DED-SHRT configuration has the lowest energy consumption, but its high capital investment makes it only economically viable for longer PBPs. The best scheme under either short or long PBP appeared to be SHRT. Since the conventional design and SHRT share close technical parameters, the former will benefit more when retrofitted into the latter when minimum process modifications are applied.