Economic, environmental, and exergy analysis of an efficient separation process for recovering low-carbon alcohol from wastewater

Extractive distillation separation is a continuous and effective process for the separation of industrial wastewater components. In this study, a method to recover high-purity ethanol and isopropanol from industrial wastewater via extractive distillation has been proposed. Three enhanced energy-saving processes were developed to reduce the economic costs and environmental impact of distillation processes. The process operation parameters with the best economic performance were obtained based on a sequential iterative optimization method with the total annual cost as the objective function. Results show that, thermally coupled technology can effectively reduce the economic cost. Compared with the conventional extractive distillation process, the total annual cost of the thermally coupled extractive distillation process was the lowest, accounting to a reduction of 33.14%. The heat recovery rate of the heat pump-assisted thermally coupled extractive distillation process was the highest (1979 kW), and the total energy consumption was the lowest (5762.4 kW). The gas emission (2432.72 kg/Y), GWP (1246.42 kg CO2-Eq), AP (2.23 kg SO2-Eq), HTP inf (38.66 kg DCB-Eq), Eco tox (20.04 CTUe), and exergy loss (20.73%) of the heat pump-assisted thermally coupled extractive distillation process were the lowest. This work has important guiding significance for the efficient recovery of low-carbon alcohols from industrial wastewater and promoting cleaner production in the chemical industry.