Application of heat pump technology to recover 1,4-dioxane and acetonitrile from wastewater via triple-column distillation

Abstract An effective method of triple-column pressure-swing distillation is introduced to recover 1,4-dioxane and acetonitrile from wastewater in this study. In order to save energy, heat pump technology is applied for utilizing the latent heat of the overheads. Besides, the heat exchange network is used for optimizing the heat exchange of the process. For better analysis of the heat pump process, the temperature-enthalpy diagram is taken to present the utilization, heat recovery and pinch point. And the temperature-entropy diagram is adopted to illustrate the thermodynamic parameters of the overhead during the heat exchange process. Several different processes with heat pump are designed and the triple-heat pump assisted pressure-swing distillation with splitting arrangement is the optimal process with the second-law efficiency of 1.45%. Compared with the conventional pressure-swing distillation, the savings of total annual cost and total energy consumption are 45.83% and 65.82% and the reduction of greenhouse gas emissions are 62.36% in CO2, 63.72% in SO2 and 63.72% in NOx.