Externally Heat-Integrated Multiple Diabatic Distillation Columns (EHImxDC): Basic Concept and General Characteristics

This paper introduces a new type of distillation column structure that is externally heat-integrated in multiple diabatic distillation columns (EHImxDC). By matching the temperatures of different column sections (from the same distillation column or different distillation columns), heat integration of different distillation column sections is carried out to improve the thermodynamic reversibility of the distillation operation. First, the structure of the column shell is proposed, which may exist in this kind of distillation column. Second, the mathematical model describing EHImxDC is established, and a concise method is proposed to construct the EHImxDC structure. At last, based on two conventional distillation columns for the separation of a hexane–heptane system and a hexane–octanane system, the heat integration in two diabatic distillation columns (EHImtDC) is established. Through simulation, the results show that the reversibility of EHImtDC is significantly higher than that of the conventional distillation column. By comparing the annual operating costs of the EHImtDC and the double-effect distillation process, it is found that the EHImtDC saved about 10% of the annual operating cost compared to the double-effect distillation process. It can be seen that EHImxDC can greatly improve the second law energy efficiency of the distillation column and reduce the energy consumption of the distillation operation.