A New Methodology to Reduce the Exergy Loss of Distillation Columns Using Rigorous Process Simulation

Abstract

Abstract In this work we simulate and optimize an industrial distillation system to produce bioethanol, manipulating the number of stages aiming to reduce the total exergy loss inside the columns taking into account the cost associated (exergoeconomic analysis). The optimization of operational parameters such as feed stage and reflux ratio were done using Aspen Plus through the analysis of the exergy loss profile, which has a direct relation with the overall energy consumption of the column. However, the variation of the number of stages is not straightforward in processes simulators because it is necessary, to evaluate the optimal position to insert a stage in the column (i.e., stripping or rectification section); moreover, this variable has a high impact in the improvement of the energy efficiency of the column. To relate the total exergy loss inside the column with its cost, an algorithm was developed in Matlab to identify the point with greater exergy loss in the column, insert new stages (defined by the user) to reduce the heat duty and calculate the capital cost associated. The results show that is possible to thermodynamically optimize the distillation column without violating the critical specifications of the process. The optimum process requires less energy than the original process, despite the greater investment. The exergoeconomic evaluation conclude that, even with the increased investment to implement a process with greater efficiency, it becomes viable, reducing the hot utility required and the exergy loss in more than 27% for a payback lower than two years.