Economic feasibility of a novel energy efficient middle vessel batch distillation to reduce energy use

It has long been recognized that the highly irreversible operation of batch distillation involves more wastage of energy compared to continuous flow distillation. For boosting its energy efficiency, the middle vessel batch distillation (MVBD) column has been invented. In this paper, a rigorous model for an MVBD process for the separation of a ternary hydrocarbon system is developed to simulate its transient behavior. In order to obtain the products at their maximum achievable purities, we device the two operating policies for the representative configuration. This contribution introduces a heat pumping system in the MVBD aiming to further improve its energetic and economic potentials. This novel heat integration technique is operated with a variable speed compressor for pressurizing the overhead vapor before thermally coupling it with the reboiler liquid. Interestingly, along with the compression ratio (CR), the other two manipulated variables are the inflow rate of overhead vapor to the compressor and that of an external medium (here, steam) that provides makeup heat to the reboiler. The operation of this adaptive heat pump assisted column originally involves the simultaneous adaptation of two variables throughout the entire batch processing. The simulation results show that a cost savings predicted in the heat integrated MVBD scheme can be achieved along with a substantial reduction in energy consumption. (C) 2012 Elsevier Ltd. All rights reserved.