Batch distillation optimization

Distillation is one of the most widely used separation processes in chemical industry. Recent interest in smart and distributed manufacturing has increased focus on batch processing as it offers operational flexibility, low capital investment and shorter time for commercialization. However, conventional batch distillation, especially in the case of multicomponent separation, suffers from long batch time and low energy efficiency. Our group is working on improving energy efficiency of batch distillation through various initiatives.

In one of the directions, we are focusing on multi-effect distillation as a means of reducing energy consumption. We use an economic performance index to quantify optimality of operation by combining separation and energy efficiency. In this context, a middle vessel column operation is used as a model configuration. We show that the performance of this column can be improved significantly through dynamic optimization. Specifically, in the case of ternary separation, there is dynamic redistribution of holdup among the three vessels to optimize/prioratize the separation tasks.

In the other direction, we are developing methods to identify optimal separation sequence in the case of multicomponent batch distillation. This explores possibility of using non-standard separation sequences (apart from direct sequence as per conventional batch distillation or indirect sequence as per inverse column configuration). In the case of open operation with finite reflux ratio, we have extended the marginal vapor rate method used for continuous distillation for separation sequencing in batch distillation. For the case of closed operation with total reflux, we have developed a novel marginal Nmin method to obtain the optimal separation sequence.