Heat integration and process improvement of a batch distillation unit using a gradual feeding strategy: A case study on MIBK-water separation

Abstract

This work focuses on upgrading a batch distillation unit in terms of energy efficiency and production capacity. Dehydration of methyl isobutyl ketone (MIBK) is performed as a case study. Since the MIBK-water mixture forms a heteroazeotrope, a decanter is applied to facilitate the separation process. The unit performance is evaluated in terms of specific product flow (SPF) and specific energy cost (SEC). Studying the impact of feed quantity in the range of 20 to 80 kg showed that due to the almost equal holdup loss, a larger batch feed quantity results in higher energy efficiency and production performance. Gradual feeding policy with different feeding strategies and locations (i.e., top feeding and bottom feeding) is also assessed in detail and compared with the conventional batch distillation process. Also, three feeding rate profiles (increasing, fixed, and decreasing) with varying feeding durations are evaluated in order to reach the optimal feeding time and profile. Overall, gradual feeding is found to be an efficient approach to upgrade the unit operation in terms of energy efficiency and production rate. Top feeding (also known as batch stripping or inverted batch distillation) has proved to be a more efficient policy for MIBK-water separation over bottom feeding. In addition, the decreasing feed flow rate scenario offers a more efficient operation compared to other feed rate profiles. Accordingly, employing the top feeding policy with a decreasing feed rate profile can lead to a 10 % improvement in production rate and energy cost over a conventional batch distillation unit equipped with a decanter. Moreover, based on the gradual feeding approach, a novel and easy-to-apply strategy for heat integration and recovery in the batch distillation process is proposed, and its potential is assessed for different feeding scenarios. The proposed strategy is also found to be significantly effective in process intensification and acceleration. Applying this strategy to a batch distillation unit with top feeding at a fixed feed rate offers over 47 % improvement in energy efficiency and production rate compared to a conventional batch distillation unit equipped with a decanter.