IDENTIFYING OPTIMAL MIXTURE PROPERTIES FOR HIDiC APPLICATION

Internally heat-integrated distillation columns (HIDiC) are a new design option to provide a sustainable separation system. Although significant energy savings can be achieved using this setup, a considerable increase in investment cost penalizes the application. One major cost driver is the compressor cost, which depends on the relative volatility of the mixture to be separated. While mixtures with large relative volatility are easy to separate in distillation, they require a large pressure increase in the compressor of the HIDiC design, which raises the investment and operating costs of the design. Mixtures with low relative volatility are generally difficult to separate in distillation but favour the application of the HIDiC concept. Although it is clear that close boiling components are favourable from an energetic point of view, the influence of the equipment cost can not be neglected. In this contribution, HIDiC column designs for different mixtures are optimized via rigorous MINLP optimization to identify a relative volatility region which provides optimal operating conditions for maximum cost reduction. The mixtures with a low relative volatility favour a highly integrated design, while for a high relative volatility the conventional design is more cost efficient. The optimal design identified for mixtures with low relative volatility is conceptually very similar to a conventional column with heat pump.