An MINLP formulation for the optimization of multicomponent distillation configurations

Gooty

2019

Ind. Eng. Chem. Res.

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Numerous configurations are available for the separation of a multicomponent mixture by distillation; each of which has different energy requirements. We classify heat integration (a valuable method of reducing energy requirements) within distillation into two categories: conventional thermal coupling with mass exchange between columns (TCM) and thermal coupling via heat transfer without mass exchange (TCH). The sharp split distillation configurations, with the lowest number of distillation sections and transfer streams, provide simple distillation configurations but are known to have heat duties that are much higher than the fully thermally coupled (FTC) or Petlyuk configuration. However, for a mixture with four or more components, FTC, having the maximum number of column sections, is a complex configuration to build and operate. Through specific examples of four and five component distillations, we present, for the first time, sharp split configurations, using only one TCH and no TCM, which have a lower heat duty than the corresponding FTC containing only TCM, without requiring substantial pressure changes in the system.

Section: Introductionmentioning

confidence: 99%

110th Anniversary: Thermal Coupling via Heat Transfer: A Potential Route to Simple Distillation Configurations with Lower Heat Duty

Gooty

2019

Ind. Eng. Chem. Res.

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“…Simulation or optimization of shortcut models : Fidkowski and Królikowski, 22 Fidkowski and Agrawal, 28 Giridhar and Agrawal, 29 Nallasivam et al., 30 Tumbalam Gooty et al 31,32 . have written models for minimizing the energy consumption of distillation configurations for zeotropic separations, while employing the CMO framework with the simplified VLE (Equation ).…”

Section: Applications Of the Latent‐heat Transformationmentioning

confidence: 99%

Relaxing the constant molar overflow assumption in distillation optimization

2023

AIChE Journal

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The constant molar overflow (CMO) framework, while useful for shortcut distillation models, assumes that all components have the same latent heats of vaporization. A simple transformation, from molar flows to latent‐heat flows, allows shortcut models to retain the mathematical simplicity of the CMO framework while accounting for different latent heats, resulting in the constant heat transport (CHT) framework for adiabatic distillation columns. Although several past works have already proposed this transformation in the literature, it has not been well utilized in recent times. In this article, we show the utility of this transformation in upgrading various applications such as identifying energy‐efficient multicomponent distillation configurations based on heat duty rather than surrogate vapor flow. The method transforms the diagram to a diagram. Furthermore, we derive new and insightful analytical results in distillation, such as cumulative latent‐heat stage fractions having monotonic profiles within a distillation column under the CHT framework.

“…As a proxy for energy consumption, we use the vapor duty of a configuration, which is the sum of vapor duties that must be externally supplied for each reboiler. Most algorithms that search for configurations with minimum vapor duties do not consider heat integration within the multicolumn distillation configuration and thereby potentially miss configurations with lower heat duties. − …”

Section: Introductionmentioning

confidence: 99%

Identifying Heat-Integrated Energy-Efficient Multicomponent Distillation Configurations

Nogaja

2022

Ind. Eng. Chem. Res.

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We present a tractable nonlinear programming (NLP) formulation that models a given multi-component distillation configuration and searches for its global minimum heat duty. The novelty in the current model is that it can explore feasible heat integrations with a pre-specified desired minimum approach temperature between various condensers and reboilers while simultaneously optimizing the operating conditions within the configuration. We do not use cumbersome thermodynamic models for the equilibrium temperature calculation of a saturated multicomponent mixture. Instead, we propose a modified version of the well-known Antoine equation that reduces the calculation of the temperature at a given pressure to a simple function of component mole fractions and relative volatilities while retaining the fidelity of more complex models. We explore possible heat integrations by creating a heat exchange network between column condensers, reboilers, and side draw product locations. Considering these integrations along with the heat duty minimization is essential because it is often possible to alter the operating conditions of the columns and reduce energy consumption by admitting more heat integration possibilities. Finally, we demonstrate the power of our framework in identifying optimal configurations that yield large energy savings for several four- and five-component zeotropic distillation systems.