Synthesis of separation flowsheets for multicomponent azeotropic mixtures on the basis of the distillation theory. synthesis: Finding optimal separation flowsheets

134

The thermodynamic efficiency of five ternary distillation configurations to distill ideal saturated liquids into pure product streams are calculated and compared. A striking result of this study is that for the fully coupled column (Petlyuk) configuration, which is known to have the lowest heat demand for ternary distillation, the range of values of feed composition and relative volatilities for which it is the most thermodynamically efficient configuration is quite limited. Among the three thermally coupled column configurations, the side-rectifier and side-stripper configurations tend to provide the most efficient configuration more often than the fully coupled configuration. Generally, the modified direct and indirect split configurations together provide the most thermodynamically efficient configuration for more feed compositions and relative volatilities than do the three thermally coupled column configurations. The high thermodynamic efficiency of these two configurations is primarily due to their ability to either accept or reject heat at the intermediate temperatures of binary mixtures.

Section: Introductionmentioning

confidence: 99%

Are Thermally Coupled Distillation Columns Always Thermodynamically More Efficient for Ternary Distillations?

Fidkowski

1998

134

“…Even so, the addition of an appropriate third component (solvent or entrainer) significantly alters the vapor–liquid equilibrium (VLE) to make pure component recovery feasible using an appropriate distillation sequence. As an example, we have the celebrated homogeneous extractive and heterogeneous azeotropic distillation sequences for breaking a binary azeotrope. , In addition, the distillation literature is replete with innovative sequences for separating a given mixture into its constituent pure components (see, for example, refs − ). The flowsheet structure depends on the specific VLE characteristics of the particular mixture to be separated.…”

Section: Introductionmentioning

confidence: 99%

“…The flowsheet structure depends on the specific VLE characteristics of the particular mixture to be separated. Over the years, the residue curve map has emerged and has been applied as a powerful visual tool enabling feasible distillation separation scheme synthesis to separate highly nonideal mixtures. ,,− …”

Section: Introductionmentioning

confidence: 99%

Synthesis, Design, and Control of an Azeotropic Distillation System for Methanol–Isopropyl Acetate Separation

Mishra

Kaistha

2018

The existence of a minimum boiling homogeneous azeotrope precludes the separation of a methanol− isopropyl acetate (MeOH−IPAc) binary mixture into its constituent pure components using simple distillation. In this work, alternative separation processes for recovering pure MeOH and pure IPAc are synthesized. Three promising flowsheet alternatives, denoted as FS3a−c, are further analyzed for energy-efficient operation. The analyzed flowsheets use water as an entrainer for MeOH and consist of a liquid−liquid extractor (LLX) and three columns. The flowsheets differ in where the fresh feed is fed. The dominant design variables for the process are the entrainer (water) recirculation rate to the LLX and the number of extractive trays. A design steady state is obtained by adjusting these dominant variables for (near) minimum total reboiler duty. For the nominal equimolar binary fresh feed, FS3a is found to be significantly more energy efficient than the other two variants. A decentralized plantwide control system is synthesized for its recommended process design and is shown to reject large throughput and fresh feed composition changes. It is also shown that the flowsheet recommendation can change for extreme fresh feed compositions. Thus, for a MeOH-lean feed, FS3b is clearly superior, while, for a MeOH-rich feed, FS3c is superior. The recommended flowsheet, FS3a, is more energy-efficient over a large fresh feed composition range.

“…In this paper, the minimum-energy expressions for the three-product Petlyuk arrangement shown in Figure are generalized to handle any feed quality and nonsharp product splits. We also illustrate by examples that we can easily handle more than three feed components.…”

Section: Introductionmentioning

confidence: 99%

Minimum Energy Consumption in Multicomponent Distillation. 2. Three-Product Petlyuk Arrangements

Halvorsen

Skogestad

2003

132

115

We show that the minimum energy requirement for separation of a multicomponent mixture in a three-product Petlyuk arrangement is equal to the minimum energy for the most difficult of the two separations (top/middle or middle/bottom product) in a conventional single column. In the V min diagram (part 1 of this series), this is simply the highest peak. These results are based on an analytical solution for columns with an infinite number of stages, assuming constant relative volatilities and constant molar flows. The previous analytical results for the Petlyuk column are extended to include nonsharp separations, multicomponent feeds, and any feed quality.