Consequences of property errors on the design of distillation columns

Wakeham, W. A.; Cholakov, Georgi St.; Stateva, Roumiana P.

doi:10.1016/s0378-3812(01)00490-3

Cited by 10 publications

(9 citation statements)

References 14 publications

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“…The high precision achieved by the present correlations opens up possibilities for future work in a direction of high relevance to chemical engineering studies. In particular, it becomes possible to investigate the influence of uncertainties in calculated thermophysical parameters on the final solution of designs and simulations of existing applications, in which the effects of small changes in the properties are important …”

Section: Discussionmentioning

confidence: 99%

Liquid Density and Critical Properties of Hydrocarbons Estimated from Molecular Structure

2002

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The paper provides new correlations for the estimation of the relative liquid density and critical parameters of hydrocarbons. The correlations employ molecular descriptors from computer simulation of molecular mechanics, which proved valuable in our previous work. High precision is achieved, without the use of unduly complex descriptors and rules, as a result of improved methodology. The new methodology includes a limit upon the functionality of the property database and its predesign by expanding the range and improving the distribution of the repeating structural features in the selected compounds.A compilation of estimated data for the liquid density and critical properties of some hydrocarbons of industrial importance for which no values have been available before is provided.

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Section: Discussionmentioning

confidence: 99%

Liquid Density and Critical Properties of Hydrocarbons Estimated from Molecular Structure

2002

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“…The ratios of the critical properties from the experimental data, the simulation, and the proposed method are close to each other but are quite different from the value estimated by the group-contribution method of Joback. (2) Wakeham et al discuss the influence of property estimation methods on the design of distillation columns. They compare various methods for estimating critical properties for a few heavy hydrocarbons for which reliable experimental data is not available.…”

Section: Further Validation Of the Methods Based On Recent Experiment...mentioning

confidence: 99%

“…However, low to medium molecular weight compounds were used for the determination of the group parameters of these methods and, thus, their extrapolation capabilities may be difficult to assess. In many cases, it has been reported 2,3 that critical properties estimated by such literature methods are in error when compared with measured values or lead to substantial differences in the design of separation processes, e.g., distillations, based on cubic EoS …”

Section: Introductionmentioning

confidence: 99%

Approach Suitable for Screening Estimation Methods for Critical Properties of Heavy Compounds

Zbogar

Lopes

Kontogeorgis

2005

Ind. Eng. Chem. Res.

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A simple theoretical-based correlation of the ratio of the critical temperature to the critical pressure (T c /p c ) as a function of the van der Waals surface area (Q w ) has been previously developed based on an extensive database of critical data published prior to 1996. The final equation was the following: T c /p c ) 9.0673 + 0.43309(Q w 1.3 + Q w 1.95 ) where T c is the critical temperature in kelvin and p c is the critical pressure in bar. This correlation is further validated here based on recent experimental data for various families of organic compounds, including some heavy ones (mono-and diacids, alkenes, cyclo/phenylalkanes, and squalane). This and previous validations verify that this correlation has a much broader application range, up to (T c /p c ) ratios of 200, than the data used in its development (compounds with ratios up to 100). It seems that most organic compounds, including the very heavy and complex ones, follow the trend suggested by this equation. This equation can be used for testing existing group-contribution estimation methods. It is shown here that direct comparison of the Joback and Constantinou-Gani methods for two families of compounds (alkenes and carboxylic acids) is in agreement with their validation via the proposed equation. Similar results have been obtained for other compounds. Both group-contribution methods are of equal accuracy for heavy alkenes and acids, provided that experimental boiling point temperatures are available for the Joback method. If such data are not available, e.g., for heavy compounds, the Constantinou-Gani method should be preferred. The proposed correlation does not offer an alternative to group-contribution methods as it only provides a single relationship of the two critical properties. Its universal character, though, and validation for many heavy compounds offer a way to test and compare existing group-contribution methods and, finally, to select the one that best conforms with the proposed correlation. It is recommended that the proposed correlation is indeed used for high molecular weight compounds for which experimental critical properties are typically not available.

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“…The predicted distillation column parameters, i.e., reflux ration, flows, and composition of the phases on the stages were different when using the three different VLE data sets. This indicates that the design results are highly sensitive to changes in the equilibrium data (Xin and Whiting, 2000;Whiting et al, 1999;Dong et al, 2005;Mathias, 2014;and Wakeham et al, 2001). This stresses the importance of accurate equilibrium data.…”

Section: Introductionmentioning

confidence: 99%

CFD analysis of laboratory scale phase equilibrium cell operation

Jama

Nikiforow

Qureshi

et al. 2017

Review of Scientific Instruments

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For the modeling of multiphase chemical reactors or separation processes, it is essential to predict accurately chemical equilibrium data, such as vapor-liquid or liquid-liquid equilibria [M. Šoóš et al., Chem. Eng. Process.: Process Intensif. 42(4), 273–284 (2003)]. The instruments used in these experiments are typically designed based on previous experiences, and their operation verified based on known equilibria of standard components. However, mass transfer limitations with different chemical systems may be very different, potentially falsifying the measured equilibrium compositions. In this work, computational fluid dynamics is utilized to design and analyze laboratory scale experimental gas-liquid equilibrium cell for the first time to augment the traditional analysis based on plug flow assumption. Two-phase dilutor cell, used for measuring limiting activity coefficients at infinite dilution, is used as a test case for the analysis. The Lagrangian discrete model is used to track each bubble and to study the residence time distribution of the carrier gas bubbles in the dilutor cell. This analysis is necessary to assess whether the gas leaving the cell is in equilibrium with the liquid, as required in traditional analysis of such apparatus. Mass transfer for six different bio-oil compounds is calculated to determine the approach equilibrium concentration. Also, residence times assuming plug flow and ideal mixing are used as reference cases to evaluate the influence of mixing on the approach to equilibrium in the dilutor. Results show that the model can be used to predict the dilutor operating conditions for which each of the studied gas-liquid systems reaches equilibrium.

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Consequences of property errors on the design of distillation columns

Cited by 10 publications

References 14 publications

Liquid Density and Critical Properties of Hydrocarbons Estimated from Molecular Structure

Liquid Density and Critical Properties of Hydrocarbons Estimated from Molecular Structure

Approach Suitable for Screening Estimation Methods for Critical Properties of Heavy Compounds

CFD analysis of laboratory scale phase equilibrium cell operation

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