Step by step algorithm to calculate VLE data from Redlich-Kwong?

In summary: Gohil provides a summary of the conversation, stating that the Redlich-Kwong equation is an EOS used to predict PVT behavior of a pure vapor species at pressures above the ideal gas region. It can also be used to predict VLE behavior of a vapor mixture in equilibrium with a liquid phase. Some people use Redlich-Kwong to predict fugacities of species in the gas phase. A source for more information is the book "Smith and Van Ness."
  • #1
maistral
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I keep on reading that VLE data may be calculated from the Redlich-Kwong. In line with this, I have these questions:

1) How accurate is the VLE data generated with the Redlich-Kwong as compared to using the vapor pressures to calculate these VLE data?
2) Can you guys give me a link, or even better, a rundown which includes step by step instructions on how to calculate VLE using Redlich-Kwong?

Thanks and more power.
 
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  • #2
maistral said:
I keep on reading that VLE data may be calculated from the Redlich-Kwong. In line with this, I have these questions:

1) How accurate is the VLE data generated with the Redlich-Kwong as compared to using the vapor pressures to calculate these VLE data?
2) Can you guys give me a link, or even better, a rundown which includes step by step instructions on how to calculate VLE using Redlich-Kwong?

Thanks and more power.
The Redlich-Kwong equation is an EOS used to predict PVT behavior of a pure vapor species at pressures above the ideal gas region. If you are dealing with a vapor mixture in equilibrium with a liquid phase at a pressure above which the ideal gas equation applies, one can use ideal solution theory to predict the VLE behavior. Part of this procedure makes use of an equation of state to predict the fugacities of the various species in the gas phase. Sometimes people use Redlich-Kwong. See Smith and Van Ness.

Chet
 
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1. How is the Redlich-Kwong equation used to calculate VLE data?

The Redlich-Kwong equation is a thermodynamic model that is used to predict the vapor-liquid equilibrium (VLE) behavior of a mixture. It takes into account the temperature, pressure, and composition of the mixture, and uses these variables to calculate the vapor and liquid phase compositions and their corresponding equilibrium constants.

2. What are the steps involved in using the Redlich-Kwong equation to calculate VLE data?

The first step is to gather the necessary data, including the temperature, pressure, and composition of the mixture. Then, the Redlich-Kwong equation must be rearranged to solve for the vapor and liquid phase compositions. This can be done using a step-by-step algorithm, which involves successive approximations to determine the phase compositions and equilibrium constants. Finally, the calculated data can be compared to experimental data to assess the accuracy of the model.

3. How accurate is the Redlich-Kwong equation in predicting VLE data?

The accuracy of the Redlich-Kwong equation in predicting VLE data depends on several factors, including the temperature and pressure range of the mixture, the accuracy of the input data, and the complexity of the mixture. In general, the Redlich-Kwong equation is more accurate for simple mixtures at moderate temperatures and pressures, but may deviate from experimental data for more complex mixtures or at extreme conditions.

4. Can the Redlich-Kwong equation be used for any type of mixture?

The Redlich-Kwong equation is a generalized equation and can be used for a wide range of mixtures, including hydrocarbons, alcohols, and organic compounds. However, it may not be suitable for highly polar or associating mixtures, in which case other equations such as the Peng-Robinson equation may be more appropriate.

5. Are there any limitations to using the Redlich-Kwong equation for calculating VLE data?

Yes, there are some limitations to using the Redlich-Kwong equation for calculating VLE data. As mentioned before, it may not be accurate for highly polar or associating mixtures. It also does not take into account the effects of non-ideality, such as azeotropy or chemical reactions. Additionally, it may not accurately predict VLE data for mixtures at extreme temperatures or pressures, or for mixtures involving highly volatile components. In these cases, more advanced equations or experimental data should be used to obtain more accurate results.

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