Category: Multicomponent Systems

10.1. For a separations process it is necessary to determine the VLE compositions of a mixture of ethyl bromide and n-heptane at 30°C. At this temperature the vapor pressure of pure ethyl bromide is 0.7569 bar, and the vapor pressure of pure n-heptane is 0.0773 bar. Calculate the bubble pressure and the composition of the vapor in equilibrium…

P10.1. The stream from a gas well consists of 90 mol% methane, 5 mol% ethane, 3 mol% propane, and 2 mol% n-butane. This stream is flashed isothermally at 233 K and 70 bar. Use the shortcut K-ratio method to estimate the L/F fraction and liquid and vapor compositions. (ANS. L/F = 0.181) P10.2. An equimolar mixture of n-butane and n-hexane at pressure P is isothermally flashed at…

The concepts in this chapter are relatively simple but far-reaching. A simple extension of the chain rule to multicomponent systems led to the equilibrium constraint for multicomponent multiphase equilibria. A simple application of the entropy of mixing derived in Chapter 4 led to the ideal solution model, Gibbs energy for a component in a mixture, and fugacity…

The discussion in Sections 10.8–10.11 sets the stage for the next few chapters. The principles discussed here form the basis for these chapters and a thorough understanding facilitates rapid understanding of the extensions. There are two main approaches to modeling nonideal fluids. They differ in the way that they treat the fugacities in the vapor and liquid…

By our equilibrium constraint, By our ideal solution approximation in both phases, the equilibrium criteria becomes Now we need to substitute the expressions for fiV and fiL that we developed in Chapter 9. The fugacity of the pure vapor comes from Eqn. 9.25: The fugacity of the liquid comes from Eqn. 9.39: Combining Eqns. 10.70–10.72, Writing in terms of the Ki ratio, Note: at reasonably low…

Ideal solutions are similar to ideal-gas mixtures, but they to not follow the ideal-gas law. The internal energy and enthalpy for ideal solutions were introduced in Section 3.5. Since these properties are additive, the partial molar properties are equal to the pure component properties, As for the entropy change of mixing, the loss of order due…

We have introduced the concepts of energy of mixing, enthalpy of mixing, and volume of mixing in Section 3.4. We can now relate the mixing behavior to the partial molar properties. The partial molar quantities for ideal gases must be the same as the pure component properties. Entropy for an ideal-gas mixture is more complicated because,…

Generalization of pure-component principles to multicomponent systems requires that we consider how the thermodynamic properties change with respect to changes in the amounts of individual components. For a pure fluid, the natural properties were simply a function of two state variables. In multicomponent mixtures, these energies and the entropy also depend on composition.  These equations…

We introduced some major points about the importance of distillation in Section 3.2. Roughly 80% of separations are done involving distillation and 70% of the capital cost of a chemical plant goes into distillation equipment, and thus the proper application of vapor-liquid equilibria and design are essential. Usually, one distillation column is required to separate any…

Hydrocarbon emission monitoring is an important aspect of environmentally conscious chemical manufacturing and processing. The United States Environmental Protection Agency (EPA) has published guidelines8,9,10 on the calculations of emissions of volatile organic compounds (VOCs), and VOC emissions are monitored in the U.S. Most of the emission models apply the ideal gas law and Raoult’s law and thus the calculation…