Vapor-liquid equilibrium with Excel

Chapters 2-5 deal with chemical engineering problems that are expressed as algebraic equations - usually sets of nonlinear equations, perhaps thousands of them to be solved together. In Chapter 2 you can study equations of state that are more complicated than the perfect gas law. This is especially important because the equation of state provides the thermodynamic basis for not only volume, but also fugacity (phase equilibrium) and enthalpy (departure from ideal gas enthalpy). Chapter 3 covers vapor-liquid equilibrium, and Chapter 4 covers chemical reaction equilibrium. All these topics are combined in simple process simulation in Chapter 5. This means that you must solve many equations together. These four chapters make extensive use of programming languages in Excel and MATE AB. 

Using the proposed procedure in conjunction with literature values for the density (11) and vapor pressure (12) of solid carbon dioxide, the solid-formation conditions have been determined for a number of mixtures containing carbon dioxide as the solid-forming component. The binary interaction parameters used in Equation 14 were the same as those used previously for two-phase vapor-liquid equilibrium systems (6). The value for methane-carbon dioxide was 0.110 and that for ethane-carbon dioxide was 0.130. Excellent agreement has been obtained between the calculated results and the experimental data found in the literature. As shown in Figure 2, the predicted SLV locus for the methane-carbon... 

Vapor Pressure Thermometry. The pressure exerted by a saturated vapor in equilibrium with its liquid is a very definite function of temperature, and can be used to measure the temperature of the liquid. A number of useful fixed points for several cryogenic fluids are given in Table 8.3. With a good pressure-measuring device, the vapor pressure thermometer is an excellent secondary standard since its temperature response depends upon a physical property of a pure compound or element. Many expressions have been... 

Data at two temperatures were obtained from Zeck and Knapp (1986) for the nitrogen-ethane system. The implicit LS estimates of the binary interaction parameters are ka=0, kb=0, kc=0 and kd=0.0460. The standard deviation of kd was found to be equai to 0.0040. The vapor liquid phase equilibrium was computed and the fit was found to be excellent (Englezos et al. 1993). Subsequently, implicit ML calculations were performed and a parameter value of kd=0.0493 with a standard deviation equal to 0.0070 was computed. Figure 14.2 shows the experimental phase diagram as well as the calculated one using the implicit ML parameter estimate. 

Azeotropic distillation and extractive distillation have been used for many decades. There is a rich literature of the subject with many hundreds of papers and several books published on the subject. The recent textbooks that contain discussions of azeotropic and extractive distillation are Doherty and Malone and Stichlmair and Fair. The authors provide an excellent treatment of conceptual design of azeotropic systems. Both of these books give examples of azeotropic separation phase equilibrium and flowsheets in both binary and ternary systems. The chapter by Doherty and Knapp Azeotropes in the Kirk—Othmer Encylcopedia of Chemical Processes also provides an excellent discussion of vapor-liquid-liquid equilibrium (VLLE) fundamentals and conceptual design of a number of azeotropic systems. 

The experiment began by charging the equilibrium cell with about 30 cm3 of either phenoPp-cresol or phenol-water solution mixture. The cell was then pressurized with either methane or carbon dioxide until the phenol clathrate formed under sufficient pressure. The systems were cooled to about 5 K below the anticipated clathrate-forming temperature. Clathrate nucleation was then induced by agitating the magnetic spin bar. After the clathrates formed, the cell temperature was slowly increased until the clathrate phase coexisted with the liquid and vapor phases. The nucleation and dissociation steps were repeated at least twice in order to diminish hysteresis phenomenon. The clathrates, however, exhibited minimal hysteresis and the excellent reproducibility of dissociation pressures was attained for all the temperatures and found to be within 0.1 K and 1.0 bar at each time. When a minute amount of phenol or p-cresol clathrate crystals remains and the system temperature was kept constant for at least 8 hours after attaining pressure stabilization, the pressure was considered as an equilibrium dissociation pressure at that specified temperature. 

Figures 3 and 4 are the predicted profiles of vapor and liquid composition along the column with 43 ml of catalyst and a reflux flow rate of 22 g/tnin. It is important to note that both the liquid and vapor concentration profiles for acetone in the column are relatively high and hence it is favorable for the formation of DAA. The equilibrium constants calculated from the equilibrium conversion data [9,10] are given in Figure 5, which indicates that at 54 °C, the Ac conversion at equilibrium conversion is only 4.3 wt %. In order to carry out the aldol condensation of acetone in the CD column, the temperature at the reaction zone of the CD column will be near the boiling point of Ac in order to maintain liquid vapor equilibrium. Our CD experimental results show that a maximum concentration of 55 wt% of DAA concentration was obtained which clearly exceeds the equilibrium conversion. The aldol condensation of Ac to produce DAA is an excellent example to demonstrate that in situ separation in a CD column results in an increased yield for equilibrium limited reactions.

HI. [VBA required] Using the spreadsheet in Appendix B of Chapter 4 or your own spreadsheet, solve the following problem. A methanol water mixture is being distilled in a distillation column with a total condenser and a partial reboiler. The pressure is 1.0 atm, and the reflux is returned as a saturated liquid. The feed rate is 250 kmol/h and is a saturated vapor. The feed is 40 mol% methanol. We desire a bottoms product that is 1.1 mol% methanol and a distillate product that is 99.3 mol% methanol. L/D = 4.5. Find the optimum feed stage, the total number of stages, D and B. Assume CMO is valid. Equilibrium data are available in Table 2-7. Use Excel to fit this data with a 6th-order polynomial. After solving the problem, do What if simulations to see what happens if the products are made purer and if L/D is decreased. 

Perluorosulfonated ionomer membranes have high water permeabilities and excellent selectivities for water over most gases and organic liquids. These membranes have been shown to be useful for dehydration applications. Water transport in these membranes is non-Fickian. Water permeability and solubility coefficient vary with water vapor pressure. Concentration dependent thermodynamic diffusion coefficients have been obtained by combining the steady state water permeability data and the equilibrium sorption data. These diffusion coefficients correspond to what would be obtained from an experiment with infinitismal partial pressure drop across the membrane. 

Liquid-vapor equilibrium of chain molecule fluids. Both analytic and numerical work has been recently done by Schweizer and co-workers. The compressibility route predictions of PRISM for this problem are extremely sensitive to closure approximation since the relevant fluid densities are very low and large-scale density fluctuations are present. The atomiclike MSA closure leads to qualitatively incorrect results as does the R-MMSA closure. However, the R-MPY/HTA approximation appears to be in excellent accord with the computer simulation studies of n-alkanes and model chain polymers, including a critical density that decreases weakly with N and a critical temperature that increases approximately logarithmically with N. 

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