Equilibrium curve additives

These are azeotropic points where the azeotropes occur. In other words, azeotropic systems give rise to VLE plots where the equilibrium curves crosses the diagonals. Both plots are however, obtained from homogenous azeotropic systems. An azeotrope that contains one liquid phase in contact with vapor is called a homogenous azeotrope. A homogenous azeotrope carmot be separated by conventional distillation. However, vacuum distillation may be used as the lower pressures can shift the azeotropic point. Alternatively, an additional substance may added to shift the azeotropic point to a more favorable position. When this additional component appears in appreciable amounts at the top of the column, the operation is referred to as an azeotropic distillation. When the additional component appears mostly at the bottom of the column, the operation is called extractive distillation. 

Additional isothermal treatments at neighbouring temperatures small step annealing) yield plateau values of resistivity corresponding to equilibrium values at certain temperatures which reflect the order parameter in thermal equilibrium as a function of temperature ( equilibrium curve , curve 4 in Figure 1). This study can be used for an analysis of the kinetics of order-order relaxations (see Figure 3 below). 

Equilibrium curve for silver chloride. Silver chloride (s) is in contact with Ag+ and Cl- ions in aqueous solution. The product Q of the concentration of ions [Ag+] X [Cl-] is equal to Ksp (curved line)when equilibrium exists. If 0 > K,p, AgCI(s) tends to precipitate out until equilibrium is reached. If 0 < Ksp, additional solid dissolves. 

In addition to the experimental results of phase equilibria, the correlation with the widely known GE models was assigned to. It was indicated by many authors that SLE, LLE, and VLE data of ILs can be correlated by Wilson, NRTL, or UNIQUAC models [52,54,64,79,91-101,106,112,131,134]. For the LLE experimental data, the NRTL model is very convenient, especially for the SLE/LLE correlation with the same binary parameters of nonrandom two-liquid equation for mixtures of two components. For the binary systems with alcohols the UNIQUAC equation is more adequate [131]. For simplicity, the IL is treated as a single neutral component in these calculations. The results may be used for prediction in ternary systems or for interpolation purposes. In many systems it is difficult to obtain experimentally the equilibrium curve at very low solubilities of the IL in the solvent. Because this solubility is on the level of mole fraction 10 or 10 , sometimes only... 

As for the values of HTU (see Equation 6.1-37), it is possible to write the equations that express the addition of individual resistances in terms of the number of transfer units. For example, when m, the slope of the equilibrium curve, is constant, the equations applicable to either dilute or concentrated systems are ... 

Figure 14.23 gives the (solid + liquid) phase diagram for (tetrachloromethane + 1,4-dimethylbenzene).19 The maximum in the (solid + liquid) equilibrium curve at X2 = 0.5 results from the formation of a solid addition compound with the formula CCl4-l,4-C6H4(CH3)2 that melts at the temperature corresponding... 

In case of heat removal or addition, there is no q-line. In such a case, the second point thet is used to construct the minimum-reflux component balance line is the point on the equilibrium curve representing the compositions of the liquid and vapor stream leaving the heat-addition or heat-removal stage. 

Fig. 15.1. S02 oxidation efficiency in two catalyst beds with gas cooling between beds. The 1st bed oxidizes 69.2% of 1st catalyst bed feed S02 - the 2nd bed an additional 25%. Note that the equilibrium curve is exactly the same for both catalyst beds, Section 15.1.1.

The change in the solvent freezing point is a little less obvious. First, consider the triple point—the intersection of the solid-vapor and the liquid-vapor equilibrium curves. It is clear from Figure 6.5-2 that the effect of the vapor pressure lowering is to lower the triple point of the solution relative to pure solvent. If in addition the solid-liquid equilibrium curve for the solution is (like that for the pure solvent) almost vertical, then the freezing point at an arbitrary pressure Po aiso drops—on the diagram, from for the pure solvent to 7 ms for the solution. 

Let us consider now the number of additional ideal stages required in the rectifying section (NR) to achieve the desired distillate concentration xD - 0.001. This portion of the column behaves like a water absorber with very dilute solutions of water in methanol. From the construction in Figure 6.18, the vapor entering the absorber contains 2.3 mol% water (97.7 mol% methanol), while the vapor leaving it contains only 0.1 mol% water. The liquid entering it has a concentration x = xD = 0.001. To calculate the absorption factor for the absorber, we must estimate the slope of the equilibrium curve in the limit as xg tends to zero (mab)- In that portion of the column, the temperature is very close to the normal boiling point of pure methanol then Tab = 337.7 K. From the modified form of Raoult s law,... 

If a warm gas-vapor mixture is contacted with a cold liquid so that the humidity of the gas is greater than that at the gas-liquid interface, vapor will diffuse toward the liquid and the gas will be dehumidified. In addition, sensible heat can be transferred as a result of temperature differences within the system. For air-water mixtures (Le = 1) contacted with cold water, the methods of analyzing water cooling presented in the preceding section apply with only obvious modifications. The operating line on the // versus TL diagram will be above the equilibrium curve. Likewise,... 

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