Pseudo binary components

Drawing pseudo-binaryjy—x phase diagrams for the mixture to be separated is the easiest way to identify the distillate product component. A pseudo-binary phase diagram is one in which the VLE data for the azeotropic constituents (components 1 and 2) are plotted on a solvent-free basis. When no solvent is present, the pseudo-binaryjy—x diagram is the tme binaryjy—x diagram (Eig. 8a). At the azeotrope, where the VLE curve crosses the 45° line,... 

Fig. 8. Pseudo-binary (solvent-free)jy-x phase diagrams for determining which component is to be the distillate where (—) is the 45° line, (a) No solvent (b) and (c) sufficient solvent to eliminate the pseudo-a2eotiope where the distillate is component 1 and component 2, respectively (51) and (d) experimental VLE data for cyclohexane—ben2ene where A, B, C, and D represent 0, 30, 50, and 90 mol % aniline, respectively (52).

Step 3. Calculate the weight average critical temperature and critical pressure for the remaining heavier components to form a pseudo binary system. (A shortcut approach good for most hydrocarbon systems is to calculate the weight average T only.)... 

Step 4. Trace the critical locus of the binary consisting of the light component and psuedo heavy component. When the averaged pseudo heavy component is between two real hydrocarbons, an interpolation of the two critical loci must be made. 

The use of the K-factor charts represents pure components and pseudo binary systems of a light hydrocarbon plus a calculated pseudo heavy component in a mixture, when several components are present. It is necessary to determine the average molecular weight of the system on a methane-free basis, and then interpolate the K-value between the two binarys whose heavy component lies on either side of the pseudo-components. If nitrogen is present by more than 3-5 mol%, the accuracy becomes poor. See Reference 79 to obtain more detailed explanation and a more complete set of charts. 

If the metal atoms are not mobile (as is the case in low—temperature reactions) only hydride phases can result in which the metal lattice is structurally very similar to the starting intermetallic compound because the metal atoms are essentially frozen in place. In effect the system may be considered to be pseudo-binary as the metal atoms behave as a single component. 

If the presence of the other components does not significantly affect the volatility of the key components, the keys can be treated as a pseudo-binary pair. The number of stages can then be calculated using a McCabe-Thiele diagram, or the other methods developed for binary systems. This simplification can often be made when the amount of the non-key components is small, or where the components form near-ideal mixtures. 

Jaques and Furter (37,38,39,40) devised a technique for treating systems consisting of two volatile components and a salt as special binaries rather than as ternary systems. In this pseudo binary technique the presence of the salt is recognized in adjustments made to the pure-component vapor pressures from which the liquid-phase activity coefficients of the two volatile components are calculated, rather than by inclusion of the salt presence in liquid composition data. In other words, alteration is made in the standard states on which the activity coefficients are based. In the special binary approach as applied to salt-saturated systems, for instance, each of the two components of the binary is considered to be one of the volatile components individually saturated with the... 

A procedure is presented for correlating the effect of non-volatile salts on the vapor-liquid equilibrium properties of binary solvents. The procedure is based on estimating the influence of salt concentration on the infinite dilution activity coefficients of both components in a pseudo-binary solution. The procedure is tested on experimental data for five different salts in methanol-water solutions. With this technique and Wilson parameters determined from the infinite dilution activity coefficients, precise estimates of bubble point temperatures and vapor phase compositions may be obtained over a range of salt and solvent compositions. 

The composition dependence of Yj is based on the treatment of each component in turn as a pseudo-binary with all the other components. For each component, then, a simple model of the form ... 

Plot the component balance lines, using compositions printed out by the computer (expressed as the appropriate binary equivalents or pseudo-light-component compositions as per item 1 above)... 

For each representative stage, select light key and heavy key components, and calculate the composition of the pseudo binary mixture as... 

This method provides the exact solutions for ideal systems at constant temperature and pressure. It is successful in describing diffusion flow in (i) nearly ideal mixtures, (ii) equimolar counter diffusion where the total flux is zero (Nt = 0), (iii) diffusion of one component through a mixture of n — 1 inert components, and (iv) pseudo-binary case and the diffusion of two very similar components in a third. 

Therefore, the approach followed in this chapter considers pseudo-binary diagrams, i.e., equilibria involving the third component are, however, neglected, but modifications due to the presence of the solute are considered on the binary system. We will observe in the analysis of the experimental results that this approach can provide interesting information regarding the evolution of the SAS process, and the morphology and dimension of the precipitated particles. A rationalization of the experimental results is also proposed. 

Therefore, measurements carried out over a range of concentrations Ci and C2 with pure binary solutions, allow the determination of fci, Ai,mi,fc2, A2 and m2. From the retention times measured with pseudo-binary systems, i.e., for pulses of component 1 over concentration plateaus of solutions of component 2 alone (Cl = 0) and for pulses of component 2 over plateaus of solutions of component 1 alone (C2 = 0), one can derive from Eq. 4.96 ... 

Like distillation, the McCabe-Thiele analysis is strictly valid only for a binary system. However, only two components are usually present at significant concentrations within each individual section of the coliunn (and, besides, in practice, the SMB process is essentially used to separate binary mixtrues). A preliminary analysis in which each section is considered as a pseudo binary McCabe-Thiele system can therefore provide useful guidance in the design of a multicomponent adsorption system. 

A feed stream at the rate of 100 kmol/h contains 50% mole acetone and 50% mole chloroform. The two components form a maximum boiling azeotrope which prevents their separation by conventional distillation. It is proposed to separate them by extractive distillation using benzene as a solvent, at a rate of 800 kmol/h. Both the main feed and the solvent are at 75 C and 110 kPa, and the column pressure is assumed uniform, also at 110 kPa. A total condenser is used, with a reflux ratio of 4. The distillate composition is specified at 95% mole acetone and the bottoms at 5% mole acetone on a solvent-free basis. Using the pseudo-binary... 

The benzene recovery section, between the condenser and the solvent feed stage, is represented on a Y-X pseudo-binary diagram where the acetone and chloroform are lumped as one component in solution with the benzene. 

The graphical-based shortcut methods for binary batch distillation may be applied to multicomponent distillation only when the separation is between two key components to produce one distillate product and the residue. In this case the calculations may be approximated by lumping the other components with either of the key components and treating the system as a pseudo-binary. 

But there are not a few systems in which the number of molecular species is greater than the number of components that is, substances which have the same chemical composition (but which may be isomeric forms) may give rise to different molecular species, between which, in the liquid or vapour state, a condition of equilibrium can exist. This fact may alter very markedly the behaviour of a system. Although, therefore, a system may appear to be unary, so far as chemical composition is concerned, it may, as a matter of fact, behave in some respects as a binary system. It forms a pseudo-binary system. The behaviour of these systems, as we shall see, depends largely on the rate at which the internal equilibrium between the different molecular species in the liquid or vapour phase is established. In the present chapter some of the more important aspects of these pseudobinary systems will be considered. 

Phosphorus as Pseudo-binary System.—For the purpose of illustrating the behaviour of a one-component system as interpreted by means of the theory of allotropy put forward by Smits, a brief discussion of the behaviour of phosphorus may be given. ... 

Considering only components 2 and 3 and using x and y for the pseudo-binary system ... 

The product rule for the divergence operator is applied to both terms on the right-hand side of equation (9-27). In any coordinate system, the divergence of the product of a scalar and a vector is expanded as a product of the scalar and the divergence of the vector plus the scalar (i.e., dot) product of the vector and the gradient of the scalar. This vector identity was employed in equation (9-14). The pseudo-binary mass transfer equation for component i is... 

Hence, one term each on the left- and right-hand sides of equation (9-29) is zero. Since the mass density of component i, p, and the molar density of component i, Q, are related by molecular weight, division by MW, produces the final form of the mass transfer equation for incompressible pseudo-binary mixtures with constant physical properties ... 

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