Conventional residual curve

Process synthesis and design of these non-conventional distillation processes proceed in two steps. The first step—process synthesis—is the selection of one or more candidate entrainers along with the computation of thermodynamic properties like residue curve maps that help assess many column features such as the adequate column configuration and the corresponding product cuts sequence. The second step—process design—involves the search for optimal values of batch distillation parameters such as the entrainer amount, reflux ratio, boiler duty and number of stages. The complexity of the second step depends on the solutions obtained at the previous level, because efficiency in azeotropic and extractive distillation is largely determined by the mixture thermodynamic properties that are closely linked to the nature of the entrainer. Hence, we have established a complete set of rules for the selection of feasible entrainers for the separation of non ideal mixtures... 

An ideal mixture of n components requires a sequence of n - 1 conventional distillation columns (two product streams) to separate the components completely. The columns can be arranged sequentially without recycle between them. This picture changes when mixtures forming azeotropes must be separated. Nonideal systems sometimes require complex distillation arrangements involving more than n - 1 columns with recycle of material between the columns. For the analysis of such systems, we recommend the use of residue curve maps. We base the following summary on the excellent book by Doherty and Malone (1998), who pioneered the use of these techniques. 

We adopt here the convention that the direction of a trajectory points-out from lower to higher temperatures. For example, on the segment representing the binary mixture the trajectory is oriented from the light to the heavy component. The shape of the residue curves depends on the relative volatility of components. It may be observed that in Fig. 9.2 all the residue curves have the same vertices as origin and terminus. More specifically, all the trajectories emanate from the benzene comer and terminate in the ethyl-benzene vertex. These species are the lowest and the highest boilers, respectively. The vertex of toluene is only an intermediate destination, where the residue curves enter from the benzene and leave to the ethyl-benzene. Note that the residue curves do never intersect each other. 

The residue curve mapping (ROM) technique has traditionally been considered a powerful tool for flowsheet development and preliminary design of conventional multicomponent separation processes. It represents a good approximation of actual equilibrium... 

The RCM technique has been considered a powerful tool for the flowsheet development and preliminary design of conventional multicomponent, nonideal separation processes (Fien and Liu, 1994). It represents a good approximation to actual equilibrium behavior and allows the designer to perform feasibility analysis of separation processes where nonideal and azeotropic mixtures are involved. Traditionally, nonreactive residue curves have been used to predict the liquid-composition trajectories in continuous distillation... 

Residual current in polarography. In the pragmatic treatment of the theory of electrolysis (Section 3.1) we have explained the occurrence of a residual current on the basis of back-diffusion of the electrolysis product obtained. In conventional polarography the wave shows clearly the phenomenon of a residual current by a slow rise of the curve before the decomposition potential as well as beyond the potential where the limiting current has been reached. In order to establish the value one generally corrects the total current measured for the current of the blank solution in the manner illustrated in Fig. 3.16 (vertical distance between the two parallel lines CD and AB). However, this is an unreliable procedure especially in polarography because, apart from the troublesome saw-tooth character of the i versus E curve, the residual current exists not only with a faradaic part, which is caused by reduction (or oxidation)... 

For onshore facilities, water may be supplied from local public water mains, storage tanks, lakes and rivers. In these cases a conventional horizontal pump is used. The preferred design for onshore fire water pumps is a horizontal centrifugal type with a relatively flat performance curve (i.e., pressure versus quantity). The discharge pressure is determined by the minimum residual pressure required at the most remote location of the facility flowing its highest practical demand with allowances added for piping friction losses. 

The simplest window on the processes that operate when a crystal is subject to plastic deformation is the stress-strain curve. As shown in flg. 2.10, once the stress exceeds the elastic limit, not only is there a marked deviation from linearity, but the crystal is also permanently deformed. If such stresses are reached and the crystal is subsequently unloaded, there will be a residual plastic strain. One conventional measure of the yield point is to consider that stress for which there is a 0.2% residual plastic strain upon unloading. If the sample is reloaded, it will be found that the yield point has moved to higher stresses - the crystal has hardened. 

Metallocompounds with variable coordination numbers and plastic coordination stereochemistries may not behave in this conventional way the energy-distance curves for any one bond could vary with the number and lengths of the other bonds. With this variability of the primary bonding, the residual, more weakly bonded interactions could be expected to be even more variable. Thus an open mind is required in developing parameters for weakly bonded interactions for metallocompounds. Further development of fundamental theory for long, weak interactions to metal atoms is required. 

The viscosity of hydrogen is more conventional in its behavior. In this case, liquid-phase viscosity data have been extrapolated [i -32] from close to atmospheric conditions to a critical-point condition in the coordinates of residual viscosity vs. density. Both papers report nearly identical results ( 30 x 10 g/cm-sec) for the critical-point viscosity. Brebach and Thodos indicate that this value should be increased to bring it more in line with their reduced correlations for other diatomic gases and give a final value of rjc =37.6 x 10 g/cm-sec. Values of viscosity for hydrogen from both sources, over the liquid range for which no data exist, lie very close to the hydrogen curve of Fig. 3. The data from these sources, however, extend to values for the critical viscosity which appear to be somewhat low (see Table IV). No comparable studies for deuterium and tritium have previously been made. 

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