The method proposed in this monograph has a firm thermodynamic basis. For vapo/-liquid equilibria, the method may be used at low or moderate pressures commonly encountered in separation operations since vapor-phase nonidealities are taken into account. For liquid-liquid equilibria the effect of pressure is usually not important unless the pressure is very large or unless conditions are near the vapor-liquid critical region.  [c.2]

The words "condensable" and "noncondensable" as used here are discussed in the footnote near Equation (13) of Chapter 2.  [c.40]

See footnote near Equation 13 of Chapter 2.  [c.57]

Our experience with multicomponent vapor-liquid equilibria suggests that for system temperatures well below the critical of every component, good multicomponent results are usually obtained, especially where binary parameters are chosen with care. However, when the system temperature is near or above the critical of one (or more) of the components, multicomponent predictions may be in error, even though all binary pairs are fit well.  [c.61]

In most cases only a single tie line is required. When several are available, the choice of which one to use is somewhat arbitrary. However, our experience has shown that tie lines which are near the middle of the two-phase region are most useful for estimating the parameters. Tie lines close to the plait point are less useful, since no common models for the excess Gibbs energy can adequately describe the flat region near the  [c.68]

On triangular diagrams, comparisons of calculated and experimental results can be deceiving. A more realistic representation is provided by Figure 18, comparing experimental solute distributions with those calculated from the UNIQUAC equation for four ternary systems. For three of these systems, calculations were made using the parameters determined from binary data plus one ternary tie line however, for the 2,2,4-trimethylpen-tane-furfural-cyclohexane system, parameters were obtained from binary data alone. With the exception of the region very near the plait point, calculated distributions are good. Fortunately, commercial extractions are almost never conducted near the plait point since the small density difference in the plait-point region causes hydrodynamic difficulties (flooding).  [c.71]

Figure 4-18. Calculated distribution for ternary liquid-liquid systems show good agreement with experiment except very near the plait point. Figure 4-18. Calculated distribution for ternary liquid-liquid systems show good agreement with experiment except very near the plait point.
The Newton-Raphson approach, being essentially a point-slope method, converges most rapidly for near linear objective functions. Thus it is helpful to note that tends to vary as 1/P and as exp(l/T). For bubble-point-temperature calculation, we can define an objective function  [c.118]

In application of the Newton-Raphson iteration to these objective functions [Equations (7-23) through (7-26)], the near linear nature of the functions makes the use of step-limiting unnecessary.  [c.119]

Liquid-liquid equilibrium separation calculations are superficially similar to isothermal vapor-liquid flash calculations. They also use the objective function. Equation (7-13), in a step-limited Newton-Raphson iteration for a, which is here E/F. However, because of the very strong dependence of equilibrium ratios on phase compositions, a computation as described for isothermal flash processes can converge very slowly, especially near the plait point. (Sometimes 50 or more iterations are required. )  [c.124]

The criterion used for "too near the plait point" is that ratio of K s for the two "solvent" components is less than seven with the feed composition in the two-phase region.  [c.127]




The simplest type of centrifugal device is the cyclone separator (Fig. 3.4), which consists of a vertical cylinder with a conical bottom. The centrifugal force is generated by the fluid motion. The mixture enters in a tangential inlet near the top, and the rotating motion so created develops centrifugal force which throws the particles radially toward the wall.  [c.71]

In principle, extractive distillation is more useful than azeotropic distillation because the process does not depend on the accident of azeotrope formation, and thus a greater choice of mass-separating agent is, in principle, possible. In general, the solvent should have a chemical structure similar to that of the less volatile of the two components. It will then tend to form a near-ideal mixture with the less volatile component and a nonideal mixture with the more volatile component. This has the effect of increasing the volatility of the more volatile component.  [c.82]

Heuristic 4 Favor near-equimolar splits between top and bottom products in individual columns.  [c.133]

Heuristic 4 Favor near-equimolar splits between top and bottom products  [c.134]

It is interesting to note that this is the sequence that would have been obtained had only heuristic 4 been used (favor near-equimolar splits between top and bottom products) throughout.  [c.139]

The most flammable mixture usually approximates the stoichiometric mixture for combustion. It is often found that the concentrations of the lower and upper flammability limits are approximately one-half and twice that of the stoichiometric mixture, respectively. Flammability limits are affected by pressure. The effect of pressure changes is specific to each mixture. In some cases, decreasing the pressure can narrow the flammable range by raising the lower flammability limit and reducing the upper flammability limit until eventually the two limits coincide and the mixture becomes nonflammable. Conversely, an increase in pressure can widen the flammable range. However, in other cases, increasing the pressure has the opposite effect of narrowing the flammable range.  [c.256]

Locate producing and consuming plants near each other so that hazardous intermediates do not have to be stored and transported.  [c.272]

If air is used, then a single pass with respect to each feedstock is used and no recycle to the reactor (Fig. 10.4a).-Thus the process operates at near stoichiometric feed rates to achieve high conversions. Typically, between 0.7 and 1.0 kg of vent gases are emitted per kilogram of dichloroethane produced.  [c.283]

The reaction uses a fixed-bed vanadium pentoxide-titanium dioxide catalyst which gives good selectivity for phthalic anhydride, providing temperature is controlled within relatively narrow limits. The reaction is carried out in the vapor phase with reactor temperatures typically in the range 380 to 400°C.  [c.332]

It is rare for there to be two process pinches in a problem. Multiple pinches usually arise from the introduction of additional utilities causing utility pinches. However, cases such as that shown in Fig. 16.18 are not uncommon, where there is, strictly speaking, only one pinch (one place where occurs), but there is a near-pinch. This  [c.383]

Figure 16.18 A near-pinch might require the design to be treated as if it had multiple pinches. Figure 16.18 A near-pinch might require the design to be treated as if it had multiple pinches.
As the feed composition approaches a plait point, the rate of convergence of the calculation procedure is markedly reduced. Typically, 10 to 20 iterations are required, as shown in Cases 2 and 6 for ternary type-I systems. Very near a plait point, convergence can be extremely slow, requiring 50 iterations or more. ELIPS checks for these situations, terminates without a solution, and returns an error flag (ERR=7) to avoid unwarranted computational effort. This is not a significant disadvantage since liquid-liquid separations are not intentionally conducted near plait points.  [c.127]

Outside the two-phase region, ELIPS yields a value of 0 for E/F on the R-phase side and 1 for E/F on the E-phase side. Con-, vergence to these values again requires about eight or fewer iterations, except near the plait-point region where convergence is somewhat slower.  [c.127]

The calculational procedure employed in BLIPS, when used with the particular initial phase-composition estimated included in the subroutine, has converged satisfactorily for all systems we have encountered (except very near plait points as noted).  [c.128]

Liquid phase compositions and phase ratios are calculated by Newton-Raphson iteration for given K values obtained from LILIK. K values are corrected by a linearly accelerated iteration over the phase compositions until a solution is obtained or until it is determined that calculations are too near the plait point for resolution.  [c.334]

Storage. Some of the largest inventories of hazardous materials tend to be held up in the storage of raw materials and products and intermediate (buffiBr) storage. The most obvious way of reducing the inventory in storage is by locating producing and consuming plants near to each other so that hazardous intermediates do not have to be stored or transported. It also may be possible to reduce storage requirements by making the design more flexible. Adjusting the capacity could then be used to cover delays in the arrival of raw materials, upsets in one part of the plant, etc. and thus reduce the need for storage.  [c.265]

See pages that mention the term Nares : [c.36]    [c.37]    [c.51]    [c.56]    [c.59]    [c.118]    [c.139]    [c.334]    [c.339]    [c.34]    [c.34]    [c.120]    [c.383]    [c.384]    [c.475]    [c.12]    [c.38]    [c.42]    [c.60]    [c.70]   
Industrial ventilation design guidebook (2001) -- [ c.196 , c.237 ]