Ternary Distillation Research Articles

Diffusional models of multicomponent distillation and their experimental verification

In the present paper the equimolar, non-equimolar and simultaneous mass and heat transfer models of multicomponent distillation are developed and verified. The equations composing the models are based on the linearized diffusion theory and can be divided into three separate groups: (1) interfacial conditions describing the gas-liquid interface; (2) kinetic relations, which define the mass fluxes and whose general form results from the type of transfer assumed; (3) balance equations, associated with the model employed for a contact stage and determined by the fluxes previously estimated. The main purpose of the work was to develop the methods for calculating the mass fluxes for various types of diffusion occurring in distillation; hence, the quantitative basis for these methods was provided by the two first groups of relationships. The verification of the equimolar and non-equimolar models was carried out using the experimental results obtained by the authors for ternary distillation in a 0.25 m I.D. sieve-plate column and literature data for a bubble-cap column. The model for simultaneous mass and heat transfer was analysed only qualitatively. The calculations performed employing the various models differed only slightly from each other and agreed very well with the experimental findings.

Binary and ternary distillation in a stirred mass transfer cell

A continuous flow stirred cell operating at point conditions has been developed for the study of mass transfer in distillation. Results for the methanol-isopropanol and methanol-ethanol binary systems showed that 85–100% of the resistance to mass transfer resided in the vapour phase, and that the vapour side coefficients correlated well with those obtained in the same cell for gas phase controlled absorption. Flux rates for the ternary system methanol-ethanol-isopropanol were in fair agreement with those predicted from the binary data, using a modified form of the Krishna-Standart theory. It is concluded that the experimental technique shows considerable promise, but requires further development to overcome discrepancies in the interfacial heat balance.

Mass and heat transfer in ternary distillation of methanol-ethanol-water systems by a wettec-wall column.

Experimental study of vapor-phase sensible heat and mass fluxes in ternary distillation of the methanol-ethanol-water system was made with a wetted-wall column at total reflux conditions. From heat and mass balances for the liquid film, a theoretical expression was derived for the interfacial velocity caused by mass fluxes. The interfacial velocity was shown to be a function of the sensible heat and diffusion fluxes. Observed vapor-phase sensible heat fluxes showed good agreement with the theoretical values obtained by laminar flow theories. Observed vapor-phase diffusion fluxes obtained from mass flux measurements also showed good agreement with the theoretical values, but a poor correlation was obtained for vapor-phase mass fluxes. Observed interfacial velocities were compared with the calculated values.

Prediction of multicomponent distillation efficiencies

The prediction of multicomponent distillation efficiencies from binary data is highly desirable as it is physically impossible to perform the experimental study of all the systems of industrial importance. In the present work a new method of predicting ternary efficiencies is presented. The validity of the method is assessed comparing experimental ternary distillation lines with predicted distillation lines. Experimental results obtained in a 38mm diameter seven plate sieve-plate column with the binary systems cyclohexane/n-heptane, cyclohexane/toluene and n-heptane/toluene and the ternary system cyclohexane/n-heptane/toluene are used for such comparison. Experimental results obtained with the ternary system show the existence of Murphree efficiencies greater than unity for the intermediate component. Such interesting physical situations are also predicted using the new method.

Murphree and vaporization efficiencies in multicomponent distillation

A quantitative comparison between Murphree and vaporization efficiencies is presented based on ternary distillation data for the systems acetone/methanol/ethanol, acetone/benzene/chlorobenzene, benzene/toluene/mxylene and n-hexane/methylcyclopentane/benzene. The influence of experimental errors on calculated values of Murphree efficiencies is also analysed. It is shown that the vaporization efficiency model fails to describe the behaviour of distillation plates and it is suggested that Murphree's model gives a more useful representation of the behaviour of distillation columns.

Using pseudo-linearization in simulating the dynamics of a multicomponent distillation column

This paper describes a method for using the S/360 CSMP digital simulation language to implement the computer simulation of a nonlinear model of a multi component distillation column. The method makes it unnecessary to linearize the nonlinear vapor-liquid equilibrium relationship by employing a "pseudo- linearization" approach to this nonlinearity. This approach yields a computer simulation capable of operating over the complete range of the original model. The method is applied to a model of a ternary (benzene-toluene-xylene) distillation column which consists of 11 plates, a condenser, and a reboiler. The simulation results are then compared to known experimental results as a means of validating the simulation. Except for initial transients, the two sets of results are in close agreement, which sug gests that the pseudo-linearization technique pro duces a satisfactory model of the distillation column.

Ternary vapour‐liquid equilibrium: The use of a multi‐stage still

AbstractThe construction of a six‐stage vapour‐liquid equilibrium unit based on the Ellis still is described. Its application to the measurement of equilibrium data in the ternary system benzene—cyclohexane—n‐hexane was investigated. Results are presented for this ternary system and for the three associated binary systems. The nature of the resulting ternary distillation lines is discussed.

Validity and Consequences of Schreinemakers' Theorem on Ternary Distillation Lines

Validity and Consequences of Schreinemakers' Theorem on Ternary Distillation Lines

Validity and Consequences of Schreinemakers' Theorem on Ternary Distillation Lines

The tangential behavior of distillation lines in a ternary mixture, as brought forward by Schreinemakers more than half a century ago, was denied some time ago by Redlich and Kister. We give another proof of the correctness of Schreinemakers' theorem. We define parameters Q0 governing the course of the distillation lines in each corner of the composition triangle. The Q0 values are, in principle, derivable from accurate binary boiling point curves. The occurrence of distillation lines with one or two points of inflection in a ternary system without complications from azeotropes or demixing is discussed at some length.

Graphical Solution of Ternary Distillation Problems

Graphical Solution of Ternary Distillation Problems