The model of the multicomponent, multistage distillation column has been extended to three coexisting phases. The new model contains the well-known modeling equations of the two-phase distillation column as a special case. The versatility of the new simulation model is demonstrated with practical distillation problems. ULRICH BLOCK SCOPEThe models of multicomponent, multistage countercurrent unit operations, such as distillation and liquidliquid extraction, are usually restricted to two countercurrent phases. A significant number of chemical engineering processes, however, have two partly miscible liquid phases and a vapor phase. This type of system cannot be simulated adequately by assuming only two phases. Therefore, a model of the distillation column with three-phase stages has been derived.The more recent approaches to solving the modeling equations of two-phase multistage countercurrent operations use the Newton-Raphson technique within iterative solution procedures. The calculation method for the threephase distillation problem presented here requires the conversion of the modeling equations into forms similar to those of the two-phase distillation problem. These equations are then solved by a Newton-Raphson iterative procedure for correction of the liquid compositions.The simulation model presented can be used not only for the simulation of three-phase distillation columns, but also for columns with any combination of two-and three-phase stages. This is believed to be an essential feature of the method, because in a distillation process involving components which may form regions of immiscibility the phase type of a column is usually not known until the computation is completed. CONCLUSIONS AND SIGNIFICANCEA new model has been employed to simulate the steady state distillation column. I t takes into account three phases, a vapor phase and two partly miscible liquid phases. Thus, the model also includes the simulation of a liquid-liquid phase separator within the distillation column.To describe analytically the phase separation of the liquid at a stage, the phase splitting parameter is introduced. A three-phase stage is defined by 0 < 7 < 1, a two-phase stage by 7) = 1. If 7) = 1 for all stages, the new modeling equations reduce to the well-known equations of the two-phase distillation. Therefore, with the presented set of modeling equations, all types of stages can be adequately simulated.A computational scheme for the three-phase distillation problem is presented. It is based on an iterative solution method which uses a Newton-Raphson technique and consists of linearizing the component mass balances with the liquid compositions as the independent variables. The method can be regarded as a modified bubble point procedure which has a block tridiagonal form rather than the usual tridiagonal structure. This was found to be a very efficient solution algorithm because of the highly composition dependent equilibrium ratios encountered in three-phase distillation.It is known that industrial distillations frequen...

Nachdem es moglich ist, die Stoffaustauschflache in verschiedenen Gas/Fliissigkeits-Kontaktapparaten wie Riihrkessel, Blasensaule, mit Strahldiisen begaste Blasensaule, Rohrreaktor-Strahlduse, Strahlwaschertypen und Gleichstrom-Fullkorperkolonne mit einem einheitlichen Modellansatz turbulenter Wechselwirkung zwischen den Phasen zu korrelieren, wird ein Kriterium erarbeitet, anhand dessen 1.) fur jeden Reaktortyp die Abhangigkeit der Stoffaustauschflache von der Geometrie und den Betriebsvariablen in einem allgemeinen Arbeitsdiagramm dargestellt und die hydrodynamisch sinnvollen Belastungsbereiche gekennzeichnet werden konnen, 2.) eine Auswahl des Reaktortyps nach den Gesichtspunkten sowohl des von den Betriebsvariablen her sinnvollen Belastungsbereiches als auch des wirtschaftlichen Optimums zwischen Investitions-und Betriebskosten gelingt und 3.) eine Ubertragung der im Technikumsmafistab gewonnenen Ergebnisse auf die GroBanlage leicht durchgefiihrt werden kann.

Criteria for the choice and design of gasbiquid reactors. The mass transfer area in a given reactor volume can be varied over several orders of magnitude by the choice of operating parameters. The way in which the volume-specific conversion can be altered by variation of the volume-specific mass transfer area depends upon the rate of the chemical reaction. The greater the volume-specific mass transfer area chosen, the more power is required per unit reactor volume. Analysis shows that not only the attainable conversion but also the yield can be greatly influenced by the volume-specific mass transfer area. This applies both to parallel and to consecutive reactions. In the case of consecutive reactions, the liquid retention time must also be included as a parameter in yield determination. If a reactor system requires economic optimization, then, in addition to the yield, the power required for mixing and the investments in reactor volume are also of importance. All three parameters can be modified by means of quantities accessible to the engineer, such as gas throughput, specific power dissipation, and residence time. The quantitative relations depend upon reactor type. The relation between these parameters can be plotted quantitatively in a working diagram for each reactor type. Its plotting and use in reactor optimization on the bases of laboratory experiments are considered.

942 0 ~iS1zil Wossergeholt in der Flussigkeit Abb. 1. Phaeengleichgewicht WasserlEssigsiiure bei 760 Torr.

No abstract