Homogeneous flowsheet

Exploitation of Homogeneous Azeotropes Homogeneous azeotropic distillation refers to a flowsheet structure in which azeotrope formation is exploited or avoided in order to accomplish the desired separation in one or more distillation columns. The azeotropes in the system either do not exhibit two-hquid-phase behavior or the hquid-phase behavior is not or cannot be exploited in the separation sequence. The structure of a particular sequence will depend on the geometry of the residue curve map or distillation region diagram for the feed mixture-entrainer system. Two approaches are possible ... 

Laroche L, Bekiaris N, Andersen HW and Morari M (1992) Homogeneous Azeotropic Distillation Separability and Flowsheet Synthesis, Ind Eng Chem Res, 31 2190. 

There is a standard flowsheet pattern for breaking heterogeneous binary azeotropes, but that, of course, is not applicable here. It is possible to break homogeneous azeotropes by pressure shifting the azeotrope or by extractive distillation with a suitable high-boiling solvent, in this case for example, ethylene... 

Fixation of Cesium. The final step in the conceptual cesium purification flowsheet is loading cesium onto Linde AW-500 zeolite, which is essentially chabazite. We will select the best cement formulations from our sludge work to demonstrate the incorporation of cesium-chabazite in cement. In a preliminary test at 1150°C, we made an homogeneous glass with 40 wt % chabazite. 

The intended homogenized data model, realized by the wrapper to be designed, is addressed in Fig. 5.65. The class Document represents a Comos PT flowsheet, indicated by the return value of method id(), which returns a reference to an instance of class IComosDDocument. 

In the following, we will show, how a method addDevicesO of class Document is modeled. The method (i) reads all devices out of the flowsheet, (ii) determines whether it is a device according to the homogenized data model, and, if applicable, (iii) creates a new instance of class Device. The modeling of the method takes place in three steps ... 

For our second nonideal system, we look at a process that has extremely nonideal VLB behavior and has a complex flowsheet. The components involved are ethanol, water, and benzene. Ethanol and water at atmospheric pressure form a minimum-boiling homogeneous azeotrope at 351K of composition 90mol% ethanol. Much more complexity is introduced by the benzene/water system, which forms two liquid phases with partial miscibility. The flowsheet contains two distillation columns and a decanter. There are two recycle streams, which create very difficult convergence problems as we will see. So this complex example is a challenging simulation case. 

When a homogeneous azeotrope is formed or the mixture is very close boiling, the procedures shown in Section 8.2 cannot be used. However, the engineer can add a solvent (or entrainer) that forms a binary or ternary azeotrope and use this to separate the mixture. The trick is to pick a solvent that forms an azeotrope that is either heterogeneous (then the procedures of Section 8.2 are useful) or easy to separate by other means such as extraction with a water wash. Since there are now three components, it is possible to have one or more binary azeotropes or a ternary azeotrope. The flowsheet depends upon the equilibrium behavior of the system, which can be investigated with distillation curves and residue curves rSection 8.51 A few typical exanples will be illustrated here. 

Figure 6.16 Flowsheet for the manufacture of three different types of solid lipid microcarriers for controlled nutrient or drug delivery using membrane homogenization approach. The dashed area represents the temperatnre-controlled operations carried out at 80°C (above the melting point of oil).

Fig. 10-1. Schematic fuel-processing flowsheet for a two-region homogeneous thorium breeder reactor.

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