The different types of packings commonly used in distillation columns possess different wetting characteristics due to their shape and the nature of their surfaces. The way interfacial area is created, renewed, and maintained in these different geometries has a marked effect on the efficiency of the packings, as well as on the response of the column to different operating conditions. This paper explores the effect of the interfacial area behavior of different packings on the way the distillation column responds to varying loads. Implications for the design of control strategies are discussed as well. Experimental data obtained previously were used to establish the basis for the analysis. The data clearly show that different geometries and surface treatment characteristics have a strong influence on the amount and rate of change of interfacial area with column loading.
The thermodynamic phase behavior of two polymerliquid crystal blends was investigated in both the solid and molten states. One of the blends (p-hexyloxybenzoic acid and poly(ethy1ene glycol]] contains a semi-crystalline polymer. The second example (p-pentyloxycinnamic acid and bisphenol-A polycarbonate) contains a high-impact-resista n t amorphous thermoplastic. Whereas, the former system is almost completely immiscible at ambient temperature, yet advantageous for applications in the microelectronics industry, the latter blend exhibits partial (concentration-dependent] miscibility. Our multi-technique assessment of miscibility/phase separation includes highresolution carbon-13 solid state NMR spectroscopy, differential scanning calorimetry (DSC), and group-contribution thermodynamics (Universal Quasi-Chemical Functional-Group Activity Coefficient formalism including a Free Volume correction for the small molecule activity, UNIFAC-FV). Approximate temperature-composition (equilibrium) phase diagrams are constructed for both blends in light of the results from NMR, DSC, and UNIFAC-FV.
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