Thesis (Ph. D.)--University of Wisconsin--Madison, 1968. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

This thesis presents a review of the theories currently being used to describe the structure of the liquid-vapor interface. The fluids considered are those consisting of "argon-like" molecules, which have radially symmetric potentials. "Wall effects" upon the interface are assumed to be negligible. The derivations of several theories have been recast into forms which depend upon a few common principles. The technique of functional differentiation is extensively used in this regard. This allows each theory to be identified with one of three different approaches: mean-field theory, integro-differential equations, or fluctuation theory. Good agreement is found between the results of theories within each class. The three approaches are shown to be different aspects of a single consistent model of the liquid-vapor interface. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

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Two new apparati have been developed to measure solid-liquid and liquid-liquid equilibria via a synthetic visual method by determination of thermal signatures. One apparatus adopts a technique of using Peltier modules for cooling, and the other is a well-known design that uses a cryogenic fluid in a thermostatted glass cell for cooling of the sample. The Peltier design is for small sample volumes, with a 10 cm3 aluminium equilibrium cell and has a minimum operating temperature of 253.15 K. The glass design is developed to complement the Peltier and has a larger volume of 140 cm3 and a minimum operating temperature of 223.15 K. Both apparati have been semi-automated in order to increase the accuracy and improve the efficiency of data measurements. Therefore the experimenter no longer has to wait for many hours for the determination of equilibrium. This was done by incorporating software, which was specially designed for the apparati using Labview8TM, for controlling the cooling and heating rates. The uncertainty of the temperature measurements was found to be ±0.03 K for the Peltier apparatus and ±0.02 K for the Glass apparatus. Liquid-liquid equilibria data has also been measured on the Peltier apparatus, to demonstrate its versatility. This was done using a digital camera, controlled through the Labview software to identify cloud points. The results have been found to be comparable with literature values. For solid-liquid equilibria new systems of n-alkyl carboxylic acid binary mixtures have also been measured: heptanoic acid + butyric acid and heptanoic acid + hexanoic acid. These systems were measured using both apparati and both systems exhibited eutectic behaviour. All eutectic temperatures were measured on the Glass apparatus. Experimental data for these systems was modelled using the local composition models: Wilson, NRTL and UNIQUAC models. The NRTL model was found to give the best results for both systems with root mean square deviations (RMSD) of 2.16 K and 1.27 K and absolute average deviations (AAD) of 0.61 K and 0.49 K, between temperature measurements of this work and those calculated from the models, for the heptanoic acid + butyric acid and heptanoic acid + hexanoic acid systems, respectively. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2010.

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The equilibrium partial pressures of monoethanolamine (MEA), piperazine (PZ), and water were measured in a stirred reactor with a recirculating vapor phase by FTIR analysis at 35 - 70 Celsius degrees. MEA and PZ volatility were measured in two separate pilot plant campaigns to capture CO₂ from flue gas under a range of absorber conditions. The laboratory data were regressed to determine NRTL binary interaction parameters that predicted the experimental points within 10 - 20%. It was proven that MEA volatility (0.45<MEA<0.55) is a viable concern in CO₂ capture processes from an economic, environmental, and overall health perspective. PZ, on the other hand, was not observed to be as volatile (0.06<PZ<0.08) as predicted by previous models and therefore volatility loss would not be a significant drawback for using it as a CO₂ capture solvent. Pilot plant results show an average MEA gas phase concentration at the absorber outlet to be approximately 45 ppm while the PZ concentrations averaged 6 ppm and 8 ppm at the absorber inlet and outlet, respectively.

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