Thesis (Ph. D.)--University of Texas at Austin, 2005. / Vita. Includes bibliographical references.

Th.--Sci.--Bordeaux 1, 1979. N°: 615.

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The production of uniform-sized drops without small follower drops or "trailers" in liquid-liquid systems was studied using a periodic injection technique for dispersing one liquid through a sharp edged nozzle into the other. Previous investigators using a continuous flow technique found that uniform sized drops without trailers were limited to systems of higher interfacial tension. The effects of nozzle inside diameter, nozzle material, and of velocity-time profile of the dispersed fluid through a nozzle at drop formation were examined using two systems; n-butanol and water of very low interfacial tension, and methyl isobutyl ketone and water of low interfacial tension. These two systems were chosen so that the results of this study could be integrated with other work. The velocity-time profiles were obtained by using a positive displacement bellows pump, the stroke of which was controlled by a cam follower through a variable ratio linkage using three different cam profiles. The conditions under which uniform sized drops without trailers were formed, were located for both systems. The effects of surface active contaminants and the wetting of the nozzle tip by the dispersed phase were considered. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

A study has been made using computer simulation of a fractionating column with simultaneous distillation and chemical reaction occurring. The assumptions of 100% efficient trays and ideality of vapor-liquid equilibrium and thermal properties were made. Results show that the extent to which a reversible reaction can be driven, or an irreversible side reaction inhibited, is a strong function of the ease with which the reaction products may be removed using the separating capacity of the fractionating column. The quantity of liquid holdup per plate is also a factor of considerable importance in the performance of a fractionating column with chemical reaction, but its effect is not simple, interacting as it does with the reflux ratio. The effect of system pressure is complex. Increasing pressure raises temperatures, and therefore reaction rates but decreases separation factors. The influence of this with respect to the main reaction and any undesirable side reactions is so specific to the chemical reaction being studied that no overall generalization can usefully be made. Considering only the point of view of the amount of reaction achieved, a fractionating column can show considerable improvement over a continuous stirred tank reactor. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

No description available.

La distillation est le procédé de séparation le plus répandu dans l'industrie chimique. Pour la séparation des mélanges azéotropiques, une méthode spéciale de distillation doit être appliquée. Le but de mon travail était d'améliorer la séparation des mélanges azéotropiques par distillation discontinue (DD). Un nouvel algorithme a été présenté pour la détermination de la séquence des produits de DD pour des mélanges multicomposants azéotropiques. Contrairement aux méthodes publiées précédemment, cet algorithme n'a pas besoin des paramètres d'équilibre. Configurations non-conventionnelles de DD ont été étudiées par simulation rigoureuse avec un accent sur l'opération fermée. Nombreux modes d'opération fermés étaient proposés, lesquelles diffèrent en l'opération de réservoir supérieur. Les effets du recyclage des fractions sur un procédé de séparation existant de 6 lots d'un mélange déchet azéotropique ont été étudiés. Les études ont été étendues pour un procédé de distillation extractive discontinue (DED). Un volume minimal de pré-fraction doit être incinéré. Le cas optimal de DED a donné un profit plus grand que celui de DD. DED a été étudié pour la séparation des deux mélanges azéotropiques. La séparation a été infaisable ou le rendement a été bas par DD, mais DED et le procédé hybride ont donné des rendements élevés. Une nouvelle politique de DED a été aussi proposée. Un modèle généralisé de la distillation hétéroazéotropique discontinue avec une rétention variable de décanteur a été développé. Dans une analyse de faisabilité, toutes les politiques opérationnelles possibles ont été identifiées. Ce modèle a été étendu pour la distillation extractive hétérogène discontinue. / Distillation is the most widespread method for separating liquid mixtures. The separation of azeotropic mixtures requires a special distillation method. My aim was to improve the batch distillation separation of azeotropic mixtures. A new algorithm was presented for the determination of product sequences of batch distillation of multicomponent azeotropic mixtures. Non-conventional configurations were studied by simulation with emphasis on closed operation. The effects of off-cut recycle on a six-batch separation process of a waste solvent mixture were also investigated. Batch extractive distillation was studied for the separation of two azeotropic mixtures. A new extractive policy was also proposed. A generalised model of batch heteroazeotropic distillation with variable decanter hold-up was developed. This model was extended for batch heterogeneous extractive distillation.

Thesis (MEng) -- Stellenbosch University, 2014. / ENGLISH ABSTRACT: Distillation is one of the most widely used processes for the separation of fluids with different volatilities. Due to the popularity of this process it is often assumed that the hydrodynamic behaviour inside distillation columns is well-defined. However, this is not always the case and this study therefore endeavoured to provide additional insight into the topic through a systematic investigation into the hydrodynamics and the capacity limitations of a sieve tray distillation column. The objective of the study was to measure and evaluate the effects of the following variables on entrainment and weeping: - Fluid flow rate (gas and liquid). - Plate geometry (i.e. hole diameter and fractional hole area). - Liquid properties (i.e. surface tension, viscosity and density). - Gas properties (i.e. viscosity and density). The hydrodynamic effects were evaluated at zero mass transfer in a pilot-scale tray column, by passing pure liquids and gases in counter current configuration. The pilot column was rectangular in shape with internal dimensions of 175 mm by 635 mm. A chimney tray was used to capture the weeping liquid, while a de-entrainment tray was used in combination with a mist eliminator pad to capture the entrained liquid. The fractional hole areas for the sieve trays under investigation were 7%, 11% and 15% and the hole diameters were 3.2 mm (⅛ in.), 6.4 mm (¼ in.) and 12.7 mm (½ in.). The experimental liquids were ethylene glycol, butanol, water and silicone oil, while the gases were air and carbon dioxide (CO2). These experimental measurements produced over 10 000 data points for entrainment and over 7 000 data points of weeping. The results were repeatable and the entrainment values compared reasonably well with previous data produced by Nutter (1971) and Uys (2012). The differences between entrainment for the different liquids were more significant in the spray regime than in the froth regime, and butanol was entrained more readily than silicone oil, ethylene glycol and water. Fluids that caused a larger spray layer in the dispersion zone produced more entrainment. Entrainment increased with decreasing liquid density, decreasing liquid surface tension and decreasing liquid viscosity. The more unstable the dispersion layer, the higher the entrainment. The liquid density strongly influenced weeping, i.e. weeping increased with increasing liquid density. On the other hand, gases with higher densities – and thus with a higher mass flow rates at similar volumetric flow rates through the sieve tray – displayed less weeping and more entrainment than less dense gases, because of an increased upward drag force on the fluids. When considering tray geometry and when operating in the spray regime, the magnitude of entrainment increased with decreasing fractional hole area, while the dependency of entrainment on fractional hole area was more prominent at lower fractional hole areas. When operating in the froth regime – typically above 23 m3/(h.m) – the fractional hole area had a relatively small influence on the magnitude of entrainment, while the cross-flowing liquid rate dominated related effects. In the spray regime, i.e. typically below 23 m3/(h.m), the entrainment increased with increasing sieve tray hole diameter, while hole diameter had a relatively small influence on entrainment at higher liquid flow rates between 23 and 60 m3/(h.m). However, at even higher liquid flow rates in the froth regime, i.e. above 60 m3/(h.m), the effect of hole diameter on the entrainment became more prominent again, with increased entrainment for smaller hole diameters. The effect of hole diameter on weeping differed with changing fluid combinations and the 12.7 mm hole size caused notably less weeping than the 3.2 mm and 6.4 mm trays at higher liquid flow rates. It is believed that weeping occurred preferentially at so-called localised high pressure zones on the sieve tray. At high gas and liquid flow rates, the resultant extended dispersion layer allows minimal intimate contact between the plate and the liquid (minimising such localized high-pressure zones). In effect, the liquid ‘jumps’ over the entire flow path length in the test rig, thus resulting in low weeping rates at high gas and liquid rates. The effects of fractional hole area and hole diameter on entrainment and weeping can be correlated with combinations of well-known hydrodynamic dimensionless numbers, such as the Weber number (We), Froude number (Fr) and Reynolds number (Re). Within the limitations of this study, the flow-Froude number was shown to be the most useful dimensionless number, since it displayed a monotonic relationship with magnitude of entrainment for different combinations of fluid systems and tray configurations. Furthermore, both the construction number and fluid density ratio could be used in a sensible manner to correlate some of the effects of tray geometry on entrainment. / AFRIKAANSE OPSOMMING: Distillasie word wêreldwyd op groot en klein skaal toegepas as ʼn metode om chemiese komponente van mekaar te skei, gebasseer op hul verskil in vlugtigheid. Die hidrodinamiese gedrag van vloeistowwe en hul damp binne ʼn distillasiekolom beïnvloed die effektiwiteit van die skeidingsproses. Hierdie studie beoog dus om bykomende insig te verskaf tot die hidrodinamika en kapasiteitsbeperkings van ʼn plaat-distilleerkolom. Die doelwit van die studie was om die invloed van die volgende veranderlikes op die meesleuring en deurdripping van vloeistowwe te ondersoek: - Gas- en vloeistof vloeitempo. - Plaatgeometrie (i.e. gatdeursnit en fraksionele deurvloei-area). - Vloeistofeienskappe (i.e. oppervlakspanning, viskositeit en digtheid). - Gaseienskappe (i.e. viskositeit en digtheid). Die hidrodinamiese studie is uitgevoer in ʼn reghoekige plaatkolom met interne afmetings van 175 mm x 635 mm. Die vloeistof en gasfases is in kontak gebring op ʼn teenstroom basis, met geen massa-oordrag wat plaasvind nie. ʼn Skoorsteenplaat het die vloeistof opgevang wat deurdrip terwyl ʼn ekstra plaat aan die bokant van die kolom die meegesleurde vloeistof opgevang het. Hierdie ekstra plaat is gebruik tesame met ʼn mis-elimineerder om al die meegesleurde vloeistof op te vang. Plate met verskillende deurvloei-areas (7%, 11% en 15%) en gat deursnitte (3.2 mm, 6.4 mm en 12.7 mm) is gebruik in die ondersoek. Die vloeistowwe wat gebruik is, sluit in etileen glikol, butanol, water en silikon olie. Lug en koolstofdioksied is as gasse gebruik. Die eksperimentele data het goeie herhaalbaarheid getoon en is vergelykbaar met die gepubliseerde data van Nutter (1971) en Uys (2012). Meer as 10 000 data punte is gemeet vir vloeistofmeesleuring en meer as 7 000 vir deurdripping. Die verskil in hoeveelheid meesleuring tussen die vloeistowwe, soos ondersoek in hierdie studie, was mees beduidend in die spoei-regime. Butanol is die meeste meegesleur, gevolg deur silikon olie en dan etileen glikol. Water is die minste meegesleur is. Vloeistowwe wat ʼn groter sproeivolume in die dispersielaag bo die plaat gevorm het, is die meeste meegesleur. Meesleuring het toegeneem met ʼn afname in digtheid, oppervlakspanning en viskositeit van die vloeistof. ʼn Onstabiele dispersielaag bo die plaat het meer meesleuring tot gevolg gehad. Vloeistofdeurdripping is sterk beïnvloed deur vloeistofdigtheid, i.e. deurdripping het sterk toegeneem met digtheid. Gasse met ʼn hoër digtheid veroorsaak weer ʼn afname in deurdripping a.g.v. die hoër opwaartse sleurkragte wat ʼn gas met hoë digtheid op die vloeistof uitoefen. In die sproei-regime (tipies by vloeistofvloeitempos laer as 23 m3/(h.m) is gevind dat meesleuring toeneem met ʼn afname in fraksionele deurvloei-area. Meesleuring se afhanklikheid van fraksionele deurvloei-area was meer beduidend by laer fraksionele deurvloei-areas. In die skuim-regime (tipies by vloeistofvloeitempos hoër as 23 m3/(h.m)) was die afhanklikheid van meesleuring op fraksionele deurvloei-area relatief klein. In die sproei-regime is gevind dat meesleuring toeneem met ʼn toename in gat deursnit, terwyl dieselfde veranderlike ʼn minder beduidende invloed op meesleuring getoon het by hoër vloeistofvloeitempos (tussen 23 en 60 m3/(h.m)). By vloeitempos hoër as 60 m3/(h.m) het meesleuring weer begin toeneem met ʼn afname in gat deursnit. By hoë vloeistofvloeitempos het die plaat met 12.7 mm gat deursnit aansienlik minder deurdripping getoon as plate met 3.2 mm en 6.4 mm deursnitte. Daar word vermoed dat deurdripping hoofsaaklik plaasvind by lokale hoëdruk gebiede op die plaat. By hoër vloeistof- en gasvloeitempos beslaan die dispersielaag ʼn groter volume en is daar dus minder gebiede van digte vloeistofkontak met die plaat, wat ʼn afname in die lokale drukgebiede veroorsaak. Dit lei tot ʼn afname in deurdripping by hoër gas- en vloeistofvloeitempos. Die invloed van fraksionele deurvloei-area en gatdeursnit op meesleuring en deurdripping korreleer goed met kombinasies van welbekende hidrodinamiese dimensielose getalle, i.e. die Webergetal (We), die Froudegetal (Fr) en die Reynoldsgetal (Re). Die vloei-Froudegetal is mees bruikbaar om die invloed van vloeistof-en-gas kombinasies en kolomuitleg op meesleuring te korreleer. Die konstruksiegetal asook die digtheidsverhoudings tussen vloeistof en gas kan op ʼn sinvolle manier aangewend word om van die invloede van plaatgeometrie op meesleuring te beskryf.

Thesis (MScEng (Process Engineering))--University of Stellenbosch, 2005. / Catalytic Distillation (CD) is a hybrid technology that utilizes the dynamics of si- multaneous reaction and separation in a single process unit to achieve a more compact, economical, efficient and optimized process design when compared to the traditional multi-unit designs. The project goal (and key question) is (how) to design a cost-effective, simple and accurate laboratory-scale continuous CD system that will sufficiently and accurately supply useful data for model validation. The system to be investigated is the continuous hydrogenation of an a-olefin C6 (1-hexene) feed stream to the corresponding alkane (n-hexane) product with simultaneous reactant/product separation. Hypothetically, a system can be constructured to determine whether hydrogenation will benefit from the heat and mass transfer integration observed under CD conditions in terms of energy usage, temperature control and the catalyst's surface hydrogen concentration. System convergence with commercial distillation simulation packages ...