Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Liquid-liquid extraction is a branch of solvent extraction that employs addition of an immiscible solvent, as a separating agent, to a liquid feed. Various types of equipment can be used, however if the process requires more than three stages, typically an extraction column, operated in a countercurrent manner would be employed. In order to scale-up and design a commercial extraction column, it is necessary to quantify the extraction system hydrodynamics and mass transfer characteristics. The principal objectives of countercurrently operated extraction columns concern the mass transfer rate and permissible throughput. The performance of a countercurrent extraction column can be adversely affected by axial mixing, which disturbs countercurrent plug flow. Various methods have been devised whereby it is possible to evaluate the performance of a column extraction and scale it up to ensure that the commercial operation achieves the same separation achieved on a pilot scale. Classical axial dispersion models allow quantification of axial mixing and mass transfer rates. Two Backflow models were derived to describe the performance of a Vibrating Plate Extraction (VPE) Column, one for steady state and one for unsteady state operation. The steady state model consisted of a series of simultaneous equations, which were solved using the Excel solver function. The unsteady state model consisted of 54 ordinary differential equations, which were solved stagewise using a fourth order Runge Kutta procedure. The steady state model was based on a dissociation extraction process, whereby meta-cresol (mcresol) was separated from para-hydroxy-benzaldehyde (PHB). The process used the differing de-protonation constants of the two components and the fact that the solubility of the ionic species of each was low in the organic solvent. The extraction system was quantified using a combination of acid-base and extraction theory. Experimentally determined concentration profiles, measured along the length of the column, were force fitted to the model, thereby allowing determination of the model parameters. The mass transfer coefficients ranged between 0.0098 and 0.189 Imin, and it was found that backmixing of the dispersed phase was negligible, while that of the continuous phase was low (varying between 0 and 0.3). The unsteady state model, used to describe the dynamic response of a VPE, was based on a system whereby tert-butyl hydroquinone (TBHQ) was recovered from a purge stream. Conductivity measurements of the raffinate were used to determine the residence time distribution in the column, and hence allowed determination of the extent of axial mixing. It was preferable that the column be operated with minimum settler volumes, otherwise buffering in the settlers occurred, thereby masking axial mixing effects. This method did not facilitate accurate determination of backmixing, at least two other conductivity measurements in the column needed to be measured. / AFRIKAANSE OPSOMMING: Vloeistof-vloeistofekstraksie is 'n vertakking van oplosmiddelekstraksie wat gebruik maak van die toevoeging van 'n onmengbare oplosmiddel as 'n skeidingagent tot die vloeistofvoer. Verskeie tipes apparaat kan gebruik word, maar as die proses meer as drie stadia vereis, sal 'n ekstraksiekolom, in teenstroom bedryf, tipies gebruik word. Om dit moontlik te maak om 'n kommersiele ekstraksiekolom te skalleer en te bedryf, moet die ekstraksiesisteem se hidrodinamika en massa-oordragkarakteristieke gekwantifiseer word. Die hoof doelwitte van ekstraksiekolomme wat teenstroom bedryf word, gaan om die massa-oordrag en toelaatbare deurset. Die skeidingsdoeltreffendheid van 'n teenstroom ekstraksiekolom kan nadelig beinvloed word deur aksiale vermenging, wat teenstroom propvloei versteur. Verskeie metodes is voorgestel wat dit moontlik maak om die doeltreffendheid van 'n ekstraksiekolom te evalueer en te verseker dat dieselfde skeiding verkry word vir 'n kornmersiele aanleg as vir 'n loodsaanleg. Klassieke aksiale dispersiemodelle laat kwantitatiewe berekening van aksiale vermenging en massa-oordragtempos toe. Twee terugvloeimodelle is afgelei om die werksverrigting van 'n Vibrerende Plaat Ekstraksiekolom (VPE) te beskryf. Die gestadidge toestand model bestaan uit 'n stelsel gelyktydige vergelykings wat opgelos is d.m.v. Excel. Die ongestadige toestand model bestaan uit 54 gewone differensiaalvergelykings, wat stapsgewys opgelos is d.m.v. die vierde orde Runge-Kutta metode. Die gestadigde teostand model is gebaseer op 'n dissosiasie ekstraksieproses, waardeur m-kresol geskei is van p-hidroksiebensaldehied (PHB). Die proses maak gebruik van die verskillende protoneringskonstantes van die twee verbindings en die feit dat die oplosbaarheid van beide die ioniese spesies laag is in die organiese oplosmiddel. Die ekstraksiestelsel is gekwantifiseer deur gebruik te maak van 'n kombinasie van suur-basis- en ekstraksieteorie. Die model is gepas op eksperimenteel bepaalde konsentrasieprofiele, gemeet langs die lengte van die kolom. Die massa-oordragkoeffisiente het waardes aangeneem tussen 0.0098 en 0.189 Imin en daar is gevind dat die terugvermenging van die verspreide fase weglaatbaar was, terwyl die van die kontinue fase laag was (tussen 0 en 0.3). Die ongestadige toestand model wat gebruik is om die dinamiese respons van die VPE te beskryf, is gebaseer op 'n stelsel waar tert-butielhidrokinoon (TBHQ) herwin is vanuit 'n bloeistroom. Geleidingsmetings van die raffinaat is gebruik om die residensietydverspreiding in die kolom te bepaaI en het derhalwe toegelaat dat die mate van aksiale vermenging bepaaI kon word. Die kolom moet by voorkeur met minimale skeiervolumes bedryf word, anders is daar 'n buffereffek in die skeiers, wat die aksiale vermenging verskuiI. Hierdie metode Iaat nie die akkurate bepaling van terugvermenging toe nie en minstens twee ander geleidingsmetings in die kolom was benodig.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Current global trends in government, industry and popular OpInIOn indicate that recycling will become essential in the future. Vacuum pyrolysis is a new technology with many recycling applications that have not yet been investigated. This study is a contribution towards the better understanding of the vacuum pyrolysis process and also towards finding possible economically favourable recycling applications. A batch operated tube furnace, which allowed the controlled heating of different materials in a vacuum, was designed and built. The gases and vapours passed though a series of progressively colder vacuum traps, condensing the vapours for further study. The products from the process are charcoal, oil, an aqueous phase and noncondensable gases. The charcoal and oils' possible economic values (R2500- R5000/ton of charcoal, while the plant product oil can be sold as a low sulphur fuel, with a retail value of approximately R1.42 per litre) were determined along with the oils' chemical composition. Several possible feedstocks were studied, including intruder plant species, leather wastes, sewage sludge and a simplified representation of municipal solid waste. The three intruder plants studied were Kraalbos (Galenia africane), Scholtzbos (pteronia pallens) and Asbos (Psilocaolon absimile). These plants yielded 40%, 42% and 48% (charcoal per kilogram dry feedstock) respectively at their maximum oil yield temperatures of 380°C, 480°C and 450°C respectively. The maximum oil yields were 36%, 32% and 20% respectively (also on a dry feedstock basis). It was found that the plants with ash contents below 10% yielded commercially competitive charcoal, and that all of the plants yielded oils with heating values in the range of 24MJ/kg, containing several high value compounds. Asbos was the only plant that did not produce usable charcoal, as its ash content of 40% was double that of commercial charcoals. The leather wastes represent a previously unrecognised application of the technology that could bring huge financial rewards to the tanning industry and could provide a more environmentally friendly alternative to lined landfilling. The cost of landfilling for a medium sized tannery can be as high as RIOOO 000 a year. Apart from the volume reductions achieved (up to a factor 8) it was found that landfilling might be totally avoided if the chrome contained in the charcoal product could be extracted and reused. Sewage sludge was studied, as it is a hazardous waste that requires costly disposal in a lined landfill. It was revealed that volume reductions of up to a factor 3.5 were possible with corresponding charcoal and oil yields of 40% and 38% respectively at 500°C. It was also found that the charcoal product could be used as compost, which would then turn a costly waste into a commodity product. The oil from both the leather and sewage sludge had high energy values (26.7MJ/kg and 30.9MJ/kg respectively) and might either be sold as a bunker fuel or used in the process as a make-up heat source. The value of the oil depends on the problems posed by the oils' high nitrogen content (±5%-6%). A further study was also made of the co-pyrolysis of PVC and wood to determine the interaction between the feedstocks and as a simplified representation of municipal solid wastes. It was found that the HCI released from the PVC caused acid hydrolysis of the wood and led to lower charcoal (reduced from 32.6% to 29.7% on dry feedstock basis, at the maximum co-pyrolysis oil yield temperature of 460°C) and much higher oil yields (42.4% for the co-pyrolysis compared to 23.6% for the plant material at 460°C). An existing computer program (CEA by Gordan and McBride) was also employed in order to find explanations for some of the vacuum pyrolysis results. Although large specialist vacuum pyrolysis plants have been designed in the past (mostly to dispose of used tyre waste) it will be necessary to determine the process economics for small-scale applications if the technology is to be applied at the source of the problem. Overall vacuum pyrolysis appears to be a very promising technology that could solve many waste problems in an environmentally friendly and economically beneficial manner. / AFRIKAANSE OPSOMMING: Hedendaagse neigmgs in regenng, industrie en populêre opirue toon dat hergebruikstegnologieë al hoe meer noodsaaklik sal word in die toekoms. Vakuum pirolise is 'n nuwe tegnologie met vele moonlike hergebruik toepassings wat nog nie bestudeer is nie. Hierdie studie is 'n bydrae tot 'n dieper begrip van vakuum pirolise en ook tot die verdere soeke na nuwe toepassings vir die tegnologie. 'n Enkellading buis-oond, wat die beheerde verhitting van verskillende materiale in vakuum toegelaat het, is ontwerp en gebou. Die gevormde gasse en dampe het deur 'n progressief kouer reeks van vakuum valle beweeg waar dit vir verdere studie gekondenseer en opgevang is. Die produkte van die proses is houtskool, olie, 'n waterryke fase en nie-kondenseerbare gasse. Die houtskool en olie se moontlike waarde (R2500-R5000/ton houtskool, terwyl die plant produk olie verkoop kan word as 'n lae swael verhittings olie met 'n kleinmaat kommersieële verkoopswaarde van R1.42/1), saam met die chemiese samestelling van die olie fase, is bepaal. Die vakuum pirolise van verskeie moontlike voerstowwe is bestudeer, insluitende indringerplante, leerafval, rioolslyk en 'n vereenvoudigde voorstelling van munisipale afval. Die drie plant spesies wat bestudeer is, is: Kraalbos (Galenia africane), Scholtzbos (Pteronia pal/ens) en Asbos (Psilocaolon absimile). Die plante het opbrengste van 40%, 42% en 48% (houtskool per kilogram droë voerstof) onderskeidelik gelewer by elk van die plante se maksimum olie opbrengs temperature van 380°C, 480°C en 450°C onderskeidelik. Die maksimum olie opbrengste was 36%, 32%, 20% (olie per kilogram droë voerstof) vir die onderskeie plante. Daar is bevind dat die plante met as-inhoude van minder as 10% kommersieel kompeterende houtskool gelewer het. Dit is ook gevind dat die olie van al die plante verbrandingswaardes in die orde van 24MJ/kg lewer en dat die olies ook verskeie waardevolle chemikalieë bevat. Asbos was die enigste van die bestudeerde plante wat nie maklik bruikbare houtskool gelewer het nie. Die Asbos houtskool was minder bruikbaar as gevolg van die uiters hoë as-inhoude van tot 40% met gevolglike lae energie waarde. Die vakuum pirolise van leerafval is 'n toepassing wat nog nie voorheen ondersoek is nie. Dit kan moontlik lei tot groot finansiële voordele vir die leerlooi industrie en kan ook 'n meer omgewingsvriendelike alternatief tot belynde afval storting bied. Die koste verbonde aan die storting van leer afval van 'n medium grootte looiery kan tot R1000 000 per jaar beloop. Behalwe vir die volume verkleining behaal (tot 'n faktor 8), is daar ook gevind dat afvalstorting totaal vermy kan word as die hoë hoeveelheid chroom (12% van die houtskool) uit die houtskool verwyder en hergebruik kan word. Rioolslyk is ook bestudeer, siende dat dit ook 'n probleem afvalstof is wat teen groot koste gestort moet word. Die studie het getoon dat volume verkleinings van tot 'n faktor 3.5 en houtskool en olie opbrengste van onderskeidelik 40% en 38% by 500°C behaal kan word. 'n Ondersoek van die houtskool het getoon dat dit gebruik kan word as 'n kompos, wat dan sal beteken dat 'n probleem afvalstof verander word na 'n omgewingsvriendelike en ekonomies waardevolle produk. Die olie van beide die rioolslyk en leer het hoë energiewaardes (26.7MJ/kg en 30.9MJ/kg onderskeidelik) en kan verkoop word as verbrandingsolie of gebruik word in die vakuum pirolise proses as 'n hulp-hitte bron. Die gebruikswaarde van die olie sal baie afhang van die probleme wat deur die uiters hoë stikstof-inhoud (±5%-6%) veroorsaak gaan word. 'n Verdere studie van die ko-pirolise van PVC en hout is ook gedoen om die interaksie tussen die afvalstowwe te bestudeer en ook om as 'n vereenvoudigde voorstelling van munisipale afval te dien. Daar is gevind dat die HCI wat afkom as PVC verhit word, suur hidrolise van die houtstrukture veroorsaak en lei tot laer houtskool (verminder van 32.6% na 29.7% droë voerstofbasis, by die maksimum olie opbrengs temperatuur van 460°C) en veel hoër olie opbrengste (42.4% vir die kopirolise in vergelyking met 23.6% vir die plant materiaal by 460°C). 'n Studie van die energie wat verkry kan word uit die olie en houtskool het getoon dat 16% tot 28% meer energie verteenwoordig word deur die produkte per kilogram droë voerstof vir die ko-pirolise proses bo normale vakuum pirolise. Alhoewel groot spesialis vakuum pirolise aanlegte in die verlede ontwerp is (meestal vir die verwerking van gebruikte motor buitebande) sal dit nogstans noodsaaklik wees om die winsgewindheid van kleinermaat prosesse te bestudeer sodat vakuum pirolise by die oorsprong van die afvalstoftoegepas kan word. Dit blyk dat vakuum pirolise 'n baie belowende tegnologie IS wat verskeie afval probleme op 'n omgewingsvriendelike en ekonomies winsgewinde wyse kan oplos.

Dissertation PhD--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Adsorption tests were conducted with four different ion-exchange resins to determine the equilibrium adsorption of a range of precious and base metals. The adsorption characteristics were determined for synthetic single metal, as well as for multicomponent and base metal solutions. The effect of the el- concentration on the equilibrium adsorption was established for three different Hel concentrations in the above solutions. From the ion-exchange characteristics determined, a selective adsorption sequence is proposed for the separation of precious and base metals. Pure platinum, palladium and gold were dissolved in aqua regia and diluted to 2000 ppm (as metal) in 4M Hel. Ruthenium, rhodium and iridium were dissolved from pure salts in Hel. A 2000 ppm base metal solution was prepared by dissolving all the required components, including precious metals, to match an in-plant industrial basemetals solution composition. For each precious metal the equilibrium adsorption was determined for a couple of solution concentrations. Data points for adsorption curves were established by varying the amount of resin added to the test solution of a specific concentration. The equilibrium solution concentrations were determined by Iep analysis after 24 hours of exposure, using the bottle-roll technique. The experimental results obtained indicate a possible process route for the separation of precious metals with ion-exchange resin. The XAD7 resin is highly selective for gold from mixed solutions containing precious and base metals. It is also evident that, with the gold removed from the solution, the A22 resin adsorbs only palladium. IR200 resin adsorbs only the base metals from the solution. With all other precious metals removed from the solution (platinum and ruthenium must be extracted by other means), iridium can be adsorbed from the solution by IRA900 resin which is highly selective for iridium over rhodium. For all of the anion resins, XAD7, IRA900, and A22, the chloride concentration of the solution did not have a big effect on the adsorption capacity. However, the adsorption of base metals on IR200 is sensitive to chloride concentration, with a rapid reduction in adsorption at higher chloride concentrations. Statistical models were developed for the adsorption of each of the precious metals, as well as for the base metal solution. All adsorption data, obtained for a resin (typically 250 equilibrium data points), was used in the development of the model. The SPSS statistical software package was used to develop linear regression models. The interaction between all the input parameters, e.g. the interaction of gold and chloride ions, was modelled by specifying the product of the gold and the chloride concentrations as an input variable. The variables that determine the adsorption quantities were identified. High solution concentrations of the target adsorption component increase the adsorption quantity. It has been established that a higher platinum concentration increases the adsorption quantity of gold on XAD7 resin. However, the adsorption quantity is reduced at higher ruthenium concentrations. The adsorption quantity of iridium on IRA900 is reduced with increased rhodium concentration. The adsorption quantity of palladium on A22 is increased by the presence of rhodium and decreased by larger concentrations of iridium and platinum. The adsorption of base metals on IR200 is decreased at higher acid concentrations. Higher concentrations of gold in the base metal solution also decrease the adsorption quantity of base metals. The model predicted adsorption of each component compares well with the actual measured values. In batch adsorption tests the counter ion is not removed from the resin. The resin capacity for a specific ion concentration could therefore not be determined. As such, the adsorption models are only valid for the initial part of the ion-exchange process. The effect of kinetics on the adsorption was not determined. / AFRIKAANSE OPSOMMING: Adsorpsietoetse is gedoen met vier verskillende ioonuitruilharse om die ewewig adsorpsie van edelmetale en basismetale te bepaal. Die adsorpsie karakteristieke is bepaal vir sintetiese enkelmetaal-, meermetaal-, en basismetaaloplossings. Die effek van die Cl konsentrasie op die ewewigadsorpsie is bepaal vir drie soutsuurkonsentrasies in al die bogenoemde oplossings. 'n Prosesvloeidiagram vir die selektiewe adsorpsie van edelmetale en basismetale met behulp van die vier verskillende ioonuitruilharse word voorgestel. Suiwer platinum, palladium en goud is opgelos in koningswater en verdun na 2000 dpm (uitgedruk as metaal) in 4 molaar HCl. Rutenium-, rodium- en iridiumoplossings is verkry deur die oplos van suiwer edelmetaalsoute in HCl. 'n Basismetaaloplossing van 2000 dpm is voorberei deur die individuele komponente, wat die edelmetale ingesluit het, in die regte verhouding te kombineer om die samestelling van 'n industriële basismetaaloplossing te verkry. Vir elke edelmetaal is die ewewigadsorpsie bepaal vir tipies twee konsentrasies van edelmetaaloplossings. Verskillende data punte by 'n spesifieke edelmetaalkonsentrasie is bepaal deur die hoeveelheid hars wat by die toets oplossing gevoeg word te varieer. Die oplossingkonsentrasies by ewewig is bepaal deur IGP analise na 24 uur blootstelling met die roterende botteltegniek. Die resultate wat verkry is dui op 'n moontlike ioonuitruiigebaseerde proses vir die skeiding van edelmetale. Die XAD hars is selektief vir goudadsorpsie uit gemengde oplossings wat al die edelmetale, asook basismetale bevat. Dit is ook bevind dat indien goud uit die gemengde oplossing verwyder word, die A22 hars slegs palladium adsorbeer uit die oplossing. Die IR200 hars adsorbeer slegs basismetale. Wanneer al die ander edelmetale uit die oplossing verwyder is (platinum en rutenium moet met alternatiewe prosesse verwyder word) kan iridium geadsorbeer word met !RA900 hars vanuit 'n iridium- en rodium- gemengde oplossing. Vir al drie die anioonharse wat getoets is, naamlik, XAD7, !RA900 en A22, het die chloriedkonsentrasie nie 'n groot effek op die adsorpsie gehad nie. Die hoeveelheid basismetale wat op IR200 hars geadsorbeer word is egter baie sensitief vir die chloriedkonsentrasie, met 'n vinmge afname In adsorpsie by hoër chloriedkonsentrasies. Statistiese modelle is ontwikkel vir elke hars en vir elk van die edelmetale, asook die basismetaaloplossing. Al die eksperimentele data wat vir elke hars verkry is, tipies 250 ewewigspunte, is gebruik in die ontwikkeling van lineêre regressie modelle vir die primêre absorberende spesie op die hars. Hoër konsentrasies van die teiken adsorpsie komponent verhoog die adsorpsie daarvan. Hoër platinumkonsentrasies verhoog die adsorpsie van goud op XAD7, maar die teenwoordigheid van rutenium verlaag adsorpsie. Die adsorpsie van iridium op IRA900 word verlaag met hoër rodiumkonsentrasies. Die adsorpsie van palladium op A22 verhoog met die teenwoordigheid van rodium, maar neem af met hoër konsentrasies van iridium en platinum. Die adsorpsie van basismetale op IR200 neem af by hoër suurkonsentrasies. 'n Hoër goudkonsentrasie verlaag ook die adsorpsie van basismetale. Die gemodelleerde adsorpsie hoeveelhede vergelyk goed met die gemete waardes. Aangesien die uitgeruilde ioon nie verwyder word uit die toetsoplossing nie, kon die harskapasiteit vir 'n spesifieke ioonkonsentrasie nie bepaal word nie. Die modelle is derhalwe slegs getoets vir die aanvanklike deel van die ewewigsdata en die kinetika van adsorpsie is nie in ag geneem nie.

Dissertation (PhD)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: A mathematical model is presented which conceptualises fluid flow and heat transfer in cellular metallic foams completely saturated with a fluid in motion. The model consists of a set of elliptic partial differential governing equations describing, firstly, a momentum balance in the fluid by the spatial distribution of its locally mean velocity, and secondly, an energy balance in the fluid and in the solid matrix of the metallic foam, by the spatial and temporal distribution of their locally mean temperatures. The separate energy balance descriptions for the fluid and the solid matrix extend the application of the model to conditions of thermal equilibrium and thermal non-equilibrium between the fluid and the solid matrix. A computational solution algorithm is presented which allows the universal application of the model to porous domains of arbitrary shape, with spatially and temporally variable heat loads in a variety of forms. / AFRIKAANSE OPSOMMING: 'n Wiskundige model word voorgestel wat vloei en warmteoordrag voorspel in sellulêre metaalsponse wat in geheel gevul is deur 'n bewegende vloeier. Die vloeier kan in gasof vloeistoffase verkeer. Die model bestaan uit 'n stel elliptiese parsiële differensiaalvergelykings wat in die eerste plek 'n momentum-ewewig in die vloeier beskryf in terme van 'n ruimtelike, lokaal-gemiddelde snelheidsveld, en wat tweedens 'n energie-ewewig in die vloeier en in die soliede matriks van die metaalspons beskryf in terme van ruimtelike en tydelike lokaal-gemiddelde temperatuur verspreidings. Die aparte energie-ewewig beskrywings vir die vloeier en vir die soliede matriks van die metaalspons brei die aanwending van die model uit na gevalle waar die vloeier en die soliede matriks in termiese ewewig of in termiese onewewig verkeer. 'n Numeriese oplossingsalgoritme word ook voorgestel vir die universele toepassing van die model op ruimtelik-arbitrêre metaalspons geometrië wat onderwerp word aan 'n aantal verskillende ruimtelik-en tydveranderlike termiese laste.

Thesis (PhD)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: In this study the deoiling and fractionation of paraffin wax using supercritical fluid extraction (SCFE) has been investigated. SCFE was compared with state-of-the-art processes such as wax crystallisation, static crystallisation and short path distillation. Ethane and carbon dioxide were investigated as supercritical solvents for the supercritical fluid extraction of paraffin wax. Supercritical phase equilibrium data for ethane - n-alkane and CO2 - n-alkane systems close to the mixture critical region were obtained from the literature, and were correlated with several equations of state. Statistical mechanical equations of state failed to correlate the data close to the mixture critical region due to the neglect of density fluctuations which influences phase behaviour close to critical points, or due to inadequate mixing rules. It was found that simple cubic equations of state such as Soave-Redlich-Kwong, Peng-Robinson and Patel-Teja could correlate the data using two interaction parameters. This can be attributed more to their flexibility as correlating tools than to their fundamental accuracy. The Patel-Teja EOS was modified by fitting it to predict low vapour pressure data for long-chain n-alkanes. This modified Patel-Teja EOS was then fitted to the phase equilibria by adjusting two interaction parameters per binary system. The interaction parameters for each solvent (ethane or CO2) system were then fitted to generalised correlations to enable extrapolation to solvent - n-alkane systems for which no equilibrium data were available. The Simplified Perturbed Hardchain theory (SPHC) equation of state was used to correlate lower-pressure solubility data used to model the extract separator. A pilot plant SCFE unit was constructed and used to obtain experimental fractionation data of a low-molecular weight Fischer-Tropsch wax. The experimental results indicate that fractionation of the wax is possible and that the separation efficiency is enhanced by returning some of the extract to the column as reflux. An equilibrium stage model was constructed and used to simulate the extraction experiments. It was possible to obtain good agreement between the experimental results and model predictions. Deoiling of petroleum waxes with a low n-paraffin content (which are not currently deoiled commercially) was investigated. Experimental SCFE and SPD results indicated that selective deoiling is not possible, since the separation is based on differences in molecular weight (or vapour pressure). Simulations of wax crystallisation or solvent extraction and practical tests indicate that deoiling is possible, based on differences in structure and therefore melting point of the components in the wax. Practical problems associated with crystallisation or solvent extraction such as filtration, the use of chlorinated solvents and low yields currently prevent the commercial deoiling of these waxes. During crystallisation of these waxes a soft wax cake is formed which impedes the operation of static crystallisation. A detailed study of the economics of n-paraffin wax deoiling using SCFE was conducted. Flow sheets were proposed to minimise the energy consumption of the SCFE process. Comparison of SPD, static crystallisation and SCFE indicates that a SPD plant will be the cheapest option for deoiling the wax feed investigated. Fractionation of heavier waxes using SPD might not be economically feasible, since the distillation temperature increases dramatically with increasing molecular weight, which leads to higher energy cost. For medium to long chain n-paraffin waxes SCFE should be very competitive, since the capacity of the supercritical solvent can be manipulated to extract longer chain waxes without increasing the extraction temperature. Static crystallisation appears to be the more expensive deoiling option, due primarily to the large initial capital investment cost. / AFRIKAANSE OPSOMMING: Die olieverwydering en fraksionering van paraffienwasse met behulp van superkritiese ekstraksie is in hierdie studie ondersoek. Die modellering van moderne olieverwyderings- en fraksioneringsmetodes soos waskristallisasie, statiese kristallisasie en kortpad distillasie is ook ondersoek. Etaan en koolstofdioksied is ondersoek as superkritiese oplosmiddels vir die superkritiese ekstraksie van paraffienwasse. Literatuurdata van superkritiese fase-ewewigte vir etaan - n-alkaan en CO2 - n-alkaan stelsels naby die mengselkritiese punt is versamel en gekorreleer met verskeie toestandsvergelykings. Statisities-meganiese toestandsvergelykings kon nie data naby mengselkritiese punte korreleer nie, moontlik weens digtheidsvariasies wat afwykings van klassieke gedrag teweegbring, of onakkurate mengreëls. Eenvoudige kubiese toestandsvergelykings soos Soave-Redlich-Kwong, Peng-Robinson en Patel-Teja kon op die ewewigsdata gepas word deur gebruik van twee interaksieparameters. Dit kan eerder toegeskryf word aan hulle buigsaamheid eerder as hulle fundamentele akkuraatheid. Die Patel-Teja toestandsvergelyking is gemodifiseer deur dit te pas op lae dampdruk data van langketting n-alkane. Hierdie gemodifiseerde toestandsvergelyking is gepas op die fase-ewewig data deur twee interaksieparameters te gebruik per binêre sisteem. Die interaksieparameters vir die oplosmiddel stelsels (etaan of CO2) is gekorreleer met algemene vergelykings sodat dit vir ekstrapolasie na oplosmiddel - n-alkaan stelsels gebruik kan word waarvoor ewewigsdata nie beskikbaar is nie. Die "Simplified Perturbed Hardchain" teorie (SPHC) toestandsvergelyking is gebruik om laer druk oplosbaarheidsdata te korreleer vir gebruik in die modellering van die ekstrak skeier. In Superkritiese ekstraksie loodsaanleg is gebou en gebruik om eksperimentele fraksioneringsdata van 'n lae molekulêre massa Fischer- Tropsch was te genereer. Vanaf die eksperimentele resultate blyk fraksionering van was moontlik te wees. Die doeltreffendheid van die skeiding kan verhoog word deur terugvloei van ekstrak na die kolom. 'n Ewewigsmodel is opgestel en gebruik om die ekstraksie eksperimente te modelleer. Deur die ekstraksiedruk en aantal stadia te verander kon goeie ooreenstemming met eksperimentele resultate verkry word. Die verwydering van olie uit petroleumwasse met In lae n-paraffien inhoud (wat nie tans kommersiëel ontolie word nie) is ondersoek. Eksperimentele resultate vir superkritiese ekstraksie en kortpad distillasie dui daarop dat selektiewe olieverwydering nie moontlik is nie, omdat die skeiding gebaseer is op verskille in molekulêre massas en dus (of dampdrukke). Simulasies van waskristallisasie dui op die moontlikheid van olieverwydering gebaseer op verskille in strukture van die komponente in die was. Praktiese probleme geassosieer met kristallisasie of oplosmiddel ekstraksie soos filtrasie, lae opbrengste en gebruik van gechlorineerde koolwaterstowwe as oplosmiddel belemmer die kommersialisering van olieverwydering vir hierdie tipes wasse. 'n Gedetaileerde studie van die ekonomiese lewensvatbaarheid van superkritiese olieverwydering is uitgevoer. Vloeidiagramme is voorgestelom die energieverbruik van die superkritiese ekstraksieproses te minimeer. Vergelyking van kortpad distillasie, statiese kristallisasie en superkritiese ekstraksie dui daarop dat kortpad distillasie die goedkoper opsie vir die olieverwydering van die spesifieke was is. Fraksionering van swaarder wasse met kortpad distillasie sal moontlik nie haalbaar wees nie omdat die distillasietemperatuur drasties toeneem met molekulêre massa. Die skeiding van medium tot langketting wasse met superkritiese ekstraksie behoort meer mededingend te wees, want die kapasiteit van die superkritiese oplosmiddel kan maklik verstel word om langer kettinglengtes wasse te ekstraeer sonder om die temperatuur te verhoog. Statiese kristallisasie blyk die duurder olieverwyderingsopsie te wees hoofsaaklik weens die hoë kapitaalkoste van so 'n aanleg.

Thesis (PhD)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Lignocellulose is the principal form of biomass in the biosphere and therefore the predominant renewable source in the environment. However, owing to the chemical and structural complexity of lignocellulose substrates, the effective and sustainable utilization of lignocellulose wastes is limited. Many environments where lignocellulose residues are ordinarily stored can be highly acidic (e.g. landfills), and under these circumstances biodegradation of the lignocellulose is slow and unhygienic. Owing to the metabolic activities of the micro-organisms, the initially acidified habitats rapidly undergoes self-neutralization. A number of pathogenic bacteria (coliforms and Salmonella sp.) are present during this slow degradation process and it is therefore imperative to improve the efficiency and hygienic effects of the biodegradation of the lignocellulose. Although the fundamentals of biodegradation of lignocellulose have been widely investigated, many issues still need to be resolved in order to develop commercially viable technology for the exploitation of these waste products. For example, owing to the complex, heterogeneous structure of lignocellulose, the degree of solubilization, modification and conversion of the different components are not clear. Likewise, the overall anaerobic degradation of lignocellulose is not understood well as yet. In this study, the emphasis was on the promotion of solid anaerobic digestion of lignocellulose wastes for environmental beneficiation and waste reutilization. The degradation of lignocellulose in landfill environments was first simulated experimentally. Once the microbial populations and the degradation products of the system were characterized, the promotion of anaerobic digestion by use of activated sludge was studied. This included acidogenic fermentation, as well as recovery of the methanogenic phase. Moreover, special attention was given to the further disposal of humic acids or humic acid bearing leachates formed in the digestive system, since these acids pose a major problem in the digestion of the lingocellulose. With ultrasonication, approximately 50% of the lower molecular weight fraction of humic acids could be decomposed into volatile forms, but the higher molecular weight fraction tended to aggregate into a colloidal form, which could only be removed from the system by making use of ultrasonically assisted adsorption on preformed aluminium hydroxide floes. This was followed by an investigation of the microbial degradation of humic acids and the toxicity of these acids to anaerobic consortia. Further experimental work was conducted to optimize the biological and abiological treatment of lignocellulose in an upflow anaerobic sludge blanket (DASB) reactor fed with glucose substrate. The humic acids could be partially hydrolysed and decomposed by the acid fermentative consortia of the granules in the DASB reactor. Finally, solid mesothermophilic lignocellulose anaerobic digestive sludge can be viewed as a humus-rich hygienic product that can improve the fertility and water-holding capacity of agricultural soil, nourish plants and immobilize heavy metals in the environment as a bioabsorbent. / AFRIKAANSE OPSOMMING: Lignosellulose is die hoofbron van biomassa in die biosfeer en is daarom ook die belangrikste hernubare bron in die omgewing. As gevolg van die chemiese en strukturele kompleksiteit van lignosellulose substrate, is die doeltreffende en volhoubare benutting van lignosellulose afval egter beperk. Die suurgehalte van die omgewings waar lignosellulose reste gewoonlik gestoor word, soos opvullingsterreine, kan hoog wees en onder hierdie omstandighede is die biodegradasie van die lignosellulose stadig en onhigiënies. As gevolg van die metaboliese aktiwiteite van die mikro-organismes ondergaan die aanvanklik aangesuurde habitatte vinnig self-neutralisasie. 'n Aantal patogeniese bakterieë (koliforme en Salmonella sp.) is deurgaans gedurende dié stadige natuurlike proses teenwoordig en dit is dus van die grootste belang om die effektiwiteit en die higiëne van die bioafbreking van die lignosellulose-substraat te verhoog. Alhoewel die grondbeginsels van die bioafbreking van lignosellulose reeds wyd ondersoek is, moet verskeie probleme nog opgelos word ten einde kommersieel haalbare tegnologie te ontwikkel vir die ontginning van afvalprodukte. Byvoorbeeld, as gevolg van die komplekse, heterogene struktuur van lignosellulose, is die graad van solubilisering en die modifikasie en omskakeling van verskillende komponente nog onduidelik. Net so word die algehele anaerobiese afbreking van lignosellulose ook nog nie ten volle verstaan nie. In hierdie ondersoek het die klem geval op die bevordering van soliede anaerobiese digestie van lignosellulose afval vir omgewingsverbetering en die benutting van die afval. Die afbreking van lignosellulose in opvullingsterreine is eers eksperimenteel gesimuleer. Nadat die mikrobiese populasies en die afbrekingsprodukte gekarakteriseer is, is die bevordering van anaerobiese digestie deur die gebruik van geaktiveerde slyk bestudeer. Dit het asidogeniese fermentasie ingesluit, sowel as herwinning van die metanogeniese fase. Spesiale aandag is gegee aan die verdere verwerking van humus sure en humussuurbevattende legate wat in die digestiewe stelsel gegenereer is, aangesien die sure probleme veroorsaak het met die vertering van die lignosellulose. Met ultrasoniese straling is nagenoeg 50% van die lae-molekulêre massafraksie van die humussure ontbind in vlugtige vorm, maar die hoë-molekulêre massafraksie het geneig om in 'n kolloïdale vorm te aggregeer, wat slegs uit die stelsel verwyder kon word deur middel van ultrasonies ondersteunde adsorpsie op voorafgevormde aluminiumhidroksiedvlokkies. Dit is gevolg deur 'n ondersoek na die mikrobiese afbreking van humus sure en die toksisiteit van die sure ten opsigte van anaerobiese konsortia. Verdere eksperimentele werk is gedoen ten opsigte van die biologiese en abiologiese behandeling van lignosellulose in 'n opwaartsvloeiende anaerobiese slikkombersreaktor (OASK) gevoer met glukosesubstrate. Die humus sure kon gedeeltelik gehidroliseer en ontbind word deur die suurgistende konsortia van die granules in die OASK reactor. Ten slotte kan die vaste termofiliese-mesofiliese anaerobiese lignosellulose verteringslik ook gesien word as 'n humusryke higiëniese produk wat die vrugbaarheid en die waterhoudende vermoë van landbougrond kan verhoog, plante kan voed en kan funksioneer as bioabsorbeerder van swaarmetale in die omgewing.

Dissertation (PhD(Eng))--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Coal pyrolysis liquors are a major source of phenolic compounds. The separation of the phenolic compounds from the neutral oils and nitrogen bases also present in the pyrolysis liquors is difficult due to low relative volatilities and the formation of azeotropes. The desired phenolic recovery and phenolic product purity of 99.5 % can therefore not be achieved by means of conventional separation processes. Alternative processes such as liquid-liquid extraction with various low-boiling solvents, mixtures of high-boiling solvents and extractive distillation have been investigated. Disadvantages of these processes include the high solvent ratios required, low recovery of the higher substituted phenolic compounds, inability to treat a wide-boiling feedstock in one process step and complex post-purification of the phenolic product. A solvent system consisting of a selective solvent, water as a co-solvent, and hexane as a countersolvent, is proposed. An industrial heavy naphtha stream was analysed and the most prevalent phenolic compounds, neutral oils and nitrogen bases identified. Three synthetic feed streams were compiled to represent the industrial stream, namely: 1. phenol + benzonitrile + aniline + mesitylene + 5-et-2-me-pyridine 2. m-cresol + o-tolunitrile + o-toluidine + pseudocumene + undecane + indene 3. 2,4-xylenol + 3,5-xylenol + 3,4-xylenol + indane + dodecane + naphthalene The stream containing phenol was used as a basis for solvent selection, with emphasis on the separation of phenol from benzonitrile. A variety of molecules containing hydroxyl and ether functional groups were identified as potential solvents by means of computer-aided molecular design using a genetic algorithm. Of the commercially available solvents tested on batch extraction scale, triethylene glycol achieved the highest phenol-benzonitrile, phenol-aniline and phenol-5-et-2-me-pyridine separation factors as well as the highest phenol recovery. It was concluded from the solvent selection process that effective solvents for the problem under investigation were those containing hydroxyl groups positioned on the molecule backbone in such a way as to facilitate hydrogen bonding with more than one phenolic molecule at a time. Two commercially unavailable solvents, 1,3-(ethoxy-2- hydroxy)-propane-2-01 and 1,3-(diethoxy-4-hydroxy)-propane-2-01 were therefore synthesised from ethylene glycol and diethylene glycol respectively. The molecular structures of these two solvents are analogous to that of triethylene glycol, and contain an additional hydroxyl group. The performance of the synthesised solvents was evaluated and compared to that of triethylene glycol on the basis of m-cresol-otolunitrile, 2,4-xylenol - o-tolunitrile, and 2,4-xylenol - o-toluidine separation factors and phenolic recoveries achieved by means of batch extraction tests. 1,3-(Diethoxy-4- hydroxy)-propane-2-01 yielded higher phenolic recoveries, but lower separation factors than did triethylene glycol. Triethylene glycol was therefore selected for further process development as it is commercially available. A series of batch extractions were carried out on each of the synthetic feed streams using the proposed solvent system. For phenol and m-cresol, recoveries in excess of 99% were obtained in a single stage. Recoveries in excess of 98% were obtained for the xylenol isomers. It was found that the recoveries of the xylenol isomers were more sensitive to changes in the solvent ratios. The separation of phenolic compounds from paraffins, naphthalene, indene, indane and the alkyl-substituted benzenes was trivial using the proposed solvent system. Highly satisfactory separation of the phenolic compounds from pyridines and aromatic nitriles was achieved. The separation of phenol from aniline, although satisfactory, was not as good. The optimum solvent to feed, water to solvent and hexane to feed ratios were identified as being 3.0, 5.0 and 0.25 respectively. Binary interaction parameters for the NRTL equation were obtained by regression of the equilibrium data from the batch extraction tests. The NRTL model fitted the equilibrium data satisfactorily. The proposed solvent system was tested on pilot plant scale. The performance of the extraction column was optimised using a synthetic feed stream consisting of m-cresol, p-cresol, aniline and o-tolunitrile. The optimum solvent ratios and operating parameters were then implemented in further tests on an industrial heavy naphtha stream. A phenolic product purity of 99.75% was achieved for this stream. The corresponding phenolic recovery was in excess of 91 %. The proposed separation process, including solvent recovery was simulated using the NRTL model with the experimentally determined interaction parameters. A single stream consisting of all the components used in the batch extraction tests was specified as the feed stream to the simulated process. A final simulated phenolic product purity of 99.5% and recovery in excess of 94% was obtained after solvent recovery. The optimum solvent to feed, hexane to feed and water to solvent ratios were determined as being 3.0, 5.0 and 0.25 in both the pilot plant tests and the simulated extraction process. It can be concluded that the proposed separation process is successful in recovering high purity phenolic compounds from tar liquors. Further development of the process has commenced in industry. / AFRIKAANSE OPSOMMING: Die pirolise van steenkool is 'n belangrike bron van fenoliese verbindings. Die skeiding van die fenoliese komponente vanuit die neutrale olies ook teenwoordig in die pirolise mengsel word bemoeilik deur lae relatiewe vlugtighede en die vorming van aseotrope. Dit is dus nie moontlik om die gewenste hoë fenoliese herwinning en fenoliese produk suiwerheid van 99.5% d.m.v. konvensionele distilleerprosesse te behaal nie. Alternatiewe prosesse soos ekstraktiewe distillasie en vloeistof-vloeistof ekstraksie met verskeie laagkokende oplosmiddels en mengsels van hoogkokende oplosmiddels is al ondersoek. Die hoë oplosmiddel verhoudings wat benodig word, lae herwinning van die hoërgesubstitueerde fenoliese verbindings, onvermoë om in een prosesstap 'n prosesstroom met In wye kookgebied te behandel en die ingewikkelde suiwering van die fenoliese produk tel onder die nadele van hierdie prosesse. 'n Oplosmiddelsisteem wat In selektiewe oplosmiddel, water as polêre oplosmiddel en heksaan as teenoplosmiddel bevat is as 'n alternatiewe proses voorgestel. 'n Industriële swaar nafta prosesstroom is ge-analiseer en die fenoliese verbindings, neutrale olies en stikstofbasisse met die hoogste konsentrasies daarin geïdentifiseer. Drie sintetiese strome is op grond van hierdie analise saamgestelom die industriële stroom te verteenwoordig: 1. fenol + benzonitriel + anilien + mesitileen + 5-et-2-me-piridien 2. m-kresol + o-tolunitriel +o-toluïdien + pseudokumeen + undekaan + indeen 3. 2,4-xilenol + 3,5-xilenol + 3,4-xilenol + indaan + dodekaan + naftaleen Die fenolbevattende stroom is as basis vir oplosmiddelkeuring gebruik, met die klem op die skeiding van fenol vanuit benzonitriel. Verskeie molekules wat hidroksie- en eter funksionele groepe bevat is as potensiële oplosmiddels uitgeken d.m.v. rekenaargesteunde molekulêre ontwerp met In genetiese algoritme. Hierdie oplosmiddels is d.m.v. enkellading ekstraksie toetse geëvalueer. Die kommersieel beskikbare oplosmiddel wat die hoogste fenol-benzonitriel, fenol-anilien en fenol-5-et-2-me-piridien skeidingsfaktore, sowel as die hoogste fenol herwinning op enkellading ekstraksie toetsvlak gelewer het, was triëtileenglikol. Vanuit die proses vir die keuse van 'n oplosmiddel was dit duidelik dat, vir hierdie skeidingsprobleem, die mees effektiewe oplosmiddels dié is met hidroksiel groepe wat so geposisioneer is in die oplosmiddel molekuul dat dit waterstofbindings kan vorm met meer as een fenoliese molekuul. Twee oplosmiddels wat nie kommersiëel beskikbaar is nie, 1,3-(etoksie-2-hidroksie)-propaan-2-01 en 1,3-(diëtoksie-4-hidroksie)-propaan-2- ol, is gesintetiseer vanuit etileenglikol en diëtileenglikol onderskeidelik. Die molekulêre strukture van hierdie twee oplosmiddels is analoog aan dié van triëtileenglikol en bevat 'n addisionele hidroksielgroep. Die effektiwiteit van die gesintetiseerde oplosmiddels is geëvalueer en met dié van triëtileenglikol vergelyk op grond van rn-kresol-o-tolunltriel, 2,4-xilenol - o-tolunitriel en 2,4-xilenol - o-toluïdien skeidingsfaktore en fenoliese herwinning behaal d.m.v. enkellading ekstraksie toetse. Hoër fenoliese herwinning en laer skeidingsfaktore is behaal met 1,3-(diëtoksie-4-hidroksie)-propaan-2-01as met triëtileenglikol. Triëtileenglikol is dus gekies vir verdere prosesontwikkeling aangesien dit kommersiëel beskikbaar is. Enkellading ekstraksie toetse is op elk van die sintetiese voerstrome uitgevoer met die voorgestelde oplosmiddelsisteem. Fenol- en m-kresol herwinning van meer as 99% en xilenol herwinning van meer as 98% is behaal. Die skeiding van fenoliese verbindings vanuit paraffiene, naftaleen, indeen, indaan en die alkielgesubstitueerde benseenverbindings is triviaal met die voorgestelde oplosmiddelsisteem. Hoogs aanvaarbare skeiding van fenoliese verbindings van die piridiene en aromatiese nitriele is vermag. Die skeiding van fenol en anilien is nie so goed nie, maar is nog steeds aanvaarbaar. Die optimum oplosmiddel tot voer, water tot oplosmiddel en heksaan tot voer is as 3.0, 5.0 en 0.25 vasgestel. Binêre interaksie parameters vir die NRTL vergelyking is verkry d.m.v. regressie van die ewewigsdata wat deur die enkelladingstoetse gegenereer is. Die NRTL model het die ewewigsdata goed gepas. Die voorgestelde oplosmiddelsisteem is op loodsaanlegvlak getoets. Die werking van die ekstraksie kolom is ge-optimeer met In sintetiese voerstroom wat uit m-kresol, pkresol, anilien en o-tolunitriel bestaan. Die optimum oplosmiddel verhoudings en bedryfstoestande is verder toegepas op 'n industriële swaar naftastroom. 'n Fenoliese suiwerheid van 99.75% is behaal met hierdie stroom. Die ooreenkomstige fenoliese herwinning was groter as 91%. Die voorgestelde skeidingsproses, insluitende oplosmiddelherwinning is gesimuleer met die NRTL model wat op die eksperimentele data gepas is. 'n Enkele stroom wat bestaan het uit al die komponente wat in die enkelladingstoetse gebruik is, is as die voerstroom tot die gesimuleerde proses gespesifiseer. 'n Finale gesimuleerde fenoliese produksuiwerheid van 99.5% en herwinning groter as 94% is na oplosmiddelherwinning behaal. Die optimum oplosmiddel tot voer, heksaan tot voer en water tot oplosmiddel verhoudings is vasgestel as 3.0, 5.0 en 0.25 onderskeidelik vir beide die gesimuleerde proses en die loodsaanleg toetse. Die voorgestelde skeidingsproses kan dus 'n hoogs suiwer fenoliese produk uit pirolisestrome herwin. Verdere ontwikkeling van die proses is in die industrie begin.

Thesis (PhD)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: This study describes the design, construction, complete industrialisation and operation of a dual bed vacuum swing adsorption (VSA) demonstration plant, which operates at atmospheric and sub-atmospheric conditions. All design objectives as set out initially were met. The plant removes contaminants such as methanol and water from neutral wine spirit. Neutral wine spirit is a key component of various local and international spirituous products which include liqueurs, gin, vodka, fortified wines and brandy. Neutral wine spirit can chemically be described as the azeotropic mixture of ethanol and water, which occurs at an ethanol content of 96.4 vol. %. Methanol is naturally present in all products from the vine. Fermentation and distillation concentrate methanol even more, and due to physical and chemical characteristics, its separation consumes as much as 45 % of total production costs. Neutral wine spirit is produced by the proven technology of continuous atmospheric distillation. Continuous improvement of the distillation process is limited due to the physical constraints of an old facility, but also due to previous design philosophies and approaches. The VSA plant consists of two adsorbers, packed to a total height of 1.71 m and a diameter of 0.4 m. Adsorption took place at 100 °C and regeneration at the same bed temperature with purified nitrogen gas at 170 °C and a vacuum of 17 kPa (abs). Experiments were divided into Group I and Group II experiments. Group I investigated the ability to separate methanol and water from the azeotrope and to which efficiency it occurred. It consisted of 120 adsorption cycles of 5 minutes each and 60 samples were drawn for analyses. Breakthrough was not allowed to occur. The azeotropic feed was consistently dehydrated to a water content < 0.05 wt %, while methanol was reduced to < 4 mg/100mLAA. The type of 3A molecular sieve (MS 564 CS) was specifically selected to ensure analytic as well as organoleptic compliance with the product specification. Molecular sieve 4A was removed due to organoleptic problems with the product. Group" experiments were performed in the format of a sensitivity analysis. The effects of various process parameters on the methanol breakthrough curves were individually assessed. Eighteen experiments were performed over a period of 8 days, with 86 samples drawn. The duration of an adsorption cycle was 30 minutes, allowing methanol breakthrough to occur. Water was preferentially adsorbed. Negative methanol bed loadings during high water loadings confirmed that water was able to displace methanol molecules. In the presence of water, molecular sieve 3A was capable of adsorbing 0.6 mg methanol/100mLAA, while in the absence of water with synthetically dosed methanol, molecular sieve 3A achieved a maximum loading of 12.3 mg methanol/100mLAA. The latter corresponded with a maximum methanol feed content of 1118 mg/100mLAA. In general, quicker breakthrough occurred at higher flow rates and feed concentrations. Continuous breakthrough caused bed contamination and a 24-hour thermal regeneration was performed following experiment 12. The feed flow rate was increased from the theoretical 50 f/hr to 70 f/hr without any additional capital layout. Selected process conditions were found to be effective in continuously separating methanol from ethanol. Depending on the strategy of integration, profitability studies shows a Return on Investment of between 110.1% - 220.8% for the adsorption project. Adsorption is superior to distillation in the separation of methanol. Due to the level of innovation involved, it is recommended that the contents of this study remain confidential and patent protection is to be extended. This dissertation speaks to both the wine making as well as the chemical engineering fraternity. It seeks to provide credibility to both parties, by clarifying the unknown issues fundamental to the respective disciplines. / AFRIKAANSE OPSOMMING: Hierdie studie definieer die ontwerp, vervaardiging en volledige industrialisasie van 'n dubbelbed vakuum adsorpsie demonstrasie aanleg (VSA) wat by atmosferiese en sub-atmosferiese kondisies bedryf word. Alle ontwerpsdoelwitte is bereik. Die aanleg verwyder selektief metanol en water vanuit neutrale wynspiritus. Neutrale wynspiritus is 'n sleutelkomponent van verskeie spiritualieë in die plaaslike en internasionale wyn en spiritus bedryf. Hierdie produkte sluit in likeurs, jenewer, vodka, gefortifiseerde wyne en brandewyn. Chemies, kan neutrale wynspiritus beskryf word as die azeotropiese mengsel van etanol en water teen 96.4 vol. %. Metanol het 'n natuurlike teenwoordigheid in alle produkte vanaf die wynstok. Gisting en distillasie konsentreer metanol tot 'n hoër mate en weens fisiese en chemiese eienskappe word metanol teen hoë koste vanaf die etanol stroom geskei. Die metanol verwyderingskomponent beloop soveel as 45 % van die produksiekoste van die totale proses. Neutrale wynspiritus word deur die gevestigde tegnologie van kontinue atmosferiese distillasie geproduseer. Kontinue verbetering van die proses word beperk deur die fisiese ouderdom en toestand van die fasiliteite, maar is ongelukkig ook die resultaat van vorige ontwerpsfilosofieë en benaderings. Die adsorbeerders is gepak tot 'n hoogte van 1.71 m met 'n deursnit van 0.4 m. Adsorpsie het by 100°C plaasgevind en regenerasie by dieselfde bedtemperatuur met stikstofgas by 170°C en 'n vakuum van 17 kPa (abs). Eksperimentele werk is in Groep I en Groep II eksperimente verdeel. Groep I het die effektiewe prosesvermoë om metanol en water vanuit die azeotroop te verwyder ondersoek. Dit het bestaan uit 120 adsorpsie siklusse van 5 minute elk. Sestig monsters is getrek vir analise. Deurbreek van metanol was nie toe gelaat om plaas te vind nie. Die azeotropiese toevoer is konsekwent tot 'n water inhoud < 0.05 massa % gedehidrateer is. 'n Metanol inhoud < 4 mg/100 mLAA is bereik. Die tipe 3A molekulêre sif (MS 564 CS) was spesifiek vir die toepassing geselekteer om sodoende 'n analities sowel as organolepties aanvaarbare produk te lewer. Molekulêre sif 4A was verwyder weens die vorming van produk wangeure. Groep II eksperimente is in die vorm van 'n sensitiwiteits analise uitgevoer. Die effek van verskeie veranderlikes is individueel op die metanol deurbreekkurwe getoets. Agtien eksperimente is oor 'n tydperk van 8 dae gedoen, met 'n totaal van 86 monsters wat getrek is. 'n Adsorpsie siklus het 30 minute geduur en het deurbreek van metanol toegelaat. Water is by voorkeur geadsorbeer. Negatiewe metanol bed ladings tydens hoë waterteenwoordigheid toon dat water wel metanolmolekule op 'n adsorpsie-posisie kan verplaas. In die teenwoordigheid van water is 'n bedlading van 0.6 mg metanol/100mLAA verkry, met 'n maksimum van 12.3 mg metanol/100mLAA in die afwesigheid van water. Laasgenoemde verteenwoordig 'n toevoer met 'n metanol inhoud van 1118 mg/100mLAA. In die algemeen is gevind dat 'n toename in toevoer vloeitempo en konsentrasie die tyd vir deurbreek verkort. Kontinue deurbreek het kontaminasie van die bed teweeg gebring en 'n termiese regenerasie is vir 24 ure na eksperiment 12 gedoen. Die teoretiese ontwerps vloeitempo was 50 .elhr, maar resultate het getoon dat die aanleg tot 70 .t'/hr kan verwerk sonder addisionele koste. Die geselekteerde proseskondisies was effektief in die versekering van die kontinue skeiding van metanol en etanol. Die lewensvatbaarheidstudie toon, afhangende van die strategie van integrasie, 'n Opbrengs op Belegging van tussen 110.1% - 220.8%. Adsorpsie het 'n beter skeidingsvermoë as konvensionele distillasie vir die verwydering van metanol vanuit etanol. Weens die vlak van innovasie betrokke, word dit voorgestel dat die inhoud van hierdie studie vertroulik gehou word en dat patent beskerming verleng sal word. Hierdie verhandeling spreek tot beide die wynmaak sowel as chemiese ingenieurs dissiplines. Daar is gepoog om geloofwaardigheid vir beide partye te skep deur die onbekende aspekte van albei dissiplines aan te spreek.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The hydrodynamics of a hollow fibre membrane module for the ultrafiltration of potable water were investigated. The purpose was to use a hydrodynamic model to predict the permeate flux for modules of various dimensions. Various models were considered, but most of them could not account for important effects such as macroscopic radial gradients and wet fibre expansion, found in hollow-fibre membrane modules. The Porous Medium Model was found to be a suitable model and it was used together with a finite element software package, Fastflo, to solve for the pressure distributions inside the membrane modules and predict permeate flux. The permeability of the membranes was obtained using a combination of numerical and experimental procedures and was found to be 2.3 x 10-13m. A cost analysis was performed to find the most economical module dimensions (outer diameter and length) for any required product flow rate. It was assumed that the cost of the fibres and module housing comprised the capital cost, while the operating cost consisted of the pumping energy. A capital recovery factor of 0.3 was used to convert capital costs to a yearly cost. It was found that the optimum module dimensions are an outer diameter of between 90mm and 160mm and a length of 0.6m. Finally the pressure distributions on the lumen and shell sides during both cross-flow filtration and backwash were examined. Shade plots proved useful for identifying possible areas of stagnant flow, as well as indicating where backwash is the most effective. / AFRIKAANSE OPSOMMING: Die hidrodinamika binne-in 'n holvesel membraanmodule vir die ultrafiltrasie van drinkwater is ondersoek. Die doel was om 'n hidrodinamiese model te gebruik om die permeaatvloed vir modules van verskeie dimensies te voorspel. Verskillende modelle is oorweeg, maar die meeste kon nie belangrike faktore soos makroskopiese radiale drukqradiente of nat veselverlenging in ag neem nie. Die Poreuse Medium Model was die mees geskikte model en is gebruik saam met Fastf/o, 'n sagteware pakket wat gegrond is op die eindige element metode, om vergelykings vir die drukverspreiding binne-in die module op te los en permeaatvloed te voorspel. Die permeabiliteit van die membrane is verkry met behulp van numeriese en eksperimentele prosedures en 'n waarde van 2.3 x 10-13 m is bepaal. Hierna is 'n koste-analise uitgevoer om die mees ekonomiese module afmetings (Iengte en buitedeursnit) te bepaal vir 'n gegewe produk vloeitempo. Daar is aanvaar dat kapitaalkoste bestaan uit die koste van vesels en module-omhulsel, terwyl bedryfskoste bereken is deur die hoeveelheid energie benodig om die pomp aan te dryf. 'n Kapitaalherwinningsfaktor van 0.3 is gebruik om kapitaalkoste om te skakel na 'n jaarlikse koste. Die optimum module afmetings is 'n lengte van 0.6m en 'n buite-deursnit van tussen 90mm en 160mm. Laastens is die drukverspreidings tydens beide kruisvloeifiltrasie en die terugspoelproses ondersoek. Areas van stagnante vloei kan deur middel van skadu-grafieke geYdentifiseer word, terwyl dit ook moontlik is om die terugspoelproses te optimeer.

Thesis (MScEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: In excess of24 x 106 tons (1997, Eskom) of coal-derived fly ash is produced annually in South Africa for the production of electric power. A large quantity of this ash is disposed of as a solid waste in landfills, thus posing a serious environmental problem. Due to the shortage of landfill sites, new ways of utilising fly ash are needed. Recently several authors have shown that various combustion fly ashes can be converted into zeolites to obtain industrial products with applicability In environmental management. Geopolymerisation has emerged during the last few years as a possible solution to some waste stabilisation and solidification problems. Phenolic compounds have been shown to be toxic to soil microorganisms at the partsper- million level. Indeed several of the organic compounds classified by the U.S. Environmental Protection Agency as priority pollutants, are phenols. Immobilisation of phenols by adsorption on zeolites and encapsulation in a geopolymer appears to be a promising solution to this problem. This thesis reports a technique for the production of a low-silica sodium zeolitic material from fly ash (zeolite NaP1), and its application for the stabilisation of phenols by adsorption and subsequent encapsulation in a geopolymer matrix. A commercial zeolite, clinoptilolite was also utilised as an adsorbent. Due to their uniform pore sizes and large surface areas, zeoli tic materials are suitable for ion exchange and adsorption of certain organic substances. Adsorption data show that the commercial zeolite, clinoptilolite was an effective adsorbent for organics. Adsorption data showed that between 51.2ppm and 74.3ppm of chlorophenol or between 15.4ppm and 32.5ppm of phenol could be adsorbed. Physical encapsulation of the coated zeolite loaded with organic within a geopolyrneric matrix increased the compressive strength of the matrix from 28.80 kN to 40.79 kN. Leaching data for the various geopolymer matrices with encapsulated and loaded zeolites show no organics being leached from the system at a detection level of 2ppm. According to the SABS these would have been acceptable organic concentrations within a waste water stream. In utilising waste materials (fly ash and organic waste) and their reactive properties, it is now possible to create various geopolyrners that are not only strong enough to be used as constructionlbuilding materials, but are also effective immobilisation systems for organic waste containment. / AFRIKAANSE OPSOMMING: Meer as 24 x 106 tons (1997, Eskom) vlieg-as word jaarliks deur die verbranding van steenkool vir die produksie van elektrisiteit geproduseer. Die as, wat tans in groot hoeveelhede as soliede afval in vaste-afval stortingsterreine gestort word, word gesien as 'n groeiende omgewingsprobleem. 'n Tekort aan geskikte stortingsterreine maak die ontwikkeling van nuwe gebruike vir die vlieg-as dringend nodsaaklik. Geopolimerisasie van vlieg-as materiale, 'n proses wat die laaste paar jaar ontwikkel is, blyk 'n potensiele oplossing te wees vir sommige afval stabilisering en solidifikasie toepassings. Daar is bewyse dat fenoliese verbindings, selfs op 'n dele per miljoene (dpm) vlak, toksies is vir grondorganismes. Verskeie van die komponente wat deur die Amerikaanse Omgewingsbeskermingsagentskap (US EPA) as prioritats kontaminants geklassifiseer is, is ondermeer fenole. Die huidige werk ondersoek die adsorbsie van fenol op zeoliet NaPI en clinoptiloliet, gevolg deur fisiese omsluiting deur geopolimerisasie. Verskeie outeurs het onlangs verwys na die omsetting van verskeie verbrandings vlieg-asse na zeoliete om bruikbare industriele produkte (vir gebruik in die omgewingsveld) te vorm. Die tesis rapporteer 'n metode vir die produksie van 'n iae silika natrium zeolitiese material (zeoliet NaP!) uit vlieg-as en die gebruik daarvan in die stabilisering van fenole. 'n Kommersieel beskikbare zeoliet, clinoptiioliet, is ook gebruik as adsorbent. Uniforme porie groottes en hoe oppervlak areas maak zeolitiese materiale geskik vir ioonuitruiling, asook die adsorbsie van verskeie orgamese verbindings. Deur die fisiese omsluiting van die zeolitiese materiaal binne 'n geopolimeer matriks, kan materiale met beduidend hoe druksterktes, geproduseer word. Adsorbsie data het getoon data die kornmersiele zeoliet, klinoptilotiet, 'n effektiewe adsorbent vir organiese stowwe is. Adsorbsie waardes het gewissel tussen 51.2dpm tot 74.3dpm vir chlorofenol en 15.4dpm tot 32.5dpm vir fenol. Fisiese enkalsulering van die bebandelde zeoliet (coated fzeo) binne 'n geopolimeer matriks het die saamdrukbaarheidsterkte van die betrokke matriks verhoog van 28.80 kN to 40.79 kN. Logingsdata verkry vir die onderskeie geopolimeer matrikse het getoon dat geen van die organiese stowwe uit die matrikse vrygestel word nie. Indien die organiese stowwe wel vrygestel sou word, sou die waterfase konsentrasie onder 2 dpm, binne die aanvaarbare spesifikasie vir uitvloeisels volgens die SABS standard, gewees het. Verskeie geopolimere, wat nie slegs sterk genoeg is om as konstruksie materiale te dien nie, maar addisioneel effektief as immobilisasie medium dien, kan dus uit die reaktiewe eienskappe van afval materiale (vlieg-as en organiese afval) vervaardig word.