No abstract available. / Thesis (Ph.D.)-University of Natal, 1973.

The development of a supersonic chemical reactor is examined. The central concept of such a reactor is that gases can be expanded to supersonic speed which will result in a decrease in their static temperature to the extent that no reaction will occur when the gases are mixed together. After mixing has occurred the mixture can then be passed through a standing shock to raise this temperature very rapidly, thus controlling the product spectrum. The main areas of interest for such a reactor, namely the establishment of a shock and the mixing of two gases at supersonic speed are examined. / Thesis (Ph.D.)-University of Natal, Durban, 1977.

When designing or optimizing flotation circuits in mineral processing plants, it is necessary to have accurate values of the flotation kinetics to ensure the correct mass pulls and material balances on the plant. Previous studies have shown that rate constants measured by single cell batch testing can cause a shift in the recovery—grade curve. The shift in the recovery—grade curve is the result of poor separation in conventional laboratory flotation devices. This project involved the development and modelling of a flotation device that provides a better separation than a conventional batch flotation cell. The device is called a semi—batch flotation apparatus (SBFA) because it simulates the operations of a pilot plant in a laboratory environment. It also provides dynamic data which facilitates the evaluation of model parameters. The SBFA tested a synthetic ore made from limestone, talc and silica. The synthetic ore was used as it was economical and easy to analyze. The results from the SBFA were compared to results obtained from conventional batch flotation tests; by using recovery—grade curves to assess the degree of separation achieved from both devices. The SBFA separated the limestone from the gangue (silica and talc) much better than the batch tests. For instance the final grade for a concentrate obtained from a single cell batch test was 20 % limestone while the final grade for a concentrate obtained from the SBFA was between 40 % and 70 % limestone. The improvements in separation can be attributed to the multistage design of the SBFA which has a pulp recycle between the stages. A model has been developed for the SBFA. The model fitted the experimental data well with a correlation coefficient close to unity. The cumulative recoveries predicted from the SBFA model was compared to the actual cumulative recoveries, by using a global set of parameters (&2 and RMAX)- The investigation showed that the model had problems in fitting the data for the early periods of the experiments because of the complex interaction between the stages in the SBFA. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.

Polytetrafluoroethylene (Teflon®) is encountered in many environments – frying pans, clothing, osmotic distillation membranes, to name a few – yet the solubility and clustering behaviour of water with this material was not found in the open literature. This information may be useful in applications where an absence of water is desired, such as in clothing and textiles. Previous work on polyethylene + water has shown that small water clusters form in the amorphous portion of the polymer. This work investigated this phenomenon for the case of polytetrafluoroethylene + water. Initially, a test system of light alcohols + water + n-dodecane was investigated using Gibbs Ensemble Monte Carlo simulations and compared to previous laboratory experiments. This test system was investigated in order to gain expertise in the methodologies and theory behind Monte Carlo simulation, as well as to gain experience with using the necessary software. For this test system, it was found that the TraPPE parameters representing the interactions between the alcohols and the n-dodecane were not adequate and lead to increasing deviations with increasing carbon number in the alcohol. To replicate the conditions of the amorphous polymer matrix, liquid-liquid equilibrium between water and the polymer was investigated. Gibbs Ensemble Monte Carlo simulations have been performed for systems of perfluoroalkanes and water to determine the influence of temperature and carbon number on the solubility and clustering behaviour of water within the perfluoroalkanes. The temperature range in this study was from 450 K to 600 K, and the perfluoroalkane carbon number range was from 8 to 300 carbon atoms. With increasing carbon number, it was found that there was an asymptotic value of 98.0 mole percent water in the polymer phase. With increasing temperatures it was found that there were exponential increases in solubility of water into the polymer matrix. Previous work on clustering and supramolecular structure of perfluoroalkanes described the rigidity of the perfluoroalkane chains in comparison to alkane chains, thus explaining the large increases in free volume with increasing temperature in the polymer matrix observed in this work. A discontinuity with regard to both solubility and clustering behavior was observed for a polymer carbon number of 10 to 12 carbon atoms. Prior work on the energy contributions towards the helical structure of perfluoroalkanes showed a shift in the energy contribution regime for carbon numbers larger than ~10 carbon atoms, which may explain this discontinuity. It was found that linear water clusters accounted for up to ~90 percent of the water clusters, concurring with previous work on water clustering in polyethylene. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

Froth flotation has been used to concentrate minerals for over a century (Finch and Dobby, 1990) and it is essential for the economical recovery of metals which are present at low concentrations. The traditional flotation cell consists of a stirred tank incorporating air injection. In recent decades columns have appeared to offer advantages for platinum flotation. This project is a comparative study of the use of column and mechanical cells as cleaners for the flotation of an UG-2 (Upper Group 2) platinum ore. A laboratory column cell, 1.8 m high and 60 mm in diameter, was constructed to have the same volume as a conventional 5L Denver mechanical cell. Batch cleaning tests were used to compare the two types of cells, while varying the depressant dosage and conditioning technique. The performance of the column cell when the pulp was recycled was also compared. Finally the effect of doubling the column height, whilst maintaining the same mass percent of solids as in the original column, was investigated. Samples were subjected to acid digestion to determine Copper (Cu) and Nickel (Ni) recovery as an indicator of platinum recovery. Platinum Group Metals and Gold (PGM+Au) assays were performed on samples from a final series of tests that used a different but similar ore sample. The investigations showed that the mechanical cell performed better than the column. The PGM grade in the mechanical cell was 6.5ppm higher for a common recovery of 80% PGM in both cells. The performance of the column cell was only marginally improved when the pulp was recycled. Mass recovery data indicated that the column cell required less depressant for reducing the mass recovery. The corresponding grade recovery curves showed that for a 10 g/t depressant addition, the grade of the concentrate produced in the column cell doubled whilst that of the mechanical cell revealed no significant change. It was suggested in literature (Whitney and Yan, 1996) that the depressant was more effective in a column cell, due to the absence of agitation by an impeller. Platinum recovery data from the final series did not confirm the interesting trend observed with the preliminary tests (Cu/Ni) at a low depressant dosage (10g/t), but marginal improvements were noted at higher dosages. The effect of agitation during conditioning with depressant was also investigated. Gentle conditioning of the depressant, prior to column flotation, resulted in a higher grade and recovery of PGM as compared to conditioning by means of the recirculation pump. The PGM grade when gentle conditioning was employed was 9 ppm higher for a common PGM recovery of 80% for both conditioning techniques. Finally it was found that increasing the column height improved the grade-recovery relationship. The PGM grade obtained by the longer column was 8 ppm higher for a common PGM recovery of 75% in both columns. The performance of the longer column was similar to that of the mechanical cell. Tests were also conducted at a platinum concentrator, to compare the performance of a 378L pilot-plant column (5.5m high and 0.3m diameter), to that of a pilot-plant consisting of six mechanical cells. The pilot test rig of mechanical cells (FCTR) achieved a significantly better recovery than a pilot column. However, by decreasing the column feed flowrate and thereby increasing the residence time, a substantial improvement in the PGM grade and recovery was obtained by the column cell. / Thesis (M.Sc.Eng.)--University of KwaZulu-Natal, Durban, 2012.

The performance of a WO3/SiO2 catalyst has been investigated for the metathesis of 1-hexene in an isothermal, gas-phase fixed bed tubular reactor between 420-500°C and at latm. The reactor was fabricated from stainless steel and was placed in an electric tube furnace. The study focused on the effect of operating conditions (reaction temperature, feed gas composition and space time) on the yield of heavy olefins (C7 - C16) and the primary product, decene, using a full factorial experimental design. The objective was to determine the optimum operating conditions for the production of decene. Compositions of condensed liquid and vapour product streams were determined via gas-liquid chromatography. Oxidative and reductive pre-treatments of the catalysts were compared to a conventional pre-treatment under nitrogen in terms of their effect on conversion and product distribution. Experimental tests for the existence of external and internal mass transfer resistances were also conducted. An improved yield of decene was obtained after oxidative pre-treatment of the catalyst. The conversion of l-hexene, selectivity and yield of decene dropped after pre-treatment under hydrogen and nitrogen only. This may be due to over-reduction of the tungsten centres and the formation of an inactive non-stoichiometric surface phase. The best yield of decene obtained from the experimental design was 2.19% at 420°C, 51% feed composition and 661g.min.mo1-1. The yield of decene decreased by 0.11% when the reaction temperature was raised by 40°C, and by 0.17% when the feed gas composition was raised by 17.5% and increased by 0.21% when the space time was increased by 223g.min.mol-1. The large amount of ethylene and propylene produced as well as the formation of polynuclear aromatics suggest significant cracking of 1-hexene. For the size range and flow-rates that were employed, the reaction does not suffer from intraparticle and external mass transfer resistance effects. It was concluded that a combination of lower temperature, lower feed gas composition and higher space time should be used to maximize the yield of decene. A final experiment was conducted to test this conclusion. At 380°C, 55% feed composition and 2875g.min.mol-1, the yield of decene was 12.80%, which represented a significant improvement. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2008.

An outline is given of the South African sugar industry, with particular emphasis on the unit operations which make up the industrial process for manufacturing sugar from cane. Current knowledge of the chemistry of soluble polysaccharides is reviewed and the structures of several polysaccharides, including starch, dextran, and pullulan, are discussed. It has been found that changes take place in the chemical composition of the juice in sugar cane (Saccharum officinarum) during post-harvest storage. With increasing storage time, there is a proportional decrease in the starch content of the juice, and a considerably larger proportional increase in the soluble polysaccharide content. The increased polysaccharide content was found to be due to a single glucan which, contrary to most previous publications on this subject, is definitely not a dextran. Following structural analysis, it has been established that the polysaccharide formed in stored cane had not been described before and the name "sarkaran" , derived from the Sanskrit word "Sarkara", meaning "sugar" is proposed for it. The polysaccharide was isolated from cane juice by precipitation with ethanol after the starch in the juice had been removed by centrifugation. The polysaccharide was purified by repeated dissolution in water and reprecipitation with ethanol. Analysis by gel chromatography resulted in a single symmetrical peak, indicating that the isolated polysaccharide is homogeneous. This was confirmed by hydrolysing fractions representing a section of the ascending and a section of the descending part of the peak of the chromatogram, using the enzyme pullulanase. Chromatographic separation and quantitative analysis of the isolated oligosaccharides showed that the compositions of the two enzymes digests were identical. Acid hydrolysis of the polysaccharide resulted in a single hexose. This was identified as glucose by paper chromatography, comparing the Rf value with that of pure glucose. Confirmation was obtained by comparing the osazone with that of glucose, using microscopic examination and determination of the melting points. Paper electrophoresis showed the molecule to be uncharged. Several techniques, both absolute and non absolute, were used to determine the molecular weight of the polysaccharide. A method involving viscosity determination indicated a molecular weight of 34 000 while a figure of 50 000 was obtained by gel chromatography on a Sephadex column, comparing the peak elution volume of the polysaccharide with that of dextrans of a defined molecular weight. Both these techniques are non absolute and yield rough estimates of the molecular weight. Osmometric measurement, an absolute method, showed the number average molecular weight to be 51 500. An absolute value for the weight average molecular weight of 250 000 was obtained by light scattering techniques. Data from the light scattering experiments were also used to determine a value of 200 - 250 A for the radius of gyration RG of the polysaccharide. End group analysis after exhaustive methylation resulted in a value of 24 000 for the number average molecular weight Mn. This indicates either that some degradation of the polysaccharide molecule occurs , during the methylation procedures or that there is a certain degree of association between individual molecules. Periodate oxidation showed that 32 percent of the glucosidic linkages are in ( 1 + 6 ) position. The polysaccharide was exhaustively methylated by several Haworth methylations followed by a number of Kuhn methylations. The fully methylated product was methanolysed and the methyl glucopyranosides analysed by gas liquid chromatography. The results were compared with those obtained from fully methylated starch and dextran. From the absence of disubstituted methyl derivatives in the methanolysate it was concluded that the polysaccharide is an unbranched glucan. From the quantities of Methyl 2,3,4,6 tetramethyl-O-Dglucopyranoside, Methyl 2,3,6, trimethyl-O-D-glucopyranoside and Methyl 2,3,4? trimethyl-0-D-glucopyranoside, it was concluded that the only linkages in the glucan are ( 1 + 4 ) and ( 1 + 6 ) and that these are present in the ratio 68:32. Enzymic hydrolysis, using pullulanase, was followed by paper chromatographic separation. Quantitative determination of the oligo-saccharides present in the enzyme digest resulted mainly in two oligosaccharides, maltotriose and maltotetraose, in nearly equal proportions. For this reason it was postulated that the polysaccharide is a maltotriose-maltotetraose polymer, and that the individual units are linked in ( I + 6 ) position, a linkage for which pullulanase is specific in certain configurations. The sequence of the maltotriose and maltotetraose units in the polymer has not been investigated further, although this could be carried out by partial acid hydrolysis, followed by isolation and identification of the various oligosaccharides formed. An alternate method for the determination of the sequence of the monomers is discussed. It was subsequently shown that the linkages in the polysaccharide are in the a configuration. The polysaccharide is highly dextra rotary and the magnitude of the rotation is comparable to that of other polysaccharides linked in a position, . such as starch and dextran. Infrared spectroscopy was used to confirm the configuration. The spectrogram of the polysaccharide contained an absorption peak at 840 cm-1 , which is typical of the a-anomeric absorption occurring, for example, in the IR spectrum of starch. The spectrogram exhibited no absorption peak at 891 cm-1 , the wavelength typical of the B-anomeric absorption in the IR spectrum of cellulose. In addition, it was found that all polysaccharides containing a ( 1 + 4 ) linkages show an absorption peak at 700 cm 1. This absorption peak was absent in all IR spectra obtained from various dextrans. This phenomenon has not been reported previously and it is suggested that the presence of this absorption peak in the IR spectrum of a glucan can be used to support the evidence of the presence of a( 1 + 4 ) linkages. It was not possible to correlate the formation of the polysaccharide with the occurrence of a specific micro organism. It is suggested that the formation of the polysaccharide is the result of enzymic reactions in the sugar cane after harvesting. The investigation of the composition of juices from deteriorated cane has not been confined to polysaccharides. Ethanol has been isolated from the juice of some samples of stored cane which had been burnt before harvesting. The ethanol was isolated by fractional distillation and identified by measurement of the boiling point. It was confirmed, by the formation of the molybdate-xanthate complex, that the product isolated was an alcohol. The identification was further confirmed by oxidising the ethanol to acetic acid and proving the identity of the acids by paper chromatography. It has been shown that, with the exception of two acids, the carboxylic acid composition of cane juice remains unaltered during post-harvest storage of the cane. The two exceptions , succinic and aconitic acids, were identified from their melting points and by specific spot tests. Ion exchange was used to isolate the acids from the juice. The eluate from the ion exchange column was concentrated and the acids separated by liquid-liquid chromatography, using a silica gel column. The levels of both aconitic and succinic acids were found to increase during the early period of storage but decreased again slowly thereafter. The percentage change was greater in the case of succinic acid, although aconitic acid was the most abundant carboxylic acid in the juice. Lactic acid was absent from the cane juices analysed. This is surprising, as lactic acid is a common product of the metabolism of carbohydrates by micro organisms. It is suggested that the changes in acid composition during the storage of harvested cane are caused by deactivation of enzymes of the Krebs cycle. Post-harvest deterioration of sugar cane can have serious consequences which can affect the whole Sugar Industry. Not only is crystallisable sugar lost but the products of the deterioration have adverse effects on factory processing and laboratory analysis. The problem, which will become more acute with the introduction of mechanical cane harvesting, can only be resolved through the cooperative efforts of all the parties concerned. / Thesis (Ph. D.)-University of Natal, Durban, 1973.

No abstract available. / Thesis (Ph.D)-University of Durban-Westville, 2003.

Pectin is a polysaccharide found in plant cell walls. It is a linear molecular chain of D-galacturonic acid units linked by a 1—»4 glycosidic bonds. Pectin is widely used in the food industry. The main sources of pectin are citrus fruits and apple. In South Africa, pectin is still imported whereas it can be produced from waste peels that result from citrus processing. A consortium was formed by CSIRBio/Chemtek, Chemin, Kat River Co-op and University of KwaZulu Natal (UKZN) to investigate pectin production. UKZN was to develop the drying (for off-season purposes) and extraction technology required for pectin production. The project was categorized into two phases; the drying and the extraction phases. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.

Phase equilibrium data is essential in the operation, design and development of industrial / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2008.