Browsing by Subject "Applied Science"
Now showing 1 - 20 of 51
Results Per Page
Sort Options
- ItemOpen AccessThe abrasive wear resistance of austempered spheroidal graphite irons(1987) Shepperson, S V; Allen, ColinA study has been made of the structure and abrasive wear resistance of two austempered commercial spheroidal cast irons. Heat treatments have been carried out for different times between 2 and 120 minutes for a range of austenitising temperatures between 850°C and 950°C and austempering temperatures between 250°C and 450°C. The morphology and constitution of the resulting dual phase ferrite/austenite structure has been examined using optical and scanning electron microscopy and x-ray analysis. The maximum quantity of retained austenite in the structure has been shown to vary up to 50% and to be strongly dependent on heat treatment parameters and the composition of the iron. Laboratory abrasive wear testing has been carried out on these austempered irons and compared with the results of similar tests on a range of abrasion resistant carbon steels. All the austempered irons were found to have better abrasion resistance than proprietary abrasion resistant steels. These austempered irons derive their outstanding properties from the morphology of the dual phase ferritic/austenitic matrix coupled to the high work hardening characteristics brought about by the stress induced austenite to martensite transformation during abrasion. The influence of microstructure and mechanically induced transformation has been studied as a function of austempering temperature and time.
- ItemOpen AccessActivity and selectivity of transition metal (Fe, Mo and W) carbides in the Fischer-Tropsch synthesis(2007) Patterson, Veronica A; Van Steen, EricThis study focused on the Fischer-Tropsch activity and selectivity of transition metal (iron, molybdenum and tungsten) carbides. The carbide catalysts were prepared by a temperature programmed method. The properties of the materials were characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM), BET measurements and temperature programmed desorption of carbon monoxide (CO-TPD). The performance of the materials was tested in a Berty reactor. A reduced, precipitated iron oxide catalyst was used as a reference catalyst.
- ItemOpen AccessThe application of biogas technology in South Africa for small-scale energy production(1994) Thom, Cecile; Eberhard, AntonThis study has aimed to contribute to the development of low-cost or "simple" biogas technology, i.e. the design, construction, operation and utilisation of relatively simple biogas systems in South Africa, and to explore the utilisation of the technology by lower-income groups in the rural areas of the country, particularly in the former homelands. Specific objectives included the development of biogas plants suitable for application in South Africa, and the assessment of the acceptability of the technology among potential users. Five biogas plants were constructed during the study, which provided the opportunity to test various designs and obtain response from some of the potential users of the technology.
- ItemOpen AccessAromatization over platinum/zeolite L catalysts : the effect of oxygenates(1997) Nash, Robin John; Dry, MarkIn 1980, Bernard reported that platinum dispersed on zeolite LTL (Pt/KU had exceptionally high selectivity for the aromatization of n-hexane to benzene. The selectivity was ca. 95 at 99 conversion of n-hexane. This Pt/KL catalyst has been extensively studied to determine the reasons for the exceptional stability and benzene yields relative to platinum supported on silica (Pt/Si0₂ ) and alumina (Pt/Al₂0₃). The Pt/KL catalyst was found to be monofunctional with all the activity occurring on platinum metal clusters inside the pores of zeolite L. The catalyst exhibits excellent stability and the Aromax Process developed by Chevron Ltd., using I a barium doped Pt/KL catalyst, PtBa/KL, has been reported to operate continually for the equivalent of one year during accelerated deactivation testing at 450°C and a hydrogen partial pressure of 6 bar. However, sulphur-containing I compounds such as thiophene, result in rapid and irreversible deactivation of the catalyist due to sintering of platinum clusters. Thus the level of sulphur-containing I compounds, especially thiophene, must be kept below 50 ppb of the feed to avoid deactivation by sintering. SASOL Ltd. may be in a unique position to use Pt/KL as a catalyst for the aromatization of hexanes and heptanes to benzene and toluene respectively, as their products which are produced by the Fischer-Tropsch process are sulphur free. However, a substantial amount of oxygenates are formed in the Fischdr-Tropsch process and as yet no study has been undertaken to determine the effect of these compounds on the activity and selectivity of the catalyst.
- ItemOpen AccessBattery performance characterisation for stand-alone photovoltaic systems(1991) Purcell, C J de V; Eberhard, Anton; Cowan, BillOne of the main factors limiting optimisation of PV system designs over the life of the system has been the lack of battery test data appropriate to PV applications. The main objective of this study was to determine accurate empirical data for locally available lead-acid batteries which could be used in photovoltaic systems and to present this data in a format directly applicable to PV system designers. The study included (i) a review of battery performance regimes typical of PV systems; (ii) a literature review of lead-acid battery performance and reactions important to PV applications, battery electrical models, battery life models, a review of specialist PV battery designs and the interaction of battery and voltage regulator in PV systems;. (iii) a review of testing and research literature, and the design of a suite of experimental procedures suitable for characterising batteries under PV operating regimes; (iv) the design and construction of a specialised battery test-unit to automatically perform tests and capture data; (v) selection, testing and characterisation of five generic types of batteries which could be used in local PV applications. The five types of lead-acid battery were: 1) conventional calcium alloy positive and negative grids, flat plate, flooded electrolyte, vented casing; 2) low antimony alloy positive grid, conventional calcium negative grid, flat plate, flooded electrolyte, vented casing; 3) low antimony alloy positive grid, heat treated calcium negative grid, flat plate, immobilised absorbed electrolyte, sealed casing with 0 2 cycle gas recombination; 4) antimony alloy positive and negative grids, flat plate, flooded electrolyte, vented casing; 5) antimony alloy positive and negative grids, tubular plate, flooded electrolyte, vented casing. Selenium grid alloy cells and gelled electrolyte batteries were not represented amongst the batteries tested, owing to problems of availability or cost.
- ItemOpen AccessThe characterisation and cetane number determination of synthetic diesel fuels(1991) Forrester, Robert David; O'Connor, CyrilSouth African synthetic fuel plants produce large quantities of lower alkenes which can be catalytically oligomerized to liquid transportation fuels. In the screening of experimental catalysts for the production of diesel-range fuels, it is important to measure the quality, as well as the quantity, of the fuel being produced. Cetane number is an important indicator of the quality of a diesel fuel ru1d is measured by a standard engine test (ASTM D 613) which requires l litre of fuel and is therefore not suitable for the routine testing of the small volumes of fuel produced by experimental catalysts. Alternative cetane number prediction methods exist but these have generally been developed to predict the cetane number of crude-oil based fuels and are therefore not suitable for use with synthetically derived fuels. This thesis details the development of a formula which accurately predicts the cetane number of a fuel from other, easily measured parameters. Several samples of fuel were produced under varying reaction conditions and were hydrogenated to ensure that they were virtually 100% alkane. Differences in cetane number should therefore be due to differences in the degree of branching. By measuring the cetane number on a. standard test engine and correlating the result with the amount of branching as measured by ¹Hnmr, a formula was developed which was found to accurately predict the cetane number of these types of synthetic fuels. The results obtained also show that for the conversion of ethene over a supported nickel catalyst, cetane number decreases as temperature increases. This decrease is probably caused by secondary butane oligomerization reactions.
- ItemOpen AccessCharacterisation of acidic/basic properties of alumina supports(2002) Ferreira, Riki; Fletcher, Jack; Visagie, Kobus; Böhringer, WalterPrevious experience with the preparation and testing of Co/alumina catalysts for Fischer-Tropsch synthesis has revealed that, while commercial available aluminas result in materials of significantly different catalytic performance, no correlation between the physical properties of the aluminas and the resulting catalytic performance was evident. Consequently, it was proposed that differences in the chemical (acid/base) nature of the alumina surfaces might be responsible for the observed differences in catalytic behaviour. In this study, isopropanol conversion was evaluated as a possible test reaction for characterisation of the acid/base nature of commercial aluminas - literature indicates acetone to result from isopropanol reaction on basic sites, and DIPE and propene products to result from isopropanol conversion over acid sites of varying strength.
- ItemOpen AccessCombustion characteristics of South African grown fuelwoods(1990) Davis, Mark; Eberhard, AntonThe principle objective of this investigation was to establish a methodology to compare and rank fuelwoods. This methodology would allow a wide range of tree species to be compared and ranked according to their combustion properties. Such a comparison would assist in the selection of species for woodlot development. This investigation attempted to examine the combustion kinetics of small samples in an attempt to achieve the stated aim. Initially a literature review was performed. This covered anecdotal information on fuelwood preferences, an overview of wood composition, structure and combustion, and an in depth review of existing work on small sample combustion.
- ItemOpen AccessA comparative evaluation of manufacturing technologies and their effect on morphology and mechanical properties of poly-(propylene-ethylene) copolymers(2002) Sello, Maitse P; Marcus, Kashif; Sole, Brian MichaelThis project is a technological benchmark exercise for Sasol Polymers where different poly (propylene-ethylene) copolymer grades from five foremost licensed manufacturing PP technologies are evaluated. These copolymer grades were manufactured using the following processes: Novolen PP technology (Sasol grades), Innovene PP technology (BP grades), Spheripol PP technology (Basell grades), Univation PP technology (DOW grades) and Borstar PP technology (Borealis grades). Form this investigation, thirty different grades where evaluated to determine their structural morphology in relation to their physical and mechanical properties. For the ease of analysis, the grades are grouped into three ethylene content ranges; low ethylene contents (below 8%), medium ethylene contents (between 8 -10%) and high ethylene contents (above 10%). Within each of these ethylene content ranges, there is a melt flow index (MFI) range, which increases from low to high. The differences in the MFI added further complications, especially when trying to determine optimum mechanical properties of the copolymer grades. The impact test results show that the toughness is at a maximum at low MFI, and then drops drastically as the MFI increases. Since an addition of ethylene improves the toughness of the copolymer, it was observed that by considering MFI's below 35 g/10 min, the toughness could be enhanced by increasing ethylene content. Grades with MFI's below 35 g/10 min show a drastic increase in impact strength at ethylene content around 8.5%. SEM results show that particle size and spacing are independent of ethylene contents for the grades examined. However, for the BP and DOW grades, the ratio between interparticle distance and particle size decrease steadily with increasing ethylene content. The Basell and BP grades showed a narrow rubber particle size distribution followed by Sasol grades. The DOW grades showed a broad particle size distribution. TEM results show that the internal morphology of the rubber particles differ from grade to grade, with the Sasol and BP grades showing several numbers PE inclusions within the rubber particles, whilst Basell grades having only few PE inclusions. It was observed that those grades with several PE inclusions have a better impact performance compared with those with fewer inclusions.
- ItemOpen AccessCrystallisation of PFA glasses(1994) Emms, S; Heckroodt, R OGlasses with various compositions, falling in the CaO-AI20rSi02 and MgO-CaOAI20rSi02 systems were made, using pulverised fuel ash and silica, hydrated lime, kaolin and magnesium carbonate. Titania or ferric oxide and chromia were used as nucleants. Various crystallisation heat treatments were carried out and the nucleation and crystallisation behaviour was studied. A minimum MgO:CaO was found to be necessary for bulk nucleation to occur. The activation energy for viscous flow decreased with increased MgO:CaO ratios. This was accompanied by an increase in the surface crystal growth rates and a decrease in the activation energy for surface crystal growth. Titania also lowered the activation energies for viscous flow and surface crystal growth and caused an increase in the surface crystal growth rates.
- ItemOpen AccessThe detection of wetlands using remote sensing in Qoqodala, Eastern Cape(2003) Gibson, Lesley Anne; Rivett, UlrikeThis dissertation aims to establish the possibilities of mapping wetlands in Qoqodala, Eastern Cape Province, South Africa, using Landsat and/or Aster imagery. The methodology for mapping wetlands using Landsat imagery, proposed by Thompson, Marneweck, Bell, Kotze, Muller, Cox and Smith (2002) is adapted and applied to the study area. The same methodology is modified for use with Aster imagery and applied to the study area. In addition, the possibilities of treating Aster as a hyperspectral image are investigated, and a methodology using hyperspectral processing techniques is implemented.
- ItemOpen AccessDeterioration of reinforced concrete in a marine environment : repair costs and maintenance strategies(1994) Strohmeier, Jörg Harald; Alexander, Mark Gavin; Stevens, Alan J; Mackechnie, James RThis dissertation comprises an investigation into the rate at which reinforced concrete structures deteriorate in the Cape Peninsula due to reinforcement corrosion, the reasons for this deterioration, and the accompanying repair costs. The costing of repair work is calculated per m2 of reinforced concrete and is based on quoted labour rates and material rates of repair materials supplied by four major suppliers in the Western Cape. Formulas are included which enable a person using the data listed in tables and figures to calculate what repair costs will be in future, and also enable the calculation of monthly/annual deposit amounts in order to save sufficient money for future maintenance at a specified date. Life cycle costing and decision models for the maintenance of concrete structures are discussed and guidelines for the establishment of optimal maintenance cycles are included. Based on the results of the life cycle costing exercise the importance of planned preventative maintenance is highlighted. Finally, locally and internationally available maintenance management computer systems are reviewed.
- ItemOpen AccessThe development of an energy education package for secondary schools(1994) Oxenham, Peter Eric Clinton; Cowan, BillThe central objective of this project was to develop a package of energy education workshops for secondary schools. The package contains nine energy workshops. Each workshop comprises a teacher's guide and a student worksheet. The package production process included choosing an education methodology, reviewing energy themes for selection as workshop topics and evaluating the energy workshop package. This dissertation provides insight into the processes of producing this package. My participation in the Community Education Resource's Masters programme introduced he goal of producing university resources in formats which are accessible to a broader audience. Energy themes for the workshops were drawn from a review of existing resources, particularly those f the Energy for Development Research Centre, and were selected for their relevance to energy as an agent of development, energy production and environmental concerns, energy policy formulation and vocational interest.
- ItemOpen AccessDomestic energy transition in South Africa in the context of rapid urbanization(1989) Viljoen, R P; Eberhard, AntonThis dissertation deals with the energy transition process which is de-fined herein as the process whereby energy consumption patterns o-f fuels used by a population change over time. The focus is on the domestic sector only and specific attention is paid to the black population o-f South Africa which is urbanizing rapidly. The existing data on -fourteen Sub-Saharan African countries are analysed and indications that the energy transition process is occurring are found. The process is influenced by both the level o-f urbanization and economic development but the rates o-f growth of these indicators do not appear to be influential.
- ItemOpen AccessThe effect of CO2 on the activation of a precipitated iron Fischer-Tropsch catalyst(2000) Harding, Samantha; Van Steen, EricThe effect of CO2 on the activation of a precipitated iron catalyst by hydrogen and carbon monoxide was investigated. The iron-based catalyst was precipitated from a mixture of iron nitrate and copper nitrate then bounf by the addition of potassium waterglass to achieve a final catalyst precursor composition of 3.8K2O/4.8Cu/26.0SiO2/100Fe. The activation procedures used four different gas compositions.
- ItemOpen AccessThe effect of fully anoxic conditions and frequency of exposure to anoxic and aerobic conditions on the growth of low F/M filaments in nitrogen remova(1991) Ketley, David Andrew; Ekama, George AFilamentous bulking, caused predominantly by low F/M filaments (Blackbeard et al, 1986, 1988), results in considerable settling problems in full scale nitrogen (N) and nutrient (N & P) removal activated sludge plants in South Africa. The development of specific methods for control of low F/M filaments in these plants would lead to significant savings because higher flows and loads could be treated in existing plants. From the findings of Blackbeard et al (1986, 1988) an extensive research project was undertaken by Gabb et al (1989a) into specific control of low F/M filament bulking. This project investigated the effectiveness of selectors, the proposed method of low F/M filamentous bulking control and found them to be ineffective. Consequently a second comprehensive laboratory research investigation was commenced in 1989. The work presented in this thesis forms a part of this investigation; the experimental investigation was conducted in 3 phases investigating (1) the effect of fully anoxic conditions and low nitrate concentrations during the anoxic phase of an intermittent aeration cycle on low F/M filament growth in continuously fed completely mixed single reactor systems receiving a synthetic sewage feed; (2) the effect of fully anoxic conditions on low F/M filament growth in continuously fed completely mixed single reactor systems receiving real sewage; and (3) the effect of alternating the frequency of exposure of low F/M filaments to anoxic/aerobic conditions (i.e. increasing the length of the aeration cycle but maintaining the aerobic mass fraction) in intermittently aerated continuously fed single completely mixed reactor systems receiving real sewage.
- ItemOpen AccessThe effect of nitrite and nitrate concentrations on low F/M filament bulking in nitrogen removal activated sludge systems(1994) De Villiers, M E; Ekama, George A; Marais, Gerrit van RooyenFilamentous bulking and its associated poor sludge settleability is a considerable problem in South African activated sludge plants, as indicated by the two surveys undertaken on these plants in 1985 and 1988 (Blackbeard et al., 1986, 1988). Amelioration of this problem would enable a greater daily flow and load of wastewater to be treated by these plants. From the surveys it is apparent that bulking in long sludge age activated sludge plants is mainly due to the proliferation of the group of so-called low F/M filaments (as classified by Jenkins et al., 1984). In the course of a 4-year research program investigating specific bulking control methods, Gabb et al. (1989) concluded that the selector effect, which was proposed as a method for controlling low F/M filament bulking, was ineffective. This research also indicated that in fully aerobic systems low F/M bulking was ameliorated, but in intermittently aerated anoxic-aerobic systems low F/M filament bulking was promoted. The research presented in this thesis forms part of a follow-up bulking research program into low F/M bulking which led to the formulation of a bulking hypothesis by Casey et al. (1992b) and focuses on the effect of different anoxic-aerobic conditions and their effect on the concentration of nitrate and nitrite entering the aerobic zone/reactor in single intermittently aerated and multi-reactor nitrification-denitrification systems.
- ItemOpen AccessThe effect of operating parameters on the wear behaviour of disc poppet valves in reciprocating slurry pumps(1988) Joffe,S.H.D; Allen, ColinAn investigation has been carried out to determine the factors controlling the wear characteristics of disc poppet valves in reciprocating slurry pumps used in the transportation of quartzite slurries. A laboratory test rig has been designed and built which closely simulates the operating conditions experienced by slurry pump valves. Experiments have been conducted to determine the effect of the design parameters, namely - slurry constitution, valve closure velocity and valve angle, on the wear resistance of a low alloy steel, as a function of its mechanical properties. It has been shown that the wear of the valves is a sensitive function of the operating parameters. Significant improvements in the life of the valves can be achieved through increasing material hardness, reducing valve closure velocity, slurry density and valve angle. A detailed study has been made of the mechanisms contributing to valve wear. It has been established that both percussive impact and three body abrasion wear mechanisms predominate. The influence of each mechanism has been shown to be a function of the slurry constitution and the material hardness.
- ItemOpen AccessThe effect of ore blends on the mineral processing of platinum ores(2011) Van Tonder, Erika; Deglon, DavidThis thesis investigates the effect of ore blends on milling and flotation performance. Anglo Platinum's Waterval UG2 concentrator in Rustenburg processes ore from various shafts.
- ItemOpen AccessThe effect of sulphur in fuel on the performance of automotive catalysts(1994) Siemelink, Johannes Jacobus; Dutkiewicz, Ryszard KarolCatalysts have been used on cars since 1974 to reduce tailpipe emission levels of carbon monoxide, hydrocarbons and oxides of nitrogen. Initially, oxidation catalysts were used that operated under very lean air/fuel conditions and gave rise to increased sulphate particulate emissions. These sulphate emissions could fortunately be reduced by better air/fuel control. However, the introduction of more active catalyst compositions, in particular the use of cerium oxide components on the wash coat, led to bad odour complaints from motorists. In the report it is shown that under fuel-lean conditions, sulphur, originating from the fuel, is stored as aluminium and cerium sulphates onto the washcoat. Upon a rapid change to fuel-rich engine operation the stored sulphates are released as hydrogen sulphide and is the cause for the smell observed. The sulphur storage/release process results in hydrogen sulphide emissions many times higher than is possible from steady-state conversion from the fuel sulphur level. By using a catalyst/engine combination on a testbed the experiments have shown that the hydrogen sulphide release is a kinetically limited reaction and, apart from the air/fuel control, depends mainly on the catalyst temperature.
- «
- 1 (current)
- 2
- 3
- »