3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item An investigation into the use of weathered fly ash (WFA) and coal gasification ash (CGA) as partial replacements for portland cement in concrete(2019) Maboea, Dikeledi MamelloThe cement industry has recognised the need to reduce the output of CO2 emissions in the atmosphere. This investigation considers the use of alternative binders. Three supplementary cementitious materials (SCMs), namely, fly ash (FA), coal gasification ash (CGA), and weathered fly ash (WFA) were used to replace 10%, 15%, and 30% of Portland cement (PC) by mass. Each mix used water/binder (w/b) ratios of 0.50 and 0.60. 100% PC concrete was the primary control and FA concrete the secondary control. Samples were subjected to slump, compressive and tensile strength, durability and shrinkage tests. The compressive strength results of WFA blends at 28-days of testing were observed to be equal to or greater than those of FA blends. At 56-days the compressive strength results of WFA blends measured below those of 28-days. The compressive strength results of 15% CGA blend at 28-days of testing was equal to that of 15% FA with 0.50 w/b and greater than that of 15% FA with 0.60 w/b ratio. The 56-days strength of 30% CGA-0.50 and 30% CGA-0.60 were greater than the corresponding 30% FA blends at 28-days of testing. Indicating an increase in strength with age for CGA blends. Due to the loss of compressive strength at 56-days for WFA, CGA was concluded to be the Sasol ash with the higher potential to be used as a partial replacement of PC in concrete for strength purposes. The durability index tests conducted had varying overall results, CGA blends were less permeable to oxygen, FA blends had the lowest absorption rates and WFA blends were the most resistant to chloride ingress. In conclusion, from the observed results, CGA and WFA can be used as partial replacements of PC in concrete, but further research is required. The research into WFA and CGA as supplementary cementitious materials will assist in gaining knowledge on their impact on the concrete characteristics to allow for greater exploitationItem Spontaneous combustion liability of coals and coal-shales in South African coalfields(2018) Onifade, MoshoodSpontaneous combustion is one of the major challenges in the South African coal mining sector. The event involves a range of complex physical and chemical processes, caused by the chemical reaction between coal, coal-shale and oxygen. Coal and coal-shale undergo lowtemperature oxidation when exposed to oxygen in the air. The frequent occurrence of selfheating of coal-shale was reported in some South African coal mines to be the likely cause of spontaneous combustion but not the coal alone. Coal-shale found between layers (above and below) of coal seams vary considerably in intrinsic properties and proneness to spontaneous combustion. This thesis evaluates the main factors which most strongly affect the spontaneous combustion liability of coal and coal-shale. In South Africa, the widely accepted spontaneous combustion liability index, the Wits-Ehac Index was used to measure the spontaneous combustion liability index of fourteen (14) bituminous coal samples and 14 coal-shale samples respectively. The results of the Wits-Ehac Index show that most of the samples are liable to spontaneous combustion. However, the WitsEhac Index was unable to obtain a liability index during the testing of some coal-shale samples. This necessitated the development of a new device. A new apparatus which accurately measures the spontaneous combustion liability by using the reactivity of oxygen within coal and coal-shale was developed. A series of spontaneous combustion tests were conducted with this apparatus and a new liability index referred to as the Wits-CT Index was created. The Wits-CT Index uses the total carbon content and the temperature variations obtained from the samples during their reaction with oxygen to predict their spontaneous combustion liability. It was found that coal and coal-shale with a high WitsCT Index are more liable to spontaneous combustion. The results from the two liability indices were compared with respect to what is happening in the mines and proved that samples with higher spontaneous combustion liability indices are more prone to spontaneous combustion than those with lower liability indices. The relationships between the spontaneous combustion liability (obtained from the Wits-Ehac Index and Wits-CT Index) and the geochemical data ((proximate and ultimate analysis, total sulphur and sulphur forms, petrographic composition, X-ray fluorescence (XRF) and X-ray diffractometer analysis (XRD)) of the samples were evaluated. The experimental results show that intrinsic properties of these materials complement the spontaneous combustion liability test results. Comparative analyses of the intrinsic properties and spontaneous combustion liability indicated similarities between the mechanism of coal oxidation and that of the oxidative processes undergone by coal-shale. It was found that the coal samples have higher intrinsic properties and spontaneous combustion liability than the coal-shale samples. This study indicates that the South African coal and coal-shale are enriched with more inertinite macerals than the vitrinite and liptinite macerals. The distribution of the macerals has been shown to have reasonable influences on spontaneous combustion liability. The contents of the main ash oxides are strongly related to the mineral constituents of the samples as indicated by the XRF. The quantity and mineral constituents in coal and coal-shale were evaluated by chemical procedures and optimised by the XRD analysis. The XRD analysis confirmed the presence of mineral constituents in the samples as identified by the XRF. The influence of the intrinsic properties of coal-shale in relation to coal properties affecting spontaneous combustion liability was established using a statistical method (regression analysis). The results provide quantitative descriptions and show the relationships between the dependence of the spontaneous combustion liability index (the Wits-Ehac Index and the WitsCT Index) and independent variables (intrinsic properties). The linear regression analysis shows that the spontaneous combustion liability index indicates linear relationships with some of the intrinsic properties based on the set criterion and thus, identifies the major intrinsic factors affecting spontaneous combustion liability. It was found that a definite positive or negative correlation coefficient exists between the intrinsic factors and spontaneous combustion liability. A set of models to predict the spontaneous combustion liability was derived by using multiple regression analysis between the dependent variables and independent variables. The best significant correlation along with the most appropriate model as indicated by the R-squared values, the coefficient of correlations and standard error was used to predict the most reliable spontaneous combustion liability index. The results obtained from these models have been used as a reliable tool to support previous works on the role of intrinsic properties on spontaneous combustion liability. The application of chemical inhibitors on coal and coal-shale under laboratory studies were found to create an oxidative barrier on the surface of these materials to prevent self-heating and spontaneous combustion. The study indicated that by altering the self-heating characteristics (i.e. chemical and physical characteristics of a coal and coal-shale surface) through the use of chemical inhibitors, spontaneous combustion liability can be minimizedItem Estimation of surface moisture in a composite coal stockpile(2018) Enslin, KyleThis dissertation, through a literature survey, investigated the different types of moisture in coal, what parameters affect coal moisture content as well as technologies and methods for drying coal. It was found that the parameter that affects surface moisture the greatest was particle size and in particular, the -500µm size fraction. Based on this knowledge a hypothesis was developed. The hypothesis states that each size fraction contributes to the total surface moisture content relative to the size fractions equilibrium surface moisture content and weighting within the overall size distribution. The total surface moisture content is then the sum of these individual contributions. Where SMi = relationship (equation) between the equilibrium surface moisture content and the geometric mean of the individual size fraction (%) fi= weighting of size fraction in particle size distribution (%) In order to test this hypothesis the relationship between equilibrium surface moisture and size fraction had to be established first. This was done by performing drainage tests on nine different size fractions and determining the equilibrium surface moisture content for each. Tests were then done in two stages on composite coal samples to determine the equilibrium surface moisture content. The size distribution for stage one (PSD1) was different to stage two (PSD2). The samples had a fixed +500µm size distribution while the fines fraction (-500µm) increased by 1% for each test from 0% to 10%. Increasing the fines content resulted in a direct linear relationship between the fines fraction and surface moisture content. This was found to be true for the test data as well as the estimated data. Both the test and estimated data showed that for every 1% increase in fines content there was about 0.25% increase in equilibrium surface moisture content. This was true for both size distributions. Although the relationship was consistent, the size distribution did make a difference to the overall result. The finer size distribution resulted in a higher overall surface moisture content. Finally the model (equation 1.1) was used to estimate the surface moistures of 90 Eskom mill feed samples from five different power stations. Between the 25L drum, drainage pipe tests and Eskom data, the model estimated the Eskom data the best. The Eskom data also showed that in order to reach a minimum surface moisture of 6% the fines content should be kept below 9%.Item Weathering of coals from the Waterberg and Limpopo Coalfields, South Africa(2018) Sebola, Mandy-Jane TlouThis study investigated the effects of weathering on coal from the Waterberg and Limpopo Coalfields with the aim to understand how the quality of these coals changed during the early stages of oxidative weathering under dry and wet conditions. Coal was sampled from freshly exposed seams in both coalfields to provide, as best as possible, an un-weathered parent sample from which the extent of weathering could be determined. The Middle Seam was sampled from the Limpopo Coalfield whereas Benches 3, 5, 9B and 11 were sampled from the Waterberg Coalfield. This suite of samples enabled investigation into the impact of weathering on coals with similar properties but originating from different localities (Waterberg Coalfield vs Limpopo Coalfield), as well as coal with different properties originating from the same locality (Benches 3, 5, 9B and 11). Furthermore, the impact of weathering was studied on the coking properties (Middle Seam vs Bench 3) and heating properties using thermal coal (Bench 5). The experiment was conducted over a duration of six months during which a subset of the samples from each coalfield was kept dry in perforated containers, whilst the remaining samples were frequently watered to simulate the effect of rainfall under controlled settings. The particle size of the samples was reduced to -1mm to enhance the surface area for a more rapid reaction. Thereafter the samples were left to weather outdoors, on the roof of a building at the University of the Witwatersrand, Johannesburg. The average temperature conditions affecting the samples during the research period ranged between 9.40-27.23 °C. Several conventional coal analyses (proximate analysis, ultimate analysis, coal petrography, XRF & XRD) were used in conjunction with advanced techniques (EMPA, FE-SEM & Raman spectroscopy) to detect early signs of weathering on the organic and inorganic coal constituents. The impact of weathering on technological properties of the coal samples were investigated using calorific value, thermogravimetry and free swelling index. After six months of weathering, very small changes were observed in the coal quality due to weathering. The chemical and petrographic composition of the coals remained relatively unaffected by weathering, whereas the mineral matter and swelling properties of the coals were more susceptible to weathering under wet conditions. The alteration of minerals was more evident in the samples that were watered throughout the experiment, irrespective of their original locality. These samples were characterized by the precipitation of gypsum on the surface of the wet coals, as well as the appearance of red calcite grains. Analysis of the red calcite grains revealed rare growth rims associated with the precipitation of siderite. Although the findings of the thermogravimetric analysis suggested that the reactivity of the thermal coal had been slightly reduced by weathering (especially by weathering under wet conditions), the CV trend for this coal did not appear to be impaired. Hence, the effect of weathering on the heating properties of this sample are inconclusive. Ultimately, after 6 months of exposure to weathering the quality of the coals remained very similar to their fresh parent samples. However, the swelling properties of the coking coals from each coalfield were diminished. Therefore, caution is advised for the stockpiling of the coking coals outdoors, which should not exceed longer than 4-6 months, especially in the case of the Waterberg coking coal.Item Reliability improvement of the boiler-coal processing plant in eskom using reliability centred maintenance principles(2016) Sibanda, Ray Takudwanashe JonesThe objective of this report is to compare the existing maintenance methods in Eskom to RCM and then test the applicability of RCM in improving boiler reliability. Firstly, a comparative study was conducted on different RCM methods and the RCM method to apply selected and compared to the Eskom’s initiatives. The RCM method is piloted to a sample system and the results are compared with those from the current Eskom’s initiatives. The biggest change due to the RCM analysis was the way to document the results of the RCM process as compared to the current practice. It was also found that intervals between maintenance tasks proposed by the RCM study are different from the intervals currently used. In conclusion, the report recommends that the RCM results be used as a guide for continuous improvement in order to fill in gaps that are crucial in determining reliability goals.Item Estimation of the propensity of remnant underground coal pillars to spontaneously combust during opencast mining at a colliery in the Witbank coalfield(2017) Gemmell, Graham BarrySpontaneous combustion of coal may occur when coal is mined, stored or transported and is influenced by a combination of intrinsic and /or extrinsic factors. While it is unusual for intact seams to burn in the highwall, the most common occurrence is when surface mines extract seams previously partially mined by underground bord and pillar operations. The aim of the study is to provide a predictive model (matrix) of the spontaneous combustion potential of remnant pillars at Colliery X. A number of different thermal, chemical and petrographic tests (coal factors) will be undertaken to determine their individual and collective impacts on the sponcom predictive model. The primary geology at the mine is conformable with that of the Witbank Coalfield. Battacharyya (1982) described 3 main factors in the spontaneous combustion of coal, mining factor, coal factor and geological factor which have an aggregate effect. Some of the main historical and present theories of sponcom are the pyrite theory, the bacterial theory, the oxidation theory and the humidity theory. It is important to note that no single factor is responsible for spontaneous combustion. The oxidation of coal occurs constantly. The temperature of the coal is a function of the rate of heat generation versus the rate of heat loss. Fires can start at outcrops and move through interconnected workings with heat transfer by conduction (into the overburden) or convection (between panels).The overburden can also insulate the burning coal seam. Geological factors such as depth of overburden, the degree of fracturing, and the nature of the overlying strata vary between coalfields. A coal seam fire or mine fire is the underground smouldering of a coal deposit, often in a coal mine. Such fires have economic, social and ecological impacts In order to extinguish a fire, one of three elements, fuel, oxygen, or energy, must be removed. The components of the fire triangle can be further subdivided into conventional mine control techniques and more or less unconventional or unproven mine fire control techniques. The thermal techniques discussed include the crossing point temperature, thermogravimetric analyses and oxygen absorption. Macerals, the microscopically identifiable organic constituents of coal, are one of the three basic parameters that define coal. The other two parameters are the coal rank and the mineral matter Vitrinite is the principal maceral group of the No.5 seam and inertinite dominates the No.2 and No.4 seams. The results obtained from the 22 drill-core samples and 2 ROM samples were matched to the existing borehole dataset (2296 boreholes) based on similarity of heat value (figure 3.11). A total of 24 test results (thermal, chemical and petrographic) from borehole A and borehole B were thus assigned to the borehole database which has approximately 1500 samples for each seam. By linking the laboratory datasets (borehole A and B) and the existing borehole database used for resource modelling, the sponcom variables could be modelled in a similar way to the coal resources. The overall risk matrix was calculated on a full seam basis by combining 15 variable scores, each variable having a score of 0, 1 or 2 (low-mod-high probability). The overall results from this research produced clear and unambiguous contour plans of different factors effecting sponcom of coal using single variable and combined variable datasets. In conclusion, it appears that the acceptability of a method for determining spontaneous heating characteristics of coal mainly depends upon how closely it predicts the spontaneous heating behaviour in the field conditionsItem Feasibility study for maize as a feedstock for liquid fuels production based on a simulation developed in Aspen Plus®(2018) Naidoo, SimoneSouth Africa’s energy sector is vital to the development of its economy. Instability in the form of disruption in supply affects production costs, investments, and social and economic growth. Domestic sources are no longer able to meet the country’s demands. South Africa must find a local alternative fuel source in order to reclaim stability and encourage social and economic development. Biomass is one of the most abundant renewable energy sources, and has great potential as a fuel source. Currently biomass contributes 12% of the world’s energy supply, while in some developing countries it is responsible for up to 50% of the energy supply. South Africa is the highest maize producer on the African continent. Many studies carried out indicated that maize, and its residue contain valuable materials, and has the highest lower heating value in comparison to other agricultural crops. This indicates that maize can be a potential biomass for renewable energy generation in South Africa. A means for energy conversion for biomass, is the process of gasification. Gasification results in gaseous products H2, CO and CO2. Since the process of biomass gasification involves a series of complex chemical reactions involving a number of parameters, which include flow, heat transfer and mass transfer, it is very difficult to study the process of gasification by relying on experimentation only. Numerical simulation was used to provide further insight on this process, and accelerate development and application of maize gasification in a cost effective and efficient manner. The objective of this study was therefore, to verify and evaluate the feasibility of maize gasification and liquid fuels production in South Africa from an economic and energy perspective. The simulation model was developed in Aspen Plus® based on two thermodynamic models specified as Soave – Redlich – Kwong and the Peng Robinson equation of state. All binary parameters required for this simulation were available in Aspen Plus®. The gasification unit was modelled based on a modified Gibbs free energy minimization model. Gasification of maize and downstream processing in the form of Fischer-Tropsch (FT) synthesis and gas to liquids (GTL) processing for liquid fuels production was modelled in Aspen Plus®. Sensitivity analyses were carried out on the process variables: equivalence ratio (ER), steam to biomass ratio (SBR), temperature and pressure, to obtain the optimum gasification conditions. The optimum reactor conditions, which maximized syngas volume and quality was found to be an ER of 0.22 and SBR of 0.2 at a temperature of 611ºC. An increase in pressure was found to have a negative effect; therefore atmospheric conditions of 101.325 kPa were chosen, in order to maximize CO and H2 molar volumes. Based on these conditions the produced syngas consisted of 35% H2, 16% CO, 24% CO2 and 3%CH4. The results obtained from gasification, based on a modified Gibbs free energy model, show a closer agreement with experimental data, than other simulations based on the assumption that equilibrium is reached and no tar is formed. However, these results were still idealistic as it under predicted the formation of CO and CH4. Although tar was accounted for as 5.5% of the total product from the gasifier (Barman et al., 2012), it may have been an insufficient estimation resulting in the discrepancy in CO and CH4. The feasibility of maize as a feed for gasification was examined based on quality of syngas produced in relation to the requirements for FT synthesis. A H2/CO ratio of 2.20 was found, which is within range of 2.1 – 2.56 found to support greater conversions of CO with deactivation of the FT catalyst (Lillebo et al., 2017). The syngas produced from maize was found to have a higher H2/CO ratio than conventional fossil fuel feeds; implying that maize can result in a syngas feed which is both renewable and richer in CO and H2 molar volumes. Liquid fuels generation was modelled based on experimental production distributions obtained from literature for FT synthesis and hydrocracking. The liquid fuel production for 1000 kg/hr maize feed, was found to be 152 kg/hr LPG, 517 kg/hr petrol and 155 kg/hr diesel. The simulation of liquid fuels production via the Fischer-Tropsch synthesis and hydrocracking process showed fair agreement with literature. Where significant deviations were found, they could be reasonably explained and supported. This simulation was found to be a suitable means to predict liquid fuels production from maize gasification and downstream processing. The feasibility of liquid fuels production from maize in South Africa was examined based on the country’s resource capacity to support additional maize generation. It was found that based on 450 000 hectares of underutilized land found in the Homelands, an additional 1.216 billion litre/annum of synthetic fuels in the form of diesel and petrol could be produced. This has the potential to supplement South African liquid fuels demand by 6% using a renewable fuel source. This fuel generation from maize will not impact food security due to the use of underutilized arable land for maize cultivation, or impact water supply as maize does not require irrigation. In addition, fuel generation in this manner supports the Biofuels Industry Strategy (2007) by targeting the use of underutilized land, ensuring minimal impact on food security, and exceeds its primary objective of achieving a 2% blending rate from renewable sources. The economic feasibility of liquid fuels derived from maize was determined based on current economic conditions in 2016. Based on these conditions of 49 $/bbl Brent Crude, 40 $/MT coal and 6.5 $/mmBTU of natural gas at a R/$ exchange rate of R14.06 per U.S. dollar, it was found that coal, natural gas and oil processing are more economically viable feeds for fuel generation relative to maize. However, based on projected market conditions for South Africa, the R/$ exchange rate is expected to weaken further, the coal supply is expected to diminish and supply of natural gas is expected to be a continued issue for South Africa. Based on this, maize should be considered as a feed for fuel generation to reduce the dependency on non-renewable fossil fuel sources. The energy feasibility of liquid fuels produced from maize was only evaluated from a thermal energy perspective. It was found that maize gasification and FT processing requires 0.91 kg steam/kg feed. This 0.91kg of steam accounts for the raw material feed, distillation and heating required for every 1kg of maize processed. It was found that 2.56 kg steam/kg feed was generated from the reactor units. This was assumed to be in the form of 10 bar steam, as in this form it can be sent to steam turbines for electricity generation to assist with overall energy efficiency for this process. In addition, the amount of CO2 (kg/kg feed) produced, was examined for maize processing in comparison to fossil fuel feeds: natural gas and coal. The CO2 production from liquid fuels processing based on a maize feed, was found to be the highest at 0.66 kg/kg feed. However, a coal feed has higher ash and fix carbon content indicating greater solid waste generation in the gasifer. While dry reforming of natural gas is a net consumer of CO2, but had significantly higher steam requirements in order to achieve the same H2/CO ratio as maize. This indicates that although maize results in more CO2/kg feed, it is 88% more energy efficient than dry methane reforming. Additional experimental work on FT processing using syngas derived from maize is recommended. This will assist in further verification of liquid fuels quantity, quality and process energy requirements.Item Behaviour of selected South African coals in circulating fluidised bed (CFB) in comparison with Russian coal(2017) Belaid, MohamedSouth Africa (SA) has an energy-intensive coal mining industry, where coal accounts for approximately 72% of total primary energy consumption in the country, particularly in the electricity sector, where 95% of total electricity generated is derived from coal. Pulverised coal combustion has been the preferred technology adopted for power generation in South Africa for many decades. These coal-fired power plants have no flue gas desulphurisation (FGD) equipment fitted at present. Therefore, these plants account for the majority of annual SO2, CO2, and NOx emissions, making them environmentally unsustainable for power generation. Such environmental issues add to the challenges for the power producer, who is required to meet not only energy demand, but also to compete with the export market for quality coals, and to ensure that electricity generation complies with ever-changing air quality standards. Circulating fluidised-bed combustion (CFBC), a technology for the combustion of coal, biomass, waste, has not been adequately explored or tested in South Africa previously. CFB combustion is currently under intense scrutiny amongst researchers evaluating its potential as an economic and environmentally acceptable technology, in particular for the burning of lowgrade coals. The main objective of this study is to undertake a case study using CFBC technology and to establish its potential for use in South Africa as a clean and cost-effective method in power generating for high-ash, low-grade coals. Experimental tests were conducted in a CFBC pilot plant in Finland, using two high ash coals, discarded coal from South Africa (SA) and a better quality coal from Russia for comparative purposes. A review was conducted of discard coals in South Africa in order to establish an inventory in support of their potential utilisation for power generation in circulating fluidised bed boilers. A further study established a comparison between pulverised coal (PC), and fluidised bed (FBC) technologies as a future benefit analysis. All four coals proved to have very high combustion efficiencies, despite significant quality differences in terms of petrographic composition and ash content. More specifically, the SA coals achieved combustion efficiencies of 99.6 %, 99.7 % and 99.8 %, where the Russian coal achieved 98.7 percent. The Russian coal was characterised as being low in ash and high in the reactive maceral vitrinite, the two South African coals possessed high ash content (35 to 45%), one with relatively high vitrinite, and the other very low vitrinite, whilst the South African discard possessed an ash content of 65-70% and extremely low reactive vitrinite content. All these factors lean towards the suitability of SA coals to the CFB technology. In terms of NOx emissions, all coals tested showed that their NOx and N2O emission meet the minimum requirements for small plants as set out by the European and SA standards, i.e. <300 ppm for a plant with generating capacity below 100 MW. This result is in agreement with data from the literature. The emission of SO2 depends on the sulphur content in the initial coal, which also has an impact on the Ca/S Ratio. SO2 emitted from the South African coals was higher than the national permitted standard, due to the low Ca/S ratio used. This was especially the case for South African discard. Vast reserves of discard coal containing from 2MJ/kg to 14 MJ/kg in calorific value have accumulated in South Africa since the last inventory of 2001, i.e. close to 1.5 billion tonnes are in existence. It is apparent that one of the looming challenges regarding discard coal is putting this ever-accumulating material to use. From the combustion results obtained in this research, it is proposed that such materials can be combusted in a CFBC boiler, and that it produces the same efficiency as other coals from South Africa and a clean coal from Europe. Ash distribution within the boiler was found to change in proportion of bed ash to fly ash, subject to the quality of the coal used. This is also likely to change the proportions of sulphur-absorbing sorbents in future. CO2 emissions from the coals under review were found to be very close, in the region of 12.8 to 13.8 percent.Item Factors affecting the spontaneous combustion index(1992) Eroglu, Huseyin NeharThe self-heating of coal is a problem which concerns the mining industry not only in South Africa, but also in many other countries. This thesis deals with the contouring of spontaneous combustion liabilities (WITS-ERAC index values) of different seams at the Durban Navigation Colliery and the relationship between the WITS-EHAC index values and the properties of the coal samples. In the determination of the spontaneous combustion liabilities 58 different coal samples were tested with an ignition-temperature test apparatus, crossing-point temperature tests and differential thermal analysis were conducted simultaneously. [Abbreviated abstract. Open document to view full version]Item Application of Oxy-fuel combustion on South African Coals using Thermogravimetric Analyses (TGA)(2017) Molise, DorcasThe quality and grade of South African coal is declining simultaneously with depleting seams. This has a negative impact on power generation and the economics of coal mining and power production. The reason is that good quality coal is more difficult to mine and hence costly, thus affecting coal prices and the ability of mines to supply coal quality of the required specifications. There is a global environmental awareness around the CO2 greenhouse gas and its effect on global warming. Legislations are becoming more stringent in limiting the amount of greenhouse gases and air pollutants we produce. In power generation, the most prominent greenhouse gas is carbon dioxide (CO2) and the most prominent air pollutants are oxides of Nitrogen and Sulphur (NOx and SOx). Oxy-fuel combustion (OFC) is a process change that can reduce the production of CO2 by increasing the concentration of oxygen in combusting air. A study is presented here, that focuses on the application of this process (OFC) to South African coals. Three different coal types were studied and characterized by conventional proximate and ultimate analyses and further characterized and graded by more specialized analyses; petrographic analyses and the quantitative evaluation of minerals b scanning electron microscopy (QEMSCAN). The gasification of the coals was then modeled to determine, qualitatively, its magnitude in comparison to combustion (oxidation) in oxy-fuel combustion. However, when modeling and conducting experiments to determine this, it was found that existing empirical formulae used to quantify char burnout are not suitable for all South African types of coal. The formulae found in literature (for both oxidation and gasification) could only be applied to two of the three samples. For the two samples that were successfully modeled, it was found that reactivity in gasification was probable but not to a significant level. For the third sample that couldn’t be modeled successfully, a recommendation was made that a new model be developed to take into account the nature of low grade, high inertinite South African coal. This is required in order to successfully formulate the char burnout of South African coals and thus depict with certainty, the applicability of Oxy-fuel combustion on South African coals. Such a step would benefit the forthcoming studies on modeling the char burnout of South African coal and therefore contribute to addressing the challenge of declining coal quality in South Africa.