With increasing energy demand globally and, in particular, in South Africa coupled with depletion of the earth’s fossil energy resources and growing problem of disposal of nonbiodegradable waste such as waste tyres, there is a need and effort globally to find alternative energy from waste material including waste tyres. One possible way of exploiting waste tyre for energy or chemicals recovery is through gasification for the production of syngas, and this is what was investigated in this study. The possibility of gasification of waste tyre blended with coal after pyrolysis was investigated and two Bituminous coals were selected for blending with the waste tyre in co-gasification. A sample of ground waste tyre / waste tire, WT, a high vitrinite coal from the Waterberg coalfield (GG coal) and a high inertinite coal from the Highveld coalfield (SF coal) were used in this investigation. The waste tyre sample had the highest volatile matter content of 63.8%, followed by GG coal with 27% and SF coal with 23.8%. SF coal had the highest ash content of 21.6%, GG coal had 12.6% and waste tyre had the lowest of 6.6%. For the chars, SF char still had the highest ash of 24.8%, but WT char had higher ash, 14.7%, when compared to GG char with 13.9% ash. The vitrinite content in GG coal was 86.3%, whilst in SF coal it was 25% and SF coal had a higher inertinite content of 71% when compared to GG coal with 7.7%. SF char had the highest BET surface area of 126m2/g, followed by GG char with 113m2/g, and WT had the lowest value of 35.09m2/g. The alkali indices of the SF, WT and GG chars were calculated to be 8.2, 4.2 and 1.7 respectively. Coal samples were prepared by crushing and milling to particle sizes less than 75μm before charring in a packed bed balance reactor at temperatures up to 1000oC.Waste tyre samples were charred at the same conditions before milling to < 75μm particle size. Coal and WT chars were blended in ratios of 75:25, 50:50 and 25:75 before gasification experimentation. Carbon dioxide gasification was conducted on the blends and the pure coal and WT chars in a Thermogravimetric analyser (TGA) at 900oC, 925oC, 950oC and 975oC and ambient pressure. 100% CO2 was used at a flow rate of 2L/min. Reactivity of the pure char samples was found to be in the order SF > GG > WT, and the relationship between the coal chars’ reactivities could be explained by the high ash content of the SF char and low reactivity of the WT char corresponds to its low BET surface area. In general, the coal/WT char mixtures were less reactive than the respective coal, but more reactive than the pure WT char, the only exception being the 75% GG char blend which was initially more reactive than the GG char, and reactivity decreased with increasing WT content. For all samples reactivity increased with increasing temperature. The relationship between the reactivities of the GG char and its blends and that of the SF char and its blends was found to be affected by the amount of WT char added, especially at the lower temperatures 900oC and 925oC. SF coal is more reactive than GG coal, but at 900oC and 925oC, the reactivity of GG/WT blends improves in relation to the SF/WT blends with an increase in the ratio of WT in the blends, i.e. the 25% GG char blend is more reactive than the 25% SF char blend. The reactivity of the coal/WT blends was also checked against predicted conversion rates based on the conversion rates of the pure WT and coal samples. At 900oC and 925oC, the reactivities of the blends of both coal chars with WT char were found to be greater than the predicted conversion rates, and for the GG/WT blends the deviation increased with increasing WT ratios, while for the SF/WT blends the deviation increased with increasing SF ratios. These findings suggest the presence of synergism or enhancement between the coal chars and WT char in gasification reactions. The random pore model (RPM) was used to model the gasification results and it was found to adequately describe the experimental data. Activation energies determined with the RPM were found to be 205.4kJ/mol, 189.9kJ/mol and 173.9kJ/mol for SF char, WT char and GG char respectively. The activation energies of the coal/WT blends were found to be lower than those of both the pure coal and the pure WT chars. For the GG/WT blends the activation energy decreased with increasing WT char ratio, while for the SF/WT blends the activation energy decreased with increasing SF char ratio. The trends of the activation energies and conversion rates of the blends point to synergism or enhancement between the coal and WT chars in CO2 gasification reactions, and in the GG/WT blends this enhancement is driven more by the WT char, while in SF/WT blends it is driven by SF chars. It is possible that enhancement of the reactions is caused by mineral matter catalysis of the gasification reactions. The ash contents and alkali indices of the pure samples follow the order SF > WT > GG. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Thesis (MPhil (Public Management and Planning))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: South Africa has a mean annual precipitation far lower than the global average. This is a fundamental constraint to development, especially when the country has already run out of surplus water and dilution capacity. To add further pressure, southern Africa’s water resources are expected to decrease as a result of climate change. Despite the potential devastation, the country’s response to climate change has been limited. South Africa’s energy sector is dominated by coal power stations and is the country’s primary emitter of carbon dioxide. Given the significantly higher water usage of coal-fired power plants compared to that of most renewable energy power plants, the transition to a clean energy infrastructure might be more successfully motivated by water scarcity than by the promise of reduced carbon emissions. This article analyses more critically the impact of coal-fired electricity generation on South Africa’s water resources, by estimating a water-use figure that extends backwards from the power plant to include water used during extraction of the coal. This figure can then be compared to the water usage of alternative electricity generation options. It is then possible to estimate how much water could be saved by substituting these alternatives in place of additional coal-fired plants. / AFRIKAANSE OPSOMMING: Suid-Afrika se gemiddelde jaarlikse neerslag is baie laer as die wêreldwye gemiddelde. Dit plaas ’n wesenlike beperking op ontwikkeling, veral aangesien die land se surplus water- en verdunningskapasiteit reeds uitgeput is. Om die saak verder te vererger, word verwag dat Suidelike Afrika se waterbronne gaan kleiner word as gevolg van klimaatsverandering. Ten spyte van die potensiële ramp, was die land se reaksie op klimaatsverandering tot dusver baie beperk. Steenkoolkragstasies, wat Suid-Afrika se energiesektor oorheers, is die land se primêre bron van koolstofdioksieduitlating. Gegewe die beduidend hoër waterverbruik van steenkoolkragstasies teenoor dié van die meeste kragstasies wat met hernubare energie werk, kan die verandering na ’n skoonenergie-infrastruktuur meer suksesvol gemotiveer word deur waterskaarste as deur die belofte van verminderde koolstofuitlatings. Hierdie artikel analiseer die impak van steenkoolgedrewe elektrisiteitsopwekking op Suid-Afrika se waterbronne meer krities deur te beraam hoeveel water verbruik word van die kragstasie terug tot by die ontginning van die steenkool. Hierdie syfer kan dan vergelyk word met die waterverbruik van alternatiewe kragopwekkingsopsies. Dit is dan moontlik om te beraam hoeveel water gespaar kan word deur hierdie alternatiewe op te rig in plaas van bykomende steenkoolkragstasies.

Thesis (MBA)--Stellenbosch University, 2011. / The objective of this study is to recommend the optimal coal preparation plant feed strategy for the Tweefontein Optimisation Project (TOP) at Xstrata Coal South Africa’s Tweefontein Complex operations. In this research report the specific challenges relating to the mining, stockpiling and quality of coal relating to this problem are presented together with the decision analysis modelling used to solve the optimal plant feed strategy. Interviews were held and relevant literature studies were consulted to gain a deeper understanding of the challenges relating to the opencast mining of coal pillars remaining from historically mined underground operations, together with the coal quality variability and complexity relating to the Tweefontein Complex. Further literature studies were conducted to gain an understanding of the most favourable decision modelling tools to be applied. Three different types of models were developed. The first was to test various washing philosophies influenced by the combination of coal from various sources and seams over individual week periods. The second was to simulate the coal process flow from arrival at the run-of-mine (ROM) pad through to the loading of trains, influenced by production profiles, system constraints and dynamic stochastic processes. The final model had to test the combined financial impact of washing and stockpile philosophies on the net present value of the Tweefontein Complex over the life of the mine. Due to the nature of the modelling techniques applied, the establishment of scenarios was necessitated. Six washing philosophy scenarios and three base stockpile philosophy scenarios (developed to 39 scenarios when sensitivity and limit tests are included) were tested. Thereafter the relevant combined permutations were used to establish 12 feed strategy scenarios that were compared for their financial impact. From the individual philosophies recommended from a washing and stockpiling perspective, a final three scenarios were recommended from a net present value perspective. These include: (a) the individual feeding of five different quality-groups of coal with a ROM stockpile capacity of 128 000 tonnes and excluding a plant buffer stockpile, applying a wash approach based on the “randomly” estimated cut point density of the respective quality-group; (b) the individual feeding of two quality-groups of coal (export and Eskom) with a ROM stockpile capacity of 50 000 tonnes and a plant buffer stockpile (using a bridge reclaimer system) with a capacity of 80 000 tonnes, applying a wash approach whereby the optimal cut point density of the previous week is utilised the following week; (c) a similar feed strategy as for b, but with the application of coal valves as the reclaimer system on the plant buffer stockpile. A final recommendation was made to implement the scenario given in c above. This was concluded following a combination of additional considerations. This research report contains the knowledge gained in the personal interviews and the literature reviewed. It further discusses the methodology followed to achieve the objectives of the study, it illustrates the models and scenarios that were developed and it discusses the analysis of the results and conclusions formulated. It finally concludes with a recommendation for the optimal feed strategy for the TOP, together with additional work proposed to be conducted subsequent to this study.

M. Tech. (Cost and Management Accounting, Faculty of Management Sciences), Vaal University of Technology / Statistics in South Africa show that the fatality and injury rates within the mining industry have dropped since the end of the apartheid era. Regardless of the drop the fact remains that the mine workers, who are often the breadwinners, are still dying in the country’s mines leaving their families behind without any source of income. If they do not die they may suffer crippling injuries due to mine accidents making it impossible for them to perform their daily duties at work which results in the loss of income, loss of quality of life and this produces a humanitarian and a socio-economic problem. Mining companies incur enormous costs due to fatalities and injuries. Hence a target for zero fatalities was set in the mining industry for 2013. However, the industry has failed to reach this target that it set for itself and it is therefore of the utmost importance to encourage mining companies to invest more than they do currently in safety in order to prevent these fatal and crippling injuries due to mine accidents. The purpose of this study was to determine whether or not the requirements of safety legislation are observed and complied with by a single Colliery in South Africa that was selected for this study. The study also sought to investigate whether or not the employees of this mine observe the safety regulations to ensure safety and to maintain an accident free working environment. An analysis of organizational safety control mechanisms and production cost was conducted through the use of a structured questionnaire, completed by 151 participants. Descriptive statistics, frequency tables, exploratory factor analysis (EFA), one-way analysis of variance (ANOVA) and t-test were utilized to analyse the data. The results indicate that the Colliery was compliant with the safety legislations, a positive employee safety attitude had been cultivated and there was provision of adequate safety facilities through safety investments. Cost reduction due to the application of safety controls was also established, yet it was found necessary for the Colliery to enforce and encourage the application of safety measures to reduce the costs that are still incurred as it is evident that the application of safety controls results in reduced costs. Although the Colliery was considered compliant, with its employees showing a positive attitude towards safety controls, and with safety investments made and cost reduction achieved due to safety measures, ANOVA revealed different perceptions based on the departments in which the employees work, years of experience, English proficiency and qualifications. However, no differences were found in relation to gender and designation.

M.Sc. (Geology) / Please refer to full text to view abstract

A mild gasification method has been developed to provide an innovative clean coal technology. The objective of this study is to developed a numerical model to investigate the thermal-flow and gasification process inside a specially designed fluidized-bed mild gasifier using the commercial CFD solver ANSYS/FLUENT. Eulerain-Eulerian method is employed to calculate both the primary phase (air) and secondary phase (coal particles). The Navier-Stokes equations and seven species transport equations are solved with three heterogeneous (gas-solid), two homogeneous (gas-gas) global gasification reactions. Development of the model starts from simulating single-phase turbulent flow and heat transfer to understand the thermal-flow behavior followed by five global gasification reactions, progressively with adding one equation at a time. Finally, the particles are introduced with heterogeneous reactions. The simulation model has been successfully developed. The results are reasonable but require future experimental data for verification.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering, 2016 / Spontaneous 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 conditions / CK2018

The Matimba and soon to be completed Medupi power stations located in close proximity to the town of Lephalale are a cause for environmental concern due to the known effects that coal combustion has on air, soil and water quality. The Medupi power station is currently being constructed, while the Matimba power station may have already negatively altered the water quality of the rivers especially those downwind of the power stations. The Lephalala (perennial river, upwind), the Mokolo (perennial river, upwind) and Matlabas (seasonal river, downwind) Rivers were selected due to the locations relative to the power stations. The concentrations and flux of cations and sulphate ions within the rivers in the Waterberg District Municipality were investigated for any seasonal or annual patterns using monthly data from a single sampling station along each river. Data for the concentrations of sodium, potassium, magnesium, calcium, ammonium and sulphate were analysed in conjunction with river discharge, rainfall and ambient temperature data available for each hydrological year from 1999 to 2010. The data were converted to seasonal and annual values in order to determine the influence of the quality and quantity of coal combusted as well as climatic variables (rainfall, temperature and discharge) on ion fluxes measured. Sodium was the dominant cation in all rivers, reaching a maximum concentration of 0.0015 mol.ℓ-1 (in 2007), 0.0007 mol.ℓ-1 (in 2007) and 0.0006 mol.ℓ-1 (in 2001) in the Lephalala, Mokolo and Matlabas Rivers, respectively. Other cation concentrations were four times lower in the Lephalala and Mokolo Rivers, while they were eight times lower in the Matlabas Rivers. Sulphate concentrations were approximately nine, five and 15 times lower than the cation concentrations measured within the Lephalala, Mokolo and Matlabas Rivers, respectively. The mean summed cation flux was highest in the Lephalala River (0.0015 ± 0.0010 Eq.ℓ-1), which was approximately 1.7 and 2.1 times higher than summed cation fluxes measured in the Mokolo (0.0009 ± 0.0002 Eq.ℓ-1) and Matlabas (0.0007 ± 0.0006 Eq.ℓ-1) Rivers. Cation fluxes were highest during the rainfall season (summer and spring) in the river closest to the Matimba power station (Mokolo Rivers) while summed cation flux in the Lephalala and Mokolo Rivers (located further away from the power station) showed no specific seasonality. It was, however, noted that the cation fluxes during spring and winter were elevated for both rivers, possibly indicating

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master in Science in Engineering, Johannesburg September 1998 / Combustion modelling of utility furnace chambers provides a cost efficient means to extrapolate the combustion behaviour of pulverised fuel (pf) as determined from drop tube furnace (DTF) experiments to full scale plant by making use of computational fluid dynamics (CFD). The combustion model will be used to assimilate essential information for the evaluation and prediction of the effect of • changing coal feedstocks • proposed operational changes • boiler modifications. TRI comrnlssloned a DTF in 1989 which has to date been primarily used for the comparative characterisation of coals in terms of combustion behaviour. An analysis of the DTF results allows the determination of certain combustion parameters used to define a mathematical model describing the rate at which the combustion reaction takes place. This model has been incorporated into a reactor model which can simulate the processes occurring in the furnace region of a boiler, thereby allowing the extrapolation of the DTF determined combustion assessment to the full scale. This provides information about combustion conditions in the boiler which in turn are used in the evaluation of the furnace performance. Extensive furnace testwork of one of Eskom's wall fired plant (Hendrina Unit 9) during 1996, intended to validate the model for the ar plications outlined above, included the measurement {If : • gas temperatures • O2, C02, CO, NOx and S02 concentrations • residence time distributions • combustible matter in combustion residues extracted from the furnace • furnace heat fluxes. The coal used during the tests was sampled and subjected to a series of chemical and other lab-scale analyses to determine the following: • physical properties • composition • devolatilisation properties " combustion properties The same furnace was modelled using the University of Stuttgart's AIOLOS combustion code, the results of Which are compared with the measured data. A DTF derived combustion assessment of a coal sampled from the same site but from a different part of the beneficiation plant, which was found to burn differently, was subsequently used in a further simulation to assess the sensitivity of the model to char combustion rate data. The results of these predictions are compared to the predictions of the validation simulation. It was found that the model produces results that compare well with the measured data. Furthermore. the model was found to be sufficiently sensitive to reactivity parameters of the coal. The model has thereby demonstrated that it can be used in the envisaged application of extrapolating DTF reactivity assessments to full scale plant. In using the model, it has become apparent that the evaluations of furnace modifications and assessments of boiler operation lie well within the capabilities of the model. / MT2017

Considerando a crescente demanda por energia e tendo em vista uma matriz diversificada, faz-se necessário o estudo das jazidas carboníferas não exploradas, como é o caso da Jazida de Morungava, em cujas últimas pesquisas datam da década de 1980. A jazida situa-se no nordeste do estado do Rio Grande do Sul, com uma área de abrangência de cerca de 250km2. Realizou-se um poço exploratório para estudar o carvão e avaliar a economicidade da jazida, por meio de caracterização petrográfica, química e tecnológica das camadas obtidas no poço CBM 001-MO-RS, que atingiu a profundidade de 387,70m, uma espessura cumulativa de carvão de 9,22m. Identificou-se 6 camadas de carvão, das quais obteve-se 27 amostras. Para caracterizar as amostras, realizou-se: descrições de litotipos do carvão, refletância da vitrinita, contagem de macerais, análises imediatas, poder calorífico superior, enxofre total, difração de raios-X e teste de beneficiamento. O litotipo carvão fosco é predominante nas amostras, com um rank variando de carvão betuminoso alto volátil A à antracito.As amostras, estão afetadas progressivamente por intrusão vulcânica sotoposta. O grupo maceral vitrinita predomina nos carvões na porção inferior, enquanto inertinita predomina na superior. Matéria mineral apresenta uma tendência de aumento da base para o topo. Os carvões apresentaram altos teores de cinza (>50%m.b.s.), matéria volátil (6,04-30,69%m.b.s), enxofre (0,20-2,88%m) e poder calorífico superior (777-4.732Kcal/Kg). Ocorre um predomínio mineralógico de quartzo, caulinita, e illita. A maioria das camadas são classificadas como rocha carbonosa (>50% cinza/b.s.). Em ensaios de beneficiamento foi observado um baixo rendimento (<7%vol.), na obtenção de produtos nobres. / Considering the growing demand for energy and with a view to a diverse energy matrix, it is necessary to study the coal deposits not or little exploited, such as the Morungava coalfield, where the latest research is dating back to the 1980s. The Coalfield is located in the northeast of Rio Grande do Sul State, Brazil. The present study characterizes coal seams obtained from borehole CBM 001-MO-RS, which reached a depth of 387,70 m. 6 coal seams were identified, with a cumulative coal thickness of 9,22 m, from which 27 coal samples were taken for analyses. The following methods were applied: lithotype description, vitrinite reflectance measurement, maceral analyses, proximate analysis, calorific value analysis, sulphur determination, x-ray diffraction and beneficiation tests. The lithotype dull coal is prevalent in the samples. Coal rank ranges from high volatile bituminous A coal to anthracite, with samples progressively affected by an overlying volcanic intrusion. The vitrinite maceral group dominates the coals in the lower portion, whereas inertinite prevails at the top. The coals show high ash content (> 40 wt.% d.f.). Volatile matter ranges from 6.04 to 30.69 wt.% d.f,,sulfur ranges from 0.20 to 2.88 wt.%, and gross calorific values range from 777 - 4732 Kcal/kg). There is a predominance of quartz, kaolinite and illite in the mineral fraction. Beneficiation tests indicate a very low yield in better quality, low ash coal. Most of the coal seams are classified as carbonaceous rock (> 50% Ash/d.f.).