Made available in DSpace on 2014-10-09T12:49:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:09Z (GMT). No. of bitstreams: 1 09832.pdf: 3928671 bytes, checksum: 13613e04f579c429d158f6531d8f9eac (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:54:57Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:12Z (GMT). No. of bitstreams: 0 / As cinzas de carvão podem ser convertidas em produtos zeolíticos por tratamento hidrotérmico alcalino. No presente estudo, a capacidade de zeólitas sintetizadas a partir de cinzas de carvão brasileiras (6 amostras da cinza volante do filtro de mangas e 6 amostras da cinza leve do filtro ciclone) na remoção de Zn2+ e Cd2+ de soluções aquosas foi investigada. O tempo de equilíbrio alcançado pela maioria das zeólitas foi de 24 horas. Os dados de equilíbrio obtidos se ajustaram à isoterma de adsorção de Langmuir. As capacidades de troca catiônica máximas estavam entre 25,9 e 39,5 mg g-1 para o Zn2+ e entre 49,5 e 72,3 mg g-1 para o Cd2+. A zeólita sintética (ZM1) apresentou área superficial no valor de 66,38 m2 g-1, baixa relação Si/Al (1,65) e a formação de zeólitas sodalita e faujasita, que contribuíram para seu melhor desempenho. Estudos de adsorção de íons metálicos com a ZM1 indicaram a seguinte seqüência de seletividade: Pb2+ > Cd2+ > Cu2+ > Zn2+ > Ni2+. Para a ZM1, a maior porcentagem de remoção de Zn2+ e Cd2+ foi obtida em pH 5 e a recuperação de metais foi efetivamente realizada com solução de NaCl 2 mol L-1. Comparou-se o desempenho das zeólitas sintetizadas a partir das cinzas de carvão com as zeólitas sintéticas comerciais, bem como o custo de ambas. As zeólitas sintetizadas com cinza de carvão apresentaram melhor eficiência de retenção do zinco e do cádmio do que as zeólitas comerciais. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Ph.D. (Mineral Economics) / Please refer to full text to view abstract

The purpose of this study was to determine if any amount of PAH (Polycyclic aromatic hydrocarbons) was leaching from the paved road surface of road 805 in Jokkmokk municipality. The study was also meant to determine which factors affected the leaching of PAH in the studied area.The surveyed road was divided into eight sections. Groundwater pipes were inserted into drilled holes, three in each section. Samples from soil, water and asphalt were collected from each section and analyzed for its content of PAH. The groundwater level was measured before each sampling. Some soil samples were analyzed for TOC (total organic carbon) and all the water samples for DOC (dissolved organic carbon). The results showed that PAH was leaching in very different amounts. There was a similarity in the amount of coal tar in the road surface and the amount of PAH in most sections. Although in one section the asphalt sample showed low amount of coal tar but high amount of PAH in the soil- and water samples. This anomaly could not be explained - the assumption was that the sampling had been incorrectly handled. The pollution in the surveyed area is assumed to be caused by the road surface and tire wear. Further studies are necessary to determine with certainty how PAH is leaching in different conditions and with different road pavements.

M.Sc. / The potential target areas for coalbed methane in South Africa are reviewed and a case study based on borehole data from the north-eastern Karoo basin was undertaken. The Early Permian coal seams of the Karoo Supergroup occur in several discrete sedimentary basins in South Africa, of which the Karoo basin is the largest. Using screening criteria based on geological, petrographical and analytical data some of the coal deposits can be excluded as potential coalbed methane producers. These include the Molteno Coalfield, large parts of the Karoo basin coal deposits and some of the Northern Province's coal deposits which are structurally disturbed. The traditional mining areas in the Free State, Witbank and Highveld coalfields are excluded from the coalbed methane study because the target seams occur at less than 200 metres below surface, too shallow for gas retention. Some of the coal seams in the Waterberg Coalfield occur at depths of several hundred metres below surface and these are unlikely to be mined by conventional means. These deep coals may be ideal coalbed methane producers. This regional overview was based on available, published data and two important parameters, permeability of coal and coalbed hydrology are unknown but important factors that will need to be taken into account in any future evaluations. The case study focused on an area close to Amersfoort that has a predicted potential for coalbed methane production. The study utilized 465 borehole descriptions from which isopach maps and geological cross-sections were constructed. Limited samples of borehole core provided lithological information from which a facies analyses was undertaken so as to establish the hydrodynamic origin of each facies types. The main lithofacies associated with the coal seams are mudstones, carbonaceous shales and fine- to coarse-grained sandstone. These data were combined with analyses from limited permeability data, petrographical data and proximate analyses for the Gus and Alfred seams. In addition to the sedimentary rocks, the role of dolerite intrusions was found to be significant as these occur as thick sills and dykes that occur below, within and above the coal seams. These may compartmentalize the seams into secondary targets within the study area. Thick sills overlying the coal zone also increase static loading and may be advantageous with respect to reducing the minimum depthbelow- surface requirements. Potential coalbed methane target areas are identified, although the entire study area is not suitable due to structural displacement of the coal seams, thinning of coal in places and devolatization caused by the dolerites.

Magister Scientiae - MSc / The waste products acid mine drainage formed during coal mining and fly ash from coal burning power generation, pose substantial environmental and economic problems for South Africa. Eskom has developed a remediation system employing alkaline fly ash to neutralize and precipitate heavy metals from toxic acidic acid mine drainage streams. The aim of this study was to assess the microbial diversity in and microbial impact on this remediation system. / South Africa

The energy demands by the industrial world are continuing to rise, while the rate of new oil discoveries is falling. Within the next 30 years, available petroleum supplies are likely to fail to meet the demand, and oil will no longer be able to serve as the world’s major energy source. Coal, being relatively abundant worldwide and potentially adaptable for use in existing plants that have been engineered for petroleum use, can serve as an inexpensive substitute for, or successor to, the more expensive oil fuels in use today. Graphitisable carbon is one of the high-value products from petroleum as its value lies partly in the nuclear industry. Making graphitisable isotropic carbon from well-purified coal is therefore a primary motivation for this study. However, its purity is far too low. Substantial purification is obtained by dissolving the organic part of coal in dimethylformamide with the addition of a little alkali. Results indicated that more than 90% of the organic part of a 10% ash flotation product dissolved in N, N dimethylformamide on addition of 10% NaOH. The bulk of the impurities are removed by centrifugation and the dissolved organic material is recovered by water precipitation. Subsequently, the ash level is lowered from 10% in the coal to < 1.60% in the coal extracts at a washing efficiency of 33 %. The addition of Na2S (the molar ratio of NaOH to Na2S was 1:1) lowered the ash level further to 0.70%. The coal extract solution obtained showed an absorbance of 1.00 with an organic content of 8%. However, addition of sodium sulphide to the extraction medium at 25 ± 1oC lowered the organic content to 5.6%. At high temperature of 90 ± 2oC, the organic content was further lowered to 2.6% with subsequent loss in colour. The coal extract obtained by water precipitation showed low C/H atomic ratio on the addition of S-2. Nucleophiles such as cyanide, thiosulphate made no substantial change to the hydrogen content nor the degree of extraction. On coking by step heating under nitrogen to 480oC at a rate of 10oC min-1 for 1h, then to 900oC with a soaking period of 2h, the coal extracts melt, then reorganise into a liquid crystal phase around 500oC, which then solidifies into a semi-coke on further heat treatment. The heat-treatment of the coal extracts produced 75% carbon yield. When polished specimens of the cokes were observed by reflectance microscopy, flow textures with domain sizes of a few to many microns were observed. Isotropic, poorly graphitising cokes showed little or no structure. Anisotropic cokes were produced when these domains of liquid crystal grew and coalesced. The cokes were found to be highly graphitisable. However, in the heat treated coal extracts prepared at high temperature, the liquid crystal domains were graphitisable but appeared not to have coalesced. Nevertheless, the random orientation of the domains allowed isotropic blocks to be formed with extremely low crystallinity. The precursors that form these liquid crystals are generally materials known to have a high aromatic carbon content. The precursors that form these liquid crystals are generally materials with a high purity and aromatic carbon content, and low in heteroatoms. Optical microscopy of the polished samples prepared at 90  2oC revealed surfaces with much less ordered coke, having smaller crystalline domains than the heat–treated coal extracts derived at room temperature. Essentially, isotropic graphites were obtained. Addition of S-2 produced an extensive flowing texture, and a highly crystalline domain cokes. The carbon yield lowered. The graphitisability of the carbon improved. The X-ray diffraction data on the graphitised carbon showed that the degree of graphitisation decreased in the following order: high S-2 coal extracts derived at room temperature (GSF-25RT) > high S-2 coal extracts derived at high temperature (GSF-25HT) and no S-2 coal extracts derived at room temperature (GSF-0RT) > no S-2 coal extracts derived at high temperature (GSF-0HT), corresponding to 79 > 75% and 67 > 25% respectively. The interlayer spacing (d002 -value) of the graphites follows the order GSF-25RT (3.37Å) < GSF- 25HT (3.38 Å) and GSF-0RT (3.38 Å) < GSF-0HT (3.42 Å). Subsequently, the Raman spectroscopy, consistent with the X-ray diffraction data, showed the ratio of the d-peak (degenerate) to g-peak (graphitic) in the order: GSF-0HT < GSF-0RT and GSF-25HT < GSF-25RT, corresponding to 1.26 <1.75 < and 6.7 < 7.0 respectively. Because the quality of the coke depends on the nature and quality of the starting material, addition of the carbon additives in the starting material prior heat-treatment affected the flow texture of the coke. The carbon black, which has a spherical shape, forms aggregates that disperse much more easily than the flat chains of aggregates of acetylene black. The difficulty in dispersing the carbon additives was, however, overcome by using a high-shear mixer. Analysis of the coal extracts revealed that the hydrogen content in the coal extracts decreased linearly on addition of the carbon additives, favoring dehydrogenative polymerisation. The addition of carbon additives in the coal extract solution produced an isotropic carbon on heat treatment. Optical microscopy of the resin-mounted cokes revealed decreasing size of the crystalline domain with increasing dosage of the carbon additives. The optimum amount of carbon additives required was found no to exceed 0.44%. Beyond this threshold, the anisotropy of the cokes could not be observed through the resolution of the optical microscope. In addition, the amounts of volatiles released were found to decrease with increasing dosage of the carbon additives. At low dosage of the carbon additives, the heat-treated coal extracts produced graphitisable isotropic carbon with low level of crystallinity. However, at high dosage of the carbon additives, the cokes did not graphitise. The temperature of graphitisation decreased from 2976 to 2952oC with increasing dosage of the carbon additives. The decreasing order of graphitisation was 69 > 61 > 62%, corresponding to 0.44 > 0.88 > 1.60 acetylene black. With the addition of carbon black, the decreasing order of graphitisation was 57.7 > 56.5 > 51.5%, corresponding to 0.44 > 0.88 > 1.60 wt % respectively. The interlayer spacing d002, increased in the same order, suggesting a shift towards a turbostratic and formation of a poorly graphitised, and turbostratic carbon. Raman spectroscopy revealed that the intensity ratio R of the g to the d peak decreased with increasing dosage of the carbon additive. Cokes produced from the coal extracts prepared at 25oC but without S-2 showed also a remarkable degree of flow texture. Its crystalline domain units were relatively small. The resin-mounted coke samples observed under an optical microscope (objective x 25) showed reduced flow texture with the addition of carbon black. The graphitisability of the resultant cokes also decreased on addition of carbon black. The optimum dosage observed for reducing the flow texture without reducing the crystallinity was found to be < 0.22%. Improved degree of graphitisation of the carbon was studied on addition of iron (lll) compounds. Iron (lll) compounds showed a promising improvement in the graphitisability of the carbon when added in small amounts. The intracellular hard carbon is converted to soft carbon, thereby improving the degree of graphitisation. The overall effect was a more isotropic graphitic carbon but the degree of graphitisation obtained was far too low: on addition of 1% and 3% (by wt) of iron (lll), the compounds were 21% and 27% respectively. Oxygen intrusion into the precursor’s coal material prior to heat treatment is thought to have inhibited the degree of graphitisation. Increasing the amounts of the iron (lll) compound and prohibiting the intrusion of oxygen during mixing could improve the graphitisability of carbon. However, the optimum amount to be used remains an important subject to be explored in future. / Thesis (PhD (Chemistry))--University of Pretoria, 2007. / Chemistry / unrestricted

The investigation of the geological history (i.e., stratigraphy and sedimentology) and the dynamics of coal depositional environments, in particular, the forces responsible for changes in the accommodation space (e.g., subsidence vs. sedimentation rates) in the Permian coal-bearing Karoo strata in the Central Kalahari Karoo Basin (Botswana) revealed new details about the depositional processes and environments. Detailed review of the temporal and spatial stratigraphic variation of the coal-bearing Ecca Group successions via the analysis of facies changes based on core descriptions, gamma logs, field observations and palaeo-current measurements, lead to the identification of two main informal stratigraphic units, namely the Basal and Upper Units. The Basal Unit is characterised by an upward-coarsening succession, and it is interpreted as a product of a progradational deltaic setting (i.e., regressive deltaic cycle). This is followed by five sequences of fining-upward successions of sandstones and siltstones in the Upper Unit, interpreted as deposits of distributary channels (the basal arenaceous member) capped by finer argillaceous sequences of the deltaic floodplains (the upper coal-bearing member). The Upper Unit thus is interpreted as a delta plain facies association which was formed during transgressive phases when conditions for coal-quality peat accumulation (e.g., high water table) were present and the available accommodation space was partly controlled by tectonic uplift (repeated?) at basin margins. Limited palaeo-current analysis indicates deposition by channels flowing from the east, south-east and north-east. The lack of good quality exposures hampers the reconstruction of the plan form of the channel patterns. However, the little available evidence indicates a high-energy fluvio-deltaic system with irregular discharge and a high proportion of bedload sediments. Coal-seam thickness in the upper coal-bearing member reflect the complex control of the geological processes associated with and following peat formation, such as differential compaction of the underlying lithology, and the erosive or protective nature of the immediately overlying lithology.

This thesis outlines a study carried out to understand the effects of coal dissolution variables. Several parameters that are thought to have a direct influence on the degree of coal dissolution in organic solvents were investigated by means of a series of experiments. The work done constitutes part of the research being carried out for the PBMR Company, whose aim is to synthesise nuclear-grade graphite from coal based materials. To enhance the efficiency of the process, it was necessary to gain a clear-cut understanding of the parameters that affect the process. The work carried in this project was divided into two sections. The first section involved the solubilisation of coal in polar aprotic organic solvents with the addition of a small amount of alkali. In this section as well, many parameters that influence the process were investigated. The second section involved the use of various analytical techniques to obtain information on the composition of coal extracts. The conclusions reached were as follows: <ul> <li>An alkali is required for the solubilisation of coal to occur in polar organic solvents. This also gives an overall high extraction percentage of ~ 92%. In pure dimethylformamide (DMF), the sodium hyroxide (NaOH) does not go into solution but on the addition of coal, the NaOH goes into solution.</li> The characteristic smell of the Refcoal solution confirms the presence of dimethylamine, although the titration results show otherwise. <ul> <li>The texture of the alkali used in the extraction affects the rate and degree of extraction. Finely ground alkali gives a faster dissolution rate, as well as a high extraction percentage.</li> <li>There is no hydrolysis of solvent during the extraction of coal.</li> <li>The concentration of the alkali used in the extraction process affects the degree to which coal can be extracted.</li> <li>The use of a strong alkali increases the rate at which coal can be dissolved in the solvent.</li> <li>Temperature does not affect the degree of extraction, as shown by the closeness of the extractions done at different temperatures. Also, external factors, such as oxidation and weathering of coal, have little effect on the extent of extraction.</li> <li>Coal characterization techniques provide information about the composition of coal extracts. The coals used in this process consisted of aliphatic and aromatic compounds. </li> / Dissertation (MSc (Chemistry))--University of Pretoria, 2007. / Chemistry / unrestricted

In this work the combustion characteristics of coal, charcoal, microalgae biomass and blends between these three components were evaluated by means of non-isothermal thermogravimetry. Blends between coal, charcoal and microalgae biomass were made according to the specifications of a D-optimal mixture design so as to be able to model interactions between the three components with maximum precision despite multiple constraints built into the design. These constraints specified that coal can have a minimum value of 70 mass percent in any blend, while microalgae can have a maximum value of 20 mass percent. While coal and charcoal were blended by mixing the two respective dry components, microalgae biomass was incorporated into the blends by first absorbing microalgae onto fine coal from concentrated slurry of the microalgae in water. The microalgae in these blends were therefore intimately associated with the coal. This approach differed substantially from the normal practice of preparing coal – biomass blends (which are usually dry-mixed as for coal – charcoal blends). Proximate analyses of the starting materials showed that the microalgae biomass has a significantly higher volatile matter: fixed carbon content than both coal and charcoal, which should improve the combustion of these materials by providing a more stable combustion flame. Analyses of the thermogravimetric data obtained showed that coal and charcoal have much simpler combustion profiles than microalgae biomass for which five different thermal events could be observed in the DTG combustion profile. Qualitative kinetic analyses showed that the combustion of coal and charcoal follows first-order kinetics, but for microalgae biomass combustion, the first two combustion stages appear to follow first-order kinetics. The TG and DTG profiles for coal, charcoal, microalgae and blends of these three components were used to derive values for the so-called comprehensive combustion property index (S-value), which provides a combined measure of the ease of ignition, rate of combustion, and burn-out temperature. The S-values so obtained were used as response variable for the construction of a response surface model in the experimental domain investigated. Following statistical validation of the response surface model, the model was used to predict an optimum S-value or a blend that would display optimum combustion behaviour. Two optimum blends were obtained from the optimisation process, one in which only charcoal is added to coal, and one in which only microalgae is added to coal. Adding both charcoal and microalgae produced an antagonistic effect compared to when only one of these are used. Qualitative kinetic analyses of the combustion data of blends indicate that blends of coal and charcoal combust in a manner similar to the individual components (hence following first-order kinetics), but blends of coal and microalgae follow more complex kinetics despite the fact that the combustion profile is visibly more simple compared to the combustion profile for microalgae alone.