A project report submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg in partial fulfilment of the requirements for the degree of Master of Science in Engineering Johannesburg, 1993 / Superfines of less than 200 micron are generated when mining coal. They have not been successfully beneficiated in the past and are not acceptable to the consumer. A processh as been developed whereby the superfines are beneficiated, briquetted without the use of binders and devolatilised to produce a premium smokeless briquette which will attract a premium price in the export market. [Abbreviated abstract. Open document to view full version] / MT2017

The vegetation of greenstone hills in the Kalgoorlie area of the Eastern Goldfields region of Western Australia was studied to identify the key environmental influences on community and species distribution. This information was needed to determine if plant communities of the hills could provide analogues for the rehabilitation of waste rock dumps that are produced as a consequence of open cut mining. The ridges, slopes and flats adjacent to the main slope were examined and the floristic data sorted into communities. Two structurally and floristically distinct alliances were identified, one dominated by eucalypt species and the other by Acacia quadrimarginea. The eucalypt woodland displayed a taller upper stratum and few groundlayer species and was the dominant vegetation of the flats at the base of the hills. The acacia community was a low woodland and is the dominant vegetation of the hill slopes. Both communities were dominant at an equal number of sites on the ridges of the hills. An investigation of the environmental variables found that edaphic, rather than topographic, factors were responsible for the community distribution on the hills. The eucalypt woodland showed a strong affinity to soils derived from calcrete, which had higher levels of electrical conductivity and lower exchangeable sodium percentages than the soils of the acacia low woodland. Under such conditions, the clay fraction of the soil remains in a more flocculated state allowing higher rates of water infiltration and hydraulic conductivity compared to the acacia soils. Soil nutrients were found to have a secondary influence on community distribution and had a greater effect on species distribution within alliances. A study of the seasonal variation in water content of the soils showed that more moisture is retained in the upper soil horizons in the acacia community than in the eucalypt community during the wetter part of the year, indicating the acacia soils had poorer infiltration properties than the eucalypt soils. The distribution of drought tolerant species such as A. quadrimarginea and Prostanthera incurvata was found to be correlated to soil moisture content of the dry season whilst no correlation was found for the eucalypts at any time of the year. Seasonal comparisons of leaf moisture content and xylem pressure potential showed that the eucalypts maintained their total leaf moisture content throughout the year whereas species such as A. quadrimarginea and Allocasuarina campestris recorded high levels of desiccation of their leaf tissue over the summer. The eucalypts also maintained a more consistent pre-dawn xylem pressure potential throughout the year than either A. quadrimarginea or the shrub species Dodonaea microzyga, indicating a greater degree of stomatal control and access to a more consistent soil water supply. The eucalypts require access to a greater soil volume than the acacias or shrubs in order to ensure sufficient water supplies for the maintenance of tissue moisture levels throughout the year. In this way, the eucalypts are able to effectively avoid the summer drought, whereas the acacias and shrubs are able to tolerate desiccation of their leaf tissues over this period. Investigations of the germination requirements and early seedling survival of prominent species from the greenstone hills indicated that fire may be a factor in the regeneration of most hills species. All studied species were either tolerant of or responded positively to the application of dry heat. In relation to seedling establishment on waste dumps, increasing the soil moisture content of waste dump soils increased the germination rate of most species but did not result in greater seedling survival at the end of the first summer. The provision of microsites which encouraged root development and provided protection for the young seedlings was found to be more important in reducing mortality rates in the first year than increasing the total germination. The study emphasized the importance of physical soil factors and the soil moisture regime in the distribution of eucalypt and acacia communities on the greenstone hills. A species’ response to drought stress strongly influences its ability to compete for soil water on different soil types. The eucalypts studied in this project dominated on soils where there is better recharge of subsoil water reserves which can be accessed over the summer period to maintain tissue water levels. Acacias are tolerant of tissue desiccation and will compete successfully on shallower soils and where hydraulic conductivity is poor. Although the project was valuable in identifying water relations as the main control on community distribution on the hills, waste dumps are not strictly analogues of intact greenstone hills due to the differences in rock type and profile formation. Electrical conductivity levels are also higher due to extraction processes. However, the environmental relationships of the different species show that the more drought tolerant species such as Allocasuarina campestris, Acacia quadrimarginea and understorey species associated with them, may be suitable species to form the basis of vegetation reinstatement on waste dumps in the Kalgoorlie region.

Thesis (M.L.(Prof.))--University of Pretoria, 2004. / Includes summary. Includes bibliographical references.

M.Sc. (Geography) / Coal mined in South Africa for the competitive international market, has to be selected to meet the many quality specifications of customers. This upgrading is done by washing the coal in a heavy medium separation plant. Marketable coal, discard and slurry are produced from this washing. Discard consists mainly of poor quality coal, carbonaceous shale and waste rock. Iron pyrite (FeS2) occurs in all of the above in higher concentrations than in the marketable coal. Both the carbonaceous materials and pyrites generate heat when oxidizing. If this oxidation is not arrested at an early stage on a discard dump and the temperature of the dump increases above BOoC, spontaneous combustion is quite likely. The South African Council for Scientific and Industrial Research (CSIR) has estimated that smouldering discard dumps in the Eastern Transvaal highveld region contribute approximately 400 000 tons of S02 per annum to the atmospheric pollution in that area. As a result, significant localized acid rain occurs, Louw (1990). The oxidation of iron pyrites to sulphuric acid, and the oxidation of other trace elements, is accelerated under the high temperature conditions generated by spontaneous combustion. Leaching of these oxidation products results in local groundwater and surface water contamination. This study describes different disposal technique and pilot study aimed at minimising the oxidation within the dumps. Slurry, which consists of discard and/or coal of less than 1 mm in diameter is co-deposited with discard in sequential layers of approximately 200 mm thick. This has resulted in reducing the permeability, porosity and air and water exchange within the dump. This in turn has led to a reduction in spontaneous combustion, pollution and costs. A visual increase in stability of the discard dumps, moisture content and operational ease of placement were experienced. The saleable value of the dump as a low value heat source is also preserved.

This paper provides a risk assessment of pertinent toxic contaminants in the tailings of the Iron King Mine using a model of aeolian transport fated in human alveolar lung. Here, we studied particulate matter of tailings that are 10 microns (𝜇𝑚) or less in diameter (𝑃𝑀₁₀) because these is most hazardous fraction. We used in-vitro bioaccessibility and in-vivo Microtox® data to determine the relationships between chronic inhalation of these tailings. Our data suggest that arsenic and zinc are the two principle drivers for toxicity of the Iron King Mine’s PM₁₀ tailings and that arsenic will solubilize in human alveolar biofluids at the expense of other noteworthy elemental contaminants in the tailings. The principle contaminant of concern for chronic exposure is arsenic, due to its increased bioaccessibility over time. Our data show that synthetic lung fluid (SLF) mitigates the toxic effects of arsenic, despite its increase in bioaccessibility over time. Therefore, we suggest a buffering mechanism of phosphate competition with arsenate to explain this mitigation of toxicity in SLF. We conclude that public health risk of chronic inhalation of IKM PM₁₀ tailings may be less severe than would otherwise be suggested by high concentrations of toxic contamination in the tailings impoundment.

Coarse coal refuse is difficult to reclaim due to high potential acidity and coarse fragment content, low water holding capacity, low fertility, and other problems. Little is known about coal refuse properties, particularly as they relate to revegetation potential. This study was undertaken to determine the physical and chemical properties of composite samples from 27 coal waste piles of varying age. Selected physical and chemical properties varied widely across this sample set. The mean coarse fragment (>2mm) content of these materials was 60%. The average texture of the fine (<2mm) fraction was a sandy loam with 15% clay. The mean water retention difference, between 0.03 MPa and 1.5 MPa of soil moisture tension, on a whole sample basis was 0.08 g water/g refuse. The pH values varied from 8.3 to 3.0, and the older piles generally had lower pH values than the more recent piles. The saturated paste electrical conductivity (EC) was higher in the younger coal waste materials. Total elemental analysis revealed that Si, Al, Fe, and K were the most abundant elements in these materials. The mineralogy of three selected samples was found to be dominated by quartz in the sand and silt fraction and mica in the clay fraction. The physical factor most limiting to plant growth was found to be low water holding capacity. Low pH was found to be the chemical factor most limiting to plant survival. These findings indicate that some refuse piles may be suitable for direct seeding, but many will require heavy lime and/or organic treatments. / Master of Science

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A research report submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Science. Johannesburg, South Africa, 2015. / Unable to load abstract

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, for the Degree of Master of Science. / storage and waste dumps from coal mining tend to spontaneously combust. This is mainly as a result of the oxidation process which is accelerated by the availability of oxygen and the exothermic nature of the oxidation process. In cases of poor ventilation the heat accumulation within the bed is thought to lead to the spontaneous combustion of coal. The work in this dissertation aims to investigate the change in oxygen concentration in a bed of coal and also measure the rate of oxidation (oxygen absorption) in a closed reactor under isothermal conditions. Drying rate of coal under nitrogen was also looked into. An analysis of the oxygen concentration profile in a three metre 20 cm ID plastic column filled up with coal has been carried out. As the coal ages (becomes oxidised) its reactivity towards oxygen decreases and changes in the oxygen concentration profile are noticed. Experiments have been carried out up to 8 months and from the results obtained, a simple pseudo-steady-state model has been developed to describe the diffusion of oxygen into a reacting coal bed. The findings could prove useful in trying to find a solution to coal and waste dump fire control. The second experiment is a simple isothermal oxygen absorption experiment in which the rate of absorption of oxygen on a given coal sample is measured at different initial concentrations of oxygen. The initial concentration of oxygen is varied over a fairly wide range in order to determine the dependence of the rate of oxidation on the oxygen concentration. The rate- limiting step in low temperature oxidation of coal is found to be the absorption of oxygen. Moisture also plays a role in coal oxidation. Drying experiments were also carried out so as to quantify and investigate the rate of loss of moisture. Models have been developed which try to explain the mechanisms involved in the drying process. The modelling suggest that the bound water model is more appropriate to the type of behaviour exhibited during the drying process / Andrew Chakane 2018

A dissertation submitted to the Faculty of Engineering, University of the Witwatersrand, Johannesburg, for the Degree of Master of Science. / Storage and waste dumps from coal mining tend to spontaneously combust. This is mainly as a result of the oxidation process which is accelerated by the availability of oxygen and the exothermic nature of the oxidation process. In cases of poor ventilation the heat accumulation within the bed is thought to lead to the spontaneous combustion of coal. The work in this dissertation aims to investigate the change in oxygen concentration in a bed of coal and also measure the rate of oxidation (oxygen absorption) in a closed reactor under isothermal conditions. Drying rate of coal under nitrogen was also looked into. An analysis of the oxygen concentration profile in a three metre 20 cm ID plastic column filled up with coal has been carried out. As the coal ages (becomes oxidised) its reactivity towards oxygen decreases and changes in the oxygen concentration profile are noticed. Experiments have been carried out up to 8 months and from the results obtained, a simple pseudo-steady-state model has been developed to describe the diffusion of oxygen into a reacting coal bed. The findings could prove useful in trying to find a solution to coal and waste dump fire control. The second experiment is a simple isothermal oxygen absorption experiment in which the rate of absorption of oxygen on a given coal sample is measured at different initial concentrations of oxygen. The initial concentration of oxygen is varied over a fairly wide range in order to determine the dependence of the rate of oxidation on the oxygen concentration. The rate- limiting step in low temperature oxidation of coal is found to be the absorption of oxygen. Moisture also plays a role in coal oxidation. Drying experiments were also carried out so as to quantify and investigate the rate of loss of moisture. Models have been developed which try to explain tile mechanisms involved in the drying process. The modelling suggest that the bound water model is more appropriate to the type of behaviour exhibited during the drying process. / Andrew Chakane 2018