The flow of fluids through porous materials is a subject of importance in the study of the gas emission in coal mines. Air is commonly used as the fluid medium in gas permeability tests. In this case, it is advisable to take into account the existence of gas slippage phenomena. The experimental results showed that the value of the observed permeability is always larger than the true permeability by 25 to 150 per cent. The geometrical shape of the specimen has no effect on the permeability value. Comparisons were made for cylindrical specimens of one inch, two inch, and four inch diameters versus the corresponding dimensions of the cube specimens. It has been found that the permeability value of coal increases with an increase in specimen size. The experimental results showed that specimen size of three inches in diameter can be considered as the representative size for coal permeability for the coal tested. / M.S.

As the nature of coal mInmg changes, to higher production associated with higher mechanization, the way in which mine safety is approached must also change. This situation was clearly shown in a very devastating coal mine fire in late 1984. In the absence of effective fire-fighting procedures and equipment the affected mine was quickly rendered helpless. Of particular concern with coal mine fires is the possibility of entering a fuel-rich state. In this state current practices have proven to be of little use in gaining control over the conflagration. Recent experiences with the application of water mist to industrial fires has shown that use of fog can be an efficacious agent in controlling large scale fires. The postulations of this phenomenon concern the ability of the water, as a fog, to get deeply within the fire structure. In this manner it works to remove the three legs of the fire triangle~ heat, oxygen, and fuel. The research contained in this thesis dwells in three associated areas. These are: the general theory of water mist application relative to current practices~ the design and construction of a fire tunnel for experimental work; and the results obtained from experiments with fuel-rich fires in the simulated coal mine entry. The results of this research are most encouraging, not only for the more devastating fuelrich fires, but also for application from the onset of fire fighting activities in the coal mine environment. / Master of Science

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

The majority of research studying the ecological impacts of the coal mining industry on freshwater systems has focused on abandoned-mined land, and the associated acid drainage and metals toxicity. Treated discharges from active mining and preparation facilities, however, can also impair lotic ecosystems through total dissolved solids (TDS) toxicity, caused primarily by the reagents used for pH modifications and the oxidation of reduced sulfur. Such impairment was best detected through application of (1) benthic macroinvertebrate surveys using metrics of biotic impairment such as relative Ephemeroptera abundance and Ephemeroptera-Plecoptera-Trichoptera (EPT) minus the tolerant caddisfly family Hydropsychidae (2) in situ growth of Corbicula fluminea during 96-d exposure and (3) laboratory testing using Ceriodaphnia dubia. Traditional metrics such as total taxa richness, EPT, diversity and biotic indices were not sensitive to elevated TDS levels. Further study using strength of evidence, regression analysis and manipulation of laboratory formulated media, indicated that the mine effluent was the primary causal agent of the observed biotic impairment, and its toxicity could be attributed to sodium/sulfate-dominated TDS, which is significantly ameliorated by water hardness. Finally, although testing with lentic cladocerans, such as Ceriodaphnia, is consistent, cost-effective and sensitive to TDS related toxicity, the ecological relevance and protective capability of such testing is questionable when assessing contaminant effects on sensitive macroinvertebrates indigenous to lotic systems. A more ecologically relevant laboratory bioassay using the mayfly, Isonychia bicolor, in simulated lotic microcosms provided more sensitive endpoints than Ceriodaphnia and Pimephales promelas. Although the heartiness of Isonychia in laboratory conditions is poorly understood relative to standardized test organisms, these results, along with potential toxic impacts from numerous sodium/sulfate-dominated wastewaters discharging into freshwater systems, may have important implications to future national pollution discharge and elimination system (NPDES) permit testing. Currently, however, strong recommendations can only be made using Ceriodaphnia endpoints. Potential acute toxicity to aquatic organisms in high hardness solution (~790 mg/L as CaCO₃) is possible where sodium/sulfate-dominated TDS levels exceed ~7000 uS/cm (5167 mg/L), with potential chronic toxicity occurring at ~3200 uS/cm (2342 mg/L). These endpoints were significantly reduced in solutions of lower hardness (88 mg/L as CaCO₃), with acute and chronic toxicity occurring at 5100 uS/cm (3754 mg/L) and ~2100 uS/cm (1523 mg/L), respectively. Point source discharges causing instream TDS concentrations to exceed these levels risk impairment to aquatic life. / Master of Science

Sulfur dioxide emissions, which are produced through the combustion of coal, are thought to be a leading contributor to acid rain. A number of postcombustion techniques for the reduction of sulfur dioxide emissions are being tested; however, the reduction in the pyritic sulfur content of coal through physical cleaning methods may be the most economically viable alternative to the S02 problem. In this investigation, the microbubble column flotation process (MCF), developed at VPI&SU, was tested as a means of reducing the pyritic sulfur content of several high-sulfur coals targeted by the u.S. Department of Energy. A wide variety of pyrite rejection schemes were tested including the use of pyrite depressants, dispersants and elevated pH conditions. The overall efficiency of the MCF process was characterized using a technique known as "release analysis". This technique was used to provide the optimum grade versus recovery relationship for a given coal and a given set of reagent conditions. It was also used as a means for evaluating the various schemes for rejecting coal pyrite. The results of this work indicate that the MCF process is capable of producing a separation very close to that generated by release analysis. The release analysis technique was also found to be an effective means of characterizing pyrite liberation and pyrite rejection for a given coal. In general, it was found that liberation was the most important factor in the rejection of pyrite, although elevated pH conditions seemed to provide improvements for some coals. / Master of Science

Traditionally, coal combustion residuals (CCRs) were disposed of with little engineering consideration. Initially, common practice was to use a wet-scrubbing system to cut down on emissions of fly ash from the combustion facilities, where the ash materials were sluiced to the disposal facility and allowed to sediment out, forming deep deposits of meta-stable ash. As the life of the disposal facility progressed, new phases of the impoundment were constructed, often using the upstream method. One such facility experienced a massive slope stability failure on December 22, 2008 in Kingston, Tennessee, releasing millions of cubic yards of impounded ash material into the Watts Bar reservoir and damaging surrounding property. This failure led to the call for new federal regulations on CCR disposal areas and led coal burning facilities to seek out geotechnical consultants to review and help in the future design of their disposal facilities. CCRs are not a natural soil, nor a material that many geotechnical engineers deal with on a regular basis, so this thesis focuses on compiling engineering characteristics of CCRs determined by different researchers, while also reviewing current engineering practice when dealing with CCR disposal facilities. Since the majority of coal-burning facilities used the sluicing method to dispose of CCRs at one point, many times it is desirable to construct new "dry-disposal" phases above the retired ash impoundments; since in-situ sampling of CCRs is difficult and likely produces highly disturbed samples, a sample reconstitution technique is also presented for use in triaxial testing of surface impounded CCRs. / Master of Science

Experiments were performed to determine a suitable binder material for silicon carbide-based ceramic filter. These experiments included exposure of 42% and 60% alumina, aluminosilicates to potassium and sodium containing environments for the purpose of determining the phases that would form and to determine concentration profiles. In addition, thermodynamic calculations were performed to predict the phases that would form when the alkali reacted with the aluminosilicate. The results of the thermodynamic calculations indicated that the alkali compounds will react at temperatures as low as 800°C. The exposure experiments verified this result. The phases that formed during the sodium vapor exposures and confirmed the thermodynamic calculations and were as follows: 1. sodium metasilicate and a solid solution of sodium aluminum silicates and carnegieite and for potassium vapor exposure. 2. potassium disilicate, kaliophilite-nepheline, potassium aluminate, and 5K₂O-5Al₂O₃-8SiO₂. Experiments also revealed that penetration depth by alkali compounds was restricted to a region near the surface of the material when the combination of temperature and sodium concentration alowed a melt to form. The results also indicated that the 42% alumina, aluminosilicate had superior resistance to alkali attack than the 60% alumina, aluminosilicate at temperatures below 1225°C. / Master of Science

Backfilling is a technique used to place material in the voids created by underground mining. This technique has been used extensively abroad to reduce surface subsidence, fire hazards, and temperatures in underground workings. It can also help to eliminate environmental problems caused by coal waste dumps, improve coal recovery, and improve mine ventilation. However, backfilling is an additional operation in the coal mining cycle that can reduce productivity and increase production costs. This thesis identifies the backfilling methods applicable for coal mines in southwest Virginia. Following identification of variables that can affect the selection of a backfilling method, a multi-attribute decision analysis technique is developed. This technique is applied to a mine model which is representative for the mining conditions in southwest Virginia. An evaluation of the two most Suitable backfilling methods using coal refuse as fill material is then made and compared to the surface disposal of coal refuse. / Master of Science

Lignite is a low grade of coal widely distributed throughout the world. A complete analysis of lignite has not been made, due to the difficulty encountered in the separation of the complex organic compounds bonded therein.

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