Nearly half of the electrical power produced in the United States is generated with coal. Coal power is inexpensive and reliable, but coal combustion releases harmful pollutants including NOx and SOx into the atmosphere if not controlled. CO2, a greenhouse gas, is also released during coal combustion and may contribute to global warming. A promising technology enabling carbon capture is oxy-coal combustion. During oxy-combustion, coal is burned in an atmosphere of O2 and recycled flue gas to eliminate nitrogen which makes up the majority of air-combustion flue gas. Oxy-combustion flue gas is mainly composed of CO2 and H2O. H2O can be condensed out of the gas, and the CO2 can then be captured and permanently stored relatively easily. The composition of the gas inside an oxy-fired boiler will be different due to the absence of nitrogen and the recycling of flue gas. Corrosive sulfur and chlorine gas species concentrations will be higher, and CO and NOx concentrations will be effected. An understanding of the differences in gas concentrations is critical to oxy-combustion boiler design. Four different pulverized coals were combusted in a reactor under staged and unstaged oxy-combustion conditions with warm recycled flue gas (420°F) to simulate conditions in an oxy-fired coal boiler. The gas composition was measured in the reducing and oxidizing zones for staged combustion, and in the same locations, 57 cm and 216 cm from the burner, for unstaged combustion. The results were compared to the results from similar staged air-combustion experiments using the same coals and burner. CO concentrations were higher for staged oxy-combustion compared to air-combustion, and the increase was more substantial for lower rank coals. H2S concentrations in the reducing regions were also higher, and the fraction of gas phase sulfur measured as H2S was higher for oxy-combustion. SO2 concentrations were 2.9 to 3.8 times as high as air-combustion concentrations. The measured conversion of coal sulfur to SO3 was lower for oxy-combustion, and ranged from 0.61% to 0.98%. The average fraction of coal sulfur measured in the gas phase was 84%, 80%, and 85% for staged oxy-combustion, unstaged oxy-combustion, and staged air-combustion respectively. HCl concentrations were 2.8 to 3.1 times higher in the staged oxy-combustion oxidizing zone, and a smaller fraction of coal chlorine was measured in the reducing zone. On average 70.8%, 79.5%, and 71.1% of the coal chlorine was measured as HCl for staged oxy-combustion, unstaged oxy-combustion, and staged air-combustion respectively. The fractions of coal chlorine and sulfur measured in the gas phase for staged combustion were not significantly affected by combustion media. Some staged oxy-combustion NO concentrations were lower than air-combustion concentrations while others were slightly higher, and NO emission rates were much lower due to recycling NO through the burner.

In the increasingly competitive coal market, it is becoming more important for coal operators to develop mathematical models for surface mining which can estimate mining costs before the actual mining begins. The problem becomes even more acute with the new reclamation laws, as they affect surface coal mining methods, productivity, and costs. This study presents a computer simulator for a mountaintop removal type of surface mining operation. It will permit users to compare the costs associated with different overburden handling and reclamation plans. It may be used to minimize productivity losses, and, perhaps, to increase productivity and consequently to reduce operating costs through design and implementation of modified mountain top removal methods. / M.S.

The conclusion of this investigation, based on field mapping and measured sections, is the Price Formation was deposited on a high-energy shoreline. Sediments for the shoreline were initially transported from a northern deltaic source. The Cloyd Conglomerate Member represents offshore barrier bars, while the Lower Price unit was deposited in a lagoon behind the bars. At the top of the Lower Price unit, the "marker bed" sandstone includes sedimentary features of marine and fluvial origin. This sandstone is interpreted as a delta-front sand, reworked from distributary mouth bars. The Langhorn and Merrimac coal seams were deposited in swamps formed across the sandstone. / Master of Science

Call number: LD2668 .T4 1979 U57 / Master of Science

Call number: LD2668 .T4 1984 M84 / Master of Science

Coal can be converted to different chemical products through processes such destructive distillation. The destructive distillation of coal yields coke as the main product with byproducts such as coal tar pitch (CTP). CTP has a wide range of applications, especially in the carbon-processing industries. Typical applications include the manufacture of anodes used in many electrochemical processes, as well as Söderberg electrodes used in different ferroalloy processes. Söderberg electrodes are made from the thermal treatment of Söderberg electrode paste. The Söderberg electrode paste is a mixture of CTP (binding material) and coke/calcined anthracite (filler). Söderberg electrodes are characterised by a baking isotherm temperature. This temperature is located in the baking zone of the Söderberg electrode system. In the baking zone, the liquid paste is transformed into a solid carbonaceous material. Knowing the baking isotherm temperature is essential as it will ensure the safe, profitable and continuous operation of submerged arc furnaces. Thermomechanical analysis (TMA) was used in this study to determine the baking isotherm temperature of CTP samples. The baking isotherm temperature for all samples was found to lie between 450 and 475 °C irrespective of the initial chemical and physical composition of the CTP. TMA was also used to measure the dimensional changes that take place in the binding material (CTP) at temperatures above the baking isotherm. The dimensional changes of 12 CTP samples when heated from room temperature up to a maximum of 1300 °C were measured. The results indicated that all CTP samples shrank by approximately 14% in the first heating and cooling cycle. The second and third heating and cooling cycles gave a small change in dimensions of approximately 2% for all samples. The significant change in dimensions observed for all CTP samples during the first TMA thermal treatment cycle was attributed to the structural rearrangement that takes place within the carbonaceous material. The structural ordering of all CTP samples thermally treated was evaluated by X-ray diffractometry (XRD). XRD is widely used in the determination of crystallinity/amorphousness of carbonaceous materials, interlayer distance (d-spacing), as well as the degree of ordering (DOG) in a given material. For comparison of structural ordering, XRD analysis was also performed on raw (as-received) CTPs, as well as CTPs thermally treated at 475 and 1300 °C. Prebaked electrode graphite was also analysed. From the XRD results, raw CTP was found to be amorphous with no significant ordering. The interlayer spacing (d002) for all raw CTP samples averaged 3.70 Å, compared to 3.37 Å for prebaked electrode graphite. CTPs thermally treated at 1300 °C had a d-spacing of 3.51 Å. The DOG of raw samples was found to be negative which was indicative of the amorphousness of the raw CTP. The DOG increased with an increase in thermal treatment temperature, as was seen from the DOG of CTPs thermally treated at 1300 °C, which was calculated to be approximately -81% for all 12 samples. The calculated DOG for prebaked electrode graphite was 81%. Prior to determining the baking isotherm temperature, as well as the changes in dimensions during thermal treatment, the chemical compositions of the 12 CTP samples were determined. In the chemical composition determination, fundamental properties such as softening point (SP), coking value (CV), toluene and quinoline insolubles (TI and QI, respectively) were evaluated. This was in addition to proximate and ultimate analysis. The information obtained from this diverse characterisation showed significant differences in the chemical composition of the 12 CTPs. By making use of multi-linear regression analysis (MLR), it was possible to predict or calculate less commonly determined characteristics (CV, TI and QI) from the more commonly obtained parameters (proximate and ultimate analysis parameters). It was found that MLR could be used successfully to calculate CV and TI, but less so for QI. Additional chemical composition of CTP was determined by analytical techniques such as Fourier Transform Infra-Red spectroscopy (FT-IR) and Nuclear Magnetic Resonance spectroscopy (NMR). Results from the FT-IR analysis showed that the spectra for all 12 raw CTPs were similar, with differences only being in the FT-IR band intensities. The differences in FT-IR band intensities were supported by NMR analysis data, which gave quantitative information on the different structural parameters found in all CTPs. The structural composition of CTPs changed during thermal treatment, as was shown by the FT-IR analysis performed on raw CTPs samples, CTPs thermally treated at 475, 700, 1000 and 1300 °C, as well as prebaked electrode graphite. / PhD (Chemistry), North-West University, Potchefstroom Campus, 2014

Mineral matter affect various coal properties as well as the yield and composition of products released during thermal processes. This necessitates investigation of the effect of the inherent minerals on the products derived during pyrolysis, as pyrolysis forms the basis of most coal utilisation processes. A real challenge in this research has been quantifying the changes seen and attributing these effects to specific minerals. Thus far it has been deemed impossible to predict product yields based on the mineral composition of the parent coal. Limited research regarding these aspects has been done on South African coal and the characterisation of pyrolysis products in previous studies was usually limited to one product phase. A novel approach was followed in this study and the challenges stated were effectively addressed. A vitrinite-rich South African coal from the Highveld coal field, was prepared to an undersize of 75 μm and divided into two fractions. HCl/HF acid washing reduced the ash yield from 14.0 wt% d.b. to 2.0 wt% d.b. (proximate analysis). Pyrolysis was carried out with the North-West University (NWU) Fischer Assay setup at 520, 750 and 900°C under N2 atmosphere and atmospheric pressure. The effect of acid washing and the addition of minerals on the derived pyrolysis products were evaluated. Acid washing led to lower water and tar yields, whilst the gas yields increased, and the char yields were unaffected. The higher gas yield can be related to increased porosity after mineral removal as revealed by Brunauer-Emmett-Teller (BET) CO2 adsorption surface area analysis of the derived chars. Gas chromatography (GC) analyses of the derived pyrolysis gases indicated that the acid washed coal fraction (AW TWD) derived gas contained higher yields of H2, CH4, CO2, C2H4, C2H6, C3H4, C3H6 and C4s when compared to the gas derived from the raw coal fraction (TWD). The CO yield from the TWD coal was higher at all final pyrolysis temperatures. Differences in gas yields were related to increased tar cracking as well as lower hydrogen transfer and de-hydrogenation of the acid washed chars. Analyses of the tar fraction by means of simulated distillation (Simdis), gas chromatography mass spectrometry (GC-MS) –flame ionization detection (–FID) and size exclusion chromatography with ultraviolet (SEC-UV) analyses, indicated that the AW TWD derived tars were more aromatic in nature, containing more heavier boiling point components, which increased with increasing final pyrolysis temperature. The chars were characterised by proximate, ultimate, X-ray diffraction (XRD), X-ray fluorescence (XRF), diffuse reflectance infrared Fourier-transform (DRIFT) and BET CO2 analyses. Addition of either 5 wt% calcite, dolomite, kaolinite, pyrite or quartz to the acid washed fraction (AW TWD) was done in order to determine the effect of these minerals on the pyrolysis products. These minerals were identified as the most prominent mineral phases in the Highveld coal used in this study, by XRD and quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) analyses. It was found that mineral activity decreased in the order calcite/dolomite>pyrite>kaolinite>>>quartz. Calcite and dolomite addition led to a decrease in tar yield, whilst the gas yields were increased. Markedly, increased water yields were also observed with the addition of calcite, dolomite and pyrite. Kaolinite addition led to increased tar, char and gas yields at 520°C, whilst the tar yield decreased at 750°C. Pyrite addition led to decreased tar and gas yields. Quartz addition had no noteworthy effect on pyrolysis yields and composition, except for a decrease in char yield at all final pyrolysis temperatures and an increased gas yield at 520°C. Regarding the composition of the pyrolysis products, the various minerals had adverse effects. Calcite and dolomite affected the composition of the gas, tar and char phases most significantly, showing definite catalytic activity. Tar producers should take note as presence of these minerals in the coal feedstock could have a significant effect on the tar yield and composition. Kaolinite and pyrite showed some catalytic activity under specific conditions. Model coal-mineral mixtures confirmed synergism between coal-mineral and mineral-mineral interactions. Although some correlation between the pyrolysis products derived from the model coal-mineral mixtures and that of TWD coal was observed, it was not possible to entirely mimic the behaviour of the coal prior to acid washing. Linear regression models were developed to predict the gas, tar and char yields (d.m.m.f.) with mineral composition and pyrolysis temperature as variables, resulting in R2 coefficients of 0.837, 0.785 and 0.846, respectively. Models for the prediction of H2, CO, CO2 and CH4 yields with mineral composition and pyrolysis temperature as variables resulting in R2 coefficients of 0.917, 0.702, 0.869 and 0.978, respectively. These models will serve as foundation for future work, and prove that it is feasible to develop models to predict pyrolysis yields based on mineral composition. Extending the study to coals of different rank can make the models universally applicable and deliver a valuable contribution in industry. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

The search for efficient and economical ways to beneficiate fine coal remains an active research area. Recent developments have shown that the reflux classifier can successfully be used on Australian coals, and based on that, a number of pilot plant investigations have been done in South Africa. While pilot scale units are usually used to test the applicability of a new technology on specific coals, a need exists to gather more fundamental data at a laboratory scale in order to save manpower, costs and time. This study has aimed at introducing a way to pre-test material prior to pilot plant trials in the design chain. The study shows that a laboratory water only reflux classifier can be used as a density fractionator, which accurately produces washability data for coal – this was also investigated by Callen et al. (2008). There is also a linear correlation between density cut-point and fluid velocity within the plates. Only when looking at the model proposed in Walton (2011:68), does it become clear that the relationship is indeed slightly curved. Many investigations from laboratory and pilot tests accept the linear relationship, and describe it as slightly curved due to the settling being in the intermediate settling regime (Iveson et al., 2014; Galvin & Lui, 2011). The separation procedures that produce two products – an overflow and underflow – compare well with fractionation results produced. Thus, fractionation results can generate washability data and predict batch separation operations. The laboratory reflux classifier setup is also dependent on particle size, where individual size ranges achieve e.p.m. values of 0.012 and 0.030, while the combined separation efficiency is 0.039. It was, however, found that the respective laboratory scale reflux classifier that was designed and built was not suitable for continuous operation. The vertical fluidisation section was not high enough to enable a steady fluidised bed. This was necessary for density separation within the bed and to produce a significant pressure differential. It is also recommended to obtain a PID controller. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015

Coal can be converted to different chemical products through processes such destructive distillation. The destructive distillation of coal yields coke as the main product with byproducts such as coal tar pitch (CTP). CTP has a wide range of applications, especially in the carbon-processing industries. Typical applications include the manufacture of anodes used in many electrochemical processes, as well as Söderberg electrodes used in different ferroalloy processes. Söderberg electrodes are made from the thermal treatment of Söderberg electrode paste. The Söderberg electrode paste is a mixture of CTP (binding material) and coke/calcined anthracite (filler). Söderberg electrodes are characterised by a baking isotherm temperature. This temperature is located in the baking zone of the Söderberg electrode system. In the baking zone, the liquid paste is transformed into a solid carbonaceous material. Knowing the baking isotherm temperature is essential as it will ensure the safe, profitable and continuous operation of submerged arc furnaces. Thermomechanical analysis (TMA) was used in this study to determine the baking isotherm temperature of CTP samples. The baking isotherm temperature for all samples was found to lie between 450 and 475 °C irrespective of the initial chemical and physical composition of the CTP. TMA was also used to measure the dimensional changes that take place in the binding material (CTP) at temperatures above the baking isotherm. The dimensional changes of 12 CTP samples when heated from room temperature up to a maximum of 1300 °C were measured. The results indicated that all CTP samples shrank by approximately 14% in the first heating and cooling cycle. The second and third heating and cooling cycles gave a small change in dimensions of approximately 2% for all samples. The significant change in dimensions observed for all CTP samples during the first TMA thermal treatment cycle was attributed to the structural rearrangement that takes place within the carbonaceous material. The structural ordering of all CTP samples thermally treated was evaluated by X-ray diffractometry (XRD). XRD is widely used in the determination of crystallinity/amorphousness of carbonaceous materials, interlayer distance (d-spacing), as well as the degree of ordering (DOG) in a given material. For comparison of structural ordering, XRD analysis was also performed on raw (as-received) CTPs, as well as CTPs thermally treated at 475 and 1300 °C. Prebaked electrode graphite was also analysed. From the XRD results, raw CTP was found to be amorphous with no significant ordering. The interlayer spacing (d002) for all raw CTP samples averaged 3.70 Å, compared to 3.37 Å for prebaked electrode graphite. CTPs thermally treated at 1300 °C had a d-spacing of 3.51 Å. The DOG of raw samples was found to be negative which was indicative of the amorphousness of the raw CTP. The DOG increased with an increase in thermal treatment temperature, as was seen from the DOG of CTPs thermally treated at 1300 °C, which was calculated to be approximately -81% for all 12 samples. The calculated DOG for prebaked electrode graphite was 81%. Prior to determining the baking isotherm temperature, as well as the changes in dimensions during thermal treatment, the chemical compositions of the 12 CTP samples were determined. In the chemical composition determination, fundamental properties such as softening point (SP), coking value (CV), toluene and quinoline insolubles (TI and QI, respectively) were evaluated. This was in addition to proximate and ultimate analysis. The information obtained from this diverse characterisation showed significant differences in the chemical composition of the 12 CTPs. By making use of multi-linear regression analysis (MLR), it was possible to predict or calculate less commonly determined characteristics (CV, TI and QI) from the more commonly obtained parameters (proximate and ultimate analysis parameters). It was found that MLR could be used successfully to calculate CV and TI, but less so for QI. Additional chemical composition of CTP was determined by analytical techniques such as Fourier Transform Infra-Red spectroscopy (FT-IR) and Nuclear Magnetic Resonance spectroscopy (NMR). Results from the FT-IR analysis showed that the spectra for all 12 raw CTPs were similar, with differences only being in the FT-IR band intensities. The differences in FT-IR band intensities were supported by NMR analysis data, which gave quantitative information on the different structural parameters found in all CTPs. The structural composition of CTPs changed during thermal treatment, as was shown by the FT-IR analysis performed on raw CTPs samples, CTPs thermally treated at 475, 700, 1000 and 1300 °C, as well as prebaked electrode graphite. / PhD (Chemistry), North-West University, Potchefstroom Campus, 2014

Mineral matter affect various coal properties as well as the yield and composition of products released during thermal processes. This necessitates investigation of the effect of the inherent minerals on the products derived during pyrolysis, as pyrolysis forms the basis of most coal utilisation processes. A real challenge in this research has been quantifying the changes seen and attributing these effects to specific minerals. Thus far it has been deemed impossible to predict product yields based on the mineral composition of the parent coal. Limited research regarding these aspects has been done on South African coal and the characterisation of pyrolysis products in previous studies was usually limited to one product phase. A novel approach was followed in this study and the challenges stated were effectively addressed. A vitrinite-rich South African coal from the Highveld coal field, was prepared to an undersize of 75 μm and divided into two fractions. HCl/HF acid washing reduced the ash yield from 14.0 wt% d.b. to 2.0 wt% d.b. (proximate analysis). Pyrolysis was carried out with the North-West University (NWU) Fischer Assay setup at 520, 750 and 900°C under N2 atmosphere and atmospheric pressure. The effect of acid washing and the addition of minerals on the derived pyrolysis products were evaluated. Acid washing led to lower water and tar yields, whilst the gas yields increased, and the char yields were unaffected. The higher gas yield can be related to increased porosity after mineral removal as revealed by Brunauer-Emmett-Teller (BET) CO2 adsorption surface area analysis of the derived chars. Gas chromatography (GC) analyses of the derived pyrolysis gases indicated that the acid washed coal fraction (AW TWD) derived gas contained higher yields of H2, CH4, CO2, C2H4, C2H6, C3H4, C3H6 and C4s when compared to the gas derived from the raw coal fraction (TWD). The CO yield from the TWD coal was higher at all final pyrolysis temperatures. Differences in gas yields were related to increased tar cracking as well as lower hydrogen transfer and de-hydrogenation of the acid washed chars. Analyses of the tar fraction by means of simulated distillation (Simdis), gas chromatography mass spectrometry (GC-MS) –flame ionization detection (–FID) and size exclusion chromatography with ultraviolet (SEC-UV) analyses, indicated that the AW TWD derived tars were more aromatic in nature, containing more heavier boiling point components, which increased with increasing final pyrolysis temperature. The chars were characterised by proximate, ultimate, X-ray diffraction (XRD), X-ray fluorescence (XRF), diffuse reflectance infrared Fourier-transform (DRIFT) and BET CO2 analyses. Addition of either 5 wt% calcite, dolomite, kaolinite, pyrite or quartz to the acid washed fraction (AW TWD) was done in order to determine the effect of these minerals on the pyrolysis products. These minerals were identified as the most prominent mineral phases in the Highveld coal used in this study, by XRD and quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) analyses. It was found that mineral activity decreased in the order calcite/dolomite>pyrite>kaolinite>>>quartz. Calcite and dolomite addition led to a decrease in tar yield, whilst the gas yields were increased. Markedly, increased water yields were also observed with the addition of calcite, dolomite and pyrite. Kaolinite addition led to increased tar, char and gas yields at 520°C, whilst the tar yield decreased at 750°C. Pyrite addition led to decreased tar and gas yields. Quartz addition had no noteworthy effect on pyrolysis yields and composition, except for a decrease in char yield at all final pyrolysis temperatures and an increased gas yield at 520°C. Regarding the composition of the pyrolysis products, the various minerals had adverse effects. Calcite and dolomite affected the composition of the gas, tar and char phases most significantly, showing definite catalytic activity. Tar producers should take note as presence of these minerals in the coal feedstock could have a significant effect on the tar yield and composition. Kaolinite and pyrite showed some catalytic activity under specific conditions. Model coal-mineral mixtures confirmed synergism between coal-mineral and mineral-mineral interactions. Although some correlation between the pyrolysis products derived from the model coal-mineral mixtures and that of TWD coal was observed, it was not possible to entirely mimic the behaviour of the coal prior to acid washing. Linear regression models were developed to predict the gas, tar and char yields (d.m.m.f.) with mineral composition and pyrolysis temperature as variables, resulting in R2 coefficients of 0.837, 0.785 and 0.846, respectively. Models for the prediction of H2, CO, CO2 and CH4 yields with mineral composition and pyrolysis temperature as variables resulting in R2 coefficients of 0.917, 0.702, 0.869 and 0.978, respectively. These models will serve as foundation for future work, and prove that it is feasible to develop models to predict pyrolysis yields based on mineral composition. Extending the study to coals of different rank can make the models universally applicable and deliver a valuable contribution in industry. / MIng (Chemical Engineering), North-West University, Potchefstroom Campus, 2015