This study describes tripper car operators’ exposure to coal tar pitch volatiles at an operation at Coal Distribution Steam Plant that involves the use of coal tar mix to feed as fuel the steam generating boilers. A cross-sectional task-based exposure assessment approached was used. The objectives of this study were to monitor tripper car operators’ exposures to coal tar pitch volatiles as benzene soluble fraction and to then compare the measured concentrations with the occupational exposure limit. The general aim of the study was to accumulate data about employee exposure to coal tar pitch volatiles in South African Petrochemical Refineries. A total of 56 samples was collected and analyzed for coal tar pitch volatiles – benzene soluble fraction. Of the 56 samples, 41 were personal samples collected on the breathing zones of the workers and 15 samples were field blank samples. The method used for the collection of the samples was the United States Department of Labor, Occupational Safety & Health Administration Method 58. In South Africa the available occupational exposure limit for coal tar pitch volatiles is the time weighted average occupational exposure limit – recommended limit for cyclohexane soluble fraction which is 0.14 mg/m3. For the evaluation of personal exposure to compare with the occupational exposure limit, the UK Health & Safety Executive Method for the Determination of Hazardous Substances (MDHS) 68 was adopted in the past to monitor workplace air. This method was since withdrawn by the Health & Safety Executive after research conducted by the Health & Safety Laboratory revealed that unacceptable variability were introduced into the method due to the small mass changes involved and the difficulty in accurately weighing the filters before and after the cyclohexane extraction. Due to the unavailability of a suitable and acceptable method to assess workers’ exposure to coal tar pitch volatiles – cyclohexane soluble fraction to compare to the South African occupational exposure limit, the Occupational Safety & Health Administration Method Number 58 was used during this study for the collection of the samples. This is a validated method. This method follows a similar approach as the MDHS 68 however benzene is used instead of cyclohexane during sample extraction. The Occupational Safety and Health Administration have the permissible exposure limit of 0.2 mg/m3 for coal tar pitch volatiles – benzene soluble fraction to use when assessing worker exposure. This limit was used during this study for assessing tripper car exposure to coal tar pitch volatiles. No coal tar pitch volatiles were detected on the samples collected during the study. The results revealed concentrations below detection limit of the test laboratory analytical method. The detection limit used thereof was 0.1 mg per sample. The tripper car operators were therefore exposed to coal tar pitch volatiles at concentrations that complied with the permissible exposure limit 0.2 mg/m3. The hypothesis of this study was that the tripper car operators at Coal Distribution Steam Plant are over exposed to coal tar pitch volatiles – benzene soluble fraction. This hypothesis is therefore rejected. Based on the results derived from this study it is recommended that further research studies be conducted specifically with focus on different methods of exposure assessment to workers exposed to coal tar pitch volatiles in South African Petrochemical Refinery Plants. - ii - Since the method used was limited to the particulate phase of the contaminant exposure, with the gaseous phase of exposure to coal tar pitch volatiles only looked at when the PEL is exceeded. A method that can measure both the gaseous and particulate phase of the contaminant must be investigated.

The aims of this research project were to identify and classify the binder-filler interfaces formed in carbon electrodes and to determine the effects of the interfacial quality on important electrode properties. The effects of raw materials and some fabrication process variables on interfacial characteristics and quality of laboratory produced test electrodes were also studied, and the development of binder-filler interfaces during the carbonisation process followed. Electrode quality was assessed by measurement of density, electrical resistivity and tensile strength. Pore structural data were also obtained by using a computerised image analysis system allied to an optical microscope. Interface quality data were obtained by examining etched surfaces in a scanning electron microscope and classifying the binder-filler interface observed into one of five categories. The category depending on the extent of contact between the binder and filler. Accordingly, test electrodes were produced from combinations of four filler carbons, comprising three grades of calcined petroleum coke and an electro-calcined anthracite, and four coal-tar binder pitches which varied in the type and quantity of insoluble matter content. Examination of these test electrodes showed that the nature of the filler carbon used had a dominant influence on the quality of the interface formed, as assessed by this technique. A combination of one filler carbon and one binder pitch was used to study the effects of some fabrication process variables. These were pitch content and, mixing time and temperature. Of these process variables, pitch content and mixing temperature were found to have the major effects on the binder-filler interface and electrode quality. Investigation of the development of the binder-filler interfaces during the carbonisation process showed three distinct zones of interface development and transformation. These zones were associated with three temperature dependent mechanisms; thermal stress relaxation between 200-350 degrees C, volatile gas evolution from coal-tar pitch decompositionb etween3 50-600 degrees C and stresses induced by thermal contraction of the binder phase between 600-1000 degrees C.

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

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

Motivation: The accurate and reliable measurement of the concentration of coal tar pitch volatiles (CTPVs) in ambient air has proved to be a challenge for occupational hygienists. The challenge must however be confronted due to, amongst others, the carcinogenic properties of some poly–aromatic hydrocarbons (PAHs) contained in CTPVs. Aim: To determine the feasibility of a thermal desorption (TD) technique based method as an alternative method to be used for the measurement of the concentration of CTPVs in ambient air by assessing it along criteria such as ease of use, cost, accuracy and precision by comparing it to NIOSH’s Method 5515 and OSHA’s Method 58 and to determine the level of exposure to CTPVs on the anode paste floor of an electric furnace, used for the smelting of platinum group metals (PGMs) concentrate. Methodology: To satisfy the research objective, two accepted methods the National Institute of Occupational Safety and Health’s (NIOSH) method 5515 and the Occupational Safety and Health Administration’s (OSHA) method 58 were used for the measurement of the concentration of CTPVs with a TD technique based method used as a third, alternative method. All three methods were used concurrently to measure the concentration of CTPVs in ambient air, at the anode paste floor of a platinum group metals (PGMs) concentrate smelter. Results and conclusions: The NIOSH method proved to be the most precise method while the TD technique based method proved to be the most accurate. The TD technique based method proved to measure the widest range of individual CTPVs and were able to measure the highest concentration of Benzo(a)pyrene, an individual CTPV that is classified as a Group 1 (carcinogenic to humans) chemical substance by the International Agency for Research on Cancer (IARC). The OSHA method measured on average almost four times less total CTPVs than either the NIOSH or the TD technique based method and failed to readily measure individual CTPVs with a molecular weight lower than that of Phenanthrene. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2012.

Motivation: The accurate and reliable measurement of the concentration of coal tar pitch volatiles (CTPVs) in ambient air has proved to be a challenge for occupational hygienists. The challenge must however be confronted due to, amongst others, the carcinogenic properties of some poly–aromatic hydrocarbons (PAHs) contained in CTPVs. Aim: To determine the feasibility of a thermal desorption (TD) technique based method as an alternative method to be used for the measurement of the concentration of CTPVs in ambient air by assessing it along criteria such as ease of use, cost, accuracy and precision by comparing it to NIOSH’s Method 5515 and OSHA’s Method 58 and to determine the level of exposure to CTPVs on the anode paste floor of an electric furnace, used for the smelting of platinum group metals (PGMs) concentrate. Methodology: To satisfy the research objective, two accepted methods the National Institute of Occupational Safety and Health’s (NIOSH) method 5515 and the Occupational Safety and Health Administration’s (OSHA) method 58 were used for the measurement of the concentration of CTPVs with a TD technique based method used as a third, alternative method. All three methods were used concurrently to measure the concentration of CTPVs in ambient air, at the anode paste floor of a platinum group metals (PGMs) concentrate smelter. Results and conclusions: The NIOSH method proved to be the most precise method while the TD technique based method proved to be the most accurate. The TD technique based method proved to measure the widest range of individual CTPVs and were able to measure the highest concentration of Benzo(a)pyrene, an individual CTPV that is classified as a Group 1 (carcinogenic to humans) chemical substance by the International Agency for Research on Cancer (IARC). The OSHA method measured on average almost four times less total CTPVs than either the NIOSH or the TD technique based method and failed to readily measure individual CTPVs with a molecular weight lower than that of Phenanthrene. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2012.