Dust is a well-known occupational hygiene challenge and has been throughout the years, especially in the coal mining industry. The hazards arising from coal dust will differ between geographical areas due to the unique characteristics of dust from the coal mining environment. It is therefore of upmost importance to identify these qualities or characteristics of coal dust in order to understand the potential hazards it may pose. It is also important to consider the presence of nanoparticles which until recently remained neglected due to the absence of methods to study them. Aim: The aim of this study was to collect significant quantities of airborne dust through static sampling to characterise the physical, morphological as well as elemental properties of inhalable and respirable dust produced at two South African underground and two opencast coal mines. Personal exposure quantification was therefore not the primary concern in this study. Method: Static dust sampling was done at two mining areas of the two opencast and underground coal mines using four Institute of Occupational Medicine (IOM) and four cyclone samplers per area at each mine. A condensation particle counter (CPC) was also used at the opencast areas. The opencast areas included blast hole drilling, drag line and power shovel operations. The underground areas included the continuous miner and roof bolter operations. Gravimetric analyses of the cyclone and IOM samples were done as well as scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis. Results: Mine A (opencast and underground) produces higher grade coal in comparison to mine B (opencast and underground). Gravimetric analysis indicated higher average inhalable (55.35 mg/m3) and respirable (2.13 mg/m3) concentrations of dust in the underground areas when compared to the opencast areas (34.73 mg/m3 and 0.33 mg/m3). Blast hole drilling operations indicated higher average inhalable and respirable dust concentrations (39.02 mg/m3 and 0.41 mg/m3) when compared to the drag line and power shovel operations (30.44 mg/m3 and 0.246 mg/m3). CPC results showed higher average concentrations of sub-micron particles at the blast hole drilling areas per cubic metre (63132 x 106) compared to the drag line and power shovel operations (38877 x 106). EDS analysis from the opencast areas indicated much higher concentrations of impurities (with lower concentrations of carbon – 33.33%) when compared to samples taken from the underground mining activities (65.41%). The EDS results from the opencast areas differed substantially. The highest concentrations of silica were found at the blast hole drilling areas. EDS results from the underground areas indicated that mine A has slightly higher concentrations of carbon (66.2%) with less impurities when compared to mine B (64.62%). The continuous miner operations showed a higher concentration of impurities when compared to the dust from the roof bolter. SEM results from the opencast areas revealed that the majority of particles are irregularly shaped and the presence of quartz and agglomerations are evident. SEM results from the underground areas were similar except that the roof bolter produced smaller sized particles when compared to the continuous miner. It also seemed that the areas with higher levels of impurities produced more sub-micron particles. Conclusions: It is possible to identify the majority of physical and elemental characteristics of coal dust by means of gravimetric analysis, particle counting, SEM and EDS. There were differences found, regarding the morphological; chemical and physical characteristics, between the different opencast and underground areas at mine A and mine B due to the type of mining activity and amount of overburden present. Silicosis, Pneumoconiosis and Chronic obstructive pulmonary disease are some of the possible health concerns. It has been seen that dust from higher grade coal mines contributed to more developed stages of these diseases. / MSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2015

Dust is a well-known occupational hygiene challenge and has been throughout the years, especially in the coal mining industry. The hazards arising from coal dust will differ between geographical areas due to the unique characteristics of dust from the coal mining environment. It is therefore of upmost importance to identify these qualities or characteristics of coal dust in order to understand the potential hazards it may pose. It is also important to consider the presence of nanoparticles which until recently remained neglected due to the absence of methods to study them. Aim: The aim of this study was to collect significant quantities of airborne dust through static sampling to characterise the physical, morphological as well as elemental properties of inhalable and respirable dust produced at two South African underground and two opencast coal mines. Personal exposure quantification was therefore not the primary concern in this study. Method: Static dust sampling was done at two mining areas of the two opencast and underground coal mines using four Institute of Occupational Medicine (IOM) and four cyclone samplers per area at each mine. A condensation particle counter (CPC) was also used at the opencast areas. The opencast areas included blast hole drilling, drag line and power shovel operations. The underground areas included the continuous miner and roof bolter operations. Gravimetric analyses of the cyclone and IOM samples were done as well as scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis. Results: Mine A (opencast and underground) produces higher grade coal in comparison to mine B (opencast and underground). Gravimetric analysis indicated higher average inhalable (55.35 mg/m3) and respirable (2.13 mg/m3) concentrations of dust in the underground areas when compared to the opencast areas (34.73 mg/m3 and 0.33 mg/m3). Blast hole drilling operations indicated higher average inhalable and respirable dust concentrations (39.02 mg/m3 and 0.41 mg/m3) when compared to the drag line and power shovel operations (30.44 mg/m3 and 0.246 mg/m3). CPC results showed higher average concentrations of sub-micron particles at the blast hole drilling areas per cubic metre (63132 x 106) compared to the drag line and power shovel operations (38877 x 106). EDS analysis from the opencast areas indicated much higher concentrations of impurities (with lower concentrations of carbon – 33.33%) when compared to samples taken from the underground mining activities (65.41%). The EDS results from the opencast areas differed substantially. The highest concentrations of silica were found at the blast hole drilling areas. EDS results from the underground areas indicated that mine A has slightly higher concentrations of carbon (66.2%) with less impurities when compared to mine B (64.62%). The continuous miner operations showed a higher concentration of impurities when compared to the dust from the roof bolter. SEM results from the opencast areas revealed that the majority of particles are irregularly shaped and the presence of quartz and agglomerations are evident. SEM results from the underground areas were similar except that the roof bolter produced smaller sized particles when compared to the continuous miner. It also seemed that the areas with higher levels of impurities produced more sub-micron particles. Conclusions: It is possible to identify the majority of physical and elemental characteristics of coal dust by means of gravimetric analysis, particle counting, SEM and EDS. There were differences found, regarding the morphological; chemical and physical characteristics, between the different opencast and underground areas at mine A and mine B due to the type of mining activity and amount of overburden present. Silicosis, Pneumoconiosis and Chronic obstructive pulmonary disease are some of the possible health concerns. It has been seen that dust from higher grade coal mines contributed to more developed stages of these diseases. / MSc (Occupational Hygiene), North-West University, Potchefstroom Campus, 2015

Land-based turbine engines are currently used to burn heavy fuel oil (HFO), which is a lower cost fuel. HFO contains inorganic material that forms deposits on turbine blades reducing output and efficiency. Magnesium based additives are used to inhibit vanadium pentoxide deposition and reduce the corrosive nature of the gas and deposits in the hot gas path of the gas turbine. The focus of this study was to determine particle morphology and elemental composition of ash when firing HFO in an atmospheric combustor at various fuel injector atomization pressures. Prior to firing, the HFO was washed with water to remove sodium and potassium. A commercially available magnesium based additive was used to inhibit the vanadium in the HFO. Fuel was injected using an air-blast atomizer at air blast atomization gage pressures of 117, 186, and 255 kPa. Ash was collected from three locations downstream of combustion: immediately following combustion (pre-cyclone), from a cyclone separator (cyclone), and finally from a position located after the cyclone separator (post-cyclone). A Philips XL30 Scanning Electron Microscope (SEM) provided images, weight percent of elements of the ash, and element maps. Images taken from the SEM clearly show two particle types: 1) hollow spherical particles, or cenospheres, and 2) submicron agglomerated spherical particles. The cenospheres contained high carbon concentrations and were found primarily in the cyclone and probe bag filter. Element maps show that cenospheres, regardless of size, predominately contain carbon, oxygen, and sulfur with lesser amounts of sodium, magnesium, aluminum, and silicon. Particles collected downstream of the cyclone were primarily sub-micron in size and inorganic in composition. It is postulated that the cenospheres are the result of incomplete combustion of fuel oil droplets while the submicron spheres are nucleated inorganic material that initially evaporated from the liquid droplets. Particle size analysis was performed for each sample location. As the injection pressure was increased; the pre-cyclone and cyclone locations had similar number mean diameters that would decrease with increasing pressure. The diameter of the post-cyclone location did not change significantly with increasing air atomization. While increasing atomization pressure decreased the carbon content of the ash at all measurement locations, the atomization had little influence on the inorganic composition of the particles. The fine condensed phase particles and the larger cenosphere particles both produced similar compositions of inorganic material.

No description available.