A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfilment of the requirements for the degree of Master of Science in Engineering. Johannesburg 2016 / The quantity and particle size distribution of pulverised coal supplied to combustion equipment downstream of coal pulverising plants are critical to achieving safe, reliable and efficient combustion. These two key performance indicators are largely dependent on the mechanical condition of the pulveriser. This study aimed to address the shortfalls associated with conventional time-based monitoring techniques by developing a comprehensive online pulveriser condition monitoring philosophy. A steady-state Mill Mass and Energy Balance (MMEB) model was developed from first principles for a commercial-scale coal pulveriser to predict the raw coal mass flow rate through the pulveriser. The MMEB model proved to be consistently accurate, predicting the coal mass flow rates to within 5 % of experimental data. The model proved to be dependent on several pulveriser process variables, some of which are not measured on a continuous basis. Therefore, the model can only function effectively on an industrial scale if it is supplemented with the necessary experiments to quantify unmeasured variables. Moreover, a Computational Fluid Dynamic (CFD) model based on the physical geometry of a coal pulveriser used in the power generation industry was developed to predict the static pressure drop across major internal components of the pulveriser as a function of the air flow through the pulveriser. Validation of the CFD model was assessed through the intensity of the correlation demonstrated between the experimentally determined and numerically calculated static pressure profiles. In this regard, an overall incongruity of less than 5 % was achieved. Candidate damage scenarios were simulated to assess the viability of employing the static pressure measurements as a means of detecting changes in mechanical pulveriser condition. Application of the validated pulveriser CFD model proved to be highly advantageous in identifying worn pulveriser components through statistical analysis of the static pressure drop measured across specific components, thereby demonstrating a significant benefit for industrial application. / MT2016

The objective of this work is to optimize high-power low-frequency sonication (US) pretreatment of sludge, and especially to investigate for the first time possible improvements by higher pressure and audible frequency. After a preliminary examination of regular process conditions (sludge conditioning, sludge type, prior alkalization, temperature control, etc), effects of US parameters (power -PUS, intensity -IUS, specific energy input -ES, frequency -FS, etc.) and of hydrostatic pressure (Ph) were specifically looked into, separately and in combination, first under cooling at constant temperature (28°C), then under the progressive temperature rise provoked by sonication. First, it was confirmed that specific energy input (ES) plays a key role in sludge US disintegration (i.e. solubilisation of organic matter) and that temperature rise during adiabatic-like sonication is beneficial through additional effects of thermal hydrolysis and cavitation. At a given ES value, low FS (12 kHz vs. 20 kHz) and high PUS enhance soluble chemical oxygen demand (SCOD) due to more violent cavitation, while hydrostatic pressure gives rise to an optimum value due to its opposite effects on cavitation threshold and intensity. One major result is that optimal pressure depends on IUS (P¬US) as well as temperature profile, but not on ES, FS, nor sludge type. Setting the other parameters at the most favorable conditions expected, i.e. 12 kHz, 360 W , 28 gTS/L, and adiabatic conditions, final optimization was achieved by searching for this pressure optimum and examining sequential procedure to avoid too high temperature dampening cavitation intensity and damaging the transducer. Such conditions with sequential mode and Ph of 3.25 bar being selected succeeded in achieving very high SCOD, but only marginally improved subsequent methanization yield.

In this study, we developed and standardized a sanding method to evaluate the emission of airborne particles from products that contain carbon nanotubes (CNTs) under different conditions, including three types of sandpaper and three sanding disc speed. We also characterized the emission of the airborne particles from one neat epoxy test sample, four CNTs-incorporating test samples with different CNTs loading, and two commercial products. The total number concentration, respirable mass concentration, and particle size number/mass distribution of the emitted particles were calculated and compared, followed by an electron microscopy (EM) analysis. These data suggest that the sanding process can produce substantial quantities of airborne particles. Also, the emission of airborne particles was associated with different test conditions. EM analysis of the airborne particle samples showed embedded CNTs protruding from the outer surface, which was different from CNTs-incorporating bulk material. Our study suggests a potential generation of particles during the life cycle event of sanding. Further studies should be carried out to investigate the potential human health hazard in other life cycle events.

<p>One important driving force in nanotechnology today is the change which can be made in the properties of a material when the dimensions of its individual building blocks are decreased below approximately 100 nm. Such small building blocks, typically nanoparticles, may induce new and unique properties compared to those of the corresponding bulk material. The challenge in nanotechnology is to make nanoparticles with a discrete particle size within the range 1-10 nm. It is also important to develop appropriate assembly methodologies in order to construct devices composed of such small building blocks.</p><p>This thesis reports iron nanoparticle synthesis using laser-assisted photolysis of ferrocene. The particles were protected against oxidation by a carbon shell formed in situ during their growth. By varying the experimental conditions such as fluence, repetition rate and laser beam area, particles could be synthesized in the size range 1 to 100 nm. Their size was measured using a differential mobility analyser (DMA), transmission electron microscopy (TEM) and X-ray diffraction (XRD). DMA was also used successfully to size-select particles to facilitate the deposition of monodisperse nanoparticle films.</p><p>A theoretical "residence time approach (RTA)" model was developed to relate particle volume to the laser parameters used. The growth of these particles was studied in situ using optical emission spectroscopy; the results were compared with those from quantum mechanical calculations. The particles were characterised ex situ by TEM, convergent beam electron diffraction, XRD, X-ray photoelectron spectroscopy and Raman spectroscopy. Results from the TEM investigations revealed that the carbon shell was graphitic close to the iron core, while the outer part of the carbon shell was amorphous, indicating different growth mechanisms. Both bcc and fcc iron particles were observed. </p>

Summary: A process is under investigation for the manufacture of dicalcium phosphate by the hydrolosis of concentrated superphosphate containing recycled monocalcium phosphate. The hydrolysis also results in the formation of an aqueous solution of monocalcium phosphate and free phosphoric acid. The phases are separated, followed by washing and drying of the solid dicalcium phosphate. The wash water is used in the hydrolyzer. The solution is returned to the superphosphate production step, where phosphate rock and additional phosphoric acid are added, and where water is evaporated to form the solid superphosphate. Pilot plant results have indicated that filtration rates vary widely under almost identical mixing conditions, presumably due to variations in particle size ranges. It was thought worthwhile, therefore, to study the effects of different mixing variables on the relative particle sizes as indicated by the settling rates of the mixture.

One important driving force in nanotechnology today is the change which can be made in the properties of a material when the dimensions of its individual building blocks are decreased below approximately 100 nm. Such small building blocks, typically nanoparticles, may induce new and unique properties compared to those of the corresponding bulk material. The challenge in nanotechnology is to make nanoparticles with a discrete particle size within the range 1-10 nm. It is also important to develop appropriate assembly methodologies in order to construct devices composed of such small building blocks. This thesis reports iron nanoparticle synthesis using laser-assisted photolysis of ferrocene. The particles were protected against oxidation by a carbon shell formed in situ during their growth. By varying the experimental conditions such as fluence, repetition rate and laser beam area, particles could be synthesized in the size range 1 to 100 nm. Their size was measured using a differential mobility analyser (DMA), transmission electron microscopy (TEM) and X-ray diffraction (XRD). DMA was also used successfully to size-select particles to facilitate the deposition of monodisperse nanoparticle films. A theoretical "residence time approach (RTA)" model was developed to relate particle volume to the laser parameters used. The growth of these particles was studied in situ using optical emission spectroscopy; the results were compared with those from quantum mechanical calculations. The particles were characterised ex situ by TEM, convergent beam electron diffraction, XRD, X-ray photoelectron spectroscopy and Raman spectroscopy. Results from the TEM investigations revealed that the carbon shell was graphitic close to the iron core, while the outer part of the carbon shell was amorphous, indicating different growth mechanisms. Both bcc and fcc iron particles were observed.

This thesis dissertation assessed workers who work in poultry barns and their occupational environment in relation to the type of bird housing in which they were exposed (cage-housed birds (CH) or floor-housed birds (FH)) and examined the environmental variables including dust and endotoxin and potential relationships to respiratory symptoms of workers. <p>A cross sectional study was undertaken to assess the environmental exposure levels and respiratory health effects of workers who worked in CH and FH poultry operations. The respiratory results suggested an asthma-like syndrome in these workers. Workers who worked in CH facilities reported greater current and chronic respiratory symptoms and significantly greater current and chronic phlegm as compared to workers from FH facilities. Workers from CH poultry facilities were exposed to greater endotoxin load than workers from FH facilities, but workers from FH operations were exposed to greater levels of total dust. It was found that endotoxin load (EU/mg) was a significant predictor of chronic phlegm for all poultry workers.<p>The effects on dust and endotoxin measurements when utilizing a Marple impactor with greased or ungreased impaction surfaces when sampling in an agricultural environment were unknown, and the potential for effects was tested. There were no significant differences in the aerosol mass median aerodynamic diameters between the greased and ungreased Marple impactors. Endotoxin analysis results appeared to be influenced by impaction grease particularly when very low amounts of endotoxin were present. <p>Size fractioning the dust and endotoxin using Marple impactors in CH and FH poultry operations showed that endotoxin load (EU/mg) was significantly higher in the respirable fraction of area samples in CH poultry operations as compared to FH operations. There were no differences in endotoxin load in the non-respirable size fractions for area samples between CH and FH operations. FH poultry operations had significantly greater dust mass and dust concentration in both respirable and non-respirable fractions for FH operations. There was significantly greater endotoxin load (EU/mg) in the 3.5-6.0 micron size fraction for the CH poultry operations as compared to the FH operations.

This thesis dissertation assessed workers who work in poultry barns and their occupational environment in relation to the type of bird housing in which they were exposed (cage-housed birds (CH) or floor-housed birds (FH)) and examined the environmental variables including dust and endotoxin and potential relationships to respiratory symptoms of workers. <p>A cross sectional study was undertaken to assess the environmental exposure levels and respiratory health effects of workers who worked in CH and FH poultry operations. The respiratory results suggested an asthma-like syndrome in these workers. Workers who worked in CH facilities reported greater current and chronic respiratory symptoms and significantly greater current and chronic phlegm as compared to workers from FH facilities. Workers from CH poultry facilities were exposed to greater endotoxin load than workers from FH facilities, but workers from FH operations were exposed to greater levels of total dust. It was found that endotoxin load (EU/mg) was a significant predictor of chronic phlegm for all poultry workers.<p>The effects on dust and endotoxin measurements when utilizing a Marple impactor with greased or ungreased impaction surfaces when sampling in an agricultural environment were unknown, and the potential for effects was tested. There were no significant differences in the aerosol mass median aerodynamic diameters between the greased and ungreased Marple impactors. Endotoxin analysis results appeared to be influenced by impaction grease particularly when very low amounts of endotoxin were present. <p>Size fractioning the dust and endotoxin using Marple impactors in CH and FH poultry operations showed that endotoxin load (EU/mg) was significantly higher in the respirable fraction of area samples in CH poultry operations as compared to FH operations. There were no differences in endotoxin load in the non-respirable size fractions for area samples between CH and FH operations. FH poultry operations had significantly greater dust mass and dust concentration in both respirable and non-respirable fractions for FH operations. There was significantly greater endotoxin load (EU/mg) in the 3.5-6.0 micron size fraction for the CH poultry operations as compared to the FH operations.

The objectives of this study are to investigate the biodiversity in different unit of treatment systems, and to detect the function in a salt water type of constructed wetland. We investigated the benthic invertebrate community in different stage from 2010 July to 2011 May, while the parameters of TKN, NH3-N, organic nitrogen, TP, TOC and particle size were measured in the sediments of each sampling site at the same time in the wetland system. The results show that concentrations of organic matter and nutrients in the sediments were increased with time monthly. In May of 2010, the concentration of NH3-N were found the highest one(ANOVA, p<0.05). The particle size in sampling site 1 were the highest (ANOVA, p<0.05), while in November of 2010 all sampling sites were found exhibiting significantly different with other months (ANOVA, p<0.05). Further more, for the diversity of benthic invertebrate, we found that the parameter of the temperature was strongly negatively related to the species diversity, species abundance and species evenness, respectively (r=-387[H¡¦]¡F-533[d]¡F-438[J¡¦] ). The species diversity was increased with organic nitrogen concentrations in the sediments (r=0.492[TKN]¡F0.408[NH3-N]¡F0.493[org-N]), and were negatively related to the parameters of DO and particle size(r=-0.402[Particle size]¡F-0.287[DO] ). In addition, PCA shows that the parameters of particle size¡Borg-N¡BNH3-N¡BTKN and TOC were all important factors. Generally, it was concluded that the constructed systems, which is functioned of wetland was wastewater treatment mainly, exhibit no significant function in biodiversity.

Grinding of clinker is the last and most energy-consuming stage of the cement manufacturing process, drawing on average 40% of the total energy required to produce one ton of cement. During this stage, the clinker particles are substantially reduced in size to generate a certain level of fineness as it has a direct influence on such performance characteristics of the final product as rate of hydration, water demand, strength development, and other. The grinding objectives tying together the energy and fineness requirements were formulated based on a review of the state of the art of clinker grinding and numerical simulation employing the Markov chain theory. The literature survey revealed that not only the specific surface of the final product, but also the shape of its particle size distribution (PSD) is responsible for the cement performance characteristics. While it is feasible to engineer the desired PSD in the laboratory, the process-specific recommendations on how to generate the desired PSD in the industrial mill are not available. Based on a population balance principle and stochastic representation of the particle movement within the grinding system, the Markov chain model for the circuit consisting of a tube ball mill and a high efficiency separator was introduced through the matrices of grinding and classification. The grinding matrix was calculated using the selection and breakage functions, whereas the classification matrix was defined from the Tromp curve of the separator. The results of field experiments carried out at a pilot cement plant were used to identify the model's parameters. The retrospective process data pertaining to the operation of the pilot grinding circuit was employed to validate the model and define the process constraints. Through numerical simulation, the relationships between the controlled (fresh feed rate; separator cut size) and observed (fineness characteristics of cement; production rate; specific energy consumption) parameters of the circuit were defined. The analysis of the simulation results allowed formulation of the process control procedures with the objectives of decreasing the specific energy consumption of the mill, maintaining the targeted specific surface area of the final product, and governing the shape of its PSD.