The effect of utilization of pulse flours with coarse and fine particle size milled from green lentils, yellow peas, navy beans, and pinto beans in pita bread and pan bread was studied. Composites containing 25, 50, 75, and 100% pulse flours were studied for pita baking, and 10, 15, and 25% for pan bread baking. Addition of the pulse flours produced pitas with the pockets, but they were smaller in diameter and firmer in texture than the wheat control. Supplemented pan bread had lower specific loaf volume and firmer crumb with coarser grain. The recommended tolerance levels of pulse flour addition were 25% for pita bread and 10-15% for pan bread depending on the pulse flour and particle size. It appears that navy beans and pinto beans are more suitable for baking applications using composite flours than lentils and yellow peas, and coarse flours produced breads with improved quality compared to fine flours.

Background: Tailings dam workers are exposed to tailings dust that has a potential health risk due to the element contents in the dust. The extent of exposure of tailings dam workers is unknown. Consequently, the elements, level of exposure, the potential adverse effects to health, compliance to legislative requirements and the efficiency of the current control measures were investigated. Design and Method: During the trials, 69 personal dust samples were collected during three full production shifts from tailings dam workers in three different tailings dam environments. The field filters were weighed to calculate the total dust concentrations. Bulk samples and field filters were analysed using the 32-element and particle size distribution scans. The between-dam, between-days and between-group variances were determined to assess the changes in exposure levels. Results: The tailings dam workers were not overexposed to tailings dust. Mean exposures were below the OEL for PNOC, measuring 0,124 mg/m3 (TD 1) 0,366 mg/m3 (TD 2) and 2,956 mg/m3 (TD 3). Three outliers in the data were present in TD 3 and exceeded the action level for PNOC. A major part of the particle size distribution consisted of inhalable sizes (>I0 μm). Cyclone tailings dams have smaller particle sizes than spigot tailings dams, though 85% of the particles in all tailings dams were larger than 10 μm. Some elements identified in the dust have potential respiratory health effects. No significant differences existed between the three tailings dams regarding tailings dust concentrations (p=0,527 on 5% significant level and p=0,292 on 10% significant level). There was, however, a significant difference on a 5% significant level between the days (p=0,003 and p=0,006). The workers on the cyclone tailings dams had smaller exposures than workers on the spigot tailings dams, and the pipeline labourers were more exposed than the mudguards. The tailings dams did comply with legislative control measures. However, washing facilities for the cleaning of overalls due to elements in the dust, such as nickel, chromium and manganese need to be considered. Workers need to be educated in work practices and procedures, personal hygiene and symptoms that can be experienced after exposure. Engineering control measures such as water sprayers covering the entire tailings dam, the use of fixed or temporary windscreens in the area where work is done and covering of the roads on the tailings dam with gravel or water spray can be considered as dust suppressant controls. Conclusion: The study met the issues set out in chapter 1, hypotheses were rejected and accepted and future studies were suggested. / Thesis (M.Sc. (Occupational Hygiene))--North-West University, Potchefstroom Campus, 2007.

The effect of utilization of pulse flours with coarse and fine particle size milled from green lentils, yellow peas, navy beans, and pinto beans in pita bread and pan bread was studied. Composites containing 25, 50, 75, and 100% pulse flours were studied for pita baking, and 10, 15, and 25% for pan bread baking. Addition of the pulse flours produced pitas with the pockets, but they were smaller in diameter and firmer in texture than the wheat control. Supplemented pan bread had lower specific loaf volume and firmer crumb with coarser grain. The recommended tolerance levels of pulse flour addition were 25% for pita bread and 10-15% for pan bread depending on the pulse flour and particle size. It appears that navy beans and pinto beans are more suitable for baking applications using composite flours than lentils and yellow peas, and coarse flours produced breads with improved quality compared to fine flours.

ABSTRACT A study is carried out on the production of aluminum foams via powder processing. The study deals mainly with the effect of TiH2 particle size on the process of foaming. Mainly two TiH2 particle sizes were used / namely 27,5 &amp / #61549 / m and 8,5 &amp / #61549 / m. Foaming experiments were carried out at temperatures between 675oC &ndash / 840oC. The viscosity of the system is adjusted by controlled addition of Al2O3. The study shows that choice of foaming agent size is influential in the foaming process. With the use of fine foaming agent, temperatures in excess of 800oC would be required for successful foaming. The study further showed that the relation between foaming and viscosity was also dependent on the particle size. Viscosity of 2.3 mPa.s was found to be a limiting value for successful foaming with fine foaming agent. This value appears to increase with increasing particle size. An analysis is presented with regard to temperature dependence of foaming which takes into account the effect of particle size.

Athabasca asphaltenes were characterized using small-angle X-ray scattering (SAXS) with synchrotron radiation. Two methods were used to separate asphaltenes from Athabasca bitumen. Conventional chemical separation by precipitation with n-pentane, and physical separation realized by passing bitumen through a zirconia membrane with a 20 nm average pore size. The Athabasca permeates and chemically separated samples were dispersed in 1-methylnaphtalene and n-dodecane, with temperature and asphaltene concentration ranges of 50-310 C and 1-8 wt. %, respectively. Two approaches were also taken in the analysis of the SAXS emissions. A model-independent approach provided radii of gyration and scattering coefficients. A model-dependent fit provided size distributions for asphaltenes aggregates assuming that they are dense and spherical. Physically and chemically separated asphaltenes showed significant differences in nominal size and structure, and their structural properties exhibited different temperature dependencies. The results challenge the merits of using chemically separated asphaltene properties as a basis for asphaltene property prediction in crude oil/bitumen.

The addition of coarse particles to a flocculating fine particle slurry increases the Bingham yield stress of the resulting mixture, which can drastically alter the laminar-to-turbulent transition velocity. The objective of this study is to quantify the effect of coarse particle size and volume concentration on mixture rheology. Fine particle (kaolin) mixtures of 10% to 22% (by volume) were prepared, to which sand particles were added to provide a coarse solid concentration of 5% to 20% (by volume). Sand particles of two different sizes – 90 and 190 microns – were added and these kaolin-sand-water mixtures tested with a concentric cylinder viscometer. At higher total solids concentrations, the Bingham yield stress of the bimodal mixture can increase by as much as 80% over that of a kaolin-only slurry. Coarse particle diameter had little effect. This study demonstrates that the use of existing correlations should be eschewed. System-specific high-quality measurements are necessary. / Chemical Engineering

Filtration performance of mineral concentrate is mainly controlled by solid particle size and surface hydrophobicity. Filtration of coarser particles with more hydrophobic surfaces produces better filtration performance characterized by higher filtration rate (U) and lower final moisture content (FMC) in the final cake. Some filtration aids could improve filtration performance by flocculating solid particles and enhancing surface hydrophobicity. For the mineral concentrate used in this study, many filtration aids tested could only improve either U or FMC: one type was effective in improving U, and another type was effective in improving FMC. The combination of the two types of filtration aids at certain dosages could achieve better filtration performance than the optimum performance achieved by each individual filtration aid. Based on the experimental results, the working mechanism of filtration aids behind the filtration behavior was explored to deepen the understanding of the chemical-enhanced filtration of Cu/Ni concentrate. / Chemical Engineering

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 4 uppsatser.