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A two-dimensional constant heating rate thermoelastic model has been used to develop design and selection criteria for refractory components of linings of high-temperature furnaces and process vessels. The criteria are in the form of resistance to fracture initiation and resistance to damage parameters which account for the influence of thermal and mechanical properties, geometry, and temperature range, while distinguishing between the heating and cooling cases. The resistance to fracture initiation parameter ɸs is the maximum rate at which a shape can be heated or cooled through a specified temperature range without causing fracture. The damage resistance parameter Rd is expressed as the ratio of surface energy per unit area to the elastic strain energy available for crack propagation. Both parameters can be quickly estimated for arbitrary conditions with the aid of tabulated solutions for the maximum principal tensile stress and total strain energy Thermoelastic analyses were used to interpret published results of a variety of thermal shock experiments. Thermal conditions associated with water quenching, radiative furnace heating, gas burners, and controlled heating were simulated using appropriate analytical solutions. Finite element analysis was used to compute maximum principal tensile stresses and elastic strain energy. A simple procedure was developed to invert the stress solution and thereby determine the instant of fracture. Good agreement between thermoelastic predictions and published experimental results with regard to strength retained versus thermal shock relationships, location of fracture, and safe heating rates provided justification for a thermoelastic approach to the thermal shock. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Please read the abstract in the section, 00front of this document / Dissertation (MSc (Metallurgy))--University of Pretoria, 2004. / Materials Science and Metallurgical Engineering / MSc / unrestricted

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In this study, solidification and stabilization processes were evaluated for use as a treatment method for electric arc furnace dust. Specific objectives were (1) to develop a solidified material capable of meeting EPA requirements for heavy metal leaching, and (2) to develop a solidified material that could be used for construction. Results from the studies of the untreated electric arc furnace dust showed that the solubility of cadmium is controlled by the hydroxide species. Lead solubility is more complex because its solubility is controlled by a species other than hydroxide and therefore it is more difficult to predict. Studies also indicated that approximately 1.9% of the composition of the electric arc Furnace dust is made up of lead. This study demonstrated that solidification and. stabilization is a viable treatment process for electric arc. furnace dust. Success in treating the electric arc furnace dust by this method, however, depends upon such factors as the compressive strength of the solidified waste, the amount of electric arc furnace dust incorporated in the concrete, and the ability of the solidified waste to remain intact during the Toxicity Characteristic Leaching Procedure (TCLP). Based on these factors, approximately 165 lb dust/cu yd concrete was determined to be the upper limit on the amount of electric arc furnace dust that can be incorporated in such a system. Efforts to improve the quality of the concrete by the addition of a chelating agent was moderately successful; however, the addition of salts to speed the concrete set times was not successful. A model was developed which predicts the required compressive strength of the solidified dust based upon the amount of electric arc furnace dust that is incorporated in the concrete. The model effectively predicts, without performing the TCLP test, whether the solidified material will meet limits for heavy metal required by the EPA. / Master of Science

The heat transfer coefficient between a horizontal tube and a shallow fluidized bed of alumina particles (335-1261 micron) was measured, and the effects of the tube elevation (10-40 mm), static bed height (10-40 mm), and the design of the distributor were investigated. The cloud zone effect i.e. a sudden increase of the heat transfer coefficient when the tube was located right above the static bed height, has been verified as a feature of shallow bed systems; furthermore, the jet region has shown a dominant effect on the behavior of the shallow bed heat transfer. The results showed that the heat transfer coefficient increased monotonically with increasing air velocity when the tube was located in the jet region, and the heat transfer coefficient increased when a distributor which induced a deeper jet penetration was used. However, the erosion problem and the relatively high pressure drop across the distributor still need to be solved in further studies, so that the greatest economic value of a shallow bed can be achieved. / M. S.