Thesis (M.F.A.)--University of Iowa, 1965. / eContent provider-neutral record in process. Description based on print version record.

Thesis (M.F.A.)--University of Iowa, 1965.

Thesis (M.F.A.)--West Virginia University, 1999. / Title from document title page. Document formatted into pages; contains iii, 28 p. : ill. Includes abstract. Includes bibliographical references (p. 19).

Thesis (M.F.A.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains iv, 50 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 50).

The elutriation of fine materials from the solids bed in rotary kilns was studied in a laboratory scale steel cylinder of 0.2m in diameter and 2.4m in length. The cylinder was charged with a batch of fine alumina particles having a mean size of 64jum and the average elutriation rate measured at different air flow rates, rotational speeds and percentage of solids fill. All measurements were done at room temperature. To show the effect of fines concentration and segregation in the solids bed, a binary mixture of fine alumina and coarse Ottawa sand was used. Local dust concentration profiles were measured in the freeboard through a probe equipped with a filter. Design factors such as the geometry of the kiln exit dams, were found to influence dust carryover into the cleaning equipment by accelerating the flowing gas and or obstructing the flow of solids in the gas phase. Wall roughness and imperfections also affected elutriation especially at higher rotational speeds by exposing trapped fines directly into the flowing gas. Dust concentration measurements revealed that most of the solids in the gas phase travelled in saltation within about 2 cm above the bed surface. With the wall effect eliminated by an insert, increasing the rotational speed was found to exhibit a negative effect on the elutriation rate. Dust concentrations were higher in the gas phase above the lower edge of the rotating bed than at the upper edge or midpoint. However, while the concentration above the rest of the bed remained fairly constant with increased rotational speeds, at the lower edge of the bed it decreased. Banding segregation occurred in the beds composed of fine and coarse particles. Elutriation increased with the number of fine bands formed which was proportional to the concentration of fines. The location of the bands from the exit also influenced elutriation. Saltating particles returning to the bed close to the exit had a better chance of ejecting other particles if they landed on fine bands than they would if they landed on coarse bands. Gas velocity exhibited the strongest influence on elutriation rate. A correlation of experimental results showed a velocity dependence of U⁶ regardless of initial fines concentration in the bed. An entrainment mechanism has been formulated based on the collision of saltating particles on the solids bed. Subsequently, a simple mathematical model was developed to describe the influence of the operating variables on elutriation. The model predictions were verified with the experimental data and the scanty data in the literature. The model requires knowledge of the saltation height and the threshold shear stress for particle movement. Model predictions for typical industrial kilns are presented. The predictions are in fairly good agreement with values reported in a survey of industrial kiln operations made prior to the experimental program, given that the effect of kiln internals was not accounted for in the model. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Two modes of transverse solids motion, slumping and rolling, in rotary kiln operation have been experimentally characterized and mathematically modelled in this study. Other modes of bed behaviour encountered in rotary cylinders; slipping, cascading, cataracting and centrifuging have been formulated mathematically. The models have been verified using experimental observations reported in the literature. An experimental study of those conditions under which the bed changed from slumping to rolling was undertaken and the characteristics of these modes of motion quantified using different types of solids in three horizontal rotary cylinders and a small pilot kiln. A Bed-Behaviour Diagram which is a plot of bed depth versus rotational speed was developed to delineate the various areas of dominance of slumping and rolling and it was shown using this Diagram that bed behaviour observations made on batch cylinders were representative of solids motion in a continuous kiln operation, the effects of bed depth, particle size, particle shape and cylinder diameter on the position of the slumping-rolling boundary were also experimentally investigated. The quantitative characterization of slumping and rolling indicated that a new interpretation of the change in bed motion from slumping to rolling was required. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

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Thesis--University of Missouri, School of Mines and Metallurgy, 1908. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed November 18, 2008)

At the time of publication of this thesis little if any reliable technical data was available on the design, construct ion and operation of gas fired pottery kilns. A few publications have some information but for the most part very little information on the proportional relationships of the various' aspects of gas kiln designs are available. If one was to use only the information available in previous publications, inefficient, unsafe and illegally built kilns could easily be manufactured. Students, teachers and various public institutions are finding it necessary to design, build and operate gas kilns to fulfill the education of their students or fully explain the traditional methods of combustion firing and its unique results. It becomes more apparent that guidelines are necessary so that an efficient, safe and inexpensive kiln can be built and utilized without hampering the usefulness of a variety of designs available. This search for information about kiln design and construction had two main directions, the author consulted authorities having jurisdiction over gas kilns in British Columbia and Alberta and secondly he built and tested kilns using the data collected. These two sources of information were compared in relevant locations to publications available up to publication time. For the most part the investigation into kiln operation comes from informal instruction from a number of successful kiln builders and operators and provincial gas inspectors. It has been the researcher's finding that there is a very strong indication that the parameters given are a reliable and useful guide to safe, efficient and pollution controlled kiln design. The main parts of kiln design seem to be dimensional and dynamically interrelated and the parameters of design have shown a very high improvement in efficiency and pollution control which are important benefits. The dynamics of kiln design are only preliminary and broad in this thesis. Much more could be done with closer testing using more elaborate equipment and controls and with the guidelines used from this paper and further investigation even further improvements in design parameters may improve the efficiency and safety of future kilns. This thesis is designed to serve as a handbook which is the result of applied research. The thesis is set out in three parts. A brief essay establishing a rational for having a gas kiln, the model for designing a gas fired pottery kiln, and lastly examples of research and kiln firing logs from kilns designed using the model. Methods of construction, brick laying application of insulation and arch construction are not covered in this paper as they are well covered in the Olsen and Rhodes books. (see bibliography) / Education, Faculty of / Graduate

The overall heat-transfer mechanism within a direct-fired rotary kiln has been examined theoretically. To accomplish this task, the work has been divided into three parts: (1) the characterization of radiative heat transfer within the freeboard area; (2) the overall heat transfer mechanism in the absence of freeboard flames; and, (3) the overall heat transfer mechanism in the presence of freeboard flames. The radiative heat transfer between a nongray freeboard gas and the interior surface of a rotary kiln has been studied by evaluating the fundamental radiative exchange integrals using numerical methods. Direct gas-to-surface exchange, reflection of the gas radiation by the kiln wall, and kiln wall-to-solids exchange have been considered. Graphical representations of the results have been developed which facilitate the determination of the gas mean beamlength and the total heat flux to the wall and to the solids. These charts can be used to account for both kiln size and solids fill ratio as well as composition and temperature of the gas. Calculations using these charts and an equimolal CO₂-h₂O mixture at 1110 K indicate that gas-to-surface exchange is a very localized phenomenon. Radiation to a surface element from gas more than half a kiln in diameter away is quite small and, as a result, even large axial gas temperature gradients have a negligible effect on total heat flux. Results are also presented which show that the radiant energy either reflected or emitted by a surface element is limited to regions less than 0.75 kiln diameters away. The radiative exchange integrals have been used, together with a modified reflection method, to develop a model for the net heat flux to the solids and to the kiln wall from a nongray gas. This model is compared to a simple resistive network/gray-gas model and it is shown that substantial errors may be incurred by the use of the simple models. To examine the overall heat-transfer mechanism in the absence of freeboard flames a mathematical model has been developed to determine the temperature distribution in the wall of a rotary kiln. The model, which incorporates a detailed formulation of the radiative and convective heat-transfer coefficients in a kiln, has been employed to examine the effect of different kiln variables on both the regenerative and the overall heat transfer to the solids. The variables include rotational speed, per cent loading, temperature of gas and solids, emissivity of wall and solids, convective heat-transfer coefficients at the exposed and covered wall, and thermal diffusivity of the wall. The model shows that the regenerative heat flow is most important in the cold end of a rotary kiln, but that generally the temperature distribution and heat flows are largely independent of these variables. Owing to this insensitivity it has been possible to simplify the model with the aid of a resistive analog. Calculations are presented indicating that both the shell loss and total heat flow to the bed may be estimated within 5 per cent using this simplified model. Finally, to examine the overall heat-transfer mechanism in the presence of freeboard flames a mathematical model has been developed to determine both the temperature and heat flux distributions within the flame zone of a rotary kiln. The model, which is based on the one-dimensional furnace approximation, has been employed to examine the effects of fuel type, firing rate, primary air, oxygen enrichment and secondary air temperature on the flame temperature, solids heat flux shell losses, and overall flame length. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate