Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1934. / The entire thesis text is included in file. Typescript. Title from title screen of thesis/dissertation PDF file (viewed June 2, 2010) Includes bibliographical references (p. 53-54).

Thesis (M.S.)--West Virginia University, 2005. / Title from document title page. Document formatted into pages; contains vii, 96 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 77-79).

Heat transfer tubes suffer erosion when immersed in fluidized beds. This has caused problems, especially in fluidized bed combustors. The mechanism of erosion for horizontal tubes in fluidized beds is not well understood. The purpose of this study was to investigate the erosion mechanism in fluidized beds and to investigate the influence of operating parameters and the mechanical properties of the particles and tube materials. Horizontal tube erosion tests were carried out in a room temperature three-dimensional fluidized bed with a cross-section of 216 mm by 203 mm and height of 1.52 m. Sample rings of ten different materials were mounted on a solid bar and were weighed before and after each test to determine the erosion rate. The parameters tested were particle size (0.30 to 1.51 mm), particle sphericity (0.84 to 1.0), particle density, particle hardness, superficial air velocity (0.88 to 2.52 m/s), tube diameter (15 mm to 32 mm), tube configuration and material mechanical properties. Two additional types of experiments were also conducted to help understand the mechanism of erosion. In one particles were dropped freely in an empty column to impact on test specimens at different velocities determined by the dropping distance, in order to investigate erosion due to solid particle impact under known conditions. In the other the particle movement was filmed in the vicinity of a horizontal tube in a two-dimensional fluidized bed in order to investigate the particle flow pattern around a tube. A small number of tests were also conducted at high temperatures. The erosion of a horizontal tube in fluidized beds was found to be caused mainly by the impact of solid particles on the lower surface. Erosion was found to be strongly dependent on the particle impact velocity, which is closely related to the void (bubble or slug) rise velocity. The void rise velocity, in turn, is determined by the mean void size which depends on the superficial air velocity, column size and other fluidizing conditions. Particle diameter also has a strong influence on erosion. The target material Young's modulus appears to be the major mechanical property which is closely related to the erosion rate caused by solid impact erosion. Of the materials tested, all non-ferrous metals suffer much more erosion than ferrous metals. Localized high particle velocities due to jets and at bends or near feed points can be extremely harmful. The mechanism of erosion caused by low velocity (< 6m/s) solid particle impacts appears to be different than that caused by high velocity (> 30m/s) impacts reported in the literature, although there are some similarities in trends. The erosion at low impact velocities appears to be mainly due to a surface fatigue process, which, instead of plastically deforming a small amount of target material for every impact, deforms the target materials in the elastic range and causes them to crack on or underneath the surface leading to removal of materials. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

This thesis project studied a number of aspects relating to the fluid, mechanics of circulating fluidised beds. Studies of the macrostructure of a 9.3 m high x .15 m dia. riser showed a strong dependence of one important macroscopic descriptor, the density profile, upon the geometry of the gas/solids exit and the location of the solids return. It was found that abrupt exits promoted inertial solids separation from the conveying gas which generated strong internal circulation patterns and high slip velocities. Microstructural studies, in support of the macrostructural investigation, and using a needle capacitance probe, showed how the radial density profile develops with height causing a gradual density decay. The structure, characterised by an "intermittency index," was strongly radially non-uniform at all locations in the lower regions of the column with pronounced aggregation or clustering at the highest densities. However, the cluster-like structures present at the base rapidly gave way to a more dilute core-annular type flow slightly further up the column. This radially non-uniform structure was used to explain a number of macroscopic phenomena. These included the effects of exit type, solids return location, secondary air addition and gas mixing. The results of the various studies, drawn together, allow fast fluidisation to be defined tentatively with respect to its relationships to choking, pneumatic transport, and other fluidisation regimes. Separate studies were performed to examine gas mixing and the transition to turbulent fluidisation. The gas residence time distribution was found to be substantially different from plug flow and could be characterised crudely by a two-zone model. The turbulent transition was found to be gradual, but nonetheless a transition, although a developed turbulent zone did not exist until well beyond transport conditions. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

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Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 1979. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Vita. / Bibliography: leaves 274-279. / Sc.D.

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The ironmaking blast furnace (BF) remains the most significant and important process for the production of liquid iron. For the achievement of stable furnace operation and good performance, mathematical modellings at different levels increasingly become a powerful tool in developing better understanding of this multiphase flow system, in particular the gas-solid flow. This thesis represents an effort in this area. A simplified and continuum-based mathematical model is proposed and tested to predict the BF gas-solid flow at a macroscopic level. The results show that the simple model is able to predict the general features of the solid flow, including the effects of gas and solid flowrates, and materials properties. The simplified model can be readily implemented in a full process model that needs to have a quick response to change for the purpose of control and optimization. To overcome the difficulties encountered in continuum modelling, i.e. determination of constitutive correlations, and particularly the description of the stagnant zone when related to BF, a discrete model based on the coupling approach of discrete element method (DEM) and computational fluid dynamics (CFD) is then employed to investigate the gas-solid flow in a model BF at a microscopic level. The results confirm the effects of variables such as gas flow rate, solid flow rate, particle properties, and model types. More importantly, such an approach can generate abundant microscopic information such as flow structure (particle velocity, porosity, coordination number) and force structure, which are of paramount importance to elucidate the gas-solid flow mechanisms, and develop a more comprehensive understanding of BF gas-solid flow, such as the formation mechanism of the stagnant zone. Further, the transient gas-solid flow phenomena, together with the considerations of cohesive zones and hearth liquid, can be predicted. Further, in order to develop understanding of thermal behaviour and elucidate the heat transfer mechanisms occurring in particle-fluid flow system, a new model is proposed by extending the DEM-CFD, and then tested in gas fluidization. The model considers the three heat transfer modes, and demonstrates its ability in investigating the heat transfer mechanisms, and offers an effective method to elucidate the mechanisms governing the heat transfer in particle-fluid systems at a particle scale. It is recommended to apply to the study of BF thermal behaviour.