Thesis (Ph.D.)--Aberdeen University, 1989. / Title from web page (viewed on Mar. 4, 2010). Includes bibliographical references.

Thesis (Ph.D.) - University of Queensland, 2004. / Includes bibliography.

Presented as Fritsche's Thesis (Ph. D.)--University of Wisconsin--Madison, 1932. / Includes bibliographical references.

No description available.

Gasification is a flexible technology which is applied in industry for electricity generation, hydrogen production, steam raising and liquid fuels production. Furthermore, it can utilize one or more feedstocks such as coal, biomass, municipal waste and petroleum coke. This versatility, in addition to being adaptable to various emissions control technologies (including carbon capture) renders it an attractive option for years to come. One of the most common gasifier types is the entrained-flow slagging gasifier. The behaviour of inorganic fuel components in these gasifiers is still ill-understood even though it can be the determining factor in their design and operation. A literature review of inorganic matter transformation sub-models for entrained-flow slagging gasifiers is provided. Slag viscosity was identified as a critical property in the sub-models. Slag viscosity models are only applicable to a limited range of slag compositions and conditions, and their performance is not easily assessed. An artificial neural network model was developed to predict slag viscosity over a broad range of temperatures and slag compositions. Furthermore, a toolbox was developed to assist slag viscosity model users in the selection of the best model for given slag compositions and conditions, and to help users determine how well the best model will perform. The slag viscosities of coal, petroleum coke and coal/petroleum coke blends were measured in the temperature range of 1175-1650ºC. Interaction of vanadium-rich slags with various materials was investigated. The results from the first two parts of a three-part research program which involves fuel characterization, testing in a 1 MWth gasifier, and computational fluid dynamics (CFD) modeling for entrained-flow slagging gasification are presented. The end goal is to develop a CFD model which includes inorganic matter transformations. Fuel properties were determined with prioritization based on their application; screening of potential fuels, ensuring proper gasifier operation, gasifier design and/or CFD modeling. Using CanmetENERGY’s 1 MWth gasifier, five gasification tests were completed with the characterized coals. Solid samples from the refractory liners, in-situ gas sampling probe sheaths and impingers, the slag tap, the slag pot, quench discharge water and scrubber water were collected and characterized.

Different mechanisms are proposed in the literature to describe the formation and behaviour of inclusions during electroslag remelting: - dissolution in the liquid metal of the inclusions already present in the electrode and then renucleation in the freezing ingot. - total or partial dissolution in the slag. - exchange reactions between inclusions in the metal and the slag. - entrapment in the freezing ingot of pieces of slag skin or droplets of slag. The mechanism of dissolution of alumina inclusions in a 70/30 CaF₂/Al₂0₃ slag has been studied in detail. For this a new equilibrium diagram for the system CaF₂/Al₂0₃ has been proposed and the diffusion coefficient of alumina in the slag has been determined by the rotating disk system. In a 70/30 CaF₂/Al₂0₃ slag at 1518°C the diffusion coefficient was estimated as D = 8.5 10⁻⁹ m² sec⁻¹. Calculations of the extent of the dissolution of alumina particles in the slag predicted that big particles (800 μ) might dissolve only partially in the slag. Particles of this size were introduced artificially in electrodes, but after electroslag remelting a much larger number of relatively small (15 μ max) alumina, iron aluminates and iron oxide inclusions were found in the ingot. The same types of inclusions could also be observed in ingots obtained after remelting a Ferro Vac-E electrode. The presence of these inclusions cannot be explained by one the mechanisms proposed precedently (dissolution in the liquid metal and then renucleation or partial dissolution in the slag), but only by an electrolytic oxidation and electrolytic aluminum dissolution on the electrodes and then nucleation of deoxidation products in the freezing ingot. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A study involving in-plant measurements, laboratory analysis and mathematical modelling was conducted to elucidate the kinetics of the zinc slag fuming process. The traditional assumption has been that the process operates at thermodynamic equilibrium. The results of industrial measurements at five different companies has demonstrated that this approach is not correct. Chemical assays of the slag show carbon levels in the range of 0.1 - 1.0% and char particles have been extracted from slag samples. Tuyere back-pressure measurements revealed that the predominant mode of gas injection behavior is bubbling. This evidence indicates that a portion of the coal injected into the furnace is entrained in the slag. A model of the direct coal particle-slag reaction was developed and incorporated into an overall model of the slag bath. This model included the behavior of the water-jacketed wall, a treatment of coal combustion in the tuyere gas stream, and a model of the entrained coal residence time. Fitting of the data to eleven industrial fuming cycles showed that the fraction of coal entering the bath was consistently about 35%. About 50% of the coal is combusted in the tuyere gas stream and 10% passes through the bath unconsumed. Calculated oxygen utilization ranged from 70-95%, dependent on slag depth. The slag fuming process is therefore kinetically controlled. There are essentially two critical parameters: the fraction of coal entrained in the slag, and the rate of ferrous iron oxidation. The rate of ferric reduction balances ferric inputs to the bath by displacing previously reduced zinc from the entrained coal-slag reaction bubbles. Process efficiency can be increased therefore by increasing entrainment of coal in the bath, perhaps by the use of high pressure injection, and by reducing ferrous iron oxidation. The latter objective may be achieved by more complete combustion of tuyere coal or pre-combustion. A significant control advantage might be gained by separating these two functions to different sets of tuyeres. In continuous fuming operations the model would suggest that improved efficiencies could be obtained by using a more coarsely ground coal, higher fixed carbon coals, and operating at intermediate temperatures. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

No description available.

No description available.

Abstract A procedure is defined for commercializing slags arising as by-products of steelmaking, and this is used to develop certain products. The outcome of the present work comprised three products or groups of products: 1) slag-based binding agents, 2) a road structure improved by means of stabilization with such binding agents, and 3) a procedure for designing stabilized structures. The commercialization procedure was drawn up by examining the technical properties of the initial materials, excluding environmental acceptability and the mechanisms of their chemical reactions. The research proceeded in stages, of which the first was a reconsideration of the results presented in the author's licentiate thesis concerning factors affecting the stabilization of road construction aggregates with blast-furnace slag-based binding agents and their significance. This was followed by a series of experiments designed to test the validity of these results. At the third stage the selection of slag-based binding agents was extended to include LD steel slag products, while the final stage consisted of the implementation of a set of test structures and associated preliminary experiments and monitoring measurements. The binding properties of three blast-furnace slag products and three LD steel slag products, used separately or in various combinations, were examined in the course of this work, taking cement as a reference material. Materials were then eliminated as the research proceeded, either on account of their poor binding properties or on economic grounds. The final construction experiments were performed with three combinations: cement-activated granulated blast-furnace slag, LD steel slag-activated granulated blast-furnace slag and a mixture of ground granulated blast-furnace slag and cement. The actual novel product among the slag-based binding agents to be introduced here is LD steel slag-activated granulated blast-furnace slag, which was found to be similar in its technical properties to cement-activated granulated blast-furnace slag. Structural layers stabilized with these two binding agents showed very similar bearing capacities, although the former did not reach the same compression strengths at an age of 91 days. The reasons for these similarities lay in a larger amount of binding agent used when activated with LD steel slag and the greater thickness of the stabilized layer, factors which both tended to compensate for the poorer compression strength. The new information gained on the properties of cement-activated granulated blast-furnace slag and the mixture of ground granulated blast-furnace slag and cement opens up fresh opportunities for selecting binding agents and designing road structures. Formulae were developed here for predicting the uniaxial compression strength at 91 days, used as a stabilization criterion, from the value for a sample taken at 28 days, a technique which will speed up the assessment of stabilization results, especially when using slowly reacting slag-based binding agents.