Of all coke properties the influence of the catalytic mineral matter on reactivity of metallurgical cokes is least understood. There is limited information about the form of minerals in the metallurgical cokes and no information about their relative concentration. A comprehensive study was undertaken for characterisation of mineral matter in coke (qualitative and quantitative), which enabled quantification of the effect of catalytic minerals on the reaction rate, and establishment of the effect of gasification on the mineral phases. Also, the relative importance of coke properties on the gasification reaction rate was determined. The reactivity experiments were performed at approximately 900??C using 100% CO2 under chemically controlled conditions. The mineralogical composition of the investigated cokes was found to vary greatly as did the levels of catalytic mineral phases. These were identified to be metallic iron, iron sulfides and iron oxides. The gasification reaction rate at the initial stages was strongly influenced by the content of catalytic mineral phases and also by the particle size of the catalytic mineral matter. The reaction rate increased as the contact surface between catalyst and carbon matrix increased. Catalytic mineral phases showed a strong influence on the reaction rate at early stages of reaction. But their influence diminished during gasification. At later stages of reaction the influence of micropore surface area became more important. The influence of the catalytic mineral phases diminished during gasification because the catalyst was inactivated to some degree and the contact surface between the catalyst and carbon matrix diminished due to the strong gasification of the carbon around the catalyst particles. The partial inactivation of the catalytic mineral phases occurred because metallic iron and pyrrhotite were oxidised by CO2 to iron oxide, and in turn iron oxide reacted with other mineral phases, which it is associated with, to form minerals that are not catalysts. It is noteworthy that a significant percentage of the mineral matter present in the investigated cokes was amorphous (44 - 75%). The iron, potassium and sodium present in the amorphous phase did not appear to catalyse gasification, but their potential contribution to gasification could not be completely excluded.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains xii, 102 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 80-81).

In this thesis a fluidized bed containing a draft tube has been studied with the aim of developing the apparatus for coal gasification. The process has the capability of producing synthesis quality gas using air for combustion, and of being able to accomodate poor quality coal feeds containing heavy fines loads. These advantages arise from two special features of a draft tube fluidized bed. In the first place, the bed may be operated as two separate and independent reaction zones, one contained within the draft tube and the other in the annulus region surrounding it. As a result, the gasification reactions may be carried out in one compartment and the combustion reactions in the other, allowing the useful gasification products to be taken off separately and undiluted with the combustion flue gases. Secondly, the fluidized material in the bed may be induced to circulate up the draft tube and down the annulus. These circulating solids provide the heat carrier from the combustion to the gasification zones within the bed. Furthermore, circulation of the bed in this way leads to a much longer residence time of fine particles within the bed and results in a high fine coal utilization efficiency. In order to achieve these benefits in practice, it is necessary to separate the gases supplied to and emitted from the draft tube from those of the annulus, but at the same time allowing free movement of solids between these regions. The thesis deals with how this may be accomplished in three parts: Firstly, the principles underlying division of a fluidized bed with a draft tube into discrete reaction zones are formulated, and strategies for achieving zonal separation, based on these arguments, are experimentally tested. As a result a reactor configuration and operating conditions suitable for coal gasification have been empirically identified. Secondly, a model describing the bulk circulation of solid material in the bed is presented, for the draft tube operating in the slugging mode. This model allows the average solids residence time and the particle velocities in the annulus and draft tube to be predicted, provided that slug velocities and spacings are known. The necessary correlations between hydrodynamic behaviour and the system properties are available in the literature for round nosed and wall slugs, but not for square nosed slugs, which appear to be characteristic in the apparatus used here. The third part consequently examines the square nosed slugging regime, and a theory to describe this behaviour, based on interparticle stress analysis, is presented. This regime is identified as having significant advantage over other bubbling modes because of the high dense phase gas flow rates which are sustained, and the resulting improved gas-solid contacting. The three models together mathematically describe the operation of the draft tube fluidized bed, allowing gas partition between the annulus and the draft tube regions as well as solids circulation to be predicted, for different bed configurations and operating conditions. The predictions compare well with experimental results. The last part of the thesis deals with the application of the system to coal gasification on a one ton coal per day pilot plant. A high quality gas, containing up to 80% CO + H2, (balance CO2), has been produced by steam gasification in the draft tube, using air for the combustion reaction in the annulus. The H2/CO ratio can be varied from about 1 to 3, by changing the operating temperature of the reactor. / Thesis (Ph.D.)-University of Natal, Durban, 1984.

No description available.

There have been many studies in the energy field to achieve different goals such as energy security, energy independence and production of cheap energy. The consensus of the general population is that renewable energy sources can be used on a short-term basis to compensate for the energy requirement of the world. However, the prediction is that fossil fuels will be used to provide the majority of energy requirements in the world at least on a short-term basis. Coal is one of the major fossil fuels and will be used for a long time because there are large coal reservoirs in the world and many products such as hydrogen, ammonia, and diesel can be produced using coal. In the present study, the performance of a clean energy system that combines the coal gasification and alkaline water electrolyzer concepts to produce hydrogen is evaluated through thermodynamic modeling and simulations. A parametric study is conducted to determine the effect of water ratio in coal slurry, gasifier temperature, effectiveness of carbon dioxide removal, and hydrogen recovery efficiency of the pressure swing adsorption unit on the system hydrogen production. In addition, the effects of different types of coals on the hydrogen production are estimated. The exergy efficiency and exergy destruction in each system component are also evaluated. Although this system produces hydrogen from coal, the greenhouse gases emitted from this system are fairly low.

Of all coke properties the influence of the catalytic mineral matter on reactivity of metallurgical cokes is least understood. There is limited information about the form of minerals in the metallurgical cokes and no information about their relative concentration. A comprehensive study was undertaken for characterisation of mineral matter in coke (qualitative and quantitative), which enabled quantification of the effect of catalytic minerals on the reaction rate, and establishment of the effect of gasification on the mineral phases. Also, the relative importance of coke properties on the gasification reaction rate was determined. The reactivity experiments were performed at approximately 900??C using 100% CO2 under chemically controlled conditions. The mineralogical composition of the investigated cokes was found to vary greatly as did the levels of catalytic mineral phases. These were identified to be metallic iron, iron sulfides and iron oxides. The gasification reaction rate at the initial stages was strongly influenced by the content of catalytic mineral phases and also by the particle size of the catalytic mineral matter. The reaction rate increased as the contact surface between catalyst and carbon matrix increased. Catalytic mineral phases showed a strong influence on the reaction rate at early stages of reaction. But their influence diminished during gasification. At later stages of reaction the influence of micropore surface area became more important. The influence of the catalytic mineral phases diminished during gasification because the catalyst was inactivated to some degree and the contact surface between the catalyst and carbon matrix diminished due to the strong gasification of the carbon around the catalyst particles. The partial inactivation of the catalytic mineral phases occurred because metallic iron and pyrrhotite were oxidised by CO2 to iron oxide, and in turn iron oxide reacted with other mineral phases, which it is associated with, to form minerals that are not catalysts. It is noteworthy that a significant percentage of the mineral matter present in the investigated cokes was amorphous (44 - 75%). The iron, potassium and sodium present in the amorphous phase did not appear to catalyse gasification, but their potential contribution to gasification could not be completely excluded.

Bibliography: leaves 322-335. / xxxvii, 343 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Highlights the need for extensive testing of large particle coal devolatilization models with both volatile matter evolution and particle temperature data in order to ensure that the predictions generated by the model can be thoroughly trusted. By undertaking an in-depth investigation into the particle temperature measurements and associated model predictions, shows that accurate model predictions can be obtained for the evolution of volatile matter, and of individual volatile species. The model is also capable of predicting the behaviour of wet coal particles by assuming that drying is heat transfer controlled and that the enthalpy of drying observed by Chen is applicable. Ultimately, this model forms a sound basis for the on-going development of a model encompassing all of the reactions required to model the behaviour of a typical coal particle in a fluidished bed combustor or gasifier. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1999

Bibliography: leaves 322-335. / xxxvii, 343 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Highlights the need for extensive testing of large particle coal devolatilization models with both volatile matter evolution and particle temperature data in order to ensure that the predictions generated by the model can be thoroughly trusted. By undertaking an in-depth investigation into the particle temperature measurements and associated model predictions, shows that accurate model predictions can be obtained for the evolution of volatile matter, and of individual volatile species. The model is also capable of predicting the behaviour of wet coal particles by assuming that drying is heat transfer controlled and that the enthalpy of drying observed by Chen is applicable. Ultimately, this model forms a sound basis for the on-going development of a model encompassing all of the reactions required to model the behaviour of a typical coal particle in a fluidished bed combustor or gasifier. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1999

Thesis (M.S.)--Chemical Engineering, Georgia Institute of Technology, 2005. / Jones, Christopher, Committee Member ; White, David, Committee Member ; Teja, Amyn, Committee Member ; Realff, Matthew, Committee Chair. Includes bibliographical references.