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  • (2001) Pham, T. S.
    Thesis
    An ironmaking blast furnace is the main route for producing pig iron commercially, and it has been continuously improved to optimize operation and process efficiency over the last century, resulting in higher production rates with relatively low operating costs. In the last decade, the most important new technology implemented in the ironmaking blast furnace is Pulverized Coal Injection. PCI has become more and more attractive to iron makers due to its economic and environmental benefits. Yet problems associated with incomplete combustion of pulverized coal in the raceway during high rates of injection have capped the full potential of this technology. Understanding the hydrodynamics of unburnt char within the blast furnace is therefore of great importance. Despite this, PCI research has not been directed towards understanding the interactions between phases (particularly unburnt char and liquid iron and slag in the lower part of the blast furnace), because of the complexity of the problem. This thesis focuses on quantifying the hydrodynamics of gas-powder-liquid multiphase flow in moving particles simulating blast furnace operating conditions, providing a sound basis to improve the four-fluid flow mathematical models for blast furnace applications related to operations, and sheds more light on the problems of PCI at higher injection rates. A systematic experimental study of the hydrodynamics of gas-powder two-phase and gas-powder-liquid three-phase flows in fixed and moving packed beds was carried out. Glass and plastic powders and glass beads of various sizes were used to simulate pulverized coal and coke particle, respectively. From the gas-powder two-fluid flow in moving packed bed study, solid particle movement was found to have a significant effect on powder hold-up behaviour in a packed bed. On the basis of the experimental results, new static and dynamic hold-up correlations, as well as the porosity function are proposed to account for the effect of solid movement. The interaction between gas, solid and powder phases was also investigated. Incorporation of the proposed powder hold-up correlations and porosity function into the existed Fanning and Ergun equations was found to give very good predictions. As well, several gas-powder flow regimes in the packed bed have been identified and a new technique for quantifying the powder transport velocity is proposed. The study of the so-called four-fluid flow under blast furnace conditions, i.e. gas powder- liquid three-fluid flow in moving particles, is the primary objective of this thesis. The results indicate that steady-state gas-powder-liquid three-phase flow m moving particles can be achieved under certain flow conditions, giving rise to "operational" and "non-operational" regimes. The steady state condition or operational regime, for four-fluid flow, is primarily due to the downward movement of the packed particles which provides a higher porosity, enhances powder and liquid flow and removes the accumulated powder. Quantification of the hydrodynamics i.e. powder hold-up and pressure drop of four-fluid flow is possible within the operational regime. The effect of flow variables such as gas, powder, liquid and solid flowrates has been studied experimentally. On the basis of these results empirical correlations for powder hold-up and pressure drop are proposed in dimensionless form for the purpose of blast furnace modelling.


  • (2003) Gan, Mingle
    Thesis