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The aim of this study is to evaluate the potential of using solidification/stabilisation (S/S) for the treatment of electric arc furnace dust (EAFD) and examine the effects of using a variety of industrial by-products, i.e., pulverised fuel ash (PFA), hydrated lime (hlime), steel slag and low-grade magnesium oxide (LGMgO) as cement replacements. LGMgO, steel slag and PFA with 0%, 40% and 70% EAFD additions met the Waste Acceptance Criteria (WAC) requirements with respect to unconfined compressive strength (UCS), initial and final setting times and consistency results. The acid neutralisation capacity (ANC) results showed that PFA and steel slag do not have as high buffering capacity as LGMgO and hlime when exposed to acid attacks. The pH level •• »:' was reduced to 5 when 10 meq/g acid was added into both LGMgO and hlime-blended mixtures. ' The monolithic leaching test results showed that the fixation of the heavy metals was hardly possible in almost all the mixtures studied. The granular leaching tests yielded very good results with no metals leaching except for Mo. Mo fixation was achieved only for CEMI-hlime and CEMI-LGMgO 1:2:40 mix ratios at 28 days', and for CEMI-LGMgO 1:4:40 and CEMI-slag 1:4:70 mix ratios at both 7 and 28 days' curing age. Depletion-controlled release was observed throughout most ofthe testing (intervals 1-7) and was the dominant leaching mechanism for LGMgO, PFA, slag, hlime and CEMI blended samples. X-ray Diffraction (XRD) analyses showed that EAFD is mainly composed of zincite (ZnO), franklinite (ZnFe204) and magnetite (Fe304)' Scanning Electron Microscopy (SEM) analysis confirmed the presence of zincite, a compound known to hinder strength development. The XRD results of LGMgO and waste blended products at 28 days' curing age indicated the presence of zincite. Overall, this study demonstrated that the optimum combinations where S/S of EAFD was successful were for CEMI-LGMgO 1:4:40 and CEMI-slag 1:4:70 mix ratios.

This work documents the research, design and implementation of devices to improve the balance of junction splits in the pneumatic conveying systems of conventional coal fired power stations. The organisation of the thesis follows the design process chronologically, culminating in the installation of the prototype designs in operational pneumatic conveying systems.

Meeting energy demand while mitigating catastrophic climate change is a serious challenge faced by governments around the globe. The role of coal in the energy mix is integral to this problem: coal is a relatively cheap, flexible and plentiful energy resource; however it is also one of the most polluting. CO2 emissions from coal-fired power plants contribute to global warming. Development and deployment of carbon capture and sequestration (CCS) technology is vital in order to reduce the environmental impact of burning coal. CCS involves capturing and purifying C02 from the emission source and then sequestering it safely and securely to avoid emission to the atmosphere. Oxyfuel combustion, in which the fuel is burnt in a mixture of pure oxygen and recycled flue gas instead of air, is a viable option for CCS from coal-fired power plants. The subject of this discourse is modelling and simulation of oxy-coal combustion. Accurate prediction of the operating characteristics of oxy-coal plants is a vital step towards deployment of the technology. This requires a fundamental understanding of the processes involved and how they might differ from conventional air-firing operation. The distribution of the furnace heat transfer determines the integration between the gas and the water/steam cycles. In order for existing boiler technology to be converted to oxyfuel operation, heat transfer in an oxy-coal furnace should be very similar to air-firing. A combination of fundamental modelling, fluid dynamics, and process simulation have been applied in order to study the impact of oxyfuel combustion on electricity generation. Effectively, nitrogen is replaced with CO2 in the combustion gases and this will affect the gas specific heat capacity, thermal conductivity, diffusivity and absorptivity/emissivity and hence change the rate of convective and radiative heat transfer. The gas-side heat transfer processes are intrinsically linked to chemical reactions and turbulence, and these are accounted for using a CFD model of the furnace. The CFD-generated data are then linked to a full plant simulation in order to investigate the impact of oxyfuel combustion on plant operation. The heat transfer components in the full plant model are developed specifically for detailed prediction of heat transfer and account for changes in composition and mass flow of the flue gases. A range of inlet oxygen concentrations varying from 21-35 vol-% and recycle ratios varying from 80-65% are investigated and the combined simulations reveal a 'working range' of approximately 30-33% inlet oxygen and 72-68% recycle ratio where the distribution of heat transfer is sufficiently similar to allow the plant to operate within the given set- points for air-firing.

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