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Title: Modelling and simulation of oxy-coal fired power plants
Author: Edge, Penelope Jayne
ISNI:       0000 0004 2714 6042
Awarding Body: University of Leeds
Current Institution: University of Leeds
Date of Award: 2011
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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.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available