Dynamic modelling of oxyfuel power plant

Abstract

Abstract Oxyfuel combustion technology is one of several Carbon Abatement Technologies (CATs) currently being developed. The technology offers a means of generating carbon dioxide rich flue gas requiring minimal treatment prior to sequestration or beneficial application. The oxyfuel process is based on excluding the inert components (mainly nitrogen) of air from the combustion process. In oxyfuel combustion, nitrogen is largely absent from the flue gas, since the fuel is combusted with a mixture of nearly pure oxygen (∼95% O 2 -separated from air in an air separation unit (ASU)) and CO 2 rich recycled flue gas. It is recognised as a leading Carbon Capture technology for new and retrofit power plant. Previous studies undertaken by Doosan Power Systems, Air Products, University of Edinburgh and others have shown that there is significant scope to optimise overall plant efficiency, both at the design stage and during normal operation. Therefore the current work seeks to realise these benefits through the adoption of optimised designs and the development of appropriate control and dynamic optimisation strategies. Recycling flue gas in the Oxyfuel process gives rise to a number of operational and control features not seen in conventional air-fired power plant systems. Comprehensive dynamic models of the Oxyfuel process systems and associated controls are being developed as part of the TSB collaborative project “Optimisation of Oxyfuel PF Power Plant for Transient Behaviour” to study these aspects. The Oxyfuel specific models are coupled to a whole cycle, non-linear, dynamic model of the boiler and turbine systems allowing development of control schemes, which can meet the full range of operational requirements and capabilities of the Oxyfuel plant. Early results from the model suggest that operation in Oxyfuel mode may provide an opportunity to improve plant flexibility and both primary and secondary response, a capability which is of increasing importance as the mix of conventional, nuclear and renewable generation changes.