Numerical and experimental investigation of the oxy-coal combustion in carbon capture technologies

• Main Author: Gharebaghi, Maryam
• Published: University of Leeds 2011
• Subjects: 628.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.659033

The coal-fired power generation industry is responsible for a large portion of the CO2 emission to the atmosphere. In many countries, Carbon Capture and Storage (CCS) is suggested as a long-term solution for CO2 mitigation. Oxy-coal combustion, one of the CO2 capture processes in the CCS, with Recycled Flue Gas (RFG) can be applied to the conventional coal combustion plants with modifications. However, based on the · preliminary investigations and laboratory-scale data, technical challenges have to be undertaken before oxy-coal combustion reaches the demonstration phase. In this thesis, prediction of the performance of an oxy-coal Combustion Test Facility (CTF) with RFG, and defining the challenges, are the main objectives. Technical challenges of the oxy-coal combustion are addressed, combustion physical submodels are discussed and challenges regarding modelling of the oxy-coal combustion are addressed. State-of-the-art char combustion models, along with a comprehensive set of microscopic studies (SEM, EOX and XRO) of the fly ash from air- and oxy-coal combustion tests, are discussed. Following that, a requirement for revision of the standard char burnout models for application to oxy-coal combustion is presented. An updated gas-phase mercury chlorination mechanism is presented and validated with the unbiased experimental data. In parallel, the solid-phase mercury retention and oxidation processes on the fly ash are investigated. Furthermore, an empirical correlation for the prediction of mercury speciation in the NOx removal unit is suggested. Following the development of a combined homogeneous-heterogeneous mechanism, recommendations regarding a global model for predicting the mercury transformation through the power plant are addressed. The 1 MWth CTF of interest is modelled using advanced numerical simulation (CFO) methods. The geometry set up, the boundary conditions and the approach for grid independency and optimization are discussed. Two variations of turbulence modelling techniques for simulation of air- and oxy-coal combustion have been used to assess the CFO modelling predictions. Finally a techno-economic analysis of the oxy-coal combustion process is given in detail. This includes a comparison of the thermodynamics and the costs of typical air-coal, post-combustion and oxy-coal combustion processes in the UK and China.