Computational Fluid Dynamics and Process Co-simulation Applied to Carbon Capture Technologies

In the energy supply sector, coal will still remain as a dominate role in the foreseeable future because: it is comparatively cheap and widely distributed around the world and more importantly, carbon capture and storage (CCS) technologies make it possible to depend on coal with almost zero emission of carbon dioxide (CO2). CCS involves capturing and purifying CO2 from the emission source and then sequestering it safely and securely to avoid emission to the atmosphere. Both the post-combustion and the oxy-fuel technologies can be applied to existing power plants for CCS retrofit. Accurate prediction of the performance of a CCS plant plays an important role in reducing the technical risk of future integration of CCS with existing power plants. This research combines the fundamental computational fluid dynamics (CFD) and system process simulation technologies so that an efficient co-simulation strategy can be achieved.
A 250 kWth coal combustion facility combined with a CO2 post capture plant is taken to test the conception of the CFD and process co-simulation approach. The CFD models are employed to account for the combustion facility and the predicted results on the outlet gas compositions, temperatures and mass flow rates are used to generate reduced order models to linked to the model for the PACT CO2 post capture plant so that a pilot scale whole plant model is achieved and validations have been made where it is possible.
Afterwards, the a large scale conventional air-coal firing power plant is taken into investigation: the CFD models for the boiler and the process models for the whole plant have been developed. Further, the potential of retrofitting this power plant to oxy-firing is evaluated using a CFD and process co-simulation approach. The CFD techniques are employed to simulate the coal combustion and heat transfer to the furnace water walls and heat exchangers under air-firing and oxy-firing conditions. A set of reduced order models has been developed to link the CFD predictions to the whole plant process model in order to simulate the performance of the power plant under different load and oxygen enrichment conditions in an efficient manner. Simulation results of this 500 MWe power plant indicate that it is possible to retrofit it to oxy-firing without affecting its overall performance. Further, the feasible range of oxygen enrichment for different power loads is identified to be between 25% and 27%. However, the peak temperature on the superheater platen 2 may increase in the oxy-coal mode at a high power load beyond 450 MWe.