Design of Steam Cycles for Oxy-combustion Coal based Power Plants with Emphasis on Heat Integration

The Oxy-combustion method of CO2 capture is considered to have several advantages over other methods for CO2 capture from coal based power plants. The capture process is energy intensive and hence expensive. Heat integration is often recommended to recover part of the energy expended in the capture process. In this study, pinch analysis is used as a tool to integrate heat from the CO2 capture process into the steam cycle of the power plant. This way of heat integration provides an opportunity to make better use of the available low grade heat at the power plant premises by approaching the minimum allowable temperature difference between the hot and the cold streams. This ultimately results in a better overall efficiency by generating additional power for the same fuel input and also by reducing the consumption of cooling required in the capture process. The resulting steam cycle will be a custom design for oxy-combustion coal based power plants and will be tightly integrated with the capture process. As this method brings a lot of changes to the steam cycle configuration, this is best suited for new power plants rather than retrofit of existing plants. Results show that the Pinch method of heat integration achieves better overall thermal efficiency compared to the conventional method of steam cycle design and heat integration. A techno-economic is however required to justify the efficiency gains achieved. Further work will be done later to optimize some of the simulation assumptions and to arrive at the network design.