Vol 1 Chapter 27: Zero Recycle Oxyfuel Boiler Plant with CO2 Capture
Mark Simmonds and Graeme Walker
Abstract: The Carbon Capture Project has been established by eight leading energy companies to develop novel technologies that significantly reduce the cost of capturing CO2 for long-term storage. One area considered by the CCP is the use of oxygen in combustion systems (oxyfuel combustion). This is attractive to the CCP as it produces a flue gas essentially containing only CO2 and water, from which CO2 can be easily captured. This study reviews two oxyfuel schemes, one that incorporates a recycle of some of the flue gas and one that does not. Recycling a proportion of the flue gas helps to mitigate the combustion temperatures in the furnace and thereby permit the use of conventional boiler designs. Eliminating the flue gas recycle and burning fuel gas in a near-pure oxygen environment is beneficial as it leads to a more thermally efficient and thereby compact boiler design, and has a lower volumetric throughput, thus reducing the size of all equipment and ducting. Very high temperatures are reached in the zero recycle case and novel boiler design are required. This study evaluates the technical feasibility of the zero recycle case and assesses the justification for developing new boiler designs as part of the CCP. The study concludes that the zero recycle scheme is technically feasible. A boiler design is proposed that is capable of withstanding the high combustion temperatures but, although such a design has been tested in a pilot study, it is not currently commercially proven. The zero recycle case is an attractive option for raising steam and generating electrical power. It is cheaper than the alternative scheme that does recycle part of the flue gas and, for identical feed conditions, generates more electrical power. However, both cost- and thermal-efficiency benefits are only marginal and it is concluded that there is insufficient justification to warrant the development of boiler designs suited to fuel gas combustion in a near-pure oxygen environment within the CCP.
Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO2 Capture Project Capture and Separation of Carbon Dioxide from Combustion Sources - Volume 1
Edited by: David C. Thomas, Senior Technical Advisor, Advanced Resources International Inc, USA
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