3 Anthropogenic CO2 Properties
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Published:2012
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This chapter highlights and explores compositional quality scenarios of anthropogenic CO2 for the different capture technologies and pipeline transportation. Anthropogenic CO2 originates largely from power plants which employ the post-combustion, pre-combustion and oxyfuel capture technologies. The levels of impurities present are driven by the economic, environmental and safety considerations for both capture technology and pipeline transportation. While this chapter highlights both globally, Chapter 5 details pipeline related issues with respect to impact of impurities on pipeline design and specifications.
Whether the source is natural or anthropogenic, the CO2 stream will always contain impurities. It has been established that anthropogenic CO2 will likely contain more and different impurities compared to natural sources of CO2. Their influence on the properties of CO2 will have important implications for the safety, regulation, design, and operation of CO2 pipelines. Therefore, this chapter focuses on the current compositional specification for currently operating pipelines and provides an overview of current knowledge of the CO2 quality from the capture plants.
The CO2 used for EOR demands relatively high purity [1], and therefore must adhere to a stringent specification for both miscible and immiscible oil recoveries. Miscible recovery can be used when the reservoir pressure is large enough and occurs when the injected CO2 mixes with the oil such that the interfacial tension between the oil and the CO2 disappears and the capillary number becomes infinite. This technique is generally used for reservoir depths >1200 m and oil lighter than 22 API gravity. Immiscible recovery is when the injected CO2 remains physically distinct from the oil, causing the oil to swell, thus reducing the density and viscosity, increasing permeability, increasing pressure buildup, and improving the mobility. This is less efficient than miscible recovery and is used for very low-pressure reservoirs and/or when the oil gravity is relatively high.