Title:
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Transporting the next generation of CO2 for carbon capture and storage
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Climate change has been attributed to greenhouse gases with carbon dioxide (C02) from
power plants being the major contributor. Governments and industry worldwide are now
proposing to capture CO2 from their power plants and either store it in depleted reservoirs
or saline aquifers ('Carbon Capture and Storage', CCS), or use it for 'Enhanced Oil
Recovery' (EOR) in depleting oil and gas fields. The research reported will have
significant implications on the feasibility for future CO2 transportation for CCS.
The United States has over 30 years experience with the transportation of carbon
dioxide by pipeline, mainly from naturally OCCUlTing, relatively pure CO2 sources for
onshore EOR. CCS projects differ significantly from this past experience as they will be
focusing on anthropogenic sources from major polluters such as fossil fuel power plants.
The fossil fuel power plants will produce CO2 with varying quality/purity of CO2
depending on the capture technology used. It was concluded that power plant impurities
such as Ar, SOx and NOx have never been transported before and that gaseous
transportation of C02 should be considered as an option in the .early stages of CO2
deployment.
Application of current design and operational procedures to the new generation
pipelines may not be deemed feasible due to the effect of anthropogenic CO2 on pipeline
hydraulics. This could potentially yield an unsafe pipeline facility, with excessive
investment and operating cost. In particular, the presence of impurities has a significant
impact on the physical properties of the transported CO2 which affects: pipeline design;
compressor/pump power, repressurisation distance and pipeline capacity. The effect of
impurities on C02 is generally to raise the critical pressure and increase the two-phase
region. An increase in the critical pressure and two-phase area reduces the operating
flexibility of the pipeline. Large temperature and pressure drops are associated with the
operating pressures and temperatures in the pipeline in the region of two-phase flow.
Another alternative being considered for C02 transportation is the re-use of
existing pipeline infrastructure. However, it has been identified that some limitation
exists due to the operating parameters of these pipeline such as the maximum allowable
operating pressure (MAOP), integrity and also the design capacity. Therefore, gaseous
transportation may prove to be more feasible in these cases. Nevertheless, in order to
meet emission targets, supercritical transport will be required, as it is able to transport the
required amount of CO2 in order to meet emission targets due to the size of the
infrastructure required. All these effects will have to be carefully considered as it has
direct implications for both the technical and economic feasibility of developing a carbon
dioxide pipeline infrastructure both in the UK and internationally.
Transient power plant operation will lead to changes in the CO2 produced.
Therefore, the transportation system must be designed to handle these changes in flow
and options such as linepacking should be considered. It has been shown that linepacking
gaseous pipelines are more feasible than operating supercritical CO2 pipelines. Therefore,
venting needs to be considered as a potential option for supercritical CO2 pipelines. This
could in turn incur additional costs due to potential regulatory requirements.
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