CO2 transportation in carbon capture process

CO2, one of the major green house gases, has become a big concern of modern society. A large amount of Carbon dioxide is generated by burning fossil fuels, for example, coal and petroleum.  Nowadays, some practical methods have been developed to reduce CO2 concentration in atmosphere, such as post-combustion capture, pre-combustion, oxyfuel combustion and industrial separation. CO2 transportation is then the next important step to bring those captured CO2 to its final destination.

Transport is that stage of carbon capture and storage that links sources and storage sites. Transportation usually happens in three stages which are gas, liquid and solid. The most commonly used and cost-effective way are pumping compressed CO2 via pipeline and CO2 liquefaction  which is used for gas transport by ship. Solidification is not typically used due to high energy use and cost.

Some technical parts involved in CO2 pipeline design including corrosion, metering and pressure. For dry carbon dioxide design, Carbon-manganese pipelines will not corrode if relative humidity is below 60%. Carbon steel doesn’t exhibit any corrosion concerns. For wet carbon dioxide design, stainless steel should be used if free water is present. Metering system, which tracks input and output of CO2 volume, is also important in pipeline design.  One existing example for metering system is called Supervisory Control and Data Acquisition (SCADA) which can measures pressure drops along the pipeline and manage emergencies. Since CO2 is compressed in the pipeline, pressure is also a concern. High pressure pipeline usually has a pressure of at least 9.6 MPa.  The advantages are helping keep gas dense at a wide range of temperatures and cutting the cost.

The figure below shows an general map of the CO2 pipeline system in the U.S.. Some existing systems are Canyon Reef Pipeline, Bravo Dome Pipeline, Cortez Pipeline, Sheep Mountain Pipeline and Weyburn Pipeline. The other key specification for designing is CO2 Quality Criteria which includes Carbon Dioxide Content, Water, Hydrogen Sulfide, Total Sulfur, Temperature, Nitrogen, Hydrocarbons, Oxygen and Glycol.

Although several methods have be developed to control CO2 concentration in the atmosphere. There is still a long way to go to control GHG and protect our environment.

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sources:
¨Carbon Dioxide Capture and Storage IPCC, 2005 – Bert Metz, Ogunlade Davidson, Heleen de Coninck, Manuela Loos and Leo Meyer (Eds.) Cambridge University Press, UK. pp 431.
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