Several power producing companies as well as oil- and gas companies and state organisations are planning to implement projects of CO2 capture, transport and storage (CCS). In many cases cross country pipelines are required to connect CO2 “production” and the storage location, often several hundred kilometres of length.
Internationally applied norms and regulations for pipeline design, construction and operation are today
- ISO 13623: Petroleum and natural gas industries – pipeline transportation systems (this norm correlates with DIN EN 14161)
- ASME B31.4: Pipeline transportation systems for liquid hydrocarbons and other liquids
- ASME B31.8: Gas transmission and distribution piping systems
By far most of the items of the a.m. norms are applicable also to CO2 pipelines; however, some specifics of CO2 require a particular consideration. In several countries working groups have been established by companies or jointly with authorities in order to fill these gaps.
CO2 is odourless and can collect in topographic low points. It is non-toxic at low concentrations but beyond 20% it is life threatening. Hydrogen Sulphide (H2S) and/or Sulphur Dioxide (S02) may also be impurities in higher quantities in the CO2 stream captured from power generation and can be life threatening in certain concentration as well. In case of free water CO2 and these impurities are highly corrosive.
Further specific technical aspects result from the fact that CO2, when transporting in supercritical or liquid state, is cooling down to ca. - 78°C (in case of depressurization) and may result in either brittle or ductile long running fractures which must be prevented by suitable material / wall thickness specification.
Therefore – with reference to the above mentioned ISO 13623, the following aspects shall be covered by a supplementary regulative guidance: Route selection (particular topography and populated areas), Strength / toughness requirements (fracture control), Section isolation valves (spacing of valve stations), Emergency shut down systems (depressurization, venting), Corrosion management (drying procedures, absolute avoidance of free water), Risk assessment (among others dispersion models to be developed) .
Partially aspects of risk management and route selection could be resolved by a different categorization of CO2 within the ISO 13623. It is today categorized within group C (same as Argon, Nitrogen and air) and is considered to be categorized within group E (among others toxic or flammable liquids conveyed from gases, like ethylene, hydrogen, natural gas liquids). It must be remarked that this would have significant cost impacts mainly due to higher resulting safety factors and consequently higher wall thicknesses.
One world wide accepted standard would be desirable for the a.m. issues.