5. C๐ถ ๐ Transport by pipelines
โ Carbon dioxide by its chemical nature forms what is called a โdense phaseโ or
โsupercriticalโ state at temperatures above 88ยฐF when compressed above 7.59
MPa (1,100 psi) (or 1,200 psi at any temperature). Dense phase is a state which
is neither a true liquid nor a true vapour. It has the density near that of water (0.8
grams/cc at 27ยฐC and 10.34 MPa), but is still quite compressible.
โ A single cubic foot of CO2 in the dense phase is equal to about 1,200 cubic feet
of the gas at ambient conditions. Thus, large quantities of CO2 can be
transported in a relatively small volume while in the dense phase.
โ Although CO2 is an inert, non-flammable gas, it still has the potential to be
dangerous. As CO2 is 1.5 times heavier than air it will displace oxygen in
confined spaces (such as valleys). At high concentrations, CO2 can lead to a
range of adverse health effects, including asphyxiation.
6. CO2 pipeline route selection, similar to most other pipelines
transporting potentially hazardous fluids, is influenced by a
number of factors. These are listed below:-
โ Environmental impacts and mitigation.
โ Sociological impacts and mitigation.
โ Public safety during construction and subsequent operation.
โ Constructability and terrain.
โ Access during construction and subsequent operation.
โ Failure consequences.
7. Pressurized tank cars
โ Railroad tank cars, are primarily used to transport flammable and non-
flammable gases. The tank car can be top-loading and provided with a housing
or dome to protect valves and gauges. These tank cars may be insulated.
โ However, CO2 in railroad tankers needs to be liquefied and kept refrigerated, so
that more mass of CO2 can be contained in every tanker vessel. While CO2 can
be transported in smaller pressurized containers at a temperature of 21.1ยฐC, the
corresponding vapour pressure of 5.78 MPa (58.92 kg/cm2) at that temperature,
refrigeration can minimize the use of multiple but smaller higher rated pressure
vessels.
โ Instead a larger refrigerated single pressurized vessel per carriage at a pressure
of not more than 1.72 MPa (17.58 kg/cm2) can be used. As such, the lower
pressure liquid CO2 is contained in refrigerated tanker/trailers, rail cars, or
refrigerated storage tanks that are normally maintained at pressures below 250
psig and at temperatures of about -23.3ยฐC..
8.
9. Disadvantage of these method
โ The cryogenic condition of CO2 in this mode of transport poses special hazards
due to its extremely cold temperature.
โ Contact of human tissue with cryogenic liquids such as refrigerated liquefied
CO2 can cause immediate freezing.
โ Additionally, accidental release of CO2 to atmosphere at this condition could
cause sudden gas expansion, and CO2 being a simple asphyxiant may displace
oxygen down to critical levels in localized areas around the container.
10.
11. Transport of CO2 by truck tankers or
semi or full trailers
โ It is necessary that the temperature of the contained gas in the tanker be much
lower than ambient in order to keep the vapour pressure of the content below
the tank vessel pressure rating.
โ Other means of CO2 land transport utilize pressurized vessels with rigid frames
or mounts around the vessel. These frames are provided with anchors that will
fit into the flatbed decks of trailers or trucks that will carry them. Refrigeration
equipment is essentially part of the fit-up.
12.
13. Transport of CO2 by ship loading
โ A well designed loading terminal can provide safe and efficient loading of
CO2 for ship transport.
โ As there could be various means of CO2 transport from capture points to this
terminal, all these means of transport must converge at the loading terminal.
โ Considering that there could be barriers towards accumulating huge stocks of
CO2 near populated areas, a transition station, such as a Floating Production
Storage and Loading (FPSL) Vessel, can be provided in order to provide a safe
distance between the CO2 temporary storage and loading area and the shore.
โ This concept is actually adopted from the currently used Floating Production,
Storage and Offloading (FPSO) vessel in the oil and gas industry.
โ The FPSO is a type of floating tank system equipped with all necessary
facilities and designed to take all the oil and gas for offloading onto waiting
tankers.
14.
15. The advantages of this floating
system are:
โ It will enable bigger and heavier ships with bigger drafts to load CO2 at a certain
distance from the shoreline;
โ It provides a greater distance of bulk storage of CO2 from heavily populated
areas onshore; and
โ It can serve as stationary buffer for scheduling coordination between tanker
dispatch and land transport deliveries towards the terminal.
