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12.7 CO 2 Transportation 379

12.7.1 Pipeline Transportation

Prior to transportation via pipeline, CO 2 is compressed to a supercritical fluid or
liquid state for efficient pipeline transportation [51]. The critical point of CO 2 is
31.1 °C and 73 atm. However, temperature and pressure drops along the pipeline,
therefore, prior to delivery CO 2 is compressed to a pressure that is more than
73 atm.
The pressure drop per unit length of pipeline can be described as

DP qU 2
¼ f D ð12:61Þ
DL 2d
where DP is the pressure drop per unit length of pipeline (Pa/m), f D is the dimen-
DL
sionless Darcy friction factor, d is the diameter of the pipeline, q is the density of
the fluids, CO 2 in this case, and U is the average speed of the fluid.
The Darcy friction factor can be calculated using the Colebrook-White equation
[14].

!
1=2 e 2:51
f ¼ 2log þ ð12:62Þ
D 10 1=2
3:7d Ref D
where e is the pipeline inner surface roughness, which is about 46 lm; for typical
commercial steel pipes. Re is the Reynolds number in pipeline and it can be
calculated using Eq. (12.63)

qUd 4 _ m
Re ¼ ¼ ð12:63Þ
l lpd

Example 12.5: Pressure drop in a pipeline
Consider a pipeline made of commercial steel with an inner diameter of 40 cm for
transporting CO 2 at a flow rate of 3.5 Mega tons per year. Use CO 2 properties under
3
11 MPa and 25 °C as follows: q ¼ 877 kg=m and l ¼ 7:73 10 5 Pa s.
Estimate the pressure drop over a distance of 100 km.
Solution
Convert the unit of the CO 2 flow rate as

6
Mt 3:5 10 1000 kg
_ m ¼ 3:5 ¼ ¼ 111 kg=s
year 365 24 3600 s