“IF THE CO2 GAS comes from a gas fired power plant,
coal-fired power plant or industry, it is almost never 100 per cent
pure CO2,” says Gaute Svenningsen of the Institute for Energy
Technology at Kjeller outside of Oslo.
“Depending on how well the CO2 gas is purified, it will
contain a greater or lesser degree of impurities in the form of particles,
water, sulphur or nitrogen compounds.”
CO2 IN VARIOUS MIXTURES
In the project that Svenningsen is managing,the goal is to determine
what degree of impurities can be accepted. Many of the impurities can
react and form products that can destroy the steel pipes that are to
transport the CO2.“
If we envision an infrastructurefor CO2 transport with many
different sources, the CO2 may contain various impurities that
both separately and in mixture can result in destructive reactions,” says
“CO2 captured from a coal-fired power plant may, for
example, contain small amounts of sulphuric gas. If this is exposed to
water and oxygen, sulphuric acid can form and corrode the steel in a pipeline.
CO2 from other sources may contain other impurities that can
result in other reaction products, including solid particles.
Particles in the gas or detachedparticles from corrosion processes can
also create problems, especially at the final station where the CO2
is injected into the underground storage site.
All the experiments are conducted at a laboratory at Kjeller, where
different types of impurities from separate sources are added to the CO2
in very exact doses and at specific time intervals Then the effect on steel
corresponding to what is used in pipelines is measured over time.
“Corrosion and cross chemical reactions are studied in autoclave and flowlabs
in which all of the variables are under precise control,” Svenningsen explains.
Spectrometers, laser light and infrared light are used to measure
the content of impurities and reaction products. If impurities disappear
from a gas mixture, it is an indication that a chemical reaction is taking
place,which is generally not desirable.
SMALL VOLUMES, LARGE CONSEQUENCES
“What we have seen is what would normally be regarded as very
small amounts of impurities, but which can have large consequences over
time. CO2 with sulphuric acid can eat through 40 mm steel pipe
in the course of a year,” says Svenningsen.“
When there are plans to transport many millions of tonnes of CO2 over
many kilometres for many years to come, it is important that costly pipelines
do not rust away in a short period of time. With knowledge of how much, and
which, impurities the infrastructure can withstand over time, it is
possible to stipulate precise requirements for the purification of CO2 from
different sources before transport and storage.
The project will establish a basis for the recommendation of limit
values for various types of impurities in CO2
mixtures that are transported in pipelines. This knowledge will be of
decisive importance to anyone who is responsible for the operation of pipelines
and other plants that handle impure CO2.