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Carbon Capture, Utilization and Storage (CCUS) has been proposed as a promising technology for the mitigation of CO2 emissions into the atmosphere from fossil-fuel- operated power generation plants. As the reliability and cost effectiveness of the Pipeline transport network is crucial to the Overall operability and resilience of the CCUS system, it is vital to realize the possible corrosion risks of the employed Pipeline steels corresponding to the impurity Level of the gas source. Recent studies have shown that even the high alloyed materials might be susceptible to General and/or localized corrosion by the condensates forming from the impurities such as SOx, NOx, CO, O2 and water.
Up to now, however, there is no regulation procedure which defines the maximum acceptable level of impurities and the combination of them for each employed pipeline steels. Herein, systematic experiment series were conducted by mixing pure CO2 gas with varying concentration of each impurity and with the varying combination of them. Each time, the mixture was then fed (1 L/min) into the reactor containing 12 specimens for 120-600 h at 5°C (to simulate the sub-level Pipeline transport). The resulted condensate was collected and analyzed by ionic chromatography and atomic Absorption spectroscopy to determine the chemical composition. In this study, the “worstcase scenario” gas mixture, containing 2.5 % H2O, 1.8 % O2, 1000 ppm NO2, and 220 ppm SO2 as impurities, resulted in the condensate containing H2SO4 0.114 M and HNO3 0.0184 M (pH 2.13).
This “original” condensate was then reproduced to carry out exposure tests and electrochemical characterization including corrosion potentials and impedance spectroscopy in CO2 saturated condition for 7-14 days at the same temperature. The corrosion rate was also measured by mass loss method.
We can conclude that, at the initial stage, HNO3 plays the dominant role in Fe dissolution process, while H2SO4 is responsible for the pit initiation followed by pitting corrosion. Future studies will be focused on the combination effect from the impurities and the exposure test under the regularly changing condensate to mimic the real CO2 pipeline system.
Im ISO/TC 265 werden Normen zur Entwicklung, Konstruktion, Betrieb, Umweltplanung und -Management, Risikomanagement, Quantifizierung, Monitoring und Verifizierung sowie weitere Aktivitäten für die einzelnen Stufen der CCS-Prozesskette erstellt.
Als neuer Aspekt wurde die Zusammensetzung des CO2-Stroms angesprochen. In Form eines "State-of-the-Art-Reports" soll der derzeitige Kenntnisstand zusammengestellt werden. Dieses soll für einen späteren Normenentwurf als Grundlage dienen.
Geogenic gases such as CH4 or CO2 from natural sources, gases (CCS-CO2, H2, Natural
gas, City gas …) from a geological repository, or a leaking gas pipeline can present serious
risks in industrial and urban areas where the density of infrastructural elements increases as
well as above and below ground. To extend the lead time for risk treatment in such critical
regions, reliable detection of gases within the shallow subsurface is required to observe
critical gas accumulations before degassing into the atmosphere.
A near real-time monitoring approach is introduced to determine the volumetric expansion of
such a gas escaping from a leak in the subsurface. Considering the pressure relaxation with
the ambient air pressure, the approach enables the forecasting of the final size of a
pressurized gas body in terms of characteristic lengths. According to theoretical basics, such
a characteristic length, which allows to perform a gas (safety) measurement based on a
purely geometrical measure, behaves independently of subsurface properties, i.e., it enables
a reliable quantification of the escaping gas, irrespective of its heterogeneous flow path
distribution. A field test for a 10 l/min pinhole leakage of CO2 injected in an unsaturated Chernozemic soil (agricultural test field Bad Lauchstädt)that was equipped with linear gas sensors demonstrates the lateral-vertical volumetric gas expansion along the environment of these gas sensors, and confirms the applicability of the new characteristic length approach.
CCUS-Technologie (CO2-Abtrennung; Nutzung und Speicherung, engl. Carbon Dioxide Capture, Utilization and Storage) gilt als eine vielversprechende Methode zur Abschwächung des Beitrags von fossilen Emissionen zur globalen Erwärmung. Dabei wird das in den Verbrennungsprozessen entstandene Treibhausgas aufgefangen, zu verschiedenen Lagerstätten transportiert und langzeitig gespeichert bzw. einer chemischen Nutzung zugeführt.
In bisher veröffentlichten Untersuchungen wurde gezeigt, dass die CO2-Transport-Pipelines in hohem Maße gefährdet sind, wenn sie korrosiven Begleitstoffen des CO2-Stroms, wie SOx, NOx bei einem hohen Wasserdampfanteil ausgesetzt sind. Screening-Tests zeigten, dass bei einer Konzentration von 1000 ppmv H2O die Reaktionen und Kondensation von SO2 und NO2 mit O2 und H2O zu Säuretropfen (pH ~ 0,5) auf der Oberfläche von Metall-Prüfkörper und Gefäß führen. Die Werkstoffe 1.0582, 1.8977, 1.4313 und 1.4562 wurden in CO2-gesättigtem Kondensat mit unterschiedlichem Verhältnis der säurebildenden Komponenten untersucht. Diese Studien zeigten grundsätzlich den Mechanismus sowie die Rolle jedes CO2-Strom-Begleitstoffes auf den Korrosionsprozess. Allerdings spiegeln die bei Auslagerung und elektrochemischen Messungen in der künstlichen CO2-gesättigten Kondensat-Lösung auftretenden Bedingungen nicht im Detail die Realität in der Praxis, wo sich nur Tröpfchen bilden, wider.
Diese Arbeit konzentriert sich auf den Korrosionsprozess von Kondensat in Form von Tröpfchen, auf der Oberfläche von Rohrleitungswerkstoffen unter CO2-Atmosphäre bei 5 °C (Simulation des Transportzustandes). Die Experimente wurden nicht nur für Auslagerungsversuche, sondern auch für elektrochemische Tests mit nur einem Tröpfchen (weniger als 20 µL) konzipiert. Die Auslagerungs-versuche wurden sowohl unter Normaldruck als auch bei hohem Druck (> 70 bar) durchgeführt, wobei das CO2 als dichte – den Tropfen umgebende - Phase vorliegt. Die korrodierten Prüfkörper wurden rasterelektronenmikroskopisch (REM) und mittels Energiedispersiver Röntgenspektroskopie (EDX) analysiert, um nicht nur Korrosionsform, sondern auch die Elementverteilung der Korrosionsprodukte zu zeigen.
Carbon Capture Utilization and Storage (CCUS) is a promising technology for the reduction of CO2 emissions from fossil-fuel operated power plants, steel and cement mills or refineries. Crucial points for a sustainable and future-proof CCUS procedure are reliability and cost efficiency of the pipeline transport network especially concerning corrosion risks under impurities and moisture in the CO2 stream. Recent studies have shown that even high alloyed steels might be susceptible to general and/or localized corrosion caused by condensates. It was concluded from our study on carbon steels in normal and high pressure conditions, that the combination of these gas impurities, resulted in the acidic condensate, is not only a simple sum of each corrosive effect, but highly accelerates the corrosion rate of the pipeline steel, indicating the need of dynamic tests before installing the network pipeline system.
This contribution provides current findings regarding materials susceptibility for carbon capture, utilization and storage (CCUS) applications. Basing on results gathered in 2 German long-term projects (COORAL and CLUSTER) suitable materials are introduced as well as dominating impurities of the CO2-stream and corrosion mechanisms. Investigations cover the whole CCUS process chain and provide material recommendations for certain parts.
Commercially available carbon steels are suitable for compression and pipelines as long as moisture content and impurities are limited. (water 50 to 100 ppmv, SO2 and NO2 ca. 100 ppmv).
Corrosion rates increase with increasing water content.
(0.2 – 20 mm/a).
Condensation of acids and therefore droplet formation is always possible, even at low water contents.
A low SO2 content within the CO2-stream might be more important than a low water content.
Cr13-steels showed a general susceptibility to shallow pitting and pitting. So, they seem to be not suitable for CCUS applications.
Low alloyed steels showed better corrosion behavior. (predictable uniform corrosion)
For direct contact with saline aquifer fluids only high alloyed steels shall be used.
Commercially available carbon steels are suitable for compression and pipelines as long as moisture content and impurities are limited. (water 50 to 100 ppmv, SO2 and NO2 ca. 100 ppmv) Corrosion rates increase with increasing water content. (0.2 – 20 mm/a) Condensation of acids and therefore droplet formation is always possible, even at low water contents. A low SO2 content within the CO2-stream might be more important than a low water content. Cr13-steels showed a general susceptibility to shallow pitting and pitting. So, they seem to be not suitable for CCUS applications. Low alloyed steels showed better corrosion behavior (predictable uniform corrosion). For direct contact with saline aquifer fluids only high alloyed steels shall be used.
To reveal the corrosion resistance of casing steel/mortar interface in CO2 injection condition, sandwich samples were prepared and exposed up to 20 weeks in aquifer fluid under 10 MPa and 60 °C.
Cross section analysis revealed the crevice corrosion as main mechanism instead of pitting corrosion despite very high concentration of Cl in NGB.
EDS element line scan analysis of the 20-week-exposed metal/mortar coupon showed Chloride distribution, which still not reached the metal/mortar interface, explaining no pitting was observed.
It was confirmed that FeCO3 cannot protect the steel surface in CO2 saturated NGB.
To verify the protective possibility of passivation happened on casing steel/mortar interface, simulated pore solution was synthesized and used to passivate the steel for 42 days. OCP and EIS confirmed the formation of passive layer.
The 42 day passivated layer was broken during the first minute of exposure in CO2 saturated NGB.
However, due to high concentration of Ca2+, a new carbonate CaCO3 dense layer was formed, increased the corrosion resistance of steel surface.