Ingenieurwissenschaften und zugeordnete Tätigkeiten
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Eingeladener Vortrag
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CO2 streams captured from power stations or industrial plants may contain impurities that impact the consecutive steps of the CO2 capture and storage (CCS) chain. As the basis for an optimization of CO2 purity over the whole CCS chain, impacts of different impurities were investigated at key steps including studies on (i) corrosion of metallic materials in CO2 streams and brine, (ii) fluid and interfacial properties as a function of pressure, temperature and CO2 stream composition and their implications for CO2 transport, injection and geological storage, (iii) costs of different pipeline design options, (iv) geochemical alterations at typical reservoir conditions and their implications for geomechanical rock properties. Major findings are synthesized for two exemplary single source-single sink CCS chain scenarios involving CO2 stream compositions typical for pre-combustion capture and oxyfuel combustion. Recommendations for material selection for compression, transport and injection were derived for various CO2 stream compositions. To reliably control corrosion, a limitation of water contents to 50 ppmv is recommended for pipeline transportation of all CO2 streams. At geological storage conditions, the presence of either O2, NOx or SO2 only weakly affected fluid-mineral/rock interactions that still impacted geomechanical rock properties.
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 [1]. 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 “worst-case 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 re-produced 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.
Since geothermal wells are a feasible energy source to replace fossil fuel supply, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal fluids and temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities.
The corrosion behavior of different high-alloyed metals including duplex and austenitic stainless steels as well as a nickel alloy have been evaluated in artificial geothermal fluids simulating the conditions in some locations with geothermal potential in Germany as well as two sites in Indonesia.
The suitability of carbon steel 25CrMo4, stainless steels X2CrNiMo17-12-2, X2CrNiMo-22-5, X2CrNiMoCuWN25-7-4 and super austenitic steel X1CrNiMoCu32-28-7 in these geothermal fluids obtained by electrochemical measurements and exposure tests is limited. The nickel alloy NiCr23Mo16Al shows an excellent corrosion resistance against pitting corrosion. Excluding its high cost, it is a very good alternative to be used in the construction of geothermal facilities having highly saline brines. Stainless and duplex steels exhibit a limited corrosion resistance concerning pitting and crevice corrosion.
Beside of the higher alloyed materials, also the low-alloyed steel 25CrMo4 could be employed as a constructional material for the geothermal power plant in stagnant highly acidic non saline environments, as long as the wall thickness of the material vs. corrosion rate is taken into account.
Derzeit wird der Einsatz metallener Werkstoffe in CCU-/CCS-Anlagen hinsichtlich deren Korrosionsbeständigkeit und eine eventuell daraus resultierende Herausforderung diskutiert. Während des CO₂-Transportes vom Abscheide- zum Injektionsort kann es aufgrund der den CO₂-Strom begleitenden Beimengungen, wie Wasser, O₂, SOₓ , NOₓ , Temperaturschwankungen durchaus zu Kondensationseffekten und daraus resultierenden Schäden kommen.
Es konnte gezeigt werden, dass die sich möglicherweise innerhalb einer CO₂-Rohrleitung bildenden Kondensate infolge von Begleitstoffen wie SO2 und NO2 eine viel korrosivere Wirkung auf Rohrleitungswerkstoffe entfalten, als in reinem CO₂.
In letzter Zeit kommen immer mehr alternative Energiequellen als Ersatz fossiler Brennstoffe zum Einsatz, so auch die Solarthermie. Jedoch sind die Betriebsbedingungen aufgrund der chemischen Zusammensetzung der Wärmeträgermedien und herrschenden Temperaturen extrem hinsichtlich Korrosion. Da die Kraftwerke bei maximaler Lebensdauer ökonomisch vertretbar sein müssen, ist eine Werkstoffauswahl basierend auf Voruntersuchungen notwendig, um einen sicheren und verlässlichen Betrieb dieser Anlagen zu gewährleisten.
Die Werkstoffauswahl hängt von der Betriebstemperatur eines Kraftwerks bzw. der chemischen Zusammensetzung des Wärmeträgermediums ab. In hochkorrosiven Umgebungen werden aufgrund ihrer sehr guten Korrosionsbeständigkeit Nickelbasislegierungen nicht nur für stark korrosiv beanspruchte Bauteile als die Lösung angesehen. Jedoch kann es durchaus beständigkeitsbedingte Einschränkungen für den Einsatz geben, wofür die hier vorgestellten Ergebnisse dienen sollen.
In diesem Beitrag wird die Beständigkeit ausgewählter hochlegierter Werkstoffe (inklusive einer neuentwickelten Legierung in einer Nitrat-Salzschmelze (60 % NaNO3/40 % KNO3) vorgestellt, die mittels elektrochemischer Messungen und Auslagerungsversuchen ermittelt wurde.
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.
Since geothermal wells are a feasible energy source to replace fossil fuel supply, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal fluids and temperatures, in many cases, extreme in terms of corrosion.
Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities. The corrosion behavior of different high-alloyed metals including Duplex and austenitic stainless steels as well as a nickel alloy have been evaluated in artificial geothermal fluids simulating the conditions in some locations with geothermal potential in Germany as well as two sites in Indonesia. The suitability of carbon steel 25CrMo4, stainless steels X2CrNiMo17-12-2, X2CrNiMo-22-5, X2CrNiMoCuWN25-7-4 and super austenitic steel X1CrNiMoCu32-28-7 in these geothermal fluids obtained by electrochemical measurements and exposure tests is limited. The nickel alloy NiCr23Mo16Al shows an excellent corrosion resistance against pitting corrosion. Excluding its high cost, it is a very good alternative to be used in the construction of geothermal facilities having highly saline brines. Stainless and Duplex steels exhibit a limited corrosion resistance concerning pitting and crevice corrosion. Beside of the higher alloyed materials, also the lowalloyed steel 25CrMo4 could be employed as a constructional material for the geothermal power plant in stagnant highly acidic non Saline environments, as long as the wall thickness of the material vs. corrosion rate is taken into account.
Within the last years the use of feasible alternative energy sources has risen and is going to replace fossil resources more and more. Nevertheless, service conditions in solar facilities are due to the chemical composition of heat transmission media and temperatures, in many cases, extreme in terms of corrosion. Since the construction of power plants shall be economical with maximum life service, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of those facilities.
The materials selection depends on the operation temperature of a power plant on the chemical composition of the transmission fluid used. In high corrosive environments Ni-based alloys are often used as an all-round solution for the construction of corrosion resistant parts, because of their good corrosion properties. However, there might be limits for their use regarding their corrosion behavior, with which this contribution deals.
By means of electrochemical measurements and exposure tests the suitability of two high alloyed materials X8NiCrSi38 18 and NiCr25FeAlYB in molten nitrate salt (60 % NaNO3/40 % KNO3) was characterized at 600 °C.
Since geothermal wells are a feasible energy source to replace fossil fuel supply, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal fluids and temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities.
This contribution deals with the evaluation of the corrosion behavior of duplex steel S31803 (318LN, X2CrNiMoN22-5-3, 1.4462) conducted by electrochemical measurements and exposure tests in artificial geothermal waters simulating the conditions in different locations with geothermal potential in Germany.
The duplex steel S31803 shows limited suitability for applications in artificial geothermal waters due to its susceptibility to pitting and crevice corrosion.
For low saline geothermal waters it can be considered suitable at moderate temperatures. Slight crevice corrosion susceptibility needs to be considered.
Results are being incorporated into a materials catalogue for geothermal applications which shall provide basic information for designers and users of geothermal facilities.
Since geothermal wells are a feasible energy source to replace fossil fuel supply, many technologies have been developed to take advantage of geothermal energy. Nevertheless, service conditions in geothermal facilities are due to the chemical composition of hydrothermal fluids and temperatures, in many cases, extreme in terms of corrosion. Therefore, materials selection based on preliminary material qualification is essential to guarantee a secure and reliable operation of the facilities.
This contribution deals with the evaluation of the corrosion behavior of duplex steel S31803 (318LN, X2CrNiMoN22-5-3, 1.4462) conducted by electrochemical measurements and exposure tests in artificial geothermal waters simulating the conditions in different locations with geothermal potential in Germany.
The duplex steel S31803 shows limited suitability for applications in artificial geothermal waters due to its susceptibility to pitting and crevice corrosion.
For low saline geothermal waters it can be considered suitable at moderate temperatures. Slight crevice corrosion susceptibility needs to be considered.
Results are being incorporated into a materials catalogue for geothermal applications which shall provide basic information for designers and users of geothermal facilities.