Assessment of Erosion-Corrosion as Possible Failure Mechanism of Reboiler at Technology Centre Mongstad
“Being on the forefront of technology development and testing is not without its risks. After experiencing an equipment failure during a testing campaign, Technology Centre Mongstad (TCM DA) joined forces with specialists from the Corrosion Technology Department at the Institute for Energy Technology in Kjeller, to find the cause of the failure. As a result of a successful series of laboratory experiments performed at IFE, a mechanism involving erosion-corrosion was demonstrated to be the likely cause, providing valuable feedback for mitigating measures”, says Attila Palencsár.
During a series of test campaigns for CO2 capture using monoethanolamine (MEA) at the Technology Centre Mongstad (TCM), a failure occurred in the reboiler of the amine plant caused by severe damage to the plate heat exchanger made of AISI 316L Stainless Steel. Considerable material loss (ca. 200-250 µm reduction in thickness) including two perforations led to leakage between the solvent and heating fluid sides. Preliminary investigations by TCM revealed that during a test period when oxygen scavenger was injected, a rise in the concentration of metal cations occurred; it was considered very likely that the failure was related to this “scavenger period”. A collaboration was subsequently started with the Institute for Energy Technology (IFE) to assess the failure mode of the reboiler plates. As reported earlier elsewhere, three plausible hypotheses were identified: the “erosion” hypothesis considers that erosion alone is sufficient to cause the failure by damaging the passive film from the stainless-steel surface and allowing corrosion attacks to develop even under normal operation conditions (or abrading the steel itself); the “erosion and enhanced corrosivity” hypothesis considers that erosion could remove passivity, but the specific chemistry in the scavenger period is also required to prevent rapid re-passivation and to sustain severe corrosion; the “enhanced corrosivity” hypothesis implies that the specific chemistry in the scavenger period can cause depassivation and sustain a considerably high corrosion rate, even in the absence of erosion. This paper presents the results of laboratory testing to validate the erosion and enhanced corrosivity hypothesis. An experimental setup based on the radial impeller concept was developed around a commercial glass autoclave. Experiments were conducted with used solvent from the TCM plant, simulating i.a. different plant conditions: anoxic rich MEA with an excess of oxygen scavenger and oxygenated rich MEA with scavenger and an excess of oxygen. Significant damage of the stainless-steel specimens occurred with erosive action in a used rich solvent with excess oxygen scavenger (i.e. anoxic conditions). The observations agree with damage of passive film, allowing activation of the corrosion process. The surface likely fails to re-passivate in an anoxic environment. The same mechanism is not sustained in an oxygenated environment where the surface can re-passivate. The results obtained suggest that the erosion and enhanced corrosivity hypothesis is valid and plausible. This mechanism may be the actual failure mode in the TCM reboiler.
Real-time monitoring of 2-amino-2-methylpropan-1-ol and piperazine emissions to air from TCM post combustion CO2 capture plant during treatment of RFCC flue gas
“Removing CO2 from industrial flue gases to mitigate climate change should not come at the cost of our local environment. Amine-based capture can introduce trace pollutants to the treated flue-gas and can potentially cause harm if not adequately controlled. TCM have through many years worked to demonstrate that we can monitor and control these contaminants. In this work, we show that commercially available industrial monitoring equipment can help full scale plants monitor their emissions down to low Parts Per Billion (ppb) concentrations”, says Audun Dragset.
Monitoring and understanding the emissions of pollutants is vital for safe implementation of new industries. To ensure the safe adoption of amine-based post-combustion carbon capture to combat climate change, reliable and accurate monitoring technologies must be available for commercial projects to ensure they can monitor and control any new pollutants that might results from capturing CO2 from an industrial flue gas. As a test site for carbon capture technologies, Technology Centre Mongstad (TCM) monitors pollutants emitted in the flue gas via online sampling and analysis as per regulatory requirements. This work presents the first results from a newly installed ion-molecule reaction mass spectrometer (IMR-MS) that was employed during a test campaign with the amine solvent blend of 2-amino-2-methylpropan-1-ol (AMP) and piperazine (PZ) to monitor trace pollutants in the emitted flue gas. The primary pollutants were monitored and reported in real time in the range from 100 ppb (parts per billion) to 10 ppm (parts per million) and compared with extractive isokinetic sampling during a test campaign with an oil refinery cracker gas. The instrument allowed for real-time trending of the amine pollutants AMP and PZ in ppb range, which is the expected range required by regulators for some full-scale plants.
Development of process model of CESAR1 solvent system and validation with large pilot data
“It was great pleasure to work with National Energy Technology Laboratory (NETL) on the development of process model for CESAR 1 solvent for CO2 capture process. This work is crucial for the deployment of non-proprietary blended solvent system for CO2 capture. I would like to thank NETL team for their major contributions”, says Koteswara Rao Putta.
The United States (U.S.) Department of Energy (DOE)-sponsored Carbon Capture Simulation for Industry Impact (CCSI2) is collaborating with Norway’s Technology Centre Mongstad (TCM) on the development and validation of a process model of the CESAR1 solvent system for post-combustion carbon capture applications. The CESAR1 solvent, developed through the CO2 Enhanced Separation and Recovery (CESAR) project, is an aqueous blend of 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) with concentrations of approximately 3 M and 1.5 M, respectively. The process model, developed in the Aspen Plus® software platform, uses thermodynamic and kinetic models from the AMP-H2O-CO2 and PZ-H2O-CO2 system models distributed by Aspen Tech. Enhancements in this work include calibrating the interaction parameters for the AMP-PZ pair with thermodynamic data from the open literature for the AMP-PZ-H2O-CO2 system and updating the reaction kinetics parameters to ensure thermodynamic consistency with the chemical equilibria. The process model is validated with a set of seven steady-state test runs, collected over a wide range of operating conditions at the pilot plant at TCM (12 MWe scale) with natural gas-based combined cycle turbine flue gas (~ 3.5 vol% CO2). The integrated process model developed for the TCM pilot plant includes rate-based models for the CO2 absorption and solvent regeneration processes and predicts key output variables (e.g., CO2 capture percentage, specific reboiler duty) within ± 5% for the validation data set. This paper presents model development and validation work for an initial version of the CESAR1 process model along with discussion of future updates to be made to the model prior to its open-source release.