This work aims to understand oxygen solubility in pure and aqueous amine solvents for CO₂ capture. Commercially available dissolved oxygen sensors were studied to evaluate whether these can be used for measuring oxygen solubility in the carbon capture processes. It also aims to understand the possible discrepancies from realistic concentrations of oxygen when using a dissolved oxygen sensor. Two independent measurement principles were used for this purpose, both electrochemical and optical. Furthermore, a Winkler titration method was used to aid the validation of the sensors as well as understanding salting-out effects. A simple model for predicting oxygen solubility in CO₂-loaded ethanolamine solutions was made, which also has potential for predicting oxygen solubility in other loaded amine solutions. The results of the study show that dissolved oxygen sensors may be applied for measurement of oxygen concentrations in amine solutions and that different amines and different concentrations in water only show small variations in oxygen solubility. The sensors may also be used in CO₂-loaded amine solutions, but here the increased conductivity of the solution may give a higher measured concentration of oxygen, than it is in reality. In ethanolamine, the consumption of oxygen is faster than the mass transfer of oxygen from gas to liquid phase, giving lower concentrations of oxygen than it should be in absence of a chemical reaction between oxygen and amine.

One of the major issues encountered in the Post Combustion CO₂ Capture processes is the degradation of the solvent which can be in great part attributed to the presence of oxygen in the solution. The present report focuses on the demonstration of DORA (Dissolved Oxygen Removal Apparatus), a technology developed by TNO as a counter-measure of oxidative degradation. The DORA was first operated in combination with TNO's mobile bench-scale CO₂ capture pilot (5 Nm³/h flue gas capacity) with artificial flue gas, showing an instant drop of 15% and an overall reduction of approximately 70% in the ammonia emissions from the absorber, which is an indication of reduced degradation. The technology was also demonstrated using the same pilot in an industrial environment in collaboration with the facility PlantOne bringing DORA from TRL5 to TRL6. This campaign proved that DORA contributed to the deacceleration of solvent degradation. The tests were executed with a porous membrane, and it was observed that exposure to degraded solvents led to solvent leakage through this membrane. Therefore, the use of a coated membrane was proposed to optimize the operation and increase oxygen removal. The use of this membrane is demonstrated at TRL3. Along with that, a model was developed to determine mass transfer resistances and the membrane area required to remove different levels of dissolved oxygen.

Oxidative degradation is a serious concern for upscaling of amine-based carbon capture technology. Different kinetic models have been proposed based on laboratory experiments, however the kinetic parameters included are limited to those relevant for a lab-scale system and not a capture plant. Besides, most of the models fail to recognize the catalytic effect of metals. The objective of this work is to develop a representative kinetic model based on an apparent auto-catalytic reaction mechanism between solvent degradation, corrosion and ammonia emissions. Measurements from four different pilot plants: (i) EnBW's plant at Heilbronn, Germany (ii) TNO's plant at Maasvlakte, The Netherlands; (iii) CSIRO's plants at Loy Yang and Tarong, Australia and (iv) DONG Energy's plant at Esbjerg, Denmark are utilized to propose a degradation kinetic model for 30 wt % ethanolamine (MEA) as the capture solvent. The kinetic parameters of the model were regressed based on the pilot plant campaign at EnBW. The kinetic model was validated by comparing it with the measurements at the remaining pilot campaigns. The model predicted the trends of ammonia emissions and metal concentration within the same order of magnitude. This study provides a methodology to establish a quantitative approach for predicting the onset of unacceptable degradation levels which can be further used to devise counter-measure strategies such as reclaiming and metal removal.

Degradation of amines is one of the most important issues to be addressed for absorption-desorption based post-combustion CO₂ capture. Several laboratory studies have been performed to identify the degradation products and understand the mechanisms of degradation. However, there seems to be a gap in knowledge from translating the lab scale studies to observations from the pilot campaigns. Moreover, the observations from different pilot plant campaigns can be quite different. The objective of this study is to compare the solvent degradation behavior from different campaigns and highlight their causes in terms of solvent metal content and ammonia emissions. Results from the following different pilot plants are evaluated: (a) TNO's CO₂ capture plant at Maasvlakte, the Netherlands, (b) EnBW's CO₂ capture plant at Heilbronn, Germany and (c) ENEL's CO₂ capture plant at Brindisi, Italy. The different rate of oxidative degradation are correlated to the different operating conditions and layout of the pilot plants. Along with these results, kinetic models based on laboratory studies are used to compare the pilot plant observations, highlighting the differences between lab-scale studies and pilot plant studies.

CEMCAP is an international R&D project under the Horizon 2020 Programme preparing the ground for the large-scale implementation of CO₂ capture in the European cement industry. This paper concerns the performance modeling of membrane-assisted CO₂ liquefaction as a possible retrofit application for post combustion CO₂ capture. For the relatively large CO₂ concentrations that are typical for the flue gas in conventional cement kilns, it may be possible to capture CO₂ by combining a single membrane unit for bulk separation and a CO₂ liquefaction train in which the waste stream is recycled and mixed with the feed to the membrane system. The required membrane surface area is strongly correlated with the CO₂ concentration in the cement kiln flue gas, as well as targeted CO₂ recovery, pressure ratio across the membrane, membrane separation factor and CO₂ permeance. Specifications for flue gas pre-conditioning and an overall techno-economic evaluation are planned to follow the evaluation of experimental results for membrane performance under realistic conditions, as well as for CO₂ liquefaction performance. Published by Elsevier Ltd.

In view of its promise as sustainable process for CO₂ capture and its potential in the production of feed, food and natural high value products such as omega-3 fatty acids and anti-oxidants such as astaxanthin, large scale algae cultivation is gaining commercial interest. Currently, most systems are based on directly contacting CO₂ containing gas, e.g. flue gas, with the algae culture. However, applicable on small scale, this approach is not applicable on a commercially relevant large scale due to mass transfer limitations. There is need for a cost effective and scalable system. TNO has developed a scalable system for efficient capture of CO₂ as feedstock for algae production. In this system, CO₂ is absorbed in an absorption liquid as bicarbonate. Subsequently, the enriched absorption liquid is fed to the algae, which convert the solubilized CO₂ into biomass and biobased products. Finally, biomass is recovered and the lean absorption liquid is recycled. TNO's integrated process concept was successfully demonstrated with continuous algae cultivation on a 2 L-scale for more than 150 days of which 40 days using flue gas as CO₂ source.

Extensive research efforts have been applied to obtain more efficient and less cost-intensive absorption-based processes and solvent systems for CO₂capture during the last 15-20 years. High concentratedaqueous solutions of piperazine (PZ) have been suggested as a good replacement for the current bench-mark solvent mono-ethanolamine (MEA). So far, the research on concentrated PZ solutions has mainlyfocused on the development and evaluation of various configurations for the post-combustion CO₂cap-ture process. The present paper studies the integration of a configuration based on high-pressure flashregeneration with the upstream power plant. The main focus is on the overall energy performance, but aqualitative analysis of the effect of flexible operation is added as this is important for the optimization ofthe total plant. A power plant integrated with the optimal PZ-based capture plant is found to have a netelectric efficiency of 37.4%, which is 7.2% less than the reference power plant without CO₂capture. Theefficiency penalty when using an MEA-based capture plant including lean-vapour compression is 9.1%.

A major consideration for post-combustion CO₂ capture is the adverse effect of the presence of SO₂ on the absorption desorption process. The most common approach is to remove the SO₂ from the flue gases in a flue gas desulfurization (FGD) unit prior the CO₂ recovery process. This paper reports the experimental and modeling results of a new process for simultaneous removal of CO₂ and SO₂ for post-combustion applications. This process is named CASPER (CO ₂-capture And Sulphur Precipitation for Enhanced Removal), and is based on the precipitation of K₂SO₄ for sulphur removal. The selected CO₂ absorbing solvent is an amino-acid, preferably a potassium amino-acid salt solution. The presence of potassium leads to the subsequent formation of K₂SO₄, which solubility in the CO₂ loaded aqueous solvent solution changes depending on the applied conditions. The optimal crystallization conditions were first determined by characterization of K₂SO₄ solubility window and then evaluated in the lab-scale crystallization unit. In the next step the model system based on potassium beta-alanate solutions, also with addition of sulphate, were tested for CO₂ absorption and desorption pressures by performing VLE (Vapor Liquid Equilibrium) measurements at 40°C and 120°C, respectively. Obtained values were included in preliminary technical assessment, which showed an energetic improvement of 0.7%-points for the CASPER model solvent system in comparison to the baseline 30wt% MEA case.