Amine-based Post-combustion CO2 Capture Research Articles

The role of flexible CCS in the UK's future energy system

That CCS will be required to operate in a flexible and load following fashion in the diverse energy landscape of the 21st century is well recognised. However, what is less well understood is how these plants will be dispatched at the unit generator scale, and what effect this will have on the performance and behaviour of the plant at the individual unit operation level. To address this gap, we couple an investment and unit commitment energy system model with a detailed plant-level model of a super-critical coal-fired power station integrated with an amine-based post-combustion CO2 capture process. We provide insight into the likely role of coal and gas CCS plants in the UK's energy system in the 2030s, 2040s and 2050s. We then evaluate the impact that this has on the performance of an individual coal CCS plant operating in this system, and chart its evolution throughout this period. Owing to the increased frequency and duration of part-load operation, asset utilisation and average efficiency suffer, leading to a substantially increased LCOE, implying that CCS costs will need to decrease more rapidly than is currently expected. Further, as a direct consequence of the dynamic operation, the interaction of the CCS plants with the downstream CO2 transport network is characterised by highly transient behaviour, including periods during which no CO2 is injected to the transport network, implying that the transport system must therefore be designed to incorporate this variability of supply.

Thermal degradation of piperazine and diethanolamine blend for CO2 capture

In amine-based post-combustion CO2 capture, solvent loss contribute to process operation problems like corrosion, fouling, foaming as well as is responsible for economic deficit. In this work, thermal degradation of blended 3.2m DEA and 0.8m was investigated at 135°C, simulating the stripper temperature. CO2 loading of the system was varied from 0.0 to 0.4mole CO2/mole alkalinity to explore its effect on degradation of the blended system. Experiments were conducted in 316 stainless steel cylinders, fitted with Swagelok® endcaps made of 316 stainless steel, which were kept in convection ovens. Degraded samples were analyzed by using gas chromatography (GC) for final concentration and identification of the degradation products. Thermal loss of PZ was high in the PZ/DEA blend than other investigated blends of PZ like PZ/MDEA, PZ/AMP, and PZ/MEA under similar experimental conditions. CO2 loading increased the rate of degradation of both PZ and DEA; however, rate of degradation of PZ was higher at high CO2 loading and increased abruptly than that of DEA. Concentration of PZ approached to zero within 300h of experiment at high CO2 loading. Mechanism for the formation of major degradation products is proposed in the study. An empirical rate law is articulated to determine the loss of PZ. Results of model are in good agreement with experimental results.

Dynamic modelling, identification and preliminary control analysis of an amine-based post-combustion CO2 capture pilot plant

Solvent-based post combustion CO2 capture (PCC) is considered as a mature technology for dealing with CO2 emissions from fossil-fired power plants. In this study, a mathematical black box model is developed to analyse the dynamic responses of a PCC pilot plant. The model identification reported the dynamics of variables of the key units in the plant, the absorber, rich/lean heat exchanger and desorber. Pilot plant dynamic data were used to develop a data-driven model for each unit operation. Individual models were integrated to produce a simplified 4 × 3 PCC process model of the PCC plant. The fastest dynamic with a time constant ranging from 2 to 3 min featured in the relationship between power plant flue gas flow rate and CO2 concentration in the absorber off gas. Whereas, the slowest response with a process time constant between 9 and 27 min occurred in CO2 concentration at the top of the stripper due to changes in reboiler heat duty. Preliminary control analysis using relative gain array (RGA) analysis suggested that carbon capture efficiency, CC (%), and energy performance, EP (MJ per kg of CO2 captured), can be controlled by manipulating the lean solvent flow rate and reboiler heat duty, respectively. The proposed control structure was tested and tracked CC and EP random set point step changes in the range between 7–25 h and 4–5 h respectively. This study contributes to understanding transient variable behaviours in PCC plants; concurrent with current industrial requirements for controllability and flexible operation of PCC plants, in response to the dynamics of power plant load, electricity and carbon prices.

Dynamic modelling and control strategies for flexible operation of amine-based post-combustion CO2 capture systems

The abatement of anthropogenic CO2 gas and extensive demand for electrical energy has motivated cleaner power production from fossil fuels. This paper presents a mechanistic model of amine-based post-combustion CO2 capture (PCC) process. Validation of the proposed model is performed using pilot plant data available from literature. Process control analysis is then performed using this model whereby three control schemes are proposed; a standard PID feedback control scheme, a cascade-PID scheme and thirdly a model-based strategy in the form of model predictive control (MPC). Stepwise set point tracking and disturbance rejection scenarios are employed to evaluate the performance of the proposed controllers for flexible operation, i.e., under variable plant load condition surrogate to electricity and carbon market prices patterns. Three elements of constraints include operational, economic and environmental are considered in selecting the best control strategy. The closed-loop simulation results showed that the MPC strategy handles very well the servo and regulator problems without violating the above mentioned constraints.

Efficiency improvements for the coal-fired power plant retrofit with CO 2 capture plant using chilled ammonia process

Abstract Development of clean coal technologies for power generation is crucial in meeting the European Union 2050 target to reduce greenhouse gas emissions. CO2 capture technology using chemical solvents currently has the highest potential to decarbonise coal-based power generation. Substitution of amine solvent with NH3 has been proposed as a viable option to reduce the efficiency penalty. In this study, the scenario of a supercritical coal-fired power plant retrofitted with a chilled ammonia process capture plant and CO2 compression unit was modelled in a common simulation environment. To fully assess the integration impact on power plant performance, the pressure loss due to steam extraction has been taken into account by using the Stodola ellipse law. Analysis of a basic integration scenario revealed that the efficiency penalty fell between 10.4% and 10.9% points depending on the stripper pressure. The quality of extracted steam became insufficient to meet the reboiler heat requirement above a stripper pressure of 21.8 bar, and the lowest efficiency penalty was obtained when reboiler condensate was returned to the deaerator in the power plant. In evaluating measures to improve integration, the efficiency penalty was reduced to 8.7–8.8% points through the integration of a single-stage or two-stage auxiliary steam turbine, respectively, and a back-pressure turbine. Nevertheless, the analysis has indicated that the net impact on power plant performance is similar to that of an amine-based post-combustion CO2 capture plant.

An overview of solvent management and emissions of amine-based CO2 capture technology

Increasing global carbon dioxide (CO2) emissions are a rising concern for the global climate change. Amine-based post-combustion CO2 capture (PCC) technology is one of the mature options to contribute to the mitigation of these emissions. The technology is approaching toward its commercialization. However, there are two important problems, which should properly be addressed, solvent management and the amine-based PCC emissions. Major losses in amines are due to the oxidative and thermal degradation. Concentration of oxygen (O2) is the driving force for the oxidation. Temperature, CO2 loading and amine concentration affect both thermal and oxidative degradation. This manuscript reviews solvent selection, thermal and oxidative degradation of amines used for CO2 capture. Furthermore, amine-based PCC emissions have also been highlighted, with some of their concerns. Based on literature reviewed and discussions provided, conclusions are made. In addition, some of the future work is also directed in form of suggestions.

Toward Understanding Amines and Their Degradation Products from Postcombustion CO2 Capture Processes with Aerosol Mass Spectrometry

Amine-based postcombustion CO2 capture (PCCC) is a promising technique for reducing CO2 emissions from fossil fuel burning plants. A concern of the technique, however, is the emission of amines and their degradation byproducts. To assess the environmental risk of this technique, standardized stack sampling and analytical methods are needed. Here we report on the development of an integrated approach that centers on the application of a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) for characterizing amines and PCCC-relevant species. Molecular characterization is achieved via ion chromatography (IC) and electrospray ionization high-resolution mass spectrometry (ESI-MS). The method has been optimized, particularly, by decreasing the AMS vaporizer temperature, to gain quantitative information on the elemental composition and major nitrogen-containing species in laboratory-degraded amine solvents commonly tested for PCCC applications, including ethanolamine (MEA), methyldiethanolamine (MDEA), and piperazine (PIP). The AMS-derived nitrogen-to-carbon (N/C) ratios for the degraded solvent and product mixtures agree well with the results from a total organic carbon and total nitrogen (TOC/TN) analyzer. In addition, marker ions identified in the AMS spectra are used to estimate the mass contributions of individual species. Overall, our results indicate that this new approach is suitable for characterizing PCCC-related mixtures as well as organic nitrogen species in other sample types. As an online instrument, AMS can be used for both real-time characterization of emissions from operating PCCC plants and ambient particles in the vicinity of the facilities.

Amines and amine-related compounds in surface waters: A review of sources, concentrations and aquatic toxicity

This review compiles available information on the concentrations, sources, fate and toxicity of amines and amine-related compounds in surface waters, including rivers, lakes, reservoirs, wetlands and seawater. There is a strong need for this information, especially given the emergence of amine-based post-combustion CO2 capture technologies, which may represent a new and significant source of amines to the environment. We identify a broad range of anthropogenic and natural sources of amines, nitrosamines and nitramines to the aquatic environment, and identify some key fate and degradation pathways of these compounds. There were very few data available on amines in surface waters, with reported concentrations often below detection and only rarely exceeding 10μg/L. Reported concentrations for seawater and reservoirs were below detection or very low, while for lakes and rivers, concentrations spanned several orders of magnitude. The most prevalent and commonly detected amines were methylamine (MA), dimethylamine (DMA), ethylamine (EA), diethylamine (DEA) and monoethanolamine (MEAT). The paucity of data may reflect the analytical challenges posed by determination of amines in complex environmental matrices at ambient levels. We provide an overview of available aquatic toxicological data for amines and conclude that at current environmental concentrations, amines are not likely to be of toxicological concern to the aquatic environment, however, the potential for amines to act as precursors in the formation of nitrosamines and nitramines may represent a risk of contamination of drinking water supplies by these often carcinogenic compounds. More research on the prevalence and toxicity of amines, nitrosamines and nitramines in natural waters is necessary before the environmental impact of new point sources from carbon capture facilities can be adequately quantified.

Atmospheric Chemical Reactions of Monoethanolamine Initiated by OH Radical: Mechanistic and Kinetic Study

Monoethanolamine (MEA) is a benchmark and widely utilized solvent in amine-based postcombustion CO2 capture (PCCC), a leading technology for reducing CO2 emission from fossil fuel power plants. The large-scale implementation of PCCC would lead to inevitable discharges of amines to the atmosphere. Therefore, understanding the kinetics and mechanisms of the transformation of representative amine MEA in the atmosphere is of great significance for risk assessment of the amine-based PCCC. In this study, the H-abstraction reaction of MEA with ·OH, and ensuing reactions of produced MEA-radicals, including isomerization, dissociation, and bimolecular reaction MEA-radicals+O2, were investigated by quantum chemical calculation [M06-2X/aug-cc-pVTZ//M06-2X/6-311++G(d,p)] and kinetic modeling. The calculated overall rate constant [(7.27 × 10(-11)) cm(3) molecule(-1) s(-1)] for H-abstraction is in excellent agreement with the experimental value [(7.02 ± 0.46) × 10(-11) cm(3) molecule(-1) s(-1)]. The results show that the product branching ratio of NH2CH2 · CHOH (MEA-β) (43%) is higher than that of NH2 · CHCH2OH (MEA-α) (39%), clarifying that MEA-α is not an exclusive product. On the basis of the unveiled reaction mechanisms of MEA-radicals + O2, the proton transfer reaction mass spectrometry signal (m/z 60.044), not recognized in the experiment, was identified.

Impact of Flue Gas Contaminants on Monoethanolamine Thermal Degradation

The buildup of flue gas contaminants in amine-based postcombustion CO2 capture processes is an important concern due to its potential impact on solvent degradation and reclaiming. In this research, in order to explore the impact of flue gas contaminants on solvent thermal degradation, sodium nitrite, fly ash, sodium sulfate, and sodium thiosulfate were each added into carbon-loaded 5.0 M monoethanolamine (MEA) solution and the solutions were exposed to high-temperature degradation conditions. MEA degrades significantly more in the presence of nitrite (5000 ppm) than MEA alone at the same amine mole concentration. The MEA degradation activation energy of MEA–nitrite solution is calculated and found to be approximately one-seventh of that of MEA solution without nitrite. Addition of nitrite not only enhanced generation of several MEA thermal degradation products but also induced formation of diethanolamine (DEA) and N-(2-hydroxyethyl)piperazin-3-one (HEPO), which have been known to form during MEA oxidative...

Evaluation of Post-Combustion CO<sub>2</sub> Capture Technologies

This paper evaluates the results of two recent studies of advanced amine-based, post-combustion CO2 capture plant designs. The first study was conducted by the IEA Greenhouse Gas R&D Programme (IEA GHG), while the second study was conducted by Parsons for the US DOEs National Energy Technology Laboratory (NETL). Fluors improved monoethanolamine (MEA) process, known as the Econamine FG PlusSM technology, is utilised for both studies. Cost and performance estimates for both pulverized coal and natural gas-fired combined cycle plants are summarized. Differences between the design bases and assumptions for the two studies are discussed. The Econamine FG PlusSM technology, as an improved process in amine-based post-combustion CO2 capture described in this paper is leading to lower increases in the cost of electricity (COE). Both the DOE/Parsons and IEA GHG studies show that the increase is now down to 42 to 43% from as high as 60 to 70% indicated from previous studies for PC plants with CO2 capture.

Amine-based post-combustion CO2 capture in air-blown IGCC systems with cold and hot gas clean-up

This paper focuses on the thermodynamic performance of air-blown IGCC systems with post-combustion CO2 capture by chemical absorption. Two IGCC technologies are investigated in order to evaluate two different strategies of coal-derived gas clean-up. After outlining the layouts of two power plants, the first with conventional cold gas clean-up and the second with hot gas clean-up, attention is paid to the CO2 capture station and to issues related to exhaust gas recirculation in combined cycles.The results highlight that significant improvements in IGCC performance are possible if hot coal-derived gas clean-up is realized before the syngas fuels the combustion turbine, so the energy cost of CO2 removal in an amine-based post-combustion mode is less strong. In particular, IGCC net efficiency as high as 41.5% is calculated, showing an interesting potential if compared to the one of IGCC systems with pre-combustion CO2 capture. Thermodynamic effects of exhaust gas recirculation are investigated as well, even though IGCC performance does not significantly vary against a more complicated plant layout.

Application of neuro-fuzzy modeling technique for operational problem solving in a CO2 capture process system

A good understanding about relationships among key process parameters is important in optimizing operation and enhancing efficiency of the CO2 capture process system. This understanding would enable the operator to better analyze process conditions and become aware of ongoing trends or events so that timely and effective control actions can be taken for adjusting the relevant process parameters and efficiency of plant operations can be enhanced. The studies that focused on exploring the key parameters of the amine-based post-combustion CO2 capture process system implemented at the International Test Center of CO2 Capture (ITC) have revealed that among multiple data modeling techniques adopted, the adaptive-network-based fuzzy inference system (ANFIS) modeling approach generated satisfactory models for adequately describing the process system. This paper presents development and application of the four ANFIS models for solving four real-life problems encountered in operation of the CO2 capture process system. The testing results of the four developed models show that they can be applied for satisfactory solution of these problems. Some lessons and observations made during the application process are also discussed.

Integrated Techno-economic and Environmental Assessment of an Amine-based Capture

A systematic methodology for integrated techno-economic and environmental assessment of CCS value chains is presented and applied to assess the impact of the CO2 concentration on an amine-based post-combustion CO2 capture process. In this methodology, the technical assessment, economic evaluation, and environmental assessment (focusing on the global warming effect) are integrated in order to avoid the unilateral understandings obtained when these assessments are performed separately. Seven cases with CO2 concentrations between 2.5 and 20.5% (mol) are investigated in terms of energy consumptions, the overall costs, as well as the climate impact of the capture process. The process simulation is performed with Aspen Plus®, and the techno-economic evaluation using Aspen Process Economic Analyzer®. A hybrid life cycle assessment approach is used to estimate the climate impact of the capture based on the results of techno-economic assessment. The CO2 avoided capture cost, which reflects both the techno- economic and environmental performances, is used to assess the comprehensive impact of the CO2 concentration on the capture process.

Dynamic modelling and analysis of an amine-based post-combustion CO2 capture absorption column

A dynamic, non-equilibrium model of a packed column for the chemisorption of CO2 from dilute gas streams using a monoethanolamine solvent has been proposed. The model uses the SAFT-VR equation of state to describe the thermophysical properties and fluid-phase behaviour of this process. The SAFT-VR equation-of-state is used to account for all of the inter-species interactions in the fluid, including the reactions. In this way, we avoid the use of enhancement factors. Further it is not necessary to include a detailed description of the reaction mechanisms or the reaction products. Steady state validation of the proposed model is performed using pilot plant data. The position and extent of the mass transfer zone is found to be a function of competing interphase fluxes of H2O and CO2. We evaluate through dynamic simulation the effect of changing the lean solvent flowrate and thermodynamic state on column behaviour. The influence of flue gas humidity on the position and shape of the mass transfer zone is also highlighted and discussed.

Feasibility of integrating solar energy into a power plant with amine-based chemical absorption for CO2 capture

Solar thermal energy has the potential to supply the thermal demand of stripper reboiler in the power plant with amine-based post combustion CO2 capture. The performance of a power plant integrated with solar assisted post combustion CO2 capture (SCC) is largely affected by the local climatic conditions, such as solar irradiation, sunshine hours and ambient temperature, the type of solar thermal collector and CO2 recovery ratio. The feasibility evaluation results about such a power plant show that the cost of electricity (COE) and cost of CO2 avoidance (COA) are mainly determined by the local climatic conditions. For the locations having higher solar irradiation, longer sunshine hours and higher ambient temperature, the power plant with SCC has lower COE and COA. COE and COA are sensitive to the prices of solar thermal collectors. In order to achieve lower COE and COA compared to the power plant integrated with non-solar assisted post combustion capture, the price of solar thermal collector has to be lower than 150USD/m2 and 90USD/m2 for the solar trough and vacuum tube, respectively.

Safety assessment of emissions from amine-based post combustion CO2-capture

Safety assessment of emissions from amine-based post combustion CO2-capture

Experimental research on the performance of CO2-loaded solutions of MEA and DEA at regeneration conditions

Amine-based post combustion CO2 capture is considered as one of the most advanced technologies to be implemented in new and existing coal-fired power plants for CCS. Although it has proven technically viable, it has not been installed on a large-scale application yet. The main drawback of the process is the high energy requirement for the regeneration of the amine solution. Values around 4MJ/kg of CO2 for the standard MEA-based process have been reported. The heat duty must be supplied by means of low-pressure steam from the power plant, which causes a decrease in the power plant net efficiency of up to 13%-points. Therefore, improvements in process technology and solvent development are important to reduce the penalty in the power plant efficiency.Results from lab-scale research on the absorption and desorption of MEA and DEA at different concentrations are presented and discussed. Absorption and desorption capacities, as well as the regeneration of the CO2-loaded solutions in a stripper column and the influence of different operating parameters have been experimentally investigated.