MEA-based CO2 Capture Process Research Articles

A Tchebycheff-based multi-objective combined with a PSO–SQP dynamic real-time optimization framework for cycling energy systems

The aim in this work is to develop an optimization framework to address cycling of baseload energy systems due to the penetration of renewables into the grid. The developed strategy corresponds to a multi-objective and dynamic real-time optimization (MOO-DRTO) framework applied to a postcombustion MEA-based CO2 capture process from a baseload coal-fired power plant under cycling conditions. A Tchebycheff-based method is used for the multi-objective optimization (MOO) component. Also, a hybrid approach consisting of Particle Swarm Optimization (PSO) and Sequential Quadratic Programming (SQP) is implemented for the first time in process systems engineering to solve the dynamic real-time optimization (DRTO) component. The objectives considered in the MOO-DRTO framework are economic and environmental. The proposed MOO-DRTO strategy is successfully implemented and 24-h optimal output trajectories for the carbon capture system under cycling are generated. Also, the optimal compromise is chosen from the Pareto front according to a set of selected weights for the objectives with minimal interaction between the framework and decision maker. The results indicated that the developed framework has potential to be extended to plant-wide optimization applications under cycling.

Alternative production of methanol from industrial CO2

Carbon dioxide valorization into value added products have become subject to much study to reduce industrial CO2 emissions and fossil energy resource consumption. In this context, the purpose of this study is to evaluate and highlight the interest of CO2 conversion into methanol through a complete techno-economic and environmental assessment of the entire process chain. The integrated process, successfully implemented in Aspen Plus®, is designed to treat the CO2 coming from a conventional cement plant. A MEA-based CO2 capture process is considered, and the captured CO2 is then directly sent to the conversion unit for its catalytic conversion. Consequently, combining the two units leads to relevant integrations, especially regarding the reuse of the heat provided by the exothermal methanol reactions for the regeneration of the CO2 capture solvent. An economic assessment is proposed to estimate the operational and investment costs, as well as the net present value, which demonstrates that the economic feasibility strongly depends on electricity and H2 production costs. A Life Cycle Analysis method is finally performed to identify the main environmental hotspots. The underlying process design offers a significant reduction in greenhouse gases (besides other categories) when compared to the conventional fossil production from natural gas.

Simulation and optimization study on aqueous mea-based co2 capture process

Chemical absorption with monoethanolamine (MEA) is the most common technology used in the CO2 removal unit for a power plant. However，the application is hindered by its high energy consumption for absorbent regeneration. In this study, a rate-based model of the typical MEA-based CO2 capture process was built for a power plant with Aspen Plus software. The thermodynamic model of ENRTL-RK was adopted. Temperature fields and the flow rates changes of components in absorber and stripper were obtained. And process analysis using the equilibrium stage model was performed to investigate the effects of operation parameters (CO2 loading in lean solution and stripper pressure) on the regeneration energy consumption. With heat pump technology adopted to assist lean solution regeneration, two processes were proposed and the reboiler duties decreased to 2.77 GJ/t CO2 and 2.38 GJ/t CO2, respectively, owing to the recovery of latent heat and part of sensible heat. Moreover, condenser duties were reduced obviously.

Nonlinearity Analysis and Multi-Model Modeling of an MEA-Based Post-Combustion CO2 Capture Process for Advanced Control Design

The monoethanolamine (MEA)-based post-combustion CO2 capture plant must operate flexibly under the variation of the power plant load and the desired CO2 capture rate. However, in the presence of process nonlinearity, conventional linear control strategy cannot achieve the best performance under a wide operation range. Considering this problem, this paper systematically studies the multi-model modeling of the MEA-based CO2 capture process for the purpose of (1) implementing well-developed linear control techniques to the design of an advanced controller and (2) achieving a wide-range flexible operation of the CO2 capture process. The local linear models of the CO2 capture process are firstly established at given operating points using the method of subspace identification. Then the nonlinearity distribution at different loads of an upstream power plant and different CO2 capture rates is investigated via the gap metric. Finally, based on the nonlinearity investigation results, the suitable linear models are selected and combined together to form the multi-model system. The proposed model is validated using the measurement data, which is generated from a post-combustion CO2 capture model developed in the go-carbon capture and storage (gCCS) simulation platform. As the proposed multi-linear model has a simple mathematical expression and high prediction accuracy, it can be directly employed as the control model of a practical advanced control strategy to achieve a wide operating range control of the CO2 capture process.

Nonlinear model predictive control and H∞ robust control for a post-combustion CO2 capture process

This work focuses on the design of a nonlinear model predictive controller (NMPC) and an H∞ robust controller for an MEA-based CO2 capture process. The model used in the NMPC is a nonlinear, additive, autoregressive model with exogenous (NAARX) inputs. Uncertainties are unavoidable in chemical processes. Therefore, a robust controller is designed for the CO2 capture process based on μ-synthesis with a DK-iteration algorithm. The effects of uncertainties due to measurement noise and model mismatches are evaluated for both the NMPC and robust controller. The system disturbances include a number of input and output disturbances such as the flue gas flowrate and composition and variable capture targets. This study shows that the tradeoff between the fast tracking performance of the NMPC and the superior robust performance of the robust controller must be considered while designing the control system for the CO2 capture units.

Amine-based post-combustion CO2 capture mediated by metal ions: Advancement of CO2 desorption using copper ions

For the large-scale implementation of amine-based post-combustion CO2 capture, the energy consumption associated with the absorbent regeneration remains the most critical challenge. Despite efforts to reduce regeneration duty, such as using new amine formulations and modifying process configurations, an advanced method of overcoming this technical barrier is still required. Here, we introduce a novel approach to decreasing the heat requirement of absorbent regeneration by introducing metal ions catalyst into aqueous amine solution. Our approach uses the dual ability of amine in aqueous solution to both react with CO2 and complex with transition metal ions to reduce the heat of CO2 desorption via metal–amine complexation. Based on benchmarking monoethanolamine (MEA) absorbent and copper (Cu) ions, we developed a model that describes the process chemistry of Cu(II)–MEA–CO2–H2O to understand the speciation profiles under various conditions, particularly for Cu–MEA complexes. We conducted the comprehensive experiments to investigate the influence of Cu(II) addition on the performance of MEA-based CO2 capture process, including the CO2 absorption/desorption capacity, CO2 absorption/desorption rate, CO2 absorption temperature increase and heat of CO2 desorption. The results showed that adding Cu(II) to MEA solution significantly improved the CO2 capture performance, i.e. it mitigated the temperature increase during CO2 absorption, enhanced the CO2 desorption rate, increased the solvent’s cyclic CO2 capacity due to deep CO2 stripping. More importantly, the heat of CO2 desorption was reduced by 13.2–24.0% depending on the copper ion concentration. Our results indicate that metal–amine complexes play an important role in advancing the amine-based CO2 capture process and have potential application to industrial practice.

A process simulation study of CO2 capture by ionic liquids

This study was aimed to simulate a new ionic liquids (ILs)-based CO2 capture process which is useful to capture CO2 from model flue gas, by using two promising CO2 absorbents, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF6]). Thermodynamic properties such as vapor pressure, heat capacity and density were modeled. Vapor-liquid equilibrium (VLE) data were calculated by Redlich-Kwong (R-K) equation and NRTL model. The calculated VLE data were in good agreement with the experimental values. This ILs-based CO2 capture process is characterized with few advantages such as there is no issue of water; solvent (ILs) loss is negligible as compared to monoethanolamine (MEA)-based CO2 capture process (e.g., 0.299g/tCO2 for [bmim][BF4] and 0.391g/tCO2 for [bmim][PF6] respectively, while 178g/tCO2 for MEA); potential corrosion risk is excluded; the energy consumption in [bmim][BF4]- and [bmim][PF6]-based processes are lowered up to 26.7% and 24.8% respectively than that in MEA-based process. Thus, such an ILs-based CO2 capture process is more competitive than traditional MEA-based CO2 capture process.

Energy minimization of MEA-based CO2 capture process

CO2 capture processes using aqueous monoethanolamine (MEA) require significant energy expenditure. There are various possible structural modifications which can be implemented to reduce these energy requirements and enhance energy efficiency. However, as the optimal configuration may contain a combination of different modifications a systematic approach is necessary to consider all possibilities. In this study a superstructure including the conventional amine-based CO2 capture configuration and four different types of structural modifications is constructed in the process simulator UniSim®. Optimization of this superstructure reveals the configuration and operating conditions giving the minimum energy costs, systematically and simultaneously considering all of the possible modifications included. This methodology is applied to a CO2 capture case study to illustrate how the proposed modeling and optimization framework can effectively investigate design options available for improving energy efficiency.

Development of Model and Model-Predictive Control of an MEA-Based Postcombustion CO2 Capture Process

This work focuses on the development of a dynamic model for an MEA-based CO2 capture process for a 550 MWe postcombustion, supercritical, pulverized coal (PC) plant. The dynamic model also provides the design of controllers for both traditional proportional-integral-derivative (PID) and advanced linear model predictive control (LMPC), using Aspen Plus and Aspen Plus Dynamics. To represent accurately the dynamics of the rigorous rate-based calculations provided in the steady-state simulator, the equilibrium dynamic model was exported from an optimized rate-based, steady-state model. Subsequently, modifications to the Murphree efficiencies in the columns and a rigorous pressure drop calculation method were implemented in the dynamic model to ensure consistency between the design and off-design results from the steady-state and dynamic models. The results from the steady-state model indicate that between three and six parallel trains of CO2 capture processes are required to capture 90% CO2 from a 550 MWe sup...

Time-dependent electrochemical behavior of carbon steel in MEA-based CO2 capture process

Time-dependent electrochemical behavior of carbon steel was evaluated in CO2-loaded monoethanolamine (MEA) solutions in simulated carbon capture environments. Tests were conducted in 30wt.% MEA solution with different combinations of controlling factors (oxygen [O2], heat stable salts [HSS], flow and temperature) for 7 days. Corrosion behavior of carbon steel was evaluated by using electrochemical techniques (linear polarization resistance [LPR] and potentiodynamic polarization measurements), weight loss method and surface analytical techniques. Solution pH and ferrous/ferric ion concentration were also measured to monitor the change of water chemistry with time. The results showed that the corrosion rate of carbon steel decreased with time and then stabilized to very low values in the MEA/CO2 condition. XPS characterization revealed formation of a very thin protective FeCO3 layer on the surface, as well as adsorption of MEA. However, when O2 was present in the system, the corrosion rates remained at relatively high values, further increasing with flow. The presence of HSS resulted in a higher corrosion rate at the initial stage, but had a minimal effect on the corrosion rate for longer time exposure. Temperature had a slight effect on the corrosion rate because the solubility of CO2 and O2 decreases with increasing temperature.

Environmental Due Diligence of CO2 Capture and Utilization Technologies – Framework and application

This article presents an overview of an environmental due diligence framework developed as part of the EDDiCCUT project, and presents analysis and results from the first test case – MEA based CO2 capture process. The framework draws upon well-established technical, economic and environmental assessment methods and integrates technical performance, uncertainties, cost estimation and life cycle inventory data to ensure consistency and enhance quality. Results show that for the modelled coal power plant of about 800 MW gross power output, the CO2 capture system lowers the net efficiency by 10.4% efficiency points and results in a 68% increase in the cost of electricity. Environmental performance evaluated on a broad range of 24 impacts and emission categories indicates a 68% reduction in climate change warming potential with 20-90% increase in other impacts. By comparing the quality of the inventory data used for environmental assessment with the state-of-art data in available life cycle assessment literature, it is found that the due diligence analysis brings significant improvement in the quality of data for certain processes in the value chain.

Calcium Looping Cycle for CO2 Capture: Performance, Cost And Feasibility Analysis

Abstract Calcium looping (CaL) systems have been proposed as a lower-cost method of CO2 capture for power plants. This paper presents the results of a techno-economic assessment of a CaL system for post-combustion CO2 capture at a pulverized coal (PC) power plant. Comparisons are made with a conventional MEA-based CO2 capture process in terms of performance and cost. Considering the significant quantities of solid flows required for a CaL process, the applicability and operational feasibility of a CaL system for new or existing PC power plants also is studied. It was found that though the CaL system has better performance than the MEA-based CO2 capture process, the capital cost of the power plant and the cost of electricity is much higher than when the MEA-based system is used.

Effects of flue gas composition on carbon steel (1020) corrosion in MEA-based CO2 capture process

The effects of flue gas composition on carbon steel (1020) corrosion in the MEA-based CO2 capture process was studied by varying impurities which represented different levels of components in the flue gas stream over a base-case condition of just an aqueous MEA, CO2 and O2. The components studied were NaCl, HCl, FeCl2, Na2SO4, FeSO4·7H2O, H2SO4 (from fly ash), HNO3 (from NO2); and H2SO4 and H2SO3 (from SO3 and SO2, respectively). The results illustrated that NaCl, HCl, Na2SO4, FeSO4·7H2O, H2SO4, and HNO3 all accelerated the corrosion process; while, FeCl2 slowed down rate of carbon steel corrosion. Surprisingly, H2SO3, NaHSO3, and Na2SO3, either behaved as corrosion promoters, or corrosion inhibitors; depending strongly on their concentrations.

A novel integrated system with power generation, CO2 capture, and heat supply

Nowadays, CO2 capture in coal-fired power plants is of great significance for reducing CO2 emission in China and abroad. Monoethanolamine (MEA)-based chemical absorption is a comparatively mature technology for large-scale CO2 mitigation in power plants. However, this technology causes great energy consumption and decreases the efficiency of power generation unit. After conducting an in-depth analysis of a typical MEA-based CO2 capture process, this paper proposes a new integrated system with power generation, CO2 capture and heat supply. By system integration, the low-temperature energy released from CO2 capture process are recovered to heat the condensed water in the power generation unit and the circulating water in the radiant floor heating system. Results show that the new system exhibits well from perspective of thermodynamic and techno-economic analysis and the promising results obtained provide a new approach for CO2 removal with low energy penalties.

Performance Analysis of Existing 600MW Coal-Fired Power Plant with MEA-Based CO<sub>2</sub> Capture

This paper presents the techno-economic performance of 600 MW coal-fired power plant with and without MEA-based CO2 capture process, based on the operating data of an existing power plant. The simulation and analysis are based on ASPEN PLUS, with fully consideration of features of existing coal-fired power plants and the integration of CO2 capture process with steam cycle. The results show that, when adopting CO2 capture process, the plant efficiency will decrease significantly. And the cost for electricity will increase dramatically. Through further system integrated optimization, the efficiency fall from 40.28% to 29.61%, which is still tremendous but obviously better performance than before.

CAPRICE project—Engineering study on the integration of post combustion capture technology into the power plant gas path and heat cycle

Abstract The engineering options for integrating the gas path components of a post combustion capture plant into a power plant have been investigated. In addition, an established power plant model and a verified post combustion capture process model have been integrated to simulate power plant equipped with post combustion CO2 capture and compression. A power plant simulation tool was used to optimize the overall thermal efficiency resulting from the introduction of an MEA based CO2 capture process into state of the art power plant. The optimum approach to integration of the capture process into the power plant steam cycle is reported.