Amine-based CO2 Capture Process Research Articles

Techno-economic Optimization of a Green-Field Post-Combustion CO2 Capture Process Using Superstructure and Rate-Based Models

A techno-economic optimization of a commercial-scale, amine-based, post-combustion CO2 capture process is carried out. The most economically favorable process configuration, sizing and operating conditions are identified using a superstructure formulation. The superstructure has 12 288 possible process configurations and unit operations in the superstructure are described using rigorous, rate-based models. In order to simplify the optimization problem, the problem is decomposed and process simulations are explicitly handled in the process simulator. Optimization is performed externally using a genetic algorithm. The best found process configuration includes the absorber intercooling, the rich vapor recompression, and the cold solvent split. The result of this study is compared in terms of the cost of capture basis and shows 38% reduction on the annual operation cost, compared to the conventional amine-based CO2 capture process. Moreover, the savings on the total annualized cost is ∼13%, which is an increa...

Off-design point modelling of a 420 MW CCGT power plant integrated with an amine-based post-combustion CO2 capture and compression process

The use of natural gas for power generation is becoming increasingly important in many regions in the world. Given that the combined cycle gas turbine (CCGT) power stations are lower in capital cost and carbon intensity than their coal-fired counterparts, natural gas fired power stations are considered a vital part of the transition to a low carbon economy. However, CCGTs are not themselves “low carbon” and in order to reach a carbon intensity of less than 50kgCO2/MWh, it will be necessary to decarbonise them via CCS, with post-combustion CCS currently regarded as being a promising technology for this application. In this study, we present a detailed model of a 420MW triple-pressure reheat CCGT and evaluate its technical and economic performance under full and part load conditions. We evaluate the technical performance of our CCGT model by comparison to an equivalent model implemented in Thermoflow THERMOFLEX and observe agreement of power output and efficiency to within 4.1% and the temperature profile within the HRSG within 2.9%. We further integrate the CCGT with a dynamic model of an amine based CCS process, and observe a reduction in the base plant efficiency from 51.84% at full-load and 50.23% at 60% load by 8.64% points at full-load and 7.93% points at 60% load. A core conclusion of this paper is that CCGT power plants equipped with post-combustion CCS technologies are well suited to dynamic operation, as might be required in an energy system characterised by high penetrations of intermittent renewable power generation.

An improved fast screening method for single and blended amine-based solvents for post-combustion CO2 capture

Abstract An improved fast screening method, i.e. the multiple fast screening method, was developed to quickly screen high efficiency solvents for post combustion CO2 capture, especially for the existing amine-based CO2 capture processes. The method was based on an integrated CO2 absorption-desorption process, where the absorption process was performed at 40 °C with a certain initial lean loading, obtained by a pretreatment process, and desorption process is done at the temperature of 80 °C. The duration of each of the two processes was set to be 60 min. This screening method, taking into account the CO2 absorption capacity as well as the absorption and desorption efficiency, was tested on five single alkanolamines in aqueous solutions with concentration of 30 wt%, and blended MEA/DEEA solutions with different ratio at a certain total molar concentration of 5 mole/L. The repeatable screening results of the single amines by this improved method show that the cyclic capacities of the amines are different from the experimental results obtained by using the equilibrium-based screening method, the experimental results of single amine solutions were finally further validated by a simulation process in Aspen Plus and show good agreement. For the blended amine systems screening, the molar ratio of MEA/DEEA of 2.5:2.5 presents the highest cyclic capacity, while no optimal ratio is found by using traditional equilibrium-based screening method. The absolute average difference (AAD) of mass balance between gas and liquid phases for both the single and blended amines screening experiments was calculated, and it turns out to be reliable with the value of 2.65% and 2.80%, respectively.

Assessing the risk of corrosion in amine-based CO2 capture process

This paper presents a study on the risk of corrosion within a post-combustion and amine-based carbon capture installation with the use of selected risk assessment methods like the HAZard and OPerability study (HAZOP), Delphi technique and Fault Tree Analysis (FTA). As in alkanolamine plants, due to economic reasons most of the equipment and piping is constructed of carbon steel, these parts of the installations may suffer from corrosion by several agents like wet acid gases, oxygen and products of the degradation of amines. The study presented within this paper shows this does not only occur in the case of carbon steel, but also other types of materials used within the installation may suffer from corrosion. The correct choice of materials is vital in ensuring the long-term performance, safety and operational availability of CO2 capture plants. A lack of information about previous operational problems or accidents within one-to-one size installations presents a great challenge when conducting risk assessment. This is why a methodology of risk identification and evaluation for CO2 capture installations is proposed, along with its practical application. This method is based on the experience gained from worldwide pilot plants and from a Polish research project on the CO2 capture process. All new technologies need to be investigated with special care, especially when having little knowledge about their behaviour while connected to the existing equipment of any power plant.

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.

Improved CO2 Absorption in a Gas–Liquid Countercurrent Column Using a Ceramic Foam Contactor

Solid foams are porous, monolithic materials with higher specific surface areas than the random packings that are commonly used in amine-based CO2 capture processes. In this work, the hydrodynamic characteristics (e.g., pressure drop, flooding point, and liquid holdup) and CO2 absorption performance of α-Al2O3 ceramic foam packings of different porosities were investigated experimentally in a gas–liquid countercurrent column. With a 30 wt % diglycolamine (DGA) solvent as the CO2 absorbent, the foams allowed higher flow rates of gas and liquid than a random packing before undesirable flooding was reached. Ceramic foams with lower porosities have larger operating capacities than those with higher porosities. A parametric study of a one-dimensional flow model was performed by investigating the effects of gas velocity, liquid velocity, and CO2 solvent loading on the CO2 removal performance. Lower gas velocities and higher liquid velocities increased the CO2 removal efficiency. The CO2 removal efficiency decre...

Ca–Cu looping process for CO2 capture from a power plant and its comparison with Ca-looping, oxy-combustion and amine-based CO2 capture processes

This study reports the technical performance of an advanced configuration of the calcium looping (Ca-looping) process, called Ca–Cu looping, for the reduction of CO2 emissions from a subcritical CFB power plant with a net output of 250MWe. In this new process concept, the thermal power requirement in the calciner is satisfied using a chemical looping combustion cycle. Thus, the power consumption associated with the air separation unit that is required in the conventional Ca-looping process scheme can be eliminated. The reference power plant has also been modified to integrate oxy-combustion, Ca-looping and amine scrubbing technologies for comparison. The fully integrated process flowsheets have been simulated using Honeywell's UniSim Design Suit R400. For a more accurate prediction of the CO2 capture efficiency in the carbonator of the Ca–Cu looping process, the experimentally obtained cyclic activity of a novel copper-functionalised, calcium-based composite sorbent has been implemented yielding a rigorous carbonator model. The process simulations also include a comprehensive analysis of the CO2 compression and purification unit as well as a heat exchanger network optimized using pinch analysis for the recovery of excess heat from the high temperature gas and solid streams available in the Ca-looping and Ca–Cu looping processes. Compared to the energy penalty of 10.5 percentage points for a conventional amine scrubbing configuration, the Ca–Cu looping process evaluated in this study achieves the same overall CO2 capture efficiency with a significantly reduced energy penalty of 3.5 percentage points; the lowest value for all CO2 capture architectures assessed here.

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.

Catalyst design for mitigating nitrosamines in CO2 capture process

Nitrosamines formation during amine based CO2 capture process has recently gained strong attention due to potential health and environmental concerns. In this paper, catalytic nitrosamine destruction in aqueous amine solutions with amine recovery approach is proposed. An up-flow fixed-bed reactor was designed for laboratory experiments in which a nitrosamine solvent stream along with hydrogen was passed into the reactor over a selected catalyst bed. A number of Pd, Fe and Ni metal catalysts were synthesized based on metal-support interaction and were evaluated toward nitrosamine hydrogenation. The Ni based catalyst was found to possess excellent activity (>95%) toward the destruction of 100mg/L nitrosopyrrolidine in 5mol/kg MEA solution at 120psi hydrogen pressure and 120°C temperature in 4h. Catalyst reusability study was conducted for 15 cycles showed high catalyst activity and stability lasting more than 60h. This catalyst was prepared by incipient-wetness technique and was characterized by SEM, TPR, N2 adsorption–desorption and XRD to determine its intrinsic structural properties. The catalyst was further studied with several different nitrosamines to prove its utility toward multiple nitrosamines.

The multi-period optimisation of an amine-based CO2 capture process integrated with a super-critical coal-fired power station for flexible operation

In this work, we present a model of a super-critical coal-fired power plant integrated with an amine-based CO2 capture process. We use this model to solve a multi-period dynamic optimisation problem aimed at decoupling the operation of the power plant from the efficiency penalty imposed by the CO2 capture plant, thus providing the power plant sufficient flexibility to exploit price variation within an electricity market. We evaluate four distinct scenarios: load following, solvent storage, exhaust gas by-pass and time-varying solvent regeneration. The objective is to maximise the decarbonised power plant's short run marginal cost profitability. It is found that while the solvent storage option provides a marginal improvement of 4% in comparison to the load following scenario, the exhaust gas bypass scenario results in a profit reduction of 17% whereas the time-varying solvent regeneration option increases the profitability of the power plant by 16% in comparison to the reference scenario.

Post-combustion CO2 capture applied to a state-of-the-art coal-fired power plant—The influence of dynamic process conditions

A dynamic model of the amine-based CO2-capture process is presented and applied to investigate the transient behavior of the absorption system during and after load changes in Nordjyllandsværket, a state-of-the-art coal-fired power plant with a thermal efficiency of 47.5%. Two scenarios of flexible operation in the power plant are investigated: part-load and peak load operation. Simulations of the load-variation scenarios show that implementation of active control strategies improves capture system performance with respect to capture efficiency and the heat requirement. The reboiler duty can be decreased considerably during part load operation compared to a case where no control strategy is applied. Integration of the capture process with the power plant results in an efficiency decrease of around 9 percentage points at full load and in the range of 8–12 percentage points during 60% part load operation, depending on if a process controller is used or not. Energy requirement for CO2 compression is not included in these numbers. In addition, the response time of the absorption system is significantly decreased in the cases where a process control strategy is implemented, both for part load and peak load operation.

Solubility of CO2 in Nonaqueous Absorption System of 2-(2-Aminoethylamine)ethanol + Benzyl Alcohol

A mixture of 2-(2-aminoethylamine)ethanol (AEEA) with benzyl alcohol (BP) as absorbent was developed to reduce energy consumption in an amine-based CO2 capture process. The solubility of CO2 in the AEEA + BP solution was compared with AEEA + diethylene glycol (DEG), AEEA + triethylene glycol (TEG), and AEEA + H2O. The CO2 loading (mol CO2/kg amine) at the same CO2 partial pressure was in the order AEEA + H2O > AEEA + BP > AEEA + TEG > AEEA + DEG, and CO2 loading of all these solutions increased with increasing vapor pressure of CO2. Besides, the CO2 loading in AEEA + BP solution significantly decreased with increasing reaction temperature. The desorption rate of AEEA + BP solution was about 1.3 times faster than that of aqueous AEEA solution at the same desorption temperature, and AEEA + BP solution needed 30% time less than AEEA + H2O solution to reach reaction end point. The AEEA + BP solution showed stable repeatability in four cycles of absorption–desorption tests.

An expert system for monitoring and diagnosis of ammonia emissions from the post-combustion carbon dioxide capture process system

The amine-based carbon dioxide (CO2) capture technology has become an important method for ensuring reduction of greenhouse gas emissions from electricity generation plants. While the amine is a comprehensive solvent that has been used in the post-combustion carbon capture process, the amine-based CO2 capture process emits the primary gas of ammonia (NH3). Since ammonia emissions are hazardous to human health and contribute to acidification of air, soil and water, it is critical that the ammonia from the amine-based carbon capture process be closely monitored.The research objective is to investigate monitoring and diagnosis of ammonia emissions from an amine-based carbon capture process system using an automation approach. This paper presents design and construction of an expert system for monitoring and diagnosis of ammonia emissions from a carbon dioxide capture system. The expert system can conduct automated monitoring and diagnosis of ammonia emissions from the post-combustion CO2 capture process system at the International Test Centre for CO2 Capture (ITC) located at the University of Regina in Saskatchewan, Canada. The system is called the Expert System for Monitoring and Diagnosis of AMmonia emissions (ESMDAM), and application of the system in three case scenarios demonstrates validity of the system recommendations.

Catalytic Solvent Regeneration Using Hot Water During Amine Based CO2 Capture Process

Experiments for CO2 stripping/amine regeneration were performed using single and blended amines (namely, MEA, MEA– MDEA, MEA–DEAB (4-(diethylamine)-2-butanol)) with and without solid acid catalysts (γ-Al2O3 or HZSM-5) at 90–95∘C. The heat duty to regenerate 5M MEA without catalyst was taken as 100% and as the base line. The results showed that the amine regeneration performance in terms of lowest heat duty followed the order: MEA–DEAB with HZSM-5 (38%) > MEA–DEAB with γ-Al2O3 (40%) > MEA–DEAB with no catalyst (51%) > MEA with HZSM-5 (65%) > MEA with γ-Al2O3 (73%) > MEA– MDEA with γ-Al2O3/no catalyst (74%), all relative to MEA with no catalyst (100%). The results further showed that the addition of MDEA or DEAB (as tertiary amines) in a blended solvent provided R3N and HCO −, which split and thus decreased the free energy gaps in the solvent regeneration pathway. The implication is that the use of blended amines in conjunction with solid acid catalysts could result in stripper size and heat duty reductions during solvent regeneration.

Catalytic Solvent Regeneration Using Hot Water During Amine Based CO2 Capture Process

Experiments for CO2 stripping/amine regeneration were performed using single and blended amines (namely, MEA, MEA–MDEA, MEA–DEAB (4-(diethylamine)-2-butanol)) with and without solid acid catalysts (γ-Al2O3 or HZSM-5) at 90–95∘C. The heat duty to regenerate 5M MEA without catalyst was taken as 100% and as the base line. The results showed that the amine regeneration performance in terms of lowest heat duty followed the order: MEA–DEAB with HZSM-5 (38%) > MEA–DEAB with γ-Al2O3 (40%) > MEA–DEAB with no catalyst (51%) > MEA with HZSM-5 (65%) > MEA with γ-Al2O3 (73%) > MEA–MDEA with γ-Al2O3/no catalyst (74%), all relative to MEA with no catalyst (100%). The results further showed that the addition of MDEA or DEAB (as tertiary amines) in a blended solvent provided R3N and HCO3−, which split and thus decreased the free energy gaps in the solvent regeneration pathway. The implication is that the use of blended amines in conjunction with solid acid catalysts could result in stripper size and heat duty reductions during solvent regeneration.

Development of a CO2 Capture Process Based on Ammonia Solvent and a Dedicated Composite Hollow Fibre Membrane Contactor

Abstract CO2 capture is recognized as necessary to achieve significant greenhouse gas emission reduction before 2050. Regarding these technologies, the main issue is the high cost of avoided CO2 related to capture (≈40 €/t). In conventional amine-based CO2 capture process, the four main key parameters driving the cost of avoided CO2 are the regeneration duty, the compression works, the compressor cost and the solvent make-up cost. On the one hand, the use of hollow fibre membrane contactor (HFMC) for CO2 capture is foreseen to be an efficient technology for absorber intensification; but regarding the impact of the absorber cost on the cost of avoided CO2, the use of HFMC for process intensification does not seem relevant. On the other hand, ammonia as solvent for CO2 capture is a cheap solvent with no degradation problem. Moreover, it allows a high pressure regeneration reducing the compression works. The key idea of this work is to find a membrane with high CO2/NH3 selectivity and high permeability in order to use aqueous ammonia as a solvent in a HFMC in order to reduce significantly the ammonia slip in flue gases while maintaining high absorption rate. The work has been divided in three main steps: the screening of available material for the membrane, the laboratory test of the membrane and the modelling of the system for process assessment. For this absorption device a total equivalent work of 240 kWh/tCO2 has been calculated for CO2 capture on a coal-fired power plant.

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...

Cost and energy sensitivity analysis of absorber design in CO2 capture with MEA

Amine-based CO2 capture processes appear to be the near-term technology for post-combustion CO2 removal from fossil fuel power plants. However, there is no experience with large-scale application of CO2 capture on power plants. A good absorber design is necessary to handle the large volumes of dilute flue gas with high performance, low cost and energy requirement of the plant. In the present work, multi-scale simulations of the absorber were investigated using Aspen RateSep, and a cost estimation model was developed based on mass and energy balances produced by the Aspen Plus simulations, and data from Turton et al. (2012) were applied for cost estimation. Investment costs (CAPEX) and energy requirements of the lean amine circulation pump and absorber blower for variations in the absorber design were compared for two cases: CO2 absorption from a coal-fired power plant, and CO2 absorption from a gas-fired power plant both with a net power output of 400MWe. The flue gas flow rate in the gas-fired power plant case is higher than for the coal-fired power plant, over the same net power output. In the gas-fired power plant case the absorber needs to be designed to process high volumes of flue gas and the pressure drop will often be higher than for a coal-fired power plant due to higher gas velocity. This results in higher capital and operatingcosts. Possible re-design of the absorber is studied and the results show that large electrical energy savings in the feed gas blower can be obtained when a design is chosen giving reduced absorber pressure drop. This can be achieved if the column cross sectional area is increased. This is offset by extra capital cost by a need for slightly more volume of packing. The operational design flexibility in a CO2 capture plant for a gas-fired power plant is higher than for a coal-fired power plant.

Optimization of CO2 Capture Process with Aqueous Amines—A Comparison of Two Simulation–Optimization Approaches

Aqueous amine is a solvent considered for carbon dioxide (CO2) recovery from the flue gas of a refinery gas turbine by chemical absorption/desorption process. The performance and the economics of this process depend on the choice of the amine absorbent, the concentration of the amine absorbent, the number of stages in the absorber and stripper columns, and the operating conditions. We used response surface methodology (RSM)—a simulation–optimization technique, which uses local searches to estimate an appropriate direction to reduce the objective function—to optimize the amine-based CO2 capture process in a previous work [Nuchitprasittichai and Cremaschi Comput. Chem. Eng. 2011, 35, 1521–1531]. However, RSM does not provide any information about the quality of the obtained solution. In this paper, the RSM results are compared to those obtained by optimizing a global surrogate model of the system over the whole decision space with a global solver. We used an artificial neural network (ANN) as the global sur...

Energy analysis of underground coal gasification with CO2 capture and auxiliary power production

Underground coal gasification is a method of converting in situ coal into synthesis gas through the same chemical reactions that occur in surface gasifiers. If underground coal gasification systems are combined with carbon capture and storage methods, CO2 emissions can be greatly reduced. Carbon capture and storage methods require considerable amount of energy to separate CO2 and prepare it for transport and storage, which is typically considered a parasitic loss. This study investigates utilizing waste heat rejected during processing of syngas from underground coal gasification using an auxiliary power plant, to supply the required energy associated with amine-based CO2 capture and compression processes necessary for transport and sequestration. The system investigated is the Newman Spinney underground coal gasification test plant coupled with a basic Rankine cycle. It is shown that the energy requirement for CO2 processing can be met through the use of an auxiliary plant. The basic model illustrates that the power produced by the auxiliary plant is 2.1 times greater than that required by CO2 compression, while supplying the required heat for amine-based CO2 capture. Parametric analyses are performed to investigate the impact of air injection rate, syngas cooling and CO2 capture and compression requirements on system performance.