Post-combustion Capture Process Research Articles

Advance Stripper Configuration for Energy-Saving Designs Using Standard Monoethanolamine Absorbent for Post-Combustion Carbon Capture

In a standard post-combustion carbon capture (PCC) process, the regeneration energy of the CO2 lean solvent dominates the overall energy consumption. The energy reduction achieved by stripper modifications, such as the cold-split bypass, interheated stripper, and integration of both configurations, have been reported in the literature. In the cold-split bypass, the cold rich stream is split to recover the energy contained in the overhead vapor that was directly fed into the condenser in the traditional stripper configuration. The interheated stripper draws the semi-rich solvent from the middle of the stripper and exchanges heat with the hightemperature lean solvent from the reboiler; thereby, the overall column temperature can be raised that favors CO2 desorption along the column. Therefore, the literature reported that the integrated modification, combining the cold-split bypass with the interheated stripper, takes both advantages of above modifications that can further reduce the energy requirement. However, the present work shows that energy-saving effect of integrated process is not as promising as the literature claimed. Once the feed stage of the warm-rich solvent is determined properly, the cold-split process can achieve the similar energy-saving performance as that achieved by the integrated process.

Post-combustion carbon capture

CCS, Carbon Capture and Storage, is considered a promising technology to abate CO2 emissions from point sources. The present review deals with the principle of post-combustion capture techniques, including thermal or pressure swing principles, adsorption or absorption, and electrical swing or membrane separation processes. Opportunities and challenges are assessed. In the first section of absorption processes, several commercial technologies are compared and complemented by the aqueous or chilled ammonia (NH3) process, and a dual or strong alkali absorption. The second section deals with adsorption where fixed beds, circulating fluidized beds and counter-current bed configurations will be discussed, with particular focus on the different adsorbents ranging from zeolites or activated carbon, to more complex amine-functionalized adsorbents, nanotubes or metal organic frameworks (MOFs), and alkali-promoted oxides. Thirdly, membrane processes will be analysed. The review will finally summarize challenges and opportunities.Several research groups confirmed that absorption is the most mature post-combustion capture process: among the assessment of post-combustion CCS, 57% apply absorption, 14% rely on adsorption, 8% use membranes, and 21% apply mineralization or bio-fixation. This conclusion was in-line with expectations since absorption gas separation has been largely applied in various petrochemical industries. All other systems need further development prior to large scale application.

Integrated adsorption and absorption process for post-combustion CO2 capture

This study explored the feasibility of integrating an adsorption and solvent scrubbing process for post-combustion CO2 capture from a coal-fired power plant. This integrated process has two stages: the first is a vacuum swing adsorption (VSA) process using activated carbon as the adsorbent, and the second stage is a solvent scrubber/stripper system using monoethanolamine (30 wt-%) as the solvent. The results showed that the adsorption process could enrich CO2 in the flue gas from 12 to 50 mol-% with aCO2 recovery of > 90%, and the concentrated CO2 stream fed to the solvent scrubber had a significantly lower volumetric flowrate. The increased CO2 concentration and reduced feed flow to the absorption section resulted in significant reduction in the diameter of the solvent absorber, bringing the size of the absorber from uneconomically large to readily achievable domain. In addition, the VSA process could also remove most of the oxygen initially existed in the feed gas, alleviating the downstream corrosion and degradation problems in the absorption section. The findings in this work will reduce the technical risks associated with the state-of-the art solvent absorption technology for CO2 capture and thus accelerate the deployment of such technologies to reduce carbon emissions.

Techno-economic assessment of optimised vacuum swing adsorption for post-combustion CO2 capture from steam-methane reformer flue gas

This study focuses on the techno-economic assessment integrated with detailed optimisation of a four step vacuum swing adsorption (VSA) process for post-combustion CO2 capture and storage (CCS) from steam-methane reformer dried flue gas containing 20 mol% CO2. The comprehensive techno-economic optimisation model developed herein takes into account VSA process model, peripheral component models, vacuum pump performance, scale-up, process scheduling and a thorough cost model. Three adsorbents, namely, Zeolite 13X (current benchmark material for CO2 capture) and two metal–organic frameworks, UTSA-16 (widely studied metal–organic framework for CO2 capture) and IISERP MOF2 (good performer in recent findings) are optimised to minimise the CO2 capture cost. Monoethanolamine (MEA)-based absorption technology serves as a baseline case to assess and compare optimal techno-economic performances of VSA technology for three adsorbents. The results show that the four step VSA process with IISERP MOF2 outperforms other two adsorbents with a lowest CO2 capture cost (including flue gas pre-treatment) of 33.6 € per tonne of CO2 avoided and an associated CO2 avoided cost of 73.0 € per tonne of CO2 avoided. Zeolite 13X and UTSA-16 resulted in CO2 avoided costs of 90.9 and 104.9 € per tonne of CO2 avoided, respectively. The CO2 avoided costs obtained for the VSA technology remain higher than that of the baseline MEA-based absorption process which was found to be 66.6 € per tonne of CO2 avoided. The study also demonstrates the importance of using cost as means of evaluating the separation technique compared to the use of process performance indicators. Accounting for the efficiency of vacuum pumps and the cost of novel materials such as metal–organic frameworks is highlighted.

Techno-economic feasibility of ionic liquids-based CO2 chemical capture processes

A techno-economic assessment of Ionic Liquids (ILs)-based post-combustion, biogas and pre-combustion CO2 chemical capture processes was carried out using Aspen Plus and Aspen Process Economic Analyzer (APEA). This cost estimation procedure is newly integrated to our COSMO-based/Aspen Plus methodology used to design the chemical absorption processes with 90% of CO2 capture. The equipment investment and variable operating cost were analyzed relating to the process operating conditions and the IL performance. The total annualized cost was used as the index to economically evaluate the processes at three CO2 treatment capacities and employing three different ILs: [P2228][CNPyr], [P66614][CNPyr] and [Bmim][acetate]. It benefits from economy of scale as well as it is directly related to both IL enthalpy of reaction and process gap capacity, being [P2228][CNPyr] -which has the most exothermic reaction and highest gap capacity- the solvent achieving the lowest costs. Current results indicate that operating at vacuum pressure to better regenerate the IL entails a remarkable cost penalty. Hence, both capital (CAPEX) and operational expenses (OPEX) could be reduced to achieve a total cost of 81.32 $/tCO2 for [P2228][CNPyr] in post-combustion CO2 capture when regenerating the IL at atmospheric pressure and 121.5 °C. Three IL pricing basis were considered when calculating the solvent cost. A conservative IL scaled up price of 50 $/kg only increments around 5% the total annualized cost of the process.

Nonlinear model predictive control (NMPC) of the solvent-based post-combustion CO2 capture process

The flexible operation capability of solvent-based post-combustion capture (PCC) process is vital to efficiently meet the load variation requirement in the integrated upstream power plant. This can be achieved through the deployment of an appropriate control strategy. In this paper, a nonlinear model predictive control (NMPC) system was developed and analysed for the solvent-based PCC process. The PCC process was represented as a nonlinear autoregressive with exogenous (NARX) inputs model, which was identified through the forward regression with orthogonal least squares (FROLS) algorithm. The FROLS algorithm allows the selection of an accurate model structure that best describes the dynamics of the process. The simulation results showed that the NMPC gave better performance compared with linear MPC (LMPC) with an improvement of 55.3% and 17.86% for CO2 capture level control under the scenarios considered. NMPC also gave a superior performance for reboiler temperature control with the lowest ISE values. The results from this work will support the development and implementation of NMPC strategy on the PCC process with reduced computational time and burden.

CO2 Utilization via Integration of an Industrial Post-Combustion Capture Process with a Urea Plant: Process Modelling and Sensitivity Analysis

Carbon capture and utilization (CCU) may offer a response to climate change mitigation from major industrial emitters. CCU can turn waste CO2 emissions into valuable products such as chemicals and fuels. Consequently, attention has been paid to petrochemical industries as one of the best options for CCU. The largest industrial CO2 removal monoethanol amine-based plant in Iran has been simulated with the aid of a chemical process simulator, i.e., Aspen HYSYS® v.10. The thermodynamic properties are calculated with the acid gas property package models, which are available in Aspen HYSYS®. The results of simulation are validated by the actual data provided by Kermanshah Petrochemical Industries Co. Results show that there is a good agreement between simulated results and real performance of the plant under different operational conditions. The main parameters such as capture efficiency in percent, the heat consumption in MJ/kg CO2 removed, and the working capacity of the plant are calculated as a function of inlet pressure and temperature of absorber column. The best case occurred at the approximate temperature of 40 to 42 °C and atmospheric pressure with CO2 removal of 80.8 to 81.2%; working capacity of 0.232 to 0.233; and heat consumption of 4.78 MJ/kg CO2.

Optimization of energy requirements for CO2 post-combustion capture process through advanced thermal integration

The energy optimization modeling work described here was performed to determine efficiency improvements that could be achieved for existing coal-fired power plants to retrofit a partial CO2 capture from the post-combustion flue gas for carbon sequestration through thermal integration. The work presented includes optimization of the mono-ethanol amine (MEA)-based post-combustion CO2 capture to reduce energy requirements that could be achieved at existing power plants by thermal integration of the steam turbine cycle, boiler, CO2 compression train and post-combustion CO2 capture process to offset efficiency and capacity losses that would be incurred by retrofit or implementation of post-combustion CO2 capture. Partial CO2 capture, involving treatment of less than 100% of the flue gas leaving the plant and modular design of the CO2 scrubbing system, was also investigated. Thermal integration of the steam turbine cycle with boiler and CO2 compression train improved cycle and plant performance and offset, in part, the negative effects of post-combustion CO2 capture. The best-analyzed integration options improved gross power output by 5% and net unit efficiency by 1.57%, relative to the conventional MEA process. Operating with 40% CO2 capture increased gross power output by 11.6–14% (depending on the MEA thermal integration option), relative to the conventional MEA integration and 90% CO2 capture. The improvement in net unit performance is larger compared to the improvement in turbine cycle performance because of the CO2 compression work, which is also reduced by partial CO2 capture.

Energy-saving performance of advanced stripper configurations for CO2 capture by ammonia-based solvents

In an ammonia-based post-combustion carbon capture (PCC) process, the regeneration energy of CO2-lean solvent comprises the main fraction of overall energy consumption. The use of a pressurized CO2 stripper to enhance the CO2 purity in the overhead vapor is one option for reducing the regeneration energy. Further energy reductions can be achieved by modifying stripper configurations reported in the literature. In this study, the energy-saving performance of advanced stripper configurations is investigated, including cold split bypass (CSB), lean vapor compression (LVC), and rich vapor compression (RVC). Our results show that the energy reduction by CSB has been underestimated in the literature because the effect of the warm rich feed stage has been neglected. Compared with a standard stripper operated at 10 atm, the CSB modification achieves 34.2% of energy reduction, and the combination of CSB and LVC reaches 34.4%. In other words, LVC only improves the energy saving of CSB by 0.2%.

CO2 capture and fluidity performance of CaO-based sorbents: Effect of Zr, Al and Ce additives in tri-, bi- and mono-metallic configurations

The Calcium-looping (CaL) technology is based on the reversible carbonation reaction of CaO with CO2 and has been developing rapidly as a potential low cost process for post-combustion CO2 capture. One of the main challenges of CaL process, is the identification of CaO-based sorbents that can maintain their activity in multiple cycles and have proper fluidization. The present study focusses on the influence of Zr, Al and Ce additives in mono-, bi- (Zr/Ce, Zr/Al and Al/Ce) and tri-metallic (Zr/Al/Ce) configurations on the performance of synthetic CaO-based sorbents. The developed sorbents presented a substantially improved performance over multiple cycles compared to limestone-derived CaO, due to the formation of stable, mixed Ca-inert phases. Incorporation of Al, Al/Ce and Zr/Al/Ce in CaO structure led to the development of sorbents with small crystallites and porous morphology, resulting in improved stability with less than 25 % deactivation after 50 cycles. The enhanced stability of the Zr/Al/Ce-promoted sorbent was attributed to the formation of CaZrO3 and Ca3Al2O6 mixed phases in the CaO matrix, providing a porous and stable structure. The fluidizability of the most promising sorbents was also investigated. SiO2 nanoparticles were mechanically mixed with the sorbents in different fractions to improve their fluidization performance. A minimum amount of 15 wt% SiO2 was required in order to achieve a completely smooth and homogeneous fluidization without gas channeling, bubbles or even fine agglomerates. The highest bed expansion, accompanied by a high Richardson-Zaki index n (5.9) and low Umf (2.2 cm/s) were obtained with a Ca/Zr/Al/Ce +15 wt% SiO2.

Generic techno-economic optimization methodology for concurrent design and operation of solvent-based PCC processes

A techno-economic equation-based methodology is developed for optimal design and operation of integrated solvent-based post-combustion carbon capture (PCC) processes using a rate-based model for the interaction of gas and liquid. The algorithm considers a wide range of techno-economic design and operation parameters such as number of absorber/desorber columns, height of columns, diameter of columns, operating conditions (P, T) of columns, pressure drop, packing type, percentage of CO2 mitigated, captured CO2 purity, amount of solvent regeneration, flooding velocities of columns, and number of compression stages. A case study is conducted to showcase two common objective-functions i) minimizing total capital investment, and ii) minimizing levelized capture costs, both for a 300 MW coal-power plant in Australia. The former objective leads to the lowest possible total capital cost of $312.4 M corresponding to levelized carbon capture cost of 58.1 $/tonne−CO2. For objective (ii), however, the lowest levelized carbon capture cost is found to be around ten percent lower (52.8 $/tonne−CO2), though it leads to a higher total capital cost ($325.2 M). The results indicate that the design and operation variables are markedly interactive, and no unique optimal design exists which can deliver all desired outcomes at once. Therefore, decisions on the selection of right variables become dependent on the decision-makers techno-economic objectives.

Energy minimization of carbon capture and storage by means of a novel process configuration

Carbon capture and storage is considered a key technology for decarbonizing the heat and power industries and achieving net zero emission targets. However, the significant energy requirements of the process as currently utilized hinders its widespread implementation. This work presents a novel process configuration by which the energy expenditures of carbon capture and storage can be minimized. This configuration is intended to enhance heat integration during the capture process through an innovative combination of three stripper modifications, namely lean vapor compression, a rich solvent split with vapor heat recovery and reboiler condensate heat recovery using a stripper inter-heater in a single flow-sheet. For carbon dioxide compression, a novel pressurization strategy involving carbon dioxide multi-stage compressors, a heat pump system and a supercritical carbon dioxide power cycle was designed and evaluated. The heat pump was used for carbon dioxide liquefaction while the supercritical carbon dioxide power cycle was employed to recover the intercooling heat. Through a comprehensive parametric investigation of the proposed configuration, the optimum value of the key operating parameters i.e., the split fraction, flash pressure, stripper inter-heater location, stripper inter-heater solvent flowrate, carbon dioxide liquefaction pressure and supercritical carbon dioxide cycle turbine pressure ratio were estimated. The performance of the proposed design at the optimized condition was quantified in terms of the reboiler heat duty, the carbon dioxide pressurization power and the equivalent work and compared to a baseline case post-combustion carbon capture and storage process. The proposed case reduced the reboiler heat duty from 3.36 GJ/TonneCO2 to 2.65 GJ/TonneCO2 and the electric power required for carbon dioxide compression from 16,691 kW to 14,708 kW. The results demonstrate that the new design can significantly reduce the reboiler duty, compression power and equivalent work by 21.1%, 11.88%, and 15.8%, respectively.

Developing new alkaline ceramics as possible CO2 chemisorbents at high temperatures: The lithium and sodium yttriates (LiYO2 and NaYO2) cases

Lithium and sodium yttriates (LiYO2 and NaYO2) were synthesized, characterized and tested as possible carbon dioxide (CO2) captors. All the experimental syntheses and analyses were supported by the theoretical thermodynamic calculations, showing that both ceramics would be able to chemisorb CO2 in a wide temperature range. Therefore, both ceramics were prepared by solid-state reaction and structurally characterized. In fact, the structural characterization evidenced that sodium atoms are located in a octahedral close-packed structure, while lithium ions are not so packed. The lithium ions are, indeed, in a highly distorted tetrahedron, tending to square-planar coordination. Then, based on the theoretical and structural analysis, LiYO2 and NaYO2 samples were investigated for the CO2 capture process through dynamic and isothermal thermogravimetric experiments. All these experiments showed that LiYO2 has better CO2 capture properties than NaYO2, which was further correlated with the crystal structures of each ceramic. Furthermore, both ceramics presented similar CO2 capture efficiencies regardless of the CO2 concentration. Finally, LiYO2 sample was tested for cyclic CO2 chemisorption-desorption processes. The obtained results showed that the CO2 capture efficiency is maintained high at least through 10 cycles. Therefore, these alkaline yttriates seem to present interesting alternatives as high and moderate temperature CO2 captors, applicable for post-combustion industrial capture processes.

Hybrid membrane process for post-combustion CO2 capture from coal-fired power plant

Post-combustion CO2 capture is a promising way to reduce CO2 emissions at the coal-fired power plants. Even though several studies have been conducted regarding a wide variety of CO2 capture techniques, gas separation membrane process has shown potential as an energy-efficient, low-cost CO2 capture option. However, most of the previous researches focused only on CO2-selective membrane, and there's limited literature about the application of N2-selective membrane.In this study, both CO2-selective and N2-selective membranes are considered and relevant issues regarding the CO2-selective membrane, such as pressure ratio, attainability, and multistage configuration, are studied and extended to the N2-selective membrane. Polaris® membrane is served as a typical CO2-selective membrane; on the other hand, membrane properties of N2-selective membrane with selectivity up to 200 are considered. Hybrid membrane process applying both CO2- and N2-selective membranes for capturing at least 90% CO2 from a typical 550 MW subcritical coal-fired power plant is designed, simulated and analyzed using Aspen Plus® simulation software. The optimization and economic analysis are also applied with the cost factor defined in this work, which is a comprehensive index to evaluate the applicability of the membrane, including permeance, membrane lifetime and membrane price. The results reveal the relationship between the optimal design variables and membrane properties. Moreover, the selectivity-limited region is identified, which leads to two different dominant strategies for the cost reduction in a different region, either by the increase in selectivity or the reduction of the cost factor.

Experimental and Simulation Study on CO2 Adsorption Dynamics of a Zeolite 13X Column during Blowdown and Pressurization: Implications of Scaleup on CO2 Capture Vacuum Swing Adsorption Cycle

A 13X column Vacuum Swing Adsorption (VSA) has been widely studied as a promising separation process for post-combustion carbon capture, as it has been claimed that it would be more economical than...

A novel pinch-based method for process integration and optimization of Kalina cycle

Low-and-medium waste heat utilization is crucial for alleviating energy dilemma and carbon dioxide emissions in industrial plants. Although Organic Rankine Cycle (ORC) has made significant advances in waste heat recovery, other equally important thermodynamic ways to recover waste heat such as Kalina Cycle (KC) have not been fully explored. In this study, a novel pinch-based mathematical model is developed for process integration and optimization of Kalina Cycle. The model performs heat integration with variable heat capacities and enables the modifications of KC simultaneously, in a bid for generating maximum net power output without increasing the amount of hot utility. The proposed model allows for non-isothermal phase transition of working fluid and can be extended to handle multiple Kalina Cycles combined with process integration, thus enhancing waste heat recovery efficiency. The effectiveness of the proposed method is verified by a well-studied example from literature, in which the net power output is increased by 12.2% compared to the results using existing literature approaches. Furthermore, the developed model has been successfully applied to the post-combustion carbon capture process, where proper integration of process and Kalina Cycle leads to a 15.8% increase in net power output and a 4.13 percentage point decrease in the efficiency penalty.

Sodium carbonate-based post combustion carbon capture utilising trona as main sorbent feed stock

In the pursuit of shifting technology towards sustainable, environmentally benign processes, post-combustion carbon capture technology is recognised to be a timely mitigation option. This paper presents the development of a novel sodium carbonate-based post combustion carbon capture process utilising the carbonate mineral trona (trisodium hydrogendicarbonate dihydrate) as main sorbent feedstock source. The energy penalty, the fraction of energy sacrificed to capture CO2 relative to the net energy produced serves as main performance indicator. Investigations on the correlative relationship between energy penalty as a function of capture efficiency are carried out by retrofitting the process to a 600 MW reference coal-fired power plant. The energy penalty of the global system features a distinct local minimum of 3.99%, corresponding to a CO2 capture efficiency of 90.00% and a CO2 outlet purity of 99.90%. The Specific Primary Energy Consumption for CO2 Avoided (SPECCA) index corresponding to this minimum is evaluated to be SPECCA = 0.514MJkgCO2-1. Sensitivity analyses on the effect of increasingly high SO2 flue gas volume fractions ySO2 show that the capture efficiency is virtually unimpaired for calcination temperatures of 190 ⩽T⩽280 °C and ySO2 ranging from 0.50 to 0.70%. Whilst commercially available CO2 capture technology is energy intense and prone to sorbent degradation, the process developed retains high capture efficiencies of calcium oxide-based looping cycles at low operating temperatures and eliminates the predisposition of amine-based sorbents utilised in scrubbing capture schemes to deplete due to the presence of SO2 in the inlet flue gas stream. It can be concluded that sodium carbonate based post-combustion capture processes are a competitive alternative to existing CO2 capture technologies.

Novel Postcombustion Capture Process for CO2 from the Flue Gas of Coal-Fired Power Plants Using a Green Deep Eutectic Solvent

Green, efficient, and low energy consumption capture of CO2 from the flue gas of coal-fired power plants has been one of the most popular research topics in the world. In this work, a concept proce...

Investigation into an energy-saving mechanism for advanced stripper configurations in post-combustion carbon capture

Abstract In a standard post-combustion carbon capture (PCC) process, the regeneration energy of CO2 lean solvent constitutes the majority of overall energy consumption. The energy reduction achieved by advanced stripper configurations, such as the cold-split bypass (CSB), interheated (IH) stripper, and lean vapor compression (LVC), have been reported in relevant literature. Energy-saving performance may be enhanced by combining the different modifications. In this study, the energy-saving mechanism for advanced stripper configurations was investigated using a standard amine-based process, in which 30 wt% monoethanolamine (MEA) aqueous solution was applied. Contrary to the literature reviewed, the energy-saving performance attained by combining the different modifications was limited. This was due to the major contribution of energy reduction in the various modifications sharing the similar mechanism. In addition, this study demonstrated that the overall energy required, as needed by the heat recovery in the cross-flow heat exchanger (HX) and the reboiler duty, is dominated by overhead vapor generation. Reducing the amount of vapor generated may effectively relieve the overall energy burden. Thus, when energy reduction is reliant on a HX with a poor heat recovery system, the energy-saving purpose is not fulfilled. Therefore, a successful energy-saving design may significantly reduce the amount of vapor generated, whilst maintaining a reliable heat recovery.

Rapid thermal swing adsorption process in multi-beds scale with sensible heat recovery for continuous energy-efficient CO2 capture

Abstract A rapid thermal swing adsorption (RTSA) process with heat integration is considered to be an energy-efficient method for large-scale CO2 capture. Herein, we propose a new heat-integrated RTSA process for post-combustion CO2 capture as a proof-of-concept based on rationally designed multi-fixed beds by incorporating the internal heat integration concept of the moving bed adsorption process. Our proposed RTSA process consists of multiple beds, each of which undergoes four sequential processes, including adsorption, heating, desorption, and cooling in a continuous cyclic mode. Also, the switching time of adsorption/desorption process is determined by CO2 adsorption/desorption kinetics while that of the heating/cooling process is determined by the heat transfer rate. Our unique RTSA design enables internal heat integration by recovering sensible heat from the cooling process. Furthermore, it can enhance the CO2 cyclic capacity of hollow fiber sorbents with high CO2 recovery by performing multiple adsorption processes simultaneously. Most importantly, our economic analysis based on experiments and rigorous mathematical modeling revealed that the energy demand of the optimized RTSA process is estimated to be approximately 272 kWh/t-CO2 with 58% sensible heat recovery. Such low energy penalty is comparable to that of the most mature amine-based absorption process (271 kWh/t-CO2) due to a combination of internal heat integration and enhanced CO2 cyclic capacity, supporting the feasibility of a RTSA process for post-combustion CO2 capture.