Post-combustion Flue Gas Research Articles

Systems Analysis of SO2-CO2 Co-Capture from a Post-Combustion Coal-Fired Power Plant in Deep Eutectic Solvents

In this study, CO2 and SO2 captures from post-combustion flue gas from a pulverized coal-fired power plant were evaluated using deep eutectic solvents (DES) to replace existing mono-ethanol amine (MEA) and CanSolv technologies. The system design of the DES-based CO2 and SO2 capture was based on the National Energy Technology Laboratory’s (NETL) 550 MWe pulverized coal-fired power plant model using Illinois #06 coal. Two of the most studied DES (choline chloride and urea at a 1:2 molar ratio and methyltriphenylphosphonium bromide (METPB) and ethylene glycol at a 1:3 molar ratio) for CO2 and SO2 capture were evaluated for this system analysis. Physical properties of DES were evaluated using both density functional theory (DFT)-based modeling as well as with documented properties from the literature. A technoeconomic assessment (TEA) was completed to assess DES ability to capture CO2 and SO2. Both solvents were able to fully dissolve and capture all SO2 present in the flue gas. It was also found from the system analyses that choline chloride and urea outperformed METPB and ethylene glycol (had a lower final cost) when assessed at 10–30% CO2 capture at high operating pressures (greater than 10 bar). At high system sizes (flow rate of greater than 50,000 kmoles DES per hour), choline chloride:urea was more cost effective than METPB:ethylene glycol. This study also establishes a modeling framework to evaluate future DES for physical absorption systems by both thermophysical and economic objectives. This framework can be used to greatly expedite DES candidate screening in future studies.

Combining soft-SAFT and COSMO-RS modeling tools to assess the CO2–SO2 separation using phosphonium-based ionic liquids

The development of efficient CO2 separation techniques from post-combustion flue gases is a key area of research to green-house gas control. However, CO2 capture is typically affected by the presence of other acid impurities, such as traces of SO2. In that sense, this work assesses CO2 separation from a CO2/SO2 mixture with a set of phosphonium-based ILs. Two different modeling tools, soft-SAFT and COSMO-RS, have been used cooperatively to study the CO2 gas separation on ILs. From one side, the soft-SAFT equation of state, which has been employed for the first time in this family of ILs, has been used to effectively reproduce the absorption properties of these promising CO2 absorbents in a wide range of pressures/temperatures. Additionally, COSMO-RS, employed to evaluate the charge distribution so as to develop representative models for soft-SAFT, has been capable of reproducing the low-pressure absorption region in a purely predictive way. In both cases, the enthalpy and entropy of dissolution and the selectivity of the mixtures are predicted. Also, several ternary diagrams have been built to analyze different acid gas compositions.

Building a Consistent and Reproducible Database for Adsorption Evaluation in Covalent-Organic Frameworks.

We present a workflow that traces the path from the bulk structure of a crystalline material to assessing its performance in carbon capture from coal’s postcombustion flue gases. This workflow is applied to a database of 324 covalent–organic frameworks (COFs) reported in the literature, to characterize their CO2 adsorption properties using the following steps: (1) optimization of the crystal structure (atomic positions and unit cell) using density functional theory, (2) fitting atomic point charges based on the electron density, (3) characterizing the pore geometry of the structures before and after optimization, (4) computing carbon dioxide and nitrogen isotherms using grand canonical Monte Carlo simulations with an empirical interaction potential, and finally, (5) assessing the CO2 parasitic energy via process modeling. The full workflow has been encoded in the Automated Interactive Infrastructure and Database for Computational Science (AiiDA). Both the workflow and the automatically generated provenance graph of our calculations are made available on the Materials Cloud, allowing peers to inspect every input parameter and result along the workflow, download structures and files at intermediate stages, and start their research right from where this work has left off. In particular, our set of CURATED (Clean, Uniform, and Refined with Automatic Tracking from Experimental Database) COFs, having optimized geometry and high-quality DFT-derived point charges, are available for further investigations of gas adsorption properties. We plan to update the database as new COFs are being reported.

A comprehensive performance evaluation of temperature swing adsorption for post-combustion carbon dioxide capture

Carbon dioxide capture from the post-combustion flue gas via temperature swing adsorption is supposed to be a valid technology to mitigate carbon emissions. With regard to the adsorbent development and process improvement, the technologies of temperature swing adsorption for post-combustion carbon dioxide capture have been reviewed and compared in terms of fixed bed, fluidized bed and moving bed. A comprehensive evaluation framework of fixed-bed temperature swing adsorption for CO2 capture has been established. In a four-step fixed-bed cycle, a shortcut model has been utilized. Four typical adsorbent materials, such as activated carbon, zeolite 13X, zeolite NaUSY and Mg-MOF-74, have been chosen in this assessment. The comparative study has been conducted under the same operating conditions, from four aspects using eight performance indicators. Results indicate that Mg-MOF-74 and zeolite 13X reveal excellent performance among the four selected adsorbents. Thereinto, Mg-MOF-74 performs well at four indicators including purity, productivity, specific thermal energy consumption and second-law efficiency; zeolite 13X excels in the other four indicators such as selectivity, recovery, minimum separation work and capture cost. Future work will complete a thorough assessment criterion in evaluating the TSA process for CO2 capture.

Nitrogen-doped asphaltene-based porous carbon nanosheet for carbon dioxide capture

Abstract A series of porous carbon nanosheets having abundant micropore, nanoscale thickness and doped nitrogen were synthesized using asphaltene by three different facile routes. The three carbon nanosheets exhibited high CO 2 adsorption capacity of 4.0, 4.3, 3.6 mmol/g (25 °C, 1 bar) and 5.3, 6.3, 5.1 mmol/g (0 °C, 1 bar), which should be ascribed to their developed microporous structures and surface nitrogen-containing groups. In order to evaluate their practical application, the separation performance of CO 2 from CO 2 /N 2 and CO 2 /CH 4 was investigated according to breakthrough curves under simulate post-combustion flue gas and coalbed methane, it showed CO 2 adsorption quantities at 25 °C from CO 2 /N 2 (15/85, v/v) and CO 2 /CH 4 (10/90, v/v) reached up to 1.22 mmol/g and 1.18 mmol/g. Furthermore, the selectivity factors for CO 2 compared with N 2 and CH 4 were demonstrated as 15.3 and 7.3 by both ideal adsorbed solution theory model and initial slope method. Moreover, these porous carbon nanosheets could be easily regenerated and showed good stability in >10 times adsorption-desorption cycle, suggesting it promising adsorbents for CO 2 capture.

Metal-Organic Framework with Rich Accessible Nitrogen Sites for Highly Efficient CO2 Capture and Separation.

A novel microporous metal-organic framework (FJU-44), with abundant accessible nitrogen sites on its internal surface, was constructed from the tetrapodal tetrazole ligand tetrakis(4-tetrazolylphenyl)ethylene (H4TTPE) and copper chloride. Notably, the CO2 uptake capacity (83.4 cm3/g, at 273 K and 1 bar) in the activated FJU-44a is higher than most of tetrazolate-containing MOF materials. Particularly, FJU-44a exhibits superior adsorption selectivity of CO2/N2 (278-128) and CO2/CH4 (44-16), which is comparable to some well-known CO2 capture materials. Furthermore, the fixed-bed breakthrough experiment indicates that the postcombustion flue gas flow over a packed column with FJU-44a adsorbents can be effectively separated.

A sorbent-focused techno-economic analysis of direct air capture

Direct air capture, the removal of carbon dioxide from air, requires special sorbents, with high capture capacity, fast kinetics and long lifetime. Beyond that they also need to be affordable. However, since air capture is still in an early development stage, costs are still uncertain.We present a techno-economic model to value a sorbent based on the CO2 market price and the most important sorbent characteristics: cycle time, loading capacity, and rate of degradation. The model gives a net present value equation for any air capture sorbent, whether it uses a moisture swing, pressure swing or thermal swing for regeneration and makes it possible to estimate the maximum allowable budget for any air capture sorbent, i.e., the sorbent value.The analysis aims to focus the rapidly growing field of air capture sorbent development onto the most important parameters. The value of a sorbent is dramatically affected by its longevity. To be economically viable, the typical sorbent must survive tens if not hundreds of thousands of loading and unloading cycles. The model can also be used to investigate the interactions between different sorbent parameters. For example, the correlation between loading capacity and cycle time makes it possible to determine the cycle time that optimizes the economics of an air capture device.Our analysis highlights the significance of some neglected parameters in air capture cost analysis such as cycle duration and stability of the sorbent. Finally, the analysis can also be adapted to post-combustion flue gas sorbents.

Synthesis of Soluble Metal Organic Framework Composites for Mixed Matrix Membranes.

A general, green, efficient, and easily scalable methodology has been developed to more effectively incorporate (disperse) metal-organic frameworks (MOFs) into polymer technologies via solid state synthesis of any MOF nanocrystals within soluble mesoporous polymers. The resulting solid hybrid materials (pellets) can be directly transformed into colloidal MOF polymeric suspensions (inks) by simple dissolution in organic solvents. The straightforward use of novel colloidal MOF polymeric inks as ultimate additive for mixed matrix membranes resulted in unprecedented snakeskin microstructure exhibiting outstanding selectivity for CO2 over N2 (>100) from post-combustion flue gas at very low and well-dispersed MOF nanocrystal concentrations ranging from 1 to 7 wt %. This novel methodology brings one of the most versatile routes yet reported to transform any MOF into more functional forms that can be directly integrated into any conventional polymer technology at the commercial scale.

Transition metal cation-exchanged SSZ-13 zeolites for CO2 capture and separation from N2

CO2 capture from post-combustion flue gas mixture (CO2/N2:15/85) is challenging and requires adsorbents with high capacity and high selectivity toward CO2. Our work validated the potential of transition metal cation-exchanged SSZ-13 zeolites for efficient CO2 capture, as evaluated by unary static isothermal adsorption and binary dynamic column breakthrough experiments as well as predicted performance in pressure/vacuum swing adsorption (P/VSA) process. Among the investigated transition metals (Co(II), Ni(II), Zn(II), Fe(III), Cu(II), Ag(I), La(III), and Ce(III)) exchanged SSZ-13, Co(II)/SSZ-13 and Ni(II)/SSZ-13 showed the highest CO2 uptake (4.49 and 4.45 mmol/g, respectively) and superior selectivity of CO2 over N2 (52.55 and 42.61, respectively) at 273 K and 1 atm. We attribute such outstanding separation performance to the Pi backdonation exclusively formed between CO2 and transition metal cation sites. This demonstrates a new approach of developing adsorbents for CO2 capture in the real-world industrial processes.

Effect of Ionic Liquid Impregnation in Highly Water-Stable Metal–Organic Frameworks, Covalent Organic Frameworks, and Carbon-Based Adsorbents for Post-combustion Flue Gas Treatment

In this work, a comparative study on water-stable microporous adsorbents is conducted computationally in the quest of a suitable adsorbent for post-combustion CO2 capture. In this regard, three met...

Analysis of a Batch Adsorber Analogue for Rapid Screening of Adsorbents for Postcombustion CO2 Capture

A simplified proxy model based on a well-mixed batch adsorber for vacuum swing adsorption (VSA) based CO2 capture from dry postcombustion flue gas is presented. A graphical representation of the model output allows for the rationalization of broad trends of process performance. The results of the simplified model are compared with a detailed VSA model that takes into account mass and heat transfer, column pressure drop, and column switching, in order to understand its potential and limitations. A new classification metric to identify whether an adsorbent can produce CO2 purity and recovery values that meet current U.S. Department of Energy (US-DOE) targets for postcombustion CO2 capture and to calculate the corresponding parasitic energy is developed. The model, which can be evaluated within a few seconds, showed a classification Matthew correlation coefficient of 0.76 compared to 0.39, the best offered by any traditional metric. The model was also able to predict the energy consumption within 15% accurac...

Measurement of competitive CO2 and N2 adsorption on Zeolite 13X for post-combustion CO2 capture

Single component CO2 and N2 equilibrium loadings were measured on Zeochem Zeolite 13X from 0 to 150 °C and 0–5 bar using volumetry and gravimetry. CO2 equilibrium data was fit to a dual-site Langmuir (DSL) isotherm. The equilibrium data for N2 was fit using four isotherm schemes: two single site Langmuir isotherms, the DSL with the equal energy sites and the DSL with unequal energy site pairings. A series of single and multicomponent CO2 and N2 dynamic column breakthrough (DCB) experiments were measured on Zeolite 13X at 22 °C and 0.98 bar. The adsorption breakthrough experiments were able to provide accurate data for CO2 competitive adsorption, while failing to provide reliable N2 data. It was shown that desorption experiments from a bed fully saturated with the desired composition provides a better estimate of the competitive N2 loading. A detailed mathematical model that used inputs from the batch equilibrium experiments was able to predict the composition and thermal breakthrough curves well while underpredicting the single component N2 loading. The DSL isotherm with unequal energy sites was shown to predict the competitive loading and breakthrough curves well. The impact of the chosen adsorption isotherm model on process performance was evaluated by simulating a 4-step vacuum swing adsorption process to concentrate CO2 from dry post-combustion flue gas. The results show that the purity, recovery, energy and productivity are affected by the choice of the competitive adsorption isotherm.

Example Application of LGGH High-efficiency Coal-fired Flue Gas Treatment Technology in Yudian Dabu Power Plant

This paper describes the severe air pollution and ultra-low emission process route in China today, based on which it studies and analyzes the LGGH high-efficiency coal-fired flue gas treatment technology applicable to the upgrading of the ultra-low emission with respect to its origin, composition, characteristics and advantages. Then this paper gives a case study on the application of this technology in Yudian Dabu Power Plant where ultra-low emission is required, in particular the project profile of Yudian Dabu Power Plant, and specific proposal, process layout, main design parameters, technical features and operating result of the technology in the power plant. According to the testing, after this technology is put into use in the plant, the dust and SO₃ emissions of Unit 2# chimney drop to 2.3mg/m³ and 2.4 mg/m³ respectively, much lower than the national ultra-low emission limits. All these can demonstrate that the large-scale coal-fired power units can achieve a significant result by adopting the optimized LGGH high-efficiency coal-fired flue gas treatment technology, this technology provides higher precipitation efficiency, energy conservation and emission reduction, and high-efficiency SO₃ removal, solves the problem of "Gypsum rain" and visual pollution, and realizes dry chimney discharge, indicating that this technology deserves promotion and has great potential to become a popular post-combustion flue gas treatment technology.

Techno-Economic Assessment of Novel vs. Standard 5m Piperazine CCS Absorption Processes for Conventional and High-efficiency NGCC Power Plants

CO2 capture and storage (CCS) can play a key role in the mitigation of greenhouse gas emissions, as it is generally applicable to many industrial sectors to limit the environmental impacts from fossil fuels usage. In this regard, natural gas-fired power plants are a suitable application for CCS technologies, although they produce flue gases with a much lower CO2 concentration (i.e. ~4 %mol) than coal-fired power plant flue gases. Amine-based solvent absorption has been widely studied as a practical solution to decarbonize post-combustion flue gases from natural gas combined cycle power plants (NGCC). This paper presents the methodology and the results of a techno-economic assessment of 5 molal (5m) piperazine (PZ) as a new potential baseline solvent for carbon capture from NGCC in three different case studies that have been considered relevant from a preliminary literature analysis. The three evaluated configurations are (i) conventional F-class NGCC coupled with the conventional absorber configuration with a direct contact cooler (DCC), (ii) conventional F-class NGCC coupled with an advanced absorber configuration (no DCC – flue gas cooling integrated within the absorber) and (iii) high efficiency, state-of-the-art H-class NGCC, coupled with the advanced absorber configuration. The present work is based on the most recent findings from University of Texas at Austin (UT) research activities, and it has been carried out by Laboratorio Energia e Ambiente Piacenza (LEAP) and Politecnico di Milano (POLIMI) researchers supported and sponsored by the CO2 Capture Project (CCP).

Synthesis of Fluidized CO2 Sorbents Based on Diamine Coordinated to Metal-Organic Frameworks by Direct Conversion of Metal Oxides Supported on Mesoporous Silica.

A general and efficient method for shaping MOFs into fluidized forms has been developed by direct conversion of metal oxides supported on fluidized mesoporous silica. The resulting fluidized MOF hybrid materials containing diamines coordinated at the open metal sites have been studied as CO2 solid sorbents from post-combustion flue gas showing similar performance than their bulk counterparts. These new fluidized MOF hybrid materials can be used for other applications involving fluidized bed reactor configurations, in which MOFs have never been considered.

A comparative study of CO2 capture by amine grafted vs amine impregnated zeolite 4A

Zeolite 4A was functionalized via grafting and impregnation techniques using 0.3 wt% of isopropylamine (IPA) and (3-aminopropyl) trimethoxysilane (APTMS) respectively. Physicochemical properties of zeolite 4A containing binder were changed after amine loading, as both specific surface area and pore volume was decreased by 1.52 % 18.18 % and 28.06 % 90.90 % for Z4A-IPA (IPA impregnated zeolite 4A) and Z4A-APTMS (APTMS grafted zeolite 4A) respectively. The adsorbed CO2 amount of Z4A, Z4A-IPA, and Z4A-APTMS were 1.58 mmol g-1 (6.95 wt%), 2.31 mmol g-1 (10.16 wt%) and 1.05 mmol g-1 (4.62 wt%) respectively at 1 bar and 25 °C. Noticeably, among all the studied adsorbents, Z4A-IPA displayed the highest adsorption capacity of 1.39 mmol g-1 (6.11 wt%) at 0.15 bar, which is akin to the CO2 partial pressure of post-combustion flue gas. The multilayer tethering of the bulkier APTMS on the zeolite external surface resulted in the partial blockage of the pores and hence the facile access of CO2 inside the pores of zeolite was hindered. However, Z4A-APTMS was found to be more thermal stable than Z4A-IPA. Furthermore, we observed that physisorption was playing a vital role in CO2 adsorption for pristine zeolite 4A (Z4A), whereas, after amine incorporation, the presence of amine induced the heterogeneous interaction between CO2 and sorbents.

Nanostructured MgO Sorbents Derived from Organometallic Magnesium Precursors for Post-combustion CO2 Capture

Nanostructured MgO sorbents show promise for intermediate-temperature CO2 capture from post-combustion flue gas stream. However, their CO2 capture behaviors can be affected by the magnesium precursors applied for sorbent synthesis. To screen potential precursors for fabricating excellent CO2 trappers, MgO nanoparticles (NPs) were synthesized by calcining several organometallic precursors, including magnesium ethoxide, magnesium acetate tetrahydrate, magnesium oxalate dehydrate, magnesium lactate dihydrate, magnesium citrate nonahydrate, and magnesium gluconate hydrate. The precursors and MgO NPs were characterized by thermogravimetric analysis, X-ray diffraction, N2 adsorption–desorption, field emission scanning electron microscopy, and CO2 temperature-programmed desorption. A fixed-bed reactor was used to evaluate the CO2 capture performances of the MgO NPs in a simulated flue gas stream. The effect of organometallic precursors on CO2 capture behaviors of the sorbents was further demonstrated. Results in...

Pyrrolic N-enriched carbon fabricated from dopamine-melamine via fast mechanochemical copolymerization for highly selective separation of CO2 from CO2/N2

A pyrrolic N-enriched microporous carbon composite was synthesized using mechanochemical strategy via copolymerized melamine/dopamine (PDA/MA) within ultra-short reaction time (30 min) for CO2 capture from gaseous mixture of CO2/N2. Dopamine doping efficiently restrained the sublimation of melamine during calcination, which leaded to higher yield (>70 wt%) in comparison with pure C3N4. The synthesized carbon composite possessed ultra-microporous structure (5.3–5.6 Å) and abundant (pyrrolic N of 13.1 wt%) CO2-philic sites. Results showed that PDA0.3/MA0.7-2 exhibited high CO2 capacity of 16.0 wt% (3.64 mmol/g) at 298 K and 20.3 wt% (4.6 mmol/g) at 273 K and 1.0 bar pressure. The isosteric heat of adsorption (Qst) was 37.4 kJ/mol, indicating a strong interaction of the composite with CO2 molecules. Ideal adsorption solution theory demonstrated that PDA0.3/MA0.7-2 possessed a super high CO2 selectivity (108) in CO2/N2 (10:90) mixture at 273 K. High CO2 capacity and selectivity, green and fast fabrication strategy and cost effective raw materials make the proposed novel PDA/MA carbons as promising candidates for CO2 capture from post-combustion flue gases.

Molten Carbonate Fuel Cells for Retrofitting Postcombustion CO2 Capture in Coal and Natural Gas Power Plants

The state-of-the-art conventional technology for postcombustion capture of CO2 from fossil-fueled power plants is based on chemical solvents, which requires substantial energy consumption for regeneration. A promising alternative, available in the near future, is the application of molten carbonate fuel cells (MCFC) for CO2 separation from postcombustion flue gases. Previous studies related to this technology showed both high efficiency and high carbon capture rates, especially when the fuel cell is thermally integrated in the flue gas path of a natural gas-fired combined cycle or an integrated gasification combined cycle plant. This work compares the application of MCFC-based CO2 separation process to pulverized coal fired steam cycles (PCC) and natural gas combined cycles (NGCC) as a “retrofit” to the original power plant. Mass and energy balances are calculated through detailed models for both power plants, with fuel cell behavior simulated using a 0D model calibrated against manufacturers' specifications and based on experimental measurements, specifically carried out to support this study. The resulting analysis includes a comparison of the energy efficiency and CO2 separation efficiency as well as an economic comparison of the cost of CO2 avoided (CCA) under several economic scenarios. The proposed configurations reveal promising performance, exhibiting very competitive efficiency and economic metrics in comparison with conventional CO2 capture technologies. Application as a MCFC retrofit yields a very limited (<3%) decrease in efficiency for both power plants (PCC and NGCC), a strong reduction (>80%) in CO2 emission and a competitive cost for CO2 avoided (25–40 €/ton).

Flying MOFs: polyamine-containing fluidized MOF/SiO2 hybrid materials for CO2 capture from post-combustion flue gas

Solid-state synthesis ensures a high loading and well-dispersed growth of a large collection of metal-organic framework (MOF) nanostructures within a series of commercially available mesoporous silica. This approach provides a general, highly efficient, scalable, environmentally friendly, and inexpensive strategy for shaping MOFs into a fluidized form, thereby allowing their application in fluidized-bed reactors for diverse applications, such as CO2 capture from post-combustion flue gas. A collection of polyamine-impregnated MOF/SiO2 hybrid sorbents were evaluated for CO2 capture under simulated flue gas conditions in a packed-bed reactor. Hybrid sorbents containing a moderate loading of (Zn)ZIF-8 are the most promising sorbents in terms of CO2 adsorption capacity and long-term stability (up to 250 cycles in the presence of contaminants: SO2, NO x and H2S) and were successfully prepared at the kilogram scale. These hybrid sorbents demonstrated excellent fluidizability and performance under the relevant process conditions in a visual fluidized-bed reactor. Moreover, a biochemically inspired strategy for covalently linking polyamines to MOF/SiO2 through strong phosphine bonds has been first introduced in this work as a powerful and highly versatile post-synthesis modification for MOF chemistry, thus providing a novel alternative towards more stable CO2 solid sorbents.