Pre-combustion CO2 Capture Research Articles

Carbon-negative hydrogen from biomass using gas switching integrated gasification: Techno-economic assessment

Ambitious decarbonization pathways to limit the global temperature rise to well below 2 °C will require large-scale CO2 removal from the atmosphere. One promising avenue for achieving this goal is hydrogen production from biomass with CO2 capture. The present study investigates the techno-economic prospects of a novel biomass-to-hydrogen process configuration based on the gas switching integrated gasification (GSIG) concept. GSIG applies the gas switching combustion principle to indirectly combust off-gas fuel from the pressure swing adsorption unit in tubular reactors integrated into the gasifier to improve efficiency and CO2 capture. In this study, these efficiency gains facilitated a 5% reduction in the levelized cost of hydrogen (LCOH) relative to conventional O2-blown fluidized bed gasification with pre-combustion CO2 capture, even though the larger and more complex gasifier cancelled out the capital cost savings from avoiding the air separation and CO2 capture units. The economic assessment also demonstrated that advanced gas treatment using a tar cracker instead of a direct water wash can further reduce the LCOH by 12% and that the CO2 prices in excess of 100 €/ton, consistent with ambitious decarbonization pathways, will make this negative-emission technology economically highly attractive. Based on these results, further research into the GSIG concept to facilitate more efficient utilization of limited biomass resources can be recommended.

Engineering MOF surface defects in mixed matrix membranes: An effective strategy to enhance MOF/polymer adhesion and control interfacial gas transport

MOF/polymer adhesion in Mixed Matrix Membranes (MMMs) has been mainly enhanced so far via MOF and/or polymer functionalization to strengthen the interactions between the two components. This strategy, albeit effective, is generally accompanied by a drop in the permeability and/or selectivity performance of the MMMs. In this contribution, engineering structure defects at the MOF surfaces is proposed as an effective route to create pockets that immobilize part of the polymer chain, which is of crucial importance both to avoid plasticization issues and to enhance the MOF/polymer affinity while overcoming the adhesion/performance trade-off in MMMs. This engineered interfacial interlocking structure also serves as a bridge to accelerate the gas transport from the polymeric region towards the MOF pore entrance. This concept is showcased with a model MMM made of the prototypical UiO-66 MOF and the glassy Polymer of Intrinsic Microporosity-1 (PIM-1) and tested using CO2, CH4 and, N2 as guest species. Our computational findings reveal that a defective UiO-66 MOF surface improves the MOF/PIM-1 adhesion and contributes to accelerate the interfacial gas transport of the slender molecules CO2 and N2 and in a lesser extent of the spherical molecule CH4. This translates into a selective enhancement of the CO2 transport once combined with CH4 which paves the ways toward promising perspective for pre-combustion CO2 capture.

Techno-economic comparison of optimized natural gas combined cycle power plants with CO2 capture

Natural gas combined cycle (NGCC) power plants account for a large share of the global energy market. Although many alternative layouts of NGCC plants have already been addressed in the scientific literature, there are still relevant gaps of knowledge in comparative techno-economic performances of the previously proposed alternatives. This article presents a comprehensive comparative study of 19 alternative NGCC power plants with pre-combustion, post-combustion or oxy-fuel combustion CO2 capture processes involving different choices of CO2 absorbents and organic Rankine cycles for energy savings. The purpose of this study is to shed light on comparative techno-economic performances of power plants with different CO2 capture strategies and various organic Rankine cycle configurations. First, performance of each alternative was optimized from a technical (equivalent work) standpoint. Then, the economic performance of each optimized alternative was evaluated. Based on the results within the sample of NGCC plants, using activated methyldiethanolamine could lead to better technical and economic performances than monoethanolamine in pre- and post-combustion capture systems. Moreover, the efficacy of organic Rankine cycles for enhancing the technical and economic performance of NGCC plants with CO2 capture was shown, with a reduction of up to 1.39 years in the payback period for various process configurations.

Characteristics of MgO-based sorbents for CO2 capture at elevated temperature and pressure

MgO-based sorbents are promising candidates for precombustion CO2 capture performed at elevated temperature and pressure in thermodynamics, where the development of efficient sorbents is of great importance. Herein, we report MgO-Na2CO3-KNO3 sorbents with fast sorption kinetics, high capture capacity and good cyclic stability at elevated conditions. The effects of nitrate species, Na2CO3 doping amounts and sorption conditions on the MgO conversion were investigated during cyclic test. In comparison with LiNO3 and NaNO3, the sample with KNO3 possesses the highest MgO conversion, which increases from 0.78 to 0.86 after 30 cycles with sorption at 400 °C, 2 MPa. For nitrate-promoted MgO, Na2CO3 plays an essential role in the initial fast sorption rate. The sorbent with 60 mol%Na2CO3 possesses the highest MgO conversion of 0.89 after 30 cycles. Moreover, during the operation range of 400 ℃-480 ℃, 2 MPa, the sorbent exhibits an excellent cyclic stability with porous structure. Density functional theory calculations are further conducted to investigate the mechanism of performance improvement brought by Na2CO3. We find dissolved CO32– ions will provide chemisorption sites through the formation of C(CO2)-O(CO32–) bonds and can serve as the CO2 carrier in molten nitrate salts, thus improving both sorption and diffusion rates of CO2.

Significance of wettability of porous media and its implication for hydrate-based pre-combustion CO2 capture

Gas hydrate-based pre-combustion CO2 capture is considered a promising technology for CO2 separation. To further improve hydrate-based CO2 capture from gaseous mixtures (i.e., CO2 + H2) generated from pre-combustion processes, it is necessary to enhance the hydrate thermodynamic stability and formation kinetics. Surfactants and interstitial pore materials have been suggested to enhance formation kinetics, but the optimum confined space and wettability of the porous media, which are the key factors affecting kinetic performance, have not been fully determined when using thermodynamic promoters. In this study, the thermodynamic stability and formation kinetics (e.g., induction time, formation rate, gas composition, and gas uptake) of THF (5.56 mol%) hydrates of CO2 (40%) + H2 (60%) mixtures in the presence of SDS (0, 100, or 500 ppm) were evaluated in silica gels of various hydrophobicities. The results revealed that the hydrophobicity of the porous media significantly affects both the thermodynamic phase equilibria and kinetic properties. Interestingly, the weak hydrophobic silica gel enhanced the thermodynamic stability, induction time, formation rate, and gas uptake with 96% CO2 composition. The SDS (particularly 500 ppm) also improved the kinetic properties of the hydrate. The present findings provide a new guideline for designing the optimum hydrophobicity of porous media to enhance the thermodynamic stability and formation kinetics for hydrate-based pre-combustion CO2 capture.

Carbon spheres synthesized from KHCO3 activation of glucose derived hydrochar with excellent CO2 capture capabilities at both low and high pressures

In the current work, we reported a facile synthesis method for carbon spheres utilizing KHCO3 activation. Glucose was hydrothermally reacted at 200 °C to produce spherical hydrochar at high yield, and cetyltrimethylammonium bromide (CTAB) was added to mediate the morphology. The hydrochar was then activated with KHCO3 in the presence of urea. The obtained carbon spheres exhibited ultrahigh specific surface area of 3576 m2/g. It was also found that urea effectively promoted pore formation during activation. Superior CO2 capture performances were achieved at both 1 and 20 bar. At 25 °C and 1 bar, the carbon spheres showed high CO2 uptake of 4.26 mmol/g. While at 20 bar, impressively high uptakes of 35.57 mmol/g (0 °C) and 23.04 mmol/g (25 °C) were achieved, which were the highest among the reported results for porous carbons at 20 bar. At 1 bar, ultramicropore (<0.7 nm) was the most important factor in deciding CO2 uptake, while nitrogen doping significantly enhanced adsorption heat and selectivity. At 20 bar, the uptake showed clear dependence on surface area. The carbon spheres in our work showed great potential in pre-combustion CO2 capture.

Techno-economic assessment of decarbonized biogas catalytic reforming for flexible hydrogen and power production

Biogas got significant attention as a promising renewable energy source and an energy-efficient way of converting various biowastes into energy carriers. As relevant research contributions of present analysis, the detailed technical and economic assessment of decarbonized biogas catalytic reforming process for flexible hydrogen & power generation was assessed. The production capacity of evaluated concepts is 50,000 Nm3/h high-hydrogen (>99.95% vol.) and up to 40 MW net power output. Reactive gas–liquid (using one illustrative amine) and the gas–solid (iron & calcium looping) processes are used for pre-combustion CO2 capture. The overall process simulation results for investigated designs were exploited for the calculation of techno-economic key performance indexes. As results show, the iron/calcium looping systems are very promising in terms of increasing the overall efficiency (up to 2.5 net percentage points), the plant decarbonization rate (72–75 vs. 64%), reducing CO2 emissions (120–144 kg/MWh vs. 175 kg/MWh) and improving key economic parameters (e.g., lower hydrogen cost by at least 5%, CO2 capture cost by at least 25%) than the chemical scrubbing concept (benchmark). Furthermore, the overall hydrogen and power flexibility brings relevant advantages e.g., higher cumulative energy efficiency, improved cyclic operation etc.

Pre-combustion CO2 capture using amine-based absorption process for blue H2 production from steam methane reformer

A novel pre-combustion CO2 capture process using methyl diethanolamine with piperazine (MDEA/PZ) was investigated for the production of blue H2 from a steam methane reformer (SMR). A sensitivity analysis was performed at various operating parameters (such as MDEA or PZ concentration, flash drum pressure, CO2 loading in a lean-amine solvent, and CO2 removal efficiency) using a validated rate-based model. The energy consumption to capture CO2 from SMR gas at 21 bar was evaluated, including the compression energy (up to 30 bar) for the dehydration of captured CO2. For 90% and 95% CO2 removal efficiency, reboiler duties were 1.318 GJ/tonCO2 and 1.364 GJ/tonCO2, and CO2 compression works were 11.673 kW/molCO2 and 11.615 kW/molCO2. The results indicated more than 40% lower reboiler duty than the energy consumption of conventional CO2 capture processes in post-combustion. Subsequently, artificial neural network model (ANN)-based optimization using the differential evolution method was performed. The developed ANN-based optimization suggested the possibility of additional 0.3 % reduction in the equivalent work at a low computational cost. The results indicated that the developed pre-combustion CO2 capture for a SMR was highly competitive in industrial applications. Moreover, the H2 mixture produced at 21 bar is beneficial for a H2 recovery unit because of no need for additional compression energy. Therefore, the MDEA/PZ-based absorption process can effectively contribute to centralized or semi-central blue H2 production from a SMR. This study provides a guideline for the feasible optimization and control of the CO2 absorption process at high feed pressures.

Dynamic CO2 sorption on MgO-based sorbent in the presence of CO and H2O at elevated pressures

The presence of gas species other than the target adsorbate in practical conditions causes complications in implementing a sorption-based process because of synergistic or detrimental effects on the sorption mechanism. MgO-based sorbents have attracted massive attention for the pre-combustion CO2 capture, where H2O and CO co-exist in emission gas. Although H2O has been reported to greatly enhance CO2 sorption kinetics, CO2 sorption behavior and mechanism under a large quantity of H2O as in the practical condition remain unclear. Furthermore, CO2 sorption behavior in the presence of CO has not been adequately examined. Here, the dynamic CO2 sorption behavior of MgO-based sorbent was understood by coupling the breakthrough experiment under practically relevant conditions with in situ DRIFTS results. At elevated pressures, the sorption performance was considerably enhanced, whereas the influence by temperatures was insignificant. In addition, H2O enhanced CO2 sorption kinetics and initial CO2 sorption on MgO-based sorbent, whereas CO hindered them. In situ DRIFTS analyses for the mechanism study revealed that OH groups generated from H2O dissociation created highly basic sites that promoted the formation of monodentate carbonate, thereby enhancing the initial CO2 sorption. In contrast, CO hampered CO2 sorption through two mechanisms: (1) competitive sorption between CO2 generated from the water–gas shift reaction and CO2 in the feed; (2) interference of the promoted sorption by the molten nitrate salts. This study demonstrated that the practical condition of the pre-combustion CO2 capture significantly alters the CO2 sorption behavior of MgO, thereby providing insights for the ultimate implementation of MgO-based sorbents.

Aspen plus supported design of pre-combustion CO2 capture processes based on ionic liquids

H2 production processes from steam methane reforming and combined cycle power plants require carbon dioxide removal from raw synthesis gas to obtain a useful H2-rich product stream. In this work, a wide variety of operating configurations were techno-economically evaluated in Aspen Plus commercial process simulator to improve the efficiency and costs of the pre-combustion CO2 capture process based on chemical absorption using [P2228][CNPyr] ionic liquid. Multiple absorption (from 30 °C to 70 °C) and regeneration (between 90 °C and 120 °C) temperatures were tested along with four different regenerating pressures: 0.1, 0.25, 0.5 and 1 bar. Energy and solvent consumptions and capital and operating costs were calculated for nine configurations using the COSMO-based/Aspen methodology combined with Aspen Economic Analyzer tool. The most promising results were obtained when regenerating the IL at 1 bar and at elevated absorption and regeneration temperatures, due to the higher operating and equipment costs associated with vacuum and the greater utilities cost related to heat transfer when the gap between both temperatures grows. The minimum cost achieved was 64.1$/tCO2 considering an IL scaled up price of 50 $/kg, but it could even be further less than 40 $/tCO2 goal for new generation solvents, when only direct costs were considered.

Synchronous Design of Membrane Material and Process for Pre-Combustion Co2 Capture: A Superstructure Method Integrated Membrane Material Selection

Synchronous Design of Membrane Material and Process for Pre-Combustion Co2 Capture: A Superstructure Method Integrated Membrane Material Selection

Performance of Hydrophobic Physical Solvents for Pre-Combustion Co2 Capture at a Pilot Scale Coal Gasification Facility

Performance of Hydrophobic Physical Solvents for Pre-Combustion Co2 Capture at a Pilot Scale Coal Gasification Facility

Comparative Techno-Economic Analysis of Carbon Capture Processes: Pre-Combustion, Post-Combustion, and Oxy-Fuel Combustion Operations

Evaluation of economic aspects is one of the main milestones that affect taking rapid actions in dealing with GHGs mitigation; in particular, avoiding CO2 emissions from large source points, such as power plants. In the present study, three kinds of capturing solutions for coal power plants as the most common source of electricity generation have been studied from technical and economic standpoints. Aspen HYSYS (ver.11) has been used to simulate the overall processes, calculate the battery limit, and assess required equipment. The Taylor scoring method has been utilized to calculate the costliness indexes, assessing the capital and investment costs of a 230 MW power plant using anthracite coal with and without post-combustion, pre-combustion, and oxy-fuel combustion CO2 capture technologies. Comparing the costs and the levelized cost of electricity, it was found that pre-combustion is more costly, to the extent that the total investment for it is approximately 1.6 times higher than the oxy-fuel process. Finally, post-combustion, in terms of maturity and cost-effectiveness, seems to be more attractive, since the capital cost and indirect costs are less. Most importantly, this can be applied to the existing plants without major disruption to the current operation of the plants.

Tunable Supramolecular Cavities Molecularly Homogenized in Polymer Membranes for Ultraefficient Precombustion CO2 Capture.

Processable molecular-sieving membranes are important materials for realizing energy-efficient precombustion CO2 capture during industrial-scale hydrogen production. However, the promising design of mixed matrix membranes (MMMs) that aims to integrate the molecular-sieving properties of nanoporous architectures with industrial processable polymers still faces performance and fabrication issues due to the formation of segregated nanofiller domains in their polymer matrices. Here, an unconventional nanocomposite membrane design is proposed using soluble organic macrocyclic cavitands (OMCs) with tunable open cavity sizes that not only mitigate the formation the discrete nanofiller phases but also deliver distinct molecular-sieving separations. The versatile organic-solvent solubility coupled with highly interactive functionalities of OMCs allows them to obtain molecularly homogeneous mixing with matrix polymers and form only one integral continuous phase crucial to the robust processability of polymers. A series of polybenzimidazole-based molecularly mixed composite membranes (MMCMs) are fabricated via the incorporation of a soluble and thermally stable OMC choice, sulfocalixarenes, with various cavity sizes. These membranes achieve outstanding high-temperature mixed-gas H2 /CO2 separation performances comparable with several state-of-the-art molecular-sieving membranes owing to effective size-sieving gas passages through the open or partially-intruded supramolecular cavities. The broadly tunable structures and functionalities of OMCs would make their MMCMs attractive for other energy-intensive molecular separations.

Highly Selective Separation of CO2 and H2 by MIL-88A Metal Organic Framework

CO2 capture is indispensable for a cleaner environment and the mitigation of global warming. The pre-combustion CO2 capture relates to the separation of CO2 from H2 in the syngas mixture. Recently, metal-organic frameworks have proven to be excellent candidates for this purpose. In the current work, MIL-88A (Fe, V, Ti, Sc) were studied for the first time by using the grand canonical Monte Carlo simulations for the CO2/H2 mixture. The adsorption capacity of CO2 and H2 in the absence and presence of water medium in MIL-88A was analyzed. We found that the magnitude of the CO2 capacity is many times higher than that of the H2 capacity, which leads to rather high CO2/H2 selectivity. The presence of water decreases the maximum selectivity of MIL-88A(Fe), increases that of MIL-88A(Ti and Sc), while it influences differently on the maximum selectivity of MIL-88A(V) for the different CO2/H2 mole fractions. The order of the maximum selectivity was found to be MIL-88A(Sc) &gt; MIL-88A(Ti) &gt; MIL-88A(V) &gt; MIL-88A(Fe). The MIL-88A(Sc) achieved the maximum CO2/H2 selectivity of ~ 900 and 1300 in the absence and the presence of water medium, respectively. These values are significantly higher than those of many well-known metal-organic frameworks. The favorable adsorption sites of the CO2/H2 mixture in MIL-88A were also elucidated.

Integrated Coproduction of Power and Syngas from Natural Gas to Abate Greenhouse Gas Emissions without Economic Penalties.

Natural gas (NG)-fired power plants are significant greenhouse gas (GHG) emitters because of their substantial CO2 release. To avoid these emissions, precombustion and postcombustion CO2 capture alongside oxy-fuel combustion were considered in the literature. However, because of additional energy requirements, these options generally induce an approximately 7–10% decrease in net heat-to-power efficiencies regarding regular NG-air-fired stations without CO2 capture. To compensate for this declination, in this study, a simultaneous generation of power and syngas (CO and H2) was proposed in an integrated NG-oxygen-fired gas turbine unit (GTU). Hence, the combustion chamber in the NG-oxygen-fired gas turbine cycle was replaced by an NG partial oxidation reactor, which converts it into syngas. The syngas was separated from the working fluid of the cycle by the condensation of water vapor (steam), and a part of it was withdrawn from the GTU to be utilized as a chemical feedstock. A benchmark thermodynamic analysis at the same input–output conditions and requirements for carbon capture was conducted to compare the proposed unit with NG-air and NG-oxygen-fired power plants. The integration effect was shown by increasing the heat-to-power efficiency from 48 to 54%. With carbon monoxide (CO) as an intermediate, the author proposed capturing carbon in NG (methane) in liquid formic acid, which is a good commodity for transportation to a place where it can be reconverted into CO or H2 to manufacture various industrial chemicals. Simple economic considerations show that because of a substantially higher cost of formic acid than an equivalent power, CO conversion into formic acid substantiates the integrated approach as economically attractive.

Molten Salt-Promoted MgO Adsorbents for CO2 Capture: Transient Kinetic Studies

Optimization of MgO adsorbents is predominantly focused on the regulation of appropriate adsorption sites for CO2 associated with Mg2+-O2- sites of low coordination. Here, for the first time, we conducted transient kinetic experiments to identify and characterize changes of the CO2 molecular path in MgO-based CO2 adsorbents upon the addition of molten salt modifiers. Among the optimized samples, addition of 10 mol % NaNO2 on the surface of MgO exhibited the highest CO2 uptake (15.7 mmol g-1) at 350 °C compared to less than 0.1 mmol g-1 for the unpromoted MgO. Kinetic modeling showed that the interaction of molten salt-promoted MgO with CO2 at 300 °C involves three different processes, namely, fast surface adsorption associated with surface-active basic sites, chemical reaction associated with MgCO3 formation, and a slow diffusion step being the rate-limiting step of the carbonation process. Furthermore, transient kinetic studies coupled with mass spectrometry under low CO2 partial pressure agreed well with the kinetic simulation results based on TGA measurements, demonstrating an in-depth understanding of the CO2-capturing performance gained and its considerable significance for future practical designs of precombustion CO2 capture.

Optimal design and operation of a waste tire feedstock polygeneration system

The optimal design and operation of a polygeneration system that uses a waste tire feedstock to produce a mix of electricity, fuels and chemicals is presented. Rigorous mass and energy balance models for the process are developed from which data are generated to fit surrogate models. The optimization problem is formulated as a nonconvex Mixed-Integer Nonlinear Program (MINLP) and solved to global optimality using ANTIGONE. The influence of variation in product prices and carbon dioxide (CO2) tax rates on the optimal process design and operation is also presented. In all scenarios studied, the optimal product portfolio favors generation of one fuel or chemical together with electricity. Electricity generation is favored in a base case with historically average market prices, while methanol, liquefied Synthetic Natural Gas (SNG) and Dimethyl Ether (DME) are favored in relatively probable scenarios in which the corresponding product fetches higher prices. Pre-combustion CO2 capture is favored at lower CO2 tax rates while post-combustion CO2 capture is only optimal in scenarios with higher rates. The optimal product portfolio changes substantially with varying market conditions thus motivating future work on designing flexible polygeneration processes that have the capacity to adjust operating conditions in order to maximize profitability by exploiting price peaks.

BECCS Opportunities in Brazil: Pre and Post-Combustion Comparison in a Typical Sugarcane Mill

In order to make feasible the efforts that would limit the rise of Earth's temperature to no more than 2°C, profound changes are required in the energy systems. In this sense, BECCS (sustainable bioenergy systems, combined with carbon capture and storage) are considered instrumental to attain possible negative emissions. This brings the attention to the sugarcane industry in Brazil, in which it is possible to produce fuel ethanol at a relative low cost and a large amount of relatively cheap biomass is available. The already good results related to the avoided emissions could be further improved with the storage of the CO2 produced during fermentation. In addition, with not yet commercial BIG-CC systems (biomass-integrated gasification to combined cycle), it would be possible to at least double the generation of electricity at a sugarcane plant, compared to the results of conventional cogeneration systems. In this case, as biomass gasification is required, it would be possible to use pre-combustion capture technologies, reducing energy penalties. This article is part of a research that aims to study the combined production of liquid fuels and electricity, using sustainable sources of biomass and maximizing carbon capture. In both cases evaluated, the capture is based on amine technology: pre-combustion capture of CO2 from the fuel gas derived from biomass gasification, and post-combustion capture from gas turbine exhaust gases. Modelling is based on literature information for all systems, as well as for estimating energy penalties associated with CO2 capture, transport and storage. The results indicate technical feasibility for both technologies, but difficulties in setting the full integration of the BIG-CC unit with the sugarcane mill and the CCUS system, due to the high demand for thermal energy as low pressure steam. The estimated CO2 abatement cost is in the range 66–77 €/tCO2 for pre-combustion capture, and 58–68 €/tCO2 in the case of post-combustion. Feasibility results are impacted by the scale of CO2 capture from the combustion gases (0.54–1.11 MtCO2/year), mainly in the pre-combustion case, and by the relatively high cost of electricity generation (46 €/MWh).

Process Simulation and Economic Analysis of Pre-combustion CO2 Capture With Deep Eutectic Solvents

The purpose of this paper is to identify firstly the most important solvent characteristics in the CO2 capture process and secondly to determine how they contribute to the total cost of CO2 separation and analyze the economic feasibility of current deep eutectic solvents (DESs) in literature. A rate-based modeling approach was adopted to simulate pre-combustion CO2 capture. The effects of the flow model and the number of segments were investigated for the Selexol process. Different mass transfer correlations due to Bravo et al. (1985), Billet and Schultes (1993) and Hanley and Chen (2012) were adopted for the rate-based models and compared with the equilibrium modelling approach. Subsequently, property and process models were developed for a mixture of decanoic acid and menthol, in equal quantities. A physical property study was conducted with this DES. The CO2 solubility is found to be very important in all rate-based models, as expected, but properties such as the surface tension, thermal conductivity, heat capacity and volatility had a minor influence on the absorption performance. The solvent viscosity strongly affects the mass transfer rate when using the Hanley and Chen (2012) correlations, whereas it plays only a small role in the other two sets of correlations. Using a high CO2 solubility as criterion, two mixtures of allyl triphenylphosphonium bromide (ATPPB) and diethylene glycol (DEG) were screened out from literature. The conventional Selexol process was set as the benchmark for the evaluation of the performances of these DESs. The optimum capture cost for Selexol process is 27.22, 26.66 and 30.84 $2018/tonne CO2 for the adopted correlations, respectively. When employing two of the three studied mass transfer correlations, the estimated process costs for a capture process using this DES can be similar to the costs of the Selexol process. However, when the liquid viscosity strongly affects the mass transfer rate, as is the case when using the Hanley and Chen (2012) correlations, the Selexol process remains more economical. This strongly indicates the need for further experimental and modelling studies on mass transfer rates in absorption columns (with higher viscosity liquids) to help directing the development of suitable DESs for pre-combustion CO2 capture.