Combined CO2 Capture Research Articles

Process Development and Techno-Economic Analysis for Combined and Separated CO2 Capture-Electrochemical Utilization

Combining CO2 capture and utilization into a single unit operation offers a feasible solution for converting a sustainable feedstock into marketable commodity chemicals, while reducing energy requirements from separated processes. In this research, we developed a process model and performed a techno-economic analysis (TEA) for point-source CO2 capture and electrochemical-based utilization in light olefins production under both separated and integrated scenarios. CO2 containing flue gas from a 500 MW power plant was utilized as a feed while CO2 utilization involved electrochemical reduction reactions to produce light olefins directly from CO2. A meticulous analysis was conducted, probing into the multifaceted impacts of various operating parameters, material properties, and downstream treatment units. Factors such as pressure, temperature, H2O/CO2 molar ratio, catalyst and adsorbent activities, deactivation rate, and heat integration were optimized to achieve 95 % CO2 recovery and > 90 % conversion, and > 85 % ethylene yield. Through a comprehensive TEA, our findings unveiled that the combined process utilizing bifunctional adsorbent/catalyst materials (BFMs) incurs costs of approximately $284/ton CO2, whereas the separated process reported expenses of ∼$516/ton CO2. This study, pivotal in its contributions, evaluated economic feasibility of combined capture-conversion method based on BFMs for CO2 removal and subsequent utilization via a promising advanced process model for sustainable feedstocks conversion to commodity chemicals.

Addition of Imidazolium-Based Ionic Liquid to Improve Methanol Production in Polyamine-Assisted CO2 Capture and Conversion Systems Using Pincer Catalysts.

Ionic liquids have been studied as CO2 capture agents. However, they are rarely used in combined CO2 capture and conversion processes. Utilizing imidazolium-based ionic liquids, the conversion of CO2 to methanol was greatly improved in polyamine assisted systems catalyzed by homogeneous pincer catalysts with Ru and Mn metal centers. Among the ionic liquids tested, [BMIM]OAc was found to perform the best under the given reaction conditions. Among the polyamine tested, pentaethylenehexamine (PEHA) led to the highest conversion rates. Ru-Macho and Ru-Macho-BH were the most active catalysts. Direct air capture utilizing PEHA as the capture material was also demonstrated and produced an 86 % conversion of the captured CO2 to methanol in the presence of [BMIM]OAc.

Carbon capture in polymer-based electrolytes.

Nanoparticle organic hybrid materials (NOHMs) have been proposed as excellent electrolytes for combined CO2 capture and electrochemical conversion due to their conductive nature and chemical tunability. However, CO2 capture behavior and transport properties of these electrolytes after CO2 capture have not yet been studied. Here, we use a variety of nuclear magnetic resonance (NMR) techniques to explore the carbon speciation and transport properties of branched polyethylenimine (PEI) and PEI-grafted silica nanoparticles (denoted as NOHM-I-PEI) after CO2 capture. Quantitative 13C NMR spectra collected at variable temperatures reveal that absorbed CO2 exists as carbamates (RHNCOO- or RR'NCOO-) and carbonate/bicarbonate (CO32-/HCO3-). The transport properties of PEI and NOHM-I-PEI studied using 1H pulsed-field-gradient NMR, combined with molecular dynamics simulations, demonstrate that coulombic interactions between negatively and positively charged chains dominate in PEI, while the self-diffusion in NOHM-I-PEI is dominated by silica nanoparticles. These results provide strategies for selecting adsorbed forms of carbon for electrochemical reduction.

Thermodynamics analysis of a novel designation of LNG solid oxide fuel cells combined system with CO2 capture using LNG cold energy

The solid oxide fuel cells (SOFC) – proton exchange membrane fuel cells (PEMFC) and waste heat recovery utilization systems employing liquefied natural gas (LNG) as fuel are designed and integrated. The cold energy from LNG supply system is harvested and supported to the CO2 capture system. The gas turbine (GT), organic Rankine cycle (ORC), steam Rankine cycle (SRC) are integrated to use LNG cold energy and waste heat of system and transfer it into useful work and power. PEMFC is constructed and coupled in an integrated system to address the disadvantage of SOFC's delay in starting and maneuvering period of vessel. To adapt regulations and standards from international and local authorities, the CO2 capture system is designed and integrated. The ORC-SOFC-GT-PEMFC-ORC-SRC-CO2 capture system is analyzed and investigated thermodynamically based on the first and second laws of thermodynamics. ASPEN HYSYS V12.1 are used to simulate and optimize the LNG SOFC integrated system combined CO2 capture utilizing LNG cold energy. Laws of thermodynamics were employed to build up the thermodynamics equations and estimate the system performance indicators. The exergy destruction of major components was established and estimated to optimizing the designation and operation of suggested system. The energy and exergy efficiencies of proposed system was calculated at 68.76% and 33.58%, respectively. The waste heat recovery combined cycles generated more 2100.42 kW which equivalent to 35.6% of the total output of system. The innovated models were validated against experiment data from literature with good agreement. Furthermore, the parametric study show that the current density varied from 930 to 1930 A/m2 influencing the main indicator which total energy efficiency varied by 33.18% from 3.29% to 5.11%. The ORC took both advantages on cold energy and high-temperature of waste heat results high efficiency of energy recovery. The use of exhaust gas boiler for waste heat recovery provides 9000 kg/h of superheated vapor at 151.5 ℃and 498 kPa for accommodating of seafarers and heating the lubricating oil on board. The combination of harvesting LNG cold energy and exhaust gas waste heat recovery to the CO2 capture system contributing to greener of exhaust gas adapting the regulations of International Maritime Organization (IMO) for emission from marine vessels.

Catalytic Synthesis of CO by Combining CO2 Capture and Hydrogenation over Three-Dimensional Ni/CaO Networks

Three-dimensional Ni/CaO networks were synthesized using a precipitation–combustion method and applied for the combined CO2 capture and catalytic hydrogenation as dual functional materials. NiO species were highly dispersed in the CaO substrate and generated small metallic Ni nanoparticles upon reduction with H2. It was found that, compared with pure CaO, the addition of Ni not only greatly lowered the reaction temperature of calcium carbonate species with H2 to CH4 and/or CO but also enhanced the conversion rate of calcium carbonate species, resulting in the clear increase in the productivity of CO. Ni/CaO exhibited excellent cyclic stability with a CO2 adsorption capacity of 9.7 mmol/g and a CO2 conversion of 57.5% after 20 cycles for the combined CO2 capture and hydrogenation, which was due to the elasticity of the three-dimensional network structure consisting of meso- and macropores to inhibit the growth and sintering of CaO particles.

Cyclic operation of CO2 capture and conversion into methane on Ni-hydrotalcite based dual function materials (DFMs)

Ni-hydrotalcite-based dual function materials (DFMs) have been prepared and applied for the combined CO2 capture and methanation in a single reactor. The materials have been synthesized with different chemical properties (by partial substitutions of Mg with Ni, by changing the M2+/M3+ molar ratio – i.e., the (Ni2++Mg2+)/Al3+ ratio, and by impregnation with Cs (≈10 wt%)) and the effect of reduction temperature on their cyclic performance was studied. After calcination, the materials were reduced at increasing temperatures, from 400° to 600°C. The cyclic operation started with the capture of CO2 from a 15% CO2/N2 stream (feeding for 20 min), followed by the methanation stage with pure H2. The Cs-promoted sample reduced at 450 °C featured a CO2 sorption capacity of 0.48 molCO2·kgcDFM-1 and produced ca. 0.33 molCH4·kgcDFM-1. Its good performance was associated to a higher number of medium and strong basic sites. The sample containing the highest M2+/M3+ molar ratio (≈3) exhibited the highest selectivity towards methane (≈ 100%) and fastest methanation kinetics.

Effective CO2 Capture and Selective Photocatalytic Conversion into CH3OH by Hierarchical Nanostructured GO-TiO2-Ag2O and GO-TiO2-Ag2O-Arg.

The attenuation of greenhouse gases, especially CO2, as one of the main causes of global warming and their conversion into valuable materials are among the challenges that must be met in the 21st century. For this purpose, hierarchical ternary and quaternary hybrid photocatalysts based on graphene oxide, TiO2, Ag2O, and arginine have been developed for combined CO2 capture and photocatalytic reductive conversion to methanol under visible and UV light irradiation. The material's band gap energy was estimated from the diffuse reflectance spectroscopy (DRS) Tauc analysis algorithm. Structural and morphological properties of the synthesized photocatalysts were studied using various analytical techniques such as Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The calculated band gaps for GO-TiO2-Ag2O and GO-TiO2-Ag2O-Arg were 3.18 and 2.62 eV, respectively. This reduction in the band gap showed that GO-TiO2-Ag2O-Arg has a significant visible light photocatalytic ability. The investigation of CO2 capture for the designed catalyst showed that GO-TiO2-Ag2O-Arg and GO-TiO2-Ag2O have high CO2 absorption capacities (1250 and 1185 mmol g-1, respectively, at 10 bar and 273 K under visible light irradiation). The amounts of methanol produced by GO-TiO2-Ag2O and GO-TiO2-Ag2O-Arg were 8.154 and 5.1 μmol·gcat1·h-1 respectively. The main advantages of this study are the high efficiencies and selectivity of catalysts toward methanol formation. The reaction mechanism to understand the role of hybrid photocatalysts for CO2 conversion is deliberated. In addition, these catalysts remain stable during the photocatalytic process and can be used repeatedly, proving to be enlightening for environmental research.

Novel process design for waste energy recovery of LNG power plants for CO2 capture and storage

In an liquefied natural gas (LNG) power plant, the amine scrubbing and CO2 liquefaction process are generally employed for CO2 capture and storage (CCS) because it is suitable for large-scale plants. However, a large amount of hot and cold energy is required for CO2 absorption, regeneration and liquefaction. As a solution, the waste LNG cold energy from the LNG regasification process and waste hot energy from natural gas combined cycle (NGCC), which are generally disposed into the seawater, can be recovered and utilized for the abovementioned purposes. Hence, this study suggested a novel process for waste hot and cold energy recovery of the LNG power plants for CCS. The suggested process model consists of the following four steps: LNG regasification, natural gas combined cycle, CO2 capture and regeneration and CO2 liquefaction. In the process model, the waste LNG cold energy is recovered at the lean amine cooler in the CO2 capture process and each heat exchanger in the CO2 liquefaction process. Furthermore, for CO2 regeneration, the waste hot energy from NGCC is recovered at the stripper reboiler. The exergy and economic analyses were addressed to evaluate the economic feasibility of energy conversion of the proposed process. As a result, compared to the base process, the net power generation and exergy efficiency of the proposed process increased by 16% and 8%, respectively. In addition, the net profit of the proposed process increased by 75%, indicating high economic feasibility. The overall energy efficiency and economic feasibility using waste cold and hot energy were observed to increase, which resulted in decreased fuel usage. Therefore, we believe that the proposed approach can contribute significantly to the economic improvements and environmental protection efforts.

MxOy (M = Mg, Zr, La, Ce) modified Ni/CaO dual functional materials for combined CO2 capture and hydrogenation

The integrated CO2 capture and utilization has recently attracted attention as a promising approach to reduce CO2 emissions as well as produce value-added chemicals and fuels. Herein, metal oxides (MxOy, M = Mg, Zr, La, and Ce) modified Ni/CaO dual functional materials (M-Ni/Ca DFMs) were synthesized and applied to the combined CO2 capture and hydrogenation using a single reactor at one temperature. The La–Ni/Ca showed the highest CO2 adsorption capacity (13.8 mmol/g), CO2 conversion (64.3%) and CO yield (8.7 mmol/g). Results indicated that the addition of metal oxides increased the number of basic sites which played important role in efficient CO2 capture. The high activities of M-Ni/Ca were attributed to the formation of highly dispersed small-sized Ni particles. Furthermore, the La–Ni/Ca exhibited excellent cyclic stability after 20 cycles due to the La2O3 as a physical barrier and a support for inhibiting the growth and sintering of CaO and Ni particles.

Bifunctional Artificial Carbonic Anhydrase for the Integrated Capture and Electrochemical Conversion of CO2

To valorize waste and atmospheric CO2, carbon capture and utilization (CCU) technologies are currently receiving a lot of attention. Alkali base solutions have shown to be efficient capture solutions, and the electrochemical CO2 reduction (eCO2R) is a promising approach to convert CO2 using renewable energy. However, the capture and conversion have been investigated almost exclusively as separate processes to date. This strategy has the disadvantage that CO2 must be desorbed and compressed after capture, which increases the capital and operational costs of the technology significantly. To improve the valorization potential of CCU technologies, integrating both the capture and electrochemical conversion steps by directly utilizing the postcapture solution as an electrolyte (in the form of bicarbonate) for the eCO2R is a highly promising approach. However, bicarbonate electrolysis cannot compete yet in terms of energy efficiency with analogous CO2-fed electrolyzers. Nevertheless, given its huge potential, there is interest in optimizing the overall technology by, for instance, decreasing the costs of capturing the CO2 by shortening the operational time or promoting the electrochemical conversion of CO2 in bicarbonate solutions. In this study, we have synthesized and optimized for the first time ever bioinspired catalysts that were able to fulfill and improve steps in a combined CO2 capture and conversion system. In the best-case scenario, the rate of the conversion of CO2 to bicarbonate (mimicking the capture step in CCU) increased by 91% when the biomimetic catalyst [Zn(cyclen)]2+ was present in the capture solution. On the other hand, the same catalyst promoted the electrochemical conversion of CO2 to formate from a bicarbonate postcapture solution by inhibiting the competing hydrogen evolution reaction (HER). The partial current density toward the HER decreased from 18 mA cm–2 in control experiments to 0.7 mA cm–2 in the presence of [Zn(cyclen)]2+.

Assessment of enhanced activity of co-integration pathways for CO2 capture and CO2 utilization

Over the past century, the concentration of carbon dioxide (CO2) has significantly increased in our atmosphere, creating numerous catastrophic effects and environmental impacts. There are three main CO2 capture methods: (a) post-combustion, (b) pre-combustion, and (c) oxy-fuel combustion implemented to capture CO2 from significant CO2 emitting sources. Further, the captured CO2 is utilized to convert it into value-added products. The current status of potential combined CO2 capture and CO2 utilization methods provide the solution to the issues of greenhouse-gas CO2 emissions from anthropogenic activities and the ever-growing energy demand challenges. These unique approaches dramatically reduce the overall energy penalty, cost-effective, and have a low environmental impact. As of now, carbon management is more intensively shifting toward the carbon utilization for minimizing energy consumption and replacing fossil fuel with the cleaner energy sources. This paper presents an idea of co-integration pathways for CO2 capture and CO2 utilization.

Sulfur tolerance and self-regeneration mechanism of Na-Ru/Al2O3 dual function material during the cyclic CO2 capture and catalytic methanation

The combined CO2 capture and methanation with Dual Function Materials (DFM) is emerging as a vibrant field of research for its potential to increase the efficiency and reduce the cost of current multistage CCU processes. In this work, we set out to investigate for the first time the impact of sulfur poisoning over a Na-Ru/Al2O3 DFM operated in a fixed bed reactor with alternate feeds under realistic conditions including the presence of SO2, H2O and O2 in the process gas stream. The results of the extensive characterization of the fresh and sulfated (reaction-aged) DFM evidenced a remarkable intrinsic tolerance of the combined CO2 capture and methanation process to high concentrations of SO2 in the feed due to a self-regeneration mechanism of the Ru catalytic sites.

Direct 2D cement-nanoadditive deposition enabling carbon-neutral hydrogen from natural gas

Currently, hydrogen is mainly produced by conversion from natural gas via steam methane reforming (SMR), generating massive amounts of CO2. Here, we present a novel production scheme that can neutralize the CO2 from natural gas-based hydrogen productions by direct deposition of 2-dimensional carbon as cement-nanoadditive. Our tests demonstrated that cement-compatible particles can be used effectively as substrates to grow carbon nanosheets. Our analysis showed that the scheme, bridging hydrogen and cement industries, translates a ~268.7 tons cement reduction per ton of produced hydrogen with > 99% reduction of carbon nanosheets costs. Correspondingly, 375.5 Mt CO2 generated from the current SMR-based hydrogen production in the USA, China, and Australia could be neutralized by adopting this approach. We showed that combining CO2 capture in SMR and 5% replacement by our scheme can produce carbon-neutral hydrogen to meet the predicted global demand in 2045.

Performance Projection of a High-Temperature CO2 Transport Membrane Reactor for Combined CO2 Capture and Methane-to-Ethylene Conversion

Direct conversion of methane into ethylene through the oxidative coupling of methane (OCM) is a technically important reaction. However, conventional co-fed fixed-bed OCM reactors still face serious challenges in conversion and selectivity. In this paper, we apply a finite element model to simulate OCM reaction in a plug-flow CO2/O2 transport membrane (CTM) reactor with a directly captured CO2 and O2 mixture as a soft oxidizer. The CTM is made of three phases: molten carbonate, 20% Sm-doped CeO2, and LiNiO2. The membrane parameters are first validated by CO2/O2 flux data obtained from CTM experiments. The OCM reaction is then simulated along the length of tubular plug-flow reactors filled with a La2O3-CaO-modified CeO2 catalyst bed, while a mixture of CO2/O2 is gradually added through the wall of the tubular membrane. A 12-step OCM kinetic mechanism is considered in the model for the catalyst bed and validated by data obtained from a co-fed fixed-bed reactor. The modeled results indicate a much-improved OCM performance by membrane reactor in terms of C2-yield and CH4 conversion rate over the state-of-the-art, co-fed, fixed-bed reactor. The model further reveals that improved performance is fundamentally rooted in the gradual methane conversion with CO2/O2 offered by the plug-flow membrane reactor.

Parametric and global seasonal analysis of a hybrid PV/T-CCA system for combined CO2 capture and power generation

Current solar-driven carbon capture by adsorption (CCA) technologies are mostly based on applying solar-thermal devices to power the regeneration process, which results in a very low solar exergy efficiency and requires external power input. This paper integrates solar photovoltaic/thermal (PV/T) and CCA technologies to form a new solar cascade utilization-based hybrid system where the collected heat is supplied for the CCA regeneration process, and the PV power is provided to end-users. We first validate the PV/T and CCA subsystems by experimental and simulation references, then couple them through a thermodynamic energy balance model. Furthermore, we developed an optimal hybrid system configuration based on Hong Kong’s actual weather conditions by conducting two parametric analyses. To explore the flexibility of the proposed system, we operated it under different CO2 concentration sources and distinct time-varying weather conditions of 17 cities worldwide. Results show that when the PV panel area of PV/T is 38 m2, and the adsorbent mass is 5000 kg, the optimal system in Hong Kong can capture 1300 kg CO2 and produce 419.52 kWh electricity in 12 average days. Moreover, the system demonstrates generality in different scenarios and performs better with sufficient sunlight in cold and dry places.

Screening of Adsorbent/Catalyst Composite Monoliths for Carbon Capture-Utilization and Ethylene Production.

Combining CO2 adsorption and utilization in oxidative dehydrogenation of ethane (ODHE) into a single bed is an exciting way of converting a harmful greenhouse gas into marketable commodity chemicals while reducing energy requirements from two-bed processes. However, novel materials should be developed for this purpose because most adsorbents are incapable of capturing CO2 at the temperatures required for ODHE reactions. Some progress has been made in this area; however, previously reported dual-functional materials (DFMs) have always been powdered-state composites and no efforts have been made toward forming these materials into practical contactors. In this study, we report the first-generation of structured DFM adsorbent/catalyst monoliths for combined CO2 capture and ODHE utilization. Specifically, we formulated M-CaO/ZSM-5 monoliths (M = In, Ce, Cr, or Mo oxides) by 3D-printing inks with CaCO3 (CaO precursor), insoluble metal oxides, and ZSM-5. The physiochemical properties of the monoliths were vigorously characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2 physisorption, elemental mapping, pyridine Fourier transform infrared spectroscopy (Py-FTIR), H2-temperature-programmed reduction (H2-TPR), and NH3-temperature-programmed desorption (NH3-TPD). Their performances for combined CO2 adsorption at 600 °C and ODHE reaction at 700 °C under 25 mL/min of 7% C2H6 were then investigated. The combined adsorption/catalysis experiments revealed the best performance in Cr-CaO/ZSM-5, which achieved 56% CO2 conversion, 91.2% C2H4 selectivity, and 33.8% C2H4 yield. This exceptional performance, which was improved from powdered-state DFMs, was attributed to the high acidity and numerous oxidation states of the Cr2O3 dopant which were verified by NH3-TPD and H2-TPR. Overall, this study reports the first-ever proof-of-concept for 3D-printed DFM adsorbent/catalyst materials and furthers the area of CO2 capture and ODHE utilization by providing a simple pathway to structure these composites.

Insights into the cyclic CO2 capture and catalytic methanation over highly performing Li-Ru/Al2O3 dual function materials

The combined CO2 capture and in-situ methanation using renewable hydrogen over dual function sorbent-catalyst materials is a chemical looping process with strong potential to increase the efficiency and reduce the cost of current CCU technologies. In this work, we set out to develop highly performing Lithium-Ruthenium/Al2O3 investigating synergic and mechanistic aspects involved in the alternate CO2 adsorption and hydrogenation phases. Catalysts with low Ru loading (max 1% wt.) and fixed dispersion on Al2O3 spheres were promoted with variable amounts of Li (1–5% wt.) and characterized by BET, PSD, XRD, H2 chemisorption, CO2-TPD, TG-MS, H2-TPSRx and CO2 catalytic methanation under continuous flow conditions. Transient CO2 storage/methanation cycles were studied in a fixed bed reactor that was operated at several temperature levels (250–350 °C) with alternate feed conditions of variable duration. The cycled CO2 adsorption and methanation were also investigated by in-situ DRIFT comparing results for xLi-Ru/Al2O3 materials against the reference Ru/Al2O3 catalyst. The favourable synergism existing at the nanoscale between the Li-aluminate sorbent phase and the catalytic Ru sites enhances the intrinsic activity of the DFMs that can guarantee high methane productivity and selectivity with low noble metal loadings.

Conceptual MINLP approach to the development of a CO2 supply chain network – Simultaneous consideration of capture and utilization process flowsheets

A large fraction of anthropogenic CO2 emissions comes from large point sources such as power plants, petroleum refineries, and large industrial facilities. A significant decrease of these CO2 emissions can be achieved with CO2 capture, utilization, and storage (CCUS) technologies. This study proposes a conceptually simplified model for the optimization of combined CO2 supply networks and capture and utilization technologies by the mixed-integer non-linear programming (MINLP) approach. The objective is to maximize the profit of CCUS technologies, considering chemisorption using methyl-diethanolamine (MDEA) as a capture technology and conversion of CO2 to CH3OH as a utilization technology. Additionally, avoided tax from reduced CO2 emissions is considered as a revenue. A hypothetical case study of five larger point sources of CO2 was investigated, namely coal power plants, biogas plant, aluminium production plant and two cement plants. Two scenarios were considered: i) Scenario A considering different values of the CO2 tax, and ii) Scenario B considering different flue gas flowrates at different values of the CO2 tax. The results show the potential of model-based optimization in reducing the amount of CO2 in the atmosphere by CCUS technology. Furthermore, the results in Scenario A show that CCUS technology is only profitable if the price of CO2 emissions is higher than 110 €/t emitted CO2. Moreover, the results in Scenario B show that both the profit and the production of CH3OH depend to a large extent on the flue gas flow.

Innovative Gas-Liquid Membrane Contactor Systems for Carbon Capture and Mineralization in Energy Intensive Industries.

CO2 mineralization is an alternative to conventional geological storage and results in permanent carbon storage as a solid, with no need for long-term monitoring and no requirements for significant energy input. Novel technologies for carbon dioxide capture and mineralization involve the use of gas-liquid membrane contactors for post-combustion capture. The scope of the present study is to investigate the application of hollow fiber membrane contactor technology for combined CO2 capture from energy-intensive industry flue gases and CO2 mineralization, in a single-step multiphase process. The process is also a key enabler of the circular economy for the cement industry, a major contributor in global industrial CO2 emissions, as CaCO3 particles, obtained through the mineralization process, can be directed back into the cement production as fillers for partially substituting cement in high-performance concrete. High CO2 capture efficiency is achieved, as well as CaCO3 particles of controlled size and crystallinity are synthesized, in every set of operating parameters employed. The intensified gas-liquid membrane process is assessed by calculating an overall process mass transfer coefficient accounting for all relevant mass transfer resistances and the enhanced mass transfer due to reactive conditions on the shell side. The obtained nanocomposite particles have been extensively characterized by DLS, XRD, TGA, SEM, TEM, and FTIR studies, revealing structured aggregates (1–2 μm average aggregate size) consisting of cubic calcite when the contactor mode is employed.

Hydro-mechanical-chemical modeling of sub-nanopore capillary-confinement on CO2-CCUS-EOR

Nanopore/subnanopore networks comprising tight reservoirs exhibit special behaviors in the storage and transport of capillary-confined fluids. We develop a hydro-mechanical-chemical model coupling the response of capillary-confined phase behavior, multicomponent flow, reservoir deformation and reaction-controlled porosity evolution to explore the effect of nanopore confinement on enhanced oil recovery and CO2 storage. The results reveal that confinement effects change both in chemical potential and isothermal compressibility of individual components and thus increases volume expansion for any given pressure drop. For constrained mixtures, the CO2 K-value (at fixed pressure) and the MMP(at fixed aperture) will shift to smaller than the bulk state. Moreover, capillary-confinement causes an increased production of heavier components when reservoir pressure is below MMP and a higher production of all components and a smaller reservoir inflation when reservoir pressure is higher than MMP - where miscibility dominates. Meanwhile, capillary-confinement causes a slight increase in CO2 retention rate in the calculation for two cases of native oils with contrasting light oil fractions but in identical reservoirs. Thus any production strategy for a combined CO2 capture and storage (CCS) operation needs to be formulated in full consideration of the rock and fluid properties for each potential site.