CO2 Recycling Research Articles

Numerical investigation of the influences of geological controlling factors on heat extraction from hydrothermal reservoirs by CO2 recycling

Injection of CO2 into deep hydrothermal reservoirs is considered as an attractive way for heat extraction, which has been proved in the previous studies. However, how different geological factors govern the heat extraction efficiency by CO2 circulation are not clearly understood. In this study, the mechanisms of geological factors in controlling the heat mining process by CO2 injection are numerically explored. The effects of horizontal correlation length, degree of permeability heterogeneity, permeability anisotropy, and the magnitude of mean permeability on the heat extraction performance are systematically investigated. The simulation results show that heat extraction using CO2 as working fluid can obtain a high heat mining rate, but the CO2 plume in the subsurface exhibits severe segregation effect. Heat extraction by CO2 recycling is more sensitive to the variation of horizontal correlation length in comparison with that by water circulation. The increase of horizontal correlation length and mean permeability can effectively promote the heat mining rate. The increase of permeability heterogeneity and anisotropy can cause a reversed trend of heat mining rate variation. The findings from this study may provide important implications for the selection of feasible hydrothermal reservoirs or deep high water cut oil reservoirs for heat extraction by CO2 recycling.

Catalytic cycloaddition of CO2 to epoxides by the synergistic effect of acidity and alkalinity in a functionalized biochar

Cycloaddition of CO2 to epoxides is an efficient way for CO2 fixation and recycling. Currently, the mainly used metal-containing homogeneous catalysts and halide co-catalysts for cycloaddition of CO2 could bring out metal leaching problem, which is harmful to the environment. Herein, we propose a facile way to prepare nitrogen and oxygen-rich porous biochar by one-pot pyrolysis of chitosan under CO2 atmosphere, and demonstrate the high performance of the obtained metal-free carbon material catalyst with plenty of Lewis base sites and Lewis acid sites on cycloaddition of CO2 to epoxides. The doped nitrogen and oxygen show a synergistic effect for this addition reaction, and the catalytic efficiency can be enhanced through tuning the content of nitrogen and oxygen. The yield and selectivity of epichlorohydrin (ECH) can reach to 90% and 97% with no solvents or co-catalysts under relatively mild reaction conditions, respectively. Materials characterizations and theory calculation results suggested that the high catalytic performance of the N,O-codoped porous biochar was ascribed to its excellent adsorption of CO2 and epoxide molecules due to its high specific surface area and consequent activation by its integrated acid–base active sites. This work illustrates a new strategy for recycling CO2 by using it as a pyrolytic agent and a feedstock for the synthesis of cyclic carbonates.

Utilization of a high-temperature depleted gas condensate reservoir for CO2 storage and geothermal heat mining: A case study of the Arun gas reservoir in Indonesia

In this study, field scale reservoir simulations and production history matching are performed to investigate CO2 storage and CO2 heat mining potential in the high-temperature Arun gas condensate reservoir in Indonesia. Our study shows that CO2 injection into the depleted Arun reservoir can produce 51 MMbbl of condensate over 16 years. Afterwards, continuous CO2 injection without any production over 20 years can allow 1.2 Gt of CO2 to be stored by raising the reservoir pressure to the initial value. In addition, subsequent recycling of CO2 can produce substantial amount of geothermal energy for electricity production.Analyses show that at an oil price of $60/bbl, CO2 cost of $30/ton, and a discount rate of 7%, the produced condensate can generate a net present value (NPV) of $1,910 MM. This profit is enough to pay for storing 205 Mt CO2 in two years after condensate recovery. Alternatively, it can be also used to generate 1.1 × 1010 kWh of electricity in seven years through CO2 heat mining. Results, however, are even more encouraging if CO2 cost is zero or negative through CO2 pricing.Furthermore, by applying CO2-enhanced gas recovery (EGR) to all gas condensate reservoirs in Indonesia, we estimate that the low, mid and high values of condensate recovery is 2,100, 2,900 and 3,700 MMbbl, respectively. This, in turn, gives low, mid and high values of 6.6, 7.0 and 7.4 Gt of CO2 storage capacity, respectively. The gas condensate reservoirs have enough capacity to store 45 years of CO2 emission from power and industrial plants in Indonesia if one assumes 45% of the emission is capturable. Additionally, a significant portion of the geothermal resource of 2.06 × 1019 J in the gas condensate reservoirs in Indonesia may be developed by CO2 heat mining after CO2-EGR and CO2 storage.

Leveraging CO2 to directionally control the H2/CO ratio in continuous microwave pyrolysis/gasification of waste plastics: Quantitative analysis of CO2 and density functional theory calculations of regulation mechanism

To recover syngas from waste plastics (Low-density polyethylene, LDPE) and CO2 simultaneously, the advanced continuous microwave pyrolysis and in situ reforming of CO2 were used. The ability of CO2 to tune LDPE carbon reallocation was evaluated, as was that of CO2 to directionally control the H2/CO ratio. The CO2 utilization efficiency and energy balance were quantitatively analysed, and the mechanism through which CO2 controlled H2/CO ratio was explored via experimental results and density functional theory calculations. The results showed that increasing pyrolysis temperature from 450 °C to 650 °C and introducing CO2 changed the carbon reallocation ability, increased syngas content, and controlled H2/CO ratio. The pyrolysis gas yield and syngas content reached the maximum values of 96.44% and 66.61 vol%, respectively. However, introducing excessive CO2 led to the double waste of resources and energy due to side reactions and high energy consumption. The maximum value of CO2 utilization efficiency and energy recovery efficiency was 78.95% (75 vol% CO2) and 75.09% (50 vol% CO2), respectively. CO2 directionally controlled the production of syngas and H2/CO ratio (from 0.65 to 2.88) by stimulating the LDPE pyrolysis reaction and the reforming reactions of its pyrolysis intermediates to form oxidized carbon radicals (such as Rn-O-C-O*, Rn-CO*, and Rn-O*) to generate CO. Therefore, different pyrolysis systems could regulate the degree of CO2 reforming reaction by controlling CO2 concentration based on the goal of optimizing the efficiency of resource or energy. This work provides basic theory and technical support for realizing the efficient recycling of waste plastics and CO2.

Versatile Ni-Ru catalysts for gas phase CO2 conversion: Bringing closer dry reforming, reverse water gas shift and methanation to enable end-products flexibility

Advanced catalytic materials able to catalyse more than one reaction efficiently are needed within the CO2 utilisation schemes to benefit from end-products flexibility. In this study, the combination of Ni and Ru (15 and 1 wt%, respectively) was tested in three reactions, i.e. dry reforming of methane (DRM), reverse water–gas shift (RWGS) and CO2 methanation. A stability experiment with one cycle of CO2 methanation-RWGS-DRM was carried out. Outstanding stability was revealed for the CO2 hydrogenation reactions and as regards the DRM, coke formation started after 10 h on stream. Overall, this research showcases that a multicomponent Ni-Ru/CeO2-Al2O3 catalyst is an unprecedent versatile system for gas phase CO2 recycling. Beyond its excellent performance, our switchable catalyst allows a fine control of end-products selectivity.

Dicarbonyl compounds in the synthesis of heterocycles under green conditions

Abstract Carbon–carbon and carbon-heteroatom bond forming reactions are strategically employed for the generation of a variety of heterocyclic systems. This class of compounds represents the most general structural unit, present in many natural compounds. They are recognized for their valuable biologically properties and wide range of applications in medicinal, pharmaceutical, and other related fields of chemistry. This is an updated review on the use of dicarbonyl compounds under environmentally friendly conditions to access a series of heterocyclic structures, e.g., quinoxaline, quinazolinones, benzochalcogenazoles, indoles, among others. Synthetic protocols involving copper-catalyzed, multicomponent and cascade reactions, decarboxylative cyclization, recycling of CO2, and electrochemical approaches are presented and discussed.

Hydrogenation of CO2 on Fe-Based Catalysts: Preferred Route to Renewable Liquid Fuels

Catalytic hydrogenation of CO2 can be conducted either in one pot (CO2 hydrogenation) or in two stages (RWGS and CO hydrogenation). Its configuration consists of either three reactors in series with interim water removal (one-pot process) or CO2 separation and recycling (two-stage process) to reach high CO2 conversion. The two-stage process enables to reach optimal H2/CO and temperature in the hydrogenation reactor to yield higher productivity while minimizing production of the aqueous phase, which offset the advantages of the one-pot process. The techno-economic study determined that there is no apparent advantage in operating the hydrogenation reaction in one stage at current green hydrogen prices. The decision between the two routes should be based on catalyst stability and selectivity toward desired products. Blending 10% of liquid product from both processes with fossil fuels at current prices increases the fuel production cost by 30%, which can be offset by higher carbon pricing or equivalent incentives.

Improving inter-plant integration of syngas production technologies by the recycling of CO2 and by-product of the Fischer-Tropsch process

This paper deals with the emission reduction in synthesis-gas production by better integration and increasing the energy efficiency of a high-temperature co-electrolysis unit combined with the Fischer-Tropsch process. The investigated process utilises the by-product of Fischer-Tropsch, as an energy source and carbon dioxide as a feedstock for synthesis gas production. The proposed approach is based on adjusting process streams temperatures with the further synthesis of a new heat exchangers network and optimisation of the utility system. The potential of secondary energy resources was determined using plus/minus principles and simulation of a high-temperature co-electrolysis unit. The proposed technique maximises the economic and environmental benefits of inter-unit integration. Two scenarios were considered for sharing the high-temperature co-electrolysis and the Fischer-Tropsch process. In the first scenario, by-products from the Fischer-Tropsch process were used as fuel for a high-temperature co-electrolysis. Optimisation of secondary energy sources and the synthesis of a new heat exchanger network reduce fuel consumption by 47% and electricity by 11%. An additional environmental benefit is reflected in emission reduction by 25,145 tCO2/y. The second scenario uses fossil fuel as a primary energy source. The new exchanger network for the high-temperature co-electrolysis was built for different energy sources. The use of natural gas resulted in total annual costs of the heat exchanger network to 1,388,034 USD/y, which is 1%, 14%, 116% less than for coal, fuel oil and LPG, respectively. The use of natural gas as a fuel has the lowest carbon footprint of 7288 tCO2/y. On the other hand, coal as an energy source has commensurable economic indicators that produce 2 times more CO2, which can be used as a feedstock for a high-temperature co-electrolysis. This work shows how in-depth preliminary analysis can optimise the use of primary and secondary energy resources during inter-plant integration.

An overview of CO2 capture and utilization in energy models

The recycling and utilization of CO2 is gaining interest in the fight against global warming. Considering CO2 not as a waste or a pollutant but as an opportunity is a concept that could prove promising for producing clean fuels in the future, as well as for producing chemicals, plastics and building materials. The extent of the benefits of Carbon Capture and Utilization (CCU) is still uncertain due to its many interactions with the rest of the energy system, and several energy models are trying to explore this area. As the global climate issue becomes an urgent policy priority, the scientific community is helping decision-makers choose the optimal technologies to successfully meet climate targets and decarbonize society. This paper reviews energy models that represent CCU as a decarbonization solution in an effort to understand and identify knowledge and modeling gaps. The results first show that CO2 utilization is still poorly represented, and that when it is, it is rarely fully integrated. The conversion of CO2 into fuels or chemicals is by far the most modeled of all the options CCU encompasses, while other key technologies for the decarbonization of the industry sector are barely considered. We discuss current CCU modeling methods and provide recommendations for future modelers who want to implement this set of technologies in their models. Additionally, we discuss the socioeconomic drivers and barriers that could support or discourage the deployment of CCU in the future energy mix.

Deep Decarbonization of the Cement Sector: A Prospective Environmental Assessment of CO2 Recycling to Methanol

Current decarbonization pressures are prompting efforts to reimagine the future of the hard-to-abate cement sector. To date, fuel switching has arisen as the most readily operational strategy, and its application in the cement sector is expected in the short to midterm. However, around two-thirds of the cement CO2 emissions come from the calcination of limestone. The implementation of CO2 capture utilization and/or storage will be crucial to support a reliable net-zero carbon future by 2050–2070. CCS is considered as the most carbon-neutral technology in the cement decarbonization roadmap, while CO2 recycling (CCU) has arisen as a suitable strategy for those locations where there is an industrial symbiosis between the cement market and CO2-based chemical markets (e.g., methanol, formic acid, etc.). Despite that the CCU strategy cannot be carbon-neutral by itself, it could be a powerful option in combination with CCS. To date, most CO2 recycling technologies are still emerging, and their development has to be boosted in the next decades. In this study, a prospective environmental analysis has been conducted through life cycle thinking to explore the benefits of cement long-term decarbonization by implementing a carbon recycling plant (CRP) based on the emerging electrochemical reduction (ER) of CO2 to produce methanol (MeOH). The study aims to demonstrate the synergic decarbonization and defossilization for both cement and MeOH markets, respectively. Cell energy efficiency and MeOH concentration have been identified as the key performance parameters that should be around 60% and 40% wt, respectively, to ensure a future sustainable implementation of ER to the MeOH technology. A CRP powered by low-carbon renewable electricity (<0.02 kg CO2eq/kW h) and with a low-fossil depletion (FD) impact (<0.01 kg oileq/kW h) could lead to an integrated cement and MeOH production with sharp reductions in the carbon footprint (∼75%) and FD (∼66%) of the integrated cement and MeOH production compared to the conventional fossil-based productions. The proposed CO2 recycling scheme can contribute to accelerating the innovation of carbon capture and recycling technologies and their deployment in these hard-to-abate sectors.

Investigation into the influencing factors and adsorption characteristics in the effective capture of carbon dioxide in flue gas by chitosan grafted Leca biocomposite

ABSTRACT The main goal of this research was to evaluate the capability of chitosan (CS)-lightweight expanded clay aggregate (Leca) composite as a green adsorbent for efficient capture of carbon dioxide (CO2). The adsorption process was modelled by response surface methodology (RSM). The composite was recognised by BET, SEM, EDX, XRF, XRD, TGA, XPS and FTIR analysis. It was evidenced the CS-Leca properties attributing to its adsorption ability were eminently improved as compared to pristine Leca. Maximum removal efficiency of CO2 (91.59%) was achieved at 40°C, 40 mL/min gas flow rate and 5% moisture content. Under aforementioned provisions, the actual CO2 removal percentage was found to be 90.4%. According to uptake isotherm studies, the Toth model indicated good affinity between the sorbent and sorbate. This model declares adsorption of CO2 onto CS-Leca involves a heterogeneous and uneven adsorption behaviour. The monolayer adsorption capacity (qm) was determined to be 351.24 mg/g. The outcomes of thermodynamic studies displayed that the adsorption was physical and exothermic in nature. The exothermic isosteric heat of adsorption (IHA) was found as 37.1–48.3 kJ/mol which represented weak chemical interactions between CS-Leca and CO2 molecules. Adsorption mechanism studies revealed that multiple mechanisms are involved in the adsorption reaction of CO2. Regeneration tests of CS-Leca exhibited multiple potential applications. All these results enlightened that the CS-Leca, due to its grafting polymer, can be applied as a potential sorbent to the recycle of CO2 and other acidic gases.

Post-combustion emission control of a gas turbine cooperated solar assisted CO2 based-reforming utilizing CO2 capture technology

Solar methane reforming in the coexisting of a gas turbine, a combustion chamber, a CO2 capture, and recycle system is represented. The primary purpose of this study is to evaluate and compare the mentioned hybrid system within several reforming technologies (dry-reforming, bi- reforming, tri-reforming, and auto-reforming). After comparing the reforming systems, the performance of the gas turbine, the solar tower plant and the CO2 capture and recycle unit is studied in each case. The side reactions are neglected during this study. The system is analyzed with respect to both energy and exergy approaches. Solar tower characteristic evaluations are done, and the required heliostats field area for each system is specified. The reforming process and its exhaust gases are studied. Reforming process completion occurred at 1200 K in all four reforming systems. Bi-reforming and auto-reforming are proved to absorb the least thermal energy from the solar tower plant. The combustion chamber is noticed as the main exergy destructive component. Among all, the tri-reforming coupled system resulted in the highest power production of gas turbine, in which the efficiency of gas turbine reaches 42.5 % for 1200 K temperature of the reformer.

Closing the Carbon Cycle with Dual Function Materials

Carbon dioxide (CO2) is one of the most harmful greenhouse gases, and it is the main contributor to climate change. Its emissions have been constantly increasing over the years due to anthropogenic activities. Therefore, efforts are being made to mitigate emissions through carbon capture and storage (CCS). An alternative solution is to close the carbon cycle by utilizing the carbon in CO2 as a building block for chemicals synthesis in a CO2 recycling approach that is called carbon capture and utilization (CCU). Dual function materials (DFMs) are combinations of adsorbent and catalyst capable of both capturing CO2 and converting it to fuels and chemicals in the same reactor with the help of a coreactant. This innovative strategy has attracted attention in the past few years given its potential to lead to more efficient synthesis through the direct conversion of adsorbed CO2. DFM applications for both postcombustion CCU and direct air capture (DAC) and utilization have been demonstrated to date. In this review, we present the unique role DFMs can play in a net zero future by first providing backgrounds on the types of CCU methods of varying technological maturity. Then, we present the developed applications of DFMs such as the synthesis of methane and syngas. To better guide future research efforts, we place an emphasis on the connection between DFM physiochemical properties and performance. Lastly, we discuss the challenges and opportunities of DFM development and recommend research directions for taking advantage of their unique role in a low-carbon circular economy.

Solar-Driven CO2 Reduction Using a Semiconductor/Molecule Hybrid Photosystem: From Photocatalysts to a Monolithic Artificial Leaf.

The synthesis of organic chemicals from H2O and CO2 using solar energy is important for recycling CO2 through cyclical use of chemical ingredients produced from CO2 or molecular energy carriers based on CO2. Similar to photosynthesis in plants, the CO2 molecules are reduced by electrons and protons, which are extracted from H2O molecules, to produce O2. This reaction is uphill; therefore, the solar energy is stored as the chemical bonding energy in the organic molecules. This artificial photosynthetic technology mimicking green vegetation should be implemented as a self-standing system for on-site direct solar energy storage that supports CO2 recycling in a circular economy. Herein, we explain our interdisciplinary fusion methodology to develop hybrid photocatalysts and photoelectrodes for an artificial photosynthetic system for the CO2 reduction reaction (CO2RR) in aqueous solutions. The key factor for the system is the integration of uniquely different functions of molecular transition-metal complexes and solid semiconductors. A metal complex catalyst and a semiconductor appropriate for a CO2RR and visible-light absorption, respectively, are linked, and they function complementary way to catalyze CO2RR under visible-light irradiation as a particulate photocatalyst dispersion in solution. It has also been proven that Ru complexes with bipyridine ligands can catalyze a CO2RR as photocathodes when they are linked with various semiconductor surfaces, such as those of doped tantalum oxides, doped iron oxides, indium phosphides, copper-based sulfides, selenides, silicon, and others. These photocathodes can produce formate and carbon monoxide using electrons and protons extracted from water through potential-matched connections with photoanodes such as TiO2 or SrTiO3 for oxygen evolution reactions (OERs). Benefiting from the very low overpotential of an aqueous CO2RR at metal complexes approaching the theoretical lower limit, the semiconductor/molecule hybrid system demonstrates a single tablet-formed monolithic electrode called "artificial leaf." This single electrode device can generate formate (HCOO-) from H2O and CO2 in a water-filled single-compartment reactor without requiring a separation membrane under unassisted or bias-free conditions, either electrically or chemically. The reaction proceeds with a stoichiometric electron/hole ratio and stores solar energy with a solar-to-chemical energy conversion efficiency of 4.6%, which exceeds that of plants. In this Account, the key results that marked our milestones in technological progress of the semiconductor/molecule hybrid photosystem are concisely explained. These results include design, proof of the principle, and understanding of the phenomena by time-resolved spectroscopies, synchrotron radiation analyses, and DFT calculations. These results enable us to address challenges toward further scientific progress and the social implementation, including the use of earth-abundant elements and the scale-up of the solar-driven CO2RR system.

Electroreduction of CO2/CO to C2 Products: Process Modeling, Downstream Separation, System Integration, and Economic Analysis.

Direct electrochemical reduction of CO2 to C2 products such as ethylene is more efficient in alkaline media, but it suffers from parasitic loss of reactants due to (bi)carbonate formation. A two-step process where the CO2 is first electrochemically reduced to CO and subsequently converted to desired C2 products has the potential to overcome the limitations posed by direct CO2 electroreduction. In this study, we investigated the technical and economic feasibility of the direct and indirect CO2 conversion routes to C2 products. For the indirect route, CO2 to CO conversion in a high temperature solid oxide electrolysis cell (SOEC) or a low temperature electrolyzer has been considered. The product distribution, conversion, selectivities, current densities, and cell potentials are different for both CO2 conversion routes, which affects the downstream processing and the economics. A detailed process design and techno-economic analysis of both CO2 conversion pathways are presented, which includes CO2 capture, CO2 (and CO) conversion, CO2 (and CO) recycling, and product separation. Our economic analysis shows that both conversion routes are not profitable under the base case scenario, but the economics can be improved significantly by reducing the cell voltage, the capital cost of the electrolyzers, and the electricity price. For both routes, a cell voltage of 2.5 V, a capital cost of $10,000/m2, and an electricity price of <$20/MWh will yield a positive net present value and payback times of less than 15 years. Overall, the high temperature (SOEC-based) two-step conversion process has a greater potential for scale-up than the direct electrochemical conversion route. Strategies for integrating the electrochemical CO2/CO conversion process into the existing gas and oil infrastructure are outlined. Current barriers for industrialization of CO2 electrolyzers and possible solutions are discussed as well.

Moisture-tolerant diamine-appended metal–organic framework composites for effective indoor CO2 capture through facile spray coating

Reducing the concentration of indoor carbon dioxide (CO2) to an acceptable safe level of 1,000 ppm is an important issue because a high level of CO2 in closed spaces causes lethargy and fatigue. Although diamine-functionalized metal–organic framework (MOF) adsorbents with high CO2 capacities under indoor air conditions are available, the moisture-induced degradation of MOFs and their shaping remains a challenge for practical applications. Herein, we report the fabrication of epn-functionalized Mg2(dobpdc) composites, which proceeded by mixing with a polystyrene-block-polybutadiene-block-polystyrene (SBS) hydrophobic polymer (epn = 1-ethylpropane-1,3-diamine; dobpdc4− = 4,4′-dioxido-3,3′-biphenyldicarboxylate). The composites were successfully shaped in the form of membranes with different amounts of MOF (epn-MOFX@SBS; X = 60–80 wt%). Specifically, epn-MOF80@SBS exhibited a significant CO2 adsorption of 2.8 mmol g−1 at 1,000 ppm with recyclable working capacity. The composites were further coated on the surfaces of different supports, such as a Ti mesh, an air filter, and granular activated carbon via a facile and simple spraying method. The experimental conditions were 1,000 ppm CO2 and 60% relative humidity in a 50-L chamber; the coated materials displayed invariant CO2 removal performances over 10 cycles and even after 7 days of exposure. The recyclable and long-term CO2 adsorption capacities demonstrate that the MOF-polymer composites and their coating on various supports provide a useful and effective route for indoor CO2 capture under realistic conditions.

Light olefins synthesis from CO2 hydrogenation over mixed Fe–Co–K supported on micro-mesoporous carbon catalysts

Recycling CO2 into light olefins is a promising approach to reduce CO2 emissions. To promote this technology, an efficient catalyst with high activity and selectivity towards light olefins is imperative. In this work, a series of Fe–Co–K supported on micro-mesoporous carbon (MMC) and microporous carbon (MC) with different metal loading contents (20–80 wt%) were prepared for CO2 hydrogenation to light olefins. Impregnating mixed metal oxides on both MMC and MC reduced particle sizes and enhanced their dispersion and reducibility, yielding a higher CO2 conversion compared to the unsupported Fe–Co–K catalyst. The metal oxides were highly dispersed inside the micropores of MC support, achieving the highest CO2 conversion. However, the high dispersion of metal oxides inside micropores led to the formation of isolated particles with a low interfacial contact with each other, resulting in a low light olefins selectivity. The MMC support provided a lower degree of metal dispersion, creating more interfacial contact area, promoting the selectivity towards olefins. Overall, the 60 wt% Fe–Co–K supported on MMC catalyst exhibited the highest light olefins yield of 10.8% at 400 °C and 20 bar and excellent stability.

Co-Optimization of CO2 Storage and Enhanced Gas Recovery Using Carbonated Water and Supercritical CO2

CO2-based enhanced gas recovery (EGR) is an appealing method with the dual benefit of improving recovery from mature gas reservoirs and storing CO2 in the subsurface, thereby reducing net emissions. However, CO2 injection for EGR has the drawback of excessive mixing with the methane gas, therefore, reducing the quality of gas produced and leading to an early breakthrough of CO2. Although this issue has been identified as a major obstacle in CO2-based EGR, few strategies have been suggested to mitigate this problem. We propose a novel hybrid EGR method that involves the injection of a slug of carbonated water before beginning CO2 injection. While still ensuring CO2 storage, carbonated water hinders CO2-methane mixing and reduces CO2 mobility, therefore delaying breakthrough. We use reservoir simulation to assess the feasibility and benefit of the proposed method. Through a structured design of experiments (DoE) framework, we perform sensitivity analysis, uncertainty assessment, and optimization to identify the ideal operation and transition conditions. Results show that the proposed method only requires a small amount of carbonated water injected up to 3% pore volumes. This EGR scheme is mainly influenced by the heterogeneity of the reservoir, slug volume injected, and production rates. Through Monte Carlo simulations, we demonstrate that high recovery factors and storage ratios can be achieved while keeping recycled CO2 ratios low.

Particle migration and formation damage during geothermal exploitation from weakly consolidated sandstone reservoirs via water and CO2 recycling

Coupled migration and retention of suspended injection particles and reservoir particles can severely damage the formation, especially for weakly consolidated sandstone geothermal reservoirs. Understanding their migration and retention is significant to prevent undesired formation damage. The forces acted on these particles were calculated, and then a comprehensive simulation model was established to analyze the coupled particle migration and retention. Massive detachment of reservoir particles, formation of wormhole-like preferential flow paths, and retention of the injected suspended particles are identified as three successive stages during geothermal energy exploitation via water recycling. The mobile reservoir particles play a leading role in the first two stages, while the injected suspended particles mainly affect the last stage. Sensitivity analysis indicates that the high injection-production pressure difference and low concentration of injected suspended particles are conducive to form preferential flow paths, but a severe local reservoir blockage may occur under high mobile reservoir particles. CO2 can effectively reduce reservoir damage caused by particle migration due to its high mobility and low drag force. Although the region of reservoir particle detachment is large during geothermal energy exploitation via CO2 recycling, more preferential flow paths can form to reduce the formation blockage caused by particle migration.

Exploring the effects of energy transition on the industrial value chains and alternative resources: A case study from the German federal state of North Rhine-Westphalia (NRW)

Defossilizing the energy and industrial systems and transformation towards a circular economy have versatile impacts on the availability and demand of alternative resources. However, systematic analyses on these interrelations are very sparse. Thus, this paper investigates the interlinkages between the energy transition and the transformation towards a circular economy in Germany. The study is based on material flow analysis models of the steel and cement industries as well as the coal and lignite power plants in order to depict a comprehensive description of the material, energy and emission flows of these sectors and their interdependencies.The analyses prove the inherent interrelation between energy transition and circular economy. On the one hand, energy transition does not only bear various techno-economic challenges and have substantial effects on the production costs, but it also affects the availability of secondary materials. For instance, the coal phase-out and the introduction of green steel imply that the current supplies of blast furnace slag, fly ash and FGD gypsum cannot be maintained.On the other hand, circularity approaches can also influence the energy transition. For example, banning single-use plastics and increasing recycling rates of plastics can deprive the cement industry from significant amounts of energy resources with low-carbon footprint. Contrariwise, CO2 recycling can promote the energy transition by means of mitigating CO2 emissions via carbonation. Therefore, the study can help policymakers to understand the indirect effects of existing and future policies. Also, it can help to develop future strategies to handle associated impacts and avoid material shortages.