CO2 In Solution Research Articles

Techno-economic-environmental study of CO2 and aqueous formate solution injection for geologic carbon storage and enhanced oil recovery

As carbon capture, utilization, and storage (CCUS), carbon-dioxide enhanced oil recovery (CO2 EOR) has inherent shortcomings, such as inefficient oil recovery and carbon storage, and low storage security with mobile CO2. This paper presents a techno-economic-environmental analysis of using formate species, a product of CO2 electrochemical reduction, as an alternative carbon carrier for sequestration and EOR in a carbonate oil reservoir in the Gulf of Mexico Basin. CO2 injection, water-alternating-CO2 injection, and aqueous formate solution injection were compared using a compositional reservoir simulation model and an economic calculator. Formate solution injection yielded greater levels of oil recovery and net carbon storage, where the carbon-bearing species resided in the dense aqueous phase without having to rely on petrophysical trapping mechanisms (structural and capillary). The enhanced oil production, net carbon storage, and storage security can be promoted by providing formate-based CCUS with more incentives (e.g., greater tax credit) in comparison to CO2-based CCUS for EOR and the manufacture of chemicals and products. In establishing carbon storage incentive policies and regulations, policymakers should include alternative carbon carriers.

The precipitation mechanisms of scheelite from CO2-rich hydrothermal fluids: Insight from thermodynamic modeling

Scheelite and wolframite are two main tungsten-bearing ore minerals in tungsten deposits. Compared to wolframite formed mostly by NaCl–H2O fluids, scheelite in many but not all tungsten deposits is associated with CO2–bearing hydrothermal fluids, but its precipitation mechanisms from these fluids are poorly understood. The replacement of wolframite by scheelite is common among tungsten deposits where these two tungstates coexist, but how CO2, as the pH-buffering agent, affects their replacement remains unclear. To answer these questions, we first tested the pH-buffering effect of CO2 by comparing available experimental pH values of H2O–CO2±NaCl solutions at 200–280 °C and the corresponding thermodynamic modeling results. The mean absolute errors between the calculated and experimental pH values are 0.14 log units in H2O–CO2 solutions and 0.13 log units in H2O–CO2–NaCl solutions, indicating that the calculated acitivities of H+ in CO2-bearing solutions are reliable. Then, the solubilities of scheelite, scheelite-ferberite, and scheelite-hübnerite in NaCl–H2O–CO2 systems were modeled in this study. Our modeling results suggest that scheelite solubility in CO2-rich fluids is highly dependent on fluid pressure but is insensitive to fluid temperature. A decrease in fluid pressure from lithostatic to hydrostatic levels at a depth of 3–8 km causes CO2 escape and pH rise and precipitates over 70 % of tungsten contents in fluids on average. Therefore, CO2 escape is an efficient mechanism for precipitating scheelite from CO2–rich hydrothermal fluids. The independence of scheelite solubility on temperature at high pressures and the slightly retrograde solubility at low pressures allows CO2–rich hydrothermal fluids to carry a great amount of tungsten far away from its sources. This may be one of reasons why some scheelite deposits occur at greater distances (>500 m) from the granite or extend along its strike for several kilometers. Similar to the cases in NaCl–H2O systems, two mechanisms for scheelite replacing wolframite in CO2–rich fluids are identified, a single decrease in fluid pressure or simple cooling plus an increase in the ratios of total Ca contents to total Fe (or Mn) contents in fluids.

Highly efficient direct air capture using solid–liquid phase separation in aqueous diamine solution as sorbent

Abstract To reduce climate change, absorbing CO2 directly from the air (DAC) with high-efficient CO2 absorption, low-cost, and environmentally friendly system has been attracted much attention for several decades. In this work, a series of aqueous diamine solutions was examined for 400 ppm CO2 absorption at ambient temperature. The absorbents exhibited CO2 absorption with molar ratio of 1 molCO2/molamine, and aqueous isophorone diamine (IPDA) in particular showed >99% CO2 removal even under a 500 mL min−1 flow of 400 ppm CO2–N2 with the contact rate of 13,761.5 h−1 between CO2 and IPDA aqueous solution and the CO2 absorption rate of 4.46 mmol/L min. A precipitate of carbamic acid of IPDA was formed by reaction with CO2, and the CO2 removal efficiency was enhanced by increasing the solution viscosity by the formation of this precipitate. The CO2 was absorbed in aqueous IPDA solution as carbamic acid of IPDA and bicarbonate/carbonate species, and the absorbed CO2 could desorb by heating under O2-containing gas flow, which indicates our system is applicable to the CO2 condensation for a plant growth. This work provides fundamental information to establishing a solid–liquid phase change system with a high-efficient and environmentally friendly DAC system using aqueous solvent.

Exploring nanobubble technology for enhanced anaerobic digestion of thermal-hydrolysis pre-treated sewage sludge

Nanobubble technology was used to enhance anaerobic digestion (AD) of thermal-hydrolysis pre-treated sewage sludge for bioenergy recovery. The prepared air, CO2, and H2 nanobubble solutions, with concentrations of 9.88–10.2 × 107 bubbles/mL, remained stable for at least 7 days. After adding them into AD reactors, significantly higher CH4 production (37.1 %) was observed for the CO2 nanobubble treatment, followed by air (25.6 %) and H2 (14.5 %) nanobubble treatments, compared to the control group. CO2 nanobubble treatment performed the best in improving acidogenesis/acetogenesis, resulting in significantly higher volatile fatty acid generation during the initial 3–4 days. A comparison of reactors supersaturated and non-saturated with oxygen has demonstrated most of the biogas uplift observed to result from the nanobubbles rather than from initial oxygen soluble levels, demonstrating the crucial role of nanobubbles in upgrading AD. This study demonstrates, for the first time, that nanobubbles can provide additional benefits when combined with stablished sludge pre-treatment technologies.

Review on the Potential Co-Application of Aqueous CO2 Solution in Cementitious Material

The escalating concerns over climate change and the urgent demand for sustainable development have propelled significant efforts to mitigate carbon footprints by sequestering carbon dioxide (CO<sub>2</sub>) into cementitious materials. One promising approach involves the incorporation of calcium-rich materials along with super-saturated aqueous solutions in cement, a method demonstrated to be effective in various studies. However, further research is necessary to address technical challenges and optimize the process. This paper presents a comprehensive review of the existing knowledge on the impact of different calcium-rich materials and curing conditions on the workability and compressive strength of concrete, with a particular focus on aqueous CO<sub>2</sub>. Utilizing the Systematic Literature Review (SLR) method, this study identifies the problem, selects the subject of investigation, and gathers pertinent information from suitable databases. The selected documents were analyzed, evaluated, and synthesized to combine the findings. Additionally, the parameters of carbonated concrete utilized in recent studies were analyzed and discussed, providing a thorough understanding of the current advancements and areas requiring further investigation.

An Experimental Investigation of Surfactant-Stabilized CO2 Foam Flooding in Carbonate Cores in Reservoir Conditions

Carbon dioxide (CO2) injection for enhanced oil recovery (EOR) has attracted great attention due to its potential to increase ultimate recovery from mature oil reservoirs. Despite the reported efficiency of CO2 in enhancing oil recovery, the high mobility of CO2 in porous media is one of the major issues faced during CO2 EOR projects. Foam injection is a proven approach to overcome CO2 mobility problems such as early gas breakthrough and low sweep efficiency. In this experimental study, we investigated the foam performance of a commercial anionic surfactant, alpha olefin sulfonate (AOS), in carbonate core samples for gas mobility control and oil recovery. Bulk foam screening tests demonstrated that varying surfactant concentrations above a threshold value had an insignificant effect on foam volume and half-life. Moreover, foam stability and capacity decreased with increasing temperature, while variations in salinity over the tested range had a negligible influence on foam properties. The pressure drop across a brine-saturated core sample increased with an increasing concentration of surfactant in the injected brine during foam flooding experiments. Co-injection of CO2 and AOS solution at an optimum concentration and gas fractional flow enhanced oil recovery by 6–10% of the original oil in place (OOIP).

Numerical investigation on the influence of CO2-induced mineral dissolution on hydrogeological and mechanical properties of sandstone using coupled lattice Boltzmann and finite element model

The impact of CO2-induced mineral reactions, specifically the CO2-water-rock interactions, has been widely recognized for its potential to compromise the hydrogeological and mechanical properties of porous media, thereby deteriorating their integrity and mechanical characteristics. This raises concerns regarding the safety of numerous projects such as CO2 geological storage. However, the mechanism underlying the influence of CO2-induced mineral reactions on these parameters is still not fully understood, thereby introducing uncertainty into the reliability of predicted outcomes. Direct pore-scale simulation plays a crucial role in deepening the understanding of CO2 -water-rock interaction and its associated impacts. The present study proposes a novel simulation model that integrates the lattice Boltzmann and finite element methods to simulate the dissolution of calcite in a 3D sandstone sample invaded by saturated CO2 solution, aiming to investigate the resulting evolution of hydrogeological parameters (i.e., porosity and permeability) and mechanical properties (i.e., bulk and shear moduli). The injection rates of reactive fluid (i.e., CO2 solution) were varied in the model to simulate different operational conditions of CO2 geological storage project. The simulation results demonstrate that the decrease in injection velocity inhibits the dissolution of calcite in the middle and downstream regions, concentrating it near the inlet. These distinct modes of calcite dissolution result in differentiated permeability and mechanical properties within rocks possessing identical porosity levels. In general, the increase in fluid injection velocity leads to a more pronounced enhancement in permeability and a greater attenuation in bulk and shear moduli under the same porosity. Thus, it is confirmed that the utilization of porosity is inadequate in accurately characterizing the evolution of rock permeability and mechanical properties resulting from mineral reactions. We ascertain that the application of fractal parameters, i.e., succolarity and fractal dimension, can more precisely depict the progression of permeability and bulk/shear modulus, respectively.

Preparation of MoSi2-particle reinforced Ni-W alloy coatings and their anti-corrosion behavior in CO2-saturated 3.5 % NaCl solution

In the process of oil and gas production, the use of Ni-W electroplated coatings as a protective layer for oil well tubing has been widely used. In this study, the effect of MoSi2 particles as reinforcing material on the properties of electrodeposited coatings was investigated in order to improve the resistance of Ni-W alloy deposits against CO2 corrosion. The purchased MoSi2 sample was subjected to detailed material characterization, including microscopic morphology, crystallographic properties, particle size distribution and dispersion in the plating solution. After the introduction of MoSi2 particles into the deposits, the diffuse phase strengthening mechanism improved the properties of alloy. By comparing the electrochemical behavior of 3.5 % NaCl solution in saturated CO2, it can be concluded that the composite coatings prepared have the best corrosion resistance when MoSi2 is added to the plating solution at 0.02 g/L. This study provides new horizons for the application of Ni-W coatings in CO2-rich environments or CCUS conditions.

A novel compact supercritical CO2 solar receiver based on impinging jet: Heat transfer performance and thermal stress analysis

The compact solar receiver can withstand high temperature and high pressure, which provides promising solutions for direct supercritical CO2 (S-CO2) solar receiver applications. However, it still suffers from local high temperature and large thermal stress due to the non-uniform heating boundary condition. The impinging jet method can significantly enhance the local heat transfer coefficient, holding significant potential in reducing the local high temperature of the compact S-CO2 receiver. Inspired by this, a novel design for a compact S-CO2 receiver using the impinging jet was proposed in this work. The heat transfer performance and stress behavior of the jet channel within the receiver were numerically investigated. The results showed that the jet channel has a significantly higher heat transfer performance than the rectangular channel, and the shorter flow path of the jet channel also effectively reduces the pressure loss. Meanwhile, the jet pattern significantly enhances the temperature uniformity, thereby reducing the thermal stress. In addition, increasing the channel aspect ratio improves the thermo-hydraulic performance, but increase the stress at the same time. The increase in the number of jet holes and the jet hole diameters not only enhance the thermo-hydraulic performance, but also reduce the stress of the jet channel.

Effect of mineral dissolution on fault slip behavior during geological carbon storage

Geological carbon dioxide storage is one of the most effective technologies to reduce greenhouse gas emissions to the atmosphere. The mineral dissolution is inevitable during the long-term storage process, while the chemical effect on fault slip behavior remains poorly understood. In this paper, we present a hydro-chemical–mechanical coupled fault reactivation study using the unified pipe-interface element method (UP-IEM). The impact of chemical dissolution on stress redistribution is considered. The accuracy of the numerical method to simulate reactive solute transport and fault frictional slip are confirmed by analytical solution and numerical verification. Two different fault tectonic scenarios, of which fault locating in the caprock and fault crosscutting the reservoir and caprock, are designed to investigate the fault slip behavior induced by mineral dissolution. The effect of dissolved CO2 solute concentration, fault aperture, reservoir permeability and chemical reaction rate are discussed. Results show that fault locating in the caprock is easier to be activated. The chemical reaction has a more significant effect on fault slip behavior than fluid pressure during the long-term low-velocity CO2 leakage. The increase of CO2 solute concentration and reservoir reaction rate cause an obvious growth on fault slip displacement. The decrease of fault initial aperture results in the fault slip velocity slower and the slipping area smaller. The high-permeability reservoir keeps the fault more stable than low-permeability reservoir under the influence of mineral dissolution.

Microbial nitrogen bubble formation in porous media

Microbially induced nitrogen (N2) gas bubbles can desaturate subsurface areas and thus have been considered as an alternative ground improvement technique for mitigating soil liquefaction potential caused by earthquakes. However, the detailed mechanisms of subsurface N2 bubbles are not well understood and remain a subject of ongoing research. In this study, a transparent microfluidic device was utilized to mimic biological N2 gas bubble formation by nitrate-reducing bacteria and to visually characterize the entire process. During N2 gas formation, a limited number of bubble nucleation sites were identified, which gradually expanded upward through the preferential pore channels. N2 gas bubbles tended to create interconnected gas pockets rather than existing as evenly distributed small gas cavities. The degree of water saturation gradually reduced over a week as the bubbles were produced. The gas ganglia repeatedly grew until they reached the top boundary, which triggered a drastic expulsion of bubbles by ebullition. Despite fluctuations in saturation level, the residual saturation was maintained at around 73 %. Comparative experimental case studies of CO2 gas bubble formation were conducted to identify contrasting gas formation mechanisms. CO2 gas bubbles were generated via the abiotic decompression of a supersaturated CO2 solution under two distinct rates of pressure reduction. Rapid CO2 bubble formation led to uniform nucleation and 41 % residual saturation, while slower formation yielded 35 % due to stable liquid displacement by the gas front. This study highlights the potential of the microfluidic device as an experimental tool for visualizing subsurface gas formation mechanisms. The insights gained could further enhance and optimize geotechnical applications involving gas formation in highly saturated soils.

A Strategy for Enhanced Carbon Storage: A Hybrid CO2 and Aqueous Formate Solution Injection to Control Buoyancy and Reduce Risk

A Strategy for Enhanced Carbon Storage: A Hybrid CO2 and Aqueous Formate Solution Injection to Control Buoyancy and Reduce Risk

Investigating the role of local acidosis in hypothalamic vasopressin cell excitation during hypoxia

The supraoptic nucleus (SON) of the hypothalamus plays a key role in the regulation of fluid homeostasis through the synthesis and release of vasopressin (VP). In this population, VP release can occur at both dendritic and axonal sites, allowing for both localized and distal effects such as renal water retention and vasoconstriction. Recent work from our laboratory demonstrated an inverse neurovascular coupling (iNVC) response in which VP cell activation by acute salt loading resulted in dendritic release of VP, leading to localized vasoconstriction and hypoxia. Additionally, we demonstrated that the hypoxic milieu in turn potentiates VP cell activity and increases firing, suggesting that these mechanism constitutes a positive feedback loop that optimized VP activation in order to cope with the homeostatic challenge (Roy et al., Cell Reports 2021). Still, the biophysical mechanism by which the iNVC-hypoxia elicits increased firing in VP neurons has not yet been explored. We hypothesized that hypoxia-induced acidosis, via activation of acid sensitive ion channels (ASICs) (which are present in SON VP neurons; Ohbuchi et al in 2010) is a key mechanism contributing to VP cell excitation in the iNVC positive feedback loop. We investigated this with whole cell patch clamp electrophysiology using eGFP-VP transgenic rats. We recorded from identified SON VP cells and measured deflections in voltage as bath pH was changed from 7.25 to 6.3 (10 mins). Bath solution was either HCL-buffered artificial cerebrospinal fluid (aCSF) aerated with 95% O2/5% CO2 or HEPES-buffered solution (HBS). We observed an excitatory response to the decreases in pH in most SON VP cells recorded (68.75%, n = 11/16). These responses were reversible and, in many cases, repeatable following a second stimulation. To examine cell-type specificity, ongoing studies are focusing on comparing these responses to those obtained from oxytocin cells. Further, we plan to repeat these experiments in the presence of the ASIC-blocker amiloride and determine whether the hypoxia-induced excitatory effect during iNVC is indeed dependent on ASIC-channels. Together, our results support our hypothesis that tissue acidosis (likely via activation of ASIC-channels) contributes to the excitatory feedback loop evoked during salt-induced iNVC in VP neurons. This abstract was supported by the National Heart Lung and Blood Institute of the National Institutes of Health [R01 HL162575-01 (J.E.S.)]. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

An Experimental Investigation of Interaction between CO2 Solution and Rock under Reservoir Conditions in the Jimsar Shale Oil Formation

Chemical sequestration is one important manner of CCUS. The injection of CO2 into an oil reservoir can not only sequestrate CO2 but also raise the oil recovery factor. The performance of chemical sequestration of CO2 depends on the interaction between CO2 solution and reservoir rock. In this paper, we have conducted three different scales of experiments, e.g., microscopic scale, core scale, and time scale, to fully investigate the interaction and resultant variation to mineral content, microscopic structure, porosity, and permeability under reservoir conditions (i.e., reservoir temperature of 90 °C) in Jimusar shale oil formation. The microscopic-scale experiment applied SEM and hyperspectral scanning to obtain microscopic pore throat structure and element distribution before and after soaking the rock in CO2 solution. The core-scale experiment employed XRD to evaluate mineral content variation caused by CO2 solution. Core flooding experiments were conducted to evaluate porosity and permeability variation caused by the dissolution of CO2 solution into the core samples. The third type of experiment was employed to investigate the effect of time sequence on the dissolution, in which the time ranged from 1 day to 14 days continuously. The experimental results indicate that, under Jimsar reservoir conditions, CO2 solution exhibits a relatively robust dissolution capability, causing significant alterations to the properties of the core samples. Specifically, the CO2 solution effectively dissolves carbonate upon contact. Calcite is the primary target for dissolution, followed by dolomite. In the presence of sufficient CO2, complete dissolution of all carbonates is achievable. On a microscopic scale, dissolution primarily occurs in the calcium-rich areas, leaving other regions unaffected. The typical pore size resulting from CO2 solution-induced dissolution ranges from several to dozens of micrometers. This dissolution process significantly enhances both porosity and permeability. For Jimsar shale core samples, porosity experienced an increase of over 20%, and permeability nearly doubled. Under Jimsar reservoir conditions at 90 °C, CO2 solution can consume all carbonates present in core samples within 8 days. The increase in porosity and permeability is rapid during the initial days and stabilizes around the 6th day. These research findings establish a theoretical foundation for CO2 chemical sequestration.

Study on the process of mass transfer and deterioration of limestone under dynamic dissolution of CO2 solution

The long-term erosion of rock by solution can induce a series of karst problems. Therefore, this study focused on limestone and conducted dynamic dissolution experiments under deionized water and CO2 solution conditions to study the deterioration mechanism of limestone under nonequilibrium conditions. The results showed that the degree of degradation of the mechanical properties of the samples in a CO2 solution was obviously greater. In a deionized water environment, the degradation of the mechanical properties of the sample is mainly controlled by the physical softening action of the solution. In the CO2 solution environment, the degradation process can be divided into two stages. In the early stage of the experiment (10 days to 20 days), the degradation of mechanical properties of the sample is also controlled by the physical softening action of the solution. With increasing soaking time, the main rock-forming minerals of limestone gradually react with the CO2 solution, the degradation of the sample is controlled mainly by the chemical corrosion of the CO2 solution, and its degradation rate is much greater than that of physical softening. The results can be used as a reference for assessing the long-term stability of underground engineering in limestone karst development areas.

Improved concrete ITZ and performance via pre-soaking of inert recycled red brick aggregates in carbonation solution

Compared to recycled concrete aggregate (RCA), the high-water absorption of recycled red brick aggregate (RBA) has limited its utilization in concrete production. However, this study takes the advantage of its high-water absorption capacity as a carrier for carbonation solutions, aiming to compensate the strength loss by enhancing the interfacial transition zone (ITZ) properties of incorporated concrete. The effects of carbonation solutions (e.g., CO2 and NaHCO3) by varying the CO2 injection times (10 s, 60 s and 600 s) and NaHCO3 dosages (1%, 3% and 5%) on the physical (i.e. density and water absorption) and mechanical (i.e. compressive and tensile bond strengths) properties of concrete, in particular focus on the ITZ changes, were systematically investigated. In addition, the microstructure changes of concrete ITZ were studied using thermogravimetric analysis (TGA), scanning electron microscope-backscattered electron (SEM-BSE) image analysis and mercury intrusion porosimetry (MIP). The results indicated that it was feasible to enhance the ITZ properties by using CO2 solution as the pre-soaking agent of RBA. The adoption of CO2 solution could significantly improve the bond strength of ITZ by up to 22.5% and resulted 8.6% improvement in 28-day compressive strength. The CO2 solution contributed to the formation of CaCO3 can accelerate the cement hydration of surrounding matrix and hence densified the microstructure of ITZ. For the case of pre-soaking with NaHCO3, although the release of solution from RBA could improve the early strength of concrete, the later strength significantly reduced due to the effect of sodium ions in NaHCO3 on the growth of outer C–S–H gel.

Highly efficient hydrogen production and selective CO2 reduction by the C3N5 photocatalyst using only visible light.

The production of energy sources by metal-free photocatalysts based on graphitic carbon nitride (g-C3N4) has garnered substantial attention. In this study, nitrogen-rich carbon nitride (C3N5) was successfully synthesized through the thermal polycondensation of 3-amino-1,2,4-triazole. The structural and physical characterization has suggested that a portion of the triazine rings, which constitute the structural framework of g-C3N4, may be substituted with five-membered rings in C3N5. Furthermore, the polymerization of C3N5 proceeded more extensively than that of g-C3N4 from melamine precursors. The increased nitrogen content in C3N5 resulted in a heightened number of π-electrons and a narrowed energy bandgap, with the potential of the valence band maximum being negatively shifted. Additionally, photocatalytic assessments encompassing nitro blue tetrazolium reduction, H2 production from triethanolamine aqueous solution, and CO2 reduction in the liquid phase were performed. All findings demonstrated that C3N5 exhibits significantly superior photocatalytic properties compared to g-C3N4. It is particularly noteworthy that C3N5 selectively generates methanol and H2 from oversaturated CO2 solutions under visible light irradiation, while g-C3N4 selectively generates formaldehyde. These outcomes strongly indicate that C3N5 serves as a metal-free, visible-light-responsive photocatalyst, capable of contributing to both the production of renewable energy sources and the reduction of greenhouse effect gases.

A near-infrared spectroscopic study of the conformational equilibria of lidocaine molecules in a highly concentrated lidocaine solution in supercritical CO2

In this work, we studied conformational equilibria of molecules of lidocaine in its highly concentrated solutions in scCO2 at the CO2 density values ranging from ∼1.5 to ∼2.0 of the critical value along the isotherm of 35 °C. The study was based on analyzing the spectral band related to the first overtone of the stretching vibrations of the lidocaine molecule N–H fragment. To determine the key factor affecting the formation of intermolecular hydrogen bonds between the lidocaine molecules in the solution we divided our experiment into two stages. First, in the pressure range of 100–180 bar we analyzed the spectra evolution associated with an increase in the concentration of the saturated solution. Then, in the pressure range of 180–300 bar we analyzed the spectra evolution for a solution, where the lidocaine concentration, which was reached at 180 bar, remained constant.We found that the probability of intermolecular hydrogen bond formation considerably increased with lidocaine concentration growth, which, in turn, led to a rise in the population of lidocaine molecules without an intramolecular hydrogen bond. We concluded that the formation of intermolecular hydrogen bonds caused redistribution of the conformer fractions with and without an intramolecular hydrogen bond. Finally, we showed that the key factor affecting the formation of intermolecular hydrogen bonds between the molecules of lidocaine in its solution in scCO2 is the solute concentration rather than the pressure.

Study on the heat transfer characteristics of CO2 and liquid desiccant CaCl2 aqueous solution in the gas cooler and evaporator

The heat exchangers are essential components in the CO2 heat pump-driven liquid desiccant dehumidification system since the heat transfer performance of heat exchangers directly affects the energy efficiency of the system. However, the heat transfer characteristics of CO2 and liquid desiccant in the heat exchanger have yet to be fully revealed, resulting in a lack of appropriate strategies to improve the heat transfer performance. To address this issue, numerical gas cooler and evaporator models are developed and verified. The effects of parameters such as the weight concentration of the CaCl2 aqueous solution, the CO2 inlet pressure, mass flow rates, and the length of the heat exchanger on the heat transfer performance are investigated respectively under various operating conditions. Results show that the heat exchange load of the gas cooler can be significantly impacted by various inlet parameters of both fluids. In particular, the increase in the weight concentration from 36 to 54 wt.% deteriorates the heat exchange load by over 15 %. Nevertheless, the heat exchange load of the evaporator is hardly influenced by the weight concentration. This is attributed to a great gap in the two fluids’ heat capacity rates, causing the evaporator to be in the maximum heat transfer state. The sign of the maximum heat transfer state of the heat exchanger is whether the thermal effectiveness is close to 1, which is related to the heat transfer area. Therefore, modifying the heat exchanger length could avoid the thermal effectiveness approaching 1. Results indicate that the appropriate length of the evaporator is 3–4 m under the designed operating conditions.

Geo-Spatial Economic Assessment of the Potential Development of Bioenergy Combined with Direct Air Carbon Capture (BEDAC) in the USA.

This study presents a geo-spatial and economic framework to localize future bioenergy power plants combined with direct air capture (BEDAC). This framework is applied to two regions in the USA to assess the optimal use of forest biomass and in situ carbon sequestration under three specific short-term sequestration targets. Results show that there are many locations that have both the necessary biomass and geology required for storage. The Southeast has greater potential for forestry biomass due to both the rate of growth and forested areas, but the sequestration potential is mostly limited to a CO2 solution in saline aquifers. The Pacific Northwest has more sequestration potential than the Southeast given the location of managed forests and storage sites in carbonate mineralization in bedrock. The two combined regions have a total potential sequestration of 9.3 GtCO2 for the next 20 years that can be achieved under an implicit carbon value of $249/tCO2.