Capture Process Research Articles

The impact of mass uncertainties on r-process nucleosynthesis in neutron star mergers

Theoretically predicted yields of elements created by the rapid neutron capture (r-) process carry potentially large uncertainties associated with incomplete knowledge of nuclear properties and approximative hydrodynamical modeling of the matter ejection processes. One of the dominant uncertainties in determining the ejecta composition and radioactive decay heat stems from the still unknown nuclear masses of exotic neutron-rich nuclei produced during the neutron irradiation. We investigate both the model (systematic) and parameter (statistical) uncertainties affecting nuclear mass predictions and explore their impact on r-process production, and subsequently on the composition of neutron star merger ejecta. The impact of correlated model uncertainties on masses is estimated by considering five different nuclear mass models that are known to provide an accurate description of known masses. In addition, the uncorrelated uncertainties associated with local variation of model parameters are estimated using a variant of the backward-forward Monte Carlo method, to constrain the parameter changes to experimentally known masses before propagating them consistently to the unknown masses of neutron-rich nuclei. The impact of nuclear mass uncertainties is propagated to r-process nucleosynthesis in a 1.38-1.38 M_⊙ neutron star merger model considering a large and representative number of trajectories. We find that the uncorrelated parameter uncertainties lead to ejected abundance uncertainties of 20% up to A ≃ 130 and 40% between A=150 and 200, with peaks around A ≃ 140 and A ≃ 203 giving rise to deviations around 100 to 300%. The correlated model uncertainties remain larger than the parameter ones for most nuclei. However, both model and parameter uncertainties have an important impact on heavy nuclei production. Improvements to nuclear models are still crucial in reducing uncertainties in predictions related to r-process nucleosynthesis. Both correlated model uncertainties and coherently determining parameter uncertainties are key in the sensitivity analysis.

A Hybrid Mechanism and Data-Based Modeling Approach to a Post-Combustion Carbon Capture Process in a Coal-Fired Power Unit

Chemical absorption carbon capture systems use solutions with complex compositions to further reduce energy consumption and improve performance. Modeling and simulation are essential methods for studying the characteristics of these systems and optimizing them. However, existing methods cannot be used to build models of systems with complex or unknown solutions. This study proposes a hybrid modeling method integrating mechanism modeling and operational data for a chemical absorption carbon capture system. This method interprets the physical and chemical properties of solvents under various operating conditions based on operational data. To validate the effectiveness of this method, it is applied to a real-life post-combustion carbon dioxide capture system in a 1000 MW coal-fired power unit, which has an annual capture capacity of 10,000 tons. The results of the case study indicate that the proposed method can obtain values of key property parameters of solvents, including absorption heat, cyclic carbon capacity, and heat capacity. The average relative error between operational data and simulation data ranges from 0.2% to 8.0%.

Efficient Catalysis for Zinc-Air Batteries by Multiwalled Carbon Nanotubes-Crosslinked Carbon Dodecahedra Embedded with Co-Fe Nanoparticles.

The design and fabrication of nanocatalysts with high accessibility and sintering resistance remain significant challenges in heterogeneous electrocatalysis. Herein, a novel catalyst is introduced that combines electronic pumping with alloy crystal facet engineering. At the nanoscale, the electronic pump leverages the chemical potential difference to drive electron migration from one region to another, separating and transferring electron-hole pairs. This mechanism accelerates the reaction kinetics and improves the reaction rate. The interface electronic structure optimization enables the CoFe/carbon nanotube (CNT) catalyst to exhibit outstanding oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) performance. Specifically, this catalyst achieves an ORR half-wave potential (E₁/₂) of 0.895V, outperforming standard Pt/C and RuO₂ electrocatalysts in terms of both specific activity and stability. It also demonstrates excellent electrochemical performance for OER, with an overpotential of only 287mV at a current density of 10mA cm⁻2. Theoretical calculations reveal that the carefully designed crystal facets reduce the energy barrier of the rate-determining steps for both ORR and OER, optimizing O₂ adsorption and promoting the oxygen capture process. This study highlights the potential of developing cost-effective bifunctional ORR-OER electrocatalysts, offering a promising strategy for advancing Zn-air battery technology.

Reactive carbon capture using saline water: evaluation of prospective sources, processes, and products.

Reactive carbon capture (RCC) processes involve the capture of carbon dioxide (CO2) and conversion to a value-added product using a single sorbent/reaction medium. Not only can RCC processes generate valuable byproducts that can reduce the cost of carbon capture, but RCC tends to have lower energy demand than processes involving the transfer of CO2 between the mediums used for capture and subsequent reactions. Saline water has been proposed as a potential medium for RCC due to it's relative abundance and low cost. Additionally, the composition and chemistry of many saline water sources: (1) elevates the CO2 content (as compared to atmospheric concentrations), (2) provides various cations that can form valuable products with CO2, and (3) enhances the kinetics of chemical reactions used to convert CO2 to stable byproducts. In addition to established industrial processes for converting CO2 into inert or valuable byproducts, we found 20 new processes and technologies that have been developed specifically to capture and convert CO2 using saline water. Both preexisting and emerging processes can be broadly classified as electrochemical or chemical titration processes. When assessing the potential viability of applying any of these processes for large scale carbon capture, several factors must be considered, such as the net carbon footprint of the process, the market size, location of customers and value of the end product, the energy demand and chemical costs of the process, and any other environmental impacts. The feasability of many emerging saline-based RCC processes is difficult to determine, as many technologies were tested using synthetic saline waters and/or concentrated CO2 sources. Notwithstanding the early stage of development of many saline-based RCC technologies, the major limitation to implementation of this approach to carbon capture is the mismatch in the scale of the markets for products of saline-based RCC and the scale of carbon capture needed to meet climate goals. However, because the products of many of the processes reviewed here are stable and non-hazardous, these technologies may also be used for carbon sequestration efforts where the products are managed as waste, in which case the carbon capture potential of these technologies can surpass the market-imposed limitations on RCC. Thus, the potential benefits of saline water-based RCC identified in this review encourage further study and development of these technologies.

Surrogate modeling and optimization of Pressure/Vacuum Swing Adsorption (P/VSA) processes for carbon capture from post-combustion CO2 point sources

In the present work, a surrogate-based modeling framework has been developed to simulate and optimize Pressure/Vacuum Swing Adsorption (P/VSA) processes, for the efficient separation of CO2 from post-combustion carbon point sources. A single-stage 4-step P/VSA process is considered, using zeolite 13X as adsorbent, aiming to minimize the energy requirements with minimum CO2 purity and recovery targets of 95% and 90%, respectively. The developed P/VSA surrogate model consists of simple non-linear algebraic expressions developed by the ALAMO algorithm, which describe the key process performance indicators as functions of several process variables. In all cases examined, the optimization results from the P/VSA surrogate model are in excellent agreement with the ones obtained from the respective mechanistic model, with a relative deviation of less than 1% between the optimal solutions of the mechanistic and the surrogate model. On the other hand, the computational time for the optimization of the surrogate model is 3-4 orders of magnitude lower compared to that required for the optimization of the mechanistic model, which renders surrogate models particularly suitable for online applications that involve rapid and continuous responses to various input fluctuations.

Design of Multi-sorbent Adsorption Processes for Post-combustion Co2 Capture

Design of Multi-sorbent Adsorption Processes for Post-combustion Co2 Capture

Electrochemical valorization of captured CO2: recent advances and future perspectives.

The excessive emission of CO2 has led to severe climate change, prompting global concern. Capturing CO2 and converting it through electrochemistry into value-added products represent promising approaches to mitigating CO2 emissions and closing the carbon cycle. Traditionally, these two processes have been performed independently, involving multiple steps, high energy consumption, and low efficiency. Recently, the electrochemical conversion of captured CO2, which integrates the capture and conversion processes (also referred to as electrochemically reactive CO2 capture), has garnered increasing attention. This integrated approach bypasses the energy-intensive steps involved in the traditional independent process, including CO2 release, purification, compression, transportation, and storage. In this review, we discuss recent advances in the electrochemical conversion of captured CO2, focusing on four key aspects. First, we introduce various capture media, emphasizing the thermodynamic aspects of carbon capture and their implications for integration with electrochemical conversion. Second, we discuss product control mediated by the selection of different catalysts, highlighting the connections between the conversion of captured CO2 and gas-fed CO2. Third, we examine the effect of reactor systems and operational conditions on the electrochemical conversion of captured CO2, shedding light on performance optimization. Finally, we explore real integration systems for CO2 capture and electrochemical conversion, revealing the potential of this new technology for practical applications. Overall, we provide insights into the existing challenges, potential solutions, and thoughts on opportunities and future directions in the emerging field of electrochemical conversion of captured CO2.

A novel post-combustion CO2 capture process for natural gas combined cycle power plant based on waste energy utilization and absorption heat transformer

A novel post-combustion CO2 capture process for natural gas combined cycle power plant based on waste energy utilization and absorption heat transformer

Effective Area Evaluation of Rotating Packed Beds in a Flexible CO2 Capture Process

Effective Area Evaluation of Rotating Packed Beds in a Flexible CO2 Capture Process

Study on the process of submerged combustion vaporizer flue gas membrane-cryogenic hybrid carbon capture for coupled liquefied natural gas cold energy power generation

ABSTRACT Under the background of “carbon peaking and carbon neutrality goals,” China has put forward the requirements for the low-carbon development of Liquefied Natural Gas (LNG) industrial chain. Carbon capture technology is an effective means to reduce direct carbon emissions and can promote the decarbonization of the LNG industry chain. So far carbon capture is still an energy-intensive process. Based on the traditional membrane-cryogenic hybrid CO2 capture process, a membrane-cryogenic hybrid CO2 capture process coupled with Liquefied Natural Gas cold energy generation was proposed in this paper. In the proposed process, LNG cold energy and high temperature flue gas heat energy were used to drive Organic Rankine Cycle power generation and reduced carbon capture energy consumption. The effects of key parameters (membrane pressure, membrane temperature, cryogenic pressure, and cryogenic temperature) on the performance of the process (CO2 purity, CO2 recovery, and specific energy consumption) were analyzed by single factor analysis. The process parameters were optimized by response surface analysis, the optimized system resulted in an CO2 purity of 98.39%, CO2 recovery of 90.16%, and specific energy consumption of 605 kJ/kg which was much lower than that of the same type of carbon capture process. This process opens up a new technological path for the development of low energy consumption in carbon capture and the decarbonization of the LNG industry chain, and provides a new solution to meet the challenges in the context of “dual carbon.”

Impact of gate bias on TID responses of BCD MOSFETs

The total ionizing dose (TID) effect on MOSFETs, which use the Bipolar-CMOS-DMOS (BCD) technology, is investigated under different gate biases utilizing X-rays. The threshold voltage, maximum transconductance and subthreshold swing of the device before and after irradiation were obtained. The results indicate that the TID effect is significantly influenced by gate bias. For NMOSFET, the maximum threshold voltage shift occurs at a positive gate bias of 3 V. For PMOSFET, the minimum threshold voltage shift occurs at a negative gate bias of −3 V. The mechanism was revealed to be the result of the combined effects of initial recombination, hole capture, and electron tunneling processes. However, the case of PMOSFET differs from NMOSFET due to the disappearance of electron tunneling and the change in the direction of hole movement under negative gate bias.

Thermodynamic integration in combined fuel and power plants producing low carbon hydrogen and power with CCUS

Demand for low-carbon sources of hydrogen and power is expected to rise dramatically in the coming years. Individually, steam methane reformers (SMRs) and combined cycle gas power plants (CCGTs), when combined with carbon capture utilisation and storage (CCUS), can produce large quantities of on-demand decarbonised hydrogen and power respectively. The ongoing trend towards the development of CCUS clusters means that both processes may operate in close proximity, taking advantage of a common infrastructure for natural gas supply, electricity grid connection and the CO2 transport and storage network. This work improves on a previously described novel integration process, which utilizes flue gas sequential combustion to incorporate the SMR process into the CCGT cycle in a single “combined fuel and power” (CFP) plant, by increasing the level of thermodynamic integration through the merger of the steam cycles and a redesign of the heat recovery system. This increases the 2nd law thermal efficiency by 2.6% points over un-integrated processes and 1.9% points the previous integration design. Using a conventional 35% wt. monoethanolamine (MEA) CO2 capture process designed to achieve two distinct and previously unexplored CO2 capture fractions; 95% gross and, 100% fossil (CO2 generated is equal to the quantity of CO2 captured). The CFP configuration reduces the overall quantity of flue gas to be processed by 36%–37% and increases the average CO2 concentration of the flue gas to be treated from 9.9% to 14.4% (wet). This decreases the absorber packing volume requirements by 41%–56% and decreases the specific reboiler duty by 5.5% from 3.46–3.67 GJ/tCO2 to 3.27–3.46 GJ/tCO2, further increasing the 2nd law thermal efficiency gains to 3.8%–4.4% points over the un-integrated case. A first of a kind techno economic analysis concludes that the improvements present in a CO2 abated CFP plant results in a 15.1%–17.3% and 7.6%–8.0% decrease in capital and operational expenditure respectively for the CO2 capture cases. This translates to an increase in the internal rate of return over the base hurdle rate of 7.5%–7.8%, highlighting the potential for substantial cost reductions presented by the CFP configuration.

Measurement of the Se78(n,γ)Se79 cross section up to 600 keV at the n_TOF facility at CERN

The Se78(n,γ)Se79 cross section has a high impact on the abundances of Se78 produced during the slow neutron capture process (s process) in massive stars. A measurement of the Se78 radiative neutron capture cross section has been performed at the Neutron Time-of-Flight facility at CERN using a set of liquid scintillation detectors that have been optimized for a low sensitivity to neutrons. We present resonance capture kernels up to 70 keV and cross section from 70 to 600 keV. Maxwellian-averaged cross section (MACS) values were calculated for stellar temperatures between kT=5 and 100 keV, with uncertainties between 4.6% and 5.8%. The new MACS values result in substantial decreases of 20–30% of Se78 abundances produced in the s process in massive stars and AGB stars. Massive stars are now predicted to produce subsolar Se78/Se76 ratios, which is expected since Se76 is an s-only isotope, while solar Se78 abundances have also contributions from other nucleosynthesis processes. Published by the American Physical Society 2024

Amine-Based Solvents and Additives to Improve the CO2 Capture Processes: A Review

The use of amine-based solvents for carbon dioxide (CO2) capture has shown significant promise; however, operational challenges such as high energy requirements, solvent degradation, and equipment corrosion highlight the need for enhanced solutions. This review focuses on identifying amine-based solvents and additives that can improve CO2 capture efficiency while minimizing costs and avoiding substantial modifications to existing industrial facilities. Specifically, the study emphasizes the development of a comprehensive database of additives to optimize CO2 capture processes. A detailed analysis of recent advancements in amine-based solvents was conducted, with a focus on (i) process optimization strategies, (ii) sector-specific CO2 emission profiles, and (iii) equipment issues associated with conventional chemical solvents. The study evaluates these solvents’ kinetic and thermodynamic properties and their potential to address critical operational challenges, including reducing corrosion, solvent viscosity, and evaporation rates. The findings highlight the pivotal role of amino group-containing compounds, particularly alkanolamines, in enhancing CO2 capture performance. The structural versatility of these compounds, characterized by the presence of hydroxyl groups, facilitates aqueous dissolution while offering kinetic and thermodynamic benefits. This review underscores the importance of continued innovation in solvent chemistry and the integration of amine-based solvents with emerging technologies to overcome current limitations and advance the implementation of efficient and sustainable CO2 capture technologies.

Deep level transient spectroscopy: Tracing interface and bulk trap‐induced degradation in AlGaN/GaN‐heterostructure based devices

AbstractThe exceptional physical properties of gallium nitride (GaN) position GaN‐based power devices as leading candidates for next‐generation high‐efficiency smart power conversion systems. However, GaN's multi‐component nature results in a high density of epitaxial defects, whereas the introduction of dielectric layers further contributes to severe interface states and dielectric traps. These factors collectively impair reliability, manifesting as threshold voltage instability and current collapse, which pose significant barriers to the advancement of GaN‐based electronics. Establishing the intrinsic relationship between device reliability and defects is crucial for understanding and addressing reliability degradation issue. Deep level transient spectroscopy (DLTS) offers valuable insights by revealing defect‐induced changes in electrical parameters during the capture and emission processes under varying biases, thereby elucidating the influence of defects from GaN buffer layers, AlGaN barriers, dielectric layer, and even at dielectric/(Al)GaN interfaces. This research aims to provide a foundational understanding of reliability degradation whereas further enabling enhancements in device performance from the perspectives of epitaxial growth and process preparation, ultimately striving to improve the reliability of GaN‐based devices and unlock their full potential for practical applications.

Chemical Evolution of R-process Elements in Stars (CERES). III. Chemical abundances of neutron capture elements from Ba to Eu

The chemical abundances of elements such as barium and the lanthanides are essential to understand the nucleosynthesis of heavy elements in the early Universe as well as the contribution of different neutron capture processes (for example slow versus rapid) at different epochs. The Chemical Evolution of R-process Elements in Stars (CERES) project aims to provide a homogeneous analysis of a sample of metal-poor stars ( Fe/H $<$$-1.5$) to improve our understanding of the nucleosynthesis of neutron capture elements, in particular the $r$-process elements, in the early Galaxy. Our data consist of a sample of high resolution and high signal-to-noise ratio UVES spectra. The chemical abundances were derived through spectrum synthesis, using the same model atmospheres and stellar parameters as derived in the first paper of the CERES series. We measured chemical abundances or upper limits of seven heavy neutron capture elements (Ba, La, Ce, Pr, Nd, Sm, and Eu) for a sample of 52 metal-poor giant stars. We estimated through the mean shift clustering algorithm that at Ba/H =$-2.4$ and Fe/H =$-2.4$ a variation in the trend of X/Ba with X=La,Nd,Sm,Eu, versus Ba/H occurs. This result suggests that, for Ba/H $<$$-2.4$, Ba nucleosynthesis in the Milky Way halo is primarily due to the $r$-process, while for Ba/H $>$$-2.4$ the effect of the $s$-process contribution begins to be visible. In our sample, stars with Ba/Eu compatible with a Solar System pure $r$-process value (hereafter, $r$-pure) do not show any particular trend compared to other stars, suggesting $r$-pure stars may form in similar environments to stars with less pure $r$-process enrichments. Homogeneous investigations of high resolution and signal-to-noise ratio spectra are crucial for studying the heavy elements formation, as they provide abundances that can be used to test nucleosynthesis models as well as Galactic chemical evolution models.

Harnessing Ammonia as a Hydrogen Carrier for Integrated CO2 Capture and Reverse Water-Gas Shift.

In this paper, a concept of integrated CO2 capture and reverse water-gas shift (ICCrWGS) process was proposed using NH3 as the H2 carrier. The CO2 efficiency and total thermal energy consumption for the conventional rWGS, ICCrWGS using H2 (H2-ICCrWGS) and NH3 (NH3-ICCrWGS), were calculated. ICCrWGS using H2 and NH3 was conducted over the thermally stable Ni/CaZr dual-function materials (DFMs). NH3 decomposition, CO2 capture capacity, CO2 conversion, and CO selectivity were addressed at different reaction temperatures, and the optimal temperature was determined to be 650 °C. The Ni/CaZr DFMs exhibited stable CO2 capture capacity and CO productivity during ICCrWGS using the NH3 carrier. A carbonate spillover mechanism for CO production over the Ni/CaZr DFMs in NH3-ICCrWGS was proposed using in situ diffuse reflectance infrared Fourier transform spectroscopy. It was found that CO is produced from the bridged bidentate carbonate route in the Ni-CaO interface.

High-performance AlGaN/GaN HEMTs with Hf0.5Zr0.5O2-based ferroelectric gate by pulsed laser deposition

This Letter demonstrates AlGaN/GaN high-electron-mobility transistors (HEMTs) with Hf0.5Zr0.5O2 (HZO) ferroelectric gate dielectric using pulsed laser deposition (PLD). An ultrathin Al2O3 interlayer grown by atomic layer deposition is used to avoid destroying the AlGaN surface and decreasing the electron density of a two-dimensional electron gas channel before PLD. The high-quality HZO on AlGaN/GaN heterostructure contributes to the good insulating and ferroelectric properties of the HZO film, yielding a superior ON/OFF current ratio of 4 × 1011 and a low sub-threshold slope (SS) of 53.2 mV/dec. Moreover, the electrical characteristics of the device are systematically investigated before and after gate poling. In combination with the analysis of schematic band diagrams, we found that ferroelectric polarization can effectively regulate the capture and release processes of channel electrons by Al2O3/AlGaN interface defects. These results show that HZO-based ferroelectric HEMTs have great potential for high frequency, low power consumption, and multi-functional devices.

Two-neutrino double electron capture of 124Xe in the first LUX-ZEPLIN exposure

Abstract The broad physics reach of the LUX-ZEPLIN (LZ) experiment covers rare phenomena beyond the direct detection of dark matter. We report precise measurements of the extremely rare decay of 124Xe through the process of two-neutrino double electron capture, utilizing a 1.39 kg × yr isotopic exposure from the first LZ science run. A half-life of T 1 / 2 2 ν 2 EC = ( 1.09 ± 0.1 4 stat ± 0.0 5 sys ) × 1 0 22 yr is observed with a statistical significance of 8.3σ, in agreement with literature. First empirical measurements of the KK capture fraction relative to other K-shell modes were conducted, and demonstrate consistency with respect to recent signal models at the 1.4σ level.

Tailoring Borate Mediator Species Enables Industrial COProduction with Improved Overall Energy Efficiency by Sustainable Molten Salt CO2 Electrolysis.

The electrochemical conversion of CO2 into CO represents a promising strategy for mitigating excessive global greenhouse gas emissions. Nevertheless, achieving industrial-scale electrochemical CO2-to-CO conversion with enhanced selectivity and reduced energy consumption presents significant challenges. In this study, a borate-enhanced molten salt process for CO2 capture and electrochemical transformation is employed, achieving over 98% selectivity for CO and over 55% energy efficiency without the necessity for complex and costly electrocatalysts. Cathodic CO2 electro-reduction (CO2ER) with the anodic oxygen evolution reaction (OER) at an overall current density of 500mAcm-2 using non-nanostructured transition-metal plate electrodes at 650°C is coupled. By regulating the electrolyte's oxo-basicity with earth-abundant borax (Na2B4O7), a borate-enhanced electrolyte is established that accelerates the overall electrochemical reaction efficiently. This system involved a series of well-designed target borate species (BO3 3-, BO2 -, and B4O7 2-) that acted as mediators shuttling between the cathode and anode, favoring CO as the primary cathodic product. Manipulating the atmosphere above the anode facilitated a spontaneous transformation of borates, further enhancing OER performance with long-term operational stability over a cumulative period of 50h, while also reducing overall energy consumption. This work presents a cost-effective strategy for the industrial-scale production of CO derived from CO2, contributing to a lower carbon footprint by establishing a sustainable borate-mediated closed loop.