Mixture Of CO Research Articles

An innovative moment balanced inference engine for predicting recycled concrete aggregate strength and minimizing mixture CO2 emissions

Recycled concrete aggregate (RCA) has an important role to play in reducing CO2 emissions and encouraging sustainable practices in the construction industry. This study introduces Optical Microscope Algorithm - Moment Balance Machine (OMA-MBM) as an innovative AI-based inference engine to improve the accuracy of RCA strength prediction. MBM improves the principles of Support Vector Machine (SVM) by considering moments to identify the optimal moment hyperplane. Backpropagation Neural Network (BPNN) is employed for weight assignment, and OMA is utilized for parameter optimization. The performance of the developed OMA-MBM was benchmarked against several machine learning models, including SVM, BPNN, PSO-SVM, and GWO-SVM, achieving the lowest error metrics with RMSE values of 9.711, 0.708, and 0.709 for compressive, flexural, and tensile strengths, respectively. It also scored the highest overall performance, represented by Reference Index of 1.000. Moreover, the model was successfully used to identify optimal RCA mixture designs in terms of achieving designated material strength requirements with the lowest CO2 emissions. The robustness of model predictions was further validated across diverse applications, i.e., Boston housing prices, vehicle fuel consumption, and building energy efficiency. These findings confirm the robustness and generalizability of OMA-MBM as an accurate predictive tool for development of sustainable construction.

Thermal Desalination Through Forward Osmosis Coupled With CO2-Mixture Power Cycles for CSP Applications

This work, performed in the framework of the H2020 EU project “DESOLINATION”, analyses the coupling between CSP plants using transcritical power cycles with CO2-mixtures and an innovative thermal desalination technique based on Forward Osmosis. Calculations are presented for a large scale CSP plant with central tower receiver and direct storage with solar salts in Dubai, adopting the mixtures CO2+SO2 and CO2+C6F6 in the power cycles. The heat rejected from the cycle condenser is recovered directly by the FO plant, where the draw solute is heated up from 40 °C to 76 °C, to allow for the regeneration of the draw solution used in the forward osmosis membrane. The thermo-responsive polymer adopted is PAGB2000, already considered in literature as a promising option. Results show a very effective synergy between the electricity and the freshwater production: high yearly solar to electric efficiencies are possible (around 19%), with a low freshwater specific thermal consumption (around 100 kWhth/m3). The proposed desalination method is more effective than a conventional MED system (with + 50% of yearly freshwater produced), while a larger solar field (+ 28% in surface area) is necessary for a PV+RO plant to produce annually both the energy and freshwater produced by the CSP+FO plants.

Modulating the coordination environment and metal choice in carbon buckypapers supported metal phthalocyanines for enhanced electrocatalytic carbon dioxide reduction

In the search of versatile electrocatalysts for the electrochemical reduction of carbon dioxide (CO2RR), different transition metal phthalocyanines (MPc, where M=Fe, Co, Ni and Cu) have been immobilized by an easy and scalable wet impregnation on carbon nanotubes (CNTs) in the form of buckypaper (BP). Both the nature of the metal and the surface chemistry of the carbon support were found to play a pivotal role in determining their CO2RR efficiency and selectivity. We disclose here a potentiodynamic strategy for the controlled surface modification of BP with N- and P-containing polymeric species as a simple heterogenization strategy for molecular catalysts, enabling to easily tune their electrocatalytic performance. Syngas (mixture of H2 and CO) was obtained as the main product from CO2RR using FePc, CoPc and NiPc as electrocatalysts on functionalized (BPf) or non-modified BP. In contrast, CuPc was found to mainly catalyze the hydrogen evolution reaction (HER), with small amounts of formate as the only CO2RR product. It is possible to modulate the H2/CO ratio in the final product through the appropriate selection of the metal in MPc, the modification of the coordination environment by the controlled functionalization of the carbon support and the adjustment of the operating conditions. In particular, H2/CO ratios in a range between 0.17 and 1.28 have been obtained with good stability during electrolysis. Among all the MPc studied, CoPc surfaced as the most promising candidate for the reduction of CO2 to CO and H2 production, a finding substantiated by computational studies highlighting the positive impact of phosphate ligands on CoPc. This strategy outlines the starting line of a potential route toward the controlled generation of CO2RR-related products.

Energy, exergy, economic, and environmental analyses and optimization of a multigeneration system considering high-temperature island environment

Renewable energy based multigeneration systems help satisfy the diverse demand for marine resources exploration in off-grid island area, where the storage of fluctuating renewable energy for continuous power supply becomes necessary. Therefore, this paper proposes a solar-driven multigeneration system for island environment integrated with energy storage and production of electricity, cooling, heating, and freshwater. The system comprises an ejector power subsystem, a multiple-effect distillation subsystem, and a CO2 binary mixture-based compressed gas energy storage subsystem. The system performance from the perspectives of energy, exergy, economics, and environment, as well as the impact on performance of the working fluid and several key system parameters, are investigated in this paper. According to the results, an increase in the mass fraction of organic in the CO2 mixture leads to an improvement in system energy efficiency and exergy density at the cost of lower system power efficiency. Increasing the high-pressure tank pressure enhances system performance except for system power efficiency. Increased low-pressure tank pressure leads to improved system energy efficiency and exergy density, accompanied by lower system power efficiency and exergy efficiency. When the ambient temperature increases from 298 K to 303 K, the system energy efficiency noticeably decreases, whereas an increase in direct normal irradiance improves various system performance indicators. Among several mixtures, CO2/R32 mixture was chosen for further analysis and optimization for its wider operating range with R32 mass fraction and better system performance. The optimal operating point had system energy efficiency, exergy density, and modified levelized cost of energy of 1.281, 22.216 kWh/m3, and 0.131 $/kWh, respectively. The proposed system in this research is proven to be a novel technical solution to meet the diverse energy demands on unique island environments.

Robot-assisted optimized array design for accurate multi-component gas quantification

Designing sensor arrays is a common strategy for detecting mixtures. However, a sensor array designed based on human experience leads to inaccuracies due to cross-sensitivity and information overlap. This difficulty led to the realization that arrays should be optimized as a whole. The conventional array optimizing method involves selecting the best subarray from a limited sensor pool. However, this method did not consider the vast continuous multi-dimensional variable space of each sensing element’s recipe, thus only generating a simpler array with limited detection capacity. To address this problem, we developed a Robot-assisted Optimized Array Design (ROAD) method. This innovative method holistically optimizes the sensor array across a continuous and vast variable space, overcoming the bottlenecks of high dimensionality and high-quality data collection. We applied ROAD to an optoelectronic nose, tasked with detecting a mixture of CO2, NH3, and water vapor. The method explored an immense space, estimated at the order of 2^(10^7). The implementation of ROAD led to a revolutionary quantitative accuracy, achieving an average relative standard deviation of 1.90%. This advancement has propelled the application of optoelectronic nose from qualitative to quantitative. The successful ROAD of system-wide array optimization has been demonstrated in the optoelectronic nose, validating the potential of the holistically optimized sensor array for accurately quantifying each component in a gas mixture.

On the phase behavior of sorbitol/water/H2/CO2 mixtures at high pressures and temperatures by in situ infrared spectroscopy

On the phase behavior of sorbitol/water/H2/CO2 mixtures at high pressures and temperatures by in situ infrared spectroscopy

Investigating Internal Heat Exchanger Performance in a VCR System with a CO2 and LPG Refrigerant Mixture

In this study, an attempt was made to develop a cooling system with an internal heat exchanger using a mixture of carbon dioxide (CO2) and liquefied petroleum gas (LPG) as refrigerants to help eliminate the global warming potential and other harmful environmental effects caused by conventional refrigerants'. The CO2 and LPG refrigeration experimental setup was constructed with varying sizes of capillary tubes, a pressure controller, an evaporator, and a gas hob. The working ranges were initially confirmed through exploratory experiments with low-pressure and high-pressure flow circuits, using and without an internal heat exchanger (IHE). The evaporator temperature helped to determine the proportional changes in the coefficient of performance (COP). The REFPROP software design was used to conduct experiments and determine the important process parameters. A confirmation test was performed to validate the expected results of the REFPROP software technique. The results showed that the experiments conducted using IHE had a COP with greater performance levels as follows: mean of 1.398 and SD of 0.367 which is greater than the value of the experiments undertaken without IHE which had a COP performance levels as follows: mean of 0.67 and SD of 0.19. The Paired Samples T-test found these differences to be significant, at p-value < 0.033. The null hypothesis was rejected, hence there is evidence to suggest that the COP of the experiment with IHE is statistically greater than the COP of the experiment without IHE, with a 95% confidence interval of -1.357 and -0.099

Effect of composition and processing conditions on the direct reduction of iron oxide pellets

In this paper, HSC software is used to estimate the effects of composition and processing conditions on the reduction behavior of iron oxide pellets, i.e., hematite (Fe2O3), magnetite (Fe3O4), wustite (FeO), pure iron (Fe), and iron carbide (Fe3C), in a wide temperature range from room temperature (RT) to 1000°C in the presence of H2 and CO mixtures. The reducibility of iron ores, in particular Fe2O3, Fe3O4, FeO, Fe is discussed. The choice of reducing agents CO and H2 is explained, with CO proving to be the more effective reducing agent at high temperatures from a thermodynamic point of view. However, the free Gibbs energy of iron reduction is lowest in the presence of a 100% H2 atmosphere. In addition, H2 reduces tortuosity and increases porosity by reducing it at cooler temperatures and promoting diffusion. In contrast, CO increases tortuosity and reduces initial porosity because it requires higher temperatures for effective reduction and causes structural changes. The presence of impurities other than iron oxides has been shown to impair the activity of reduced pure iron by acting as catalyst poisons or participating in competing reactions. CaO accelerates the reduction of FeO, which is due to the formation of calcium ferrite, but the effect decreases at higher temperatures. MgO can either promote or hinder reduction, depending on its concentration and its influence on pellet porosity. The presence of several non‑iron oxides has been shown to affect the overall direct reduction of iron ore pellets, resulting in a significant impact of the overall process.

Physical and Chemical Properties of Galactic Molecular Gas toward QSO J1851+0035

Atacama Large Millimeter/submillimeter Array (ALMA) data toward QSO J1851+0035 (l = 33.°498, b = +0.°194) were used to study absorption lines by Galactic molecular gas. We detected 17 species (CO, 13CO, C18O, HCO+, H13CO+, HCO, H2CO, C2H, c-C3H, c-C3H2, CN, HCN, HNC, CS, SO, SiO, and C) and set upper limits to 18 species as reference values for chemical models. About 20 independent velocity components at 4.7–10.9 kpc from the Galactic center were identified. Their column density and excitation temperature estimated from the absorption study, as well as the CO intensity distributions obtained from the FUGIN survey, indicate that the components with τ ≲1 correspond to diffuse clouds or cloud outer edges. Simultaneous multiple-Gaussian fitting of CO J = 1–0 and J = 2–1 absorption lines shows that these are composed of narrow- and broad-line components. The kinetic temperature empirically expected from the high HCN/HNC isomer ratio (≳4) reaches ≳40 K and the corresponding thermal width accounts for the line widths of the narrow-line components. CN-bearing molecules and hydrocarbons have tight and linear correlations within the groups. The CO/HCO+ abundance ratio showed a dispersion as large as 3 orders of magnitude with a smaller ratio in a smaller N(HCO+) (or lower A V) range. Some of the velocity components are detected in single-dish CO emission and ALMA HCO+ absorption but without corresponding ALMA CO absorption. This may be explained by the mixture of clumpy CO emitters not resolved with the ∼1 pc single-dish beam surrounded by extended components with a very low CO/HCO+ abundance ratio (i.e., CO-poor gas).

Electrostatically driven kinetic inverse CO2/C2H2 separation in LTA-type zeolites

The identical molecular size and similar physical properties of carbon dioxide (CO2) and acetylene (C2H2) make their adsorptive separation extremely challenging to achieve with most adsorbents. Reports on the separation of CO2 and C2H2 mixtures by zeolites are even rarer with the mechanism of adsorptive separation requiring further exploration. In this paper, we report that ion modulation of zeolite 5A promotes the difference in kinetic diffusion of CO2 and C2H2, realizing the inverse separation of zeolite from selective adsorption of C2H2 to selective adsorption of CO2. Creating a compact pore space restricting the orientation of gas molecules enables charge recognition. The positive electrostatic potential at the pore openings was utilized to hinder the diffusion of C2H2 between the cages while ensuring the transfer of CO2, increasing their diffusion differences in pore channels and leading to the CO2/C2H2 kinetic selectivity of 31.97. Grand canonical Monte Carlo (GCMC) simulation demonstrates that the CO2 distribution in K-5A-β is significantly higher than that of C2H2. Dynamic breakthrough experiments verify the excellent performance of material in practical CO2/C2H2 separation, for CO2/C2H2 (50/50 and 1/99, V/V) mixtures can be separated in one step, thus directly generating high purity C2H2 (> 99.95%), which provides a promising thought for the zeolite-based separation of CO2 and C2H2.

New and accurate thermodynamic property data of CO2-EGS relevant working fluids with data fitted to existing thermodynamic models

The article presents a new setup for the accurate measurements of the phase behaviour of CO2 mixtures relevant to CCS as well as a CO2-H2O working fluid for EGS, designed to cover the temperature range from -60 to 200 °C and up to 100 MPa in pressure. Included in the article are a description of the experimental setup, methodology, and results of the experimental campaign conducted in the SINTEF Energy Research labs for the EnerGizerS project. Phase equilibrium of the CO2-water system has been investigated at the temperature of 50 °C and pressures between 1 and 17.5 MPa, using the analytical isothermal technique. These measurements are compared and verified against the existing data, followed by a presentation of the fit of GERG-2008/EOS-CG for CO2 and H2O. The maximum mole fraction of water in the CO2H2O mixture at measured conditions should not exceed 0.35 % and even less than 0.3481 % at 7.8 MPa to maintain the vapour phase of the mixture. The accuracy with respect to GERG-2008/EOS-CG varies from 1.044 % to 10.683 % near the critical values of sCO2. The estimated uncertainty of the setup is 31 mK for temperature measurements, from 0.4 to 2.5 kPa for pressure measurements and from 0.2 to 2.1 % of total combined relative uncertainty as regards the mole fraction. Despite the fact that the EGS reservoir could reach conditions above 150 °C and 50 MPa, lower values were adopted to validate the setup at 50 °C. Knowledge gaps at higher pressure and temperature values are still in dire need of filling.

Polymerization-induced self-assembly amino acid ionic liquid/poly(ethylene oxide) thin-film composite membranes for CO2 separation

It is well known that crosslinking poly(ethylene oxide) (PEO) membranes exhibit high CO2/N2 solubility selectivity, and are suitable for separating CO2 from flue gas. However, the high CO2/N2 selectivity is temperature sensitive and decreases rapidly with increasing temperature. To overcome this deficiency, imidazolium-based amino acid ionic liquids (AAILs) are introduced into the PEO membranes. A series of (AAILs-PEO)/PAN thin-film composite (TFC) membranes were prepared by a polymerization-induced self-assembly process. Due to the hydrogen and Coulomb interactions between the imidazolium ring of AAILs and the ether groups of PEO monomers, the morphology of the selective layer changed from micellar to granular upon the introduction of the AAILs into the PEO membranes, while the chain-segment flexibility and interspacing of the PEO are also changed. Compared with the original PEO/PAN TFC membrane, the (AAILs-PEO)/PAN TFC membranes show much higher CO2/N2 selectivity, which increases from ∼41 to ∼ 74. In addition, the AAILs show strong hydrophilicity, which leads to a significant increase in CO2/N2 selectivity under the wet-gas feed, reaching ∼105. Compared with the original PEO/PAN TFC membranes with CO2/N2 selectivity of ∼10 at 70 °C, the (AAILs-PEO)/PAN TFC membranes show the selectivity of ∼30, coupled with CO2 permeance of ∼1300 GPU at 70 °C. Under the 40: 60 mixtures of CO2: N2, which is a common lime kiln exhaust gas, by using the (AAILs-PEO)/PAN TFC membrane, the CO2 concentration on the downstream side can reach over 90 % at 20 °C and over 70 % at 70 °C, respectively, under a pressure ratio of 5.

Theoretical study of the expansion of Roper's theory on the laminar jet diffusion flame length in 2D and 3D in natural gas and hydrogen mixtures

In this work, three mathematical models were developed to study the laminar jet diffusion flame in mixtures of natural gas, hydrogen, and CO2 by extending and applying Roper's theory. Model M1 consists of derivation of the Roper's original equation described in the two-dimensional steady state without convection, thus showing the theoretical equations for the length of the diffusion flame for burners with circular, square, and rectangular cross sections and for regimes in which the flames are dominated by the momentum effects, the buoyancy effect, and in the transition regime. Models M2 and M3 extend the Roper's original theory by deriving analytical solutions of the two- and three-dimensional diffusion flame equation with convection in steady and transient states, taking into account the spatially variable velocity and diffusion coefficients. The flame lengths obtained with models M1 and M2 were compared with model M3 by Relative Percentage Difference (RPD) considering 5 mixtures of NG-H2-CO2. For t = 0.1, the maximum RPD in the circular cross-section for M1 in Gas20:60%NG-25%H2–15%CO2 was 14.75%, while for M2 in Gas14:70%NG-15%H2–15%CO2 was 6.47% and the minimum RPD in Gas1:100%NG was 9.78% and 4.83% for M1 and M2, respectively. The same analysis was developed for the square and rectangular (Fr ≪ 1) cross-sections and showed good agreement. The model M3 was tested under transient conditions, studying the effects of time and velocity on the distribution of the profile in the radial direction, in order to better understand the flame phenomenon, which cannot be observed with the Roper's original model M1. Finally, the models M2 and M3 were validated with experimental results and other analytical solutions showing a good performance considering the characteristics of each mixture.

Fabrication of porous high-entropy Mn-Fe-Co-Ni-Cu-Zn alloys by vapor phase dealloying

Porous multicomponent 3d transition-metal (TM) alloys were fabricated by eliminating Zn from rapidly quenched ribbons with distinct compositions, TM7Zn93 and TM4Zn96 (TM – a mixture of Mn, Fe, Co, Ni, and Cu) using vapor phase dealloying (VPD). Phase composition and microstructure of the ribbons in an as-quenched state and resulting porous materials were investigated in detail by S/TEM-EDS, XRD, SEM, and EDXRF methods. In the as-quenched state, the majority of the alloy is composed of the CoZn13 type structure (C2/m space group). Atomically resolved EDS mapping clarified the chemical site occupancy of the TM elements in the structure. The resulting fabricated porous high-entropy alloys (HEA) have a spongy microstructure with a bimodal pore size and their surface area was estimated at 2–4 m2/g. Analysis of pore size distribution revealed their macro-mesoporous structure. The formation of the solid solution with the FCC (Fm3̅m space group) crystal structure during VPD was confirmed by XRD data. STEM-EDS analysis revealed the existence of several FCC solid solution phases within the porous HEA. A nanoscale elemental/phase separation into Co- and Cu-rich FCC solid solution regions with coherent interfaces across the individual crystalline grains has been found. A general route to prepare porous HEA using rapid solidification and vapor phase dealloying has been discussed.

CO2 Removal in Hydrogen Production Plants

Hydrogen is an industrial raw material both for the production of chemicals and for oil refining with hydrotreating. It is the subject of increasing attention for its possible use as an energy carrier and as a flexible energy storage medium. Its production is generally accomplished in Steam Methane Reforming (SMR) plants, where a gaseous mixture of CO and H2, with a limited number of other species, is obtained. The process of production and purification generates relevant amounts of carbon dioxide, which needs to be removed due to downstream process requirements or to limit its emissions to the atmosphere. A work by IEAGHG focused on the study of a state-of-the-art Steam Methane Reforming plant producing 100 kNm3/h of H2 and considered chemical absorption with MethylDiEthanolAmine (MDEA) solvent for removing carbon dioxide from the PSA tail gas in a baseline scheme composed of the absorber, one flash vessel and the regeneration column. This type of process is characterized by high energy consumption, in particular at the reboiler of the regeneration column, usually operated by employing steam, and modifications to the baseline scheme can allow for a reduction of the operating costs, though with an increase in the complexity of the plant. This work analyses three configurations of the treatment section of the off gas obtained after the purification of the hydrogen stream in the Pressure Swing Adsorption unit with the aim of selecting the one which minimizes the overall costs so as to further enhance Carbon Capture and Storage in non-power industries as well.

Experimental study of electron bombardment ion electric propulsion based on a CO2/Xe mixed working medium

An experimental study was carried out on the use of a mixture of CO2 and Xe as the propellant for an electron bombardment ion thruster. The working performance parameters of the ion thruster under different flow mixing conditions were investigated using measurements and diagnostics such as power supply electrical parameter measurements, thrust measurements, and plasma diagnostics. In-depth studies of the particle species and the main electron collision reactions in the discharge chamber were carried out. The results showed that the CO2 in the discharge chamber led to a significant increase in the mean anode voltage and voltage oscillation amplitude, and the direct participation of CO2 in the discharge reaction could effectively improve the beam current and thrust of the ion thruster. When 5 sccm of CO2 was injected into the discharge chamber, the maximum measured thrust was increased by approximately 31.8 % compared to the state without CO2 injection. The addition of Xe led to a significant decrease in the discharge voltage and hence an increase in the electron number density, which significantly promoted CO2 dissociation and ionization. The insights obtained from this work can provide ideas for subsequent research related to an ion thruster using a mixed propellant.

Experimental isochoric apparatus for bubble points determination: Application to CO2 binary mixtures as advanced working fluids

Carbon dioxide binary mixtures are increasingly considered as working fluids in transcritical power cycles, due to the capability to perform liquid-phase compression even at high environmental temperatures. However, a robust thermodynamic model is essential for optimal and reliable design conditions. It is widely recognised that fine-tuning the equation of state with experimental vapour-liquid equilibrium data of the mixture significantly enhances its reliability.In this work, a new apparatus dedicated to vapour-liquid equilibrium measurements of mixtures is presented. The proposed method consists of a constant-volume system, where bubble points are identified from the divergence of slope of the isochoric lines between the two-phase and liquid regions, in the temperature-pressure plane. The temperature and pressure limits of the apparatus are 503 K and 25 MPa.Bubble points of CO2 binary mixtures with hexafluorobenzene (C6F6) and n-pentane (C5H12) have been measured and compared with previous literature data for validation purposes. Then, the CO2 mixture with octafluorocyclobutane (c-C4F8) is experimentally studied, addressing a literature gap in bubble point data. The data are used to calibrate the thermodynamic model, leading to affordable design conditions of the power cycle compared to the non-optimised thermodynamics scenario, in a concentrated solar power tower plant.

Off-design performance analysis of supercritical CO2 mixture Brayton cycle with floating critical points

The thermodynamic performance of supercritical CO2 (sCO2) Brayton cycle deteriorates significantly due to the mismatch between the cold source temperature and the working fluid’s critical point. Here, we present the first study on the off-design performance of a novel supercritical CO2 mixture Brayton cycle with floating critical points. A distillation based regulation subsystem is integrated into the power cycle to dynamically adjust the circulating composition of the binary CO2 mixture, thereby making its critical point float with the ambient temperature and achieving good temperature matching. The off-design behavior of the system operating with the representative mixture is investigated based on an in-house code. The influence of trigger conditions of critical point regulation on energy consumption of the regulation process is investigated. When the maximum temperature difference of the design points for consecutive days is set to 3 °C, the equivalent power consumption can be limited to 2.34 × 106 MJ per year, which affects the annual efficiency by less than 1 %. The results confirms that using the floating critical point method can improve the annual efficiency by 7 %-10.9 % and improve the specific output power by 6.1 %-9.4 % compared to the sCO2 cycle, depending on the power plant locations.

Plasma-solution synthesis of cobalt oxides

The production of nanosized oxide materials is an important practical problem. This is due to the fact that many of these substances are intensively used as catalysts, microelectronic devices, medical applications, etc. Among the various methods for their production, methods based on the use of gas-discharge plasma are the least studied. But these methods, compared to others, have a number of significant advantages. Among them, the main ones are high process rates and the absence of additional reagents. Therefore, in this work the regularities of the processes of formation of insoluble compounds under the action of a direct current discharge of atmospheric pressure in air on aqueous solutions of cobalt (II) nitrate have been studied. The solutions served as the cathode and anode of the discharge. The discharge was excited by applying a high voltage to two pointed titanium electrodes placed above the liquid anode and liquid cathode in the H-shaped cell. The range of discharge currents was (20–80) mA, and the range of concentrations was (20–60) mmol l−1. It was discovered that when a discharge acts on a liquid anode, a colloidal solution is formed in it, the destruction of which leads to the formation of precipitates. Based on measurements of the kinetics of consumption of Co2+ ions (spectrophotometric method) and the power inputted in the discharge, the rates of this process, effective rate constants, as well as the degree of conversion of Co2+ ions and energy yields of conversion were determined. These parameters depended on the discharge current and the initial concentration of the solution. The values of the constants were ∼(0.2–6) × 10−1 s−1, the energy yields were ∼(0.2–0.5) ions per 100 eV, and the degrees of conversion were ∼(0.1–0.5). The resulting powders were analyzed by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and energy-dispersive x-ray spectroscopy (EDS). The sizes of the powder aggregates were estimated from the results of scanning electron microscopy (SEM), transmission electron microscope (TEM) and Scherrer’s relation. It turned out that the resulting precipitates were a mixture of amorphous Co2+ and Co3+ hydroxides. Their calcination in air led, depending on the temperature, to the formation of predominantly cubic either CoO or Co3O4. The size of the aggregates of the calcined samples was ∼500 nm. The specific surface area of the powders, determined by the Brunauer–Emmett–Teller (BET) method, was ∼53 m2 g−1. The average pore volume and their size was ∼17 cm3 g−1 and ∼240 Å. The advantages of the proposed method over other methods are high process rates (process time ∼10 min) and the absence of any additional reagents.

Evaluation of parameters impacting grey H2 storage in coalbed methane formations

Injecting grey hydrogen into coalbed methane formations has the potential to transform coal into a geologically temporary “H2-Battery” and a permanent “CO2-sink”. This study aims to thoroughly evaluate crucial parameters-sorption, diffusion, and matrix swelling/shrinkage-that impact grey hydrogen injection in CH4-enriched coalbed formations. In terms of sorption capacity, CO2 exhibits the highest, followed by CH4 and then H2. Sorption data affirmed that anthracite coal has a certain degree of adsorption capacity for H2, with H2 demonstrating superior diffusive gas deliverability as indicated by its diffusion coefficient, which is approximately six times higher than that of CO2. These characteristic position coal as a promising candidate for temporary H2 storage and cleaning, optimizing injectivity and depletion efficiency. Interestingly, H2 adsorption induced matrix shrinkage in coal, in contrast to other strong sorption gases such as CH4 and CO2, which resulted in matrix swellings. Matrix deformations induced by H2–CO2 mixture (grey hydrogen) injection were conducted and quantified to evaluate grey hydrogen injection in future field trials. The results reveal that the majority of directional strains indicated that when the partial pressure of CO2 in the H2–CO2 mixture is equivalent to pure CO2 pressure, the latter case induces elevated swelling strains. This finding implicitly supports the hypothesis that H2–CO2 mixture injection causes less matrix swelling than pure CO2 injection at equivalent CO2 pressure. This work provides essential parameters to illustrate an enhanced synergism among hydrogen storage, carbon sequestration, and enhance coalbed methane recovery through grey hydrogen injection in coal formations.