CO2 Flow Rate Research Articles

Experimental study of CO2 jet field and CO2-MQL-assisted turning of Ti-6Al-4V based on mass flow rate and pressure

The effectiveness of jet cooling is significantly influenced by both mass flow rate and pressure, which are interrelated and exhibit a coupled relationship. This study examined the effects of mass flow rate and pressure from the perspectives of thermodynamic theory, jet field temperature, micromorphology, and the performance of CO2-MQL-assisted turning of Ti-6Al-4V alloys. Comparative experiments demonstrated that a small mass flow rate of CO2 (1.00 g/s) can achieve cooling and lubrication effects comparable to those of a larger mass flow rate (1.83 g/s) when applied at pressures of 7.38 and 6.00 MPa, respectively. For varying pressures, the maximum differences in improving the CO2-MQL on turning force, turning zone temperature, and surface roughness were 2.36%, 26.31%, and 39.63%, respectively. Conversely, the maximum differences for varying mass flow rates were 1.32%, 17.53%, and 19.66%. The results indicate that pressure has a more significant impact and that optimizing the combination of pressure and mass flow rate is substantial for cooling and lubrication. This study offers a reference for reducing CO2 consumption in CO2-MQL applications, thereby enhancing the alignment of CO2-MQL with sustainable manufacturing practices.

Combining Activated Carbon Adsorption and CO2 Carbonation to Treat Fly Ash Washing Wastewater and Recover High-Purity Calcium Carbonate

Fly ash washing wastewater was carbonated with carbon dioxide (CO2) to remove calcium (Ca) by forming a calcium carbonate (CaCO3) precipitate. An investigation of the factors affecting carbonation showed that Ca removal was highly dependent on the initial pH of the wastewater. The Ca removal was 10%, 61%, 91% and more than 99% at initial wastewater pH levels of 11.8, 12.0, 12.5 and 13.0, respectively. The optimal conditions for carbonation were initial pH of 13.0, carbonation time of 30 min and CO2 flow rate of 30 mL/min. The Ca concentration in the wastewater decreased to <40 mg/L, while 73 g of CaCO3 precipitate was produced per liter of wastewater. However, heavy metals, specifically Pb and Zn, co-precipitated during carbonation, which resulted in a CaCO3 product that contained as much as 0.61 wt% of Pb and 0.02 wt% of Zn. Activated carbon modified by a quaternary ammonium salt was used to selectively adsorb the Pb and Zn first. The Pb- and Zn-free water was then carbonated. By combining adsorption with carbonation, the Ca concentration in the treated wastewater was decreased to about 28 mg/L, while the Na, Cl and K were retained. The wastewater thus treated was ready for NaCl and KCl recovery. In addition, the precipitate had a Ca content of more than 38 wt% and almost no heavy metals. The average particle size of the precipitate was 47 μm, with a uniform cubic shape. The quality of the precipitate met the requirements for the industrial reuse of CaCO3. In summary, adsorption and carbonation combined were able to remove pollutants from wastewater while recovering useful resources.

Microenvironment regulation for high-performance acidic CO2 electroreduction on Poly(ionic liquid)-modified Cu surface

Electrocatalytic reduction of CO2 (CO2RR) under acidic conditions provides a feasible way for converting CO2 to multi-carbon products (C2+) with high feedstock conversion and high energetic efficiency (EE). In this work, poly(ionic liquid) (PIL)-Cu hybrids were employed as excellent acidic CO2RR electrocatalysts. A high faradaic efficiency towards C2+ products (FEC2+) of more than 61.0 % was achieved within a wide pH range from 2 to 14 at –700 mA cm–2. The optimum FEC2+ of 83.1 % was obtained at –700 mA cm–2 and pH = 2, corresponding to an EEC2+ of 37.6 %. By reducing the inlet CO2 flow rate to 1.59 mL min–1, a very high CO2 single-pass conversion of 98.7 % was achieved at –300 mA cm–2. The confinement of PIL layer caused by the semi-rigid abundant porous structure and dense cationic-anionic network enables the maintenance of a moderate local alkaline microenvironment and enrichment of K+ cations at the active sites. These effects jointly promote the C–C coupling at the Cu-PIL interface under acidic conditions. Remarkably, the CO2RR pathway can be regulated by functionality and morphology of the PIL layer.

Direct CO2 mineralization and evolution behavior of fine CaCO3 from ammonia-induced phosphogypsum mineral carbonation

The mineral carbonation of phosphogypsum (PG) presents considerable potential for simultaneous CO2 sequestration and high-value utilization of PG. Variations in carbon footprints are crucial for enhancing carbonation efficiency and regulating product formation. This study explores the mechanism of direct CO2 mineralization by PG and the evolution of the resulting product. The results demonstrate that 97.14% of the CaSO4·2H2O in PG can be converted to calcite under conditions including a nitrogen–sulfur molar ratio of 3, a liquid–solid ratio of 6, a CO2 flowrate of 0.4 L/min, and a stirring rate of 800 rpm for 60 min. The carbonation rate exhibits significant variation with time, occurring in three distinct stages. Initially, CO2 reacts with ammonia to form (NH4)2CO3, releasing greater heat. This heat inhibits the dissolution of Ca2+ from PG, resulting in a lower carbonation efficiency, as only a limited amount of Ca2+ reacts with CO32– to preferentially form amorphous CaCO3 (ACC). As CO32– formation reaches equilibrium, the endothermic properties of the reaction between CaSO4 and (NH4)2CO3 promote the dissolution of Ca2+ from PG, further accelerating CO2 mineralization and resulting in significant increases in carbonation efficiency and ACC production. The ACC is rapidly transformed into calcite via a “dissolution-reprecipitation” mechanism. However, the carbonation rate of PG decreases as saturation is approached, mainly resulting from the aggregation of fine CaCO3 particles on the PG surface. As a result, the direct CO2 sequestration process by PG follows a carbon footprint sequence of “CO2–(NH4)2CO3–ACC–calcite”. This study provides significant insights into the mechanisms of direct CO2 mineralization and product evolution and offers a basis for optimizing carbonation processes enhancement and regulating product phases.

Fracture propagation characteristics driven by liquid CO2 BLEVE for coalbed methane recovery

Fracture propagation induced by liquid CO2 phase transition blasting (LCO2-PB) is the major reason for the spotty fracturing performance of LCO2-PB for enhancing coalbed methane (ECBM). Measures to effectively control the fracture propagation are of significant importance for ECBM recovery. Many researches to date have conducted the responses of the fracture propagation upon the CO2 fracturing under various injection conditions, and some have found that the thermodynamic state of CO2 can dominate the cracks distribution to some extent. This study therefore investigates the effect of various operated parameters of LCO2-PB on the fracture propagation alteration of coal seam subjected to the thermodynamic state of CO2 with different reservoir conditions. A series of fracture process simulations were performed based on the pressure–temperature-phase coupling model, and results indicate that high temperature of CO2 flow in the fracture process greater fracture expansion; the fracture width decreased around by 66.8 % from smaller smash district to larger one, especially for low CO2 flow rate; high elastic modulus and the temperature of coal seam favors greater length reduction and extensive crack connection, and as temperature of CO2 induces the interlaced fractures earlier formation in the higher reservoir temperature.

Exploring carbon dioxide sequestration in desalination reject brine via NaOH reaction: A kinetics study

Seawater desalination is one of the most sustainable means of water supply in arid and semi-arid regions. Despite its undeniable potential to meet the global water demands, there are several environmental impacts associated with its operation, including the generation of reject brine and the emission of considerable amounts of CO2. Recently, the mineralization of carbon dioxide using desalination reject brine has emerged as a potential solution for simultaneous brine management and CO2 sequestration. In this study, the reaction kinetics of desalination reject brine with CO2 in the presence of NaOH are evaluated. The effect of various operating parameters, such as the temperature, CO2 concentration, NaOH dosage, brine salinity, CO2 flowrates and inert particles volume percent were investigated by varying them within the range of 15–55 °C, 3–20 %, 6–16 g/L, 5–72 g/L, 1–5 L/min and 0–20 %, respectively. The experimental data showed that the overall rate of CO2 conversion is equal to the sum of the rates observed for Ca2+ and Mg2+ carbonation reactions and increases proportionally with the increase in CO2 concentration. The addition of NaOH improved the Ca2+ carbonation reaction rate but had no effect on Mg2+ carbonation reactions within the investigated reaction conditions. Interestingly, increasing brine salinity had a negative effect on the reaction rate, while the change in temperature and inert particles had minimal effect on the overall reaction rate. Analysis of the solid products showed that Hydromagnesite and Calcite were the two major products obtained. Finally, experimental data were used to develop a rate model representing the CO2-Brine-NaOH system. The developed model will assist in successfully predicting the performance of the process and pave the way for efficient brine management and CO2 sequestration.

Effect of Electrodeposition Time on the Growth Rate of Carbon Nanotubes (CNTs)

Carbon Nanotubes (CNTs) are nano-sized carbon that resembles tubes and has the potential to be used in various aspects of applications. Some of the CNT carbon capture methods include arc discharge, lasser ablation, CVD and electrodeposition. The advantage of the electrodeposition method is that the production cost is cheap and the preparation is easy. Electrodeposition is the precipitation of substances by using a direct electric current, with CO2 as the reactant. Factors that affect the growth rate of CNT are voltage, temperature, carbon source, electrode and time. The variation of the electorative time used was 60 minutes, 90 minutes, 120 minutes, 150 minutes, 180 minutes. The data collection process begins by shaping and measuring the weight of the electrode (Ni) with a diameter of 2 cm CNT deposition area. measuring the weight and melting Li2CO3 at a temperature of 750. then the CO2 flow rate setting, voltage setting 5V and time setting were then characterized by SEM-EDX and XRD. The results of the study showed that the optimal time obtained with a time of 120 minutes, the resulting CNT deposition rate was 1,618 g cm-2 h-1. Then based on the characterization of XRD and SEM, it shows that the longer the electrodeposition time, the less impurities are contained in the results obtained.

Characteristics of Circulating Fluidized Bed Combustion (CFBC) Ash as Carbon Dioxide Storage Medium and Development of Construction Materials by Recycling Carbonated Ash.

This study validates the attributes of the mineral carbonation process employing circulating fluidized bed combustion (CFBC) ash, which is generated from thermal power plants, as a medium for carbon storage. Furthermore, an examination was conducted on the properties of construction materials produced through the recycling of carbonated circulating fluidized bed combustion (CFBC) ash. The carbonation characteristics of circulating fluidized bed combustion (CFBC) ash were investigated by analyzing the impact of CO2 flow rate and solid content. Experiments were conducted to investigate the use of it as a concrete admixture by replacing cement at varying percentages ranging from 0% to 20% by weight. The stability and setting time were subsequently measured. To produce foam concrete, specimens were fabricated by substituting 0 to 30 wt% of the cement. Characteristics of the unhardened slurry, such as density, flow, and settlement depth, were measured, while characteristics after hardening, including density, compressive strength, and thermal conductivity, were also assessed. The findings of our research study validated that the carbonation rate of CFBC ash in the slurry exhibited distinct characteristics compared to the reaction in the solid-gas system. Manufactured carbonated circulating fluidized bed combustion (CFBC) ash, when used as a recycled concrete mixture, improved the initial strength of cement mortar by 5 to 12% based on the 7-day strength. In addition, it replaced 25 wt% of cement in the production of foam concrete, showing a density of 0.58 g/cm3, and the 28-day strength was 2.1 MPa, meeting the density standard of 0.6 grade foam concrete.

Electroreduction of CO2 to HCOOH on 3D-Ag nanosheet array supported on carbon membrane

Regulating local CO2 concentration and pH near the catalytic active sites could induce effective reaction pathways for electroreduction of CO2 to chemicals. Here, a membrane nanofluid reactor for efficient electroreduction of CO2 to formic acid was prepared by constructing high-density active sites of 3D-Ag nanosheet array on the surface and within the pores of carbon membrane (3D-Ag NA/CM). The local microenvironment of CO2 and H+ concentration was controlled by adjusting the pore size, CO2 flow rate, and mass transfer mode. In the flow-through mode, the CO2 was electro-reduced to formic acid with Faraday efficiency of 94% and the partial current density of 35.8 mA/cm2. Both the selectivity and activity were higher than those in flow-by mode. The low local concentration of CO2 in the channel was the key to the high selectivity of formic acid. When CO2 flowed through the membrane nanopores, the high collision frequency of CO2 with catalyst on the pore walls facilitated the electroreduction of CO2. It found that the presence of OV promoted the adsorption of CO2 and reduced the energy barrier for its activation into ∗CHOO. It lays a foundation for the research on optimizing the performance of CO2 electroreduction with nanofluid reactors.

Performance analysis of precooling systems for cryogenic carbon capture: A comparative study of theoretical, numerical, and experimental methods

The urgency of addressing climate change has necessitated innovative and practical approaches to reducing greenhouse gas emissions. Cryogenic Carbon Capture (CCC) technology has emerged as a promising solution for capturing CO2 from industrial emissions. This study investigates a simplified design for a precooling system within CCC technology, focusing on optimizing the efficiency and reliability of the system while minimizing energy consumption. The research examines the effects of CO2 concentration in a gas mixture (simulated flue gas, nitrogen and carbon dioxide), cooling bath temperature, and gas mixture flow rate on the performance of heat exchangers in the precooling system. Theoretical, numerical, and experimental analyses were conducted to assess the system's performance. The use of liquid nitrogen at −196 °C in the cooling bath was found unsuitable due to CO2 freezing within the pipes. Instead, a mixture of dry ice and isopropyl alcohol at −78.5 °C proved effective in maintaining consistent temperature and pressure conditions without causing CO2 blockages. Numerical simulations highlighted the importance of optimizing pipe length to balance temperature control and pressure dynamics, with a 140 cm pipe length identified as optimal for heat exchanger design. Experimental results revealed that longer pipes enhance cooling performance due to increased heat exchange surface area, while higher CO2 compositions and flow rates result in higher outlet temperatures and pressures. The study emphasizes the need for further research and simulation work to refine heat exchanger designs for industrial applications, aiming to develop systems that maximize cooling efficiency while ensuring reliable operation.

Analysis of cyclone separator solutions depending on spray ejector condenser conditions

The core design strategy for minimizing CO2 emissions in gas power plant entails combining a spray ejector condenser (SEC) and separator to accomplish steam condensation and CO2 purification. This innovative process involves direct-contact condensation of steam with CO2, facilitated by interaction with a subcooled water spray, along with a cyclone separator mechanism intended for generating pure CO2. The investigation of the SEC section, both experimentally and analytically, provides crucial insights into its operational dynamics. Given the susceptibility of cyclone efficiency to fluctuations in SEC conditions, this research endeavors to examine the impacts of CO2 volumetric flow rate and droplet break-up within the SEC on the separation efficacy of the cyclone separator. Additionally, the impact of cone size on the performance of the cyclone has been investigated. Here, a three-dimensional, transient, and turbulent cyclone separator is numerically simulated using Ansys Fluent 2021 R1. The Reynolds Stress Model is employed to simulate turbulent flow, while a mixture model is utilized to replicate swirl two-phase flow within the separators. The findings revealed that reductions in steam and CO2 flow rates were associated with a decrease in outlet temperature but an increase in SEC inlet temperature, leading to a rise in temperature difference and heat transfer rate. Furthermore, an augmentation in cyclone cone size (from 0.2 to 0.5 m) resulted in enhanced separation efficiency (from 77.30 % to 80.98 %) alongside an elevation in pressure drop (from 6.08 Pa to 10.91 Pa), suggesting a compromise between CO2 purification and energy consumption. Additionally, elevated CO2 flow rates induced a rise in pressure drop and separation efficiency, ultimately achieving maximum efficiency at a rate of 24 gs. Moreover, the exploration into droplet breakup manifesting in a boost in separation efficiency from 50.98 % to 100 % across droplet diameters ranging from 1 to 20 μm.

Optimizing CO2 hydrate storage: Dynamics and stability of hydrate caps in submarine sediments

Addressing the escalating impacts of climate change, this study explores the potential of CO2 storage in submarine sediments, presenting a promising strategy for sustainable global warming mitigation. We examine the dynamics and stability of CO2 hydrate caps using magnetic resonance imaging to investigate their spatial-temporal distribution under varying flowrates and storage pressures. Our findings indicate that hydrate caps predominantly expand along the flow direction, influenced significantly by the state of CO2 (liquid or gas) and operational parameters (storage pressure and CO2 flowrate). Notably, higher flowrates and pressures expedite hydrate formation, thereby mitigating the risks of injection well blockages and enhancing cap stability. However, excessively rapid formation may compromise cap thickness and effectiveness. The study delineates optimal conditions that sustain hydrate cap integrity, advocating for a minimum safety pressure of 9000 kPa to prevent failure. These insights significantly advance the development of efficient CO2 storage strategies in submarine environments, offering vital guidance for policy and industry practices aimed at achieving carbon neutrality. By highlighting the technological challenges and solutions associated with deep-sea CO2 storage, this research contributes to the broader discourse on innovative approaches to climate change mitigation.

Production of Fucoxanthin from Microalgae Isochrysis galbana of Djibouti: Optimization, Correlation with Antioxidant Potential, and Bioinformatics Approaches.

Fucoxanthin, a carotenoid with remarkable antioxidant properties, has considerable potential for high-value biotechnological applications in the pharmaceutical, nutraceutical, and cosmeceutical fields. However, conventional extraction methods of this molecule from microalgae are limited in terms of cost-effectiveness. This study focused on optimizing biomass and fucoxanthin production from Isochrysis galbana, isolated from the coast of Tadjoura (Djibouti), by testing various culture media. The antioxidant potential of the cultures was evaluated based on the concentrations of fucoxanthin, carotenoids, and total phenols. Different nutrient formulations were tested to determine the optimal combination for a maximum biomass yield. Using the statistical methodology of principal component analysis, Walne and Guillard F/2 media were identified as the most promising, reaching a maximum fucoxanthin yield of 7.8 mg/g. Multiple regression models showed a strong correlation between antioxidant activity and the concentration of fucoxanthin produced. A thorough study of the optimization of I. galbana growth conditions, using a design of experiments, revealed that air flow rate and CO2 flow rate were the most influential factors on fucoxanthin production, reaching a value of 13.4 mg/g. Finally, to validate the antioxidant potential of fucoxanthin, an in silico analysis based on molecular docking was performed, showing that fucoxanthin interacts with antioxidant proteins (3FS1, 3L2C, and 8BBK). This research not only confirmed the positive results of I. galbana cultivation in terms of antioxidant activity, but also provided essential information for the optimization of fucoxanthin production, opening up promising prospects for industrial applications and future research.

Early-stage recovery of lithium from spent batteries via CO2-assisted leaching optimized by response surface methodology

Recycling lithium (Li) from spent lithium-ion batteries (LIBs) due to the depletion of natural resources and potential toxicity is becoming a progressively favourable measure to realize green sustainability. Presently, the prevalent recycling technique relying on pyrometallurgy lacks the capability to extract lithium. Meanwhile, conventional hydrometallurgical processes frequently employ robust acidic solutions like sulfuric acid and precipitation agents such as sodium carbonate. Unfortunately, this approach tends to result in the extraction of lithium at the end of a lengthy process chain, leading to associated losses and creating challenges in managing complex waste. This study addresses a cost-effective and environmentally friendly early-stage lithium recovery from the thermally conditioned black mass. In this sense, a thermally conditioned black mass is subjected to the carbonization process in a water solution to transform the water-insoluble Li phase into soluble lithium bicarbonate (LiHCO3) and carbonate (Li2CO3) facilitating its selective separation from other elements. Response surface methodology (RSM)—a statistical tool integrated with central composite design (CCD) is employed to optimize the parameters for Li recovery. Temperature, solid–liquid (S/L) ratio, leaching time and CO2 flow rate are considered as variable factors in modelling the optimum recycling process. A quadratic regression model is developed for Li recovery and based on ANOVA analysis, (S/L) ratio, temperature and time are identified as statistically significant factors. Experimental results demonstrate a maximum leaching efficiency of lithium with optimized parameter set, achieving a recovery rate of 97.18% with a fit response of 93.54%.

Tensile-Strained Cu Penetration Electrode Boosts Asymmetric C-C Coupling for Ampere-Level CO2-to-C2+ Reduction in Acid.

The synthesis of multicarbon (C2+) products remains a substantial challenge in sustainable CO2 electroreduction owing to the need for sufficient current density and faradaic efficiency alongside carbon efficiency. Herein, we demonstrate ampere-level high-efficiency CO2 electroreduction to C2+ products in both neutral and strongly acidic (pH=1) electrolytes using a hierarchical Cu hollow-fiber penetration electrode (HPE). High concentration of K+ could concurrently suppress hydrogen evolution reaction and facilitate C-C coupling, thereby promoting C2+ production in strong acid. By optimizing the K+ and H+ concentration and CO2 flow rate, a faradaic efficiency of 84.5 % and a partial current density as high as 3.1 A cm-2 for C2+ products, alongside a single-pass carbon efficiency of 81.5 % and stable electrolysis for 240 h were demonstrated in a strong acidic solution of H2SO4 and KCl (pH=1). Experimental measurements and density functional theory simulations suggested that tensile-strained Cu HPE enhances the asymmetric C-C coupling to steer the selectivity and activity of C2+ products.

Tensile‐Strained Cu Penetration Electrode Boosts Asymmetric C–C Coupling for Ampere‐Level CO2‐to‐C2+ Reduction in Acid

The synthesis of multicarbon (C2+) products remains a substantial challenge in sustainable CO2 electroreduction owing to the need for sufficient current density and faradaic efficiency alongside carbon efficiency. Herein, we demonstrate ampere‐level high‐efficiency CO2 electroreduction to C2+ products in both neutral and strongly acidic (pH = 1) electrolytes using a hierarchical Cu hollow‐fiber penetration electrode (HPE). High concentration of K+ could concurrently suppress hydrogen evolution reaction and facilitate C–C coupling, thereby promoting C2+ production in strong acid. By optimizing the K+ and H+ concentration and CO2 flow rate, a faradaic efficiency of 84.5% and a partial current density as high as 3.1 A cm–2 for C2+ products, alongside a single‐pass carbon efficiency of 81.5% and stable electrolysis for 240 h were demonstrated in a strong acidic solution of H2SO4 and KCl (pH = 1). Experimental measurements and density functional theory simulations suggested that tensile‐strained Cu HPE enhances the asymmetric C–C coupling to steer the selectivity and activity of C2+ products.

A parametric study on syngas production by adding CO2 and CH4 on steam gasification of biomass system using ASPEN Plus

Abstract Biomass gasification technology is increasingly employed as an environmentally friendly energy source, primarily due to its minimal impact on the environment and its ability to mitigate pollution. This technology excels in producing gas with exceptionally high hydrogen content, making it a valuable source for both fuel and energy carriers. Hydrogen (H2), renowned for its stability and lack of detrimental environmental effects, holds great significance in various applications related to energy utilization and sustainability. In the current work, wood sawdust was utilized as the biomass feedstock for syngas production. The research focused on examining the impact of introducing carbon dioxide (CO2) and methane (CH4) gases into the Gibbs reactors. The steam gasification process was modeled by the ASPEN Plus software, allowing for comprehensive analysis and simulation of the gasification reactions. According to the obtained results, the modeling performed in this study demonstrates good predictive capability when compared to the experimental data. It was shown that when the ratio of CO2 to biomass (C/B) increases, the MFR (mass flow rates) of H2 as well as CH4 decrease, whereas the flow rates of CO2 and carbon monoxide (CO) increase. These findings indicate the influence of the C/B ratio on the distribution of different gases within the gasification process. The reduction in MFR of hydrogen when transitioning from C/B = 0 to C/B = 1 in modes a and b is quantified as 17.51 % and 16.39 %, respectively. These percentages represent the magnitude of the decrease in hydrogen MFR for each specific mode when comparing two carbon dioxide to biomass ratios. When the CH4 to biomass (M/B) ratio increases, the mass flow rates of H2 exhibit a consistent upward trend, while the MFR of CO2 displays a descending form. Specifically, when in the Gibbs reactor, M/B rises from 0 to 1 for modes a and b, the mass flow rates of H2 experience significant increases of 265 % and 243 %, respectively. These findings underscore the direct relationship between the M/B ratio and hydrogen production, highlighting the potential for enhanced hydrogen yields with higher M/B ratios in the studied modes.

Исследование адсорбционного разделения газовых смесей в условиях нестационарности

The influence of the initial concentration, rate and temperature of adsorption on the adsorption separation of gas mixtures (CO2, CH4, N2, H2S) is investigated. Components: N2 – 5%, H2S – 5%, CO2 – 5% and CH4 – 85%. And as an adsorbent granule of clinoptilolite of irregular shape were used. Isothermal adsorption of CO2 was obtained at different temperatures (293, 313, and 323 K). The obtained isotherms of CO2 adsorption showed that with an increase in temperature, the adsorption of CO2 decreased. The type of isotherms corresponds to Langmuir. The output curves of gas mixture adsorption depending on the gas flow rate and various main components of CO2 were also experimentally studied. The output curves of the adsorption of the CO2 component were studied at various gas flow rates of 20, 50, and 80 mL/min. Equilibrium time increases with a decrease in the gas flow rate. Output curves were also obtained depending on the initial CO2 concentrations of 5%, 10% and 20%. It was determined that with a decrease in the initial concentration of CO2, the equilibrium time also increases. Gas mixture components sorbed downwards: H2S→CO2→CH4→N2. The resulting system of model equations describing the adsorption separation of gas mixtures in a fixed adsorbent layer represents a complete mathematical model of the process under unsteady conditions. The obtained regularities of the process of adsorption of gas mixtures testify to the fact that the process takes place under non-stationary conditions. The proposed models for the optimal design of industrial absorbers can be used for adsorption separation of gas mixtures in the conditions of their unsteady flow.

Carbon dioxide hydrate crystallization thickening & morphology in a micro-confined environment for carbon capture & sequestration processes

Carbon dioxide capture and sequestration (CCS) are critical processes that are necessary to mitigate the impacts of climate change. In pipelines used for CCS and for ocean sequestration, the formation of CO2 hydrates can occur and be detrimental to the safety and integrity of the CCS equipment and process. Understanding the crystallization thickening behavior of CO2 hydrates is vital for understanding hydrate formation in CO2 pipelines and in other CCS applications, such as sequestration and CO2 capture or storage. In this study, a microfluidic chip reactor was used to crystalize and thicken CO2 hydrates at the channel walls. The morphology of the CO2 hydrates was visually analyzed and quantified using in situ Raman spectroscopy. Two hydrate layers were consistently observed. An annealed, dense layer of hydrate shared an interface with liquid water, while a porous hydrate layer shared an interface with CO2 gas. Capillary-like pore spaces could be observed in the porous layer, which confirms one proposed mechanism for hydrate film thickening. Subcooling (0.5–1.5 K), pressure (2.51, 3.10 MPa), and flow rate of CO2 (0.167, 1.67 mm3/s) were studied for their impact on the overall CO2 hydrate film thickness over time. Over the ranges of these chosen parameters, only CO2 flow rate was found to have a significant impact on the thickening of CO2 hydrates, and a higher flow rate led to thicker crystalline hydrate films. A first principles mass transfer model for hydrate film thickness was developed and applied to the measurement data collected for overall hydrate film thickness.

Physicochemical properties and CO2 absorption performance of poly(ethylene glycol) 300 + hydroxyethyl ethylenediamine mixed solution

Density (ρ) and viscosity (η) data of the polyethylene glycol 300 (PEG300) and hydroxyethyl ethylenediamine (AEEA) mixed solution were measured at P = 1005 hPa and T = (298.15–318.15) K. Following these data, Jouyban-Acree model exhibited superior correlation to density in the mixed system compared to nonlinear least square method, while the McAllister four-body equation yielded a better fitting for kinematic viscosity than other models. Utilizing ρ and η data, the Redlich-Kister equation was employed for the systematic computation and analysis of excess molar volume (VmE), excess activation Gibbs free energy (ΔG*E), partial molar volumes (V1¯ and V2¯), and viscosity deviation (Δη) in the PEG300 (1) + AEEA (2) mixed solution. These excess properties indicated the advantageous nature of intermolecular binding in the PEG300 (1) + AEEA (2) mixed solution, further substantiated on the basis of various spectroscopic characterizations. Finally, under conditions of CO2 flow rate at 150 mL/min, absorption experiments were conducted for 4 h in the PEG300 (1) + AEEA (2) mixed solution, pure AEEA, and pure PEG300, which indicated that the mixed solution exhibited the highest CO2 absorption capacity of 0.95 mol CO2/mol AEEA, demonstrating superior absorption performance compared to the two pure substances.