Search Results (607)

The supercritical carbon dioxide (sCO₂) Brayton cycle has advantages such as a compact system and high energy density. Axial turbines, the key component of the cycle, have lower rotational speeds, pressure ratios and engineering difficulties compared to radial turbines. This study focuses on the initial design parameters and the complete design process of a small-scale axial turbine based on nuclear power and utilizing supercritical carbon dioxide. The design objective of this study is a 150 kW single-stage axial turbine. AXIAL software is used for batch calculations in the preliminary turbine design to determine the most reasonable initial design parameters, including back pressure, rotational speed, average radius, and mass flow rate. These initial parameters serve as the starting point for the overall turbine design process. The one-dimensional design results of the turbine show an isentropic efficiency of 77.15%, and numerical simulations validate the accuracy of this efficiency. Full article

Polylactic acid (PLA) is considered as an attractive polymer due to its renewable origin, biodegradability, and promising tensile strength and modulus. However, its inherent brittleness, characterized by a low impact resistance and elongation at break, can significantly restrict its application. This work proposes a new insight to improve the toughness of PLA while keeping its biocompatibility by incorporating two biocompatible ionic liquids (ILs), 1-ethyl-3-methylimidazolium ethyl sulfate ([emim][EtSO₄]), and tris(2-hydroxyethyl) methylammonium methylsulfate ([Tris][MeSO₄]). The modified PLA systems were thoroughly characterized to evaluate their mechanical and thermal behavior. Results demonstrated that the addition of 1 wt% of either IL resulted in significant improvement in modulus. Increasing the amount of IL resulted in an increase in the toughness while maintaining the material’s original stiffness and also the thermal stability. Furthermore, the foaming potential of the modified PLA using supercritical CO₂ was investigated as an environmentally friendly processing method. The ionic liquids contributed positively to the foamability of the material, suggesting improved gas solubility and cell nucleation during the foaming process. The addition of both IL decreased the cell size and resulted in narrower cell size distribution. These findings highlight the potential of ionic liquid-modified PLA systems for the processing of lightweight, and high-performance packaging materials. Full article

Currant pomaces were valorised using food-grade supercritical CO₂ to examine how pre-drying (convective vs. freeze-drying) and species (black vs. red currant) shape extract composition and antioxidant readouts. Total phenolics (TPCs), DPPH capacity, tocopherols and fatty acids were determined; statistics employed included the Welch test with Holm adjustment and one-way ANOVA. Blackcurrant showed consistently higher TPCs than redcurrant, whereas DPPH responses were maximised in freeze-dried redcurrant. Freeze-drying increased PUFAs and concomitantly lowered SFAs within both species, with MUFAs varying within a narrower band and tending to be higher in blackcurrant. Tocopherol profiles in residues displayed homologue- and species-specific redistribution (e.g., α higher after convective drying in blackcurrant; γ/δ preferentially retained after freeze-drying), consistent with microstructure-dependent mass transfer and homologue-specific partitioning during SFE. Collectively, pre-drying emerged as the principal lever to tailor lipid class balance and antioxidant performance under fixed extraction conditions. Practically, freeze-drying is suited to PUFA-rich, antioxidant-active fractions, whereas convective drying favours more oxidation-resilient profiles. These results support process-informed ingredient design for clean-label applications and motivate yield-normalised mass balances and scale-up studies. Full article

In this study, supercritical carbon dioxide (scCO₂) was investigated as a sustainable medium for cotton yarn sizing and desizing, eliminating the need for water and conventional organic solvents. Cellulose acetate was employed as the sizing agent with acetone as a co-solvent, achieving a 10% add-on comparable to conventional starch-sized yarns. Since starch sizing is typically reported in the range of 3–10% add-on, a 3% starch level was selected as the industrially relevant benchmark for 20/1 cotton yarn. Trials conducted at 15–20 MPa and 40–60 °C demonstrated uniform size deposition and efficient removal during desizing, as confirmed by weight gain distribution and friction testing. Mechanical characterization further revealed that scCO₂-sized yarns exhibited tensile strength and break elongation within the range of industry benchmarks. Overall, these findings establish scCO₂-based sizing as a viable and eco-friendly alternative, with encouraging preliminary performance that suggests potential alignment with textile industry standards. The process also shows promise for solvent recovery and effluent reduction; however, full quantification of recovery yields, energy requirements, and wastewater impacts remains an important direction for future investigation. Full article

The aim of this work was to investigate the evolution of the mechanical integrity of the selected offshore oil reservoir during its life cycle. The geomechanical stability of the reservoir formation, including the caprock and base rock, was investigated from the exploitation phase through waterflooding production to the final phase of enhanced oil recovery (EOR) with CO₂ injection. In this study, non-isothermal flow simulations were performed during the process of cold water and CO₂ injection into the oil reservoir as part of the secondary EOR method. The analysis of in situ stress was performed to improve quality of the geomechanical model. The continuous changes in elastic and thermal properties were taken into account. The stress–strain tensor was calculated to efficiently describe and analyze the geomechanical phenomena occurring in the reservoir as well as in the caprock and base rock. The integrity of the reservoir formation was then analyzed in detail with regard to potential reactivation or failure associated with plastic deformation. The consideration of poroelastic and thermoelastic effects made it possible to verify the development method of the selected oil reservoir with regard to water and CO₂ injection. The numerical method that was applied to describe the evolution of an offshore oil reservoir in the context of evaluating the geomechanical state has demonstrated its usefulness and effectiveness. Thermally induced stresses have been found to play a dominant role over poroelastic stresses in securing the geomechanical stability of the reservoir and the caprock during oil recovery enhanced by water and CO₂ injection. It was found that the injection of cold water or CO₂ in a supercritical state mostly affected horizontal stress components, and the change in vertical stress was negligible. The transition from the initial strike-slip regime to the normal faulting due to formation cooling was closely related to the observed failure zones in hybrid and tensile modes. It has been estimated that changes in the geomechanical state of the oil reservoir can increase the formation permeability by sixteen times (fracture reactivation) to as much as thirty-five times (tensile failure). Despite these events, the integrity of the overburden was maintained in the simulations, demonstrating the safety of enhanced oil recovery with CO₂ injection (EOR-CO₂) in the selected offshore oil reservoir. Full article

Phoenix Dancong tea essential oil possesses unique aroma characteristics and bioactivities, offering broad application potential in the food, pharmaceutical, and daily chemical fields. To achieve efficient extraction and expand its use in functional textiles, supercritical CO₂ (SC-CO₂) extraction was employed to optimize the extraction process of Phoenix Dancong tea essential oil. Based on single-factor experiments, the optimal extraction conditions were determined as follows: pressure of 25 MPa, temperature of 50 °C, CO₂ flow rate of 8 L/h, and extraction time of 3 h, resulting in an essential oil yield of 1.12%. Response surface methodology (RSM) revealed that the experimental data fit the regression model well (R² = 95.49%, R²Adj = 89.69%). Furthermore, the extracted essential oil was blade-coating to cotton, nylon, polyester, and wool fabrics to evaluate its aroma retention performance. Results indicated that cotton fibers exhibited the best absorption and sustained fragrance retention, maintaining a high odor grade even after 8 weeks. This study provides a theoretical basis and practical reference for the green extraction of Phoenix Dancong tea essential oil and its application in smart aromatic textiles. Full article

Silica aerogels are highly attractive due to their outstanding properties, including their low density, ultralow thermal conductivity, large porosity, high optical transparency, and strong sorption activity. However, their inherent brittleness has limited widespread applications. Constructing a robust, highly porous three-dimensional network is critical to achieving the desired mechanical properties in aerogels. In this study, we introduce a novel synthesis route for fabricating lightweight and mechanically strong aerogels by incorporating poly(ethylene-co-vinyl alcohol) (EVOH) through thermally induced phase separation (TIPS). EVOH exhibits upper critical solution temperature (UCST) behavior in a mixture of isopropanol (IPA) and water, which can be utilized to reinforce the silica skeletal structure. Robust aerogels were prepared via the sol–gel process and TIPS method, followed by supercritical CO₂ drying, yielding samples with bulk densities ranging from 0.136 to 0.200 g/cm³. N₂ physisorption analysis revealed a mesoporous structure, with the specific surface area decreasing from 874 to 401 m²/g as EVOH content increased from 0 to 80 mg/mL. The introduced EVOH significantly enhanced mechanical performance, raising the flexural strength and compressive strength to 0.545 MPa and 18.37 MPa, respectively—far exceeding those of pure silica aerogel (0.098 MPa and 0.74 MPa). This work demonstrates the effectiveness of the TIPS strategy for developing high-strength, low-density silica aerogels with well-preserved porosity. Full article

Recycling multilayer films (MLFs) presents significant challenges to achieving circularity. Mechanical recycling, solvolysis (chemical recycling), and dissolution (physical recycling) have been introduced in the past with their strengths and weaknesses. This study uses a series of advanced, pilot-scale processes to improve the quality of recyclates. These include Near Infrared/Digital Watermarking (NIR/DW), super-critical CO₂ decontamination, dissolution, and innovative mechanical recycling techniques (METEOR and multi-nano layering, MNL). Findings from TRL 5–8 pilots show that recycling different MLF compositions with two routes (dissolution-based and METEOR/MNL-based) can improve the overall quality but this comes with a trade-off. Using 10% recycled content from PET/PE and metalized PP films in 2050 could even increase greenhouse gas (GHG) emissions by 21% and 85%, respectively, compared to landfill incineration. However, PE/PA and PE/EVOH films showed GHG reductions of 0.5% and 4%, respectively. Raising recycled content from 0% to 50% can cut GHG emissions by 36%. These results challenge the current 10% recycled content target, advocating for a more ambitious goal of exceeding 25% by 2050 to enhance sustainability. Full article

Injecting carbon dioxide (CO₂) into underground geo-structures, such as depleted oil and gas reservoirs, reduces man-made CO₂ emissions into the atmosphere or removes what is already there. Studies have identified the risks of CO₂ leaks from these underground geo-structures through wellbores back into the atmosphere due to the high mobility of CO₂ in gaseous and supercritical states. This work aims at proposing a novel method of CO₂ storage using the Joule–Thomson cooling effect to effectively produce CO₂ hydrates on seafloors, with an objective to avoid the leakage risks of storage in depleted oil and gas reservoirs. Through the combination of thermodynamic data, analysis of hydrate stability, and engineering design with established working parameters, this study proposes an innovative concept and an enabling process for CO₂ placement onto seafloors for safe storage. The results of case analysis of typical seawater conditions reveal that the appropriate seafloor depth ranges for different applications (>1900 m for liquid CO₂ and 700–1900 m for CO₂ hydrate). An engineering design procedure for real applications is outlined. Full article

The growing need for sustainable protein and functional food ingredients has made edible insects stand out as a flexible source of bioactives. Black Soldier Fly larva (BSFL) bioactives, such as chitooligosaccharides (COSs) and peptides, present potential benefits for gut health; nevertheless, their molecular pathways, clinical validation, and commercial scalability have yet to be thoroughly investigated. This study systematically analyzes current progress in BSFL bioactive extraction and characterization, emphasizing enzymatic and thermal processing, controlled enzyme development, and integrated supercritical fluid enzymatic pipelines. We assess preclinical and animal research that illustrates prebiotic modulation of Bifidobacterium, Lactobacillus, and Faecalibacterium populations; antimicrobial peptide-mediated immune signaling; and antioxidant activity. Multi-omics frameworks that connect the microbial metabolism of COS to gut health help us understand how these processes function. A comparison of the regulatory environments for food and feed applications in the EU, North America, and Asia shows that there are gaps in human safety trials, harmonized standards, and techno-economic assessments. Finally, we suggest some next steps: randomized controlled human trials in groups with irritable bowel syndrome (IBS) and metabolic syndrome; standardized data integration pipelines for multi-omics; and life cycle and cost–benefit analyses of modular, vertically integrated BSFL biorefineries with AI-driven reactors, digital twins, and blockchain traceability. Addressing these issues will hasten the conversion of BSFL bioactives into safe, effective, and sustainable functional meals and nutraceuticals. Full article

Supercritical carbon dioxide (SC-CO₂) jetting has emerged as a promising technique for rock fracturing due to its superior physical properties such as low viscosity, high diffusivity, and zero surface tension. However, the complex interaction mechanisms between SC-CO₂ jets and heterogeneous rock media remain inadequately understood. In this study, a coupled Smooth Particle Hydrodynamics–Finite Element Method (SPH-FEM) framework is established to simulate the dynamic fracturing process of rocks under SC-CO₂ jet impact. The Riedel–Hiermaier–Thoma (RHT) constitutive model is incorporated to describe the nonlinear damage evolution of brittle rocks, and key material parameters are calibrated via sensitivity analysis and SHPB experimental validation. A series of numerical simulations are performed to investigate the effects of jet standoff distance, jet velocity, and rock lithology (marble, granite, red sandstone) on fracturing efficiency. Damage area, damage volume, and a novel metric—block size distribution—are employed to quantify the fracturing quality from both macro and meso scales. The results indicate that SC-CO₂ jets outperform conventional water jets in creating more extensive and homogeneous fracture networks. An optimal standoff distance of 1–2 cm and a velocity threshold of 0.2 cm/μs are identified for maximum fracturing efficiency in marble. Furthermore, smaller block sizes are achieved under higher velocities, indicating a more complete and efficient rock fragmentation process. This study provides a comprehensive numerical insight into SC-CO₂ jet-induced rock failure and offers theoretical guidance for optimizing green and water-free rock fracturing techniques in complex geological environments. Full article

This study evaluated the extraction of oils from the seeds of bacupari (Garcinia brasiliensis Mart.) and leiteira (Tabernaemontana catharinensis), using carbon dioxide (CO₂) in the supercritical state. The effects of temperature (40, 50, and 60 °C) and pressure (20, 24, and 28 MPa) on the yield and extraction kinetics were investigated. The results indicated that, within the studied limits, temperature had a negligible influence on the process, while pressure had a greater impact on the yields owing to its effect on the density of supercritical CO₂ and the solubility of the extracted compounds. The maximum yields obtained were 14.8% for bacupari and 15.2% for leiteira, with most of the oil extracted within the first 30 min, indicating initial rapid extraction. Chemical composition analysis revealed relevant bioactive compounds in bacupari, including oleic acid (35%) and delta-tocopherol (19.6%). In leiteira, the main compounds identified were hexanedioic acid (29.2%) and stigmast-5-ene (7.95%). These results suggest the potential application of these oils in the pharmaceutical, cosmetic, and food sectors, while also highlighting the feasibility of using supercritical CO₂ as an extraction method for these plant matrices. Full article

Supercritical CO₂ (sCO₂) pipeline transport is a critical link for the large-scale implementation of Carbon Capture, Utilization, and Storage (CCUS) technology, yet its safety is severely challenged by residual impurity gases (e.g., H₂O, O₂, SO₂, H₂S, and NO₂) from the capture process. This review systematically consolidates recent research advances, with the key findings being the following. Firstly, it reveals that the nonlinear synergistic effects among impurities are the primary cause of uncontrolled corrosion, whose destructive impact far exceeds the simple sum of individual effects. Secondly, it delineates the specific roles and critical thresholds of different impurities within the corrosion chain reaction, providing a theoretical basis for targeted control. Consequently, engineering management must enforce strict impurity concentration thresholds integrated with material upgrades and dynamic operational optimization. Future research should focus on developing multi-impurity reaction kinetic models, elucidating long-term corrosion product layer evolution, and establishing standardized experimental systems. This review provides crucial theoretical support for establishing impurity control standards and optimizing anti-corrosion strategies for the safe transport of CO₂ in supercritical CCUS pipelines. Full article

The flaring of associated gas in oil and gas operations contributes significantly to greenhouse gas emissions and represents a loss of valuable hydrocarbon resources. While amine absorption is widely applied for acid gas removal, the use of supercritical carbon dioxide (sc-CO₂) for flare gas treatment remains largely unexplored, despite its proven selectivity for hydrocarbons in other industries such as natural product extraction and polymer processing. Conventional flare gas treatment methods face trade-offs: amine absorption achieves high acid gas removal efficiency but offers limited selectivity for heavier hydrocarbons, whereas sc-CO₂ extraction enables efficient recovery of higher hydrocarbons but does not fully remove acid gases. This study addresses these gaps by evaluating three two-stage flare gas treatment configurations—dual-stage amine absorption, dual-stage sc-CO₂ absorption, and a hybrid of sc-CO₂ followed by amine absorption—using Aspen HYSYS V12.1 simulations, with recycling processes considered in each case. The dual-stage sc-CO₂ process achieved nearly complete hydrocarbon recovery (100%) and complete H₂S removal, but CO₂ remained at elevated concentrations in the treated gas. The dual-stage amine process completely removed CO₂ and H₂S, though with higher energy demand for solvent regeneration. The hybrid configuration combined the advantages of both approaches, achieving complete H₂S removal, 100% hexane recovery, 95.02% methane recovery, and a drastic reduction in CO₂ concentration (to 0.0012 mole fraction). These results demonstrate that integrating sc-CO₂ with amine absorption resolves the trade-off between hydrocarbon selectivity and acid gas removal, establishing a technically viable pathway for flare gas utilization with potential application in gas-to-liquids (GTL) and carbon management strategies Full article

This study investigates the solubility correlation of oil extracted from Sabah green Robusta coffee (Coffea canephora) beans through supercritical carbon dioxide (SC-CO₂) extraction. Sabah, recognized as the largest coffee-producing region in Malaysia, serves as a significant source of Robusta beans for this research. The solubility of coffee bean oil was evaluated under varying pressures (10–30 MPa) and temperatures (40–80 °C). The maximum solubility, 2.681 mg/g CO₂, was recorded at 30 MPa and 40 °C, whereas the lowest solubility, approximately 0.440 mg/g CO₂, occurred at 20 MPa and 80 °C. A clear inverse relationship between solubility and temperature was observed, with solubility decreasing as temperature increased to 80 °C. Conversely, elevated pressure, particularly at 30 MPa, enhanced solubility due to the increased density and solvent power of SC-CO₂. Experimental data exhibited strong agreement with Chrastil’s equation, yielding a relatively low percentage error of 3.37%, compared with 14.57% for the del Valle-Aguilera model. These findings demonstrate the reliability of Chrastil’s model in predicting the solubility of Sabah green coffee bean oil in SC-CO₂. Overall, the research highlights the potential of SC-CO₂ extraction as a sustainable, solvent-free approach for obtaining high-quality coffee oil extracts, with promising applications in the food industry and possible extension to the recovery of other bioactive compounds in food processing. Full article