Search Results (215)

The efficient adsorption and storage of gases within nanoporous materials are critical for technologies such as adsorbed natural gas systems and energy storage. A paramount goal is to maximize the adsorbent’s gas uptake capacity. However, the fundamental relationship between pore structure and adsorption performance in disordered aerogels remains unclear, hindering rational material design—specifically, where within the complex pore network adsorption predominantly occurs and how the pore size distribution (PSD) should be engineered to enhance capacity. To address this, we conduct molecular dynamics simulations investigating nitrogen adsorption in silica aerogels with tunable PSDs (achieved via tensile deformation) and varied gas–solid interaction strengths (ε). Our results reveal a kinetic-capacity trade-off: microporous-dominated structures saturate rapidly but have limited total uptake, whereas structures with developed mesoporosity (2–10 nm) achieve higher equilibrium capacity via capillary condensation, despite slower kinetics. The interaction strength ε is identified as a key factor governing both capacity and selectivity. Synthesizing these insights, we establish dual design guidelines: to maximize storage capacity, a hierarchical network combining micropores and interconnected mesopores is essential; for optimal reversible performance in cyclic applications like adsorbed natural gas, prioritizing open mesopores with moderately tuned surface chemistry is key. This work clarifies key aspects of the structure–performance relationships and provides evidence-based design guidelines for designing advanced aerogel adsorbents tailored for efficient, low-pressure gas storage. Full article

The growing global demand for sustainable biotechnological routes for bioenergy production has paved the way for Brazil to position itself as a strategic leader due to its vast agricultural production and, consequently, agricultural residues, among which rice husk stands out. Although rice husk is widely used for energy cogeneration, its potential for producing high-value platform chemicals remains underexplored. This study aims to evaluate the production of value-added pyrolytic derivatives from rice husk by investigating the synergy between acid pretreatments and fast pyrolysis temperatures (350–600 °C). Thus, the experimental strategy involved intensifying the production of target compounds in the condensable fraction (bio-oil) from pyrolysis gases using different biomass pretreatments before fast pyrolysis according to the following conditions: (i) acid washing using acetic acid (10%), (ii) acid washing using nitric acid (0.1%) followed by impregnation using sulfuric acid (0.1–0.3%), and (iii) impregnation using sulfuric acid alone (0.1–0.3%). Fast pyrolysis was carried out over a temperature range of 350–600 °C using a pyroprobe microreactor coupled to a mass spectrometer (GC/MS). The best results, regarding overall volatile fraction, were observed when impregnation with 0.3% sulfuric acid was used prior to pyrolysis at 600 °C, resulting in around an 8.88-fold increase compared with untreated biomass. Nevertheless, the experimental conditions that favored the formation of our main chemical targets, such as levoglucosan, furfural and some phenols, were different. For instance, levoglucosan, furfural and eugenol increased by 21-, 10- and 22-fold, respectively, for biomass treated with HNO₃ (0.1%)/H₂SO₄ (0.2%) at 450 °C, whereas phenol and 4-vinylphenol increased by 35- and 14-fold at 500 °C. These findings can be considered satisfactory, highlighting the potential of the thermochemical conversion process as a valuable tool for the production of high-value chemicals from agricultural waste like rice husk. Full article

In electric propulsion for space applications, searching for alternative propellants is increasingly important due to limited resources and economic considerations. Among the candidates, iodine has emerged as promising thanks to its favorable chemical and physical properties for propulsion and its lower cost and simpler storage compared with xenon. However, its corrosive behavior is a drawback, as iodine reacts with many aerospace materials, and its condensable nature prevents using propellant management systems like those for noble gases. At the University of Pisa, activities on fluidics for iodine-fed electric propulsion systems and material compatibility studies led to the development of a mass flowmeter within the “iFACT-MP” Horizon EU project. The device is a spectrophotometric flow meter measuring instantaneous mass flow through a cell in series with the iodine feeding line, upstream of a thermal throttle. A beam splitter directs part of the light to a reference photodiode to compensate for laser intensity variations. Temperature and absorption measurements allow inferring iodine pressure in the cell, while the thermal throttle ensures sonic conditions, enabling correlation with instantaneous mass flow. The mass flow meter shows good behavior and repeatability, especially at low mass flow rates. Full article

The high emissions of carbon dioxide (CO₂) into the atmosphere have driven the development of carbon capture, transport, and storage (CCTS) technologies. These focus on capturing CO₂ from industrial exhaust gases and transporting it through existing pipeline networks. Although various capture techniques are available, they may introduce impurities such as O₂, N₂, Ar, H₂O, NH₃, and others into the CO₂ stream. These contaminants can significantly alter the thermophysical behaviour of the fluid, making the phase behaviour predictions, reliable for pure CO₂, much more complex. Pressure and temperature variations along pipelines can induce unexpected phase transitions, affecting fluid composition and potentially triggering corrosion. This review examines the formation of condensates within pipelines and their role in initiating corrosion phenomena, with a focus on top of the line corrosion (TLC) and conventional CO₂-induced corrosion (sweet corrosion). The main literature findings highlight how phase changes and altered fluid composition due to corrosion processes can significantly intensify degradation mechanisms during CO₂ transport. Full article

The Colombian Caribbean is a strategic area for avocado production, not only because of its favorable climatic conditions, but also because of the availability of varieties with a high content of compounds of industrial interest. The Creole-Antillean avocado grown in Montes de María represents a significant source of raw material with potential for processing, both because of the lipid fraction of its pulp and the chemical composition of its seed. However, the use of this resource has been limited by low technology incorporation and poor coordination of agro-industrial chains that would allow its valorization beyond fresh consumption. In view of this situation, the design of a plant for the simultaneous production of oil and biochar is proposed, with the aim of migrating from a linear model to a comprehensive biomass valorization scheme. The study analyzes the performance of the process from a thermodynamic perspective, applying an exergy analysis that allows for the evaluation of the quality of the energy used and the quantification of irreversibilities at each stage. The results indicate that the highest exergy destruction occurs during seed washing (12.37%), oil extraction and centrifugation (19.71%), distillation and condensation (20.64%), and pyrolysis with by-product separation (28.72%). Although the seed washing stage showed high exergy efficiency (99.81%) when integrated into biochar production, stage 12 recorded a significant loss of 2438.52 MJ/h, associated with the non-use of the volatile gases generated in pyrolysis. Overall, the exergy efficiency of the system reached 30.07%, reflecting the high thermodynamic demands involved in transforming the seed into a high-value product such as biochar. This type of assessment not only identifies critical points of exergy destruction, but also establishes technical bases for optimizing energy consumption, reducing losses, and moving towards a more efficient and sustainable process. Full article

Nutritional strategies for reducing greenhouse gases that negatively impact climate change have been investigated in recent years. Secondary compounds such as tannins are found in tree legumes, which have forage potential and the ability to reduce enteric methane emissions. The aim of this research is to evaluate the effect of forage legumes as a tannin source on enteric methane mitigation and rumen fermentation. The species studied were Acacia dealbata, Acacia melanoxylon, Albizzia lophantha, Lupinus pubescens, Inga insignis, Senna multiglandulosa, and Tecoma stans. The range of crude protein content in all species was variable. The neutral detergent fiber content was much higher in I. insignes, while S. multiglandulosa and L. pubescens had a lower content of acid detergent fiber and lignin detergent acid. I. insignes presented a statistically different lower gas production when compared with the other species subjected to in vitro fermentation. The species that presented the greatest potential for the reduction in enteric methane produced were I. insignes and A. melanoxylon. Additionally, a significant variation was evidenced in the pH of the inocula at 24 h of fermentation in a range of 6.82–7.25. S. multiglandulosa presented concentrations for acetate, propionate, and butyrate that differed significantly compared to the other species. Similarly, the highest concentration of NH₃-N was for S. multiglandulosa. However, the highest EDDM_4% and IVDDM were for I. insignes with 381.28 and 791.46 g/kg, respectively. it can be concluded that forages (e.g., I. insignes) with a higher content of condensed tannins favor rumen digestion and fermentation, probably increasing microbial protein synthesis and thereby reducing ruminal gas and methane production. Full article

Shell-and-tube falling film condensers are critical in fields like energy, petrochemicals, and waste heat recovery. Their operation predominantly involves the complex mixed condensation of steam and non-condensable gases. This process couples multi-physical phenomena—gas flow, liquid film dynamics, phase change, and non-condensable gas accumulation—making accurate prediction challenging. To better understand the underlying mechanisms, this paper develops a practical CFD simulation scheme. The scheme strongly couples the Species Transport model and the Eulerian-wall-film (EWF) model via User-Defined Functions (UDFs) to simulate condensate generation, inter-tube migration, and interphase transfer. Its reliability is validated through grid independence tests and comparisons with theoretical and experimental data. Using this model, the effects of inlet velocity, temperature difference, and non-condensable gas mass fraction are analyzed. Results indicate that higher inlet velocity significantly enhances heat and mass transfer, with the average wall heat transfer coefficient stabilizing at high velocities. While a larger temperature difference increases total heat transfer, its marginal benefit decreases, accompanied by reduced efficiency. A high non-condensable gas mass fraction severely inhibits condensation. Furthermore, the outer wall heat transfer coefficient of the tube bundle is highly non-uniform, with the liquid film thickness varying by over two orders of magnitude. This study provides theoretical and numerical insights for the optimal design and operation of falling film condensers. Full article

The transition toward carbon-neutral energy systems has revived interest in nuclear technologies, particularly small and micro modular reactors (SMRs and MMRs) as flexible, safe and efficient alternatives to conventional large-scale power plans. In the Czech Republic, Centrum výzkumu Řez (CVŘ) is developing Energy Well (EW), a molten salt-cooled micro modular reactor concept employing FLiBe (Fluoride Lithium Beryllium) as primary and secondary coolant and a supercritical CO₂ (sCO₂) tertiary loop. A dedicated experimental facility was built to reproduce EW operating conditions and provide critical data on thermohydraulic behavior, fuel properties and heat-transfer mechanisms. This paper presents the development and assessment of a TRACE (TRAC/RELAP Advanced Computational Engine) model of the experimental facility, including specific methodologies for the main heater and the heat exchanger. Model accuracy was assessed through comparison with experimental commissioning data. The simulations demonstrated overall model consistency, especially regarding the heat exchanger and the main heater general performances, while some discrepancies were observed inside the main heater graphitic core. Other discrepancies were observed along the loop, mainly resulting from modeling simplifications and lack of information regarding certain experimental loop phenomena. In particular, the pressure calculation showed large inconsistencies mainly connected to the complexity of pressure measurements in molten salt circuits and the lack of specific head loss correlations. This study also helped identify broader issues in both the code (persistent error in generating CO₂ property tables and instabilities resulting from FLiBe interactions with non-condensable gases) and the experimental loop (defect in the heat exchanger filling and uncertainties on sensors location), also contributing to resolving sensor-related inconsistencies in the facility. Results confirm TRACE as a reliable tool for modeling molten salt systems, regarding the temperature distribution and the heat transfer. However, depending on the specific experimental case, this paper introduces specific limitations, such as some inconsistencies in the pressure drops distribution, in order to support the future development of TRACE code. Beyond technical advances, this work provides unique experimental data and fosters international collaboration in advancing SMR and molten salt reactor technologies. Full article

Polyester/cotton blended fabrics—valued for comfort and durability—face significant fire hazards due to a synergistic “scaffold effect” during combustion. Conventional treatments with high temperature or some acidic phosphorus flame retardants during preparation often compromise the mechanical strength. Inspired by mussel adhesion chemistry, a mechanically enhanced polyester/cotton fabric was developed by using a novel bio-inspired phosphorus/nitrogen (P/N) synergistic coating. A uniform polydopamine-polyethylenimine (PDA-PEI) layer is rapidly deposited via co-deposition, suppressing dopamine self-polymerization. Subsequent covalent bonding with 2,2-dimethyl-1,3-propanediyl bis (phosphoryl chloride) (DPPC) establishes a robust P/N network. The fabricated PDA-PEI/DPPC coating reduces peak heat release rate (pHRR) and total heat release (THR) by 57.7% and 32.6%, respectively, in cone calorimetry, achieving self-extinguishment and a high limiting oxygen index (LOI) of 24.6%. Remarkably, the coating simultaneously increases the weft-direction breaking strength by 55% and elongation at break by 27.2%; these changes overcome the typical mechanical degradation associated with acidic phosphorus flame retardants. A comprehensive analysis reveals a synergistic mechanism: phosphoric acids catalyze cellulose dehydration and char layer formation in the condensed phase (90% stable C–C bonds), while radical scavengers (PO·, HPO·, and PDA) and non-flammable gases suppressed gas-phase combustion. This work presents a facile and effective strategy for fabricating high-performance and mechanically robust flame retardant polyester/cotton textiles, demonstrating the significant potential for improving fire safety in practical applications. Full article

The buccal micronucleus cytome assay (BMCyt) is a validated, non-invasive biomonitoring method used to detect early genotoxic and cytotoxic changes linked to environmental and occupational exposures. Healthcare workers, especially nurses and dentists, are routinely exposed to genotoxic agents such as anesthetic gases, cytotoxic drugs, ionizing radiation, and heavy metals. This study compared seven cytological biomarkers in exfoliated buccal cells from female nurses, dentists, and teachers to assess multivariate cytogenetic differences and potential occupational influences. Samples were collected from 32 nurses, 41 dentists, and 47 teachers, and 3000 cells per participant were evaluated for micronuclei (MN) and six additional nuclear abnormalities. Group differences were examined using MANOVA and permutation MANOVA, followed by pairwise tests, and visualized with Principal Component Analysis (PCA). Significant multivariate differences were found between nurses and both dentists and teachers (p = 0.003), supported by permutation tests, while dentists and teachers did not differ. PCA explained 56% of the variance and showed apparent clustering of nurses. Chromatin condensation and MN were the main contributors to group separation. Nurses had significantly higher MN (p ≤ 0.001) and karyorrhexis (p ≤ 0.0004) than dentist and teachers. Overall, nurses showed a distinct cytogenetic profile consistent with greater genotoxic susceptibility. Full article

At DLR’s electric space propulsion vacuum test facility in Goettingen, spontaneous pressure rise events were observed, which led to interruptions of thruster testing. This study investigates the causes of four such events and presents a model that is able to simulate pressure rise events due to xenon ice sheet detachment from operating cryogenic pumps. The model results show good agreement with the observed pressure curves and can reproduce the pressure rise slope, event duration, down slope, and maximum pressure during these events. The masses of the detached xenon ice sheets are in the range from 2 g to 0.4 kg, which is reasonable with respect to the amount of ice on cryopump cold plates. This first modeling step is based on a phenomenological approach, but the good results show that it is worth expanding and refining the model, e.g., by introducing more ice shape options, adding ice bonding layer properties, and adding other gases and physical condensate properties. Full article

Background: Hospitals generate large volumes of single-use plastic waste, which are predominantly incinerated. To improve sustainability, standardized procedure-specific surgical trays have been implemented, reducing waste and setup time. This early feasibility study investigated whether all residual plastics from surgical procedures could be recycled via pyrolysis into high-quality oil for circular reuse in medical supply production. Methods: All residual plastics from five transurethral resection (TUR) trays were subjected to pyrolysis at 430–460 °C in a batch reactor. Condensable fractions were separated into heavy (HF) and light (LF) oils, while non-condensable gases and coke were quantified. Chemical analyses included the density, water content, heating value, and elemental composition. Results: From 1.102 kg of input material, the process yielded 78 weight percent (wt%) oil (HF 59.1%, LF 40.9%), 20.5 wt% gas, and 1.5 wt% coke. HF solidified at room temperature, whereas LF remained liquid, reflecting distinct hydrocarbon chain distributions. The oils exhibited densities of 767.0 kg/m³ (HF) and 748.9 kg/m³ (LF), heating values of 46.39–46.80 MJ/kg, low water contents (<0.05 wt%), and minimal contamination (silicone ≤ 193 mg/kg; chlorine ≤ 110 mg/kg). Conclusions: Pyrolysis of surgical tray plastics produces decontaminated high-energy oils comparable in quality to fossil fuels, with a material recovery rate exceeding 75% and potential CO₂ savings of ~ 2.9 ton per t plastic compared with incineration. This process provides a technically and ecologically viable pathway toward a scalable circular economy in healthcare. Full article

Torrefaction, a mild thermochemical pretreatment process, generates the fuel-torrefied biomass along with non-condensable and condensable gases. The latter can be condensed to yield a dark, viscous liquid called torrefaction condensate (TC). In this study, we investigated the effect of TC on growth and exopolysaccharide (EPS) production by the green microalgae Chlamydomonas reinhardtii, a well-known model organism. Aspen wood pellets were torrefied at different temperatures, and the condensate formed at each temperature was analyzed. Based on the GC-MS analysis, 225 °C TC was selected and used for the cultivation of C. reinhardtii. Results show that at 2 mL/L and 2.5 mL/L concentrations, TC negatively impacts growth, EPS production, as well as the composition of amino acids, lipids, and fatty acids n of C. reinhardtii. However, C. reinhardtii gradually adapted to TC and attained the growth patterns comparable to the control, showing the resilience of the culture. The biochemical and antioxidant properties of the EPS showed significant differences to that of the control. Therefore, cultivating these microalgae in TC suggests a new microalgal biorefinery approach through the utilization of low-value TC for the production of value-added products, such as EPS. Full article

The transformation of energy systems towards low emission is one of the key assumptions of the climate and energy policy of the European Union and many countries around the world. These changes include not only the power and transport sectors but also the heating of residential buildings, which consume significant amounts of energy and emit large amounts of greenhouse gases. This article presents a detailed comparative analysis of the costs of heating using an air-to-water heat pump and a condensing gas boiler. The study concerned a retrofitted single-family building from the 1990s, located in southern Poland. The calculations were made taking into account daily meteorological data for two full heating seasons: 2022/2023 and 2023/2024. This approach made it possible to more precisely reproduce real operating conditions. The study was conducted for various configurations of the central heating system: surface and radiator. The following parameters were also taken into account: (1) variable heat pump parameters, such as supply temperature LWT and coefficient of performance COP; (2) current tariffs for electricity and natural gas; and (3) forecasted tariffs for electricity and natural gas in the conditions of market liberalization and phasing out of protective mechanisms. A comparison of the two heating seasons revealed lower costs with a heat pump. In some cases, the cost of heat generated by a gas boiler was over 100% higher than with a heat pump. This applies to both heating seasons. Under the current tariffs, the calculated gas cost for the first season was PLN 6856 (EUR 1605) (1 EUR = 4.27 PLN) compared to heat pump heating costs ranging from PLN 3191 to PLN 4576 (EUR 747 to 1072). For future gas and electricity tariffs, the costs were PLN 8227 (EUR 1926) for gas and PLN 3841 to PLN 5304 (EUR 899 to 1242) for a heat pump. Similarly, for the second heating season, these values were PLN 6055 (EUR 1418) for gas heating and PLN 2741–3917 (EUR 642–917) for a heat pump under the current tariffs, and PLN 7267 (EUR 1702) and PLN 3307–4540 (EUR 774–1064) under future tariffs. This means percentage savings of between approximately 33% and 55%, depending on the heating type and tariff. Therefore, the obtained results indicate the higher profitability of using an air heat pump compared to a gas boiler. This advantage was maintained in all the discussed scenarios, and its scale depended on the type of installation, supply temperature, and the selected electricity tariff. The highest economic profitability was noted for low-temperature systems. These results can provide a basis for making rational investment and design decisions in the context of the energy transformation of single-family housing. Full article

Biomass pellets are widely used for combustion but can also serve as sustainable feedstocks for pyrolysis. This study examined wood (WP), palm-pruning (PP), reed (RD), and daphne (DP) pellets. We present a compact framework linking composition (proximate/ultimate and lignocellulosic fractions) with TG/DTG, FTIR, TGA-derived indices (CPI, D_dev, R_w), T_pmax and R_av to predict product selectivity and temperature ranges. TG/DTG showed the following sequence: hemicellulose (≈200–315 °C) first, cellulose (≈315–400 °C) with a sharp maximum, and lignin ≈200–600 °C. Low-ash WP and DP had sharper, higher peaks, favoring concentrated devolatilization and condensables. Mineral-rich PP and RD began earlier and showed depressed peaks from AAEM catalysis, shifting toward gases and ash-richer chars. Composition shaped these patterns: higher cellulose increased R_av and CPI; links to T_pmax were moderated by ash. Lignin strengthened a high-T shoulder, while hemicellulose promoted early deacetylation (RD’s 1730 cm⁻¹ acetyl C=O) and release of CO₂ and acids. Correlations (|r| ≥ 0.70) supported these links: VM with total (m_∞) and second stage mass loss; cellulose with R_av and CPI (T_pmax moderated by ash); lignin and O/C with T_f and last stage mass loss; ash negatively with T_i, T_pmax, and m_∞. The obtained results guide the sustainable valorization of biomass pellets by selecting temperatures for liquids, H₂/CO-rich gases or low-ash aromatic chars. Full article