Search Results (1,073)

With the expansion of ammonia energy applications, long-distance liquid ammonia pipelines are expected to support large-scale cross-regional ammonia transport. In the liquid ammonia pipeline commissioning process, gaseous ammonia purging involves ammonia–nitrogen mixing and possible liquefaction, while liquid ammonia injection may induce flashing and severe local cooling, all of which can affect commissioning safety. To characterize these thermodynamic phenomena, a transient gas–liquid two-phase flow model was established and validated using OLGA 2022.1.0 software for simulating the long-distance liquid ammonia pipeline commissioning. The model adopts the cross-sectionally averaged one-dimensional approach. A volume-corrected Soave–Redlich–Kwong (SRK) equation of state for ammonia was adapted, validated, and used to generate OLGA-compatible thermodynamic property tables. The results show that, during gaseous ammonia purging, a higher flowrate shortens the displacement time by accelerating nitrogen removal, and this effect is more pronounced at higher ambient temperatures due to enhanced molecular diffusion. Along the pipeline, pressure gradually decreases from frictional resistance, with a steeper drop near the outlet caused by gas acceleration, and temperature gradually approaches ambient through heat exchange with the pipe wall and surrounding soil. A high gaseous ammonia flowrate can cause partial liquefaction, regasification, and temperature fluctuations. During liquid ammonia injection, local condensation and slight liquid accumulation occur before the liquid front arrives, and the low-temperature region moves with the liquid front. The liquid ammonia mass flowrate has the strongest influence on the injection process, as it reduces the completion time but increases the outlet temperature, outlet pressure, and the low-temperature risk downstream of the valve. Therefore, it should be controlled within an appropriate range to balance efficiency and low-temperature safety risks. This work provides a rapid and efficient prediction model for key thermo-hydraulic parameters during liquid ammonia pipeline commissioning, and the overall analyses offer insights for on-site process design and safety control. Full article

Global demand for sustainability drives interest in bioenergy from sustainable feedstock. Agro-industrial waste such as brewer’s spent grains (BSG) is an important by-product of brewing. This study provides a comprehensive review of the current technologies of BSG for energy recovery and BSG-based materials for energy storage applications. The latest scientific progress, not only from conventional processes on anaerobic digestion, combustion, gasification, pyrolysis, torrefaction, and hydrothermal liquefaction but also from several integrated technologies, pretreatment methods, and additives/catalysts regarding the improvement of energy efficiency and process sustainability, was reviewed. In addition, the co-feedstock practices (co-combustion, anaerobic co-digestion, hydrothermal co-liquefaction, anaerobic co-fermentation) and co-production were examined. AD of BSG yields about 302 NL CH₄/kg COD, generating roughly 0.39 kWh of electricity/kg BSG and 1.71 MJ of thermal energy/kg BSG. Ultrasonic pretreatment enhances methane production up to four times (107 L CH₄/kg TVS) and reduces CO₂ emissions by 0.083 t CO₂eq/t BSG. Anaerobic co-digestion of BSG with other brewery waste increased the yield up to 88 mL CH₄/g TVS, generated approx. 0.348 kWh/kg TVS electricity, and reduced emissions by 0.114 kg CO₂eq/kg TVS. Bioethanol yields can reach 72%, while biohydrogen generation was up to 5154 mL H₂/g glucose. BSG pyrolysis provides up to 71.8% bio-oil, and its calorific value is 18–25 MJ/kg. BSG-derived activated biocarbon has a notable surface area (1792 m²/g) for lithium–sulfur batteries. The assessment showed that BSG’s transformation into bioenergy and energy storage materials aligns with waste reduction and sustainable development goals. However, future research on combined alternative wastes, integrated technologies, green nanotechnology, and artificial intelligence technology could lead to optimal performance and facilitate their industrial application. Full article

The introduction of sustainable practices into waste management can have a favorable environmental impact, increase resource value, and yield economic gains. Hydrothermal technologies have strong potential for the production of up-cycled ingredients from biowaste (amino acids, sugars, phenols, pharmacologically active compounds, etc.), enabling high energy recovery (50–80%) from biowaste with net-negative carbon emissions. This review discusses the use of subcritical and supercritical water technologies for sustainable valorization of biowaste and conversion of biomass into high-value chemicals and biofuels. The potential for the extraction/generation of bioactive compounds from plant and animal waste is presented, emphasizing the efficiency, compound stability, and bioactivity of the fractions obtained. The possibilities of simultaneous extraction of added-value compounds and hydrolysis of feedstock biopolymers by these technologies are elaborated. The review further addresses the production of biofuels through hydrothermal carbonization for solid fuels, hydrothermal waste liquefaction for liquid fuels, and supercritical water gasification for gaseous fuels. The paper highlights the environmental and economic advantages of technologies based on sub- and supercritical water over conventional chemical and fermentative routes, emphasizing their contribution to a circular bioeconomy by converting biowaste into value-added products and sustainable energy sources. Full article

Thermoacoustic oscillations are excited sound waves in systems with large temperature gradients. Thermoacoustic engines and refrigerators can be constructed using porous materials to enhance the acoustic power produced and facilitate heat pumping for refrigeration. Porous materials can also be utilized as catalytic beds to convert between the two spin-isomers of hydrogen: orthohydrogen and parahydrogen. The conversion between ortho- and parahydrogen is either endothermic or exothermic, and the composition of the isomers manipulates the heat capacity of the fluid. This study experimentally investigates ortho-parahydrogen conversion in a thermoacoustic standing-wave engine with different oxidized catalytic materials. Recorded experimental measurements include the onset temperature ratio, acoustic pressure amplitude, and frequency of the thermoacoustic engine. The results depict a relationship between the oxidized materials and the acoustic amplitude. All oxidized materials promoted an increase in acoustic amplitude versus the pure metallic components. Steady-flow conversion was measured for brass oxide and iron oxide pellets; however, no conversion was detected for aluminum oxide or copper oxide pellets. The initial datapoints provide evidence that future cryogenic hydrogen thermoacoustic devices will need to account for the spin isomer conversion inside the stack. New flow-through regenerating liquefiers can also be constructed, which convert orthohydrogen to parahydrogen during liquefaction. Full article

Liquefaction phenomena are strongly influenced by the depositional evolution of the area, including sediment grain size, depositional age, shallow layering, and groundwater depth. This study focuses on a 560 km² wide sector of the eastern Po River Plain (northern Italy), encompassing part of the modern Po Delta, to evaluate the susceptibility of the different geological units to liquefaction. A comprehensive dataset was compiled, integrating lithological, chronological (¹⁴C), geomorphological, hydrological, and hydrogeological information, together with satellite imagery, historical and modern maps, archaeological evidence, and subsurface data from core drilling and CPTu tests. The integrated analysis allowed us to reconstruct a liquefaction susceptibility map recognizing four classes: very high (4% of the investigated area), high (26%), moderate (20%), and non-susceptible (50%). CPTu-based statistical analyses confirm that the Liquefaction Potential Index (LPI) increases with higher susceptibility classes and decreases with increasing groundwater depth (0.5, 1.5, and 3.0 m scenarios). These results provide a scientific basis to support sustainable land management and governance strategies in the Po Delta, an area of high environmental, cultural, and economic value, a large sector of which is included in the Natura 2000 network. Full article

Daqu is a key starter used in Baijiu production, and its microbial composition and associated metabolic functions play critical roles in fermentation performance and flavor development. This work aimed to reveal how Daqu-making temperature regulates microbial community divergence and subsequent metabolite formation via multi-omics analysis so as to provide theoretical guidance for Daqu quality control. In this study, physicochemical analysis, metagenomic sequencing, and metabolomic profiling were combined to investigate the microbial community structure, functional differentiation, and metabolite characteristics of nine Daqu samples collected from six major Baijiu-producing regions in China. The temperature during Daqu preparation was found to be a primary factor driving microbial community assembly and functional specialization. Medium-temperature Daqu exhibited higher saccharifying activity (up to 867 U) and greater microbial diversity with the enrichment of amino acid metabolism-related pathways, indicating enhanced protein degradation and amino acid utilization for the formation of flavor precursors. In contrast, high-temperature Daqu showed stronger capacities for carbohydrate degradation and conversion, particularly in starch and sucrose metabolism, which were closely associated with the enrichment of thermotolerant fungi and bacteria. LEfSe analysis identified 47 distinct microbial biomarkers (LDA score > 3.0), which could differentiate between medium- and high-temperature Daqu. Redundancy analysis indicated that environmental factors (moisture and acidity) together with functional properties (fermentation, esterification, liquefaction, and saccharification) act as key drivers of microbial functional patterns. Metabolomic analysis further revealed that medium-temperature Daqu had higher abundances of esters and fatty acids, whereas high-temperature Daqu had higher proportions of alcohols and ketones. Taken together, these results provide a multi-omics perspective on temperature-driven microbial functional differentiation in Daqu and offer a scientific basis for quality-oriented regulation and process optimization in Baijiu production. Full article

The development of hydrogen fueling processes is an essential infrastructure component needed for the adoption of hydrogen-fueled vehicles as a transportation technology. This study provides techno-economic analysis (TEA) for two hydrogen fueling pathways (Case A, Case B), one of which (Case A) does not employ hydrogen liquefaction, while the other one (Case B) does. Both cases consider the same conditions as one another, of gaseous hydrogen inlet availability and gaseous hydrogen outlet dispensing. The TEA analysis carried out is based on data supported from the literature and process flowsheet UNISIM^® software simulations. The obtained TEA results indicate that the levelized cost of hydrogen (LCOH) of the gaseous hydrogen Case A is USD 4.20/kg H₂, which is lower than the LCOH of the liquefied hydrogen Case B, which is USD 10.14/kg H₂. Given the energy equivalence of a gallon of gasoline to kg H₂, and the higher efficiencies of hydrogen fuel cell vehicles over gasoline vehicles, the above conditions suggest that Case B fueling (with hydrogen liquefaction) involves high energy consumption and may delay the growth of hydrogen-fuel-based transportation technology, while Case A fueling (no hydrogen liquefaction) will likely become preferrable over both Case B hydrogen fueling and gasoline fueling, thus accelerating the growth of hydrogen-fuel-based transportation technology. Full article

Cyclic triaxial tests are often used to evaluate the behavior of soils under seismic loads. The stress conditions imposed on a soil specimen during a cyclic triaxial test, however, are very different than those acting on an element of soil during an earthquake. One major difference is that the element in the field is subjected to a change in total confining stress, whereas in a conventional cyclic triaxial test the total confining stress (as applied through the cell pressure) is held constant. This use of constant cell pressure is usually justified by the assumption that in a saturated specimen the change in total stress is offset by a change in pore pressure, thus resulting in no change in the effective confining stress or liquefaction susceptibility. A laboratory study using cyclic triaxial tests was conducted on several soils to assess the validity of this assumption. For each soil, two series of stress-controlled cyclic triaxial tests were run: one set with a constant cell pressure, and thus a constant total confining stress, and a second set with a variable total stress/cell pressure. These tests were then compared in terms of both the resulting cyclic resistance curves and the amount of energy dissipated to trigger liquefaction. It was found that the two conditions of confining stress yielded results that were not statistically different. Therefore, the assumption that the change in pore pressure caused by the variation in total stress is offset by the change in pore pressure and thus results in no change in effective stress or liquefaction susceptibility appears valid. Based on these findings, cyclic triaxial tests performed with constant cell pressure, and thus a constant total confining stress, provide valid results for liquefaction analyses. Full article

Traditional cryogenic air separation units are unsuitable for distributed, small-scale liquid oxygen production. Cryocooler-based liquefaction technology offers an alternative solution, featuring a large cooling capacity, high efficiency, a compact structure, and rapid start–stop capability. In this paper, an oxygen liquefaction system based on a high-capacity Stirling cryocooler was developed. Because the heat transfer performance of cryocoolers varies significantly across different temperature ranges, heat exchanger designs must be tailored to specific operating conditions. However, research on cold-end heat exchangers for large-capacity cryocoolers used in liquefaction systems remains limited. In the liquid oxygen temperature range, factors such as liquid film formation and incomplete condensation severely affect heat transfer performance and must be considered. In this paper, numerical simulations were performed to analyze the condensation behavior of oxygen, with particular attention paid to the matching between the heat exchange structure and the cooling capacity. Subsequently, a small-scale experimental system was constructed and tested. The successful operation of the experimental system validated the feasibility of the proposed heat exchanger design. Under the conditions of 300 K and an oxygen inlet gauge pressure of 0.45 MPa, the system achieved a liquefaction capacity of 7.4 L/h, corresponding to a cooling capacity of 787 W. The specific power consumption was 0.89 kW·h/kg, with a coefficient of performance (COP) of 0.116. This performance is competitive among small-scale cryocooler-based oxygen liquefaction systems. This study provides both theoretical and experimental support for further performance optimization and engineering application of such cryocoolers in liquid oxygen production. Full article

Hydrothermal liquefaction (HTL) is a promising route for converting wet biomass into bio-oil, but isolated model-component results do not necessarily describe naturally integrated lignocellulosic matrices. Here, lignin, cellulose, and hemicellulose were examined under subcritical HTL conditions (240–320 °C, 5–60 min, and water-to-biomass ratios of 2:1–20:1), and peanut shell and bamboo were used as two representative real feedstocks. At 300 °C and 30 min, lignin gave the highest bio-oil yield (45.36 wt%) and an oil enriched in phenolic compounds (>80% relative GC-MS peak area), whereas cellulose and hemicellulose gave lower oil yields (23.00 and 13.06 wt%, respectively) and larger aqueous-phase fractions. Oil-phase carbon and energy recoveries followed the order lignin (48.2% and 50.5%) > cellulose (32.4% and 35.9%) > hemicellulose (17.7% and 19.2%). A weighted additive reference constructed from the independent model-component results underpredicted phenolics and overpredicted carbohydrate-derived oxygenates in the real-biomass oils. For peanut shell and bamboo, the measured phenolic fractions were 68.85% and 64.11%, compared with additive-reference values of 47.66% and 34.17%, while the measured furanic fractions were 1.27% and 9.76%, compared with 12.12% and 17.88%. These directionally consistent deviations indicate non-additive product redistribution in the tested real-biomass samples. Full article

The stability of tailings dams is governed predominantly by the physical properties and geotechnical behavior of their primary construction material—tailings. Consequently, a systematic understanding of these characteristics is of great significance for the rational design and long-term stable operation of tailings dams. This review focuses on the physical properties and geotechnical behavior observed in different types of tailings. In terms of physical properties, the particle size distribution exhibits a pronounced hydraulic classification characteristic within the impoundment, consisting predominantly of silt-sized particles and displaying an overall trend toward finer gradation. The mineralogical and chemical composition is dominated by quartz, hematite, and silicates. However, significant spatial variability exists both between different tailings types and across distinct zones within the same tailings pond. Regarding geotechnical behavior, the permeability of tailings is governed by a fines content threshold: below this threshold, permeability decreases with increasing fines content, while beyond it, the permeability stabilizes. When studying consolidation and compression behavior using slurry specimens, the compression curves exhibit nonlinear characteristics, primarily described by the modified Gibson theory. The shear behavior of tailings is significantly influenced by confining pressure, drainage conditions, anisotropy and stress paths. The presence of transitional behavior leads to the critical state line determined based on a single sampling method erroneously assessing the dilation/cosntraction characteristics of in situ tailings, thereby affecting the assessment of liquefaction risk. Future research should focus on the seepage, consolidation and shear properties of clayey fine-grained tailings and unsaturated tailings, and aim to elucidate the key controlling factors of transitional behavior to enhance the reliability of tailings dam stability assessments. Full article

Main engine load varies continuously, whereas onboard carbon capture columns are installed with fixed capacities. For liquefied natural gas (LNG)-fueled ships, this mismatch between design and operation makes off-design robustness, rather than nominal-point performance, the governing sizing criterion. This study developed a variable-load design window for onboard monoethanolamine CO₂ capture and evaluated a dual-loop organic Rankine cycle (ORC) as a secondary thermal integration option. A verified process model was applied to a 5 × 5 design–operating matrix (D50–D90/O50–O90). The mismatch was strongly asymmetric. When operating load did not exceed design load, capture rate remained near 90%; under overload, absorber treated only the design-point-equivalent exhaust-gas flow, causing capture performance to deteriorate rapidly. The mean CO₂ avoided rate increased from 57.4% at D50 to 70.4% at D90, while absorber diameter increased from 3.23 to 4.06 m. D70 emerged as the balanced option for low- to medium-load services, D80 marked the transition before full robustness, and D90 was robustness-oriented for frequent high-load operation. The ORC recovered 104–185 kW net power and supplied 231–410 kW LNG-side heating. Results support capacity selection before ORC application; CO₂ liquefaction and storage, voyage-weighted validation, and shipboard ORC feasibility remain outside the present scope. Full article

This study presents a comprehensive analysis of a landslide that occurred in February 2024 in the Tau-Samal district of Almaty, Kazakhstan. Characterized by rapid onset and anthropogenic influence, this event resulted from a complex interaction of environmental and anthropogenic factors. Specifically, the landslide was triggered by seasonal temperature fluctuations leading to multiple freeze–thaw cycles, localized microseismicity (magnitude 3.5 on 4 February 2024), and a major water main break resulting in localized flooding of loess soils. The study utilizes an integrated landslide susceptibility index (LSI) model, which combines the analytic hierarchy process (AHP) for factor weighting. Validation was conducted by comparing the spatial distribution of high-susceptibility zones derived from the LSI model with the actual location of the landslide. Geotechnical studies highlight the susceptibility of Almaty loess, focusing on parameters such as cohesion, internal friction angle, and liquefaction potential. The findings highlight the need for climate-adapted urban policies and improved geotechnical monitoring in high-risk loess areas. This study contributes to a regional understanding of Tien Shan geohazards by placing the Tau-Samal event within the broader context of seismically and hydrologically driven slope processes. Full article

This work presents the thermodynamic design and performance assessment of an integrated process line for the separation, liquefaction, storage, and valorization of carbon dioxide (CO₂) and nitrogen (N₂) from flue gas streams. The proposed system aims to combine carbon capture with cryogenic energy storage by exploiting the thermophysical properties of the main flue gas constituents. A representative flue gas derived from complete methane combustion (9.5% CO₂, 71.5% N₂, and 19% H₂O by volume) is considered as the feed stream. The process is developed and simulated in DWSIM v9.0.5, adopting a steady-state mass and energy balance framework coupled with rigorous thermodynamic modeling of phase equilibria and unit operations. The plant configuration is based on sequential cooling, compression, and expansion stages, enabling the selective condensation of H₂O, CO₂, and N₂ at different temperature levels. The system integrates heat exchangers, compressors, pumps, turboexpanders, phase separators, and cryogenic storage tanks, while a portion of the liquefied CO₂ is reused as an energy carrier through vaporization and expansion in a dedicated turbine. The results demonstrate that the process achieves a CO₂ capture ratio of 81.7%, with a specific electric consumption (SEC) of 10.44 kWh/kg_CO2 and 1.71 kWh/kg_N2. The overall net electric demand is 1.29 kWh/kg of treated flue gas, while the round-trip efficiency (η_RT,CO2) is 18.6%. A significant amount of energy can further be recovered from the “waste” exhaust water stream (12.94 kg_L-H2O/kg_flue-gas, at 91 °C and 1.2 bar) up to 800 Wh/kg_flue-gas, improving the performance of the entire process (SEC_CO2: 3.86 kWh/kg_CO2, η_RT,CO2: 69.8%). The study confirms the thermodynamic feasibility of the proposed configuration and identifies nitrogen liquefaction as the dominant energy-intensive step. Future optimization efforts should therefore focus on reducing exergy destruction in the deep cryogenic section through improved heat integration, enhanced cold-energy recovery, optimized compression–expansion staging, and reduced pressure losses. Full article

Understanding the atomic-scale mechanisms of coal pyrolysis is essential for efficient coal utilization and carbon-neutral energy strategies, yet conventional computational approaches often struggle to balance between the high accuracy of quantum-chemical calculations and the efficiency of reactive force fields. To overcome this limitation, we proposed a multiscale computational framework integrating high-throughput density functional theory (DFT) calculations, ReaxFF-based configuration sampling, YARP reaction enumeration, and DPA3-based machine learning potentials (MLPs). Two coal-specific MLPs, DPA3-coal and DPA3-coal@dftb, were constructed and systematically benchmarked on both small molecular systems and larger C20–30 coal fragments extracted from MD simulations. DPA3-coal@dftb model demonstrated significantly improved accuracy over ReaxFF in predicting energies and atomic forces while maintaining good transferability. To balance computational efficiency and accuracy in large-scale simulations, the DPA3-coal model was employed to perform accelerated reactive molecular dynamics simulations of a Solomon-type bituminous coal molecule from 1600 to 2600 K. The simulations revealed temperature-dependent evolution of coke, tar, and gas products, including secondary condensation and deep-cracking processes at elevated temperatures. Higher-level DFT calculations further confirmed the thermodynamic consistency of key reaction pathways involving radical formation, H-transfer, recombination, and CO generation, indicating that coal-specific MLPs provide an effective atomistic tool for investigating mechanistic trends in coal pyrolysis. Full article