Search Results (946)

During natural gas production and transportation, multi-stage pressure regulation is often required to meet downstream pressure demands, resulting in substantial waste of residual pressure energy at high-pressure wellheads. This study focuses on high-pressure natural gas at the wellhead of the XC gas well in western Sichuan. Based on thermodynamic and exergy analysis, Aspen HYSYS was employed to simulate residual pressure power generation processes, and a systematic comparison was conducted between single-stage and multi-stage expansion schemes. Under operating conditions of an inlet pressure of 20 MPa, an inlet temperature of 70 °C, and a flow rate of 50 × 10⁴ m³/d, the influence of operating parameters on power generation performance was analyzed. The results indicate that power output increases with increasing natural gas flow rate and inlet temperature but decreases with increasing outlet pressure. Under large pressure differential conditions, single-stage expansion is unable to meet the requirements of high-pressure wellhead residual pressure power generation due to excessive temperature drop and limitations in existing expander performance. On this basis, two-stage, three-stage, and four-stage expansion power generation processes were further developed, and the effects of intermediate pressure selection on power output, heating demand, and pressure energy recovery efficiency were systematically examined. The results show that operating under equal expansion ratio conditions enhances pressure energy utilization. By comprehensively comparing power generation performance, heating power requirements, and economic feasibility, the two-stage expansion scheme was identified as the most favorable option under the investigated operating conditions, providing a practical reference for process design and engineering applications of high-pressure natural gas wellhead residual pressure power generation. Full article

Mobile thermal energy storage (M-TES) demonstrates significant commercialization potential in industrial waste heat recovery, distributed heating, and clean heating applications, which is primarily based on three technical pathways: sensible heat storage, latent heat storage using phase change materials (PCMs), and thermochemical heat storage. The updated status of M-TES, mainly on PCMs and thermochemical ones, and the challenges facing application were reviewed, and potential development trends were discussed in the present study. Sensible heat storage is relatively mature and cost-effective; however, it suffers from low energy density and comparatively high heat loss during storage and transport. Latent heat storage utilizes the phase transition enthalpy of PCMs to store thermal energy, offering higher energy density and near-isothermal heat release, making it a focal point of current academic and industrial research. Nevertheless, latent heat storage still faces technical bottlenecks, including low thermal conductivity, phase separation, and supercooling of PCMs. Thermochemical heat storage relies on reversible chemical reactions to convert and store thermal energy as chemical energy, theoretically achieving the highest energy density and minimal heat loss. However, due to its technical complexity and high system cost, thermochemical storage remains largely in the early stages of research and demonstration. Overall, as a bridge between heat supply and demand, the development trend emphasizes the design of high-performance composite PCMs, enhanced system integration, and intelligent operational management. However, its large-scale deployment is still constrained by challenges related to energy density, heat transfer enhancement, long-term material stability, and techno-economic feasibility. Full article

Biodiesel fuel produced through transesterification is mainly used in blends with conventional diesel fuel (D100). The analysis of the combustion process parameters for each specific biodiesel fuel represents the basis for a rational approach to the utilization of available motor fuel quantities. In this study, the differential and cumulative heat release laws during the combustion of D100 and blends of biodiesel fuel made from waste grape seed oil and D100 were analyzed. In addition, the engine efficiency and economy for the cases of using the aforementioned fuels were analyzed. The tests were conducted on a single-cylinder, air-cooled diesel engine with direct fuel injection. The engine testing was conducted for two engine loads; that for which the brake was a mean effective pressure of 4.2 bar, and for the full load, that for the brake was a mean effective pressure of 5.6 bar at engine speeds of 1635 rpm, 1937 rpm, and 2239 rpm. All experimental work was conducted for conventional diesel fuel D100 and for biodiesel diesel blends B7 and B14. The combustion rates of D100, a blend containing 7% of biodiesel by volume (B7), and a blend containing 14% of biodiesel by volume (B14) were examined. However, the higher combustion rate of the B14 blend, particularly during the combustion of the first 50% of the fuel mass per cycle, could have a positive impact on the fuel economy of the working cycle and the brake thermal efficiency (BTE). The maximum heat release rates for D100, B7, and B14 at full load and an engine speed of 2239 rpm are 115.65 J/deg, 148.01 J/deg, and 152.99 J/deg, respectively. At full load and engine speeds of 1635 rpm and 2239 rpm, the brake thermal efficiencies (BTEs) for D100, B7, and B14 were 0.301, 0.285, and 0.296 and 0.281, 0.273, and 0.277, respectively. Under other tests, the highest BTE was observed for the B14 blend. Therefore, from the perspective of brake thermal efficiency (BTE), the most favorable blend for application is B14. Full article

Thermoacoustic power generation holds significant promise for applications such as solar thermal utilization, industrial waste heat recovery, and distributed energy systems, owing to its high efficiency and reliability. Conventional standing-wave and traveling-wave thermoacoustic generators, however, are often limited by bulky resonators and substantial acoustic power dissipation. Replacing the resonator with a linear alternator (LA) offers an effective means to improve system compactness and output performance. Nonetheless, under standing-wave acoustic conditions, the LA’s large piston swept volume increases the device size, thereby constraining overall compactness. To address this limitation, a novel moving-magnet LA with electromagnetic components integrated into the moving piston is proposed. Compared to conventional configurations, this design significantly reduces the size and weight of the alternator. Furthermore, the influence of different magnetic circuit configurations on output performance is systematically investigated, enabling optimization of the alternator design. Results demonstrate that the proposed alternator achieves a more compact structure while delivering output performance comparable to that of conventional external magnetic-circuit designs, thereby validating the feasibility of the proposed approach. Full article

The steam generator is a core component of nuclear power plants that facilitates heat exchange between the primary and secondary circuits, directly impacting the overall operation of the plant in terms of safety and reliability. During prolonged operation, the heat transfer tubes of the steam generator are subjected to erosion, corrosion, and cracking due to high-temperature, high-pressure fluid impact and vibration. Existing in-service inspection strategies for heat transfer tubes generally employ fixed intervals and coverage, failing to effectively differentiate the actual risk of tubes in various regions, leading to wasted inspection resources or safety hazards. This paper proposes a dynamic inspection and plugging management strategy based on flow-induced vibration (FIV) analysis, specifically utilizing the flow stability ratio (FSR). By calculating the FSR of heat transfer tubes, the strategy categorizes them into high-risk, medium-risk, and low-risk regions, and dynamically adjusts inspection frequency and coverage based on these risk levels. Theoretical analysis and validation with actual data demonstrate that this strategy can improve inspection efficiency and ensure the safety of the steam generator. Full article

Thermochemical/catalytic co-processing of biomass and solid wastes is a promising route for waste valorization, low-carbon energy recovery, and the co-production of fuels, chemicals, and carbon materials. Conventional pathways, including pyrolysis, gasification, liquefaction, and carbonization, provide the basic framework for mixed-feed conversion. Emerging routes, such as flash Joule heating, microwave-assisted conversion, plasma processing, supercritical water treatment, solar-driven systems, and machine-learning-assisted optimization, further expand opportunities for process intensification and selective upgrading. Owing to feedstock complementarity, including hydrogen donation from plastics, catalytic effects of ash minerals, and interactions among reactive intermediates, co-processing can enhance deoxygenation, hydrogen generation, aromatization, and carbon utilization. Major challenges remain, however, including feedstock heterogeneity, reactor scale-up, catalyst stability, and the limited transferability of laboratory-scale synergy to realistic waste streams. Future progress should therefore focus on continuous validation, mechanistic clarification, and integrated techno-economic, life-cycle, and data-driven assessments. Full article

To achieve the large-scale, high-value utilization of vanadium–titanium slag (VTS) in the metallurgical industry, this study replaces blast furnace slag (BFS) with VTS to construct a quaternary all-solid-waste cementitious system composed of VTS, BFS, steel slag (SS), and desulfurization gypsum (DG). It systematically investigates the effects of VTS content (0–60%) on the mechanical properties, leaching toxicity, and hydration heat behavior of the system. XRD, TG–DSC, and SEM–EDS techniques are employed to explore the influence of VTS on hydration behavior and microstructural evolution. The results show that when VTS replaces 30% of the BFS (A3, VTS:BFS:SS:DG = 3:3:3:1), the 28-day compressive strength reaches 31.33 MPa. The leaching concentrations of heavy metals in all specimens are far below the standards for drinking water quality. Hydration heat analysis reveals that the incorporation of VTS advances the acceleration period of hydration. The A3 specimen maintains a relatively high heat release rate in the middle and later stages (after 72 h), and its cumulative heat release is significantly higher than that of the system without VTS, revealing the “slow hydration” mechanism of VTS at later stages. The [SiO₄]–[AlO₄] bonds in VTS undergo a depolymerization–repolymerization process. In addition, an appropriate amount of VTS promotes the deposition of hydration products such as ettringite (AFt), C–S–H, and C–A–S–H gels through micro-filling effects and heterogeneous nucleation, thereby improving the microstructure of the system. However, excessive VTS (≥45%) significantly inhibits the hydration reaction and reduces gel formation due to the decrease in highly reactive BFS components and the increased TiO₂ content. This study provides new insights into the resource utilization of VTS in multi-solid-waste cementitious materials. In addition, VTS-based cementitious materials are suitable for practical scenarios with low early strength requirements, such as goaf backfilling. Therefore, future studies should further investigate the long-term sulfate resistance and carbonation resistance of these materials under real application conditions. Full article

Alternative fuel and greenhouse emissions are always a keen focus for researchers aiming to cater to energy demands. There is an urgent need to find new clean and inexhaustible energy sources. In the past few years, hydrogen has gained attention from researchers as a green fuel. The scientific and policy maker circles have now widely recognized the practicality of hydrogen as an energy carrier through the due to its clean combustion, ease of transportation, distribution, and utilization. Different ways of its production and its use in different applications have also been widely studied. In this study, a review is carried out on how to produce hydrogen using the electrolysis process by renewable energy and its potential for application in different industries. Hydrogen gas can be used as a fuel to power catalytic boilers, gas-powered heat pumps, and direct-flame combustion boilers that are more or less the same as natural gas boilers. A large variety of district heating techniques can be repurposed to employ hydrogen cost-effectively. The use of hydrogen gas is not limited to combustion engines and industrial applications but is also applicable for house heating purposes. Finally, it is suggested that an alkaline electrolyzer could be energized with renewable sources to produce hydrogen which could be used as an alternative auxiliary fuel for the incineration system in managing municipal solid waste. This could be a step towards a green environment in terms of alternative clean fuel and municipal solid waste management. Full article

A low-titanium-slag-based multi-solid-waste cementitious system was developed for cemented paste backfill. The cementitious binder was prepared from low-titanium slag (LTS), steel slag (SS), municipal solid waste incineration (MSWI) fly ash, and flue gas desulfurization gypsum (FGDG), while lead–zinc tailings were used as the aggregate for backfill materials preparation. The activation of low-titanium slag, proportion optimization, and strength development mechanisms were systematically investigated. Mechanical grinding effectively activated low-titanium slag, and its activity index reached 108% after 90 min of grinding at 28 d. Steel slag alone could not fully activate low-titanium slag in the ternary system, whereas the incorporation of MSWI fly ash significantly enhanced the synergistic activation effect. The quaternary system with 40% MSWI fly ash replacement showed higher cumulative heat release and better later-age strength. The optimum backfill proportion was a solid mass concentration of 81% with a binder-to-tailings ratio of 1:4, yielding a 28 d compressive strength of 11.07 MPa with satisfactory flowability and setting behavior. Microstructural results indicated that the continuous formation of ettringite and gel phases promoted pore refinement and matrix densification. Moreover, the leaching concentrations of Pb, Zn, Cr, and soluble Cl were all below the relevant groundwater quality limits. These results demonstrate a feasible route for the high-value co-utilization of low-titanium slag and MSWI fly ash in cemented backfill materials. Full article

Aiming to improve cooling and dehumidification performance in air conditioning systems and to meet the trend toward environmentally friendly refrigerants, this study proposes a coupled system that combines a CO₂ transcritical refrigeration cycle (CTRC) with a liquid desiccant dehumidification cycle. The system takes advantage of high-grade waste heat from the exothermic side of the CTRC to drive the regenerating process of the liquid desiccant dehumidification. A cooling evaporator is adopted to cool indoor air, while another evaporator (i.e., Evaporator II) is utilized to cool the concentrated solution, improving dehumidification capacity and enabling independent control of sensible and latent heat loads. Through thermodynamic modeling and the exergy analysis model, a mathematical model of the system is developed to examine how key parameters (such discharge pressure and the CO₂ mass flow rate ratio in Evaporator II (λ)) affect performance and to analyze exergy loss features. Results show that the system’s coefficient of performance (COP) and dehumidification coefficient of performance (COP_deh) initially rise and then fall with increasing CTRC discharge pressure, achieving an optimal pressure of around 10,500 kPa (COP up to 4.32) under a specific working condition, surpassing those of standalone CTRC systems. Properly increasing λ enhances dehumidification capacity and energy efficiency, with a low specific dehumidification energy (SDE) of 0.2033 kWh/kg, indicating high economic efficiency. Most exergy losses occur in the CO₂-solution heat exchanger and dehumidifier (over 60% of total losses). The system’s maximum exergy efficiency reaches 12.4%, leaving room for further improvements. This coupled system offers an efficient, eco-friendly way for air conditioning in high-humidity environments, combining cooling and dehumidification with the potential for energy recovery. Full article

This study presents a fully integrated process for the flexible conversion of biogenic waste into synthetic natural gas (bio-SNG) and electricity centred on a 100 kWth dual concentric bubbling fluidised bed steam gasifier. The raw syngas is processed in a high-temperature gas cleaning section, and the resulting clean, H₂-rich syngas is directed to three alternative downstream configurations: (i) conventional methanation, (ii) enhanced methanation with external H₂ supplied by a reversible solid oxide cell (rSOC), and (iii) electricity generation via the same rSOC operating in fuel cell mode. The overall process is modelled in Aspen Plus, in which the gasification section is constrained by experimentally derived syngas data, while downstream units are described through thermodynamic and kinetics-based models. Methanation is simulated using a plug-flow reactor model based on validated kinetic expressions, while the rSOC operating in electrolysis and fuel cell mode is modelled using performance parameters of commercial stacks. A plant-wide heat integration strategy based on composite curve analysis is implemented to maximise internal heat recovery and minimise external utilities. The enhanced methanation configuration enables the production of bio-SNG with high methane content (up to 93.3 vol.% dry, N₂-free), with a yield 0.72 kg/kg_Biomass and a fuel efficiency of 70.1%. In electricity production mode, the system reaches an electrical efficiency of 43.1% with complete elimination of auxiliary fuel through thermal integration. These results demonstrate the capability of a single integrated plant to flexibly switch between fuel synthesis and power generation, enhancing adaptability to fluctuating electricity and methane market conditions while maintaining high efficiency. Full article

The energy utilization of residual woody biomass is a relevant strategy for the decentralized energy transition and local waste management in rural areas. The objective of this study was to characterize (physically, chemically, and energetically) five types of residual biomass: pine branches, huinumo (this material refers to the long, thin pine needles that, after drying and falling, form a layer on the forest floor), cherry branches and leaves, and grass waste generated in the community of San Francisco Pichátaro, Michoacán, Mexico, in order to evaluate its viability for the production of densified solid biofuels. A comprehensive analysis was conducted, including moisture content, higher heating value, proximate characterization, structural chemical analysis (using the Van Soest method), elemental CHONS analysis, ash microanalysis (by ICP-OES), and a multicriteria analysis with normalized energy and compositional indicators. The results showed that huinumo and cherry leaves were the most outstanding biomasses, presenting the highest heating values (20.7 MJ/kg) and low moisture and ash contents. Pine branches obtained the most balanced results, characterized by their equilibrium in fixed carbon and lignin, as well as their low potassium content. The multicriteria analysis showed that there is no absolute optimal biomass; however, it indicates that pine branches and huinumo are the most robust feedstocks for the production of briquettes or pellets. The results confirm the significant technical and environmental potential of local lignocellulosic residues for the production of solid biofuels and for contributing to sustainable energy solutions at the local scale. Full article

This study investigates the development of a composite material based on agricultural plant waste from Kazakhstan, utilizing a multicomponent binder incorporated with rice husk ash. The implementation of low-clinker binders enables the full utilization of ash dumps from the Kyzylorda thermal power plant (TPP) and rice husk residues from local rice-processing enterprises. Physical and chemical analysis of the ash–cement stone revealed a reduction in portlandite content compared to control samples. Phase composition analysis indicated the presence of hydroaluminate C₄AH₁₃ and a reduction in calcite, suggesting accelerated crystallization of calcium silicate hydrates. The formation of crystalline phases and intergrowth structures is assumed to contribute to the strengthening of the gel-like matrix. Experimental optimization of the ash–cement binder with rice husk ash yielded compressive strengths ranging from 3.03 to 4.10 MPa at densities of 790–900 kg/m³, depending on the type of organic filler. These results confirm the feasibility of using locally sourced agricultural waste for the production of heat-insulating and structurally stable composite materials. Full article

Waste tyres, with their high carbon content and heating value that is greater than that of coal and biomass, present a potential feedstock for energy recovery. Similarly, automotive paint sludge (APS) is a hazardous waste rich in volatile and inorganics compounds, making it difficult to dispose of safely, but it also has potential for thermochemical conversion. Gasification is a thermochemical process which can turn such wastes into syngas, a mixture mainly composed of carbon monoxide and hydrogen that can be utilized to generate power and produce liquid fuels. To deal with challenges of single feedstock gasification, co-gasification combines two or more feedstocks, taking advantage of synergistic interactions to enhance syngas yield and overall efficiency. In this work, Aspen Plus simulation software is used to develop a model for the co-gasification of waste tyres and automotive paint sludge. Sensitivity analysis was performed with the aim of investigating and optimizing the overall process conditions of waste tyre and APS co-gasification. This study investigated the effect of air (ER) and water feed (SFR) and blend ratios on the adiabatic reaction temperature, product gas composition and heat value of the product syngas. Optimal operating ranges were identified as ER = 0.35–0.40 and SFR = 1.0–1.2 for tyre gasification, ER ≈ 0.50–0.55 for APS-only gasification, and ER = 0.40–0.48 with SFR = 0.8–1.0 for co-gasification blends. Adiabatic temperatures under recommended conditions were typically 700–800 °C. The LHV of syngas decreased with increasing ER, SFR, and APS fraction, falling from ~13 MJ/kg for tyre gasification to below 10 MJ/kg for APS-rich cases due to oxidation and dilution by CO₂ and ash. No positive synergistic effect in syngas quality was observed under thermodynamic equilibrium conditions. APS primarily acted as an ash-rich, low-carbon diluent, reducing CO concentration, heating value and adiabatic temperature. However, potential catalytic interactions from APS mineral matter, which are not represented in the equilibrium model, may produce synergistic effects in practical gasifiers. Full article

Carbon dioxide (CO₂) capture is a cornerstone of global carbon neutrality, yet the high energy penalty associated with solvent regeneration—particularly for monoethanolamine (MEA) systems—remains a major barrier to its sustainable deployment. This study presents a sustainable and high-performance catalytic solution using micro-sized iron oxyhydroxide (β-FeOOH). Characterized by a high specific surface area ($287 m²/g) and a synergistic distribution of abundant Lewis and Brønsted acid sites, the β-FeOOH catalyst significantly enhances CO₂ desorption kinetics. Experimental results demonstrate that the incorporation of β-FeOOH into a 30 wt% MEA solution increases the CO₂ desorption rate by 10.9% while simultaneously lowering the regeneration temperature from the conventional 120 °C to 85 °C. Such a reduction in thermal requirements offers a pathway to utilize low-grade industrial waste heat, drastically improving the process’s energy efficiency. Furthermore, the catalyst exhibited remarkable cyclic stability over ten consecutive cycles, maintaining its structural integrity and catalytic activity. These findings highlight β-FeOOH as an eco-friendly, cost-effective, and robust catalyst that aligns with the principles of green chemical engineering, offering a scalable strategy to enhance the sustainability of carbon capture operations. Full article