Search Results (1,213)

The operation of the superheated steam temperature system significantly impacts the safety and economy of thermal power units. To ensure its stable operation under large-scale variable load conditions, a modified active disturbance rejection control strategy based on parameter adaptation is proposed. Firstly, a typical superheated steam temperature system model is introduced, and the cascade control structure is applied to the model. Then, on this basis, a modified active disturbance rejection control strategy based on parameter adaptation is proposed, and the parameter tuning method of the modified active disturbance rejection control is introduced. Finally, the control performance of the proposed control strategy under a wide range of variable loads is verified through comparative simulations under nominal working conditions and uncertain working conditions. To further illustrate the effectiveness of the proposed strategy, the method is applied to a certain 660 MW unit in the field. After implementing the method, the fluctuation range of superheated steam temperature on the A and B sides decreased to only 34.0% and 53.0% of the original, respectively, and the fluctuation variance on the A and B sides decreased to only 28.5% and 43.3% of the original, respectively. The above field application results fully demonstrate that the control strategy proposed does not merely remain at the theoretical simulation level, but is a key technical means that can be effectively implemented and effectively solve the problem of superheated steam temperature control in thermal power units. Full article

Carbon capture is pivotal for achieving carbon neutrality; however, its high energy consumption severely limits the operational flexibility of power plants and remains a key challenge. This study, targeting a full flue gas carbon capture scenario for a 1000 MW coal-fired power plant, identified the dual-element (“steam” and “power generation”) coupling convergence mechanism. Based on this mechanism, a comprehensive set of mathematical model equations for the “carbon–electricity–heat” coupling process is established. This model quantifies the dynamic relationship between key operational parameters (such as unit load, capture rate, and thermal consumption level) and system performance metrics (such as power output and specific power penalty). To address the challenge of flexible operation, this paper further proposes two innovative coupled modes: steam thermal storage and chemical solvent storage. Model-based quantitative analysis indicated the following: (1) The power generation impact rate under full THA conditions (25.7%) is lower than that under 30% THA conditions (27.7%), with the specific power penalty for carbon capture decreasing from 420.7 kW·h/tCO₂ to 366.7 kW·h/tCO₂. (2) Thermal consumption levels of the capture system are a critical influencing factor; each 0.1 GJ/tCO₂ increase in thermal consumption leads to an approximate 2.83% rise in unit electricity consumption. (3) Steam thermal storage mode effectively reduces peak-period capture energy consumption, while the chemical solvent storage mode almost fully eliminates the impact on peak power generation and provides optimal deep peak-shaving capability and operational safety. Furthermore, these modeling results provide a basis for decision-making in plant operations. Full article

The increasing penetration of variable renewable energy sources intensifies grid imbalance and challenges the reliability of small-scale power systems. This study addresses these challenges by developing and analyzing a fully integrated hybrid energy system that combines biogas upgrading to biomethane, photovoltaic (PV) generation, hydrogen production via alkaline electrolysis, hydrogen storage, and a gas-steam combined cycle (CCGT). The system is designed to supply uninterrupted electricity to a small municipality of approximately 4500 inhabitants under predominantly self-sufficient operating conditions. The methodology integrates high-resolution, full-year electricity demand and solar resource data with detailed process-based simulations performed using Aspen Plus, Aspen HYSYS, and PVGIS-SARAH3 meteorological inputs. Surplus PV electricity is converted into hydrogen and stored, while upgraded biomethane provides dispatchable backup during periods of low solar availability. The gas-steam combined cycle enables flexible and efficient electricity generation, with hydrogen blending supporting dynamic turbine operation and further reducing fossil fuel dependency. The results indicate that a 10 MW PV installation coupled with a 2.9 MW CCGT unit and a hydrogen storage capacity of 550 kg is sufficient to ensure year-round power balance. During winter months, system operation is sustained entirely by biomethane, while in high-solar periods hydrogen production and storage enhance operational flexibility. Compared to a conventional grid-based electricity supply, the proposed system enables near-complete elimination of operational CO₂ emissions, achieving an annual reduction of approximately 8800 tCO₂, corresponding to a reduction of about 93%. The key novelty of this work lies in the simultaneous and process-level integration of biogas, hydrogen, photovoltaic generation, energy storage, and a gas-steam combined cycle within a single operational framework, an approach that has not been comprehensively addressed in the recent literature. The findings demonstrate that such integrated hybrid systems can provide dispatchable, low-carbon electricity for small communities, offering a scalable pathway toward resilient and decentralized energy systems. Full article

Crude distillation units operate as the most energy-intensive refinery operations and generate substantial carbon dioxide emissions. This research models the crude distillation system through its three main components: the atmospheric distillation unit, the naphtha stabilisation unit, and the vacuum distillation unit. The simulation platform Aspen HYSYS version 14.1 enabled optimisation of the preflash drum under product quality constraints, and the analysis included pinch analysis techniques and techno-economic evaluation. The optimisation results demonstrated an 8.95% reduction in atmospheric furnace duty, a 7.38% decrease in total hot utility consumption with the crude distillation system, and an increase in heat recovery capability from 35.57% to 42.71%. Although the preflash process alone decreases profitability because of increased steam demand, combining preflash operation with heat recovery measures maintains both energy conservation and favourable economic performance. The study shows that refinery optimisation requires treating the crude distillation system as a fully integrated process. This approach offers effective strategies to improve energy performance and reduce carbon dioxide emissions while sustaining economic viability. The work differs from previous studies by evaluating the entire distillation system as an integrated sequence and demonstrating how preflash optimisation affects overall energy demand, heat-recovery potential, and economic outcomes while maintaining product quality. Full article

With the expansion of renewable energy deployment, characterized by its variability, stabilizing power and heat supply has become a critical issue. To address this challenge, large-scale and low-cost energy storage technologies are essential, and thermal energy storage (TES) is considered one of the promising solutions. Among large-scale TES systems, Circulating Fluidized Bed TES (CFB TES) is a technology that stores energy as sensible heat in high-temperature sand and utilizes it for power generation using high-temperature steam or steam turbines when needed, offering high compatibility with existing infrastructure. While the underlying circulating fluidized bed system is a well-established technology, precise control of circulating particle flow rates remains a technical challenge due to differences from conventional circulating fluidized beds. In this study, we propose a mechanically simple and thermally durable flow control system that combines an orifice for stepwise flow adjustment and a J-valve (loop seal) for on/off particle transport. In this study, the flow characteristics of the orifice, the minimum fluidization velocity ($u_{mf}$≈ 0.076 m/s), the transient stabilization behavior, and the effects of downstream pressure (back pressure) were evaluated in lab-scale experiments. The results showed that particle flow rate follows a power-law relationship with the orifice diameter, stabilizes when fluidization velocity exceeds $u_{mf}$, and decreases linearly with increasing back pressure. Based on these findings, we established design guidelines incorporating orifice sizing, fluidization control, and back pressure compensation. Full article

The aim of this study is to assess the impact of extensive husbandry on slaughter characteristics and turkey meat quality in two utility types. The experiment was divided into two stages: for the first 6 weeks, 200 medium-heavy (MH) and heavy (H) turkey females were kept in intensive rearing conditions and then divided into a control (MHC/HC) and an extensive group (MHE/HE), with five replications in each group (10 birds per replication) for 10 weeks. In E groups, the balanced mixtures were gradually replaced with wheat at 30, 50, and 70% in subsequent feeding periods. Additionally, birds received green fodder (nettles, clover, and alfalfa) and steamed potatoes. After 16 weeks of rearing, birds were slaughtered, their carcasses were dissected, and the meat was assessed for technological traits (pH, L*a*b*, WHC, and tenderness), chemical composition (protein, ash, and fat), fatty acid profile, and sensory analysis. A higher proportion of liver and gizzard and a lower proportion of abdominal fat were found in the E groups, which resulted from more intensive mobility. Meat from these birds was less tender than that from females in the C groups, but it also contained considerably more protein and less fat. Lower values of fatty acid indices such as PI and AI, as well as a higher content of MUFA and a narrower n-6:n-3 ratio in meat from MH birds, indicate a stronger response of these birds to the extensive rearing system and confirm the health-promoting properties of their meat. The sensory evaluation of the meat meets the expectations of modern consumers regarding both the origin and taste of poultry meat. Full article

To balance the quantity of heat generated and consumed, thermal energy storage systems are crucial for power plants and district heating systems. Particularly when phase transitions and pressure variations are not adequately covered in the existing literature, their work frequently takes place under complicated, changing temperature and fluid dynamic settings. The goal of this research is to create a thermodynamic model that incorporates the effects of steam condensation, steam injection, and heating failures to describe the transient behaviour of temperature and pressure in pressure vessels containing single-phase and two-phase fluids. To account for nonlinear, temperature-dependent steam properties, as well as initial and boundary constraints, the study proposes energy balance models for hot water and saturated steam cases. Numerical simulations evaluating sensitivity to parameter changes are presented alongside analytical solutions for isochoric and isobaric systems. The model also includes direct steam injection heating and the use of a heat exchanger. It explains the changes in temperature and pressure that occur in thermal energy storage systems over time, including significant events such as steam cushion collapse and condensate drainage. According to the sensitivity analysis, the main factors influencing the system’s safety limitations and transient dynamic phenomena are thermal power, heat exchanger capacity, and thermal insulation efficiency. The proposed thermodynamic model closes a major gap in the literature by providing reliable predictions of the transient behavior needed for the safe design and reliable operation of pressure vessels utilized for heat storage in district heating networks. This model can be used by engineers and researchers to optimize system design and steer clear of risky operational situations. Full article

This paper introduces the composition of the combined heat and power (CHP) generation system with low-temperature return water. Focusing on the Gujiao–Taiyuan heating system, it systematically analyzes the effects of key operational parameters, such as supply–return-water temperatures, circulating water flow, maximum back-pressure, and minimum supply-water temperature, on overall system energy consumption. The results indicate that lowering supply and return-water temperatures, increasing circulating water flow, raising the maximum back-pressure, and reducing the minimum supply temperature generally contribute to a decrease in the heating equivalent electricity. Furthermore, the study compares several operation regulation modes of the heating system, including two-stage quality regulation, two-stage quantity regulation, and staged quality–quantity regulation. It is concluded that staged quality–quantity regulation achieves the lowest energy consumption. The impacts of heating steam allocation and variable back-pressure under different heating loads are also examined. Based on these findings, an extraction steam reduction sequence is proposed following the principle of minimizing the system’s heating equivalent electricity, along with a strategy to lower the back-pressure of selected units during the early and late heating periods. Finally, an economic operation strategy for the CHP system with low-temperature return water is developed, integrating recommendations on circulating water flow, temperature settings, steam allocation, and back-pressure regulation across different heating loads, leading to improved energy efficiency and economic performance. Full article

Chemical looping gasification (CLG) based on interconnected fluidized beds is a viable technology to produce a syngas stream for chemical and fuel production. In this work, microalgae are studied for use in the CLG process; more specifically, the intrinsic kinetics of char gasification have been analyzed, as it is important for the fuel conversion and design of reactor systems. Char produced from fast pyrolysis was used in a thermogravimetric analyzer (TGA) for intrinsic kinetics analysis, and measures were made to eliminate the interparticle and external particle gas diffusion. The effect of typical operational variables, such as temperature, concentration of gasification agents (H₂O and CO₂), and concentration of gasification products (H₂ and CO), were investigated. The TGA data is used to derive a suitable gasification model that can best fit the experimental data. The fitting with experiments then generates values of the model’s kinetics parameters. Based on the model and the kinetics values, the activation energies in the gasification with steam and CO₂ were calculated to be 43.3 and 91.6 kJ/mol, respectively. The model has a good capability in the prediction of the gasification profile with H₂O and CO₂ under a complex reacting atmosphere. Full article

Decarbonizing industry, improving urban sustainability, and expanding clean energy use are key global priorities. This study presents a techno-economic analysis (TEA) and life-cycle assessment (LCA) of green hydrogen (GH₂) production via water electrolysis for low-carbon applications in the Central Asian region, with Uzbekistan considered as a representative case study. Solar PV and wind power are used as renewable electricity sources for a 44 MW electrolyzer. The assessment also incorporates recent advances in alkaline water electrolyzers (AWE) enhanced with metal–organic framework (MOF) materials, reflecting improvements in efficiency and hydrogen output. The LCA, performed using SimaPro, evaluates the global warming potential (GWP) across the full hydrogen production chain. Results show that the MOF-enhanced AWE system achieves a lower levelized cost of hydrogen (LCOH) at 5.18 $/kg H₂, compared with 5.90 $/kg H₂ for conventional AWE, with electricity procurement remaining the dominant cost driver. Environmentally, green hydrogen pathways reduce GWP by 80–83% relative to steam methane reforming (SMR), with AWE–MOF delivering the lowest footprint at 1.97 kg CO₂/kg H₂. In transport applications, fuel cell vehicles powered by hydrogen derived from AWE–MOF emit 89% less CO₂ per 100 km than diesel vehicles and 83% less than using SMR-based hydrogen, demonstrating the substantial climate benefits of advanced electrolysis. Overall, the findings confirm that MOF-integrated AWE offers a strong balance of economic viability and environmental performance. The study highlights green hydrogen’s strategic role in the Central Asian region, represented by Uzbekistan’s energy transition, and provides evidence-based insights for guiding low-carbon hydrogen deployment. Full article

This study investigates the influence mechanism of key factors on the heating value of syngas during underground coal gasification (UCG) and proposes an optimization path for enhanced energy conversion efficiency based on typical global field test data. Integrating data review and pattern analysis, it systematically explores the influence of core factors, including coal seam characteristics, reactor structure, and gasification agent ratio. It is found that the relationship between syngas heating value and coal rank is not simply linear, with representative heating values ranging from 4.13 to 11.96 MJ/m³. Medium-rank coal, characterized by “medium volatile matter and low ash content”, yields high-heating-value syngas when paired with air/steam as the gasification agent. Shaftless reactor structures demonstrate superior overall performance compared to shaft-based designs, with the representative heating value improving from 3.83 MJ/m³ to 7.8 MJ/m³. The combination of U-shaped horizontal wells with the Controlled Retracting Injection Point (CRIP) technology improves the heating value. Effective control over the syngas heating value can be achieved by optimized composition and ratio of the gasification agent, with representative value of 9.10 MJ/m³ in oxygen-enriched steam gasification compared to 4.28 MJ/m³ in air gasification. Based on an evaluation of data fluctuation characteristics, the significance ranking of the factors is as follows: gasification agent, coal rank, and reactor structure. Consequently, an engineering optimization path for enhancing UCG syngas heating value is proposed: prioritize optimizing the composition and ratio of the gasification agent as the primary means of heating value control; on this basis, rationally select coal rank resources, focusing on process compatibility to mitigate performance fluctuations; and then incorporate advanced reactor structures to construct a synergistic and efficient gasification system. This research can provide theoretical support and data references for engineering site selection, process design, and operational control of UCG projects. Full article

The Paris Agreement and related international climate frameworks aim to reduce global carbon intensity; however, carbon dioxide emissions from electricity generation remain high, motivating the development of coal–renewable coupling technologies to lower the carbon intensity of power production. Coal–renewable coupling refers to the technical integration of conventional coal-fired power systems with renewable energy sources such as wind and solar to form a synergistic and complementary energy supply system. At present, systematic reviews and comprehensive analyses of coal–renewable coupling technologies are still limited. Accordingly, this paper categorizes existing approaches into two pathways—deep flexible load regulation and co-firing-based emission reduction—and systematically reviews the current state of technological development, identifies key challenges, and discusses potential future directions. Deep flexible load regulation includes flexibility retrofitting of coal-fired units and the integration of energy storage modules, whereas co-firing-based emission reduction mainly involves the co-combustion of coal with zero-carbon fuels. The analysis focuses on large-scale coal-fired units, covering low-load stable combustion technologies, steam turbine retrofitting, and rapid start-up and shut-down strategies. For energy storage-assisted load regulation, both conventional options and emerging technologies such as molten salt and high-temperature solid particle thermal energy storage are examined. Zero-carbon fuels considered include biomass, ammonia, and hydrogen. Furthermore, the economic feasibility of the various technologies is evaluated, providing reference value for deep flexibility retrofitting and substantial emission reduction in large-scale coal-fired power plants. Full article

There is a significant demand for flexibility in steam turbines, including rapid cold starts and load changes, as well as operation at low partial loads. Both industrial plants and systems for electricity and heat generation are impacted. These new operating modes result in complex, asymmetric temperature fields and additional thermally induced stresses. These lead to casing deformations, which affect blade tip gap and casing flange sealing integrity. The exact progression of heat flux and heat transfer coefficients within the cavities of steam turbines remains unclear. The current methods used in the calculation departments rely on simplified, averaged estimates, despite the presence of complex flow phenomena. These include swirling inflows, temperature gradients, impinging jets, unsteady turbulence, and vortex formation. This paper presents a novel sensor and its thermal measurements taken on a full-scale steam turbine test rig. Numerical calculations were performed concurrently. The results were validated by measurements. Additionally, the distribution of the heat transfer coefficient along the cavity was analysed. The rule of L’Hôpital was applied at specific locations. A method for handling axial variation in the heat transfer coefficient is also proposed. Measurements were taken under real-life conditions with a full-scale test rig at MAN Energy Solutions SE, Oberhausen, with steam parameters of 400 °C and 30 bar. The results at various operating points are presented. Full article

Accurate monitoring of shaft voltages and bearing currents in large turbo-generators is essential for promoting the sustainable operation of critical power infrastructure. Conventional monitoring systems often rely on threshold triggers that fail to identify early-stage degradation in shaft-earthing brushes. This paper presents an advanced diagnostic approach based on real-time shaft voltage and current measurements collected from four large utility-scale steam turbine generators. Through detailed analysis of time-domain waveforms, frequency-domain spectra, and current scatter plots, characteristic electrical signatures were established for four operational case studies for faults: (i) a floating voltage brush, (ii) a floating current brush, (iii) a worn brush, and (iv) oil/dust contamination. This study demonstrates that each fault produces a distinctive pattern, such as the suppressed RMS shaft voltage with transient spikes in floating voltage brushes, elevated DC offsets and even-order harmonics in floating current brushes, erratic waveforms and intermittent surges in worn brushes, and elevated DC bias with increased current under contamination. These findings establish actionable thresholds for predictive maintenance, fostering enhanced reliability, optimized asset life, and reduced maintenance-related environmental impact. Full article

This paper addresses the axiom of balance in Flow Theory from a physiological-and-group-based approach by a quasi-experimental study using mixed methods across two action–research cycles, each divided into pre-test, intervention, and post-test phases. The study involved 56 students in two control and two experimental groups attending robotics and design STEAM courses in natural settings, wearing Polar H10 bands. Each group participated in nine one-hour sessions, with the same instructor. While flow in control groups was measured with intuition-based teacher actions, in experimental groups the teacher received support from a synchronous physiological flow advisory system. Data from these groups were analysed using nonlinear techniques, finding preliminary evidence that suggests (1) more quickly reaching of the Zone of Proximal Development when the teacher has physiological guidance, (2) mathematical physiologically-based support for the axiom of balance of Flow Theory, and (3) nonlinear analysis in group contexts offer quantification to the previously found contradictions in Flow Theory. Moreover, these findings propose new hypotheses and potential redefinitions in Flow Theory. Full article