Search Results (446)

This study conducts an in-depth analysis of the dynamic characteristics of a single reheat steam turbine generator unit and its speed control system under variable operating conditions. A comprehensive simulation model was constructed to comprehensively evaluate the impact of the heat extraction system on the dynamic behavior of the unit, which integrates the speed control system, actuator, single reheat steam turbine body, and once-through boiler dynamic coupling. This model focuses on revealing the mechanism of the heat extraction regulation process on the core operating parameters of the unit and the system frequency regulation capability. Based on the actual parameters of a 300 MW heat unit in a power plant in Guangxi, the dynamic response of the established model under typical dynamic conditions such as extraction flow regulation, primary frequency regulation response, and load step disturbance was simulated and experimentally verified. The results show that the model can accurately characterize the dynamic characteristics of the heat unit under variable operating conditions, and the simulation results are in good agreement with the actual engineering, with errors within an acceptable range, effectively verifying the dynamic performance of the heat system module and the rationality of its control parameter design. This study provides a reliable theoretical basis and model support for the accurate simulation of the dynamic behavior of heat units in the power system and the design of optimization control strategies for system frequency regulation. Full article

Sanicro 25 (X7NiCrWCuCoNb25-23-3-3-2) steel is specifically designed for use in superheater components within the latest generation of conventional power plants. These power plants operate under conditions often referred to as super-ultra-supercritical, with steam parameters that can reach up to 30 MPa and temperatures of 653 °C for fresh steam and 672 °C for reheated steam. While last-generation supercritical power plants still rely on fossil fuels, they represent a significant step forward in more sustainable energy production. The most sophisticated facilities of this kind can achieve thermodynamic efficiencies exceeding 47%. This study aimed to conduct a detailed analysis of the initial precipitation processes occurring in Sanicro 25 steel within the temperature range of 700–900 °C. The temperature of 700 °C corresponds to the operational conditions of this material, particularly in secondary steam superheaters in thermal power plants that operate under ultra-supercritical parameters. Understanding precipitation processes is crucial for optimizing mechanical performance, particularly in terms of long-term strength and creep resistance. To accurately assess the microstructural changes that occur during the early stages of service, a digital twin approach was employed, which included CALPHAD simulations and experimental heat treatments. Experimental annealing tests were conducted in air within the temperature range of 700–900 °C. Precipitation behavior was simulated using the Thermo-Calc 2025a with Dictra software package. The results from Prisma simulations correlated well with the experimental data related to the kinetics of phase transformations; however, it was noted that the predicted sizes of the precipitates were generally smaller than those observed in experiments. Additionally, computational limitations were encountered during some simulations due to the complexity arising from the numerous alloying elements present in Sanicro 25 steel. The microstructural evolution was investigated using various methods, including light microscopy (LM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Full article

Magnetite (Fe₃O₄) provides a protective corrosion layer in the steam generators of nuclear power plants. The presence of monoethanolamine (MEA) in coolant water has a beneficial effect on corrosion processes. In that context, the adsorption of MEA and ethanol–ammonium cation on the {111} surface of magnetite was studied using the molecular dynamics (MD) method. A modified version of the mechanical force field (ClayFF) was used. The systems were simulated at different temperatures (423 K; 453 K; 503 K). Surface coverage data were obtained from adsorption simulations; the root-mean-square deviation (RMSD) of the target molecules were calculated, and their minimum distance to the magnetite surface was traced. The potential and adsorption energies of MEA were calculated as a function of temperature. It has been established that the interaction between MEA and magnetite is due to electrostatic phenomena and the adsorption rate increases with temperature. A comparison was made with existing experimental results and similar MD simulations. Full article

Heuristic optimization is used to find sustainable cogeneration steam power plants with steam reheat and supercritical main steam parameters. Design solutions are analyzed for steam consumer (SC) pressures of 3.6 and 40 bar and a heat flow rate of 40% of the fuel heat flow rate. The objective functions consisted in simultaneous maximization of global and exergetic efficiencies, power-to-heat ratio in full cogeneration mode, and specific investment minimization. For 3.6 bar, the indicators improve with the increase in the ratio between reheating and main steam pressure. The increase in SC pressure worsens the performance indicators. For an SC steam pressure of 40 bar and 9 feed water preheaters, the ratio between reheating and main steam pressure should be over 0.186 for maximum exergetic efficiency and between 0.10 and 0.16 for maximizing both global efficiency and power-to-heat ratio in full cogeneration mode. The average global efficiency for an SC requiring steam at 3.6 bar is 4.4 percentage points higher than in the case with 40 bar, the average specific investment being 10% lower. The Pareto solutions found in this study are useful in the design of sustainable cogeneration supercritical power plants. Full article

The operational efficiency of the main steam pipelines at thermal power plants is reduced due to several factors, including operating temperature, pressure, service life, and the frequency of process shutdowns, which contribute to the degradation of heat-resistant steels. The study aims to identify the features of changes in the sizes of grains and carbides along their boundaries, as well as mechanical properties (hardness, strength, plasticity and fracture toughness) along the wall thickness of both pipes in the initial state and after operation with block shutdowns. Preliminary electrolytic hydrogenation of specimens (before tensile tests in air) showed even more clearly the negative consequences of operational degradation of steel. The degradation of steel was also assessed using fracture toughness (J_IC). The value of J_IC for operated steel with a smaller number of shutdowns decreased by 32–33%, whereas with a larger number of shutdowns, its decrease in the vicinity of the outer and inner surfaces of the pipe reached 65 and 61%, respectively. Fractographic signs of more intense degradation of steel after a greater number of shutdowns were manifested at the stage of spontaneous fracture of specimens by changing the mechanism from transgranular cleavage to intergranular, which indicated a decrease in the cohesive strength of grain boundaries. Full article

In high-pressure thermal power systems, corrosion-induced wall thinning in steam pipelines poses a significant threat to operational safety and efficiency. This study investigates the effects of gas–liquid two-phase flow on corrosion-induced wall thinning in pipe bends of high-pressure heaters in power plants, with particular emphasis on the mechanisms of void fraction and inner wall surface roughness. Research reveals that an increased void fraction significantly enhances flow turbulence and centrifugal effects, resulting in elevated pressure and Discrete Phase Model (DPM) concentration at the bend, thereby intensifying erosion phenomena. Simultaneously, the turbulence generated by bubble collapse at the bend promotes the accumulation and detachment of corrosion products, maintaining a cyclic process of erosion and corrosion that accelerates wall thinning. Furthermore, the increased surface roughness of the inner bend wall exacerbates the corrosion process. The rough surface alters local flow characteristics, leading to changes in pressure distribution and DPM concentration accumulation points, subsequently accelerating corrosion progression. Energy-Dispersive Spectroscopy (EDS) and Scanning Electron Microscopy (SEM) analyses reveal changes in the chemical composition and microstructural characteristics of corrosion products. The results indicate that the porous structure of oxide films fails to effectively protect against corrosive media, while bubble impact forces damage the oxide films, exposing fresh metal surfaces and further accelerating the corrosion process. Comprehensive analysis demonstrates that the interaction between void fraction and surface roughness significantly intensifies wall thinning, particularly under conditions of high void fraction and high roughness, where pressure and DPM concentration at the bend may reach extreme values, further increasing corrosion risk. Therefore, optimization of void fraction and surface roughness, along with the application of corrosion-resistant materials and surface treatment technologies, should be considered in pipeline design and operation to mitigate corrosion risks. Full article

In this study, the effects of pregelatinization on the physicochemical properties of corn grits and the quality of cooked waxy corn wrapped in plant leaves were investigated. This investigation was conducted to address the issues of partial gelatinization and poor texture in corn grits when applied to food processing such as cooked waxy corn wrapped in plant leaves. After the corn grits were soaked at 55 °C, they were steamed for 30 min and dried at 45 °C (steam temperature maintained at 100 °C), reaching a gelatinization degree of 48.28%. The modified grits were characterized using Rapid Visco Analyzer (RVA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) to analyze pasting properties, retrogradation behavior, crystallinity, molecular structure, and morphology. The results showed that pregelatinization significantly reduced setback viscosity (from 274.83 to 154.52 mPa·s), crystallinity (from 11.12% to 3.62%), and retrogradation tendency while improving solubility, swelling power, and water-holding capacity. When used in cooked waxy corn wrapped in plant leaves, pregelatinized grits enhanced the gelatinization degree (96.11%), texture (reduced hardness by 19.49%, increased chewiness and cohesiveness), and moisture retention during storage. The findings demonstrate that pregelatinization optimizes starch functionality, mitigates retrogradation, and improves the overall quality of traditional corn-based foods, providing a practical approach for industrial applications. Full article

The article discusses the causes of excessive noise and vibrations of a live steam pipeline in a power unit. A scanning laser vibrometer was used to measure the vibrations of the live steam pipeline for two power units. Additionally, the sound (noise) level of the live steam pipeline was measured with an acoustic camera. A discrete model of the pipeline was created, and FEM modal analysis was performed. Based on experimental tests and numerical simulations, the sources of noise were identified. The final conclusions propose methods of eliminating the harmful noise. Full article

The microstructural evolution and mechanical properties of WWER 440 steam generator steel GOST 22K after long-term operation were thoroughly examined in this study. The samples were taken directly from a steam generator using the small punch test method. The uniqueness of these samples lies in the fact that they were real operating materials used in a nuclear power plant with different years of operation. The microstructure was characterized using optical microscopy and transmission electron microscopy supplemented by selective electron diffraction and semi-quantitative chemical microanalysis. It was found that with the prolongation of the operation time of the steam generator, the density of carbides increased slightly, which was reflected in a decrease in the mean distance between particles, but these differences were very small, which indicates the microstructural stability of GOST 22K steel. The stability of this steel was also confirmed by measuring its mechanical properties, which changed only minimally depending on the years of operation. The tensile strength values were in the range of 508 to 579 MPa. In the case of the ductile-to-brittle transition temperature (DBTT), a slight increase was found after 6 years of operation. The DBTT did not change significantly with subsequent operation. Full article

The planned construction of a steam–gas unit at the Adamów Power Plant raises questions about the potential hydrological impact on the neighboring Natura 2000 protected areas, particularly the Middle Warta Valley (PLB300002) and the Jeziorsko Reservoir (PLB100002). These ecosystems play a key role in protecting bird habitats and biodiversity, and any changes in water management can affect their condition. This paper presents a detailed hydrological analysis of the Warta River and Jeziorsko Reservoir for 2018–2022, with a focus on low-flow periods. The Peak Over Threshold (POT) method and Q_70% threshold were used to identify the frequency, length, and seasonality of low-flow periods in three water gauge profiles: Uniejów, Koło, and Sławsk. The longest recorded low-flow episode lasted 167 days. The permissible water intake for the investment (up to 0.8 m³∙s^–1) is in accordance with the applicable permits and is used mainly for cooling purposes. Calculations indicate that under maximum intake conditions, the water level reduction in the Jeziorsko Reservoir would be between 1.7 and 2.0 mm∙day^–1, depending on the current level of filling. Such changes do not disrupt the natural functions of the reservoir under typical conditions, although during prolonged droughts, they can pose a threat to protected areas. An analysis of the impact of periodic water overflow into the Kiełbaska Duża River indicates its negligible effect on water levels in the reservoir and flows in the Warta River. The results underscore the need for the integrated management of water and power resources, considering the increasing variability in hydrological conditions. Ensuring a balance between industrial needs and environmental protection is key to minimizing the potential impact of investments and implementing sustainable development principles. Full article

This paper presents an exergy analysis of a 500 MW unit based on actual measurement data. The mathematical model of the system was built in the Aspen HYSYS 2.4 software. The analysis was carried out for two operating states of the unit, at nominal load and at minimum technical load, based on data from two measurement campaigns carried out specifically for this study. The use of measurement data allows an accurate representation of the unit’s current operating conditions, which is crucial for the accuracy of the analysis and the practical implementation of the results obtained. The results show that the dominant sources of exergy losses are the irreversibilities associated with combustion and boiler heat transfer, which account for more than 60% of total exergy losses. The article makes an important contribution to sustainability by identifying opportunities to increase the operating efficiency of the power unit and reduce CO₂ emissions. Proposed technical modifications, such as the modernisation of air heaters, the use of inverters in ventilation systems, or the optimisation of heat exchangers in the turbine system, can significantly improve energy efficiency and reduce the unit’s environmental impact. The analysis provides a valuable resource for the development of energy technologies that promote efficiency and sustainable resource use. Full article

Nuclear energy is a cornerstone of the global energy mix, delivering reliable, low-carbon power essential for sustainable energy systems. However, the safety of nuclear reactors is critical to maintaining operational reliability and public trust, particularly during accidents like a Loss of Coolant Accident (LOCA) or a Steam Line Break Inside Containment (SLBIC). This study introduces a Bayesian Network (BN) framework used to enhance nuclear energy safety by predicting accident severity and identifying key factors that ensure energy production stability. With the integration of simulation data and physical knowledge, the BN enables dynamic inference and remains robust under missing-data conditions—common in real-time energy monitoring. Its hierarchical structure organizes variables across layers, capturing initial conditions, intermediate dynamics, and system responses vital to energy safety management. Conditional Probability Tables (CPTs), trained via Maximum Likelihood Estimation, ensure accurate modeling of relationships. The model’s resilience to missing data, achieved through marginalization, sustains predictive reliability when critical energy system variables are unavailable. Achieving R² values of 0.98 and 0.96 for the LOCA and SLBIC, respectively, the BN demonstrates high accuracy, directly supporting safer nuclear energy production. Sensitivity analysis using mutual information pinpointed critical variables—such as high-pressure injection flow (WHPI) and pressurizer level (LVPZ)—that influence accident outcomes and energy system resilience. These findings offer actionable insights for the optimization of monitoring and intervention in nuclear power plants. This study positions Bayesian Networks as a robust tool for real-time energy safety assessment, advancing the reliability and sustainability of nuclear energy production. Full article

The critical consequence of climate change resulting from global warming is the increase in temperature. In combined cycle power plants (CCPPs), the Electric Power Output (PE) is affected by changes in both Ambient Temperature (AT) and Sea Surface Temperature (SST), particularly in plants utilizing seawater cooling systems. As AT increases, air density decreases, leading to a reduction in the mass of air absorbed by the gas turbine. This change alters the fuel–air mixture in the combustion chamber, resulting in decreased turbine power. Similarly, as SST increases, cooling efficiency declines, causing a loss of vacuum in the condenser. A lower vacuum reduces the steam expansion ratio, thereby decreasing the Steam Turbine Power Output. In this study, the effects of increases in these two parameters (AT and SST) due to global warming on the PE of CCPPs are investigated using various regression analysis techniques, Artificial Neural Networks (ANNs) and a hybrid model. The target variables are condenser vacuum (V), Steam Turbine Power Output (ST Power Output), and PE. The relationship of V with three input variables—SST, AT, and ST Power Output—was examined. ST Power Output was analyzed with four input variables: V, SST, AT, and relative humidity (RH). PE was analyzed with five input variables: V, SST, AT, RH, and atmospheric pressure (AP) using regression methods on an hourly basis. These models were compared based on the Coefficient of Determination (R²), Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), Mean Square Error (MSE), and Root Mean Square Error (RMSE). The best results for V, ST Power Output, and PE were obtained using the hybrid (LightGBM + DNN) model, with MAE values of 0.00051, 1.0490, and 2.1942, respectively. As a result, a 1 °C increase in AT leads to a decrease of 4.04681 MWh in the total electricity production of the plant. Furthermore, it was determined that a 1 °C increase in SST leads to a vacuum loss of up to 0.001836 bar_a. Due to this vacuum loss, the steam turbine experiences a power loss of 0.6426 MWh. Considering other associated losses (such as generator efficiency loss due to cooling), the decreases in ST Power Output and PE are calculated as 0.7269 MWh and 0.7642 MWh, respectively. Consequently, the combined effect of a 1 °C increase in both AT and SST results in a 4.8110 MWh production loss in the CCPP. As a result of a 1 °C increase in both AT and SST due to global warming, if the lost energy is to be compensated by an average-efficiency natural gas power plant, an imported coal power plant, or a lignite power plant, then an additional 610 tCO₂e, 11,184 tCO₂e, and 19,913 tCO₂e of greenhouse gases, respectively, would be released into the atmosphere. Full article

Heavy fuel oil (HFO) is a widely used fuel in compression ignition engines, primarily in Brazilian thermoelectric plants, mainly due to its availability, low cost, and low operational expenses. However, heavy fuel oil is not compatible with most diesel engines and combustion systems in use and must be treated to maintain combustion process efficiency. The high viscosity of heavy fuel oil must be reduced before being introduced into the engine. To achieve this, appropriate heating devices are added to the fuel lines, with steam being the primary working fluid in these devices. Steam-generating boilers that burn fossil fuels, including HFO itself, are the most viable option from an economic standpoint and in terms of utilizing locally available fuels for this function. However, the need to mitigate the effects of environmental pollution has encouraged the adoption of other types of boilers, such as electric ones. In this work, a case study of a combustion steam generator installed in a Brazilian thermoelectric plant is developed. This study involves the thermodynamic and combustion modeling of the steam generator through the balancing of the respective thermodynamic and combustion equations. The models and the proposed chemical formula of HFO were validated, and through simulations using real data collected during the boiler’s operation throughout 2024, it was also possible to estimate the carbon dioxide emissions produced. Additionally, a hypothetical scenario was simulated in which the combustion boiler currently installed in the plant is replaced by two electric boilers. A simple economic analysis demonstrated that such a replacement would result in a total steam production cost of only 25% of the amount spent on the current combustion boiler, in addition to reducing $C{O}_2$ emissions to the atmosphere by 62.55 tons. Full article

As the integration of renewable energy sources continues to increase, thermal power units are increasingly required to enhance their operational flexibility to accommodate grid fluctuations. However, frequent load variations in conventional thermal power plants result in decreased efficiency, accelerated equipment wear, and high operational costs. In this context, molten-salt thermal energy storage (TES) has emerged as a promising solution due to its high specific heat capacity and thermal stability. By enabling the storage of surplus energy and its regulated release during peak demand periods, molten salt TES contributes to improved grid stability, reduced start-up frequency, and minimized operational disturbances. This study employs comprehensive thermodynamic simulations to investigate three representative schemes for heat storage and release. The results indicate that the dual steam extraction configuration (Scheme 3) offers the highest thermal storage capacity and peak-load regulation potential, albeit at the cost of increased heat consumption. Conversely, the single steam extraction configurations (Scheme 1 and 2) demonstrate improved thermal efficiency and reduced system complexity. Furthermore, Scheme 3, which involves extracting feedwater from the condenser outlet, provides enhanced operational flexibility but necessitates a higher initial investment. These findings offer critical insights into the optimal integration of molten-salt thermal-storage systems with conventional thermal power units. The outcomes not only highlight the trade-offs among different design strategies but also support the broader objective of enhancing the efficiency and adaptability of thermal power generation in a renewable-dominated energy landscape. Full article