Thermal Power Plants Research Articles

Effect of Cr on the high-temperature corrosion of dissimilar AISI 904L and Inconel 625 joints employed in the coal-fired thermal power plant tubes

ABSTRACT The hot corrosion behaviours of 5-mm-thick plates of dissimilar AISI 904L and Inconel 625 weldments produced by continuous current gas tungsten arc welding process using Ni-Cr-Mo-enriched filler wires (ERNiCrMo-4 and ERNiCrCoMo-1) were investigated. Optical microscopy was used to examine the microstructure of these weldments. The corrosion performance of the weldments and base metals was determined in the mixture of K2SO4 + 60% NaCl molten salt (MS) and air oxidation conditions at 700°C for 50 cycles. The thermogravimetric plots derived the corrosion kinetics of the weldments. The microstructure and the elemental analysis of the scales formed on the corroded samples were evaluated by scanning electron microscopy and energy-dispersive spectroscopy. The phases developed on the oxide layers during the corrosion were analysed using X-ray diffraction. The fusion zones of ERNiCrCoMo-1 weldment and AISI 904L base metal were vulnerable to degradation in the MS environment, causing severe cracks and spallation compared to ERNiCrCoMo-1 weldment.

Exploring the Synergistic Governance of Water Conservation and Carbon Reduction in Thermal Power Plants

In the industrial sector, thermal power plants not only use a lot of water, but also cause more carbon emissions. In today's era of carbon neutral carbon peaking and water scarcity in China, thermal power plants should not only do a good job of water conservation, but also reduce carbon emissions. But water-saving behaviours mostly consume more energy and cause more carbon emissions. This study explores how thermal power plants can save water and reduce carbon synergistically, and introduces a carbon footprint model to study the synergistic benefits of water saving and carbon reduction in thermal power plants, and takes a thermal power plant in the south as a typical case. Considering the environmental benefits of water conservation from a more systematic perspective helps to promote the synergistic effect of water conservation and carbon reduction.

Analysis of Slag-Containing Steamed Concrete's Composition Efficiency.

Thermal power plant slag is a waste that is presently obtained from many power stations all over the world. A possible method for its utilization is using it to produce concrete. This paper analyses the effect of thermal power plant slag on the technological properties of concrete mixtures and the mechanical properties of concrete subjected to heat-moisture processing. Quantitative estimates of the investigated factors' influence on the concrete mixture's water demand and the strength of steamed concrete were obtained. The influences of TPP slag content and its water demand on concrete composition features as well as concrete strength are shown. The novelty of the work lies in the use of an experimental-statistical model to optimize the composition of steamed concrete using slag from the viewpoint of maximum strength per kilogram of cement. It has been demonstrated that the optimal part of slag in aggregate, which provides maximum strength at 4 h and 28 days after steaming, is 0.5-0.55 and 0.45-0.55, respectively. A method for the design of concrete composition using slag from thermal power plants is proposed.

Statelets extraction-guided contrastive learning for detection of control performance degradation with varying degrees

Detection of control performance degradation (CPD) in time series plays a vital role in modern industry. However, most CPD detection methods tend to neglect the following recognitions: 1) control performance is often assessed over small segments of the time series rather than the long-term entire one, and 2) CPD may exhibit different degrees in practice, resulting in the time-varying data distribution problem. These two considerations necessitate the development of algorithms that can extract information-rich small segments, defined as statelets, to discriminate the control performance with varying degrees. To this end, a Statelets Extraction-based Contrastive Learning (SECL) model is proposed for the detection of CPD. First, a varying-length statelet generation algorithm is developed to split the original multivariate time series into multiple statelet candidates with different time lengths, which can avoid the problem of information-rich small segments being obscured by the long-term trend of the time series. A contrastive learning encoder is then constructed to map statelet candidates into a uniform feature space with the designed triplet loss, keeping features of similar statelets tight and features of dissimilar statelets far away. In this way, we can extract discriminative feature candidates to distinguish the control performance with varying degrees. An information entropy-based selection strategy is proposed to choose information-rich statelet features that can best identify different control performances. After that, a statelets distance-based classifier is designed by computing the match distance between features of a testing sample and the extracted statelet features. The proposed SECL model focuses on the extracted statelets that can significantly reveal changes related to control performance rather than comparing the entire time series, which is more accurate and robust in detecting CPD with varying degrees. The effectiveness of the proposed method is illustrated through a real-world thermal power plant process. The experiment results show that SECL can capture the discriminative features and achieve prominent detection performance.

Thermal energy storage integration for increased flexibility of a power plant with post-combustion CO2 capture

Flexible operation of thermal power plants will become increasingly relevant in the coming years. This work evaluates the effect of integrating a steam accumulator into a 598 MW supercritical coal-fired power plant with moving bed temperature-swing adsorption CO2 capture. Charging the accumulator with reheat steam from the turbine train can reduce the net power output by up to 1.4 % (8.2 MW) for around 200 min. Small charging flow rates are recommended to maximize the final pressure of the accumulator. Covering the sorbent regeneration duty and meeting the demand of two feedwater heaters were considered as alternatives for discharging of the accumulator. Thermal storage discharging was found to give relative power plant load increases between 1.7 and 11.2 % (10.2–66.9 MW) for up to 37.5 min, which exceeds the requirement for primary reserve. Increases in the electrical energy output of 10.5–11 MWh were achieved. The flexibility modes studied in this work are compatible with high CO2 recovery rates.

Substructure-based design method for vertically irregular steel buckling-restrained braced frame structures

Buckling-restrained braces (BRBs) can mitigate the uneven inter-story drifts of vertically irregular steel frame structures during earthquakes, preventing unfavorable seismic forces and failure patterns. However, the structural lateral displacement profile of vertically irregular steel buckling-restrained braced frame structures (VSBFSs) can hardly be predicted; hence, parameter tuning and iterative designing are commonly required in conventional direct displacement-based design (DDBD) methods, which strongly rely on the experience of designers and consumes a considerable amount of time. This study proposes a substructure-based design (SBD) method developed explicitly for VSBFSs. In this method, the substructures of every story of a VSBFS are separated from the entire structure and individually analyzed in the subsequent procedures. The boundary conditions of the substructures are initially simplified as hinges, and an explicit equation of BRB stiffness and inter-story drift for the substructures is established. An iterative calculation procedure is consequently applied to correct the equation by considering the influence of the constraints of adjacent stories. In this manner, the inter-story drifts of all the stories of the entire structure uniformly converge to the predetermined targets, in which the demand of BRBs for each story is also determined. Compared with conventional DDBD methods, the proposed method does not assume the structural lateral displacement profile and is not based on experience, yielding relatively economical and safe design outcomes in a timely manner. The proposed SBD method was first validated by comparing it with existing elastic and elastoplastic design methods through a 15-story VSBFS example. Then, the applicability of the SBD method was further explored through four 6-story VSBFSs with different plan layout reductions and two VSBFSs with heights of 20 stories and 30 stories. Finally, the SBD method was applied to redesign the BRBs of a vertically irregular thermal power plant model (an example of a VSBFS) in a shaking table test.

Creep-fatigue life estimation of circumferential welds in thermal high energy piping systems

ABSTRACT To prevent accidents in high energy piping systems of thermal power plants, it may be important to accurately estimate the creep-fatigue life of circumferential piping welds. The main failure mode in the damage cases was Type IV damage which was creep-dominated damage occured at the fine-grained HAZ(FGHAZ). The damege mode is considered to change from longitudinal failure at the base metal to circumferential Type IV failure when the ratio of axial stress to hoop stress exceeds a certain value. The allowable thermal expansion stress in the design, the stress relaxation property of the material, and the creep rupture strength of welded joints are investigated, as factors affecting creep damage of circumferential piping welds. Fundamental creep-fatigue tests were perfomed using cross-weld specimens and their lives were estimated by a linear damage summation rule. In the life estimation, it seems necessary to consider elastic follow-up phenomena where strain transfers to the HAZ.

Synergistic effects of melamine functionalized graphene oxide and imidazolium ionic liquid on the tribological performance and thermal stability of polyalphaolefin based hybrid nanolubricants

Tribological and thermophysical characteristics of a new hybrid nanolubricant that incorporates melamine functionalized graphene oxide (mGO) and imidazolium cation based ionic liquid (IL) in a polyalphaolefin (PAO-6) base oil have been investigated. Different formulations of nanolubricants with 0.05 wt%, 0.1 wt% nanosheets and 1 wt% ionic liquid were studied to examine the synergistic effects of surface functionalization and ionic liquid addition on the antifriction and antiwear properties of the PAO-6 base oil. Thermal stability studies involved Thermogravimetric analysis to analyze the oxidation onset and decomposition temperature of different formulatons at varying weight concentrations of nanoadditives. Anti-friction performance was quantified by the coefficient of friction (COF) reduction compared to neat lubricant. The highest reduction in COF was observed for 0.05 wt% mGO + 1 wt% IL with an outstanding 73.33% reduction followed by 0.05 wt% mGO and 0.05 wt% GO with 73% and 67% reduction respectively. Post-wear analysis of the wear scars was performed using 3D optical profiler, SEM micrographs, EDX elemental composition and Raman spectra. The highest reduction in wear depth was observed in the case of PAO-6 + 0.05% mGO with a value of 46.3% followed by a 39.9% reduction in the case of PAO-6 + 0.05% GO. The morphologies of samples containing both ionic liquid and nanosheets exhibited a much smoother surface with the absence of deep grooves and pits which was attributed to the formation of a strongly bonded tribofilm owing to the chemical interactions between ionic liquid capped nanosheets and metal substrate. Strong interfacial interactions also induced a significant increase in the thermal stability of the nanofluids. The maximum shift observed in the oxidation onset temperature compared to neat PAO-6 was 68◦C while the decomposition temperature increased by 61◦C. Due to their excellent friction, wear, and thermal properties, these hybrid nanofluids could be applied in various highly demanding industrial sectors such as automotive, machining operations, aerospace, thermal power plants and micro/nano-electromechanical systems.

Integrated Systems of a Solar Thermal Energy Driven Power Plant

Integrated Systems of a Solar Thermal Energy Driven Power Plant

Optimization on Microbial Anti-Scaling and Corrosion Inhibition Technology for Low Alkalinity and Low Hardness Circulating Cooling Water in Thermal Power Plants

This paper analyzed the potential effectiveness of microbial anti-scaling and corrosion inhibition technology for low alkalinity and low hardness circulating cooling water in thermal power plants and used response surface models to study the effects and optimal conditions of key technical parameters. The results showed that when the nutrient solution dosage, bacterial agent dosage and aeration rate were set at 0.1-0.3 ‰, 0.1-0.5 ‰, and 1-3 L/min, respectively, the calcium hardness, corrosion rate of brass and stainless steel 304 in the water could be controlled within 9.77-15.30 mmol/L, 0.77-6.58 μm/a, and 1.20-4.50 μm/a, respectively. The variance analysis results indicated that the response surface linear model was the most suitable for evaluating the effects of key operation parameters on the application efficiency of the technology. The obtained model furtherly revealed that the nutrient solution dosage and bacterial agent dosage were extremely significant explanatory variable factors affecting the application of microbial technology in inhibition and corrosion control (P < 0.01). Still, the aeration rate did not reach a significant effect (P > 0.05). Based on the regression equation of actual factors, the study further revealed through the hill climbing algorithm that the optimal comprehensive effect of microbial technology in inhibition and corrosion control was achieved when the nutrient solution dosage, bacterial agent dosage, and aeration rate were set at 0.3‰, 0.5‰, and 1 L/min, respectively.

Application of ensemble learning approach on anomaly detection of a dual induced draft fan system

Intelligent monitoring of thermal power plants has been receiving growing interest. As one of the promising technologies in intelligent monitoring, machine learning-based fault detections for auxiliary equipment in the thermal power plant have been widely investigated. In this work, we constructed normal behavior models to predict the current of a dual-induced draft fan system by gradient-boosting tree regression. For anomaly detection, we evaluated the residual by calculating the mean value and meanwhile added a control boundary based on statistical analysis. As a result, we successfully identified the abnormal fan in the dual-induced draft fan system and assisted in the schedule of maintenance work.

ISSUES OF WATER USE IN THERMAL POWER PLANTS. PROBLEMS AND SOLUTIONS

The article considers the most effective methods of water treatment for thermal power plants. Water treatment is one of the most important processes in the operation of thermal power plants (TPP). The quality of water treatment for use in boiler units of thermal power plants is of fundamental importance to ensure the efficiency and durability of process equipment. This article reviews the main aspects of water treatment in TPP plants, including treatment methods, water quality characteristics and standards, and the impact of water treatment on the overall energy efficiency and safety of power generation in TPP plants.

Concept of a Regional Liquefied Natural Gas Fuel Complex Based on a Thermal Power Plant

Concept of a Regional Liquefied Natural Gas Fuel Complex Based on a Thermal Power Plant

Concept and Design of a Velocity Compounded Radial Four-Fold Re-Entry Turbine for Organic Rankine Cycle (ORC) Applications

The energy sector faces a pressing need for significant transformation to curb CO2 emissions. For instance, Czechia and Germany have taken steps to phase out fossil thermal power plants by 2038, opting instead for a greater reliance on variable renewable energy sources like wind and solar power. Nonetheless, thermal power plants will still have roles, too. While the conventional multistage axial turbine design has been predominant in large-scale power plants for the past century, it is unsuitable for small-scale decentralized projects due to complexity and cost. To address this, the study investigates less common turbine types, which were discarded as they demonstrated lower efficiency. One design is the Elektra turbine, characterized by its velocity compounded radial re-entry configuration. The Elektra turbine combines the advantages of volumetric expanders (the low rotational speed requirement) with the advantages of a turbine (no rubbing seals, no lubrication in the working fluid, wear is almost completely avoided). Thus, the research goal of the authors is the implementation of a 10 kW-class ORC turbine driving a cost-effective off-the-shelf 3000 rpm generator. The paper introduces the concept of the Elektra turbine in comparison to other turbines and proposes this approach for an ORC working fluid. In the second part, the 1D design and 3D–CFD optimization of the 7 kW Elektra turbine working with Hexamethyldisiloxane (MM) is performed. Finally, CFD efficiency characteristics of various versions of the Elektra are presented and critically discussed regarding the originally defined design approach. The unsteady CFD calculation of the final Elektra version showed 46% total-to-static isentropic efficiency.

Активность и изотопный состав радионуклидов, образующихся в реакторах ПАТЭС в течение всего жизненного цикла

The authors have estimated the activity and composition of radionuclides accumulated in the reactors of the floating nuclear thermal power plant (FNPP) upon completion of the last fuel run. An analysis of the previously occurred criticality events at transport nuclear power facilities has shown that the most harmful consequences for the population and environment arise due to the self-sustain chain reaction (SCR) with depressurized reactor. Such an event can occur at a floating nuclear power plant (FNPP). The researchers have obtained estimates for the KLT-40S reactor using the calculation for the KLT-40 reactor. They have taken into account the design-base power production, fuel enrichment, as well as the FNPP service life.

Economic enhancement and grid‐frequency control of a wind farm‐CAES‐fuel cell‐based hybrid system

AbstractIn the present era, the electrical network faces difficulty owing to the restricted supply of conventional energy resources. Solar and wind power are supremely acceptable renewable energy around the globe due to their cheap availability, zero fuel costs, and environmental safety features. Maintaining power balance in a renewable combined day‐ahead power network becomes challenging owing to the uncertainty of renewable sources, resulting in economic instability. An energy‐storing device is essential for combining renewable sources with existing thermal power plants to control the energy supply and maintain system stability. Any government agency in the deregulated market does not set up energy pricing. The ISO (independent system operator) is the primary organization in the day‐ahead power network that is responsible for collecting energy bids from DISCOs (distribution companies), TRANSCOs (transmission companies), and GENCOs (generation companies). The energy pricing is set by the market regulator at a rate known as Location‐based marginal pricing (LBMP), which provides benefits to GENCOs, and DISCOs as well as the customers. In a deregulated market, the unpredictability of renewable sources affects system profit owing to the creation of instability cost (ISC), induced by mismatching the bidding power production from the renewable plant. To lessen these concerns, the presented approach has proposed an innovative model that employs ideal scheduling of the WF (wind‐farm)‐CAES (compressed‐air‐energy‐storage)‐fuel cell (FC) hybrid systems to enhance system economic profitability while keeping the grid frequency (GF) in the safe zone. The fuel cell acts as the energy‐storing device that can be utilized during high‐demand times on the grid, with the ultimate goal of maximizing profits for the overall system. The CAES system's energy level is separated into four dissimilar points, and this study presents an optimum approach for efficiently using it to maintain grid frequency. The new strategy outperformed the previous methods in all categories. The study was performed using the IEEE 30 bus test system.

Performance evaluation and operation optimization of a combined heat and power plant integrated with molten salt heat storage system

Combined heat and power is an effective way to enhance the energy efficiency of thermal power plants. The solar and wind power are intermittent, and dispatchable power sources are critical to balance the supply and demand sides. To facilitate the high penetration of renewable energy, combined heat and power (CHP) plants should provide more and more peak shaving services for the power grid. The thermal energy can be stored in and released from the molten salt heat storage system (MSHSS). The integration of MSHSS can enlarge the adjustable range of the power load of CHP plants, so it is a potential way to enhance the operational flexibility of CHP plants supplying industrial steam and power. In this study, the MSHSS integrated within CHP plants are proposed, which store a part of sensible heat energy carried by extraction steam before supplying to industrial users. The heat storage capacity dominates the flexibility enhancement, and indicators to evaluate energy performances of the proposed system are defined. Moreover, models for the operation optimization of CHP plants integrated with the MSHSS are developed, and a case study of a 350 MW CHP unit is conducted. When the reheat steam is extracted to supply to industrial steam, the maximum and minimum adjustable power loads can be increased and decreased by 17.13 and 12.01 MW, respectively with the integration of the MSHSS. Moreover, during the peak, flat, valley time of reference day, the heat supply coal consumption rates are 73.94, 74.19 and 81.03 kg t−1,respectively. With the operation scheduling of CHP plant integrated with MSHSS, the MSHSS with reheat steam as heat source show the lowest coal consumption rate as 1553.79 ton/day.

WITHDRAWN: Trace metals translocation from soil to plants: Health risk assessment via consumption of vegetables in the urban sprawl of a developing country

The study was conducted at 15 locations around the thermal power plant of Patuakhali district at the coastal area of Bangladesh to determine trace elements in vegetable and assess risk of toxicity. Eight vegetables, namely, tomato (Solanum lycopersicum L.), radish (Raphanus raphanistrum L.), bean (Phaseolus vulgaris L.), brinjal (Solanum melongena L.), bottle gourd (Lagenaria siceraria L.), red amaranth (Amaranthus cruentus L.), arum (Arum maculatum L.) and lady's finger (Abelmoschus esculentus L.) were analyzed for nine trace metals (Cr, Ni, Cu, As, Cd, Pb, Fe, Mn and Zn) to assess contamination load of trace elements in agricultural soil, and health risks posed from vegetable consumption. The mean concentrations of Cr, Cr, Ni, Cu, As, Cd, Pb, Fe, Mn, and Zn in soil were 16.6, 14.8, 5.8, 1.3, 0.72, 9.7, 55261, 456.1, and 105.8 mg/kg, respectively. Average concentrations of As, Cd, and Pb in vegetable species were higher than the maximum allowable concentration (MAC), indicating vegetables species were contaminated by these elements and may pose potential risk to human. Fe, Mn, Zn, Cr, Cu, Pb, and As in soil and vegetables of the study area may arise from anthropogenic activities. The present study suggests that surface soil used for vegetables production should be continuously monitored to check the transfer of toxic metals into the vegetables to minimize the adverse health impacts on consumers and potential threats to food safety.

Explicit Representation and Customized Fault Isolation Framework for Learning Temporal and Spatial Dependencies in Industrial Processes.

Typically, industrial processes possess both temporal and spatial dependencies due to intravariable dynamics and intervariable couplings. The two dependencies have different manifestations, indicating diverse process characteristics. However, the existing methods fail to separate temporal and spatial information well, leading to inappropriate representation and inaccurate fault detection and isolation results. This study proposes an explicit representation and customized fault isolation framework to tackle temporal and spatial characteristics, so as to identify and locate anomalies affecting different dependencies. First, we design a double-level separation method for temporal and spatial information. In the first level, we construct two independent auto-encoding modules to extract temporal correlation and spatial graph structure in parallel. In the second level, we propose an information aliasing loss function to guild the two modules to distinguish between temporal and spatial characteristics, further facilitating information separation. By monitoring the explicit temporal and spatial statistics obtained by the two modules, spatiotemporal dependencies of anomalies can be determined for subsequent isolation. Furthermore, we propose a customized isolation strategy for anomalies in temporal and spatial characteristics. By quantifying changes in intravariable temporal dynamics and intervariable spatial graph structure individually, temporal impact and spatial propagation of faults can be finely characterized and isolated. Three examples are adopted to verify the performance of the proposed framework, including a numerical example, a real condensing system of the thermal power plant process, and the Tennessee Eastman benchmark process.

Powering through Challenges: Analyzing the Energy Crisis in the Western Balkans during the Pandemic Context

This paper examines the current challenges in the energy sector of the Western Balkan countries, focusing on the energy sector of Kosovo as a case study during the pandemic. These countries are at crucial stages of their development, marked by significant achievements but with ongoing challenges in the energy sector as a factor for sustainable development. The region remains highly vulnerable to energy crises and geopolitical tensions, particularly due to its heavy dependence on fossil fuels such as brown coal for energy production. Our research focuses on the energy system in Kosovo, highlighting its historical reliance on a fragile energy sector, particularly characterized by inflexible thermal power plants using outdated technology and a lack of additional, more flexible capacity. The purpose of this study is to examine Kosovo's energy system, assess the challenges it encounters, and identify the factors that have contributed to the energy crisis from 2021 to 2023. Doi: 10.28991/HIJ-2024-05-01-08 Full Text: PDF