High Pressure Feedwater Heater Research Articles

Deep Reinforcement Learning for Dynamic Opportunistic Maintenance of Multi-Component Systems With Load Sharing

Opportunistic maintenance (OM), which shows its superiority on complex multi-component systems by integrating the maintenance activities of multiple components to reduce the maintenance cost, has been widely studied over the past decade. To our knowledge, most of the existing OM works are developed based on fixed maintenance thresholds without fully utilizing the health state of the multi-component system. This article presents an OM optimization problem of multi-component systems with load sharing, solved by a modified proximal policy optimization approach based on deep reinforcement learning algorithm. The load sharing effect is reflected in the hazard rate function, which further changes the failure probability of the components. Meanwhile, the health states can be recovered by executing imperfect maintenance and corrective maintenance. The optimization problem is formulated as an infinite-horizon MDP with mixed discrete and continuous state and action space to maximize the total discounted reward, taking into account the system reliability and the maintenance cost. The difficulty caused by the mixed action space is solved by designing a parameterized action space structure and multi-task reinforcement learning framework. The effectiveness of the proposed algorithm is tested on a four-component system and a real-world scenario configured with the high-pressure feedwater heater system in the nuclear power plant. The results show that the performance of the algorithm is stable when facing large-scale problems. The algorithm proposed in this study also contributes to the imperfect maintenance optimization with state-of-the-art optimization techniques.

Liquid Level Measurement and Control in High Temperature and High-pressure Environments of Nuclear Power Plant

There are many pieces of high-temperature and high-pressure system equipment in nuclear power plants, such as deaerators, high-pressure feedwater heaters, steam-water separation reheaters, etc. The media parameters in these systems and equipment are high and the working conditions are complex. It is necessary to solve the above problems by adopting multi-channel averaging, increasing the slope of the condensing line, and separating the sampling ports of multiple channels. After practical verification, the above solution can effectively solve or reduce the above problems, which can provide a reference for the liquid level measurement and control in subsequent similar high-pressure and high-temperature environments in nuclear power plants.

Performance Analysis of HP Heater with Comparison of the Number of Plugging Tubes in a 400 MW Coal-Fired Power Plant

Each of Units 1-4 SLA PGU has a capacity of 400 MW and seven feedwater heaters, namely three lowpressure feedwater heaters (LPH 1, 2, and 3), a deaerator, and three high-pressure feedwater heaters (HPH 5, 6, and 7). HPH 5 in Unit 2 has experienced 30% tube plugging, which is equivalent to 480 out of 1579 tubes. Plugging is expected to reduce the performance of HPH. If the plugging exceeds the maximum limit, the HPH needs to be retubed to restore equipment reliability. Furthermore, a comparison of the performance of HPH 5 was calculated with plugging variations of 0%, 22%, and 30% when the unit was at full load. The calculation results of terminal temperature difference (TTD), drain cooler approach (DCA), and log mean temperature difference (LMTD) showed an increase with the increase in plugging in HPH. Meanwhile, the calculation of heat rate and effectiveness showed a decrease caused by the additional plugging in the HPH. The largest heat transfer occurs in the condensing zone of the HPH, where the value is around 80% to 85% of the total heat transfer that occurs. All calculations of the relationship between performance parameters and HPH plugging variations have an R-square value of more than 0.67, indicating a strong relationship.

Thermal and economic performances comparison of different pulverized coal power systems augmented by solar trough or tower technologies

In this study, three different solar-assisted pulverized coal power (SPCP) systems utilizing solar trough or tower technologies are investigated and compared. In scheme 1, the parabolic trough solar collector is parallel to the high-pressure feed-water heaters. In scheme 2, the solar tower field is parallel to the boiler. In scheme 3, the solar tower field is connected in series between intermediate- and low-pressure cylinders. Results show that even though the same amount of solar energy is introduced into the three SPCP systems, the exergy that can be efficiently utilized differs due to the varying integrating temperature range in these three SPCP systems. The standard coal consumption rates of SPCP systems are lower when compared with the pulverized coal power system, but the levelized costs of electricity of SPCP systems are higher due to the heavy solar field investment. Among all the SPCP systems, scheme 3 owns the lowest standard coal consumption rate (275.11 g/kWh) and levelized cost of electricity (4.30 US$/kWh). Therefore, scheme 3 is recommended for the development of SPCP in the near and midterm. The economic performance of SPCP systems will improve as coal price rises or solar field cost falls when compared with the pulverized coal power system.

Transient and troubleshoots management of aged small-scale steam power plants using Aspen Plus Dynamics

This study is motivated by the insufficient studies on the dynamic simulation, operation control optimization, and operation strategies for small-scale old plants. In such small power plants, there is a need for cautions and stability during various troubleshoots. This study aims at developing a simulation model that accurately predicts the behavior of small-scale real plants under various part loads and troubleshoots. The actual operation of a 110-MW steam power-plant was modeled using Aspen Plus Dynamics, which employs a single-input single-output proportional integral (PI) controller. The controller tuning constants, K and IT, were optimized, and operation strategies for handling five troubleshoots are proposed. The simulation results are in good agreement toward the measured values, with a maximum relative error of 2%. The recommended operation strategies could prevent plant trip and return to steady state in a maximum of 5 min when two different halts are mimicked. Full-load thermal efficiencies of 94%, 97.9%, 92.6% were achieved when four burners were shutdown, high-pressure feedwater heaters tripped, and all the heaters tripped, respectively. The simulation presents the possibility of stabilizing the old power plants operation with maximum possible efficiency under various conditions. An updated operation and troubleshoot manual can be provided for various circumstances.

RAM analysis and availability optimization of thermal power plant water circulation system using PSO

This paper presents reliability, availability, and maintainability (RAM) analysis framework for evaluating the performance of a circulation system of water (WCS) used in a coal-fired power plant (CFPP). The performance of WCS is evaluated using a reliability block diagram (RBD), fault tree analysis (FTA), and Markov birth–death probabilistic approach. In this work, the system under study consists of five subsystems connected in series and parallel configuration namely condensate extraction pump (CEP), low-pressure feed water heater (LPH), deaerator (DR), boiler feed pump (BFP), high-pressure feed water heater (HPH). The reliability block diagram (RBD) and fault tree approach (FTA) have been employed for the performance evaluation of WCS. The Markov probabilistic approach based simulation model is developed. The transition diagram of the proposed model represented several states with full working capacity, reduced capacity, and failed state. The ranking of critical equipment is decided on the basis of criticality level of equipment. The study results revealed that the boiler feed pump affects the system availability at most, while the failure of deaerator affects it least. The availability of the system is optimized using the particle swarm optimization method. The optimized availability parameter (TBF, TTR) based modified maintenance strategy is recommended to enhance the availability of the plant system. The optimized failure rate and repair rate parameters of the subsystem are used to suggest a suitable maintenance strategy for the water circulation system of the thermal power plant. The proposed RAM framework helps the decision-makers to plan the maintenance activity as per the criticality level of subsystems and allocate the resources accordingly.

Investigation of the regulatory range expansion at Krasnodar combined heat and power plant due to the partial displacement of regenerative extractions of the K-150-130 unit by steam from the backpressure turbine

The article describes a new way to increase the technical maximum load of Krasnodar CHPP. It involves the joint operation of block part turbo generators and additionally installed backpressure turbine with the displacement of steam extraction to high pressure regenerative heaters. We provided a detailed overview of the power plant equipment. We calculated the effectiveness of joint operation and shutdown of the high pressure feed water heater (HPFH) 1, 2. It showed that when implementing the proposed technical solution, the power increase in the technical maximum mode for each unit amounted to 7.8 MW. The total increase in the power plant is 43.6 MW. The joint operation scheme allows to increase the technical maximum of the power plant with higher energy efficiency: the specific consumption of reference fuel for electricity generation is 4 g r.f./kW*h, lower than when the HPFH 1, 2 is turned off. The economic effect of the applied solution was estimated for Krasnodar CHPP conditions. It was shown that the annual increase in net profit amounted to 33.7 million rubles, and the payback period of investments is 4.7 years.

Study of TGM-94 boiler with variable feed water temperature using a calculation model

The article substantiates the need to test performance capability and effectiveness of a steam boiler in the new conditions under any changes in the regenerative heating circuit of the feed water in a steam turbine plant. Such changes may include: the displacement of steam extractions onto high pressure feed water heaters by the sun, by heat from biomass or garbage burning, or by steam from third-party sources. For this purpose we have developed a mathematical model of the steam boiler TGM-94 from steam turbine installation K-150-130. The model was created with Boiler Designer program. Verification of the calculated and experimental data provided by Krasnodar TTP showed sufficient convergence in both the steam-water and gas paths. We observed differences in the following temperatures: feed water temperature after the first stage of the economizer, flue gases and air temperature at the inlet to the furnace. The maximum difference between calculation and experiment here is 6 °C. We studied the boiler operation at a variable load, but with a constant temperature of the feed water equal to the nominal value of 230 °C. It was shown that in order to work in this mode, and in order to maintain the superheat temperature of the primary and secondary steam, it is necessary to turn on the flue gas recirculation smoke exhausters. We studied the operation of the boiler at a reduced feed water temperature. It turned out that such work leads to a decrease in steam production, if we keep the fuel consumption unchanged. In the case of sustaining steam production, it is required to assess the temperature state of the heating surfaces additionally due to a significant increase in the superheat temperature of both the primary and secondary steam.

Investigation on shell side performance in half-cylindrical desuperheating zone of ladder type helical baffle heat exchangers

The shell-side flow and heat transfer performance in half-cylindrical desuperheating zones of high pressure feedwater heaters were simulated by Fluent. The investigated structures include three ladder type helical baffle heat exchangers, i.e. the two unilateral ladder types with folded and inclined plane strip baffles, and the bilateral plane type, and two comparative schemes of eggcrate support type and double-segmental type and all baffle types are of three different baffle pitches. The visualized flow patterns in the desuperheating zone were demonstrated on special slices to clearly reveal the mechanisms and impacts of baffle configurations and geometrical parameters on thermal-hydraulic performances. The numerical results show that the shell-side heat transfer coefficients ho of all ladder type helical models are superior to those of both eggcrate support and double-segmental ones, among which the bilateral plane model has the best performances. The average values of ho and evaluation indexes hoΔpo−1 and hoΔpo−1/3 of nine helical models raise 2.99%, 149.50% and 36.26% respectively in contrast to those of the corresponding double-segmental models, and the average values of evaluation performance η for schemes of three baffle pitches 80, 120 and 160 (mm) are respectively 1.202, 1.367 and 1.525.

Plugging criteria and stress determination for high-pressure feedwater heater tubes with local wall-thinning

Tubes with local wall-thinning defects are often found in the heat exchangers of high-pressure feedwater heaters in thermal power plants. When serious damage is found in a tube, the tube is taken out of service by plugging it to prevent rupturing at the location of the local wall-thinning defect. This paper introduces a theoretical and numerical analysis of the stresses found in feedwater heater tubes with local wall-thinning defects under pressure and thermal loads. The effect of the dimensions of this defect on these stresses is also studied.Using finite element analysis and regression, analytic equations for the hoop and axial stress on the inner surface of a tube with a local wall-thinning defect are proposed. The plugging criteria for a tube with this form of defect are also determined using von Mises stress theory. It is found that maximum stress occurs on the inner surface of the tube. The radial stress on the inner surface does not depend on the c/t and c/b ratio; rather, depth (c) is the main factor influencing overall stress (i.e., hoop, axial, and von Mises stress), with hoop and axial stress increasing as the depth increases. The longitudinal length (2b) also has an effect on hoop and axial stress. When the depth increases (c/t = 0.3-0.5), the effect of b is more prominent. The procedure used in this study is independent of the material properties and operating conditions, so it can be applied to other tube materials under various operating conditions in high-pressure feedwater heaters.

Factors Involved in Stress Corrosion Cracking of Tubes from a Nuclear Power Plant Feedwater Heater

This study has been carried out to identify the operating factors involved in the failure of two tubes made of 304 stainless steel removed from a high pressure feedwater heater working in a nuclear power plant. The samples cut from tubes have been analyzed by different methods: visual examination, optical (metallographic) microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Following analyses, on the surface of tubes was highlighted the presence of many pits in which cracks have started. Inside the pits, impurities of the type S, Cl, K, Ca were detected too. The branched cracks most likely have occurred as a result of precipitation of small amounts of chlorides deposited and concentrated on the surface of the tubes over a long period of operation. The stresses that favored this type of corrosion cracking were both residual stresses and stresses occurring at the torsion and bending of the tubes, while the high water temperature from feed heater was also a favorable factor for corrosion. The final conclusion was that the tubes failed by a chloride induced stress corrosion cracking mechanism.

Factors Involved in Stress Corrosion Cracking of Tubes from a Nuclear Power Plant Feedwater Heater

This study has been carried out to identify the operating factors involved in the failure of two tubes made of 304 stainless steel removed from a high pressure feedwater heater working in a nuclear power plant. The samples cut from tubes have been analyzed by different methods: visual examination, optical (metallographic) microscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Following analyses, on the surface of tubes was highlighted the presence of many pits in which cracks have started. Inside the pits, impurities of the type S, Cl, K, Ca were detected too. The branched cracks most likely have occurred as a result of precipitation of small amounts of chlorides deposited and concentrated on the surface of the tubes over a long period of operation. The stresses that favored this type of corrosion cracking were both residual stresses and stresses occurring at the torsion and bending of the tubes, while the high water temperature from feed heater was also a favorable factor for corrosion. The final conclusion was that the tubes failed by a chloride induced stress corrosion cracking mechanism.

Failure Analysis in High Pressure FeedWater Heaters and Method to Find the Defect in Tubes

The aim of this study is to analyze the causes of tube failure of the high pressure feed water heaters in thermal power plants and to find out the defective tubes in high pressure feed water heaters using simple and economical method. A feed water warmer is utilized to preheat the kettle feed water in warm power plant. The majority of the feed water radiator utilized in warm power plant is shell and cylinder type. In this kind of feed water warmer, water streaming inside the cylinder and steam consolidating in outside of the cylinder i.e., shell side. The wellspring of warmth utilized in high weight feed water warmer is steam seep from the turbine. The high weight feed water radiators are utilized to improve the thermodynamic effectiveness of the cycle and furthermore diminish the coal utilization of the warm power plant. Test of the disappointment cylinder were taken to investigate the reasons for cylinder disappointment in high weight feed water radiator by visual review, utilizing tube thickness estimation examination, Examining Mechanical properties and substance structure of the cylinder material and strategies for finding the cylinder disappointment ahead of time to counteract the breakdown of high weight feed water warmers. In light of the above investigations, it is seen that the high weight feed water warmer cylinders disappointment happened because of cylinder external distance across disintegration.

Failure Analysis in High Pressure Feed Water Heaters and Method to Find the Defect in Tubes

Failure Analysis in High Pressure Feed Water Heaters and Method to Find the Defect in Tubes

Plugging criteria for thinned high-pressure feedwater heater tubes considering pressure and thermal loading

When heat exchanger tubes have critical thinning which could cause unsafe conditions, it is general practice to plug the tubes so that they are out of service to prevent rupture failure at the thinnest location. Plugging criteria for the high-pressure feedwater heater tubes of fossil power plant were studied. Tubes in the desuperheating zone were considered due to their high internal pressure and the high temperature difference across the tube wall. Theoretical analysis of uniform thinning and eccentric thinning of the tube was conducted to determine the stress conditions at the thinnest location under internal/external pressure and thermal gradient across the tube. The minimum required tube thickness was determined using the maximum shear stress criterion (Tresca theory). Accuracy and effectiveness of the analytic solutions of the stresses were verified by comparing the results obtained with those obtained from finite element analysis. Using finite element analysis, the stresses for eccentric thinning were determined. Thermal loading due to temperature difference across the wall was considered even though the contribution of pressure loading to the stress of the tube was known to be higher than that of the thermal loading. As case studies, the tube plugging criteria of three high pressure feedwater heaters were determined using actual temperature and design pressure industry data. The procedure used in this study can be applied to different pressure and temperature operating conditions, and different tube materials.

주성분분석을 이용한 고압급수가열기의 고장탐지 및 진단

주성분분석을 이용한 고압급수가열기의 고장탐지 및 진단

Analisis Kinerja High Pressure Heater (Hph) Tipe Shell and Tube Heat Exchanger

Heat exchanger is one of the supporting production equipment that move the heat energy from one of fluid to another fluid flow. One example of a heat exchanger in power plant industry is High Pressure Heater (HPH). HPH is high pressure feedwater heater that using hot steam turbine waste product used as heating medium before entering the economizer on boiler to reduce the work of boiler. This research was conducted to determine the effective efficiency of High Pressure Heater at Power Plant Industry. This efficiency determination is based on thermodynamics and heat transfer analysis with Log Mean Temperature Difference (LMTD) method and Number of Transfer Unit (NTU) method. The analysis is to determining the effective heat transfer, overall heat transfer coefficient (U), Effectiveness and the analysis of pressure drop (∆P). The analysis results obtained the efffective heat transfer of 37.013 kW, overall heat transfer coefficient (U) of 502,48, effectiveness of 0,47 and the number of pressure drop of 23.498,06 Pa.

Safety and efficiency assessment of a solar-aided coal-fired power plant

Hybridizing solar energy with a coal-fired power plant has proven to be an efficient way of reducing coal consumption and discharged pollutants. In this study, solar energy was employed to heat boiler inlet feedwater through a solar high-pressure feedwater heater H0 to increase its temperature. Solar-aided feedwater heating of aN600-24.2/566/566 supercritical coal-fired power plant is discussed asa case study. An all-condition mechanism model (ACMM) of SACFPP was proposed and simulated by MATLAB/Simulink. The maximum solar energy input for the safeoperation of a boiler was determined as 66,544kW based on ACMM simulation results. Moreover, the boiler efficiency and solar-to-electricity efficiency plummetedas solar energy inputincreased. The solar-to-electricity efficiency decreased from 23.33% to 20.33% when the solar energy input increased from 16,636kW to 66,544kW (in 100%THA). The solar-to-electricity efficiency decreased from 16.76% to 13.29% when the solar energy input increased from 16,636kW to 66,544kW (in 35%BMCR). A high unit load corresponds to high solar-to-electricity efficiency. SACFPP had a high coal saving rate when it operated in a lower load condition.

Performance simulation on unilateral ladder type helical baffle heat exchanger in half cylindrical space

A unilateral ladder type helical baffle heat exchanger (ULHBHX) which is a novel countercurrent U-tube heat exchanger was proposed and investigated for better characteristics of high heat transfer coefficient, low resistance, anti-vibration and anti-fouling with a spiral flow pattern than those of the conventional segment one. The numerical model of ULHBHX was established and simulated by CFD software with 38 heat transfer tubes and 2 rod and spacing tube assemblies in the lower half cylindrical space under the parameters of subcooling of a high pressure feedwater heater in power plants. Different views such as on baffle-parallel slices and polygonal slices were presented to show the flow patterns of the main helical flow, secondary vortex flow and the leakage flow. The influences of geometrical parameters of baffle pitch and projection length of the inclined section on heat transfer and pressure drop were discussed quantitatively. The results show that the shell-side heat transfer coefficient ho of the ULHBHXs is 13.2%–18.2%, with an average of 16.0%, higher than those of the corresponding segment schemes, and the comprehensive index hoΔpo−1/3 is 15.7%–46.4%, with an average of 28.3%, higher than those of the corresponding segment schemes with identical baffle pitches in the discussed range.

THERMODYNAMICAL ANALYSIS OF HIGH-PRESSURE FEED WATER HEATER IN STEAM PROPULSION SYSTEM DURING EXPLOITATION

Nowadays diesel engines prevail as ship propulsion. However, steam propulsion is still primary drive for LNG carriers. In the presented paper high-pressure feed water heater was analyzed, as one of the essential components in LNG carrier steam propulsion system. Measurements of all operating parameters (fluid streams) at the analyzed heat exchanger inlets and outlets were performed. Change of the operating parameters was measured at different steam system loads, not at full load as usual. Through these measurements was enabled the insight into the behaviour of the heat exchanger operating parameters during the whole exploitation. The numerical analysis was performed, based on the measured data. The changes in energy and exergy efficiency of the heat exchanger were analyzed. Energetic and exergetic power inputs and outputs were also calculated, which enabled an insight into the change of energetic and exergetic power losses of the heat exchanger at different steam system loads. Change in energetic and exergetic power losses and operating parameters, which have the strongest influence on the high-pressure feed water heater losses, were described. Analyzed heat exchanger was compared with similar heat exchangers in the base loaded conventional steam power plants. From the conducted analysis, it is concluded that the adjustment and control modes of these high- pressure heat exchangers are equal, regardless of whether they were mounted in the base loaded conventional steam power plants or marine steam systems, while their operating parameters and behaviour patterns differ greatly.