Feedwater Heater Research Articles

АЭС малой мощности с аккумулятором теплоты фазового перехода

Nuclear power plants (NPP) are characterized by low maneuverability. This fact exacerbates the problem of the balance of generated and consumed power when nuclear power plants are used as an energy source. This problem is especially relevant for isolated power systems. One of the ways to increase the maneuverability of nuclear power plants is to use heat accumulators directly in the NPP circuit. The study is carried out for two most attractive options of including a heat accumulator in the NPP circuit: 1) parallel to a high-pressure heater to heat feed water; 2) to generate additional steam for a low-pressure cylinder. The efficiency of each of the options is determined based on the calculation of thermal schemes of nuclear power plants with a heat accumulator. The authors have calculated the power of the turbine unit and electricity generation when a heat accumulator is included in the nuclear power plant circuit. The analysis of the data obtained shows that when using a heat accumulator in the NPP circuit in parallel with high pressure heater to heat feed water, the power of the turbine unit is increased by 7,2 % in the accumulator discharge mode, and additional electricity generation due to accumulated heat is 0,63 MJ for each kilogram of waste steam. When using a heat accumulator to generate additional steam for a low-pressure cylinder, the power of the turbine unit is increased by 6,6 % in the accumulator discharge mode, and the additional power generation due to the accumulated heat is 0,40 MJ per kilogram of waste steam. Application of heat accumulators in the NPP circuits will allow using the accumulated heat to generate additional electricity during high demand hours. Thus, the use of heat accumulators in NPP circuits is a way to increase the maneuverability of nuclear power plants, to reduce the negative impact of maneuverable modes on NPP equipment, and to reduce the number of liquid radioactive waste. The most effective and simple way to use the heat accumulator in the NPP circuit is to install it in parallel to the high-pressure heaters. In future, it is planned to determine the design of the heat accumulator, to model heat exchange processes in the heat accumulator

A feedheat-integrated energy storage system for nuclear-powered steam plant

The paper provides thermodynamic analysis of an energy storage concept in which thermal stores are coupled with the feedwater heating train of nuclear-powered steam plant. This allows the electrical output of the plant to be flexed whilst maintaining constant reactor power, thereby providing the equivalent of an electricity storage system and facilitating the adoption of a load-following role for nuclear plant. The concept falls under the umbrella of ‘generation-integrated energy storage’, which exploits existing hardware required for generation to reduce storage costs, and benefits also from fewer energy transformations when compared to ‘electricity-in-electricity-out’ forms of storage. This means that a high (effective) round-trip efficiency can be achieved at low cost. An important feature of the proposed system is that the turbine bleed flows (at their various pressures and temperatures) automatically provide good thermal matching with the feedwater temperature profile, so that heat can ultimately be transferred to and from sensible-heat thermal-storage media with high exergetic efficiency. Various options are discussed for the thermal stores, including pressurised water tanks, thermal oils and packed beds. The analysis also includes consideration of the off-design behaviour of cycle components.

Performance enhancement of a solar-assisted pulverized coal power system by integrating a supercritical CO2 cycle

Current solar-assisted pulverized coal power (SPCP) systems lack the efficient cascading utilization of solar energy, resulting in its wastage. Therefore, there is a need to optimize the integration scheme between solar energy and pulverized coal power systems. In this study, the integration of two different supercritical CO2 cycles with SPCP systems is proposed to enable the cascaded utilization of solar energy. The thermal performances of the two proposed power systems are presented. Then, a sensitivity analysis is performed to examine the effects of supercritical CO2 cycle variables on the system. Finally, an economic evaluation is conducted to examine and compare the economic performance. The results demonstrate significant reductions in the extraction steam superheat and the exergy loss in feedwater heaters. Compared to SPCP systems, both proposed systems exhibit a decrease in the standard coal consumption rate by approximately 4.7 g/kWh. Sensitivity analysis shows that the CO2 mass flow rate has the most important effect on the system performance. The economic evaluation reveals that the cost of electricity for the two suggested systems increases by only about 0.04 cents/kWh. In summary, the findings suggest that the proposed power systems exhibit superior thermal performance and confirm its economic feasibility in the future.

Exergy Audit of Thermodynamic Parameters and Performance Analysis of OgorodeThermal Power Plant in Delta State, Nigeria.

The exergy analysis of the Ogorode steam plant is presented. The aim was to determine and identify the magnitudes and locations of real exergy losses in order to improve plant efficiency. The exergy losses occurred in the various components of the steam plant, such as the boiler, economizer, turbine, super heater, condenser, pump, feed water heater, reheater, and air pre-heater, and these have been calculated using the concepts of availability or available exergy and irreversibility. The temperature and pressure of the plant's running conditions were combined to determine the process irreversibility (exergy losses) and the exergy efficiency of the plant. The exergy losses of the individual components of the plant show that the maximum exergy losses are in steam turbine operation one (STO ) and steam turbine operation two (STO ). STO and STO are 813 kJ/kg, 1 2 1 2 820 kJ/kg, 822 kJ/kg, and 815 kJ/kg that occurred in the turbine between 2019 and 2021, while the minimum exergy losses in STO and STO are 68 kJ/kg, 150 kJ/kg, 1 2 280 kJ/kg, and 276 kJ/kg that occurred in the boiler system between 2019 and 2021. There was a high energy efficiency of 82% and 80% in the superheater between 2019 and 2021, while 89% in the feed water heater and 73% in the superheater had the same duration. The efficiency of 15% and 21% were the minimum in the pump system between 2019 and 2021, while the turbine had a minimum of 20% and 27% from 2019 to 2021. The highest losses of exergy occurred in the turbine as a result of the irreversibility inherent in the turbine process, corroded turbine blades as a result of wet steam, and low energy delivered to the superheater tubes. It was concluded that the turbine inlet temperature should be increased, more energy delivered to the superheater should be increased, boiler pressure should be increased, and weak feed water heaters should be replaced for better performance of the thermal plant.

A novel concept to improve the flexibility of steam power plants using an electric feedwater heater

The concepts of operational flexibility enhancement for steam turbine power plants described in the trade literature focus on thermal energy accumulation and utilization. In this paper a new concept of flexibility improvement is presented for steam turbine power plants, using an electric heater to preheat the feedwater for the boiler. The proposed method does not require extensive alterations in the power plant process systems, and no large thermal energy storage is necessary. It is important to note that this solution is only applicable if the boiler and its control system have the capability to work under this reduced load condition. By using electric feedwater heating it is possible to reduce the power transferred to the grid and keep the plant in operation at low loads. Thanks to the developed model of a 200 MW reference power plant using the Ebsilon Professional 15 software, the authors carried out simulation tests, based on which it has been proven that it is possible to reduce the minimum load for grid production from 92 MW to 78 MW. Although the efficiency of the electricity production decreased, the cost analysis has shown that the proposed modifications are reasonable, thanks to the improved cooperation of the 200 MW power plant with the grid. The NPV in the analysed system was PLN 35 million, and the sensitivity analysis showed that the profitability will increase with the increased number of necessary shutdowns of power plants without modifications. This is particularly important considering the development of renewable energy sources and the random and stochastic nature of their electricity generation.

The recovery of blowdown heat using steam dryer in biomass power plant

The main objective of this paper is to propose the blowdown heat recovery system using a steam dryer. A flash tank is used to reduce blowdown water pressure and generate flash steam. Flash steam is supplied to the steam dryer to decrease fuel moisture content. Exhaust vapor vented from the steam dryer is also used to increase air temperature in an air heater. Furthermore, due to decreased fuel moisture content and increased air temperature, the exhaust flue gas temperature may be decreased by increasing the air heater surface area in the boiler. This method of blowdown heat recovery has never been proposed before. Therefore, it may be considered as knowledge gap that is worth an investigation. The use of blowdown heat for steam drying is compared with the use of blowdown heat for feed water heating. Simulation results show that using blowdown heat for steam drying results in a significantly larger net power output. Furthermore, the integration of this heat recovery system is economically feasible.

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.

Energy, exergy, and economic evaluation of integrated waste incineration facility with a thermal power plant

Increased waste production and poor waste management have created severe negative environmental impacts. Waste incineration is a way to produce energy and decreases environmental impacts; however, this technique cannot be considered independently as a source of power generation because of its low performance. This study aims to evaluate the integration of a waste incineration system with a natural gas-fired power plant in terms of energy, exergy, and economic points. As a result of the proposed configurations, in addition to promoting efficiency and net power production, some equipment is removed from power plants. Efforts are made to increase the accuracy of simulation results by paying attention to the combustion process in boilers and predicting the actual working condition of feed water heaters. Results showed that the hybrid scheme improves electricity generation by up to 2.87 MW and boosts energy, and exergy efficiency by up to 0.32%, and 0.3%, respectively.

Comparison of exergy and exergy economic evaluation of different geothermal cogeneration systems for optimal waste energy recovery

Since energy sources are limited, any activity aimed at recycling energy waste or facilitating energy conversion systems is invaluable. Against this background, most scientists focus on the integration of energy systems and the coupling of different technologies. In this study, a variety of power systems are investigated for optimal power conversion configurations of geothermal sources. Three configurations, Organic Rankine Cycle Geothermal Cooling (GPR/ORC), Kalina Cycle Geothermal Cooling (GPR/Kalina), and Rankine Cycle and Feed water Heater (GPR/FWH) Geothermal Cooling, are classified according to exergy and Study energy economic analysis. Calculations show that the GPR/FWH system has the highest net output power of 2963 kW. In addition, the GPR/Kalina system has the lowest output power and lowest energy efficiency among the systems launched. Across the three proposed systems, the fuel cell generates 1254 kW of electricity, while the Kalina cycle in the GPR/Kalina system generates 487 kW. Exergy studies show that the GPR/Kalina and GPR/FWH systems have the lowest and highest irreversibility (3795.4 kW and 4365.56 kW, respectively). Furthermore, the fuel cell was found to have the greatest exergy destruction rate among the three configurations. The results of the economic analysis show that the fuel cell has the highest cost ratio among all designs. In addition, the values of the dissipation factor show that the absorption chiller has the highest dissipation factor value among the three configurations. Furthermore, the comparative parametric analysis provides new aspects to introduce into the system.

Two-stage distributionally robust optimization for joint system design and maintenance scheduling in high-consequence systems

The failures of high-consequence systems can cause serious harm to humans, including loss of human health, life security, finance, and even social chaos. To protect high-consequence systems, both optimal system design and maintenance activities contribute to improving system reliability and social safety. The existing works generally optimize these two problems sequentially and assume that the degradation process of components is precisely known. However, sequential optimization often results in significant losses due to redundancies, and such a presumption usually cannot be guaranteed in practice, due to limited historical data or a lack of expert knowledge, referred to as epistemic uncertainty. To fill this gap, in this article, we consider an integrated optimization of system design and maintenance scheduling for multi-state high-consequence systems in which the component’s degradation is known with limited distributional information. To address this issue, we utilize the framework of distributionally robust optimization to provide a risk-averse decision to decision-makers even under the worst realizations of random parameters, and develop a two-stage integer distributionally robust model with moment-based ambiguity set to determine the system design and maintenance scheduling simultaneously. The proposed model can be converted to a tractable approximation as an integer linear stochastic programming problem. In order to solve large-scale problems, we develop a sample-based adaptive large neighborhood search algorithm to find the optimal system designs. In the numerical experiments, we present a case study on feedwater heating systems in nuclear power plants and demonstrate that an integrated optimization consideration creates significant benefits in profitability. We also present the out-of-sample performance of the distributionally robust design to avoid extreme risk.

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.

Analysis of Exhaust Gas Heat Utilization in Waste Heat Recovery Power Generator at Indarung V Factory PT Semen Padang

Increasing energy efficiency in the cement production process at PT Semen Padang is carried out by reusing exhaust gas to produce electricity using Waste heat recovery power generation (WHRPG) with a capacity of 8.5 MW. WHRPG is a technology for utilizing exhaust gas heat as a source of heat energy to heat feed water into steam by using a suspension preheater (SP) boiler and air quenching cooler (AQC) boiler. This study aims to calculate the power potential of the steam heat influenced by the steam temperature and the mass flow rate of the steam produced by the boiler, to calculate the efficiency of the boiler using the direct method by comparing the boiler output heat against the boiler input heat, to calculate the turbine efficiency based on the difference between the steam enthalpy enter the turbine against the steam enthalpy out of the turbine and the isotropic enthalpy of the steam out of the turbine and to calculate the power generated by WHRPG at PT Semen Padang. The results obtained in this study are the total potential power of steam heat is 19.778 MW, the boiler AQC efficiency is 70.30%, the boiler SP efficiency is 94.04% and the turbine efficiency is 78.64%. The electricity generated by PT Semen Padang's WHRPG is 3.70 MW.

Performance analysis of nuclear powered desalination unit based on MED-TVC: a case study for Saudi Arabia

Abstract Nuclear desalination has been identified as an alternative option with much lower carbon dioxide emissions to provide fresh water by driving high capacity desalination plants. This work considers a theoretical analysis of using nuclear desalination to provide fresh water in three selected Saudi Arabian cities. It presents a theoretical model that integrates the characteristics of nuclear reactor, power cycle and desalination blocks. The power block includes three steam turbines and five feed water heaters. It is coupled via low pressure turbine to a multiple effect desalination unit integrated with a thermal vapor compressor encompassing eight effects, seven feed preheaters and a down condenser. The output includes work generated as function of fuel mass and reactor type, enrichment percentage, power and water production with different nuclear reactor type. Desalination performance indicators such as the fresh water production rate, gain output ratio (GOR), specific energy consumption (SEC) and specific cooling water mass flow rate have been evaluated and analyzed as function of sea water temperature for three specific Saudi cities. It was found that these indicators reflect better performance along a year for Jizan city than for Jubail and Tabuk. The case of Jizan city gives over the whole year more uniform values of water production rates, gain output ratio, specific energy consumption and cooling water mass flow rates.

Design and Performance Evaluation of Integrating the Waste Heat Recovery System (WHRS) for a Silicon Arc Furnace with Plasma Gasification for Medical Waste.

A hybrid scheme integrating the current waste heat recovery system (WHRS) for a silicon arc furnace with plasma gasification for medical waste is proposed. Combustible syngas converted from medical waste is used to drive the gas turbine for power generation, and waste heat is recovered from the raw syngas and exhaust gas from the gas turbine for auxiliary heating of steam and feed water in the WHRS. Meanwhile, the plasma gasifier can also achieve a harmless disposal of the hazardous fine silica particles generated in polysilicon production. The performance of the proposed design is investigated by energy, exergy, and economic analysis. The results indicate that after the integration, medical waste gave rise to 4.17 MW net power at an efficiency of up to 33.99%. Meanwhile, 4320 t of the silica powder can be disposed conveniently by the plasma gasifier every year, as well as 23,040 t of medical waste. The proposed design of upgrading the current WHRS to the hybrid system requires an initial investment of 18,843.65 K$ and has a short dynamic payback period of 3.94 years. Therefore, the hybrid scheme is feasible and promising for commercial application.

Repowering a Coal Power Plant Steam Cycle Using Modular Light-Water Reactor Technology

This article presents the results of a techno-economic analysis of repowering a coal-fired power plant’s steam turbine system to instead accept heat produced by a pressurized water reactor-type small modular nuclear system (PWR SMR). This type of repowering presents a challenge due to the significantly lower steam pressure and temperature produced by the nuclear system. A 460 MW supercritical power unit with steam parameters of 28 MPa/560 °C/580 °C, operated in the Łagisza Power Plant in Poland, was selected for the analysis. After repowering, the turbine system would be fed with saturated steam from the steam generators of the SMRs at a pressure of 7 MPa and a temperature of 285 °C. In total, four options for repowering were analyzed. In all cases, the existing high-pressure section of the turbine was disconnected, and the existing low-pressure stages of the turbine, as well as all auxiliary and outward components (feedwater heaters, pumps, generator, condenser, condenser cooling, etc.), are re-used in their existing configurations, except for a feedwater-heater pump that needs to be replaced. In three cases, the existing intermediate pressure turbine section acts as the high-pressure stage of the repowered system. These cases include repowering without an additional reheater (case A), with an added single-stage reheater (B) and with an added two-stage reheater (C). In the fourth case (D), the existing intermediate pressure section was replaced by a new high-pressure turbine stage suited to the SMR live steam conditions. While all four repowering options are technically possible and may represent an economic advantage compared to a complete greenfield SMR installation, option D with a new high-pressure stage is clearly the best option available, with significant cost savings, leading to a lower levelized cost of electricity (LCOE) and a higher net present value (NPV) and net present value ratio (NPVR) than the greenfield case and all other repowering. For relatively new coal power plants with equipment in good condition, this type of repowering may present a cost optimal near-term pathway.

Assessing economic feasibility of retrofitting steam dryer and steam-air preheater to existing biomass power plant

Conventionally, the thermal design a biomass power plant is aimed at maximizing the energy efficiency by using extracted steam to increase feed water temperature in feed water heaters and installing heating surface areas of heat exchangers in boiler to recover flue gas energy. The temperature of flue gas at the boiler outlet must not be so low that a risk of acid corrosion is unacceptable. The energy efficiency can also be improved by reducing fuel moisture content in steam dryer and increasing air temperature in steam-air preheater. However, both devices require extracted steam, which is already used for raising feed water temperature in an existing power plant. In this paper, it is hypothesized that retrofitting steam dryer and steam-air preheater to an existing power plant can improve the energy efficiency. Performances of the existing power plant and the retrofitted power plant integrated with steam dryer and steam-air preheater are compared. Simulation results indicate that, despite lower final feed water temperature in the retrofitted power plant, the retrofitted power plant is more energy efficient than the existing power plant. Economic assessment is carried under the condition that both power plants generate the same power output, which means that the retrofitted power plant consumes less fuel than the existing power plant. The payback period for the retrofitting investment is approximately 7 years.

Second law evaluation and environmental analysis of biomass-fired power plant hybridized with geothermal energy

Two novel configurations for hybridization of geothermal and biomass energies are proposed and analyzed in this paper. In the first system (named Configuration 1) geothermal heat is employed for feed water heating, while in second one (named Configuration 2) the geothermal energy is employed for steam generation to be entered into the low pressure steam turbine stage. The method of hybridization of geothermal and biomass resources in this paper is quite different than the schemes proposed in previous researches. Another unique feature of the proposed hybrid configurations is the ability of utilizing geothermal resources with various temperature level. In order to assess the feasibility of proposed systems and to compare their performance, detailed simulation models are made based on the first and second laws. Also, the systems’ performances are evaluated from the environmental perspective using three exergo-environmental factors. In addition, the optimal operating conditions of the systems are determined with respect to the maximum exergy efficiency. For a wide range of practical operating conditions it is found that, the proposed Configuration 2 outperforms the Configuration 1 due to the direct steam injection into the law-pressure turbine in the former. Under the optimal operation, it yields 8.65 % higher exergy efficiency as well as 12.5% lower environmental damage effectiveness compared to Configuration 1. Also it is concluded that, the gasification and combustion processes own more than 55% of overall exergy destruction in both systems.

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.

Exergy analysis of modified-supercritical power plant with solar assisted feedwater heating and CO<SUB align="right">2 capture

Solar energy is the most readily available energy in India, which can be utilised in coal-fired thermal power plants for feedwater heating and Monoethanolamine (MEA) for MEA regeneration in post-combustion CO2 capture unit. The present study deals with 4-E (energy, exergy, environment, and economic) analysis of a 500 MWe Supercritical (SupC) coal-based thermal power plant with solar-assisted feedwater heating and MEA regeneration in CO2 capture unit. Results show that the plant efficiency is improved by 8.2% points, and the coal consumption rate is reduced by 18%. The levelised cost of electricity (LCoE) generation is increased to INR 6, and the cost for CO2 avoided is INR 3607 per tonne of CO2.

Exergy analysis of modified-supercritical power plant with solar assisted feedwater heating and CO<SUB align="right">2 capture

Exergy analysis of modified-supercritical power plant with solar assisted feedwater heating and CO<SUB align="right">2 capture