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The boiler efficiency is improved with the help of economizer it is one of the main accessory part in the boiler. Boiler feed water is preheated with the entry of reused flue gas through economizer. This present work is planned to analyze the overall heat flux and overall heat transfer in the boiler economizer. Higher amount of flue gases passing around the economizer to preheat the feed water at the same time much more heat is transferred. The heat transfer is analyzed by statistical method with influence of different process parameters. Economizer fin dimensions are major consideration to taken for this analysis and estimate the overall heat flux and overall heat transfer. The process parameters of this study are named as thickness of the fin (3.5 mm, 4 mm, 4.5 mm and 5 mm), Height of the fin (4 mm, 5 mm, 6 mm and 7 mm), Fin gap (12 mm, 14 mm, 16 mm and 18 mm and Tube diameter (44 mm, 46 mm, 48 mm and 50 mm). The response values are finding as overall heat flux and overall heat transfer.

Photocatalytic membrane reactors (PMRs) are a promising treatment technology for degradation of organic compounds discharged from wastewater treatment facilities. This review presents information about TiO2 nanoparticles, which are the widely used photocatalyst semiconductor in PMRs, and how doping can be used to make TiO2 able to absorb part of the visible spectrum. Then, many examples are presented showing PMR applications for various feedwater types ranging from dyes, oils, pharmaceuticals, and antibiotic resistant bacteria, either in simulated wastewater or water from real matrices. Although the results are dependent on the feed, photocatalyst, and type of reactor, the PMR technology can achieve removal efficiency higher than 95% for some situations. PMRs have also shown antimicrobial properties in removing 99.9% of antibiotic-resistant bacteria in one study presented. Additionally, PMRs have demonstrated antifouling properties due to their surface modification – resulting in their reuse and extended lifespan. Although photocatalytic membrane reactors can achieve quantitative removal in some feed water types, more development is needed before employing them for more widespread wastewater treatment. In this sense, the article ends with a perspective section where some possible advances in the photocatalyst and reactor design are suggested which can expand the range of PMR applications.

Daily start-up is a typical feature of concentrated solar power plants (CSPs) due to solar energy intermittency. Therefore, appropriate start-up operation strategies are significant for CSPs. A parabolic trough concentrated solar power plant (PTCSP) with molten salt (MS) is a potential technical route. However, little attention has been paid to the dynamic start-up performance of PTCSP using MS. To mend the research gap, the dynamic start-up simulation of PTCSP using MS is conducted. Main contributions of this study are the dynamic start-up simulation of PTCSP using MS and evaluation of two MS anti-freezing solutions. Results indicate that the outlet MS temperature of solar field transiently exceeds nominal values during start-up processes. The inlet feedwater temperature of the preheater is much lower than MS freezing temperature during start-up processes. Therefore, two anti-freezing solutions were used to avoid MS solidification. Compared with utilizing the recirculating pump, utilizing the low-load regenerative heater can enhance anti-freezing performance, which could reduce the maximum control deviation of the preheater inlet feedwater temperature by 2.0 °C and increase the average outlet MS temperature of the preheater by 2.4 °C. This study may provide guidance for the dynamic simulation and operation optimization of CSPs during start-up processes.

Herein, the water depth in a pyramidal solar still was kept constant using an automatic feedwater system through an auxiliary tank. Six water depths ranging from 5 to 50 mm were investigated. All variables were measured continuously but were logged automatically every hour. Increasing the water depth increased the water volume, thereby increasing the thermal capacity of the solar still. Therefore, increasing water depth increases the nocturnal yield but decreases the diurnal yield. Over the whole day, lower water depths resulted in higher accumulated yields. These accumulated yields increased by 37% by decreasing the water depth by 90% from 50 mm. The desalination system can work without human intervention, improving its sustainability. Moreover, the automatic feedwater system facilitates the end-user operation processes and succeeds in maintaining a constant optimal water depth in the solar still.

In coal-fired power plants, most of the working fluids used in a mid–low-temperature flue gas waste heat recovery system (FGWHRS) are low-temperature boiler supply air or condensate water in the flue gas condenser. This is prone to cause low-temperature corrosion, as the system temperature is lower than the acid dew point of the flue gas. In this study, an experimental apparatus was set up at the entrance of the desulfurization tower of a 330 MW unit in Xinjiang, China, which uses the technology of high-temperature boiler feed water (above 80 °C) to recover the waste heat of mid–low-temperature flue gas. The heat exchange performance of the mid–low-temperature FGWHRS was evaluated under different working conditions, and the optimal input parameters of the system for each considered working condition are given based on the analysis. It was found that the low-temperature corrosion in the system could be avoided using this technology. To eliminate low-temperature corrosion, the lowest temperature for the inlet water was predicted to be 69 °C in our study via curve fitting based on the experimental data. The results could provide a theoretical basis and engineering guidance for determining the best heat recovery strategy of mid–low-temperature FGWHRS.

Regression models of demineralizing filters for a nuclear power plant will increase the efficiency of the desalination process for turbine condensate. To identify the control object, experimental and statistical research methods were applied. To detect the presence and study the extent of relations between the process factors and output variables, the STATISTICA (StatSoft) analytical system was used. The impact of factors on the studied traits was assessed using a nonlinear estimation module. Upon the analysis of the desalination plant operation, the following initial parameters were identified. These parameters influence the control decisions in managing the object, can be predicted over time and are not random variables such as the values of specific conductivity and hydrogen index. For specific electrical conductivity: Xh is the specific electrical conductivity of the condensate after the desalination plant; Na is the concentration of sodium ions in the condensate behind the condensate electric pump of the first stage; CN2H4 is the concentration of hydrazine in the feedwater of the steam generator; CFe is the concentration of iron ions in the condensate on the condensate electric pump of the first stage; T is the temperature of the condensate sample on the condensate electric pump of the first stage; CCl is the concentration of chlorine ions in the purge water of the salt compartment of the steam generator; and CSO4 is the concentration of sulfate ions in the purge water of the salt compartment of the steam generator. For the hydrogen index: pH is the hydrogen index of the condensate after the desalination plant; CN2H4 is the concentration of hydrazine in the feedwater of the steam generator; T is the temperature of the condensate sample on the condensate electric pump of the first stage; and CFe is the concentration of iron ions in the condensate behind the condensate electric pump of the first stage. To detect the presence and study the extent of relations between the selected factors of relevant process and output variables, a correlation analysis was conducted and input factors were subsequently ranked. The correlation analysis allowed ranking all the variables and their possible interaction effects in a descending degree of impact on the outputs. In accordance with the selected system outputs, based on the ranking of input variables, regression analysis was performed and corresponding mathematical dependences were obtained with alternate inclusion of factors in a decreasing degree of their influence on the output variable to establish functional dependencies between the experimental data on desalination plant operation. The regression dependence for the experimental data of specific conductivity on the selected state parameters was obtained. The coefficient of determination is equal to 0.7245. The regression dependence describing the change of the hydrogen index has also been obtained. The coefficient of determination is equal to 0.7231. The proposed models explain 72% of the variation in the dependent variable. The correlation ratio is 0.82, which determines the close relationship between the values. Regression models adequately describe the operational data of the nuclear power plant and can be used as part of the control system of the filter unit.

Due to its danger and complexity, the identification and prediction of major severe accident scenarios from an initiating event of a nuclear power plant remains a challenging task. This paper aims to classify severe accident at the Advanced Power Reactor (APR) 1400, which includes the loss of coolant accidents (LOCA), total loss of feedwater (TLOFW), station blackout (SBO), and steam generator tube rupture (SGTR) using a standard probabilistic neural network (PNN) and Particle Swarm Optimization Based Probabilistic Neural Network (PSO PNN). The algorithm has been implemented in MATLAB. The experiment results showed that supervised PNN PSO could classify severe accident of nuclear power plant better than the standar PNN.

Energy efficiency is one of the major challenges in water desalination systems. In the present study, a novel improvement for the Evacuated tube collector as a vapor generator was proposed. This improvement is achieved by decreasing the heat capacity using a film of feed water beside the absorber tube. The proposed system operated in continuous feedwater flow with backup. An inclined tubular still was used for vapor condensation. The inclination angle of the still and its diameter were investigated. The study was performed experimentally with a theoretical analysis of the thermal energy conversion. Water film thicknesses (WFT) of 2, 4, and 6 mm were examined. The 2 mm WFT achieved the optimum overall efficiency of 53%. The tested diameters of the tubular still were 80, 120, and 160 mm. The 160 mm diameter achieved the highest overall efficiency of 60.2%. Moreover, the 160 mm diameter condenser achieved the best vapor storage option. The tested inclination angles of the still were 80°, 62°, and 45°. The 45° angle achieved the best overall efficiency of 48.1%. The cost of the distilled water reaches 0.01205 $/L per unit collector area.

Based on the example of a two-stage modernization of all turbine feedwater pumps of the Kostroma State District Power Plant (SDPP), the experience of development, optimization, and successful operation of this equipment with a high degree of reliability is described. All the tasks assigned by the plant management were completed as demonstrated by the long-term maintenance-free operation of the feedwater pumps. As a result, employees were able to concentrate on fulfilling the priority task of generating electricity at optimal energy conversion efficiency and maximal availability factor.

The design and operating conditions of the low-pressure circut of Ep-258/310/35-15.0/3.14/0.44- 540/535/263 (P-132) heat-recovery steam generator (HRSG) as part of 795 MW CCGT were studied to reduce the wear of its tubes. Reliable and effective operating conditions of the natural-circulation loop are presented. The design of the low-pressure loop of P-132 is described. Modifications of the operating conditions to reduce the velocity of steam-water mixture in the natural-circulation loop, which, in turn, reduces the flow-accelerated corrosion, are described. In particular, the effect of changes in the drum pressure at constant and variable feedwater temperature on the velocity of the steam-water mixture is described. Methods and designs for eliminating gas shunts to equalize the heat absorption by the evaporator tubes in the HRSG are proposed. Several modifications of the HRSG design intended to reduce flow-accelerated corrosion are considered: a new evaporator design with outlet bends replaced with straight tubes; a new design of the riser system with more independent movement of the mixture from the evaporator; a different longitudinal spacing of evaporator tubes. The combined effect of modifications to the design and operating conditions on the reliability of the low-pressure loop is studied. It is concluded that the optimal solutions to reduce flow-accelerated corrosion are to increase the pressure in the low-pressure drum, to redesign the outlet section of the low-pressure evaporator and the low-pressure riser system, and to install anti-shunt partitions in the heating surfaces. These measures will allow steel 20 to be used to manufacture evaporation and riser tubes of the low-pressure loop due to the reduction of the velocity of steam-water mixture.

Mathematical thermodynamic modeling is used in desalination systems to obtain unknown values and predict various properties such as enthalpy or phase equilibrium. These models are useful to understand system behavior. Zuara desalination plant is a multi-effect evaporation plant without vapor pressure (MED) with three total units of 40,000 m3/day. A mathematical modeling of the desalination plant thermal components was performed to simulate and forecast the temperatures, mass flow rates, and the productivity of each cell of steam. The total productivity of the desalination unit and the performance rate in different operating conditions was also found. A Python program was used to solve the model equations. The obtained results show that the productivity of the system and the gain output ratio are directly proportional to seawater temperature and inversely proportional to plant load.

An advanced cogeneration system based on biomass direct combustion was developed and its feasibility was demonstrated. In place of the traditional single heat source (extraction steam), the extraction steam from the turbine, the cooling water from the plant condenser, and the low-pressure feedwater from the feedwater preheating system were collectively used for producing district heat in the new scheme. Hence, a remarkable energy-saving effect could be achieved, improving the overall efficiency of the cogeneration system. The thermodynamic and economic performance of the novel system was examined when taking a 35 MW biomass-fired cogeneration unit for case study. Once the biomass feed rate and net thermal production remain constant, an increment of 1.36 MW can be expected in the net electric production, because of the recommended upgrading. Consequently, the total system efficiency and effective electrical efficiency augmented by 1.23 and 1.50 percentage points. The inherent mechanism of performance enhancement was investigated from the energy and exergy aspects. The economic study indicates that the dynamic payback period of the retrofitting project is merely 1.20 years, with a net present value of 5796.0 k$. In conclusion, the proposed concept is validated to be advantageous and profitable.

For target or stabilizing the operation of ammonia converter R-107 is Semadco CTALKHA II Fertilizer Company that is by designing appropriate control system for the "HP BFW heater E-127" CHigh Pressure Boiler Feed Water heater) which governs the system inlet temperature; It is very important to construct a mathematical model which simulates perfectly the practical system construction and operation, Such a model is not clearly and accurately presented in references. So; this work deals with formulating and constructing suitable mathematical model for this E -127 heater. The modeling procedure is based on dividing the chemical system into subsystems coupled through boundary conditions. The suggested mathematical model is tested numerically by computing the system open loop performances, which are then compared with the recorded experimental performances from the field. The results obtained show good agreement between both of the suggested model and the physical system.

To obtain the dynamic characteristics of reactor secondary circuit under transient conditions, the system analysis program was developed in this study, where dynamic models of secondary circuit were established. The heat transfer process and the mechanical energy transfer process are modularized. Models of main equipment were built, including main turbine, condenser, steam pipe and feedwater system. The established models were verified by design value. The simulation of the secondary circuit system was conducted based on the verified models. The system response and characteristics were investigated based on the parameter transients under emergency shutdown and overload. Various operating conditions like turbine emergency shutdown and overspeed, condenser high water level, ejector failures were studied. The secondary circuit system ensures sufficient design margin to withstand the pressure and flow fluctuations. The adjustment of exhaust valve group could maintain the system pressure within a safe range, at the expense of steam quality. The condenser could rapidly take out most heat to avoid overpressure.

One of the important elements produced from the factory support units is air products. Regional water balance (integration) is important to support factory operations. Raw water is treated in the unit section to produce demin water and further process into Boiler Feed Water (BWF) to produce 80 kg/cm2 pressurized steam in the boiler unit, to meet the specifications as demin water it is necessary to carry out several treatments to remove mineral ions (cations and anions) dissolved in the air. In the mixed bed polisher, there is a resin regeneration process to eliminate saturation of the resin which can no longer bind mineral ions. Regeneration or regent is carried out after the resin pile is saturated which is characterized by an increase in product productivity conductivity with the desired product conductivity target of

The safe and secure designs of any nuclear power plant together with its cost-effective operation without accidents are leading the future of nuclear energy. As a result, the Reliability, Availability, Maintainability, and Safety analysis of NPP systems is the main concern for the nuclear industry. But the ability to assure that the safety-related system, structure, and components could meet the safety functions in different events to prevent the reactor core damage requires new reliability analysis methods and techniques. The Fault Tree Analysis (FTA) is one of the most widely used logic and probabilistic techniques in system reliability assessment nowadays. The Dynamic fault tree technique extends the conventional static fault tree (SFT) by considering the time requirements to model and evaluate the nuclear power plant safety systems. Thus this paper focuses on developing a new Dynamic Fault Tree for the Auxiliary Feed-water System (AFWS) in a pressurized water reactor. The proposed dynamic model achieves a more realistic and accurate representation of the AFWS safety analysis by illustrating the complex failure mechanisms including interrelated dependencies and Common Cause Failure (CCF). A Simulation tool is used to simulate the proposed dynamic fault tree model of the AFWS for the quantitative analysis. The more realistic results are useful to establish reliability cantered maintenance program in which the maintenance requirements are determined based on the achievement of system reliability goals in the most cost-effective manner.

For the structural integrity evaluation of pressurized water reactor (PWR) steam generator (SG) tubes subjected to transient hydraulic loading, determination of the tube-to-tube gap velocity and static pressure distributions along the tubes is prerequisite. This paper addresses both computational fluid dynamics (CFD) and analytical approaches for predicting the tube-to-tube gap velocity and static pressure distributions during blowdown following a feedwater line break (FWLB) accident at a PWR SG. First of all, a comparative study on CFD calculations of the transient velocity and pressure distributions in the SG secondary sides for two different models having 30 or no tubes is performed. The result shows that the velocities of sub-cooled water flowing between any adjacent two tubes of a tubed SG model during blowdown can be roughly estimated by applying the specified SG secondary side porosity to those of the no-tubed SG model. Secondly, simplified analytical approximate solutions for the steady two-dimensional SG secondary flow velocity and pressure distributions under a given discharge flowrate are derived using a line sink model. The simplified analytical solutions are validated by comparing them to the CFD calculations.

THE PURPOSE. To consider the problems of the increasing dissolved oxygen concentration in feedwater, especially after the condensate pumps. To estimate the opportunity of the vacuum thermic deaeration intensification inside the PT-60-130/13 LMZ steam turbine condenser to reduce the feedwater system rate of corrosion. Perform a thermal test of the external deaerating hotwell, which provides reducing dissolved oxygen concentration by the hot drains and recirculating feedwater. To evaluate the march of the dissolved oxygen concentration in feedwater after the inclusion of the deaerating hotwell. METHODS. The thermal test of the external deaerating hotwell was chosen for evaluating water deaeration. RESULTS. In this paper, the results of the thermal tests are given. The relation of the dissolved oxygen concentration from heating fluid flow is also presented. CONCLUSION. The use of the external deaerating hotwell allows achieving dissolved oxygen concentration below the norms established by the сode of operation for electrical power plants and grids to ensure the maintenance of an acceptable water-chemical regime of the feedwater. During the tests, the dissolved oxygen concentration decreased by 70% and reached a value of 8 mcg/dm3. The deaerating hotwell of the considered type can be recommended for the operation, especially during start-up modes and modes with the low thermal load on the condenser cooling surface.

This paper reports on a new and open-source dataset, curated from facility-specific engineering reports, that details facility features for an aggregated total of 70 operating, demonstration, pilot and unbuilt U.S. potable water reuse systems. The dataset and our following analysis reviews treatment train design, estimated electricity consumption, facility capital and operation and maintenance costs, and air emission externalities of those systems. Despite a wide variety of feedwater qualities and augmentation strategies, we observe remarkable consistency in potable reuse treatment train design. We estimate potable reuse electricity intensity for each facility as a function of feedwater quality and installed unit processes, finding that advanced treatment train electricity intensities fall within the range of 0.23–2.5 kWh m−3. This range excludes the energy required for conveying water to advanced treatment facilities or pumping the water for supply augmentation. For 25 facilities with capital cost data, we find that potable reuse capital costs normalized by system design capacity fall between 1000 and 5300 $ per m3 d. Subsequent cost analysis of the subset of full advanced treatment (FAT) systems suggests capacity normalized capital costs between 1800 and 4100 $ per m3 d and capacity normalized operation and maintenance costs between 100 and 200 $ per m3 d. These ranges validate previously reported bottom-up cost estimates for FAT facilities. Finally, we use the Water AHEAD model to estimate the annual human health, environmental, and climate damages for representative advanced treatment trains. Air emission externalities from U.S. potable reuse facilities fall between 10 and 40 $ per thousand m3, with the majority of damages associated with electricity consumption at potable reuse facilities.

This paper presents a numerical prediction of the transient hydraulic loads acting on the tubes and external supports of a pressurized water reactor (PWR) steam generator (SG) during blowdown following a sudden feedwater line break (FWLB). A simplified SG model was used to easily demonstrate the prediction. The blowdown discharge flow was treated as a flashing flow to realistically simulate the transient flow fields inside the SG and the connected broken feedwater pipe. The effects of the SG initial pressure or the broken feedwater pipe length on the intensities or magnitudes of transient hydraulic loads were investigated. Then predictions of the decompression pressure wave-induced impulsive pressure differential loads on SG tubes and the transient blowdown loads on SG external supports were demonstrated and the general aspects of transient responses of such transient hydraulic loads to the FWLB were discussed.

Membrane fouling has been claimed as a significant culprit ruining all membrane processes. Feed spacer is a component that helps to mitigate the membrane fouling by creating turbulence over the feedwater flow. In recent years, three-dimensional (3D) printing technology has been adopted to produce feed spacers with complex geometry as well as maintaining high accuracy. Despite the fact that common 3D printing techniques and materials have been studied by numerous researchers, the contributing factors towards the improvement of feed spacers efficiency for membrane filtration systems in water treatment remains unclear. In fact, the performance of feed spacers are highly associated with their mechanical strength, the water flux produced and the fouling resistance of membrane sheets when tested simultaneously with the feed spacers. These characteristics are closely related to membrane fouling and they can be influenced by the 3D printing materials, methods and designs. This paper provides updates on the progress of 3D printed feed spacer development related to how the 3D printing process works, the materials associated with the 3D printing methods and how the spacer designs affect the membrane separation processes.

A circulating fluidized bed boiler is designed and built to conduct visualization study by combining the circulating fluidized bed heat transfer technology and boiler. Water and polyformaldehyde particles are selected as the working media. The effect of the operating parameters such as the amount of added particles and feedwater flow rate on the fluidization and distribution of particles are investigated by using a charge coupling device. Results show that the particles can be normally fluidized and circulated at proper feedwater flow rate and amount of added particles. The solid holdup in the riser bundle increases with increased feedwater flow rate and amount of added particles. With increased feedwater flow rate, the nonuniform degree of particle distribution decreases. The amount of added particles has less influence on particle distribution than feedwater flow rate. The average solid holdup in the water wall tubes is close to that in the splayed flue tubes.

Reverse osmosis (RO) is the leading technology in desalination for both, brackish and seawater. Modeling RO process is a complex task as there are a high dependence on the operating conditions and feedwater characteristics. One of the main drawbacks of this technology is the performance decay due to fouling impact. Usually, fouling make the pressure drop to increase. This increase has not been reflected in the proposed models in RO process. The aim of this work was to proposed a time-dependent model for the pressure drop in RO process. For this purposes long-term experimental data of two full-scale brackish water RO desalination plants with two stages each were used. The first desalination plant was operating along 11 years in continuous regime while the second desalination plant was in operation during 14 years in intermittent regime. In the first desalination plant, the pressure drop ranges were 75-250 kPa and 25-150 kPa in the first and second stage respectively while in the second desalination plant were 50-200 kPa and 20-125 kPa. The behavior of the experimental data in both cases was close to an exponential function. The mentioned function was fitted in time domain using the standard deviation as error function.

Thermal power plants (TPP) with cross connections and having a minimum reference fuel rate of 321 g/(kW h) prevail in the structure of the generating capacities in Russia. In practice, this characteristic is often above 500 g/(kW h). Application of parallel-type, dual-fuel combined-cycle units (CCUs) using coal as the main fuel, for improving the efficiency of power plants with cross connections is considered. Such CCUs have high efficiency and are suitable for modernization of operating subcritical power plants with cross connections. The power of CCUs with gas turbines manufactured in Russia or having a high degree of production localization in Russia can be as high as 200–250 MW. In all the cases, a new heat-recovery steam generator (HRSG) and a new steam turbine for a live-steam pressure of 12.8 and 8.8 MPa must be developed. The paper considers the process features of such dual-fuel cogeneration CCUs based on a 6FA gas turbine. A CCU thermal scheme is developed. Bled steam conditions under different operating conditions are determined considering the bypass of the main condensate and feedwater lines. GCU performance indices as a function of ambient air temperature are determined. In addition, an option was considered for modernizing the existing cogeneration power plant (TETs) in the town of Seversk by implementation of a dual-fuel CCU based on an 82 MW 6FA gas turbine and a T-96/122-8.8 steam turbine while maintaining the coal-fired power steam boilers in operation. It is demonstrated that the proposed modernization option makes it possible to reduce the fuel cost by approximately 240 million rubles per year while increasing the electricity delivery under cogeneration conditions by 1.7 times.

The present study reports the characterization of reverse osmosis (RO) technology at water treatment plant Cogen-2 in paper and Board mills, Pakistan. RO is a commonly used process to obtain de-mineralized water for high-pressure boiler operation in thermal power plants. Scaling and fouling in three-stage RO plants is a major challenge in chemical industry due to the use of raw brackish water in the power plant of paper and board mills. In our study, the feed water quality of RO was changed from soft water to raw water to make it economical. The cleaning frequency was increased three times than normal, which was unsafe for operation and it was required to control scaling and fouling to achieve the desired result. Differential pressures behavior of all stages for 2-month data was observed without acid treatment, and the results of Langelier Saturation Index (LSI) control parameters (temperature, pH, total dissolved solids, calcium hardness, and alkalinity) clearly showed the abnormality. To optimize scaling and fouling of RO, the LSI factor was controlled in total reject water for the next 2 months by acid treatment in feed water. Duration of chemical cleaning and membranes’ life has been extended by fouling and scaling control. Understanding the effect of operational parameters in RO membranes is essential in water process engineering due to its broad applications in drinking water, sanitation, seawater, desalination process, wastewater treatment, and boiler feed water operation. The product flow increased from 18.3 to 19.9 m3/h, and this was due to a decrease in the rejection flow from 8.2 to 6.7 m3/h. The total reject stream pressure also increased from 8.1 to 9 bar. A lower value of LSI of 1.6 is obtained in the reject water stream after the acid treatment.

Helical-coil steam generator (HCSG) technology is a major design candidate for small modular reactors due to its compactness and capability to produce superheated steam with high generation efficiency. In this paper, we investigate the feasibility of the passively autonomous power maneuvering by coupling the 3-D transient multi-physics of a soluble-boron-free (SBF) core with a time-dependent HCSG model. The predictor corrector quasi-static method was used to reduce the cost of the transient 3-D neutronic solution. In the numerical system simulations, the feedwater flow rate to the secondary of the HCSGs is adjusted to extract the demanded power from the primary loop. This varies the coolant temperature at the inlet of the SBF core, which governs the passively autonomous power maneuvering due to the strongly negative coolant reactivity feedback. Here, we simulate a 100-50-100 load-follow operation with a 5%/minute power ramping speed to investigate the feasibility of the passively autonomous load-follow in a 450 MWth SBF PWR. In addition, the passively autonomous frequency control operation is investigated. The various system models are coupled, and they are solved by an in-house Fortran-95 code. The results of this work demonstrate constant steam temperature in the secondary side and limited variation of the primary coolant temperature. Meanwhile, the variations of the core axial shape index and the core power peaking are sufficiently small.

The system optimization scheme of adopting outer steam coolers (OSCs) to utilize turbine extraction superheat (conventional scheme) is considered an effective way to improve the thermal efficiency of power plants. However, adopting the conventional scheme in a built unit would increase the feedwater temperature, thus generating under-temperature reheat steam for some units. A novel system optimization scheme was proposed with turbine extraction for preheating feedwater and cold reheat steam simultaneously. Case analysis shows that the proposed scheme attains a better energy-saving effect than the conventional scheme under the considered load conditions. The investment payback period (IPP) of the novel scheme is 3.98 years, which is better than the attained 6.93 years of the conventional scheme.

Premature failure of seamless tubes made of 316Ti stainless steel in a boiler feed-water (BFW) heat exchanger occurred at a local steel complex, which led to about 65–70% service-life reduction. The heat exchanger is a fixed-tube-sheet type with hydrogen gas flowing inside the tubes and water circulating through the shell side. The cooled hydrogen gas is purged to box annealing furnaces to create a reducing atmosphere. Failure analysis was conducted on the tubes to determine the contributing factors to premature failure of the heat exchanger. Four issues including corrosion fatigue, pitting corrosion attack, under-deposit corrosion, and fouling contributed to the failure of the tubes in the heat exchanger. The pitting corrosion attack was caused by chloride in circulating water. Chloride was also detected in accumulated deposits on the tubes causing the under-deposit corrosion issue. Contamination of boiler feed-water with Ca, Si, Mg, and Cl occurred during the water treatment process, a congruent phosphate–pH treatment in an in-house water treatment unit. The quality of the supplied water to the heat exchanger does not meet the recommended specifications. As a major recommendation, the tubes of the heat exchanger must be manufactured of super duplex stainless steel UNS S32750, based on specifications of the ASTM A789 standard.

The modern state in design, calculation, and operation of heaters used in the steam-turbine regeneration systems in Russia and abroad is reviewed and analyzed. The first part of the article gives a list of companies producing steam-turbine feedwater heaters and the market shares occupied by the countries producing these apparatuses. The ranges of operating parameters for the feedwater heaters of Russian and foreign steam turbines are indicated. The article gives the types of heat exchangers included in the regenerative feedwater heating system and serving as high- and low-pressure heaters that are adopted in Russia and abroad, including contact apparatuses and plate-type heaters. Specific examples of arranging such apparatuses at power plants in different countries are given. Advantages and drawbacks associated with the use of contact and plate-type apparatuses as turbine unit feedwater heaters are discussed. Different designs of shell-and-tube high- and low-pressure feedwater heaters adopted in the United States, Europe, and Russia are presented. The designs of particular high- and low-pressure heaters characteristic of different domestic and foreign producers are described. Methods for arrangement and structural makeup of different functional areas of the heater’s heat-transfer surface are shown. The advantages and drawbacks of header-and-helical coil-type high-pressure heaters and tubular apparatuses for the similar purpose, including chamber-type apparatuses, are discussed in terms of thermal efficiency, reliability, and repairability. It follows from the presented data that there is no commonly accepted approach to designing the considered apparatuses, and that there is mutual influence of manufacturing experience, design trends, and heater manufacturing traditions in different countries.

Industrial process heating has been identified as a potential field for solar thermal applications. In this paper, a comparative study was carried out on the performance of an individual solar collector under laboratory conditions and performance of the collector array under field condition. Compound Parabolic Concentrator (CPC) has been used as a solar collector for the application of boiler feed water preheating. The characterization of CPC has been done in liquid phase with water as a working fluid as per the standard, IS 16648 (Part-5):2017. The optical efficiency of the CPC is found to be 64.8% under standard test conditions. In the field, total 200 number of CPCs, each having 3 m2 area, were installed. The performance monitoring and evaluation of the actual installation was carried out over a period of 10 months. The system was designed to supply average 448,500 kWh- Thermal/year, saving the equivalent amount of fossil fuel. The comparative study of the performance of CPC collector under standard conditions and actual operating conditions in the field shows significant variation. The average variation in the performance was about 9% with a maximum variation of 14.7%. The major reasons behind the lower performance output than expected, attribute to the heat losses through the collector manifold and piping (3.9%), soiling of reflector and absorber of CPC (1.72%), uncertainties of instruments (1.49%) and other unaccounted losses like dislocation of the evacuated tubes from the original position, loss of vacuum through evacuated tubes, shadow effect, heat utilization pattern etc. (1.89%), which should be considered while designing the solar field to meet the required output.

PurposeIndia's textile industries play a vital role in the Indian economy. These industries consume the highest thermal energy (steam power). The demand of the steam in process industries is increasing rapidly, and this demand can be met by increasing the capacity utilization of steam boilers. The purpose of this paper is to present a new approach for reliability analysis by expert judgment method.Design/methodology/approachA lack of adequate life data is one of the biggest challenge in the reliability analysis of mechanical systems. This research provides an expert judgment approach for assessing the boiler's reliability characteristics. For this purpose, opinions of experts on time to failure and time to repair data were elicited in the form of statistical distributions. In this work, reliability analysis of the boiler system is carried out by expert judgment method and by using best-fit failure model. The system reliability along with preventive maintenance intervals of all components is also evaluated.FindingsIt is observed that the reliability analysis results obtained by expert judgment method and best-fit failure model method indicate that there are no significant differences. Therefore, in case when insufficient data are available, the expert judgment method can be effectively used. The analysis shows that the feedwater tank, feedwater pump, supply water temperature sensor, strainer, return water temperature sensor, condensate filter, mechanical dust collector, coal crusher and fusible plug are identified as critical components from a reliability perspective, and preventive maintenance strategy is suggested for these components.Originality/valueIn this research paper, a system reliability model by the expert judgment method is developed, and it can be effectively used where insufficient failure data are available. This paper is useful for the comparative evaluation of reliability characteristics of a boiler system by expert judgment method and best-fit failure model method.

The boiler is a steam-producing installation that is used to drive steam turbines as power plants in palm oil mills. It is working to remove the heat generated by fuel into the form of steam containing enthalpy, which is used to drive a steam turbine.This study was conducted for 15 days started from May 27, 2017, until June 15, 2017. The location of the study was conducted at PMKS South Sumatra Province. The average boiler efficiency is 81% with a heating value of 2117.6717 kcal/kg compared to other dates that have a higher heating value but efficiency is below 80%. This shows the success of the boiler's performance is not only determined by the heating value contained in the fuel but also determined by the temperature of the feedwater entering the boiler, the amount of fuel in the boiler and the condition of the fuel in the boiler combustion chamber.

Conventional contacting plain face seals develop severe wear, heat checking, or leakage problems in high pressure–velocity water sealing applications such as in boiler feedwater pumps, boiler circu...

The characteristic operational features of different flowmeters and devices for measuring the coolant and feedwater flows in the loops of nuclear steam generating facilities (NSGF) currently operating in NPP are analyzed. A new design has been developed for labeled nuclear-magnetic flowmeter-relaxometers with a new flow measuring regime. This regime and other new structural solutions in the new devices have made it possible to perform measurements with accuracy to within

According to the rise in the use of PV-powered reverse osmotic (RO) systems due to the current global water crisis, brine management has become a serious issue for scientists. To deal with such difficulty, this study proposes a method in which the rejected brine is used to improve the efficiency of the PV panels by cooling the PV panels and also increase the productivity of the conventional RO systems by preheating the feedwater. Thus, an experimental investigation has been performed on a stand-alone PV-powered RO system to assess the electrical and thermal performance of the solar system and to study in parallel the influence of the thermal treatment on the feeding saline water. Conducting a series of tests under five feeding temperature levels (20, 25, 30, 35, 40 °C), with three feedwater salinity levels (1500, 3000 and 4500 mg L-1) at the outdoor conditions, the cooling performance of the brine with various operating parameters was achieved in terms of the growth in PV electrical efficiency. The experimental results demonstrated that when the temperature of the feedwater increases, the salt rejection decreases which leads to a higher recovery factor. Moreover, for the PV cooling purpose, when the brine with temperature below or equal to the ambient temperature is used as the coolant, the temperature reduction on the PV modules is more significant. The maximum improvement in electrical efficiency was found as 3.3% on the PV panels, which shows a 20% increase compared to without cooling conditions. The economic approach also revealed that, if the conventional water used for PV cooling is replaced with the brine rejected from RO systems, the payback period will decrease by 2–4 years depending on the working parameters.

The desalination fuel cell (DFC) is a novel technology for co-production of electricity and desalinated water from a clean energy source, the H2/O2 redox couple. A DFC utilizes a fuel cell anode and cathode to catalyze the chemical-to-electrical energy conversion, as well as a cation and anion exchange membrane to desalinate the feedwater flowing through the cell. To identify key bottlenecks in this nascent technology, it is important to quantify voltage losses associated with major elements of the cell. We here provide first-time detailed experimental breakdowns of voltage losses at electrodes and across membranes in a custom-built DFC, operated both with near-neutral pH water streams and in a pH-gradient mode. The results allow us to pinpoint sources of major voltage losses, provide hypothesis for underlying causes, and can serve to focus future DFC materials development and cell engineering efforts.

The utility industry is currently undergoing a substantial change from analogue to digital infrastructure. Not only plant performance and utility profits are dependent on accurate plant operational parameters but, more importantly, set safety limits need to be met in order to ensure safe operation of nuclear power plants in particular. Using nonquality-assured process data for operational decisions can result in significant over- or under-power events in the plant. In addition, all new technologies such as AI, IIoT, and digital twin technology rely on robust process data as input, putting at risk the significance of the results from the continuing data processing (“garbage in, garbage out”). One method, certified process data reconciliation, or certified process data reconciliation (CPDR), cuts through the vast amount of available process data and generates all relevant process values with the smallest uncertainty possible. In addition, 95% of all collected process data can be discarded after introduction of CPDR. With CPDR, plant operation and maintenance can be significantly optimized and utilities can profit by realizing, e.g., power recovery and measurement uncertainty recapture (MUR). Because the focus on reconciled instead of measured values constitutes a paradigm shift, the application of CPDR needs to be communicated to nuclear regulators. This paper describes the approach and experience of the regulator acceptance process in various countries around the globe.

In this study, a small-scale two-stage multi-stage flash (MSF) desalination unit equipped with a vacuum pump and a solar parabolic collector (PDC) with a conical cavity receiver were integrated. To eliminate the need for heat exchangers, a water circulation circuit was designed in a way that the saline feedwater could directly flow through the receiver of the PDC. The system’s performance was examined during six days in July 2020, from 10:00 a.m. to 3:00 p.m., under two distinct scenarios of the MSF desalination operation under the vacuum (−10 kPa) and atmospheric pressure by considering three saline feedwater water flow rates of 0.7, 1 and 1.3 L/min. Furthermore, the performance of the solar PDC-MSF desalination plant was evaluated by conducting energy and exergy analyses. The results indicated that the intensity of solar radiation, which directly affects the top brine temperature (TBT), and the values of the saline feedwater flow rate have the most impact on productivity. The maximum productivity of 3.22 L per 5 h in a day was obtained when the temperature and saline feedwater flow rate were 94.25 °C (at the maximum solar radiation of 1015.3 W/m2) and 0.7 L/min, respectively, and the MSF was under vacuum pressure. Additionally, it was found that increasing the feedwater flow rate from 0.7 to 1.3 L/min reduces distillate production by 76.4% while applying the vacuum improves the productivity by about 34% at feedwater flow rate of 0.7 L/min. The exergy efficiency of the MSF unit was obtained as 0.07% with the highest share of exergy destruction in stages. The quality parameters of the produced distillate including pH, TDS, EC and DO were measured, ensuring they lie within the standard range for drinking water. Moreover, the cost of freshwater produced by the MSF plant varied from 37 US$/m3 to 1.5 US$/m3 when the treatment capacity increased to 8000 L/day.

The introduction of intermittent renewables such as wind and solar has created a major integration problem that has to be addressed to ensure operational stability for power generation grid systems. While there is some expectation that large scale batteries may provide a solution, this still appears to be far from commercial viability. Consequently, in most cases coal fired power generation has needed to adapt to a new operating regime so that there is adequate energy system stability. This includes being able to achieve, at low minimum load, rapid ramp rates and cycling together with fast start-up. Flexible operation can have significant impact on a coal power plant with most components being affected. This is because of the increase in thermal and mechanical fatigue stresses in the different parts of the plant, which together with corrosion, differential expansion and other effects, often occurring in synergy, reduce the life time of many plant components. There has been considerable development work undertaken to counter these adverse effects while balancing the grid, including new technologies, processes and skills. There are several means to achieve low minimum load combustion, with the critical need to maintain stable combustion. These include the need to understand and mitigate the technical limitations to low burning rates, such as fire stability, flame monitoring, and minimising unburned coal and CO emissions. Fire stability itself depends on many factors, such as changes in firing rate or fuel quality, inaccurate fuel/air ratio or uneven coal flow. Another impact to consider is the effect of low load operation on downstream NOx control systems and connected equipment. Measures for achieving minimum load include ensuring coal quality, air/fuel flow optimisation and coal fineness, operation with a reduced number of mills or smaller mills, indirect firing, thermal energy storage for feedwater heating, tilting burners, reliable flame scanners and economiser modifications. Start-up procedures are complex and expensive as they usually require auxiliary fuel such as gas or oil, during burners the ignition period. Start-up times in power plants can be shortened through application of reliable ignition, turbine integration, reduced thickness of walls in boiler and turbine design, external heating of boiler thick wall components, measures in the turbine (sliding pressure, advanced sealings, steam cooling of the outer casting), proactive cleaning of boiler deposits plus more effective instrumentation and control. Measures to improve high ramp up rates include exploring mill storage capacity, use of a dynamic classifier instead of a static one; measures in the turbine such as opening of throttled main steam valves, condensate throttling, thermal storage for feedwater heater bypass and HP stage bypass, lower thicknesses of pressure parts, and increased number of headers. Preservation during standby periods is important including targeted plant chemistry management of the boiler and turbine. These and other issues are considered and examples presented.

In this study, the pressure drop and heat transfer behaviors of the microchannel evaporators using the boiler feed water were investigated experimentally. The physical and chemical components of the boiler feed water were also determined for this case study. The results of the pressure drop obtained from two measurement methods are the same, with the maximum percentage error is less than 3%. At the low flow rate, the microchannel evaporator with short channel length has lower pressure drop; however, this evaporator has higher pressure drop at the high flow rate. The experimental data above are essential for designing the microchannel evaporators.

Multiple steam generator tube rupture (MSGTR) accidents are considered in seismic level-1 probabilistic risk assessments (PRAs), because a huge earthquake could cause simultaneous damages to steam generator tubes. Although the occurrence frequency of MSGTR is quite low, the accident may directly lead to a core damage. Therefore, effective recovery actions against MSGTR are essential to avoid the core damage. In order to improve the PRA for MSGTR, the recovery actions should be examined. A MSGTR test with ruptures in multiple loops using the Primärkreisläufe Versuchsanlage (PKL) test facility was conducted in the OECD/NEA-PKL-4 project in order to investigate effectiveness of the recovery actions. The experiment assumed that MSGTR occurred in three out of four loops with a total failure of high-pressure injection system of emergency core cooling system. In the present study, a post-test analysis on the PKL test was carried out with RELAP5/MOD3.3 code (RELAP5). Although discrepancies from the test data appeared in some parameters, the code well predicted the overall trends of the major thermal-hydraulic responses observed in the PKL test. Case studies were also performed to confirm the effects of auxiliary feedwater injection into the secondary side of one or more broken steam generators (SGs) on the core cooling.

NuScale is a small nuclear reactor that relies on natural circulation. Its modular production and inherent safety can not only be used to generate electricity in some remote areas, but also provide energy for water desalination and regional heating. However, the dynamic characteristics of the NuScale are different from those of the traditional PWRs because of its passive characteristic. Therefore, it is necessary to study and analyze the system dynamic characteristics of NuScale. The NuScale PWR model is established based on MATLAB&Simulink. It includes point-reactor kinetics model with six groups delayed neutrons, coolant system and steam generator system. The model is established based on the conservation equations of mass, energy and momentum. And the correctness of the model is verified by the comparison between the steady-state calculation results and the design parameters. Transient calculation results are verified by mechanism analysis. To evaluate the dynamic characteristics of NuScale, the sine function changes with different frequencies in reactor reactivity and feedwater mass flow rate are introduced. The amplitude and phase responses of reactor power, secondary loop steam pressure, secondary loop mass flow rate, secondary loop steam temperature, and coolant average temperature are recorded. Then the Bode plot can be drawn with amplitude and phase responses in different frequencies. To evaluate the NuScale dynamic characteristics, frequency domain analysis is performed.