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Evaporative condenser for steam condensing of mini-turbine of steam feeding water pump for 1000 MW air-cooled unit is designed. Variable working condition is analyzed based on the reverse flow between steam and air. The results show that the condensing temperature of the steam in the tube increases with the air temperature and water film temperature increasing. The condensing temperature of the steam decreases with the water flow rate increasing and the wind velocity increasing. The evaporation capacity of the water outside the tube increases with wind velocity increasing. This paper can be refered when evaporation condenser is applied in thermal power plant.

Thermal power stations and process industries all over the world are facing the problem of boiler tube failure frequently. This affects the performance of the power plants leading to a huge amount of money loss. This study performs detailed efficiency testing and simulation of thermal flow inside an industrial boiler. The simulations were carried out using commercial available CFD software. The analysis of the temperature distribution for every location inside the domain is conducted by setting constant heat fluxes, and varying parameters such as mass flow rate of steam, steam inlet temperature and scale thickness. The results showed that the temperature distribution at the tube wall decreases with increase in mass flow rate of steam; decrease in steam inlet temperature; and increase in scale thickness.

When the unit is under normal operating, the steam source of plant-steam is from the fourth steam extraction of turbine. But at the low load operating condition, during the process that the steam source of plant steam switches to reheat cold section from the fourth steam extraction, steam power capability in the turbine is further reduced. In this paper, in order to improve the economy when the turbine is operating under the low load, reheat cold section steam is used as high-pressure steam to extract the fourth steam by the steam technology, which turns the low-pressure steam into the medium-pressure steam for recycling. This paper, taking 300MW unit as an example, discusses the influence on the thermal economy of unit after putting the steam ejector into the plant steam system of thermal power plant.

The Pulverized Coal Fired Boiler is a control object with time-varying parameters, large delay and multivariate tight-coupling. This paper, aiming at improving the actualities of excessive parameters and suboptimal data clustering effect in the Steam Drum Pulverized Coal Boiler running, proposes a new algorithm Fuzzy Clustering Algorithm (APFM) to fulfill the efficiency optimization of the boiler combustion. Based on the Adaptive Particle Swarm Optimization Algorithm (APSO), this new algorithm overcomes the disadvantages of FCM algorithm such as the sensitivity to initial value and the easy involvement in partial optimum, and enhances the abilities of APSO algorithm such as global search and escape from partial optimum. Finally, the feasibility and effectiveness of this clustering method is demonstrated through the simulation experiment.

The power plant boiler mainly constitutes of pipelines for the main steam, hot sections of the reheated steam, cold sections of the reheated steam and the high pressure feed water. Material selection of the four main pipelines will have a marked effect on the security and economy of the power plant operation. The main steam pressure of the 1000MW ultra supercritical unit in Tianjin SDIC Jinneng Electric Power CO.LTD is 27.56MPa, and the main steam temperature is 605°C. It puts forward the high mechanical performance and high temperature performance of the four main pipelines. The thermal stress, coefficient of the heat expansion, operation reliability and the economy, and the compositions of the four main pipelines material selection should be taken into account when demonstration is processed.

The radial temperature difference calculation of a steam drum shell is an important step in the process of calcu-lating its heat stress, so the current Chinese Standard recommended a computing method which was derived from the further modification to the simplified solution for the radial temperature of a steam drum shell. In order to derive the feasibility for the application of the current Chinese Standard computing method to a supercharged boiler, the computing method for the temperature difference of a steam drum shell, which was based on the approximate solution for the radial temperature of a steam drum shell and highly approaches to its analytic solution, was exercised. By analysing the computed results of examples, the conclusions show as follows: The current Chinese Standard computing method for the radial temperature difference of a steam drum shell can’t meet the calculation requirements of all the running work conditions and their courses of a supercharged boiler, and as a universal computing method, it can’t serve as a computing method for the same problem of a supercharged boiler. Whereas the approximate solution can apply to calculating the same problem of a supercharged boiler and a peak shaving utility boiler. Thereby the basis is offered for the selection and usage of the computing method for the radial temperature difference of a supercharged boiler steam drum shell, the pioneering researches on its interrelated problems and prac-tical applications.

The radial temperature difference calculation of a steam drum wall is an important step in the process of calculating the low-cycle fatigue lifetime of a steam drum. So the German Standard TRD301 recommended a temperature difference computing method based on the simplified solution for the radial temperature of a steam drum wall. In order to validate the feasibility for the application of this computing method to solving the same problem of a supercharged boiler, on the basis of the reasonable simplifications to the unstable heat conduction problem across a steam drum wall, its heat-conduction equations and definite conditions were determined, then the analytical solution for the radial temperature of a steam drum wall, together with its approximate and simplified solutions, is derived. The running example of one super-charged boiler was calculated and analyzed by use of the radial temperature difference computing methods based on the approximate and simplified solutions respectively. The com-puted results show that the German Standard computing method of TRD301 has great limitations in the same problem calculation of a supercharged boiler, and it can’t apply to the researches on the same problem and its relevant problems of a supercharged boiler as a universal computing method.

On the basis of the proposed computing method for the low-cycle fatigue lifetime of a supercharged boiler steam drum, and the two computing principles, which super-pose the resultant stress of the internal pressure stress and the radial temperature difference heat stress at the boiler steam drum fatigue checking point, whose influences on the low-cycle fatigue lifetimes of one supercharged boiler steam drum were calculated, compared and analyzed, there out the computing principle of a supercharged boiler for superposing the resul-tant stress of the above-mentioned two stresses was opened out. The simplified computing method, which will be applied to calculating the alternating stress range in a stress cycle at the supercharged boiler steam drum fatigue checking point, was also derived from combining the design feature of a super-charged boiler steam drum with theory analysis, and com-paring with the Chinese Standard computing method, this computing method not only can reduce the calculational work-load, but also can simplify the calculational steps greatly. Thereby the proposed computing method for the low-cycle fatigue lifetime of a supercharged boiler steam drum was also further simplified.

Advanced Heavy Water Reactor (AHWR) is a pressure tube type boiling water reactor employing natural circulation as the mode of heat removal under all the operating conditions. Main heat transport system (MHTS) of AHWR is essentially a multi-loop natural circulation system with all the loops connected to each other. Each loop of MHTS has a steam drum that provides for gravity based steam–water separation. Steam drum level is a very critical parameter especially in multi-loop natural circulation systems as large departures from the set point may lead to ineffective separation of steam–water or may affect the driving head. However, such a system is susceptible to steam drum level anomalies under postulated asymmetrical operating conditions among the different quadrants of the core like feedwater flow distribution anomaly among the steam drums or power anomaly among the core quadrants. Analyses were carried out to probe such scenarios and unravel the underlying dynamics of steam drum level using system code RELAP5/Mod3.2. In addition, a scheme to obviate such problem in a passive manner without dependence on level controller was examined. It was concluded that steam drums need to be connected in the liquid as well as steam space to make the system tolerant to asymmetrical operating conditions.

The mass flow rate is determined in the steam turbine system by the area formed between the stem disk and the seat of the control valve. For precise control the steam mass flow rate should be known given the stem lift. However, since the thermal hydraulic characteristics of steam coming from the generator or boiler are changed going through each device, it is hard to accurately predict the steam mass flow rate. Thus, to precisely determine the steam mass flow rate, a methodology and theory are developed in designing the turbine system manufactured for the nuclear and fossil power plants. From the steam generator or boiler to the first bunch of turbine blades, the steam passes by a stop valve, a control valve and the first nozzle, each of which is connected with piping. The corresponding steam mass flow rate can ultimately be computed if the thermal and hydraulic conditions are defined at the stop valve, control valve and pipes. The steam properties at the inlet of each device are changed at its outlet due to geometry. The Compressed Adiabatic Massflow Analysis (CAMA) computer code is written to predict the steam mass flow rate through valves. The Valve Engineered Layout Operation (VELO) test device is built to experimentally study the flow characteristics of steam flowing inside the control valve with the CAMA input data. The Widows’ Creek type control valve was selected as reference. CAMA is expected to be commercially utilized to accurately design and operate the turbine system for fossil as well as nuclear power plants.

A control system for water level of boiler steam drum based on DSP microprocessor is designed in this paper. The technique of fuzzy control was applied to controlling the water level of the steam drum, the operational principle and application of the fuzzy-PID arithmetic are described. The water level controller with good control effect is developed. Firstly the hardware structure of system is introduced in the paper and then investigates the fuzzy-PID arithmetic carry out, and finally, the simplified program flowchart are given.

An experimental study on flooding in a large-diameter tube is being conducted. In a countercurrent, two-phase-flow system, flooding can be defined as the onset of flow reversal of the liquid compon...

This paper analyzed the dynamic state of the water ring, which is formed through the exothermic process of steam condensation, and its influence on heat transfer during the operating process of the high speed paper machine’s drying cylinder. The influence of perturbation on the flow condition of the water ring was also discussed. This information was used to design the steam-knife gas supply system in the drying cylinder. This system provides a so-called steam-knife to attack the water ring, which would change the dynamic state of the water ring’s fluid level. This would ultimately improve the heat transfer efficiency.

By using the technology of numerical reservoir simulation, we have compared superheated steam soak with saturated steam soak in area of heating, effect of distillation, capability of increasing oil production, volume of steam in need to evaluate the effect of superheated steam soak in heavy oil reservoirs. Analyzed the sensitivity of parameters like steam injection intensity, steam injection rate, soak time, degree of superheat to conclude the rule that they affect on recovery percentage. The research shows that, heating radius of superheated steam is greater than that of saturated steam, distillation effect of superheated steam is better than that of saturated steam, oil production of superheated steam is more than that of saturated steam, steam volume in need of superheated steam is less than that of saturated steam. Recovery percentage of superheated steam soak increases but more and more slowly with the increase in steam injection intensity, increases first and then decreases with the increase in steam injection rate, increases first and then decreases with the increase in soak time, increases but more and more slowly with the increase in degree of superheat. Influence of steam injection intensity is obvious to recovery percentage, but influence of other factors like soak time, steam injection rate, degree of superheat is insignificant.

There is so much exhaust steam in a boiler system that it causes great heat energy waste. A new type auto-reclaim facility of boiler exhaust steam heat energy is designed based on hydrokinetics, pyrology and automation. The new type facility is made up of water-gas injection pump, liquid relay deoxidization tank, field electrical control cabinet, instrument cabinet, loop booster pump and remote consoler. When the facility is used in the boiler system, not only can it reclaim the exhaust steam heat energy but also the whole steam and working medium. The facility is of high reliability under intelligent control and mechanism architecture. The facility has been applied in more than thirty China Petrochemical manufactories. This patent facility receives the high praise in the field of boiler steam heat energy reclaim.

Three element Steam Drum (SD) Level Controller has been conventionally used for most of the boilers, Nuclear power plant steam generator & Boiling Water Reactor (BWRs). Based on the process dynamic studies it was found that this scheme does not work properly for an interacting, interconnected multiple loop boiling water system i.e., Advanced Heavy Water Reactor (AHWR). It is a pressure tube type light water cooled heavy water moderated Boiling Water Reactor (BWR). It has 4-inter-connected parallel loops with 113 × 4 = 452 boiling channels in the Main Heat Transport (MHT) system. These multiple (four) interconnected loops influences the Steam Drum (SD) level control adversely. Such a behavior has not been reported in the open literature. The open loop response is stable, non-oscillatory and non-diverging for a step change in the feed flow rates. Also it is not possible to maintain a steady level in all the SDs even without any external disturbance/perturbation with 4 conventional 3-element individual SD level controllers. To overcome these interactions it is proposed to interconnect all the four steam drums in the liquid & vapor regions respectively. This makes the 4 SDs behave like a single entity. The influence of the interconnect configuration & the level controller are studied in detail to find a robust solution. The response obtained for unsymmetrical core power, symmetrical power maneuvering and reactor trip transients shows that the SD levels do not diverge and quickly settle very near to the set points assigned with SD interconnect schemes.

Steam-Assisted Gravity Drainage (SAGD) is a key in-situ recovery process being used today to extract oil from bitumen reservoirs. In SAGD, an oil-depleted chamber of steam grows within the oil sands formation along a pair of horizontal wells and heats bitumen-laden oil sands at its edge. The viscosity of bitumen drops by up to five orders of magnitude when heated to above 200 °C and mobilized bitumen at the chamber edge flows under gravity to a production well located at the base of the chamber. If the steam chamber does not grow uniformly along the wellpair, then bitumen recovery is less than ideal. To raise the thermal efficiency, and consequently the economics, of the process, efficient heat transfer from chamber to the oil sands must occur and the chamber must grow uniformly along the entire length of the wellpair. If steam fingers develop at the edge of the chamber, then the heat transfer area enlarges and raises the thermal efficiency of the process since more heat is directed to the oil sands. In this research, the stability of the interface between the steam chamber and oil sands is examined by using linear stability theory. The results show that the stability is controlled by the difference between the energy content-weighted Darcy–Rayleigh numbers of the steam/water phases (displacing fluid) and the oil phase (displaced fluid). Also, the results show that at typical SAGD steam saturation temperatures, the chamber edge is unstable providing the steam quality at the edge exceeds about 50%.

HRSG (Heat Recovery Steam Generator) is a boiler to recover heat from the exhaust gas of an engine and to generate steam for more power generation or process. For the HRSG, water-tube type boiler is commonly adopted to accommodate the working pressure or capacity requirement of the system. The water-tube type boiler has a steam drum to separate steam from the water-steam mixture supplied from the evaporator tube (riser). The drum should be sized properly to separate the steam by the gravity and auxiliary internals, such as a demister, which are installed to filter the steam. To size the steam drum and to estimate the filter efficiency of drum internals, the velocity distribution inside the drum needs to be identified. In the present study, a series of CFD has been conducted to find the velocity distributions inside steam drums for conventional HRSGs and water-tube type industrial boilers. The velocity distributions obtained from the simulation have been normalized and a correlation to predict them has been found. The correlation is applied to the steam drum design by determining a proper position of a demister to show proper separation performance.

Methanol is an important chemical with the potential to become an alternative fuel. An optimization study was performed for a Lurgi methanol synthesis reactor using the commercial process simulator Aspen Plus. The optimization routine is coupled with a steady-state model of the methanol synthesis reactor. Syngas inlet temperature, steam drum pressure, and cooling water volumetric flow rate were optimized so that methanol production in the reactor outlet was maximized. The methanol yield increased by 7.04 %.

Summary Steam-assisted gravity drainage (SAGD) has become the preferred process to recover bitumen from Athabasca deposits in Alberta. The method consists of a lower horizontal production well, typically located approximately 2 m above the base of the oil zone, and an upper horizontal injection well located roughly 5 to 10 m above the production well. Steam flows from the injection well into a steam chamber that surrounds the wells and releases its latent heat to the cool oil sands at the edge of the chamber. This research re-examines heat transfer at the edge of the steam chamber. Specifically, a new theory is derived to account for convection of warm condensate into the oil sand at the edge of the chamber. The results show that, if the injection pressure is higher than the initial reservoir pressure, convective heat transfer can be larger than conductive heat transfer into the oil sand at the edge of the chamber. However, enhancement of the heat-transfer rate by convection may not necessarily imply higher oil rates; this can be explained by relative permeability effects at the chamber edge. As the condensate invades the oil sand, the oil saturation drops and, consequently, the oil relative permeability falls. This, in turn, results in the reduction of the oil mobility, despite the lowered oil viscosity because of higher temperature arising from convective heat transfer.

The operative steam production and distribution system of Karsto natural gas processing plant at four operating conditions was studied by exergy analysis. The eight boilers, of which two are direct fired produce steam at a single pressure. The steam (at 59 bar, 420 °C) is then distributed by extensive use of throttling. Most of the steam is utilized at low pressure (7 bar, 200 °C). The effect of implementing steam turbines in steam distribution system, increase of steam production pressure (from 59 to 120 bar) or two-stage pressure steam production (120/59 bar) were examined. The exergy efficiency of the existing system was 44.3%. Implementing steam turbines or elevation of production pressure (single/dual) resulted in marginal exergy efficiencies of 92%, 89.8% and 98.7%, respectively. Combinations of steam turbines and elevated pressure gave a ratio of 90.9%. In terms of lower heating value, the marginal electric efficiencies ranged from 89% to 104%. The single most fuel exergy demanding alternative was the elevated pressure, with 3.6% increase, which resulted in 18.5 MW of extra electric power. The corresponding figures for steam turbines and two-stage pressure were 3.0%/16.2 MW and 2.6%/15.6 MW. Thus, the study provided an example from an existing, industrial steam system that illustrates both the losses in throttling and low-pressure steam production, and the practical potentials for improvement.

Superheated steam was applied to food processing because of advantages that include efficient heat transfer by latent heat and the prevention of product oxidation. Superheated steam solves problems such as water absorption and the dissolution of solid content from foods caused by hot water or saturated steam heating ; however, it causes low product yield due to its high drying capacity. In order to extend the application of superheated steam to food processing, a new oven system (Aqua-gasTM) using superheated steam and micro droplets of hot water has been developed. In this system, a mixture of superheated steam and hot water was achieved under normal pressure by spraying pressurized boiling water into a heating chamber through a nozzle. It was found that Aqua-gas has a higher heat transfer rate than ordinal superheated steam, especially with cold materials. Fresh vegetables have been pasteurized effectively with little change in texture by heating with this system. The moisture content of the food product processed with this oven system can be controlled by regulating the amount of micro droplets used in the superheated steam. This system is currently used in the food industry for cooking potato salad, preprocessing meat, and in the pasteurization of fish products in Japan.

In direct UHT (Ultra high temperature) treatment, milk is pumped through a closed system where it is preheated, high temperature heated, cooled, homogenised and packed aseptically [1] .Continuous direct steam injection is used to quickly raise the temperature of a product, either for pure heating or for a sterilization process. The injector can be of either annular gap type (also called ring nozzle steam injector), or multi hole type. In this study we have analyzed the details of the condensation process by visualizations and by mapping the temperature fields. It was found that steam condensation in steam injectors is an intense process with heat transfer rates in the order of 1 MW/(m 2 K). The steam is always condensed at the equilibrium temperature and the turbulence created in the condensation zone mixes the hot condensate and heated product with the cold product. The efficiency of this turbulent transport determines the sufficient heat transfer area and thus the size of the steam/product interface. If the condensation rate is faster than the steam addition rate the condensation process is unstable which results in detachments, fluctuations, noise and vibrations.

Prototype Fast Breeder Reactor (PFBR) is a 500 MWe pool type sodium cooled reactor. The main function of Steam Generator (SG) is to extract the reactor heat through secondary sodium system and convert the feed water into superheated steam in the tubes of SG. The Steam Generator is a vertical, once through, shell and tube type heat exchanger with liquid sodium in the shell side and water/steam in the tube side. The highly reactive nature of sodium with water/steam requires that the sodium to water/steam boundaries of the steam generators must possess a high degree of reliability against failure. This is achieved in design and manufacture by maximizing the tube & tubesheet integrity and more importantly by proper selection of tube to tubesheet joint configuration. Modified 9Cr-1Mo material is selected as major material of construction for steam generator as this material has excellent high temperature mechanical properties and has high resistance to stress corrosion cracking in caustic & chloride environment. Steam Generator has inlet and outlet nozzles which are made from the pullout shells of SG. Pullouts are made by hot forming process by heating the shell inside the furnace to the temperature of 950- 1100oC followed by die & punch pressing. After forming, the pullouts are subjected to normalizing at 1040-1050oC followed by tempering at 780oC to restore the original material properties. The forming of nozzle pullouts is really difficult and challenging task as the dimensions are too large & dimensional tolerances are very tight. Steam Generator shell assembly is fabricated in horizontal condition after completion of tube bundle which requires insitu welding of shells around the tube bundle. Dimension control during shell welding is extremely difficult as internal fixtures/spiders for ovality control is ruled out due to existence of tube bundle. Utmost care is required during shell welding to avoid arc strike/fusion on the tube (i.e sodium/water boundary), as the gap between tube bundle and shells is very less. After completion of tube bundle and shell assembly, entire 26 meter length SG undergoes Post Weld Heat Treatment (PWHT) in a single charge at 760 ± 10oC for 4 hours soaking time to relieve the welding stresses and to get the homogenous tempered martensite structure. Special arrangements were made to take care of about 240 mm thermal expansion of complete SG assembly during PWHT. Due to asymmetric shape of SG, drying of the water after hydro test & surface treatment is difficult. The effective surface treatment process requires special thought of rotation of the job by 180 degree after completion of partial chemical cleaning due to air pockets on the top surfaces of the shell assembly. This paper highlights the experience gained during welding of tube to tubesheet joints, hot forming of nozzle pullouts, shell assembly and post shell assembly activities of PFBR Steam Generators in detail.

] This paper introduces the composition of a boiler steam drum control system. It uses the application of a programmable PLC control unit for the boiler steam drum control system. By relying on MCGS configuration software, real-time automatic monitoring was accomplished.

Nuclear steam power plants (NPP) are characterized by low efficiency, compared to steam power plants using fossil fuels. This is due to the relatively low temperature and pressure-throttling conditions of the NPP compared to those using fossil fuel. The light water pressurized water reactor (LW PWR) commercially known as AP600 was suggested for Kuwait cogeneration power desalting plant (CPDP). It has 600 MW nominal power capacity and 33% overall efficiency. Meanwhile, the Kuwaiti Ministry of Electricity and Water (MEW) installed plenty of gas turbines (GTs) to cover the drastic increase in the peak electrical load during the summer season. Combining some of these GTs with the AP600 can increase the capacity and efficiency of the combined plant, compared to either the GT open cycle or the NPP separate plants. This paper investigates the feasibility of utilizing the hot gases leaving the GT to superheat the steam leaving the steam generator of the AP600 NPP, as well as heating the feed water returning to the steam generator of the NPP condenser. This drastically increases the power output and the efficiency of the NPP. Detailed modifications to the NPP power cycle and the resulting enhancement of its performance are presented.

The rebuilding of the P-67 boiler for an 800 MW unit at the Berezovskaya GRES, as well as changes in the thermal engineering characteristics of the coal from the Berezovskii-1 seam and its slagging properties, are described. The results of balance tests of the boiler and changes in the thermal efficiency of heating surfaces during 2006 – 2008, including after mechanical cleaning and modernization of the combined cleaning system, as well as with coal dust coarsening and loading of the lower burner layers and downward blast, are discussed.

The influence of external cooling system on the performance of supercritical steam turbine cyclesThe problem presented in this paper refers to the concepts applied to the design of supercritical steam turbines. The issue under the investigation is the presence of a cooling system. Cooling systems aim to protect the main components of the turbines against overheating. However the cooling flows mix with the main flow and modify the expansion line in the steam path. This affects the expansion process in the turbine and changes the performance when compared to the uncooled turbine. The analysis described here investigates the range of the influence of the cooling system on the turbine cycle. This influence is measured mainly through the change of the power generation efficiency. The paper explains the approach towards the assessment of the cooling effects and presents results of the modeling for three supercritical steam cycles.

Natural circulation as a mode of heat removal is being considered as a prominent passive feature in the innovative nuclear reactor designs, particularly in boiling-water-reactors, due to its simplicity and economy. However, boiling natural circulation system poses many challenges to designer due to occurrence of various kinds of instabilities such as excursive instability, density wave oscillations, flow pattern transition instability, geysering and metastable states in parallel channels. This problem assumes greater significance particularly at low-pressures i.e. during startup, where there is great difference in the properties of two phases. In light of this, a parallel channel loop has been designed and installed that has a geometrical resemblance to the pressure-tube-type boiling-water-reactor, to investigate into the behavior of boiling natural circulation. The loop comprises of four identical parallel channels connected between two common plenums i.e. steam drum and header. The recirculation path is provided by a single downcomer connected between steam drum and header. Experiments have been conducted over a wide range of power and pressures (1–10 bar). Two distinct unstable zones are observed with respect to power i.e. corresponding to low power (Type-I) and high power (Type-II) with a stable zone at intermediate powers. The nature of oscillations in terms of their amplitude and frequency and their evolution for Type-I and Type-II instabilities are studied with respect to the effect of heater power and pressure. This paper discusses the evolution of unstable and stable behavior along with the nature of flow oscillation in the channels and the effect of pressure on it.

Steam drum boiler is an important component of boiler on electric steam power plant which is useful to obtain steam. The obtained steam makes turbine spin. In order to obtain maximal result for the steam power plant (PLTU) 1-2 PT PJB UP Gresik, the water level of steam drum boiler must be 0.7625 m and the temperature of steam drum boiler must be 786 K. Thus, it needs some controller to keep the position of water level and the temperature stable. In this problem, we compare two controllers FLC and FOPID. It can be concluded that FLC works better than FOPID controller. Nevertheless, FOPID controller has faster response time than FLC, i.e. no overshoot and more robust when disturbance is present on the system.

The use of steam in heat exchanger networks (HENs) can be reduced by the application of heat integration with the intention of debottlenecking the steam boiler and indirectly reducing the water requirement [Coetzee and Majozi. Ind. Eng. Chem. Res. 2008, 47, 4405−4413]. By reducing the steam flow rate, the return condensate temperature to the boiler is compromised which adversely affects the boiler operation. A means of maintaining efficient boiler operation is to reheat the return flow to the boiler. Steam systems typically employ turbines of which the exhaust is frequently used as a heating utility in the background process. Since turbines operate at various steam levels, a means for incorporating these steam levels into the HEN optimization framework is necessary. Consequently this paper concerns the restructuring of all steam system heat exchangers using conceptual and mathematical analysis to create a series HEN with the aim of reducing the overall steam flow rate, while maintaining the boiler efficie...

During the generation of steam, most water impurities are not evaporated with the steam and thus concentrate in the boiler water. The concentration of the impurities is usually regulated by the adjustment of the continuous blowdown valve, which controls the amount of water (and concentrated impurities) purged from the steam drum. Since a certain amount of continuous blowdown must be maintained for satisfactory boiler performance, a significant quantity of heat is removed from the boiler. It is necessary to provide a simple-to-use method to calculate the total amount of heat that is recoverable using this system. In the present work, a simple-to-use predictive tool, which is easier than existing approaches, less complicated with fewer computations and minimize the complex and time-consuming calculation steps, is formulated to arrive at an appropriate estimation of the percent of blowdown that is flashed to steam as a function of flash drum pressure and operating boiler drum pressure followed by the calculation of the amount of heat recoverable from the condensate. Since all of the heat in the flashed steam is recoverable, the total percent of heat recoverable from the flash tank and heat-exchanger system is calculated in the final step. Results show that the proposed predictive tool has a very good agreement with the reported data wherein the average absolute deviation percent was observed to be around 1.47%.

The development of a modern 660 MW coal-dust generator unit with supercritical steam parameters is described. The major technical solutions that ensure reliability, efficiency, and low emissions of pollutants into the atmosphere are described.

On the basis of experience in commercial operation, the effect of steam seal in tire-shred pyrolysis in a screw-type reactor with superheated steam has been considered and analytically substantiated; there, local steam feed produces the above effect at the total reduced pressure and keeps air from entering the reactor without sluices or valves used for hermetization of its loading and unloading. It has been shown that the increase in the production rate of pyrolysis due to the heating by steam amounts to 10–15% and is limited by the diffusion transfer in the reactor’s charge bed.

As superheated steam is a single-phase gas, it does not fit theories of ordinary steam heat loss calculation models based on two-phase flow. By using the PVT data of superheated steam, this paper builds a calculation model of on-way parameters in the superheated steam injection wellbore. The superheated steam heating area and heating radius formulae are presented. The calculated results for on-the-way change of steams in Well X16 of the Kenneyak oilfield fit well with the field test results. The analysis shows that the temperature of superheated steam varies greatly with heat transfer, the pressure varies greater than for ordinary steam, the steam quality is high when reaching the bottom hole, the steam enthalpy is much higher than for ordinary steam, and the heating radius is wider. 摘要: 过热蒸汽是单相的气体, 以气液两相流理论为基础的普通蒸汽热损失计算模型对其不再适用。通过引入过热蒸汽PVT数据体, 建立了注过热蒸汽井筒沿程参数计算模型。在一定假设的基础上, 理论推导出了过热蒸汽带面积、加热带半径等的数学表达式。利用蒸汽沿程参数计算模型对肯基亚克油田盐上油藏X16井不同状态水蒸汽的沿程变化进行了计算, 结果表明: 计算结果与现场测试结果对应较好。分析认为, 随着热量的传递, 过热蒸汽的温度变化较大, 压力变化也大于普通蒸汽, 到达井底的蒸汽干度特别高, 其热焓值比注普通蒸汽有大幅度提高, 加热半径也有所增加。 Key words: heavy oil, superheated steam, on-way parameter, heating radius, calculation model

The purpose of this study is to develop a new BWR steam separator with a lower pressure loss of more than 20% than the current steam separator while maintaining the steam separation performance. Reducing the pressure loss of steam separators is advantageous in that it reduces the required recirculation pump power and hence increases the net electrical power output. In previous studies, a low-pressure-loss steam separator was developed by three-dimensional two-phase flow simulations verified by 1/2.22-scale model experiment. In this study, performance tests for a full-scale steam separator with an improved swirler were conducted under actual reactor operating conditions of 7.17 MPa and 287°C. The obtained results demonstrate that pressure loss decreases by about 25% and the separation performance is similar to that of the current steam separator under rated reactor conditions.

The principal objective of this study is to formulate a calculation process, based on the second law of exergy, for evaluating the thermoeconomic potential of a steam-turbine plant for trigeneration. The plant employs biomass, namely, waste wood as its energy source. Four different plant configurations are presented and assessed. ‘Their cost effectiveness is evaluated with varying economic and operating parameters’, because only the fuel price and electricity price are varied. In case 1, high pressure superheated steam generated is supplied to meet the demand for process heat as well as chilled water production in an absorption chiller. In cases 2 and 3, steam is extracted at appropriate stages of the turbine and supplied to meet the demand for process heat and chilled water production in an absorption chiller. Steam generated in case 2 produces sufficient power to meet internal demands while case 3 generates excess electricity for sale back to the utility. In case 4, low pressure saturated steam is generated to meet the demand for process heat and electricity is bought from the utilities, including those used to power an electric vapour-compression chiller. For all cases, it was found that exergy destruction is most extensive in the furnace, amounting to nearly 60%. Exergy destruction in the steam drum is the next most extensive ranging from 11% to 16%. It was also observed that the overall production cost decreases with steam pressure and increases with steam temperature.

For AHWR (Advanced Heavy Water Reactor), a pressure tube type Boiling Water Reactor (BWR) with parallel inter-connected loops, the Steam Drum (SD) level control is closely related to Main Heat Transport (MHT) coolant inventory and sustained heat removal through natural circulation, hence overall safety of the power plant. The MHT configuration with multiple (four) interconnected loops influences the SD level control in a manner which has not been previously addressed. The MHT configuration has been chosen based on comprehensive overall design requirements and certain Postulated Initiated Event (PIEs) for Loss of Coolant Accident (LOCA), which postulates a double ended break in the four partitioned Emergency Core Cooling System (ECCS) header. A conventional individual three-element SD level controller can not account for the highly coupled and interacting behaviors, of the four SD levels. An innovative three-element SD level control scheme is proposed to overcome this situation. The response obtained for a variety of unsymmetrical disturbances shows that the SD levels do not diverge and quickly settle to the various new set points assigned. The proposed scheme also leads to enhanced safety margins for most of the PIEs considered with a little influence on the 100% full power steady-state design conditions.

In boiling water reactor (BWR) design, significant acoustic pressure loads impact the steam dryer hood as a result of the main steam line break outside containment (MSLB) event. When a main steam line breaks, it is assumed that the pipe instantaneously breaks completely open to the ambient environment (double-ended guillotine break). Due to the huge pressure difference between the inside of the reactor pressure vessel (RPV) and surrounding ambient environment, a shock wave will form at the break point and burst into the surrounding environment. At the same time, an expansion wave will travel upstream through the main steam line to the RPV, which results in a pressure reduction on the outside of the steam dryer hood. This expansion wave will create a substantial pressure difference between the two sides of the steam dryer hood with a resultant high stress on the hood. This differential pressure load is the acoustic load used in the structure design evaluations for this event. A key design basis requirement for the steam dryer is to maintain structural integrity during transient, and accident conditions. Demonstration that the steam dryers meet this design basis requires a calculation of the magnitude of the acoustic load on the steam dryer during a MSLB. In this study, computational fluid dynamics (CFD) is used as an alternate calculation method to investigate the phenomenon of MSLB. Transient simulations with fine time steps were carried out. The results show that CFD is a useful tool to provide additional information on the acoustic load as compared to the traditional methods. From the CFD results, the minimum pressure value and its distribution area at different flow times was identified. Through the modeling, an understanding of the detailed transient flow field, particularly the acoustic pressure field near the dryer hood during the MSLB was achieved.

The operation of three types of separators for the removal from the hot intermediate superheater steam duct of slag particles which reach the medium pressure part of the turbine from the steam generator. Results on the industrial operation of one of these systems are examined. Possible modifications of the separators are formulated.

This paper proposes improvements to the energy management of a steam system used for potato starch production. The system consists of a steam boiler plant (fired with natural gas), and steam and condensate pipelines with a hot air heat exchanger for drying potato starch (the steam consumer). In the existing system, the boiler cooperates with two open tanks that are responsible for energy losses due to secondary evaporation. Therefore, a closed tank system is proposed to eliminate these energy losses. The coefficients of thermal efficiency and the energy losses are compared between the open and closed tank cases. This study shows that the losses of the closed steam system are consistently lower than those of the open system, improving the coefficient of efficiency by about 6%.

The computer-based boiler performance system presented in this article has been developed to provide a direct and quantitative assessment of furnace and convective surface cleanliness. Temperature, pressure, and flow measurements and gas analysis data are used to perform heat transfer analysis in the boiler furnace and evaporator. Power boiler efficiency is calculated using an indirect method. The on-line calculation of the exit flue gas temperature in a combustion chamber allows for an on-line heat flow rate determination, which is transferred to the boiler evaporator. Based on the energy balance for the boiler evaporator, the superheated steam mass flow rate is calculated taking into the account water flow rate in attemperators. Comparing the calculated and the measured superheated steam mass flow rate, the effectiveness of the combustion chamber water walls is determined in an on-line mode. Soot-blower sequencing can be optimized based on actual cleaning requirements rather than on fixed time cycles contributing to lowering of the medium usage in soot blowers and increasing of the water-wall lifetime.

The paper compares the thermodynamic performance of MS9001 gas turbine based cogeneration cycle having a two-pressure heat recovery steam generator (HRSG) for different blade cooling means. The HRSG has a steam drum generating steam to meet coolant requirement, and a second steam drum generates steam for process heating. Gas turbine stage cooling uses open loop cooling or closed loop cooling schemes. Internal convection cooling, film cooling and transpiration cooling techniques employing steam or air as coolants are considered for the performance evaluation of the cycle. Cogeneration cycle performance is evaluated using coolant flow requirements, plant specific work, fuel utilisation efficiency, power-to-heat-ratio, which are function of compressor pressure ratio and turbine inlet temperature, and process steam drum pressure. The maximum and minimum values of power-to-heat ratio are found with steam internal convection cooling and air internal convection cooling respectively whereas maximum and minimum values of fuel utilisation efficiency are found with steam internal convection cooling and closed loop steam cooling. The analysis is useful for power plant designers to select the optimum compressor pressure ratio, turbine inlet temperature, fuel utilisation efficiency, power-to-heat ratio, and appropriate cooling means for a specified value of plant specific work and process heating requirement.

This is a report of an experimental study of conditions for the cessation of complete steam condensation during movement of a steam-air mixture through the water layer in a condenser-bubbler. An analysis and generalization of the experimental data yields a dimensionless dependence of the underheating of the water at which it begins to allow the passage of steam, without condensing it completely, on the velocity of the steam-air mixture, the air content, and height of the water layer for a wide range of parameters.

The effects of the sodium-water reaction by small water/steam leaks on 2.25Cr-1Mo and Mod.9Cr-1Mo steels have been studied. Test specimens were exposed to small leaks of water/steam in 300°C stagnant sodium. The phenomenon where the size of the nozzle hole became larger with time was observed for the two types of material. Enlargement rate was slightly faster in the 2.25Cr-1Mo steel than in the Mod.9Cr-1Mo steel. Test results of the enlargement rate of the nozzle hole itself with an increasing duration of the steam injection were analyzed by using SEM and CAMSCOPE images. The maximum reaction temperature appeared at a 17 mm point from the measuring tool, which agrees with the maximum distance that was affected by a jet flame.

In this paper, typical and Pd–Ag membrane methanol loop reactors have been analyzed. In the proposed models all basic equipments in the methanol loop were included. Detailed dynamic models described by set of ordinary differential and algebraic equations were developed to predict the behavior of the overall processes. The conventional model was validated against plant data, and then the results of the hydrogen-permselective membrane loop are compared with the conventional model. Using this novel model, diffusion by membrane tubes compensates reduction of production rate due to catalyst deactivation. By use of the membrane model, dynamic optimization of temperatures was performed for improving overall methanol production. Here, differential evolution (DE) method was applied as powerful method for optimization of procedure. Optimal inlet temperatures of membrane tube, steam drum and both of them were determined. The optimization approaches enhanced additional yield throughout 4 years of operation as catalyst lifetime. Therefore, the methanol synthesis loop can be deduced to redesign based on this study.

The direct air-cooling steam turbines have been operated more and more in the north of China. The backpressure of a turbine is affected easily with weather and varies very often in a short time. The variation of backpressure in a larger range from about 10 to 60 kPa causes many problems in design and operation of the turbine. To study the properties of the wet steam flow in the low pressure direct air-cooling steam turbine, an optical—pneumatic probe was developed based on the multi-wavelength light extinction and four-hole wedge probe. Measurements with this probe in a 300 MW direct air-cooling turbine were carried out. The measured local wetness, total wetness of exhaust steam, size distribution of fine droplets, and their profiles along the blade height are presented. The measured cylinder efficiency and total wetness agree well with the results obtained by the thermal performance tests.

A statutory inspection of a boiler steam drum that had seen 10 years of service revealed a few scattered cracks on the inner surface of the drum. The drum was used in the refinery and petrochemical industry. Remnant life assessment, including inspection of other drums, showed presence of several cracks in two out of seven boiler inspected. In situ microstructural analysis revealed a variation in the microstructure in the cracked regions compared to the microstructure in uncracked regions. Additionally, a wide variation in hardness was associated with the microstructural variation. Detailed study on a sample extracted from a cracked region demonstrated that the cracking occurred in a crescent zone similar in appearance to that of a heat affected zone (HAZ) generally associated with a spot weld or other sources of hot spots in the material. Subsequent examination of more samples confirmed that repair welding was carried out at several places on the inner surface of the drums before installation and commissioning and all the cracks were around the repair welds. The failure occurred by crack initiation in the HAZ of the repair welds and the cracks then propagated progressively across the inner surface of the drums. The failure mechanism was identified to be cold cracking and the failure analysis showed that all the factors required for cold cracking, namely, vulnerable microstructure, residual stresses and hydrogen atmosphere, during welding had been present in the drum material.