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Efficiency improvement of thermal power plants is one of the key technologies to protect the global environment because of lower emission gas. There are many approaches in this regard, which are investigated and developed around the world. Thermal efficiency of fossil power plants has been improved by raising steam temperature as high as 620 C in a realization of Ultra Super Critical (USC) steam turbine system. In order to enhance the thermal efficiency further, we are developing the Advanced Ultra Super Critical (A-USC) steam turbine system using high pressure and high temperature steam of 700 C or over 700 C. The main focus of the Research & Development of A-USC steam turbine is the verification of the alloys for the large rotor, casing and valve components, and the main issue for application to the power plant is an economical aspect and field of technology for the realization of such steam conditions with cost-effectiveness, for instance, optimization of cycle heat balance, turbine design, welding technology and so on. This paper describes briefly about R&D results of A-USC steam turbine and suggests an economical strategy in order to make it possible to be realized sooner.

NuScale Power, Inc. is commercializing a 45 Megawatt electric light water nuclear reactor NuScale Power Module (NPM). Each NPM includes a containment vessel, a reactor vessel, a nuclear reactor core, an integral steam generator, and an integral pressurizer. The NuScale Power Module is cooled by natural circulation. The primary coolant in the Reactor Pressure Vessel is heated in the nuclear core, it rises through a central riser, it spills over and encounters the helical coil steam generator, it is cooled as steam is generated inside the steam generator, and it is again heated in the nuclear core. The Steam Generator also must be designed to provide adequate heat transfer, to allow adequate primary reactor coolant flow, and to provide adequate steam flow to produce the required power output. This paper presents the CFD results that describe the transport phenomena on the heat transfer and fluid flow dynamics in helical coil steam generator tubes. The ultimate goal of the CFD modeling is to predict the steam outlet conditions associated with the chosen helical coil tube geometries, solving the primary and secondary flow region together coupled with the helical coil tube. However, current studies are focused on the primary side with the heat flux boundary condition assigned on the outer surface of the helical coil steam generator. In this study, the ANSYS CFX v. 12.1 [1] was used to solve the three-dimensional mass, momentum and energy equations. The helical coil steam generator has complex geometry and modeling entire geometry requires the enormous memory that is beyond our hardware capability and is not practical. Therefore, geometry was limited to 1 degree of the wedge and 5% of the total length in the middle. Only external flow, single phase flow around the helical coils, is simulated using the standard k-e model and shear stress transport model. From the results of the numerical simulation, the pressure drop and temperature profiles were determined. It is important to understand thermal hydraulic phenomena for the design and performance prediction of the reactor internal.Copyright © 2011 by ASME

This paper presents the design and hardware validation of a unique solar powered boiler for powering a desktop scale steam Rankine power cycle. The primary purpose of the desktop Rankine cycle is to improve engineering education through a hands-on laboratory learning approach. Within this context, we have designed and validated a novel, glass-enclosed boiling chamber that generates steam entirely from the sun. Using a solar concentrator, the sun’s heat is focused onto an absorber plate that acts as a heating element. The absorber plate receives solar power via radiation and heats the working fluid through convection. Since this is a direct steam generation boiler, the entering fluid is water that stratifies upon boiling into two steady-state flow regions with both liquid and gaseous phases. A thermal model is developed to characterize the concentrated solar power (CSP), chamber geometry, and heat transfer to the working fluid. A complete solar-to-steam efficiency analysis is presented and validated with the hardware. The boiler’s estimated efficiency is 27.7% for converting typical daily solar irradiance to steam. The solar water boiling process can clearly be observed and is an excellent educational tool for both concentrated solar power as well as Rankine cycle power systems.Copyright © 2011 by ASME

We propose a novel concept for power generation that involves the combination of a low-condition heat generator (LCHG), such as a light water nuclear reactor or a biomass combustion boiler, with an advanced closed-cycle oxy-fuel combustion gas turbine—a type of complex and efficient oxyfuel gas turbine plant, in accordance with our previous studies in combination with a simple oxy-fuel gas turbine plant. In this study, a LCHG is designed to heat water to saturated steam of a few MPa, to assist in the generation of the main working fluids, instead of a compressor used in the advanced oxy-fuel gas turbine. This saturated steam can have a lower pressure and temperature than those of an existing nuclear power plant or biomass-fired power plant. We estimated plant performances from a heat balance model based on a conceptual design of a plant for different gas turbine inlet pressures of 2.5–6.5 MPa and temperatures of 1300 and 1500°C, taking into account the work to produce O2 and capture CO2 . While the net power generating efficiencies of a reference advanced oxy-fuel gas turbine plant are estimated to be about 52.0% and 56.0% at 1300 and 1500°C, respectively, and conventional steam power generation is assumed to have an efficiency of about 35% or less for pressures of 2.5–6.5 MPa, the proposed hybrid plant achieved 42.8–44.7% at 1300°C and 47.8–49.2% for 1500°C. In the proposed plant, the power output contributed by a LCHG may be obtained by subtracting the LNG contribution from the whole net power output. Even supposing that the generation efficiency of the LNG system in the proposed plant remains equal to that of the reference plant (56.0% at 1500°C), some components used in the reference plant are omitted by installation of the LCHG. The efficiency of LCHG system can be estimated 37.4% for 6.5 MPa and 33.2% for 2.5 MPa, even though the LHCG system may be regarded as consisting of fewer plant facilities than a conventional LCHG power plant.Copyright © 2011 by ASME

AREVA Solar has designed, constructed and demonstrated the first successful Once Through Solar Steam Generator (SSG) to deliver superheated steam without intermediate heat transfer fluids. Deployed at the Kimberlina Solar Thermal Power Station, SSG4 represents the state of the art for solar steam production, for stand-alone power generation and augmentation of fossil fueled steam cycles. The ASME Section I boiler was designed, constructed, stamped and commissioned during 2010, and includes a novel Model Predictive Control system capable of maintaining any two of three steam conditions (flow, pressure, temperature) under varying solar input. During field trials in September 2010, exit steam conditions were maintained at 60 +/− 3 bar and 370 +/− 20C during steady and transient conditions, while steam flow consistently exceeded predictions. In a “lights-out” test, simulating complete instantaneous cloud cover, SSG4 had sufficient thermal inertia to supply more than 18 minutes of superheated steam. AREVA Solar’s SSGs incorporate a 400m long tube bundle within an elevated insulated cavity receiver, onto which sunlight is concentrated by reflectors. The multi-pass tube bundle arranges superheater tubes in the high flux regions, and economizer/evaporator tubes in lower flux regions. This assures sufficient heat flux to sustain superheated steam temperatures throughout the operating day, and also reduces the average bundle temperature to reduce radiant heat losses. Boiler tubes were prepared in AREVA Solar’s factory to improve their absorption of solar energy and reduce radiant heat losses. The inverted cavity maintains a stagnant air layer between the tube bundle and a glass cover below the boiler tube supports, to reduce convective heat loss. SSG4 was designed for a Maximum Allowable Working Pressure of 105 bara , and a Maximum Mean Wall Temperature of 482C in the superheater section. AREVA Solar is the first Concentrated Solar Power provider with an ASME “S” Stamp and National Board authorization. Following the initial trials at 370C, the SSG is expected to operate at 450C superheated steam temperature. This paper describes the design, construction, commissioning, and testing of the Compact Linear Fresnel Reflector (CLFR) SSG4.Copyright © 2011 by ASME

The capability of modulating power and heat productions by steam injection in a recuperative cycle gas turbine was investigated. A combined heat and power system using a current state-of-the-art recuperative cycle gas turbine was modeled. Variations in engine performance characteristics due to steam injection were examined. A full off-design analysis was carried out to investigate not only the performance change but also the variation in engine operation caused by the steam injection. Impact of injecting steam at different locations (recuperator and combustor) was investigated. A special attention was given to the change in the compressor surge margin, and a couple of operations that secures a minimum surge margin were comparatively analyzed. Bypass of turbine exhaust gas around the recuperator to increase steam generation was simulated and its usefulness in controlling heat to power ratio was demonstrated. Variations in electric power and thermal energy productions in response to the modulations of injection ratio and gas bypass were presented for a wide ambient temperature range.

A prototype machine for a 150 kW class two-stage radial inflow condensing steam turbine system has been constructed. This turbine system was proposed for use in the bottoming cycle for 2.4 MW class gas engine systems, increasing the total electrical efficiency of the system by more than 2%. The gross power output of the prototype machine on the generator end was 150kW, and the net power output on the grid end which includes electrical consumption of the auxiliaries was 135kW. Then, the total electrical efficiency of the system was increased from 41.6% to 43.9%. The two-stage inflow condensing turbine system was applied to increase output power under the supplied steam conditions from the exhaust heat of the gas engines. This is the first application of the two-stage condensing turbine system for radial inflow steam turbines. The blade profiles of both high- and low-pressure turbines were designed with the consideration that the thrust does not exceed 300 N at the rated rotational speed. Load tests were carried out to demonstrate the performance of the prototype machine and stable output of 150 kW on the generator end was obtained at the rated rotational speed of 51,000 rpm. Measurement results showed that adiabatic efficiency of the high-pressure turbine was less than the design value, and that of the low-pressure turbine was about 80% which was almost the same as the design value. Thrust acting on the generator rotor at the rated output power was lower than 300 N. Despite a lack of high-pressure turbine efficiency, total thermal efficiency was 10.5% and this value would be enough to improve the total thermal efficiency of a distributed power system combined with this turbine system.Copyright © 2011 by ASME

In this work, a tool to predict the performance of fossil fuel steam power plants under variable operating conditions or under maintenance operations has been developed. This tool is based on the Spencer-Cotton-Cannon method for large steam turbine generator units. The tool has been validated by comparing the predicted results at different loads with real operating data of a 565 MW steam power plant, located in Southern Spain. The results obtained from the model show a good agreement with most of the power plant parameters. The simulation tool has been then used to predict the performance of a steam power plant in different operating conditions such as variable terminal temperature difference or drain cooler approach of the feed-water heaters, or under maintenance conditions like a feed-water heater out of service.Copyright © 2011 by ASME

Cerro Prieto Geothermal Power Plant has a capacity of 720 MW. The earliest 5 units are 23 years old, and unit 5 from Cerro Prieto Uno was restored in 2008. This paper presents a thermodynamic analysis on the effects that has the increase of non condensable gases content in geothermal steam. Results show that the cooling water temperature will rise due to the energy entering the system with the water flow of the new vacuum system that feeds the condenser. Normal operation would be limited and there exists a risk of not sustaining the condenser’s pressure. The new vacuum system, should extract from the condenser a flow 4 times larger, requiring 27% more steam at a higher pressure, as well as 4.5 times the quantity of cooling water. At this condition, the water returning to the condenser is 4.3 times larger than the original at a higher temperature, increasing in 218% the associated energy. A thermal behavior model was obtained for the cooling tower. In the most likely scenario the cooling tower exit temperature will be higher than the required, and to maintain the equilibrium it will be necessary to lower the condenser thermal load by reducing the steam flow to the turbine and accordingly, the power delivered.Copyright © 2011 by ASME

Newly developed wet steam flowrate calibration facility is introduced. It has a closed loop in which boilers generate a steam flow up to 800 kg/h. Steam flow of known wetness up to 12% is generated by cooling down a dry steam flow by a heat exchanger. The wetness is calculated from the enthalpy the heat exchanger draws from the dry steam flow. Analysis of the facility performance, calibration results of an orifice flowmeter calibration, and uncertainty analysis are described.Copyright © 2011 by ASME

Large natural gas fired combined cycle electric power plants, while being an increasingly efficient and cost effective technology, are traditionally large consumers of water resources, while also discharging cooling tower blowdown at a similar rate. Water use is mostly attributed to the heat rejection needs of the gas turbine generator, the steam turbine generator, and the steam cycle condenser. Cooling with air, i.e. dry cooling, instead of water can virtually eliminate the environmental impact associated with water usage. Commissioned in the fall of 2010 with this in mind, the Halton Hills Generating Station located in the Greater Toronto West Area, Ontario, Canada, is a nominally-rated 700 Megawatt combined cycle electric generating station that is 100 percent cooled using various air-cooled heat exchangers. The resulting water consumption and wastewater discharge of this power plant is significantly less than comparably sized electric generating plants that derive cooling from wet methods (i.e, evaporative cooling towers). To incorporate dry cooling into such a power plant, it is necessary to consider several factors that play important roles both during plant design as well as construction and commissioning of the plant equipment, including the dry cooling systems. From the beginning a power plant general arrangement and space must account for dry cooling’s increase plot area requirements; constraints therein may render air cooling an impossible solution. Second, air cooling dictates specific parameters of major and auxiliary equipment operation that must be understood and coordinated upon purchase of such equipment. Until recently traditional wet cooling has driven standard designs, which now, in light of dry cooling’s increase in use, must be re-evaluated in full prior to purchase. Lastly, the construction and commissioning of air-cooling plant equipment is a significant effort which demands good planning and execution.Copyright © 2011 by ASME

The K9 combustion test facility enables characterization of combustors at sea level with a new steam injection feature to simulate ingestion of rain and hail by the combustor. By providing steam and water directly to the combustor, DGA is now able to check its stability and its loss of efficiency under the most severe test conditions. In this paper, the description of this new water supply will be made and a brief description of quality of the spray used for the production of steam will be presented. A specific study has been made concerning the air flow measurement with some corrections due to the presence of high concentration of steam in the air. The second part of this paper is dedicated to the control of the vaporization of water, the correct control of the steam / air ratio in the flow and the consequences on the thermal behavior of the facility.Copyright © 2011 by ASME

Many industrial sectors and applications are characterized by the availability of low enthalpy thermal sources with temperatures lower than 400 °C, such as the ones deriving from both industrial processes (e.g. combustion products from gas turbines and internal combustion engines, technological processes and cooling systems) and renewable sources (e.g. solar and geothermal energy). The usual systems for the conversion of thermal energy into mechanical and/or electrical energy work due to the high temperature difference available between the source (i.e., combustion products) and the sink (i.e., the ambient). The Organic Rankine Cycle (ORC) is a promising process for conversion of heat at low and medium temperature to electricity. An ORC system works like a Clausius–Rankine steam power plant but uses an organic working fluid instead of water. A certain challenge is the choice of the organic working fluid and of the particular design of the cycle. The process should have high thermal efficiency and allow a high coefficient of utilization of the available heat source. Moreover, the working fluid should fulfill safety criteria, it should be environmentally friendly, and allow low cost for the power plant. An important aspect for the choice of the working fluid is also the temperature of the available heat source, which can range from low (about 100 °C) to medium temperatures (about 350 °C). In this paper, a model for the simulation of Organic Rankine Cycles is presented. The model is based on thermodynamics tables for the calculation of fluid properties and the Lee-Kesler method for the calculation of specific heat. Six commonly used working fluids (propane, butane, benzene, toluene, R134a and R123) are considered. Both saturated and superheated cycles are evaluated. A sensitivity analysis of the main process parameters is performed. Finally, the model is applied to a micro gas turbine/ORC combined cycle.Copyright © 2011 by ASME

A new type of low-pressure injection heater was presented. The tapered structure of the heater’s mixture space was designed. Heating performance of the low-pressure heater was studied through the experimental method. Then, the influence of entrance parameters on the outlet temperature, the outlet pressure and the ejecting coefficient were analyzed. The results show that the increase of water mass flow rate can lead to the ejecting coefficient declines under the condition of steam pressure (0.2MPa). Meanwhile, the increases temperature at the outlet can be over 60°C at the inlet water temperature Tw = 20°C. The injection heater has a good adaptability for changing the entrance parameters, which can eliminate the danger that high pressure water enters system. At the same time, based on the theory of Equivalent Enthalpy Drop Method (EEDM) and thermodynamic system state equations, the results of calculation are also shown that the optimization transformation can improve a certain economic profit. The injection heater could be used in the low-pressure feed water system of 200MW steam power plant. The calculated results also indicate that it can replace the sub-last stage surface heat exchanger and raise thermal efficiency of the whole system by 0.07%. Moreover, if all low-pressure surface heat exchangers are replaced by the injection heater, the thermal economy of the whole system can be enhanced by 0.224%.Copyright © 2011 by ASME

During ferroalloy production, a large quantity of waste gas can be utilized to generate steam and electric power. In this paper, 4 detailed thermodynamic models of single-pressure (SP) and dual-pressure (DP) waste heat recovery power generation systems are presented, to analyze the impact of the steam pressure, steam temperature and pinch temperature difference on power generating capacity. By comparing the performance of typical systems, more reasonable thermodynamic models and their parameters are proposed. It is found that the power generation capacity of dual-pressure system is higher than that of the single-pressure system, but SP system is much simpler. Using superheated steam in deaerator reduces the efficiency of heat recovery power generation systems by 1.8%. The fluctuation of waste gas source affects the power generation greatly. It should be considered when more reasonable ranges for the main parameters are required. With the improvement of thermodynamic system and parameter optimization, the gross power is increased by 15% for SP system and 17% for DP system, corresponding to the steam parameters of 3.0MPa/400°C and 6.0MPa/400°C.Copyright © 2011 by ASME

The publication of ASME Performance Test Code 6.2-2004 provided the industry with a Code document dedicated to calculating the performance of a steam turbine in a combined cycle power plant. Power output at specified steam flows and conditions was chosen as the Code’s primary performance parameter. That choice was based on the operating and cycle characteristics of a combined cycle plant operating, where the steam turbine is part of the bottoming cycle operating in a sliding pressure mode that follows ambient conditions and the gas turbine operating profile. This steam turbine generator output, corrected to reference heat consumption, is called Output Performance and is a measurement of steam turbine efficiency. Accompanying this new Code was a new correction methodology that focused on correcting the steam turbine generator output to the reference heat consumption of the cycle. In the development of the overall correction methodology, the corrections associated with high-pressure (HP) steam inlet conditions were given careful attention. The committee developing the Code and methodology concluded that three correction formulations were required to accurately and fairly correct back to the reference heat input of the high-pressure turbine inlet, and to account for changes in the as-built flow capacity versus the design flow capacity. The new correction formulations chosen were: • HP Steam Flow; • HP Steam Temperature; • HP Turbine Flow Capacity. Applying these three corrections on a sliding pressure steam turbine ensures that the output performance is corrected to the true reference high pressure steam heat input to the cycle. If any of these three corrections is excluded the calculated output performance will not be a true representation of the steam turbine efficiency.Copyright © 2011 by ASME

Steam turbine valves are the most important components before a steam turbine for the admission and control of steam flow. Steam turbine valve configurations can be all in one body or as individual valves for the large units, for the main stop (throttle) and control functions for each section of the steam turbine. Today’s thermal power plants for drum or once-through type supercritical boilers produce very high temperature steam in the final superheat and reheat section of 1055 °F or higher requiring special boiler tube metal alloys, some of which are subject to steam oxidation as in austenitic steels. The oxidation material is mainly in the form of iron oxide or magnetite which is subject to exfoliation. The exfoliated oxide material is carried over to the steam turbine valves and to the high and intermediate pressure turbines. The effect of exfoliated oxide material in valve and turbine components is to cause solid particle erosion (SPE) and therefore shortening the life of those parts due to damage. As time goes by if valves are not tested and do not meet their inspection and maintenance schedule they will build up oxidation material to form scale material called blue blush and eventually they stick and will not shut properly.Copyright © 2011 by ASME

For the air-cooled thermal power generating unit, specific climatic conditions exert fast and great impact on the condenser pressure. When equipping turbine driven feed water pumps (TDFWP), as the exhaust steam leaving the boiler feed pump turbine (BFPT) is directly discharged into the air-cooled system, the change of environmental conditions such as air temperature and wind speed will result in the distinct change of BFPT back-pressure both in scope and magnitude. For once-through boilers, such changes will cause disturbance to feed water, and further lead to the change of fuel and air feeding. The back-pressure of main steam turbine is much higher in summer climatic condition. In order to maintain rated or certain power load, steam supplied into the main steam turbine has to be increased. Meanwhile, it is necessary to increase the steam flux in the driving turbine to maintain the needed power for feed water pumps, so there is a conflict that the driving turbine for feed water pumps will compete for steam with the main steam turbine. A dynamical mathematical model of a 600MW direct air-cooled thermal power generating unit is built in this paper. The focus is on the transient analysis of the effect of TDFWP on main equipments when the back-pressure changes in the manners of slope and step mutations. Simulation results show that when the disturbance is smaller, the unit can be quickly adjusted to the operational status at given steam and feed water flow rates. The greater the magnate of back-pressure mutation, the greater the changing range of the parameters, and the longer time is needed for adjusting. Under the condition of the same change magnitude of back-pressure, when the back-pressure rise time is longer, the parameters fluctuation is smaller. When the disturbance is larger, the steam flow of TDFWP is gradually increased to its maximum value. With further increase in the back-pressure, the steam flux in the turbine of TDFWP is gradually decreased, so it is difficult to ensure the feed water flow in this case. The results in this study provide important theoretical significance and engineering reference for the implementation of utilizing direct cooling steam feed pump technology in the actual unit.Copyright © 2011 by ASME

Worldwide environmental concerns are placing center focus on effective utilization of energy and carbon dioxide emission reductions. The power generation industry has engaged in the replacement of existing aged thermal power plants with state-of-the-art natural gas fired power plants capable of achieving considerable reductions in energy consumption and emissions of green house gases. The replacement of three exiting 175MW heavy oil and coal-firing power plants with a highly effective 446MW gas-firing combined cycle power plant owned and operated by Tohoku Electric Power Company is one example of this effort. The construction of the new Sendai thermal power station, Unit No.4 started in November, 2007 achieving commercial operation in July, 2010. Mitsubishi Heavy Industries most recent 50Hz F class gas turbine upgrade, the M701F4 was adopted for this project. This engine is based on the successful M701F3 gas turbine with a 6% air flow increase and a slight bump of the turbine inlet temperature in order to achieve better thermal efficiency and more power output. The application of these advanced technologies resulted in a plant thermal efficiency of approximately 58% LHV of the new unit from the original 43% of the previous coal-firing units. The application of these advanced technologies and the use of natural gas resulted in a 2/3 carbon-dioxide emissions reduction.Copyright © 2011 by ASME

Humidified Gas Turbine (HGT) cycles such as the Evaporative Gas Turbine (EGT) and the Steam-Injected Gas Turbine (STIG) using humid air as the working medium do not require a complete steam turbine bottoming cycle; thus, their initial capital costs are not as high as those for the conventional combined cycles. The performance of a HGT cycle could be comparable to a state-of-the-art combined cycle for small loads. The availability of the steam from a HGT cycle presents opportunities for designing steam-cooled blades. Since the specific heat capacity for steam is higher than that for air, steam could potentially be a better coolant for turbine blades than air, resulting in higher cycle efficiency. In this study, three known HGT cycles are evaluated in terms of their electrical efficiencies and power outputs: the STIG, the Part-flow Evaporative Gas Turbine (PEvGT), and the combined STIG cycles. All the three HGT cycles are analyzed in two cooling options: steam and air coolings. The HGT cycles will be evaluated using consistent thermodynamic properties and assumptions. Like a simple gas turbine cycle, the HGT cycles are based on the well-known Brayton cycle whose performance is dictated by the cycle pressure ratio and turbine inlet temperature. Therefore, the electrical efficiencies and power outputs of the HGT cycles will be calculated as a function of the cycle pressure ratio and turbine inlet temperature. The steam-cooled cycles provide advantages over the air-cooled cycles in the electrical efficiency, power output, and combustion stability. The steam cooling improves the electrical efficiency by approximately 1.4 percentage points for the STIG cycle, by approximately 1.7 percentage points for the PEvGT cycle, and by approximately 1 percentage point for the combined STIG cycle. The maximum electrical efficiency of the steam-cooled PEvGT cycle is 54.6%, only 0.2 percentage points higher than that for the steam-cooled combined STIG cycle. The steam cooling generally results in more power output than the air cooling does for all the HGT cycles at most operating conditions. In addition, the steam cooling reduces the water content of the humid air entering the combustor, leading to significantly improved combustion stability.

Steam turbines in solar thermal power plants experience a much greater number of starts than those operating in base-load plants. In order to preserve the lifetime of the turbine whilst still allowing fast starts, it is of great interest to find ways to maintain the turbine temperature during idle periods. A dynamic model of a solar steam turbine has been elaborated, simulating both the heat conduction within the body and the heat exchange with the gland steam, main steam and the environment, allowing prediction of the temperatures within the turbine during off-design operation and standby. The model has been validated against 96h of measured data from the Andasol 1 power plant, giving an average error of 1.2% for key temperature measurements. The validated model was then used to evaluate a number of modifications that can be made to maintain the turbine temperature during idle periods. Heat blankets were shown to be the most effective measure for keeping the turbine casing warm, whereas increasing the gland steam temperature was most effective in maintaining the temperature of the rotor. By applying a combination of these measures the dispatchability of the turbine can be improved significantly: electrical output can be increased by up to 9.5% after a long cool-down and up to 9.8% after a short cool-down.

High efficiency and flexible operation continue to be the major requirements for power generation because of the benefits of reduced emissions and reduced fuel consumption, i.e. reduced operating costs. Ultra super critical (USC) steam parameters are the basis for state of the art technology of coal fired power plants with highest efficiency. An important part of the development process for advanced steam turbines is product validation. This step involves more than just providing evidence of customer guaranteed values (e.g. heat rate or electric output). It also involves proving that the design targets have been achieved and that the operational experience is fed back to designers to further develop the design criteria and enable the next step in the development of highly sophisticated products. What makes product validation for large size power plant steam turbines especially challenging is the fact that, due to the high costs of the required infrastructure, steam turbine manufacturers usually do not have a full scope / full scale testing facility. Therefore, good customer relations are the key to successful validation. This paper describes an extensive validation program for a modern state of the art ultra supercritical steam turbine performed at an operating 1000 MW steam power plant in China. Several measuring points in addition to the standard operating measurements were installed at one of the high pressure turbines to record the temperature distribution, e.g. to verify the functionality of the internal cooling system, which is an advanced design feature of the installed modern high pressure steam turbines. Predicted 3D temperature distributions are compared to the actual measurements in order to verify and evaluate the design rules and the design philosophy applied. Conclusions are drawn regarding the performance of modern 3D design tools applied in the current design process and an outlook is given on the future potential of modern USC turbines.Copyright © 2011 by Siemens Energy, Inc.

The operational rules for the electricity markets in Latin America are changing at the same time that the electricity power plants are being subjected to stronger environmental restrictions, fierce competition and free market rules. This is forcing the conventional power plants owners to evaluate the operation of their power plants. Those thermal power plants were built between the 1960’s and the 1990’s. They are old and inefficient, therefore generating expensive electricity and polluting the environment. This study presents the repowering of thermal power plants based on the analysis of three basic concepts: the thermal configuration of the different technological solutions, the costs of the generated electricity and the environmental impact produced by the decrease of the pollutants generated during the electricity production. The case study for the present paper is an Ecuadorian 73 MWe power output steam power plant erected at the end of the 1970’s and has been operating continuously for over 30 years. Six repowering options are studied, focusing the increase of the installed capacity and thermal efficiency on the baseline case. Numerical simulations the seven thermal power plants are evaluated as follows: A. Modified Rankine cycle (73 MWe) with superheating and regeneration, one conventional boiler burning fuel oil and one old steam turbine. B. Fully-fired combined cycle (240 MWe) with two gas turbines burning natural gas, one recuperative boiler and one old steam turbine. C. Fully-fired combined cycle (235 MWe) with one gas turbine burning natural gas, one recuperative boiler and one old steam turbine. D. Fully-fired combined cycle (242 MWe) with one gas turbine burning natural gas, one recuperative boiler and one old steam turbine. The gas turbine has water injection in the combustion chamber. E. Fully-fired combined cycle (242 MWe) with one gas turbine burning natural gas, one recuperative boiler with supplementary burners and one old steam turbine. The gas turbine has steam injection in the combustion chamber. F. Hybrid combined cycle (235 MWe) with one gas turbine burning natural gas, one recuperative boiler with supplementary burners, one old steam boiler burning natural gas and one old steam turbine. G. Hybrid combined cycle (235 MWe) with one gas turbine burning diesel fuel, one recuperative boiler with supplementary burners, one old steam boiler burning fuel oil and one old steam turbine. All the repowering models show higher efficiency when compared with the Rankine cycle [2, 5]. The thermal cycle efficiency is improved from 28% to 50%. The generated electricity costs are reduced to about 50% when the old power plant is converted to a combined cycle one. When a Rankine cycle power plant burning fuel oil is modified to combined cycle burning natural gas, the CO2 specific emissions by kWh are reduced by about 40%. It is concluded that upgrading older thermal power plants is often a cost-effective method for increasing the power output, improving efficiency and reducing emissions [2, 7].

Thermodynamic, thermal and structure calculations of the steam turbine in unsteady states are performed for a turbine heat-up from the cold state. The calculations are made for a given geometry of the turbine outer casing, inner casing, stator blade carriers, rotor and other elements of the turbine heat-up system as well as for given parameters of the steam supplied to turbine inlet/exit pipes and given heat-and-flow balance at crucial turbine flow sections. The objective of these calculations is to determine the maximum unsteady stresses in metal elements as well as temporal expansions (absolute and relative) of the turbine outer casing, inner casing, blade carriers, balance piston glands, outer shaft glands and turbine rotor during the cold start-up. For the first time the heat fluxes at the turbine heat exchange surfaces are calculated using a RANS solver in the code FLUENT. Structure computations are made using a FE model in the code ANSYS (casing) and ABAQUS (shaft), based on the given surface heat fluxes. The investigated 30 MW synchronous (50Hz) turbine was equipped with a measurement system to determine the temperature of the metal at several points and relative displacements of turbine elements at crucial locations during its heat-up. In many cases, the obtained numerical results agree well with available measurement data.

This paper presents the results of the analysis on the heat transfer in the inlet section of an ultra-supercritical steam turbine. Such power generating units become the foundation of new coal-fired power plants. The monitoring of their operation is in many aspects similar to the traditional, sub-critical steam turbines. However, higher live and reheat steam parameters result in several key differences, which must be taken into the consideration when assessing the thermal and strength states of the turbines main components for the diagnostic supervision. One of the main differences is the presence of the cooling and designs specific for ultra-supercritical steam turbines, which aim to protect their components against overheating. The research described in this paper investigates the inlet section of the turbines, which is the area exposed to the highest thermal loads. The scope of the research includes both, numerical modeling and laboratory testing. A test stand has been built for the analysis of the flows in the inlet section. Cooling flows are under special attention here as their temperature field is coupled to the temperature fields of the turbine components (the rotor and the inner casing) due to the relatively small amount of the coolant. The paper provides detailed description of the test stand and some early measurement results, which involve the operation with cooling. Also the numerical modeling results are shown and compared to the measurement data.Copyright © 2010 by ASME

A design study for a 150 kW class radial inflow steam turbine system for the bottoming cycle in 2.4 MW class gas engine systems has been completed. The total electrical efficiency of the gas engine can be increased from 41.6% to 44.2%. A two-stage condensing turbine system is applied to increase output power under the supplied steam conditions from the exhaust heat of the gas engines. The pressure ratio of a high-pressure turbine is 3.5, and that of a low-pressure turbine is 4.6. The blade profiles of both turbines are also designed to make sure the thrust does not exceed 300 N at the rated rotational speed of 51,000 rpm. To simplify the rotor system and to reduce mechanical losses, a permanent magnet generator rotor is applied that is composed of turbine rotors in a common shaft supported by two water-lubricated bearings. The oil supply system is completely eliminated in the turbine system. Design specifications of the turbines are shown, as are operating pressure ratio ranges of upper and lower limits from the start to the rated rotational speed for a stable starting operation.Copyright © 2010 by ASME

Biomass integrated gasification combined cycles (BIGCC) are an interesting solution for electricity production. In relation to other biomass conversion technologies, BIGCC is characterized by relatively high energy efficiency. This article presents models and results of simulations of the gas steam cycles integrated with pressurized gasification using biomass as a feedstock. The model and simulations are preformed with Aspen Plus® computer program. The gas generator model consists of two equilibrium reactors. The use of two reactors led to more precise simulations of the flue gas composition, than the model with one reactor. The systems used for study include high-temperature gas cleaning system and a simple gas turbine. The steam cycle consists of 1-pressure heat recovery steam generator (HRSG) and a condensing steam turbine. The main results of the work are: comparison of energy efficiency for a system with different pressure ratio in a gas turbine, sensitive analysis of the impact of steam temperature and pressure in HRSG on energy efficiency. The economic analysis includes determination of the electricity price in Polish economic conditions.Copyright © 2010 by ASME

Liquefied natural gas (LNG) contains considerable cold energy because a significant amount of energy is consumed to produce low-temperature LNG. So, finding a good way to utilize the LNG effectively, particularly its cold energy, is an important issue to solve the problem of energy crisis. In the present study, a new CCHP system utilizing liquid natural gas is proposed to provide cooling, heat and electricity output simultaneously to meet user’s different energy requirements. This CCHP system consists of a gas/steam combined cycle and an ejector refrigeration cycle. For cold energy utilization, LNG is firstly considered as a heat sink to condense the steam turbine exhaust in Rankine cycle, then cools down the suction air of compressor in Brayton cycle, and finally enters the combustion chamber after preheated by HRSG exhaust. The steam turbine has two streams of extraction steam. One is used to drive an ejector refrigeration cycle to produce the cooling effect, and the other is used to provide the heat. To evaluate the system performance, the exergy efficiency is selected as an evaluation criterion to eliminate the difference of energy quality. A thermodynamic simulation of the new CCHP system utilizing LNG is achieved using a simulation program. A parametric analysis is conducted to examine the effects of several key thermodynamic parameters on the performance of the proposed CCHP system. The results indicate that as gas turbine inlet temperature, pressure ratio of compressor and steam turbine inlet pressure increase, the exergy efficiency increases. In addition, as steam turbine back pressure, extraction mass rate ratio for heat, extraction mass rate ratio and extraction pressure for refrigeration increase, the exergy efficiency decreases.Copyright © 2010 by ASME

This paper presents performance analysis of a hybrid power generation system consisting of a solid oxide fuel cell (SOFC) and a steam injected gas turbine (GT) based on the commercial software Easy5. The steam is produced by using the hot exhaust gases heat in the heat recovery steam generator (HRSG) and is injected into the afterburner. Compared with the system without HRSG, the exhaust gas temperature decreases slightly and the power output of the gas turbine is higher because of the increase of the inlet mass flow rate. In addition, the heat exchanger reformer is used in the hybrid system to reduce space and cost. Simulation results show that the hybrid system could achieve a system efficiency of 62.6% under full load operation. And the part load and the dynamic performance of the hybrid system was presented and analyzed.Copyright © 2010 by ASME

This paper presents a solution for developing economies where power shortages require power plants in the range of 30/50 MW or larger to support industrial facilities such as mining or industrial parks where natural gas is not available and where diesel fuel is expensive, but where coal is readily available. Recent developments with Pyrolytic gasification systems by Wiley Consulting, capable of modular 500tpd of coal or biomass, were investigated for power starved sub-Saharan African countries. This Gasifier does not require an oxygen plant and produces a Syngas that can be combusted in modified FR6B gas turbines. The Syngas needs to be compressed and the parasitic load is accommodated with steam injection for NOx control and power enhancement to power the fuel gas compressor. To simplify the exhaust heat power recovery, the Cascading Closed Loop Cycle (CCLC) Organic Rankine Cycle (ORC) system was integrated into this system, resulting in a nominal 45 MW coal or biomass power plant at altitudes over 1000m achieving 40%+ efficiency. Coal fired steam plant Rankine cycle was considered expensive and inefficient due to the requirements of low emissions as well as more than 70% of the fuel energy rejected in the condensing system. Using the Gas Turbine Brayton cycle to combust Synthesis Gas (produced by an innovative Pyrolytic and modular gasification process that did not need an oxygen plant) was considered a practical alternative, especially as the Gas Turbine is air cooled. To fully capture the value of the Syngas fuel, the Gas Turbine exhaust energy would be recovered in an ORC which avoided the use of water and provided excellent load following characteristics as well as the capability to turndown to 40% or lower loads. The criteria established for the power plant was to build and commission the plant in 24 months or less. This necessitated looking at available used and refurbished generating equipment. The modular Gasifier, already demonstrated as a 250 tpd system, could readily be scaled to 500 tpd coal or biomass with about the same footprint and dispatched in modules for fast installation. The availability of a used 38 MW class GT for refurbishment and modification to Syngas fuel combustion system allowed site installation within one year and the provision of emergency power using available diesel fuel. This paper will fully describe the 45 MWe Hybrid GT/ORC Combined Cycle power plant utilizing the innovative Pyrolytic coal gasification process as the fuel source for an efficient low emissions power supply.Copyright © 2010 by ASME

The flow in low pressure (LP) cylinder of steam turbine is the well-known non-equilibrium condensing flow. If the LP cylinder is designed based on the equilibrium condensation theory, the flow parameters in the actual non-equilibrium condensing flow are different from the design condition, which will bring to additional ‘off-design’ losses besides the non-equilibrium losses due to spontaneous nucleation. In order to evaluate the difference between equilibrium and non-equilibrium condensing flows, as well as the ‘off-design’ losses, the hypothetical equilibrium condensing flow and the actual non-equilibrium condensing flow in the LP cylinder of a 300MW steam turbine were simulated by using the ANSYS CFX 11.0 software. The non-equilibrium condensing flow was computed in an Enlerian-Eulerian frame with the classical nucleation model. The computation domain involves all the six turbine stages of the LP cylinder, in which steam expands from superheated region to wet steam region. The non-equilibrium flow was compared with the equilibrium flow. It was found that the flow in the superheated steam stages is also affected by the ‘off-design’ operation of the wet steam stages. In the non-equilibrium flow, the thermal processes and the enthalpy drops in both superheated steam stages and wet steam stages are changed. The surface pressures and the wetness distributions in the wet steam stages are obviously varied. A rough evaluation was made to distinguish the ‘off-design’ and the non-equilibrium losses from the overall losses. For the LP cylinder investigated, the efficiency decrease caused by non-equilibrium losses in stage 5 is about 2%, and the efficiency decrease of about 0.26% due to ‘off-design’ losses is found in the wet steam stages (stage 4, 5, 6). In the superheated steam stages (stage 1, 2, 3), an efficiency increase of about 0.27% is obtained in stage 1, which indicates the positive influence of ‘off-design’ operation of the superheated steam stages in the LP cylinder investigated. The efficiencies of stage 2 and stage 3 are almost unchanged.Copyright © 2010 by ASME

Earlier steam plant design requirements for the US Navy steam turbines were focused on reliability and maintainability. Simplicity of design implied easy operation, maintenance and service. Efficiency was not a top priority. Now, in an atmosphere of operating budget cuts and skyrocketing fuel costs along with environmental responsibilities, efficiency improvements are expected, and in some cases demanded on main propulsion units. Additional load due to modern electronic combat systems places extra demand on SSTG sets. Modernization with improved efficiency, reliability and maintainability, while retaining design simplicity is the optimal solution. Meanwhile during the last 50 years, the turbomachinery industry has developed numerous innovative improvements through extensive R&D efforts, advanced computerized simulation of aerodynamics and flow field analysis along with finite element modeling, new manufacturing methods and improved metallurgy and surface treatments. These advances allow efficiency improvements without adding complexity to the design. Modern airfoil design, the optimized transition from partial-arc to full-arc steam admission, tangential leaning vanes, advanced seal designs, streamlined steam path configuration and improved moisture removal are major areas worthy of consideration. Mechanical reliability can be improved with Taumel (orbital) peened tenons for blade packets or integral shrouds which give a 360 degree connection to all of the blades in a row. Electron beam welded diaphragms with EDM cut horizontal joints help to minimize thermal distortions and flow irregularities, particularly at the split lines. Improved welding procedures for casing, diaphragm and rotor repairs can result in shorter repair cycles and lower costs to further promote extension of the turbine’s life cycle. Maintainability can be improved with advanced materials that no longer require regular service, such as anti-lube (greaseless) bushings and replaceable components that don’t require in place machining. Combinations of the above improvements have been used successfully within the industry in upgrading hundreds of turbines, compressors and pumps in various applications including power generation, petrochemical, oil and gas, commercial marine, and other fields. Typical examples of efficiency improvement are 8%–14% over current operating parameters. [1, 2, 3, 4, 5] This paper presents various proven advanced turbine components used to upgrade existing steam turbines, which can be successfully used in US Navy applications as well.

The efforts for reducing CO2 Emissions into atmosphere and increasing costs for fossil fuels concepts are the drivers for Energy from Waste (EfW) facilities with higher plant efficiency. In the past steam parameters for EfW were requested mainly at 40 bars and 400 °C (580 psi and 752 F). In case of coal fired power plants at the same location as the EfW facilities higher steam parameters at 90 bar, 520 °C (1305 psi, 968 F) have been used for the design of stoker and boiler. This long-term experience with higher steam parameters is the platform for the todays and future demand in higher plant efficiency. Increase in EfW plant efficiency is achievable by increasing temperature and pressure of live steam going along with optimized combustion conditions when using well proven grate technology for waste incineration. On the other hand higher steam parameters result in higher corrosion rates on the boiler tubes and the optimization of the combustion conditions are limited by the burn out quality requirements of slag and flue gas. Advantages and disadvantages have therefore to be balanced carefully. This paper will present different measures for optimized boiler and combustion conditions compared to an EfW plant with live steam at 40 bars and 400 °C (580 psi and 752 F) and 60% excess of combustion air. Plants operated at these conditions have very low maintenance costs created by corrosion of boiler tubes and show performance with very high availability. The following parameters and experiences will be evaluated: - reduction of excess air; - flue gas temperature at boiler outlet; - higher steam parameters (pressure and temperature); - heating surfaces for steam superheating in the radiation boiler section; - steam reheating; - external superheaters using auxiliary fuels. The comparison of the different methods for increasing the efficiency together with resulting technology challenges incorporates the experiences from modern EfW reference facilities built in Naples/Italy, Ruedersdorf (Berlin)/Germany and Heringen/Germany.Copyright © 2010 by ASME

Thermal power plants provide the majority of electricity used around the world and will continue to do so for some time. The goal of this paper is to provide an understanding of technology and fuels used in thermal power plants and the byproducts they create. The emphasis is on magnitudes of fuels used, emissions created and the sustainability and practicality of methods of production and control. A basic thermal power plant burns fuel to produce steam, which turns a turbine generator to produce electricity. The basic elements of thermodynamics apply to all thermal power plants: a heat source, a heat engine and a heat sink. Heat sources for thermal power plants include boilers fueled by coal, natural gas and biomass; gas turbines fueled by natural gas; and nuclear reactors fueled by uranium. Topics of discussion include the logistics involved in supplying fuels and handling their byproducts, including carbon compounds; types of heat engines utilized; methods to improve efficiency to reduce the fuel consumed; byproducts generated; and the heat sink required. The focus is on Rankine (vapor) and Brayton (gas) cycles. Although not directly affecting carbon byproducts, the heat sink used affects the heat engine efficiency and the consumption of water, a valuable resource. The types of heat sinks discussed include open-cycle water cooling, closed-cycle water cooling and air cooling. Thermal power plants provide many benefits to the electrical power system. They provide power 24 hours a day and 365 days a year, regardless of the weather. They are relatively compact, making them easier to build, operate and maintain. They also can be located close to electrical load concentrations reducing the need for transmission lines that disrupt the environment. The technologies involved in thermal power plant operation are proven effective and in use today. The challenges are to manage the fuel supply and byproduct disposal in an environmentally acceptable manner.Copyright © 2010 by ASME

Retrofitting existing power generation plants by repowering is becoming an attractive option to improve plant performance with less cost. “Hot Windbox Repowering” involves utilizing the hot exhaust gas from a combustion gas turbine and using it as combustion air for an existing fossil-fuel boiler. “Combined Cycle Repowering” or “Full Repowering” involves completely replacing the existing boiler with a combined cycle consisting of a gas turbine(s) and a heat recovery steam generator (HRSG). The existing steam turbine will be used in both repowering scenarios. This paper discusses an engineering study and summarizes the results obtained from repowering an existing heavy-oil / natural gas fired steam power plant in the north east of the United States. The plant consists of a 600 MW boiler and steam turbine. Several engineering studies were considered and evaluated thermodynamically and economically to retrofit such plant. Several options were considered involving different gas turbines, gas turbine combinations, and different repowering methods. The best option is based on retrofitting the unit by a combination of both, hot windbox repowering and combined cycle repowering. The proposed design consists of one gas turbine repowering the windbox of the existing boiler, and a second gas turbine operating in a separate combined cycle configuration with the generated superheated steam tying into the main steam line and expanding in the existing steam turbine. Several heat balances were developed to assist in obtaining meaningful results for this feasibility study. Actual costs were obtained for the gas turbines and heat recovery steam generators (HRSG), as well as installation costs for a more accurate evaluation. The results indicate that the combined output of the repowered unit will generate an additional 295 MW and reduce the heat rate by more than 11 percent at full load and annual average ambient conditions. The estimated capital cost of the project is expected to range from $235 to $245 millions.Copyright © 2010 by ASME

This paper evaluates the possibility of combining an intercooled gas turbine power cycle with a steam turbine cycle and the application of the intercooler as a feed-water heater for the heat recovery steam generator. In advance gas turbines the intercooler is used to improve the overall efficiency of the simple cycle but a noticeable amount of heat is wasted to the atmosphere. However, this energy can be recovered by using the proposed method in the current study. Accordingly, a thermodynamic study is done to investigate the improvement in efficiency achieved by feed-water heating. First the effect of intercooler parameters on the outlet condition of the water is studied. The bottoming cycle is then studied in details for the effect of feed-water temperature. An estimate of the energy saving by using the proposed method will be reported. The results show that less heat input will be required for the same amount of steam generation. The current study provides a theoretical support for waste heat recovery from the intercooler.Copyright © 2010 by ASME

Many industrial processes result in tail gas wastes that must be flared or incinerated to abide with environmental guidelines. Tail gas incineration occurs in several chemical processes resulting in high-temperature exhaust gas that simply go to the stack, thus wasting all that valuable heat! This paper discusses useful heat recovery and electric power generation utilizing available heat in exhaust gas from tail gas incinerators. Tail gas, which is considered as the main fuel in this study, is typically “free” fuel. Eventhough with low heat content, when the heat is recovered and utilized properly, heat recovery of tail gas will result in significant savings to the plant. The thermodynamic and economic study presented here assumes that heat will be recovered in a wast-heat recovery boiler from the exhaust gas out of the incinerator and will produce enough superheated steam to generate 25 MW in a condensing steam turbine generator. Data for this study were provided by an operating chemical production facility in the southeastern region of the US. Energy analysis and a total project scope cost estimate were developed for this study. Actual costs were obtained for all major equipment. Different thermodynamic scenarios were considered to identify the optimum and most economical energy system design. The main goal of the study was to fulfill the plant’s power and steam requirements and sell the additional power to the local utility. An existing old steam boiler will be retired after the incorporation of the new cogeneration plant. Process steam will be supplied via a steam turbine extraction. The results indicate that the total capital cost of a ± 25% grade estimate for the supply and installation of the 25 MW cogeneration system, is estimated to be $51,000,000 in the fourth quarter of 2008 dollars with escalation through end of 2010, representing $2000/kW. Based on an internal power demand of 12 MW by the chemical plant, a balance of 13 MW is assumed be sold to the local utility. The cost of electricity used for this study was assumed to be 9 cents per kilowatt-hour for purchased power and 6 cents per kilowatt-hour for sold power. The annual plant savings in purchased power is estimated to be over $6,300,000 while the annual plant revenue from selling the remaining power is estimated to be in excess of $6,200,000. The cost analysis, when accounting for operation and maintenance, resulted in a pay back period of less than 4 years and an internal rate of return on investment of over 13 percent after 6 years.Copyright © 2010 by ASME

Performance analysis of a 500 MWe steam turbine cycle is performed combining the thermodynamic first and second-law constraints to identify the potential avenues for significant enhancement in efficiency. The efficiency of certain plant components, e.g. condenser, feed water heaters etc., is not readily defined in the gamut of the first law, since their output do not involve any thermodynamic work. Performance criteria for such components are defined in a way which can easily be translated to the overall influence of the cycle input and output, and can be used to assess performances under different operating conditions. A performance calculation software has been developed that computes the energy and exergy flows using thermodynamic property values with the real time operation parameters at the terminal points of each system/equipment and evaluates the relevant rational performance parameters for them. Exergy-based analysis of the turbine cycle under different strategic conditions with different degrees of superheat and reheat sprays exhibit the extent of performance deterioration of the major equipment and its impact to the overall cycle efficiency. For example, during a unit operation with attemperation flow, a traditional energy analysis alone would wrongly indicate an improved thermal performance of HP heater 5, since the feed water temperature rise across it increases. However, the actual performance degradation is reflected as an exergy analysis indicates an increased exergy destruction within the HP heater 5 under reheat spray. These results corroborate to the deterioration of overall cycle efficiency and rightly assist operational optimization. The exergy-based analysis is found to offer a more direct tool for evaluating the commercial implication of the off-design operation of an individual component of a turbine cycle. The exergy destruction is also translated in terms of its environmental impact, since the irretrievable loss of useful work eventually leads to thermal pollution. The technique can be effectively used by practicing engineers in order to improve efficiency by reducing the avoidable exergy destruction, directly assisting the saving of energy resources and decreasing environmental pollution.Copyright © 2010 by ASME

During operation, sludge steadily appears at a slow pace on the secondary side of nuclear power plant steam generators. This leads to clogging of the tube bundle support plates, and consequently to a change in the thermal-hydraulic flow conditions. The circulation ratio of a steam generator is defined as the ratio between the total flowrate circulating in the riser and the steam flowrate at the outlet of the steam generator. This is a good indicator of the hydraulic pressure losses in the circulation loop. In particular, the increase in hydraulic resistance due to the tube support plate clogging leads to a drop in this parameter. For this reason, in order to check that clogging does not reach too high a level, the circulation ratio is regularly evaluated on steam generators of French nuclear power plants, and then compared to established safety limits. The purpose of this paper is to present an accurate method to determine the circulation ratio of a steam generator based on temperature measurements taken around the wall of the steam generator. This method consists of carrying out a thermal balance of the flow circulating in the downcomer. In order to accomplish this, the temperature of the water circulating in the downcomer is evaluated using thermocouple belts put on the external wall of the appliance. However, additional hypotheses in the calculation method are considered in order to take into account for the heat transfer between hot water inside the downcomer and the sensors. The steam generator circulation loop and the clogging of the tube support plates are presented in §1. Then §2 and §3 describe in detail the method and the associated hypotheses as well as the required instrumentation. Finally, §4 presents an application of this method to real cases of clogged steam generators.Copyright © 2010 by ASME

A station uprate provides an economical opportunity to improve the generation capacity of a power plant if all the major system components are able to handle the effects of increased generation. The magnitude of uprate from increased steam generation will be limited by the maximum capacity of the weakest link in the cycle, which for many plants is the condenser. The condensers on many units are already pushed to their limit. This is especially true if a cooling tower is employed, where the condenser inlet cooling water temperatures are high on high wet-bulb temperature days. This condition forces many units to throttle down load to prevent excursions above the backpressure limits on their turbines. For condensers limited by the present duty, however, the options have been historically limited to rebundling the whole condenser with a larger surface area design and perhaps changing the tube material to a material with a higher heat transfer coefficient. Recently, a very low cost option has been demonstrated that should be considered by any plant looking to increase condenser duty or prevent station power reductions. Advances in the proper management of steam, condensate and noncondensable flows have permitted an upgrade for almost all vintage condensers, unlocking inactive surface area without a bundle replacement or complete redesign. This paper reports the results of a condenser retrofit effort, with emphasis on an upgrade applied to a load limited condenser concurrent with a major reduction in its operating backpressure. The performance of the condenser is presented before and after the upgrade showing significant backpressure reduction and heat transfer improvement accompanied by exceptional condensate chemistry results. It will be shown that 30% of the effective condenser surface area (or similarly, an additional 30% average heat transfer coefficient) was unlocked by activating the previously idle surface area.Copyright © 2010 by Intek, Inc.

Previous study of a microturbine-based combined heat, cooling and power system installed on a university campus showed that the turbine exhaust energy must be fully utilized for the economics to be favorable. The system studied combined four 60 kW microturbines with a 110 ton absorption chiller that recovers exhaust waste heat. The chiller, which has the capability of providing either chilled water for cooling or hot water for heating depending on seasonal needs, was found to be mismatched to the local heating and cooling needs. This paper describes the design of an exhaust heat exchanger that will be integrated into the campus steam plant for more efficient utilization of the microturbine waste heat. The hot water generated will be used during heating season to heat a nearby building with a hydronic heating system. This will reduce boiler fuel costs, since this heating load would otherwise be met from a steam heating station. At other times of the year, the hot water generated will be used to preheat condensate return for the campus steam plant, which has a year-round steam demand.Copyright © 2010 by ASME

Xcel Energy’s Riverside Repowering Project was a voluntary emissions reduction project with the goals of improving air quality in Minnesota while, at the same time, increasing the amount of electricity produced. The Riverside Plant was converted from being a coal-fired facility to a combined-cycle facility firing natural gas. The fuel switch resulted in significant plant emission benefits, with emissions of sulfur dioxide decreasing by 99%, nitrogen oxides (NOx ) decreasing by 96%, and mercury being eliminated entirely. Plant output increased from a nominal generating capacity of 386 MW to a summer day net output of 472 MW. The three existing coal-boilers were retired. Two F-technology combustion turbine generators (CTGs) and two heat recovery steam generators (HRSGs) were installed. Each CTG fires natural gas with dry low-NOx combustors. Each HRSG includes a selective catalytic reduction (SCR) section supplied with aqueous ammonia. Steam generated from the HRSGs is fed to an existing steam turbine. The low-pressure steam from the HRSG is admitted into the steam turbine through a new connection. The steam turbine extraction lines for feedwater heating are capped. To accommodate the resulting increased flow through the turbine, two rows of blades were replaced. A new full-flow steam turbine bypass system operates during plant startup and shutdown. An auxiliary boiler was added to provide warming and sealing steam to the steam turbine. A new distributed control system (DCS) operates the facility, with workstations located in the plant’s existing control room. The existing once-through circulating water system on the Mississippi River was modified with the addition of wedgewire screens to comply with the Clean Water Act Section 316(b). The CTGs and HRSGs are fully enclosed in a new building that is integrated with the structure for the steam turbine. Due to the proximity of residential housing, sound attenuation is critical. Space for the new building was created by demolishing formerly retired units. Reclaiming this area resulted in a unique layout. The HRSGs are constructed over wood piles installed in 1914–22. The HRSG foundation consists of an elevated slab supported on concrete walls distributing load to the original pile caps. Between the HRSGs and the CTGs are retired concrete coal hoppers that divide the site. The CTGs sit approximately 20 feet higher than the base of the HRSGs. The combined cycle achieved commercial operation on May 1, 2009.Copyright © 2010 by ASME

The production of clean water in the US as well as other countries is a critical need along with non-greenhouse gas electrical power generation. Low-temperature waste heat from nuclear power plants can be used to produce the large quantities of clean water for reactor cooling (∼25,000 acre-ft/yr), potable water for culinary and agricultural use and many other applications. Cogeneration of nuclear electrical power and clean water is reviewed and discussed in this paper. These cogeneration systems can utilize grey and/or brackish water that can markedly extend potential sites for future nuclear plants in areas where only poor water sources are available. A steam adsorption system for on-line production of clean water and refrigeration using nuclear power plant waste heat is also proposed and discussed. This improved design for more energy-efficient use of the steam adsorption cooling has the potential to substantially reduce the intense electrical power consumption for food processing and storage, ice- and snow-making and air-conditioning.Copyright © 2010 by ASME

As a measure of power plant thermodynamic performance, heat rate (H.R.) is used. As heat rate is inversely proportional to thermal efficiency, the thermal efficiency of a power plant increases as the heat rate decreases. The major thermodynamic performance parameters in a plant thermal cycle affecting the electrical output include but are not limited to: the initial pressure of main steam at the turbine inlet, the initial moisture content or superheated condition of main steam at the turbine inlet, the effectiveness of the feedwater heating cycle, the effectiveness of the moisture separator, the effectiveness of the reheater, the condenser pressure, the level of cycle separation and the accuracy of electric output measurement. A review of thermodynamic principles involved in a thermal performance plan is needed to understand the changes in the parameters and recognize the thermal performance status and trends, which will lead us to propose corrective actions when appropriate. This paper focuses on the effects of main steam temperature and thermal power.Copyright © 2010 by ASME

DONG Energy owns and operates seven power stations in Denmark fueled by internationally traded bituminous coal. Since the early 1980s, competitiveness has been supported by an efficient conversion from coal to wire in super critical boilers and turbines. DONG Energy also operates a double reheat plant with ultra super critical steam parameters, and based on experience from this plant, a revised concept for the double reheat steam cycle has been developed. The revised design (named the Master Cycle or MC) solves the problems with the very strong superheating of the bleed steam from the IP turbines and paves the way for an affordable double reheat technology. The core component of the revised design is a small separate turbine (named the tuning turbine or T-turbine) driving a 100% boiler feed pump in combination with a balancing motor/generator and delivering relatively cold bleed steam for the heaters normally bleeding on the IP turbines. The T-turbine is fed with steam from the first cold reheat steam line meaning reduced steam flow through the reheaters and higher main steam flow which is advantageous for cooling of the furnace walls. Based on the Master Cycle and Ultra Super Critical (USC) steam parameters, net efficiency of a single reheat plant can be improved from 47% to 48.5% without any deterioration of availability. Many double reheat plants with elements similar to those of the Master Cycle are in operation in the USA and their operational records are excellent. Higher net efficiency of a Master Cycle plant would mean solid CO2 reductions of 4% by comparison with a new single reheat plant. Much higher reductions could be achieved by replacing an old plant.Copyright © 2010 by ASME

The objective of this paper is to evaluate methods to increase the efficiency of a gas turbine power plant. Advanced intercooled gas turbine power plants are quite efficient, efficiency reaching about 47%. The efficiency could be further increased by recovering wasted heat. The system under consideration includes an intercooled gas turbine. The heat is being wasted in the intercooler and a temperature drop happens at the exhaust. For the current system it will be shown that combining the gas cycle with steam cycle and removing the intercooler will increase the efficiency of the combined cycle power plant up to 60%. In combined cycles the efficiency depends greatly on the exhaust temperature of the gas turbine and the higher gas temperature leads to the higher efficiency of the steam cycle. The analysis shows that the latest gas turbines with the intercooler can be employed more efficiently in a combined cycle power application if the intercooler is removed from the system.Copyright © 2009 by ASME

For future parabolic trough plants direct steam generation in the absorber pipes is a promising option for reducing the costs of solar thermal power generation. These new solar thermal power plants require innovative storage concepts, where the two phase heat transfer fluid poses a major challenge. A three-part storage system is proposed where a phase change material (PCM) storage will be deployed for the two-phase evaporation, while concrete storage will be used for storing sensible heat, i.e. for preheating of water and superheating of steam. A pinch analysis helps to recognize interface constraints imposed by the solar field and the power block and describes a way to dimension the latent and sensible components. Laboratory test results of a PCM test module with approx. 140 kg NaNO3, applying the sandwich concept for enhancement of heat transfer, are presented, proving the expected capacity and power density. The concrete storage material for sensible heat was improved to allow the operation up to 500 °C for direct steam generation. A storage system with a total storage capacity of approx. 1 MWh is described, combining a PCM module and a concrete module, which will be tested in 2009 under real steam conditions around 100 bar.

Gas turbine is widely applied in power-generation field, especially combined gas-steam cycle. In this paper, the new scheme of steam turbine driving compressor is investigated aiming at the gas-steam combined cycle power plant. Under calculating the thermodynamic process, the new scheme is compared with the scheme of conventional gas-steam combined cycle, pointing its main merits and shortcomings. At the same time, two improved schemes of steam turbine driving compressor are discussed.Copyright © 2009 by ASME

eSolar has developed a cost-effective, utility-scale solar power tower plant that uses mass-manufactured components which are designed for modularity, rapid deployment and construction, and are easily scalable. eSolar’s design for a full commercial power tower plant consists of 16 receiver-heliostat field modules that generate superheated steam to power a 46 MWe turbine. Each receiver-heliostat field module comprises a north and south rectangular-shaped subfield that reflects concentrated sunlight onto a receiver located between the subfields. The receiver absorbs the concentrated sunlight in a dual cavity. It is a natural-circulation boiler consisting of economizer, evaporator, and superheater panels. A steam drum separates the saturated steam, which is superheated in the superheater panels of the receiver. The steam flows to a turbine generator to produce electricity. After passing through the turbine, the steam is condensed and returns to the cycle. Heat from the condenser is rejected by a wet cooling tower. eSolar is constructing the Sierra Solar Generating Station in Lancaster, California to demonstrate its technology. This power tower plant consists of two full-scale receiver-heliostat fields that can produce 5 MWe. This project will demonstrate the full functionality of two receiver-heliostat field modules coupled with a small Rankine-cycle turbine.Copyright © 2009 by ASME

It is extremely important in managing nuclear power plants to accurately confirm the thermal power of reactor for controlling and monitoring the plant power output. For pressurized water reactors (PWRs), feedwater flowrates have been typically used for mass and energy balance calculations to confirm the reactor thermal power. The feedwater flowrates are calculated from pressure drop measurements across venturis in plant feedwater systems. There have been so far many reports on the fouling of venturi, which has lead to erroneous high pressure drop measurements. This gives high mass flowrates, leading to high calculated reactor thermal power. The high calculated thermal power causes plant operators to reduce the power output to comply with the licensed operating power level. This causes losses in plant electrical output, typically about 2 ∼ 3% of the plant rating. One method to overcome the overestimation of reactor power due to high calculated feedwater flowrates due to venturi fouling is using steam flow measurements in reactor thermal power calculations. Plant operating experiences have shown that steam flows are a closer indicator of plant power. In addition they are known to show little fouling problem. A new power calculation methodology based on steam flow measurements is proposed herein for mass and energy balance calculations of reactor thermal power. A mathematical mass flowrate equation is developed for measured steam flows in a similar way to feedwater flows. The steam flow correction factors are determined from the operating data gained at the beginning of operation cycle. This is a way to calibrating steam flow measurements to feedwater flow indications to allow for the calorimetric heat balance to be based on steam flow rather than feedwater flow. Routine calibration testing procedure is developed to determine discharge coefficients for each operation cycle. The results of application to the Optimized Power Reactor 1000 (OPR1000) plants show good performance in plant power monitoring.Copyright © 2009 by ASME