Repowering and Retrofitting

2002 ◽  
Author(s):  
Andreas Pickard
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Free Market ◽  
Leading Edge ◽  
Project Planning ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Planning Stage ◽  
Reheat Steam ◽  
Plant Optimization

At the start of this new century, environmental regulations and free-market economics are becoming the key drivers for the electricity generating industry. Advances in Gas Turbine (GT) technology, allied with integration and refinement of Heat Recovery Steam Generators (HRSG) and Steam Turbine (ST) plant, have made Combined Cycle installations the most efficient of the new power station types. This potential can also be realized, to equal effect, by adding GT’s and HRSG’s to existing conventional steam power plants in a so-called ‘repowering’ process. This paper presents the economical and environmental considerations of retrofitting the steam turbine within repowering schemes. Changing the thermal cycle parameters of the plant, for example by deletion of the feed heating steambleeds or by modified live and reheat steam conditions to suit the combined cycle process, can result in off-design operation of the existing steam turbine. Retrofitting the steam turbine to match the combined cycle unit can significantly increase the overall cycle efficiency compared to repowering without the ST upgrade. The paper illustrates that repowering, including ST retrofitting, when considered as a whole at the project planning stage, has the potential for greater gain by allowing proper plant optimization. Much of the repowering in the past has been carried out without due regard to the benefits of re-matching the steam turbine. Retrospective ST upgrade of such cases can still give benefit to the plant owner, especially when it is realized that most repowering to date has retained an unmodified steam turbine (that first went into operation some decades before). The old equipment will have suffered deterioration due to aging and the steam path will be to an archaic design of poor efficiency. Retrofitting older generation plant with modern leading-edge steam-path technology has the potential for realizing those substantial advances made over the last 20 to 30 years. Some examples, given in the paper, of successfully retrofitted steam turbines applied in repowered plants will show, by specific solution, the optimization of the economics and benefit to the environment of the converted plant as a whole.

Coordinated Control of Gas and Steam Turbines for Efficient Fast Start-Up of Combined Cycle Power Plants

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Yasuhiro Yoshida ◽  
Kazunori Yamanaka ◽  
Atsushi Yamashita ◽  
Norihiro Iyanaga ◽  
Takuya Yoshida
Keyword(s):  
Thermal Stress ◽  
Steam Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Thermal Stresses ◽  
Control Method ◽  
Coordinated Control ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Start Up

In the fast start-up for combined cycle power plants (CCPP), the thermal stresses of the steam turbine rotor are generally controlled by the steam temperatures or flow rates by using gas turbines (GTs), steam turbines, and desuperheaters to avoid exceeding the thermal stress limits. However, this thermal stress sensitivity to steam temperatures and flow rates depends on the start-up sequence due to the relatively large time constants of the heat transfer response in the plant components. In this paper, a coordinated control method of gas turbines and steam turbine is proposed for thermal stress control, which takes into account the large time constants of the heat transfer response. The start-up processes are simulated in order to assess the effect of the coordinated control method. The simulation results of the plant start-ups after several different cool-down times show that the thermal stresses are stably controlled without exceeding the limits. In addition, the steam turbine start-up times are reduced by 22–28% compared with those of the cases where only steam turbine control is applied.

Repowering Considerations for Converting Existing Power Plants to Combined Cycle Power Plants

2002 ◽  
Author(s):  
Anup Singh ◽  
Don Kopecky
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Current Status ◽  
Entire System ◽  
Steam Turbines ◽  
Good Shape ◽  
The Usa ◽  
Overall Performance ◽  
Cost Studies

Most of the recent combined cycle plants have been designed and constructed as Greenfield Plants. These new plants have been designed mostly as Merchant Plants, owned and operated by Independent Power Producers. There is about 260,000 MW of conventional coal-fired and gas-fired capacity in the USA that is more than 30 years old. About 30,000 MW of conventional gas-fired capacity exists in the area of The Electric Reliability Council of Texas (ERCOT) with relatively poor heat rates in comparison to modern combined cycle plants. These plants are good candidates for HRSG repowering. In addition, there are several coal-fired units in the 200 MW range with steam turbines in relatively good shape or in a condition that can be refurbished and used in repowering. The installed cost of repowered (also called Brownfield) capacity is about 20%–40% less than for comparable Greenfield capacity. There are also other advantages to repowering. Since the site is already existing, it is easier to get the various environmental and construction permits. The efficiency of the repowered units will be significantly higher than the existing units in their current status thus increasing the overall performance of the entire system. The paper will discuss various considerations required for repowering, including steam turbine refurbishment, demolition/relocation of existing equipment, recent cost studies, and various considerations for equipment such as HRSGs.

An Integrated Steam/Gas Turbine-Generator for Combined-Cycle Applications

1989 ◽  
Author(s):  
J. H. Moore
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Gas Temperature ◽  
Turbine Generator ◽  
Fully Integrated ◽  
Reheat Steam ◽  
Exhaust Gas Temperature ◽  
Steam Cycle

Combined-cycle power plants have been built with the gas turbine, steam turbine, and generator connected end-to-end to form a machine having a single shaft. To date, these plants have utilized a nonreheat steam cycle and a single-casing steam turbine of conventional design, connected to the collector end of the generator through a flexible shaft coupling. A new design has been developed for application of an advanced gas turbine of higher rating and higher firing temperature and exhaust gas temperature with a reheat steam cycle. The gas turbine and steam turbine are fully integrated mechanically, with solid shaft couplings and a common thrust bearing. This paper describes the new machine, with emphasis on the steam turbine section where the elimination of the flexible coupling created a number of unusual design requirements. Significant benefits in reduced cost and reduced complexity of design, operation, and maintenance are achieved as a result of the integration of the machine and its control and auxiliary systems.

Effect of Inlet Steam Temperature on the HP Section Efficiency of a Steam Turbine

2015 ◽  
Author(s):  
Yiping Fu ◽  
Thomas Winterberger
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Pressure Ratio ◽  
Control Valve ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Steam Temperature ◽  
Load Range ◽  
Lp Turbine ◽  
The Relationship

Steam turbines for modern fossil and combined cycle power plants typically utilize a reheat cycle with High Pressure (HP), Intermediate Pressure (IP), and Low Pressure (LP) turbine sections. For an HP turbine section operating entirely in the superheat region, section efficiency can be calculated based on pressure and temperature measurements at the inlet and exhaust. For this case HP section efficiency is normally assumed to be a constant value over a load range if inlet control valve position and section pressure ratio remain constant. It has been observed that changes in inlet steam temperature impact HP section efficiency. K.C. Cotton stated that ‘the effect of throttle temperature on HP turbine efficiency is significant’ in his book ‘Evaluating and Improving Steam Turbine Performance’ (2nd Edition, 1998). The information and conclusions provided by K.C. Cotton are based on test results for large fossil units calculated with 1967 ASME steam tables. Since the time of Mr. Cotton’s observations, turbine configurations have evolved, more accurate 1997 ASME steam tables have been released, and our ability to quickly analyze large quantities of data has greatly increased. This paper studies the relationship between inlet steam temperature and HP section efficiency based on both 1967 and 1997 ASME steam tables and recent test data, which is analyzed computationally to reveal patterns and trends. With the efficiencies of various inlet pressure class HP section turbines being calculated with both 1967 and 1997 ASME steam tables, a comparison reveals different characteristics in the relationship between inlet steam temperature and HP section efficiency. Recommendations are made on how the results may be used to improve accuracy when testing and trending HP section performance.

Optimization of a 900 mm Tilting-Pad Journal Bearing in Large Steam Turbines by Advanced Modeling and Validation

2018 ◽  
Author(s):  
Ümit Mermertas ◽  
Thomas Hagemann ◽  
Clément Brichart
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Journal Bearing ◽  
Leading Edge ◽  
Success Factor ◽  
Steam Turbines ◽  
Oil Supply ◽  
Modeling Methods ◽  
Tilting Pad ◽  
Tilting Pad Journal Bearing

Modernization of steam turbine components can extend the life of a power plant, decrease maintenance costs, increase service intervals and improve operational flexibility. However, this can also lead to challenging demands for existing components such as bearings, e.g., due to increased rotor weights. Therefore, a careful design and evaluation process of bearings is of major importance. This paper describes the advanced modeling methods applied for the optimization of a novel 900 mm three-pad tilting pad journal bearing followed by validation results that showed a high bearing temperature sensitivity to the fresh oil supply temperature during operation. The bearing was especially developed to cope with increased rotor weights within the framework of low pressure steam turbine modernizations at two similar 1000 MW nuclear power plants. With a static bearing load of approximately 2.7 MN at a rotor speed of 1500 rpm, it represents one of the highest loaded applications for tilting pad journal bearings in turbomachinery worldwide. After identification of the reasons for the sensitivity, advanced modeling methods were applied to optimize the bearing. For this purpose, a more comprehensive bearing model was developed taking into account the direct lubrication at the leading edge of the pads and the thermo-mechanical pad deformation. For the latter, a co-simulation between the bearing computation code and structural mechanics software was performed. The results of the entire analyses indicated modifications of bearing and pad clearance, pad pivot position, circumferential and axial pad length as well as pad thickness. Furthermore, the oil distribution into the pads was optimized by modifying the orifices within the bearing. The optimized bearing was then implemented on both units and proved its excellent operational behavior at increased fresh oil supply temperatures of up to 55°C. In addition, inspections during scheduled outages after 18 months of operation and subsequent restarts with reproducible bearing behavior confirmed the robustness of the optimized bearing. In conclusion, the application of advanced modeling methods proved to be the key success factor in the optimization of this bearing, which represents an optimal solution for large steam turbine and generator rotor train applications.

Mechanical Design of Highly Loaded Large Steam Turbines

2011 ◽  
Author(s):  
N. Lu¨ckemeyer ◽  
H. Almstedt ◽  
T.-U. Kern ◽  
H. Kirchner
Keyword(s):  
Steam Turbine ◽  
Nuclear Power ◽  
Power Plants ◽  
Mechanical Design ◽  
Ductile Failure ◽  
Combined Cycle ◽  
Material Behavior ◽  
Integral Approach ◽  
Steam Turbines ◽  
Creep Fatigue

There are no internationally recognized standards, such as the ASME Boiler and Pressure Vessel Code or European boiler and pipe codes, for the mechanical design of large steam turbine components in combined cycle power plants, steam power plants and nuclear power plants. One reason for this is that the mechanical design of steam turbines is very complex as the steam pressure is only one of many aspects which need to be taken into account. In more than one hundred years of steam turbine history the manufacturers have developed internal mechanical design philosophies based on both experience and research. As the design of steam turbines is pushed to its limits with greater lifetimes, efficiency improvements and higher operating flexibility requested by customers, the validity and accuracy of these design philosophies become more and more important. This paper describes an integral approach for the structural analysis of large steam turbines which combines external design codes, material tests, research on the material behavior in co-operation with universities and experience gained from the existing fleet to derive a substantiated design philosophy. The paper covers the main parameters that need to be taken into account such as pressure, rotational forces and thermal loads and displacements, and identifies the relevant failure mechanisms such as creep fatigue, ductile failure and creep fatigue crack growth. It describes the efforts taken to improve the accuracy for materials already used in power plants today and materials with possible future use such as advanced steels or nickel based alloys.

Development of Steam Turbines for State of the Art Combined Cycle Power Plants (CCPP)

2012 ◽  
Author(s):  
Rainer Quinkertz ◽  
Simon Hecker
Keyword(s):  
Steam Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Three Dimensional ◽  
Plant Evolution ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Electricity Grid ◽  
Capital Costs ◽  
Intermediate Pressure

In order to reduce CO2 emissions, reduce capital costs and increase the percentage of renewable energy in the electricity grid, common drivers of fossil power plant evolution continue to be efficiency, increased electricity output and operating flexibility. For CCPP, the efficiency level has reached more than 60%. Besides new and updated gas turbine frames, an improved bottoming cycle also contributes to this achievement. Without increasing steam temperatures above 565°C, improving steam turbine inner efficiency and enhancing the cold end, the overall efficiency of >60% would not be feasible. Extensive thermodynamic optimization is required to determine steam temperatures and condenser pressures. In addition, from a design standpoint, an optimum product strategy has to be developed. In order to minimize risks with future designs, both the practical and theoretical experiences from both ultra super critical applications at coal-fired steam power plants as well as from the CCPP steam turbine fleet have to be incorporated. For advanced technologies and components appropriate validation programs have to be defined. This paper presents the approach being taking to develop steam turbines for CCPP with modern gas turbines and it also displays the operating results of the first unit. Operational validation included the thermal behaviour of the high and intermediate pressure parts, a new last stage blade for the low pressure turbine and a patented start-up procedure. In particular, the paper focuses on the validation of three dimensional CFD calculations of the high and intermediate pressure turbine.

Aerodynamic Design and Prototype Testing of a New Line of High Efficiency, High Pressure, 50% Reaction Steam Turbines

2007 ◽  
Author(s):  
Joseph A. Cotroneo ◽  
Tara A. Cole ◽  
Douglas C. Hofer
Keyword(s):  
High Pressure ◽  
Steam Turbine ◽  
Power Plants ◽  
High Efficiency ◽  
Combined Cycle ◽  
Volume Flow ◽  
Steam Turbines ◽  
Aerodynamic Design ◽  
Flow Paths ◽  
Low Volume

The aerodynamic design and prototype performance testing of a new line of high efficiency, high pressure (HP), 50% reaction steam turbines is described in some detail. Three designs were carried out that can be used in a repeating stage fashion to form high efficiency steam paths. The designs were performed employing a blade master concept. The masters can be aerodynamically scaled and cut to cover a wide range of applications while maintaining vector diagram integrity. Three equivalent prototype flow paths, one each for Gen 0, 1 and 2, masters were designed and tested in a Steam Turbine Test Vehicle (STTV). These prototype designs are representative of high pressure steam turbines for combined cycle power plants. Design of experiments is used to optimize the flow path, stage counts and diameters for production designs taking into account multidisciplinary design constraints. Four such Gen 1 steam path designs have been executed to date as part of a structured series of combined cycle power plants. [1-5] There are two A14 HEAT* (High Efficiency Advanced Technology) steam turbine HP flow paths for GE’s 107FA combined cycle power plants and two A15 HEAT HP flow paths for the 109FB. The larger of the A14 HEAT steam turbine HP’s has recently been performance tested at a customer site demonstrating world class efficiency levels of over 90% for this low volume flow combined cycle turbine [1]. HP volume flows are likely to drop even lower in the future with the need to go to higher steam inlet pressure for combined cycle efficiency improvements so steam path designs with high efficiency at low volume flow will be increasingly important.

State of the Art Steam Turbine Automation for Optimum Transient Operation Performance

2007 ◽  
Author(s):  
Rainer Quinkertz ◽  
Edwin Gobrecht
Keyword(s):  
Steam Turbine ◽  
Power Plants ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Operation Performance ◽  
Control Functions ◽  
Steam Power Plants ◽  
Start Up ◽  
Full Speed ◽  
Startup Performance

The growing share of renewable energies in the power industry coupled with increased deregulation has led to the need for additional operating flexibility of steam turbine units in both Combined Cycle and Steam Power Plants. Siemens steam turbine engineering and controls presently have several solutions to address various operating requirements: - Use of an automatic step program to perform startups allows operating comfort and repeatability. - 3 start-up modes give the operator the flexibility to start quickly to meet demand or slowly to conserve turbine life. - Several options for lifetime management are available. These options range from a basic counter of equivalent operating hours to a detailed fatigue calculation. - Restarting capabilities have been improved to allow a faster response following a trip or shutdown. - In addition to control of speed, load and pressure, special control functions provide alternative work split modes during transient conditions. - Optimum steam temperatures are calculated by the steam turbine control system to achieve optimum startup performance. - Siemens steam turbines are also capable of load rejection to house load, some even to operation at full speed, no load. Several plants are already equipped with these solutions and have provided data showing they are operating with shorter start-up times and improved load rejection capabilities. Finally Siemens of course continues to pursue future development.

Fault diagnosis method of peak-load-regulation steam turbine based on improved PCA-HKNN artificial neural network

2021 ◽  
pp. 1748006X2110105
Author(s):  
Yifan Wu ◽  
Wei Li ◽  
Deren Sheng ◽  
Jianhong Chen ◽  
Zitao Yu
Keyword(s):  
Neural Network ◽  
Fault Diagnosis ◽  
Steam Turbine ◽  
Power Plants ◽  
Peak Load ◽  
Clean Energy ◽  
Steam Turbines ◽  
Peak Shaving ◽  
Diagnosis Method ◽  
Load Regulation

Clean energy is now developing rapidly, especially in the United States, China, the Britain and the European Union. To ensure the stability of power production and consumption, and to give higher priority to clean energy, it is essential for large power plants to implement peak shaving operation, which means that even the 1000 MW steam turbines in large plants will undertake peak shaving tasks for a long period of time. However, with the peak load regulation, the steam turbines operating in low capacity may be much more likely to cause faults. In this paper, aiming at peak load shaving, a fault diagnosis method of steam turbine vibration has been presented. The major models, namely hierarchy-KNN model on the basis of improved principal component analysis (Improved PCA-HKNN) has been discussed in detail. Additionally, a new fault diagnosis method has been proposed. By applying the PCA improved by information entropy, the vibration and thermal original data are decomposed and classified into a finite number of characteristic parameters and factor matrices. For the peak shaving power plants, the peak load shaving state involving their methods of operation and results of vibration would be elaborated further. Combined with the data and the operation state, the HKNN model is established to carry out the fault diagnosis. Finally, the efficiency and reliability of the improved PCA-HKNN model is discussed. It’s indicated that compared with the traditional method, especially handling the large data, this model enhances the convergence speed and the anti-interference ability of the neural network, reduces the training time and diagnosis time by more than 50%, improving the reliability of the diagnosis from 76% to 97%.

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