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.

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 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.

Design of Fast and Reliable Steam Surface Condensers

2020 ◽  
Author(s):  
Ranga Nadig
Keyword(s):  
Steam Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
Design Features ◽  
Surface Condenser ◽  
Combined Cycle Plant ◽  
Startup Time ◽  
On Line ◽  
To Come

Abstract Power plants operating in cyclic mode, standby mode or as back up to solar and wind generating assets are required to come on line on short notice. Simple cycle power plants employing gas turbines are being designed to come on line within 10–15 minutes. Combined cycle plants with heat recovery steam generators and steam turbines take longer to come on line. The components of a combined cycle plant, such as the HRSG, steam turbine, steam surface condenser, cooling tower, circulating water pumps and condensate pumps, are being designed to operate in unison and come on line expeditiously. Major components, such as the HRSG, steam turbine and associated steam piping, dictate how fast the combined cycle plant can come on line. The temperature ramp rates are the prime drivers that govern the startup time. Steam surface condenser and associated auxiliaries impact the startup time to a lesser extent. This paper discusses the design features that could be included in the steam surface condenser and associated auxiliaries to permit quick startup and reliable operation. Additional design features that could be implemented to withstand the demanding needs of cyclic operation are highlighted.

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.

scholarly journals Energy Assessment of a Combined Cycle Power Plant through Empirical and Computational Approaches: A Case Study

2021 ◽  
Vol 12 (1) ◽  
pp. 25
Author(s):  
Waseem Amjad ◽  
Mubeen Shahid ◽  
Anjum Munir ◽  
Furqan Asghar ◽  
Owais Manzoor
Keyword(s):  
Steam Turbine ◽  
Energy Management ◽  
Gas Turbines ◽  
Power Plants ◽  
Management Practice ◽  
Simulation Software ◽  
Combined Cycle ◽  
Energy Audit ◽  
Significant Information ◽  
Turbine Efficiency

Energy management on the demand side is an important practice through which to address the challenge of energy shortage. In Pakistan, power plants have no specific energy management practice and a detail energy audit is normally observed as a one-time estimation that does not give significant information. In this study, an energy audit of a combined-cycle gas turbine power station was conducted and empirical data were compared with those obtained through a model developed in ASPEN, a simulation software that forecasts process performance. Next, an optimization tool was used to modify the ASPEN results and a comparison was drawn to estimate the amount of energy saved. It was found that compressor power consumption can be decreased up to 14.68% by increasing the temperature of compressed air from 320.2 °C to 423.79 °C for gas turbines. The output of gas turbines can be enhanced up to 13.5% and 21.4% with modelled and optimized data, respectively, using a multistage air compressor and multistage expansion. The calculated efficiency of the steam turbine was found to be 30.4%, which is 27.61% less than that of its designed efficiency. Steam turbine efficiency can be increased by 5% using a variable-speed water pump, leading to an estimated energy-saving potential of 8–9%. The combustion efficiency of gas turbines is not only important for higher turbine power output but also for better steam generation through heat-recovery steam generators in case of combined-cycle operations. The overall steam turbine efficiency is estimated to have increased by 19.27%, leading to a 12.68% improvement in combined efficiency.

Past, Present and Future of Combined Cycle Power Plants: From an A/E’s Perspective

2001 ◽  
Author(s):  
Anup Singh
Keyword(s):  
Power Generation ◽  
Natural Gas ◽  
Gas Turbine ◽  
Rapid Growth ◽  
Gas Turbines ◽  
Power Plants ◽  
Combined Cycle ◽  
Electrical Transmission ◽  
Capital Costs ◽  
The U.S

In the 1970s, power generation from gas turbines was minimal. Gas turbines in those days were run on fuel oil, since there was a so-called “natural gas shortage”. The U.S. Fuel Use Act of 1978 essentially disallowed the use of natural gas for power generation. Hence there was no incentive on the part of gas turbine manufacturers to invest in the development of gas turbine technology. There were many regulatory developments in the 1980s and 1990s, which led to the rapid growth in power generation from gas turbines. These developments included Public Utility Regulatory Policy Act of 1978 (encouraging cogeneration), FERC Order 636 (deregulating natural gas industry), Energy Policy Act of 1992 (creating EWGs and IPPs) and FERC Order 888 (open access to electrical transmission system). There was also a backlash from excessive electric rates due to high capital recovery of nuclear and coal-fired plant costs caused by tremendous cost increase resulting from tightening NRC requirements for nuclear plants and significant SO2/NOx/other emissions controls required for coal-fired plants. During this period, rapid technology developments took place in the metallurgy, design, efficiency, and reliability of gas turbines. In addition, U.S. DOE contributed to these developments by encouraging research and development efforts in high temperature and high efficiency gas turbines. Today we are seeing a tremendous explosion of power generating facilities by electric utilities and Independent Power Producers (IPPs). A few years ago, Merchant Power (generation without power purchase agreements) was unheard of. Today it is growing at a very fast pace. Can this rapid growth be sustained? The paper will explore the factors that will play a significant role in the future growth of gas turbine-based power generation in the U.S. The paper will also discuss the methods and developments that could decrease the capital costs of gas turbine power plants resulting in the lowest cost generation compared to other power generation technologies.

Options to Maximize Power Output for Merchant Plants in Combined Cycle Applications

2001 ◽  
Author(s):  
Rattan Tawney ◽  
Cheryl Pearson ◽  
Mona Brown
Keyword(s):  
Power Output ◽  
Gas Turbines ◽  
Life Cycle Cost ◽  
Peak Power ◽  
Power Plants ◽  
High Reliability ◽  
Combined Cycle ◽  
Cycle Performance ◽  
Plant Design ◽  
Capital Costs

Deregulation and growth in the power industry are causing dramatic changes in power production and distribution. The demand for peak power and potentially high revenues due to premium electricity rates has attracted independent developers to the concept of Merchant Power Plants (MPPs). Over 100,000 MW of greenfield capacity is currently being developed through approximately 200 merchant plants in North America. These MPPs will have no captive customers or long-term power purchase agreements, but will rely on selling electricity into a volatile electricity spot market. Because of this, MPPs need the capability to export as much power as possible on demand. MPPs must also have the capability to produce significant assets in order to compete in the marketplace, based on both technical and commercial operation factors such as value engineering, life-cycle cost management, and information technology. It is no surprise then, that almost all merchant project developers have specified combined cycle (CC) technology. The CC power plant offers the highest thermal efficiency of all electric generating systems commercially available today. It also exhibits low capital costs, low emissions, fuel and operating flexibility, low operation and maintenance costs, short installation schedule, and high reliability/availability. However, since gas turbines (GTs) are the basis for CC power plants, these plants experience power output reductions in the range of 10 to 15 percent during summer months, the period most associated with peak power demand. In order to regain this loss of output as well as to provide additional power to meet peak demands, the most common options are GT inlet fogging, GT steam injection, and heat recovery steam generator (HRSG) supplemental firing. This paper focuses on plant design, cycle performance, and the economics of plant configuration associated with these options. Guidelines are presented in this paper to assist the owner in selecting power enhancement options for the MPP that will maximize their Return on Equity (ROE).

Integrated Diagnostic System for the Equipment of Power Plants: Part I — Formulation and Algorithms

2002 ◽  
Author(s):  
J. Kubiak ◽  
A. Garci´a-Gutie´rrez ◽  
G. Urquiza ◽  
G. Gonza´lez
Keyword(s):  
Expert System ◽  
Expert Systems ◽  
Gas Turbines ◽  
Power Plants ◽  
Cooling System ◽  
Combined Cycle ◽  
Steam Turbines ◽  
Rotor Bearing ◽  
Bearing System ◽  
Plant Efficiency

The output capacity of combined cycle power plants is reduced in many cases, and sometimes forced to outages, when its main components are affected by faults, i.e., when the rotating equipment such as turbines, generators, compressors, pumps and fans suffer a failure. Normally, the overall reduction of the efficiency, and sometimes the component efficiencies, is monitored but it is difficult to identify the primary causes of the fault of the specific equipment that causes the reduction of plant efficiency. Therefore, to reduce the time of faulty operation, a precise diagnostic tool is needed. One such tool is an expert system approach, which is presented in this work. It consists of several expert systems for the identification of the faults caused by deterioration of the inner parts of the equipment, Fig. 1. Such faults not only reduce the plant efficiency but in many cases also increase the vibrations of the rotor-bearing system. Based on knowledge, the various expert systems have been constructed and their algorithms (efficiency reduction) developed for the following equipment: steam turbines, gas turbines and compressors, condenser, pumps and water cooling system. An expert system for detecting faults that increase the vibration of the rotor–bearing system is also presented. As far as the turbo compressor expert system is concerned the fault hybrid patterns previously developed were implemented and described elsewhere [1].

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.

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