Part-Load Operation of Combined Cycle Plants With and Without Supplementary Firing

1995 ◽  
Vol 117 (3) ◽  
pp. 475-483 ◽  
Author(s):  
P. J. Dechamps ◽  
N. Pirard ◽  
Ph. Mathieu
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Power Plants ◽  
Combined Cycle ◽  
Steam Generators ◽  
Part Load ◽  
Inlet Guide Vanes ◽  
Steam Plant

The design point performance of combined cycle power plants has been steadily increasing, because of improvements both in the gas turbine technology and in the heat recovery technology, with multiple pressure heat recovery steam generators. The concern remains, however, that combined cycle power plants, like all installations based on gas turbines, have a rapid performance degradation when the load is reduced. In particular, it is well known that the efficiency degradation of a combined cycle is more rapid than that of a classical steam plant. This paper describes a methodology that can be used to evaluate the part-load performances of combined cycle units. Some examples are presented and discussed, covering multiple pressure arrangements, incorporating supplemental firing and possibly reheat. Some emphasis is put on the additional flexibility offered by the use of supplemental firing, in conjunction with schemes comprising more than one gas turbine per steam turbine. The influence of the gas turbine controls, like the use of variable inlet guide vanes in the compressor control, is also discussed.

Performance Charateristics of Advanced Gas Turbine Cogeneration Power Plants

2005 ◽  
Author(s):  
Meherwan P. Boyce
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Firing Temperature ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Power Plants ◽  
Pressure Ratio ◽  
Combined Cycle ◽  
Air Filter ◽  
Cycle Efficiency

The performance analysis of the new generation of Gas Turbines in combined cycle operation is complex and presents new problems, which have to be addressed. The new units operate at very high turbine firing temperatures. Thus variation in this firing temperature significantly affects the performance and life of the components in the hot section of the turbine. The compressor pressure ratio is high which leads to a very narrow operation margin, thus making the turbine very susceptible to compressor fouling. The turbines are also very sensitive to backpressure exerted on them by the heat recovery steam generators. The pressure drop through the air filter also results in major deterioration of the performance of the turbine. The performance of the combined cycle is also dependent on the steam turbine performance. The steam turbine is dependent on the pressure, temperature, and flow generated in the heat recovery steam generator, which in turn is dependent on the turbine firing temperature, and the air mass flow through the gas turbine. It is obvious that the entire system is very intertwined and that deterioration of one component will lead to off-design operation of other components, which in most cases leads to overall drop in cycle efficiency. Thus, determining component performance and efficiency is the key to determining overall cycle efficiency. Thermodynamic modeling of the plant with individual component analysis is not only extremely important in optimizing the overall performance of the plant but in also determining life cycle considerations.

scholarly journals Gas Turbine Heat Recovery Steam Generators for Combined Cycles Natural or Forced Circulation Considerations

1988 ◽  
Author(s):  
Akber Pasha
Keyword(s):  
Gas Turbine ◽  
Steam Generator ◽  
Heat Recovery ◽  
Power Plants ◽  
Natural Circulation ◽  
Combined Cycle ◽  
Heat Recovery Steam Generator ◽  
Steam Generators ◽  
Forced Circulation ◽  
Gas Turbine Exhaust

In recent years the combined cycle has become a very attractive power plant arrangement because of its high cycle efficiency, short order-to-on-line time and flexibility in the sizing when compared to conventional steam power plants. However, optimization of the cycle and selection of combined cycle equipment has become more complex because the three major components, Gas Turbine, Heat Recovery Steam Generator and Steam Turbine, are often designed and built by different manufacturers. Heat Recovery Steam Generators are classified into two major categories — 1) Natural Circulation and 2) Forced Circulation. Both circulation designs have certain advantages, disadvantages and limitations. This paper analyzes various factors including; availability, start-up, gas turbine exhaust conditions, reliability, space requirements, etc., which are affected by the type of circulation and which in turn affect the design, price and performance of the Heat Recovery Steam Generator. Modern trends around the world are discussed and conclusions are drawn as to the best type of circulation for a Heat Recovery Steam Generator for combined cycle application.

Exergy Evaluation of Two Current Advanced Power Plants: Supercritical Steam Turbine and Combined Cycle

1997 ◽  
Vol 119 (4) ◽  
pp. 250-256 ◽  
Author(s):  
H. Jin ◽  
M. Ishida ◽  
M. Kobayashi ◽  
M. Nunokawa
Keyword(s):  
Steam Turbine ◽  
Thermal Efficiency ◽  
Heat Recovery ◽  
Power Plants ◽  
Exergy Analysis ◽  
Combined Cycle ◽  
Exergy Loss ◽  
Heat Recovery Steam Generator ◽  
Combined Cycle Plant ◽  
Steam Plant

Two operating advanced power plants, a supercritical steam plant and a gas-steam turbine combined cycle, have been analyzed using a methodology of graphical exergy analysis (EUDs). The comparison of two plants, which may provide the detailed information on internal phenomena, points out several inefficient segments in the combined cycle plant: higher exergy loss caused by mixing in the combustor, higher exergy waste from the heat recovery steam generator, and higher exergy loss by inefficiency in the power section, especially in the steam turbine. On the basis of these fundamental features of each plant, we recommend several schemes for improving the thermal efficiency of current advanced power plants.

scholarly journals Repowering of a Small Utility: A Unique Solution to a Unique Problem

1979 ◽  
Author(s):  
L. F. Fougere ◽  
H. G. Stewart ◽  
J. Bell
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Steam Generator ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Electric Utility ◽  
Combined Cycle ◽  
Steam Boiler ◽  
Heat Recovery Steam Generator ◽  
Turbine Generator

Citizens Utilities Company’s Kauai Electric Division is the electric utility on the Island of Kauai, fourth largest and westernmost as well as northernmost of the Hawaiian Islands. As a result of growing load requirements, additional generating capacity was required that would afford a high level of reliability and operating flexibility and good fuel economy at reasonable capital investment. To meet these requirements, a combined cycle arrangement was completed in 1978 utilizing one existing gas turbine-generator and one new gas turbine-generator, both exhausting to a new heat recovery steam generator which supplies steam to an existing steam turbine-generator. Damper controlled ducting directs exhaust gas from either gas turbine, one at a time, through the heat recovery steam generator. The existing oil-fired steam boiler remains available to power the steam turbine-generator independently or in parallel with the heat recovery steam generator. The gas turbines can operate either in simple cycle as peaking units or in combined cycle, one at a time, as base load units. This arrangement provides excellent operating reliability and flexibility, and the most favorable economics of all generating arrangements for the service required.

Modeling of a 27 MW Combined Cycle Cogeneration Plant With Central Cooling Facility

2003 ◽  
Author(s):  
Sandeep Nayak ◽  
Erol Ozkirbas ◽  
Reinhard Radermacher
Keyword(s):  
Natural Gas ◽  
Electric Power ◽  
Steam Turbine ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Combined Cycle ◽  
Cogeneration Plant ◽  
Steam Generators ◽  
Centrifugal Chillers ◽  
Chilled Water

This paper describes the modeling of a 27 MW combined cycle cogeneration plant with 10,000 tons chilled water central cooling facility. The cogeneration plant is designed to provide heating, cooling and electricity from a single fuel source viz., natural gas, though the gas turbines do have an inbuilt dual fuel combustion system. The topping cycle of the combined cycle cogeneration plant consists of two gas turbines each producing 11 MW of electric power at full load. The energy of the exhaust gases from these gas turbines is then utilized to generate steam in two heat recovery steam generators. The heat recovery steam generators are duct fired using natural gas to meet the peak steam load. In the bottoming part of the combined cycle, the steam from the heat recovery steam generators is expanded in a backpressure steam turbine to supply steam to the campus at about 963 kPa, generating an additional 5.5 MW of electric power in this process. There is no condenser wherein the campus acts as a sink for the steam. The central cooling facility is designed to supply 10,000 tons of chilled water out of which 3800 tons is supplied by two steam driven centrifugal chillers, which utilize a part of the steam supplied to the campus and the remaining by the centrifugal electric chillers. The combined cycle cogeneration plant along with the central chilled watercooling facility is modeled in a commercially available flexible cogeneration software package. The model is built based on the design data available from design manuals of gas turbines, heat recovery steam generators, backpressure steam turbine and centrifugal chillers. A parametric study is also done on the model to study the effect of different parameters like fuel flow rate, temperature etc on the output of the turbine and efficiency of the plant. Modeling of the inlet air-cooling of the gas turbine using an absorption chiller and electric chiller is also presented. Finally the paper discusses these results.

Development of a Combined Cycle Gas Turbine/Steam Plant for Training Marine and Power Engineers

2007 ◽  
Author(s):  
W. Peter Sarnacki ◽  
Richard Kimball ◽  
Barbara Fleck
Keyword(s):  
Power Plant ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Power Industry ◽  
Combined Cycle ◽  
Plant Performance ◽  
Engineering Programs ◽  
Hands On ◽  
Steam Plant

The integration of micro turbine engines into the engineering programs offered at Maine Maritime Academy (MMA) has created a dynamic, hands-on approach to learning the theoretical and operational characteristics of a turbojet engine. Maine Maritime Academy is a fully accredited college of Engineering, Science and International Business located on the coast of Maine and has over 850 undergraduate students. The majority of the students are enrolled in one of five majors offered at the college in the Engineering Department. MMA already utilizes gas turbines and steam plants as part of the core engineering training with fully operational turbines and steam plant laboratories. As background, this paper will overview the unique hands-on nature of the engineering programs offered at the institution with a focus of implementation of a micro gas turbine trainer into all engineering majors taught at the college. The training demonstrates the effectiveness of a working gas turbine to translate theory into practical applications and real world conditions found in the operation of a combustion turbine. This paper presents the efforts of developing a combined cycle power plant for training engineers in the operation and performance of such a plant. Combined cycle power plants are common in the power industry due to their high thermal efficiencies. As gas turbines/electric power plants become implemented into marine applications, it is expected that combined cycle plants will follow. Maine Maritime Academy has a focus on training engineers for the marine and stationary power industry. The trainer described in this paper is intended to prepare engineers in the design and operation of this type of plant, as well as serve as a research platform for operational and technical study in plant performance. This work describes efforts to combine these laboratory resources into an operating combined cycle plant. Specifically, we present efforts to integrate a commercially available, 65 kW gas turbine generator system with our existing steam plant. The paper reviews the design and analysis of the system to produce a 78 kW power plant that approaches 35% thermal efficiency. The functional operation of the plant as a trainer is presented as the plant is designed to operate with the same basic functionality and control as a larger commercial plant.

Modified Rankine HRSG Beats Triple-Pressure System

1996 ◽  
Author(s):  
Peter Eisenkolb ◽  
Martin Pogoreutz ◽  
Hermann Halozan
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Power Plants ◽  
Fossil Fuels ◽  
Combined Cycle ◽  
Exhaust Gas ◽  
Pressure System ◽  
Exergy Losses

Gas-fired combined cycle power plants (CCP) are presently the most efficient systems for producing electricity with fossil fuels. Gas turbines have been and are being improved remarkably during the last years; presently they achieve efficiencies of more than 38% and gas turbine outlet temperatures of up to 610°C. These high outlet temperatures require modifications and improvements of heat recovery steam generators (HRSG). Presently dual pressure HRSGs are most commonly used in combined cycle power stations. The next step seems to be the triple-pressure HRSG to be able to utilise the high gas turbine outlet temperatures efficiently and to reduce exergy losses caused by the heat transfer between exhaust gas and the steam cycle. However, such triple-pressure systems are complicated considering parallel tube bundles as well as start up operation and load changes. For that reason an attempt has been made to replace such multiple pressure systems by a modified Rankine cycle with only a single-pressure level. In the case of the same total heat transfer surfaces this innovative single-pressure system achieves approximately the same efficiency as the triple-pressure system. By optimising the heat recovery from the exhaust gas to the steam/water cycle, i.e. minimising exergy losses, the stack temperature is much higher. Increasing the heat transfer surfaces means a decrease of the stack temperature and a further improvement of the overall CCP-efficiency. Therefore one has to be aware that the proposed system offers advantages not only in the case of a foreseeable increase of gas turbine outlet temperatures but also for presently available gas turbines. Using existing highly efficient gas turbines and subcritical steam conditions, power plants with this proposed Eisenkolb Single Pressure (ESP_CCP) heat recovery steam generator achieve thermal efficiencies of about 58.7% (LHV).

An Impact of Environmental Disturbances on Combined Cycle Power Plant Control

2004 ◽  
Author(s):  
Zygfryd Domachowski ◽  
Marek Dzida
Keyword(s):  
Power Plant ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Power Plants ◽  
Ambient Pressure ◽  
Combined Cycle ◽  
Steam Generators ◽  
Environmental Disturbances ◽  
Power Plant Control ◽  
Plant Control

Combined cycle power plants operate at thermal efficiency approaching 60 percent. In the same time their performance presents several problems that have to be addressed. E.g. gas turbines are very sensitive to backpressure exerted on them by the heat recovery steam generators as well as to ambient pressure and temperature.

Hot Windbox and Combined Cycle Repowering to Improve Heat Rate

2010 ◽  
Author(s):  
Tarek A. Tawfik ◽  
Thomas P. Smith
Keyword(s):  
Steam Turbine ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Heat Recovery ◽  
Heat Rate ◽  
The United States ◽  
Combined Cycle ◽  
Plant Performance ◽  
Ambient Conditions ◽  
North East

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.

Sign in / Sign up

Export Citation Format

Share Document