Methods for heat rate improvement in combined cycle applications

Conference · Wed Jul 01 04:00:00 EDT 1998

OSTI ID:20015052

Tawney, R K; Brol, M W; Brown, M S

Combined-cycle technology has become very attractive to both utility and non-utility power producers. This technology allows for high thermal efficiency, low emissions, low installed cost, fuel and operating flexibility, low operation and maintenance costs, short installation time, and high reliability/availability. Power producers can take advantage of this technology and customize the plant to better suit their needs; e.g., a plant intended for base load operation may be designed for the best heat rate (efficiency), whereas a cycling plant may be designed to maximize electrical output at the lowest possible cost. Methods such as gas turbine steam or water injection, inlet air chilling, evaporative cooling, and supplementary fired heat recovery steam generators (HRSGs) increase electrical power output. Most of these are associated with the Brayton cycle and, as a result, decrease plant efficiency. This may be acceptable for a cycling plant where output is most important; however, for a base loaded plant, the focus should be placed on optimizing efficiency. Methods for efficiency enhancement, all of which are associated with the Rankine cycle, include various HRSG and steam turbine generator (STG) configurations (two pressures vs. three pressure and reheat vs. non-reheat), pressurized deaerators vs. vacuum deaerators, fuel gas heating, selection of the STG last stage bucket size, upgrade of the heat sink, and increase in STG throttle pressure. Note that while the purpose of these options is to improve heat rate, they have the added benefit of increasing power output. For each efficiency improvement method, plant design, cycle performance, and economics will be discussed. A two pressure level, non-reheat, advanced gas turbine-based combined-cycle plant will be used as a basis. The goal of this paper is to aide in the proper selection of available methods in order to provide a power plant which is optimized to maximize economic return to the Owner.

• Research Organization: Bechtel Power Corp., Frederick, MD (US)
• OSTI ID: 20015052
• Country of Publication: United States
• Language: English

Related Subjects

03 NATURAL GAS
20 FOSSIL-FUELED POWER PLANTS
AUGMENTATION
CAPACITY
COMBINED-CYCLE POWER PLANTS
HEAT RATE
NATURAL GAS
RANKINE CYCLE
THERMAL EFFICIENCY