STAG Equipment Configuration

Features to Meet Your Application Requirements

Each GE combined cycle system is an engineered equipment package consisting of gas turbines, steam turbines, generators, heat recovery steam generators (HRSGs) and controls. The basic STAG configuration uses a three-pressure steam cycle with deaerating condenser, unfired natural circulation HRSG design, Dry Low NOx combustion system, once-through water cooling and natural gas fuel. A reheat steam cycle is also included with 9EC and F technology gas turbines.

Optional features are available to meet your application requirements, including supplementary firing capability, alternate means of controlling emissions, condenser cooling and fuels selection.

Multi-shaft and single-shaft arrangements allow customization to optimize plant performance, capital investment, construction and maintenance access, operating convenience and minimum space requirements.

Single-Shaft Configurations

GE pioneered the single-shaft STAG equipment configuration. A single-shaft STAG system consists of one gas turbine, one steam turbine, one generator and one HRSG. The gas and steam turbines are coupled to the generator in a tandem arrangement on a single shaft.

Advantages of the single-shaft configuration include:

  • Lower capital cost
  • Single generator and electricals
  • Simple unit control system
  • Smaller footprint that is ideal for optimizing space limitations
  • Single-shaft arrangements are particularly advantageous for modern reheat combined cycle plants. It simplifies the starting and steam bypass systems associated with multiple heat recovery steam generators and a single steam turbine

Multi-Shaft Configurations

Multi-shaft STAG systems have one or more gas turbine generators and HRSGs that supply steam through a common header to a separate single steam turbine generator. This configuration allows a combined cycle plant to be installed in two phases, if necessary, driven by factors such as financing availability, fuel costs and load demand. The gas turbine, for example, can be installed first and provide revenue-producing power generation while the steam system is being installed.

In a multi-shaft configuration, the generators are smaller, making the arrangement well-suited to unique steam turbine designs such as cogeneration or district heating. In addition, when two gas turbines are employed, the multi-shaft arrangement can have favorable capital costs based on the use of a single steam turbine.

Advantages of multi-shaft configurations include:

  • Phased installation
  • Simple cycle operation gas turbines can be operated without steam cycle
  • Flexible arrangement; customized unit configurations
  • The gas turbine can be run independently of the steam turbine

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