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Steam Turbine Reliability Improvement: Critical Features Evaluation with ProTRAX

In considering future process changes, a U.S. utility contracted TRAX to analyze a combined cycle power plant’s dynamics during startup, shutdown, and load maneuvering events. This client was considering adding the GE Steam Turbine Agility system with the intent to improve the plant’s startup time and reduce fuel consumption. Using modeling, TRAX can help choose process and controls changes to optimize plant operation and minimize cost before these investments are made.


Combined Cycle Steam Turbine Improvements

TRAX built a high-fidelity simulation of the combined cycle power plant heat recovery steam generator (HRSG), balance of plant (BOP), and steam turbine (ST) systems. The simulation model was validated by comparing plant historian data against model data during:

  • A cold startup
  • A hot startup
  • Plant shutdown

Once validated against plant historian data, TRAX tested incremental changes in the model to predict the behavior and evaluate the benefits and drawbacks of the client’s proposed changes. Using the modeled solution, TRAX tested changes intended to improve the client’s combined cycle startup time and reduce fuel consumption:

  • The client could add a thermal blanket to the ST to heat the turbine shell for startup as well as to keep it warm while offline in standby mode.
  • The client requested two reference startup conditions be tested to demonstrate rotor stress. In the model, TRAX was able to show the client the effects of increasing the ST loading speed by up to four times without ever placing stress on the physical turbine.
  • TRAX tested startup and turbine loading under different configurations of the thermal blanket and different components of the GE Agility system to show the client a side-by-side comparison of the startup times and stresses that each condition presented.
  • TRAX also tested a hot startup and shutdown condition.

This testing included several important data points for the client:

  • With the thermal blanket turned on in the model, the Gas Turbine (GT) Inlet Guide Vane (IGV) didn’t need to be closed to the minimum full-speed position prior to loading up the GT. (This can lead to the GT gas turbine exhaust flow and temperature profiles changing.)

TRAX tested loading rates and time for the turbines and their relationship to rotor stress calculations. The side-by-side testing exactly quantified the time cost of each startup condition, the benefit of the thermal blanket, and the ST agility maneuvering.

Steam Turbine Reliability Improvement: Critical Features Evaluation with ProTRAX

June 2, 2023

TRAX has delivered a carbon capture simulator for a 150 MW coal-fired unit that models the capture of the full flue gas stream.  The system provides both CO2 and SO2 capture, delivering the captured CO2 to a pipeline for industrial use and underground storage.

TRAX Carbon Capture Model Included:

—CO2 and SO2 capture
—Sulfuric acid plant
—CO2 and SO2 amines filtration and purification
—CO2 compression
—CO2 pipeline and cavern

As shown below, TRAX built a modular simulation replicating the plant layout using our software, ProTRAX.  ProTRAX contains a full suite of modules specific to carbon capture functions and can model a wide variety of processes.  TRAX also virtually replicated the user interface that appears in the plant.  

Model Scope

ProTRAX is a modular software that can easily integrate multiple models for larger projects.


TRAX organizes the simulator model to match the layout of the site or process being modeled.


Depending on the Absorber module selected, the module can remove water vapor (H2O), carbon dioxide (CO2), and/or sulfur dioxide (SO2) from an air or gas stream.


Each ProTRAX module is backed by comprehensive documentation, including a general description, module inputs and outputs, and mathematical formulae.


The training value of a simulator occurs in the interactive screens that replicate the site equipment.

Upon initial delivery, the TRAX simulator was used to debug control logic and processes prior to site installation and to provide operations training prior to plant startup.  There was a clear need to begin training operators as early as possible since they had multiple unfamiliar systems to learn.

Thanks to the ProTRAX simulator, our customer gained considerable insight into control functionality and system interactions, resulting in modification to some control logic and correction of simple errors.  TRAX was able to assist with controls tuning, and helped in development of initial plant Operating Procedures.

The latest upgrade brings the model into alignment with the as-built plant condition by updating and tuning the simulator models to match the current plant dynamics. In addition, TRAX has updated the simulator controls and HMI graphics to the as-built state.  Keeping the simulator aligned with the current plant condition is critical to maintaining a positive training value, and is of paramount importance to the customer.

TRAX’s modeling confirmed the startup time could be reduced by 100 minutes when using the thermal blanket
TRAX was able to show rapid improvement in a comparison of steam turbine load where the turbine reaches base load in IPC mode 80 minutes faster than the unmodified condition
Especially useful to the client, TRAX provided a direct comparison of the combined cycle total load with and without ST improvements

Areas of Concern

If any event causes a plant trip or other major upset during the evaluation of the simulation, TRAX tests a variety of corrective actions. In this case, TRAX identified several areas of change to the client, allowing them to train for specific conditions and concerns:

  • Loading the gas turbine too fast may lead to higher HP pressures (discharge through relief values or ruptured discs).
  • The new configuration showed more swings in the drum levels.
  • These changes would lead to additional thermal and mechanical stress in the HRSG.
Chart, line chartDescription automatically generated
TRAX highlighted this area as a possible concern to the client. The high pressure observed in the model indicates that an operator may need to take preventative actions to relieve the high drum pressure.