With this project, TRAX helped an EPC firm validate the design for a turbine bypass system, boiler safety valves and associated balance of plant equipment by conducting a dynamic study with ProTRAX software.
TRAX built a model for two identical circulating fluidized bed (CFB) boilers. The model included boiler safety valves at the drum, superheater and reheater, while the balance of plant system included high pressure (HP), intermediate pressure (IP), and low pressure (LP) turbines, condenser, deaerator, feedwater heaters, condensate extraction pumps, boiler feed booster pumps and boiler feed pumps. TRAX also included modeling of the relevant HP and IP/LP turbine bypass systems.
In addition to these components, TRAX developed control system models that effectively managed and regulated the operation of this equipment. This allowed TRAX to create a sophisticated simulation that accurately reflected the behavior and interactions of all interconnected systems within the CFB boilers and associated balance of plant infrastructure.
After ensuring the model faithfully mirrors the actual equipment, TRAX can test severe scenarios to give our clients new data. With the new CFB boiler models, TRAX conducted a series of tests to help the EPC determine their best course of action. In one specific test scenario, TRAX initiated a load rejection with the modeled plant operating at 102%, which immediately closed all the HP turbine stop valves and the reheat stop valves. During this transient, the boiler load ramped down from 102% to 40% at a rate of 7% per minute. Through this testing, TRAX was able to verify bypass system capacity.
Through this analysis, TRAX confirmed for the client that none of the safety valves opened during the load rejection event. TRAX also monitored conditions at the boiler feed pumps, boiler feed booster pumps and condensate extraction pumps — none of these pumps experienced cavitation during the load rejection transient. These pumps had sufficient capacity to keep levels in the steam drum, deaerator and condenser at (or near) setpoint throughout the load rejection transient.
TRAX demonstrated the bypass system was properly designed to handle the worst-case load rejection scenario without lifting any of the boiler safety valves, validating the EPC's design of the turbine bypass system.
