Performance improvement for a simple cycle gas turbine GENSET––a retrofitting example

Due to the serious power shortage in Taiwan, many simple cycle gas turbine generation sets (GENSETs) that were originally designated to serve as peak load units are forced to operate continuously during the entire summer season. The retrofitting projects have been seriously considered to convert these GENSETs (which have the advantage of fast startup, but suffer from low power output and thermal efficiency at high ambient temperature) into more advanced cycle units with higher efficiency and higher output. Among many proven technologies, such as inlet air cooling, intercooling, regeneration, reheating and steam-injection gas turbine (STIG) etc., STIG is found to be one of the most effective in boosting both the output capacity and thermal efficiency. The results from computer simulation indicated that the retrofitting of existing GE Frame 6B simple cycle unit into STIG cycle can boost the output from about 38 to 50 MW, while the generation efficiency can be increased from about 30% to 40%. Besides, the power output of STIG cycle is less sensitive to ambient temperature than that of simple cycle. NOx reduction to less then 25 ppm (when LNG is used) and operating flexibility under variable heat demand could be achieved.