GT13E2 Low Part Load Operation: Extended Flexibility Down to 30% Load

Abstract

This paper describes the development work of the Low Part Load upgrade package for the GT13E2 gas turbine fleet and the related test results of the engine validation phase. The GT13E2 gas turbine was originally designed for operation at high combined cycle efficiency and low emissions in the range from about 60% to 100% load. The upgrade package improves the minimum environmental load of the GT13E2 making it possible to operate the GT with full flexibility down to 30% relative load. In fact, in today’s energy market operational flexibility is one of the key requirements for our customers. The extended low part load capability will allow the customers to operate the power plant in combined cycle mode with high efficiency and to rapidly change the load as soon as the grid demands. The upgrade package can be retrofitted to the installed service fleet with AEV burner technology. The main challenge at low part load operation is to keep the NOx and especially the CO emissions under control. Increased emissions at lower loads were acceptable since it was not intended to operate for long periods of time at these loads. The low part load upgrade improves combustion of the gas turbine by keeping the flame temperature at higher levels. The key to success for improved combustion behavior at part load is mainly the reduction of the burner air mass flow and the redistribution of the corresponding fuel mass flow. The main measures used for the low part load concept are a further closing of the inlet guide vanes and a redistribution of the fuel gas to fewer burners. Additional measures for further reduction of the burner air mass flow at part load were also evaluated and tested. Only a combination of several measures really improves the minimum environmental load of the gas turbine and of the combined cycle efficiency, compared to the original operation concept. During the development of the low part load project each single measure was extensively validated on GT13E2 engines independently. The combination of the different measures was finally validated on a customer engine and the projected emission targets down to 30% load were successfully confirmed.