Staged Combustion System for Improved Emissions Operability and Flexibility for 7HA Class Heavy Duty Gas Turbine Engine

Abstract

Driven by global warming, a relentless march towards increased fuel efficiency has resulted in increased firing temperature for HA-class engines without an increase in baseload emissions. Moreover, emissions compliance for CO, NOx, and unburned hydrocarbons are desired over increased range in gas turbine load. In addition, exceptional gas turbine operational flexibility is desired to address potential intermittency due to the penetration of renewables in the electrical grid. Staged/sequential combustion is a state of the technology to provide operational flexibility and reduced emissions in power generation gas turbines. GE Power’s 7HA-class gas turbine combustion system combines GE’s proven DLN-2.6+ combustion technology, that has run reliably for over 1.3 million fired hours across more than eighty 9FA.03, 9F.05 & 7FA gas turbine engines, with an axially fuel staged system (AFS). Axially staging combustion to two zones allows for increased firing temperature at baseload (while maintaining the same NOx level) by operating the later/second stage hotter than the first/primary stage. During low load operation as the gas turbine firing temperature is reduced, percentage fuel split in the staged fuel system can either be reduced significantly or turned off and thereby keeping the overall combustion system into emissions compliance over a wider range of firing temperatures. This paper presents both the development testing of the staged combustion in the FA and HA class gas turbine combustion system rigs at GE Power’s Gas Turbine Technology Laboratory and the validation testing of staged combustion system for the 7HA.01 engine completed during Spring 2016 at GE Power’s engine test facility in Greenville, SC. The paper also discusses the significant simplification of operational principle and flexibility of startup, loading and baseload operation of the 7HA combustion system. Discussion of engine test results will show how axial fuel staging was utilized to demonstrate emissions compliance ( NOx (15% O2) < 25 ppm; CO < 9 ppm), operation from 14% load to 100% load with low combustion dynamics and also to enable wide wobbe capability, which is a normalized measure of fuel flexibility.