Extension of gas fuel flexibility of a current production standard SGT-400 industrial gas turbine combustor is reported in this paper.
A successful development program has increased the capability of the standard production dry low emissions burner configuration to burn a range of fuels covering a temperature corrected wobbe index from 30 to 49 MJ/m3. A standard SGT-400 13.4 MW dry low emission double skinned combustor can was tested with a standard production gas burner for a cannular combustion system. Emissions, combustion dynamics, fuel pressure and flashback monitoring via measurement of burner metal temperatures, were the main parameters used to evaluate the impact of fuel flexibility on combustor performance. High pressure rig tests were carried out to demonstrate the capabilities of the combustion system at engine operating conditions across a wide range of ambient conditions. Variations of the fuel heating value were achieved by blending natural gas with CO2 as diluent.
The standard SGT-400 combustion system employs proven dry low emissions technology for natural gas and liquid fuels such as diesel within a specified range of fuel heating values. With the aid of novel intelligent control software, the gas fuel capability of the SGT-400 standard dry low emissions burner has been extended, with the engine, achieving stable operation and reduced emissions across the load range despite variations of the composition of the fuel supply. This, combined with previous experience from high pressure rig and engine testing of the different burner configurations that covered this range, resulted in a reduction in the number of hardware configurations from three burners to two. Testing showed that the standard production burner can reliably operate with a fuel temperature controlled wobbe index as low as 30 MJ/m3 which corresponds to 20% CO2 (by volume) in the fuel.
The performance of four different fuels with heating values in terms of temperature controlled wobbe index: 30, 33, 35 and 45 MJ/m3 (natural gas), is presented for the current production hardware. Test results show that NOx emissions decrease as the fuel heating value is reduced. Also note that a decreasing temperature controlled wobbe index leads to a requirement to increase the fuel supply pressure. The tests results obtained on the Siemens SGT-400 combustion system provide significant improvement for industrial gas turbine burner design for fuel flexibility.