Extension of Fuel Flexibility in the Siemens Dry Low Emissions SGT-300-1S to Cover a Wobbe Index Range of 15 to 49 MJ/m3

Abstract

The extension of gas fuel flexibility in the Siemens SGT-300 single shaft (SGT-300-1S) is reported in this paper. A successful development programme has increased the capability of the Siemens Industrial Turbomachinery, Lincoln (SITL) dry low emissions (DLE) burner configuration to a fuel range covering a Wobbe Index (WI) from 15 to 49 MJ/m3. The standard SGT-300-1S SITL DLE combustion hardware allowed for gas and liquid fuels within a specified range typically associated with natural gas and diesel, respectively. Field operation of the standard production SGT-300-1S has confirmed the reliable operation with an extension to the fuels range to include processed land fill gas (PLG) from 32 to 49 MJ/m3. The further extension of the fuel range for the SGT-300-1S SITL DLE combustion system was achieved through high pressure testing of a single combustion system at engine operating conditions. The rig facility allowed for the actual fuel type to be tested using a mixing plant. The variations in fuel heating value were achieved by blending natural gas with diluent CO2 and/or N2. Various diagnostics were used to assess the performance of the combustion system including measurement of combustion dynamics, temperature, fuel supply pressure and emissions of NOx, CO and unburned hydrocarbon (UHC). The results of the testing showed that the standard production burner can operate for a fuel with WI as low as 23 MJ/m3 which corresponds to 35% CO2 (in volume) in the fuel. This range can be extended to 15 MJ/m3 (54.5% CO2 in the fuel) with only minor modification, to control losses through the burner and to maintain similar fuel injection characteristics. The SITL DLE combustion system is able to cover a WI range of 15 to 49 MJ/m3 in two configurations. The results of testing showed a lowering in WI, from diluting with CO2 and/or N2, a benefit in NOx reduction is observed. This decrease in WI may lead to an increased requirement in fuel supply pressure.

Effect of Change in Fuel Compositions and Heating Value on Ignition and Performance for Siemens SGT-400 Dry Low Emission Combustion System

“…A flame diluted with CO 2 showed a weaker anchorage than for the methane-air flame [26], and flame resistance to extinction was weaker as extinction strain was reduced as a result of reduced burning velocity through dilution and radiation effect [17]. Weaker flameholding was also found by Liu et al [6,7] with burner metal temperatures reducing as more diluent was added, and which also indicates the change in flame position and size [6,18,24].…”

“…The benefit of NOx reduction by using normal MCV fuels was widely reported [1,[9][10][11][12][13][14], for example: 20% reduction with 35% N 2 in the fuel [1], 40% reduction with 50% N 2 in the fuel [2] and about 50% reduction with 35% CO 2 in the fuel [6]. NOx is also sensitive to the selection of diluents, generally more NOx is produced if N 2 is selected as diluent [7,9].…”

“…Several critical points associated to the percentage of CO 2 or N 2 in the fuel have been identified for different burner geometries and when more diluent is added beyond this critical point, combustion dynamic pressure amplitude is increased. This critical point is highly dependent on burner design, for example: 25% of N 2 [1]; 55% of N 2 [2] with frequency less than 100 Hz (between 45-50% of N 2 there is a reasonable safety margin for instability); WI 27 MJ/Sm 3 [6] corresponding to 22.8% CO 2 and 8.2% N 2 in the fuel; 20% CO 2 for a 10 MW engine test [13] with a frequency shift towards to the lower value for the frequency band 40 to 45 Hz. This lower range of frequency is typical of the lean blow out frequency.…”

“…For normal MCV fuel the problems associated with lean blowout, such as weaker flameholding and higher combustion dynamic pressure amplitude when diluent concentration approaches the critical point, can be controlled by pilot fuel schedule [6,7,13] hence the operation of such fuel should not be a problem, however, the increased mass flow of fuel with increasing diluent leads to a requirement for higher supply pressure [6,7] and minor modifications of the fuel injection design may be required [6].…”

“…In this paper, the extension to the standard natural gas fuel range is considered. The considerations for such non-standard fuels for industrial gas turbine combustion systems are the robustness of the combustor to auto-ignition, flashback, acceptable combustion dynamic pressure amplitude and emissions and neutral flameholding [1][2][3][4][5][6][7][8].…”