A Study of Parameters Affecting the Combustion Stability and Emissions Behavior of Alstom Heavy-Duty Gas Turbines

Abstract

A number of factors can influence the combustion instability region and emission behavior of a heavy-duty gas turbine. Changes in the composition of the natural gas supplied have an impact that was studied in a prior investigation, which focused on parameters such as fuel temperature and composition. To further investigate the fuel sensitivity additional plants were included in this study. In addition to the fuel properties the distribution of the fuel inside the combustor was examined. To expand the fuel properties study, additional parameters were examined. Ambient conditions were paid special interest, specifically ambient temperature and humidity. Included in this study was also the effect on combustion of changes in compressor discharge pressure. With the growing interest in inlet chilling a pulsation/emission study was included to specifically look for NOx and combustion instability effects due to inlet chilling. Also, influences from special occurrences such as on-line compressor washing were examined. The turbines in this study utilize a silo-type combustor with either the DLN [Dry Low NOx] EV [EnVironmental] burners or with single diffusion burners using water or steam as NOx reduction medium. The rated power output of the gas turbines was in the range of 50–120 MW. The data acquired included frequency-analyzed combustion instabilities, various process data, as well as ambient conditions and fuel composition. The collected data shows the magnitude of the changes in the emissions and combustion noise with changes in the parameters studied. The conclusion is that some key parameters are very important for both the pulsations and the emissions, whereas others can be neglected. Some parameters affect the combustion instabilities only, without noticeable effect on emissions, and vice versa.