Gas Turbine Power Generation Utilising Low and Variable Quality Gas Fuels in Dry Low Emissions Combustion Systems

摘要

Since the late 1980s, environmental concerns over pollutants created during the combustion process have driven gas turbine manufacturers to develop combustion systems that create lower and lower emissions of nitrous oxides (NOx), carbon monoxide (CO) and unburned hydrocarbons (UHC). To meet this challenge, manufacturers developed Dry Low Emissions (DLE) or Dry Low NOx (DLN) combustion systems. Primarily employed initially in industrial applications or utility power plant using pipeline quality natural gas as the main fuel, DLE became quickly established and is now a well-proven technology with thousands of units installed and tens of millions of operating hours experience gained. Some manufacturers now only offer DLE combustion systems on some gas turbine models, such is the confidence in this technology. Upstream Oil & Gas operators face challenges that industrial users and utility companies don’t: the gas fuel available is in most cases not ‘pipeline quality’, containing varying amounts of contaminants such as inert gases or higher hydrocarbon species; the gas composition can vary depending on both source and time; toxic and corrosive contaminants, such as hydrogen sulphide, might exist within the gas stream; with no connection to an electricity grid system, the gas turbines are required to operate at constantly varying loads to match the power demand of the facilities; and unit reliability is critical to ensure continuous production and revenue generation. This paper reviews the work undertaken by Siemens Industrial Turbomachinery on their range of gas turbines between 5MW and 50MW in power output to characterize the capabilities of the DLE system with respect to the different fuel gas compositions encountered, and the variability of the gas composition, and discusses some examples of installations both in industry and offshore O&G applications where such fuels are used while still meeting the required emission limits and without affecting operability.