Purging Gas Plant Flare System Using Gas Turbine Generators Exhaust Emissions – A Novel Approach

Abstract

Abstract Within gas plant treatment operations; there are large amounts of gases used to sweep its flare piping network as purge gas to prevent air ingress and protect the system from back fire. The economic and environmental considerations to reduce greenhouse gases (GHG) & save fuel are driving organizations to find alternative solutions to replace fuel gas purge using other safe & available sources. Fundamentally, the main electrical power supply for a gas processing plant are Gas Turbine Generators (GTGs) which continuously produce large amounts of Carbon Dioxide (Co2) & Nitrogen (N2) emissions with flowing temperatures of approximately 400-500° C. Collecting these emissions in a waste heat recovery conduit & heating the hot oil medium (the main source of thermal energy to gas plant heat users) and/or Mono Ethylene Glycol (MEG) (used as hydrate inhibitor) could be used as alternative solution for flare purging. This allows us to exploit this exhaust thermal energy efficiently as well as reducing the exhaust emissions temperature. The emissions will be then compressed from its normal atmospheric pressure to around 3.5 barg to meet the flare network purging requirements of positive pressure, helping to sweep the flare header preventing atmospheric air ingress. The analysis of emissions which was done by independent third party showed high percentage of Oxygen (O2) around 14%; which makes it unsafe to be used for flare purging purpose. Oxygen membrane put forward to overcome this challenge and remove this amount of Oxygen & purge flare network by almost pure Inert gases. This proposal being discussed here is to capture all quantities of the exhaust gas emissions to be the source of an inert gas utilized within flare systems, for purging purposes & saving environment as well as fuel gas flaring cost.