Proposed Design for Gas Turbine Ingestion of Dry Gas Seal Primary Vent Fugitive Methane

Natural gas transmission systems have many sources of fugitive methane emissions that have been difficult to eliminate. This paper discusses an option for dealing with one such source for operations using turbo-compressor units fitted with dry gas seals. Dry seal leakage ultimately results in waste gas that is emitted to the atmosphere through the primary vent. A simple, cost effective, emission disposal mechanism for this application is to vent the seal leakage in to the gas turbine’s air intake. Explosion hazards are not created by the resultant ultra-lean fuel/air mixture, and once this mixture reaches the combustion chamber, where sufficient fuel is added to create a flammable mixture, significant oxidation of the seal vent gas is realized. In principle, this system is easily implemented with simple modifications to the existing vent piping. However, the inherent safety of ultra-lean fuel/air mixture applies only when the gas turbine is operating with gas turbine airflow overwhelming the seal leakage flow. A potential design solution for managing this emission avoidance mechanism including safe operation during gas turbine shutdown periods is detailed.