Is your Flare Gas Recovery (FGR) system increasing corrosion risk!?

The presence of oxygen in produced gas is undesirable as it promotes corrosion. For this reason, specification limits on gas in transport pipelines are often set at < 10 ppm. Whilst oxygen has major implications, it is not routinely monitored as it is not expected to be present; however, Qa3 has identified a route for oxygen introduction in the gas process as a result of the installation of Flare Gas Recovery (FGR) systems. These FGR systems are becoming more prevalent in the industry as companies strive to reduce carbon emissions and increase revenue.

FGR Systems are specialised compression packages, which aim to recover and repurpose off gasses, such as methane and LPG, that would normally be burned via the flaring process or sent to atmospheric vents. Nitrogen is typically used as a blanket gas in low pressure tanks and vessels on offshore and onshore facilities, applying positive pressure to direct off-gases from these vessels to flare. As such, the purity of the plant nitrogen has not been considered as this historically is sent to flare. The nitrogen is typically generated using a nitrogen generation package employing membrane filters or pressure swing adsorption, which removes between 95 – 99% of the oxygen. This oxygen rich nitrogen is introduced into the gas process as a consequence of the installation of FGR systems resulting in elevated oxygen concentrations in the processed gas. Qa3 have observed exported natural gas with concentrations up to 100 ppm oxygen (10 – 15 times higher than typical pipeline and feedstock specifications).