Enhancing Sustainability in Acid Gas Flare Operations

Abstract Facility designs consider common acid gas flare for multiple plants operating in the complex, based on cost optimization considerations. Such designs involve common Flare KOD, which is difficult to maintain, as multiple plant shutdowns are not feasible during shutdown planning. Common stand-by Flare KOD with suitable isolation provisions from different plants’acid gas headers ensures timely maintenance and thus enhances the sustainability of the Acid Gas Flare Operations. Due to presence of high levels of acid gases with moisture, acid gas flare streams tend to be highly corrosive. This poses safety threat to operating personnel, by loss of containment of toxic gas from vessel rupture or possible toxic gas leaks through KOD flanges. This situation was encountered in one of the GASCO operating complexes, where 2 existing plants shared a common flare KOD and a third existing plant via a different KOD was connected to the same acid gas flare. Original design envisaged maintenance of the acid gas flare by inter-connection with one of the existing hydrocarbon flares but safe inspection of the acid gas flare KODs could not be conducted. Non-intrusive ultrasonic scanning indicated severe corrosion in one of the existing KODs at various positions. However, due to absence of proper isolation facilities, internal inspection / replacement of the existing KODs was not possible without a total shut-down, which was not permissible. To overcome the problem, a standby flare system was studied to improve operational and maintenance flexibility, but was not implemented due to costs that were considered excessive. Instead, a more cost-effective solution based on installation of a standby KOD was implemented to address the critical Process safety issue. For installation of the new facility without any plant shutdown, several hot taps were required on the flare header. Implementation of the Standby KOD costed less than USD 8 Million, substantially less than the estimated cost of around USD 100 Million for Standby Flare project, while providing the desired level of operational and maintenance flexibility. Also, subsequent to the installation of the Standby KOD, an existing flare KOD, experiencing severe wall thinning due to corrosion, could be replaced without any plant shutdown. Reliability of existing acid gas flare KODs to resist toxic gas leaks has now improved with routine internal inspections.