The Success Story of H2S Scavenger Injection as Temporary Solution to Maintain Production During One of Two Amine Regeneration System Breakdown in X Gas Plant

Abstract

X gas plant has 4 process trains and one bypass train with capacity 800 MMscfd. Each process Train equipped with Amine contactor to reduce the CO2/H2S to below gas specification 5% mole CO2 and 8 ppm H2S. Rich Amine from contactors then regenerated through two Amine regenerator, heating media used hot water which maintained its temperature by using fired heater. X gas plant had experience breakdown of one Amine regenerator, which decreases plant capacity to 640 MMscfd. Impact of one regenerator breakdown the lean amine circulation rate decreases from total 1540 USGPM to 910 USGPM, with limited amine circulation to maintain liquid turndown at Amine contactor packing, Train-1/2/3 circulated with Amine, while Train-4 with no amine circulation. Several options were evaluated, application of H2S Scavenger Injection come up as the most probable option considering cost and time. Hydroxyethyl-triazine based was selected. Uncontrolled reaction and improper injection technique will lead to inefficient treating dosages and unwanted by-products. By combining knowledge of scavenger stoichiometric reaction with H2S, triazine content, spray nozzle injection technique, and produced water scale tendency, succeed to reduce the H2S content and reverting plant capacity to 800 MMscfd.). H2S Scavenger is injected through spray-nozzle installed in 12” gas line header upstream of Cooler Train #4 at 140OF and ±1250 psig. Initial injection is started with ±105 MMscfd treated gas which provide 24 second contact time with 0.45 L scavenger/MMscfd. As the initial treatment succeed to reduce H2S content from 35 to below 5 ppm, treated gas flowrate then increased gradually to 150 MMscfd and further to 220 MMscfd with 0.5 and 0.55 L/MMscfd scavenger dosage respectively. Increased treating dosage sufficiently maintain H2S scavenging efficiency with 50% reduced of contact time. H2S Scavenger direct injection could be considered as temporary solution program during such disturbance of amine system performance. The Amine regenerator repair was consumed 118 days, while H2S scavenger application was implemented after 34 days Amine regenerator repair activity until amine heater completed repair and back online which is for 84 days injection. In this case H2S Scavenger injection can optimize X gas plant sales gas 9.05 BSCF (equivalent with 55 MMUSD) with additional operating cost 0.916 MMUSD.