Flare gas reduction: A case study of integrating regeneration gas in flash gas compression network

•Regeneration gas from mercaptan removal unit is recycled via flash gas compression.•A new compression setup handled the new combined gas stream.•Process simulation and field operational tests were successful.•No safety or operability concern exists for the new configuration.•A 75% reduction of flare gas was achieved. The total flow rate of the outlet regeneration gas of two mercaptan removal units in South Pars Gas Complex, Phase 1, is 20,000 Nm3/hr (10,000 Nm3/hr from each unit). The outlet stream splits into two streams. The first stream, with a flow rate of 7,000 Nm3/hr, flows into the boiler as fuel. The second stream, with the flowrate of 13,000 Nm3/hr, is sent to flare. In this paper, multiple experiments, including operational tests and dynamic simulation, were performed to prevent the flaring of regeneration gas as the main flaring source and feed loss in the plant. This goal was obtained by recycling the regeneration gas and switching it from the flaring system to the production line via flash gas compressors. To accomplish this, a series of Low Pressure-Medium Pressure (LP-MP) flash gas compressors were connected to MP flash gas. The new LP-MP-MP configuration was able to handle all the regeneration gas of one gas train. This configuration reduced the flow rate of the flaring gas from 13,000 Nm3/hr to 3,000 Nm3/hr and one of the flare stacks could be turned off. In addition, CO2 and CH4 emission decreased by ∼ 75%.