Unconventional Flare Gas Recovery Systems (FGRS)

Abstract

Abstract This paper presents unconventional flare gas recovery schemes that do not include gas compressors to collect the routine daily flared gas, to send it back to the process plant. The innovative recovery systems will provide significant capital and operating cost savings by eliminating the installation and operation of gas compressor(s) as part of conventional FGRS. Two different FGRS schemes without gas compressors were established, using only static equipment for the flared gas recovery. The first scheme involves providing carefully sized pipe to flow-back the collected flare gas to the plant at the required pressure. This scheme requires careful hydraulic simulation for the entire flare system network, to ensure that the recovery system will not have any negative impact on the relief and flare systems — thereby jeopardizing the safety of the entire plant — and at the same time ensure flow from the location of the flare line to the recovered gas destination. The second scheme includes the use of a gas ejector with high pressure motive gas to boost low pressure flare gas to the intermediate pressure required to deliver the gas back to the process. The case study — of applying the established unconventional flare gas recovery system at Saudi Aramco's Qatif North Plant, to continuously recover about 5MMscfd of valuable fuel gas, which is equivalent to 5,051 MMBtu/day in fuel energy savings — was presented. The proposed FGRS schemes will minimize greenhouse gas emissions and provide positive environmental benefits.