Qatargas Operating Company Limited (QATARGAS) has executed a major debottlenecking of its existing facilities at QATARGAS 1. This Project is known as the Plateau Maintenance Project (PMP). Its purpose is to maintain the Liquefied Natural Gas (LNG) production, while coping with increased levels of H2S and CO2 in the inlet feed gas streams. Revamp of LNG trains adds new pretreatment AGRU, upstream of the existing gas sweetening facilities an additional Sulphur Recovery Unit (SRU) and Tail Gas Treatment unit (TGTU).

This paper details the challenges of the PMP project which involves the construction of an additional Acid Gas Removal Unit (AGRU) treating in a single train 1,100 MMSCFD of natural gas, an associated Sulphur Recovery Unit (SRU) and Tail Gas Treatment Unit (TGTU) within the minimum plot area allocated to the green field part of the Project. It focuses on the AGRU with integrated amine section of TGTU which was considered as the most effective solution to install a new compact plant inside the existing facilities of QATARGAS 1 LNG plant in Ras Laffan, Qatar.

The design selected by QATARGAS after an international bidding phase uses the AdvAmine™ MDEAmax technology based on open market MDEA solvent. This reliable and original design features a fully integrated AGRU + TGTU amine section unit that meets multiple process requirements with high operational flexibility: jointly to H2S and CO2 removal specifications assigned to the 1,100 MMSCFD inlet gas, the plant cleans up the H2S from tail gas installed downstream the new 880 tpd SRU to meet the environmental emissions regulation. It secures the H2S, RSH and BTX content in the acid gas (by a dedicated preflash column) in order to satisfy the design of the SRU furnace section. The final acknowledged benefit of this giant unit is the decrease of the solvent circulation and of the solvent regeneration duty achieved by the recycle of semi lean solvent from TGT column to HP absorber.

Performance tests took place at the beginning of 2015 and all the guarantees associated with the operation of AGRU and TGT Amine section at design & turndown capacities have been demonstrated without operational issues. Operators have reported the simple management of the acid gas H2S content by the preflash column, the easy adjustment of the AGRU and its stability.

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