Large scale coastal liquefaction

A method for large scale floating liquefaction of natural gas gathered from onshore gas pipeline networks, the method comprising:

• a) gathering gas from on-shore pipeline quality gas sources and treating the gas on shore by removal of mercury, removal of acid gas, dehydration and removal of C5+ hydrocarbons;
• b) compressing and cooling the treated gas of step a), thereby yielding compressed gas;
• c) piping the compressed gas of step b) from onshore to an offshore platform;
• d) mixing the gas from onshore of step c) with a compressed recycle gas flow, thereby yielding a compressed gas mixture;
• e) piping the compressed gas mixture of step d) in sub-sea pipes from the platform to a floating liquefaction, storage and offloading vessel;
• f) distributing and introducing the compressed gas mixture of step e) on the floating liquefaction, storage and offloading vessel, via a manifold, to two or more liquefaction modules;
• g) withdrawing a side draw flow of the gas introduced in step f) into each of the two or more liquefaction modules, expanding, and thereby cooling the side draw gas flow in turbo expanders;
• h) cooling remaining gas flow introduced into each of the two or more liquefaction modules to −10° C. or lower by counter-current heat exchange with the expanded side draw gas from step g);
• i) using power from turbo expanders in step g) to drive a compressor compressing gas within an internal refrigerant circulation loop onboard the floating liquefaction, storage and offloading vessel;
• j) collecting expanded side draw gas flows from step g), after the heat exchange in step h), from each liquefaction module in a manifold and piping the expanded side draw gas flows to the offshore platform as a recycle gas flow;
• k) compressing the expanded side draw gas flows from step j) the platform, thereby yielding compressed recycle gas flow, and cooling of the compressed recycle gas flow;
• l) mixing the compressed recycle gas flow from step k) with the compressed gas from from onshore from step c);
• m) further cooling and liquefaction of a part of the compressed gas from step f) on the vessel, in each liquefaction module, by heat exchange with pre-cooled and expanded refrigerant, the part of the compressed gas being the remaining gas after the withdrawing of the side draw flow of the gas from step g);
• n) powering each liquefaction module by a dedicated gas turbine for refrigerant compression;
• and
• o) introducing produced LNG in multiple membrane tanks.