Application of a divided wall column for gas separation in floating liquefied natural gas plant

A divided wall column (DWC) has widely been utilized as an energy-efficient distillation column. When it is applied to the offshore floating liquefied natural gas (FLNG) plant, its compactness can provide a favorable distillation system for the unconventional plant on top of its high energy efficiency. We investigated the design characteristic, cost evaluation and operation difficulty of the DWC at its utilization in the FLNG plant. The results from the HYSYS simulation of the DWC were compared with those of the conventional distillation system, and the following was found from the study. The DWC replacing the depropanizer and debutanizer of the conventional distillation system requires 12.5% less investment cost. While the saving of 25% in steam cost is expected from the DWC, the total utility cost including the refrigerant cost is reduced by 20.2% due to the lower cost reduction of refrigeration in the DWC.

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