Conceptual analysis of the precooling stage for LNG processes

More than 95% of the installed LNG facilities by 2012 use a precooling cycle as the first stage of the process. In this work, a technical comparison between different precooling cycles for LNG processes is carried out through computational simulations using Aspen HYSYS®. The aim is to provide future developments with a clear idea of the technical advantages/disadvantages involved in the selection of the process for the precooling cycle. A three stage propane precooled cycle was found to be the most energetically efficient among the studied cases, even better than a two stage mixed refrigerant process (C2/C3) for both climate conditions, warm (25 °C) and cold (6 °C). However, due to the reduced power share that may be reached with a propane cycle temperature restriction, the mixed refrigerant precooling cycle is the preferred alternative under the cold climate condition.

► A technical comparison between different precooling cycles for LNG processes was performed.
► Two climate conditions (warm and cold) were evaluated.
► A three stage propane precooled cycle was found to be the most energetically efficient.
► The three stage propane precooled cycle implemented is found more adequate for a warm climate.
► The two stage mixed refrigerant cycle implemented is found more convenient in a cold climate.