On the conceptual design of pre-cooling stage of LNG plants using propane or an ethane/propane mixture

Today, LNG technologies are based on pure and mixed refrigerants cycles on the pre-cooling system, but the advantages and disadvantages of considering a mixed refrigerant or pure refrigerant cycle in the pre-cooling stage is not well understood. In this work an analysis of the compressors and the refrigerants in the pre-cooling system is carried out. The most relevant aspect of the evaluation is to establish some thermodynamical criteria for the selecting of the suitable refrigerant for the pre-cooling stage. For final decision-making process of the selection of the pre-cooling stage, a proper model is required which should take into account all aspects that could affect the capital and operation costs.

► LNG technologies are differentiated by heat exchanger type, compressor/driver, refrigerant type and others.
► The design of the pre-cooling system on the LNG technologies should start by compressor definition.
► Thermodynamically, pre-cooling based on a C3 has higher advantages than C2/C3 mixed refrigerant cycle.
► The pre-cooling system needs to consider aspects: equipment number, costs, plot area, safety.
► A proper model is required for selection of the pre-cooling, including all aspects that could affect the costs.