Performance analysis of compressor unit for mixture refrigerant liquefaction cycle with a separator

• A liquefaction process of mixed refrigerant cycle with a phase separator was proposed when multi-stage compressors are employed.
• The condensation pressure is very important to not only the energy efficiency but also the minimum temperature difference.
• Both input power and minimum temperature difference increase when the first stage discharge pressure increases.

A liquefaction process of mixed refrigerant cycle with a phase separator was proposed when multi-stage compressors are employed. The process includes a sub cycle in which the vapor refrigerant is separated in the separator to be fed to the second stage compressor and the liquid refrigerant leaving the separator is throttled to the required pressure in the second valve and then mixed with the return MR (Mixed refrigerant) stream before entering the precooler. A steady state simulation of the process was undertaken to study the influence of condensation pressure (first stage discharge pressure) on the performance of both compressor unit and liquefaction cycle. Although the lower condensation pressure results in less power consumption of the compressor, the minimum temperature difference of the main LNG heat exchanger is reduced, which causes the design of the main LNG heat exchanger to be difficult. Hence, choosing the condensation pressure becomes very important to the design and operation of the liquefaction cycles considering not only the energy efficiency but also the minimum temperature difference.