Process Thermodynamics of Combined LNG and Heavy Mixed Refrigerant HMR Expanders

Current LNG liquefaction plants utilize cryogenic liquefied gas expanders in two different locations within the process. The LNG expander is located downstream the main heat exchanger and the heavy mixed refrigerant HMR expander is located in the upstream cooling cycle.

LNG and HMR expanders replace the traditional isenthalpic Joule-Thomson expansion of the condensate with a near isentropic expansion with work output across a cryogenic turbine expander.

A practical model is presented to define the process improvement of the combined operating and of the separated and individually operating LNG and HMR expanders compared to the traditional Joule-Thomson expansion.

The Gorgon LNG and HMR expanders are the largest liquid expanders to date and the presented model for the process thermodynamics is applied to this rotating machinery.