The C3MR process consists of two refrigeration cycles: a propane-refrigeration cycle to cool from ambient conditions to 235° C., and MR cycle to liquefy the natural gas stream and subcool it to 2160° C. With an end-flash system, the degree of subcooling is reduced to 2150° C. With extended end flash, subcooling is reduced to 2145° C.
The propane cycle has four pressure levels for precooling the natural gas and MR streams. The MR stream is separated into a light stream and a heavy liquid stream after it is cooled to the low-pressure propane temperature level. The heavy MR stream is subcooled in the warm and middle bundles of the main cryogenic heat exchanger (MCHE). The stream is then let down in pressure in a liquid expander and routed to the MCHE's shell side.
The light MR stream is liquefied and subcooled in the MCHE's warm, middle, and cold bundles. The stream is then let down in pressure and routed to the MCHE's shell side. NGLs are separated from relatively rich gas in the scrub column. Low-pressure propane and the warm MCHE bundle provide overhead cooling. NGLs are then routed to the fractionation unit. In the base case, the C2- cut is used as high-pressure fuel gas. In the extended end-flash cases, it combines with the main natural gas stream.
Propane, butane, and condensate from the fractionation unit proceed to the storage and loading area for export. A liquid expander reduces the pressure of subcooled natural gas from the MCHE. The natural gas stream is flashed to atmospheric pressure in the extended end-flash cases. The process recovers cold from the generated vapor and compresses the gas to high-pressure fuel level.