How does a mixed refrigerant liquefy natural gas within a heat exchanger?
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Hello, teachers. What I don’t quite understand is that the temperature of the mixed refrigerant before it enters the high-temperature heat exchanger in the cold box is in the 20s, and the temperature of natural gas before it enters the heat exchanger in the cold box is also in the 20s. The temperature difference between the two isn’t very large. So how exactly is it possible to liquefy the natural gas inside the heat exchanger?
The components of the mixed refrigerant are high-temperature (methane, ethylene, isobutane) and low-temperature (methane, nitrogen, ethylene, propane)
The cold box exhibits a temperature gradient from top to bottom; during the process from pre-cooling to deep cooling, natural gas gradually cools and liquefies. The refrigerant is pressurized by a compressor and then enters the cold box, where it is throttled to supply cooling capacity to both the natural gas and the refrigerant entering the cold box.
MRC mixed refrigeration utilizes the different boiling points of methane, ethylene, and propane to create a gradient cooling range, thereby enabling natural gas to be cooled gradually from room temperature down to -160 degrees Celsius in order to liquefy it