Mixed refrigerant system and method
A system for cooling a gas with a mixed refrigerant includes a heat exchanger that receives and cools a feed of the gas so that a product is produced. The system includes a mixed refrigerant processing system having compression devices and aftercoolers as well as a low pressure accumulator and a high pressure accumulator. A cold vapor separator receives vapor from the high pressure accumulator and features a vapor outlet and a liquid outlet. Vapor from the cold vapor separator vapor outlet is cooled, expanded and directed to a primary refrigeration passage of the heat exchanger. Liquid from the liquid outlet of the cold vapor separator is subcooled, expanded and directed to the primary refrigeration passage. Liquid from the low pressure accumulator is subcooled, expanded and directed to the primary refrigeration passage. Liquid from the high pressure accumulator is subcooled, expanded and directed to the primary refrigeration passage.
1. A method for cooling a gas with a mixed refrigerant comprising the steps of:
a) flowing the gas through a cooling passage of a heat exchanger in countercurrent, indirect heat exchange relationship with the mixed refrigerant flowing through a primary refrigeration passage;
b) conditioning and separating mixed refrigerant exiting the primary refrigeration passage in a compression system to form a high-boiling refrigerant liquid stream, a high pressure vapor stream and a mid-boiling liquid stream;
c) cooling the high pressure vapor in the heat exchanger;
d) directing the cooled high pressure vapor to a cold vapor separator and separating the cooled high pressure vapor in the cold vapor separator into a cold separator vapor stream and a cold separator liquid stream;
e) subcooling the cold separator liquid stream in the heat exchanger;
f) flashing the subcooled cold separator liquid stream to form a first cold separator mixed phase stream;
g) directing the first cold separator mixed phase stream to a CVS temperature separation device based on a liquid level within the cold vapor separator and separating the first cold separator mixed phase stream in the CVS temperature separation device to form a CVS temperature vapor stream and a CVS temperature liquid stream and directing the CVS temperature vapor and liquid streams to the primary refrigeration passage;
h) cooling the cold separator vapor stream in the heat exchanger;
i) flashing the cooled cold separator vapor stream to form a second cold separator mixed phase stream;
j) directing the second cold separator mixed phase stream to the primary refrigeration passage;
k) subcooling the mid-boiling liquid stream in the heat exchanger;
l) flashing the subcooled mid-boiling liquid stream to form a mid-boiling mixed phase stream;
m) directing the mid-boiling mixed phase stream to a middle temperature separation device that is separate and distinct from the CVS temperature separation device and separating the mid-boiling mixed phase stream in the middle temperature separation device to form a middle temperature vapor stream and a middle temperature liquid stream and directing the middle temperature vapor and liquid streams to the primary refrigeration passage;
n) subcooling the high-boiling refrigerant liquid stream in the heat exchanger;
o) flashing the subcooled high-boiling refrigerant liquid stream to form a high-boiling mixed phase stream; and
directing the high-boiling mixed phase stream to the primary refrigeration passage.
2. The method for cooling the gas with the mixed refrigerant of claim 1 wherein step p) includes combining the high-boiling mixed phase stream with the first cold separator mixed phase stream in the CVS temperature separation device.
3. The method for cooling the gas with the mixed refrigerant of claim 1 wherein step p) includes combining the high-boiling mixed phase stream with the mid-boiling mixed phase stream in the middle temperature separation device.
4. The method for cooling the gas with the mixed refrigerant of claim 1 wherein step p) includes combining the high-boiling mixed phase stream with the first cold separator mixed phase stream in the CVS temperature separation device and combining the high-boiling mixed phase stream with the mid-boiling mixed phase stream in the middle temperature separation device.