Mixed refrigerants in LNG cascade
AssigneeConocoPhillips Company
InventorsPaul Davies, James Lee Harris, Jr., Emery Jay Thomas, Gregg Sapp
Life of this patent
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Abstract
Methods and systems for liquefying natural gas using environmentally-friendly low combustibility refrigerants are provided. Methods of liquefaction include cooling a fluid in an LNG facility via indirect heat exchange with an environmentally-friendly low combustibility refrigerants that are propane, ethane and methane mixed with small amounts of fluorinated olefin, but still within close proximity to the boiling points of the pure refrigerants such that the mixed refrigerants can still be used in an optimized cascade process.
Claims22
An improved cascade process for liquifying natural gas (LNG), wherein a cascade process for making LNG uses a first pure propane refrigerant cycle, a second pure ethane refrigerant cycle, and a third pure methane refrigerant cycle, the improvement comprising making LNG in a modified-cascade process comprising:
- a. a first cycle using a first azeotropic mixed refrigerant comprising an azeotropic mix of 75-90% propane and 10-25% fluorinated olefin having a boiling point within 20° F. of pure propane;
- b. a second cycle using a second azeotropic mixed refrigerant comprising an azeotropic mix of 75-90% ethane and 10-25% fluorinated olefin having a boiling point within 20° F. of pure ethane;
- c. a third cycle using a third azeotropic mixed refrigerant comprising an azeotropic mix of 75-95% methane and 5-25% fluorinated olefin having a boiling point within 20° F. of pure methane,
- d. wherein said modified-cascade process lowers a risk of vapor cloud explosion as compared to said cascade process.
A modified-cascade process for liquifying natural gas (LNG) comprising:
- a. a first cycle using a first azeotropic mixed refrigerant comprising an azeotropic mix of 75-90% propane and 10-25% fluorinated olefin having a boiling point within 20° F. of pure propane and an LBV of about 40 cm/s;
- b. a second cycle using a second azeotropic mixed refrigerant comprising an azeotropic mix of 75-90% ethane and 10-25% fluorinated olefin having a boiling point within 20° F. of pure ethane;
- c. a third cycle using a third azeotropic mixed refrigerant comprising an azeotropic mix of 75-95% methane and 5-25% fluorinated olefin having a boiling point within 20° F. of pure methane,
- d. wherein said modified-cascade process lowers a risk of vapor cloud explosion as compared to a cascade process using pure propane, ethane and methane refrigerants.
Dependencies are inferred from the claim text.