Cryogenic liquid expansion turbine
A cryogenic liquid expansion turbine has a turbine wheel mounted on a rotary shaft, at least one radial inlet for cryogenic liquid to be expanded in the expansion turbine for the rotary shaft, and a dry gas sealing means at a position along the rotary shaft between the turbine wheel and the bearings. There is a thermal barrier member between the turbine wheel and the dry gas sealing means, a gas chamber on the dry gas sealing means side of the thermal barrier member, and an internal passage for cryogenic gas to the said gas chamber. A method is also provided.
1. A cryogenic liquid expansion turbine having a turbine wheel mounted on a rotary shaft, at least one radial inlet for cryogenic liquid to be expanded in the expansion turbine, at least one bearing provided at the rotary shaft, and a dry gas sealing means at a position around the rotary shaft between the turbine wheel and the said at least one bearing, comprising:
a thermal barrier member between the turbine wheel and the dry gas sealing means,
a gas chamber positioned on a same side of the thermal barrier member as the dry gas sealing means,
an inlet for cryogenic gas to the gas chamber,
a first exit for cryogenic gas from the gas chamber to the turbine wheel,
wherein the first exit is through a first labyrinth seal; and
wherein the gas chamber comprises a second exit for the cryogenic gas communicating with the dry gas sealing means through a second labyrinth seal.
2. The cryogenic liquid expansion turbine according to claim 1 , wherein the dry gas sealing means comprises another inlet for dry non-cryogenic gas, and said inlet for the cryogenic gas.
3. The cryogenic liquid expansion turbine according to claim 1 , wherein the turbine wheel is adapted to allow the cryogenic liquid to flash during its expansion.
4. The cryogenic liquid expansion according to claim 3 , wherein the turbine wheel is scalloped.
5. The cryogenic liquid expansion turbine according to claim 1 , wherein the dry gas sealing means is a dry gas seal.
6. The cryogenic liquid expansion turbine according to claim 1 , wherein the dry gas sealing means is a tandem dry gas seal.
7. The cryogenic liquid expansion turbine according to claim 1 , wherein the dry gas sealing means is a single dry gas seal.
8. The cryogenic liquid expansion turbine according to claim 1 , further comprising a first vent from the dry gas sealing means, the first vent communicating with at least one of a flare, an external atmosphere, and a gas recovery means.
9. The cryogenic liquid expansion turbine according to claim 8 , further comprising a second vent from the dry gas sealing means, the second vent communicating with the external atmosphere.
10. The cryogenic liquid expansion turbine according to claim 1 , wherein the at least one bearing is an oil bearing and further comprising shaft sealing means including a plurality of axially-spaced carbon rings for protecting the dry gas sealing means from oil vapour.
11. The cryogenic liquid expansion turbine according to claim 10 , wherein space between the plurality of axially-spaced carbon rings is in communication with a source of dry non-cryogenic gas.
12. The cryogenic liquid expansion turbine according to claim 1 , wherein the at least one bearing is selected from the group consisting of an oil bearing and a gas bearing.
13. A method of operating a cryogenic liquid expansion turbine having a turbine wheel mounted on a rotary shaft, at least one radial inlet for cryogenic liquid to be expanded in the expansion turbine, at least one bearing provided at the rotary shaft, and a dry gas sealing means at a position around the rotary shaft between the turbine wheel and the said at least one bearing, comprising:
providing a thermal barrier member between the turbine wheel and the dry gas sealing means,
providing a gas chamber positioned on a same side of the thermal barrier member as the dry gas sealing means,
providing an inlet for cryogenic gas to the gas chamber,
vaporizing a portion of a cryogenic liquid for forming the cryogenic gas, and
exhausting at least 90% of the cryogenic gas from the chamber through a first exit to the turbine wheel,
wherein the first exit is through a first labyrinth seal; and
wherein the gas chamber comprises a second exit for the cryogenic gas communicating with the dry gas sealing means through a second labyrinth seal.
14. The method of operating the cryogenic liquid expansion turbine according to claim 13 , further comprising maintaining a pressure in the gas chamber in a range of from 5 bar to 10 bar.
15. The method of operating the cryogenic liquid expansion turbine according to claim 14 , further comprising regulating a temperature of the cryogenic gas to maintain a single gaseous phase in the gas chamber.
16. The method of operating the cryogenic liquid expansion turbine according to claim 13 , wherein the cryogenic liquid is selected from the group consisting of natural gas, liquid nitrogen and liquid air.