High efficiency Brayton cycles using LNG

• US 7,028,481 B1
• Filed: 10/14/2004
• Issued: 04/18/2006
• Est. Priority Date: 10/14/2003
• Status: Active Grant

• Current Assignee: National Technology & Engineering Solutions Of Sandia LLC (Honeywell International Inc.)
• Original Assignee: Sandia Corporation (Martin Marietta Corporation)
• Inventors: Morrow, Charles W.
• Primary Examiner(s): NGUYEN, HOANG M
• Application Number:
  US10/965,577
• Time in Patent Office: 551 Days
• Field of Search: 606/49, 606/51, 606/59, 606/71
• US Class Current: 60/649
• CPC Class Codes: F02C 1/10 Closed cycles
• CPC Class Codes: G21D 1/00 Details of nuclear power plant control G21D3/00
• CPC Class Codes: Y02E 30/00 Energy generation of nuclear origin
• CPC Class Codes: Y02E 30/30 Nuclear fission reactors

Abstract

A modified, closed-loop Brayton cycle power conversion system that uses liquefied natural gas as the cold heat sink media. When combined with a helium gas cooled nuclear reactor, achievable efficiency can approach 68–76% (as compared to 35% for conventional steam cycle power cooled by air or water). A superheater heat exchanger can be used to exchange heat from a side-stream of hot helium gas split-off from the primary helium coolant loop to post-heat vaporized natural gas exiting from low and high-pressure coolers. The superheater raises the exit temperature of the natural gas to close to room temperature, which makes the gas more attractive to sell on the open market. An additional benefit is significantly reduced costs of a LNG revaporization plant, since the nuclear reactor provides the heat for vaporization instead of burning a portion of the LNG to provide the heat.

Claims

1. A closed-loop Brayton power conversion system, comprising:

A. a heat source;

B. a power turbine;

C. a recuperator;

D. a suction cooler;

E. a compressor;

F. a superheater;

G. an insulated storage tank for storing cold, liquefied heat sink media;

H. a pump for pumping the liquefied heat sink media from the storage tank (G) to the suction cooler (D);

I. primary coolant loop piping means for conveying a primary stream of a heat transfer gas in the following closed-loop flow sequence;

from component A to B to C to D to E, back to C, and then back to A;

wherein the entire sequence is cyclically repeated;

J. side-stream piping means for conveying a fraction of the heat transfer gas in a side-stream that splits-off from the primary coolant loop piping means at a first T-junction located in-between power turbine (B) and recuperator (C); and

then flows through superheater (F); and

finally to a second T-junction located in-between recuperator (C) and suction cooler (D);

at which point the side-stream is recombined with the primary stream of heat transfer gas before entering suction cooler (D); and

K. heat sink piping means for conveying the cold, liquefied heat sink media from storage tank (G) to pump (H);

then to suction cooler (D) where the liquefied heat sink media is substantially vaporized;

then to superheater (F); and

finally to exit piping means for delivering the vaporized heat sink media to market.

2. The system of claim 1,

wherein the suction cooler comprises a pair of coolers comprising a low pressure cooler (D_low) and a high pressure cooler (D_high);

wherein the compressor (E) comprises a pair of compressors comprising a low pressure compressor (E_low) and a high pressure compressor (E_high); and

wherein the primary coolant loop piping means (I) for conveying the primary stream of heat transfer gas comprises the following closed-loop flow sequence;

from A to B to C to D_low to E_low to D_high to E_high, back to C, and then back to A;

wherein the entire modified sequence is cyclically repeated.

3. The system of claim 1, wherein the superheater comprises a plate-and-frame heat exchanger.

4. The system of claim 1, wherein the heat transfer gas comprises one or more gases selected from the group consisting of helium, air, an inert gas, nitrogen, neon, argon, and combinations thereof.

5. The system of claim 1, wherein the liquefied heat sink media comprises a gas whose boiling point is lower than ambient temperature.

6. The system of claim 5, wherein the liquefied heat sink media comprises one or more gases selected from the group consisting of liquefied natural gas, liquefied hydrogen, liquefied ethane, liquefied methane, liquefied propane, liquefied butane, and liquefied ammonia, and combinations thereof.

7. The system of claim 1, wherein the heat source comprises one or more sources selected from the group consisting of a nuclear energy source, a oil-fired source, a coal-fired source, a gas-fired source, a solar-fired source, a hydrogen-fired source, and combinations thereof.

8. The system of claim 1, wherein the fraction of the primary stream of heat transfer gas conveyed in the side-stream comprises about 1–

10% of the total flow of heat transfer gas flowing through the primary coolant loop piping means.

9. The system of claim 1,

wherein the heat transfer gas comprises helium having a maximum temperature of about 850 C;

wherein the liquefied heat sink media comprises liquefied natural gas stored at a temperature of about −

160 C; and

wherein the vaporized natural gas leaves the exit piping means at an exit temperature greater than about 0 C.

10. The system of claim 1, wherein the liquefied heat sink media that enters the suction cooler as a liquid, exits said cooler in a substantially vaporized state.

11. The system of claim 1, further comprising a generator, driven by the power turbine, for generating electricity to market.

17. The system of claim 1, further comprising a post-superheater blower, disposed in the exit piping means, for increasing the pressure and temperature of the vaporized heat sink media after exiting from the superheater.

12. A method for converting power using a modified closed-loop Brayton power conversion system, comprising:

a) providing a heat source (A), a power turbine (B), a recuperator (C), a suction cooler (D), a compressor (E), a superheater (F), an insulated storage tank for storing cold liquefied heat sink media (G), a pump (H) for pumping the liquefied heat sink media from storage tank (G) to suction cooler (D), and associated piping means;

b) providing a heat transfer gas and a liquefied heat sink media to the system;

c) conveying a primary stream of the heat transfer gas through closed-loop primary coolant loop piping means from component A to B to C to D to E, back to C, and then back to A;

followed by cyclically repeating the entire sequence;

d) conveying a side-stream of heat transfer gas, split-off from the primary stream of heat transfer gas, from a first T-junction located in-between power turbine (B) and recuperator (C);

then to superheater (F); and

finally to a second T-junction located in-between recuperator (C) and suction cooler (D), where the side-stream is recombined with the primary stream of heat transfer gas before entering suction cooler (D); and

e) pumping the liquefied heat sink media from storage tank (G) to suction cooler (D), where the liquefied heat sink media is substantially vaporized;

then to superheater (F) where the vaporized gas is heated; and

finally to exit piping means for delivering the vaporized heat sink media to market.

13. The method of claim 12, wherein the fraction of heat transfer gas conveyed in the side-stream comprises about 1–

10% of the total flow of heat transfer gas flowing through the primary coolant loop piping means.

14. The method of claim 12,

wherein the heat transfer gas comprises helium having a maximum temperature of about 850 C;

wherein the liquefied heat sink media comprises liquefied natural gas stored at a temperature of about −

160 C; and

wherein the vaporized natural gas leaves the exit piping means at an exit temperature greater than about 0 C.

15. The method of claim 12, further comprising using the power turbine to drive a generator for making electricity.

16. The method of claim 15, further comprising using the power turbine to drive a generator for making electricity.

18. The method of claim 12, further comprising a post-superheater blower, disposed in the exit piping means, for increasing the pressure and temperature of the vaporized heat sink media after exiting from the superheater.