SIMPLE AND COMPACT LOW-TEMPERATURE POWER CYCLE

• US 20040107700A1
• Filed: 12/09/2002
• Published: 06/10/2004
• Est. Priority Date: 12/09/2002
• Status: Active Grant

• Current Assignee: Tennessee Valley Authority (Government of the United States of America)
• Original Assignee: Tennessee Valley Authority (Government of the United States of America)
• Inventors: McClanahan, Timmons S., Crim, Michael C.
• Granted Patent: US 6,751,959 B1
• Time in Patent Office: Days
• US Class Current: 60/670
• CPC Class Codes: F01K 25/08 using special vapours
• CPC Class Codes: F01K 25/106 Ammonia F01K25/065 takes precedence

Abstract

A simple, compact, and relatively efficient thermodynamic power cycle system and process for extracting heat from a heat source stream and converting a portion of the heat to mechanical power. The system and process are composed of the same series of four processing units or steps found in the most basic form of a Rankine power cycle: (1) heating (means) of a pressurized working fluid to produce a superheated gas, (2) expansion (means) to a lower pressure to produce power, (3) condensation (means) of the low pressure gas to a liquid, and (4) pumping (means) of the liquid to high pressure to complete the cycle. The working fluid is heated under pressures above critical. The working fluid must have a critical temperature more than 40° F. lower than the temperature of the heat source stream and a normal boiling point less than 32° F.

Claims

1. A thermodynamic power cycle system for extracting a flow of heat from a heat source stream and generating mechanical power from the flow of heat by means of a working fluid flowing within a closed-loop cycle comprising:

means for transferring heat from the beat source stream to the working fluid such that the working fluid warms from a first temperature to a second temperature that is more than 30°

F. greater than the critical temperature of the working fluid wherein the working fluid has a critical temperature more than 40°

F. lower than a temperature of the heat source stream and has a normal boiling point less than 32°

F.;

means for expanding the working fluid and converting work of expansion of the working fluid to mechanical power;

said means for expanding and converting work of expansion also throttling the working fluid such that a pressure of the working fluid exceeds the critical pressure of the working fluid by an amount greater than 5% of the critical pressure of the working fluid as the working fluid emerges from the means for transferring heat;

means for cooling to condense and subcool the working fluid after the means for expanding;

means for returning the working fluid to the means for transferring heat;

wherein the means for transferring heat, the means for expanding, the means for cooling, and the means for returning the working fluid to the means for transferring heat are the only four means in which energy is removed from or transferred into the working fluid in the form of heat or work.

2. The thermodynamic power cycle system of claim 1, wherein the heat source stream comprises a gas, liquid, solid or mixture thereof.

3. The thermodynamic power cycle system of claim 1, further comprising an additional means for throttling the working fluid after the means for transferring heat and before the means for expanding.

4. The thermodynamic power cycle system of claim 1, further comprising means for controlling the flow rate of the working fluid.

5. The thermodynamic power cycle system of claim 1, further comprising means for containing excess of the working fluid in the liquid state after the means for cooling to condense the working fluid.

6. The thermodynamic power cycle system of claim 1, further comprising means for redirecting the flow of the working fluid after the working fluid has exited the means for transferring heat to bypass the means for expanding, the means for redirecting the flow containing a means for throttling the working fluid such that a pressure of the working fluid exceeds the critical pressure of the working fluid by an amount greater than 5% of the critical pressure of the working fluid as the working fluid emerges from the means for transferring heat.

7. The thermodynamic power cycle system of claim 1, which comprises two or more heat source streams, with the thermodynamic power cycle system comprising additional means for transferring heat, each of which means for transferring heat is dedicated to a single heat source stream;

wherein the working fluid is divided into separate streams, with each of the separate streams of working fluid being dedicated to a separate means for transferring heat; and

wherein the separate streams of working fluid, after having been heated by transfer of heat from the heat source streams, are combined into a single working fluid stream.

8. The thermodynamic power cycle system of claim 2, further comprising means for increasing the pressure of the heat source stream to restore pressure lost by the heat source stream as it flows through the means for transferring heat.

9. The thermodynamic power cycle system of claim 8, wherein the heat source stream is a gas, and wherein the thermodynamic power cycle system further comprises ducting means to transport the gas to the means for transferring heat and wherein the means for increasing the pressure is a fan or compressor.

10. The thermodynamic power cycle system of claim 1, wherein the working fluid is ammonia, chlorodifluoromethane, sulfur dioxide or bromotrifluoromethane.

11. The thermodynamic power cycle system of claim 1, wherein the working fluid is ammonia.

12. The thermodynamic power cycle system of claim 1, wherein the working fluid is chlorodifluoromethane.

13. The thermodynamic power cycle system of claim 1, wherein the working fluid is sulfur dioxide.

14. The thermodynamic power cycle system of claim 1, wherein all means of the system except for the means for transferring heat are mounted on one or more portable transportation means.

15. The thermodynamic power cycle system of claim 14, wherein the mechanical power is 4 MW or less and wherein there is only one portable transportation means.

16. The thermodynamic power cycle system of claim 15, wherein the working fluid is ammonia.

17. The thermodynamic power cycle system of claim 15, wherein the working fluid is chlordifluoromethane.

18. The thermodynamic power cycle system of claim 1, wherein the heat source stream is a gas which contains a condensable vapor.

19. The thermodynamic power cycle system of claim 18, wherein the heat source stream is a stream of pressurized hot gas which has been quenched in water.

20. The thermodynamic power cycle system of claim 19, wherein the stream of pressurized hot gas has been produced by the reaction of coal and oxygen in a coal gasifier.

21. The thermodynamic power cycle system of claim 20, wherein the working fluid is ammonia.

22. The thermodynamic power cycle system of claim 20, wherein the mechanical power is utilized to provide supplemental drive power to an air compressor of an air separation unit, the air separation unit being employed to provide oxygen to the coal gasifier.

23. The thermodynamic power cycle system of claim 22, wherein the working fluid is ammonia.

24. The thermodynamic power cycle system of claim 1, wherein the heat source stream is generated by a topping cycle.

25. The thermodynamic power cycle system of claim 24, wherein the topping cycle comprises a combustion turbine and wherein the heat source stream is exhaust gas from a combustion turbine.

26. The thermodynamic power cycle system of claim 25, wherein the combustion turbine is a peaking unit.

27. The thermodynamic power cycle system of claim 26, wherein the working fluid is sulfur dioxide.

28. The thermodynamic power cycle system of claim 26, wherein the working fluid is ammonia.

29. The thermodynamic power cycle system of claim 25, wherein the exhaust gas has been partially cooled by heat exchange with compressed air.

30. The thermodynamic power cycle system of claim 29, wherein the working fluid is ammonia.

31. A thermodynamic process for the production of mechanical power from a heat source stream of gas, liquid solid, or mixture thereof comprising:

a. transferring heat from the heat source stream to a working fluid;

wherein the working fluid is at a pressure more than 5 percent greater than the critical pressure of the working fluid;

wherein the working fluid has been heated to a temperature more than 30°

F. greater than the critical temperature of the working fluid; and

wherein the working fluid has a critical temperature more than 40°

F. lower than the temperature of the heat source stream and the working fluid has a normal boiling point less than 32°

F.;

b. expanding the working fluid to produce mechanical power;

c. cooling to condense and subcool the working fluid;

d. pressurizing the working fluid;

e. directing the flow of the working fluid in a continuous loop through the above described process steps a, b, c, d, in that order, and returning to step a to continue the continuous loop;

f. process steps a, b, c, and d being the only four process steps in which energy is removed from or transferred into the working fluid in the form of heat or work.