Power recovery system using a rankine power cycle incorporating a two-phase liquid-vapor expander with electric generator

• US 20120235415A1
• Filed: 09/13/2011
• Published: 09/20/2012
• Est. Priority Date: 09/13/2010
• Status: Active Grant

• Current Assignee: Elliott Company (Ebara Corporation)
• Original Assignee: Ebara International Corporation (Ebara Corporation)
• Inventors: Madison, Joel V.
• Granted Patent: US 8,664,785 B2
• Time in Patent Office: Days
• US Class Current: 290/54
• CPC Class Codes: F01K 25/10 the vapours being cold, e.g. ammonia, carbon dioxide, ether
• CPC Class Codes: F01K 7/00 Steam engine plants characterised by the use of specific types of engine F01K3/02 takes precedence; Plants or engines characterised by their use of special steam systems, cycles or processes reciprocating-piston engines using uniflow principle F01B17/04; Control means specially adapted for such systems, cycles or processes; Use of withdrawn or exhaust steam for feed-water heating
• CPC Class Codes: F03B 13/00 Adaptations of machines or engines for special use; Combinations of machines or engines with driving or driven apparatus if the apparatus aspects are predominant, see the relevant subclasses for such apparatus, e.g. H02K7/18; Power stations or aggregates incorporating only machines or engines of positive-displacement type F03C; hydraulic engineering aspects E02B; combinations with wind energy converters F03D9/008
• CPC Class Codes: F03G 6/005 Binary cycle plants where the fluid from the solar collector heats the working fluid via a heat exchanger
• CPC Class Codes: F03G 7/05 Ocean thermal energy conversion, i.e. OTEC
• CPC Class Codes: Y02E 10/30 Energy from the sea, e.g. using wave energy or salinity gradient
• CPC Class Codes: Y02E 10/46 Conversion of thermal power into mechanical power, e.g. Rankine, Stirling or solar thermal engines

Abstract

A power recovery system using the Rankine power cycle incorporating a two-phase liquid-vapor expander with an electric generator which further consists of a heat sink, a heat source, a working fluid to transport heat and pressure energy, a feed pump and a two-phase liquid-vapor expander for the working fluid mounted together with an electric generator on one rotating shaft, a first heat exchanger to transport heat from the working fluid to the heat sink, a second heat exchanger to transport heat from the heat source to the working fluid.

Claims

1. A power recovery system for recovery of part of the required energy input during regasification of LNG using a Rankine power cycle, the power recovery system comprising:

a working fluid;

a system containing the working fluid in a closed loop;

a pump two-phase liquid-vapor expander generator further comprising a feed pump, an induction generator and a two-phase liquid-vapor expander, all mounted on a common, rotating axial shaft, the feed pump pumping the incoming liquid-phase working fluid to a high pressure, the pressurized liquid-phase working fluid then passing through the induction generator, partly heated and vaporized therein and then flowing out the pump two-phase liquid-vapor expander generator for further heating;

a heat source connected to the pump two-phase liquid-vapor expander generator via the pipe system, the heat source heating the pressurized working fluid into higher vapor content, the heated and pressurized two-phase working fluid then re-entering the pump two-phase liquid-vapor expander generator at the two-phase liquid-vapor expander wherein the heated and pressurized two-phase working fluid expanded and driving the rotating center shaft, and subsequently the induction generator, the expanded two-phase working fluid flowing out of the pump two-phase liquid-vapor expander for cooling and condensation; and

a heat sink connected to the pump two-phase liquid-vapor expander generator via the pipe system, the heat sink cooling the expanded two-phase working fluid, the two-phase working fluid condensed back to the liquid state, the liquid-phase working fluid then re-entering the pump two-phase liquid-vapor expander generator at the feed pump, and repeating the cycle.

2. The LNG regasification power recovery system of claim 1 in which the heat source is sea water.

3. The LNG regasification power recovery system of claim 1 in which the heat source is steam.

4. The LNG regasification power recovery system of claim 1 in which the heat sink is pressurized liquefied natural gas.

5. The LNG regasification power recovery system claim 1 in which the working fluid is liquefied natural gas.

6. A two-phase liquid-vapor expander generator for expanding working fluid and generating electricity during LNG regasification processes, the two-phase liquid-vapor expander generator comprising:

a stationary outer housing portion having an inlet and an outlet, the inlet located at a lower end on one side of the outer housing portion, letting in the heated and pressurized two-phase working fluid, and the outlet located at an upper end, letting out the expanded two-phase working fluid; and

an inner induction generator mounted on a rotating center shaft, the induction generator driven by the rotating center shaft, generating electricity as a result; and

an inner two-phase hydraulic assembly mounted on said rotating center shaft on top of the induction generator for expanding the pressurized incoming two-phase working fluid, converting angular momentum and internal energy of the incoming two phase working fluid into torque, driving the rotating center shaft.

7. A pump two-phase liquid-vapor expander generator for pumping, expanding working fluid and generating electricity during LNG regasification processes, the pump two-phase liquid-vapor expander generator comprising:

a stationary outer housing portion having one lower inlet, one side inlet, a plurality of side outlets, the lower inlet letting in the liquid-phase working fluid, and the side outlet located at an upper end of the outer housing, letting out the expanded two-phase working fluid;

an inner feed pump on top of the lower inlet, mounted on a rotating center shaft extending most of the length of the pump two-phase liquid-vapor expander generator, the pump pressurizing the liquid-phase working fluid entering from the lower inlet;

an inner induction generator further having a casing, mounted on said rotating center shaft, on top of the pump, the induction generator driven by the rotating center shaft, generating electricity as a result, the pressurized liquid-phase incoming working fluid passing through the casing of the induction generator and flowing out through the side outlet for heating; and

an inner two-phase hydraulic assembly mounted on said rotating center shaft on top of the induction generator for expanding the heated and pressurized two-phase incoming working fluid from the side inlet, converting angular momentum and internal energy of the heated and pressurized two-phase incoming working fluid into torque, driving the rotating center shaft.

8. The pump two-phase liquid-vapor expander generator of claim 7, in which the two-phase hydraulic assembly further comprises:

a casing containing the entire two-phase hydraulic assembly;

a stationery flat circular nozzle ring portion at the bottom of the two-phase hydraulic assembly, the nozzle ring portion further having a center aperture and a plurality of converging nozzles on its rim for generation of high velocity vortex flow of the pressurized and heated two-phase working fluid as it flows through;

a rotating turbine runner portion sitting on top of the aperture of the nozzle ring portion and mounted on and driving the rotating center shaft as the turbine runner portion converting angular momentum of the high velocity vortex flow of the two-phase working fluid into torque;

a rotating jet exducer portion sitting on top of the turbine runner portion and mounted on the rotating center shaft, the jet exducer portion further having a plurality of blades, orientation of the blades further reducing the angular momentum of the working fluid and driving the rotating center shaft; and

a stationery two-phase draft tube having an upper end and a lower end, sitting on top of the jet exducer portion and mounted on the rotating center shaft, the two-phase draft tube further having a plurality of radial blades, orientation of the stationery radial blades regulating the flow of working fluid, the working fluid exiting the upper end to the outlet.

9. The pump two-phase liquid-vapor expander generator of claim 7, in which the working fluid is liquefied natural gas.

10. The pump two-phase liquid-vapor expander generator of claim 7, in which the feed pump is a cryogenic centrifugal pump.

11. The pump two-phase liquid-vapor expander generator of claim 7, in which the induction generator operating as an induction motor when the two-phase liquid-vapor expander generator started, below a synchronous speed.

12. The pump two-phase liquid-vapor expander generator of claim 11, in which the induction generator resuming to a generator mode, operating above the synchronous speed after the shaft power of the two-phase two-phase hydraulic assembly exceeding the shaft power of the feed pump.

13. A method for power recovery using a two-phase fluid Rankine power cycle in an LNG regasification plant, the method comprising the following steps:

Passing the working fluid through 2 heat exchangers and a pump two-phase expander generator, the pump two-phase expander generator consisting of a compact assembly of a pump, a two-phase expander and an induction generator integrally mounted on one rotating, axial shaft, such that the following steps are performed in the following sequence;

In a first step, with work input, the pump, P, pressurizes the liquid single phase working fluid from low pressure to high pressure;

In a second step, the pressurized single phase working fluid is heated and partially vaporized by passing through the generator, G, and the heat exchanger with the heat provided by sea water or other heat sources;

In a third step, the pressurized and heated two-phase saturated working fluid expands from high-pressure to low-pressure across the two-phase expander, T, generating a work out put; and

In a fourth step, the low pressure two-phase saturated working fluid passes through a heat exchanger with the heat sink, the LNG for regasification, such that the working fluid condenses from saturated liquid-vapor two-phase to non-saturated, liquid single phase.

14. A method for power recovery using a two-phase fluid Rankine power cycle in an LNG regasification plant, the method comprising the following steps:

With work input, pressurizing the liquid, single phase working fluid from low pressure to high-pressure across pump P;

Heating and partially vaporizing the working fluid by passing it through generator G, and then through second heat exchanger where heat is transferred to the working fluid by sea water or other heat source;

Expanding the pressurized and heated two-phase saturated working fluid from high-pressure to low-pressure across the two-phase expander T, thereby generating a work output; and

Passing the low pressure two-phase saturated working fluid through a second heat exchanger with the heat sink, the LNG for regasification, such that the working fluid condenses from saturated liquid-vapor two-phase to son-saturated, liquid single phase.

15. A heat sink, such as a cryogenic fluid like LNG, or a non-cryogenic fluid like cold sea water, or other heat sinks,

a heat source, such as steam, warm water, air or other heat sources, a working fluid to transport heat and pressure energy,

comprising

a feed pump and a two-phase liquid-vapor expander for the working fluid mounted together with an electric generator on one rotating shaft,

a first heat exchanger to transport heat from the working fluid to the heat sink,

a second heat exchanger to transport heat from the heat source to the working fluid,

the working fluid passing from the first heat exchanger to the feed pump, increasing the pressure of the working fluid, passing the pressurized working fluid through the electric generator to cool the generator and absorb additional heat from the generator, passing the working fluid through the second heat exchanger, increasing the temperature of the working fluid approximately to the saturation temperature of the working fluid,

expanding the saturated working fluid across a two-phase liquid-vapor expander to a lower pressure, passing the working fluid through the first heat exchanger, reducing the temperature and condensing the working fluid to single phase liquid.