DIRECT EVAPORATOR APPARATUS AND ENERGY RECOVERY SYSTEM
In one aspect of the present invention provides a direct evaporator apparatus for use in an organic Rankine cycle energy recovery system, comprising: (a) a housing comprising a heat source gas inlet, and a heat source gas outlet, said housing defining a heat source gas flow path from said inlet to said outlet; and (b) a heat exchange tube disposed entirely within said heat source flow path, said heat exchange tube being configured to accommodate an organic Rankine cycle working fluid, said heat exchange tube comprising a working fluid inlet and a working fluid outlet, said heat exchange tube defining three zones, a first zone adjacent to said heat source gas outlet, a second zone adjacent to said heat source gas inlet, and a third zone disposed between said first zone and said second zone, said working fluid inlet being in direct fluid communication with said first zone, and said working fluid outlet being in direct fluid communication with said third zone; wherein said first zone is not in direct fluid communication with said third zone. An organic Rankine cycle energy recovery system and a method of energy recovery are also provided.
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The invention relates generally to an organic Rankine cycle energy recovery system, and more particularly to a direct evaporator apparatus and method for energy recovery employing the same.
So called “waste heat” generated by a large number of human activities represents a valuable and often underutilized resource. Sources of waste heat include hot combustion exhaust gases of various types including flue gas. Industrial turbomachinery such as turbines frequently create large amounts of recoverable waste heat in the form of hot gaseous exhaust streams.
Organic Rankine cycle energy recovery systems have been deployed as retrofits for small- and medium-scale gas turbines, to capture waste heat from the turbine's hot gas stream and convert the heat recovered into desirable power output. In an organic Rankine cycle, heat is transmitted to an organic fluid, typically called the working fluid, in a closed loop. The working fluid is heated by thermal contact with the waste heat and is vaporized and then expanded through a work extraction device such as a turbine during which expansion kinetic energy is transferred from the expanding gaseous working fluid to the moving components of the turbine. Mechanical energy is generated thereby which can be converted into electrical energy, for example. The gaseous working fluid having transferred a portion of its energy content to the turbine is then condensed into a liquid state and returned to the heating stages of the closed loop for reuse. A working fluid used in such organic Rankine cycles is typically a hydrocarbon, which is a liquid under ambient conditions. As such, the working fluid is subject to degradation at high temperature. For example, at 500° C., a temperature typical of a hot heat source gas from a turbine exhaust stream, even highly stable hydrocarbons begin to degrade. Worse yet, a hydrocarbon working fluid useful in an organic Rankine cycle energy recovery system may begin degrade at temperatures far lower than 500° C. Thus, the use of an organic Rankine cycle energy recovery system to recover waste heat from a gas turbine system is faced with the dilemma that the temperature of the exhaust is too high to bring into direct thermal contact with the working fluid of the organic Rankine cycle energy recovery system.
In order to avoid the aforementioned issue, an intermediate thermal fluid system is generally used to convey heat from the exhaust to an organic Rankine cycle boiler. In an example, intermediate thermal fluid system is an oil-filled coil, which moderates the temperature of the working fluid in the organic Rankine cycle boiler. However, the intermediate thermal fluid system can represent significant portion of the total cost of an organic Rankine cycle energy recovery system. Furthermore, the intermediate thermal fluid system both increases the complexity of the organic Rankine cycle energy recovery system and represents an additional component the presence of which lowers the overall efficiency of thermal energy recovery.
Therefore, an improved organic Rankine cycle system is desirable to address one or more of the aforementioned issues.
BRIEF DESCRIPTIONIn one aspect the present invention provides a direct evaporator apparatus for use in an organic Rankine cycle energy recovery system, comprising: (a) a housing comprising a heat source gas inlet, and a heat source gas outlet, said housing defining a heat source gas flow path from said inlet to said outlet; and (b) a heat exchange tube disposed entirely within said heat source gas flow path, said heat exchange tube being configured to accommodate an organic Rankine cycle working fluid, said heat exchange tube comprising a working fluid inlet and a working fluid outlet, said heat exchange tube defining three zones, a first zone adjacent to said heat source gas outlet, a second zone adjacent to said heat source gas inlet, and a third zone disposed between said first zone and said second zone, said working fluid inlet being in direct fluid communication with said first zone, and said working fluid outlet being in direct fluid communication with said third zone; wherein said first zone is not in direct fluid communication with said third zone.
In another aspect, the present invention provides an organic Rankine cycle energy recovery system comprising: (a) a direct evaporator apparatus comprising (i) a housing comprising a heat source gas inlet and a heat source gas outlet, said housing defining a heat source gas flow path from said inlet to said outlet; and (ii) a heat exchange tube disposed entirely within said heat source gas flow path, said heat exchange tube being configured to accommodate an organic Rankine cycle working fluid, said heat exchange tube comprising a working fluid inlet and a working fluid outlet, said heat exchange tube defining three zones, a first zone adjacent to said heat source gas outlet, a second zone adjacent to said heat source gas inlet, and a third zone disposed between said first zone and said second zone, said working fluid inlet being in direct fluid communication with said first zone, and said working fluid outlet being in direct fluid communication with said third zone; (b) work extraction device; (c) a condenser; and (d) a pump; wherein the direct evaporator apparatus, work extraction device, condenser and pump a configured to operate as a closed loop.
In yet another aspect, the present invention provides a method of energy recovery comprising: (a) introducing a heat source gas having a temperature into a direct evaporator apparatus containing a liquid working fluid; (b) transferring heat from the heat source gas having a temperature T1 to the working fluid to produce a superheated gaseous working fluid and a heat source gas having temperature T2; (c) expanding the superheated gaseous working fluid having a temperature T3 through an work extraction device to produce mechanical energy and a gaseous working fluid having a temperature T4; (d) condensing the gaseous working fluid to provide a liquid state working fluid; and (e) returning the liquid state working fluid to the direct evaporator apparatus; wherein the direct evaporator apparatus comprises (i) a housing comprising a heat source gas inlet, and a heat source gas outlet, said housing defining a heat source gas flow path from said inlet to said outlet; and a heat exchange tube disposed entirely within said heat source gas flow path, said heat exchange tube being configured to accommodate the working fluid, said heat exchange tube comprising a working fluid inlet and a working fluid outlet, said heat exchange tube defining three zones, a first zone adjacent to said heat source gas outlet, a second zone adjacent to said heat source gas inlet, and a third zone disposed between said first zone and said second zone, said working fluid inlet being in direct fluid communication with said first zone, and said working fluid outlet being in direct fluid communication with said third zone; and wherein said first zone is not in direct fluid communication with said third zone.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
In the following specification and the claims, which follow, reference will be made to a number of terms, which shall be defined to have the following meanings.
The singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
It is also understood that terms such as “top,” “bottom,” “outward,” “inward,” and the like are words of convenience and are not to be construed as limiting terms. Furthermore, whenever a particular feature of the invention is said to comprise or consist of at least one of a number of elements of a group and combinations thereof, it is understood that the feature may comprise or consist of any of the elements of the group, either individually or in combination with any of the other elements of that group.
Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about”, is not to be limited to the precise value specified. In some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Similarly, “free” may be used in combination with a term, and may include an insubstantial number, or trace amounts, while still being considered free of the modified term.
As noted, in one embodiment the present invention provides a direct evaporator apparatus for use in an organic Rankine cycle energy recovery system, comprising (a) a housing comprising a heat source gas inlet, and a heat source gas outlet, said housing defining a heat source gas flow path from said inlet to said outlet; and (b) a heat exchange tube disposed entirely within said heat gas source flow path. The heat exchange tube is configured to accommodate an organic Rankine cycle working fluid, and the heat exchange tube comprises a working fluid inlet and a working fluid outlet. The heat exchange tube is defined by three zones, a first zone adjacent to said heat source gas outlet, a second zone adjacent to said heat source gas inlet, and a third zone disposed between said first zone and said second zone. The working fluid inlet is in direct fluid communication with said first zone, and said working fluid outlet being in direct fluid communication with said third zone. The first zone is not in direct fluid communication with said third zone.
The
Working fluid in the liquid state enters the first zone 20 of the direct evaporator apparatus via working fluid inlet 40 where it is preheated as it moves towards zone 22 of the heat exchange tube. Thus second zone 22 receives an inflow of the working fluid 12 from the first zone 20 and vaporizes the working fluid 12. As shown in
As noted, the heat source gas 16 enters the direct evaporator apparatus at heat source gas inlet 36 and is hottest at the heat source gas inlet. In one embodiment, the heat source gas entering the direct evaporator apparatus at the heat source gas inlet is at a temperature in a range between about 400° C. and about 600° C. In an alternate embodiment, the heat source gas entering the direct evaporator apparatus at the heat source gas inlet is at a temperature in a range between about 400° C. and about 500° C. In yet another embodiment, the heat source gas entering the direct evaporator apparatus at the heat source gas inlet is at a temperature in a range between about 450° C. and about 500° C. As noted, the heat source gas first contacts zone 22, sometimes referred to as the evaporation zone, and cools as heat is transferred from the heat source gas to the portion of the heat exchange tube constituting zone 22. Internal structures, for example baffles and flow channels, present in the heat source gas flow path, not shown in
One of the advantages provided by certain embodiments of the present invention represented by
Returning to
As noted, the working fluid 12 may in one embodiment, be a hydrocarbon. Non-limiting examples of hydrocarbons include cyclopentane, n-pentane, methylcyclobutane, isopentane, methylcyclopentane propane, butane, n-hexane, and cyclohexane. In another embodiment, the working fluid can be a mixture of two or more hydrocarbons. In one embodiment, the working fluid is a binary fluid such as for example cyclohexane-propane, cyclohexane-butane, cyclopentane-butane, or cyclopentane-cyclohexane mixtures. In yet another embodiment, the working fluid is a hydrocarbon is selected from the group consisting of methylcyclobutane, cyclopentane, isopentane, cyclohexane, and methycyclopentane.
In various embodiments of the invention, the heat source may be any heat source, which may be used to produce a gas stream susceptible to introduction into the direct evaporator apparatus via the heat source gas inlet. In one embodiment, the heat source is a gas turbine, the exhaust from which may be used as the heat source gas. Other heat sources include exhaust gases from residential, commercial, and industrial heat sources such as home clothes dryers, air conditioning units, refrigeration units, and gas streams produced during fuel combustion, for example flue gas. In one embodiment, geothermal heat is employed as the heat source.
During operation the direct evaporator apparatus illustrated in
Referring to
In one embodiment, a method of energy recovery is provided. The method includes (a) introducing a heat source gas having a temperature into a direct evaporator apparatus containing a liquid working fluid; (b) transferring heat from the heat source gas having a temperature T1 to the working fluid to produce a superheated gaseous working fluid and a heat source gas having temperature T2; (c) expanding the superheated gaseous working fluid having a temperature T3 through an work extraction device to produce mechanical energy and a gaseous working fluid having a temperature T4; (d) condensing the gaseous working fluid to provide a liquid state working fluid; and (e) returning the liquid state working fluid to the direct evaporator apparatus. In one embodiment, the heat source gas has a temperature T1 in a range from about 400° C. to about 600° C. In another embodiment, the heat source gas has a temperature T1 in a range from about 400° C. to about 550° C. In one embodiment, the heat source gas has a temperature T2 in a range from about 100° C. to about 250° C. In another embodiment, the superheated gaseous working fluid has a temperature T3 in a range from about 200° C. to about 300° C. In one embodiment, the working fluid in the first zone is at a temperature in a range from about 20° C. to about 150° C. In another embodiment, the working fluid in the second zone is at a temperature in a range from about 50° C. to about 300° C. In yet another embodiment, the working fluid in the third zone is at a temperature in a range from about 200° C. to about 300° C.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
Claims
1. A direct evaporator apparatus for use in an organic Rankine cycle energy recovery system, comprising:
- (a) a housing comprising a heat source gas inlet, and a heat source gas outlet, said housing defining a heat source gas flow path from said inlet to said outlet; and
- (b) a heat exchange tube disposed entirely within said heat source flow path, said heat exchange tube being configured to accommodate an organic Rankine cycle working fluid, said heat exchange tube comprising a working fluid inlet and a working fluid outlet, said heat exchange tube defining three zones, a first zone adjacent to said heat source gas outlet, a second zone adjacent to said heat source gas inlet, and a third zone disposed between said first zone and said second zone, said working fluid inlet being in direct fluid communication with said first zone, and said working fluid outlet being in direct fluid communication with said third zone;
- wherein said first zone is not in direct fluid communication with said third zone.
2. The direct evaporator apparatus according to claim 1, wherein said heat exchange tube comprises a plurality of bends in each of the first zone, second zone and third zone.
3. The direct evaporator apparatus according to claim 2, wherein the heat exchange tube is configured in parallel rows in each of the first zone, second zone and third zone.
4. The direct evaporator apparatus according to claim 3, wherein in each of the first zone, second zone and third zone of the heat exchange tube is configured in at least one row.
5. An organic Rankine cycle energy recovery system comprising:
- (a) a direct evaporator apparatus comprising (i) a housing comprising a heat source gas inlet and a heat source gas outlet, said housing defining a heat source gas flow path from said inlet to said outlet; and (ii) a heat exchange tube disposed entirely within said heat source flow path, said heat exchange tube being configured to accommodate an organic Rankine cycle working fluid, said heat exchange tube comprising a working fluid inlet and a working fluid outlet, said heat exchange tube defining three zones, a first zone adjacent to said heat source gas outlet, a second zone adjacent to said heat source gas inlet, and a third zone disposed between said first zone and said second zone, said working fluid inlet being in direct fluid communication with said first zone, and said working fluid outlet being in direct fluid communication with said third zone;
- (b) work extraction device;
- (c) a condenser; and
- (d) a pump;
- wherein the direct evaporator apparatus, work extraction device, condenser and pump a configured to operate as a closed loop.
6. The energy recovery system according to claim 5, wherein said heat exchange tube comprises a plurality of bends in each of the first zone, second zone and third zone.
7. The energy recovery system according to claim 5, wherein the heat exchange tube is configured in parallel rows in each of the first zone, second zone and third zone.
8. The energy recovery system according to claim 5, further comprising a recouperator.
9. The energy recovery system according to claim 5, wherein the work extraction device comprises a turbine.
10. The energy recovery system according to claim 9, further comprising a turbine by-pass duct.
11. A method of energy recovery comprising:
- (a) introducing a heat source gas having a temperature into a direct evaporator apparatus containing a liquid working fluid;
- (b) transferring heat from the heat source gas having a temperature T1 to the working fluid to produce a superheated gaseous working fluid and a heat source gas having temperature T2;
- (c) expanding the superheated gaseous working fluid having a temperature T3 through a work extraction device to produce mechanical energy and a gaseous working fluid having a temperature T4;
- (d) condensing the gaseous working fluid to provide a liquid state working fluid; and
- (e) returning the liquid state working fluid to the direct evaporator apparatus;
- wherein the direct evaporator apparatus comprises (i) a housing comprising a heat source gas inlet, and a heat source gas outlet, said housing defining a heat source gas flow path from said inlet to said outlet; and a heat exchange tube disposed entirely within said heat source flow path, said heat exchange tube being configured to accommodate the working fluid, said heat exchange tube comprising a working fluid inlet and a working fluid outlet, said heat exchange tube defining three zones, a first zone adjacent to said heat source gas outlet, a second zone adjacent to said heat source gas inlet, and a third zone disposed between said first zone and said second zone, said working fluid inlet being in direct fluid communication with said first zone, and said working fluid outlet being in direct fluid communication with said third zone; and wherein said first zone is not in direct fluid communication with said third zone.
12. The method according to claim 11, wherein the heat source gas has a temperature T1 in a range from about 400° C. to about 600° C.
13. The method according to claim 11, wherein the heat source gas has a temperature T2 in a range from about 100° C. to about 250° C.
14. The method according to claim 11, wherein the working fluid is a hydrocarbon.
15. The method according to claim 11, wherein the working fluid is a hydrocarbon is selected from the group consisting of methylcyclobutane, cyclopentane, isopentane, cyclohexane, and methycyclopentane.
16. The method according to claim 11, wherein the superheated gaseous working fluid has a temperature T3 in a range from below 300° C.
17. The method according to claim 11, wherein the work extraction device is a turbine
18. The method according to claim 11, wherein the working fluid in the first zone is at a temperature in a range from about 20° C. to about 150° C.
19. The method according to claim 11, wherein the working fluid in the second zone is at a temperature in a range from about 50° C. to about 300° C.
20. The method according to claim 11, wherein the working fluid in the third zone is at a temperature in a range from about 200° C. to about 300° C.
Type: Application
Filed: Sep 15, 2009
Publication Date: Mar 17, 2011
Applicant: GENERAL ELECTRIC COMPANY (SCHENECTADY, NY)
Inventors: Matthew Alexander Lehar (Munich), Sebastian W. Freund (Bavaria), Thomas Johannes Frey (Bavaria), Richard Aumann (Muenchen), Gabor Ast (Garching)
Application Number: 12/559,871
International Classification: F01K 7/34 (20060101); F01K 25/00 (20060101);