WO2024121760A1

WO2024121760A1 - Power production cycle with alternating heat sources

Info

Publication number: WO2024121760A1
Application number: PCT/IB2023/062276
Authority: WO
Inventors: Jeremy Eron Fetvedt; Justin Miller; JR. James Powell CUSTER; Steve MILWARD
Original assignee: 8 Rivers Capital, Llc
Priority date: 2022-12-06
Filing date: 2023-12-05
Publication date: 2024-06-13

Abstract

The present disclosure provides power production cycles. The power production cycles utilize direct heat sources and indirect heat sources that are combined to provide efficient and reliable power production.

Description

POWER PRODUCTION CYCLE WITH ALTERNATING HEAT SOURCES

FIELD OF THE DISCLOSURE

The present disclosure provides for production of power (e.g., electricity) and apparatuses and methods that are effective for the power production. More particularly, power production is achieved using a direct heat source and an indirect heat source with periodic switching between the heat sources and with optional overlapping of the heat sources.

BACKGROUND

Power production cycles typically require a heat source to heat a circulating fluid that is then utilized to generate power, such as through causing rotation of a turbine. The circulating fluid can be directly heated (e.g., passing through a combustor where a fuel is combusted with oxygen to produce heat that heats the circulating fluid and produce combustion products that mix with the circulating fluid), or the circulating fluid can be indirectly heated (e.g., by passing through a heat exchanger against a heating fluid that itself has been heated). Each heating arrangement has advantages and disadvantages. Accordingly, there remains a need in the art for power production cycles that can maximize the advantages of one or both of the heating arrangements while also minimizing the disadvantages of one or both of the heating arrangements.

SUMMARY OF THE DISCLOSURE

The present disclosure relates to power production cycles whereby one or more heat sources suitable for providing indirect heating of a circulating fluid (e.g., such as using solar energy, nuclear energy, etc.) may be effectively integrated with one or more heat sources for providing directing heating of a circulating fluid (e.g., such as using a combustor in a supercritical CO2 power cycle). As such, the present disclosure encompasses power production systems and methods whereby a power cycle can be configured for using one or more direct heating arrangements with one or more indirect heating arrangements in a manner that allows for combined use of the different types of heating arrangements altematingly or in parallel. When used in parallel, each of the different types of heating arrangements can be utilized in a manner that provides heat in an amount that is in the range of about 1% to about 99% of a maximum operating heat output for the respective heat sources. When used altematingly, the indirect heating source may be operable to fully supplant the direct heating source for maintaining full operation of the power cycle and power production.

The combination of different heat sources and different types of heat sources can be particularly beneficial to enable down time for one of the heat sources without the necessity of taking the entire power production plant offline. The combination likewise can be particularly useful when bringing online a new source of the indirect heating since the direct heat source can be operated with lesser or greater heat output, as needed, as the new indirect heating source is tested and configured for the desired operating parameters while still providing necessary power to, for example, an electrical grid, or any other load configured to receive all or part of the power output. In some embodiments, the power production plant can be configured to operate primarily from one of the direct heat sources or indirect heat sources, and the remaining heat sources can be utilized only at certain times, such as when first bringing the power production plant online, when servicing one of the heat sources, during a period of other planned servicing, and the like.

In some embodiments, the power production cycle can be configured so that direct heating can be used acutely while the indirect heat source is used chronically. More particularly, the indirect heat source may be a heat source that is available for relatively long periods of time but subject to intermittent down times or that requires occasional servicing or is subject to other, relatively infrequent disruptions. Such indirect heat sources can be ideal for use in a power production cycle due to a reduction in the amounts of consumable resources that are required (e.g., relative to the need to bum fuels in typical, direct heat sources). The present disclosure thus can enable utilization of such indirect heat sources for power production in an SCO2 power cycle (which may be an open cycle, a partially closed cycle, or a completely closed cycle). When in the operational mode, the indirect heat sources can have a capacity factor near 100% during normal operation. The power cycle, however, can still be responsive to quickly and safely adjust to variations in the heat produced by the indirect heat source and otherwise retain the direct heat source in “backup mode” (e.g., operational so as to be in condition to immediately or rapidly be brought up to normal operating conditions as opposed to being required to undergo a prolonged start-up procedure from being in a shutdown mode) at times when the indirect heat source is in fact operating at near 100% capacity and producing consistent heat that is converted to power though thermal transfer into the sCCT power cycle. The disclosed systems and methods thus can provide an overall power production cycle that is durable, cost-saving, and reactive to any changes in power output requirements and/or heat input availability (from the indirect heat source, in particular) so that the power cycle is configured for reliable power production at each and every operating and transitional stage that may be encountered.

In some embodiments, the present disclosure provides methods for power production. In an example embodiment, such method can comprise: operating a power cycle so that a working fluid is compressed, heated in at least a primary power cycle heat exchange (PCHE1) unit, passed through a primary combustor for mixing with combustion products, expanded for power production, cooled in at least the PCHE1 unit, purified for removal of one or more of the combustion products, and recycled for compression; passing one or more streams of the power cycle through a primary external process heat exchange (EPHE1) unit that is operably connected to an external heat producing source; passing at least a first stream from the external heat producing source through the EPHE1 unit in a heat exchange relationship with one or more streams of the power cycle; and controlling flow of the one or more streams of the power cycle through the EPHE1 unit based upon a heating value of the at least a first stream from the external heat producing source. In further embodiments, the methods can be also defined in relation to any one or more of the following statements, which statements can be combined in any number and/or order.

The external heat producing source can be a nuclear reactor.

The external heat producing source can be a solar heater or an industrial process.

The EPHE1 unit can be arranged relative to the power cycle so that the one or more streams of the power cycle passing through the EPHE 1 unit are streams that are being heated for passage to the primary combustor. The one or more streams of the power cycle passing through the EPHE1 unit can be heated in the PCHE1 unit.

The one or more streams of the power cycle passing through the EPHE1 unit can comprise a stream of the working fluid.

The one or more streams of the power cycle passing through the EPHE1 unit can comprise one or both of a fuel stream and an oxidant stream.

The heating value of the at least a first stream from the external heat producing source can be a positive heating value, and the at least a first stream from the external heat producing source and the one or more streams of the power cycle can be passed through the EPHE1 unit so that heat from the at least a first stream from the external heat producing source can be transferred to the one or more streams of the power cycle.

The one or more streams of the power cycle can comprise all of a fuel stream, an oxidant stream, and a stream of the working fluid.

The power cycle can include a secondary combustor.

The one or more streams of the power cycle passed through the EPHE1 unit can comprise a stream of heated combustion products from the secondary combustor.

The heating value of the at least a first stream from the external heat producing source can be a negative heating value, and the at least a first stream from the external heat producing source can be passed through the EPHE1 so that heat from the stream of heated combustion products from the secondary combustor can be transferred to the at least a first stream from the external heat producing source.

The stream of heated combustion products from the secondary combustor can be controllably passed to the EPHE1 unit based upon the heating value of the at least a first stream from the external heat producing source.

The method further can comprise passing a second stream from the external heat producing source through a secondary external process heat exchange (EPHE2) unit in a heat exchange relationship with one or more streams of the power cycle.

The one or more streams of the power cycle can comprise a stream of the working fluid.

The second stream from the EPHE2 unit can be passed through at least the PCHE1 unit so as to transfer heat to the one or more streams of the power cycle in the PCHE1 unit.

The working fluid can comprise predominantly carbon dioxide.

In one or more embodiments, the present disclosure can provide power production systems. In an example embodiment, such system can comprise: a power cycle including a primary combustor, a power producing turbine, at least a primary power cycle heat exchange (PCHE1) unit, and at least one compression unit; a primary external process heat exchange (EPHE1) unit arranged upstream from the primary combustor and configured to transfer heat from an external process to one or more streams in the power cycle, the one or more streams being controllably deliverable to the EPHE1 unit; and a secondary combustor arranged upstream from the EPHE1 unit and configured to provide a stream of heated combustion products, the secondary combustor being controllably openable to the EPHE1 unit and controllably isolatable from the power cycle. In further embodiments, the system can be additionally defined by any one or more of the following statements, which statements can be combined in any number and order.

The power production system further can comprise a controller.

The PCHE1 unit can be a single heat exchanger comprising a plurality of sections operable at different temperature ranges or wherein the power cycle can include a secondary power cycle heat exchange (PCHE2) unit in an operable connection with the PCHE1 unit.

The power production cycle further can comprise a secondary external process heat exchange (EPHE2) unit arranged upstream from the PCHE1 unit.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 illustrates a power production cycle that incorporates one or more direct heat sources and one or more indirect heat sources according to example embodiments of the present disclosure.

FIG. 2 provides a flow chart for a system and method for power production according to example embodiments of the present disclosure wherein an external heat source can provide heating at one or more points of a power production cycle to supplement or alternate with one or more combustors of the power production cycle.

DETAILED DESCRIPTION OF THE DISCLOSURE

The present subject matter will now be described more fully hereinafter with reference to exemplary embodiments thereof. These exemplary embodiments are described so that this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. Indeed, the subject matter can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. As used in the specification, and in the appended claims, the singular forms “a”, “an”, “the”, include plural referents unless the context clearly dictates otherwise.

The present disclosure relates to power production cycles and power production plants and thus can provide one or more systems for power production and/or one or more methods for power production. The systems and methods can be exemplified in relation to various embodiments whereby a power cycle wherein a high pressure, high temperature recycle CO2 stream is further heated, expanded in a turbine for power production, cooled in a recuperator heat exchanger, re-pressurized, and re-heated in the recuperator heat exchanger. Such power cycle can be referenced herein as an oxy -fuel SCO2 power cycle, or simply an SCO2 power cycle.

Non-limiting examples of systems and methods for power production, and elements thereof, that may be suitable for use according to the present disclosure are described in U.S. Pat. No. 9,068,743 to Palmer et al., U.S. Pat. No. 9,062,608 to Allam et al., U.S. Pat. No. 8,986,002 to Palmer et al., U.S. Pat. No. 8,959,887 to Allam et al., U.S. Pat. No. 8,869,889 to Palmer et al., U.S. Pat. No. 8,776,532 to Allam et al., and U.S. Pat. No. 8,596,075 to Allam et al, the disclosures of which are incorporated herein by reference. As a non-limiting example, a power production system useful according to the present disclosure can be configured for combusting a fuel with an oxidant (in some instances air and, in some instances substantially pure O2, which may be optionally mixed with a diluent) in the presence of a CO2 circulating fluid in a combustor, preferably wherein the CO2 is introduced at a pressure of at least about 8 MPa (e.g., in the range of about 10 MPa to about 50 MPa or about 20 MPa to about 40 MPa) and a temperature of at least about 300°C, to provide a combustion product stream comprising CO2, preferably wherein the combustion product stream has a temperature of at least about 500°C. Such power production system further can be characterized by one or more of the following statements.

The combustion product stream can be expanded across a turbine with a discharge pressure of about 1 MPa or greater to generate power and provide a turbine discharge stream comprising CO2.

The turbine discharge stream can be passed through a heat exchanger unit to provide a cooled discharge stream.

The cooled turbine discharge stream can be processed to remove one or more secondary components other than CO2 to provide a purified discharge stream.

The purified discharge stream can be compressed to provide a supercritical CO2 circulating fluid stream.

The supercritical CO2 circulating fluid stream can be cooled to provide a high density CO2 circulating fluid (preferably wherein the density is at least about 200 kg/m³).

The high density CO2 circulating fluid can be pumped to a pressure suitable for input to the combustor.

The pressurized CO2 circulating fluid can be heated by passing through the heat exchanger unit using heat recuperated from the turbine discharge stream.

All or a portion of the pressurized CO2 circulating fluid can be further heated with heat that is not withdrawn from the turbine discharge stream.

The heated pressurized CO2 circulating fluid can be recycled into the combustor.

An SCO2 power cycle can be particularly useful as a power cycle for combination of direct heating and indirect heating in tight of the flexibility for operating the power cycle under a variety of different arrangements of components and/or different operational features. Configuring an sCCb power cycle with a plurality of direct heating components (e.g., combustors) can particularly provide several advantages. For example, in some embodiments, such sCCb power cycle can be effectively operated without any heat output at all from the indirect heat source (such as when the indirect heat source is undergoing maintenance or when circumstances cause the indirect heat source to be inoperable or only capable of operating at very low heat output) in light of the stable heating provided by the direct heat source. In some embodiments, the SCO2 power cycle can be effectively operated with only a partial load from the indirect heat source, which partial load can reduce the amount of direct heating that is required. In some embodiments, the sCCh power cycle can be effectively operated using only heat from the indirect heat source with essentially no heat output from the direct heat source, for at least a defined period of time. In some embodiments, the sCCh power cycle can be effectively operated so that the indirect heat source (or a portion thereof) and/or a stream entering the indirect heat source can be pre-heated with heat taken from the direct heat source (such as during a start-up phase) instead of requiring parasitic heat sources, such as an electrical heater that requires an electrical load to be back-fed from the grid in order to heat the indirect heat source prior to bringing the indirect heat source online for full operation. In some embodiment, the sCCh power cycle can be effectively operated in a “double fire” mode whereby the direct heat source is used to both pre-heat the indirect heat source (or a stream entering the indirect heat source) and also heat a stream leaving the indirect heat source. In some embodiments, the sCCh power cycle can be effectively operated as a baseload from the indirect heat source and then provide additional loading, as needed from the direct heat source as demand varies in order to correctly control the process in a safe and reliable manner.

The presently disclosed power cycles can utilize components and can be operated similarly to known power production cycles, including the prior sCOi oxy -combustion cycles, such as those already referenced above. The present disclosure, however, should not be constmed as being limited solely to sCCh power production cycles. Rather, the present disclosure can be applied to power production cycles that utilize any possible material as the circulating fluid or working fluid. Non-limiting examples of suitable materials for use as a circulating fluid or working fluid in a power production cycle according to the present disclosure can encompass CO2 (including sCCh), argon (Ar), helium (He), water (H2O, including liquid, gases, and combinations thereof), nitrogen (N2), and the like, and combinations thereof. Any discussion herein of a CO2 power production cycle or an sCCh power production cycle is thus understood to be an example embodiment, and any components or operational aspects of a CO2 power production cycle or an SCO2 power production cycle that are described herein may equally apply to other power production cycles that utilize circulating fluids as an alternative to, or in combination with, CO2.

The working fluid stream in the power production cycle typically can be compressed in one or more steps (e.g., in one or more compressors and/or one or more pumps) prior to being reheated by heat exchange with the turbine exhaust stream in the recuperator heat exchanger. The compressed and heated working stream leaving the power cycle recuperator can pass through a heat exchanger where it can be heated against a stream from the indirect heater prior to or instead of being heated in the direct heater.

A direct heater as used herein particularly can mean a combustor wherein a fuel is combusted with oxidant in the presence of the working fluid. A hydrocarbon fuel, such as natural gas, may be used, particularly when CO2 is used as the working fluid. In such instances, the combustion will produce primarily water and more CO2, and this allows for convenient recycling of the CO2 working fluid by removing water and delivering any net produced CO2 for sequestration. A single combustor may be used or a plurality of combustors may be used. In particular, a second combustor can provide advantages for controlling heat transfer and allowing for heat transfer back to the indirect heat source when useful.

An indirect heat source may be alternatively referenced as an external heat source or an external heat producing source. For example, a nuclear reactor (or part thereof) may be utilized as an indirect heat source in that a stream from the nuclear reactor can be passed through a heat exchanger of the power cycle. In nuclear reactors, a stream of molten salt can be used to cool the reactor, and such stream is typically used to heat a water stream to form steam to produce power from the nuclear reactor. In the present disclosure, the molten salt is an example of how indirect heating can be provided (i.e., the nuclear reactor is the external heat producing source, and the heat is added to the power cycle indirectly through heat exchange in one or more heat exchangers of the power production cycle). Reference to a nuclear reactor can encompass nuclear fission or nuclear fusion and can mean any component of a nuclear power plant capable of providing a heated stream.

The recycle stream is heated to the final turbine inlet temperature with the heat from the indirect heat source. The recycle stream can pass through a combustor in the power cycle (the combustor being an example of a direct heat source according to the present disclosure). The combustor can be operated at any heat level output needed to supplement the indirect heating, including passing the recycle stream through the combustor without combustion occurring. The recycle stream then can be expanded in the turbine to generate power. The turbine exhaust then can pass through the main recuperator where it is cooled by heating the high pressure recycle stream. The fluid then can be compressed and pumped to form the recycle stream. In this manner, the power production cycle can be operated as an indirectly fired power production cycle using heat from the indirect heat source while only be supplemented as needed by the direct heat sources of the power production cycle.

A variety of external heat producing sources can be utilized for indirect heat in the presently disclosed power production cycles. As noted above, a nuclear reactor may be utilized. In other embodiments, a solar power source can be used as the indirect heat source. In some embodiments, fuel production systems (e.g., gasifiers, partial oxidation combustors, etc.) can be useful for providing added heating, and such systems may likewise be utilized as an external heat producing source and, optionally, as a source of fuel for one or more combustors as described herein. Various sources of industrial heating may likewise be used as the indirect heat source. Solar power, industrial heat sources, and similar heat sources can fluctuate, pulse, or otherwise change over time, and nuclear reactors likewise can suffer from such variations, particularly when the nuclear reactor is first being brought online. In addition, with these types of indirect heat sources, the desired response from the power cycle for load following on the grid may not be as rapid as desired. The presently disclosed systems and methods provide power production cycles that can effectively compensate for such shortcomings in that a fuel source and oxidant can be combusted in one or more combustors, which function as a direct heat source, in order to control the turbine inlet temperature independent from the heat provided by the indirect heat source. A fuel, as an example, can be a carbonaceous material (e.g., CO), a hydrocarbon more particularly (e.g., natural gas and/or petroleum products, which encompasses solid, liquid, and gaseous fuel materials), hydrogen-based products (e.g., H₂ gas or NH₃), synthesis gas, or any other combustible material, including biomass and/or industrial waste materials.

The above thus allows for operation and control of the power cycle to be disconnected and independent from the operation of only the indirect heat source. In one or more embodiments, the present disclosure is particularly beneficial since the indirect heat source can be a preferred heat source for reasons related to one or more of cost, environmental concerns, sustainability, or the like, and the direct heat source, while perhaps being less preferred in relation to one or more of these factors, can be available as a supplement that is a highly reliable and time-tested heat source that is only used as needed in order to maximize the advantages associated with the use of the indirect heat source.

Further to the above, another combustor can be added to the recycle line before the heat exchanger. This can configure the recycle stream to be heated to a temperature higher than the stream that is being used in heat exchange from the external heat sources. This arrangement can lead to a power cycle that is configured to add heat to the external heat source and also minimize the parasitic load on the electrical grid that may otherwise exist when heating for the external heat source itself is required. After rejecting heat into the indirect heat source, the recycle stream can be reheated again in the main combustor (or other direct heat source of the power production cycle) for proper operation of the power cycle. The power production cycle beneficially can be operated in a variety of manners so that heat provided by the external heat source can be added into the power production cycle in a variety of different locations and/or at a variety of different temperature levels.

An example embodiment of a system and method useful in power production according to the present disclosure is illustrated by the flowchart provided in FIG. 1. The example embodiment is based on a power cycle 10 operating with a circulating working fluid and is combined with an external system/process 20. The combination is effective to allow for transfer of heat from the external system/process 20 to the power cycle 10 and/or transfer of heat from the power cycle 10 to the external system/process 20. This can be achieved, in some embodiments, using an external process heat exchanger 30. In some embodiments, a combustor 40 can be used for additive heating that can be beneficial for providing heat to one or both of the power cycle 10 and the external system/process 20. The noted elements of the system and method can be interconnected with a number of different streams and can be primarily combined by streams of the working fluid from the power cycle 10.

In an example embodiment, the power cycle 10 can be configured as otherwise described above, such as being an sCO2 power production cycle; however, it is understood that the working fluid may be any suitable working fluid material. In use, the power cycle 10 can be operated so that the working fluid is compressed and heated (e.g., in a recuperative heat exchanger) to form a recycle working fluid stream 11 that is deliverable to a combustor where fuel is combusted with an oxidant to further heat the working fluid before it is expanded across a turbine for power production. The stream exiting the turbine is then processed for being recycled back to the combustor again. All of the foregoing can be carried out, for example, in the manner specified more particularly in relation to FIG. 2 below. For combination with the external system/process 20, a stream of the working fluid in line 11 can be passed through line 12 in the external process heat exchanger 30 to be heated against one or more heating streams and exit as heated working fluid in line 13, which connects to line 14 for passage back to one or more further components of the power cycle 10 (e.g., passage into the combustor or into a power producing turbine). In this manner, additional heat can be added to the working fluid in lines 11 and 12, and this heat can be additive to heating that will also be provided in the combustor of the power cycle 10 or can partially or completely replace heating from a combustor of the power cycle 10. The heating provided in external process heat exchanger 30 can come from the external system process 20 via a heated stream in line 21, which enters the external process heat exchanger 30, transfers its heat to one or more streams therein, and then leaves in line 22 for return to the external system/process 20. The external system/process can provide heated streams capable of transferring heat in a temperature range of about 100°C to about 500°C, about 150°C to about 450°C, or about 200°C to about 400°C. While this is an expected range in practice, to the extent that an external system/process 20 is capable of providing heat at a higher temperature range, transfer in such higher temperature range is also useful and encompassed according to the present disclosure. It is beneficial to be capable of providing heat at sufficiently high temperature ranges since the heat transfer from the external system/process can supplement or substantially completely replace heat that would otherwise be provided by a combustor in the power cycle 10. This enables operation switching between heat sources for the power cycle 10. Specifically, when the external system/process 20 is operational for providing a heating stream in line 21 of a sufficiently high temperature, the combustor of the power cycle 10 may be operated in a low temperature mode, a standby mode, or a shutdown mode whereby little to no heating is being provided by the combustor and substantially all of the heating for the power cycle is being provided by the indirect heating provided via external process heat exchanger 30 and the stream received from the external system/process 20. When the external system/process 20 is operating at a lower temperature (such as being shut down for maintenance), the combustor of the power cycle 10 can be returned to full operational mode and combust fuel for heat production that is not supplemented or is only minimally supplemented by the external system/process 20.

In some embodiments, the external system/process 20 may not be operational to provide all of the heating that is needed to replace or supplement the heating of the combustor in the power cycle 10. Likewise, in some embodiments, the external system/process 20 may actually require heat input instead of providing heat output. For example, a solar power station may require heat input during low sunlight hours. In such instances, an additive combustor 40 may be brought online to combust fuel and provide further heating. Specifically, the combustor 40 may be isolatable from the power cycle 10 and the external process heat exchanger 30 but may be controllably integrable with the power cycle 10 and the external process heat exchanger 30, such as by opening/closing one or more valves in lines feeding fuel and oxidant to the combustor 40 as well as a portion of the working fluid. As noted in FIG. 1, the working fluid from the power cycle 10 in line 11 may be controllably branched in line 14 to pass into the combustor 40, where the working fluid is heated through combustion of fuel with oxidant (i.e., delivered to the combustor 40 in lines, such as illustrated in FIG. 2). Heated working fluid in line 41 thus can pass through the external process heat exchanger 30 where it can pass heat to the stream entering the external process heat exchanger 30 through line 21 and thereby deliver a heated stream back to the external system/process 20 via line 22. This likewise can provide additive heating to the power cycle 10. The stream of working fluid and combustion products leaving the external process heat exchanger 30 in stream 31 can merge with the working fluid in stream 13 to form stream 14, which passes back into the power cycle as already discussed above. It should be noted that lines 12 and 13 may include valves that allow for said lines to be closed in embodiments where combustor 40 is operational. Thus, in external process heat exchanger 30, heat exchange may occur so that any of the follow may occur: a) heat may be passed from stream 21 to stream 12; b) heat may be passed from stream 21 and from stream 41 to stream 12; c) heat may be passed from stream 41 to stream 12; d) heat may be passed from stream 41 to stream 21; e) heat may be passed from stream 12 to stream 21; f) heat may be passed from stream 12 and from stream 41 to stream 21. Likewise, controls may be implemented for switching between any of the noted heat transfer conditions and for opening and closing appropriate flow lines to allow for said switching.

A detailed flowchart of a power production cycle according to example embodiments of the present disclosure is illustrated in FIG. 2. While FIG. 2 illustrates a number of components and flow streams, it is to be understood that the figure illustrates one example embodiment, and it will be evident from the full disclosure herein that the power production system and method can be operable in the express absence of one or more components and/or more of the flow streams. Such exclusions are expressly noted where applicable, but the disclosure is not limited to only the express notations of such, and such notations are provided as examples.

With reference to FIG. 2, a pressurized and heated exhaust stream 401 exits a primary combustor 801 and is expanded in turbine 802 for power production, such as generation of electrical power with generator 816. The primary combustor 801 and the turbine 802 can be configured to operate within temperature ranges that are achieved through combustion in the primary combustor 801 as well as ranges that can be provided by the indirect heat source (i.e., the external process or system from which a heating stream is obtained). In some embodiments, a desired temperature range for operation of the power production cycle whether supported by the direct heat source of the indirect heat source can be in the range of about 100°C to about 1200°C, about 200°C to about 900°C, or about 400°C to about 700°C. In certain embodiments, a specifically low range can be desired, such as about 100°C to about 500°C or about 200°C to about 400°C, or a specifically high range can be desired, such as about 400°C to about 1200°C or about 600°C to about 1000°C. The pressure ratio across the turbine 802 can be about 6 to about 40, about 8 to about 35, or about 10 to about 30.

The turbine exhaust in stream 601 can be cooled in one or more heat exchangers, which preferably is a recuperator heat exchanger so that heat removed from the turbine exhaust can be used to re-heat the working fluid stream being recycled back to the turbine 802. As illustrated in FIG.1, two recuperator heat exchangers as used, a primary power cycle heat exchange (PCHE1) unit 805 receives turbine exhaust from stream 601 and outputs a cooled stream 602, which enters a secondary power cycle heat exchange (PCHE2) unit 806, where the exhaust is further cooled and leaves as cooled turbine exhaust in stream 603. It is understood that PCHE2 may be optional. Likewise, PCHE1 may be a multi-section heat exchange unit with multiple sections operated at different temperature levels. The cooled turbine exhaust stream 603 is processed for purification in order to provide a substantially pure stream of the working fluid for recycle back to the turbine. In some embodiments, it may not be necessary to implement the purification steps, such as embodiments where having water in the working fluid is acceptable. In the illustrated embodiment, wherein a CO2 working fluid is preferred, it is beneficial to remove part or substantially all of the water in a water separator 807, which provides a bottom water product in stream 701. A substantially pure stream of the working fluid (e.g., a substantially pure stream of CO2) is provided in stream 604. A portion of stream 604 may be divided for use as further described below, but a bulk of the purified working fluid is routed for compression before being returned to the turbine for power production.

In the illustrated example embodiment, the bulk of the working fluid from stream 604 is passed through a direct contact cooler 810 so that any remaining water can be removed as a bottom product, which is pumped by pump 817 to provide a stream that is divided so that a portion of the water is recirculated back to the direct contact cooler 810 through water cooler 1, and the remaining portion in stream 702 combines with water in stream 701 to form the total water export in stream 703. Stream 605 leaving the top of the direct contact cooler 801 comprises substantially pure CO2 (or other purified working fluid), and part thereof is divided out via stream 606 as the net export CO2, which can be sent for sequestration. The remaining CO2 in stream 607 defines the bulk portion of the recycled working fluid stream, which is compressed for return to the turbine 802. The direct contact cooler 810 can be optional but can be useful to scrub various contaminants (if present) from the recycle stream, and this can be carried out though the recycle loop passing through water cooler 1. Likewise, when a hot gas compressor is used (see discussion of compressor 809 herein) to adjust the thermal profile in the heat exchanger, the direct contact cooler is useful for full drying of the recycle stream. .

The working fluid in stream 608 is compressed in compressor 811 to a suitable pressure for power production depending upon the desired operating conditions of the power cycle. In some embodiments, the compressor 811 may be a single stage compressor, which may be operated adiabatically, or may be an intercooled, multi-stage compressor. The compressor 811 can be configured to compress the working fluid to a first pressure in stream 608. Since the working fluid in the example embodiment can be CO2, it is beneficial to cool the compressed stream to increase the density of the working fluid and reduce the pump load for return to the turbine, and compression thus may be carried out stepwise through a compression train. In FIG. 2, the working fluid in stream 608 is cooled in water cooler 2 to form stream 609, which is pumped from the first pressure to a second pressure in pump 812 to form stream 610, which is cooled again in water cooler 3 to form stream 611. The working fluid in stream 611 can be divided for plural pathways back to the turbine. As illustrated, part of the working fluid from stream 611 is passed via stream 625 to provide for dilution of the substantially pure oxygen (e.g., at least 95% molar, at least 98% molar, or at least 99% molar O2) that is provided in stream 201. The CO2 plus O2 combine to form stream 202 with about 15% to about 60%, about 20% to about 50%, or about 25% to about 45% molar O2, and this stream is compressed with pump 815 to form oxidant stream 203 at the final pressure for use in the primary combustor 801. The remaining portion of the working fluid in stream 612 is also compressed in pump 813 to form working fluid stream 613 at the final pressure for recycling for power production. The compression train can be configured to provide the working fluid alone and/or the working fluid plus oxidant stream with a pressure in the range of about 100 bar to about 600 bar, about 150 bar to about 500 bar, or about 200 bar to about 400 bar. Fuel stream 301 is similarly compressed in compressor 814 for form stream 302, which preferably is in a similar pressure range. The working fluid, fuel, and oxidant in streams 613, 302, and 203, respectively, can then be reheated. All three streams are first passed through PCHE2 805 for heating against stream 602 and form first heated working fluid stream 614, first heated fuel stream 303, and first heated oxidant stream 204. Oxidant stream 204 and fuel stream 303 are then further heated in PCHE1 805 to form the second heated oxidant stream 205 and the second heated fuel stream 304. Working fluid stream 614 merges with stream 632 to from stream 615, which is further heated in PCHE2 806 to form second heated working fluid stream 616, which is further discussed below.

The working fluid stream 616, fuel stream 304, and oxidant stream 205 can be controlled (either manually or with an automated control unit with necessary input and output to control opening and closing of pertinent valves to direct necessary flows to the desired units) so that they are passed to the primary combustor 801 or a secondary combustor 803. The manner of flow at this stage can be controlled based upon a desired operating design or may be controlled based on a heating value of a stream that is being provided from an external heat producing source. This enables a variety of operating conditions. In some embodiments, operation can be carried out so that the secondary combustor 803 is isolated from the power cycle. In such configuration, the external heat producing source 100 can be providing a stream with a sufficiently positive heating value to supplement the heating that is provided directly in the primary combustor 801 via combustion. In some embodiments, operation can be carried out so that the secondary combustor 803 is isolated from the power cycle and so that the primary combustor 801 is in standby or off mode and is not producing any heat or is only producing a nominal amount of standby heating. In such configuration, the external heat producing source 100 can be providing a stream with a sufficiently positive heating value to give the full amount of necessary heating for operation of the power cycle without need for additional heat from either the primary combustor 801 or the secondary combustor 803. The primary combustor 801 is simply a flow-through unit under this condition and is not adding to the heating of the working fluid. In some embodiments, operation can be carried out so that the secondary combustor 803 is operable and is functioning as part of the power cycle. In such configuration, the secondary combustor 803 is arranged to provide supplemental heating that may be required for one or both of the primary combustor 801 and the external heat producing source 100. For example, the external heat source 100 may be providing an insufficient amount of heat to supplement the primary combustor 801 (i.e., a positive heating value but not sufficiently positive to provide the necessary additive heating), and the secondary combustor 803 can be activated to pick up the additional heat requirement that is needed for the full operation of the power cycle. As another example, the external heat source 100 may be a process that itself requires a certain level of heat maintenance. For example, a solar heater may require supplemental heating during nighttime hours or long cold periods in order to retain a certain, minimum heat in the heat medium that is utilized. In such situations, the secondary combustor 803 can provide heat that can be delivered to the external heat source via the same process stream or a different process stream. This would be an example of a negative heating value from the external heat source 100 in that a circulating stream from the external heat source would have insufficient heat to add to the power cycle, and said stream would instead receive heat from the power cycle. Returning to FIG. 2, in one example arrangement, the power production system can be configured to operate with the primary combustor 801 in full combustion mode, and the external heat producing source 100 can be providing a stream 101 that has a sufficiently positive heating value to supplement the heating that is provided directly in the primary combustor 801. In this arrangement valves Vi, V2, and V3 can be closed so that the secondary combustor remains isolated from the power cycle, and no flows are passing through streams 208, 307, and 633. Valve V4 is open so that working fluid from stream 616 passes to stream 617 and is heated in EPHE1 804 before leaving in stream 618 to merge with steam 619 for passage into the primary combustor 801. Fuel in stream 304 and oxidant in stream 205 pass through open valves V5 and Ve, respectively, pass through streams 305 and 206, respectively, and are heated in EPHE1 before leaving in streams 306 and 207, respectively to enter the primary combustor 801. The working fluid stream 617, fuel stream 305, and oxidant stream 206 are all heated in EPHE1 804 by entry stream 101 received from the external heat source 100, which flows through EPHE1 804 and exits as exit stream 102 to pass back to the external heat source to be re-heated. This example mode of operation be useful, for example, in embodiments where fuel for combustion is readily available at a favorable cost, and the additive heating from the external heat source 101 is used to boost efficiency of the power cycle.

In one example embodiment, the power production system can be configured to operate with the external heat producing source 100 functioning as the primary or sole heat source (e.g., providing more than 50%, more than 75%, more than 90% or providing substantially all of the heat) for operation of the power cycle. In such configuration, the external heat source 100 can be providing a stream with a sufficiently positive heating value to give the full amount of necessary heating for operation of the power cycle or give a majority of the necessary heating. Fuel valve V5 and oxidant valve Ve can be controllably opened so that enough fuel and oxidant enter primary combustor 801 to provide any additional heating that supplements the heat coming from the external heat source. In arrangements where the external heat source is providing substantially 100% of the heating needed for the operation of the power cycle (i.e., in addition to heat recuperated in PCHE1 805 and/or PCHE2 806), fuel valve V5 and oxidant valve Ve can be completely closed. Likewise, valves Vi, V2, and V3 can be closed so that the secondary combustor remains isolated from the power cycle. Working fluid valve V4 can be open so that substantially only working fluid in line 617 and the entry fluid in line 101 from the external heat source 100 are passing through EPHE1 804, and the working fluid is heated by the fluid in entry stream 101. Heated working fluid in stream 618 then passes to stream 619 for passage through primary combustor 801 and then stream 401 to the turbine 802 for expansion and power production. When operating according to such embodiments, a bypass line 619a may be utilized so that the heated working fluid passes directly to line 401 without passage through the combustor. It is understood that appropriate valves can be present in line 619 and line 619a so that flow of the working fluid can be properly routed depending upon the operating condition of the primary combustor 801. Likewise, since no combustion is being carried out in such embodiments, additional bypass lines and valves may be utilized. For example, the fluid in line 603 may be directed to bypass one or both of the water separator 807 and direct contact cooler 810 (see bypass line 603a) and thus directly link with line 605 or line 607 (see bypass line 603b) to flow into the compressor 811. It may still be useful, however, to configure the bypass line(s) so that a portion of the working fluid from stream 603 can be branched off for passage through line 630 and the additional downstream units, which are further discussed below.

In embodiments wherein the external heat source 100 is operational as the primary or sole heat source for the power cycle, it can be useful to provide supplemental working fluid into the power production cycle. It is expected during operation that some minor portion of the working fluid will be lost, and it is desirable to maintain a substantially constant volume flow of fluid through the cycle. Makeup working fluid can be provided directly through an inlet that is preferably at a low pressure point in the cycle (e.g., see line 621 upstream from compressor 811). This can be a stream directed from a pipeline or other source of the working fluid (e.g., a CO2 pipeline). When a material such as CO2 is used as the working fluid, makeup working fluid can be provided by operating primary combustor 801 and/or secondary combustor 803 at a nominal level wherein sufficient fuel is combusted for form the required content of CO2 even without providing a significant quantity of heating to the power cycle. Alternatively, a makeup combustor 910 may be present and can be operational to combust fuel with oxidant so as to form CO2 that can be delivered to the power cycle, such as directly through line 621.

In one example embodiment, the power production system can be configured to operate so that the secondary combustor 803 is a functioning part of the power cycle, and this can be advantageous when the external heat source 100 is not providing a sufficiently positive heating value to supplement the heating in the primary combustor 801. The secondary combustor preferably is functional for operation over a wide range of temperatures, which encompasses the same temperature ranges suitable for the primary combustor 801 and the ranges in which the external heat source 100 is expected to operate. In such embodiments, oxidant valve Vi, fuel valve V2, and working fluid valve V3 can be open so that oxidant in stream 205 passes to stream 208, fuel in stream 304 passes to stream 307, and working fluid in stream 616 passes to stream 633, and all of streams 208, 307, and 633 are passed through secondary combustor 803. Therein, the fuel in stream 307 is combusted with oxidant from stream 208 to form combustion products that mix with and heat the working fluid from stream 633, and a heated secondary combustor product stream exits through line 402 for passage through EPHE1 804. Now in stream 403, the secondary combustor product merges with working fluid from stream 618 in stream 619 for entry into the primary combustor. Valves V4, V5, and Ve can all be open for normal operation of the primary combustor 801 as already described above. Heat in stream 402 thus can supplement any heating value provided by entry stream 101 from the external heat source 100 in EPHE1. Alternatively, flow of the entry stream 101 may be stopped so that no heating fluid is being received from the external heat source 100 while the secondary combustor 803 is operable and providing the additive heating.

In one example embodiment, the power production system can be configured to operate so that the secondary combustor 803 is a functioning part of the power cycle and is actually providing heat that can be delivered to the external heat source. The power cycle can be operable as just described above where valves V4, V5, and Ve can all be open for normal operation of the primary combustor 801, and valves Vi, V2, and V3 can all be open so that the secondary combustor 803 is an operable part of the power cycle. The secondary combustor 803 can be configured to produce a sufficient amount of heating so that heat from the secondary combustor product from stream 402 can be transferred to the entry stream 101 from the external heat source 100 in EPHE1. As such, entry stream 101 may be a low temperature stream (i.e., at a temperature lower than the temperature of the secondary combustor product stream 402), and the exit stream 102 may be a high temperature stream (i.e., at a temperature approaching the temperature of the secondary combustor product stream 402). The heat in exit stream 102 may be used to drive an external process that is carried out by the external heat source or to supplement heat that is otherwise being produced by the external heat source but in an insufficient amount to fully drive the underlying process.

While the external heat source 100 can provide heat in EPHE1 804 as discussed in the example embodiments above, the external heat source 100 can also provide heating at other points in the power cycle. For example, as discussed above, a portion of the working fluid in stream 604 leaving the water separator 807 can be branched into stream 630 for compression and passage back to PCHE1. The external heat source 100 can be used to heat the working fluid in stream 630. Particularly, stream 630 can pass through a secondary external process heat exchange (EPHE2) unit to leave as working fluid stream 631, which has been heated by entry stream 103 that is cooled and leaves as exit stream 104 for return to the external heat source 100. Heated working fluid stream 631 can be compressed in compressor 809 to the necessary pressure for passage to the turbine 802 and then merges with the bulk portion of the working fluid in stream 614 to form working fluid stream 615. By this, the branch portion of the working fluid in stream 630 bypasses heating from PCHE2 806, but such heating is made up using heat from the external heat source 100 in EPHE2 808. Use of the branch passing through compressor 809 can be useful for adjusting the heating profile of the PCHE1 808 unit.

As a further example embodiment, heat from the external heat source 100 also can be used for boosting heating value provided by the recuperator heat exchanger(s). With reference to FIG. 2, an entry stream 105 from the external heat source 100 can be first passed through PCHE1 805, leave as intermediate stream 106, and then pass through PCHE2 806 and leave as exit stream 107 for return to the external heat source 100. Heat added to PCHE1 805 and/or PCHE2 806 in this manner can be in a temperature range of about 100°C to about 400°C and can be useful to improve efficiency of the power cycle so that the temperature of the recycled working fluid passing back to the primary combustor 801 close approaches (e.g., within about 50°C) the temperature of the turbine exhaust stream in line 601.

A control unit 900 is included in the power production system and can be use for controlling a number of components thereof. The control unit 900 particularly can enable switching of the power cycle between the different modes of operation described above. When an external process is utilized as an external heat source, the heat available therefrom may not be constant, may vary at specific periods of the day, or may be purposefully limited, such as during a maintenance phase. The control unit 900 thus can be configured to receive necessary inputs in order to execute commands and provide outputs that define the operation state of at least the primary combustor 801, the secondary combustor 803, and any valves present in the system. In an example embodiment, the control unit 900 may receive an input from a temperature sensor in any of entry lines 101, 103, and 105 and may open or close valves in said lines based upon a temperature of the flow stream in said lines being below a threshold value to provide necessary heating value. Said temperatures may also be used to control opening of valves Vi, V2, and V3 and beginning operation of the secondary combustor 803 to provide heating to the entry stream 101 in EPHE2 804. When the external heat source 100 enters a low heating value or negative heating value condition, the control unit 900 specifically may be used to bring the secondary combustor 803 online by opening valves Vi, V2, and V3 while valves V4, V5, and Ve remain open so that the primary combustor 801 provides heating for the power cycle, and the secondary combustor 803 provides heating to the external process at the external heat source 100. Once the external heat source 100 is operational for providing necessary heating to the power cycle, the control unit 900 may shut down the secondary combustor 803 and close valves Vi, V2, and V3 accordingly. Similar controls can be applied to open and close valves in any bypass lines, such as 619a, 603a, and 603b. For example, in embodiments where the external heat source 100 is providing all heat needed for the power cycle, the control unit may open a valve in bypass line 619a so that the primary combustor 801 is bypassed and/or may open valves in bypass lines 603a and 603b so that the water separator 807 and direct contact cooler 810 may be bypassed.

The terms “about” or “substantially” as used herein can indicate that certain recited values or conditions are intended to be read as encompassing the expressly recited value or condition and also values that are relatively close thereto or conditions that are recognized as being relatively close thereto. For example, unless otherwise indicated herein, a value of “about” a certain number or “substantially” a certain value can indicate the specific number or value as well as numbers or values that vary therefrom (+ or -) by 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less. Similarly, unless otherwise indicated herein, a condition that substantially exists can indicate the condition is met exactly as described or claimed or is within typical manufacturing tolerances or would appear to meet the required condition upon casual observation even if not perfectly meeting the required condition. In some embodiments, the values or conditions can be defined as being express and, as such, the term “about” or “substantially” (and thus the noted variances) can be excluded from the express value.

Many modifications and other embodiments of the presently disclosed subject matter will come to mind to one skilled in the art to which this subject matter pertains having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the present disclosure is not to be limited to the specific embodiments described herein and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

Claims

CLAIMS:

1. A method for power production, the method comprising: operating a power cycle so that a working fluid is compressed, heated in at least a primary power cycle heat exchange (PCHE1) unit, passed through a primary combustor for mixing with combustion products, expanded for power production, cooled in at least the PCHE1 unit, purified for removal of one or more of the combustion products, and recycled for compression; passing one or more streams of the power cycle through a primary external process heat exchange (EPHE1) unit that is operably connected to an external heat producing source; passing at least a first stream from the external heat producing source through the EPHE1 unit in a heat exchange relationship with one or more streams of the power cycle; and controlling flow of the one or more streams of the power cycle through the EPHE1 unit based upon a heating value of the at least a first stream from the external heat producing source.

2. The method of claim 1, wherein the external heat producing source is a nuclear reactor.

3. The method of claim 1, wherein the external heat producing source is a solar heater or an industrial process.

4. The method of claim 1, wherein the EPHE1 unit is arranged relative to the power cycle so that the one or more streams of the power cycle passing through the EPHE 1 unit are streams that are being heated for passage to the primary combustor.

5. The method of claim 4, wherein the one or more streams of the power cycle passing through the EPHE1 unit have been heated in the PCHE1 unit.

6. The method of claim 1, wherein the one or more streams of the power cycle passing through the EPHE1 unit comprise a stream of the working fluid.

7. The method of claim 1, wherein the one or more streams of the power cycle passing through the EPHE1 unit comprise one or both of a fuel stream and an oxidant stream.

8. The method of claim 1, wherein the heating value of the at least a first stream from the external heat producing source is a positive heating value, and wherein the at least a first stream from the external heat producing source and the one or more streams of the power cycle are passed through the EPHE1 unit so that heat from the at least a first stream from the external heat producing source is transferred to the one or more streams of the power cycle.

9. The method of claim 8, wherein the one or more streams of the power cycle comprise all of a fuel stream, an oxidant stream, and a stream of the working fluid.

10. The method of claim 1, wherein the power cycle includes a secondary combustor.

11. The method of claim 10, wherein the one or more streams of the power cycle passed through the EPHE1 unit comprises a stream of heated combustion products from the secondary combustor.

12. The method of claim 11, wherein the heating value of the at least a first stream from the external heat producing source is a negative heating value, and wherein the at least a first stream from the external heat producing source is passed through the EPHE1 so that heat from the stream of heated combustion products from the secondary combustor is transferred to the at least a first stream from the external heat producing source.

13. The method of claim 11, wherein the stream of heated combustion products from the secondary combustor is controllably passed to the EPHE1 unit based upon the heating value of the at least a first stream from the external heat producing source.

14. The method of claim 1, further comprising passing a second stream from the external heat producing source through a secondary external process heat exchange (EPHE2) unit in a heat exchange relationship with one or more streams of the power cycle.

15. The method of claim 14, wherein the one or more streams of the power cycle comprises a stream of the working fluid.

16. The method of claim 14, wherein the second stream from the EPHE2 unit is passed through at least the PCHE1 unit so as to transfer heat to the one or more streams of the power cycle in the PCHE1 unit.

17. The method of claim 1, wherein the working fluid comprises predominantly carbon dioxide.

18. A power production system comprising: a power cycle including a primary combustor, a power producing turbine, at least a primary power cycle heat exchange (PCHE1) unit, and at least one compression unit; a primary external process heat exchange (EPHE1) unit arranged upstream from the primary combustor and configured to transfer heat from an external process to one or more streams in the power cycle, the one or more streams being controllably deliverable to the EPHE1 unit; a secondary combustor arranged upstream from the EPHE1 unit and configured to provide a stream of heated combustion products, the secondary combustor being controllably openable to the EPHE1 unit and controllably isolatable from the power cycle.

19. The power production system of claim 18, further comprising a controller.

20. The power production system of claim 18, wherein the PCHE1 unit is a single heat exchanger comprising a plurality of sections operable at different temperature ranges or wherein the power cycle includes a secondary power cycle heat exchange (PCHE2) unit in an operable connection with the PCHE1 unit.

21. The power production cycle of clam 18, further comprising a secondary external process heat exchange (EPHE2) unit arranged upstream from the PCHE1 unit.