Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B1/00—Methods of steam generation characterised by form of heating method
  • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
  • F22B1/18—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines
  • F22B1/1807—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines using the exhaust gases of combustion engines
  • F22B1/1815—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being a hot gas, e.g. waste gas such as exhaust gas of internal-combustion engines using the exhaust gases of combustion engines using the exhaust gases of gas-turbines
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
  • F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
  • F01K23/06—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle
  • F01K23/10—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle with exhaust fluid of one cycle heating the fluid in another cycle
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
  • F01K25/00—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for
  • F01K25/08—Plants or engines characterised by use of special working fluids, not otherwise provided for; Plants operating in closed cycles and not otherwise provided for using special vapours
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B37/00—Component parts or details of steam boilers
  • F22B37/02—Component parts or details of steam boilers applicable to more than one kind or type of steam boiler
  • F22B37/10—Water tubes; Accessories therefor
  • F22B37/12—Forms of water tubes, e.g. of varying cross-section

Definitions

• the embodiments of the subject matter disclosed herein generally relate to power generation systems and more particularly to Organic Rankine Cycle (ORC) systems.
• ORC Organic Rankine Cycle
• Rankine cycles use a working fluid in a closed cycle to gather heat from a heating source or a hot reservoir by generating a hot gaseous stream that expands through a turbine to generate power.
• the expanded stream is condensed in a condenser by transferring the heat to a cold reservoir.
• the working fluid in a Rankine cycle follows a closed loop and is re-used constantly.
• a system for power generation using a Rankine cycle is shown in Figure 1. These systems for power generation can be described based on the power generated as primary power generation and secondary power generation systems. Additionally, secondary power generation systems tend to use the waste heat, e.g., hot exhaust gases, from the primary power generation system to improve overall system efficiency.
• the power generation using the Rankine cycle is traditionally used as a secondary power generation system.
• the power generation system 100 includes a heat exchanger 2, or in some cases a boiler, a turbine 4, a condenser 6 and a pump 8. Walking through this closed loop system, beginning with the heat exchanger 2, an external heat source 10, e.g., hot flue gases, heats the heat exchanger 2. This causes the received pressurized liquid medium 12 to turn into a pressurized vapor 14 which flows to the turbine/generator 4.
• the turbine 4 receives the pressurized vapor stream 14 and can generate power 16 by, for example, rotating a mechanical shaft (not shown) as the pressurized vapor 14 expands inside the turbine 4.
• the expanded lower pressure vapor stream 18 then enters a condenser 6 which condenses the expanded lower pressure vapor stream 18 into a lower pressure liquid stream 20.
• the lower pressure liquid stream 20 then enters a pump 8 which both generates the higher pressure liquid stream 12 and keeps the closed loop system flowing.
• the higher pressure liquid stream 12 then is pumped to the heat exchanger 2 to continue this process.
• ORC organic rankine cycle
• ORCs systems have been deployed as retrofits for small-scale and medium-scale gas turbines, to capture waste heat from the hot flue gas stream generated by an engine. These systems may generate up to an additional 20% power on top of the engine's baseline output, i.e., ORC systems are typically used in secondary power generation systems.
• This ORC working fluid is typically a hydrocarbon with a boiling temperature slightly above the International Organization for Standardization's baseline for atmospheric pressure.
• a currently used method for limiting the surface temperature of the heat exchanging surfaces in an evaporator which contains the ORC working fluids is to introduce an intermediate thermo-oil loop into the heat exchange system, i.e., to avoid the ORC liquid circulating through the exhaust stack of the gas turbine.
• the intermediate thermo-oil loop can be used between the hot flue gas and the vaporizable ORC fluid.
• the intermediate thermo-oil loop is used as an intermediate heat exchanger, i.e., heat is transferred from the hot flue gas to the oil, which is in its own closed loop system, and then from the oil to the ORC fluid using a separate heat exchanger. Separating the ORC fluid from direct exposure to the hot flue gas can protect the ORC fluid from degradation and decomposition. Additionally, while the oil used in the intermediate thermo-oil loop is flammable, this oil is generally less flammable than ORC
• thermal oil system takes additional physical space and can represent up to one quarter of the cost of an ORC system.
• a system for power generation using an Organic Rankine Cycle includes: a heat exchanger configured to be mounted inside an exhaust stack that guides hot flue gases and having an inlet and an outlet, the heat exchanger being configured to receive a liquid stream of a first fluid through the inlet and to generate a vapor stream of the first fluid and the heat exchanger is configured to include a double walled pipe, wherein the first fluid is disposed within an inner wall of the double walled pipe and a second fluid is disposed between the inner wall and an outer wall of the double walled pipe; an expander fluidly connected to the outlet of the heat exchanger and configured to expand the vapor stream of the first fluid, to generate power; a condenser fluidly connected to an outlet of the expander and configured to receive and condense an expanded vapor stream; and a pump fluidly connected to an outlet of the condenser and configured to receive the liquid stream of the first fluid, to pressurize the liquid stream of the first fluid and
• ORC Organic Rankine Cycle
• the method includes: transferring heat from a flue gas in an exhaust stack through a first wall of a heat exchanger 303
• the heat exchanger includes: a first pipe configured to receive a heat pipe fluid and further includes a second pipe, wherein a volume between the first pipe and the second pipe is hermetically sealed and is divided into compartments which are bound by an inner wall of the first pipe, an outer wall of the second pipe and separating walls between the compartments; the second pipe configured to receive an Organic Rankine Cycle (ORC) fluid; and the separating walls configured to link the first pipe to the second pipe, the heat exchanger configured to receive heat from the hot flue gases and configured to receive a liquid stream of the ORC fluid through an inlet and to generate a vapor stream of the ORC fluid through an outlet.
• ORC Organic Rankine Cycle
• Figure 1 depicts a conventional Rankine Cycle
• Figure 2 illustrates a heat exchanger which uses an organic fluid disposed within an exhaust stack according to exemplary embodiments
• Figure 3 shows a double walled pipe according to exemplary
• Figure 4 illustrates a partial cross section of the double walled pipe of
• Figure 5 shows a view of the double walled pipe with toroid compartments according to exemplary embodiments
• Figure 6 is a flowchart for a method for heat exchange according to exemplary embodiments
• Figure 7 illustrates exhaust paths according to exemplary embodiments.
• Figures 8 shows a flowchart for a method for vaporizing an ORC fluid according to exemplary embodiments.
• a Rankine cycle can be used in secondary power generation systems to use some of the wasted energy from the hot exhaust gases of the primary power generation systems.
• a primary system produces the bulk of the energy while also wasting energy.
• a secondary system can be used to capture a portion of the wasted energy from the primary system.
• An Organic Rankine Cycle (ORC) can be used in these power generation systems depending upon system temperatures and other specifics of the power generation systems. According to exemplary embodiments, ORCs can be used for small to mid-sized gas turbine power generation systems to capture additional heat/energy from the hot flue gas which may be released directly to the atmosphere.
• heat can be introduced into the cycle through a heat exchanger 2 or some similar process, e.g., an evaporator or boiler.
• Previous ORC systems have used an intermediate thermo-oil loop system to transfer heat from the hot flue gases to the ORC working fluid. In these cases the ORC system is 303
• thermo-oil loop removes the need for thermo-oil loop and locates the heat exchanger for the ORC system in the exhaust stack in contact with the hot flue gases, e.g., temperatures between 350 degrees Celsius and 600 degrees Celsius, which can be found in electrical power generation systems.
• temperatures and temperature ranges may be used.
• heat exchanging coils 202 can wind in a serpentine manner through a stack 204, or equivalent waste heat exhaust structure, as shown in Figure 2.
• the pressurized liquid ORC fluid 12 enters from an inlet side into the heat exchanger 200.
• This working fluid may enter into the cooler side of the heat exchanger 200 and travel through the heat exchanging coils 202 and exit from the heat exchanger 200 from the hotter side, e.g., closer to the heat source, as a pressurized vapor ORC fluid 14 at the outlet side.
• the coils shown closer to arrow 206 are closer to the heat source (not shown).
• Heat sources for ORCs include, but are not limited to, exhaust gases from combustion systems (power plants or industrial processes), hot liquid or gaseous streams from industrial processes, geothermal and solar thermal sources.
• a double walled pipe (which can also be considered as a pipe within a pipe) can be used as the heat exchanging coils 202 in the heat exchanger 200 of the ORC system to protect the ORC working fluid from decomposition and degradation.
• ORC fluid can degrade and/or decompose at localized temperatures of 300° C or possibly average temperatures of 240° C in larger volumes of the ORC fluid. This operating range is generally applicable to whichever hydrocarbon is used as the ORC fluid except for aromatic hydrocarbons, e.g., thiophene, which may be able to operate at higher temperatures.
• the heat exchanging coil 202 of Figure 2 can include a double walled pipe 300 with an outer wall 302 and an inner wall 306.
• a heat pipe fluid can be placed in the outer section 304 between the two walls and the ORC working medium is located in the inner section 308, i.e., the volume constrained by the inner wall 306.
• This exemplary arrangement can allow a high temperature flue gas 206, e.g., in the range of 350 - 600 degrees Celsius, to transfer heat to the heat pipe fluid in outer section 304 through the outer wall 302.
• the heat pipe fluid then transfers heat to the ORC fluid in the inner section 308 through inner wall 306.
• this heat exchange between the heat pipe fluid to the ORC fluid can be performed such that the temperature used, and potential temperature fluctuations, can be controlled such that the temperature of the ORC fluid stays below a degradation temperature while still allowing the ORC fluid to vaporize before leaving the heat exchanger 200.
• the heat pipe fluid selected needs to be, at the desired pressure, able to use the 303
• the heat pipe fluid vapor then circulates toward the inner wall 306, where the heat pipe fluid vapor is cooled, e.g., releases heat energy, and condenses into a heat pipe fluid liquid and circulates back toward the outer wall 302.
• the temperature of the heat pipe fluid remains relatively constant as the heat pipe fluid is capable to absorb large amounts of heat from the hot flue gases without increasing its temperature, due to the liquid to gas phase change.
• the heat pipe fluid may be hermetically sealed within section 304.
• the heat pipe fluid may be selected from various mediums which have some, or possibly all, of the following characteristics: being less flammable than the ORC fluid, capable to undergo a phase change to transfer heat at the desired
• a heat pipe fluid may include water, sodium, thermal oil and silicon-based thermal oil.
• the ORC fluid may be a hydrocarbon, 303
• FIG. 4 shows a partial cross section of the double walled pipe 300 between the outer wall 302 and the inner wall 306.
• Figure 5 shows a view of the double walled pipe 300 with a plurality of toroid shaped compartments 406.
• the outer section 304 (extending the length of the outer pipe) located between the outer wall 302 and the inner wall 306 can be further compartmentalized with a plurality of compartments 406.
• These compartments 406 contain the heat pipe fluid, e.g., water or sodium, in liquid and gaseous phases.
• the heat pipe fluid can be under a higher pressure than the ORC working fluid in the inner area 308. Pressures used in both the piping section containing the ORC fluid and the piping section containing the heat pipe fluid, which can be at different pressures, can be established to set the desired boiling point of the respective fluid. Additionally, spacers 404 can be used to assist in creating the compartments 406 as well as providing structural support for the heat exchanging coil 202. These compartments 406 may be, for example, toroids in shape, i.e., the spacers 404 can be circular spacer between the inner and outer pipe.
• the piping used in the heat exchanger can be of varying sizes and shapes to promote the desired heat exchange and to allow for/assist in the desired self circulation of the heat pipe fluid, however the diameter of the outer wall 302 is larger than the diameter of the 303
• the diameter of the inner most pipe may be in the range of about 12.77 mm - 25.4 mm
• the diameter of the outer pipe may be in the range of 25.4 mm - 50.8 mm.
• the spacers 404 which connect/support the inner wall 306 to the outer wall 302 may have a length in the range of 5 mm - 25.4 mm with a potential separation of up to 152.4 mm between each spacer.
• other dimensions can be used.
• a capillary structure e.g., a wire mesh capillary structure
• the capillary tubes are configured to increase the heat pipe fluid in its liquid phase brought into contact with the heated surface.
• compartment 406 is bounded by spacers 404, inner wall 306 and outer wall 302. Additionally, some of the spacers 404 may be configured to allow fluid communication between selected adjacent compartments.
• Heat exchange from the hot exhaust gas to the ORC fluid can be realized through a series of exemplary steps as shown in the flowchart of Figure 6. Initially convection from the hot exhaust gas to the heat exchanger outer wall 302 occurs in step 602. Then a phase change, e.g., vaporization, of the heat pipe fluid occurs on the inner surface of the outer wall 302 in step 604. The vaporized heat pipe fluid flows toward the inner wall 306 in step 606. Condensation of the heat pipe fluid occurs on the outer surface of the inner wall 306 in step 608. On the ORC fluid side, convection (if preheating or superheating) or a phase change (if boiling) of the ORC fluid occurs on or near the inner wall 306 in step 610. Continuous back 303
• compartment 404 in part via capillaries on the heat exchanging surfaces and the spacers 404
• evaporation and condensation of the heat pipe fluid does not need to occur, instead buoyancy-driven self circulation can occur without the driving mechanisms of evaporation and condensation, as thermal differences within the compartment can drive self circulation which still results in the desired heat exchange occurring with the ORC fluid.
• the double walled pipe configuration can improve the safety in power generation systems.
• the heat pipe fluid in the outer section is at a higher pressure than the ORC fluid in the inner section.
• Sensors can be used to monitor a pressure of the heat pipe fluid such that if a leak were to occur it could be detected and allow the system to be shutdown. Similarly, if a leak were to occur that allowed the heat pipe fluid to enter the exhaust stack, the pressure loss could be detected and again allow for a shutdown of the system.
• heat pipe fluids can be chosen which are inflammable or significantly less flammable than the ORC fluid.
• this double walled pipe can be used in various heat exchanger designs, such as, for example, shell, tube 303
• an ORC system in lower temperature applications, can be placed in the path of the exhaust gases without the use of a double walled pipe. In this case care is to be taken to avoid allowing the ORC fluid to leak into the path of the exhaust gases. However, it is envisioned that low level leakage may occur which is difficult to detect. This low level leakage (very low rate leakage of the ORC fluid) can be of a concern when the system is not in operation for extended periods of time.
• the hot exhaust gas follows a path from the heat source through over the heat exchanger coils 702 and out an exhaust stack 714 as shown by directional arrow 704.
• a baffle 706 is placed in a closed position A such that the only flow path available is the flow path shown by directional arrow 704.
• the exhaust follows the path designated by directional arrow 708, 303
• the baffle 706 is place in an open position B such that the only flow path available is the flow path shown by directional arrow 708. As described above, if the power generation system is shut down for an extended period of time, and a leak of ORC fluids has occurred that was too small to be detected while the unit was operating, a flammable concentration of ORC fluid vapor may accumulate slowly over time within the exhaust stack.
• baffle 710 is opened which allows air to enter the stack at this point and flush the area around the heat exchanger coils 702 such that no appreciable amount of combustible ORC fluids can stay in the area.
• the path of the flushing air is shown by the directional arrow path 712. Note that during normal operations baffle 710 is in a closed position C.
• various circulating methods can be used to introduce this air into the stack, e.g., fans.
• the controls for opening and closing the baffles 706 and 710 may be interlinked or not as desired.
• the heat exchanger coils 702 may be of the double walled pipe design described above.
• a method for vaporizing an ORC fluid is shown in the flowchart of Figure 8. Initially a method for vaporizing an ORC fluid in a power generation system includes:

Landscapes

• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Sustainable Development (AREA)
• Sustainable Energy (AREA)
• Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)
• Engine Equipment That Uses Special Cycles (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=43922671

Family Applications (1)

Country Status (11)

Families Citing this family (12)

Family Cites Families (13)

• 2009
  • 2009-10-30 US US12/609,348 patent/US20110100009A1/en not_active Abandoned
• 2010
  • 2010-10-27 CN CN2010800600551A patent/CN103228912A/zh active Pending
  • 2010-10-27 MX MX2012005081A patent/MX2012005081A/es unknown
  • 2010-10-27 WO PCT/EP2010/066282 patent/WO2011051353A2/en active Application Filing
  • 2010-10-27 PE PE2012000599A patent/PE20130026A1/es not_active Application Discontinuation
  • 2010-10-27 EP EP10770842.2A patent/EP2780558A2/en not_active Withdrawn
  • 2010-10-27 BR BR112012010150A patent/BR112012010150A2/pt not_active IP Right Cessation
  • 2010-10-27 CA CA2779074A patent/CA2779074A1/en not_active Abandoned
  • 2010-10-27 AU AU2010311522A patent/AU2010311522A1/en not_active Abandoned
  • 2010-10-27 RU RU2012116621/06A patent/RU2012116621A/ru not_active Application Discontinuation
• 2012
  • 2012-04-27 CL CL2012001098A patent/CL2012001098A1/es unknown

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events