Classifications

• • 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
  • F01K23/04—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 condensation heat from 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
  • F01K25/10—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 the vapours being cold, e.g. ammonia, carbon dioxide, ether
  • F01K25/103—Carbon dioxide
• • 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
  • F01K25/10—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 the vapours being cold, e.g. ammonia, carbon dioxide, ether
  • F01K25/106—Ammonia
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B35/00—Control systems for steam boilers
  • F22B35/06—Control systems for steam boilers for steam boilers of forced-flow type
  • F22B35/08—Control systems for steam boilers for steam boilers of forced-flow type of forced-circulation type
  • F22B35/083—Control systems for steam boilers for steam boilers of forced-flow type of forced-circulation type without drum, i.e. without hot water storage in the boiler
  • F22B35/086—Control systems for steam boilers for steam boilers of forced-flow type of forced-circulation type without drum, i.e. without hot water storage in the boiler operating at critical or supercritical pressure

Definitions

• the present invention concerns a system and method for waste heat energy recovery or waste heat energy utilization .
• waste heat is contained in the flue or exhaust gases of various industrial processes and the exhaust gases of different drives and engines and the net efficiency values in the discussion below are based on waste heat utilization from flue/exhaust gases. This is as distinct from waste heat utilization in solid bodies, such as solar collectors or some other high temperature solid structures, which may produce significantly higher values of net efficiency.
• Waste heat can be utilized by turbine-generator systems which employ thermodynamic methods, such as the Rankine cycle, to convert heat into work.
• this method is steam-based with the waste heat being used to raise steam in a boiler to drive a turbine.
• a key short-coming of a steam-based Rankine cycle is its high temperature requirement; that is, it usually requires a relatively high-temperature waste heat stream (e.g. 300°C or higher) or a very large overall heat content.
• the complexity of boiling water at multiple pressures/temperatures to capture heat energy at multiple temperature levels as the heat source stream cools is costly.
• a steam-based Rankine cycle is not a practical option for streams of low flow rate and/or low temperature.
• the organic Rankine cycle addresses short-comings of a steam-based Rankine cycle by replacing water with a lower-boiling-point fluid, such as a light hydrocarbon like propane or butane, or a HCFC fluid (e.g. R245fa) .
• a lower-boiling-point fluid such as a light hydrocarbon like propane or butane
• a HCFC fluid e.g. R245fa
• the boiling heat transfer restrictions remain, however, and new issues such as thermal instability, toxicity or flammability of the fluid arise.
• ORC organic Rankine cycle
• widely implementing the organic Rankine cycle (ORC) technology does not permit a utilization of all the waste heat potential due to the limited thermal stability of the organic fluid, which affects thermal efficiency of ORC systems when the waste heat source temperature exceeds 250°-300°C.
• the total net efficiency of existing ORC units does not exceed a value of about 10%, such that up to 90% of the thermal energy is still wasted to the atmosphere.
• Supercritical carbon-dioxide (S-CO2) waste heat utilization technology has been used to address some of these issues.
• the supercritical state of CO2 provides improved thermal coupling with multiple heat sources and allows for development of more effective (up to 20% net efficiency) and very compact units compared with ORC systems for a variety of applications.
• Such S-CO2 systems often require very complex system layouts and unique heat transfer equipment, however, which lead to high capital costs and also technical difficulties. Examples ' of such known systems for waste heat recovery and utilization are described in the patent publications WO2011/119650A2, WO2012/074905A2, WO2012/074911A2, and WO2012/074940A2.
• an object of the present invention is to provide a new and improved system and method for utilizing and/or recovering waste heat energy from a waste heat source, such as flue gases or exhaust gases.
• the invention provides a system for recovering and/or utilizing waste heat energy from a waste heat source, comprising:
• a first heat engine having a first working fluid, such as carbon-dioxide (C0 2 ) , the first heat engine configured and arranged to transfer heat from the waste heat source to the first working fluid, and
• a first working fluid such as carbon-dioxide (C0 2 )
• a second heat engine especially an organic Rankine cycle (ORC) heat engine, having a second working fluid, the second heat engine configured and arranged for transfer of heat from the first working fluid to the second working fluid, especially for cooling the first working fluid after expansion thereof in a turbine of the first heat engine.
• ORC organic Rankine cycle
• the present invention may provide a new system of combined supercritical carbon-dioxide (S-C0 2 ) (first cycle) and ORC (second cycle) waste heat recovery or utilization.
• the layout of the system may include a single waste heat exchanger and two turbines with respective coolers (heat sinks) and respective pumps/compressors for the first (S-C0 2 ) cycle and the second (ORC) cycle.
• the invention thus provides a layout which allows high net efficiency (e.g. of about 20%) of waste heat utilization from flue gases with a single waste heat exchanger while avoiding complex known S-C0 2 system layouts that require expensive recuperators for supercritical carbon-dioxide.
• the first heat engine typically defines a first thermodynamic circuit for circulation of the first working fluid.
• the first heat engine includes: a first heat exchanger arranged in the first circuit and configured to transfer heat from the waste heat source to the first working fluid, and a second heat exchanger in the first circuit for cooling the first working fluid after an expansion thereof in a turbine of the first heat engine.
• the second heat exchanger is configured and arranged to transfer residual heat from the first working fluid to the second working fluid in the second heat engine.
• only the first heat engine obtains heat energy directly from the waste heat exchanger. Heat energy transferred to the second heat engine is non- utilized heat from the first circuit.
• first cycle cooler/second cycle heater The transfer of heat energy transfer between the two heat ' engines of this combined cycle system is thus performed in a "first cycle cooler/second cycle heater” device which interfaces or joins the two circuits of the combined cycle.
• a joint “first (S-CO 2 ) cycle cooler/second (ORC) cycle heater” contributes to heat transfer equipment costs optimization.
• the "first (S-CO 2 ) cycle cooler/second (ORC) cycle heater” may be represented by a one-piece recuperator in the case where the second (ORC) cycle is operating at supercritical parameters or it may comprise two parts (e.g. preheater and evaporator) for a subcritical second (ORC) cycle.
• the second heat engine includes a second turbine for expansion of the second working fluid at a position in the second circuit following or downstream of the second heat exchanger. This second turbine converts the heat energy of the second working fluid into work.
• the second heat engine optionally includes a by-pass conduit or path in the second circuit for by-passing the second turbine.
• the second heat engine also -includes a third heat exchanger for cooling the second working fluid after expansion thereof in the second turbine.
• the second heat engine includes a fourth heat exchanger which is configured as a recuperator for recuperating heat energy from the second working fluid after an expansion thereof in the second turbine.
• the fourth heat exchanger is to arranged to transfer heat to the second working fluid at a position in the second circuit adjacent to and/or upstream of the second heat exchanger .
• the first heat engine includes a fifth heat exchanger for further cooling the first working fluid after expansion thereof in the first turbine, wherein the fifth heat exchanger is arranged or located following or downstream of the second heat exchanger .
• the invention provides a waste heat utilization system, comprising:
• a supercritical carbon-dioxide heat engine having carbon dioxide (C0 2 ) as working fluid, the first heat engine having a first heat exchanger for transferring heat from a waste heat source to the carbon-dioxide and a second heat exchanger for cooling the carbon-dioxide after expansion thereof in a first turbine; and
• an organic Rankine cycle (ORC) heat engine having a second working fluid, wherein the second heat exchanger is configured and arranged to transfer heat from the carbon-dioxide (C0 2 ) working fluid to the second working fluid.
• ORC organic Rankine cycle
• the present invention provides a method of recovering and/or utilizing waste heat energy from a waste heat source, comprising:
• first heat engine having a first working fluid, especially carbon-dioxide, and defining a circuit for circulation of the first working
• a second heat engine especially an organic Rankine cycle (ORC) heat engine, having a second working fluid and defining a second circuit for circulation of the second working fluid,
• ORC organic Rankine cycle
• the step of transferring heat from the first working fluid in the first heat engine to the second working fluid in the second heat engine will typically comprise both cooling the first working fluid (i.e. after thermal expansion thereof in a turbine of the first heat engine) and heating the second working fluid in the second heat engine.
• the method may additionally comprise the step of further cooling the first working fluid after the step of transferring heat from, the first working fluid to the second working fluid.
• the second heat engine includes a second turbine for expansion of the second working fluid at a position in the second circuit following or downstream of the second heat exchanger.
• the method . of the invention preferably further includes cooling the second working fluid in the second heat engine after thermally expanding same in a second turbine.
• the method may include directing the second working fluid to by-pass the second turbine of the second heat engine, e.g. via a by-pass conduit or path in the second circuit.
• the secondary ORC cycle can be "turned off” using an ORC turbine bypass valve.
• the second circuit may operate as a simple cooler of the primary S-C0 2 cycle, thereby providing flexible power management to meet consumer requirements and respond to variations in the waste heat source and environmental parameters .
• the method further comprises recuperating heat from the second working fluid after expansion thereof in the second turbine, especially by heat transfer to the second working fluid at a position in the second circuit adjacent to and/or upstream of the second heat exchanger.
• FIG. 1 is a schematic illustration of a waste heat recovery system according to one preferred embodiment
• Fig. 2 is a schematic illustration of a waste heat recovery system according to another preferred embodiment
• Fig. 3 is a flow diagram which schematically illustrates a method according to a preferred embodiment .
• the heat source S may be a waste heat stream, such as gas turbine exhaust, process stream exhaust, or other combustion product exhaust stream, including furnace or boiler exhaust streams.
• the thermodynamic system 1 may be configured to transform the waste heat into electricity for a range of different applications including but not limited to bottom cycling in gas turbines, diesel engine generator sets, industrial waste heat recovery (e.g. in manufacturing plants, refineries, compression stations) , and hybrid alternatives to internal combustion engines.
• the heat source S could derive thermal energy from renewable sources of thermal energy such as, but not limited to, solar thermal and geothermal sources.
• the system 1 comprises a first heat engine HI and a second heat engine H2, each of which defines a respective first and second thermodynamic cycle or circuit A, B for an associated first and second working fluid Fl, F2.
• Each of the first and second heat engines HI, H2 is used to convert thermal energy to work via thermal expansion of the respective first and second working fluid Fl, F2.
• the thermodynamic system 1 comprises a first heat engine HI having a working fluid circuit A in thermal communication with a waste heat source S via a first heat exchanger El. While it will be appreciated that any number of heat exchanger devices may be utilized in conjunction with one or more waste heat sources, in this exemplary embodiment the first heat exchanger El is a single waste heat exchanger.
• the first heat exchanger El may include multiple stages of a combined waste heat exchanger. While the waste heat source S may be a fluid stream of a high temperature source itself, in other exemplary embodiments the waste heat source S may be a thermal fluid in contact with the high temperature source. The thermal fluid may thus deliver the thermal energy to the waste heat exchanger El to transfer the energy to the working fluid Fl in the first circuit A.
• the first or waste heat exchanger El serves as a high temperature, or relatively higher temperature, heat exchanger adapted to receive a flow or stream of the waste heat source S.
• the initial temperature of the waste heat source S entering the system 1 may range from about 200°C to greater than about 700°C.
• the stream of the waste heat source S may have a temperature of about 500 °C or higher.
• operative temperatures and pressures and flow rates are given by way of example and are not in any way to be considered as limiting the scope of the disclosure.
• the working fluid Fl circulated in the first circuit A of the first heat engine HI is carbon dioxide (CO2) . Carbon dioxide as a working fluid for power generating cycles has many advantages.
• C0 2 is a neutral working fluid that is non-toxic, non-flammable, low cost, readily available, and has no need of recycling. Due in part to its relative high working pressure, a C0 2 system can be built that is much more compact than systems using other working fluids. The high density and volumetric heat capacity of C0 2 with respect to other working fluids makes it more "energy dense” meaning that the size of all system components can be considerably reduced without losing performance.
• carbon dioxide as used herein is not intended to be limited to C0 2 of any particular type, purity, or grade. In an exemplary embodiment, for example, an industrial grade C0 2 may be used without departing from the scope of this disclosure .
• the carbon dioxide (C0 2 ) first working fluid Fl circulated in the first .
• circuit A of the first heat engine HI is delivered in a pressurized state to the waste heat exchanger El via a first pump or compressor PI which is arranged in the first circuit A.
• the C0 2 first working fluid Fl is heated in the waste heat exchanger El by thermal contact with the waste heat source S.
• the compressed and heated C0 2 then undergoes an expansion in a first turbine Tl which converts a portion of the thermal energy in the working fluid Fl drawn from the waste heat source S into mechanical work.
• a first generator Gl operably coupled to the first turbine Tl may then transform that mechanical work into electrical energy .
• a second heat exchanger E2 Downstream of the first turbine Tl in the circuit A of the first heat engine HI, a second heat exchanger E2 is provided for cooling the CO2 working fluid Fl after its expansion in the turbine Tl. And this second heat exchanger E2 provides an interface with the second heat engine H2.
• the second heat engine H2 defines a second thermodynamic cycle or circuit B, specifically an organic Rankine cycle (ORC) , in which a second working fluid F2, such as a light hydrocarbon (e.g. propane or butane, or a HCFC fluid) circulates.
• ORC organic Rankine cycle
• the second heat exchanger E2 is effectively arranged in both the first circuit A and the second circuit B and is adapted or configured to transfer heat energy remaining in the carbon dioxide working fluid Fl after its expansion in turbine .
• the C0 2 working fluid Fl may only have a temperature in the range of 70°C to 250°C, and preferably 100°C to 200°C, on entry to the second heat exchanger E2, the relatively low boiling temperature of the second working fluid F2 in the ORC heat engine H2 still enables that heat energy to be recovered very effectively.
• the first working fluid Fl completes the first circuit A by returning to the first pump or compressor PI to again be pressurized downstream of the waste heat exchanger El.
• the ORC working fluid F2 circulated in the second circuit B of the second heat engine H2 is delivered in a pressurized state to the second heat exchanger E2 via a second pump or compressor P2 arranged in the second circuit B.
• the second working fluid F2 is heated by thermal contact with the first working fluid Fl in the second heat exchanger E2.
• the compressed and heated ORC working fluid F2 then undergoes an expansion in a second turbine T2 which converts a portion of the thermal energy in the second working fluid F2 into work.
• a second generator G2 which is operably coupled to the second turbine T2 may transform that work into electrical energy.
• a third heat exchanger E3 is provided as a cooler in the second (ORC) circuit B for cooling the ORC working fluid F2.
• the third heat exchanger E3 may be fluidly connected with a heat sink S2, optionally including a forced convection device (e.g. fan) or a cooling tower arrangement.
• a forced convection device e.g. fan
• the second working fluid F2 is cooled prior to returning in the ORC circuit B to be pressurized again via the second pump or compressor P2 downstream of the second heat exchanger E2.
• the second circuit B includes a bypass path or conduit BP with by-pass valve V arranged in parallel with the path through the second turbine T2.
• This by-pass path BP enables the turbine T2 of the ORC heat engine H2 to be by-passed and effectively deactivated via the by-pass valve V.
• the second circuit B may operate as a simple cooling circuit form the primary S-CO2 circuit A, thereby allowing flexible power management to meet consumer requirements and to respond to variation in the waste heat source S and/or to environmental parameters.
• the preferred embodiment illustrated in Fig. 1 thus provides a simple layout of a combined S-C0 2 and ORC system 1 which allows for flexible operation during waste heat recovery and utilization with high efficiency.
• the heat engine layout in the system 1 of Fig. 1 has at least two continuously arranged non-regenerative cycles A, B with single waste heat exchanger El and internal heat transfer to a secondary ORC cycle in the cooler of the primary S-C0 2 cycle having high net efficiency of the combined system (e.g. up to 20%) comparable with much more complex S-C0 2 prior art systems.
• the arrangement uses residual heat in the second fluid F2 after its expansion in the turbine to pre-heat the second fluid F2 at a later or downstream position in the second circuit B adjacent to the second heat exchanger E2.
• the recuperator E4 it is possible to increase an internal thermal efficiency of the second ORC heat engine H2 by adding the recuperator E4 to the system layout.
• the embodiment of the system 1 in drawing Fig. 2 differs from Fig. 1 in that the first heat engine HI includes another (fifth) heat exchanger E5 fluidly connected to a heat sink SI for further cooling the first working fluid Fl after expansion in the first turbine Tl.
• the additional heat exchanger or cooler E5 is desirable in the first (S-C0 2 ) circuit A in this case to provide the required temperature at the inlet of the first pump/compressor PI in order to keep a reasonable value of compression work.
• the embodiment of the system 1 in -Fig. 2 is more complicated than the embodiment of Fig. 1 and requires more heat transfer equipment, it has a higher overall efficiency, offers more flexibility in control, and can be particularly suitable for some applications.
• Fig. 3 of the drawings a flow diagram is shown that schematically illustrates the steps in a method of recovering and/or utilizing waste heat according to the preferred embodiments of the invention described above with respect to Figs. 1 and 2.
• the first box I of Fig. 3 represents the step of providing a supercritical C0 2 first heat engine HI having a carbon-dioxide (C0 2 ) as the first working fluid Fl .
• the second box II then represents the step of providing an organic Rankine cycle (ORC) - second heat engine H2 having a light hydrocarbon as second working fluid F2.
• the third box III represents the step of transferring heat from a waste heat source S to the first working fluid Fl (e.g.
• the final box IV in Fig. 3 of the drawings represents the step of transferring heat from the first working fluid Fi in the first heat engine HI to the second working fluid F2 in the second heat engine H2 to cool the C0 2 working fluid Fl after expansion in a turbine Tl of the first heat engine HI.
• the working fluid in the first circuit A and/or the second circuit B may be a binary, ternary, or other working fluid blend.
• the working fluid blend or combination can be selected for the unique attributes possessed by the fluid combination within the heat recovery system, as described herein.
• one such fluid combination includes a liquid absorbent and C0 2 mixture enabling the combined fluid to be pumped in a liquid state to high pressure with less energy input than required to compress C0 2 .
• the working fluid may be a combination of C0 2 or supercritical carbon dioxide (S-C0 2 ) and one or more other miscible fluids or chemical compounds.
• the working fluid may be a combination of C0 2 and propane, or C0 2 and ammonia, without departing from the scope of the disclosure.
• working fluid is not intended to limit the state or phase of matter that the working fluid is in.
• the working fluid may be in a liquid phase, a gas phase, a supercritical phase, a subcritical state, or any other phase or state at any one or more points within the fluid cycle.
• the working fluid may be in a supercritical state over certain portions of a circuit or cycle (the "high pressure side"), and in a subcritical state over other portions of the circuit or cycle (the "low pressure side") .
• an entire circuit or cycle may be operated and controlled such that the working fluid is in a supercritical or subcritical state during circulation of the entire circuit.

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• 2014
  • 2014-09-08 ES ES14846776T patent/ES2848307T3/es active Active
  • 2014-09-08 EP EP14846776.4A patent/EP3167166B1/de active Active
  • 2014-09-08 WO PCT/RU2014/000666 patent/WO2016039655A1/en active Application Filing
  • 2014-09-08 RU RU2017111353A patent/RU2673959C2/ru active

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