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
  • 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
• • 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
  • F01K25/06—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 mixtures of different fluids
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B21/00—Water-tube boilers of vertical or steeply-inclined type, i.e. the water-tube sets being arranged vertically or substantially vertically
  • F22B21/22—Water-tube boilers of vertical or steeply-inclined type, i.e. the water-tube sets being arranged vertically or substantially vertically built-up from water tubes of form other than straight or substantially straight
  • F22B21/24—Water-tube boilers of vertical or steeply-inclined type, i.e. the water-tube sets being arranged vertically or substantially vertically built-up from water tubes of form other than straight or substantially straight bent in serpentine or sinuous form
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B27/00—Instantaneous or flash steam boilers
  • F22B27/04—Instantaneous or flash steam boilers built-up from water tubes
  • F22B27/06—Instantaneous or flash steam boilers built-up from water tubes bent in serpentine or sinuous form
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F22—STEAM GENERATION
  • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
  • F22B29/00—Steam boilers of forced-flow type
  • F22B29/06—Steam boilers of forced-flow type of once-through type, i.e. built-up from tubes receiving water at one end and delivering superheated steam at the other end of the tubes
  • F22B29/067—Steam boilers of forced-flow type of once-through type, i.e. built-up from tubes receiving water at one end and delivering superheated steam at the other end of the tubes operating at critical or supercritical pressure

Definitions

• the present invention relates to an apparatus and process for energy generation by organic Rankine cycle.
• thermodynamic Rankine cycle Apparatuses based on a thermodynamic Rankine cycle that convert thermal energy into mechanical and/or electric energy in a simple and reliable manner.
• ORC thermodynamic Rankine cycle
• working fluids of the organic type are preferably used in place of the traditional water/vapour system, because an organic fluid is suitable for conversion of heat sources at relatively low temperatures, generally between 100°C and 300°C, but also at higher temperatures, in a more efficient manner.
• the ORC conversion systems therefore have recently found increasingly wider applications in different sectors, such as in the geothermic field, in the industrial energy recovery, in apparatus for energy generation from biomasses and concentrated solar power (CSP) , in regasifiers, etc.
• CSP concentrated solar power
• An apparatus of known type for conversion of thermal energy by an organic Rankine cycle generally comprises: at least one heat exchanger exchanging heat between a high-temperature source and a working fluid, so as to heat, evaporate and superheat the working fluid; at least one turbine fed by the working fluid in the vapour phase coming out of the heat exchanger so as to carry out conversion of the thermal energy present in the working fluid into mechanical energy according to a Rankine cycle; at least one generator operatively connected to the turbine, in which the mechanical energy produced by the turbine is converted into electric energy; at least one condenser where the working fluid coming out of the turbine is condensed and sent to at least one pump; from the pump the working fluid is fed to the heat exchanger.
• ORC cycles and related apparatus are known in which evaporation is sub-critical.
• Reproduced in Figs. 2a and 2b is a typical Rankine cycle, obtained with an organic fluid, by sub-critical evaporation.
• the organic fluid is pumped by the pump from pressure of point 1 (pump suction) to pressure of point 2 (pump delivery) .
• point 3 the fluid is heated until point 3.
• heating contemplates the sensible-heat exchange with the working fluid in the liquid phase (from 2 to 2'), the latent-heat exchange between saturated liquid and saturated vapour (2' to 2"), the sensible-heat exchange with vapour (2" to 3) .
• point 3 has been reached, the fluid is introduced into the turbine.
• the exit conditions out of the turbine are represented by point 4.
• thermo exchanger of known apparatus therefore comprises a preheater, an evaporator and, optionally, a superheater. This because usually a big volume is required for the evaporator as generally the vapour of a fluid has a specific volume much bigger than the liquid. In addition, large exchange surfaces are required to make the vapour acquire sensible heat because the heat exchange coefficients of vapour are very low.
• Document WO 2011/012516 of known art illustrates a steam generator including tubes passing through the generator, from a water inlet to an superheated steam outlet, disposed horizontally in banks perpendicularly passed through by fumes.
• Document WO 2006/060253 of known art depicts a method and an apparatus using an organic Rankine cycle for generating energy on a sea boat.
• the method comprises the following steps: providing an ORC device including at least one evaporator, a turbogenerator, a condenser and a cooler feeding pump; arranging the evaporator within an exhaust duct of a power plant of a sea boat; setting the power plant in operation and selectively pumping cooler through the ORC device.
• the Applicant has aimed at improving known plants under different points of view, in particular in relation to optimisation of the apparatus intended for heat exchange, based on the nature of the organic fluid used.
• the Applicant has aimed at optimising the apparatus carrying out change of state, from liquid to vapour, of the organic liquid used.
• the invention relates to an ORC apparatus for energy generation through the organic Rankine cycle comprising: an organic working fluid; at least one heat exchanger to exchange heat between a high temperature source and the working fluid, so as to heat, evaporate and superheat said working fluid; at least one turbine fed with the working fluid in the vapour phase coming out of the heat exchanger, to carry out conversion of the thermal energy present in the working fluid into mechanical energy according to a Rankine cycle; at least one condenser where the working fluid coming out of said at least one turbine is condensed and sent to at least one pump; the working fluid being then fed to said at least one heat exchanger; characterised in that the heat exchanger is of the hairpin type and comprises at least one inner tube surrounded by an outer jacket; wherein the inner tube and outer jacket extend along at least two rectilinear stretches mutually connected by at least one curvilinear stretch.
• the present invention relates to an ORC process for energy generation through the organic Rankine cycle, comprising: i) feeding an organic working fluid through at least one heat exchanger to exchange heat between a high temperature source and said working fluid, so as to heat, evaporate and superheat said working fluid; ii) feeding the organic working fluid in the vapour phase coming out of the heat exchanger to at least one turbine to carry out conversion of the thermal energy present in the working fluid into mechanical energy according to a Rankine cycle; iii) feeding the organic working fluid coming out of said at least one turbine to at least one condenser where the working fluid is condensed; iv) sending the organic working fluid coming out of the condenser to said at least one heat exchanger (30); characterised in that step i) comprises: making the organic working fluid flow through a heat exchanger of the hairpin type comprising at least one inner tube surrounded by an outer jacket; wherein the inner tube and outer jacket extend along at least two rectilinear stretches mutually connected by at least one curviline
• hairpin it is intended a heat exchanger comprising one or more inner tubes inserted into an outer shell in which the inner tubes and outer shell extend along rectilinear stretches mutually connected by curvilinear stretches, like a street with "hairpin” bends.
• a first fluid flows in the inner tubes and a second fluid flows between the inner tubes and outer shell .
• said heat exchanger is able to carry out a state conversion from liquid to superheated vapour by a single apparatus, enabling the sizes of the whole plant and the industrial spaces dedicated thereto to be reduced .
• the hairpin heat exchanger further is of easy manufacture, limited cost and high reliability, it helps in making the whole plant cheaper and more reliable .
• the hairpin heat exchanger is able to stably carry out the preheating, once-through evaporation and superheating steps both at nominal load and at partial and transitory loads, for sub-critical ORC cycles and also super-critical ORC cycles.
• once-through evaporation it is intended a process in which physical distinction between preheater, evaporator and superheater is not provided, but the fluid goes on without a break from the starting liquid state to the final superheated vapour state.
• the plant can be used with different organic fluids and optimised as a function of the nature of same.
• the hairpin heat exchanger performing all the above mentioned exchange steps in a single tube without a break is consequently also self-draining during the turning-off step.
• the exchanger of the hairpin type is able to come into operation under dry-running conditions.
• dry-running conditions is understood as indicating the conditions according to which the only hot side of the exchanger is fed with the fluid.
• the configuration of the hairpin type further has the advantage of enabling heat exchange with great temperature differences between fluid entry and fluid exit, i.e. with high thermal lengths, the mechanical stress being low. In fact, using this geometry, it is possible to uncouple the expansion on the outer shell from the expansion of the tubes.
• the hairpin heat exchanger is able to withstand high temperature differences, even beyond 100-200°C, between the incoming heating fluid (Figs. 2b and 3b, point A) and outgoing heating fluid (Figs. 2b and 3b, point B) .
• the hairpin heat exchanger is of the countercurrent type, with or without buffers.
• the hairpin heat exchanger comprises an inner-tube bundle surrounded by a jacket.
• the hairpin heat exchanger comprises a single inner tube surrounded by a j acket .
• heating of the organic working fluid is of the super-critical type.
• heating of the organic working fluid is of the sub-critical type.
• the advantage of performing the cycle making a selection between sub-critical evaporation and supercritical evaporation resides in optimising the conversion performances from thermal energy into electric energy.
• the operating conditions optimising the thermal cycle performances such as pressure of the evaporation, depend on the fluid nature.
• Fig. 1 diagrammatically shows the base configuration of an apparatus for energy generation through the organic Rankine cycle according to the present invention
• Figs. 2a and 2b respectively show an organic Rankine cycle (ORC) with sub-critical evaporation and diagram T-Q reproducing the conversions taking place in the evaporator;
• Figs. 3a and 3b respectively depict an organic Rankine cycle (ORC) with super-critical evaporation according to the present invention and diagram T-Q reproducing the conversions taking place in the evaporator .
• ORC organic Rankine cycle
• ORC organic Rankine cycle
• Apparatus 10 comprises an endless circuit in which an organic working fluid flows which has a high or medium molecular weight.
• This fluid can preferably be selected from the group comprising hydrocarbons, fluorocarbons and siloxanes.
• Fig. 1 shows the circuit of the Rankine cycle in its base configuration and contemplates: a pump 20, a heat exchanger 30, a turbine 40 connected to an electric generator 50, a condenser 60.
• Pump 20 admits the organic working fluid from condenser 60 into the heat exchanger 30.
• the fluid In the heat exchanger 30 the fluid is heated, evaporated and then fed in the vapour phase to turbine 40, where conversion of the thermal energy present in the working fluid into mechanical energy and then into electrical energy through generator 50 is carried out.
• turbine 40 Downstream of turbine 40, in condenser 60, the working fluid is condensed and sent again to the heat exchanger through the pump 20.
• the heat exchanger 30 is of the "hairpin" type, i.e. it comprises a single inner tube or several inner tubes (tube bundle) 70 in which circulation of the organic working fluid occurs. Tubes 70 are inserted in an outer shell/skirt/j acket 80 and between the tubes 70 and shell 80 a hot fluid, diathermal oil for example, is caused to flow.
• the inner tubes 70 and outer shell 80 extend along rectilinear stretches 70b, 80b connected to each other by curvilinear stretches 70a, 80a.
• the hairpin heat exchanger 30 comprises a U-shaped inner tube 70 having two rectilinear stretches 70b connected by a curvilinear connecting stretch 70a.
• the inner tube 70 extends inside the outer shell 80 that will takes the same U-shaped configuration with two rectilinear stretches 80b connected by a curvilinear connecting stretch 80a.
• a first end 90 (inlet) of the inner tube 70 is in fluid connection, through suitable pipeline, with pump 20.
• a second end 100 (outlet) of the inner tube 70 is in fluid connection, through suitable pipeline, with turbine 40.
• the outer shell 80 In the vicinity of the second end 100 of the inner tube 70, the outer shell 80 has an inlet 110 for the hot fluid and, in the vicinity of the first end 90 of the inner tube 70, the outer shell 80 has an outlet 120 for said hot fluid.
• the organic working fluid flows from the first end 90 to the second end 100 while the hot fluid runs from inlet 110 to outlet 120, so that the heat exchanger 30 shown works in counter-current.
• the heat exchanger 30 can have a bundle of inner tubes 70 and/or work in the same current direction and/or have "n" rectilinear stretches connected by "n- 1" curvilinear stretches.
• the working fluid running in the hairpin heat exchanger 30 passes without a break from the initial liquid state to the final state of superheated vapour. Evaporation takes place in the absence of contact between liquid and vapour and therefore under the so-called "once- through" condition.
• apparatus 10 it is possible to carry out ORC processes either with sub- critical heating/evaporation or super-critical heating/evaporation .
• Figs. 2a and 2b describe the heat exchange during heating of the organic fluid in the more general case of sub-critical heating.
• the hot fluid diathermic oil, for example
• the organic fluid coming out of pump 20 at the described conditions from point 2 absorbs heat Q and is heated.
• the thermal profile followed by the fluid during heating is reproduced by curve 2-2'-2"-3 in Fig. 2a.
• Figs. 3a and 3b Reproduced in Figs. 3a and 3b is an organic Rankine cycle, ORC, with super-critical evaporation.
• ORC organic Rankine cycle
• the fluid is pumped by the pump until a pressure higher than the critical one.
• points 2' and 2" characterising the phase transition.
• the specific fluid volume changes continuously, without discontinuity from liquid to vapour. This is true at the nominal pressure, but it should be pointed out that during the starting and turning-off transients, crossing of the sub-critical region is unavoidable.
• the conversion of state from liquid to vapour in the single hairpin exchanger is able to exchange both the sensible heat necessary to bring the fluid to conditions of saturated liquid (preheating, PH, Fig. 2a, stretch 2-2'), and the latent heat for bringing the saturated liquid to the conditions of saturated vapour (evaporation, EV, Fig. 2a stretch 2 '-2"), as well as the sensible heat necessary for vapour superheating (superheating, SH, Fig. 2a stretch 2"-3) .
• the thermal energy exchanged in the apparatus with hairpin exchanger according to the invention enables the fluid to carry out conversions either involving sensible and latent heat (sub-critical conditions, see Fig. 2a) or involving heat exchange under super-critical conditions (see Fig . 3a) .

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Engine Equipment That Uses Special Cycles (AREA)

Priority Applications (4)

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Citations (11)

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• 2011
  • 2011-02-18 IT ITMI2011A000244A patent/IT1404174B1/it active
• 2012
  • 2012-01-27 ES ES12705427.8T patent/ES2628616T3/es active Active
  • 2012-01-27 EP EP12705427.8A patent/EP2676008B1/en not_active Revoked
  • 2012-01-27 WO PCT/IB2012/050385 patent/WO2012110905A1/en active Application Filing
  • 2012-01-27 PT PT127054278T patent/PT2676008T/pt unknown
  • 2012-01-27 HU HUE12705427A patent/HUE034699T2/hu unknown
  • 2012-01-27 US US13/984,770 patent/US20140026575A1/en not_active Abandoned
• 2017
  • 2017-06-20 HR HRP20170934TT patent/HRP20170934T1/hr unknown

Patent Citations (11)

Non-Patent Citations (5)

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