Apparatus and process for generation of energy by organic rankine cycle

Abstract

An apparatus ( 10 ) and a process for generation of energy through organic Rankine cycle (ORC) in which the heat exchanger ( 70 ) is of the hairpin type, so as to make the apparatus more flexible and optimise the cycle efficiency. The hairpin heat exchanger is able to stably carry out the preheating, once—through evaporation and superheating steps both at the nominal load and at the partial and transitory loads, either for sub-critical ORC cycles or for super-critical ORC cycles.

1 . An ORC apparatus for generation of energy by organic Rankine cycle, comprising:
 an organic working fluid;   at least one heat exchanger ( 30 ) to exchange heat between a high temperature source and the working fluid, so as to heat and evaporate said working fluid;   at least one turbine ( 40 ) fed with the vaporised working fluid coming out of the heat exchanger ( 30 ), to make a conversion of the thermal energy present in the working fluid into mechanical energy according to a Rankine cycle;   at least one condenser ( 60 ) where the working fluid coming out of said at least one turbine ( 40 ) is condensed and sent to at least one pump; the working fluid being then fed to said at least one heat exchanger ( 30 );   characterised in that the heat exchanger ( 30 ) is of the hairpin type and comprises at least one inner tube ( 70 ) surrounded by an outer shell or jacket ( 80 ); wherein the inner tube ( 70 ) and outer shell ( 80 ) extend along at least two rectilinear stretches ( 70   b ,  80   b ) mutually connected by at least one curvilinear stretch ( 70   a ,  80   a ).   
     
     
         2 . An apparatus as claimed in  claim 1 , wherein the hairpin heat exchanger ( 30 ) is of countercurrent type, with or without buffers. 
     
     
         3 . An apparatus as claimed in  claim 1 , wherein the hairpin heat exchanger ( 30 ) comprises a single inner tube ( 70 ) surrounded by the outer shell ( 80 ). 
     
     
         4 . An apparatus as claimed in  claim 1 , wherein the hairpin heat exchanger ( 30 ) comprises a bundle of inner tubes surrounded by the outer shell ( 80 ). 
     
     
         5 . An apparatus as claimed in  claim 1 , further comprising at least one generator ( 50 ) operatively linked to said at least one turbine ( 40 ), wherein the mechanical energy produced by the turbine ( 40 ) is converted into electric energy. 
     
     
         6 . An ORC process for generation of energy by organic Rankine cycle, comprising:
 i) feeding an organic working fluid through at least one heat exchanger ( 30 ) to exchange heat between a high temperature source and said working fluid, so as to heat and evaporate said working fluid;   ii) feeding the vaporised organic working fluid coming out of the heat exchanger ( 30 ) to at least one turbine ( 40 ) to make a 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 ( 40 ) to at least one condenser ( 60 ) where the working fluid is condensed;   iv) sending the organic working fluid coming out of the condenser ( 60 ) to said at least one heat exchanger ( 30 );   characterised in that step i) comprises: making the organic working fluid flow through a heat exchanger ( 30 ) of the hairpin type comprising at least one inner tube ( 70 ) surrounded by an outer shell ( 80 ); wherein the inner tube ( 70 ) and outer shell ( 80 ) extend along at least two rectilinear stretches ( 70   b ,  80   b ) mutually connected by at least one curvilinear stretch ( 70   a ,  80   a ).   
     
     
         7 . A process as claimed in  claim 6 , wherein in step
 i) heating of the organic working fluid is of the super-critical type.   
     
     
         8 . A process as claimed in  claim 6 , wherein in step
 i) heating of the organic working fluid is of the sub-critical type.   
     
     
         9 . A process as claimed in  claim 6 , wherein the organic working fluid is selected from the group comprising: hydrocarbons, fluorocarbons and siloxanes. 
     
     
         10 . A process as claimed in  claim 6 , wherein the heat exchanger ( 30 ) of the hairpin type comes into operation in dry-running conditions.