PROCESS, PLANT AND THERMODYNAMIC CYCLE FOR PRODUCTION OF POWER FROM VARIABLE TEMPERATURE HEAT SOURCES

Abstract

A cascade process for the production of power from variable temperature heat sources, includes: circulating a main working fluid selected from perfluorinated compounds (like Perfluoro-2-methylpentane/Perfluoro-i-hexane) in a main circuit according to a main supercritical organic Rankine cycle, operatively coupling in a boiler a variable temperature heat source with the main working fluid of the main circuit to heat and vaporize the main working fluid; circulating an auxiliary working fluid in an auxiliary circuit according to an auxiliary Rankine cycle; thermally coupling in cascade the expanded main working fluid of the main Rankine cycle with the auxiliary working fluid of the auxiliary Rankine cycle, in order to cool the main working fluid and heating the vaporizing the auxiliary working fluid by heat transfer from the main Rankine cycle to the auxiliary Rankine cycle before the expansion of the auxiliary working fluid in an auxiliary expander.

Claims

1. A cascade process for the production of power from variable temperature heat sources, comprising: circulating a main working fluid selected from the perfluorinated compounds in a main circuit according to a main organic supercritical Rankine cycle, wherein said main working fluid is heated and vaporized, expanded into a main expander, enslaved to an electric generator or to a mechanical user, cooled, condensed and heated and vaporized again; operationally coupling in a boiler a variable temperature heat source to the main working fluid of the main circuit to perform said heating and vaporization of the main working fluid; circulating an auxiliary working fluid in an auxiliary circuit according to an auxiliary Rankine cycle, wherein said auxiliary working fluid is heated and vaporized, expanded into an auxiliary expander, enslaved to an auxiliary electric generator or to an auxiliary mechanical user, cooled, condensed and heated and vaporized again; thermally coupling the expanded main working fluid of the main Rankine cycle to the auxiliary working fluid of the auxiliary Rankine cycle, in order to cool the main working fluid and to heat and vaporize said auxiliary working fluid by heat transfer from said main Rankine cycle to said auxiliary Rankine cycle before the expansion of the auxiliary working fluid into the auxiliary expander.

2. The process according to claim 1, wherein the main working fluid is preheated in a main recuperator.

3. The process according to claim 1, wherein the main working fluid and the auxiliary working fluid are the same fluid and the auxiliary circuit is a branch of the main circuit; wherein the thermal coupling of the main working fluid to the auxiliary working fluid is performed in a second recuperator located downstream of the main expander and upstream of the auxiliary expander.

4. The process according to claim 3, wherein the auxiliary working fluid is separated from the main working fluid upstream of the main expander and the auxiliary expander and to re-join the auxiliary working fluid and the main working fluid downstream of the main expander and the auxiliary expander.

5. The process according to claim 3, wherein the auxiliary working fluid re-joins the main working fluid in the main recuperator.

6. The process according to claim 1, wherein the main working fluid and the auxiliary working fluid are fluidly separated; wherein the plant comprises a heat exchanger; wherein the main working fluid and the auxiliary working fluid are thermally coupled in the heat exchanger.

7. The process according to claim 6, wherein the auxiliary working fluid is different from the main working fluid.

8. The process according to claim 7, wherein the auxiliary working fluid is an organic fluid, preferably selected from the group comprising: cyclopentane, isopentane, isohexane, hexane, pentane, R245fa, R1234yf.

9. The process according to claim 1, wherein the main working fluid selected from the perfluorinated compounds comprises: Perfluoro-2-methylpentane/Perfluoro-i-hexane (Flutectm PP1), Perfluoro-methylcyclohexane (PP2), Perfluoro-1,3-dimethylcyclohexane (PP3), hexafluorobenzene.

10. A cascade plant for the production of power from variable temperature heat sources, comprising: a main circuit comprising: a boiler operatively coupled to a variable temperature heat source; a main expander; a main recuperator; a main condenser; a main pump; main pipes connecting each other the boiler, the main expander, the main recuperator, the main condenser and the main pump; a main working fluid selected from the perfluorinated compounds and flowing in the main circuit so as to implement a supercritical organic Rankine cycle; at least one auxiliary circuit thermally coupled to the main circuit and comprising an auxiliary expander; wherein an auxiliary working fluid enters the auxiliary expander after exchanging heat with the main working fluid exiting the main expander.

11. The plant according to claim 10, wherein the auxiliary circuit is a branch of the main circuit and the auxiliary working fluid is the main working fluid; wherein the plant further comprises a second recuperator located on the main circuit and downstream of the main expander and placed on the auxiliary circuit and upstream of the auxiliary expander; the heat between the main working fluid and the auxiliary working fluid being exchanged in the second recuperator.

12. Plant The plant according to claim 11, wherein the auxiliary circuit branches from the main circuit at a point located between the main recuperator and the boiler and re-joins the main circuit in the main recuperator.

13. The plant according to claim 11, wherein the main expander and the auxiliary expander are integrated in a single radial outflow turbine comprising a single rotor disc provided with a front face and a rear face; wherein ring-shaped arrays of blades are arranged concentrically on the front face to define a first radial path for the working fluid and ring-shaped arrays of blades are arranged concentrically on the rear face to define a second radial path for the working fluid; wherein the main expander is defined by the first radial path and the auxiliary expander is defined by the second radial path.

14. The plant according to claim 10, wherein the auxiliary circuit is fluidly separated from the main circuit; wherein the plant comprises a heat exchanger; wherein the main circuit and the auxiliary circuit are thermally coupled in the heat exchanger.

15. The plant according to claim 14, wherein the auxiliary circuit comprises: an auxiliary recuperator; an auxiliary condenser; an auxiliary pump; auxiliary pipes connecting each other the auxiliary expander, the auxiliary recuperator, the auxiliary condenser and the auxiliary pump; wherein the heat exchanger is placed on the main circuit between the main expander and the main recuperator and is placed on the auxiliary circuit between the auxiliary recuperator and the auxiliary expander.

16. A cascade thermodynamic cycle for the production of power from variable temperature heat sources, comprising: a supercritical main Rankine cycle with an organic main working fluid selected from the perfluorinated compounds; wherein the main Rankine cycle receives heat from a variable temperature heat source; an auxiliary Rankine cycle with an auxiliary working fluid; wherein the auxiliary cycle is thermally coupled to the main cycle to receive heat from said main cycle after an expansion of the main working fluid and before an expansion of the auxiliary working fluid; wherein in the main cycle: a reduced temperature of the main working fluid immediately before the main expansion is between 1.1 and 1.7; wherein a reduced pressure of the main working fluid immediately before the main expansion is between 1 and 2.5; wherein a reduced condensation temperature of the main working fluid is between 0.6 and 0.9; wherein a reduced condensation pressure of the main working fluid is between 0.005 and 0.3.

17. The cycle according to claim 16, wherein in the auxiliary cycle: a reduced temperature of the auxiliary working fluid immediately before the auxiliary expansion is between 0.8 and 1.2; wherein a reduced pressure of the auxiliary working fluid immediately before the auxiliary expansion is between 0.3 and 1.2; wherein a reduced condensation temperature of the auxiliary working fluid is between 0.5 and 0.75; wherein a reduced condensation pressure of the auxiliary working fluid is between 0.001 and 0.1.

18. The cycle according to claim 16, wherein in the main cycle: a main working fluid temperature immediately before the main expansion is between 250 C. and 400 C.; wherein a main working fluid pressure immediately before the main expansion is between 25 bar and 50 bar; wherein a condensation temperature of the main working fluid is between 10 C. and 50 C.; wherein a condensation pressure of the main working fluid is between 0.1 bar and 1 bar.

19. The cycle according to claim 16, wherein in the auxiliary cycle: a temperature of the auxiliary working fluid immediately before the auxiliary expansion is between 150 C. and 300 C.; wherein an auxiliary working fluid pressure immediately before the auxiliary expansion is between 20 bar and 50 bar; wherein a condensation temperature of the auxiliary working fluid is between 10 C. and 50 C.; wherein a condensation pressure of the auxiliary working fluid is between 0.1 bar and 2 bar.

Description

DESCRIPTION OF THE DRAWINGS

[0098] Such description will be made herein below with reference to the accompanying drawings, provided for indicative purposes only and therefore not limiting, in which:

[0099] FIG. 1 schematically shows a cascade plant for the production of power from variable temperature heat sources according to the present invention;

[0100] FIG. 2 shows a T-S diagram of a cascade thermodynamic cycle implemented by the plant of FIG. 1;

[0101] FIG. 3 shows a T-Q diagram relating to the heat exchange between the two circuits of the plant of FIG. 1 in subcritical conditions;

[0102] FIG. 4 shows a T-Q diagram relating to the heat exchange between the two circuits of the plant of FIG. 1 in supercritical conditions;

[0103] FIG. 5 shows a different embodiment of the plant according to the present invention;

[0104] FIG. 6 shows a T-S diagram of a cascade thermodynamic cycle implemented by the plant of FIG. 5;

[0105] FIG. 7 shows a variant of the plant of FIG. 5;

[0106] FIG. 8 shows a T-S diagram of a cascade thermodynamic cycle implemented by the plant of FIG. 7;

[0107] FIG. 9 shows a variant of the cascade plant of FIG. 1;

[0108] FIG. 10 schematically shows a turbine usable in the plants of FIG. 5 or 7.

DETAILED DESCRIPTION

[0109] With reference to the aforementioned figures, the reference numeral 1 globally designates a cascade plant for the production of (mechanical and/or electrical) power from variable temperature heat sources according to the present invention. With particular reference to FIG. 1, the plant 1 comprises a closed main circuit 2 and a closed auxiliary circuit 3 thermally coupled to each other but fluidly separated from each other.

[0110] The main circuit 2 comprises a boiler 4, a main expander 5, a main recuperator 6, a main condenser 7, a main pump 8. Main pipes connect each other the boiler 4, the main expander 5, the main recuperator 6, the main condenser 7 and the main pump 8, so as to allow the implementation of a recuperative supercritical organic Rankine cycle, by means of a working fluid that circulates through the main pipes and the aforementioned elements.

[0111] In particular, with respect to a direction of the flow of the working fluid, the main expander 5 is positioned immediately downstream of the boiler 4, the main condenser 7 is positioned downstream of the main expander 5, the main pump 8 is positioned immediately downstream of the main condenser 7 and the boiler 4 is positioned downstream of the pump 8.

[0112] The main recuperator 6 is operatively positioned on a first segment of the main pipes that extends from the pump 8 towards the boiler 4 and on a second segment of the same pipes that extends from the main expander 5 towards the main condenser 7. The main recuperator 6 has the function of pre-heating the main working fluid before the entry into the boiler 4 by means of heat transferred by the same main working fluid exiting from the main expander 5.

[0113] The main working fluid is selected from the perfluorinated compounds and it preferably is Perfluoro-2-methylpentane/Perfluoro-i-hexane (for example known by the commercial name: Flutectm PP1).

[0114] The boiler 4 is operatively coupled to a variable temperature heat source, for example fumes 9 of a turbogas or of an industrial process, with high temperature, for example with a maximum temperature of 600 C.

[0115] As is schematically shown in FIG. 1, the boiler 4 comprises a container 10 provided with an inlet and an outlet for the fumes 9 and a plurality of ducts housed in the container 10. These ducts are a part of the aforementioned main pipes and are defined by bent/curved pipes arranged in a coil. The fumes 9 directly lap the ducts to transfer heat to the main working fluid. The bent/curved pipes are preferably made of stainless steel and are made without junctions/welds.

[0116] The main expander 5 is enslaved to an electric generator 11 that generates energy by means of the rotation imparted to the main expander 5 by the working fluid expanding in said main expander 5. The main expander 5 is preferably but not exclusively a radial outflow turbine, known in itself, which comprises: a casing, a rotor disk provided with a front face and rotatably housed in the casing, annular arrays of rotor blades positioned concentrically on the front face, annular arrays of stator blades mounted on the casing and interposed between the annular arrays of rotor blades to define a first radial path for a working fluid, wherein the casing has an inlet positioned in proximity to a centre of the rotor disk and an outlet positioned in proximity to a radially peripheral portion of the rotor disk. For example, the radial outflow turbine is like the one described in the patent EP2699767 in the name of the same Applicant. In other embodiment variants, the main expander can be an axial turbine, a radial inflow turbine, a radial/axial turbine, for example like the one described in the patent EP2743463 in the name of the same Applicant.

[0117] The auxiliary circuit comprises: an auxiliary expander 12 enslaved to a respective auxiliary electric generator 13, an auxiliary recuperator 14, an auxiliary condenser 15, an auxiliary pump 16 and auxiliary pipes connecting each other the auxiliary expander 12, the auxiliary recuperator 14, the auxiliary condenser 15 and the auxiliary pump 16 so as to allow the implementation of a recuperative organic Rankine cycle, by means of an auxiliary working fluid that circulates through the auxiliary pipes and the aforementioned elements.

[0118] The auxiliary expander 12 can be an axial turbine, a radial outflow/inflow turbine, a radial/axial turbine.

[0119] The auxiliary working fluid is an organic fluid, for example cyclopentane.

[0120] The plant 1 comprises a heat exchanger 17 that thermally couples the main circuit 2 and the auxiliary circuit 3.

[0121] The heat exchanger 17 is placed on the main circuit 2 between the main expander 5 and the main recuperator 6 and is placed on the auxiliary circuit 3 between the auxiliary recuperator 14 and the auxiliary expander 12.

[0122] Through said heat exchanger 17, the main working fluid of the main circuit 2 transfers heat to the auxiliary working fluid of the auxiliary circuit 3.

[0123] In particular, with respect to a direction of the flow of the auxiliary working fluid, the main expander 12 is positioned immediately downstream of the heat exchanger 17, the auxiliary condenser 15 is positioned downstream of the auxiliary expander 12, the auxiliary pump 16 is positioned immediately downstream of the auxiliary condenser 15 and the heat exchanger 17 is positioned downstream of the auxiliary pump 16.

[0124] The auxiliary recuperator 14 is operatively positioned on a first segment of the auxiliary pipes that extends from the auxiliary pump 16 towards the heat exchanger 17 and on a second segment of the same pipes that extends from the auxiliary expander 12 towards the auxiliary condenser 15. The auxiliary recuperator 14 has the function of pre-heating the auxiliary working fluid before the entry into the heat exchanger 17 by means of heat transferred by the same auxiliary working fluid exiting from the auxiliary expander 12.

[0125] In use and in accordance with the cascade process and thermodynamic cycle according to the invention and with reference to the T-S diagram of FIG. 2, the main working fluid (Flutectm PP1) circulating in the main circuit 2 is pumped by the main pump 8 and slightly increases its own temperature passing from point A to point B. The main working fluid passes through the main recuperator 6 heating to point C and then transits into the boiler 4 where it absorbs heat from the fumes 9 (which for example have a maximum temperature of 600 C.) heating and vaporizing to point D (at approximately 400 C.). The vaporized main working fluid then expands in the main expander 5 cooling to point E and causing the rotation of the expander 5 and of the respective electric generator 11.

[0126] The main working fluid (Flutectm PP1) immediately before the main expansion (point D) has the following parameters: [0127] Temperature: 400 C. [0128] Reduced temperature: 1.5 [0129] Pressure: 40 bar [0130] Reduced pressure: 2.1

[0131] The main working fluid is cooled further in the heat exchanger 17, transferring heat to the auxiliary working fluid of the auxiliary circuit 3 and then in the main recuperator 6 (Points F and G). The subsequent passage in the main condenser 7 determines the condensation of the main working fluid that then returns to point A, ready to start a new main Rankine cycle.

[0132] The main working fluid (Flutectm PP1) has the following parameters: [0133] Condensation temperature: 25 C. [0134] Reduced condensation temperature: 0.65 [0135] Condensation temperature: 0.25 bar [0136] Reduced condensation pressure: 0.01

[0137] The auxiliary working fluid (cyclopentane) circulating in the auxiliary circuit 3 is pumped by the auxiliary pump 16 and slightly increases its own temperature passing from point H to point I. The auxiliary working fluid passes through the auxiliary recuperator 14 heating to point L and then transits into the heat exchanger 17 where it absorbs heat from the main working fluid, heating and vaporizing to point M (at approximately 250 C.). The vaporized auxiliary working fluid then expands in the auxiliary expander 12 cooling to point N and causing the rotation of the expander 12 and of the respective electric generator 13.

[0138] The auxiliary working fluid (Cyclopentane) immediately before the auxiliary expansion (point M) has the following parameters: [0139] Temperature: 250 C. [0140] Reduced temperature: 1.02 [0141] Pressure: 30 bar [0142] Reduced pressure: 0.7

[0143] The auxiliary working fluid cools further in the auxiliary recuperator 14 (point O) and then in the auxiliary condenser 15. The passage in the auxiliary condenser 15 determines the condensation of the auxiliary working fluid that then returns to point H ready to start a new auxiliary Rankine cycle.

[0144] The auxiliary working fluid (Cyclopentane) has the following parameters: [0145] Condensation temperature: 25 C. [0146] Reduced condensation temperature: 0.6 [0147] Condensation temperature: 0.32 bar [0148] Reduced condensation pressure: 0.007

[0149] FIG. 3 shows the T-Q diagram relating to the heat exchange that takes place between the two circuits of the plant of FIG. 1 at the heat exchanger 17 (points E-F and L-M) in subcritical conditions. FIG. 4 shows a T-Q diagram relating to the same heat exchange in supercritical conditions.

[0150] FIG. 5 shows a different embodiment of the plant 1 according to the present invention wherein the auxiliary circuit 3 is a branch of the main circuit 2 and therefore the working fluid is the same in the two circuits 2, 3.

[0151] The main circuit 2 comprises: the boiler 4, the main expander 5 (enslaved to the electric generator 11), the main recuperator 6, the main condenser 7, the main pump 8. In particular, with respect to a direction of the flow of the working fluid, the main expander 5 is positioned immediately downstream of the boiler 4, the main condenser 7 is positioned downstream of the main expander 5, the main pump 8 is positioned immediately downstream of the main condenser 7 and the boiler 4 is positioned downstream of the pump 8. The main recuperator 6 is operatively positioned on a first segment of the main pipes that extends from the pump 8 towards the boiler 4 and on a second segment of the same pipes that extends from the main expander 5 towards the main condenser 7.

[0152] The auxiliary circuit 3 further comprises the auxiliary expander 12 enslaved in this specific embodiment to the same electric generator 11 of the main expander 5. The auxiliary circuit 3 branches from the main circuit 2 at a branching point 18 located between the main recuperator 6 and the boiler 4 and re-joins the main circuit 2 in the main recuperator 6. The main expander 5 and the auxiliary expander 12 therefore lie fluidly in parallel and the working fluid entering the two expanders 5 and 12 has substantially the same pressure. The working fluid of the main circuit and the working fluid of the auxiliary circuit exchange heat in a second recuperator 19. The second recuperator 19 is placed on the main circuit down stream of the main expander 5 and is placed on the auxiliary circuit upstream of the auxiliary expander 12. The second recuperator 19 is a high temperature recuperator. The main recuperator 6 is a low temperature recuperator.

[0153] The single working fluid is selected from the perfluorinated compounds and it preferably is Perfluoro-2-methylpentane/Perfluoro-i-hexane (for example known by the commercial name: Flutec PP1).

[0154] In use and in accordance with the cascade process and with the thermodynamic cycle according to the invention and with reference to the T-S diagram of FIG. 6, the main working fluid (Flutec PP1) is pumped by the main pump 8 and slightly increases its own temperature passing from point A to point B.

[0155] The working fluid passes through the main recuperator 6 heating to point C and then divides into a main flow, which transits into the boiler 4 where it absorbs heat from the fumes heating and vaporizing to point E (at approximately 350 C.), and into an auxiliary flow that passes into the second recuperator 19 heating to point D.

[0156] The vaporized main flow then expands in the main expander 5 cooling to point F and causing the rotation of the expander 5 and of the respective electric generator 11 and then passes into the second recuperator 19 where it transfers heat to the auxiliary flow (which heats to point D) and cools to point G.

[0157] The auxiliary flow then expands in the auxiliary expander 12 cooling to point G and causing the rotation of the expander 12 and of the electric generator 11. The main and auxiliary flow join in the main recuperator 6 and there they transfer heat, cooling to point H. The single flow of the working fluid at this point traverses the condenser 7, condenses (at approximately 30 C.) and returns to the pump 8, i.e. to point A.

[0158] FIG. 7 shows a variant of the plant 1 of FIG. 5. With respect to the plant of FIG. 5, the variant of FIG. 7 comprises an additional auxiliary circuit 20 which is thermally coupled with the auxiliary circuit 3. The additional auxiliary circuit 20 comprises an additional auxiliary expander 21. The additional auxiliary circuit 20 branches from the branching point 18 described above or from an additional branching point 22 of the auxiliary circuit 3 positioned between the branching point 18 and the second recuperator 19. The working fluid of the auxiliary circuit and the working fluid of the additional auxiliary circuit exchange heat in a third recuperator 23.

[0159] The third recuperator 23 is placed on the auxiliary circuit downstream of the auxiliary expander 12 and is placed on the additional auxiliary circuit upstream of the additional auxiliary expander 21. The third recuperator 21 is a high temperature recuperator. The second recuperator 19 is a medium temperature recuperator and the main recuperator 6 is a low temperature recuperator.

[0160] The additional auxiliary circuit 20, the auxiliary circuit 3 and the main circuit 2 join in the main recuperator 6. The main expander 5, the auxiliary expander 12 and the additional auxiliary expander 21 therefore lie fluidly in parallel and the working fluid entering the three expanders 5, 12 and 21 has substantially the same pressure.

[0161] In use and in accordance with the cascade process and thermodynamic cycle according to the invention and with reference to the T-S diagram of FIG. 7, the working fluid is pumped by the main pump 8 and slightly increases its own temperature passing from point A to point B. The working fluid passes through the main recuperator 6 heating to point C and then divides into a main flow, which transits into the boiler 4 where it absorbs heat from the fumes, heating and vaporizing to point F (at approximately 400 C.), into an auxiliary flow that passes into the second recuperator 19, heating to point E, and into an additional auxiliary flow, which passes into the third recuperator 23, heating to point D.

[0162] The main flow then expands in the main expander 5 cooling to point G and causing the rotation of the expander 5 and of the respective electric generator 11 and then passes into the second recuperator 19 where it transfers heat to the auxiliary flow (which heats to point E) and cools to point I.

[0163] The auxiliary flow expands in the auxiliary expander 12 cooling to point H and causing the rotation of the expander 12 and of the electric generator 11 and then passes into the third recuperator 23 where it transfers heat to the additional auxiliary flow (which heats to point D) and cools to point I.

[0164] The additional auxiliary flow expands in the additional auxiliary expander 21 cooling to point I and causing the rotation of the expander 21 and of the electric generator 11.

[0165] The main, auxiliary and additional auxiliary flow join in the main recuperator 6 and there they transfer heat, cooling to point L. The single flow of the working fluid at this point traverses the condenser 7, condenses (at approximately 30 C.) and returns to the pump 8, i.e. to point A.

[0166] Other variants of FIGS. 5 and 7, not shown, comprise further cascaded additional auxiliary circuits/cycles, all operating with the same working fluid. Other variants of the plant of FIG. 1 comprise multiple cycle/circuits arranged in series, i.e. in cascade one after the other, with different fluids that exchange heat between them.

[0167] For example, FIG. 9 shows an additional auxiliary circuit 20 arranged in cascade with respect to the auxiliary circuit 3 of FIG. 1. The additional auxiliary circuit 20 is structurally similar to the auxiliary circuit 3. The additional auxiliary circuit 20 is operatively coupled with the auxiliary circuit 3 at an additional heat exchanger 24.

[0168] The additional auxiliary circuit 20 comprises an additional auxiliary expander 21 with a respective additional auxiliary electric generator 25, an additional auxiliary recuperator 26, an additional auxiliary condenser 27 and an additional auxiliary pump 28.

[0169] In other embodiments, the main expander 5 and the auxiliary expander 12 of the plants of FIG. 5 and/or of FIG. 7 are incorporated in a single radial outflow turbine 100 of the type shown in FIG. 10.

[0170] The radial outflow turbine 100 comprises a casing 101, a single rotor disk 102 rotatably housed in the casing 101. The rotor disk 102 is provided with a front face 103 and with a rear face 104, opposite to the front face 103.

[0171] Annular arrays of rotor blades 105 are arranged concentrically on the front face 103 and also on the rear face 104. Annular arrays of stator blades 106 are mounted on an inner face of the casing 101 positioned in front of the front face 103 of the rotor disk 102 and lie interposed between the annular arrays of rotor blades 105 of the front face 103 to define a first radial path for the working fluid. Annular arrays of stator blades 106 are also mounted on an inner face of the casing 101 positioned in front of the rear face 104 of the rotor disk 102 and lie interposed between the annular arrays of rotor blades 105 of the rear face 104 to define a second radial path for the working fluid.

[0172] The casing 101 has an inlet 107 positioned in front of the front face 103, in proximity to a centre of the rotor disk 102 and in fluid communication with the first radial path, an additional inlet 108 positioned in front of the rear face 104 and in fluid communication with the second radial path, and an outlet 109 positioned in proximity to a radially peripheral portion of the rotor disk 102.

[0173] In the illustrated embodiment, the additional inlet 108 is defined by openings obtained through a wall of the casing 101 positioned around a support sleeve 110 of a shaft 111 of the turbine 100 mounted in said sleeve 110 on bearings. The shaft 111 bears and supports in overhang the rotor disk 102.

[0174] The first radial path defined on the front face 103 is a part of the main circuit of FIG. 5 or 7 and the second radial path defined on the rear face 104 is a part of the auxiliary circuit of FIG. 5 or 7.

[0175] The radial outflow turbine 100 with two bladed faces therefore defines both the main expander 5 (through the first radial path) that the auxiliary expander 12 (through the second radial path) of FIG. 5 or 7. In other words, the inlet 107 corresponds to point E of FIG. 5 or 7 and the additional inlet 108 corresponds to point D of FIG. 5 or 7. These points E and D are substantially at the same pressure, so that the rotor disk 102 is intrinsically balanced.

LIST OF ELEMENTS

[0176] 1 cascade plant [0177] 2 main circuit [0178] 3 auxiliary circuit [0179] 4 boiler [0180] 5 main expander [0181] 6 main recuperator [0182] 7 main condenser [0183] 8 main pump [0184] 9 fumes [0185] 10 container body [0186] 11 electric generator [0187] 12 auxiliary expander [0188] 13 auxiliary electric generator [0189] 14 auxiliary recuperator [0190] 15 auxiliary condenser [0191] 16 auxiliary pump [0192] 17 heat exchanger [0193] 18 branching point [0194] 19 second recuperator [0195] 20 additional auxiliary circuit [0196] 21 additional auxiliary expander [0197] 22 additional branching point [0198] 23 third recuperator [0199] 24 additional heat exchanger [0200] 25 additional auxiliary electric generator [0201] 26 additional auxiliary recuperator [0202] 27 additional auxiliary condenser [0203] 28 additional auxiliary pump [0204] 100 radial outflow turbine [0205] 101 casing [0206] 102 rotor disk [0207] 103 front face [0208] 104 rear face [0209] 105 rotor blades [0210] 106 stator blades [0211] 107 inlet [0212] 108 additional inlet [0213] 109 outlet [0214] 110 sleeve [0215] 111 shaft