7  EP 2 100 011 B1 8  brication circuit (22) to the heat-exchange fluid. upstream of the degasser (11) by means of a heat-exchange fluid. supplying the combustionchamber(5) of a gas- turbine plant (3) with siderurgical gases com- pressed by a compression unit (14); supplying condensed steam along a supply cir- cuit (13) to a degasser (11) and, in succession, to a boiler (12) of a steam-turbine unit (9); and conveying the siderurgical gases burnt in the combustion chamber (5)) to the boiler (12) in whicha recoveryofheatiscarriedoutforheating the condensed steam; the method being  characterized inthat  the heat generatedbythe compression unit(14)istrans- ferred, at least in part, to the condensed steam 7. The combined-cycle plant according to any one of Claims 2 to 6,  characterized in that  it comprises at least one third heat-exchanger (39) for transferring the heatfrom the siderurgical gases compressed by the compressionunit(14)tothe heat- exchange fluid. 8. The combined-cycle plant according to Claim 7, characterized in that the compression unit ( 14) comprises a firstcompressor(16)andasecond com- pressor (17) and a recirculation duct (29) for con- necting the outlet of the first compressor(16)to inlet ofthefirstcompressor(16);the third heat- exchanger (39) being set along the recirculation duct (29) for transferring the heat of the siderurgical gases com- pressed by the first compressor (16), which are in- troduced again into the first compressor (16), to the heat-exchange fluid. 9. The combined-cycle plant according to Claim 8, characterized in that the compression unit ( 14) comprises a connection duct (30) set between the outlet of the firstcompressor(16) and the inletofthe second compressor (17); the heat- exchange unit (34) comprising a fourth heat- exchanger (40) set along the connection duct (30) for transferring the heatfromthe siderurgicalgases,compressed by the first compressor (16) and supplied to the se cond compressor (17), to the heat-exchange fluid. 10. The combined-cycle plant according to any one of Claims 2 to 9,  characterized by  comprising a fifth heat-exchanger (41) for transferring the heat from the heat-exchange fluid to the condensed vapour. 11. Thecombined-cycle plantaccording toClaim10,cha racterized in that the fifth heat- exchanger (41) is tra- versedbythe circuit(13)forsupply ofthe condensed steam and by the circuit (35) for supply of the heat- exchange fluid. 12. A method for the production of electrical energy in a combined-cycle plant (1) comprising: 13. The method according to Claim 12,  characterized by  circulating the heat- exchange fluid ina circuit(35) of the heat-exchange unit for transferring the heat from the compression unit (14) to the circuit (13) for supply of the condensed vapour. 14. The method according toClaim12orClaim13,  char- acterized by  transmitting motion from the gas-tur- bine unit (3) to the compression unit (14) by means of a hydraulic converter (18); and in that the heat of the oil of the hydraulic converter (18) is transferred to the heat-exchange fluid by means of a first heat- exchanger (37). 15. The method according to any one of Claims 12 to 14,  characterized by  transferring the heat generat- ed ina lubricationcircuit(22)ofthe compression unit (14)to the heat- exchange fluidby meansofa second heat-exchanger (38). 16. The method according to any one of Claims 12 to 15,  characterized by  transferring the heat from the siderurgical gases compressed by the compression unit (14) to the heat-exchange fluid. 17. The method according to Claim 16,  characterized in that  the compression unit (14) comprises a first compressor(16) andasecondcompressor(17)con- nected in series; the method envisaging transfer of the heat fromthe siderurgical gases compressed by the first compressor (16). 18. The method according to Claim 17,  characterized inthat  the siderurgical gases at output from the first compressor (16) are re-circulated at inlet to the first compressor (16) and  in that  the heat of the sideru- rgicalgases istransferredtothe heat- exchangefluid during the re-circulation step by means of a third heat-exchanger (39). 19. The method according toClaim17orClaim18,  char- acterized by  supplying the siderurgical gases com- pressed by the first compressor (16) to the second compressor (17) and transferring the heat of the siderurgicalgases,supplied tothe second compres- sor (17), to the heat-exchange fluid by means of a fourth heat-exchanger (40). 20. The method according to any one of Claims 12 to 19,  characterized by  transferring the heat from the heat-exchange fluid to the condensed steam by means of a fifth heat-exchanger (41). 5