GB1152441A - A Cycle For Steam Power Plant - Google Patents

Abstract

1,152,441. Steam turbine plant. L. & C . STEINMULLER G.m.b.H. March 1, 1966 [March 1, 1965; March 4, 1965], No.8909/66. Headings F1Q and F1T. [Also in Division F4] Bled steam from a turbine, used for regenerative feedwater heating, before entering the feedwater heater yields super-heat to a feedwater branch stream at higher pressure than the bled steam to evaporate and super-heat the latter, so producing secondary steam used in either a secondary turbine, or in the primary turbine cycle to increase the efficiency of the cycle. Exhaust from the main turbine is forced by pump 23 from a condenser 33 through low-pressure regenerative feedwater heaters 24, 19, 43, 61 to de-aerator 46 and then by pump 52 through high-pressure regenerative feedwater heaters 53, 56. Bled steam from line 13 condenses to heat the feedwater in heater 24 and is then pumped by pump 25 into the main feed line. Bled steam from line 12 gives up at least part of its super-heat in generator 18 to evaporate and super-heat high-pressure feedwater supplied through pump 40, before condensing in feedwater heater 19, the condensate being pumped by pump 39 into the main feed line. The secondary steam generated in generator 18 is expanded performing useful work in turbine 17 to a condition of temperature and pressure similar to that of the de-super-heated bled steam, and then rejoins the bled steam at the point 42 to pass with it to the feedwater heater 19. Similarly bled steam from lines 11 and 8 generate secondary steam in generators 28 and 38 before passing to their associated feedwater heaters 43 and 53 respectively, the condensate from which passes to the de-aerator 46. The generators 28 and 38 are supplied with feedwater from de-aerator 46 by pump 51, and the steam generated is expanded in turbine 37, the exhausted steam heating feedwater in main feedwater heater 61, the resulting condensate being pumped by pump 62 back into the de-aerator 46. Bled steam from lines 10 and 7 generate secondary steam in secondary generators 48 and 58 respectively, before passing to de-aerator 46 and main feedwater heater 56 respectively. The branch feed supply to generators 48 and 58 is taken from point 59 in the main feed line after the feedwater heating train, and the secondary steam so generated is expanded in turbine 57, the exhaust steam therefrom joining the de-super-heated bled steam from generator 58, which has similar conditions of temperature and pressure, on its way to main feedwater heater 56 to condense, the condensate being returned to the de-aerator 46. In modifications (not shown) the secondary turbines may be replaced by a single multi-stage turbine with different inlet and outlets, which may also be used to drive the main feedwater pump, whilst the branch feedwater supply for all of the secondary steam generators may be taken from the point downstream of the main feedwater heating train. In a further modification Fig. 9 (not shown) different volumes of steam having different properties of state may be raised in a single secondary steam generator (87), the volumes being fed into a multistage secondary turbine (93) at different points, corresponding to their different properties of state. Steam may also be bled from a secondary turbine at different extraction points (not shown) for admixture with bled steam of corresponding properties of state that has yielded at least part of its super-heat in the corresponding steam generator. In a further modification Fig. 8 (not shown) the secondary steam generated by the de-super-heating of the bled steam, is reintroduced into the primary steam cycle prior to the main boiler super-heaters, or else into the primary turbine. Further Fig. 10 (not shown) several of the secondary steam generators (96, 97) of the type raising steam of differing conditions of temperature and pressure, may be arranged in series as regards at least one (i.e. 101) of the working medium flows therethrough, whereby in the generator (96) the steam is preheated and partially vaporized, whilst in the generator (97) it is completely vaporized and superheated to attain the desired conditions of state for use in the appropriate part of the primary or secondary steam cycles. In all modifications the bled steam may be completely de-super-heated in the secondary steam generators, or only partially de-super-heated in which case it gives the remainder of its super-heat to the main feedwater train. The exhaust steam from the secondary turbines, where it rejoins the de-super-heated bled steam prior to the latter passing to the main feedwater heaters always has approximately the same conditions of state (i.e. temperature and pressure). This is attained by control of the pressure of the branch feedwater supply to the secondary steam generators. Reference has been directed by the Comptroller to Specification 939, 429.