GB642117A - Improvements in power plant - Google Patents

Abstract

642,117. Turbine plant. BABCOCK & WILCOX, Ltd., and ZOLLER, R. E. March 21, 1947, No. 7844. [Class 110(iii)] In a gas turbine plant the combustion product generator has a combustion space surrounded by a wall cooled by vapour from a generator heated by exhaust gases from the turbine, the vapour being finally discharged into the combustion space. The gas turbine power plant shown comprises a high pressure gas turbine 1 driven by gases supplied by a high pressure furnace 2 and two low pressure gas turbines 6, 7 supplied by two low pressure furnaces 4, 5 which re-heat the exhaust gases from the turbine 1. The high pressure furnace 2 is supplied with combustion air by the compressors 8, 9 arranged in series, the low pressure compressor 8 being driven by the turbine 7 and the high pressure compressor 9 by the turbine 1. A conduit 11 supplies combustion air to the furnaces 4, 5. The furnaces 2, 4 and 5 are fired by steam atomizing oil burners 13, 14 and 15, and are of the kind described in Specification 579,591, [Group XII]. Oil is supplied to the burners through pipes 16, 17 and 18, and steam through pipes 19, 21 and 22 fed from a small steam generator 24 heated by the exhaust gases from the low pressure turbine 6. The furnace 2 which is of the form described and claimed in Specification 622,537, [Group XII], consists generally of a pressure-resisting casing 30 having a steam cooled wall structure 31 formed by a number of tube coils 39. These coils are fed with steam from a pipe 60 supplied by a steam generator 61 having two inclined banks of steam generating tubes 62, 63 connected to a common steam and water drum 64. The tube bank 62 is arranged to be heated by the exhaust gases from the turbine 6 after they have given up heat to the generator 24 and the tube bank 63 by the exhaust gases from the turbine 7. A pump 67 ensures the circulation of fluid through the two tube banks. The combustion air from the compressor 9 cools the casing 30 and supplies the secondary combustion air through the ports 51. The steam from the coils 39 is mixed with the combustion gases and to facilitate mixing and prevent temperature stratification the coils 39 terminate in nozzles 47 arranged in the wall structure 31 so that the steam stream is partly in contact with the wall structure and has a whirling motion around the axis of the combustion space. To prevent starving of the steam coils 39 when the pressure in the furnace is increased at high loads, the steam is generated in the generator 61 at a pressure considerably higher than that in the furnace and passes through a throttle valve 68, the opening of which is controlled by a regulator 69 responsive to the furnace pressure, to the pipe pipe 60. The furnaces 4 and 6 are also of the form described and claimed in Specification 622,537, [Group XII], and are similar in form to that described above but include an additional cooled walled structure 81. The exhaust gases from the high pressure turbine 1 pass between the two cooled wall structures 81, 82 and the additional combustion air from the conduit 11 passes between the outer cooled wall structure 81 and the pressure casing. Steam is supplied from a pipe 120 to the coils of the wall structure 81 which are connected to corresponding coils in the wall structure 82. The steam supplied to the pipe 120 is generated in a steam generator 121 having two tube banks 122, 123 arranged in the exhaust ducts of the low pressure turbines 6, 7 after the tube banks 62, 63. The steam generated in the generator 121 is at a higher pressure than that in the furnaces 4 and 5 and this pressure is reduced by means of a back-pressure steam turbine 126. The feed water for the steam generators 61 and 121 is heated in economizers 130, 131 and may be pre-heated by the continuous blow-down from the generators in a heat exchanger 132. A steam connection 133 provided with a relief valve 134 allows excess steam from the generator 24 to pass into the steam pipe 60. The steam generating and economizer sections may be formed of finned and studded tubes as described in Specification 569,573, [Group XIII]. The output of the plant may be reduced by reducing the oil supply to the burners 13, 14 and 15. A branch pipe 135, provided on the conduit 70, has a relief valve 136 which is arranged to open automatically when the_ fuel supply to the burners is reduced. The air withdrawn through the pipe 135 may be used to clean the various tube banks or passed to atmosphere or a compressed air reservoir. An auxiliary direct fired steam generator 140 of the vertical multi-tubular type is provided to supply steam during starting. According to the Provisional Specification, both of the vapour generators may be used with a throttling valve or both with an auxiliary turbine in the supply pipe to the furnace cooling jacket and the auxiliary steam generator 140 may be dispensed with and the cooling jacket supplied with compressed air during starting. Specification 642,118 is referred to.