CLOSED CYCLE CO2 GAS TURBINE POWER PLANT WITH PARTIAL CONDENSATION OF THE WORKING SUBSTANCE PRIOR TO EXPANSION THEREOF

摘要

The invention relates to a closed circuit gas turbine plant in which the working fluid is C0 2 , the plant comprising at least two compressors at least two turbines in series flow, there being means between the turbines for re-heating the working fluid by means of an external heat source. A branch line extends from one point in the circuit to another point in the circuit, there being means in the branch line for liquefying working fluid and means for increasing the pressure of the working fluid in the branch line, and a line extending from the branch line between the liquefying means and the pressure raising means to a point in the gas circuit. The plant shown in Fig.1 comprises a lowpressure compressor 1 mounted on a shaft 16 driven by a low-pressure turbine 9 which also drives an external load in the form of an electric generator 15 an intermediate pressure 3, a high-pressure compressor 5 and a liquefied C0 2 pump 13 all mounted on a shaft 17 and driven by a high-pressure turbine 7 and an external heat source in the form of a nuclear reactor 8. CO 2 is compressed in compressor 1, cooled in interstage cooler 2 and further compressed in IP compressor 3, the C0 2 then dividing into two streams, one passing through cooler 11, a further cooler 12 in which the gas is liquefied, the liquefied C0 2 then passing the pump 13 where its pressure is increased, the working fluid then passing through a recuperator 14 where it is heated by working fluid discharging from the LP turbine 9, the heated fluid then passing to point 28 the second stream of working fluid from the IP compressor 3 passes directly to the HP compressor 5 and thence to point 28 where the two streams of working fluid rejoin. The combined stream then passes through a recuperator 6 where it is heated by working fluid discharging from the LP turbine 9, the heated fluid then passing to the HP turbine 7 where it is partially expanded. The working fluid is then re-heated in the nuclear reactor 8 and then passed to the LP turbine 9. The working fluid discharging from the turbine 9 passes through the recuperators 6 and 14 and then through a pre-cooler 10 finally passing back to the LP compressor 1. A portion of the liquefied C0 2 in the line between the condenser 12 and the pump 13 passes through a condensate line 19 to the inlet of the HP compressor 5. a circulating pump 18 being disposed in the line 19 and being driven from the HP shaft 17 through transmission 20. In Fig.2, (not shown), a portion of the liquefied C0 2 passes through line (19) to an intermediate point of the IP compressor (3), a flow control valve (21) in the line (19) being controlled by a device (22) responsive to pressure in the liquefied C0 2 line and to the pressure at the entry point to the IP compressor. In this embodiment, the heated C0 2 from the recuperator (6) is divided into two streams one stream passing through a first line and the other passing through a second line, that passing through the second line passing to a high-pressure section (8a) of the nuclear reactor, the two streams rejoining before passing to the HP turbine (7). The partially expanded C0 2 is re-heated in a lowpressure section (8b) of the nuclear reactor before passing to the LP turbine (9). In Fig.3, (not shown) the liquefied CO 2 pump (13) is mounted on the LP shaft (16) also the circulating pump (18) in the condensate line (19) is driven by an electric motor (27) which is responsive to speed of the HP shaft 17 as sensed by device (37). In Fig.4 an ejector 18a is provided in the condensate line 19 in place of the circulating pump 18, the operating fluid of the ejector being working fluid taken from the line downstream of the liquefied C0 2 pump 13 through line 19a under control of valve 21 a which is responsive to speed of the HP shaft 17 as sensed by device 37. In Fig.3 the working fluid is heated in a heat exchanger (8c) by a heating fluid which is itself heated in the nuclear reactor (8).