Gas turbine plant

Abstract: A gas turbine plant comprises an air compressor (8), a gas turbine (10) including at least one high temperature section, a driven equipment (11), which are operatively connected in series, a gas turbine combustor (9) arranged between the air compressor and the gas turbine, and a fuel system (12) for supplying a fuel to the gas turbine combustor. The gas turbine plant comprises further an air extraction closed circuit system (26; 35; 57) for said air compressor and a heat exchange section (16) provided for said air extraction closed circuit system for heating the fuel supplied to the gas turbine combustor from the fuel system (12). Said air extraction closed circuit system (35) is further provided with a valve opening control means (45) for detecting a fuel leak into the high pressure air by a fuel leak detector (45) provided for the heat exchange section and for closing a fuel valve (15) of the fuel system when a detection signal exceeds a predetermined value and also provided with an alarm device (47) for giving an alarm when the detection signal exceeds the predetermined value.

Description: BACKGROUND OF THE INVENTION The present invention relates to a gas turbine plant, and in particular, to a gas turbine plant which previously heats a fuel supplied to a gas turbine combustor of the gas turbine plant and enhances a quantity of heat so as to improve a plant heat (thermal) efficiency. In a gas turbine plant, it has been known that the plant heat efficiency is improves if an inlet combustion temperature of a gas turbine is made high. The plant heat efficiency is calculated from a ratio of a gas turbine power to a fuel supplied to a gas turbine combustor. Therefore, how to reduce a fuel to be supplied to the gas turbine combustor, or how to enhance an output of the gas turbine is an important matter in order to improve the plant heat efficiency. In view of the gas turbine output power in the light of the improvement of the plant heat efficiency, there is a problem of an increase in a power per unit combustion gas flow (specific power). However, an improvement of flow characteristic of a gas turbine blade and a reduction in other mechanical loss have already reached the limit, and it is difficult to greatly improve the flow characteristic and reduce the mechanical loss. On the other hand, in order to reduce fuel consumption so as to improve the plant heat efficiency, it is important to improve a quantity of heat of fuel itself. Recently, there has been disclosed Japanese Patent No. 2540646 as means for improving the quantity of heat of fuel itself. As shown in Fig. 11, the Japanese Patent No. 2540646 relates to a so-called multi-shaft type combined cycle power generation plant which is constructed in such a manner that a shaft of a gas turbine plant 2 connected to an exhaust heat recovery boiler 1 is separated, and a steam turbine plant 3 is independently provided. A gas turbine combustor 4 is provided with a heat exchanger 5, and a heated water generated from an economizer 6 of the exhaust heat recovery boiler 1 is used as a heating source to be supplied to the heat exchanger 5, and thus, a heat exchange of a fuel F supplied to the gas turbine combustor 4 is made to increase a quantity of heat. As described above, in the Japanese Patent No. 2540646, efforts have been made to reduce fuel consumption and to improve a plant heat efficiency because there is an anxiety that fossil fuel resources are exhausted in near future. In the prior art shown in Fig. 11, a heated water on an outlet side of the economizer 6 having a relatively small influence on load fluctuation is used as a heating source of the heat exchanger 5 so as to heat the fuel F, and then, a gas turbine driving gas (main flow gas) having the same temperature is generated by a fuel flow rate relatively smaller that that of the conventional case, and thus, a plant heat efficiency is improved. However, the heated water on the outlet side of the economizer 6 has been used as a heating source of the fuel F, and for this reason, there have arisen several problems. Primarily, the temperature of heated water generated from the economizer 6 is set on the basis of heat balance of the whole plant regardless of heating the fuel F. For this reason, the temperature of the heated water becomes high by heating the fuel, and then, a saturation pressure based on the high temperature of heated water excessively becomes high. Thus, a feed water pump 6a requires a high pressure rising force, and thus, this is a factor of increasing the cost. During partial load operation, when a flow rate of the heat water supplied to the heat exchanger 5 becomes low, a quantity of feed water from the feed water pump 6a passing through the economizer 6 becomes low. In this case, however, an internal pressure of the feed water pump rises, and for this reason, the heat water discharged from the economizer 6 exceeds a saturation temperature. As a result, there is the possibility that steaming is generated. Further, the heated water of the economizer 6 is used as a heating source of the fuel F. In this case, however, the aforesaid construction is applied to only the combined cycle power generation plant. For example, in the case of a simple cycle gas turbine, it is difficult to secure a heating source, and for this reason, there has been required a gas turbine plant which can readily secure the heating source. As described above, the prior art shown in Fig. 11 can improve the plant heat efficiency, but provides the aforesaid several problems. US-A-5 611 197, which forms the preamble of claim 1, refers to a gas turbine plant, comprising an air compressor, a gas turbine, a combustor and a cooling air closed circuit having an extraction line from the compressor to a hot turbine component, such as vanes, blades or shrouds, and a return line to the compressor. The compressor drives the closed circuit and is self-regulated. Further, the device is provided with a fuel system supplying a fuel to the gas turbine combustor. SUMMARY OF THE INVENTION A primary object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art described above and to provide a gas turbine plant capable of relatively reducing a flow rate of fuel so as to improve a plant heat efficiency without giving any influence to other constituent equipments when using the gas turbine plant itself as a heating source for heating a fuel. This and other objects can be achieved according to the present invention by providing a gas turbine comprising the features of claim 1. Preferred embodiments are defined by the dependent claims. According to the present invention, in the gas turbine plant according to the present invention, the high pressure air of the air compressor is used as a heating source for heating a fuel supplied from the fuel section to the gas turbine combustor. Further, the gas turbine plant is provided with means for cooling the high temperature sections of the gas turbine by reusing the high pressure air which has been used for heating the fuel. Therefore, the quantity of heat (energy) of fuel increases while the plant heat efficiency being improved, and it is possible to sufficiently deal with the high output accompanying with the high temperature gas turbine drive gas supplied to the gas turbine. Further, in the gas turbine plant according to the present invention, in the case where the high pressure air from the air compressor is used as a heating source so as to heat the fuel, there is provided a heat exchange section, and the heat exchange section is provided with safety means. Therefore, the gas turbine plant can be safely operated without giving any hindrance to other components. Further, in the gas turbine plant according to the present invention, in the case where the high pressure air which has been used for heating the fuel is reused as a cooling medium for cooling the gas turbine high temperature section, there is provided a pressure rising compressor, and the pressure rising compressor includes means capable of taking sufficient measures if an accident happens in the pressure rising compressor. Therefore, it is possible to securely cool the high temperature section of the gas turbine, and to keep the material strength of the high temperature section at a preferable state. It is to be noted that the nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings: Fig. 1 is a system diagram schematically showing a gas turbine plant not forming part of the present invention; Fig. 2 is a system diagram schematically showing another gas turbine plant not forming part of the present invention; Fig. 3 is a schematically cross sectional view of a heat exchange section cut along an arrow III-III in Fig. 2; Fig. 4 is a system diagram schematically showing a gas turbine plant comprising an air extraction closed circuit system; Fig. 5 is a system diagram schematically showing an aspect of a gas turbine plant according to an embodiment of the present invention; Fig. 6 is a system diagram schematically showing a gas turbine plant according to the present invention; Fig. 7 is a system diagram schematically showing a first modified embodiment of the heat exchange section of the gas turbine plant according to the present invention; Fig. 8 is a system diagram schematically showing a second modified embodiment of the heat exchange section of the gas turbine plant according to the present invention; Fig. 9 is a system diagram schematically showing further aspect of a gas turbine plant according the present invention; Fig. 10 is a graph showing a comparative result in a plant heat efficiency between the gas turbine plant according to each embodiment of the present invention and the prior art; and Fig. 11 is a system diagram schematically showing a conventional gas turbine plant which combines a steam turbine plant and an exhaust heat recovery boiler. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a gas turbine plant according to the present invention will be described hereunder with reference to the accompanying drawings and reference numerals shown in these drawings. Fig. 1 is a system diagram schematically showing a gas turbine plant not forming part of the present invention. A gas turbine plant 7 includes an air compressor 8, a gas turbine combustor 9, a gas turbine 10, a driven equipment 11 such as a generator, and a fuel section 12. In the gas turbine plant 7, an air AR sucked in the air compressor 8 is made high in pressure, and the high pressure air (highly pressurized air) is supplied to the gas turbine combustor 9 together with a fuel F from the fuel section 12. A gas turbine driving combustion gas (main flow gas) generated by the gas turbine combustor 9 is supplied to the gas turbine 10, and then, the gas turbine combustion gas is expanded so as to rotate and drive the driven equipment 11 with a rotating torque generated in the expanding process. On the other hand, the fuel section 12 includes a fuel tank 13, a fuel pump 14, and a fuel valve 15, and in this structure, the fuel section 12 may be called a fuel supply section or system. A heat exchange section (heat exchanger or heat exchanging unit) 16 is provided for the air compressor 8. The fuel F from the fuel tank 13 is pressurized by the fuel pump 14, and then, a flow rate of the fuel F is controlled by the fuel valve 15. Thereafter, a high pressure air (highly pressurized air) of the air compressor 8 makes heat exchange in the heat exchange section 16 so as to be used as a heating source, and at this time, the fuel F is increased in its quantity of heat (energy) and is supplied to the gas turbine combustor 9. Incidentally, a recent air compressor has a pressure ratio of 15 or more, and a high pressure air temperature of 400°C or more corresponding to the pressure ratio. Therefore, the air compressor can be sufficiently used as a heating source with respect to a temperature for heating fuel, that is, about 350 °C . When heating the fuel F, the high pressure air of the air compressor 8 is used as a heating source. Thus, the heating source can be readily obtained, and a flow rate of fuel can be relatively reduced without giving any influence to other constituent equipments as compared with the conventional case, and therefore, a plant heat efficiency can be improved. Fig. 2 is a diagram schematically showing a modification of the heat exchange section 16. In this case, like reference numerals are used to designate the same components as the above embodiment or the corresponding part, and the overlapping explanation is omitted. The heat exchange section 16 of this gas turbine is provided at a casing 17 of the air compressor 8. The heat exchange section 16 is constructed in the following manner. More specifically, as shown in Fig. 3, an outer cover 18 is formed concentrically with the casing 17 of the air compressor 8 so as to form a fuel passage 19, and one side of the fuel passage 19 is provided with a fuel inlet 22 and a fuel outlet 23. Further, the other side of the fuel passage 19 is provided with a connecting pipe 21, and a high pressure air passing through air compressor stationary blades 24 is used as a heating source so as to heat the fuel F passing through the fuel passage 19. Incidentally, a reference numeral 20 denotes a flange, and a reference numeral 25 denotes a rotary shaft (rotor). Even though the heat exchange section 16 is provided on the casing 17 of the air compressor 8, the temperature of high pressure air is high as described above, so that the fuel F can be sufficiently and preferably heated. Fig. 4 is a system diagram schematically showing another gas turbine plant not forming part of the present invention. Incidentally, like reference numerals are used to designate the same components as for the above gas turbines. In this embodiment, an air extraction closed (circuit) system 26 is provided at an outlet or a high pressure stage of the air compressor. The air extraction closed system 26 includes the heat exchanger section 16, and a high pressure air which has been used for heating the fuel F is recovered to an inlet or a low pressure stage of the air compressor 8. As described above, in this embodiment, the fuel F is heated with the utilization of the air extraction of the air compressor 8, and the extracted air is recovered to the air compressor 8. Therefore, a heating source is effectively used, so that a plant heat (thermal) efficiency can be improved. Fig. 5 is a system diagram schematically showing an aspect of a gas turbine plant according to the present invention. In this case, like reference numerals are used to designate the same components as for the above gas turbine plants. In this embodiment, an air extraction closed system 35 is provided on a high pressure stage side of the air compressor 8. The air extraction closed system 35 is provided with the heat exchange section 16 of the fuel section 12, and the heat utilizing device 36, for example, the heat exchange section 37 for co-generation heat utilizing device. Then, the high pressure air from the air compressor 8 is used as a heating source so that the fuel F from the fuel section is heated in the heat exchange section 16. Further, a medium to be heated from the heat utilizing device 36, for example, a cooling water CW, is heated in the heat exchange section 37 for the heat utilizing device, and then, the high pressure air is recovered to the air compressor 8. As described above, in this embodiment, the air compressor 8 is provided with the air extraction closed system 35, and the air extraction closed system 35 is provided with the heat exchange section 16 of the fuel section 12, the heat utilizing device 36 and the heat exchange section 37 for the heat utilizing device. Further, the high pressure air extracted from the air compressor 8 is used as a heating source so that the fuel F from the fuel section 12 is heated in the heat exchange section 16, and then, a medium to be heated from the heat utilizing device 36 is heated in the heat exchange section 37 for heat utilizing device. Therefore, the heat of high pressure air can be effectively used for multi-purpose. Fig. 6 is a system diagram schematically showing a gas turbine plant according to the present invention. In this case, like reference numerals are used to designate the same components as for the above gas turbine plants. In this embodiment, the following matter is taken into consideration. More specifically, when the high pressure air extracted from the air compressor 8 is used as a heating source and the fuel F is heated in the heat exchange section 16 of the fuel section 12, in the case where the fuel F leaks into the high pressure air, this is a factor of causing an accident. For this reason, the heat exchange section 16 is provided with a fuel leak detector 45, a valve opening control section 46, an alarm device 47 and a fuel leak display device (indicator) 48. The valve opening control section 46 is constructed so as to close a fuel valve 15 if a fuel leak signal detected by the fuel leak detector 45 exceeds a predetermined value. The alarm device 47 also gives the alarm if a fuel leak signal detected by the fuel leak detector 45 exceeds a predetermined value. The fuel leak display 48 displays a leaked fuel concentration detected by the fuel leak detector 45 so that a worker can visibly confirm the fuel leakage. As described above, in this embodiment, if the leakage of fuel F exceeds a predetermined value, the alarm is given, and further, the fuel valve 15 is automatically closed. Therefore, the gas turbine combustor 9 can be safely operated without operating the gas turbine combustor 9 in a state that the fuel leaks. Fig. 7 is a view schematically showing a first modified embodiment of the heat exchange section 16 in the gas turbine plant according to the present invention. In general, in the heat exchange section 16, a fuel flows through a heat-transfer pipe, and a heating medium flows outside the heat-transfer pipe. In the heat exchange section 16 of this embodiment, a fuel leakage from the heat-transfer pipe is taken into consideration. More specifically, the heat exchange section 16 is divided into a first heat exchange section 49 and a second heat exchange section 50. Further, a high temperature heating medium HG flows through the first heat exchange section 49 while an intermediate heating medium IG, for example, an inert gas such as nitrogen gas or the like being supplied to the second heat exchange section 50 so that the fuel F is heated. Then, the intermediate heating medium IG heated the fuel F is circulated into the first heat exchange section 49 via a pump 51. As described above, the heat exchange section 16 of this embodiment is divided into the first heat exchange section 49 and the second heat exchange section 50, and the fuel F is heated by the intermediate heating medium IG. Thus, even in the event that a fuel leakage occurs in the second heat exchange section 50, it is possible to prevent an accident such as explosion or the like, and there is no danger as compared with the conventional indirect heat exchanger, thus being advantageous. Fig. 8 is a view schematically showing a second modified embodiment of the heat exchange section 16 in the gas turbine plant according to the present invention. The heat exchange section 16 of this embodiment is divided into a high temperature chamber 52 and a low temperature chamber 53 and is attached with a heat pipe 54 in a manner of crossing these chambers 52 and 53. The high temperature heating medium HG supplied to the high temperature chamber 52 heats the heat pipe 54, and then, the heat is transferred to the fuel F of the low temperature chamber 53 so as to heat the fuel F. Thus, even in the event that a fuel leakage occurs, there is no possibility of explosion, so that a safe operation of the heat exchange section 16 can be securely performed. Fig. 9 is a system diagram schematically showing an aspect of a gas turbine plant according the present invention. In this case, like reference numerals are used to designate the same components as for the above gas turbine plants. In this embodiment, the high pressure air discharged from the air compressor 8 via a discharged air system is used as a heating source for heating the fuel F of the fuel section 12. A check valve 56 and the heat exchange section 16 of the fuel section 12 are bypassed from the midway of the discharged air system 55, and thus, there is provided a discharged air recovery system 57 connected to a low pressure state of the air compressor 8 or to an outlet thereof. The discharged air system 55 includes a discharged air valve 58. The discharged air valve 58 includes a valve opening control section 59. The valve opening is computed (operated) by the valve opening control section 59 on the basis of at least one or more signals of a rotational speed signal from a rotational speed detector 61 which detects a rotational speed of a gas turbine shaft 60 and an operating signal from a power detector 62 which detects a power of the driven equipment 11. In this manner, a control for opening and closing the valve is made on the basis of the operational signal. As described above, in this embodiment, a flow rate of the high pressure air discharged from the air compressor 8 to the atmospheric air via the discharged air system 55 is controlled by the discharged air valve 58, and then, the high pressure air thus controlled in the flow rate is used as a heating source so that the fuel F of the fuel section 12 is heated in the heat exchange section 16 provided in the discharge air recovery system 57, and thus, is recovered to the air compressor 8. Therefore, the heat is effectively used, so that a plant heat efficiency can be improved as compared with the conventional case. Fig. 28 is a graph showing a comparison in a plant heat (thermal) efficiency between a gas turbine plant according to each embodiment of the present invention and the prior art. In the gas turbine plant according to each embodiment of the present invention, the high pressure air of the air compressor 8 is used as a heating source, and the fuel F supplied from the fuel section 12 to the gas turbine combustor 9 is heated by the heat exchange section 16, and thus, the quantity of heat (energy) of the fuel F is enhanced. By doing so, it is possible to improve a plant heat efficiency by consumption of a small fuel F. In particular, in the case where the same temperature gas turbine drive gas is generated by a gas turbine plant according to each embodiment of the present invention and the prior art, the gas turbine plant according to each embodiment of the present invention and the prior art makes it possible to relatively reduce the consumption of the fuel F as compared with the prior art. Therefore, the plant heat efficiency can be improved about 0.5 to 1.0% as compared with the prior art.

Claims: A gas turbine plant which comprises: an air compressor (8); a gas turbine (10) including a high temperature section; a driven equipment (11), said air compressor, said gas turbine and said driven equipment being operatively connected in series; a gas turbine combustor (9) arranged between the air compressor and the gas turbine; a fuel system (12) for supplying a fuel to the gas turbine combustor; an air extraction closed circuit system (26; 35; 57) provided for said air compressor; and a heat exchange section (16) provided for said air extraction closed circuit system for heating the fuel supplied to the gas turbine combustor from the fuel system (12), characterized in that said air extraction closed circuit system (35) is further provided with a valve opening control means (46) for detecting a fuel leak into the high pressure air by a fuel leak detector (45) provided for the heat exchange section and for closing a fuel valve (15) of the fuel system when a detection signal exceeds a predetermined value and also provided with an alarm device (47) for giving an alarm when the detection signal exceeds the predetermined value. The gas turbine plant according to claim 1, wherein said air extraction closed circuit system is provided with the heat exchange section (16) for heating the fuel from said fuel system and another heat exchange section (37) for heating a heat utilizing device for heating a medium to be heated of the heat utilizing device. The gas turbine plant according to claim 1, wherein said air extraction closed circuit system (57) is further provided with a check valve (56) and a branch equipped with an air discharge valve (58) which opens and closes in response to at least one signal of a rotational speed signal of a gas turbine shaft and a power signal of the driven equipment so as to discharge the air from said air compressor (8).

Inventors: ITO SHOKOU, KOBAYASHI TADASHI, KOGA AKINORI, OKAMURA TAKANARI, SASAKI TAKASHI, ITO, SHOKOU, KOBAYASHI, TADASHI, KOGA, AKINORI, OKAMURA, TAKANARI, SASAKI, TAKASHI
Applicants: TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA
Application year: 1998
Main classification: F02C7
IPC codes: F02C7