WO1997021917A1

WO1997021917A1 - A power plant

Info

Publication number: WO1997021917A1
Application number: PCT/SE1996/001640
Authority: WO
Inventors: Roine Brännström; Anders Lövgren; Dirk Veenhuizen
Original assignee: Abb Carbon Ab
Priority date: 1995-12-11
Filing date: 1996-12-11
Publication date: 1997-06-19
Also published as: SE9504428D0; SE505570C2; SE9504428L

Abstract

A power plant comprises a combustion chamber (1) in which combustion of a combustible material is intended to take place while forming hot combustion gases, and a gas turbine device with a high pressure turbine (14) which is arranged in series with a low pressure turbine (27), and with a high pressure compressor (13) which is arranged in series with a low pressure compressor (30). To control the plant, regulation means (39, 41) are arranged in front of or in at least one of the low pressure compressor and the high pressure turbine, and arranged to affect the flow of oxygen-containing gas and combustion gas, respectively. The plant may further comprise an intermediate pressure turbine (20) which is arranged between the high pressure turbine (14) and the low pressure turbine (27) and arranged to extract heat energy from the combustion gases. Thereby, the regulation means (40) may be arranged in or in front of the intermediate pressure turbine (20) and arranged to affect the flow of combustion gas.

Description

A power plant

BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention refers to a first power plant comprising a combustion chamber in which a combustion of a combustible material is intended to take place while forming hot combustion gases, a gas turbine device with a high pressure turbine which is arranged m series with a low pressure turbine, and with a high pressure compressor which is arranged n series with a low pressure compressor, first conduit members which are arranged to lead the combustion gases from the combustion chamber to the high pressure turbine and thereafter to the low pressure turbine in order to drive the h gh pressure compressor and the low pressure compressor respectively, second conduit members which are arranged to lead an oxygen-containing gas, needed for the combustion, to the combustion chamber via the low pressure compressor and thereafter to the high pressure compressor for compressing the oxygen-containing gas to a desired pressure, and means for regulating the plant. Furthermore, the invention relates to a second power plant comprising a combustion chamber in which combustion of a combustible material is intended to take place while forminq hot combustion gases, a gas turbine device with a high pressure turbine, an intermediate pressure turbine and a low pressure turbine arranged in series with each other, and with a hign pressure compressor which is arranged m series with a low pressure compressor, first conduit members which are arranged to lead the combustion gases from the combustion chamber to the high pressure turbine, thereafter to the intermediate pressure turbine and finally to the _o pressure turbine m order to drive the high pressure compressor and the low pressure compressor respectively, second conduit members which are arranged to lead an oxygen- containing gas, needed for the combustion, to the combustion chamber via the low pressure compressor and thereafter the high pressure compressor for compressing the oxygen- contaming gas to a desired pressure, and means for regulating the plant. Combustible material is referred to as all fuels that can burn, such as for example pit coal, brown coal, peat, biofuel, oil shale, pet coke, waste, oils, hydrogen gas and other gases, etc.

The invention will now be discussed and elucidated through different applications in connection to a pressurized fiuidized bed, a so called PFBC-power plant (pressurized fiuidized bed combustion) . The invention is not, however, delimited to such applications, but can be used m all possible power plants, for example in connection to different types of gas turbine plants.

In a conventional PFBC-power plant the bed is supplied with combustion air in the shape of compressed air from the pressure vessel which encloses a combustion chamber, in which the fiuidized bed is kept, v a fluidizmg nozzles beneath the bed. The combustion gases that are formed during the combustion process pass a freeboard above the bed surface, whereafter they are purified and conducted to a gas turbine. The combustion gases drive the gas turbine which in its turn drives an electric generator on one hand and a compressor which provides the pressure vessel with compressed air on the other hand. In the bed the fuel is combusted at a temperature in the range of 850°C. For a generation of steam, a steam generator in the shape of a set of tubes is positioned in the bed. Energy is taken from the bed via the steam turbines to which the steam is led in a steam system. At full load the whole set of tubes is located within tne bed. A PFBC-plant is characterized by a small plant volume in relation to accomplished output m comparison to other types of plants where fuel is combusted in a fiuidized bed at atmospheric pressure conditions. The efficiency of a PFBC-plant is also high. Furthermore, the combustion in a PFBC-plant takes place under auspicious conditions from an environmental and economic point of view.

Power plants with a gas turbine for generation of mechanical energy are by tradition regulated through control of the combustion, that is the supply of or the amount of fuel in the combustion chamber. This way of regulating is, however, often too slow to meet the demands for rapid operation adaptments from, by way of example, the power mains to which the plant is to deliver electric energy. This in particular considers PFBC-plants where it is known to regulate the combustion by adjusting the height of the fiuidized bed.

Furthermore, by such power plants with one gas turbine with several turbine-compressor steps, it is known to control the flow of gas to the low pressure turbine by means of a rotatable guide-blade in front of the inlet to the low pressure turbine. By such a regulation the rotation speed of the low pressure compressor can be adjusted, and m that way the flow of combustion air to the combustion chamber is controlled. SE-B-469 039 shows a PFBC-plant which presents the features initially defined of the first power plant, and such a flow regulation by the low pressure turbine.

SE-B-452 179 shows another such PFBC-power plant with a rotatable guide-blade for regulating the flow through the low pressure turbine, the guide-blade being arranged before the low pressure turbine.

This way of regulating the flow, however, presents several drawbacks. The combustion gases delivered to the low pressure turbine still have a high temperature and may contain dust and particles. The low pressure turbine which operates at relatively low pressures has a seemingly voluminous design, which in itself gives rise to a complicated construction of different components, such as rotatable guide-blades. The high temperature also implies that the likewise voluminous regulating equipments, due to different linear expansion of different equipment components, easily can jam and thus become hardmanoevred.

As the low pressure turbine operates at a relatively low pressure but with large volumes, very high speeds of the combustion gas is obtained, at least on certain operation occasions, by which speeds even small amounts of dust and particles lead to a significant erosion of the rotor blades and other components of the low pressure turbine, which in its turn results in a too early wear thereof.

SUMMARY OF THE INVENTION

The object of the present invention is to accomplish a power plant which can be regulated in such a way that the above disadvantages can be avoided.

This object is obtained by the first power plant initially defined, which is characterized in that the regulating means are arranged in or in front of at least one of the low pressure compressor and the high pressure turbine, and arranged to affect the flow of oxygen-containing gas and combustion gas respectively.

Apart from avoiding said drawbacks, the speed can be kept at a relatively low level due to the high pressure through the arrangement of the regulation means n or m front of the high pressure turbine, which means that the erosive influence of possible dust particles in the combustion gas becomes small. As the hign pressure turbine operates at a higher pressure than the low pressure turbine, the volume of the combustion gas is smaller by the high pressure turbine. This results m the high pressure turbine being significantly more compact and smaller than the low pressure turbine, that is the diameter of the nigh pressure turbine is smaller and the blades thereof are shorter. This also leads to that corresponding regulation equipment, for example rotatable guide-blades, becomes smaller and more compact. Thereby, the regulation equipment becomes cneaper and more simple to construct and applicate.

Due to the low temperature of the air that is fed into the low pressure compressor it is possible to avoid substantially all problems connected to linear expansion, particularly different linear expansion for different components of the low pressure compressor, by arranging the regulation means m or in front of the low pressure compressor. Furthermore, the air that is taken in is substantially clean, that is it does not contain any dust particles (possible such ones can be easily filtered away) or aggressive, corroding combustion products, such as sulphuric or nitrogen compounds. This implies tnat no corrosion or erosion accomplished by the transported medium will appear by the regulation means, for example rotatable guide-blades .

According to one embodiment of the invention the regulating means may comprise members which are arranged to regulate the flow through the low pressure compressor and the high pressure turbine respectively.

The above object is also obtained by means of the second power plant initially defined, which is characterized in that the regulation means are arranged in or in front of tne intermediate pressure turbine and arranged to affect the flow of combustion gas. By arranging the regulation means n or in front of the intermediate pressure turbine substantially the same advantages are obtained as when these are arranged at the high pressure turbine, particularly in the case where there is an intermediate heater, arranged before the intermediate pressure turbine, which intermediate heater increases the temperature of the combustion gases.

According to one embodiment of the invention the regulation means may comprise members that are arranged to regulate the flow through the intermediate pressure turbine.

According to another embodiment of the invention the h gh pressure turbine and the high pressure compressor are arranged on a common first shaft, and the low pressure turbine and the low pressure compressor are arranged on a common second shaft. Thereby, a generator may be arranged on the first shaft for extraction of electric energy. In the case where there is an intermediate pressure turbine this one is, advantageously, provided on the first shaft.

According to another embodiment, the regulation means comprise at least one rotatable guide-blade row, arranged in the flow.

Advantageous further embodiments of the inventive power plant are defined in the dependent patent claims 10 to 18. Thereby, it should be particularly noted that the combustion chamber may be of a type that comprises a fiuidized oed which preferably is pressurized. A topping combustor may be arranged to increase the temperature of the combustion gases to a level suitable for the gas turbine device during the combustion of a fuel. Moreover, there might be a gasifying reactor, which is arranged to produce a combustible gas that constitutes the fuel, and means for regulating the amount of comiDustible gas that is supplied to the toppinq combustor from the gasifying reactor, and/or a container wnich is arranged to store a combustible gas that constitutes tne fuel, and means for regulating the amount of combustible gas that is supplied to the topping combustor from the container.

The topping combustor may comprise a topping combustion cnamber which is arranged between the combustion chamber and tne high pressure turbine, and/or a reheater device which is arranged downstream of the high pressure turbine and arranged to increase the temperature of the combustion gases wnen they have left the high pressure turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described more in detail by means of different embodiments, defined by way of example, one of which is illustrated on the enclosed drawing, the only Fig 1 of which schematically shows a PFBC-power plant with a combined gas and steam cycle (the latter not snown) .

DETAILED DESCRIPTION OF DIFFERENT EMBODIMENTS

A PFBC-power plant, that is a plant for combustion of particulate fuel in a pressurized fiuidized bed, is schematically shown in Fig 1. The plant comprises a combustion chamber 1 which is housed in a vessel 2 whicn may have a volume n the range of 10 m and which may be pressurized up to, for example, approximately 16 bar. Compressed oxygen-containing gas 3, air m the illustrated example, for pressurizing the combustion chamber 1 and for fluidizing a bed 4 in the combustion chamber 1 is supplied to the pressure vessel 2. The compressed air is supplied to the combustion chamber 1 via scnematically indicated fluidizing nozzles 5 whicn are arranged at the oottom of the combustion cnamber 1 for fluidization of the bed 4 whicn is enclosed m the comoustion chamber 1. The bed 4 is constituted by oed material, granular absoroent and a particulate fuel, preferably crushed coal which is compusted in the fluidizing air conducted to the bed 4. The comoustion gases from the oed 4 are tnen conducted by means of d conduit member, via a purification arrangement 6, which in the example is constituted by temperature filter, which may be of a ceramic type and which is made for high pressures, and an intercept valve 7 further on to a topping combustion chamJoer 8. Via a conduit 9 from the gasifying reactor 10 of a known type and via a further high temperature filter Il a combustible gas is also conducted to the topping combustion chamber 8. The flow of combustible gas to the topping combustion chamber 8 is regulated by means of the regulation valve 9a. In the topping combustion chamber 8 the combustible gases are combusted in connection to supply of compressed air via the conduit 12 from a high pressure compressor 13 through the influence of a burner, not shown, and is mixed with the combustion gases from the combustion chamber 1 for increasing the temperature thereof, so that the gases that leave the topping combustion cnamber 8 present a temperature of approximately 1200-1500°C, which makes them well suited as driving gas for driving a first gas turbine 14 in the shape of a high pressure turbine. By means of the topping combustion chamber 8, the temperature of said combustion gases has thus been increased from approximately 850-950°C to approximately 1200-1500°C. The high pressure turbine 14 and the high pressure compressor 13 are arranged on the same shaft as a generator 15, from which useful electric energy can be extracted. The high pressure compressor 13 also delivers compressed air to the PFBC- combustion chamber 1 via the conduit 16 from which the conduit 12 is branched off. Thereby, an intercept valve 17 is arranged between the high pressure compressor and the combustion chamber 1. The hign pressure compressor 13 also delivers air via the conduit 18 for the gasification in the gasifying reactor 10. The rest fuel that is formed m the gasifying reactor 10 during the production of the combustible gas may be supplied to the bed 4 in the combustion chamber 1 via a fuel conduit 19.

The PFBC-power plant shown in the figure is of an advanced sort, as it presents a further gas turbine 20, in the shape of an intermediate pressure turbine which is arranged on the same shaft 21 as the high pressure turbine 14 and the high pressure compressor 13. The gas which is expanded and given a decreased temperature in the high pressure turbine 14 is conducted v a a conduit 22 to a reheating device 23 which comprises a so called reheat combustion chamber or reheating combustion chamber. The reheat combustion chamber 23 obtains a flow of said combustible gases, which flow is regulated by means of the regulation valve 9b and originates from the gasifying reactor 10, and compressed air from the high pressure compressor 13 in the same way as the topping combustion chamber 8, which is shown in Fig 1, through the conduits 24 and 25 respectively, wnereby these combustible gases are combusted there by means of a burner, not shown, and the hot gases thereby created are mixed with the combustion gases from the high pressure turbine 14 in order to once again increase their temperature before they are further conducted via the conduit 26 to the intermediate pressure turbine 20. In this way the output extracted from the intermediate pressure turbine 20 can be substantially increased.

The combustion gases expanded in the intermediate pressure turbine 20 are brought to a low pressure turbine 27. The combustion gases leaving the low pressure turbine 2 ⁿ still contain energy that can be taken advantage of in an economizer 28. The low pressure turbine 27 is arranged on a shaft 29 on which also a low pressure compressor 30 s arranged. The low pressure compressor 13 is supplied with atmosphere air via a filter 31. The low pressure compressor 30 is thus driven by the low pressure turbine 27 and, from its outlet, it provides the high pressure compressor 13 with air that has been compressed in a first step. An intercooler 32 is arranged between the low pressure compressor 30 and the high pressure compressor 13 m order to decrease the temperature of the air that is supplied to the inlet of the high pressure compressor 13.

Moreover, the power plant presents a steam turbine side, which is not shown here but indicated by means of a set of tubes 33 which is submersed in the fiuidized bed 4, in which set of tubes water is circulated, steamed and superheated through heat exchange between the tubes and the bed material, in order to absorb heat generated by the combustion carried out in the bed 4.

The conduit 18 coming from the high pressure compressor 13 and for supply of compressed air to the gasifying reactor 10 comprises a compressor device 34 which, in the example shown, is constituted by a so called booster compressor. Preferably, the latter is driven by means of an electric motor 35, but may also be driven by means of a steam turbine which is supplied with steam from the set of tubes 33. By means of this compressor 34, the gas pressure of the air supplied to the gasifying reactor 10 can be further increased, as it is desirable that the flow of gas delivered by the gasifying reactor 10 has a higher pressure than the flow of combustion gas that arrives at the topping combustion chamber 8 and/or the reheating combustion chamber 23. Thereby, the combustible gases can be easily supplied to the topping combustion cnamber 8 and/or the reheating combustion chamber 23 in every given pressure situation. In the gasifying reactor 10 a liquid or solid fuel is gasified, in this example particulate coal which during a below- stoichiometric process generates combustible gases in a way- known per se. The reason for arranging a free-standing gasifier whicn operates at a higher pressure than the PFBC- bed 4 in this way is that it is simply necessary that the pressure of the gas in the gasifying reactor 10 is higher than the pressure in the combustion chambers 8, 23, in order to be able to regulate the flow of fuel and distribute the flow of fuel evenly in these combustion chambers. Accordingly, a pressure of approximately 26 bar may be accomplished in the gasifying reactor 10 at a pressure of possibly 16 bar in the PFBC-combustion chamber 1. However, to be able to regulate the air flow to the gasifying reactor 10 more precisely, the motor 35 may be connected to a schematically shown control device 36 for regulation of the rotation speed of the motor. The control device 36 may suitably constitute a part of the overall control system of the plant (not shown) . As an alternative or supplement to the rotation speed regulation it is also possible to arrange a schematically shown guide-blade device 37, for example in the shape of guide-blades which are controlled by a manoeuvring member and which are arranged on a guide-blade row m or in front of the compressor 34 to be able to, in that way, exactly control the air flow through this one ano regulate the amount of air which is supplied to the gasifying reactor 10. Thereby, the manoeuvring member may be connected to the control device 36.

Furthermore, the conduit 18 coming from the high pressure compressor 13 may comprise a heat-exchanger 38 which is arranged downstream of the compressor device 34. The conduit 9 coming from the gasifying reactor 10 also extends through the heat-exchanger 38. Accordingly, this means that the relatively cool compressed air which is supplied to the gasifying reactor 10 will be heat-exchanged with the very hot combustible gas (800-1000°C) which leaves the gasifying reactor 10. Accordingly, the temperature of the gas which is led through the heat-exchanger 38 may be lowered fc a significantly lower temperature of below 600°C, whicn means that the dust particles which are in liquid condition at the higher temperature will be n a solid condition after the heat-exchanger 38. Thereby, the risk that these gases and melted dust particles shall stop up the hign temperature filter 11 is significantly reduced. Furthermore, the filter 11 may be manufactured with conventional technique, that is it is not necessary to use sintered ceramic hot gas filters, because the temperature of the combustible gas has been decreased. A further advantage of this decrease of temperature is that the regulation valves 9a, 9b can Pe of conventional structure, that is it is not necessary with any advanced cooling through steaming of water and super-heating of the steam to secure the function of these regulation valves 9a, 9b. Such cooling is very expensive and requires extensive regulation and security equipment.

In Fig 1 three schematically drawn, flow regulating members 39, 40, 41 are illustrated and are arranged at the high pressure turoine 14, the intermediate pressure turbine 20 and the low pressure compressor 30 respectively. It should be noted that the invention is applicable with only one of these regulation members or with a combination of two or all three regulation members. Each of the regulation members 39, 40, 41 comprises controllable guide-blades which are arranged in the flow on a guide-blade row. The guide-blade row is either arranged m front of, that is upstreams of, the high pressure turbine 14, the intermediate pressure turbine 20 and the low pressure compressor 30 respectively, or in, that is between rotors of, the high pressure turbine 14, the intermediate pressure turbine 20 and the low pressure compressor 30 respectively. Through rotation of the guide-blade row the direction of the flow is controlled and the size of the opening can Pe regulated. Each guide- lade row is driven by a respective manoeuvring member 42, 43 and 44 respectively which m their turn are connected to a control unit 45 which, suitably, constitutes a part of the overall control system of the plant (not shown) .

By rotating the guide-blades of the regulation member 41 m or in front of the low pressure compressor 30, it is possible to decrease the flow and the out-going pressure. This results in a decrease of the flow and the pressure after the high pressure compressor 13 and m the combustion chamber 1 and thus also at the turbine side, whereby the output generated by the plant decreases .

By rotating the guide-blades of the regulation member 39 in or in front of the high pressure of the regulation member 39 m or in front of the high pressure turbine 14 such that the flow decreases, the pressure in front of the high pressure turbine 14 and in the combustion chamber 1 will initially increase. However, the decreased flow will result in tne rotation speeds of the low pressure turbine 27 going down, and thereby the flow through the low pressure compressor 30 and the pressure out-going therefrom decreases, which results in a decrease of the total flow through the plant and the pressure of the plant such that the generated output thereof will decrease.

By regulating the glide-blades of the regulation member 40 in or in front of the intermediate turbine 20 such that the flow decreases, also an initial increase of the pressure is obtained. However, the decreased flow, n a way analogous to that in the case of the flow regulation of the high pressure turbine, results m a decrease of the output generated by the plant.

Furthermore, the plant comprises a container or accumulator tank 46 for storage of comoustible gases. Through a closable valve member 4⁷ the accumulator tank 46 is connected tc the conduit 9 via which the gasifying reactor 10 supplies the topping combustion chamber 8 and the reheat combustion chamoer 23 with combustible gases. Thus, the accumulator tank 46 may be charged with combustible gases from the gasifying reactor 10, which gases then during extreme needs of load increase may be supplied to the topping combustion chamber 8 and the reheater combustion chamber 23.

The invention is in no way delimited to the embodiment described above, but a variety of possibilities of modifications thereof are possible within the frame of the following patent claims, and should be evident for a man skilled in the art without departing from the basic idea of the invention.

By way of example it would be possible that the plant only presents two gas turbines, that is that the intermediate pressure turbine shown in Fig 1 is excluded. Thereby, the reheating combustion chamber 23 increases the temperature of the combustion gases that come from the high pressure turbine 14 and are to arrive at the low pressure turbine 27 which, in such a case, will receive gases with a higher pressure than described above and could be named intermediate pressure turbine.

Nor is it necessary, but advantageous, that the inventive PFBC-plant presents a topping combustion chamber 8, even though the advantages of the reheating combustion chamber 23 will do justice to themselves only when there is such a topping combustion chamber 8.

Of course, it is also possible, in the case of more than two gas turbines, to arrange a reheating combustion chamber between the second and third gas turbines m the path of the combustion gases if desired. The air coming from the compressor 34 need not be led via the heat-exchanger 38, but may be supplied directly to the gasifying reactor 10.

Nor is it necessary to take the air arriving at the free¬ standing gasifying reactor 10 directly from the high pressure compressor 13, but it can be taKen directly from the atmosphere. Thereby, the inventive, regulatable compressor 34 may compress the atmosphere air to a desired pressure m one or more steps.

Claims

1 . A power plant compris ing a combustion chamber (1) in which combustion of a combustible material is intended to take place while forming hot combustion gases,

- a gas turbine device with a high pressure turbine (14) which is arranged in series with a low pressure turbine (27) and with a high pressure compressor (13) which is arranged in series with a low pressure compressor (30) ,

- first conduit members (22, 26) which are arranged to lead the combustion gases from the combustion chamber to the nigh pressure turbine (14) and thereafter to the low pressure turbine (27) in order to drive the high pressure compressor (13) and the low pressure compressor (30) respectively,

- second conduit members (16) which are arranged to lead an oxygen-containing gas, needed for the combustion, to the combustion chamber (1) via the low pressure compressor (30) and thereafter the high pressure compressor (13) for compressing the oxygen-containing gas to a required pressure, and

- means for regulating the plant, characterized in that the regulation means (39, 41) are arranged in or in front of at least one of the low pressure compressor (30) and the high pressure turbine (14) and arranged to affect the flow of oxygen-containing gas and combustion gas respectively.

2. A power plant according to claim 1, characterized in that the regulation means (39, 41) comprise members that are arranged to regulate the flow through the low pressure compressor (30) and tne high pressure turbine (14) respectively.

3. A power plant according to any of the preceding claims, cnaracterized by an intermediate pressure turbine ,20) whicn is arranged between the high pressure turbine '14) and the low pressure turbine (2^"J and arranged to extract heat energy from the combustion gases.

4. A power plant comprising

- a combustion chamber in which combustion of a combustible material is intended to take place while forming hot combustion gases,

- a gas turbine device with a high pressure turbine (14), an intermediate pressure turbine (20) and a low pressure turbine (27) , arranged m series with each other, and with a nigh pressure compressor which is arranged in series with a low pressure compressor (13),

- first conduit members (22, 26) which are arranged to lead the combustion gases from the combustion chamber (1) to the high pressure turbine (14), thereafter to the intermediate pressure turbine (20) and finally to the low pressure turbine (27) m order to drive the high pressure compressor (13) and the low pressure compressor (30) respectively, - second conduit members (16) which are arranged to lead an oxygen-containing gas, needed for the combustion, to the combustion chamber (1) via the low pressure compressor (30) and thereafter the high pressure compressor (13) for compressing the oxygen-containing gas to a desired pressure, and

- means for regulating the plant, characterized in that the regulation means (40) are arranged in or m front of the intermediate pressure turbine (20) and arranged to affect the flow of combustion gas.

5. A power plant according to claim 4, characterized m that the regulation means (40) comprise members that are arranged to regulate the flow through the intermediate pressure turbine (20) . 6. A power plant according to any of the preceding claims, characterized m that the high pressure turbine (14) and the high pressure compressor (13) are arranged on a common first shaft (21), and the low pressure turbine (27) and tne low pressure compressor (30) are arranged on a common second shaft (29) .

^π . A power plant according to claim 6, characterized by a generator (15) which is arranged on the first shaft (21) for extraction of electric energy.

8. A power plant according to claim 6 or 7, characterized in that the intermediate pressure turbine (20) is arranged on the first shaft (21) .

9. A power plant according to any of the preceding claims, characterized in that the regulation means (39, 40, 41) comprise at least one rotatable guide-blade row, arranged in the flow.

10. A power plant according to any of the preceding claims, characterized by a steam circuit comprising steam tubes (33) that are arranged in the combustion chamber (1) for generating steam, a steam turbine, driven by the steam, and a generator driven by the steam turbine.

11. A power plant according to any of the preceding claims, characterized in that the combustion chamber (1) is of a type which comprises a fiuidized bed (4) .

12. A power plant according to claim 11, characterized in that the fiuidized bed (4) is pressurized.

13. A power plant according to any of the preceding cla_ms, characterized by a topping combustor (8, 23) which is arranged to increase the temperature of the combustion gases to a level suitable for the gas turbine device (14, 20, 27) during the combustion of a fuel .

14. A power plant according to claim 13, characterized by a gasifying reactor (10) which is arranged to produce a combustible gas which constitutes the fuel, and means for regulating the amount of combustible gas that is supplied to the topping combustor (8, 23) from the gasifying reactor.

15. A power plant according to claim 13 or 14, characterized by a container (46) which is arranged to store a combustible gas that constitutes the fuel, and means (47; for regulating the amount of combustible gas that is supplied to the topping combustor (8, 23) from the container.

16. A power plant according to any of claims 13 to 15, characterized in that the topping combustor comprises a topping combustion chamber (8) which is arranged between the combustion chamber (1) and the high pressure turbine (14) .

17. A power plant according to any of claims 13 to 15, characterized in that the topping combustor comprises a reheater device (23) which is arranged downstream of the high pressure turbine (14) and arranged to increase the temperature of the combustion gases when they have left the high pressure turbine (14) .

18. A power plant according to any of the preceding claims characterized by an intercooler (32) which is arranged on the second conduit member (16) between the low pressure compressor (30) and the high pressure compressor (13) .