Patent Application
20150121871
The invention relates to a turbine plant, in particular a steam turbine plant, and to a method for cooling a turbine plant, in particular a steam turbine plant.
Steam power stations, otherwise known as thermal power stations, are extensively known, for example from
A steam power station is a type of power station for generating electricity from fossil fuels, in which thermal energy from steam is converted into kinetic energy in a steam turbine—generally a multi-part steam turbine—
In the case of such a steam power station, a fuel, for example coal, is burned in a burner space, releasing heat.
The heat released in this manner is taken up by a water-tube boiler, in short a steam generator, where it converts previously purified and prepared (feed) water, fed into the boiler, into steam/high-pressure steam. Further heating the steam/high-pressure steam in a superheater increases the temperature and specific volume of the steam.
The high-pressure steam generated moves further—via an inflow side, i.e. what is referred to as a fresh steam side, FD side for short, or a supply line (FD supply line) located there—into a high-pressure section of the steam turbine (high-pressure turbine section) where it performs mechanical work as it expands and cools.
In order to achieve a high overall efficiency, once the steam has left the high-pressure section—via the waste steam side thereof or a waste steam discharge line located there—it is returned to the steam generator and undergoes intermediate superheating.
The (intermediate-)superheated steam is again supplied—via an inflow side, i.e. what is referred to here as a hot intermediate superheater side, HZU side for short, or a supply line (HZU supply line) located there—to an intermediate-pressure section of the steam turbine (intermediate-pressure turbine section) where it performs more mechanical work as it further expands and cools.
After leaving the intermediate-pressure section via the waste steam side thereof, or a waste steam discharge line located there, the steam flows via an overflow line into a low-pressure section of the steam turbine (low-pressure turbine section), where it performs more mechanical work as it expands and cools to waste steam pressure.
The generator coupled to the steam turbine then converts the mechanical power into electrical power, which is supplied to a grid in the form of electrical current.
The waste steam from the steam turbine, or from the low-pressure turbine section, flows via the waste steam side thereof, or a waste steam discharge line located there, into a condenser where it condenses by transfer of heat to the surroundings and collects as liquid water.
Via a condensate pump and through a preheater, the water is held in a feed water container and is then once again supplied to the boiler by means of a feed pump, thus closing a (water-steam) circuit of the steam power station.
A distinction is drawn between various types of steam power station, such as coal-fired power stations, oil-fired power stations, or also gas-and-steam combined-cycle power stations (COGAS power stations), according to their different methods for generating steam or the fuel used for generating steam.
A coal-fired power station is for example a special form of steam power station, in which coal is used as the predominant fuel for generating steam. Such coal-fired power stations are known for lignite and for hard coal.
In addition to steam power stations, gas power stations, or gas turbine power stations, are also known
Such a gas turbine power station is a power station which is operated using petroleum products or combustible gases such as natural gas. These gases are in this case the fuel for a gas turbine (http://de.wikipedia.org/wiki/Gasturbine, retrieved 4/24/2012) which in turn drives the generator coupled thereto.
A COGAS power station is described in
A COGAS power station of this type is a power station in which the principles of the gas power station and of the steam power station are combined. The gas turbine serves here as a heat source for a downstream waste heat boiler which in turn serves as a steam generator for the steam turbine.
Work such as maintenance or overhaul work on a turbine of a power station, such as on a steam turbine of a steam power station, can be carried out only after rotational operation of the turbine has been switched off. To that end, it is necessary for a shafting of the turbine to be cooled from temperatures in the region of 600° C. to below 100° C.
The steam turbine cools for example—without external intervention—in roughly 8 days, or approximately 200 hours, to below 100° C., or in roughly 6 days, or approximately 150 hours, to below 150° C. This latter moment is the earliest point at which the shafting, or the shaft of the steam turbine, can be shut down, although this must then be further rotated manually in order to avoid thermally-induced deformations of rotating parts of the shafting, which would hamper rotational operation.
Although gas turbines cool down faster than steam turbines, on account of having less material than steam turbines, cooling-down times without external intervention are long here too.
In order to reduce the time necessary for overhaul work, it is desirable to minimize the cooling-down times of a turbine, such as a steam turbine but also of a gas turbine or the turbine sections thereof, while keeping to permissible cooling rates.
In order to minimize these still considerable cooling-down times, in particular in the case of steam turbines, it is known to use therein what is termed forced cooling (Forced Cooling of Steam Turbines, Performance Enhancement—Steam Turbine, Answers for energy. Siemens A G, 2009).
In a steam turbine, this forced cooling involves drawing or blowing ambient air—instead of the (high-pressure) steam—as a coolant through the steam turbine, or through the turbine sections thereof, in the operational flow direction of the turbine.
The condenser downstream of the steam turbine is used in the context of the forced cooling as the pressure sink which initiates the suction flow through the steam turbine, wherein a vacuum with respect to the ambient air is generated inside the condenser (evacuation of the condenser) by means of vacuum pumps, for example using elmo pumps.
In order to ensure that as many as possible of the hot steam turbine components are cooled, the ambient air must be able to act on all the steam-guiding components of the steam turbine.
To that end, the ambient air—aspirated via the vacuum prevailing in the evacuated condenser—is allowed to flow in via (air) pipes between quick-closing valves and control valves, in each case on the FD side and HZU side or via the FD supply line or HZU supply line located there, whereby the coolant—then aspirated by the vacuum in the condenser—flows through the steam turbine or the turbine sections thereof in the operational flow direction of the steam.
The cooling effect of the ambient air cools the steam turbine—or the components thereof—and thus achieves faster cooling of the steam turbine components.
Since permissible cooling gradients for the steam turbine components may not be exceeded, which could otherwise lead to damage to components, the quantity of ambient air aspirated by means of the pressure sink in the evacuated condenser must be regulated. To that end, the control valves in the supply lines serve as regulating members.
A disadvantage of the known forced cooling technique is the necessary presence of the condenser for generating the pressure sink, or the suction flow of the coolant.
In the meantime, however, numerous steam turbine plants having steam turbines without a low-pressure turbine section and then also without a condenser have been created, with the steam turbines working in back-pressure operation. In the case of such back-pressure steam turbine plants without a condenser, for example in back-pressure steam power stations for seawater desalination plants, the known forced cooling cannot be used or there are no known other solutions for forced cooling.
The invention is based on the object of overcoming the disadvantages and limitations of the prior art in the context of maintenance or overhaul of a power station or of a turbine, in particular of a steam power station or of a steam turbine, more particularly of a back-pressure steam power station or of a back-pressure steam turbine plant without a condenser.
The invention is also based on the object of overcoming disadvantages and limitations of the prior art in the context of cooling of the power station or of the turbine, in particular of a back-pressure steam power station or of a back-pressure steam turbine plant without a condenser, in particular in the event of switching off the rotational operation of the turbine.
The object is achieved with a turbine plant, in particular a steam turbine plant, and with the method for cooling a turbine plant, in particular a steam turbine plant, having the features as claimed in the relevant independent claim.
The turbine plant relevant to the invention has a turbine through which a process gas can be made to flow in a flow direction from a turbine inlet to a turbine outlet when the turbine plant is in operation.
It is provided, according to the invention, that a fan is coupled to the turbine inlet or to the turbine outlet of the turbine.
Using this fan, which is provided according to the invention and is coupled to the turbine, a coolant sucked into the turbine via the turbine inlet by means of the fan coupled to the turbine outlet can be blown through the turbine in the operational process gas flow direction, or a coolant sucked into the turbine via the turbine outlet by means of the fan coupled to the turbine inlet can be blown through the turbine counter to the operational process gas flow direction.
According to the method for cooling a turbine plant having a turbine through which a process gas can be made to flow in a flow direction from a turbine inlet to a turbine outlet during operation, a coolant is drawn into the turbine by means of a fan coupled to the turbine inlet or to the turbine outlet, and is drawn through the turbine in or counter to the operational process gas flow direction, whereby the turbine is cooled by the coolant.
In other words, or more simply, the invention creates, in the case of a turbine and by means of a fan coupled to the turbine inlet or to the turbine outlet, a pressure sink at the turbine inlet or at the turbine outlet.
The pressure sink initiates a suction flow in or counter to the process gas flow direction through the turbine, by means of which a coolant, aspirated at the respective other end of the turbine depending on the coupling side of the fan, is drawn through the turbine in or counter to the process gas flow direction. The turbine is cooled by the coolant drawn through the turbine.
The invention thus proves to be most advantageous in many respects.
The coolant drawn through the turbine—in or counter to the process gas flow direction—by the suction flow acts on all of the steam guiding components of the turbine and thus ensures that all of the hot components of the turbine are cooled. This achieves efficient, effective and rapid cooling of the turbine.
The invention thus makes it possible to minimize the cooling-down times of a turbine such as a steam turbine but also a gas turbine, or of their turbine sections. Overhaul times or downtime of turbines or turbine plants can thus be reduced, resulting in financial savings.
In particular, the invention makes it possible—using the fan according to the invention to create a pressure sink at the turbine inlet or outlet—to effect forced cooling also in turbines or turbine plants without a condenser or without a low-pressure turbine section and without a condenser.
It is thus possible by means of the invention to use forced cooling also in known back-pressure steam turbine plants which work without a condenser or without a low-pressure turbine section and without a condenser, such that these plants can also be cooled faster and overhaul times and downtime there can be reduced.
Preferred developments of the invention will also emerge from the dependent claims. The described developments relate both to the turbine plant and to the method for cooling a turbine plant.
According to one preferred development, the fan is coupled to the turbine outlet, in particular to a waste steam duct at the turbine outlet. In this context, the coolant then drawn into the turbine via the turbine inlet can be sucked through the turbine in the operational process gas flow direction. In particular, coupling the fan to the waste steam duct is simple to carry out in terms of construction.
A further preferred development provides that the fan is coupled to the turbine inlet, in particular to a fresh steam/HZU/overflow supply line at the turbine inlet. For example, the fan may be connected to an air pipe located there.
In this case, then, the coolant drawn into the turbine via the turbine outlet can be sucked through the turbine counter to the operational process gas flow direction.
A suction flow of the coolant through the turbine counter to the operational process gas flow direction proves to be of particular advantage since the coolant enters the turbine at the “cold” side. This produces, in the turbine components, cooling gradients which are smaller and load the component less than in the case of the coolant entering at the “hot” side of the turbine.
Furthermore, in the case of multi-part turbines, which then generally have one (or in each case a plurality of) high-pressure turbine section(s) and intermediate-pressure turbine section(s) and/or low-pressure turbine section(s), it can also be provided that the fan is coupled to the high-pressure turbine section, the intermediate-pressure turbine section and/or the low-pressure turbine section of the turbine. Multiple fans may also be provided for multiple such turbine sections.
Thus, here, it may also be further provided that, depending on how the pressure sink is created (by the fan) at a waste steam side (turbine outlet) or a supply or fresh steam side (turbine inlet) of such a turbine section, the fan is coupled to a waste steam duct or to a fresh steam/HZU/overflow supply line of the high-pressure turbine section, of the intermediate-pressure turbine section and/or of the low-pressure turbine section.
A further preferred development provides that the coolant is ambient air. This is easily available and is available in sufficient quantities and at usable temperatures.
The coolant, in particular the ambient air, can then flow into the turbine or turbine section via a pipe connected to the turbine, for example an air pipe on the fresh steam side or HZU side of the turbine or turbine section.
It is particularly preferred if the flow of the coolant into the turbine can be controlled, regulated and/or governed by means of a valve. Thus, i.e. by regulating a quantity of coolant entering the turbine or turbine section, it is possible to ensure that permissible cooling gradients are not exceeded. A control valve can be used as a regulating member.
In this context, i.e. for regulating the quantity of coolant, the valve, for example the control valve or regulating valve, can be arranged at any point in the coolant path, for example also at the fan inlet.
According to a particularly preferred development, the coolant flows into the turbine or turbine section via an air pipe arranged between valves, for example between a quick-closing valve and a control valve, on the fresh steam side or HZU side of the turbine or turbine section. The quantity of inflowing coolant can be controlled, regulated and/or governed via the control valve so as to not exceed permissible cooling gradients for the turbine components.
According to another preferred development, the process gas is steam. I.e. the turbine is a steam turbine or, respectively, the plant is a steam turbine plant.
Furthermore, in this case the turbine or steam turbine can be a multi-part turbine or steam turbine. This can have one or more turbine sections, such as high-pressure turbine sections, intermediate-pressure turbine sections and/or low-pressure turbine sections.
Particularly preferably, the turbine plant is a steam turbine plant without a condenser, for example a back-pressure steam turbine plant without a low-pressure turbine section and without a condenser. The invention provides in this case, by means of the fan used according to the invention, a pressure sink which is otherwise not present, whereby forced cooling is possible also in the case of such a steam turbine plant without a condenser. It is now possible, by means of the invention, to shorten downtime also in the case of such a steam turbine plant without a condenser.
Forced cooling according to the invention—by means of the pressure sink produced by the fan and the coolant flow thus initiated through the turbine or turbine section—can be effected separately for one or in each case multiple turbine sections, by in each case multiple separate coolant throughflows and correspondingly multiple fans, or also jointly for multiple successive turbine sections, in the case of a common coolant throughflow, by means of a single fan.
In one further preferred development, thermal protection or overheating protection is provided for the fan.
A fan as used according to the invention is limited in terms of its outlet temperature, i.e. the temperature of the medium blown out by the fan, for example to 150° C. Accordingly, therefore, the inlet temperature of the medium sucked in by the fan is also limited, for example to 120° C. if the medium flowing through the fan is assumed to be heated by 30° C.
In order to provide the thermal protection for the fan, it can be provided that a further coolant supply, for example a bypass or bypass pipe, is attached at or in the region of the inlet of the fan, via which bypass or bypass pipe a further coolant, for example also ambient air, can be admixed with the coolant leaving the turbine and drawn into the fan. A temperature sensor may also be arranged at the fan outlet, by means of which the temperature of the medium leaving the fan is measured.
If this bypass is furthermore also provided with a control valve, the further coolant can be admixed in a manner that can be controlled, governed and/or regulated with the coolant leaving the turbine and drawn into the fan, in particular taking into account the measured fan outlet temperature, and thus overheating of the fan can be prevented.
It is also possible to control, govern and/or regulate the admixing and/or the quantity of the further coolant by means of a three-way mixer at the point of bringing together the further coolant and the coolant leaving the turbine and drawn into the fan.
It is also possible to control, regulate and/or govern the admixing of the further coolant using a turbine temperature, and/or the temperature of the coolant aspirated by the fan and/or the temperature of the admixed further coolant.
At the start of the forced cooling, only a small quantity of coolant fed through the turbine is necessary in order to achieve the maximum permissible cooling rate or in order to achieve the permissible cooling gradients of the turbine components. The turbine, which at that moment is still at a high temperature, causes this small quantity of coolant—by exchange of heat with the very hot turbine components—also to be heated to a high temperature.
In order to cool the coolant—which at that moment is therefore very hot—flowing out of the turbine and to bring it to an inlet or outlet temperature which is permissible for the fan, the further coolant, for example also ambient air, is admixed via the bypass.
As the turbine temperature drops, the quantity of coolant through the turbine is increased, and at the same time the admixed further coolant quantity is reduced.
It is thus possible to effectively prevent the fan from overheating while at the same time “utilizing the maximum cooling rates of the turbine components”.
The medium leaving the fan, i.e. the fan exhaust air, may be discharged to the surroundings—with the shortest possible flow path so as to avoid pressure losses. It is thus also possible to avoid heating a machine room incorporating the turbine.
Furthermore, it can also be provided that steam-precooling of the process gas, for example steam injection cooling of the process gas, is carried out before the forced cooling according to the invention.
The above description of advantageous refinements of the invention contains numerous features which are reproduced in the individual subclaims, in some cases combined into groups. However, a person skilled in the art will expediently also consider these features individually and combine them into appropriate further combinations.
The figures show exemplary embodiments of the invention which will be explained in more detail below. Identical reference signs in the figures denote technically identical elements.
In the figures:
Exemplary embodiments: forced cooling in steam turbine plants without condensers or in steam power stations having steam turbine plants without condensers (
When the steam power station 1 is in operation, hot steam/high-pressure steam 15, which has been heated by a steam generator and further heated by a superheater and which in the following is denoted only as process gas 15, flows via a supply line 30 into the steam turbine 29 via a turbine inlet 4 on a fresh steam side 13 of said steam turbine 29, and flows through the steam turbine 29, in the process gas flow direction 27, where it performs mechanical work as it expands and cools.
A generator (not shown) coupled to the steam turbine 29 then converts the mechanical power into electrical power, which is supplied to a grid in the form of electrical current.
The expanded process gas 15 leaves the steam turbine 29 via a turbine outlet 5—in the form of a waste steam pipe 9—located on the waste steam side 31 of the steam turbine 29, and flows via a waste steam line 9 back to the steam generator, thus closing the water-steam circuit 2.
The flow of process gas 15 into or, respectively, away from the steam turbine 29 is controlled or governed by means of valves 12, 11 arranged in the supply line, i.e. a quick-closing valve 12 and a regulating valve 11, and by means of a butterfly valve 33 arranged in the waste steam line 9.
Work on the steam turbine 29, such as maintenance or overhaul work, can be carried out only after rotational operation of the steam turbine 29 has been switched off. To that end, it is necessary for a shafting (not shown) of the steam turbine 29 to be cooled from operating temperatures in the region of 600° C. to below 100° C.
Without external intervention, this cooling would take several days, specifically approximately 8 days, and would extend the overall downtime of the steam power station 1 by that time.
In order to reduce this downtime, or to shorten the cooling-down phase, forced cooling is used in the steam turbine plant 3 or in the steam turbine 29.
In this forced cooling (
In order to generate a necessary vacuum (pressure sink) which initiates the suction flow of the coolant 7 in the steam turbine 29 or in the operational process gas flow direction 27 (in this case also the coolant flow direction 28) through the steam turbine 29, a fan 6 is connected, as shown in
The coolant 7 or the ambient air 7 then enters the steam turbine 29 via an air pipe 10 between the quick-closing valve 12 (which is closed during forced cooling) and the regulating valve 11 (which is partially open during forced cooling) on the fresh steam side 13 of the steam turbine 29.
The cooling effect of the ambient air 7, as it flows through the steam turbine 29 in the coolant flow direction 28 (in this case also the operational process gas flow direction 27), cools the steam turbine 29—or, specifically, the components thereof —and thus achieves faster cooling of the steam turbine components.
The ambient air 7, aspirated, by the fan 6, through the steam turbine 29 in the operational process gas flow direction 27 or the coolant flow direction 28, is again released into the surroundings 14 as fan exhaust air 20.
Since permissible cooling gradients in the steam turbine components may then not be exceeded, which could otherwise lead to damage to the components, the quantity of the aspirated ambient air 7 is regulated. To that end, the regulating valve 11 at the turbine inlet 4 (on the fresh steam side 13) serves as regulating member.
Here too, when the steam power station 1 is in operation, hot steam/high-pressure steam 15, or process gas 15, which has been heated by a steam generator and further heated by a superheater, flows via a supply line 30 into the steam turbine 29 via a turbine inlet 4 on a fresh steam side 13 of said steam turbine 29, and flows through the steam turbine 29, in the process gas flow direction 27, where it performs mechanical work as it expands and cools.
The expanded process gas 15 leaves the steam turbine 29 via a turbine outlet 5—in the form of a waste steam pipe 9—located on the waste steam side 31 of the steam turbine 29, and flows via a waste steam line 9 back to the steam generator, thus closing the water-steam circuit 2.
Here too, the flow of process gas 15 into or, respectively, away from the steam turbine 29 is controlled or governed by means of valves 12, 11 arranged in the supply line, i.e. a quick-closing valve 12 and a regulating valve 11, and by means of a butterfly valve 33 arranged in the waste steam line 9.
In order to reduce here too the downtime, or to shorten the cooling-down phase, forced cooling is used in the steam turbine plant 3 or in the steam turbine 29.
In this forced cooling (
In order to generate a necessary vacuum (pressure sink) which initiates the suction flow of the coolant 7 in the steam turbine 29 or counter to the operational process gas flow direction 27 or the coolant flow direction 28 through the steam turbine 29, a fan 6 is in this case connected, as shown in
The coolant 7 or the ambient air 7—from the surroundings 14—then enters the steam turbine 29 via a suction line 34 (which is open during forced cooling) which has a regulating valve 35 (which is partially open during forced cooling) and is located between the turbine outlet 5 and a quick-closing valve 33 (which is closed during forced cooling).
The cooling effect of the ambient air 7, as it flows through the steam turbine 29 in the coolant flow direction 28 or counter to the operational process gas flow direction 27, cools the steam turbine 29—or, specifically, the components thereof —and thus achieves faster cooling of the steam turbine components.
The ambient air 7, aspirated, by the fan 6, through the steam turbine 29 counter to the operational process gas flow direction 27 or in the coolant flow direction 28, is again released into the surroundings 14 as fan exhaust air 20.
Since, here too, permissible cooling gradients in the steam turbine components may not be exceeded, which could otherwise lead to damage to the components, the quantity of the aspirated ambient air 7 is regulated. To that end, the regulating valve 35 in the suction line 34 at the turbine outlet 5 (on the waste steam side 31) serves as regulating member.
Alternatively, regulation may be effected by means of the regulating valve 11 on the steam turbine fresh steam side 13, thus dispensing with the regulating valve 35 in the suction line 34.
Further in this regard, i.e. for regulating the aspirated ambient air 7 during forced cooling as shown in
The fan 6 is limited in terms of the temperature of its fan exhaust air 20, for example to 150° C. Accordingly, therefore, the (fan) inlet temperature of the medium 36 sucked in by the fan 6 is also limited, for example to 120° C. if the medium flowing through the fan is assumed to be heated by 30° C.
In order not to exceed this maximum permissible fan exhaust air temperature or fan inlet temperature, in the context of the thermal protection, the supply line 30 of the fan 6 is provided, in the region of the fan inlet 16, with a bypass 17, i.e. a further coolant supply 17.
Further ambient air 8—as further coolant 8—is aspirated via this bypass 17, by means of the fan 6 and in a manner that can be regulated in terms of quantity by means of a regulating valve 18 arranged in the bypass 17, via a supply line 30 from the surroundings 14, and is admixed 140 with the ambient air 7, for the purpose of cooling the latter, which leaves the steam turbine 29 in the coolant flow direction 28 via the turbine outlet 5 (cf.
Alternatively, the quantity of further coolant 8 and the mixing or admixing 140 of the further coolant 8 and/or with the ambient air 7 may also be regulated by means of a three-way mixer at the point of bringing together the further coolant 8 and the ambient air 7.
This ambient air mixture 36 is drawn into the fan 6 via the fan inlet 16 and leaves the fan 6—as fan exhaust air 20—via a discharge line 30 on the exhaust air side 37 thereof, into the surroundings 14.
The temperature of the fan exhaust air 20 is measured by means of a temperature sensor 19 which is arranged in the region of the discharge line 30 for the fan exhaust air 20.
A governing unit 22 regulates, as a function of the measured fan exhaust air temperature, the regulating valve 17 and a fan motor 21 which drives the fan 6.
At the start of the forced cooling, only a small, minimal quantity of (cool) ambient air 7 fed through the steam turbine 29 is necessary or permissible, in order to reach the maximum permissible cooling rate or the permissible cooling gradients of the turbine components.
The steam turbine 29, which at that moment is still at a high temperature, causes this small quantity of ambient air 7—by exchange of heat with the very hot turbine components—also to be heated to a high temperature.
In order to cool the ambient air 7 flowing out of the steam turbine 29—which air is at that moment therefore very hot—to the fan exhaust air temperature which is permissible for the fan 6, a maximum quantity of the further ambient air 8 is admixed via the bypass 17, and regulated by the regulating valve 18.
As the steam turbine temperature drops over time t, the quantity of ambient air 7 through the steam turbine 29 is continuously increased (cf.
The mixture 36—of ambient air 7 through the steam turbine 29 and of ambient air 8 through the bypass 17—thus has, at all times during the forced cooling, a permissible fan inlet temperature when entering the fan 6 and, accordingly, a respective permissible fan exhaust air temperature.
It is thus possible to effectively prevent the fan 6 from overheating while at the same time “utilizing the maximum cooling rates of the turbine components”.
Although the invention has been illustrated and described in more detail by means of the preferred exemplary embodiment, the invention is not limited by the disclosed example and other variations may be derived herefrom by one skilled in the art, without departing from the scope of protection of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 12166000.5 | Apr 2012 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2013/057964 | 4/17/2013 | WO | 00 |
