FLUE GAS LINE SPRAYING APPARATUS
The invention relates to a flue gas line spraying apparatus, which is arranged in a flue gas line between a power station boiler and a gas scrubber associated with the power station boiler.
The invention additionally relates to a gas scrubber for a power plant, in particular coal-fired power plant, having a flue gas line connection, via which the gas scrubber is connected via a flue gas line to a power station boiler.
The invention additionally relates to a method of treating a flue gas flowing in a flue gas line between a power station boiler and an associated gas scrubber.
A gas scrubber, also known as an absorber, of a power plant, in particular a coal-fired power plant, serves to clean the flue gas arising in the power plant. Conventionally, a gas scrubber is used to scrub sulphur dioxide out of the flue gas. To this end, in the gas scrubber the flue gas is brought into contact with a liquid stream, so that constituents of the flue gas stream, for example sulphur dioxide, are absorbed in the liquid stream and removed by way of the liquid stream. This takes place while the power station boiler of the power plant is in operation, i.e. is in an operational phase. If the power station boiler is not in operation, for example during maintenance or repair work, such that the power station boiler is shut down for short periods, the risk arises, due to the large residual quantities of heat in the power station's boiler, of hot flue gas entering the inner chamber of the gas scrubber via a flue gas line. Because the flue gas is in this case conventionally at a very high temperature, it may happen that the gas scrubber, in particular the rubber lining of the gas scrubber,

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and/or a device downstream of the gas scrubber is damaged.
It is therefore an object of the invention to provide a solution by means of which damage caused to a gas scrubber and/or a device downstream of the gas scrubber by hot flue gas flowing out of a power station boiler during a non-operational phase of the power station boiler may be prevented.
In a flue gas line spraying apparatus of the type described in greater detail above, the object is achieved in that the flue gas line spraying apparatus is arranged in the region of a flue gas line connection of the gas scrubber and designed to discharge cooling fluid directed towards flue gas flowing in the flue gas line during a non-operational phase of the power station boiler following an operational phase.
In the case of a gas scrubber of the type described in greater detail above, the object is achieved in that a flue gas line spraying apparatus according to one of Claims 1 to 6 is arranged in the region of a flue gas line connection of a gas scrubber.
In a method of the type described in greater detail above, the object is achieved in that, during a non-operational phase of the power station boiler following an operational phase, the flowing flue gas is contacted or sprayed, in particular via nozzles, with a cooling fluid before or as it enters the downstream gas scrubber or absorber.
The object is additionally achieved by a power plant comprising a gas scrubber according to Claim 7.
Convenient configurations and advantageous further developments are indicated in the subclaims.

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By contacting the flue gas flowing out of a power station boiler with a cooling fluid, such as for example water, before or as it enters a downstream gas scrubber, it is possible to cool the flue gas before or during entry into the gas scrubber, as it passes through the flue gas line arranged between the power station boiler and the gas scrubber in a non-operational phase of the power station boiler, i.e. when the power station boiler is shut down, by way of the flue gas line spraying apparatus, such that the temperature of the hot flue gas is lower when the flue gas flows into the inner chamber of the gas scrubber via the flue gas line in the region of the flue gas line connection of the gas scrubber. This makes it possible to prevent damage to the gas scrubber, in particular in the region of the rubber lining of the gas scrubber, in the region of the spray banks and/or of the mist eliminator of the gas scrubber and/or damage to a device downstream of the gas scrubber caused by hot flue gas in the non-operational phase of the power station boiler. Contacting of the flue gas with a cooling fluid here has the advantage that cooling of the flue gas may proceed very rapidly and is thus very effective. In addition, provision of a flue gas line spraying apparatus makes operation of a circulating pump unnecessary during the non-operational phase of the power station boiler, so reducing the resultant costs otherwise arising. Contacting of the flue gas with the cooling fluid via the flue gas line spraying apparatus takes place solely during the non-operational phase of the power station boiler. During the operational phase of the power station boiler the flue gas is not contacted with the cooling fluid.
According to one preferred configuration of the invention, the flue gas line spraying apparatus comprises one nozzle arranged centrally in the flue gas line or two or more nozzles, which are arranged distributed in series over the cross-sectional area of

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the flue gas line in the region of the flue gas line connection of the gas scrubber. Thus, according to one preferred configuration of the invention, contacting of the incoming flue gas with the cooling fluid takes place via a nozzle arranged centrally in the flue gas line or via two or more nozzles arranged distributed in series over the cross-sectional area of the flue gas line. The nozzles thus serve to contact the flue gas flowing in the flue gas line of the gas scrubber as uniformly as possible with the cooling fluid. Arranging a plurality of nozzles in series next to one another makes it possible to achieve particularly uniform contacting of the flue gas with the cooling fluid over the entire width of the flue gas line, whereby cooling of the flue gas may take place very effectively and highly efficiently. The nozzles arranged in series are in this case preferably arranged identically spaced from one another. However, a plurality of rows with nozzles extending over the width of the pipe and arranged in series may also be provided, the plurality of rows being arranged parallel to one another. Alternatively, however, provision may also be made for the flue gas line spraying apparatus to comprise just one nozzle arranged centrally in the flue gas line, which nozzle is preferably constructed such that it covers the entire cross-sectional area of the flue gas line over the width thereof when the flue gas is contacted with the cooling fluid.
The nozzle or nozzles preferably take the form of full cone nozzles, in particular axial full cone nozzles. By using full cone nozzles, in particular axial full cone nozzles, it is possible to achieve particularly uniform distribution of the cooling fluid exiting the nozzles over the entire circular area of the nozzles configured as full cone nozzles. Highly precise distribution is achieved by centre-oriented fluid inflow into the nozzle's swirl mixing chamber. The swirl body of the full cone nozzle ensures high operating reliability due

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to its large through-flow openings. In addition, full cone nozzles are distinguished by simple and quick adaptation to the particular operating conditions.
According to a further preferred configuration, the flue gas line spraying apparatus comprises a fluid supply system comprising a pipe, nozzles arranged in series being connected together via the pipe. Provision is thus preferably made for the fluid to be fed to the nozzles via precisely one pipe of a fluid supply system for the flue gas line spraying apparatus. The nozzles are thus preferably connected together via a common pipe, via which the nozzles are supplied with the cooling fluid by infeed of the cooling fluid via the fluid supply system. Closed- and open-loop control of cooling fluid feed to the nozzles may thus proceed as simply as possible, without major effort. It is thereby also possible to retro-fit the flue gas line spraying apparatus into existing flue gas lines in the region of a gas scrubber. As an alternative to the precisely one pipe of a fluid supply system, however, a plurality of pipes may also be provided.
The fluid supply system preferably comprises a flow rate monitor for monitoring the quantity of cooling fluid to be discharged. In this way, the quantity of discharged cooling fluid may be determined at any time, whereby inflow of cooling fluid inside the pipes towards the nozzles may be adapted to different parameters and also operation of the fluid supply system may be continuously monitored.
The fluid supply system preferably comprises a control valve or an orifice plate for adjusting the quantity of cooling fluid to be discharged. By means of the control valve, optimum adjustment of the quantity of cooling fluid discharged via the nozzles may be variably set and controlled, so as to achieve the most effective cooling possible of the flue gas to the desired

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temperature. The orifice plate allows setting of the quantity of cooling fluid to be discharged to a constant value, such that in this way the volumetric flow rate may be set at a fixed level.
Alternatively, it is also possible to do without a flow rate monitor and a control valve or orifice plate and instead to adjust the quantity of cooling fluid to be discharged to the nozzle type used for the nozzle(s) in such a way that a constant quantity of cooling fluid is discharged via the nozzle(s) into the flue gas stream.
Provision is preferably made for a constant quantity of cooling fluid to be fed to the nozzle or the nozzles during contacting of the flue gas with the cooling fluid. In this case, a setpoint is defined for the quantity of cooling fluid, this setpoint being transmitted to the control valve, in order to bring about control as a function of this previously defined setpoint.
Provision is additionally preferably made for the flue gas line spraying apparatus to be heatable, at least in sections. In this way, the temperature of the cooling fluid may be optimally adapted to the operating conditions, in order to be able purposefully to set the degree of cooling of the flue gas. To this end, heating devices are preferably arranged at least in sections along the pipes of the flue gas line spraying apparatus.
According to a more advantageous configuration of the invention, the flue gas line spraying apparatus comprises a scavenging gas system, which is connected to the fluid supply system. By means of the scavenging gas system, it is possible for the flue gas line spraying apparatus to be scavenged with a gas, preferably air, during the operational phase of the power station boiler, i.e. when the flue gas passing

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through the flue gas line is not being contacted with a cooling fluid via the flue gas line spraying apparatus. The scavenging gas system makes it possible for the fluid supply system, in particular the pipes of the fluid supply system, and the nozzles to be scavenged by a gas, so preventing the nozzles and the fluid supply system from being damaged by corrosion, in particular by condensation of the sulphuric acid in the flue gas passing through the flue gas line, or the nozzles from becoming clogged. The scavenging gas system preferably comprises a blower, in particular an oxidation air blower, by means of which the gas is passed through the pipes of the fluid supply system and the nozzles.
The scavenging gas system additionally preferably comprises a throttle valve and a flow rate monitor. The throttle valve makes it possible to set and control precisely the quantity of gas blown via the blower into the pipes of the fluid supply system and the nozzles and to monitor it by means of the flow rate monitor. However, provision may in this case also be made for just the throttle valve or just the flow rate monitor to be provided.
The scavenging gas system preferably further comprises a nonreturn valve. The nonreturn valve prevents flue gas from entering the pipe of the scavenging gas system in the event of discontinuation of the admission pressure of the air from the blower, in particular when a shut-off valve arranged at the point of transition between the scavenging gas system and the fluid supply system during the operational phase of the power station boiler is not closed.
The method according to the invention is advantageously applied in particular when the gas scrubber is a constituent of a flue gas desulphurization plant, in particular one which has no flue gas at the flue gas line bypass passing the flue gas desulphurization

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plant. Precisely in such plants, it is not possible for hot flue gas still flowing in in the down phase to pass the flue gas scrubber, i.e. that part of the flue gas desulphurization plant. Here, it is then advantageous for flue gas flowing in to be cooled by being sprayed with a cooling fluid before or as it enters the downstream gas scrubber or absorber. The cooling fluid is advantageously cooling liquid, in particular water.
In particular in gas desulphurization plants, it is also expedient for the flowing flue gas to be contacted or sprayed with the cooling fluid when the flue gas temperature or the temperature in the flue gas line is 2>70°C.
In order to hold enough capacity in particular in the sump of a spray scrubber or absorber, i.e. of the gas scrubber, during the down phase, the invention also provides that, before the state change into the non-operational phase of the power station boiler, the filling level of the gas scrubber is lowered. In this case, it is then expedient for such a volume or capacity to be provided in the gas scrubber or absorber that cooling fluid can be sprayed and collected by the gas scrubber over a period of up to 36 hours.
To this extent, the flue gas line spraying apparatus is connected in a fluid-conducting manner to the interior of the gas scrubber or absorber. In a particularly expedient development both of the flue gas line spraying apparatus and of the method, it is provided that the flue gas line spraying apparatus is connected not only to a fluid supply system which provides the cooling fluid, but also to a cooling gas system which makes it possible for the flue gas line spraying apparatus to be scavenged with a gas during the operational phase of the power station boiler.

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The invention is explained below in greater detail with reference to the attached drawing by means of a preferred embodiment. The single figure shows a schematic representation of a flue gas line in the region of a flue gas line connection of a gas scrubber according to the invention.
The single Figure 1 shows a flue gas line 10 in the region of a flue gas line connection of a gas scrubber 12 for cleaning the flue gas leaving a power station boiler, the gas scrubber 12 being connected via the flue gas line 10 to a power station boiler (not shown here), via which line the flue gas flows into the inner chamber 14 of the gas scrubber 12. Arranged in the flue gas line 10 in the region of the flue gas line connection of the gas scrubber 12 is a flue gas line spraying apparatus 16 for contacting the flue gas flowing into the inner chamber 14 of the gas scrubber 12 with a cooling fluid, such as water for example. Spraying or contacting the incoming flue gas with the cooling fluid proceeds in a non-operational phase following an operational phase of the power station boiler, when the power station boiler is not operational and is not yet sufficiently cooled. During normal operation of the power station boiler, the flue gas entering the gas scrubber 12 is not contacted or sprayed with the cooling fluid via the flue gas line spraying apparatus 16.
In the embodiment shown in the figure, the flue gas line spraying apparatus 16 comprises fifteen nozzles 18, which are connected together in the embodiment shown here by way of a common pipe 20 of a fluid supply system 22. It is however also possible to provide more or fewer than fifteen nozzles 18. The number of nozzles 18 provided is preferably dependent on the size of the cross-sectional area of the flue gas line 10 and on the necessary volumetric flow rate of the cooling fluid. The nozzles 18 take the form, for example, of axial

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full cone nozzles. In the embodiment shown here, the nozzles 18 are arranged next to one another in series, with identical spacing from one another over the cross-sectional area, i.e. over the entire width, of the flue gas line 10 in the region of the flue gas line connection of the gas scrubber 12. One row of nozzles 18 is preferably provided. It is however also possible to provide a plurality of rows of nozzles 18 arranged parallel to one another.
Conveyance of the cooling fluid in the fluid supply system 22 proceeds via a pump or a pump system, not shown here. The fluid supply system 22 comprises a plurality of pipes 20, 24, 26 and a shut-off valve 28, a control valve 30 and a flow rate monitor 32 for monitoring the quantity of cooling fluid passing through the pipes 20, 24, 26. In addition, the fluid supply system 22 may comprise a bypass valve and one or more butterfly valves, neither of which is shown here. It is in this case possible to use existing components and control units, used to supply liquid within the gas scrubber 12 for cleaning the flue gas during the operational phase of the power station boiler, for the fluid supply system 22, such that existing components and control units of the gas scrubber 12 may be used for the flue gas line spraying apparatus 16. This may considerably reduce the installation effort and costs involved. In addition, the flue gas line spraying apparatus 16 may be straightforwardly installed or retrofitted in existing gas scrubbers 12. To be able purposefully to set a desired temperature for the fluid, the flue gas line spraying apparatus 16 may be heatable at least in places by means of a heating unit, not shown here.
The quantity of cooling fluid supplied is closed-loop controlled with the assistance of the flow rate monitor 32, a controller 34 and the control valve 30. To ensure functioning of the nozzles 18, cooling fluid,

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preferably a constant quantity of cooling fluid, is continuously supplied to the nozzles 18. To this end, a setpoint is fixed for the quantity of cooling fluid to be supplied and is transmitted to the controller 34. The setpoint is preferably between 30 and 200 1/h per square metre of cross-sectional area of the flue gas line 10.
During operation of the power station boiler, when no cooling fluid is output via the nozzles 18 for contacting the incoming flue gas, the pipes 20, 26 of the fluid supply system 22 and the nozzles 18 of the flue gas line spraying apparatus 16 are scavenged with a gas in the form of air, in order to prevent corrosion phenomena at the nozzles 18 and the pipes 20, 26. To this end, a scavenging gas system 36 is provided, which is connected to the fluid supply system 22. Connection of the scavenging gas system 36 to the fluid supply system 22 is provided between the shut-off valve 28 and the nozzles 18, at the pipe 26 of the fluid supply system 22. During scavenging with the gas in the form of air, the shut-off valve 28 is closed, such that the gas may only pass through the pipes 20, 26 and the nozzles 18 and not penetrate into the rest of the fluid supply system 22.
The scavenging gas system 36 comprises a pipe 38, via which the gas is conveyed to the fluid supply system 22. The pipe 38 of the scavenging gas system 36 is connected with the pipe 26 of the fluid supply system 22. A throttle valve 40, a flow rate . monitor 42, a nonreturn valve 44 and a shut-off valve 46 are arranged along the pipe 38. The quantity of scavenging gas is set by means of the throttle valve 40 and monitored by means of the flow rate monitor 42. The nonreturn valve 44 prevents the flue gas from entering the pipe 38 of the scavenging gas system 36 on discontinuation of the gas admission pressure, if the electrically actuated shut-off valve 4 6 is not closed.

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The flue gas line spraying apparatus 16 serves to cool the hot flue gas which continues to flow into the gas scrubber 12 after the power station boiler has been shut down from the operational phase into the non-operational phase.
The flue gas entering the inner chamber 14 of the gas scrubber 12 is contacted as soon as the power station boiler has been shut down and has entered the non-operational phase.
Before contacting of the incoming flue gas with the cooling fluid via the flue gas line spraying apparatus 16 begins, the control valve 30 and the shut-off valve 28 of the fluid supply system 22 are preferably closed. The throttle valve 40 and the shut-off valve 46 of the scavenging gas system 36 are opened. Closure or opening of the control valve 30, the shut-off valve 28 and the shut-off valve 46 preferably takes place pneumatically or electrically. The throttle valve 40 is preferably closed or opened by hand.
Before the power station boiler is shut down, i.e. before the power station boiler changes its status from the operational phase to the non-operational phase, the filling level of the gas scrubber 12 is lowered by increased discharge of the gypsum slurry contained in the inner chamber 14 of the gas scrubber 12. In this way, the cooling fluid supplied via the flue gas line spraying apparatus 16 during the non-operational phase of the power station boiler may be accommodated in the inner chamber 14 of the gas scrubber 12 without it overflowing.
At the start of contacting of the incoming flue gas with the cooling fluid via the flue gas line spraying apparatus 16, first of all the shut-off valve 46 of the scavenging gas system 36 is closed and then the shut-

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off valve 28 of the fluid supply system 22 is opened, such that no more gas can flow into the fluid supply system 22 via the scavenging gas system 36 and instead the cooling fluid may be fed via the fluid supply system 22 to the nozzles 18 to contact the flue gas flowing into the inner chamber 14 of the gas scrubber 12.
During contacting of the flue gas with the cooling fluid, the filling level of the gas scrubber 12 is monitored, to prevent the gas scrubber 12 from overflowing, since not all the cooling fluid which is sprayed into the flue gas line 10 of the gas scrubber 12 by means of the nozzles 18 evaporates, but rather some of the sprayed cooling fluid enters the inner chamber 14 of the gas scrubber 12 via the flue gas line 10. Once the filling level of the gas scrubber 12 approaches its maximum, the temperature in the flue gas line 10 is checked. Supply of the cooling fluid via the flue gas line spraying apparatus 16 may be switched off when the temperature in the flue gas line amounts to roughly < 70°C. If the temperature is roughly > 70°C, contacting of the flue gas with the cooling fluid is continued. The overflowing gypsum slurry is in this case caught in a pump sump of the gas scrubber 12. If there is a risk of the pump sump also overflowing, the gypsum slurry is pumped into a drainage tank, not shown here.
Preferably, cooling fluid is in principle supplied via the flue gas line spraying apparatus 16 in a non-operational phase of the power station boiler if the temperature in the flue gas line amounts roughly to ^ 70 °C. If the temperature in the flue gas line amounts to roughly < 70 °C, contacting with the cooling fluid via the flue gas line spraying apparatus 16 may be stopped and the flue gas line spraying apparatus 16 may be switched off. To this end, first of all the shut-off valve 28 of the fluid supply system 22 is closed. Then

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the shut-off valve 46 of the scavenging gas system 36 is reopened.
To monitor the functionality of the fluid supply system 22 and of the scavenging gas system 36, both the fluid supply system 22 and the scavenging gas system 36 each comprise the flow rate monitor 32, 42. If the fluid supply system 22 for contacting the flue gas with the cooling fluid is not in operation, but instead the scavenging gas system 36, an alarm is output by the flow rate monitor 42 if the volumetric flow rate of gas falls below a minimum value. If the fluid supply system 22 for contacting the flue gas with the cooling fluid is in operation, an alarm is output by the flow rate monitor 32 if the volumetric flow rate of cooling fluid falls below a minimum value.

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Patent claims
1. Flue gas line spraying apparatus, which is
arranged in a flue gas line (10) between a power
station boiler and a gas scrubber (12) associated with
the power station boiler,
characterized in that
the flue gas line spraying apparatus (16) is arranged in the region of a flue gas line connection of the gas scrubber (12) and designed to discharge cooling fluid directed towards flue gas flowing in the flue gas line (10) during a non-operational phase of the power station boiler following an operational phase.
2. Flue gas line spraying apparatus according to Claim 1, characterized in that the flue gas line spraying apparatus (16) comprises one nozzle (18) arranged centrally in the flue gas line (10) or in that the flue gas line spraying apparatus (16) comprises two or more nozzles (18), which are arranged distributed in series over the cross-sectional area of the flue gas line (10), the flue gas line spraying apparatus (16) preferably comprising a fluid supply system (22) comprising a pipe (20, 24, 26), nozzles (18) arranged in series being connected together via the pipe (20).
3. Flue gas line spraying apparatus according to Claim 2, characterized in that the nozzle (18) or the nozzles (18) take the form of full cone nozzles, in particular axial full cone nozzles, and/or in that the flue gas line spraying apparatus (16) may be heated at least in sections.
4. Flue gas line spraying apparatus according to Claim 2 or 3, characterized in that the fluid supply system (22) comprises a flow rate monitor (32) for monitoring the quantity of cooling fluid to be discharged and/or a control valve (30) or an orifice

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plate for adjusting the quantity of cooling fluid to be discharged.
5. Flue gas line spraying apparatus according to one of the preceding claims, characterized in that the flue gas line spraying apparatus (16) comprises a scavenging gas system (36).
6. Flue gas line spraying apparatus according to Claim 5, characterized in that the scavenging gas system (36) is connected to the fluid supply system (22) and/or comprises a throttle valve (40) and a flow rate monitor (42) and/or comprises a nonreturn valve (44) .
7. Gas scrubber having a flue gas line connection, via which the gas scrubber (12) is connected via a flue gas line (10) to a power station boiler, characterized in that a flue gas line spraying apparatus (16) according to one of Claims 1 to 6 is arranged in the region of the flue gas line connection.
8. Gas scrubber according to Claim 7, characterized in that the gas scrubber (12) is a constituent of a flue gas desulphurization plant, in particular one which has no flue gas at the flue gas line bypass passing the flue gas desulphurization plant.
9. Power plant, in particular coal-fired power plant, comprising a gas scrubber (12) according to Claim 7 or 8.
10. Method of treating a flue gas flowing in a flue gas line (10) between a power station boiler and an associated gas scrubber (12) , characterized in that, during a non-operational phase of the power station boiler following an operational phase, the flowing flue gas is contacted or sprayed, in particular via nozzles,

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with a cooling fluid before or as it enters the downstream gas scrubber (12) or absorber.
11. Method according to Claim 13, characterized in that the flowing flue gas is contacted or sprayed with a cooling liquid, in particular water.
12. Method according to Claim 10 or 11, characterized in that the flowing flue gas is contacted or sprayed when the flue gas temperature or the temperature in the flue gas line is ^10°C.
13. Method according to one of Claims 10-12, characterized in that, before the state change into the non-operational phase of the power station boiler, the filling level of the gas scrubber (12) is lowered.
14. Method according to one of Claims 10-13, characterized in that the cooling fluid is discharged in a manner directed towards flue gas flowing in the flue gas line (10) via a flue gas line spraying apparatus (16) arranged in the region of a flue gas line connection of the gas scrubber (12), in particular in the flue gas line (10).
15. Method according to Claim 14, characterized in that the cooling fluid is discharged via one nozzle (18) arranged centrally in the flue gas line (10) or
via two or more nozzles (18) of the flue gas line spraying apparatus (16), which are arranged distributed in series over the flue gas line (10), the cooling fluid being fed to the nozzle (18) or the nozzles (18) preferably via a pipe (20, 24, 26) of a fluid supply system (22).
16. Method according to one of Claims 10 to 15,
characterized in that a constant quantity of cooling
fluid, in particular 30-200 1/h per square metre of
cross-sectional area of the flue gas line (10) is

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sprayed, preferably fed to the nozzle (18) or the nozzles (18) during the non-operational phase of the power station boiler.
17. Method according to one of Claims 10 to 16, characterized in that the flue gas line spraying apparatus (16) is scavenged with a gas during the operational phase of the power station boiler.
Dated this the 10th day of May 2012. <* f ^^K
^1 (MOUTUSHL4HOWMIK)
o/SUBRAMANIAM, IMTARAJ & ASSOCIATES
Attorneys for the Applicants