DE10231879A1 - Process for influencing and checking the oxide layer on metallic components of hot CO2 / H2O cycle systems - Google Patents

Abstract

The invention relates to a method for influencing and controlling the oxide layer on metallic components of hot CO¶2¶ / H¶2¶O cycle systems, in particular CO¶2¶ / H¶2¶O gas turbine systems, wherein a hydrocarbon-containing fuel burns with oxygen and the resulting excess CO¶2¶ and H¶2¶O are taken from the circulatory system at a suitable point. The method is characterized in that an excess of oxygen is used to protect the oxide layer of the thermally stressed components, the height of which depends on the respective state of the oxide layer, and the state of the oxide layer is determined by periodic and / or continuous measurements.

Description

technical area

The invention relates to a method for influencing and controlling the oxide layer on metallic components of hot CO ₂ / N ₂ O cycle systems, in particular CO ₂ / N ₂ O gas turbines.

State of the art

CO ₂ / H ₂ O gas turbine plants with a largely closed CO ₂ gas turbine cycle are known. Such a gas turbine system consists of at least one compressor, at least one combustion chamber, at least one turbine, at least one heat sink and a water separator. In the combustion chamber, the fuel (hydrocarbon, e.g. natural gas with methane CH ₄ as the main component) reacts with the oxygen in the atmosphere prepared from O ₂ , CO ₂ and possibly H ₂ O.

The components CO ₂ and H ₂ O resulting from the combustion and any inert gases introduced with the oxygen or natural gas are continuously removed, so that a cycle with a largely constant composition of the working fluid is maintained.

In contrast to conventional gas turbine systems, in which the exhaust gases always contain a high proportion of O ₂ , the working medium consisting mainly of CO ₂ and H ₂ O can have reducing properties in such a cycle process. This can disadvantageously lead to removal of the protective oxide layer on the metal surfaces of the thermally stressed components at the high temperatures which are usually present in the combustion chamber and in the turbine. These components then corrode quickly and can lead to an unwanted early failure.

presentation the invention

The aim of the invention is to avoid the mentioned disadvantages of the prior art. The invention is based on the object of developing a method for influencing and controlling the oxide layer on components of hot CO ₂ / H ₂ O cycle systems, in particular CO ₂ / H ₂ O gas turbines. The process should be as simple as possible to implement.

According to the invention, this task is performed by one Procedure according to Preamble of claim 1 solved in that to protect the oxide layer of the thermally stressed components with an excess of oxygen is driven, its height depends on the respective state of the oxide layer, this state the oxide layer by periodic and / or continuous measurements is determined.

The advantages of the invention exist in that it is possible with the method according to the invention, an unwanted Removal of the protective Oxide layer on the surfaces to prevent the thermally stressed metallic components and thus corrosive damage and prevent premature failure of the corresponding components.

The condition is advantageous the oxide layer of the thermally stressed components based on samples with a previous calibrated surface quality determined by introducing said samples into the hot flow, this current be suspended for a period of time and then periodically taken and examined. This procedure is relatively simple to realize.

But it is also possible that the state of the oxide layer on at least one thermally stressed Component is checked online. The online control is preferably based on one Emission measurement with online reference or on an analysis of reflection spectra.

It is also an advantage if the information obtained from checking the state of the oxide layer can be combined with information from the measurement results a λ probe be won. Then an oriented towards the state of the oxide layer optimized driving style with regard to performance and efficiency Plant can be achieved.

It is useful if additional information about the local composition of the combustion gas in the turbine are taken into account. Such information can obtained with the help of a spectral emission analysis, for example become.

Finally, the method according to the invention also advantageously applicable to circulatory systems in which the Working medium through heat dissipation liquefied and a pump is used instead of the compressor, or in systems where an integrated membrane reactor takes the place of the combustion chamber occurs.

Short description of the drawings

There are four exemplary embodiments in the drawing presented the invention. Show it:

1 a circuit diagram of a gas turbine system working according to the inventive method in a first embodiment;

2 a circuit diagram of a gas turbine system working according to the inventive method in a second embodiment;

3 a circuit diagram of a plant operating according to the inventive method in a third embodiment and

4 a circuit diagram of a gas working according to the inventive method line system with integrated membrane reactor.

The figures are the same in each case Provide positions with the same reference numerals. The flow direction the media is marked with arrows.

Ways to Execute the invention

The invention is described below with the aid of exemplary embodiments and 1 to 4 explained in more detail.

In 1 a largely closed CO ₂ gas turbine cycle is shown. It essentially consists of a compressor 1 , a combustion chamber 2 , a turbine 3 , a heat sink 4 , a water separator 5 and a CO ₂ extraction point 6 , The circuit has an internal combustion of a hydrocarbon, for example a natural gas, which mainly consists of methane CH ₄ , in an atmosphere prepared from 0 ₂ , CO ₂ and optionally H ₂ O. The components CO ₂ and H ₂ O resulting from the combustion and any inert gases supplied with the oxygen or natural gas are continuously removed, so that a circuit with a largely constant composition of the working medium is maintained.

In contrast to conventional gas turbines, in which the exhaust gases always contain a high proportion of oxygen, the working medium consisting mainly of CO ₂ and H ₂ O can have reducing properties in such a cycle process. As a result, the protective oxide layer on the metal surfaces can be removed at high temperatures, such as those prevailing in the combustion chamber and the turbine. In order to counteract this process, the combustion is now operated according to the invention with a suitable excess of oxygen. The excess of oxygen is e.g. B. controlled by a λ probe arranged in the exhaust gas flow of the turbine.

Since the relationships between the excess of oxygen and the build-up and breakdown of the oxide layer can be very complex, it is advantageous if additional information about the condition of the oxide layer on the components at risk from high temperatures is used to adjust the height of the excess of oxygen. According to 1 this is accomplished by taking a sample 7 with a previously calibrated surface finish in at least one exposed position in the combustion chamber 2 arranged, removed periodically and the surface condition is examined. This sample 7 characterizes the condition of the thermally loaded component and serves as the basis for the size of the excess oxygen to be set.

2 shows a further embodiment of the invention. In contrast to the one in 1 The first exemplary embodiment shown here will not be any samples calibrated with respect to the surface condition 7 used, but here the state of the oxide layer of the thermally highly stressed components, such as the turbine guide vane 3 , continuously determined by an optical measuring method known per se 8th , which is based on an analysis of reflection spectra, is used for online measurement of the surface condition. The size of the necessary excess of oxygen is then determined and regulated on the basis of these measurements. In a further embodiment, z. B. the online control is based on an emission measurement with an online reference.

Online oxide layer monitoring relies on using a suitably designed optical (reflection) Sensor to detect whether there is an oxide layer on a metal surface.

• 1. Der Emissionsgrad einer oxidierten Oberfläche ist sehr hoch, z. B. beträgt er für eine typische Ni-Basis-Superlegierung im nahen IR >0.8. Für eine nichtoxidierte Oberfläche desselben Materials liegt der Emissionsgrad unter denselben Bedingungen wesentlich tiefer (<0.5). Dies hat als Konsequenz, dass bei einer gegebenen Temperatur ohne aktive Beleuchtung die oxidierte Oberfläche deutlich mehr Strahlung emittiert als die nichtoxidierte Oberfläche. Bei Beleuchtung mit einer externen Quelle reflektiert die oxidierte Schicht weniger als die nichtoxidierte.
• 2. Das spektrale Emissionsverhalten, d.h. abgestrahltes (oder reflektiertes) Signal als Funktion der Wellenlänge, ändert sich im oxidierten Zustand gegenüber dem nichtoxidierten.

Oxidized and non-oxidized surfaces differ in two main points:

• 1. The emissivity of an oxidized surface is very high, e.g. B. for a typical Ni-based superalloy in the near IR> 0.8. For an unoxidized surface of the same material, the emissivity is significantly lower (<0.5) under the same conditions. The consequence of this is that at a given temperature without active lighting, the oxidized surface emits significantly more radiation than the non-oxidized surface. When illuminated with an external source, the oxidized layer reflects less than the non-oxidized one.
• 2. The spectral emission behavior, ie emitted (or reflected) signal as a function of the wavelength, changes in the oxidized state compared to the non-oxidized one.

If the radiation behavior does not change significantly in the relevant temperature range, e.g. B. a purely passive sensor from the relative ratio of emitted IR radiation at two or more suitable wavelengths the surface quality conclude. The relative measurement has the advantage that it is insensitive reacts to losses in the optical path (e.g. dust on viewing window), if make themselves felt at both wavelengths.

Procedures with active, broadband lighting. The surface becomes broadband, for example, irradiated with the light of a halogen lamp and that reflected light analyzed spectrally. By comparison with that Illumination signal leaves for any wavelength determine the degree of reflection and form a quotient for different wavelength provides information about the surface quality.

The Hastelloy X alloy is mentioned as an example, for which a quotient of two optical bandpasses, around 1.6 μm (λ ₁ ) and around 2.1 μm (λ ₂ ), is suitable for analysis. In the case of a non-oxidized surface, more is reflected at λ ₂ than at λ ₁ , whereas it is exactly the opposite when an oxide layer is present is returning. Light of both wavelengths can be transmitted flexibly via optical fibers. To determine the bandpasses and lighting strategy, the optical properties of the respective combustion chamber material must be known or determined in advance.

It is advantageous if the out the control of the state of the oxide layer can be combined with information from the measurement results a λ probe be obtained for the purpose of hiring a state of Oxide layer oriented, in terms of performance and efficiency optimized operation of the system. In addition, for Example information about the local composition of the combustion gas in the turbine included, this information for example with the help of an emission analysis can be won.

Another embodiment is in 3 shown. In contrast to the one in 1 Embodiment shown is the working medium by heat dissipation in a CO ₂ liquefier 10 liquefied and a pump instead of the compressor 9 used by means of which the liquid working medium to the combustion chamber 2 brought.

To limit the maximum operating pressure can in this example, gradual compression and relaxation processes with intermediate heat or removal are provided.

A last embodiment is in 4 shown. Here the reaction of CH ₄ with O _{2 takes place} in one of a compressor 1 membrane reactor supplied with compressed air 11 , taking one side of the membrane with a sweep gas 13 is rinsed, which consists of the hot CO ₂ / H ₂ O mixture described above with a low O ₂ content. The membrane reactor 11 is therefore integrated in the sweep cycle of the gas turbine system, which also has a flow-dividing control valve 14 having. With the help of the control valve 14 the proportion of the sweep gas is regulated 13 the downstream sweep turbine 15 is fed and which portion remains in the sweep cycle. That from the membrane reactor 11 escaping hot air with reduced oxygen content 12 is in the turbine 3 relaxed.

In particular the membrane reactor 11 who have favourited Sweep Turbine 15 and any additional heat exchangers, which are not shown, must be protected against corrosion in this example, so that online measurements 8 of the surface condition of the thermally loaded component are carried out at these points.

Of course, the invention is not limited to the exemplary embodiments described. For example, the measurements can be carried out at several points, or both continuous online measurements and periodic measurements on calibrated samples can be carried out 7 respectively.

1

compressor

2

combustion chamber

3

turbine

4

Heat sink for example cooler or waste heat recovery

5

water

6

CO ₂ withdrawal point

7

sample

8th

online measurement

9

pump

10

CO ₂ liquefier

11

Membrane reactor

12

hot air with reduced O ₂ content

13

Sweep Gas

14

stream-splitting control valve

15

Sweep turbine

Claims (12)

Process for influencing and checking the oxide layer on metallic components of hot CO ₂ / H ₂ O cycle systems, in particular of CO ₂ / N ₂ O gas turbine systems; whereby a hydrocarbon-containing fuel is burned with oxygen and the resulting excess CO ₂ and H ₂ O is removed from the circulatory system at a suitable point, characterized in that an excess of oxygen is used to protect the oxide layer of the thermally stressed components, the amount of which depends on the respective condition the oxide layer is dependent, and the state of the oxide layer is determined by periodic and / or continuous measurements. A method according to claim 1, characterized in that the state of the oxide layer of the thermally loaded components using samples ( 7 ) is determined with a previously calibrated surface condition by the said samples ( 7 ) are introduced into the hot current, are exposed to this current for a certain time and then periodically removed and examined. A method according to claim 1, characterized in that the State of the oxide layer on at least one thermally stressed Component is checked online. A method according to claim 2, characterized in that in addition the State of the oxide layer on at least one thermally stressed component is checked online. Method according to one of claims 3 or 4, characterized in that that the online control on an emissions measurement with online reference based. Method according to one of claims 3 or 4, characterized in that that online control based on an analysis of reflection spectra based. Method according to one of claims 1 to 6, characterized in that that those obtained from checking the condition of the oxide layer Information is combined with information derived from the Measurement results of a λ probe be obtained for the purpose of hiring a state of Oxide layer oriented, in terms of performance and efficiency optimized operation of the system. A method according to claim 7, characterized in that additional information about the takes into account the local composition of the combustion gas in the turbine become. A method according to claim 8, characterized in that the additional Information can be obtained with the help of a spectral emission analysis. Method according to one of claims 1 to 9, characterized in that in the case of one of at least one compressor ( 1 ), at least one combustion chamber ( 2 ), at least one gas turbine ( 3 ), at least one heat sink ( 4 ), at least one water separator ( 5 ) and a CO ₂ tapping point ( 6 ) existing CO ₂ / H ₂ O cycle system of the carbonaceous fuel in the combustion chamber ( 2 ) is burned. Method according to one of claims 1 to 9, characterized in that in the case of at least one combustion chamber ( 2 ), at least one gas turbine ( 3 ), at least one heat sink ( 4 ) and at least one water separator ( 5 ) existing CO ₂ / N ₂ O cycle system of the carbonaceous fuel in the combustion chamber ( 2 ) is burned and the working medium by heat dissipation in a CO ₂ liquefier ( 10 ) liquefied and by means of a pump ( 9 ) to the combustion chamber ( 2 ) is brought. Method according to one of claims 1 to 9, characterized in that in the case of one of at least one compressor ( 1 ), at least one membrane reactor ( 11 ), at least one gas turbine ( 3 ), at least one heat sink ( 4 ) and at least one water separator ( 5 ) existing CO ₂ / H ₂ O cycle system of the carbonaceous fuel in the from the compressor ( 1 ) membrane reactor supplied with compressed air ( 11 ) is reacted with the oxygen, the CO ₂ / H ₂ O mixture on the one hand as a sweep gas ( 13 ) in the sweep cycle of the gas turbine plant with integrated membrane reactor ( 11 ) is used and on the other hand a sweep turbine ( 15 ) is supplied.