Fuel lance for a gas turbine plant and a method of operating a fuel lance

TECHNICAL FIELD

The present invention relates to the field of gas turbine engine technology. It relates to a fuel lance for a gas turbine installation and to a method for operating such a fuel lance.

STATE OF THE ART

Integrated Gasification Combined Cycle IGCCs are normally operated with a synthetic fuel gas (syngas or MBtu gas) generated by gasification of coal, biomass or other fuels. This fuel differs significantly from natural gas in terms of calorific value, density and combustion characteristics, such as flame speed and ignition retardation time. In a gas turbine with sequential combustion or intermediate superheating for IGCC power plants, therefore, essential adaptations are necessary both in the fuel supply system and in the combustion chambers in order to cope with these differences.

A gas turbine installation with intermediate overheating with its essential components is described in <figref idrefs="f0001">FIG</figref> Schematically. The gas turbine plant 10 of the<figref idrefs="f0001">FIG</figref> Comprises a device for compressing the sucked-in combustion air, which is composed of a low-pressure compressor 11a and a downstream high-pressure compressor 11b. The compressed combustion air is supplied to a first combustion chamber 12, where it is partially used for the combustion of a fuel supplied via a first fuel supply 23. The resulting hot gas is expanded in a subsequent high-pressure turbine 13 under working power and subsequently fed to a second combustion chamber 14 in which the unconsumed air portion is used for the combustion of a fuel supplied via a second fuel supply 23. In this way, The hot gas coming from the second combustion chamber 14 is decompressed in a subsequent low-pressure turbine 15 under working power and then passed through a heat recovery steam generator (HRSG) 21, where steam is produced for steam turbines (not shown) of a separate water / steam cycle becomes. The exhaust gas 22 can then be fed to a chimney. The two turbines 13 and 15 are connected via a shaft 20 to the compressors 11 a, b and a generator 16 for electrical energy and drive the latter. Compressed air from the compressors 11a and 11b can be branched off for cooling purposes, cooled down in corresponding high-pressure or low-pressure forced-flow refrigerators (OTC) 18 or 19 and then directed to the combustion chambers 23, 24 or turbines 13, 15 for cooling purposes. A comparable gas turbine installation is, for example, in the<patcit id="pcit0001" dnum="US5617718A"><text>US-A-5,617,718</text></patcit> Is disclosed.

In the second combustion chamber of the sequential combustion, the fuel is injected into the hot gas stream by means of a fuel lance, the shape of which is shown in FIG <figref idrefs="f0002">FIG</figref> of the <patcit id="pcit0002" dnum="US5617718A"><text>US-A-5,617,718</text></patcit> And its construction is described, for example, in the <patcit id="pcit0003" dnum="EP0638769A2"><text>EP-A2-0 638 769</text></patcit> Is shown in detail. When comparing different types of syngas with natural gas, it turns out that for the syngas, depending on the type and origin, a larger flow cross-section is required, which can be a factor of 3 to 9 greater than the flow cross-section for natural gas. At present, it is a great challenge to inject the large volume flows associated with syngas through the fuel lance into the combustion chamber. Theoretically, it is possible to increase the lance diameter in order to provide the required additional space. However, this would have a considerable influence on the aerodynamics of the burner and result in a redesign of the combustion chamber and the housing of the gas turbine. It is therefore desirable to keep the outside diameter of the fuel lance constant during the transition from natural gas to syngas. On the other hand, some changes are necessary to reduce the residence time of the syngas within the mixing zone of the burner, thus avoiding a back-ignition.

From the print <patcit id="pcit0004" dnum="US5615555A"><text>US-A-5,615,555</text></patcit> There is known an injection device for the combustion chamber of a gas turbine intended for two fuels in which a central nozzle for liquid fuel is concentrically surrounded by a nozzle arrangement for a gaseous fuel and externally by a first device for generating a jacket stream of combustion air. The nozzle arrangement for the gaseous fuel in turn comprises an inner-lying ring of openings oriented obliquely outwards, which is surrounded by a second device for generating a jacket flow from the gaseous fuel.

Fuel lances are also from the documents <patcit id="pcit0005" dnum="FR2570473A"><text>FR 2570473 A</text></patcit>, <patcit id="pcit0006" dnum="DE19905995A1"><text>DE 199 05 995 A1</text></patcit> and <patcit id="pcit0007" dnum="EP0718561A2"><text>EP 0718561 A2</text></patcit> known. In the<patcit id="pcit0008" dnum="DE19905995A1"><text>DE 199 05 995 A1</text></patcit> A fuel lance is disclosed which has a lance part which extends in the flow direction of a hot gas and which comprises at least one outer tube arranged concentrically to a lance axis and an intermediate tube which is arranged concentrically in the outer tube and in which the fuel leads to a lance tip and penetrates into the hot gas through injection openings , These injection openings being oriented in such a way that the fuel jets emerging from them form an angle with the lance axis.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a fuel lance and a method for its operation which allow the use of syngas as fuel in the second combustion stage of a gas turbine with sequential combustion without substantial changes in the outer dimensions.

The object is achieved by the totality of the features of claims 1, 6 and 10. For the solution according to the invention it is essential that the first injection openings are arranged directly on the lance tip and that the first injection openings are oriented in such a way that the fuel jets emerging from them form an acute angle with the lance axis, the lance tip is rounded and the first Are arranged in the region of the rounding, the intermediate tube arranged concentrically in the outer tube terminating at a distance from the lance tip and having at the end an opening which corresponds to the width of the tube.

In this way, a medium which is fed in the intermediate tube or in the intermediate space between the outer tube and the intermediate tube can be sprayed into the hot-gas stream without problems through these injection openings.

The displacement of the injection openings in the flow direction of the hot gas to the tip of the lance and the inclination / tilting of the jetted-in fuel streams in the flow direction reduces the residence time of the syngas in the mixing zone. The (acute) angle which the beams enclose with the lance axis is a parameter which can be optimized as a function of the hydrogen content of the fuel, the angle being the smaller the higher the hydrogen content.

One embodiment is characterized in that an inner tube is arranged concentrically in the intermediate tube, the inner tube is guided to the lance tip, and in that second injection openings for the injection of liquid fuel are provided at the lance tip, which liquid is supplied with the liquid fuel by the inner tube .

Preferably, the first and second injection openings are arranged on a common radius around the lance axis, the radius of the second injection openings being smaller than the radius of the first injection openings.

The second injection openings can be designed to generate a fuel jet. However, they can also be designed for producing a spray mist.

In the method according to the invention for operating a fuel lance without an inner tube, syngas is fed to the first injection openings as fuel in the intermediate tube, and is injected into the hot-gas stream through the first injection openings.

One embodiment of the method according to the invention is characterized in that, in the space between the outer pipe and the intermediate pipe, syngas is also fed as a fuel syngas to the first injection openings and through the first injection openings into the hot gas stream.

Another embodiment is distinguished by the fact that a dilution medium, in particular nitrogen or steam, is guided in the space between the outer tube and the intermediate tube to the first injection openings and is penetrated into the hot-gas stream through the first injection openings.

A further embodiment is characterized in that air in the space between the outer tube and the intermediate tube is guided as a carrier or shielding medium to the first injection openings and is penetrated through the first injection openings into the hot-gas stream.

In the method according to the invention for operating a fuel lance with an inner tube, synthetic gas is passed into the first injection openings in the space between the intermediate tube and the inner tube and is injected into the hot gas stream through the first injection openings and a liquid fuel, in particular oil, is added to the second injection openings in the inner tube And penetrated through the second injection openings into the hot gas stream.

One embodiment of this method according to the invention is characterized in that, in the intermediate space between the outer tube and the intermediate tube, syngas is also fed as a fuel syngas to the first injection openings and is penetrated through the first injection openings into the hot gas stream.

However, it is also conceivable for a dilution medium, in particular nitrogen or steam, to be fed to the first injection openings in the space between the outer tube and the intermediate tube, and to be introduced into the hot-gas stream through the first injection openings.

Furthermore, it can be advantageous if air in the space between the outer tube and the intermediate tube is guided as a carrier or shielding medium to the first injection openings and is penetrated into the hot-gas stream through the first injection openings.

However, it is also conceivable that a mixed gas of natural gas and steam or nitrogen is fed to the first injection openings in the space between the intermediate tube and the inner tube as fuel and is penetrated through the first injection openings into the hot gas stream and that a liquid fuel, To the second injection openings, and is injected into the hot-gas stream through the second injection openings.

In particular, in the space between the outer tube and the intermediate tube, air can be fed as a carrier to the first injection openings and can be sprayed into the hot-gas stream through the first injection openings.

BRIEF EXPLANATORY STATEMENT OF THE FIGURES

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail below with reference to exemplary embodiments in conjunction with the drawing. Show it<dl id="dl0001"><dt>FIG</dt><dd>FIG. 3 is a simplified schematic of a gas turbine installation with sequential combustion as known from the prior art and suitable for realizing the invention; FIG.</dd><dt>FIGS. 2 and 3</dt><dd>A first exemplary embodiment of a burner lance according to the invention for operation with syngas in the second combustion stage of a gas turbine installation <figref idrefs="f0001">FIG</figref>, In which <figref idrefs="f0002">FIG</figref> Exclusively syngas is injected; </dd><dt>FIGS. 4 to 6</dt><dd>A second exemplary embodiment of a burner lance according to the invention for use in the second combustion stage of a gas turbine installation <figref idrefs="f0001">FIG</figref>, Whereby different media are fed and sprayed outside the inner tube.</dd></dl>

WAYS FOR IMPLEMENTING THE INVENTION

In <figref idrefs="f0001">FIG</figref> and <figref idrefs="f0002">2</figref> A first exemplary embodiment of a fuel lance according to the invention is reproduced, wherein different operating modes are shown in the two figures. The fuel lance 25 of the<figref idrefs="f0001">FIG</figref> and <figref idrefs="f0002">2</figref> Initially projects vertically into the flow of the hot gas 37, then deflects at right angles and extends in the flow direction of the hot gas 37 along a lance axis 34, which is parallel to the hot gas flow. The fuel lance 25 comprises an outer tube 26 in which an intermediate tube 27 is concentrically arranged. The outer tube 26 is drawn as far as the lance tip 38 and terminates there with a rounded end region in which comparatively large injection openings 28 are arranged distributed around the lance axis 34 at a radial distance. The intermediate tube 27 already ends before the lance tip 38 with an opening corresponding to the width of the tube. In this way, a medium which is produced in the intermediate tube 27 or in the intermediate space between the outer tube 26 and the intermediate tube 27 can be sprayed into the hot-gas stream without problems through the injection openings 28.

According to <figref idrefs="f0002">FIG</figref> In a particularly simple embodiment of the invention, the entire space in the interior of the fuel lance 25 is used to introduce Syngas 29. An inner tube, which - as in the<figref idrefs="f0003 f0004">4-6</figref> Shown - is used for a liquid fuel is completely removed. Likewise, the clearance between outer tube 26 and intermediate tube 27, which is otherwise used for guiding air, is also used for transporting syngas. The injection openings are arranged opposite the known solution from the<patcit id="pcit0009" dnum="EP0638769A2"><text>EP-A2-0 638 769</text></patcit> And their radiation direction (dashed lines in FIG <figref idrefs="f0002">Figures 2, 3</figref>) Are inclined or tilted from the radial direction to the axial direction in order to reduce the residence time of the syngas in the mixing zone. The (acute) angle which the jets enclose with the lance axis 34 is a parameter that can be optimized as a function of the hydrogen content of the fuel, the angle being the smaller the higher the hydrogen content.

This results in the following advantages:<ul><li>The maximum flow cross section for the syngas is available; and</li><li>For gas injection, a minimized pressure drop is obtained;</li></ul>However, the operation is limited to the one fuel, namely Syngas.

In a modification of the <figref idrefs="f0002">FIG</figref> , The clearance between the outer pipe 26 and the intermediate pipe 27 can be used to supply a diluting medium in the form of nitrogen or steam. Alternatively, according to FIG<figref idrefs="f0002">FIG</figref> The gap between the supply of air 30 as a carrier or shielding current can be reserved. Both dilution and shielding help to improve combustion performance by achieving better mixing prior to ignition, thus reducing NOx emissions and the risk of flashback.

However, it is also conceivable, according to <figref idrefs="f0003">FIG</figref> It is possible to use a burner lance 31 in which an inner tube 32 is concentrically arranged inside the intermediate tube 27, through which liquid fuel in the form of oil 35 is guided into the lance tip 38 and is penetrated there by separate injection openings 33. The oil injection takes place in the center of the lance tip 38<figref idrefs="f0003">FIG</figref> A syngas is guided in the intermediate spaces between the outer pipe 26 and the intermediate pipe 27, and between the intermediate pipe 27 and the inner pipe 32. According to<figref idrefs="f0003">FIG</figref> The clearance between the outer pipe 26 and the intermediate pipe 27 is used to transport either a diluting medium (steam or nitrogen) or, as shown in FIG <figref idrefs="f0003">FIG</figref> - air 30 as carrier or shielding current. The injection openings 33 for the oil 35 can either be designed to produce fuel jets or a spray mist. Although the space for the syngas is slightly restricted by the introduction of the inner tube 32, the possibility arises of using back-up fuel.

Finally, it is also conceivable to use the fuel lance instead of the syngas <figref idrefs="f0003">4-5</figref> Natural gas. Since, because of the large injection openings 28, the flow velocity which can be achieved with this is too small for itself, operation with natural gas can be made possible by a dilution of the natural gas with steam or nitrogen producing a mixed gas 36 and instead of the syngas being injected (<figref idrefs="f0004">FIG</figref>). In this way, the injection rate of the natural gas can be increased to achieve better penetration and mixing. In addition, the addition of diluent media such as steam or nitrogen slows down the combustion chemistry, thus helping to improve fuel and air mixing, thereby improving emissions.

Overall, the following advantages result with the invention:<ul><li>A simple and retrofitable solution for syngas use in a sequential combustion in a gas turbine;</li><li>A maximum flow cross-section and minimal pressure drop when the inner tube is dispensed with; and</li><li>An optimal possibility for additional fuel (back-up fuel).</li></ul>

REFERENCE LIST

<dl id="dl0002" compact="compact"><dt>10</dt><dd>Gas turbine installation</dd><dt>11 a</dt><dd>Low-pressure compressors </dd><dt>11 b</dt><dd>High-pressure compressors</dd><dt>12,14</dt><dd>combustion chamber</dd><dt>13</dt><dd>High pressure turbine</dd><dt>15</dt><dd>Low-pressure turbine</dd><dt>16</dt><dd>generator</dd><dt>17</dt><dd>Air inlet</dd><dt>18</dt><dd>High pressure forced flow cooler</dd><dt>19</dt><dd>Low-pressure forced-flow cooler</dd><dt>20</dt><dd>wave</dd><dt>21</dt><dd>Heat recovery steam generator</dd><dt>22</dt><dd>Exhaust gas</dd><dt>23.24</dt><dd>Fuel supply</dd><dt>25.31</dt><dd>Fuel lance</dd><dt>26</dt><dd>outer pipe</dd><dt>27</dt><dd>Intermediate pipe</dd><dt>28.33</dt><dd>injection port</dd><dt>29</dt><dd>Syngas</dd><dt>30</dt><dd>air</dd><dt>32</dt><dd>inner tube</dd><dt>34</dt><dd>Lance axle</dd><dt>35</dt><dd>oil</dd><dt>36</dt><dd>mixed gas</dd><dt>37</dt><dd>hot gas</dd><dt>38</dt><dd>Lance tip</dd></dl>