EP0832398B1 - Catalytic combustion chamber for a gas turbine - Google Patents

Description

The invention relates to a burner, in particular for a gas turbine, with a catalytic combustion chamber such as shown in document JP-61 053 425. As a fuel is a hydrocarbon and / or hydrogen-containing Energy sources in both liquid and provided in gaseous form. Such a fuel is for example natural gas, oil or methane. Such a burner can preferably be used in a gas turbine.

A gas turbine usually consists of a compressor part, a burner part and a turbine part. The compressor part and the turbine part are usually on a common shaft that also serves as a generator Electricity generation drives. The compressor section is preheated Fresh air with a fuel of the type mentioned burned. The hot burner exhaust gas is fed to the turbine part and relaxed there.

A detailed information about the structure and the use a gas turbine gives the company script "Gasturbines and Gas Turbine Power Plants "from Siemens AG, May 1994, order no. A 96001-U 124-V 1-7600.

When a fuel of the type mentioned is burned, nitrogen oxides NO _x also arise as particularly undesirable combustion products. In addition to sulfur dioxide, these nitrogen oxides are the main cause of the environmental problem of acid rain. One is therefore - also due to strict legal limit values for NO _x emissions - willing to keep the NO _x emissions from a gas turbine particularly low and at the same time largely unaffected by the performance of the gas turbine.

For example, a reduction in flame temperature in the Burner as nitrogen oxide reducing. This is the fuel or the compressed and preheated fresh air water vapor added or water injected into the combustion chamber. Measures that reduce nitrogen oxide emissions per se are referred to as primary measures for nitrogen oxide reduction.

Accordingly, all measures are considered secondary measures referred to, where once in the exhaust gas e.g. a gas turbine or also fundamentally contained in a combustion process Nitrogen oxides can be reduced through subsequent measures.

This has become the worldwide method of selective catalytic Reduction (SCR) enforced, in which the nitrogen oxides together with a reducing agent, usually ammonia, on one Catalyst are contacted and nitrogen and water form. With the use of this technology is therefore inevitably linked to the consumption of reducing agents. The catalysts arranged in the exhaust duct for nitrogen oxide reduction naturally cause a pressure drop that at Use of the burner in a turbine caused a drop in performance entails. Even a drop in performance of some Per thousand affects the performance of the gas turbine for example 150 MW and an electricity sales price of about 0.15 DM / kWh electricity seriously on that with such a device achievable result.

As a primary measure to break down nitrogen oxides, the GB 2 268 694 A provided a catalytic combustion chamber, wherein the ignition temperature of a fuel by a partial catalytic oxidation is lowered. The intended ones Catalysts are transverse to the flow direction of the Fuel installed and extend over the entire Flow cross-section. So there is a high flow resistance given.

In the burners described above, there is therefore basically the problem that any nitrogen oxide reduction provided there, primary or secondary type, a loss of performance or a loss in the overall efficiency of the gas turbine system consequence.

The invention is therefore based on the object of a burner, especially for a gas turbine, specify which one through particularly low nitrogen oxide emissions and at the same time is characterized by a particularly high efficiency.

This object is achieved with a burner according to claim 1, in which a catalytic combustion chamber is provided, wherein the combustion chamber in the direction of flow of a fuel has essentially cylindrical extension and the Wall facing the fuel has a catalytically active coating for oxidation of the fuel. In this way, the catalytically induced combustion the fuel has a particularly low nitrogen oxide content of the burner exhaust gas reached. Is through at the same time the coating of the wall of the combustion chamber does not increase connected to the flow resistance, so that with such high efficiency in catalytic combustion chamber a gas turbine can be reached. The essentially cylindrical Shape of the catalytic combustion chamber and the catalytic active coating of the wall help that the fuel ignites from the wall and spreads out the flame front from the catalytically active surface the wall into the free flow of the fuel gas is. In particular, the cylindrical shape helps to an essentially concentric and therefore homogeneous Distribution of the flame front, creating a complete and even combustion of the fuel results.

To achieve a particularly well rotationally symmetrical design Flame front it is beneficial if a number catalytic concentric to the cylinder longitudinal axis of the combustion chamber actively coated rings is provided.

The process of forming a largely rotationally symmetrical Flame front in the combustion chamber is further supported, if the ring or rings only in the outer area of the substantially circular cross section of the Combustion chamber are arranged.

To lower the catalytic ignition temperature of the fuel in the combustion chamber it is provided that the Combustor a fuel comprising a main fuel stream, a preformed partial fuel flow and air, feedable is. Here, the main fuel flow is usually from natural gas and / or coal gas and / or hydrogen. The preformed Fuel partial flow is a partial flow of the Main fuel stream separated and through a preforming stage is directed. In this working on a catalyst basis Preforming stages are made from natural gas, for example substances that ignite catalytically more easily than natural gas, e.g. Alcohols, aldehydes and hydrogen. One with one such preformed fuel partial flow mixed fuel gas therefore has excellent catalytic ignitability.

A particularly advantageous embodiment with respect to Ignitability of the introduced into the catalytic combustion chamber Fuel can provide that a preformed Partial fuel flow, optionally premixed with air, enters the combustion chamber through holes in the wall. In this way, the comparatively easily ignited gas mixture of the preformed partial fuel flow directly with brought into contact with the catalytically active coating and ignites spontaneously, so that a reliable, reliable standing Ignition in the form of a hollow cylinder in the catalytic Combustion chamber is formed.

To protect the catalytically active coating that is on the wall of the catalytic combustion chamber facing the fuel gas is located, it can be provided to cool the wall. The wall can be cooled with air, for example are achieved, while at the same time preheating the air becomes. This preheated air can follow, for example compressed in the compressor section to the combustion chamber inlet pressure become.

The catalytic effect of the catalytically active coating occurs particularly advantageously when the catalytic active coating titanium dioxide, which is preferably flame and is plasma-sprayed, and a precious metal portion selected made of platinum, rhodium, palladium, iridium, rhenium and / or a metal oxide component consisting of one or several transition metal oxides. As transition metal oxides such oxides come into question which are strongly oxidizing have a catalytic effect, e.g. Copper oxide, Chromium oxide, iron oxide, molybdenum oxide, tungsten oxide, vanadium oxide, Manganese oxide, cerium oxide and other oxides of lanthanoids.

FIG 1

in schematischer Darstellung den Brenner einer Gasturbine mit katalytischer Brennkammer;

FIG 2

in schematischer Darstellung den Brenner einer Gasturbine gemäß Figur 1 mit geringfügig gegenüber Figur 1 modifizierter katalytischer Brennkammer; und

FIG 3

eine katalytische Brennkammer im Querschnitt.

Embodiments of the invention are explained in more detail with reference to a drawing. Show:

FIG. 1

a schematic representation of the burner of a gas turbine with a catalytic combustion chamber;

FIG 2

in a schematic representation the burner of a gas turbine according to Figure 1 with a slightly modified compared to Figure 1 catalytic combustion chamber; and

FIG 3

a cross section of a catalytic combustion chamber.

In Figures 1 to 3, the same parts have the same reference numerals.

One can see in the schematic representation according to FIG a gas turbine 2, which has a compressor part 4, a burner part 6 and a turbine part 7 comprises. The burner section 6 comprises a catalytic combustion chamber 8, the wall 10 of which Has catalytically active coating 12.

The catalytic combustion chamber 8 has one in the exemplary embodiment circular cross section. In the catalytic combustion chamber 8, a fuel gas flows in as fuel 14, which in the exemplary embodiment from compressed air in the compressor part 4 16, a main fuel stream 18 and a preformed Partial fuel flow 20 exists. This preformed partial fuel flow 20 is from an original fuel stream 22 separated and passed through a preforming stage 24. The fuel stream 22 is in the embodiment from natural gas, from which in the preforming stage 24 catalytic substances that ignite more easily than natural gas, e.g. Alcohols, Aldehydes and hydrogen are formed. The preforming level 24 includes one to perform its function Ceramic honeycomb catalyst not shown Titanium dioxide base, which additionally contains a precious metal, consisting of superficially applied to the honeycomb catalyst Includes platinum and palladium.

The catalytically active coating 12 on the wall 10 of the Catalytic combustion chamber 8 consists of a flame-sprayed Titanium dioxide layer with a thickness of about 500 microns the additional precious metal particles of platinum, rhodium and Palladium and particles of transition metal oxides, such as cerium oxide, Vanadium oxide and chromium oxide are applied. Alternatively a flame-sprayed titanium dioxide can also be a plasma-sprayed titanium dioxide layer can be provided. Both Layers are characterized by their great strength on the wall consisting mostly of an austenitic steel 10 the catalytic combustion chamber 8.

When the gas turbine 2 is operating, the fuel 14 now flows in the catalytic combustion chamber 8 and ignites at the catalytically active coating 12 of the wall 10. Die auf upstream flame front 26 thus formed is just like the downstream flame front 28 largely rotationally symmetrical, so that the temperature distribution in the catalytic combustion chamber 8 along the main flow direction approximately circular in cross-section Has isotherms. This is for even and Low-emission combustion of the fuel 14 is advantageous.

The fuel 14 catalytically burned in this way enters the turbine section at a temperature of around 1100 ° C 7 of the gas turbine 2 and is relaxed there. The in Thermal energy transferred to the turbine becomes the drive of a generator for electricity generation, not shown here used. This generator is on the same Shaft not shown here arranged as the gas turbine 2. The burner exhaust gas 30 leaving the turbine part 7 is due to the catalytic combustion of the fuel gas 14 particularly low in nitrogen oxide and has a nitrogen oxide content of about 70 ppm. The burner exhaust gas 30 cannot in one here waste heat steam generator for steam generation shown further be used.

Figure 2 shows a schematic representation of a figure 1 slightly modified gas turbine 2 '. Limit here the modifications affect the design of the catalytic combustion chamber 8. The catalytic combustion chamber shown in FIG Combustion chamber 8 'differs from FIG. 1 in that that 10 holes 32 are provided in the wall, through which the preformed fuel partial flow 20 and air 16 enter the combustion chamber 8 '.

Compared to the configuration according to FIG. 1, this measure has two advantages. The first advantage is that Fuel mixture with the lowest catalytic ignition temperature directly on the catalytically active coating 12 enters the combustion chamber 8 'and therefore comparatively ignited spontaneously. This measure therefore bears especially to stabilize the upstream Flame front 26 at. The second advantage is that the walls 10 from the mixture flowing along preformed fuel sub-stream 20 and air 16 cooled become. This cooling also reduces the thermal load the catalytically active coating 12 is reduced, which has a favorable effect on the durability of this coating 12 affects. Cooling of the wall 10 can be shown in FIG Alternatively, by a flow of air 16 can be achieved, which occurs in the compressor part 4.

Figure 3 shows a schematic representation of the cross section a modified compared to Figures 1 and 2 catalytic Combustion chamber 34. Wall 10 and 10 can be seen again the catalytically active coating 12 for the oxidation of the Fuel 14. Under the oxidation of fuel understood of course that the fuel 14, 22 oxidizes and that brought up over the air 16 and for combustion required oxygen is reduced. Under the catalytic active coating 12 for the oxidation of the fuel gas 14 is therefore the coating that covers the entire Combustion process with oxidized and reduced combustion products induced.

The combustion chamber 34 has three concentrically arranged rings 36 on. These concentric rings 36 are thin strips of sheet metal, consisting of the material of the wall 10. The rings 36 have the same catalytically active coating 12, with which the wall 10 of the combustion chamber 34 is also coated is. For the sake of clarity of presentation is the catalytically active coating 12 only in a selected one Quadrants drawn. Also the rings 36 retaining webs 38 have this catalytically active coating 12. The rings 36 are only in the outer Area of substantially circular cross section of the Combustion chamber 34 arranged to ignite the initial ignition of the Fuel 14 on the outer portion of the cross section of the Limit combustion chamber 34. An expansion of the flame front into the free flow of the fuel gas 14 then takes place automatically. The rings 36 with the catalytically active coating 12 thus help to stabilize the flame front and to ensure a complete and therefore special low-pollution combustion.

Claims (7)

1. Burner with a catalytic combustion chamber (8, 8', 34), the combustion chamber (8, 8', 34) having an essentially cylindrical extension in the flow direction of a fuel (14), and the combustion chamber wall (10) facing towards the fuel (14) exhibiting a catalytically active coating (12) for the oxidation of the fuel (14), characterized in that a fuel (14), which comprises a fuel main flow (18), a preformed partial fuel flow (20) and air (16), can be supplied to the combustion chamber (8, 8', 34), a catalytic preforming stage (24), through which the partial fuel flow (20) can flow, being provided for preforming, which preforming stage (24) decomposes the fuel (14) at least partially into easily ignited materials, in particular into alcohols, aldehydes or hydrogen.
2. Burner according to Claim 1, characterized in that a number of catalytically actively coated rings (36) are provided which are arranged concentrically about the cylindrical longitudinal axis of the combustion chamber (8, 8', 34).
3. Burner according to Claim 2, characterized in that the ring or the rings (36) are arranged exclusively in the outer region of the essentially circular cross section of the combustion chamber (8, 8', 34).
4. Burner according to one of Claims 1 to 3, characterized in that a preformed partial fuel flow (20), premixed with air (16) if appropriate, can be introduced into the combustion chamber (8') through holes (32) in the wall (10).
5. Burner according to one of Claims 1 to 4, characterized in that the wall (10) can be cooled.
6. Burner according to one of Claims 1 to 5, characterized in that the catalytically active coating (12) exhibits titanium dioxide, preferably flame-sprayed or plasma-sprayed, and a noble metal proportion, selected from one or more of the noble metals platinum, rhodium, palladium, iridium and rhenium, and/or a metal oxide proportion, selected from one or more transition metal oxides.
7. Gas turbine, comprising a burner in accordance with one of Claims 1 to 6.

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