CN1214430A - Method for combustion of gaseous, liquid and medium caloric or low caloric fuel in burner - Google Patents

Abstract

The present invention relates to a method and burner for burning gaseous, liquid and medium or low calorie fuels in a burner with a swirler, in which method the liquid fuel is rendered in the form of a conical column of liquid fuel which is sprayed by Surrounded by a swirling combustion gas flow tangentially flowing into the swirler (1), additional gas and/or liquid fuel is injected into said gas flow, and medium or low-calorie fuel is injected along the liquid through at least one injection part inside the swirler Axial and/or coaxial injection of the fuel column.

Description

Method for combusting gaseous, liquid, and medium- or low-calorie fuels in a burner

The invention relates to a method for burning gaseous, liquid and medium- or low-calorie fuels in a burner with a swirler. Furthermore, the invention also relates to a burner for carrying out the method described above.

DE19547913A ₁ discloses a burner for a heater. In the figure of this specification, a swirler 100 is shown, and axial liquid fuel is injected into the swirl in the form of a conical liquid fuel flow through a fuel nozzle 103 in the streamer. The combustion air flow in the swirler is directed between the rotating shells (Drallschalen) of the swirler tangentially and at an angle to the above-mentioned liquid fuel flow, preferably through the corresponding injection openings 117 so that the above-mentioned combustion air flow and the gaseous fuel flow mix. The above-mentioned injection port 117 is mainly used for introducing natural gas, a fuel with a high calorific value of 46MJ/kg. All other structural details of the known burner, also known as a dual burner, for use with two types of fuel are already emphasized in the above-mentioned Federal German Publishing Specification.

For example, as is known from the above description, the combustion system for the heat generator is preferably used for the drive of a gas turbine. It happens that in the future gas turbine application area, natural gas and fuel oil can be used as dual burner fuels, and medium-calorie or low-calorie fuels (Mbtu-resp. LBtu-Bennstoffe) are also preferred. . These medium-calorie or low-calorie fuels (Mbtu-resp. LBtu-Brennstoff), obtained for example from the gasification of coal or heavy oils, contain a large amount of hydrogen and carbon monoxide, so that the calorific value of the medium-calorie fuel is only about one-third of the calorific value of natural gas , ie about 15MJ/kg.

Although it is in principle possible to mix the combustion gas flow with a gaseous mesocalorific fuel like natural gas through tangential injection openings, this may create the disadvantage that there is thus a mixed large volume flow in the swirler, so that Locally very high pressure losses occur, which permanently affect the stability of the formed gas jet. In addition, mixed medium-calorie fuels contain large amounts of highly reactive hydrogen, which poses a high risk for flashback of the flame in the burner. This incorrect flow will further lead to improper combustion of the input fuel, thereby significantly deteriorating the combustion process, such as a significant increase in _NOx in the exhaust gas. Flashback of the flame in the burner will eventually cause the burner to overheat, placing certain burner components under extreme heat loads close to their thermal load critical values.

Although the injection of medium-calorie fuel near the outlet of the burner itself has little effect on the stability of the swirling airflow, and also avoids further flashback of the flame in the burner, the short mixing section makes the mixing of medium-calorie fuel and combustion gas Insufficient, so the combustion process is similar to diffusion, producing very much _NOx . Although the emission of NO _x can be reduced by a suitable intensive mixing of medium-calorie fuels with nitrogen or water vapor, such dilution of the fuel in turn leads to a reduction in the efficiency of the gas turbine. For the same consideration, increase the input when using low-calorie fuels.

The object of the present invention is to provide a burner with a swirler and a combustion method for burning gaseous, liquid and medium-calorie or low-calorie fuels, in which the liquid fuel in the form of a conical liquid fuel column is sprayed In the form of a mist, the above-mentioned column of liquid fuel is surrounded by the swirling flow of combustion gas flowing tangentially into the swirler, so that the combustion of the above-mentioned fuel can achieve the following aspects in the case of using a single fuel Effect:

a) Significantly reduce the emission of substances that have an impact on the environment, especially NO _x and CO;

b) To ensure the flow relationship established in the cyclone, especially to avoid or eliminate the hidden danger of flame backflow in the burner;

c) Ensure that the flame is stable;

d) increase energy gain by means of complete combustion of fuel; and

e) Improve gas turbine efficiency by injecting medium calorie non-diluted fuel into the combustor.

Claim 1 presents a technical solution for accomplishing the task of the invention, which describes the method of the invention. The subject-matter of claim 6 is a burner operating according to the method of the invention.

Preferred further features of the concept according to the invention are the subject of the dependent claims. The subject matter of the invention is the co-combustion of gaseous fuels (such as natural gas), liquid fuels (such as petroleum) and medium or low-calorie fuels (so-called Mbtu- or LBtu-Brennstoffe) in a burner with a swirler, wherein the medium Or low calorie fuel is injected axially and/or coaxially into the burner or swirler. Preferably, the above-mentioned fuel is injected into the swirler near the liquid fuel injection port, and the above-mentioned liquid fuel gradually forms a conical liquid fuel column inside the swirler of each burner under the injected state. In this way it is ensured that the additional fine mist of liquid fuel injected into the interior of the swirler is very well mixed with the medium or low calorie fuel.

Axially or coaxially injecting medium or low-calorie fuel into the swirler interior can lead to a significant change in the flow field of the burner, and the above-mentioned axial flow part can be enlarged by additional injection of medium-calorie fuel, while the rotating part is almost the same way to reduce. As from the example described in the Federal German Published Specification DE 19547913 A1 cited above especially from column 4, lines 55-66, the rotating part can be reduced in a known manner, thereby destabilizing the so-called recirculation bubble (Rückströmblase) in order to destabilize the recirculation zone The flame is stable.

The difference from the dual burner principle mentioned above is that the increased axial flow part can normally blow off the recirculation bubbles generated in the recirculation zone, so the hidden danger of flashback can be significantly eliminated.

As mentioned at the beginning of this article, when medium or low calorie fuels contain large amounts of hydrogen and are highly reactive, these fuels still ensure the flame stability necessary for combustion, at which point a stable flame will form and will not form efficiently recirculation zone.

Medium or low calorie fuel is also fed upstream into the liquid fuel injection inlet area for good mixing with the injected fuel and the combustion gases injected into the swirler. In this way, due to the long mixing section of the premixed combustion, it has a relatively ideal _NOx emission value, which can be obtained when the premixed combustion of natural gas is carried out.

In order to reduce the corresponding emission values it is also possible not to mix nitrogen or water vapor. The particular advantage of this is that a reduction in the efficiency of the entire gas turbine due to dilution is avoided.

The burner implementing the method of the present invention is considered to be an improvement of the double burner described in the above-mentioned Federal German Published Specification DE19547913A1. The fuel enters the third fuel system of the cyclone. Medium or low calorie fuel is injected into the interior of the swirler through the injection opening, preferably near the central injection inlet area, by liquid fuel injected into the interior of the swirler, through the swirling shell of the swirler. The input of medium or low-calorie fuel and the input of liquid fuel take place axially and/or coaxially, and they are each symmetrical to the swirler axis.

The invention will be described below according to an embodiment with reference to the accompanying drawings, but the invention is not limited to this general inventive concept.

Fig. 1 is a longitudinal sectional view of a burner built according to the present invention;

Figure 2 is a cross-sectional view of a swirler injecting medium calorie fuel.

The burner shown in FIG. 1 consists of a swirler 1 and a mixing section 2 which is connected to the swirler 1 in the flow direction. In the swirler 1 there is provided a conical formation for the entry of a plurality of tangential combustion gas streams 3 (see FIG. 2 ) from a tangential inflow. The structure and shape of the swirler 1 and the hydrodynamic phenomena that can be formed by the shape of the swirler are described in detail in Figs. 1 to 5 of the German laid-open specification DE19547913A1, which will be clearly indicated below. It is not essential to the invention that the mixing section 2 adjoining the swirler 1 consists of a transition section 21 with a transition channel 22 and an adjoining mixing tube 23 . Reference to these burner components is intended only to provide a complete description of the burner arrangement in order to be able to supply the fuel required for the combustion process.

In the swirler 1 whose upper region is conical, a nozzle 4 for feeding liquid fuel into the interior of the swirler 1 is arranged on the central axis. Concentrically arranged around the nozzle 4 is a feed line 5 (see above) for feeding the medium-calorie fuel, which runs through swirler housings 6 , 7 . The finely distributed medium-calorie fuel is added axially or coaxially in the swirler 1 via corresponding nozzles 8 into the air flow (not shown) formed inside the swirler 1 and mixed therewith.

Likewise, a gaseous fuel supply pipe 9 is also provided, and the gaseous fuel is fed into the swirler tangentially from the outside together with the combustion air (see FIG. 2 ).

Compared with the prior art, the additional coaxial supply of medium-calorie fuel will increase the axial portion of the part of the flow introduced after passing through the transition portion 21 provided with the transition duct 22 and after passing through the mixing pipe 23, so in the known In the case of the double burner, the so-called "Drall-Breakdown" (return air bubbles) formed close to the mixing tube 23 in the range of the combustion chamber 10 can normally be blown away.

The most efficient delivery of medium calorie fuel is preferably made using the fuel injection ports 8 which open coaxially into the swirler housings 6, 6', 7, 7'. Medium calorie fuel may be injected through one or more nozzles per swirler shell.

Figure 2 is a cross-sectional view of a cyclone 1 constructed in accordance with the invention. A liquid fuel nozzle 4 is arranged in the axial direction of the swirler 1, and a plurality of swirler shells 6, 6', 7, 7' are sequentially arranged at an angle around the nozzle. Combustion gases 3 are fed tangentially into the interior of the swirler 1 at the tangential between adjacent swirler shells, said combustion gases being mixed with natural gas by means of conduits 9 with corresponding injection nozzles. In the example shown, the swirler shells 6 , 6 ′, 7 , 7 ′ each pass through a fuel nozzle for feeding medium-calorie fuel. Depending on the application, a plurality of nozzles can also be provided per swirler shell, so that the amount of mid-calorie fuel supplied axially can be varied over a wide range in the direction of the burner.

Claims (10)

1. Method for burning gas, liquid and medium and low-calorie fuels in a burner with a swirler (1), in which method a conical liquid fuel column (4') which makes the liquid fuel misty The fuel column is surrounded by a swirling combustion gas stream (3) flowing tangentially into a swirler (1), into which additional gaseous and/or liquid fuel is injected and passed through at least one injection part inside the swirler ( 8) Axial and/or coaxial injection of medium or low calorie fuel. 2. A method as claimed in claim 1, characterized in that undiluted medium or low calorie fuel is injected, ie medium or low calorie fuel without addition of additional materials such as nitrogen and/or water vapour. 3. A method as claimed in claim 1 or 2, characterized in that the injected medium or low-calorie fuel is mixed with liquid and gaseous fuel and combustion gases (3) inside the swirler (1) in order to enable premixing combustion. 4. A method as claimed in any one of claims 1 to 3, characterized in that the axial flow field distributed in the burner consisting of fuel and combustion gases 3 has a large axial flow portion , by means of which the risk of flashback can be reduced or avoided. 5. The method according to any one of claims 1 to 4, characterized in that the above-mentioned medium or low calorie fuel gas is obtained from the gasification of coal or heavy oil. 6. A burner for implementing the method of claims 1 to 5 for a heater, having a swirler (1) for the combustion gas stream (3) and fuel injection means, and at least one for liquid fuel The first injection device (4) of the above-mentioned liquid fuel is a conical liquid fuel column (4') that is sprayed in the axial direction in the swirler (1), at least one of which is used for gas and/or liquid fuel The second injection device (9), the above-mentioned gas and/or liquid fuel and the combustion gas flow (3) are injected into the swirler (1) along the tangential direction, and it is characterized in that in the swirler (1) at least A third injection device (8) is provided, by means of which medium or low-calorie fuel can be fed into the interior of the swirler (1) in the axial and/or coaxial direction of the liquid fuel column (4') . 7. The burner according to claim 6, characterized in that the above-mentioned third injection device (8) is arranged countercurrently and upwardly close to the first injection device (4) on the cyclone (1) . 8. The burner according to claim 6 or 7, characterized in that the swirler (1) consists of several separate rotating shells (6, 6', 7, 7'), through which the center or Low-calorie fuel injection. 9. The burner according to claim 8, characterized in that each rotary shell is provided with one or several injection devices (8). 10. Burner according to claims 6 to 9, characterized in that said injection means (8) has at least one injection outlet through which the fuel is divided into fine fractions.

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