SK319692A3 - Torch for combustion of fuel at lower emissions of harmful matters - Google Patents

Abstract

The invention relates to a burner for combustion, which is low in pollutants, of a fuel (natural gas) with an oxidation gas. As a result of the oblong, in particular wedge-shaped design according to the invention of the outlet openings of the admission ducts for the oxidation gas, an NOx reduction is achieved as a result of increased waste gas recirculation and stepwise combustion.

Description

Obiest techniques

The present invention relates to a low emission fuel burner

All harmful substances with oxidizing gas, with at least one fuel feed channel and at least one oxidizing gas feed channel.

BACKGROUND OF THE INVENTION

Burners which have a reduced emission of harmful substances, in particular nitrogen oxides harmful to the environment, must be adapted to the combustion technique which allows the development of such harmful substances to be limited.

Nitrogen oxides formed in the process spslovscí® essentially of molecular oxygen present in the combustion air as a thermal _ΝΟ χ and nitrogen bound in the fuel, for example coal or oil to fuel topné® _ΝΟ χ *. Thermal nitrogen oxide is formed from dissociated oxygen and ^A nitrogen molecules in the region of the flame root or in hot flame zones at temperatures above 1300 ° C. The thermal evolution of NO is dependent on the concentration of the solute nitrogen and dissociated oxygen and is strongly temperature-dependent. In order to develop the fuel ΚΟ _χ , the concentration of oxygen in the switching air or in the oxidizing gas is in the first row. The main variable influencing the development of ΝΟ _χ is the air number L in both cases.

The investigation shows that the concentration of nitrogen oxides rises with the furnace room temperature and exponentially with the combustion air temperature and maximum maximum near the stoichiometric combustion ratio at air L number equal to about 1.1 ε at both lower and higher air number. than the stechlometric ratio is strongly decreasing. The concentration of nitrogen oxides can be reduced by re-circulating the flue gas, whereby the reduction in the amount of KC _is related exponentially with the amount of recirculating flue gas flow, see the discussion _in Cha. acpise Gas, fcärme International 3S, C1989), Sec. 10, Frosinec.

In the combustion technique, in order to reduce the amount of nitrogen oxide, an effort is made to reduce the partial pressures of oxygen and nitrogen and the combustion temperature.

Thus, oxygen-enriched air or pure oxygen is used as the oxidizing gas to reduce the oxygen supply. But that is enough

-2 as a result of higher flame temperature and higher oxygen partial pressure. To reduce the oxygen supply, backfeeding of the flue gases into the combustion air or oxidizing gas is used, thereby reducing both the oxygen content by dilution and, on the other hand, lowering the combustion temperature due to more flue gases which dissipate heat from the flame. Effective here is the addition of cooled flue gas to the region of the flame root.

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Staged combustion is also suitable for the same purpose, see Gas Sharme International, 39 (1990), Se.6, June. The staging burners have combustion air supply channels for downstream oxidation gas, i.e. in the flame direction, which allow only a small amount of oxygen to be supplied through the primary air holes at the bottom close to the burner, at the top of the secondary and tertiary air holes. the amount of oxygen corresponding to approximately stoichiometric combustion. The temperature of the flame remains considerably below the temperature prevailing in the single-stage combustion.

This staged combustion with the so-called secondary air barriers in the inlet duct has the disadvantages that these barriers which surround the burner in the form of sheathing are exposed to strong heat because they lie downstream of the combustion gas opening and that the sheathing has a strong influence on carbon monoxide emission, which must always be determined before the burner is deployed, and many designs make it unusable because of high carbon monoxide emissions.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an improved burner which allows optimum use of the described possibilities to reduce the generation of harmful substances and eliminates the confounding disadvantages of known burner embodiments.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The present invention is based on the object of providing a burner for burning at low emission of harmful substances with oxidizing gas, with at least one fuel inlet duct and at least one oxidant gas inlet duct. Each oxidation gas supply channel is formed with an elongated cross-section.

According to the present invention, all possibilities for reducing harmful substances are optimally utilized. long sections

The openings have a larger circumference at the same cross-sectional area as compared to the prior art circular cross-sections and thus allow the reintroduction of a larger amount of furnace flue gas into the oxidizing gas stream. This addition of flue gas sucked into the oxidizing gas jet is inert and reduces the flame temperature and oxygen partial pressure more strongly than hitherto, thus preventing efficient evolution Ν0 _χ .

A further advantage of the burner according to the invention is that the diameter of the burner head can be maintained with a small suction surface for the furnace flue gas. To date, in order to rebind a larger amount of furnace flue gas, the oxidation gas orifices had to be as far as possible from the combustion gas orifices, whereby the dimensions of the burner head became considerably light. Additionally, narrow oxidation gas inlet ducts in the immediate vicinity of the combustion gas opening were necessary to maintain the flame stable at the burner mouth and to prevent flame detachment. These costly and complex measures are unnecessary in the burner of the invention. Through the cross-sectional geometry of the oxidant gas orifices of the present invention, a large amount of furnace flue gas can be recycled to the flame and a stable flame at the mouth of the burner can be maintained without the burner head diameter being increased.

It is preferred that the outlet openings of each of each oxidation gas supply ducts are formed with a wedge-shaped cross-section. By this measure, step combustion can be provided, in particular when the outlet openings of the oxidant gas supply ducts are arranged centrally about the axis of each fuel feed duct and are aligned with the longitudinal axis in the radial emitter.

When the tips of the wedge-shaped oxidant gas outlet openings are directed towards the axis of the feed channel for the fuel, the outgoing fuel is mixed with only a small amount of oxidizing gas, so there. the flame burns substoichiometrically and at the same time is kept stable at the burner mouth. Wedge-shaped beam cross-section \ \

The oxidizing gas exacerbating the radial outward then causes. The combustion gas is only combusted with increasing amounts of oxygen corresponding to an approximately stoichiometric combustion ratio only with increasing distance from the burner mouth. In addition, in this arrangement, the radial outward surface increases the area of the oxidizer gas necessary for the suction of the furnace flue gas.

Phodo-stoichiometric combustion in the region of the flame root with combustion completing downstream of the flame is generally essential ^.

To reduce the amount of nitrogen oxides.

In this respect, it is advantageous if the internal distance than the outlet opening of the fuel inlet duct and the outlet outlet! the oxidation gas inlet passages are at least equal to at least 20% of the diameter of the fuel inlet outlet port. In most cases, it is sufficient if this distance is less than 50% of the width of the outlet opening of the fuel feed channel. On the one hand, the flame can then be kept stable at the burner mouth, on the other hand a sufficiently large suction surface for the furnace flue can be obtained without the burner mouth being oversized.

The embodiment of the burner according to the invention will be described in more detail below and its advantages will be described.

Drawings of drawings in the drawing

The sole figure of the drawings shows schematically in plan view a burner according to the present invention.

An example embodiment of the invention

Shown schematically is a plan view of a burner mouth in accordance with the invention with an inlet channel 2 for natural gas fuel arranged in the center of the burner orifice and an inlet conduit. the oxidation gas channels arranged concentrically about the axis 2 of the fuel feed channel 2. Pure oxygen is used as the oxidizing gas. The outlet opening of the fuel supply duct 2 is in this case circular, while the outlet openings 1 of the oxidation gas supply ducts according to the invention are formed with a wedge-shaped cross-section. The longitudinal axes of these wedge-shaped exit squares 7 in the radial shaft are aligned with the axis 2 of the fuel feed channel 2.

The arrangement of the wedge outlet openings 1 for oxidizing gas releases the inlet of the amount of granular oxygen flowing from the outside to the inside in the radial serum so that near the outlet openings of the natural gas fuel feed channel it is spelled with a podetechioceros, stable at the mouth of the 4 burner. In the radial direction, the oxygen wastes from the wedge outlet openings 1 flow out further downstream and mixed with the incompletely burned xeshia gas, and this finally spelled completely.

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This creates a step combustion which is very effective for reducing the amount of nitrogen oxides Ν0 _χ .

The opening angle and the cross-sectional area of the wedge-shaped oxygen outlet openings 1 as well as the number of oxidant gas inlet ducts are determined so that the flame burns approximately stoechometrically at the end region and burns at the root of the flame substoichiometrically.

In this example, the number of oxygen inlet ducts is est, the cross-sectional area of each outlet opening 1 of these inlet ducts being equal to about one third of the cross-sectional area of the natural gas outlet opening. The opening angle of the wedge outlet openings 1 is about 6 °. The internal distance between the oxygen outlet ports 1 and the natural gas inlet port 2 is 25% of the diameter of the natural gas inlet port 2.

The geometrical shape of the oxygen outlet orifices 1 of the invention for oxidation to the oxygen beams allows the suction of large amounts of furnace flue gas in the region of the flame root. This achieves a cooling flame and a reduction in the partial pressure of oxygen, as well as creating both mechanisms to prevent the generation of nitrogen oxides Κ0 _χ .

Flue gas measurement in the burner operation of the present invention at a heating power of 0.8 MW yields flue gas containing about 160 mg 0 _χ per Nnr and about 120 mg CO at 4% oxygen in the flue gas.

This results in a significant reduction in the corresponding air TA limits.

Claims (4)

PATENT CLAIM 1. Burner for combustion of fuel at low emission of pollutants v ε oxidizing gas ε at least one inlet gas channel and at least one oxidizing gas inlet channel, characterized in that the outlet openings (1) of each oxidation gas inlet channel are formed with an elongated cross-section. A burner according to claim 1, characterized in that the outlet openings (1) of the oxidation gas supply ducts are formed with a wedge-shaped cross-section. A burner according to claim 1 or 2, characterized in that the outlet openings (1) of the inlet ducts for oxidizing gas are arranged centrally about the axis (3) of each of the inlet ducts (2) for fuel and are radially directed in their radial direction. to this axis (s) (3) · 4. A burner as claimed in claim 3, wherein the internal distance between the fuel inlet port (2) and the oxidant gas inlet port (1) is at least 20% of the diameter of the fuel inlet port (2). .