JP2004093119A - Tubular flame burner and combustion method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a tubular flame burner capable of forming one part of tubular flame even outside a combustion chamber according to a combustion condition. <P>SOLUTION: This tubular flame burner comprises a tubular combustion chamber opened on one end; and a fuel blowing nozzle and an oxygen-containing gas blowing nozzle with a nozzle injection port opened on an inner face of the combustion chamber. Injection directions of the fuel blowing nozzle and the oxygen-containing gas blowing nozzle are approximately equal to a tangential direction of the inner periphery of the combustion chamber. A tubular portion on a side for exhausting exhaust gas from the nozzle injection port of the combustion chamber 3 is constituted of an inner cylinder 1 and an outer cylinder 2 sliding along the outer periphery of the inner cylinder 1, so as to make the length of the combustion chamber 3 adjustable. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a tubular flame burner, particularly to a tubular flame burner in which the length of a combustion chamber is adjustable, and a method for burning the same.

Conventionally, gas burners industrially used are generally of a type in which a flame is formed in front of the tip of the burner, but recently, a tubular flame capable of forming a flame in a combustion chamber. A burner has been developed (for example, see Patent Document 1).

FIG. 9 is an explanatory view showing a conventional tubular flame burner, in which (a) is a configuration diagram of the tubular flame burner, and (b) is a cross-sectional view taken along line AA of (a). This tubular flame burner has a tubular combustion chamber 21, one end of which is an open end serving as a discharge port for combustion exhaust gas. A long slit is formed at the other end along the pipe axis direction, and a nozzle 22 connected to the slit and separately blowing a fuel gas and an oxygen-containing gas is provided.

The nozzle 22 is provided in a direction tangential to the inner wall surface of the combustion chamber 21, and a swirling flow is formed in the combustion chamber 21 by blowing the fuel gas and the oxygen-containing gas. The nozzle 22 has a flat tip portion and a reduced opening area, so that fuel gas and oxygen-containing gas are blown at a high speed. 23 is a spark plug.

In the burner having the above-described configuration, when the mixture of the fuel gas and the oxygen-containing gas blown from the nozzle 22 to form a swirling flow is ignited, the gas in the combustion chamber 21 is stratified by centrifugal force due to the density difference. Thus, concentric gas layers having different densities are formed. That is, high-density combustion exhaust gas having a small density exists on the axis side of the combustion chamber 21, and unburned gas having a high density exists on the inner wall side (a side away from the axis) of the combustion chamber 21. Become. Such a state is very hydrodynamically stable. Although the flame is formed in a tubular shape, since the flow field is stably stratified, the flame is stable in a film shape.

炎 The flame formation position is naturally determined at a position where the speed toward the center and the flame propagation speed are balanced. In FIG. 1, reference numeral 24 denotes a tubular flame.

In addition, since unburned low-temperature gas exists in the vicinity of the inner wall of the combustion chamber in a boundary layer state, the wall surface of the combustion chamber 21 is not heated to a high temperature by direct heat transfer, and Prevent heat loss. That is, the heat insulation effect is large, and therefore, the thermal stability of the combustion field is maintained.

The gas in the combustion chamber 1 flows downstream while swirling, during which the mixed gas on the inner wall side continuously burns to form a tubular flame, and the generated exhaust gas moves to the axis side, and the open end Is discharged from

バ ー The burner with the above configuration has the following advantages. It is stratified in a rotating field, is hydrodynamically and thermally stable, and can burn even under conditions where the fuel gas component is very lean or rich, so the burner itself has a stable combustion. The range expands. In other words, even if the fuel type changes and the flame propagation speed changes, the position of the flame surface naturally moves to a position where the flame propagation speed and the speed toward the center balance, and this is a stable position, so stable combustion The range is wide.

Since the flame surface is stable, the temperature variation is small, and no local high-temperature portion is generated during combustion, and the mixed gas of fuel and oxygen-containing gas passes through the flame surface instantaneously, so the reaction time is short. The amount of harmful substances generated, such as NOx, is small due to reasons such as extremely shortening.

Since the reaction time is extremely short and a local low-temperature region cannot be formed, the residual amount of unburned components such as hydrocarbons is not very small, and the generation of soot is suppressed.
JP-A-11-281015

However, the above-mentioned conventional tubular flame burner has the following problems.
(1) In particular, in the case of oil fuel or heavy coal-based fuel such as propane, the free carbon component in the fuel emits light in the combustion process, so that a bright flame is formed. Originally, since the luminous flame itself has a large emissivity, the radiant heat from the luminous flame increases. Therefore, if the bright flame itself is located where it can be seen from the object to be heated in the furnace, the efficiency of heat transfer to the object to be heated will be high, but it will be completely burned in the combustion chamber, and will be ejected into the furnace. When it is performed, it is not a bright flame but a transparent exhaust gas having a small emissivity, and thus the heat transfer efficiency is low in the conventional combustion method.
(2) Since soot is completely burned in the combustion chamber, no soot is generated. Therefore, it cannot be used in situations where soot is required, for example, when carburizing is performed on steel materials with high efficiency.
(3) Complete combustion in the combustion chamber results in good flammability and a tendency to generate NOx.

The present invention has been made to solve the above-described problems of the prior art,
It is an object of the present invention to provide a tubular flame burner capable of forming a part of a tubular flame outside a combustion chamber in accordance with combustion conditions, and a method for burning the same.

A tubular flame burner according to the present invention includes a tubular combustion chamber having an open end, a fuel injection nozzle having a nozzle injection opening opened on an inner surface of the combustion chamber, and an oxygen-containing gas injection nozzle. In a tubular flame burner in which the injection direction of the blowing nozzle and the oxygen-containing gas blowing nozzle is substantially tangential to the peripheral surface of the combustion chamber, the cylinder on the side where exhaust gas is discharged from the nozzle injection port of the combustion chamber The portion is composed of an inner cylinder and an outer cylinder that slides along the outer peripheral surface of the inner cylinder, so that the length of the combustion chamber can be adjusted.

In the tubular flame burner according to the present invention, since the length of the combustion chamber can be adjusted, a part of the tubular flame can be formed outside the combustion chamber. Thus, bright flame or soot can be generated outside the combustion chamber, and the amount of generated NOx can be suppressed.

燃料 Fuel refers to gaseous fuel, liquid fuel that has been gasified in advance, liquid fuel that has been atomized with air or vapor, fine solid fuel that is pneumatically pumped with nitrogen, or the like.

Oxygen-containing gas refers to a gas that supplies oxygen for combustion, such as air, oxygen, oxygen-enriched air, and a mixed gas of oxygen and exhaust gas.

The method for burning a tubular flame burner according to the present invention is a combustion method using the tubular flame burner, wherein the flame is extended by increasing the length of the combustion chamber until the furnace temperature reaches a certain temperature. When the temperature inside the furnace exceeds the certain temperature, the combustion chamber is shortened so that the flame is generated so that the flame is generated outside the combustion chamber.

(4) When the flame is generated in the furnace, soot is generated in the combustion chamber in a low temperature range of the furnace where the generation of soot tends to increase, so that the generation of soot can be prevented.

Further, if the flame is generated in the combustion chamber and burned, in a high temperature range of the furnace where NOx is easily generated, the flame is burned so as to be generated outside the combustion chamber. Can be.

According to the present invention, the heat transfer amount, soot generation amount, and NOx generation amount of the tubular flame burner can be controlled.

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of the tubular flame burner of the present invention.

This tubular flame burner has a combustion chamber 3 composed of an inner cylinder 1 open at one end and an outer cylinder 2 open at both ends sliding along the outer peripheral surface of the inner cylinder 1, and a nozzle injection port. The combustion chamber 3 includes a fuel injection nozzle 4 and an oxygen-containing gas injection nozzle 5 which are opened on the inner surface of the inner cylinder 1. The outer cylinder 2 is provided so as to be slidable along the inner cylinder 1 and the outer peripheral surface of the inner cylinder 1 on the side of the combustion chamber 3 where the exhaust gas is discharged from the nozzle injection port.

The fuel injection nozzle 4 and the oxygen-containing gas injection nozzle 5 are connected such that the injection direction in the radial direction of the combustion chamber 3 is substantially tangential to the inner peripheral surface of the combustion chamber 3. Here, the oxygen-containing gas refers to a gas that supplies oxygen for combustion, such as air, oxygen, oxygen-enriched air, and a mixed gas of oxygen and exhaust gas.

Therefore, when the fuel is injected into the combustion chamber 3 from the fuel injection nozzle 4 and the oxygen-containing gas is injected from the oxygen-containing gas injection nozzle 5 and ignited by the ignition plug 6, the flame is applied to the inner peripheral surface of the inner cylinder 1 of the combustion chamber 3. It is formed along the shape of a tube. The flame thus formed is called a tubular flame 7.

Normally, the tubular flame burner is designed so that the combustion of the tubular flame 7 is terminated in the combustion chamber 3. However, in the tubular flame burner of the present invention, the tubular flame burner is provided outside the inner cylinder 1. When a part of the flame 7 is formed and the outer cylinder 2 is slid in the direction in which the length of the combustion chamber 3 becomes longer, all of the tubular flame 7 is formed in the combustion chamber 3 and the outer cylinder 2 is formed. Is slid in the direction in which the length of the combustion chamber 3 becomes shorter, a part of the tubular flame 7 is formed outside the combustion chamber 3.

の 長 The lengths of the inner cylinder 1 and the outer cylinder 2 can be theoretically determined, but may be determined by repeating experiments.

Then, as shown in FIG. 2, if the total length of the formed tubular flame 7 is L ₁ and the length of the tubular flame 7 formed outside the combustion chamber 3 is L ₂ , as shown in the graph of FIG. The amount of heat transfer and the amount of soot generation increase as the value of L ₂ / L ₁ increases. This is because, when L ₂ is increased, the ratio of bright flame having a large gas emissivity in the furnace increases, the heat transfer to the object to be heated is promoted, and the ratio of stable combustion in the combustion chamber 3 decreases. This is because soot is easily generated.

Further, as shown in the graph of FIG. 4, the NOx generation amount decreases as the value of L ₂ / L ₁ increases. This is because, if the ratio of burning in the furnace space outside the combustion chamber 3 is increased, dilution combustion can be performed while involving exhaust gas present in the space outside the combustion chamber 3, so that the oxygen concentration in the combustion field decreases and local Since the generation of a high-temperature portion is also suppressed, the thermal NOx generation reaction is suppressed, and the amount of generated NOx can be reduced.

燃 焼 A combustion experiment was conducted using the tubular flame burner of the present invention.

FIG. 5 is a graph showing the time-dependent changes in the furnace temperature (curve A) and the heated steel material temperature (curve B) at that time. In this combustion experiment, the temperature in the furnace was raised at a constant rate until the temperature in the furnace reached 1000 ° C., and was kept at that temperature after the temperature in the furnace reached 1000 ° C., and the total heating time was 15 hours. As before.

First, slide the outer tube 2 to the furnace interior, as L ₂ becomes 0 or less in FIG. 2, i.e. flame so as to occur only in the combustion chamber, the heating of the steel was performed (first Burning experiment). FIG. 6 shows the change over time in the NOx and soot concentrations at that time. In FIG. 6, the density value is indicated by an index with the allowable value being 100.

In the combustion in this case, almost no soot was generated, but the amount of generated NOx increased to a concentration of 150 until the furnace temperature reached 1000 ° C., and after the furnace temperature reached 1000 ° C., the amount of NOx increased to 150%. The concentration is maintained at a high level, and it is understood that the amount of generated NOx is a problem in this combustion.

The temperature of the steel material after heating for 15 hours was 950 ° C., which was considerably lower than the target temperature of 1000 ° C.

Next, slide the outer tube 2 to the furnace inner opposite as L ₂ is greater than 0 in FIG. 2, i.e. flame so as to occur in the furnace, the same heat as the first combustion experiment Under the conditions, the steel material was heated (second combustion experiment). FIG. 7 shows the change over time in the NOx and soot concentrations at that time. Also in FIG. 7, the density is displayed as an index with the allowable value being 100. In the combustion in this case, the amount of soot generated is a little large in the temperature rising process, but is an amount that hardly causes a problem after the furnace temperature reaches 1000 ° C. On the other hand, the amount of generated NOx is stable at a low level throughout the entire heating section. That is, in the combustion in this case, the amount of soot generated during the temperature raising process is slightly problematic, but the amount of NOx generated is not a problem.

The temperature of the steel material after heating for 15 hours was 980 ° C., which was closer to the target temperature of 1000 ° C. as compared to the first combustion experiment. It can be seen that the combustion method can more effectively heat the steel material than the first combustion method.

Next, based on the results of the first and second combustion experiments, the same as in the first combustion experiment until the furnace temperature reaches 800 ° C. so that the amounts of soot and NOx generated are below the allowable values. Then, the flame is generated only in the combustion chamber, and after the temperature exceeds 800 ° C., the flame is generated outside the combustion chamber in the same manner as in the second combustion experiment. The steel material was heated under the same heating conditions (third combustion experiment).

変 化 FIG. 8 shows the change over time in the NOx and soot concentrations at that time.

も Also in FIG. 8, the density is displayed as an index with the allowable value being 100. In the combustion in this case, the soot generation amount and the NOx generation amount are so stable that the soot concentration is 30 or less and the NOx is 80 or less throughout the entire heating section, and good heating is performed. .

The temperature of the steel material after heating for 15 hours was measured to be 975 ° C., and although the temperature was slightly lower than in the case of the second combustion experiment, heating was performed efficiently.

As described above, if the length of the combustion chamber of the tubular flame burner is fixed to a certain length, a lot of soot is generated when the furnace temperature is low, and when the furnace temperature is high, Although a large amount of NOx is generated, it is understood that the steel material can be heated under favorable heating conditions by changing the length of the combustion chamber according to the furnace temperature.

It is a longitudinal section showing an embodiment of a tubular flame burner of the present invention. It is a diagram showing the length L ₂ of the tubular flame formed in a length L ₁ and the combustion outside of the tubular flame formed in the combustion chamber. Is a graph showing the relationship between L ₂ / L ₁ and the amount of heat transfer and soot generation amount. It is a graph showing the relationship between L ₂ / L ₁ and the NOx generation amount. It is a graph which shows the time-dependent change of furnace temperature and heated steel material temperature in a combustion experiment. It is a graph which shows a change with time of NOx and soot concentration in a first combustion experiment. It is a graph which shows the time-dependent change of NOx and soot concentration in a 2nd combustion experiment. It is a graph which shows the time-dependent change of NOx and soot concentration in the third combustion experiment. It is explanatory drawing which shows the conventional tubular flame burner, (a) is a block diagram of a tubular flame burner, (b) is AA sectional drawing of (a).

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Inner cylinder 2 Outer cylinder 3 Combustion chamber 4 Fuel injection nozzle 5 Oxygen-containing gas injection nozzle 6 Spark plug 7 Tubular flame

Claims (2)

A tubular combustion chamber having an open end, a nozzle for fuel injection and a nozzle for oxygen-containing gas injection having a nozzle injection opening opened on the inner surface of the combustion chamber, wherein the fuel injection nozzle and the oxygen-containing gas injection nozzle In a tubular flame burner in which the injection direction is substantially tangential to the peripheral surface of the combustion chamber, the cylindrical portion on the side where exhaust gas is discharged from the nozzle injection port of the combustion chamber is an inner cylinder and the outer peripheral surface of the inner cylinder. A tubular flame burner comprising: an outer cylinder that slides along the cylinder, wherein the length of the combustion chamber is adjustable. 2. A combustion method using a tubular flame burner according to claim 1, wherein the combustion chamber is lengthened so that the flame is generated in the combustion chamber until the temperature in the furnace reaches a certain temperature. When the temperature exceeds the predetermined temperature, the combustion chamber is shortened to burn the flame so that the flame is generated outside the combustion chamber.

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