JP2000346316A - Combustion equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a combustion equipment capable of improving radiant heat transfer characteristics while suppressing generation of an NOx. SOLUTION: A fuel jet port 16 for injecting fuel and a primary combustion assisting gas jet port 17 for injecting primary combustion assisting gas are installed at an innermost wall of a combustion chamber 14 recessed on an inner surface of a furnace wall 11, and secondary combustion assisting gas jet port 18s for injecting secondary combustion assisting gas are installed at both sides of the port 16 of a direction parallel to the surface of a matter to be heated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a combustion device,
More specifically, the present invention relates to a combustion device suitable for various industrial furnaces that heat an object to be heated by radiant heat transfer from a flame.

[0002]

2. Description of the Related Art A combustion apparatus using pure oxygen as a combustion-supporting gas (oxidizing agent) can obtain a higher-temperature combustion flame than an apparatus using air, and also has NOx. Has the characteristic that the emission amount of methane is extremely small. However, in a general industrial furnace, a completely closed furnace is practically impossible, and the inflow of air into the furnace cannot be avoided. As the supporting gas, oxygen produced by a pressure-variable air separation device (PSA device) is frequently used, and oxygen from the PSA device contains several percent of nitrogen as an impurity. This nitrogen will produce NOx in the hot combustion flame.

[0003] Further, since the amount of NOx generated increases rapidly as the temperature increases, it is effective to reduce the flame temperature in order to suppress the amount of NOx generated, such as by two-stage combustion or recirculation of exhaust gas. Therefore, the flame temperature is lowered to reduce the generation of NOx. However, when the flame temperature is reduced, the radiation heat transfer characteristic is reduced, and thus a problem that the heating efficiency is reduced occurs.

[0004] Therefore, the present invention reduces the flame temperature to reduce NOx.
It is an object of the present invention to provide a combustion apparatus capable of improving the radiant heat transfer characteristics by expanding the flame while suppressing generation of flaming.

[0005]

In order to achieve the above object, a combustion apparatus according to the present invention comprises a fuel injection port for injecting fuel into a back wall of a combustion chamber recessed in an inner wall of a furnace wall; A primary combustible gas spout that ejects primary combustible gas near the outlet, and a secondary combustible gas that is ejected on both sides of the fuel ejector in a direction parallel to the surface of the object to be heated It is characterized in that a combustion supporting gas ejection port is provided.

Further, the combustion apparatus according to the present invention is characterized in that the primary combustible gas outlet is provided on the outer periphery of the fuel outlet.

Further, it is preferable that the ejection speed of the primary combustion supporting gas is not more than 30 m / sec, and the ejection speed of the secondary combustion supporting gas is not less than 150 m / sec and higher than the ejection speed of the primary combustion supporting gas. Further, the flow rate of the primary combustion supporting gas is set so that the oxygen ratio to the fuel is less than 1.0, and the total flow rate of the primary combustion supporting gas and the secondary combustion supporting gas is set to the oxygen flow rate for the fuel. The ratio is set to be 1.0 or more,
In particular, the oxygen concentration of the primary and secondary combustion supporting gas is 90% by volume.
It is characterized by the above.

The distance between the secondary combustible gas jets and the depth of the combustion chamber are such that the amount of combustion is 700 k.
If it is less than w, the distance between the secondary combustion supporting gas jets is 10
0 to 300 mm, the depth dimension is 100 to 300 mm, and when the combustion amount is 700 to 1500 kW, the distance between the secondary combustion supporting gas jets is 200 to 400 mm, the depth dimension is 200 to 350 mm, and the combustion amount is 1500 to 25
When the power is 00 kW, the distance between the secondary combustion supporting gas jets is 2
It is characterized in that it has a depth of from 250 to 400 mm and a depth of from 250 to 400 mm.

[0009]

1 to 3 show a first embodiment of a combustion apparatus according to the present invention. FIG. 1 is a sectional plan view, FIG. 2 is a sectional front view, and FIG. 3 is a sectional side view. . In this combustion apparatus, an opening 12 is formed in a part of a furnace wall 11, and a tile 13 made of a refractory for forming a combustion chamber is embedded in the opening 12. The tile 13 is provided with a combustion chamber 14 having an elliptical longitudinal section and a predetermined depth dimension. A fuel outlet 16 for discharging fuel, a primary combustion supporting gas, And a secondary combustible gas spout 18 for spouting secondary combustible gas.

The fuel injection port 16 and the primary combustion supporting gas injection port 17 are formed in a double pipe structure in which the primary combustion supporting gas injection port 17 is provided on the outer periphery of the fuel injection port 16. The flammable gas jets 18 are located on both sides in the horizontal direction of the jets 16 and 17, that is, at predetermined positions in a direction parallel to the surface of the object 19 to be heated by the flame generated by the combustion device. Each is provided. In the present embodiment, the primary combustible gas jet 17 is opened in a slit shape around the fuel jet 16, but a so-called multi-hole structure in which a plurality of small jets are arranged in a circle is used. Can also.

As the fuel or the supporting gas, any one can be used. Examples of the fuel include gaseous fuels such as LPG, LNG and butane, liquid fuels such as kerosene, heavy oil and light oil, and fine powders. Solid fuels, such as charcoal, or mixtures thereof can be used. The shape of the fuel ejection port 16 can be appropriately selected according to the properties of the fuel, and a flat nozzle that ejects the fuel in the horizontal direction can also be used.

Although air can be used as the combustion supporting gas, oxygen gas having an oxygen concentration of 90% by volume or more is preferable in consideration of NOx emission and radiation heat transfer performance. In addition, it is also possible to use different combustion supporting gases for the primary and the secondary.

[0013] The ejection speed of the primary combustion supporting gas from the primary combustion supporting gas outlet 17 is determined by the flow rate of the primary combustion supporting gas,
Although it can be appropriately set according to the type of fuel, the injection speed, and the like, in addition to the shape of the injection port, it is usually sufficient to set the range to 30 m or less per second so that a sufficient propulsive force can be applied to the flame. If the ejection speed of the primary combustible gas is too high, the emission amount of NOx and the radiation heat transfer characteristics are adversely affected, and the ejection port may be damaged.

Further, the ejection speed of the secondary combustion supporting gas from the secondary combustion supporting gas ejection port 18 depends on the distance from the fuel ejection port 16 and the primary combustion supporting gas ejection port 17, the shape of the combustion chamber 14, and the like. Depending on the size, fuel and the state of ejection of the primary combustion supporting gas, if the velocity is higher than the ejection speed of the primary combustion supporting gas, the higher the speed, the more the surrounding combustion gas is caught in the flame, and the flame temperature and local temperature As a result, the NOx emission can be reduced. However, the ejection speed is 1 per second
If it exceeds 50 m, the combustion in the combustion chamber 14 will be too fast, which may damage the injection port.

The amount of the primary oxidizing gas ejected from the primary oxidizing gas injection port 17 is set so that the oxygen ratio to the fuel injected from the fuel injection port 16 is less than 1.0. The total amount of the gas and the secondary combustion supporting gas from the secondary combustion supporting gas outlet 18, that is, the total combustion supporting gas amount, is such that the oxygen ratio to the fuel is 1.
It is preferable to set it to be 0 or more. In this way, by performing the incomplete combustion of the fuel by reducing the amount of the primary combustion supporting gas, a flame having a high soot amount and a high emissivity is formed, so that the radiation heat transfer capability is improved. Further, the amount of generated NOx in such a flame is small.

Further, fuel, primary flammable gas and secondary flammable gas are ejected from the inner wall 15 of the combustion chamber 14 which is a limited space, and the secondary flammable gas is separated to some extent. Since the fuel is ejected at a high speed from a distance, the flame generated at the center of the combustion chamber is drawn into the secondary combustion supporting gas ejected from the secondary combustion supporting gas outlets 18 on both sides, forming a wide flame in the horizontal direction. Is done. Thereby, the surface of the object 19 to be heated can be heated widely, and the amount of radiation heat transfer can be increased.

At this time, the supply ratio (volume ratio) between the primary combustion supporting gas and the secondary combustion supporting gas means that if the ratio of the primary combustion supporting gas is too large, the secondary combustion supporting gas is ejected. It is not preferable because it is lowered. Conversely, when the proportion of the primary supporting gas is small, it is sufficient that the fuel ejected from the fuel injection port 16 is ignited and a flame is formed. Can be expected.

Further, the shape of the combustion chamber 14 and the dimensions of each part can be defined to some extent optimal by the amount of combustion in the combustion apparatus. For example, the combustion chamber 14
The depth dimension of the combustion chamber 14 is 700 kW.
If less than 100-300 mm, combustion amount is 700-1
When the power is 500 kW, 200 to 350 mm, the combustion amount is 15
When it is 00 to 2500 kW, 250 to 400 mm is appropriate. If the depth dimension is too small with respect to the amount of combustion, the flame will not be wide, and if the depth dimension is too large, the amount of surrounding combustion gas entrained by the secondary combustion supporting gas will decrease, and the effect of reducing NOx will be sufficient. Can not be obtained.

The distance between the secondary combustion supporting gas outlets 18 with respect to the amount of combustion in the combustion chamber 14 is 100 to 300 mm when the amount of combustion is less than 700 kW, and 200 to 300 mm when the amount of combustion is 700 to 1500 kW. 400 mm, 200 to 500 when the combustion amount is 1500 to 2500 kw
mm is appropriate. Generally, the secondary combustible gas jet 18
The farther the distance between them, the lower the NOx emissions,
If it is too far, combustion becomes unstable.

The cross-sectional dimension of the combustion chamber 14 may be set according to the state of generation of the flame or the amount of combustion.
It is preferable not to hit. Conversely, if the cross-sectional dimension of the combustion chamber 14 is too large, the effect of providing the combustion chamber 14 will not be sufficiently obtained, and the amount of radiant heat from the furnace will increase, so that the injection port may be damaged. There is.

FIG. 4 is a sectional plan view showing a second embodiment of the combustion apparatus of the present invention. In this combustion apparatus, the ejection direction of the secondary combustion supporting gas ejection port 18 is directed away from the axis of the combustion chamber 14, that is, outward. In this way, by directing the ejection direction of the secondary combustion supporting gas ejected from the secondary combustion supporting gas ejection port 18 outward, it is possible to expand the horizontal spread of the flame ejected from the combustion chamber 14. . However, if the ejection direction is directed outward too much, combustion may become unstable. Therefore, the angle between the axis of the combustion chamber 14 and the ejection direction of the secondary combustion supporting gas ejection port 18 is usually 3 to 3. 20
A range of degrees is appropriate.

FIG. 5 is a sectional plan view showing a third embodiment of the combustion apparatus of the present invention. In this combustion device, a fuel injection port 16 having a double pipe structure and two primary combustion supporting gas injection ports 17 are provided in a combustion chamber 14, and secondary combustion supporting gas injection ports 18 are provided at intermediate and both sides thereof, respectively. This is an example of the provision. By forming in this manner, one combustion chamber 1
4 can increase the amount of combustion.

FIGS. 6 and 7 show a fourth embodiment of the combustion apparatus according to the present invention.
6 shows a sectional plan view, and FIG. 7 is a sectional front view. The combustion apparatus shown in the present embodiment has a fuel injection port 16, a primary combustion-supporting gas injection port 17, and a secondary combustion-supporting gas, which are independently provided on a rear wall surface 15 of a combustion chamber 14 formed in the same manner as described above. An ejection port 18 is provided.

The installation position of the primary combustible gas outlet 17 is as follows:
It suffices if the fuel ejected from the fuel ejection port 16 can be burned under predetermined conditions, and the installation position of the secondary combustible gas ejection port 18 is set such that low NOx and flame spread can be obtained as described above. Should be set to.

In the combustion device thus formed, the mixing of the fuel and the primary supporting gas is suppressed as compared with the above embodiments, so that the amount of soot increases and a flame having a higher emissivity can be obtained. . Since NOx is considered to be generated at the interface between the fuel jet having the highest flame temperature and the primary combustion supporting gas jet, the interface is reduced as compared with the case where the primary combustion supporting gas is ejected from around the fuel. Therefore, generation of NOx is also reduced.

On the other hand, since the mixing property between the fuel and the primary combustion supporting gas is lower than that of the above embodiment, the stability of the flame tends to be inferior, and a large amount of carbon monoxide and unburned hydrocarbons may be generated. However, by appropriately setting the shape of the combustion chamber 14, the position of each injection port, and the ejection amount and flow velocity of the fuel and the supporting gas, a flame having a high emissivity and a small NOx generation amount can be obtained as described above. Can be obtained.

[0027]

EXAMPLE 1 A combustion test was performed using a combustion apparatus having the structure shown in the first embodiment. Kerosene was used as the fuel, pure oxygen having an oxygen concentration of 99.99% by volume or more was used as the combustion supporting gas, and the combustion amount was 243 kW. The combustion chamber is 70 mm high and 220 mm wide.
mm, the depth was 200 mm, and the interval between the secondary combustible gas jets was 150 mm. In addition, a comparative example was prepared by using a normal double-tube burner.

The volume ratio of the primary supporting gas to the secondary supporting gas is 7: 3, and the flow rate of the primary supporting gas is 10 m / sec.
(10 m / s), the flow rate of the secondary combustion supporting gas was set to 10 m / s, 20 m / s, 50 m / s and 100 m / s.
The radiant heat flux was measured at a position at a predetermined distance from the front end of the combustion chamber at each flow rate. FIG. 8 shows the results.

Example 2 The nitrogen concentration in the combustion-supporting gas was changed, and the emission of NOx with respect to the nitrogen concentration was measured. The conditions were the same as in Example 1 except that the supporting gas was different. FIG. 9 shows the results.

Example 3 The flow rate of the secondary combustion supporting gas was fixed at 50 m / s, the volume ratio between the primary combustion supporting gas and the secondary combustion supporting gas was changed, and the radiant heat flux with respect to the volume ratio was measured. did. Other conditions were the same as in Example 1. The results are shown in FIG.

Example 4 The nitrogen concentration in the combustion supporting gas was changed, and the emission of NOx with respect to the nitrogen concentration was measured. The conditions were the same as in Example 3 except that the supporting gas was different. The results are shown in FIG.

Example 5 The intervals between the sub-jet ports were 100 mm, 150 mm, and 200 mm.
And the width of the combustion chamber is 170 mm, 220 mm, 250 m
m, and the radiant heat flux with respect to the interval between the sub-jet ports was measured. The flow rate of the secondary combustion supporting gas was fixed at 50 m / s. Other conditions were the same as in Example 1. The result is shown in FIG.

Example 6 The nitrogen concentration in the combustion-supporting gas was changed, and the emission of NOx with respect to the nitrogen concentration was measured. The conditions were the same as in Example 5 except that the supporting gas was different. FIG. 13 shows the results.

Example 7 The height of the combustion chamber was 70 mm, the width was 220 mm, and the depth was 2 mm.
00 mm, the interval between the secondary combustible gas jets is 150 mm,
The volume ratio of the primary supporting gas to the secondary supporting gas is 5: 5,
A burner having a flow rate of the secondary combustion supporting gas of 100 m / s (Example), a burner having no other combustion chamber and other dimensions and the same combustion conditions (a flat type), and the burner of the comparative example. The radiant heat flux was measured using pure oxygen as the supporting gas. The result is shown in FIG. FIG. 15 shows the result of measuring the amount of NOx emission by changing the nitrogen concentration in the combustion supporting gas. From these results, it can be seen that by having a combustion chamber, reduction in NOx and improvement in radiation heat transfer capability are simultaneously achieved.

Example 8 A combustion test was performed using a combustion apparatus having the structure shown in the fourth embodiment. Kerosene was used as the fuel, pure oxygen having an oxygen concentration of 99.99% by volume or more was used as the combustion supporting gas, and the combustion amount was 243 kW. The combustion chamber is 70 mm high and 200 mm wide.
mm, depth 200 mm, the interval between the primary supporting gas outlets is 70 mm, and the interval between the secondary supporting gas outlets is 150.
mm. The volume ratio of the primary combustion supporting gas to the secondary combustion supporting gas is 5: 5, the flow rate of the primary combustion supporting gas is 10 m / s,
The flow rate of the secondary combustion supporting gas was set to 50 m / s. In addition, a comparative example was prepared by using a normal double-tube burner.

FIG. 16 shows the result of measuring the relationship between the distance from the front end of the combustion chamber (burner front end) and the radiant heat flux, and FIG. 16 shows the result of measuring the relationship between the nitrogen concentration in the combustion supporting gas and the NOx emission. 17 is shown.

[0037]

As described above, according to the combustion apparatus of the present invention, the generation of NOx is suppressed and at the same time, the combustion chamber is recessed on the inner wall of the furnace, so that the combustion chamber is parallel to the surface of the object to be heated. A flame spreading in various directions can be formed, and a flame having improved radiation heat transfer characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional plan view showing a first embodiment of a combustion apparatus of the present invention.

FIG. 2 is a sectional front view of the same.

FIG. 3 is a sectional side view of the same.

FIG. 4 is a sectional plan view showing a second embodiment of the combustion device of the present invention.

FIG. 5 is a sectional plan view showing a third embodiment of the combustion apparatus of the present invention.

FIG. 6 is a sectional plan view showing a fourth embodiment of the combustion apparatus of the present invention.

FIG. 7 is a sectional front view of the same.

FIG. 8 is a view showing measurement results of Example 1 and showing a relationship among a flow rate of a secondary combustion supporting gas, a distance from a combustion chamber, and a radiant heat flux.

FIG. 9 is a view showing a measurement result of Example 2 and showing a relationship between a flow rate of a secondary combustion supporting gas, a nitrogen concentration in the combustion supporting gas, and a NOx emission amount.

FIG. 10 shows the measurement results of Example 3;
It is a figure which shows the relationship between the volume ratio of a secondary combustion supporting gas, the distance from a combustion chamber, and radiant heat flux.

FIG. 11 shows the measurement results of Example 4;
Volume ratio of secondary combustible gas, nitrogen concentration in combustible gas and N
It is a figure showing relation with Ox discharge.

FIG. 12 shows the measurement results of Example 5, and shows the relationship between the distance between the sub-injection ports, the distance from the combustion chamber, and the radiant heat flux.

FIG. 13 shows the measurement results of Example 6 and shows the relationship between the interval between the sub-injection ports, the nitrogen concentration in the combustion supporting gas, and the NOx emission amount.

FIG. 14 shows the measurement results of Example 7, and shows the relationship between the presence or absence of a combustion chamber, the distance from the combustion chamber, and the radiant heat flux.

FIG. 15 shows the measurement results of Example 7, and shows the relationship between the presence or absence of a combustion chamber, the nitrogen concentration in the supporting gas, and the NOx emission.

FIG. 16 is a diagram illustrating a relationship between a distance from a combustion chamber and a radiant heat flux according to the eighth embodiment.

FIG. 17 shows the measurement result of Example 8, and is a diagram showing the relationship between the nitrogen concentration in the combustion supporting gas and the NOx emission amount.

[Explanation of symbols]

Reference numeral 11: furnace wall, 12: opening, 13: tile, 14: combustion chamber, 15: inner wall surface, 16: fuel jet port, 17: primary flammable gas jet, 18: secondary flammable gas jet Exit 19: Heated object

Claims (7)

[Claims] 1. A fuel ejection port for ejecting fuel on a back wall surface of a combustion chamber recessed in a furnace wall, and a primary combustion supporting gas jet for ejecting primary combustion supporting gas near the fuel ejection port. Exit and
A combustion device comprising: a secondary combustion supporting gas ejection port for ejecting a secondary combustion supporting gas on both sides of a fuel ejection port in a direction parallel to a surface of an object to be heated. 2. The combustion apparatus according to claim 1, wherein the primary combustible gas ejection port is provided on an outer periphery of the fuel ejection port. 3. The combustion device according to claim 1, wherein an ejection speed of the primary combustion supporting gas is 30 m or less per second. 4. The combustion apparatus according to claim 1, wherein the ejection speed of the secondary combustion supporting gas is equal to or higher than the ejection speed of the primary combustion supporting gas and is equal to or lower than 150 m / sec. 5. A flow rate of the primary combustion supporting gas is set so that an oxygen ratio to fuel is less than 1.0, and a total flow rate of the primary combustion supporting gas and the secondary combustion supporting gas is a fuel flow rate. 3. The combustion apparatus according to claim 1, wherein an oxygen ratio with respect to is set to be 1.0 or more. 6. The combustion apparatus according to claim 1, wherein the oxygen concentration of the primary combustion supporting gas and the secondary combustion supporting gas is 90% by volume or more. 7. The distance between the secondary combustion supporting gas jets and the depth dimension of the combustion chamber is such that when the combustion amount is less than 700 kW, the distance between the secondary combustion supporting gas jets is 100 to 100.
300 mm, the depth dimension is 100 to 300 mm, and when the combustion amount is 700 to 1500 kW, the distance between the secondary combustion supporting gas ejection ports is 200 to 400 mm, and the depth dimension is 20.
0-350mm, combustion amount is 1500-2500k
When w, the distance between the secondary combustible gas jets is 200 to
3. The combustion device according to claim 1, wherein the combustion device has a depth of 500 to 500 mm.