JP2011080698A - Burner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a burner which suppresses oscillating combustion during low combustion and reduces NOx without providing structures such as a projection and a flange or the like within a cone guide. <P>SOLUTION: The burner 1 includes: an oil nozzle 11A spraying fuel from the tip side; an inner cylindrical member 12 having an opening on the fuel supply downstream side and storing the tip side of the oil nozzle 11A; and an outer cylindrical member 13 arranged on the outer peripheral side of the inner cylindrical member 12. On the downstream side end face 13A of the outer cylindrical member 13, a plurality of air nozzles 14 extended to the further downstream side are provided leaving intervals in the circumferential direction of the end face 13A, and main air jet holes 15 are formed on the downstream end sides of the air nozzles 14. Part of combustion air can be made to flow inside the inner cylindrical member 12 via small holes, and the cylindrical cone guide 20 covering the air nozzles 14 along the circumferential direction of the outer cylindrical member 13 is provided on the outer peripheral side of the air nozzles 14. The cone guide 20 includes a diameter expansion part 25 expanded toward the downstream side. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a burner, and more particularly to an oil-fired burner mainly used for a small boiler or the like.

Emission regulations for NOx caused by combustion are becoming stricter year by year, and technological development for NOx reduction is active. NOx generated during combustion includes fuel NOx, prompt NOx, and thermal NOx. Among these, thermal NOx is generated by oxidizing the N2 component in the combustion air in a high temperature atmosphere, and is highly temperature dependent. The higher the combustion temperature, the more rapidly the generation amount increases.
Therefore, thermal NOx is always generated as long as air is used for combustion. When the fuel is kerosene or A heavy oil with a low nitrogen content, most of the NOx discharged is said to be thermal NOx, and many reduction methods are available. Has been proposed.
Among these many reduction methods, the main NOx suppression combustion technologies include (A) split flame combustion method, (B) exhaust gas recirculation combustion method, (C) multistage combustion method, and (D) water-mixed combustion method. Etc. are known.

However, with the (A) split flame combustion type burner, flame splitting tends to be insufficient, and there is a limit to the reduction of NOx, and further technological development is required to meet the recent strict NOx regulations. Yes.
In addition, there are two types of split flame combustion systems, one with multiple main air jets and the other with multiple oil nozzles. The latter type of burner is relatively easy for large oil and gas burners. However, in the case of a burner having a small burner flame opening (diameter size of the outer cylinder member), there are difficulties in forming a divided flame, and a plurality of oil nozzles are required, resulting in an increase in cost.

(B) The exhaust gas recirculation combustion type burner is designed to reduce NOx by recirculating part of exhaust gas (combustion gas) to combustion air and lowering the oxygen partial pressure. It is roughly divided into the self-exhaust exhaust gas recirculation method.
However, the forced exhaust gas recirculation method requires a recirculation duct and a blower to recirculate a part of the exhaust gas, and its application to a small boiler is problematic in terms of cost.
The self-exhaust exhaust gas recirculation method, on the other hand, uses a phenomenon in which surrounding gas is sucked into the jet of combustion air by adding a device to the structure of the burner, etc. It is characterized by having a recirculation effect, and there is a merit in terms of cost because exhaust gas is not forced to recirculate, but the amount of exhaust gas recirculation is not sufficient and NOx reduction is still necessary There is a limit.

(C) The burner of the multi-stage combustion system is characterized in that fuel or combustion air is divided into two or more stages having different air ratios and burnt in a light and dark manner, and is caused by a decrease in flame temperature or a decrease in oxygen concentration. This is intended to reduce NOx.
However, even in this combustion system, there is a problem that the structure of the burner becomes complicated because of burning in multiple stages.

(D) The water-mixed combustion method is intended to reduce NOx by mixing water in the fuel in advance or by blowing water into the combustion chamber to lower the flame temperature.
However, in this system, corrosion may occur in the cylindrical member or the like constituting the burner by blowing water, and the boiler efficiency also decreases. Furthermore, a water supply device such as a pump is required separately, leading to an increase in cost.

As described above, each system has advantages and disadvantages, and it has been difficult to inexpensively manufacture a burner that reliably reduces NOx. On the other hand, according to the burner previously developed by the present applicant (see Patent Document 1), a low NOx burner having an inexpensive structure and capable of reliably reducing NOx is realized.
The burner described in Patent Document 1 includes an oil nozzle and a plurality of air nozzles provided along a circumferential direction centering on the oil nozzle. In the burner described in Patent Document 1, fuel is sprayed from an oil nozzle, and combustion air is jetted from an air nozzle disposed around the oil nozzle to form a flame. At this time, the ignition point (flame surface) of the flame is formed at a position where the combustion speed of the flame and the flow velocity of the combustion air jetted from the air nozzle are balanced.

  By the way, in the burner described in Patent Document 1, when the low air ratio operation is performed during the low combustion operation, the position of this ignition point is stabilized by the structure of the combustion chamber, the flow velocity of the combustion air jetted from the air nozzle, and the like. In some cases, so-called oscillating combustion that occurs without vibration occurs. When vibration combustion occurs, the pressure in the combustion chamber fluctuates, which may cause vibration of the burner and noise. Therefore, conventionally, during low combustion operation, in order to suppress the occurrence of vibration combustion, the air ratio is set to be high, and there has been a problem that the amount of exhaust gas increases and thermal efficiency decreases.

  Therefore, the present applicant has proposed the techniques described in Patent Documents 2 and 3 as techniques for suppressing vibration combustion. That is, in Patent Document 2, a combustion cone guide is attached to a burner, and a projection that is heated by a flame in a combustion air jet is provided in the cone guide, and this projection is used as a re-ignition means. The flame is stabilized. Moreover, in patent document 3, the stable recirculation area | region is formed behind the bowl-shaped part by providing the bowl-shaped throttle structure in a cone guide, and the stable ignition area is ensured by this.

Japanese Patent No. 3527456 JP 2008-133982 A JP 2008-122048 A

However, in the techniques proposed in Patent Documents 2 and 3, when the composition of the fuel oil is changed, particularly when a cracked light oil containing a large amount of aromatics is used as the fuel oil, the vibration suppressing effect cannot be sufficiently exhibited. I understood it.
Furthermore, when the cone guide proposed in Patent Documents 2 and 3 is used, there is a risk that a carbonaceous component may be deposited on the protrusions and hook-shaped portions in the cone guide, and regular maintenance is required for long-term use. There is a problem that it is necessary and troublesome.

  The objective of this invention is providing the burner which can implement | achieve the vibration combustion suppression and low NOx in low combustion, without providing structures, such as a projection part and a bowl-shaped part, in a cone guide.

  The burner according to the present invention includes an oil nozzle that sprays fuel from the front end side, an inner cylinder member that has an opening on the fuel supply downstream side and that houses the front end side of the oil nozzle, and an outer peripheral side of the inner cylinder member. A plurality of air nozzles extending further on the downstream end surface of the outer cylinder member at intervals in the circumferential direction of the end surface. A main air jet port is formed on the downstream end side, and the inside of the inner cylindrical member is cut off from the supplied combustion air, or a part of the combustion air can be introduced through a small hole. A cylindrical cone guide that covers these air nozzles along the circumferential direction of the outer cylinder member is provided on the outer peripheral side of the air nozzle, and the cone guide is directed toward the downstream side. And having an enlarged diameter portion.

  According to the present invention, by providing a plurality of main air jets, a flame division effect is obtained and the generation of NOx is suppressed. Moreover, since the main air jet port is provided in the outer cylinder member, the air ratio on the center side of the outer cylinder member becomes smaller than the air ratio on the outer side, and a two-stage combustion (light / dark combustion) effect is obtained. For this reason, ignition is suppressed in the vicinity of the opening of the inner cylinder member, which is the outlet of the primary combustion air, and the flame is held at a position further away from the opening, and the generation of NOx is suppressed. Moreover, when the exhaust gas from the main air jet port flows into the center side of the outer cylinder member, the exhaust gas is recirculated, and an exhaust gas recirculation combustion effect that reduces the combustion temperature is obtained. This also reduces the generation of NOx.

Furthermore, since the cone guide has an enlarged diameter portion, the flame formed in the cone guide is less likely to interfere with the inner surface of the cone guide, so that the flame can be made more stable and vibration combustion can be reduced. Can be suppressed. By maintaining a more stable state of the flame, vibration combustion can be reliably reduced even in fuel oil that contains a large amount of aromatics.
Moreover, since there is no need to provide a conventional protrusion or hook-shaped portion in the cone guide, no carbonaceous component is produced in such a portion, and the labor required for maintenance can be greatly reduced. .

In the burner of the present invention, the cone guide includes the enlarged diameter portion, and an upstream straight body portion that is integrally provided on the upstream side of the enlarged diameter portion and has a constant inner diameter dimension in the length direction, It is preferable to have a downstream straight body portion that is integrally provided on the downstream side of the enlarged diameter portion and has a constant inner diameter dimension in the length direction.
According to the present invention, since the cone guide has the upstream straight body portion, the gap between the upstream straight body portion and the air nozzle can be kept small, and the ejector effect is exerted on the exhaust gas that is recirculated. It can work well and exhaust gas recirculation can be performed more efficiently. Also, by providing a downstream straight body, it is possible to prevent the combustion air and fuel oil from diffusing more than necessary on the downstream side of the cone guide, so that the flame contacts the water pipe that forms the inner wall of the combustion chamber of the boiler. Can be prevented.

In the burner according to the present invention, when the overall length of the cone guide is L, the length of the upstream straight body is L1, and the length of the downstream straight body is L2, L1 and L2 Is preferably 0.1 L or more and 0.3 L or less.
According to the present invention, since the length of each straight body portion is set appropriately, for example, on the upstream side, exhaust gas recirculation can be reliably performed by the ejector effect, and on the downstream side, the boiler inner wall part due to the spread of the flame Can be surely prevented, and the flame can be reliably stabilized. If L1 and L2 are smaller than 0.1L, the ejector effect on the upstream side is not optimal, exhaust gas recirculation combustion cannot be performed efficiently, and the flame may spread too much on the downstream side. In some cases, such as when the present invention is applied to a small boiler, the flame may come into contact with the inner wall of the combustion chamber and impair the durability of the combustion chamber. On the contrary, if it exceeds 0.3L, the length dimension is too long on the upstream side, and the ejector effect is not optimal, and on the downstream side, the flame in the cone guide may come into contact with the downstream straight body portion. And the flame is not stable.

Sectional drawing which shows the burner which concerns on one Embodiment of this invention. II-II arrow directional view of FIG. The perspective view which shows a flame-holding board. The perspective view which shows the modification of a flame-holding board. The figure for demonstrating the effect regarding the maximum amplitude in the said embodiment. The figure for demonstrating the effect regarding the NOx amount in the said embodiment. The figure which shows the amount of NOx in Example 1. FIG. The figure which shows the amount of CO in Example 1. FIG. FIG. 4 is a diagram illustrating the maximum amplitude in the first embodiment. The figure which shows the amount of NOx in Example 2. FIG. The figure which shows CO amount in Example 2. FIG. FIG. 6 is a diagram showing the maximum amplitude in the second embodiment. The figure which shows the amount of NOx in Example 3. FIG. The figure which shows the amount of CO in Example 3. FIG. FIG. 10 is a diagram illustrating the maximum amplitude in the third embodiment.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2, a burner 1 is attached to a fan (not shown) for supplying combustion air via a wind box A, and includes an oil supply pipe 11 and an oil nozzle 11A on the tip side of the oil supply pipe 11. , An outer cylinder member 13 disposed on the outer peripheral side of the inner cylinder member 12, and a cone guide installed downstream of the end surface 13A of the outer cylinder member 13 (downstream in the fuel supply direction). 20.

  A plurality (eight in this embodiment) of cylindrical air nozzles 14 are arranged at equal intervals along the circumferential direction on the outer peripheral side of the joint portion with the inner cylindrical member 12 on the downstream end surface 13A of the outer cylindrical member 13. Is provided. These air nozzles 14 extend to the downstream side in parallel along the axis C of the burner 1, and the opening at the tip is a main air jet port 15. The main air jet port 15 is located downstream of the end surface 13A of the outer cylinder member 13 and jets secondary combustion air supplied through the inside of the outer cylinder member 13 to the downstream side.

In the burner 1 using such an outer cylinder member 13, the main air jet port 15 is provided at a plurality of locations (eight locations) in the circumferential direction according to the number of the air nozzles 14. Have
Further, although combustion occurs downstream of the main air jet port 15, as indicated by a two-dot chain line in FIGS. 1 and 2, exhaust gas during combustion passes between adjacent air nozzles 14 and is most negatively pressured by combustion. It goes back to the center side to become (exhaust gas recirculation). For this reason, the burner 1 also has a structure of an exhaust gas recirculation combustion system (self exhaust gas recirculation method).

  A plurality of small holes 16 are formed on the end side surface on the upstream side of the inner cylinder member 12, that is, the end side surface on the wind box A side. On the other hand, a flame holding plate 17 is provided in the opening on the downstream side of the inner cylinder member 12. As shown in FIG. 3, the flame-holding plate 17 has a fuel jet port 17A drilled at a position corresponding to the mounting position of the oil nozzle 11A, and the fuel jet port 17A is cut and raised around the fuel jet port 17A at equal intervals. And a plurality (eight) of auxiliary air jets 17B formed. The auxiliary air jet port 17B ejects the primary combustion air that has flowed into the inner cylindrical member 12 through the small hole 16 toward the downstream while swirling, and therefore, the primary combustion air and the fuel sprayed from the oil nozzle 11A. And the primary combustion air and the fuel can be mixed well.

Here, when the total opening area of the small holes 16 is S1, and the total opening area of the main air jet 15 of the air nozzle 14 is S2, S1 / (S1 + S2) is 0.3 or less, preferably 0. It is set to 2 or less, more preferably 0.1 or less.
That is, by setting the ratio of the total opening areas S1 and S2 to 0.3 or less, the amount of primary combustion air jetted from the auxiliary air jet port 17B is suppressed, and in the burner 1, the center of the outer cylinder member 13 is thereby suppressed. The air ratio on the side (in front of the oil nozzle 11A) is made smaller than the air ratio on the outer peripheral side, so that a so-called two-stage combustion effect is obtained. In this case, the flow rate of the secondary combustion air at the main air jet port 15 of the present embodiment is 20 to 70 m / sec, whereas the flow rate of the primary combustion air from the sub air jet port 17B is 10 to 20 m. / Sec or less.
If the ratio of the total opening areas S1 and S2 is set to exceed 0.3, the effect of the two-stage combustion cannot be obtained, and it becomes easy to burn in a state where the flame sticks to the flame holding plate 17, and NOx is generated. The amount increases.

  The cone guide 20 has a cylindrical shape in which the downstream diameter d2 is larger than the upstream diameter d1 and is expanded toward the downstream side. The degree of expansion is defined as an angle formed by the straight line TP with respect to the axis C of the burner 1 as a whole when the straight line passing from the upstream edge 21 to the downstream edge 22 is TP (shown by a one-dot chain line in FIG. 1). The taper angle is set to be about 10 °.

  Specifically, the cone guide 20 is provided between the upstream straight body portion 23 having the upstream end edge 21, the downstream straight body portion 24 having the downstream end edge 22, and the respective straight body portions 23, 24. And is attached to the outer cylinder member 13 via a mounting bracket (not shown) provided on the outer peripheral surface of the upstream straight body portion 23. That is, the upstream diameter d1 and the downstream diameter d2 described above are the inner diameter dimensions of the upstream straight body portion 23 and the downstream straight body portion 24 that are constant over the length direction. If the overall length dimension of the cone guide 20 is L, the length dimension L1 of the upstream straight body part 23 is 0.1L to 0.3L, and the length dimension L2 of the downstream straight body part 24 Also, it is 0.1L-0.3L.

  In such a burner 1, the fuel sprayed from the oil nozzle 11 </ b> A is first supplied with the primary combustion air from each auxiliary air jet port 17 </ b> B of the flame holding plate 17, and then the main air jet of each air nozzle 14. Secondary combustion air is supplied from the mouth 15 to form a flame. At this time, as shown in FIG. 1, the flame is formed so as to spread toward the downstream side, but the enlarged diameter portion 25 of the cone guide 20 is also expanded toward the downstream side in the same manner. There is no fear that the flame interferes with the inner surface of the cone guide 20, the entire flame can be stabilized, and the pressure fluctuation in the combustion chamber can be reduced to suppress the combustion vibration.

  In particular, when a cracked light oil containing a large amount of aromatics is used as a fuel oil, combustibility is not preferable, and the ignition speed is delayed, but the cracked light oil can be formed by being able to form a stable flame as in this embodiment. The ignition speed when using can be improved, and combustion vibration can be reliably suppressed.

  As described above, the amount of secondary combustion air jetted from the main air jet port 15 is larger than the amount of primary combustion air jetted from the sub air jet port 17B, and the center side of the outer cylinder member 13 (oil Since the negative pressure is in front of the nozzle 11A, the exhaust gas after combustion passes between the adjacent air nozzles 14 as shown in FIGS. 1 and 2, and the center side of the outer cylinder member 13 (of the oil nozzle 11A). Recirculate forward). In addition, since a plurality of air nozzles 14 are provided so as to protrude downstream from the end face 13A of the outer cylinder member 13, split flame combustion can be realized. From these facts, the divided flame combustion effect and the exhaust gas recirculation combustion effect can be obtained simultaneously, the combustion temperature can be reduced, and the amount of NOx produced can be reduced.

  FIG. 5 shows the maximum flame amplitude of an experiment in which the angle (taper angle) formed by the straight line TP with respect to the axis C is changed. According to FIG. 5, the maximum amplitude is the smallest when the taper angle is 5 °, and a stable small size can be obtained around 10 °. On the other hand, FIG. 6 shows the amount of NOx generated in the experiment in which the taper angle is changed, and the amount generated is much smaller when set to 10 ° than when the taper angle is 5 °. From the above, it can be said that setting the taper angle to around 10 ° is effective from the viewpoint of suppressing vibration combustion and reducing NOx. Here, the burner used in the experiments in FIGS. 5 and 6 is d1 = 195 mm, L = 120 mm, L1 = 20 mm, L2 = 20 mm, and the length from the end face 13A to the upstream edge 21 of the cone guide 20. L0 is set to 40 mm.

  Further, the exhaust gas is guided into the cone guide 20 through a gap between the base end side portion of the air nozzle 14 and the upstream straight barrel portion 23 constituting the cone guide 20, but in the upstream straight barrel portion 23. Since the upstream side diameter d1 is small, the gap can be made smaller, the secondary combustion air jetted from the main air jet port 15 of the air nozzle 14 can exert a good ejector effect, and the exhaust gas can be returned well. Thus, the exhaust gas recirculation combustion effect can be further improved.

  Since the diameter of the upstream side of the cone guide 20 is reduced, the space between the inner surface of the cone guide 20 and the air nozzle 14 can be narrowed in the cone guide 20, and the recirculated exhaust gas that has entered the space can be reduced. The generation of eddy currents can be suppressed, and the flame can be stabilized in this respect as well.

  In addition, the cone guide 20 in this embodiment is not provided with projections or bowl-shaped portions, so there is no risk of carbonaceous components being deposited on those portions, and maintenance is required for long-term use. It is possible to set a longer period of use until it is performed and greatly reduce the time and effort required for maintenance.

  Furthermore, in this embodiment, the ratio S1 / (S1 + S2) of the total opening area S1 of the small holes 16 to the total opening area S1 + S2 of the main air jets 15 and the small holes 16 is 0.3 or less. The amount of primary combustion air jetted from the auxiliary air jet port 17B can be reliably suppressed with respect to the amount of secondary combustion air jetted from the air jet port 15. As a result, the air ratio on the center side of the outer cylinder member 13 (in front of the oil nozzle 11A) can be made smaller than the outside air ratio, a two-stage combustion effect can be obtained, and the position further away from the flame holding plate 17 With this, the amount of NOx produced can be further reduced.

The best configuration, method, and the like for carrying out the present invention have been disclosed above, but the present invention is not limited to this. That is, the invention has been illustrated and described primarily with respect to particular embodiments, but may be configured for the above-described embodiments without departing from the scope and spirit of the invention. Various modifications can be made by those skilled in the art in terms of quantity, other details, and the like.
Therefore, the description limited to the shape, quantity and the like disclosed above is an example for easy understanding of the present invention, and does not limit the present invention. The description by the name of the member which remove | excluded the limitation of one part or all of such restrictions is included in this invention.

  In the embodiment, the cone guide 20 is configured to include the upstream straight barrel portion 23, the downstream straight barrel portion 24, and the enlarged diameter portion 25. However, as the cone guide used in the present invention, the enlarged diameter portion is used. It is sufficient that the straight body portion on the upstream side and the downstream side can be omitted.

The flame holding plate used in the burner of the present invention is not limited to the flame holding circle 17 having the shape used in the embodiment, and a flame holding plate 171 as shown in FIG. 4 may be used. The auxiliary air jet port 171B of the flame holding plate 171 is a plurality of through holes formed around the central fuel jet port 171A. An axis D indicating the penetrating direction is parallel to the axis C of the entire burner so that a swirling flow is not generated in the jetted primary combustion air.
Even with a burner using such a flame-holding plate 171, the same effects as in the embodiment can be obtained, and the following effects can be obtained.

  That is, the auxiliary air jet port 171B of the flame holding plate 171 does not have a raised portion unlike the flame holding plate 17 of the above embodiment, so that the primary combustion air is not swirled and mixed with the fuel. Can be delayed. Accordingly, the fuel can be burned after sufficiently evaporating, and sticking of flame to the flame holding plate 171 can be suppressed. As a result, it is possible to reliably hold the flame away from the flame holding plate 171 and further reduce the amount of NOx generated.

In the embodiment, the number of the air nozzles 14 is 8. However, the number of the air nozzles 14 can be arbitrarily set within a range where S1 / (S1 + S2) is 0.3 or less. That is, for example, the air nozzle 14 of the first embodiment may be provided on the end surface 13A of the outer cylinder member 13 with 7 or less, or 9 or more.
Further, the cross-sectional shape of the air nozzle 14 is not limited to a circle or rectangle, but may be arbitrarily set in consideration of the jet operation of the combustion air, use conditions of the burner, manufacturability of the air nozzle 14, etc. You can do it.

The arrangement of the air nozzles 14 is not limited to being arranged at regular intervals in the circumferential direction, and may be arranged at irregular intervals. The air nozzle 14 may not be disposed along the circumferential direction of the same radius as long as the air nozzle 14 is disposed on the outer peripheral side of the inner cylinder member 12.
The air nozzle 14 extends parallel to the axis of the inner cylinder member 12, but is inclined toward the axis of the inner cylinder member 12, or is inclined outward with respect to the axis of the inner cylinder member 12. May be.

The number of installed oil nozzles 11A is not limited to one, and may be two or more.
The flame holding plates 17 and 171 are not necessarily provided.
The small hole 16 of the inner cylinder member 12 is formed on the end side surface on the upstream side of the inner cylinder member 12, but is not limited thereto, and is formed, for example, on the side surface near the end portion on the downstream side of the inner cylinder member 12. It may be. Moreover, the small hole 16 of the inner cylinder member 12 does not necessarily need to be provided, for example, the downstream end surface of the inner cylinder member 12 is sealed, and the inside of the inner cylinder member 12 is shielded from the combustion air. May be. In this case, the combustion air is jetted only from the main air jet port 15.
The fuel can be arbitrarily selected according to the use such as kerosene in addition to heavy oil.

  Based on the above embodiment, a burner having d1 = 195 mm, d2 = 238 mm, L = 120 mm, L1 = 20 mm, L2 = 20 mm, L0 = 40 mm was manufactured as Example 1. On the other hand, as Comparative Example 1, a burner provided with a 216 mm diameter cone guide with a protrusion was prepared. The burner of Comparative Example 1 corresponds to the burner described in FIG.

  And each burner of Example 1 and Comparative Example 1 is incorporated in a commercially available small forward flow combustion type once-through boiler, a combustion test is performed by changing the air ratio in several stages between 1.1 and 1.6, and high combustion operation NOx amount (FIG. 7) and CO amount (FIG. 8) in the exhaust gas at the time, and the maximum amplitude (FIG. 9) of the boiler during the low combustion operation were measured. The amplitude of the boiler was measured at the bypass flange portion of the bypass blow line (the place where the vibration value is the largest in the boiler). The amplitude was measured using a commercially available portable vibration measuring instrument. As the fuel oil, the cracked light oil in the fuel oil property table of Table 1 was used. The combustion amount of heavy oil during high combustion operation is 65 L / hr, and the combustion amount of heavy oil during low combustion operation is 32.5 L / hr.

7 to 9 show the results of the combustion test. As shown in FIG. 7, as the NOx amount during the high combustion operation, the NOx amount in Example 1 is clearly smaller than that in Comparative Example 1 when the air ratio is 1.3 or more. This is because the exhaust gas recirculation efficiency is improved by the ejector effect and the exhaust gas recirculation combustion is favorably performed by using the cone guide of the first embodiment that is reduced in diameter on the upstream side. About the amount of CO, as shown in FIG. 8, in Example 1 and the comparative example 1, the substantially equivalent value was obtained. About the amplitude of a boiler, as shown in FIG. 9, it turns out that the amplitude is improved significantly in the air ratio 1.5 or less. This is because the shape of the cone guide increases toward the downstream side, so that the formed flame does not interfere with the inner surface of the cone guide and the flame can be formed in a stable state. From this, it was confirmed that vibration combustion can be suppressed even when a cracked light oil with a large aromatic content whose combustion is not stable is used as a fuel oil.

  In the burner having the structure of Example 1, the one using the high calorie A heavy oil in the fuel oil property table as the fuel oil is used as the burner of Example 2, and in the burner having the structure of Comparative Example 1, the high calorie A heavy oil is used. The fuel oil used was Comparative Example 2.

  10 to 12 show the combustion results. The tendency of the NOx amount is the same as in Example 1 and Comparative Example 1, but the absolute value of Example 2 and Comparative Example 2 is lower. That is, even when high-calorie A heavy oil was used, it was confirmed that the burner of the present invention can reduce the amount of NOx compared to the conventional burner. About CO amount, the substantially same result as the said Example 1 and the comparative example 1 is obtained, and it is a sufficiently low value. As for the maximum amplitude, the magnitude of the amplitude is reduced as compared with the case where the cracked light oil is used. Further, even when the high calorie A heavy oil is used, when the air ratio is 1.3 or less, Example 2 It was recognized that the amplitude was smaller than that of Comparative Example 2 and vibration combustion could be suppressed.

  In the burner having the structure of Example 1, the one using the low sulfur A heavy oil in the fuel oil property table as the fuel oil is used as the burner of Example 3, and in the burner having the structure of Comparative Example 1, the low sulfur A heavy oil is used. The fuel oil used was Comparative Example 2.

  The combustion results are shown in FIGS. The tendency of the NOx amount is the same as in Examples 1 and 2 and Comparative Examples 1 and 2, but Example 3 and Comparative Example 3 have lower absolute values. From this, it was confirmed that the burner of the present invention can reduce the amount of NOx as compared with the conventional burner even when the low sulfur A heavy oil is used. As for the amount of CO, almost the same results as in Examples 1 and 2 and Comparative Examples 1 and 2 were obtained. About the maximum amplitude, compared with the case where cracked light oil or high calorie A heavy oil is used, the magnitude of the amplitude is further reduced, and the amplitude of Example 3 is smaller than that of Comparative Example 3, but slightly. Is recognized. That is, the burner of the present invention can be said to have a more remarkable effect from the viewpoint of suppressing vibration combustion when a fuel with a large aromatic content such as cracked light oil is used.

  The burner of the present invention can be used for boilers such as a forward combustion system, a ω flow system, and a reverse combustion system, and is particularly preferably used in a small boiler.

  DESCRIPTION OF SYMBOLS 1 ... Burner, 11 ... Oil supply pipe, 11A ... Oil nozzle, 12 ... Inner cylinder member, 13 ... Outer cylinder member, 13A ... Downstream end face, 14 ... Air nozzle, 15 ... Main air jet port, 16 ... Small hole, 20 ... Cone guide, 23 ... Upstream straight body part, 24 ... Downstream straight body part, 25 ... Expanded diameter part, L, L1, L2 ... Length dimension.

Claims (3)

An oil nozzle that sprays fuel from the front end side, an inner cylinder member that has an opening on the fuel supply downstream side and that houses the front end side of the oil nozzle, and an outer cylinder member that is disposed on the outer peripheral side of the inner cylinder member And
A plurality of air nozzles extending further downstream are provided on the downstream end face of the outer cylinder member at intervals in the circumferential direction of the end face,
A main air jet is formed on the downstream end side of these air nozzles,
The inside of the inner cylinder member is a burner that is cut off from the supplied combustion air, or provided so that a part of the combustion air can flow in through a small hole,
On the outer peripheral side of the air nozzle, a cylindrical cone guide that covers these air nozzles along the circumferential direction of the outer cylinder member is provided,
The cone guide has a diameter-expanded portion that expands toward the downstream side. The burner according to claim 1, wherein
The cone guide includes the enlarged diameter portion, an upstream straight body portion that is integrally provided on the upstream side of the enlarged diameter portion and has a constant inner diameter dimension in the length direction, and a downstream side of the enlarged diameter portion. And a downstream straight body portion which is integrally provided on the side and has a constant inner diameter in the length direction. The burner according to claim 2,
When the overall length of the cone guide is L, the length of the upstream straight body is L1, and the length of the downstream straight body is L2, L1 and L2 are 0.1L or more. , 0.3 L or less.

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