JP2001116214A - Three-positional control burner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-positional control burner which can effectively suppress the production of NOx at high load combustion. SOLUTION: Fuel oil of the quantity geared to high load combustion or low load combustion is sprayed into a combustion chamber 2 from a fuel oil spray nozzle 13 which constituted one piece of constant supply oil pressure return type spray valve structure arranged in a burner throat 11. Primary air 16a less than the theoretical combustion air quantity is supplied in whirling flow into the combustion chamber 2 from the burner throat 11, and also secondary air 16b of the quantity equivalent to or less than the primary air 16a is supplied into the combustion chamber 2 from plural air jet nozzles 18 provided at the side of the burner throat 11. The air jet nozzle 18 is, in the peripheral circular region of the burner throat 11, arranged in condition that it is inclined to the axis of the combustion chamber 2, so that it may jet the secondary air 16b toward the center on downstream side of the primary combustion part 46 by the primary air 16a and that the jetted air current 56 from the air jet nozzle 18 may not interfere with it upstream of it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a three-position control burner using fuel oil such as heavy fuel oil A, and more particularly, to a boiler having a relatively small capacity (oil amount of 30 to 150 kg / h) and high load combustion.
The present invention relates to a nitrogen oxide reducing burner suitably used in a heater or the like.

[0002]

2. Description of the Related Art In a conventional three-position control burner, two fuel oil spray nozzles are arranged in a burner throat, and fuel oil is sprayed from the two fuel oil spray nozzles during high combustion (during rated operation). The fuel oil is sprayed from only one fuel oil spray nozzle at the time of low combustion. However, in such a burner, nitrogen oxide (N
As measures for reducing Ox), systems such as exhaust gas circulation combustion, hydrogenation combustion, and steam injection combustion are employed. In other words, the exhaust gas recirculation combustion system aims to reduce NOx by recirculating a part of the exhaust gas to the burner section to lower the oxygen partial pressure. It is intended to reduce NOx by blowing water and steam to lower the flame temperature.

[0003]

However, in the exhaust gas recirculation combustion system, when the exhaust gas is forcibly circulated by a combustion blower, the exhaust gas recirculation amount is reduced in order to avoid instability of the flame and contamination of the combustion air system. It cannot be increased to a certain degree or more, and it is not possible to achieve a sufficient reduction in NOx. When the exhaust gas is circulated by itself, the recirculation rate of the exhaust gas is reduced under a low load condition, so that it is not possible to effectively reduce NOx. Further, in any case, it is necessary to increase the blowing function power more than necessary, and there is a problem in cost.

In addition, in the hydrogenated combustion and steam injection combustion systems, there is a risk that the corrosion of the can body may occur due to the blowing of water, and the boiler efficiency also decreases. Further, a water blowing device such as a pump is required separately, which causes a problem in cost. On the other hand, in the steam injection combustion system, if the steam generated by the boiler is used, the boiler efficiency will be reduced. If the steam generated by the boiler is not used or cannot be used, a steam generator or the like will be required separately, resulting in a significant cost increase. Becomes

Further, during high combustion, the oil droplets sprayed from the two nozzles interfere with each other, so that the distribution of the oil droplets in the spray region becomes dark and large and the oil droplets become large. Is sufficient NOx
The reduction effect cannot be exhibited. Such a problem becomes remarkable particularly when heavy fuel oil A containing a nitrogen component is used.

According to the present invention, the generation of NOx can be significantly reduced without causing such problems in boiler function and cost, and the generation of dust and CO can be effectively suppressed. It is an object to provide a three-position control burner.

[0007]

According to the present invention, there is provided a burner throat opening to a combustion chamber, an annular flame holding plate arranged at an opening of the burner throat, and One fuel oil spray nozzle arranged in the burner throat with the spray port close to the flame holding plate, and a fuel oil spray control mechanism that controls the fuel oil spray amount from the fuel oil spray nozzle to the combustion chamber in three positions A primary combustion air supply mechanism for supplying primary air smaller than the theoretical combustion air amount from the burner throat into the combustion chamber in a swirling flow having a swirl number of 0.3 to 0.6, and provided on the outside of the burner throat. And a secondary combustion air supply mechanism for supplying secondary air in an amount equal to or less than the primary air from the plurality of air ejection nozzles into the combustion chamber. The swirl number refers to a degree of turning defined as described later. Thus, the fuel oil spray nozzle has a constant supply oil pressure return type injection valve structure having an injection valve portion having an opening for spraying and an oil supply portion and an oil return portion communicating therewith. In addition, the fuel oil spray control mechanism
An oil supply passage connected to an oil supply unit of the fuel oil spray nozzle,
A fuel pump interposed in the oil supply passage for supplying a fixed amount of fuel oil to the oil supply unit; a first on-off valve interposed downstream of the fuel pump in the oil supply passage; An oil return path connected to the oil return section of the spray nozzle and having the other end connected upstream of the fuel pump in the oil supply path, a second on-off valve interposed in the oil return path, and an oil return path And a flow control valve for adjusting the amount of oil returned from the oil return section. The first open / close valve is opened and the second open / close valve is closed at the time of high combustion, and at the time of low combustion, By opening the first and second on-off valves and closing the first and second on-off valves when the combustion is stopped, the fuel oil spray nozzle is controlled in three positions. In addition, the plurality of air ejection nozzles are arranged in a peripheral annular area of the burner throat so that the ejection air flow from the air ejection nozzle does not diffuse on the upstream side and does not interfere with each other. In order to blow out secondary air toward the center on the downstream side,
It is arranged at a predetermined interval in a state inclined with respect to the axis of the combustion chamber, and the oxidizing flame due to the airflow from each air injection nozzle is clearly distinguished around the reducing flame in the primary combustion section. It is configured so that a flame form that partially digs in occurs.

In a preferred embodiment of such a three-position control burner, the area of the center hole of the flame holding plate through which the spray oil droplets from the fuel oil spray nozzle pass is equal to the total opening of the burner throat by the flame holding plate. It is set to be 35 to 40% of the area. Further, the primary combustion air supply mechanism is configured such that the primary air passes through the center hole of the flame holding plate at a flow velocity of 15 m / s or more. The supply amount of the primary air is generally set to 0.6 to 0.9 with respect to the theoretical combustion air amount, and the total air supply amount including the secondary air is set to 1. 1 to 1.4 (more preferably 1.2
To 1.3). Also, in the fuel oil spray control mechanism, in order to completely avoid the possibility that the fuel oil leaks from the fuel oil spray nozzle into the combustion chamber at the inlet pressure of the fuel pump via the flow control valve when the combustion is stopped. Preferably, a fuel oil backflow preventer (such as a check valve) is provided downstream or on both sides of the flow control valve in the oil return path. Further, when dust or the like is attached or deposited on the oil return path from the injection valve portion of the fuel oil spray nozzle to the oil return path via the oil return section, the fuel oil (return oil) in the oil return path smoothly flows. The flow is hindered, and the fuel injection pressure (spray pressure) from the fuel oil spray nozzle fluctuates, and there is a possibility that the combustion performance may be reduced. It is preferable that a filter for preventing dust and the like from entering the oil return path is provided downstream of the pump.

According to the three-position control burner having such a configuration,
The two-stage combustion is performed by the supply of the primary air and the secondary air, and NOx, C
The generation of O and dust is effectively suppressed. Such a suppression effect is particularly achieved by arranging the air ejection nozzles in parallel with each other in the inclined state on the annular region. That is, in the region where the jet airflow of the secondary air is not diffused and interferes with the arrangement as shown in FIG. 7, the jet airflow from each air jet nozzle around the reducing flame in the primary combustion section is shown in FIG. By providing a flame form in which the oxidizing flame due to is partially eroded in a clearly distinguished state and the boundary area between the two flames is increased, effective suppression of NOx and the like is achieved.

Furthermore, since fuel oil is sprayed from one fuel oil spray nozzle even during high combustion, the oil droplet distribution in the spray region is more uniform than when two fuel oil spray nozzles are used. As a result, shading does not occur and the oil droplet diameter does not increase. Further, since the fuel oil spray nozzle has a constant supply hydraulic pressure return type injection valve structure, the fuel oil spray pressure is constant, and the oil droplets are further miniaturized. Further, since one fuel oil spray nozzle can be arranged at the center of the burner throat or flame holding plate, the two fuel oil spray nozzles are respectively deviated from the center of the burner throat or flame holding plate. The flow of the primary air from the burner throat through the flame holding plate is smoother than in the case where it is unavoidable. From these, NOx reduction can be more effectively achieved. In addition, since one fuel oil spray nozzle is used, the center hole of the flame holding plate can be made as small as possible. Therefore, by reducing the center hole of the flame holding plate, it is possible to prevent the generation of dust as much as possible even during low combustion where there is a possibility that the amount of dust generated may be greater than during high combustion. .

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.
Description will be made based on 0.

FIG. 1 shows a comparatively small capacity (oil amount 30 to 150 kg / h) including a main body case 1, a combustion chamber 2, a heat exchanger 3, a three-position control burner 4, and an igniter 6.
Shows a hot water heater of high load combustion (output 500000 kcal / h). In the following description, front and rear mean left and right in FIG.

The main body case 1 has a rectangular box-shaped metal plate wall structure, and stores a predetermined amount of heat transfer water 5.
The combustion chamber 2 has a furnace tube structure (inner diameter: 590 mm, axial length: 950 mm) having a combustion gas outlet 6 at the rear end, and is formed by being surrounded by a cylindrical metal wall 7, and its axis is Are immersed and arranged in the heat medium water 5 in a horizontal state. The heat exchanger 3 is located behind the combustion chamber 2 and immersed in the heat medium water 5, and has a combustion gas outlet 6 of the combustion chamber 3.
And a plurality of heat transfer water pipes (not shown) penetratingly supported at upper and lower ends thereof. Each heat transfer water pipe extends in the vertical direction, and the upper and lower ends are opened in the heat transfer water 5. A flue 9 composed of a metal tube is connected to the rear end of the heat exchanger 3. The combustion gas generated in the combustion chamber 2 passes between the heat transfer water pipes from the combustion gas outlet 6 and is discharged to the flue 9, and the heat transfer water 5 in each heat transfer water pipe is heated by heat exchange with the combustion gas. , Natural circulation.

As shown in FIGS. 1 to 6, the three-position control burner 4 is mounted on a furnace wall 10 constituting the front end of the combustion chamber 1 and has a circular cross section provided at the center of the furnace wall 10. A throat 11, an annular flame stabilizing plate 12 disposed at an opening (front end opening) of the burner throat 11, and one fuel oil disposed behind the flame stabilizing plate 12 and disposed at the burner throat 11. A spray nozzle 13, a fuel oil spray control mechanism 15 for controlling the fuel oil spray amount from the fuel oil spray nozzle 13 to the combustion chamber 3 at three positions, and a primary combustion for supplying primary air 16a into the combustion chamber 2 from the burner throat 11. Air supply mechanism 17,
A secondary combustion air supply mechanism 19 for supplying secondary air 16b into the combustion chamber 2 from a plurality of air ejection nozzles 18 provided on the outer side of the burner throat 11 is provided.

As shown in FIGS. 1 to 5, the burner throat 11 is constituted by a cylindrical burner throat ring (inner diameter: 116 mm) concentric with the combustion chamber 2 and has a front end opening formed therein. A frusto-conical burner cone 21 extending toward the end is continuously provided.

As shown in FIGS. 1 to 5, the flame holding plate 12 is an annular plate (inner diameter) concentrically arranged at the front end opening of the burner throat 11 (joint portion between the burner throat ring and the burner cone 21). : 28 mm, outer diameter: 110 mm). A plurality of cut-and-raised holes 23 extending radially from the center hole 22 in the outer peripheral direction are formed in the flame holding plate 12. As shown in FIGS. 4 and 5, the cut-and-raised holes 23 are formed by cutting and raising band-like portions 23a radially extending from the center hole 22 toward the combustion chamber 2, and primary air 16a to be described later. In the same direction as the swirling flow supplied to the burner throat 11 (clockwise direction in FIG. 5). Flame holding plate 1
As shown in FIG. 4 and FIG. 5, a plurality of guide projections 25 projecting from the outer peripheral portion of the burner throat 11 at equal intervals so that the radial interval with the inner peripheral portion of the burner throat 11 is not uneven. The primary air 16a supplied to the burner throat 11 is attached between the outer peripheral portion of the flame holding plate 12 and the inner peripheral portion of the burner throat 11 while being attached by the burner throat 11. An annular hole 24 having a constant radial width and capable of passing evenly is formed. Therefore, the primary air 16a supplied to the burner throat 11 is
2 through the center hole 22, the cut-and-raised hole 23,... And the annular hole 24, so as to be uniformly and smoothly supplied to the combustion chamber 2. The diameter of the center hole 22 is determined according to the spray angle from the fuel oil spray nozzle 13 described below, and is preferably set as small as possible in order to suppress dust generation during low combustion. . Specifically, the center hole 22
Is preferably set to 35 to 40% of the total opening area of the burner throat 11 by the flame holding plate 12 (total area of the center hole 22, the cut-and-raised hole 23, and the annular hole 24). In this example, the center hole 22 is
It is a circular hole having a diameter of mm.

As shown in FIGS. 1 to 5, the fuel oil spray nozzle 13 is concentric with the burner throat 11 or the flame stabilizing plate 12 and the spray port 14 is close to the rear surface of the flame stabilizing plate 12. As shown in FIG. 6, a constant supply hydraulic return type injection valve structure which is disposed on the throat 11 and has an injection valve section 26 opening the spray port 14 and an oil supply section 27 and an oil return section 28 communicating therewith. It is configured. The axial distance (front-back distance) between the spray port 14 and the rear surface of the flame holding plate 12 is usually set to 0 to 7 mm. An ignition electrode 29 is provided near the fuel oil spray nozzle 13.

As shown in FIG. 6, the fuel oil spray control mechanism 15 has an oil supply passage 31 connected to the oil supply portion 27 of the fuel oil spray nozzle 13 and a fixed amount of oil supply passage 31 interposed therebetween. Fuel pump 33 for supplying fuel oil 32 to oil supply unit 27
A first on-off valve 34 provided on the oil supply path 31 downstream of the fuel pump 33, and a filter 61 provided on the oil supply path 31 between the fuel pump 33 and the first on-off valve 34. , One end of which is the oil return portion 2 of the fuel oil spray nozzle 13
8, an oil return path 35 having the other end connected upstream of the fuel pump 33 in the oil supply path 31, a second on-off valve 36 interposed in the oil return path 35, and an oil return path. 3
5, a flow regulating valve 37 provided downstream of the second on-off valve 36 to regulate the amount of oil returned from the oil return unit 28;
Check valves 60, 60 are provided on both sides of the flow control valve 37 in the oil return path 35 and serve as fuel oil leakage prevention mechanisms. In addition, the oil supply path 31 and the oil return path 35 respectively
Oil pressure gauges 38 and 39 are provided.

According to the fuel oil spray nozzle 13 and the fuel oil spray control mechanism 15 described above, the first fuel oil spray nozzle 13 and the fuel oil spray
By opening the on-off valve 34 and closing the second on-off valve 36, the entire amount of the fuel oil 32 supplied from the oil supply path 31 to the injection valve section 26 via the oil supply section 27 by the fuel pump 33 is discharged from the spray port 14. Sprayed. That is, the oil supply unit 2
7, the fuel oil 32 supplied to the injection valve portion 26
Used as the spray oil 32a from the spray port 14. The amount of oil (spray oil amount) supplied from the oil supply unit 27 to the injection valve unit 26 is set to a value that is optimal for high combustion operation (rated operation with a load of 100%). Further, during low combustion (during low-load operation with a load of 50%), the first and second on-off valves 34, 36
, The fuel oil 32 is supplied from the oil supply passage 31 to the injection valve unit 26 via the oil supply unit 27, and a part of the fuel oil 32 supplied to the injection valve unit 26 (hereinafter, “return oil”). ) 32b is returned from the oil return section 28 to the oil supply path 31 via the oil return path 35. Therefore, the spray port 14
From the amount of oil supplied to the oil supply unit 27
The difference oil amount obtained by subtracting b is sprayed. The amount of spray oil at this time can be arbitrarily set by adjusting the return oil 32b with the flow rate adjusting valve 37. That is,
The return oil amount is adjusted by the flow control valve 37 so that the difference oil amount becomes the spray oil amount according to the low combustion condition. Such adjustment is performed before the start of operation. When the combustion is stopped, the first and second on-off valves 34 and 36 are closed. The spray pressure during high combustion and during low combustion is the same. That is, even when the spray oil amount changes due to the combustion load, the ejection pressure (spray pressure) of the spray oil 32a is kept constant. Further, the injection valve unit 2 of the fuel oil spray nozzle 13
If dust or the like adheres or accumulates in the oil return path from the oil path 6 to the oil return path 35 via the oil return section 28, the smooth flow of the fuel oil (return oil) 32b in the oil return path is hindered, There is a possibility that the spraying pressure from the fuel oil spray nozzle 13 fluctuates and the combustion performance may be reduced. However, such a risk is that the intrusion of the dust or the like into the oil return path downstream of the fuel pump 33 in the oil supply path 31. This is eliminated by providing a filter 61 for preventing the above. When the combustion is stopped, the fuel oil 32 may leak from the fuel spray nozzle 13 into the combustion chamber 2 due to the inlet pressure of the fuel pump 33 via the flow control valve 37 due to the fuel oil provided in the oil return path 35. It is eliminated by the check valves 60, 60, which are check valves. The fuel oil backflow prevention device may be any device having such a function, and is not limited to the check valve 60.

As shown in FIGS. 1 and 2, the primary combustion air supply mechanism 17 is provided with a primary air wind box 41 having a circular cross section which communicates with the upper end of the burner throat 11 and concentrically surrounds it. Become. Wind box 41
A plurality of swirling vanes 42 extending radially around the burner throat 11 are provided therein, and the primary air 16a supplied from a primary air supply port 43 provided on the peripheral wall of the wind box 41 is provided in FIG. The fuel can be supplied from the burner throat 11 to the combustion chamber 2 while turning in the counterclockwise direction. The swirl number S of the primary air 16a is determined by the diameter of the burner throat 11, the shape of the swirl vane 42, and the like. In the present invention, the swirl number S of the swirl flow is 0.3 to 0.6. Designed for If the swirl number S is less than 0.3,
When the flame becomes long and the combustion chamber 2 becomes large and exceeds 0.6, the spray oil 32a from the fuel oil spray nozzle 13 collides with the peripheral wall 7 of the combustion chamber 2 and may be carbonized. Because. The swirl number is S = Gφ / (Gx /
(G / 2: angular momentum in the jet, Gx: axial momentum in the jet, d:
Burner throat diameter). In addition, wind box 41
The primary air supply port 43 is provided with a primary air amount control damper 44, and the primary air amount (burner throat 11) supplied from the wind box 41 to the burner throat 11 is provided.
(The amount of primary air supplied to the combustion chamber 2 from the first combustion chamber 2) can be adjusted to be equal to or less than the theoretical combustion air amount, and is usually set to 0.6 to 0.9 with respect to the theoretical combustion air amount. The primary air supply port 43 is provided with a guide plate 45 for guiding the primary air 16a supplied from the supply port 43 to flow in the turning direction.

According to the primary combustion air supply mechanism 17, since the primary air 16a is supplied to the combustion chamber 2 in a state smaller than the theoretical combustion air amount, the spray oil 32a from the fuel oil spray nozzle 13 is discharged by the discharge of the ignition electrode 29. , The primary combustion section 46 that performs reduction combustion and vaporization combustion is formed. Since the primary air 16a is supplied in a swirling flow to the primary combustion section 46, the generated combustion gas, which is a reducing gas, is re-used in conjunction with the formation of the negative pressure section by the flame holding plate 12. By being circulated, the residence time is increased, the vaporization of the spray oil is promoted, and stable combustion is continued.

As shown in FIGS. 1 and 2, the secondary combustion air supply mechanism 19 includes a plurality of air jet nozzles 1
And a secondary air window box 51 surrounding the primary air window box 41 and communicating with the air jet nozzles 18.
b is ejected from each nozzle 18 into the combustion chamber 2. The air ejection nozzles 18 are arranged side by side at predetermined intervals in an annular region around the burner throat 11. The air ejection nozzles 18 are provided in the combustion chamber 2 so as to eject the secondary air 16 b toward the downstream center of the primary combustion section 46. The inclined posture is a predetermined angle (hereinafter referred to as “nozzle angle”) with respect to the axis. An air supply passage 53 is connected to an air supply port 52 formed in a peripheral wall of the wind box 51, and an air volume control damper 54 is provided. Part of the air 16 supplied from the air passage 53 to the secondary air window box 51 is supplied from the primary air supply port 43 to the primary air round box 41 as primary air 16a, and the remaining air is supplied to the secondary air window box 41. 16b is injected into the combustion chamber 2 from the air injection nozzles 18. That is, the total amount of air supplied to the combustion chamber 2 (the total amount of the primary air 16a and the secondary air 16b) is controlled by the air volume control damper 54, and the primary air volume is adjusted by the primary air volume adjustment damper 44 described above. . The secondary air amount is determined by the air amount difference controlled by the dampers 44 and 54, and generally,
It is set equal to or less than the primary air amount. For example, if the required combustion air ratio determined by the air volume control damper 54 is 1.
When the primary air ratio determined by the primary air amount control damper 44 is 0.6, the secondary air ratio is 0.6.
It is said. The control of the spray oil amount from the fuel oil spray nozzle 13 is performed in conjunction with the damper control of the primary air amount and the secondary air amount. For example, when the combustion is shifted from low combustion to high combustion, and the air volume control is switched to high combustion, the air amount in the combustion chamber 2 shifts to the high combustion condition while the second on-off valve 34 is kept open while the second on-off valve 34 is opened. The on-off valve 36 is closed, and the amount of oil for high combustion is sprayed. The reason why the air volume control is performed prior to the spray oil volume control is that the responsiveness of the spray oil volume control is higher than that of the air volume control.

The jet air flow (secondary air flow) 56 from each air jet nozzle 18 is gradually diffused toward the downstream side (forward).
8, the mutual interval, the number, and the nozzle angle
6 do not diffuse on the upstream side and do not interfere with each other, but diffuse and interfere on the downstream side and enter below the recirculation region of the primary combustion gas (hereinafter referred to as “proper secondary air supply form”). As described above, it is appropriately set according to the recirculation force of the primary combustion gas, the shape of the combustion chamber 2, and the like. In general, five to eight nozzles 18 have nozzle angles of 10 to 3
It is preferable that the air jet nozzles 18 are arranged at equal intervals in a 0 ° inclination posture. In this example, five air ejection nozzles 18 are arranged at equal intervals in a 20 ° inclination posture. The ejection speed of the secondary air 16b from the nozzle 18 is also a condition necessary to secure the above-described appropriate secondary air supply form, and is generally 20 m under the minimum load condition of the hot water heater.
/ S or more is preferably set.

According to the secondary combustion air supply mechanism 19, since the secondary air 16b is blown in the above-described appropriate secondary air supply mode, the secondary combustion by diffusion combustion is performed downstream of the recirculation region of the primary combustion gas. The portion 57 is formed, and complete combustion in the combustion chamber 2 is achieved. That is,
The jet air streams 56 are diffused and mixed on the downstream side, and uniform slow combustion is performed. On the upstream side of the jet air streams 56, remarkable oxidative combustion is performed without air diffusing. Therefore, in the upstream portion where the jet air flows 56 do not diffuse and interfere with each other, the oxidizing flame (visually transparent) 59 partially penetrates around the reducing flame (bright flame) 58 as shown in FIG. The reducing flame 58 and the oxidizing flame 59 are clearly distinguished and mixed in the annular area immediately below the nozzle 18. The boundary area between the two flames 58, 59. Is getting bigger.

Therefore, the primary air 16a as described above
By the supply of the secondary air 16b, the reducing flame 58 and the oxidizing flame 59 are clearly distinguished and mixed on the upstream side, and the flames 58 and 59 are gradually diffused and mixed toward the downstream side. NOx can be significantly reduced even in a high-load combustion and a relatively small-capacity oil-fired combustion device in which NOx reduction is difficult due to the two-stage combustion.
The generation of CO and dust can be suppressed well.

By the way, even in such two-stage combustion, as shown in FIG. 11, when three-position control using two fuel oil spray nozzles 13a and 13b arranged close to each other is performed, the combustion efficiency in high load combustion is Is low, and the NOx reduction effect is not so effective. That is, in a high combustion state in which the fuel oil is sprayed from the two fuel oil spray nozzles 13a and 13b at the same time, the spray areas of the two nozzles 13a and 13b partially overlap, and the oil droplet distribution in the oil spray area is not good. It becomes uniform and shades,
The diameter of the oil droplet increases due to the adhesion between the oil droplets. Further, two fuel oil spray nozzles 13a, 13a are provided in the burner throat 11.
3b, the cross-sectional shape of the nozzle holder becomes large and complicated, and each nozzle 13a, 1
The position of 3b is not concentric with the center hole 22 of the flame holding plate 12,
Because of the eccentricity, the flame holding plate 12
, The primary air flow passing through is not smooth, and a proper swirl flow cannot be obtained. Therefore, when two fuel oil spray nozzles 13a and 13b are used, good combustion is not performed and NOx is not reduced so much due to these. Also, the flame becomes longer.

However, in the present invention, as described above, since one fuel oil spray nozzle 13 is used, the above-described problem does not occur. That is, even during high combustion, the fuel oil (spray oil) is supplied from one fuel oil spray nozzle 13.
Since the fuel spray 32a is sprayed, the distribution of the oil droplets in the spray region becomes uniform, no shading occurs, and the diameter of the oil droplets does not increase as compared with the case where two fuel oil spray nozzles 13a and 13b are used. Further, since the fuel oil spray nozzle 13 has a constant supply hydraulic pressure return type injection valve structure, the spray oil 3
The spray pressure of 2a is constant, and the oil droplets are made finer.
In addition, one fuel oil spray nozzle 13 is connected to the burner throat 1
In the case where the two fuel oil spray nozzles 13a and 13b have to be deviated from the center of the burner throat 11 or the center of the flame holding plate 12, respectively, since they can be arranged at the center of the flame holding plate 12 or the flame holding plate 12. Burner throat 1 compared to
From 1, the flow of the primary air 16 a passing through the flame holding plate 12 becomes extremely smooth, and an appropriate swirling flow can be obtained. Therefore, from these, NOx reduction can be achieved more effectively. In addition, since one fuel oil spray nozzle 13 is used, the center hole 22 of the flame holding plate 12 can be made as small as possible.
By narrowing down 2, even during low combustion where there is a possibility that the amount of dust generated may be greater than during high combustion, good combustion is performed and dust generation can be prevented as much as possible.

The effect has been confirmed by the following experiment. That is, in the hot water heater having the above-described configuration, heavy fuel oil A (nitrogen content: 0.02 wt%) is used as the fuel oil 32, and the load is 100% and 50%.
When the combustion experiment was performed under the conditions described above, the appropriate flame form (FIG. 7) was confirmed, and as shown in FIGS.
Generation amount (ppm (O ₂ = 0% conversion, the same applies hereinafter)), CO generation amount (ppm), smoke scale N
o. (Main indicators of the degree of dust generation) were confirmed to be significantly reduced. 8 to 10, the horizontal axis indicates the oxygen concentration (%) in the exhaust gas (combustion gas), the solid line indicates the case of 100% load, and the broken line indicates the case of 50% load.

As is evident from the results of the combustion experiment, the three-position control burner 4 according to the present invention uses the heavy fuel oil A, which easily generates fuel NOx, as the fuel oil. Most stringent Tokyo regulations (NOx <80 ppm for oil-fired, NOx <6 for gas-fired)
0 ppm) can be sufficiently cleared, and in the future, even if oil-burning is regulated in the same way as gas-burning, this can be sufficiently dealt with.

On the other hand, as a comparative example, exactly the same conditions as above were used except that two fuel oil spray nozzles 13a and 13b were used as shown in FIG. 11 and the center hole diameter of the flame holding plate 12 was 40 mm. A combustion experiment was performed at the time of the test. There was not much difference. However, NOx reduction effect, especially high combustion (load 1
As shown in FIG. 12, it was confirmed that the NOx reduction effect at (00%) was significantly lower than when the three-position control burner 4 of the present invention was used (FIG. 8). FIG.
In FIG. 2, the horizontal axis shows the oxygen concentration (%) in the exhaust gas (combustion gas), the solid line shows the case of 100% load, and the broken line shows the case of 50% load.

The present invention is not limited to the above-described embodiment, and can be appropriately modified and changed without departing from the basic principle of the present invention.

[0032]

As is apparent from the above description, according to the present invention, the generation of NOx, CO, and dust can be significantly suppressed, and the recent demand for low NOx combustion can be sufficiently satisfied. Can be. In particular, small capacity boilers with high load combustion,
Even if heavy fuel oil A is used in heaters, etc., it will be possible to stay within the currently strictest Tokyo regulatory framework,
In the future, it is possible to sufficiently meet the demand for low NOx combustion, which will become increasingly strict in the future. Moreover, a boiler can be made much more compact without the necessity of an unnecessarily high-capacity blower or an apparatus for blowing water or steam, which is extremely advantageous in terms of cost.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of a three-position control burner according to the present invention.

FIG. 2 is a vertical sectional front view of a main part taken along line II-II of FIG.

FIG. 3 is a vertical sectional rear view of a main part along the line III-III in FIG. 1;

FIG. 4 is an enlarged detail view showing a main part of FIG. 1;

FIG. 5 is a longitudinal sectional view taken along line VV in FIG. 4;

FIG. 6 is a system diagram showing a fuel oil spray nozzle and a fuel oil spray control mechanism.

FIG. 7 is a vertical sectional front view taken along the line VII-VII of FIG. 1;

FIG. 8 is a graph showing a measurement result of a NOx generation amount.

FIG. 9 is a graph showing a measurement result of a CO generation amount.

FIG. 10 shows a smoke scale NO. 6 is a graph showing the measurement results of the above.

FIG. 11 is a view corresponding to FIG. 5, showing a burner in a comparative example.

FIG. 12 is a graph showing a measurement result of a NOx generation amount in a comparative example.

[Explanation of symbols]

2 combustion chamber, 4 three-position control burner 4, 11 burner throat, 12 flame holding plate, 13 fuel spray nozzle, 14
.. Spraying port, 15 fuel oil spray control mechanism, 16a primary air, 16b secondary air, 17 primary combustion air supply mechanism, 18 air ejection nozzle, 21 burner cone, 22
... center hole, 23 ... cut-and-raised hole, 24 ... annular hole, 26 ...
Injection valve part, 27 ... oil supply part, 28 ... oil return part, 29 ... ignition electrode, 31 ... oil supply path, 32 ... fuel oil, 32a ... spray oil, 32b ... return oil, 33 ... fuel pump, 34 ... 1 on-off valve, 35 ... oil return path, 36 ... second on-off valve, 37 ... flow regulating valve, 41 ... wind box for primary air, 42 ... swirl vanes 42, 43 ... primary air supply port, 44 ... primary air amount control Damper, 45: induction plate, 46: primary combustion section, 51
... wind box for secondary air, 52 ... air supply port, 53 ...
Blower path, 54 ... Airflow control damper, 56 ... Air flow, 5
7 secondary combustion part 58 58 reducing flame 59 oxidizing flame 60
Check valve (fuel oil backflow prevention device), 61 ... filter.

Continued on the front page F term (reference) 3K055 AA05 AA06 AB01 AB04 BA05 BA08 BA11 BB01 BB09 BC02 BD04 3K065 TA01 TA19 TB01 TB08 TB13 TC01 TD02 TD04 TE01 TH06 TJ03 TJ06

Claims (3)

[Claims] 1. A burner throat opening to a combustion chamber, an annular flame holding plate arranged at an opening of the burner throat,
One fuel oil spray nozzle arranged in the burner throat with the spray port close to the flame holding plate, and a fuel oil spray control mechanism that controls the fuel oil spray amount from the fuel oil spray nozzle to the combustion chamber in three positions And a swirl number of 0.3 to 0.6 of primary air smaller than the theoretical combustion air amount from the burner throat into the combustion chamber.
A primary combustion air supply mechanism for supplying a swirling flow of
A secondary combustion air supply mechanism for supplying secondary air having an amount equal to or less than the primary air into the combustion chamber from a plurality of air ejection nozzles provided on the outer side of the burner throat; A fixed supply hydraulic return type injection valve structure having an injection valve portion having an opening and an oil supply portion and an oil return portion communicating with the injection valve portion, wherein the fuel oil spray control mechanism is configured to supply oil to a fuel oil spray nozzle. An oil supply passage connected to the oil supply passage, a fuel pump interposed in the oil supply passage to supply a fixed amount of fuel oil to the oil supply unit, and a fuel pump interposed downstream of the fuel pump in the oil supply passage. 1 open / close valve, an oil return path connected at one end to the oil return section of the fuel oil spray nozzle and the other end connected upstream of the fuel pump in the oil supply path, and an oil return path. The second on-off valve and the oil return path, A flow control valve for adjusting the oil return amount, wherein the first open / close valve is opened and the second open / close valve is closed at the time of high combustion, and the first and second open / close valves are opened at the time of low combustion; When stopped, the first and second on-off valves are closed to control the fuel oil spray nozzle at three positions. The plurality of air jet nozzles are provided in the annular area around the burner throat. Of the combustion chamber is inclined with respect to the axis of the combustion chamber so that the secondary air is blown toward the downstream center of the primary combustion section by the primary air without the air flow from the upstream being diffused and interfering with each other. It is arranged at a predetermined interval in a state where it is in a state where the oxidizing flame by the jet air flow from each air jet nozzle is partly cut in a state where it is clearly distinguished around the reducing flame in the primary combustion section. Raw Three position control burner, characterized in that it is configured to so that. 2. The area of the center hole of the flame holding plate through which the spray oil droplets from the fuel oil spray nozzle pass is set to be 35 to 40% of the total opening area of the flame holding plate in the burner throat. 3. The three-position control burner according to claim 1, wherein: 3. The primary combustion air supply mechanism according to claim 1, wherein the primary air passes through the center hole of the flame holding plate at a flow velocity of 15 m / s or more. 2. The three-position control burner according to 2.