JPH0820062B2 - Two-fluid atomizer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a two-fluid atomizer, and particularly to a two-fluid atomizer that achieves high efficiency and low-pollution combustion of slurry fuel and has a large capacity (scale-up). Regarding atomizer.

[Conventional technology]

CWM (High Concentration Coal / Water Slurry) is a fluidized fuel and can be atomized and burned using an atomizer like conventional oil, but it has a problem of poor ignitability when compared with pulverized coal. It is known that the unburned content increases. The reason for the poor ignitability is that heat is consumed for the evaporation of water, and the ignition distance is considerably longer than that of pulverized coal. There are many unexplained parts as the cause of increasing unburned content, but since fine coal particles are agglomerated in the droplets, it does not burn out as individual fine particles like pulverized coal, This is because the combustion temperature decreases due to moisture. Furthermore, it is said that it is difficult to form a stable reduction zone (and does not reach a high temperature) when the flame is lifted and the flame is lifted, and it is difficult to suppress NOx emissions.
Therefore, in order to raise the combustion efficiency of CWM to the level of pulverized coal, it is essential to develop an atomizer that has excellent spraying performance and is suitable for CWM combustion.

[Fig. 13] Fig. 13 is a cross-sectional view and a plan view showing an axial cross-sectional view of an internal mixing atomizer, which is a typical example of the conventional two-fluid atomizer of Figs. 13 and 14.

In FIG. 13, at the bottom of the atomizer chip body 1 for ejecting CWM from the ejection holes 8, a fuel nozzle 4 for introducing the fuel 2, an atomizing medium supply hole 5 for introducing the atomizing medium 3, and the fuel 2 and the atomizing particles. An intermediate plate 10 for supplying the mixture to the mixing chamber 7 of the atomizer chip body 1 is provided, which is provided with each of the gas-liquid collision holes 6 for mixing the atomizing medium 3, and the atomizer chip 10 is provided to the intermediate plate 10. The body 1 is integrally connected by a cap nut 9.

In the atomizer shown in FIG. 13, the fuel 2 and the atomization medium 3 are merged and mixed in the gas-liquid collision hole 6 opening at the center of the intermediate plate 10 to perform primary atomization, and then the mixture is retained in the mixing chamber 7. After this, the particles are atomized from the ejection holes 8.

As for this kind of equipment, the 41st lecture meeting on liquid atomization (Showa 60/8), page 41, Mitsubishi Heavy Industries Tech. Vol.22, No.5 (1985-9), page 664, Ishikawajima Harima Heavy Work Technique Vol. 25, No. (1985-9), page 308.

[Problems to be solved by the invention]

However, in the conventional atomizer, when CWM is used as a fuel, the mixing is not sufficient because of its poor quality. Further, since there is only one mixing chamber, when the capacity is increased, the fuel and atomization medium are likely to be separated in the chamber, the flow rate cannot be evenly distributed to each ejection hole, and atomization in each ejection hole is performed. Tends to be inhomogeneous. As a result, it becomes difficult to control the combustion flame zone, and if the mixing of combustion air becomes poor, not only low NOx combustion becomes impossible with CWM using coal with a high fuel ratio, but also unburned content increases dramatically. .

Furthermore, when reducing the fuel, the amount of the microviscosifying medium is reduced in order to reduce the jet speed (to reduce the blow-off of the flame), but this reduces the flow velocity of the micro-viscosifying medium, resulting in gas-liquid mixing. Is insufficient, atomization is not performed well, and the velocity of the gas-liquid mixture is reduced even in the ejection holes, resulting in poor atomization. For this reason,
It is extremely difficult to obtain a large turndown ratio.
In the case of a large commercial boiler, it is possible to cope with load fluctuations by burner cutting, but in the case of an industrial boiler with a small number of burners, it is fatal that the turndown ratio cannot be made large.

It is an object of the present invention to provide a two-fluid atomizer which solves the above-mentioned problems of the prior art and improves combustion efficiency and pollution reduction.

[Means for solving problems]

In order to achieve the above object, the present name is a two-fluid atomizer that mixes fuel and atomizing medium in the atomizer, and atomizer ejection holes for ejecting the mixed fluid of fuel and atomizing medium to the outside of the atomizer. A plurality of sub-injection holes each having a diameter equal to or smaller than the diameter of the ejection hole are provided on the coaxial circumference.

[Action]

The atomizer ejection hole has a relatively large atomization particle diameter and a low ejection speed, and is suitable for large-capacity ejection.
On the other hand, in the secondary ejection holes, atomization is promoted while the ejection speed increases. Therefore, a secondary jet for assisting ignition is generated in the secondary jet hole. In this state, the slurry fuel is burned with good ignitability and flame holding property. Particularly, when the inner cylinder of the burner gun is made movable in the axial direction of the burner, the gas-liquid collision distance is adjusted and the atomization characteristics are controlled.

Example of Invention

 Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are a sectional view and a plan view of an ejection hole portion showing a first embodiment of the present invention. In this embodiment,
The same components as those in FIG. 14 are designated by the same reference numerals. Therefore, redundant description will be omitted.

In this embodiment, a plurality of ejection holes 8 opening on the same circumference of the surface of the atomizer chip body 1 on the furnace side are provided, and the ejection holes 8 are formed on the same coaxial outer circumference circle as shown in FIG. Sub-spout holes 11 each having a hole diameter smaller than that of No. 8 are provided at intervals of 90 degrees in the circumferential direction, four by four. In this example, the ejection hole (ejection hole 8) with respect to the central axis 12 of the burner
And the divergence angle Θi (i = 0 to 4) of each sub ejection hole 11) is set as follows.

[Theta] ₁ <[Theta] ₀ = [Theta] ₂ = [Theta] ₃ <[Theta] ₄ (Equation 1) Further, the inclination angle in the circumferential direction with respect to the central axis 12 of the burner is 0 [deg.] In this example.

3 (a), (b), and (c) are plan views showing examples of combined arrangement of the ejection holes 8 and the sub ejection holes 11. As shown in FIG. Fig. 3 (a)
In each of the ejection holes, a sub-ejection hole 11 is provided on the burner central axis 12 side and on the atomizer chip outer peripheral side, and one sub-ejection hole 11 is provided on the same radial axis.
This is an example in which each ke is provided. FIG. 3 (b) shows an example in which, in each ejection hole, three auxiliary ejection holes 11 are formed on the outer peripheral side of the atomizer at narrow intervals. In contrast to FIG. 3 (b), FIG. 3 (c) is constructed by collecting two auxiliary ejection holes 11 on the burner central axis 12 side. In the figure, 13 is the central axis of the ejection hole, and 14 is the central axis of the sub ejection hole.

It is preferable that the diameter of the sub-spout hole 11 is about 1/2 of that of the spout hole 8. That is, if the ejection hole diameter is 4 mm, the auxiliary ejection hole diameter is about 2 mm. If the diameter of the secondary ejection hole is made smaller than this, clogging due to coal particles or foreign matter may occur, which may cause a problem in driving operation.

Slurry coal species with high fuel ratio and high N content,
In order to burn NOx, strengthening flame holding is the most effective. Improvement of flame holding property leads to reduction of unburned content, that is, improvement of combustion efficiency. (By the way, the performance of a boiler burner is often evaluated by the amount of NOx and the amount of unburned components discharged.) In the two-fluid atomizer of the present embodiment, the jet holes having different hole diameters are provided as main jet holes or sub jet holes, respectively. If the pore size is different, the action for atomization also differs. When the pore size is large, the spray particle size is relatively large, but the ejection speed is low. And of course,
Suitable for large volume injection. Therefore, in this embodiment,
The larger ejection hole is used as the main ejection hole. On the other hand, when the hole diameter is small, the ejection speed is high, but the atomization is good (the spray particle size is small). Therefore, it is suitable for fuel assist or low O ₂ combustion spray.

4 and 5 schematically show two spray flow pattern examples when the atomizer shown in FIG. 1 is used. FIG. 4 corresponds to FIG. 3 (b), and it is possible to quickly ignite the fine surroundings of the spray flow 15 from the sub-injection holes 11 with a small hole diameter, which are arranged on the outer periphery of the atomizer in the radial direction. It is aimed at the effect of holding flame. Under such a spray condition, the swirling supply of the combustion air 17 forms a high-temperature reducing flame 16 in the center of the spray flow 15 to reduce the NOx.
Combustion is achieved.

FIG. 5 corresponds to FIG. 3 (c). A low O ₂ reducing flame 19 is formed at the center of the spray flow 20, but if the temperature is not high, combustion is delayed, resulting in low NOx and increasing the amount of unburned matter. In this example, fine particles are concentrated in the center of the spray flow and combustion is promoted to simultaneously reduce unburned NOx content. By the way, in FIG. 4 and FIG. 5, 18 is a throat burner.

The embodiment shown in FIG. 3 (a) is designed to have both the effects (b) and (c) in FIG. 3 at the same time. For combustion assist-flame holding, auxiliary jet holes 11 for spraying for combustion promotion are also provided on the outer peripheral side of the atomizer or in the circumferential direction (left, right) of the jet holes 8.

FIG. 6 shows the combustion test results in the example of FIG. 1 and the conventional example, and shows the ash unburnt fraction ratio characteristics with respect to NOx. Comparing the conventional atomizer and the unburned component at the same level, it can be seen that the atomizer of the present invention reduced NOx to about half. Furthermore, when compared at the same NOx level, the unburned content is significantly reduced to about 1/4.

Further, since the atomizer according to the present invention has a strong flame holding action by the auxiliary jet holes 11 as described above, it is possible to easily increase the capacity (scale up).

FIG. 7 and FIG. 8 are a sectional view and a plan view of a main part of an ejection hole portion showing a second embodiment of the present invention. The present embodiment is an example of an intermediate mixing type atomizer called a Y jet type atomizer.

A fuel supply hole 22 into which the fuel 2 is introduced is provided in the wall of the atomizer chip body 21 in the axial direction. The fuel supply hole 22 penetrates between the mixing chamber and the furnace side and is communicated with the fuel supply hole 22.
Is provided. In the vicinity of the main mixing ejection hole 23, a sub-mixing ejection hole 24 is provided on a predetermined radius with this as an axis. Further, at the upstream end of the main mixing ejection hole 23, a main mixing ejection hole atomizing medium supply hole 25 is provided, and a sub ejection hole fine particle communicating with the supply hole 25 and gradually increasing in diameter to the downstream side. A chemical medium supply hole 26 is provided.

This embodiment is structurally similar to that of FIG. 3 (b), and therefore the effects on atomization and combustion improvement are similar to those of the previous embodiment.

FIG. 9 is a sectional view showing a third embodiment of the present invention.
In this embodiment, the same reference numerals are used for the same parts as those in FIG.

The atomizer is a burner gun inner cylinder that distributes and supplies the fuel 2.
32, a burner gun outer cylinder 31 for supplying vapor or compressed air as the atomizing medium 3, an intermediate plate 10 for joining the fuel 2 and the atomizing medium, an atomizer chip body 1, and an intermediate plate at intermediate positions. Atomizer chip body 1 with scissors and burner gun outer cylinder 31
Is mainly composed of a cap nut 9 for fixing.

In the atomizer chip body 1, a plurality of ejection holes 8 are opened at predetermined intervals on the same circumference in the outer surface direction from the inner wall surface of the mixing chamber 7 on the furnace side. Also, the mixing chamber 7
Inside, the inner mixing chamber nozzle 35 that reduces the hole diameter from the direction of the intermediate plate 10 toward the inside of the mixing chamber and makes the minimum hole diameter about 1/2 of the inner diameter of the mixing chamber 7 is provided upstream by the spring coil 16. It is inserted to be biased. It is also possible to assemble the atomizer chip main body and the inner mixing chamber nozzle without using the spring coil 36.

The fuel 2 ejected from the fuel nozzle 33 having a predetermined spread angle at the tip of the burner gun inner cylinder 32 and the atomizing medium 3 supplied from the atomizing medium hole 5 of the intermediate plate 10 are contained in the inner mixing chamber. Collision and merge on the throat surface of the nozzle 35. That is, it is performed in the high shear atomization region immediately before entering the mixing chamber 7.

The burner gun inner cylinder 32 can be moved (finely adjusted) in the axial direction by an operation from the outside of the burner in response to the fuel load fluctuation. That is, the primary atomization characteristics are controlled by changing the distance between the outlet of the fuel nozzle 33 and the throat surface of the nozzle 35 of the inner mixing chamber or the outlet of the atomizing medium hole 5. Generally, when the load is low, the distance between the two is reduced to promote atomization, and they are separated as the load is increased.

Generally, the conventional internal mixing atomizer as shown in FIG. 13 has a primary atomization in which the fuel and the atomizing medium first collide with each other, and a secondary atomization in the injection hole opening in the mixing chamber of the atomizer chip body. The total atomization performance is determined by the combination of both. On the other hand, the atomizer of this embodiment can improve the deterioration of the atomization performance due to the load reduction by controlling the primary atomization.

FIG. 10 is an explanatory view showing the formation of the primary atomization regions in the embodiment of FIG. The fuel 2 ejected from the fuel nozzle 33 opening at the tip of the burner gun inner cylinder 32 collides with the throat surface of the nozzle 35 in the inner mixing chamber, and at the same time the atomizing medium hole 5
Atomization is performed so that the atomization medium 3 ejected at a higher speed blows it away. Therefore, the clearance δ between the outlet of the fuel nozzle 33 and the throat surface is a very important structural factor. That is, if the burner gun inner cylinder 32 is moved to the furnace side by a small distance to reduce the clearance δ, the collision speed of the fuel 2 on the throat surface is likely to be atomized. Further, as the clearance δ decreases, the atomizing medium ejected from the atomizing medium holes 5 is rapidly accelerated, and primary atomization is promoted.

FIG. 11 and FIG. 12 are comparative characteristic diagrams of the example of FIG. 9 and the conventional example of the spray average particle diameter and the unburned fraction U _B. This is the result of measuring the change in the spray average particle size ₃₂ with respect to the change in the fuel flow rate while keeping the gas liquefaction (mass flow rate ratio of the fuel to the atomization medium) constant in the same manner as the operation of the actual can. The atomizer is designed with a rated load of 1000 Kg / h. In the atomizer configured as shown in FIG. 9 by the primary atomization control, the spray average particle size ₃₂ is almost constant despite the load reduction. From this experimental result, it is confirmed that the turndown ratio can be large up to 400 Kg / h, that is, up to a low load of 2/5 even under a constant gas-liquid ratio. FIG. 12 shows the result of measurement of the unburned-content ratio U _B in ash (fly ash) by a combustion test. In the conventional type, U _B rapidly increases as the load decreases, whereas in the atomizer of this embodiment, the increase in U _B is suppressed to about 1%. The cause of this 1% increase in U _B is not due to the fact that the control of the atomization characteristics did not act, but is due to the decrease in the temperature inside the furnace due to the decrease in load, rather, by the control of the primary atomization, It said to minimize the effect of suppressing the rise in U _B was confirmed.

When the clearance δ is reduced under high load, the fuel injection pressure rises and exceeds the pump capacity limit.
It is not preferable from the viewpoint of danger prevention. Therefore,
This kind of control should not be taken.

According to this embodiment, since the load fluctuation followability can be improved, it is possible to expand the use range of the coal slurry fuel for DSS (Dairy Start-Stop) and the like.

The two-fluid atomizer according to the present invention exhibits not only the exemplified CWM, but also the effect of follow-up controllability with respect to fuel load fluctuations for almost all other liquid (or fluidized) fuels. For example, the following fuels are listed.

(1) Light oil, A / B / C heavy oil (2) COM (coal / oil slurry) (3) Metacoal (coal / methanol slurry) (4) PWM (petroleum coke / water slurry) (5) Pitch / water slurry ( 6) Poor quality residue (for example, straight asphalt) Among them, (2) to (5) are slurry fuels,
It contains relatively large solid particles. Therefore, in FIG. 9, it is difficult to extremely reduce the distance between the conical surface where the fuel injection hole at the tip of the burner gun inner cylinder 32 is opened and the collision surface provided at the inlet of the internal mixing chamber (minimum 1.5 mm). degree)
Therefore, caution is required in design.

According to each of the examples shown above, in order to improve the ignition stability and flame holding property, fly ash, clinker ash, etc., can reduce unburned content in ash, and a high fuel ratio with poor combustibility It is also advantageous for a slurry fuel using a high speed (fuel ratio = fixed carbon / volatile matter). Furthermore, since a stable high temperature reduction zone can be formed near the burner, NOx can be reduced.

Further, since the flame can be shortened, the boiler furnace can be downsized, and the economical efficiency can be improved.

Further, since the amount of atomizing medium can be reduced, the boiler efficiency can be improved, and the auxiliary equipment power cost can be reduced. Further, since low excess air combustion becomes possible, low temperature corrosion does not occur even if a coal type containing a large amount of sulfur is used.

〔The invention's effect〕

As described above, according to the present invention, since ignition is stabilized and flame holding property is improved, combustion efficiency is improved, low pollution combustion can be achieved, and scale-up (large capacity)
Can be achieved. Further, since it is possible to cope with fuel load fluctuations, it is possible to increase the turndown ratio.

[Brief description of drawings]

1 and 2 are a sectional view showing a first embodiment of the present invention and a plan view of an ejection hole portion, and FIGS. 3 (a), 3 (b) and 3 (c) show the ejection hole 8 and the sub ejection hole 11 respectively. A plan view showing an example of a combination array of
FIGS. 4 and 5 are explanatory views showing two examples of the spray flow pattern of the embodiment of FIG. 1, and FIG. 6 is an unburned ash content in ash showing the results of the embodiment and the conventional combustion test of FIG. FIG. 7 is a characteristic view, FIG. 7 and FIG. 8 are cross-sectional views and a plan view of an essential part showing a second embodiment of the present invention, and FIG. 9 is a cross-sectional view showing a third embodiment of the present invention.
The figure is an explanatory view of the formation of the primary atomization region of the embodiment of FIG.
FIG. 11 and FIG. 12 are comparative characteristic diagrams of the sprayed average particle diameter and unburned fraction of the embodiment of FIG. 9 and the conventional example, FIG. 13 is a sectional view showing a conventional two-fluid atomizer, and FIG. FIG. 13 is a plan view of FIG. 13. 1,21 …… Atomizer chip body, 4 …… Fuel nozzle, 5
…… Atomization medium hole, 6 …… Gas-liquid collision hole, 7 …… Mixing chamber,
8 ... Jet hole, 11 ... Sub jet hole, 22 ... Fuel supply hole, 23
...... Main mixing ejection hole, 24 …… Sub mixing ejection hole, 25 …… Atomization medium supply hole for main mixing ejection hole, 26 …… Atomization medium supply hole for sub ejection hole, 31 …… Burner gun outer cylinder, 32 …… Burner gun inner cylinder, 33 …… Fuel nozzle, 34 …… Fuel flow path, 35 …… Inner mixed chamber nozzle, 36 …… Spring coil.

Claims (5)

[Claims] 1. A fuel supply path, an atomization medium supply path for atomizing the fuel, a mixing chamber for mixing the fuel supplied from the fuel supply path and the atomization medium supplied from the atomization medium path, In a two-fluid atomizer provided with an atomizer ejection hole for ejecting the mixed fluid in the mixing chamber to the outside, a plurality of sub-ejection holes adjacent to the ejection hole and having a diameter equal to or smaller than the diameter of the ejection hole are provided on the coaxial circumference. A two-fluid atomizer characterized in that 2. A patent characterized in that one of the inclination angles of the central axis of the auxiliary jet hole with respect to the central axis of the burner in the burner radial direction or the circumferential direction is made to coincide with the central axis of the jet hole. The two-fluid atomizer according to claim (1). 3. A patent, characterized in that each of the inclination angles of the central axis of the sub-injection hole with respect to the central axis of the burner in the burner radial direction or in the circumferential direction is not matched with the central axis of the ejection hole. The two-fluid atomizer according to claim (1). 4. A burner gun inner cylinder for supplying fuel, which is mounted inside the burner, is arranged so as to be movable in the axial direction of the burner, and the collision-joining distance between the atomizing medium and the fuel is variable. A two-fluid atomizer according to claim (1). 5. A two-fluid atomizer according to claim 1, wherein a nozzle throat having an inlet portion having a hole diameter that becomes smaller toward the downstream side is provided at the inlet of the mixing chamber.