JPH0788940B2 - Premix atomizer - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a premixing atomizer, and particularly to a premixing atomizer suitable for achieving highly efficient and low-pollution combustion of a slurry fuel containing fine powder solids. Regarding

[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 when compared to pulverized coal. It is known that the badness and unburned content increase. The reason for the poor ignitability is that heat is spent on the evaporation of water, and the ignition distance is considerably longer than that of pulverized coal. In addition, there are many unexplained factors that cause an increase in unburned content, but since fine coal particles are agglomerated in the droplets, it is possible that individual particles do not burn out like pulverized coal. This is because the combustion is reduced by moisture. Furthermore, as a feature of coal combustion, it is difficult to form a stable reduction zone (and does not reach high temperature) when the flame is poor and the flame is lifted, and it is difficult to suppress NOx (this fact also applies to pulverized coal combustion). It can be mentioned.
Therefore, in order to raise the combustion efficiency of CWM to the level of pulverized coal, it is necessary to develop an atomizer with excellent spraying performance and suitable for CWM combustion.

6 and 7 are cross-sectional views showing two examples of the structure of a typical conventional two-fluid atomizer.

FIG. 6 shows an example of the internal mixing type, in which the fuel 2 is provided at the bottom of the atomizer chip body 1 for ejecting CWM from the ejection hole 8.
A mixing nozzle of the main body 1, each of which is provided with a fuel nozzle 4 for introducing the fuel, a finely flowing medium supply hole 5 for introducing the atomizing medium 3, and a gas-liquid collision hole 6 for mixing the fuel 2 and the atomizing medium 3. 7
An intermediate plate 10 for supplying to
The body 1 is integrally connected to the plate 10 by a cap nut 9.

In the configuration of FIG. 6, the fuel 2 and the atomizing 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.

FIG. 7 shows an intermediate mixing type atomizer called Y jet type, which has a fuel supply hole 11, a atomizing medium hole 12 at the inlet portion, and a mixing injection hole 13 at which the fuel supply hole 11 is connected at the intermediate portion. Atomizer chip body 14 provided with each and a burner gun inner cylinder 15 for supplying the atomized medium 3 introduced into atomized medium hole 12
And a burner gun outer cylinder 16 which supplies the fuel 2 introduced into the inner cylinder 15 concentrically to the fuel supply hole 11, a contact surface between the upper end of the outer cylinder 16 and the main body 14, and the inner cylinder 15. And body 14
Packings 17a, 17b and the body 14 provided on each of the contact surfaces of
Cap nut that integrally connects the burner gun outer cylinder 16
It is composed of 18 and.

In the configuration shown in FIG. 7, the fuel 2 and the atomizing medium 3 are individually supplied to the atomizer chip main body 14 via the burner gun, and the atomizing chip 13 in the main body 14 collides and joins the two, thereby mixing the mixture. The liquid is directly jetted from the mixing jet hole 13.

Both of the atomizers shown in FIGS. 6 and 7 have been used in oil-fired boilers regardless of whether they are for business or industrial use. However, when the fuel is CWM, a large amount of relatively large droplets are generated, which is insufficient for atomization, and it is extremely difficult to apply it as it is.

On the other hand, in CWM, even if the apparent viscosity and concentration or the coal particle size distribution are the same, the atomization characteristics change greatly when the rheological characteristics are different. This feature is observed with any type of atomizer described above. Compared with pseudo-plastic or Newtonian CWM, CWM exhibiting dilatant property has an increased viscosity with increasing shearing force, resulting in further poor atomization. Depending on the type of coal, manufactured CWM often exhibits dilatant properties. Even if the CWM used has a dilatant property, it is considered to be extremely advantageous if the atomization characteristics at least equivalent to those of other rheological characteristics are obtained by selecting the structure of the atomizer.

Incidentally, regarding this type of equipment, as shown in the Japan Society of Mechanical Engineers Proceedings No.865-1 (Page 61/8), page 109, Mitsubishi Heavy Industries Technical Report Vol.2
2, No.5 (1985-9) p.664, Ishikawajima Harima Heavy Industries Technical Report Vol.25,
No. 5 (1985-9), page 308.

[Problems to be solved by the invention]

However, in the conventional atomizer, when it is applied to CWM, the ignition and flame holding state becomes extremely unstable because sufficient atomization cannot be achieved, and not only unburned content but also NOx emission increases. In addition, since there is much unburned residue at the furnace outlet, it will also interfere with ash processing.

On the other hand, when the type of coal changes, the manufactured CWM changes not only the apparent viscosity but also the rheological properties. Although the rheological properties have many influences on the atomization properties, the prior art has not dealt with such a wide range of physical property changes of CWM.

The object of the present invention is to solve the above-mentioned problems of the prior art,
An object of the present invention is to provide a premix atomizer capable of improving atomization and producing a stable flame with enhanced flame holding.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention provides a fuel supply unit having a shape having different internal diameters on the upstream side of a mixing chamber, and providing at least one second mixing chamber adjacent to the mixing chamber, The atomization medium and the fuel from the fuel supply section are supplied to this mixing chamber so that two types of concentrations of CWM can be obtained.

[Action]

The mixing chamber in the center has a highly concentrated pseudoplastic CWM.
And the mixing chamber provided in the peripheral portion produces a low-concentration Newtonian CWM, which promotes atomization.
The spray flow sprayed from each of the mixing chambers has a small spray particle size as a whole, the ignition flame holding property is improved, and the unburned content is reduced.

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 showing an embodiment of the present invention. The same reference numerals are used for the same parts as those in FIG.

The atomizer according to the present invention includes an intermediate plate 19 into which the fuel 2 and the atomizing medium 3 are introduced, and an atomizer chip body 20 which is connected to the plate 19 and injects CWM, both of which are fixed by a cap nut 9. Fixed.

The intermediate plate 19 receives the fuel 2 and is made of a wear-resistant material such as ceramics, and is provided with a fuel supply nozzle 21, a fuel separation chamber 22 provided so as to be connected to the nozzle 21, and a periphery of the fuel separation chamber 22. Each of the first atomization medium supply hole 23 and the second atomization medium supply hole 24, which is provided and into which the atomization medium 3 is introduced, is provided.

Also, the atomizer chip body 20 includes a fuel separation chamber 25 communicating with the fuel separation chamber 22, a fuel nozzle 26 communicating with the fuel separation chamber 25, and a first gas-liquid mixing chamber 2 communicating with the fuel nozzle 26.
7, a second gas-liquid mixing chamber 28 communicating with the second atomization medium supply hole 24, a collision plate (target) 29 made of a wear-resistant material provided on the inner peripheral portion of the first gas-liquid mixing chamber 27, and fuel separation A fuel separation nozzle 30, which connects the chamber 25 and the gas-liquid mixing chamber 28, and a gas-liquid mixing chamber 27
Of the gas-liquid jetting surface, the jetting hole 32 formed on the gas-liquid jetting surface of the gas-liquid mixing chamber 28, the atomization medium supply hole 23 and the bottom of the gas-liquid mixing chamber 27 Each medium nozzle 33 is provided.

The diameter of the fuel separation chamber 22 is set larger than that of the fuel supply nozzle 21. Further, the atomizing medium supply holes 23 and 24 are alternately formed in the circumferential direction. The central portion on the downstream side of the fuel separation chamber 25 has a small hole diameter (fuel nozzle 26) for pressurizing the fuel in the fuel separation chamber 25. Further, the total sectional area of the fuel separation nozzle 30 is set to be smaller than the sectional area of the fuel nozzle 26.

Next, the function and effect of the premix atomizer configured as described above will be described.

The fuel 2 flows in the inner cylinder of the burner gun, and is pressurized and supplied to the fuel supply nozzle 21 that opens at the center of the intermediate plate 19. Further, vapor or compressed air which is the atomizing medium 3 flows through the annular gap between the inner cylinder and the outer cylinder, and is supplied to the atomizing medium supply holes 23 and 24 which are respectively opened in the intermediate plate 19.

The atomization medium 3 supplied via the atomization medium supply 23 and the fuel 2 supplied via the fuel nozzle 26 are both collision plates.
The two collide with each other and are mixed (primary atomization), and are injected into the mixing chamber 27. The gas-liquid in the mixing chamber 27 is discharged as a spray flow from the plurality of ejection holes 31.

On the other hand, the fuel branched from the fuel separation chamber 25 is the gas-liquid mixing chamber.
Atomization medium 3 supplied from atomization medium supply hole 24 at 28
Mixed with (steam). The mixture produced in the gas-liquid mixing chamber 28 is ejected from each of the ejection holes 32, but its properties are different from those of the ejection holes 31.

Here, it is assumed that CWM exhibiting dilatant property is supplied to the atomizer as fuel.

The fuel 2 is pressurized in the fuel supply nozzle 21 and the fuel separation chamber 25, and the fuel separation nozzle 30 having a small hole diameter undergoes a dehydration action, so that the concentration of the fuel 2 becomes lower than that when initially supplied (at the same time). CWM is supplied).
On the other hand, the CWM having a higher concentration than the original one is supplied from the fuel nozzle 26 to the gas-liquid mixing chamber 27. In this case,
Even if the concentration is increased, the apparent viscosity does not always increase.

The low concentration of CWM has a rheological property of dilatant (a property that the shearing force increases as the shearing rate increases).
To Newtonian (property that shear rate and shear stress have a proportional relationship), and it becomes easy to atomize. On the other hand, CWM with high concentration changes from dilatant to pseudoplastic (the property that shear stress decreases with increasing shear rate),
Remarkably good atomization. This action is a feature of the present invention, and will be described in detail below.

FIG. 3 shows a comparison of the particle size distribution curves of atomized droplets of the conventional atomizer and the atomizer according to the present invention. The atomizer of the present invention has many fine droplets and relatively few large droplets. That is, it can be seen that atomization is good. In the atomizer according to the present invention, when comparing the particle size distributions of the spray flow center and the outer peripheral portion, CW showing pseudoplasticity at high concentration
In the center of the atomized flow where M is atomized, the amount of fine droplets is larger, while the number of large droplets is also relatively larger.
These changes in properties are considered to be due to the difference in CWM concentration and rheological properties.

FIG. 4 shows a flame structure schematic diagram under the conditions using the atomizer according to the present invention. In FIG. 4, 20 is an atomizer chip body, 32 is a burner throat, 33 is combustion air, 34 is a high-temperature reducing flame, and 35 is an oxidizing flame. As is clear from FIG. 4, the flame center is a high-temperature reduction region where the atomized spray of the highly concentrated CWM burns, and low NOx combustion is achieved by re-burning (Re-Burning) in the downstream. .
In the past, there was a concern that combustion in the flame center would be delayed due to lack of oxygen and temperature, and unburned content would increase, but in the case of the present invention, it is possible to improve this handicap by improving atomization. Is compensating for.

Figure 5 summarizes the experimental data in relation to NOx and unburned content,
This is a demonstration of the effect of the atomizer according to the present invention.
When compared at the same unburned content level, the atomizer according to the present invention shows a 100-200 ppm reduction in NOx. Further, when compared with the same NOx rehell, the unburned content is remarkably reduced, and it can be seen that the effect of the atomizer according to the present invention is extremely large.

In the above configuration, the number and the diameter of the ejection holes 31 and 32 are the same and the opening positions are set on the same burner radial direction axis, but these conditions are not particularly specified in the present invention. By properly combining the changes in the number, the hole diameter, or the opening position, various effects associated with the effects of the present invention can be produced.

Further, the two-fluid atomizer according to the present invention is not limited to the CWM specifically taken as an example in the present text, but can be applied to a slurry fuel in which other fine powder solids are suspended in a liquid.

The applicable fuels are listed below.

(1) COM (coal / oil slurry) (2) Metacoal (coal / methanol slurry) (3) PWM (petroleum coke / water slurry) (4) Pitch / water slurry (5) Inferior residue with a large amount of solid residual coal According to the described embodiments of the present invention, the following effects are specifically obtained.

(1) Atomization characteristics are improved for any CWM properties, ignition is stabilized, and flame retention is improved.

(2) In connection with the improvement in flame holding property, the unburned content in ash in fly ash is reduced, so that the combustion effect is improved.

(3) In addition to the above effects (2) and (3), not only the total amount of sinter ash (cinders, unburned ash) and clinker ash falling to the furnace bottom that are supplemented by A / H are reduced, The unburned content in those ashes is reduced. As a result, ash processing is significantly facilitated and the range of ash utilization is expanded.

(4) The boiler furnace can be made smaller because the flame is shortened. Therefore, it is advantageous from the economical aspect.

(5) Due to the effects of (1) to (3) described above, it is also advantageous for a slurry fuel using a high fuel ratio coal (fuel ratio = fixed carbon / volatile matter) having poor combustibility.

(6) Due to the effect of (1), a stable high-temperature reduction zone is formed near the burner, and NOx can be reduced.

(7) Large capacity ratio (scale up) is possible.

(8) The amount of atomizing medium (vapor) can be reduced. Therefore, the boiler efficiency is increased and the auxiliary equipment power cost can be reduced.

(9) Low excess air combustion becomes possible. Therefore, low temperature corrosion can be prevented even by using a coal type containing a large amount of S (sulfur) (although coal generally imported into Japan has a small amount of S).

〔The invention's effect〕

As described above, according to the present invention, the atomization characteristics are improved, the ignition is stabilized, the flame holding property is improved, and the combustibility is remarkably improved. Therefore, energy saving and environmental protection measures are facilitated.

[Brief description of drawings]

1 and 2 are a sectional view and a plan view showing an embodiment of the present invention, and FIG. 3 is an atomization characteristic diagram showing a particle size distribution of spray,
FIG. 4 is a characteristic diagram showing a flow pattern of spraying in the present invention, FIG. 5 is a characteristic diagram of unburned ash content showing the results of the present invention and a conventional combustion test, and FIGS. 6 and 7 are conventional atomizers. It is sectional drawing which shows two examples. 19 ... Intermediate plate, 20 ... Atomizer chip body, 21 ... Fuel supply nozzle, 22,25 ... Fuel separation chamber, 23, 24 ... Atomization medium supply hole, 26 ... Fuel nozzle, 27, 28 ... gas-liquid mixing chamber, 29 ... collision plate, 30 ... fuel separation nozzle, 31, 32 ... ejection holes.

Claims (2)

[Claims] 1. An atomizer having a mixing chamber for mixing a fuel and an atomizing medium, which are individually supplied, and a jetting unit for jetting a mixed fluid in the mixing chamber to the outside. And a fuel supply unit disposed upstream of the mixing chamber, and at least one fuel supply unit disposed adjacent to the mixing chamber for supplying the atomizing medium and forming an injection hole at the end of the furnace. And a fuel separation nozzle that connects the second mixing chamber to the inner diameter changing portion of the fuel supply unit. 2. The mixing chamber is arranged on the central axis of the atomizer, and the second mixing chamber is arranged around the mixing chamber in an annular shape at a predetermined interval. A premixing atomizer according to item (1).