JPH0447209B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a combustion device equipped with an atomizer for spraying a liquid fuel containing solid particles, particularly a coal-water slurry, and particularly relates to a combustion apparatus equipped with an atomizer that sprays a liquid fuel containing solid particles, particularly a coal-water slurry. The present invention relates to a liquid fuel combustion device containing solid particles configured to atomize a coal-water slurry by means of an atomizing medium.

[Conventional technology]

One of the coal fluidization technologies is coal water slurry. These are new ways of using coal to replace pulverized coal, and their use in electric power or industrial boilers is progressing. Coal-water slurry can be supplied to the burner using a pump, just like conventional petroleum-based fuels, so compared to air conveyance of pulverized coal, coal-water slurry offers transportation advantages such as easier flow control and a smaller fuel supply pipe diameter. There are advantages. In addition, when considering coal-water slurry as a fuel for boilers, it is necessary to increase the calorific value of the fuel, so the concentration of coal contained in the coal-water slurry is reduced to 62%.
A highly concentrated coal-water slurry of ~70% by weight is used as fuel for boilers.

Now, when burning such a coal-water slurry that can be handled as a fluid, an atomizer is required to reduce the liquid coal-water slurry to minute spray particles. The coal water slurry contains coal particles;
Furthermore, since it is a highly viscous fluid, a two-fluid atomizer is mainly used in which air or steam is used as the atomizing medium, and the kinetic energy of the gas is used to atomize the coal-water slurry into minute particles.

Various structures have been proposed for two-fluid atomizers, and in particular, an atomizer for fluids containing coal particles, such as coal-water slurry, is described in Japanese Patent Laid-Open No. 179714/1983. The atomizer described in this publication is an atomizer that is provided with a spray medium supply hole that opens in the tangential direction of the inner wall of a coal-water slurry flow path that extends linearly. This is the principle of spraying coal-water slurry by using the swirling force of the spray medium and the shear force caused by the turbulence by colliding the spray medium ejected with a swirling flow and mixing the two well with the coal slurry. based on. However, when the spray capacity of the atomizer is increased, the spray medium cannot penetrate to the center of the coal-water slurry flow path, and the coal-water slurry and the spray medium are mixed well, making the entire spray into fine spray particles. No consideration was given to this point.

Furthermore, an atomizer is known in which a coal-water slurry flow path contacts a certain point of a spray medium flow path at an angle, and is generally called a Y-jet type atomizer. Regarding this type of atomizer, there are Utility Model Application No. 59-186626 and Utility Model Application No. 60-
Many proposals have been made, including Publication No. 12019. The atomizers described in these publications attempt to form a spray stream using the momentum and turbulence of a spray medium that collides with the flow of coal-water slurry supplied from a coal-water slurry flow path. In this type of atomizer, it is often observed that the coal-water slurry comes into contact with the inner wall of the spray medium flow path to form a film, and the film breaks at the end of the spray medium flow path on the side of the atomizer's atomizing atmosphere. . This atomization from the film formed on the end surface occurs under conditions where the air flow rate is reduced, producing coarse particles, but no consideration has been given to this point.

[Problem that the invention seeks to solve]

The conventional technology described above attempts to reduce the spray particle size of the coal-water slurry by increasing the flow rate of the spray medium, but the diameter of the spray particles of the coal-water slurry is smaller than 200 μm due to poor mixing of the spray medium and the coal-water slurry. The generation of coarse particles above has not been reduced. Furthermore, by ejecting the atomizing medium at high speed, the selected water slurry atomized particles are ejected at a speed of 200-odd m/s. In general, the velocity of sprayed particles is determined by the diameter of the sprayed particles, the initial velocity of the particles, the gas flow velocity around the particles, etc., and it is known that the coarser the particles are sprayed at a higher speed, the smaller the attenuation of the particle velocity is. For this reason, the coarse particles of the spray pass through the ignition surface of the flame without being ignited, and are ignited only when their speed is sufficiently reduced. For this reason, the residence time of combustion of the coarse particles in the furnace is short, and the coarse particles are discharged without being able to complete combustion in the furnace, resulting in a problem that the combustion rate decreases.

On the other hand, the ignition time of the sprayed particles is equal to the longer of the time required for the water in the particles to evaporate and the time required for the particles to equalize the flame propagation velocity depending on the atmosphere around the particles. . 100μ
The ignition time for coarse particles of m or more is determined by the evaporation of water, whereas for particles of several tens of micrometers or less, the rule is the time required for the particle velocity to decay. The ignition of a spray of coal-water slurry is generally determined by the ignition of microparticles of several tens of micrometers or less, and therefore the ignition of a flame is determined by the time required for the particle velocity to decay. For this reason, when spray particles are ejected at an initial velocity of 200 m/s, it takes a long time for the spray particle velocity to decay, and ignition occurs after the spray particles and combustion air have sufficiently mixed. become. This means that no local air ratio distribution is formed within the flame, and the flame burns everywhere under conditions equal to the air ratio at the furnace outlet. For this reason, when coal is burned, only the reaction that generates NOx proceeds, leading to a problem in which the NOx concentration increases. That is, when spray particles are ejected at a speed of more than 200 m/s, they burn without forming a local air ratio distribution within the flame, resulting in a problem that the NOx concentration in the exhaust gas increases.

In addition, the flow characteristics of the coal-water slurry that is the fuel are as follows:
Unlike Newtonian fluids such as water and oil, it is generally a non-Newtonian fluid. Non-Newtonian fluids have the property that their viscosity changes with shear rate. There are two types of non-Newtonian fluids: dilatant fluids whose viscosity increases with increasing shear rate, and pseudoplastic fluids whose viscosity decreases with increasing shear rate. Coal-water slurry is divided into pseudoplastic fluid and dilatant fluid coal-water slurry depending on the particle size distribution of the coal particles, the properties of the coal particles, etc. On the other hand, when the coal-water slurry is atomized with a spray medium such as air, a very high shear force of about 10 ³ to ^{10 6} S ^-1 is applied to the coal-water slurry. For this reason, even if the apparent viscosity is the same when pumping coal water slurry, the coal water slurry that is a dilatant fluid is atomized with a high apparent viscosity, and the coal water slurry that is a pseudoplastic fluid has a high apparent viscosity. This means that the particles are atomized in a low state. Generally, the average particle size of the spray when a coal-water slurry is atomized is affected by the viscosity, and the higher the viscosity of the coal-water slurry, the larger the particle size of the spray. In particular, when the spray medium is ejected parallel to the flow direction of the coal-water slurry, it is significantly affected by the viscosity. In other words, when coal water slurry is ejected to form a liquid film or liquid column, and the spray medium is ejected parallel to the flow direction of this coal water slurry, the apparent viscosity of the coal water slurry when pumped to the atomizer Even though they are the same, the average particle size of the spray of the coal-water slurry of the dilatant fluid is larger than that of the coal-water slurry of the pseudoplastic fluid. Therefore, in order to make the average particle size of the spray of coal-water slurry as a dilatant fluid equal to that of the coal-water slurry as a pseudoplastic fluid, the apparent viscosity when pumping the coal-water slurry as a dilatant fluid must be adjusted to be pseudoplastic. There arises a problem that the coal water slurry must be lower than the fluid coal water slurry, the properties of the coal water slurry are restricted by the atomizer, or a coal water slurry with a low coal weight concentration must be used.

An object of the present invention is to provide a combustion device that can effectively atomize liquid fuel containing solid particles without relying on its flow characteristics, reduce the speed of atomized particles ejected from an atomizer, and prevent the generation of coarse atomized particles. It is about providing.

[Means for solving problems]

The object is to provide a combustion apparatus equipped with an atomizer that mixes and ejects a liquid fuel containing solid particles and a spray medium, wherein the atomizer converts the liquid fuel containing solid particles into an annular flow containing the solid particles. a liquid film forming means for forming a liquid film of liquid fuel; and a liquid fuel containing solid particles that causes the spray medium to be ejected obliquely toward the exit direction near the atomizer outlet nozzle to collide with the liquid film. This is achieved by having an atomizing means for atomizing the particles.

It is desirable that the atomizing medium be ejected so as to collide with the end face of the atomizer outlet nozzle, thereby making it possible to further atomize the liquid fuel containing solid particles.

It is preferable that the atomizing medium is injected tangentially to the circumferential surface of the annular flow of liquid fuel containing solid particles to give a swirling flow to the annular flow. By improving the mixing of the fuel and the spray medium, it is possible to suppress the generation of coarse particles.

It is desirable to have an enlarged part in the vicinity of the atomizer outlet nozzle that expands and discharges the liquid fuel containing solid particles atomized by the collision of the atomizing medium in a divergent shape. The atomized particles can be further atomized by colliding with the atomizer, and a stable flame can be formed by forming a circulating flow of the atomized particles downstream of the atomizer.

[Effect]

The coal-water slurry nozzle, which is configured to prevent fuel from flowing through the center and allow fuel to flow through the outer periphery, converts the coal-water slurry into a liquid film and supplies it to a mixing chamber provided in the atomizer. By that,
Since the coal-water slurry in the form of a liquid film can contact the spray medium well, there is no local difference in the ratio of the mass flow rate of the coal-water slurry to the mass flow rate of the spray medium (hereinafter referred to as the gas-liquid flow rate ratio). Therefore, it is possible to prevent the generation of coarse particles due to a partial decrease in the gas-liquid flow rate ratio.

In addition, the spray medium supplied from the spray medium hole is
It is ejected at an angle that crosses the liquid film of coal-water slurry. As a result, vibrations caused by turbulence caused by the high-speed flow of the spray medium are transmitted to the liquid film, and the turbulence of the liquid film atomizes the particles. Furthermore, since the high-speed spray medium crosses the liquid film, the liquid film can be effectively broken up by the momentum of the spray medium. When the spray medium is ejected parallel to the liquid film, atomization is mainly caused by the turbulent force applied to the liquid film, whereas when the spray medium is ejected at an angle that crosses the liquid film, the atomization is caused by the turbulence applied to the liquid film. The coal-water slurry is atomized using two forces: the force due to the momentum of the spray medium, and the force due to the momentum of the spray medium. Therefore, the average particle size of the coal-water slurry spray is not easily influenced by the flow characteristics of the coal-water slurry.

The spray media hole has an angle to the liquid film and
Furthermore, the hole is opened in the tangential direction of the inner wall of the mixing chamber and at an angle aimed at the end surface of the mixing chamber. The atomized medium ejected from the atomized medium hole opened at an angle aiming at the end face collides with the end face of the atomizer. At this time, the spray particles generated when the liquid film of the coal-water slurry and the spray medium came into contact with each other are entrained by the flow of the spray medium and violently collide with the end face of the atomizer, and are again reduced to fine particles by the force due to the momentum of the spray medium. It will be transformed into In other words, the spray medium ejected at an angle aiming at the end face collides with the end face of the atomizer, thereby promoting gradual atomization of the coal-water slurry and dispersing it into the combustion chamber as extremely detailed atomized particles. It can be done. Further, the spray medium forms a swirling flow within the mixing chamber, collides with the end face of the atomizer, and is ejected into the combustor. Thereby, the atomizing medium ejects from the atomizer in a swirling flow after using its own energy to promote effective atomization, which can reduce the particle velocity of the atomizer faster than in conventional atomizers. ,
The ignitability of the coal-water slurry spray particles can be improved.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. FIG. 1 is a cross-sectional view of an example of an atomizer according to the present invention. FIG. 6 is a side view of the atomizer of FIG. 1. The atomizer of this embodiment includes a spray medium supply pipe 11, a coal-water slurry supply pipe 12 serving as liquid fuel, an atomizer body 13, a spray medium flow path 14,
It consists of a mixing chamber 15, two nozzle tips 16 and 18, two nozzle tip holders 17 and 19, and a nozzle tip mounting seat 20. The atomizer body 13 has a nozzle tip mounting seat 20 within the cylindrical grain passage in the center. Coal water slurry supply pipe 12 (first flow path)
The coal water slurry supplied to the atomizer main body 13 passes through the outer periphery of the nozzle tip mounting seat 20 provided at the center of the atomizer main body 13 and a cylindrical flow path formed on this outer periphery, and then enters the mixing chamber 15 (an annular second flow path). (road). The mixing chamber 15 mixes the coal-water slurry supplied to the atomizer main body 13 and the spray medium well, and then sprays the coal-water slurry into the combustor (not shown) from an annular jet hole opened on the downstream side. It releases.

The spray medium is supplied to the atomizer body 13 through an annular flow path formed by a coal-water slurry supply pipe 12 provided in the spray medium supply pipe 11 .
Thereafter, the atomizing medium is supplied into the mixing chamber 15 via the atomizing medium channel 14 in the atomizer body 13 .
At this time, the spray medium flow path 14 is sprayed at an angle that is tangential to the inner wall of the mixing chamber 15 and aims at the end surface defined by the inner wall of the mixing chamber 15 and the outer surface of the atomizer on the side where the spray is emitted.

Mixing chamber 1 with coal water slurry particles sprayed at high speed
The wall surface of the mixing chamber 15 has a ceramic nozzle tip 16 and
It is protected by a nozzle tip 18. The nozzle tip 18 protects the outer wall surface of the annular mixing chamber 15 and is attached to the atomizer body 13 with a nozzle tip holder 19. On the other hand, the nozzle tip 16 protects the inner wall surface of the annular mixing chamber 15 and is attached to the atomizer body 13 with a nozzle tip holder 17.

The cross-sectional shape of the nozzle tip 16 is not limited to a circular shape, but may be square, asymmetrical, etc., and the end surface may be arbitrarily selected from a cylindrical surface, a convex surface, a concave surface, a conical surface, etc. depending on the purpose. can. Another example of a nozzle tip is a nozzle tip 26 with one end shaped like a truncated cone, as shown in FIG. In this case, the ratio of the diameter d ₁ of the truncated cone on the combustor side and the diameter d ₂ on the upstream side of the atomizer, and Depending on the length of the truncated cone and the ejection speed of the spray medium, the nozzle tip 18
The distance h between the outer edge of the nozzle tip 26 and the outer edge of the nozzle tip 26
is selected so that the flow velocity of the spray medium at the outer end of the nozzle tip 26 is maximum, and is used as a collision plate for spray particles. The vibration energy of compression and expansion can be effectively used for re-atomization of coal-water slurry particles. At the same time, as shown in FIG. 6, by ejecting the spray particles in a direction with a certain angle from the central axis of the atomizer, a circulating flow is formed downstream of the nozzle tip 26, and the particle velocity of the spray is is less than 100 m/s at a point three times the diameter of the nozzle tip 18, which is reduced to 1/2 to 1/3 compared to conventional Y-jet type atomizers. The synergistic effect of this reduction in spray particle velocity and the formation of a circulating flow promotes radiation and convection heat transfer from the flame to the spray particles, increasing the evaporation time of water contained in the coal-water slurry and the ignition of the coal-water slurry particles. The required distance is reduced and a stable flame can be formed with no flame lift from the burner.

FIG. 3 is a sectional view of an example of an atomizer according to the present invention, and shows a case where there is one mixing chamber. The atomizer of this embodiment includes a spray medium supply pipe 11, a coal water slurry supply pipe 12, an atomizer main body 13, a spray medium channel 14, a mixing chamber 15, a nozzle tip 18, a nozzle tip holder 19, a coal water slurry nozzle 31, and a spray medium chamber 32. Consisting of The cylinder arranged at the center of the atomizer is an atomizing medium supply pipe 11 that supplies an atomizing medium. The annular flow path constituted by the spray medium supply pipe 11 as an inner pipe and the outer pipes arranged concentrically is a coal water slurry supply pipe 12 that supplies coal water slurry. An atomizer main body 13 is located downstream of the spray medium supply pipe 11 and the coal water slurry supply pipe 12 . The center of the atomizer body 13 has a cylindrical atomizing medium chamber 32 whose one end is connected to the atomizing medium supply pipe 11 .
The disc at one end of the downstream side has a plurality of atomizing medium holes 14.
has. The atomizing medium holes 14 are arranged in at least one concentric circle.

The coal-water slurry passes through the atomizer body 13 and reaches the coal-water slurry nozzle tip 31 in a gap formed by the nozzle tip 18 and a disk at one end of the downstream side of the spray medium chamber 32.

Here, the spray medium supplied from the spray medium hole 14 and the coal water slurry supplied from the coal water slurry nozzle tip 31 are well mixed in a cylindrical mixing chamber 15 with one end open located at the center of the atomizer. Ru. One open end of the mixing chamber 15 is a spray hole for discharging the spray particles of the coal-water slurry to the combustor side. Further, the spray medium hole 14 is installed at an angle such that the spray medium 14 forms a swirling flow within the mixing chamber 15 and aims at the outer end face of the mixing chamber. In this example, the radius of gyration (hereinafter referred to as
(referred to as virtual circle diameter) is 1/4 to 1/4 of the inner diameter of the mixing chamber.
At 1/1, the angle aimed at the outer end face of the mixing chamber is
The average particle size of the spray could be reduced under the conditions of 15° to 80° to the central axis of the atomizer.

Further, the nozzle tip 18, which forms the cylindrical outer wall of the mixing chamber 15, is made of a highly wear-resistant material such as ceramic to prevent wear of the atomizer due to high-velocity spray particles. Nozzle tip 18
is the atomizer body 13 with the nozzle tip presser 19.
installed on.

Further, the spray medium is ejected into the mixing chamber in a swirling flow and at an angle aimed at the outer end face of the mixing chamber. Therefore, since the spray medium flows evenly on the cylindrical inner wall of the mixing chamber 15, the mass flow ratio of the spray medium and the coal-water slurry can be made equal within the mixing chamber 15, and local coarse spray particles can be reduced. Generation can be prevented. In addition, this swirling flow is also stored within the combustion chamber, forming a recirculating flow downstream of the atomizer, promoting radiant and convective heat transfer from the flame to evaporate the water in the coal-water slurry spray particles. This contributes to shortening the time required for acceleration and ignition.

Furthermore, since the spray medium violently collides with the outer end face of the mixing chamber 15, it is effective in re-atomizing the spray particles.

The arrangement of the spray medium channels 14 is not limited to a circular shape, but may be arbitrarily selected depending on the purpose, such as at least double concentric circles, or the inner and outer spray medium jet holes rotating in forward and reverse directions. I can do it. Another example of the atomizing medium flow path is a double concentrically arranged atomizing medium flow path 41 as shown in FIG. The atomizing medium supplied to the central and peripheral atomizing medium holes can be controlled independently. For example, when spray combustion is performed under low load by reducing the supply amount of coal-water slurry, the spray medium is supplied only from the spray medium holes in the outer periphery. This operation allows the coal-water slurry to be sprayed without extremely reducing the spraying speed of the spraying medium, so it is possible to increase the spray particle size at low loads and to control the mass flow rate of the coal-water slurry, which is common with general atomizers. Coal-water slurry can be successfully combusted without problems such as an increase in the ratio of mass flow rates of the media. Another example is to vary the ejection angle of the peripheral and central atomizing media holes. At this time, by changing the ratio of the atomizing medium flow rate between the outer circumference and the center, the swirling strength within the mixing chamber 15 can be increased or decreased, and the trajectory of the atomized particles ejected from the atomizer can be controlled to suit the combustion conditions.

Another example of a coal-water slurry nozzle is a coal-water slurry nozzle, as shown in FIG. 5, which is equipped with a so-called swirler 51 that generates a swirling component in the flow of coal-water slurry inside the nozzle. The rotation direction can be either normal or opposite to the rotation direction of the spray medium. For example, if a coal-water slurry nozzle is used in a direction opposite to the swirling direction of the spray medium, the relative speed between the jetting speed of the coal-water slurry and the jetting speed of the spraying medium will increase, and the coal-water slurry and the spraying medium will mix. becomes even more intense. Therefore, the average particle size of the spray particles can be further reduced.

Although the above description has been made regarding an atomizer intended for coal water slurry, the present invention is not limited thereto, and can also be used as a conventional atomizer for coal/oil slurry.

〔Effect of the invention〕

According to the present invention, it is possible to reduce local changes in the air flow rate ratio, so the average particle size of the spray can be reduced to about 50%, which is 4/5 to 2/3 compared to conventional atomizers.
~100 μm. In addition, it is possible to generate atomized particles that are less affected by the flow characteristics of liquid fuels containing solid particles, so there is a wider selection of liquid fuels that contain solid particles, and it is necessary to use a combustion method that is compatible with the flow characteristics of the fuel. There is no effect.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a first embodiment of the atomizer of the present invention, Fig. 2 is a longitudinal sectional view showing another embodiment of the atomizer of the invention, and Figs. 3 to 5 are sectional views of the atomizer of the present invention. FIG. 6 is a longitudinal sectional view showing each embodiment, and FIG. 6 is a side view of the atomizer shown in FIG. 1. DESCRIPTION OF SYMBOLS 11... Spray medium supply pipe, 12... Coal water slurry supply pipe, 13... Atomizer main body, 14... Spray medium channel, 15... Mixing chamber, 16... Nozzle tip, 17... Nozzle tip holder, 18... ...Nozzle tip, 20...Nozzle tip mounting seat, 26...
... Nozzle chip, 31 ... Coal water slurry nozzle,
32... Spray medium chamber, 41... Spray medium flow path, 5
1... Coal water slurry nozzle.

Claims (1)

[Scope of Claims] 1. A combustion device equipped with an atomizer that mixes and ejects a liquid fuel containing solid particles and a spray medium, wherein the atomizer converts the liquid fuel containing solid particles into an annular flow to form the solid particles. a liquid film forming means for forming a liquid film of liquid fuel containing particles; and a liquid film forming means for forming a liquid film of liquid fuel containing particles, and causing the spray medium to be ejected obliquely toward the exit direction in the vicinity of the atomizer outlet nozzle to collide with the liquid film to contain the solid particles. 1. A combustion device for liquid fuel containing solid particles, characterized in that it has an atomization means for atomizing liquid fuel. 2. A combustion device for liquid fuel containing solid particles according to claim 1, characterized in that the atomization means is configured to eject the atomizing medium so as to collide with the end face of the atomizer outlet nozzle. 3. According to claim 1, the fine particles eject the spray medium tangentially to the inner peripheral surface of the annular flow of the liquid fuel containing the solid particles to give a swirling flow to the annular flow. 1. A combustion device for liquid fuel containing solid particles, characterized in that it has a means for oxidizing. 4. In claim 1, an expanding part is provided near the atomizer outlet nozzle for expanding and discharging the liquid fuel containing the solid particles atomized by the collision of the atomizing medium. A combustion device for liquid fuel containing solid particles, characterized in that: