JPS6233214A - Coal water slurry atomizer - Google Patents

Abstract

PURPOSE:To reduce the mean particle diameter of spray, reduce the particle speed of slurry spray of coal water and provide a flame stability as well as a low NOx by a method wherein a pipe for supplying coal slurry is arranged at a center of an atomizer for atomizing the slurry of coal water with spray medium such as steam and then the spray medium is injected at a high speed with a specified angle. CONSTITUTION:An atomization and mixing chamber 14 for mixing slurry of coal water and spray medium is installed at the downstream side of a coal water slurry supplying pipe 16. An inner wall of the atomization and mixing chamber has a spray medium flow passage 15 opened in a tangential direction of the inner wall and at an angle forming an end surface of atomizer of a crossing point between the inner wall of the injection and mixing chamber and a side surface faced to a point where the atomization of the atomizer is discharged. A ceramic body 12 is attached to an extremity end of the injection and mixing chamber in order to prevent a nozzle chip from being worn out. Coal water slurry is pulverized into fine particle at first under a high speed circulation force, resulting in making the high speed injection particles; then, the slurry may be struck against the end surface of the atomizer. At this time, mainly the rough particles of the spray particles are pulverized again under their striking forces: the spray particles are pulverized and further they are dispersed and injected. As a result, a stable combustion is carried out just after the dispersed flow of spray is injected from the atomizer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an atomizer for atomizing coal-water slurry, and particularly to an atomizer for atomizing coal-water slurry using a spraying medium such as high-pressure air or steam. Regarding the atomizer.

(Background of the Invention) As a new coal combustion method to replace pulverized coal combustion, combustion of coal-water slurry, which is a mixture of pulverized coal and water, is used in coal boilers.Coal-water slurry is.

Coal can be supplied to the burner using a pump in the same way as conventional petroleum-based fuels, which provides transportation advantages such as easier flow control and smaller fuel piping diameters compared to pneumatic conveyance of pulverized coal. There is. Also, when considering coal water slurry as a fuel for boilers, it is necessary to increase the calorific value of the fuel.
High-concentration coal-water slurry in which the concentration of coal contained in the coal-water slurry is increased to 62 to 70% is used as fuel for boilers.

In order to combust 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 atomizer has a two-fluid injection valve that uses air or steam as the injection medium and uses the kinetic energy of the gas to atomize the coal-water slurry into minute particles.

The average particle size of the spray from a two-fluid injection valve is generally 200
The average particle size of pulverized coal is ~300 μm, which is significantly increased compared to 40 to 70 μm, and the particle velocity of the spray particles is several to several tens of times higher than that of pulverized coal, resulting in an increase in NOx and unstable ignition. There are problems such as compatibility. Attempts have been made to create an atomizer that solves these problems by reducing the average particle size of the spray and significantly reducing the particle velocity of the spray particles compared to conventional atomizers such as the Y-jet atomizer. As a two-fluid atomizer, for example,
As shown in Japanese Patent Application No. 8-179714, an atomizer is known in which an atomizing medium supply hole is provided that opens in the tangential direction of the inner wall of a linearly extending coal-water slurry channel. This atomizer is a method of forming a mist by the swirling force of the atomizing medium. This method is advantageous in that it significantly reduces the particle velocity of the spray particles. However, there is a problem in that the coal-water slurry is discharged from the atomizer spout without being atomized. This is due to the fact that although the high-speed spray medium and the coal-water slurry come into contact to form spray particles, the spray particles coalesce again in the nozzle to form coarse particles. Even if coarse particles are formed, the combustion time of a single droplet is generally shorter than that of coal-water slurry, so the amount of unburned matter at the furnace outlet is unlikely to increase. However, the atomized particles of coal-water slurry are It is a composite of coal particles, and compared to the combustion process of petroleum-based fuels, the evaporation process of water and the combustion process of char in the coal particles are added, so the generation of coarse particles results in an increase in unburned content. Therefore, the generation of coarse particles is an important problem that must be solved in order to achieve good combustion of coal-water slurry spray particles.

jAlso, a jetting hole for the spray medium is provided in the middle of the coal-water slurry flow path extending linearly, and the jetting hole forms a certain angle with the central axis of the coal-water slurry flow path.

An atomizer is known in which an ejection hole and a central axis of a coal-water slurry flow path are on the same plane. This type of atomizer can prevent the formation of the aforementioned coarse particles by increasing the ejection speed of the atomizing medium. However, in this method, the spray particles are Loom/s~300m/
The problem arises that it erupts at s. High-velocity spray particles destabilize the flame. Therefore, in a combustion device in which this type of atomizer is attached to a burner, powerful swirling of combustion air,
Alternatively, it is essential to stably hold the flame with a flame holding plate. However, this type of flame stabilization promotes the mixing of coal-water slurry spray and combustion air near the burner, so the control of the air ratio distribution near the burner is reversed and the NOx concentration increases. There is a problem with doing so.

[Purpose of the invention]

The purpose of the present invention is to effectively reduce the coarse particles produced during atomization of coal-water slurry, reduce the average particle size of the spray, reduce the particle velocity of coal-water slurry atomized particles, and improve the flame stability. The purpose of the present invention is to provide an atomizer that achieves low NOx emissions.

[Summary of the invention]

A feature of the present invention is that a supply pipe for supplying coal-water slurry is placed in the center of the atomizer, and the spray from the atomizer is emitted in the tangential direction to the inner wall of the spray mixing chamber provided downstream of the supply pipe, and to the inner wall of the spray mixing chamber and the atomizer. The injection hole for the spray medium is provided at an angle that aims at the end face of the atomizer, which is the intersection of the surfaces on the side where the spray is applied, and the coal-water slurry is improved by the swirling force of the spray medium and the collision force when it collides with the end face of the atomizer. It has an atomizer structure that atomizes the particles.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a sectional view of an example of an atomizer according to the present invention. The atomizer of this embodiment includes a nozzle tip 11, a ceramic body 12, and a ceramic cover 13.

The nozzle tip 11 has a coal water slurry supply pipe 16 in the center.
have. On the downstream side of the coal water slurry supply pipe there is a spray mixing chamber 14 for mixing the coal water slurry and the spray medium. The inner diameter of the spray mixing chamber is suitably between 4 m and 16 m+. The inner wall of the spray mixing chamber has a spray medium channel 1 opened at an angle that is tangential to the inner wall and aims at the atomizer end face at the intersection of the inner wall of the spray mixing chamber and the side surface facing the place where the atomizer emits the spray.
5, the diameter of the spray medium flow path 15 is suitably 0.8 to 3 mm. Further, at the tip of the spray mixing chamber, a ceramic body 12 is attached to the nozzle tip by a ceramic cover 13 in order to prevent the nozzle tip from being worn out by coal-water slurry spray particles colliding at high speed. The ceramic body must be made of a material with excellent abrasion resistance, such as silicon nitride, carbon nitride, or alumina, and must not show any deterioration in performance even when used continuously. Further, the ceramic force bar 13 is attached for the purpose of protecting the ceramic body from falling off, flame radiation, etc.

FIG. 2 is a view from the ■-■ arrow in FIG. 1. As shown in FIG. 2, the jetting medium flow path 15 is provided in a direction tangent to the circular inner wall of the mixing chamber 14. As shown in FIG.

Now, the spray medium G passes through the spray medium flow path 15 provided in the nozzle chip 11 and becomes a high-speed airflow into the spray mixing chamber 14.
The coal water slurry spouted to the coal water slurry supply pipe 16
is supplied to the mixing chamber 14 by. The coal water slurry fed into the mixing chamber mixes well with the high velocity atomizing medium G.

At this time, the spray medium has swirling energy and collision energy to collide with the end face of the atomizer. Therefore, the coal-water slurry is first atomized by high-speed swirling force and becomes high-speed spray particles that collide with the end face of the atomizer. At this time, the collision force mainly re-atomizes the coarse particles in the spray particles,
Refine the spray particles.

As a result of being able to receive the swirling force of the spray medium, the spray particles have a swirling speed and are ejected in a dispersed manner.

A typical part of the flow of dispersed spray particles is the flow shown in Figure 1.0 part A1 is the flow that collides with the nozzle edge and is dispersed, and the majority of the spray particles follow this flow. The variance according to is.

Generally called a holocone. The spray angle defined by α in FIG. 1 was approximately 80'' in this example.
As the pressure decreases in the center of the swirling flow of atomized particles, part A2 of part A1 is drawn inward.Part A2 is heated and decomposed by subsequent particulates from the atomizer due to the combustion gas recirculation effect. , and the combustion of the dispersed spray flow immediately after being ejected from the atomizer can be stably performed.

Angle θ between the spray medium supply path 15 and the central axis of the atomizer
Figure 3 shows the results of the experiment.

In the experiment, the gas-liquid flow rate ratio defined by the ratio of the spray medium to the spray medium was 0.1, and the supply amount of coal water slurry as the spray medium was 100.
The test was conducted under the condition of kg/h. The diameter of the spray medium flow path at this time was 1 m. The spray particle diameter was measured by a reception method in which the spray particles 1.3 m downstream of the atomizer were collected with silicone oil applied onto a preparation.

In order to avoid the coalescence of spray particles that occurs when performing the catching method, a rotating shutter was used to collect the spray particles.
The particle size was measured using a combination of photography and a microscope, magnifying the particles 100 times. Further, as the average particle diameter, the body surface area average particle diameter d3m defined by the ratio of the sum of squares of particle diameters and the sum of squares was used. As is clear from the results in FIG. 3, it can be seen that the angle θ of the spray medium flow path is reduced favorably between 30° and 60°. It is generally said that the maximum particle size of the spray is two or two times the average particle size of the spray. Furthermore, it is known that coal-water slurry spray particles having a spray particle diameter of 500 μm or more are discharged without being completely burned in a furnace with a residence time of about 3 seconds. Therefore, in order to reduce the unburned content in the ash, the average particle size of the spray needs to be 170 to 250 μm. In order to form a spray suitable for combustion, it is suitable that the angle 0 of the spray medium flow path is 30 to 60 degrees.

It can be seen that the atomizer of this example can effectively turn the coal-water slurry into fine spray, and that the optimum spray for combustion can be obtained when the angle θ of the spray medium flow path is 30 to 60°.

A second embodiment will be explained with reference to FIG. FIG. 4 is a sectional view of an atomizer according to a second embodiment of the present invention. The atomizer of the second embodiment includes a nozzle tip 11, ceramic bodies 43, 44, and a ceramic cover 13. The nozzle tip 11 has a coal water slurry supply pipe 16 in the center. Downstream of the coal water slurry supply pipe 16 is a spray mixing chamber 41 that mixes the coal water slurry and the spray medium G1. Downstream of the spray mixing chamber 41 is a spray mixing chamber 42 that mixes the coal water slurry and the spray medium G2. The inner diameter of the spray mixing chamber 42 is larger than the inner diameter of the spray mixing chamber 41. The spray mixing chamber 41 has a spray medium flow path 45 for discharging the spray medium G1. The spray medium flow path 45 is provided in the tangential direction of the inner wall of the spray mixing chamber 41 and at an angle aimed at the downstream end surface 47 of the spray mixing chamber 41 . Furthermore, a ceramic body 43 is attached to the inner wall of the spray mixing chamber 41 in order to prevent the nozzle tip from being worn out by the coal-water slurry spray particles colliding at high speed. The spray mixing chamber 42 has a spray medium channel 46 for discharging the spray medium G.

The spray medium flow path 46 is tangential to the inner wall of the spray mixing chamber 42;
Moreover, it is provided at an angle aimed at the end face 48 on the downstream side of the spray mixing chamber 42 . Furthermore, the inner wall of the spray mixing chamber 42 is
A ceramic body 44 is attached for the purpose of preventing the nozzle tip from being worn out by coal-water slurry spray particles that collide at high speed. The ceramic body 44 is attached to the nozzle tip with a ceramic cover 13 which also serves to prevent flame radiation.

FIG. 5 is a view from the ■-■ arrow in FIG. 4. Spray medium channel 4
6 is opened in a direction in contact with the inner wall of the spray mixing chamber 42. FIG. 6 is a view taken along the line VI-VI in FIG. 4. The spray medium flow path 45 is opened in a direction in contact with the inner wall of the spray mixing chamber 41 .

Now, the spray medium G2 passes through the spray medium channel 45 and is ejected into the spray mixing chamber 41 as a high-speed airflow.

At this time, the spray medium G1 primarily atomizes the coal water slurry by the swirling force and the kinetic energy when colliding with the end face 47. The atomized coal water slurry is led to the spray mixing chamber 42 and mixed with the spray medium G2.

The spray medium G applies swirling force and collision force against the end face 48 again to the atomized coal-water slurry particles, thereby effectively re-atomizing the coarse particles.

The shape of the spray medium flow path 45 is not limited to the shape shown in FIG. 4, and the same effect can be obtained with the shape shown in FIG. 7. In FIG. 7, the spray medium G1 is opened at an angle aimed at the end face 48. In FIG.

The spray mixing chamber 14 has a simple cylindrical shape. The ratio of the total cross-sectional area of the spray medium flow path 45 to the total cross-sectional area of the spray medium flow path 46, the distance Q1 from the end surface 48 of the atomizer to the injection hole for the spray medium G1, and the distance from the end surface 48 to the injection hole for the spray medium G2. If the distance @Q□ is selected so that the current of the spray medium to be input is maximized, the swirling energy of the spray medium and the collision energy when colliding with the end face can be effectively used to re-atomize coarse particles. can be carried out effectively. FIG. 8 is a diagram showing the particle size distribution of sprayed particles and an example of the effect of re-atomization of coarse particles. The experiment was conducted under the conditions that the gas-liquid flow rate ratio was 0.124 and the coal-water slurry supply rate was 300 kg/h. The spray particle size was measured by the reception method.

A curve 81 is the weight distribution before adjustment, and a curve 82 is the weight distribution of the spray when optimized. At this time, the ratio of the total cross-sectional area of the spray medium flow rate 45 to the total cross-sectional area of the spray medium 46 is 1
6 to 75, and the distance Q□ and Q□ are standardized by the inner diameter d of the coal water slurry supply pipe, which is the ratio Q1/a to D z / d.
was 1-F. As can be seen from FIG. 8, it can be seen that the optimized atomizer of the second embodiment can effectively re-atomize coarse atomized particles.

In the atomizer of the second embodiment, the atomization performance can be further improved by selecting different substances for the spray media G1 and 02. For example, if a material is selected that causes an exothermic reaction when the spray media G1 and G2 come into contact with each other, heating of the coal water slurry will occur when the spray media G1 and G2 are well mixed in the spray mixing chamber, and the coal water slurry will be heated. The viscosity decreases and the average particle size of the spray decreases.

Moreover, the angles θ1 and 02 that the spray medium supply paths 45 and 46 make with the central axis of the atomizer are determined to be between 30° and 60° based on various experiments.
has the effect of reducing the average particle size of the spray.

A third embodiment will be explained with reference to FIG. FIG. 9 is a sectional view of the atomizer of the present invention. The atomizer of the third embodiment includes a nozzle tip 91, a ceramic body 96, 98,
The zero atomizer consisting of a ceramic cover 97 and a spray medium supply pipe 92 has a spray medium supply pipe 92 that supplies the spray medium G2 in the center, the spray medium supply pipe 92 is an inner tube, and the nozzle tip 91 is in the center. The annular flow path having the provided circular pipe as an outer pipe is a coal water slurry supply pipe 95 that supplies coal water slurry. The nozzle tip 95 has a spray medium flow path 93 that supplies the spray medium G1. The spray medium flow path 93 is
The spray medium supply pipe 92 is provided at an angle that is tangential to the outer pipe of the coal water slurry supply pipe 95 and aims at the downstream end surface 99 of the inner pipe of the coal water slurry supply pipe 95. It has an atomizing medium flow path 94 that supplies . The spray medium flow path 94 is provided at an angle aimed at the downstream end surface 100 of the outer pipe of the coal water slurry supply pipe 95 .

Furthermore, the downstream end face 99.1 of the coal water slurry supply pipe 95
Ceramic bodies 96 and 98 are attached to 00 in order to prevent wear due to coal-water slurry spray particles colliding at high speed. A ceramic body 96,98 is attached to the nozzle tip by a ceramic cover 97.

Now, the spray medium G□ passes through the spray medium flow path 93 and becomes a high-speed airflow and is ejected into the coal water slurry supply pipe 95. At this time, the spray medium G1 atomizes a part of the coal water slurry by the rotation energy and the collision energy when colliding with the end face 99, and makes it into a spray state. At this time, the ejection direction of the atomized dispersed flow is changed by the end face 99, resulting in a flow A1 shown in FIG. 9. The dispersion flow A is rapidly decelerated by the circulation flow generated on the downstream side of the ceramic body 98. On the other hand, the spray medium G2 atomizes a part of the coal-water slurry by the collision energy when it collides with the end face 100 and turns it into a spray state. The atomized dispersion is shown in FIG.
8 flows around the outer periphery of the dispersed flow A1. Therefore, the atomizer of the third embodiment has a wide spray angle of 40'' to 80'' and performs Gaussian-type spray in which the maximum of the spray flow rate distribution is located on the central axis of the atomizer. Also,
The maximum value of the flow velocity distribution in the direction of the center axis of the atomizer at any point apart in the direction of the center axis of the atomizer is 173 to 1/2 that of a single-hole Y-jet type atomizer. As a result, when the atomizer of the third embodiment is attached to a burner, the ignition position of the flame can be moved much closer to the burner side than in the case of a conventional Y-jet type atomizer. Furthermore, since the center of the flame can be easily maintained in a NOx reducing atmosphere, even lower NOx combustion can be achieved.

〔Effect of the invention〕

According to the present invention, the ignition position of the flame is moved closer to the burner side,
It has the effect of increasing the combustion rate and achieving low NOx combustion.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of the dispersion of the spray from the atomizer according to an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along the ■-■ arrow in Fig. 1, and Fig. 3 is the average particle diameter of the spray from the atomizer shown in Fig. 1. FIG. 4 is an explanatory diagram of the dispersion of the spray of the atomizer of the second embodiment, and FIG.
- ■ A view in the direction of the arrow, Figure 6 is a sectional view in the direction of the Vl-VI arrow in Figure 4,
FIG. 7 is an explanatory diagram of the atomizer spray of a modification of the second embodiment, FIG. 8 is a characteristic diagram showing the particle size distribution of the atomizer spray of the second embodiment, and FIG. 9 is a diagram of the third embodiment. FIG. 3 is an explanatory diagram of the dispersion of the spray of an example atomizer. 11... Nozzle chip, 12... Ceramic body. 13...Ceramics cover, 14. Risen WaX joint room, Fig. 2, porridge 3, street sister body year road n horse jun button I particle outside d (μ turtle).

Claims (1)

[Scope of Claims] 1. In an atomizer that atomizes coal water slurry with an atomizing medium such as steam, a supply pipe for supplying the coal slurry is disposed in the center of the atomizer, and a supply pipe is provided downstream of the supply pipe. , an angle tangent to a circle of a certain radius drawn on a cross section orthogonal to the central axis of the atomizer of the spray mixing chamber, and an intersection of the inner wall of the spray mixing chamber and the surface of the atomizer on the side where the spray is emitted. A coal-water slurry atomizer characterized in that the spray medium is ejected at high speed at an angle aimed at an end face of the coal-water slurry atomizer. 2. In the atomizer according to claim 1, two spray medium flow paths for spouting the spray medium are provided in the flow direction of the coal-water slurry, and the first spray medium flow path on the upstream side The method is characterized in that the atomizing medium ejected from the channel at high speed is mixed, and the atomizing medium is ejected at high speed from a second atomizing medium flow path provided downstream of the first atomizing medium flow path. Coal water slurry atomizer. 3. In the atomizer according to claim 1, a spray medium supply pipe for supplying the spray medium is disposed in the center of the coal water slurry supply pipe, and an outer peripheral part of the coal water slurry supply pipe is provided. and the second spray disposed at an angle that aims at the end face of the intersection of the inner wall of the coal water slurry supply pipe and the surface of the atomizer on the side of the spray discharge location in the spray medium supply pipe. A coal-water slurry atomizer characterized by the atomizing medium ejected from a medium flow path at high speed.