JPH0251088B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a slag tap type cyclone combustion furnace (hereinafter referred to as a This invention relates to improvements to slag tap furnaces.

(Prior Art) When solid combustible materials containing a large amount of ash, such as sewage sludge or pulverized coal, are burned, a large amount of fly ash is generated. This fly ash must be captured and removed because it may adhere to the boiler heat transfer surface and interfere with heat conduction or cause air pollution. However, if this atsushi is taken out in a dry state, it has no other useful use and must be thrown away.
As the amount of waste increases year by year, there is a new problem: finding a place to dump it. Therefore, it is being considered to recycle the ash into slag and use it as a building material. For example, if the ash obtained from sewage sludge is melted and turned into slag, almost no hexavalent chromium will be leached out, and it can be safely reused as cement aggregate, heat insulating material, etc.

Conventionally, quartz with a high ash content is crushed into pulverized coal and then burned in a slag tap furnace.
The ash is taken out in a molten state.

(Problem to be solved by the invention) However, this conventional cyclone combustion furnace 1
01, as shown in FIG. 1, slag is obtained by rapidly cooling molten ash with cooling water 102. As a result, the slag becomes brittle and crumbles with fine cracks. Moreover, since the molten slag flowing down from the slag tap opening is cooled as it is, the slag particles become rod-like or large-sized, and cannot be obtained as slag particles with a uniform particle size. Therefore, this water-cooled slag has no use other than being crushed into pieces of about 1 mm and used as a substitute for sand, etc., and has low commercial value.

In addition, in conventional slag tap furnaces, a cooling tank is connected to the slug tap opening, so the slug tap opening must be throttled to prevent the temperature inside the furnace from decreasing due to radiant heat loss and latent heat of evaporation of the cooling water. This is accompanied by the problem that the slug tap opening is constantly blocked when the machine is down.

SUMMARY OF THE INVENTION An object of the present invention is to provide a slag tap furnace capable of burning solid combustible materials containing a large amount of ash and recovering the ash as crystalline slag. Also,
It is an object of the present invention to provide a slag tap furnace capable of obtaining crystalline slag of uniform grain size, and a further object of the present invention is to provide a slag tap furnace in which there is no possibility of clogging of the slag tap opening during turndown.

(Means for Solving the Problems) In order to achieve the above object, the slag tap furnace of the present invention includes a slag cooling tank connected to the slag tap opening, and a slag cooling tank directly below the slag tap opening facing the slag tap opening. While installing a rotary plate, a cooling air injection port for forming a film of cooling air along the peripheral wall surface of the cooling tank is provided, and between the slug tap port and the cooling air injection port, the cooling air is passed through the slug tap port. An exhaust gas flow path is formed to suck in the exhaust gas immediately afterward and discharge it to the outside, and the molten slag in the furnace is dropped from the slag tap port onto the rotating disk, scattered around to form granules, and cooled by air. The surface of the slag is rapidly solidified by contact with the flow, and granular slag with only the surface solidified is taken out.

(Example) The configuration of the present invention will be described in detail below based on an example shown in the drawings.

FIG. 2 shows an embodiment of the slag tap furnace according to the present invention in a central vertical sectional view. This slag tap furnace includes a cyclone burner 2 that forms a swirling flame;
This is a vertical furnace consisting of a furnace body 1 that traps ash by forming a molten slag film on the lining wall, and a slag cooling tank connected directly below the furnace body 1.

The cyclone burner 2 carries solid fuel on a swirling flow of combustion air and centrifugally separates it into coarse particles and fine particles.
A swirling flame is formed that burns fine solid fuel in space while blowing coarse solid fuel toward the inner wall surface of the furnace body 1, and the solid fuel is injected along the flow of strongly swirling combustion air. . The burner 2 in this embodiment is arranged to swirl and inject fuel air from inside the powdered fuel supplied on transport air, and to supply fuel to the outside of the swirling air, that is, to the free vortex portion. There is. The fuel supplied to the free vortex portion of the swirling air is subjected to shearing force in the vortex flow, is divided into small pieces, and is quickly mixed with the combustion air. Therefore, particles with a small particle size burn in space within the free vortex, while particles with a large particle size are subjected to a violently accelerated swirling action by the swirling combustion air and scatter toward the inner wall of the furnace, forming a molten slag film. is captured and then burned under high furnace loads. In the figure, reference numeral 3 is an air nozzle that injects combustion air, 4 is a swirler, and 5 is a fuel nozzle that injects solid fuel.

The furnace body 1 has a cylindrical shape suitable for swirling of the flame, and its inner wall 6 is lined with a refractory lining 7. This refractory lining 7 is
It is cooled by a cooling fluid flowing through a flow path 9 between the inner wall 6 and the outer wall 8 to prevent it from collapsing due to spalling. As the cooling fluid, water, air, oil, or the like can be used, as in the case of cooling the upstream part of the furnace described above.

The outlet of the furnace body 1, ie, the slug tap port 10, is gradually narrowed in diameter. The diameter d of this slug tap port is determined by the diameter ratio d/D to the furnace inner diameter D, from the viewpoint of pressure loss and fly ash collection rate.
It is preferable to set it within the range of 0.2 to 0.5. Further, the length of the furnace body 1 is preferably set so that the l/D ratio with respect to the inner diameter D falls within the range of 1.5 to 3.5, in consideration of the amount of heat removed and the fly ash collection rate.

A slag cooling tank 11 is connected directly below the above-mentioned furnace body 1. This slag cooling tank 11 includes a rotary plate 12 located directly below the slag tap opening 10,
It has a cooling air injection port 14 that forms a film of cooling air along the peripheral wall 13. Further, an exhaust gas passage 15 is opened above the slag cooling tank 11, and is provided so that the exhaust gas from the furnace body 1 is discharged immediately after passing through the cooling tank 11. In the case of this embodiment, a duct/exhaust gas passage 15 is connected to a flange 16 at the bottom of the furnace body that connects the slag cooling tank 11 and the furnace body 1, and the exhaust gas immediately after being blown out from the furnace body 1 into the slag cooling tank 11 is Although it is provided so as to guide the exhaust gas to the exhaust gas cooling tower 17 outside the furnace, it is not limited thereto. For example, as in the system shown in FIG. 3, an exhaust gas passage 15 is formed integrally with the furnace body 1 to draw exhaust gas out of the furnace by passing near the slag tap port 10, and the opening faces the slag cooling tank 11. It may be provided. In any case, the exhaust gas flows out from the slag tap port 10 into the slag cooling tank 11 together with the molten slag, then makes a U-turn so as to lick the rotary plate 12, and is discharged to the outside of the tank without coming into contact with the cooling air near the peripheral wall. and separated from the molten slag.

The rotary plate 12 is installed at the center of the bottom of the cooling tank 11, and its support shaft 19 is rotatably supported by the bottom of the tank and the bearing 20 of the cooling tank support frame 18. The rotary plate 12 is connected to a drive motor 21 installed in the cooling tank 11 outside the tank,
Optimal rotation speed for granulation of molten slag, e.g.
It is rotated at 500 to 5000 rpm. Also, this rotating plate 1
A wind box 22 having a swirler 23 is provided between the shaft 19 of No. 2 and the cooling tank 11, and air is introduced from the outside and blown onto the back side of the rotary plate 12 to cool the rotary plate 12. ing. In addition, rotating plate 1
Since the material 2 comes into contact with the molten slag at approximately 1000 to 1300°C, any material may be used as long as it has heat resistance, corrosion resistance, and high temperature strength, but stainless steel is preferable, and a film on top of it is preferable. It is made of a coating of ein ceramics. The surface of the rotary plate 12 is preferably coated with oil or the like in order to eliminate wettability between the slag and the collision surface and promote granulation of the molten slag. Although the rotary plate 12 is formed of a flat disk, it may be formed into other shapes, such as a cup shape in some cases, to store the molten slag and scatter it by centrifugal force. Sometimes I do. The shaft 19 of the rotary plate 12 is sealed with a gland packing 24 to prevent exhaust gas from leaking from this portion.

Further, the cooling air injection port 14 that forms a film of cooling air, that is, an air curtain along the peripheral wall 13 of the slag cooling tank 11 is connected to the peripheral wall 13 of the annular wind box 26 installed in the upper connection tube 25 of the slag cooling tank 11. At least one continuous or intermittent annular slit is formed along the line. Of course, double
A more reliable air cooling layer can be achieved by providing triple slit-shaped annular injection ports 14 to form a plurality of cooling air films. This slit-shaped cooling air injection port 14 once straightens the air supplied from the blower 27 in the wind box 26 and then injects the air into the slag cooling tank 11 in an annular manner. The cooling air is preferably injected as a swirling flow. Thereby, the residence time of the slag particles in the cooling air is extended, and a surface cooling time sufficient to prevent the slag particles from fusing with each other or adhering to the peripheral wall 13 is obtained. In addition, the cooling air
In order to increase the cooling effect, it may contain slightly fine water droplets. However, the addition of water should be kept to a small amount because too much water causes rapid cooling, which is undesirable for obtaining crystalline slag.

In this case, in order to improve the thermal efficiency of the entire combustion system, the cooling air is circulated as shown in FIG. 3, and heat is recovered during the circulation.
That is, the air taken out together with the slag particles from the slag cooling tank 11 is separated from the slag particles in the cyclone 28, and then heat exchanged with water in the heat exchanger 29, and then sent to the cooling air injection port 14 again by the blower 27. Supplied. Of course, a part of the cooling air is discharged together with the exhaust gas from the exhaust gas passage 15 in the upper part of the cooling tank.

Furthermore, the slag cooling tank 11 has a peripheral wall 13 and a tank bottom 1.
3b, an annular trough 31 forming a part of the tank bottom, and a cooling air injection port 1.
4 and an upper connecting tube 25 having an exhaust gas passage 15. A water-cooling jacket 32 is provided on the circumferential wall 13 of the tank body 30 and the inclined tank bottom 13b, so that the wall surface is constantly cooled, suppressing a rise in the temperature inside the tank and making it difficult to solidify (cool) the slag solution. It is prevented. Further, an annular trough 31 is provided at the bottom periphery of the slag cooling tank 11 to collect slag grains 33 in one place and take them out of the tank. The trough 3
1 has water jackets 34 on both side walls through which cooling water circulates, and an air jacket 35 on the bottom through which cooling air flows. Further, the bottom of the trough 31 has an outlet 37 which is inclined downwardly toward the slag outlet 36 like a spiral staircase, and which opens slightly downstream at each step. Therefore, a portion of the cooling air flowing through the air jacket 35 is blown out along the trough bottom toward the downstream side, helping the slag grains 33 that have fallen into the trough 31 to move toward the slag outlet 36.

(Function) The slag tap furnace of the present invention configured as described above captures ash and recovers it as granular crystal slag in the following manner.

In the slag tap furnace 1, powdery solid combustibles containing a large amount of ash are quickly mixed with the combustion air by receiving a swirling force accompanied by shearing force in the free swirl portion of the combustion air, instantly burning the fine particles, and Coarse particles that cannot be burned in space are attached to the slag film on the furnace wall using centrifugal force and then burned. The coarse solid combustibles adhering to the slag film and the fine solid combustibles burned in space become ash through high-load combustion in the furnace, then melt and gradually flow down the furnace wall. On the other hand, the combustion gas passes through the slag tap port 10 together with the molten ash and is discharged to the outside of the furnace body 1, then makes a U-turn as if licking the rotary plate 12, and flows from the exhaust gas passage 15 opening into the slag cooling tank 11 to the cooling tower 17. is extracted. Therefore, since the slag tap opening 10 is constantly warmed by the combustion gas, the temperature does not drop below the melting temperature of the ash even if the combustion amount is reduced to 1/4. Therefore, the furnace can be operated over a wide range without clogging the slug tap port 7.

On the other hand, the molten slag directly below the slag cooling tank 11 falls onto the rotary plate 12 directly below the slag tap opening 10, becomes granular, and scatters around. At this time, the molten slag collides with the rotating plate 12, bounces back and becomes granular without being fused to the rotating plate 12.
That is, the molten slag that is heated by the exhaust gas and falls vertically onto the rotary plate 12 with no risk of fusion is turned 90 degrees at the collision surface and, together with the centrifugal force, flows along the collision surface and the surface of the rotary plate 12. The liquid spreads in the radial direction in a ring shape, and is further divided into droplets that are scattered around the area. Since the diameter of the slag droplet at this time depends on the head, the slag tap opening 10 and the rotating plate 1
A certain distance is required between the two.

The droplets of molten slag scattered from the rotating disk 12 enter a layer of cooling air formed along the peripheral wall 13 of the cooling tank 11 and are cooled. The air-cooled molten slag 33 solidifies only the surface, and the inside remains in a molten or semi-molten high temperature state.
The slag grains 33 whose surfaces have been cooled and solidified by the cooling air fall into the trough 31 at the bottom of the tank without fusing the grains together or adhering to the peripheral wall surface 13, and then spirally descending into the trough 31. The slag rolls on the bottom of the slag, is collected at the slag outlet 36, and is transferred to the cyclone 2.
Sent to 8th. The slag grains 33 separated from the cooling air and collected in the cyclone 28 are still in a molten or semi-molten state and are at a high temperature, so they are further slowly cooled, for example by air cooling, by stacking them in the open to cool the crystalline slag. obtain.

(Effects of the Invention) As is clear from the above description, the slag tap furnace of the present invention has a slag cooling tank connected to the slag tap opening, and a rotating circle placed directly below the slag tap opening and facing the slag tap opening in the cooling tank. While installing the plate, a cooling air injection port is provided to form a film of cooling air along the peripheral wall surface of the cooling tank, and the exhaust gas of the combustion furnace is passed through the slag tap port and then comes into contact with the cooling air stream. The molten slag in the furnace is made to fall from the slag tap opening onto the rotary plate, and is scattered around to form granules and is brought into contact with the cooling air stream. Since the surface of the slag is rapidly solidified and granular slag with only the surface solidified is recovered, by slow cooling, the slag can be recovered as crystalline slag and granular material of uniform particle size.

Furthermore, the present invention continuously warms the slug tap opening and the rotating disc by causing the exhaust gas to flow into the slag cooling tank from the slag tap opening together with the molten slag, making a U-turn as if licking the rotating disc just below the slug tap, and discharging it. Since the exhaust gas path is formed, even during turndown, the molten slag can flow down without blocking the slag tap port, and can be scattered on the rotating plate without being melted and solidified. Therefore, even during turndown, the fly ash can be recovered as crystalline slag grains of a constant grain size without causing clogging of the slag tap opening.

[Brief explanation of drawings]

FIG. 1 is a central vertical sectional view showing a conventional slag tap furnace, FIG. 2 is a central vertical sectional view showing an embodiment of the slag tap furnace according to the present invention, and FIG. 3 is a heat recovery system for the slag tap furnace according to the present invention. It is a schematic explanatory diagram showing an example incorporating. 1...furnace body, 2...cyclone burner, 10
...Slag tap port, 11 ...Slag cooling tank, 1
2... Rotating plate, 14... Cooling air injection port, 15...
...Exhaust gas flow path/exhaust gas duct, 33...Slag particles.

Claims (1)

[Claims] 1. A cyclone burner that places solid fuel on a swirling flow of combustion air, separates it into coarse particles and fine particles, and forms a swirling flame that combusts the fine solid fuel in space while blowing the coarse solid fuel toward the inner wall of the furnace body. A slag cooling tank is connected to the slag tap opening of a slag tap type cyclone combustion furnace, which is equipped with a high-fired furnace and forms a molten slag tap film on the furnace wall during high-fire furnace combustion, and traps the coarse solid fuel and fly ash in this film. , a rotary plate is installed directly below the slug tap opening in the cooling tank so as to face the slug tap opening, and a cooling air injection port is provided to form a film of cooling air along the peripheral wall surface of the cooling tank, An exhaust gas flow path is formed between the slag tap port and the cooling air injection port to suck the exhaust gas immediately after passing through the slag tap port and discharge it to the outside, and the molten slag in the furnace is transferred from the slag tap port onto the rotating disk. drop it on
A slag tap type cyclone combustion furnace characterized by scattering the slag around to form granules, rapidly solidifying the surface by contacting with a cooling air flow, and taking out the granular slag with only the surface solidified.