JP2001317722A - Method and device for preventing adhesion of dust - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably prevent adhesion of dust on the inner wall surface of an exhaust gas duct through which exhaust gas from a melting furnace is discharged. SOLUTION: A plurality of gas blowing pipes 25 are connected at equal intervals in the peripheral direction of an exhaust gas duct 10 and at equal intervals in a longitudinal direction on the outer peripheral surface of the exhaust duct 10 so that a gas flow is generated in a tangential line direction to the inner wall surface of the exhaust duct 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melting furnace for melting fly ash and incineration ash generated in a municipal solid waste incinerator, an industrial waste incinerator or the like, and an exhaust gas for discharging exhaust gas from the melting furnace. The present invention relates to a dust adhesion preventing method for preventing dust from adhering to an inner wall surface of a duct and an apparatus therefor.

[0002]

2. Description of the Related Art In recent years, in order to reduce the volume and detoxification of incineration residues and fly ash discharged from incinerators such as municipal solid wastes, attention has been paid to a method of melting and solidifying these incineration residues and the like. ing. Here, the melting and solidifying treatment method includes a method of melting and solidifying a material to be melted by electric energy using an arc melting furnace, a plasma arc furnace, an electric resistance furnace, and the like, a surface melting furnace, a rotating melting furnace, a coke bed furnace. There is a method of melting and solidifying the material to be melted by the combustion energy of the fuel, etc.When the power generation equipment is installed in the municipal waste incineration equipment, the former method using electric energy is often used .

In the melting furnace, a material to be melted containing metals such as iron and incombustible components such as glass and sand is heated to a high temperature exceeding its melting point to become a liquid molten slag having fluidity, It continuously overflows from the molten slag outlet and falls into the slag water cooling tank. On the other hand, due to the melting of the material to be melted, volatile components present therein and carbon monoxide generated by oxidation of carbon become gaseous (exhaust gas) and are discharged from the furnace top through an exhaust gas duct. After this,
The exhaust gas is sent from the exhaust gas duct to the combustion chamber, and the combustion air is added to the combustion chamber, whereby the unburned portion inside is completely burned. Further, the exhaust gas that has been completely burned is cooled by cold air or the like, and then discharged to a chimney by a draft fan through a bag filter.

Since the exhaust gas discharged from the melting furnace contains a large amount of volatile salts and low-boiling heavy metals, the temperature of the exhaust gas decreases to 400 to 7
When the temperature is in the temperature range of 00 ° C., the gaseous substance changes to solid dust having adhesiveness, and this solid dust adheres to the inner wall surface of the exhaust gas duct. As this deposit accumulates and grows, it becomes extremely difficult to remove it. Therefore, conventionally, the inner wall surface of the exhaust gas duct has been
In addition to cooling to a temperature of not more than ° C., dust adhered to the exhaust gas duct inner wall surface is regularly removed by a mechanical duct cleaning device.

[0005] As another method, an exhaust gas duct is connected to two ducts.
The inner pipe is made of a porous material such as ceramic, and a gas such as air or nitrogen is allowed to flow through a space formed between the inner pipe and the outer pipe. Methods are known in which a gaseous body flows through the body into the interior of the inner tube, thereby preventing dust from adhering to the surface of the inner tube.

[0006]

However, in the above-described method of cooling the inner wall surface of the exhaust gas duct, cooling the exhaust gas duct not only cools the exhaust gas to increase the dust concentration but also increases the dust adhesion. There is a problem in that the dust passes through the temperature range that changes into dust and the dust easily adheres and accumulates on the inner wall surface of the exhaust gas duct. Further, since the cleaning device used to remove dust adhering and accumulating on the inner wall surface of the exhaust gas duct is exposed to high temperatures, the operating frequency of the cleaning device is increased, and the life of the cleaning device is shortened. There is also a problem.

On the other hand, in the above-described method using a double-pipe exhaust gas duct, the inner pipe must be formed of a porous material over the entire length of the exhaust gas duct, and air or nitrogen or the like must be uniformly formed over the entire length of the exhaust gas duct. However, there is a problem that a large amount of gas is required because the gas needs to be blown out. Further, once dust is welded to the porous body, the porous body and the dust react with each other to promote erosion, or the porous body partially clogs, and the dust grows from the portion. Eventually, the exhaust gas duct will be blocked.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and is capable of reliably preventing dust from adhering to an inner wall surface of an exhaust gas duct for discharging exhaust gas from a melting furnace. It is an object of the present invention to provide an adhesion preventing method and an apparatus therefor.

[0009]

Means for Solving the Problems and Action / Effect To achieve the above object, a dust adhesion preventing method according to a first aspect of the present invention provides a method for preventing dust from adhering to an inner wall surface of an exhaust gas duct for discharging exhaust gas from a melting furnace. A method for preventing dust adhesion, wherein a gas inlet is opened in the exhaust gas duct so that a gas flow occurs tangentially to the inner wall surface of the exhaust gas duct, and gas is blown from the gas inlet. A gas film is formed near the inner wall surface of the exhaust gas duct, and the exhaust gas is collected at the center of the exhaust gas duct to flow.

According to the present invention, a gas inlet is opened in the inner wall surface of the exhaust gas duct through which the exhaust gas discharged from the melting furnace flows, and gas is blown tangentially to the inner wall surface from the gas inlet. Therefore, a gas film is formed near the inner wall surface of the exhaust gas duct by the injected gas, and the exhaust gas in the exhaust gas duct forms a spiral tornado and is collected at the center of the exhaust gas duct. At the downstream side. Therefore, it is possible to reliably prevent the solidified material such as the low-boiling substance in the exhaust gas from cooling and adhering to the inner wall surface of the exhaust gas duct. Fluctuations in exhaust gas volume,
When the fluctuation in the furnace pressure increases, even if a part of the dust in the exhaust gas diffuses and adheres to the vicinity of the inner wall surface of the exhaust gas duct, the dust can be easily removed using, for example, a mechanical cleaning device. . In this way, the frequency of operation of the cleaning device is extremely reduced, and an inexpensive configuration can be achieved.

Next, a dust adhesion preventing device according to a second invention is a dust adhesion preventing device for preventing dust from adhering to an inner wall surface of an exhaust gas duct for discharging exhaust gas from a melting furnace. A plurality of gas injection pipes are connected to the outer peripheral surface of the exhaust gas duct at equal intervals in the circumferential direction of the exhaust gas duct and at equal intervals in the longitudinal direction so that gas flow occurs tangentially to the inner wall surface. It is assumed that.

The present invention relates to an apparatus for realizing the dust adhesion preventing method according to the first aspect of the present invention, and has the same effect as the first aspect of the present invention. Further, since the gas injection pipes are arranged at regular intervals in the circumferential direction of the exhaust gas duct and at regular intervals in the longitudinal direction, the above-described effect of forming the gas film and the effect of forming the spiral tornado are more reliably exhibited. Thus, dust adhesion can be reliably prevented.

[0013] Next, in a third aspect based on the second aspect, each of the gas blowing pipes provided in the circumferential direction is arranged in a cross section orthogonal to a longitudinal direction of the exhaust gas duct. By doing so, the gas blown from each blow pipe applies a swirling force to the exhaust gas in the same plane.

According to a fourth aspect of the present invention, in the second aspect, each of the gas blowing pipes provided in the circumferential direction is arranged in a spiral shape as a whole by sequentially shifting the position in the longitudinal direction of the exhaust gas duct. It is. According to such an embodiment, the swirling force is continuously applied to the exhaust gas in different planes by the gas blown from each blowing pipe.

Next, a fifth aspect of the present invention is the liquid crystal display device according to any one of the second to fourth aspects, wherein each of the gas injection pipes is arranged in a direction perpendicular to an outer peripheral surface of the exhaust gas duct. It is. By doing so, a large amount of gas flow components in the circumferential direction of the exhaust gas duct can be imparted to the exhaust gas by the gas blown from each blow pipe.

According to a sixth aspect of the present invention, in any one of the second to fourth aspects of the present invention, each of the gas injection pipes is oriented in a flow direction of the exhaust gas with respect to a direction orthogonal to an outer peripheral surface of the exhaust gas duct. They are arranged at an angle. By doing so, the gas blown from each blowing pipe can provide a large amount of gas flow components in the gas flow direction to the exhaust gas.

Next, a seventh aspect of the present invention is the invention according to any one of the second to sixth aspects, wherein the gas introduced from the gas injection pipe is any one of air, nitrogen and recirculated gas. is there. As described above, the type of the gas introduced from the blowing pipe can be appropriately selected according to the use location, the temperature condition of the exhaust gas, and the like.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a specific embodiment of a method and apparatus for preventing dust adhesion according to the present invention will be described.
This will be described with reference to the drawings.

FIG. 1 shows an overall system configuration of a plasma melting furnace according to one embodiment of the present invention.

The present embodiment is applied to a direct current arc discharge graphite electrode type plasma melting furnace installed in a refuse incineration facility. In this plasma melting furnace, a melting furnace main body 1 is provided, and a container 2 is attached to the melting furnace main body 1, and a material to be melted (incineration residue, fly ash, etc.) 3 stored in the container 2 is supplied to the melting furnace main body 1. It is configured to be continuously supplied into the melting furnace main body 1 by a supply device 4 disposed below the container 2. The melting furnace main body 1 includes a graphite main electrode (-pole) 5 disposed on the furnace top and a furnace bottom electrode (+ pole) 6 disposed on the furnace bottom. The DC voltage (200 to 350 V) applied between the electrodes 5 and 6 causes the plasma arc current (1
000 to 3000 A) flows, thereby heating the material 3 to be melted in the furnace.

The main electrode 5 is formed in a hollow cylindrical shape, and nitrogen gas is continuously supplied from the nitrogen supply device 8 into the melting furnace body 1 through the hollow hole. By this nitrogen gas, the inside of the melting furnace main body 1 is kept in a reducing atmosphere, and oxidation of the main electrode 5 and the like is prevented.

The furnace bottom of the melting furnace main body 1 is air-cooled by cool air from a furnace bottom cooling fan 9, thereby preventing an excessive temperature rise near the furnace bottom electrode 6. Further, the melting furnace main body 1 itself is made of a refractory material that can withstand a high temperature of about 1800 ° C. and a heat insulating material covering the same. If necessary, an air-cooled or water-cooled jacket (not shown) is provided outside the heat-insulated material. Have been.

When the material 3 to be melted in the melting furnace body 1 is melted, volatile components present therein and carbon monoxide generated by oxidation of carbon become a gaseous substance, and this gaseous substance (exhaust gas) is deposited on the furnace top. The gas is introduced into the combustion chamber 11 through the first exhaust gas duct 10 from the outlet provided. On the other hand, the material to be melted 3 containing metals such as iron, and incombustible components such as glass and sand
Is about 1 ° C above its melting point (1200-1250 ° C).
The molten slag 7 is heated to a high temperature of 300 to 1600 ° C. and becomes a liquid molten slag 7 having fluidity. The molten slag 7 is supplied to a molten slag outlet 12 formed in the melting furnace body 1.
It overflows more continuously and is discharged to the slag yard 14 by the air-cooled slag conveyor 13.

When the melting furnace is stopped, the tapping hole 15 attached to the bottom level of the molten slag 7 drains the molten metal, and the waste discharged from the taphole 15 is discharged by the metal discharge conveyor 16. It is discharged to the metal yard 17.

The exhaust gas introduced into the combustion chamber 11 is
Unburned components inside are completely burned by the heated combustion air introduced from the hot blast stove 18. The exhaust gas which has been completely burnt passes through the second exhaust gas duct 19 and the cooling tower 20.
And cooled (water-cooled) in the cooling tower 20, and further into a third exhaust gas duct 21 and a bag filter 22.
After that, the air is discharged to the chimney 24 by the induction ventilator 23. The molten fly ash captured by the bag filter 22 is sent to a fly ash sump by a molten fly ash conveyor (not shown).

The melting furnace body 1 and the combustion chamber 11
Exhaust gas duct 10 and combustion chamber 11
The second exhaust gas duct 19 connecting the cooling tower and the cooling tower 20 has a problem that solid dust having adhesiveness adheres to the inner wall surfaces of the ducts, making it difficult to remove the dust.
In this embodiment, these exhaust gas ducts 10 and 19 are
(A) and (b). In the following description, the configuration of the first exhaust gas duct (hereinafter, simply referred to as “exhaust gas duct”) 10 will be described in detail, but the second exhaust gas duct 19 has the same configuration.

The exhaust gas duct 10 of the present embodiment is formed of a cylindrical tube. The outer peripheral surface of the exhaust gas duct 10 is arranged at regular intervals in the circumferential direction of the exhaust gas duct 10 and orthogonal to the longitudinal direction of the exhaust gas duct 10. A plurality of sets of gas injection pipes 25 are connected in the cross section, so that gas exhaust ports are opened in the exhaust gas duct 10. Here, the gas injection pipes 25 of each set are arranged at regular intervals in the longitudinal direction of the exhaust gas duct 10, and the gas injection pipes 25
Are arranged in a direction orthogonal to the longitudinal direction of the exhaust gas duct 10. In the case of the present embodiment, each set includes four gas injection pipes 25, and each gas injection pipe 25 is 90
°, and each set of gas injection pipes 25 is, for example, 200 mm to 30 mm in the longitudinal direction of the exhaust gas duct 10.
They are arranged at 0 mm intervals.

When an exhaust gas containing a low-boiling substance passes through the exhaust gas duct 10, air, nitrogen or a recirculated gas having a wind speed of about 1 to 10 m / sec is blown from each of the gas injection pipes 25, for example. The gas thus blown is tangential to the inner wall surface of the exhaust gas duct 10 (FIG. 2).
(See arrow (b)). As a result, this gas flow causes the exhaust gas duct 10
A gas film is formed near the inner wall surface of the exhaust gas duct 10 to prevent exhaust gas from contacting the inner wall surface of the exhaust gas duct 10. Further, a spiral tornado is formed in the exhaust gas duct 10 by the gas flow, and the exhaust gas containing the low-boiling substance and the one in which the low-boiling substance is cooled and solidified to be in a dust state are formed in the exhaust gas duct 10. Is collected at the center portion of the container, and flows to the downstream side in this state.

According to the present embodiment, it is possible to reliably prevent a solidified substance such as a low-boiling substance in the exhaust gas from cooling and adhering to the inner wall surface of the exhaust gas duct 10. Further, when the fluctuation of the exhaust gas amount and the fluctuation of the furnace pressure become large, even if a part of the dust diffuses near the inner wall surface of the exhaust gas duct 10 and adheres to the inner wall surface, for example, a mechanical cleaning device is required. It can be easily removed using. In the present embodiment, when selecting the type of gas to be blown from the gas blow-in pipe 25, air is selected when the temperature inside the exhaust gas duct 10 can be increased, and nitrogen is selected when the temperature should be reduced. For example, it can be appropriately selected according to the temperature condition and the like.

In the above-described embodiment, the gas injection pipes 25 are arranged in a direction perpendicular to the longitudinal direction of the exhaust gas duct 10. However, each gas injection pipe 25 is arranged as shown in FIG.
As shown in (a), it may be arranged to be inclined at a required angle θ with respect to the longitudinal direction. In this case, the gas blown from each gas blowing pipe 25 generates a gas flow component in the gas flow direction with respect to the exhaust gas.

Further, in the above-described embodiment, each set of the gas injection pipes 25 is arranged in a cross section orthogonal to the longitudinal direction of the exhaust gas duct 10, but as shown in FIG. The gas injection pipes 25 can be arranged spirally as a whole by shifting the position sequentially in the longitudinal direction of the exhaust gas duct 10. With such an arrangement, it is possible to continuously apply a turning force to the exhaust gas in different planes by the gas blown from each blowing pipe. Needless to say, even in the case where the positions are displaced in this way, as shown in FIG. 3A, the respective gas injection pipes 25 can be arranged so as to be inclined at the required angle θ with respect to the longitudinal direction.

Next, FIG. 4 shows an example in which the exhaust gas duct 10 'is a square tube having a square (or rectangular) cross section. As described above, in the rectangular cylindrical pipe, the gas blowing pipes 25 'are attached to the four corners of the exhaust gas duct 10' in parallel with each side. In this case, the gas flow blown from the gas blowing pipe 25 'becomes a flow along the inner wall surface near the inner wall surface and a swirling flow at the center as shown by an arrow in the drawing. In the case of such a rectangular tube, substantially the same operation and effects as those of the aforementioned cylindrical tube can be obtained. Also in this embodiment, the method of mounting the gas injection pipe 25 'is described in FIGS.
(A), an embodiment similar to that of FIG. 3 (b) is possible.

In each of the above embodiments, the structure of the first exhaust gas duct 10 connecting the melting furnace body 1 and the combustion chamber 11 and the structure of the second exhaust gas duct 19 connecting the combustion chamber 11 and the cooling tower 20 are described. Although described mainly, the third exhaust gas duct 21 that connects the cooling tower 20 and the bag filter 22 can also adopt the same structure as in each of the above embodiments.

[Brief description of the drawings]

FIG. 1 is an overall system configuration diagram of a plasma melting furnace according to one embodiment of the present invention.

FIG. 2 is a detailed configuration diagram (a) of the exhaust gas duct and a sectional view (b) taken along the line AA of FIG. 2 (a).

FIGS. 3 (a) and 3 (b) are diagrams showing another embodiment of a method of mounting a gas injection pipe.

FIG. 4 is a sectional view showing another embodiment of the exhaust gas duct.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Melting furnace main body 3 Melted material 7 Molten slag 10, 10 '1st exhaust gas duct 11 Combustion chamber 18 Hot blast furnace 19 2nd exhaust gas duct 20 Temperature reduction tower 21 3rd exhaust gas duct 22 Bag filter 25, 25' gas Blow pipe

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3K061 AA18 AB03 AC03 AC19 BA01 CA07 CA14 DA17 DA18 QC06 QC23 QC38 VA05 VA15 VA20 4K045 AA04 BA10 CA02 RB02 4K056 AA05 BA01 BB08 CA20 EA06

Claims (7)

[Claims] 1. A dust adhesion preventing method for preventing dust from adhering to an inner wall surface of an exhaust gas duct for discharging exhaust gas from a melting furnace, wherein a gas flow is generated tangentially to the inner wall surface of the exhaust gas duct. A gas inlet is opened in the exhaust gas duct as described above, and gas is blown from the gas inlet to form a film of gas near the inner wall surface of the exhaust gas duct and collect the exhaust gas at the center of the exhaust gas duct. A method for preventing dust adhesion, characterized in that the dust is prevented from flowing. 2. A dust adhesion preventing device for preventing dust from adhering to an inner wall surface of an exhaust gas duct for discharging exhaust gas from a melting furnace, wherein a gas flow is generated tangentially to the inner wall surface of the exhaust gas duct. Thus, a plurality of gas injection pipes are connected to the outer peripheral surface of the exhaust gas duct at equal intervals in the circumferential direction of the exhaust gas duct and at equal intervals in the longitudinal direction. 3. The dust adhesion preventing device according to claim 2, wherein each of the gas injection pipes provided in the circumferential direction is disposed in a cross section orthogonal to a longitudinal direction of the exhaust gas duct. 4. The dust adhesion preventing device according to claim 2, wherein each of the gas injection pipes provided in the circumferential direction is spirally arranged as a whole by sequentially shifting a position in a longitudinal direction of the exhaust gas duct. 5. The exhaust gas duct according to claim 2, wherein each of the gas injection pipes is arranged in a direction perpendicular to an outer peripheral surface of the exhaust gas duct.
4. The dust adhesion preventing device according to any one of 4. 6. The exhaust gas duct according to claim 2, wherein each of the gas injection pipes is arranged at an angle to a flow direction of the exhaust gas with respect to a direction orthogonal to an outer peripheral surface of the exhaust gas duct. Dust adhesion prevention device. 7. The gas introduced from the gas injection pipe,
The dust adhesion preventing device according to any one of claims 2 to 6, which is any one of air, nitrogen, and a recirculated gas.