JP2007071423A - Secondary combustion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely prevent blockage of a combustion tower caused by attachment and growing of dust. <P>SOLUTION: This secondary combustion device comprises the combustion tower 3 to which an exhaust gas including an unburnt gas is sent, and a hot air blowing zone 4 is formed to blow hot air to the exhaust gas sent into the combustion tower 3 to burn the unburnt gas included in the exhaust gas. An inert gas blowing zone 11 for blowing an inert gas toward the inside of the combustion tower 3 through a porous brick tower wall member 12, is formed near a lower side of the hot air blowing zone 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a secondary combustion apparatus that completely burns unburned gas contained in exhaust gas discharged from a melting furnace that melts incineration residues, for example.

  In recent years, methods for melting and solidifying incineration residues have been put into practical use in order to reduce the volume and innocence of incineration residues (incineration ash and dust) generated by incineration treatment of municipal waste, etc. Yes. As a method for melting and solidifying the incineration residue, an electric melting furnace such as a plasma melting furnace, an arc melting furnace or an electric resistance furnace is used. After the incineration residue is melted by electric energy, it is solidified by water cooling or air cooling. Many methods are used, such as using a surface melting furnace, a swirl melting furnace, a coke bed furnace, etc., and melting the incineration residue with the combustion energy of the fuel and then solidifying it by water cooling or air cooling. ing. Note that the molten fly ash present in the vaporized state in the exhaust gas generated during the melting process is recovered by a dust collector or the like in the downstream low temperature region. Here, molten fly ash (hereinafter referred to as “dust”) means that low boiling point heavy metals (eg, lead, zinc, cadmium, etc.) and chlorides contained in the incineration residue are volatilized by melting, It is dust collected by a downstream dust collector or the like by cooling and solidification.

Conventionally, in the electric melting furnace and the combustion type melting furnace, in order to completely burn unburned gas (CO, H _2, etc.) contained in the exhaust gas discharged from the melting furnace, the dioxin contained in the exhaust gas is also included. A secondary combustion device is attached to decompose the components. This conventional secondary combustion apparatus will be described below using FIG. 4 as an example attached to a plasma melting furnace.

  A secondary combustion apparatus 101 shown in FIG. 4 includes a combustion tower 103 to which exhaust gas generated by melting of a material to be melted (incineration residue) in the plasma melting furnace 102 is sent, and is sent into the combustion tower 103. By forming the hot air blowing zone 104 for blowing hot air into the exhaust gas, the unburned gas contained in the exhaust gas is combusted. That is, in the secondary combustion apparatus 101, the combustion tower 103 discharges exhaust gas into the combustion tower 103, an exhaust gas inlet 105 that receives exhaust gas from the plasma melting furnace 102, a hot air inlet 107 that blows hot air from the hot air furnace 106, and the exhaust gas. An exhaust gas discharge port 108 is provided in order from the lower side to the upper side. The exhaust gas from the plasma melting furnace 102 is sent to the lower part of the combustion tower 103 through the exhaust gas inlet 105. The hot air from the hot air furnace 106 is blown into the exhaust gas that has risen from the lower part of the combustion tower 103 to the height of the hot air inlet 107, in other words, the exhaust gas that has entered the hot air blowing zone 104. The unburned gas contained in the exhaust gas is secondarily burned. Thus, the unburned gas contained in the exhaust gas is completely burned in the combustion tower 103 with sufficient residence time and temperature. The exhaust gas that has been subjected to the secondary combustion treatment in the combustion tower 103 is discharged from an exhaust gas outlet 108 provided in the upper part of the combustion tower 103 and sent to the temperature reducing tower 109, where it is cooled by the temperature reducing tower 109. After that, it is discharged into the atmosphere through an exhaust gas treatment device (not shown).

  In the combustion tower 103, in the zone 110 in the vicinity of the lower side of the hot air blowing zone 104, 1) a rewinding wind of hot air colliding with the tower wall is blown in, and 2) the reducing atmosphere is shifting to the oxidizing atmosphere. 3) The temperature is near the melting point of dust. For this reason, the dust adheres and grows on the tower wall portion surrounding the zone 110 in the vicinity of the lower side of the hot air blowing zone 104, and eventually the combustion tower 103 is blocked. Therefore, in order to prevent such problems, a refractory 111 having a relatively high thermal conductivity is attached to the inner surface of the lower portion of the combustion tower 103, and a water cooling jacket 112 is attached to the outer peripheral surface thereof. By reducing the temperature of the exhaust gas sent to the lower part of the combustion tower 103, the dust present in the exhaust gas in a vaporized state is solidified as much as possible and dropped onto the dust conveyor 113 arranged below the combustion tower 103. Has been. In addition, by lowering the temperature near the wall surface, an atmosphere that easily falls even if dust adheres is formed. The dust dropped on the dust conveyor 113 is discharged out of the system by the dust conveyor 113.

  As a related prior art for the purpose of preventing the adhesion of dust, there is an exhaust gas duct proposed in Patent Document 1, for example. The exhaust gas duct according to Patent Document 1 has a double cylinder structure including an inner cylinder made of a ceramic porous body, and the exhaust gas flowing in the inner cylinder is evenly cooled from the entire inner surface of the inner cylinder (nitrogen). , Air) can be prevented from adhering and growing in the duct.

JP-A-8-219437

  However, in the sedimentation separation of dust by cooling the exhaust gas in the conventional secondary combustion apparatus 101, only about half of the dust contained in the exhaust gas can settle and separate, so the zone near the lower side of the hot air blowing zone 104 There is a problem that it is not possible to sufficiently prevent the adhesion and growth of dust at the tower wall surrounding 110. Although it is conceivable to further increase the dust sedimentation effect by further lowering the cooling temperature of the exhaust gas, in this case, a new problem of causing the generation of CO appears, which is not preferable. Further, the technical idea of the invention according to Patent Document 1 cannot be applied to the secondary combustion device as it is.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a secondary combustion apparatus that can reliably prevent the clogging of a combustion tower due to dust adhesion and growth. It is.

In order to achieve the above object, the secondary combustion apparatus according to the present invention comprises:
A combustion tower to which exhaust gas containing unburned gas is sent is provided, and a hot air blowing zone for blowing hot air into the exhaust gas sent into the combustion tower is formed to burn the unburned gas contained in the exhaust gas. In the secondary combustion device configured as follows:
In the vicinity of the lower side of the hot air blowing zone, an inert gas blowing zone for blowing an inert gas into the combustion tower through porous brick is formed (first invention).

  In the present invention, it is preferable that the inert gas blowing zone is divided into a plurality of blocks in the circumferential direction of the combustion tower, and the inert gas blowing operation in each block is controlled (second invention).

  In the present invention, an inert gas blowing zone for blowing an inert gas (nitrogen, argon, etc.) through the porous brick toward the inside of the combustion tower is formed near the lower side of the hot air blowing zone. That is, a film of an inert gas that is uniformly blown through the porous brick is formed on the surface of the tower wall portion surrounding the zone near the lower side of the hot air blowing zone. For this reason, when dust that is in a vaporized state in the exhaust gas tries to contact the tower wall part, the vaporized state is cooled and solidified by touching the inert gas film, and its adhesiveness is remarkably reduced. The Further, the cooled and solidified dust is carried by the exhaust gas flow to the downstream side without being in contact with the wall surface of the tower by the inert gas film, or is dropped below the combustion tower. Therefore, it is possible to reliably prevent dust from adhering and growing in the tower wall portion surrounding the zone near the lower side of the hot air blowing zone in the past. Blockage can be reliably prevented. Here, the reason why the gas blown toward the inside of the combustion tower through the porous brick is an inert gas such as nitrogen is as follows. If the blown gas is air, the unburned gas in the exhaust gas is burned by the air, the temperature of the tower wall rises locally to a temperature near the melting point of the dust, and the dust becomes a molten state. However, if the insufflation gas is an inert gas such as nitrogen, the unburned gas will not cause a combustion reaction, so the vaporized dust is cooled and solidified to prevent the dust from adhering. This is because it can be surely prevented.

  Further, according to the second invention, by controlling the time and order of blowing the inert gas in each block, it is possible to reduce the amount of inert gas used while ensuring the dust adhesion preventing effect. .

  Next, specific embodiments of the secondary combustion apparatus according to the present invention will be described with reference to the drawings. This embodiment is an example in which the present invention is applied to a secondary combustion apparatus attached to a plasma melting furnace.

  FIG. 1 is an overall schematic structural diagram of a secondary combustion apparatus according to an embodiment of the present invention. Further, FIG. 2 shows an explanatory diagram of the AA view structure of FIG. 1, and FIG. 3 shows an enlarged view of part B of FIG.

As shown in FIG. 1, the secondary combustion apparatus 1 of the present embodiment includes a combustion tower 3 to which exhaust gas generated by melting of a material to be melted (incineration residue) in a plasma melting furnace 2 is sent. By forming a hot air blowing zone 4 for blowing hot air (about 1100 to 1200 ° C.) with respect to the exhaust gas sent into the tower 3 (combustion chamber), unburned gas (CO, H _2, etc.) contained in the exhaust gas ) Is combusted. That is, in the secondary combustion apparatus 1, the exhaust gas is discharged to the combustion tower 3, the exhaust gas inlet 5 that receives the exhaust gas from the plasma melting furnace 2, the hot air inlet 7 that blows the hot air from the hot air furnace 6, and the exhaust gas. An exhaust gas discharge port 8 is provided in order from the lower side to the upper side. The exhaust gas from the plasma melting furnace 2 is sent to the lower part of the combustion tower 3 through the exhaust gas inlet 5. The hot air from the hot stove 6 is blown into the exhaust gas that has risen from the lower part of the combustion tower 3 to the height of the hot air blowing port 7, in other words, the exhaust gas that has entered the hot air blowing zone 4. The unburned gas contained in the exhaust gas is secondarily burned. Thus, the unburned gas contained in the exhaust gas is completely burned in the combustion tower 3 with sufficient residence time and temperature. The exhaust gas that has been subjected to the secondary combustion treatment in the combustion tower 3 is discharged from an exhaust gas outlet 8 provided in the upper part of the combustion tower 3 and sent to the temperature reducing tower 9 where it is cooled by the temperature reducing tower 9. After that, it is discharged into the atmosphere through an exhaust gas treatment device (not shown). Further, the inside of the main body of the plasma melting furnace 2 is maintained in a reducing atmosphere in order to prevent oxidation of molten slag, graphite main electrode, and the like. For this purpose, from an inert gas supply device 10 such as a PSA nitrogen production device. An inert gas such as nitrogen gas is continuously supplied into the main body of the plasma melting furnace 2 through the hollow holes of the graphite main electrode and the graphite start electrode (both not shown) formed in a hollow cylindrical shape.

  In the vicinity of the lower side of the hot air blowing zone 4, an inert gas blowing zone 11 for blowing an inert gas (nitrogen) toward the inside of the combustion tower 3 through porous brick is formed. In the present embodiment, the inert gas blowing zone 11 is divided into eight blocks 11a to 11h in the circumferential direction of the combustion tower 3 as shown in FIG. The active gas blowing operation is controlled.

  That is, in the combustion tower 3, the tower wall portion surrounding the inert gas blowing zone 11 is a cylindrical tower wall member 12 (hereinafter referred to as the following) made mainly of porous brick, as shown in FIGS. 1 and 2. "Porous brick tower wall member 12"). On the outer peripheral surface of this porous brick tower wall member 12, as shown in FIG. 2, there are formed eight air chambers 13 partitioned in the circumferential direction, and on the outer side of this porous brick tower wall member 12 An annular main pipe 14 to which nitrogen gas from the inert gas supply device 10 is supplied is disposed so as to surround the porous brick tower wall member 12. Branch pipes 14 a to 14 h branched from the main pipe 14 are connected to the respective wind chambers 13. The branch valves 14 a to 14 h are connected to the branch pipes 14 a to 14 h according to a command signal from the control device 15 to open and close the flow path 16. Is installed. The control device 15 includes a timer 17, and the control device 15 controls the valve opening operation sequence and the valve opening operation time of the on-off valves 16 according to a predetermined program.

  Here, the porous brick is a refractory having a continuous ventilation hole made of, for example, sintered alumina, and is used for degassing and desulfurization of a metal melting furnace, or for stirring the material in the silo at the time of cement production. It is a conventionally well-known thing. Currently, there are many types of porous bricks such as the pore diameter and porosity, but in this embodiment, in order to reduce the amount of nitrogen used, the one with the smallest pore diameter and porosity is used. Has been. Further, the porous brick tower wall member 12 may be either integrally formed of porous bricks, or a combination of a plurality of segmented porous bricks or plug-shaped porous bricks. The reason why the gas blown toward the inside of the combustion tower 3 is an inert gas such as nitrogen is as follows. If the blown gas is air, the unburned gas in the exhaust gas is burned by the air, the temperature of the tower wall rises locally to a temperature near the melting point of the dust, and the dust becomes a molten state. However, if the insufflation gas is an inert gas such as nitrogen, the unburned gas will not cause a combustion reaction, so the vaporized dust is cooled and solidified to prevent the dust from adhering. This is because it can be surely prevented.

  Furthermore, in the secondary combustion apparatus 1 of this embodiment, in order to lower the temperature of the exhaust gas sent to the lower part of the combustion tower 3, water cooling means similar to the conventional one is provided. That is, as shown in FIG. 1, a refractory 18 having a relatively high thermal conductivity is attached to the inner surface side of the tower wall portion surrounding the hot air blowing zone 4 and the zone near the upper side of the hot air blowing zone 4. In addition, a water cooling jacket 19 is mounted on the outer peripheral surface of the tower wall portion. Similarly, a refractory 18 'having a relatively high thermal conductivity is attached to the inner surface side of the tower wall portion surrounding the zone near the lower side of the inert gas blowing zone 11, and the tower wall portion A water cooling jacket 19 'is mounted on the outer peripheral surface. Thus, by lowering the temperature of the exhaust gas sent to the lower part of the combustion tower 3, dust present in the vaporized state in the exhaust gas is solidified as much as possible and dropped onto the dust conveyor 20 disposed below the combustion tower 3. Has been. The dust dropped on the dust conveyor 20 is discharged out of the system by the dust conveyor 20.

  In the secondary combustion apparatus 1 configured as described above, in the inert gas blowing zone 11, the nitrogen gas blowing operation in each of the blocks 11a to 11h is performed according to a predetermined order and blowing time. (See FIG. 2). Thereby, on the surface of the tower wall portion surrounding the inert gas blowing zone 11, as shown in FIG. 3, a film of nitrogen gas blown uniformly through the porous brick (porous brick tower wall member 12) is formed in each block 11a. It is formed in conjunction with the nitrogen gas blowing operation at ˜11h. And when the dust which exists in the gasified state in exhaust gas tries to contact the said tower wall part, the dust in the vaporized state touches a film | membrane of nitrogen gas, is cooled and solidified, and the adhesiveness is remarkably reduced. The cooled and solidified dust is carried by the exhaust gas flow to the downstream side without being blocked by the nitrogen gas film and coming into contact with the tower wall surface, or dropped below the combustion tower 3.

  According to the secondary combustion apparatus 1 of the present embodiment, it is possible to reliably prevent the adhesion / growth of dust in the tower wall portion surrounding the zone near the lower side of the hot air blowing zone 4, so that such dust adhesion / growth is possible. It is possible to reliably prevent the combustion tower 3 from being blocked due to the above. Moreover, since the inert gas supply device 10 originally attached to the plasma melting furnace 2 is used as a supply source of nitrogen gas blown into the combustion tower 3, there is no need to newly install a nitrogen generator, a nitrogen cylinder, or the like. Thus, the device configuration can be simplified. In addition, since the mounting range of the water cooling jackets 19 and 19 ′ and the dust settling / separation space of the dust in the lower part of the combustion tower 3 can be reduced as compared with the conventional case, there is an advantage that the degree of freedom of arrangement of the hot air inlet 7 is increased. . Moreover, since the nitrogen gas blowing operation in each of the blocks 11a to 11h is performed in accordance with a predetermined order and blowing time, it is possible to reduce the amount of nitrogen gas used while ensuring the dust adhesion preventing effect.

1 is an overall schematic structural explanatory diagram of a secondary combustion apparatus according to an embodiment of the present invention. AA structural view of FIG. Part B enlarged view of FIG. Description of the overall schematic structure of a conventional secondary combustion device

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Secondary combustion apparatus 3 Combustion tower 4 Hot-air blowing zone 11 Inert gas blowing zone 12 Porous brick tower wall member

Claims (2)

A combustion tower to which exhaust gas containing unburned gas is sent is provided, and a hot air blowing zone for blowing hot air into the exhaust gas sent into the combustion tower is formed to burn the unburned gas contained in the exhaust gas. In the secondary combustion device configured as follows:
A secondary combustion apparatus, wherein an inert gas blowing zone for blowing an inert gas toward the inside of the combustion tower through porous bricks is formed near the lower side of the hot air blowing zone.   The secondary combustion apparatus according to claim 1, wherein the inert gas blowing zone is divided into a plurality of blocks in a circumferential direction of the combustion tower, and an inert gas blowing operation in each block is controlled.

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