JPH11125415A - Direct melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a direct melting furnace wherein severe variations of pressure and temperature in a vertical shaft furnace are prevented from happening even when the amount of discharge of a molten solidified matter is increased or decreased, and hence continuously stable waste processing is achieved. SOLUTION: A vertical shaft furnace 20 is adapted such that a throwing inlet for waste is provided in an upper portion or a side trunk part, and a introduction pipe for oxygen containing gas is connected with a bottom part, whereby zones for drying, thermal decomposition 21, and combustion/melting 22 are formed therein in succession, directed downward from the throwing inlet, and further there is formed in a furnace bottom a slag discharge outlet 26 for discharging a molten solidified matter produced in the combustion/melting zone. In the vertical shaft furnace, there is provided a slag duct 30 for insulating the slag discharge outlet 26 from the outside and covering the same. Further, there is disposed heating means 31 on the slag duct 30 for heating the molten solidified matter discharged from the slag discharge outlet 26, and a return line 32 through which combustion waste gas from the heating means flows into the combustion/melting zone 22 in the vertical shaft furnace 20 from the inside of the slag duct 30.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct melting furnace used when slagging wastes using a gasification and melting technique.

[0002]

2. Description of the Related Art In recent years, in order to treat municipal waste including garbage, general waste including sludge, and industrial waste,
Waste treatment facilities using various gasification and melting processes are used. FIG. 2 shows a main part of a conventional processing facility of this kind, which is disclosed in Japanese Patent Publication No. Sho 51-42434, wherein reference numeral 1 denotes a vertical shaft furnace. The vertical shaft furnace 1 has a bottomed cylindrical shape whose inner wall is made of a refractory material, and has an inlet 2 for introducing pulverized waste into an upper side wall thereof. In addition, oxygen-enriched air is supplied to the char obtained by pyrolysis of waste to supply oxygen-enriched air to the reduced-diameter bottom portion 1a of the vertical shaft furnace 1 to maintain the inside at a high temperature. The introduction pipe 3 is connected,
Further, a slag discharge port 5 having an overhang portion 4 for discharging the molten and solidified product generated in the vertical shaft furnace 1 is formed in the furnace bottom. On the other hand, a gas combustion furnace (not shown) for completely burning the pyrolysis gas in the reducing atmosphere generated by the pyrolysis of the waste is disposed above the vertical shaft furnace 1.

[0003] An extraction chamber 7 is provided on the outer periphery of the bottom of the vertical shaft furnace 1 so as to cover the slag discharge port 5 from outside by closing the bottom with a liquid tank 6. In the liquid tank 6, a belt conveyor 9 that conveys the solidified material that has fallen from the overhanging portion 4 of the slag discharge port 5 and solidified in the cooling water to the receiving container 8 is provided. A burner 10 and an auxiliary oxygen discharge pipe 11 for heating the molten solid on the overhang portion 4 to promote smooth outflow are ejected toward the slag discharge port 5 side into the extraction chamber 7. It is attached to be.

[0004] In the waste treatment equipment having the above-mentioned configuration, first, crushed waste is put into the vertical shaft furnace 1 through the charging hole 2, and the waste is put into the upper drying zone 12.
After being dried in the thermal decomposition zone 13 in the lower portion, pyrolysis gas and carbonaceous high-calorie char are generated. And the above char
By reacting with the oxygen-enriched air supplied from the introduction pipe 3 in the lower part of the pyrolysis zone 13, a combustion / melting zone 14 maintained at a high temperature of about 1600 ° C. is formed in the lower part of the vertical shaft furnace 1. Is done. Then, in the combustion / melting zone 14, the incombustibles in the wastes become harmless molten and solidified substances (glassy molten substances), which are dropped on the furnace bottom and continuously discharged to the slag discharge port 5 side. go.

Next, the molten and solidified material that has flowed out to the overhanging portion 4 of the slag discharge port 5 drops from the overhanging portion 4 into the liquid tank 6 while being heated by the burner 10 to prevent solidification.
After being cooled here, it is conveyed by the belt conveyor 9 and collected in the receiving container 8. At this time, the high-temperature combustion exhaust gas ejected from the burner 10 is directly returned to the combustion / melting zone 14 of the vertical shaft furnace 1 through the slag discharge port 5. On the other hand, the high-temperature gas generated in the combustion / melting zone 14 ascends in the furnace and pyrolyzes the sequentially input waste in the pyrolysis zone 13 to become a flammable pyrolysis gas. With this pyrolysis gas, the waste that has just been injected through the injection hole 2 is dried.

[0006]

However, in such a conventional waste treatment facility, the amount of the molten solid discharged from the slag discharge port 5 depends on the amount of ash in the treated waste. You. For this reason, if the amount of waste input or the amount of ash (slag) in the waste increases or decreases, the amount of molten solid discharged from the slag discharge port 5 will fluctuate significantly. Therefore, when the amount of discharged molten solid is large, the void area at the slag discharge port 5 becomes small, and as a result, the inflow of the combustion exhaust gas of the burner 10 into the vertical shaft furnace 1 is restricted. Extraction room 7
The pressure inside rises. And the pressure of this extraction chamber 7 is
When the pressure exceeds the pressure balance determined by the pressure on the extraction chamber 7 side, the furnace pressure in the vertical shaft furnace 1, and the void area of the slag discharge port 5, a large amount of the fuel rapidly stays in the extraction chamber 7. Flue gas flows into the vertical shaft furnace 1. As a result, there is a problem that the pressure and the temperature in the vertical shaft furnace 1 fluctuate greatly.

SUMMARY OF THE INVENTION The present invention has been made to effectively solve the problems of the above-mentioned conventional waste treatment equipment, and a large pressure and temperature in a vertical shaft furnace can be obtained by increasing or decreasing the amount of discharged molten solid. It is an object of the present invention to provide a direct melting furnace which does not vary and can continuously and stably treat waste.

[0008]

According to the first aspect of the present invention, there is provided a direct melting furnace according to the present invention, wherein a waste inlet is provided at an upper or side body, and an oxygen-containing gas inlet pipe is connected to a bottom. By doing so, each zone of drying, pyrolysis and combustion / melting is formed sequentially from the inlet downward, and a slag outlet for discharging the molten and solidified product generated in the combustion / melting zone is formed at the bottom of the furnace. In the formed vertical shaft furnace, in a direct melting furnace provided with a slag duct that shields and covers the slag discharge port from the outside, the slag duct,
A heating means for heating the molten solid discharged from the slag discharge port is provided, and a return line through which the combustion exhaust gas from this heating means can flow from the inside of the slag duct into the combustion and melting zone of the vertical shaft furnace is provided. It is characterized by having.

According to a second aspect of the present invention, the slag discharge port is provided with an overhang projecting into the slag duct, and the end of the return line on the slag duct side is provided with the overhang. It is characterized in that it is connected to a position below the section. According to a third aspect of the present invention, in the vertical shaft furnace according to the first or second aspect, a lower portion of the pyrolysis zone has a cross-sectional area smaller than that of the pyrolysis zone and the lower combustion / melting zone. A body is provided, and the other end of the return line is connected to an upper side wall of a combustion / melting zone expanding in diameter from the straight body.

Further, the invention according to claim 4 is characterized in that the cross-sectional area of the return line according to any one of claims 1 to 3 is smaller than the cross-sectional area of the slag discharge port. The invention according to claim 5 is characterized in that an opening / closing device that opens and closes with a preset pressure is interposed in the return line. According to a sixth aspect of the present invention, the return line according to any one of the first to fifth aspects is provided with a backflow prevention device for preventing a flow from the vertical shaft furnace side to the slag duct. It is characterized by the following.

[0011] In the direct melting furnace according to any one of claims 1 to 6, the slag duct provided with a heating means for heating the molten and solidified material discharged from the slag discharge port is provided with a combustion device. A return line is provided to allow the exhaust gas to flow from the slag duct into the combustion and melting zone of the vertical shaft furnace, so the amount of waste solidified and discharged due to the amount of waste input and the amount of ash in the waste Increases, the gap area at the slag discharge port is reduced, and the inflow of the combustion exhaust gas of the heating means into the vertical shaft furnace is restricted, the combustion exhaust gas flows from the return line into the vertical shaft furnace. Bypassing and entering. As a result, the internal pressure of the slag duct does not excessively increase with respect to the pressure in the vertical shaft furnace. It does not occur.

At this time, if an overhang is provided at the slag discharge port, the molten and solidified material will drop from the tip through the overhang from the slag discharge port. Therefore, if the connecting portion of the return line is opened near the flow path of the molten solid, the molten solid dropped when the exhaust gas is discharged may be sucked and entrained in the vertical shaft furnace. Occurs. In this respect, in the invention according to the second aspect, since the end of the return line on the slag duct side is opened at a position below the overhanging portion which becomes a blind spot of the dripping flow path of the molten solid, the return line There is no fear that the combustion exhaust gas flowing from the furnace into the vertical shaft furnace entrains the molten solidified material. In addition, it is possible to prevent the molten solidified material from adhering and solidifying to the opening in the slag duct.

By the way, in this type of vertical shaft furnace, since most of the molten and solidified products generated in the combustion / melting zone are dropped along the side wall of the combustion / melting zone, the vertical line furnace of the return line is required. There is a possibility that the molten solidified material adheres to the connection opening on the shaft furnace side, and the flow of the combustion exhaust gas is hindered. In this regard, in the invention according to claim 3, first, a straight body portion having a smaller cross-sectional area than the thermal decomposition zone and the lower combustion / melting zone is provided below the thermal decomposition zone of the vertical shaft furnace. On the other hand, the molten solidified material is dropped directly from the lower end of the straight body. Therefore,
Since the molten solid does not flow down the side wall of the combustion / melting zone, the connection of the return line is connected to the combustion / melting zone.
The connection to the upper side wall of the melting zone makes it possible to avoid the problems mentioned above.

If the cross-sectional area of the return line is set to be equal to or less than the cross-sectional area of the slag discharge port, the vertical shaft from the return line is not used directly for heating the molten and solidified material. This is more preferable because the amount of flue gas returned to the furnace can be kept as low as possible. Further, as in the invention according to claim 5, if an opening / closing device that opens and closes with a preset pressure is interposed in the return line, the return line is closed unless the inside of the slag duct rises to the set pressure. Therefore, the entire amount of the combustion exhaust gas from the heating means can be used for heating the molten solid.
In addition, according to the invention described in claim 5 or 6, since the inflow of the pyrolysis gas from the vertical shaft furnace to the slag duct is reliably prevented, abnormal combustion in the slag duct can be avoided. it can.

[0015]

FIG. 1 shows an essential part of an embodiment of a direct melting furnace according to the present invention, and the upper structure is the same as that shown in FIG. As shown in FIG. 1, the direct melting furnace includes a vertical shaft furnace 20 and a slag duct 30 that covers an outer periphery of a slag discharge port 26 of the vertical shaft furnace 20.
And a discharge section of the molten and solidified material provided with the above. In this vertical shaft furnace 20, the diameter of the upper pyrolysis zone 21 and the lower combustion / melting zone 22 are located below the cylindrical pyrolysis zone 21.
Is provided with a straight body portion 23 having a diameter smaller than that of the straight body portion 23. At the lower end of the straight body 23, there is provided a weir 24 whose inner wall surface continuously extends downward from the straight body 23 over the entire circumference. Here, the weir portion 24 is formed by an inclined surface whose outer peripheral surface gradually goes from the upper side to the lower side toward the center. As a result, the weir 24
The thickness dimension gradually decreases from above to below, and the lower edge is formed in a cutting edge shape.

Each of the straight body portion 23 and the weir portion 24 is formed of a hollow metal material having excellent heat conductivity, for example, a copper casting, and is internally cooled by cooling water supplied from a cooling water pipe 25. It has become so. Further, the combustion / melting zone 2 located below the straight body portion 23
On the upper side wall of 2, an injection nozzle (introduction pipe) 27 for oxygen-enriched gas or preheated air (oxygen-containing gas) is radially arranged at a plurality of locations in the circumferential direction. As a result, the ejection port 27a of the charging nozzle 27 is arranged on the outer peripheral side with respect to the vertical vertical line from the lower end edge of the weir 24. Here, the charging nozzle 27 is attached so as to blow out the oxygen-enriched gas or the preheated air toward the center of the furnace bottom 28 as shown by a dotted line in the figure.

A slag discharge port 26 is formed on the bottom side wall of the vertical shaft furnace 20, and a projecting portion 29 that projects horizontally from the slag discharge port 26 is integrally formed. The same bottom as that shown in FIG. 2 is closed by a liquid tank on the outer periphery of the bottom of the vertical shaft furnace 20 having the above configuration, so that the slag discharge port 2 is formed.
The slag duct 30 is provided so as to cover the shield 6 from outside. At the upper part of the slag duct 30, a burner (heating means) 31 for heating the molten and solidified material on the overhang portion 29 to promote smooth outflow is mounted so as to be ejected toward the slag discharge port 26 side. Have been.

Then, between the slag duct 30 and the vertical shaft furnace 20, the flue gas from the burner 31 flows from the inside of the slag duct 30 into the combustion / melting zone 22 of the vertical shaft furnace 20. Return line 32
Is plumbed. The return line 32 is set so that the cross-sectional area is equal to or smaller than the cross-sectional area of the slag discharge port 26, and the end 32a on the slag duct 30 side is
9 are connected so as to open at a lower position. On the other hand,
The other end 32b of the return line 32 is connected to the vertical shaft 2
0 is connected to the upper side wall of the combustion / melting zone 22 whose diameter increases from the straight body portion 23. The return line 32 is provided with an opening / closing device 33 that opens when the pressure in the slag duct 30 increases to a preset pressure.

In the direct melting furnace having the above structure, a stable and strong dome 35 is formed by a dense layer in the straight body 23 having a diameter smaller than that of the pyrolysis zone 21 and the lower combustion / melting zone 22. Is done. And
The molten and solidified material generated in the combustion / melting zone 22 maintained at a high temperature by the flame from the injection nozzle 17 flows down from the straight body portion 23 along the weir portion 24, and remains as it is.
4 is dropped onto the furnace bottom 28 below. Then, the molten and solidified material dropped on the furnace bottom 28 is guided from the furnace bottom to the slag discharge port 26 side, and is heated by the burner 31 at the projecting portion 29 in the slag duct 30 to prevent solidification. , Is dropped downward from the tip, cooled in a liquid tank (not shown), and discharged out of the system. At this time,
The molten solidified material flowing down the straight body portion 23 and the weir portion 24 is cooled by the cooling water supplied from the cooling water pipe 25 to be solidified on the surface of the metal material to function as a heat insulating layer. And the surface of the dam 24 is protected.

When the amount of molten solid discharged increases due to the amount of waste input or the amount of ash in the waste, the void area at the slag discharge port 26 decreases, and as a result, the vertical shaft furnace 20 The amount of inflow of the combustion exhaust gas from the burner 31 to the burner 31 decreases. Then, the amount of combustion exhaust gas from the burner 31 directly flowing into the vertical shaft furnace 20 decreases, and the pressure in the slag duct 30 relatively increases. When the pressure reaches a preset pressure, the opening / closing device 33 of the return line 32 is opened, and the combustion exhaust gas in the slag duct 30 flows from the return line 32 into the vertical shaft furnace 20, thereby causing the vertical shaft furnace 20 to return. The pressure balance between inside 20 and inside slag duct 30 is maintained. In this way, when the combustion exhaust gas in the slag duct 30 is returned from the return line 32 to the vertical shaft furnace 20, the pressure in the slag duct 30 is reduced, so that the switching device 33 is closed.

As described above, according to the direct melting furnace,
In a slag duct 30 provided with a burner 31 for heating the molten and solidified material discharged from the slag discharge port 26, the combustion exhaust gas from the burner 31 flows from the slag duct 30 into the combustion / melting zone 22 of the vertical shaft furnace 20. Since the return line 32 that can flow in is provided, the amount of molten and solidified material increases due to the amount of waste input and the amount of ash in the waste, and the void area at the slag discharge port 26 decreases, resulting in a vertical position. When the inflow of the combustion exhaust gas from the burner 31 into the mold shaft furnace 20 is restricted, the combustion exhaust gas can flow from the return line 32 into the vertical shaft furnace 20. Therefore, since the internal pressure of the slag duct 30 does not excessively increase with respect to the pressure in the vertical shaft furnace 20, a large pressure and temperature increase in the vertical shaft furnace 20 by increasing or decreasing the discharge amount of the molten solidified material. No fluctuation occurs.

At this time, since the end 32a of the return line 32 on the side of the slag duct 30 is connected to a position below the overhanging portion 29 which is a blind spot of the flow path for the molten and solidified material, the return line 32 There is no danger that the molten solidification will accompany the combustion exhaust gas flowing through the vertical shaft furnace 20. in addition,
It is also possible to prevent the molten solidified material from adhering to and solidifying on the opening end 32a of the slag duct 30. Further, a straight body portion 23 and a weir portion 24 whose cross-sectional areas are smaller than those of the pyrolysis zone 21 and the lower combustion / melting zone 22 are provided below the pyrolysis zone 21 of the vertical shaft furnace 20. The solidified material is dripped from the lower end of the weir 24 as it is.
Since the flow does not flow down the side wall of the melting zone 22, there is no possibility that the molten solidified material adheres to the open end 32b of the return line 32 on the side of the vertical shaft furnace 20 and the flow of the combustion exhaust gas is obstructed.

Further, since the cross-sectional area of the return line 32 is set to be equal to or smaller than the cross-sectional area of the slag discharge port 26, it is returned from the return line 32 to the vertical shaft furnace 20 without being directly used for heating the molten and solidified material. The amount of combustion exhaust gas can be kept as low as possible. In addition, since the return line 32 is provided with the opening / closing device 33 that opens and closes with a preset pressure, the return line 32 is closed unless the inside of the slag duct 30 rises to the set pressure. For this reason, normally, the entire amount of the combustion exhaust gas from the burner 31 can be used for heating the molten and solidified material, which is excellent in economical efficiency. In addition, the inflow of the pyrolysis gas from the vertical shaft furnace 20 to the slag duct 30 is ensured. Since it can be prevented, abnormal combustion in the slag duct 30 can also be avoided.

In particular, in the above-mentioned direct melting furnace, the lower part of the pyrolysis zone 21 is made of a metal whose diameter is smaller than that of the pyrolysis zone 21 and the lower combustion / melting zone 22 and into which cooling water is introduced. The straight body 23 and the weir 24 are provided, so that the straight body 23 and the weir 24 can be protected by a solidified material solidified on the surface. Compared with the case where it is configured, the durability can be remarkably improved, and the solid molten material flowing down in the combustion / melting zone 22 does not drip along the side wall of the combustion / melting zone 22. Therefore, the effect of significantly extending the life of the refractory can also be obtained for the side wall of the combustion / melting zone.

In the above embodiment, only the case where the vertical shaft furnace 20 is cylindrical has been described. However, the present invention is not limited to this. For example, the same applies to a square vertical shaft furnace. It is possible to apply. Further, in the present embodiment, the case where the opening / closing device 33 is interposed in the return line 32 has been described. However, the present invention is not limited to this, and the variation amount of the solidified material, the capacity of the burner 31 or the capacity of the slag duct 30, Depending on various conditions such as the pipe diameter of the return line 32, the opening / closing device 33 may be omitted, and the vertical shaft furnace 20 and the slag duct 30 may be always communicated via the return line 32. It is also possible to interpose a backflow prevention device for preventing the flow from the vertical shaft furnace 20 to the slag duct 30 on the return line 32.

[0026]

As described above, according to the direct melting furnace according to any one of the first to sixth aspects of the present invention, the combustion exhaust gas from the heating means provided in the slag duct is supplied to the vertical shaft from inside the slag duct. Since the return line that can flow into the combustion / melting zone of the furnace is provided, the pressure and temperature in the vertical shaft furnace do not fluctuate significantly due to the increase or decrease in the amount of molten solids discharged. Continuous and stable waste disposal can be performed. In particular, according to the second aspect of the present invention, as a result of connecting the end of the return line on the slag duct side to a position below the overhanging portion serving as a blind spot of the dripping flow path of the molten and solidified material, From the flue gas flowing from the vertical shaft furnace, there is no risk of entrainment of the molten solidified, and in the opening in the slag duct,
According to the third aspect of the present invention, the molten solidified material is prevented from adhering and solidifying, and the molten solidified material does not flow down the side wall of the combustion / melting zone. There is no danger of adhesion of the molten and solidified matter at the connection portion on the furnace side.

According to the fourth aspect of the present invention, the amount of combustion exhaust gas returned from the return line to the vertical shaft furnace without being directly used for heating the molten and solidified product can be suppressed as low as possible. According to the invention described in Item 5, since the return line is closed unless the inside of the slag duct rises to the set pressure by the opening and closing device, the entire amount of the combustion exhaust gas from the heating means is used for heating the molten and solidified material. In addition, according to the invention of claim 5 or claim 6, inflow of pyrolysis gas from the vertical shaft furnace to the slag duct is reliably prevented, so that abnormal combustion in the slag duct is performed. Can be avoided.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part showing one embodiment of a direct melting furnace according to the present invention.

FIG. 2 is a longitudinal sectional view showing a main part of a waste treatment facility using a conventional vertical shaft furnace.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 20 Vertical shaft furnace 21 Pyrolysis zone 22 Combustion zone 23 Straight body part 24 Weir part 25 Cooling water pipe 26 Slag discharge port 27 Input nozzle (introduction pipe of oxygen-containing gas) 29 Overhang part 30 Slag duct 31 Burner (heating means) 32 Return line 32a Slag duct side end 32b Vertical shaft furnace side end 33 Switchgear

Claims (6)

[Claims] 1. A waste inlet is provided at an upper or side body part, and an oxygen-containing gas introduction pipe is connected to a bottom part, so that drying and heating are sequentially performed inside from the inlet downward. The slag discharge port is shut off from the outside in a vertical shaft furnace in which each zone of decomposition, combustion and melting is formed, and a slag discharge port for discharging the molten solid generated in the combustion and melting zone is formed at the bottom of the furnace. In a direct melting furnace provided with a slag duct for covering, the slag duct is provided with heating means for heating the molten and solidified material discharged from the slag discharge port, and the combustion exhaust gas from the heating means is used for heating A direct melting furnace comprising a return line that can flow from inside a slag duct into the combustion / melting zone of the vertical shaft furnace. 2. The slag discharge port is provided with an overhang protruding into the slag duct, and an end of the return line on the slag duct side is connected to a position below the overhang. 2. The method according to claim 1, wherein
The direct melting furnace according to 1. 3. The lower part of the pyrolysis zone of the vertical shaft furnace has a cross-sectional area equal to or lower than that of the pyrolysis zone.
A straight body portion smaller than the melting zone is provided, and the other end of the return line is connected to an upper side wall of the combustion / melting zone expanding in diameter from the straight body portion. 3. The direct melting furnace according to 1 or 2. 4. The direct melting furnace according to claim 1, wherein a sectional area of the return line is smaller than a sectional area of the slag discharge port. 5. The direct melting furnace according to claim 1, wherein an opening / closing device that opens and closes with a preset pressure is interposed in the return line. 6. The back line according to claim 1, wherein a backflow prevention device for preventing a flow from the vertical shaft furnace side to the slag duct is provided in the return line. Direct melting furnace.