JP3744668B2 - Ash melting furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ash melting furnace that melts and solidifies fly ash and incineration ash generated when municipal waste and industrial waste are incinerated, and more particularly to an ash melting furnace that effectively treats dioxins in exhaust gas. .
[0002]
[Prior art]
Municipal waste, sewage sludge, and other wastes were incinerated at incineration facilities, and the resulting incineration ash and dust (fly ash) were previously disposed of in landfills. However, there is a problem of depletion of landfill sites and groundwater contamination due to the leaching of toxic heavy metals, so the need for volume reduction, detoxification and recycling by melting is increasing.
[0003]
Against this background, an ash melting furnace that melts incinerated ash discharged from incinerators that use residual carbon, coke, kerosene and electric power as the heat source has been proposed. It has been broken. Among these, there are a plasma arc heating method and an electric resistance heating method as an ash melting furnace using electric power as a heat source.
[0004]
FIG. 3 is a longitudinal sectional view of a conventional ash melting furnace.
In the figure, a is an ash melting furnace. b is an ash melting chamber. c is a tap outlet provided at the lower part of the ash melting furnace a, and d is a molten metal discharge port provided at the bottom of the ash melting furnace a. e is the main electrode and f is the bottom electrode. m is a power source for flowing DC electricity between the main electrode e and the bottom electrode f, and n and o are the electric wires. g is an ash charging port provided at the top of the ash melting furnace a, and the fly ash and incinerated ash conveyed by a conveyor (not shown) are charged into the ash melting furnace a. h is an exhaust gas outlet provided at the top of the ash melting furnace a. i is an ash solid layer such as fly ash or incinerated ash charged into the ash melting chamber b, and j is a molten slag. k is a metal layer.
[0005]
[Problems to be solved by the invention]
The exhaust gas discharged from the ash melting furnace contains hydrogen chloride and a small amount of dioxin in addition to a large amount of dust containing salts, oxides and hydroxides.
[0006]
Further, in the conventional ash melting furnace, artificial graphite such as graphite is used for the main electrode, so that CO gas is generated in the ash melting furnace. At the same time, since there is a temperature gradient in the vertical direction of the ash melting furnace, dioxins in the ash tend to evaporate and be contained in the exhaust gas. In order to decompose these CO gas and dioxin, a CO gas combustor is provided on the downstream side of the ash melting furnace exhaust gas outlet. However, a space for installing the combustor is required, and auxiliary fuel for raising the temperature is required. There are some problems.
[0007]
The present invention was devised to solve the above-described problems. The CO gas combustor is abolished by burning CO gas generated during melting and decomposing dioxin in an ash melting furnace. An object of the present invention is to provide an ash melting furnace capable of saving space and energy consumption.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, an ash melting furnace for melting fly ash and incinerated ash, the partition wall provided to suspend the ash melting furnace from the top of the ash melting furnace The ash melting chamber has an ash inlet at the top and the auxiliary heating chamber has an outlet that discharges exhaust gas at the same time as the molten slag is overflowed in the middle and discharged. In addition, a communication hole is provided in the upper part of the partition wall, the main electrode in the ash melting chamber and the furnace bottom electrode in the bottom part are arranged so as to face each other, and oxygen in the upper part of the auxiliary heating chamber. There is provided an ash melting furnace provided with an exhaust gas exhaust pipe which is provided with a gas supply port and which surrounds the tap port from the outside and opens up and down.
[0009]
According to a preferred embodiment of the present invention, a plasma torch is provided instead of the oxygen gas supply port.
[0010]
Next, the operation of the present invention will be described.
The ash melting furnace is composed of two chambers, an ash melting chamber and an auxiliary heating chamber. First, fly ash and incinerated ash charged into the ash melting chamber are heated to a molten slag by a main electrode and a furnace bottom electrode disposed in the ash melting chamber in a large ash melting chamber. Here, the ash is separated into a lower molten slag layer and an ash solid layer that floats thereon. The molten slag flows into the small auxiliary heating chamber through the communication path below the partition wall, and the exhaust gas flows into the auxiliary heating chamber through the communication hole above the partition wall. Air with an increased oxygen concentration is supplied from an oxygen gas supply port disposed in the auxiliary heating chamber to burn the CO gas in the exhaust gas. Instead of reheating with oxygen gas, reheating may be performed with a plasma torch using air as a plasma gas. The molten slag and the exhaust gas are discharged from the outlet that also serves as the exhaust gas outlet, and the molten slag is discharged downward in the exhaust gas discharge pipe that surrounds the outlet from the outside, and the exhaust gas is discharged upward. The exhaust gas is mixed with the air sucked from below by an exhaust gas exhaust pipe whose upper and lower sides are opened, and is rapidly cooled and discharged. Therefore, resynthesis of dioxins decomposed in the ash melting furnace can be prevented, dust can be prevented from adhering to the downstream side of the ash melting furnace exhaust gas outlet, and the combustor can be eliminated.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an embodiment of the present invention and is a longitudinal sectional view of an ash melting furnace according to the present invention.
In FIG. 1, reference numeral 1 denotes an ash melting furnace for melting fly ash and incinerated ash, and an ash melting chamber 2 having an ash charging port 3 at the top by a partition wall 6 suspended from the top of the ash melting furnace 1, The auxiliary gas heating chamber 5 is composed of two chambers having an oxygen gas supply port 10 in the upper portion and an outlet port 4 through which the molten slag 13 overflows in the middle portion. The tap outlet 4 also serves as an exhaust gas exhaust port (exhaust port) for exhausting exhaust gas 18 including gas generated by heating the ash solid layer 12 in the ash melting chamber 2 and gas generated from the molten slag 13. . 6a is a communication hole provided in the upper part of the partition wall 6, and the exhaust gas generated in the ash melting chamber 2 passes through this communication hole 6a, and is discharged from the outlet 4 through the auxiliary heating chamber 5. 7 is a communication path provided in the lower part of the partition wall 6 so as to communicate the lower part of the ash melting chamber 2 and the auxiliary heating chamber 5. The molten slag 13 melted in the ash melting chamber 2 is connected to the communication path 7. Through the auxiliary heating chamber 5. 13 a is a molten slag that has flowed into the auxiliary heating chamber 5, and 13 b is a molten slag discharged from the spout 4. Reference numeral 8 denotes a main electrode provided so as to penetrate the top of the ash melting furnace 1, and 9 denotes a bottom electrode embedded in the bottom of the ash melting furnace 1 so as to face the main electrode 8 vertically. Reference numeral 16 denotes a power source for direct current to the main electrode 8 and the bottom electrode 9, and 17 and 17a are electric wires thereof.
[0012]
Reference numeral 10 denotes an oxygen gas supply port provided in the auxiliary heating chamber 5, and air or oxygen gas 10 a having an increased oxygen concentration is supplied to the exhaust gas 18 containing CO gas flowing into the auxiliary heating chamber 5 and burned. Reference numeral 11 denotes an exhaust gas discharge pipe which surrounds the tap outlet 4 from the outside and opens up and down.
[0013]
Reference numeral 12 denotes an ash solid layer such as fly ash or incinerated ash charged into the ash melting chamber 2 and floats on the molten slag layer 13 in an unmelted state. 14 is a molten metal layer separated from the molten slag 13 and accumulated at the bottom of the ash melting chamber 2. In the molten metal layer 14, the electrical resistance is extremely smaller than that of the molten slag layer 13, so no Joule heat is generated in this portion, most of the metal is solid, and only the upper surface is slightly melted. The molten metal layer 14 generates an arc with the main electrode 8 at an appropriate time, melts the metal, and then discharges it to the outside through the metal discharge port 15. Reference numeral 19 denotes air that flows into the exhaust gas exhaust pipe 11 from below the exhaust gas exhaust pipe 11 and mixes with the exhaust gas 18 exhausted from the outlet 4 to cool the exhaust gas 18. In addition, the reason that the tap outlet 4 is provided in the middle of the ash melting furnace 1 is to overflow from here and keep the level of the molten slag layer 13 constant.
[0014]
FIG. 2 shows another embodiment of the present invention and is a longitudinal sectional view of an ash melting furnace. Note that the ash melting furnace shown in FIG. 1 has substantially the same configuration, and redundant description is omitted.
In FIG. 2, reference numeral 20 denotes a plasma torch provided in the auxiliary heating chamber 5 in place of the oxygen gas supply port 10. The concentration of the CO gas generated in the ash melting furnace 1 is usually 2 to 3%, but may be low depending on the conditions. In that case, since oxygen alone does not generate a sufficient amount of heat, the temperature in the auxiliary heating chamber 5 is increased by the plasma torch 20 using this air as a plasma gas.
[0015]
Next, the operation of the embodiment of the present invention will be described.
The ash melting furnace 1 includes two chambers, an ash melting chamber 2 and an auxiliary heating chamber 5. First, the fly ash and incinerated ash charged into the ash melting chamber 2 are heated in the large ash melting chamber 2 by the main electrode 8 and the furnace bottom electrode 9 disposed in the ash melting chamber 2 to form molten slag 13. Here, the ash is separated into a lower molten slag layer 13 and an ash solid layer 12 that floats thereon. The molten slag 13 flows into the small auxiliary heating chamber 5 through the communication passage 7 below the partition wall 6, and the exhaust gas 18 flows into the auxiliary heating chamber 5 through the communication hole 6 a above the partition wall 6. Air with an increased oxygen concentration is supplied from an oxygen gas supply port 10 disposed in the auxiliary heating chamber 5 to burn the CO gas in the exhaust gas. Instead of reheating with oxygen gas, reheating may be performed by a plasma torch 20 using air as a plasma gas. The molten slag 13a and the exhaust gas 18 are discharged from the tap outlet 4 which also serves as the exhaust gas discharge port. Is done. The exhaust gas 18 is mixed with the air sucked from below by the exhaust gas discharge pipe 11 whose top and bottom are opened, and is rapidly cooled and discharged. Therefore, recombination of the dioxins decomposed in the ash melting furnace 1 can be prevented, dust can be prevented from adhering to the downstream side of the ash melting furnace exhaust gas outlet, and the combustor can be eliminated.
[0016]
The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.
[0017]
【The invention's effect】
As described above, according to the present invention, it is possible to prevent recombination of dioxins decomposed in the ash melting furnace, and to prevent adhesion of dust to the downstream side of the ash melting furnace exhaust gas outlet, There is an excellent effect that the CO gas combustor can be eliminated.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an ash melting furnace according to the present invention.
FIG. 2 is a longitudinal sectional view of an ash melting furnace according to another embodiment of the present invention.
FIG. 3 is a longitudinal sectional view of a conventional ash melting furnace.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Ash melting furnace 2 Ash melting room 3 Ash inlet 4 Outlet 5 Auxiliary heating chamber 6 Partition wall 6a Communication hole 7 Communication path 8 Main electrode 9 Furnace electrode 10 Oxygen gas supply port 11 Exhaust gas discharge pipe 12 Ash solid layer 13 Molten slag 14 Molten metal 15 Metal outlet 16 Power source 18 Exhaust gas flow 19 Air flow 20 Plasma torch

Claims (2)

An ash melting furnace for melting fly ash and incinerated ash, wherein the ash melting furnace has an ash inlet at the top by a partition wall provided so as to be suspended from the top of the ash melting furnace; At the same time, the molten slag is overflowed in the middle portion and discharged, and at the same time, the auxiliary heating chamber having a discharge port for discharging the exhaust gas is formed, and a communication hole is provided in the upper part of the partition wall, The main electrode at the top and the furnace bottom electrode at the bottom are arranged so as to face up and down, and the oxygen gas supply port is arranged at the top of the auxiliary heating chamber. The exhaust gas exhaust pipe is opened, and CO gas in the exhaust gas flowing into the auxiliary heating chamber from the ash melting chamber through the communication hole is supplied, and air or oxygen gas with an increased oxygen concentration is supplied from the oxygen gas supply port. ash melting furnace, characterized in that so as to burn and Instead of the oxygen gas supply port, a plasma torch using air as a plasma gas is provided, and CO gas in the exhaust gas flowing into the auxiliary heating chamber from the ash melting chamber through the communication hole is converted into air plasma gas. The ash melting furnace according to claim 1, which is burned .

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