JP2001227713A - Melting furnace for refuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem in the conventional art that a refuse melting furnace provided only with a coke bed requires a separate apparatus for producing oxygen-rich air, entailing increase in the installation cost, and a melting furnace provided only with a plasma torch is not separately equipped with a tuyere for delivering air blast, and accordingly the incineration heat of the refuse can hardly be utilized. SOLUTION: Refuse and coke are supplied into a shaft furnace, the refuse is burned and gasified in an atmosphere of at most a stoichiometric amount of air to the material to be burned, and the residue is discharged out of the furnace as a molten slag. A coke layer is formed on the furnace bottom, the plasma torch is installed so as to blast heated air to the coke layer. Further, a tuyere is provided so as to blow air to the refuse stacked on the coke layer, the pressure around the bottom is positive on an average of 0.3-50 kPa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refuse melting furnace in which refuse is burned and gasified in a furnace, and the remaining ash and char are melted in the same furnace to form molten slag and discharged outside the furnace.

[0002]

2. Description of the Related Art Conventionally, refuse has generally been incinerated in a stalker furnace or a fluidized-bed furnace, and the incinerated ash is landfilled. However, since the volume of incinerated ash has not been reduced sufficiently during landfill disposal recently, and the incinerated ash is scattered during landfill disposal and adversely affects the surrounding environment. It is recommended to landfill it. Therefore, there are two methods of melting garbage, one to convert incineration ash discharged from a conventional incinerator into molten slag in a separate melting furnace, and another to convert garbage into molten slag in one furnace. There are things.

[0003] As a method for converting garbage into molten slag in one furnace, for example, JP-B-56-2234 (prior art-1) and JP-B-60-11766 (prior art-
2), JP-A-2-298717 (prior art-
3), JP-A-4-124515 (prior art-4)
There is one described in. The melting furnaces described in the prior arts 1 and 2 use coke and refuse combustion as heating sources.
In order to burn it, oxygen-rich air is supplied, and the molten slag is discharged intermittently. The melting furnace described in Prior Art-3 uses combustion of coke and hot air from a plasma torch as a heating source. Prior art-4 uses coke combustion and hot air from a plasma torch as a heating source.

[0004]

However, in the prior arts 1 and 2 among the above-mentioned prior arts, a separate device for producing oxygen-enriched air is required, and in order to discharge the molten slag intermittently. There is a problem that it is necessary to open and close the discharge port. Prior art 3,
In No. 4, a plasma torch is used, but a tuyere for blowing air for burning dust and the like is not separately provided, so that the combustion heat of the dust can hardly be used. There is a problem that an auxiliary heat source such as electric power increases. An object of the present invention is to solve the problems described above and to provide a dust melting furnace that enables continuous discharge of molten slag and requires less external heat source to be added from outside.

[0005]

According to the present invention, dust and coke are supplied into a shaft furnace, and the dust is burned and gasified in an atmosphere having a stoichiometric amount of air or less for the combustible substances, and the residue is melted. A melting furnace for refuse discharged to the outside of the furnace as slag, in which a coke layer is formed at the bottom of the furnace, and a plasma torch is provided so as to blow hot air toward the coke layer, and is deposited on the coke layer. The tuyere is provided so as to blow air toward the garbage layer. Further, the vicinity of the furnace bottom is 0.3 to 5 on average.
The pressure is a positive pressure of KPa, and furthermore, the molten slag is continuously discharged from a molten slag discharge port provided in a furnace bottom.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The refuse melting furnace of the present invention forms a coke layer on the bottom of a shaft furnace, heats this coke layer with hot air blown from a plasma torch, and burns a part of the coke layer. This heat causes the waste accumulated on the coke layer to burn and gasify in an atmosphere with a stoichiometric amount of air or less, and the resulting ash is converted into molten slag in the coke layer and discharged outside the furnace. To discharge. Since ash and char form molten slag, when cooled, the molten slag becomes glassy material, reducing the volume of ash and char to about 1/5, and heavy metals etc. are confined in the glassy material. No elution.

In the melting furnace of the present invention, the hot air of the plasma torch is blown toward the coke layer. The amount of hot air from the plasma torch is the sum of the plasma air and the shroud air. The temperature of the hot air from the plasma torch is 1000 ~ 2500 ℃, so that the coke layer is heated and a part of the coke layer is burned by the oxygen in the hot air, so the temperature in the coke layer is stable at about 1500 ℃ Can be maintained. Set the temperature of the coke layer to 1500
In order to maintain the temperature, it is necessary to use oxygen-enriched air only to maintain the temperature, for example, only by the heat of combustion of coke. However, in the melting furnace of the present invention, a plasma torch is used. The air may be ordinary air, and if necessary, nitrogen. At that time, since heat due to coke combustion cannot be expected, it is necessary to increase the output of the plasma torch.

[0008] The blowing pressure of the plasma air and shroud air of the plasma torch is a positive pressure of 147 KPa.
It becomes a positive pressure of 5 KPa. The pressure near this furnace bottom is 5 KPa
When the molten slag discharge port communicates with the inside of the furnace, the hot air of about 1500 ° C. in the furnace is strongly blown out, thereby causing a disadvantage that a large amount of heat in the furnace is taken out of the furnace. , There is a danger of burns to those working around the furnace. When the pressure in the vicinity of the furnace bottom is lower than 0.3 KPa, the force for pushing out the molten slag generated by the pressure difference from the outside air becomes small, and it becomes difficult to discharge the molten slag.

Since the melting furnace of the present invention uses a plasma torch for the shaft furnace, the furnace has an extremely rugged structure without a movable body and the plasma torch has excellent operability. Easy to do. In addition, since the melting furnace of the present invention has a structure in which the furnace bottom can be separated, inspection and repair around the furnace bottom and the plasma torch, which are exposed to the most severe conditions both in temperature and environment in the furnace, are required. It can be done very easily.

Next, an embodiment of a refuse melting furnace according to the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a refuse melting furnace system according to the present invention, and FIG. 2 is a sectional view showing a refuse melting furnace of the present invention. 1 and 2, reference numeral 2 denotes a furnace body, a plasma torch 1 near the furnace bottom, and a first tuyere 3 and a second tuyere 4 above the plasma torch 1.
Is provided. In this embodiment, the plasma torch 1 is provided at two places on the circumference of the same height of the furnace body, and the direction of the hot air blown out from the plasma torch is the diameter direction of the furnace body in a plane, and the direction of the furnace bottom in the elevation. The direction was the direction of the intersection of the bottom and the vertical part. The first tuyere 3 and the second tuyere 4 were also provided at six locations on the circumference. As the air blown from the first tuyere 3 and the second tuyere, the air that has been heated to a high temperature by exchanging heat with a high-temperature gas in a secondary combustion furnace described later by a heat exchanger is used. The furnace body 2 has a refractory material 202 applied inside an outer shell 201. In the present embodiment, the furnace body 2 has a structure in which the furnace body 20 and the furnace bottom body 21 are connected to each other, and the furnace bottom body 21 is suspended from the furnace body 20. And move it to the designated place. By doing so, the repair of the furnace bottom 21 and the repair of the inside of the furnace main body 20 are facilitated.

A supply port 5 is provided at a substantially middle portion of the furnace body 2 in an elevational direction, and a pusher 6 is provided in connection with the supply port 5. The pusher 6 has a dust supply device 7 and a coke supply device. 8 are connected. Although not shown, the dust supply device 7 and the coke supply device 8 are provided with double butterflies so as to block invasion of outside air as much as possible. An exhaust gas port 9 is provided near the upper part of the furnace body 2, and the secondary combustion furnace 10, the primary cooling tower 11, the heat exchanger 12, the secondary cooling tower 13, and the dust collector 14 are connected to the exhaust gas port 9. Yes, dust collector 14
After that, an unillustrated induction fan and an exhaust tower are connected. The furnace bottom 2 of the furnace body 2 is provided with a molten slag discharge port 23 communicating with the inside of the furnace body 2.
5 and a slag cooling water tank 16 are provided.

Next, the operation and operating conditions of the melting furnace of the present invention will be described. First, when starting the temperature rise of the furnace body 2 in the normal temperature state, the furnace bottom 22 is filled with coke and the coke layer 25 is filled.
And then ignite the plasma torch 1 for about 1
Hot air at 800 ° C. is blown toward the coke layer 25.
The furnace bottom 22 and the coke layer 25 are heated by the hot air of the plasma torch 1 and the heat of combustion of the coke for about three hours.
Raise the temperature to about 0 ° C. The dust is supplied from the dust supply device 7 into the furnace body 2 by the pusher 6 and the mixture of coke and limestone is supplied from the coke supply device 8 by the pusher 6. In this embodiment, the weight ratio of coke to dust is 2%. When dust and coke are supplied, a dust layer 26 is formed on the coke layer 25 in which dust and coke are alternately formed in a substantially layered shape. In the present embodiment, the air supplied into the furnace body 2 is supplied from the plasma torch 1 and the first and second tuyeres 3, 4, and the total amount of air is the combustible material such as coke and dust in the furnace body 2. Stoichiometric air amount or less, and the ratio of stoichiometric air amount: total air amount is actually 1:
0.2 to 0.5.

The dust layer 26 deposited on the heated coke layer 25 is dried and a part thereof is burned by the combustion air, and another part is gasified because the combustion air consumes the combustion air. The ash generated by the combustion of the refuse and the char generated by the gasification are melted by the hot air from the coke layer 25 heated to about 1500 ° C. to become molten slag, which flows down the coke layer 26 and accumulates in the furnace bottom 22.
The molten slag accumulated in the furnace bottom 22 is discharged from the furnace through a molten slag discharge port 23 provided in the furnace bottom. As described above, the supply of garbage and the supply of coke are performed at a ratio of 3: 1. Therefore, it is considered that the garbage and the coke form a layer substantially alternately, and the quantitative ratio is about 2%. Since combustion is much quicker than coke, most of the combustion air described above is consumed for the combustion of dust, and coke is difficult to burn, and consequently coke is less consumed.
As a result, the upper part of the garbage layer 26 is a zone 26 where garbage is rich.
1 and the garbage layer 2 where garbage combustion and gasification progress
A zone 262 where dust and coke coexist is formed in the middle of the zone 6, and a zone 263 where almost all coke is formed below the dust layer 26. As a result, the coke layer 25 is continuously formed at a predetermined height in the furnace bottom 22, and the level of the coke layer 25 is maintained when the consumption amount and the supply amount of coke are balanced. is there.

In the melting furnace of the present invention, the heat input in the heat balance in the furnace is covered by the calorific value of the plasma torch, the calorific value of burning refuse, and the caloric value of burning coke.
For example, nitrogen may be used instead of air as the hot air source of the plasma torch. At that time, of course, the coke combustion is smaller than the air and the heat input is also reduced,
To compensate for this, it is necessary to increase the output of the plasma torch.

(Embodiment) Next, an embodiment in which refuse is melted using the melting furnace of the present invention will be described. The properties of the garbage used in this example are shown below. Dust type: General waste (mainly household waste) Moisture content: 55% Lower heating value: 358 KJ / Kg Ash content: 8% The above-mentioned garbage was melted under the following conditions. Dust supply amount: 1000 kg / hour Coke supply amount: 20 kg / hour Total air amount: 700 Nm ³ / hour Air amount from the plasma torch: 150 Nm ³ / hour The test was carried out under the above conditions, but the hot air from the plasma torch at that time The temperature was about 1800 ° C., the ambient temperature of the coke layer 25 at the furnace bottom was 1500 ° C., and the pressure at the furnace bottom 22 was 1.5 KPa on average as a positive pressure.

The temperature of each part in the furnace body 2 was substantially constant at about 1500 ° C. in the coke layer, and was 500 to 900 ° C. in the space above the dust layer 26. Since the garbage is supplied in batches of once / one minute, the temperature is lowered at the moment when it is supplied, because the water in the garbage evaporates and the temperature is reduced. It is.
About 60 minutes after the start of supplying the refuse, the molten slag began to be discharged from the molten slag discharge port. Discharge of molten slag was on average about 80 kg per hour. Although the amount of hot air from the plasma torch was 150 Nm ³ / hour in the present embodiment, if the amount was 250 Nm ³ / hour, the furnace bottom 2
2 and the temperature in the coke layer 26 decreased, and it became impossible to maintain 1500 ° C., and the discharge of the molten slag became stagnant.

When refuse and coke are supplied to this furnace for combustion and gasification, the following process is performed. Since the upper part of the deposited dust layer has just been supplied, it is a dust-rich part in which the amount of coke in the dust is small. The garbage burns or gasifies in the lower part from there, and the amount decreases rapidly.However, the amount of coke in the garbage is less than the amount of coke in the garbage because it is harder to burn and the amount of the coke is harder to reduce. It becomes a mixed part that gradually becomes larger. Furthermore, in the lower part, the refuse is burned or gasified and turned into ash or char, but a large amount of coke still remains, and this becomes a coke-rich part (coke layer). The ash that has reached the coke layer has a high temperature of about 1500 ° C. and is melted to form molten slag, which flows down the coke layer and accumulates at the bottom of the furnace, and is sequentially discharged out of the furnace through an outlet. Since the coke layer is a packed bed with a large number of gaps, the molten slag easily flows down between them, and does not solidify partly because it is evenly exposed to the hot air while it is stored in the furnace bottom. In addition, since the hot air of the plasma torch is blown toward the lower part of the coke layer, the whole coke layer can stably maintain a high temperature of about 1500 ° C, and the molten slag maintains a stable molten state. Can be.

In this embodiment, the blowing pressure of the shroud air blown from the plasma torch is set at 147 KPa. And acts as a pressure difference sufficient to extrude the molten slag from the furnace bottom 22. However, even if the liquid level of the molten slag drops and hot air blows out in the furnace, the momentum is weak and does not cause danger. Furnace bottom 2 as described above
The low furnace pressure near 2 enables continuous discharge of molten slag. In the present embodiment, an example is shown in which the dust supply port 5 is provided at a substantially intermediate portion of the furnace body 1, but the present invention is not limited to this. For example, the dust supply port 5 may be provided near the furnace top of the furnace body 1. .

[0019]

As described above, the refuse melting furnace of the present invention has the above-mentioned construction, so that the molten slag can be continuously discharged.
In addition, it is possible to provide a refuse melting furnace that requires a small amount of auxiliary heat source to be added from the outside.

[Brief description of the drawings]

FIG. 1 is a schematic view of a system relating to a refuse melting furnace of the present invention.

FIG. 2 is a sectional view showing a refuse melting furnace of the present invention.

[Explanation of symbols]

1 plasma torch, 2 furnace body, 3, 4 tuyere, 5
Supply port, 7, garbage supply device, 8 coke supply device,
9 exhaust gas port, 20 furnace body, 21 furnace bottom, 22 furnace bottom, 23 molten slag discharge port, 25 coke layer, 2
6 garbage layer

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Hiroyuki Hagiwara 6010 Sankajiri, Kumagaya-shi, Saitama F-term in Hitachi Metals Co., Ltd. Production System Laboratory (reference) 3K061 AA16 AB02 AB03 AC01 BA07 CA08 CA14 DB16

Claims (3)

[Claims] 1. Dust and coke are supplied into a shaft furnace, and the refuse is burned and gasified in an atmosphere having a stoichiometric amount of air or less for the combustible substances, and the residue is discharged out of the furnace as molten slag. A dust melting furnace, in which a coke layer is formed at the bottom of the furnace, a plasma torch is provided so as to blow hot air toward the coke layer, and air is directed toward the dust layer deposited on the coke layer. A refuse melting furnace characterized by having tuyeres provided to blow it. 2. The average value in the vicinity of the furnace bottom is 0.3 to 5 KPa.
2. The refuse melting furnace according to claim 1, wherein the pressure is positive. 3. A molten slag is continuously discharged from a molten slag discharge port provided at a furnace bottom.
2. A refuse melting furnace according to 1.