JP2001263643A - Method of heating melt and tapping structure of melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of heating melt capable of continuously discharging slag and preventing or avoiding a blockade in the vicinity of a slag discharge hole so that the melting furnace can be operated continuously and stably. SOLUTION: The method of heating melt at a slag discharge hole in a plasma arc type melting furnace includes a process of heating the melt from above a slag discharge gutter in the process of conveying the melt from the slag discharge hole to a melt discharging system through the slag discharge gutter. The tapping structure of the melting furnace comprises heating means for heating the melt from above the slag discharge gutter in the course from the slag discharge hole of the melting furnace to the melt discharging system through the slag discharge gutter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for heating a molten material in a slag port of a plasma arc melting furnace, and more particularly, to incinerated ash such as sewage sludge, municipal solid waste and industrial waste, and thermal power generation for business use. The present invention relates to a method for heating a molten material in the vicinity of a discharge port of a plasma arc type melting furnace for melting incineration ash discharged from a combustion furnace of a plant or the like by electric plasma, and an outlet structure of the melting furnace.

[0002]

2. Description of the Related Art Conventionally, incinerated ash (powder inorganic substance) such as sewage sludge, municipal solid waste and industrial waste has been used, for example, as shown in FIG. It is melted by a simple plasma arc melting furnace 11 and taken out as slag. In order to melt the incineration ash in the furnace body using such a melting furnace 11, the incineration ash discharged from the refuse incinerator is screened by a dry ash extraction device, a magnetic separator, an incineration ash silo, a measuring device, and an ash. After passing through a pretreatment system such as a supply conveyor, the ash is supplied from the ash supply hopper 12 into the furnace body, and the supplied incinerated ash is melted by the high-temperature plasma 20.
At this time, fly ash similarly discharged from the incinerator is mixed with the incinerated ash discharged from the incinerator via a fly ash silo or a measuring instrument and supplied from an ash supply conveyor.

[0003] The molten slag 21 generated in the melting furnace 11
Is discharged from a slag port 23 through a slag gutter 24 to a dry slag apparatus, guided to a slag discharge system via a slag conveyor, and used for various uses. At the top and bottom of the furnace body 11,
Main electrode 1 of plasma electrode connected to DC power supply 13
8 and electrodes are provided, and nitrogen gas is supplied from the nitrogen gas generator to the upper part of the furnace main body. Further, the furnace main body of the plasma arc type melting furnace 11 is composed of a refractory and a steel shell of a water cooling jacket (cooling structure 15) covering the outside thereof. Normally, the refuse incinerator is communicated with the chimney via a bag filter, while the exhaust gas generated in the melting furnace main body 11 passes through a secondary combustion chamber covered with a slag outlet cover 26, and then passes through a bag filter and a wet washing. It is being led to an exhaust gas treatment system consisting of a smoke tower and a chimney. Air is supplied from a combustion air fan to the secondary combustion chamber, and the bag filter is connected to a molten fly ash treatment device or the like.

By the way, normally, in the latter stage of the melting furnace as shown in FIG. 2, the molten slag accumulated in the furnace overflows and moves from the melting furnace 2 through the slag port 3 to the slag gutter 4. It is sent to a melt discharge system (slag discharge system) provided with a conveyor 6 and the like. The slag coming out of the slag port 3 is already considerably lower than the temperature in the furnace immediately before reaching the slag gutter 4. This is because the slag gutter 4 itself is usually
Because it is composed of a water-cooled copper block,
This is because the durability of the gutter itself is improved by using the water-cooled copper block. Therefore, when the molten slag of the incinerated ash melted in the furnace is continuously discharged from the slag port 3 by overflow, and when the exhaust gas of the furnace is further discharged from the same slag port, the salt vapor generated in the furnace is Was cooled and solidified in the vicinity of the slag port 3 and was fixed, so that there was a problem that the slag port, which is also the discharge port of the furnace gas, was blocked. In other words, the slag that is melted near the melting temperature flows from the slag port 3 to the slag gutter 4.
, It is rapidly cooled, so that it is likely to be solidified near the introduction of the slag port or the sluice gutter and may be blocked. Then, in order to release such a closed state, it was necessary to temporarily stop the operation and remove the solidified matter attached to the vicinity of the slag outlet. Therefore, it is difficult for the conventional apparatus to continuously and stably perform the melting process in the furnace,
It was necessary to constantly monitor the state of blockage, and when the blockage occurred, stop the operation to remove solidified slag.

On the other hand, in a structure in which the molten slag of the incinerated ash melted in the furnace is continuously discharged from the slag port 3 by overflow, the slag port is heated and kept warm by the heat taken out of the molten slag. Was. However, when the amount of slag from the molten slag is smaller than planned, for example, when the amount of incinerated ash generated is small due to a decrease in the amount of refuse treated, the molten slag is cooled and solidified by cooling at the slag outlet to form a weir-like structure. And the clogging state which hinders continuous slag discharge of molten slag frequently occurred.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, the inventors of the present invention have made it possible to continuously discharge slag so that the melting furnace can be operated continuously and stably, and to block the vicinity of the slag outlet. Prevent
In order to develop a method for heating the molten material that can be avoided, the present inventors have conducted intensive studies. As a result, the present inventors include a heating step of heating the melt from above the slag gutter during the step of moving the melt from the slag port to the melt discharge system through the slag gutter. thing,
Alternatively, as a melting furnace outlet structure at the slag outlet, by heating the melt by a heating means from above the slag outlet from the slag outlet to the melt discharge system through the slag gutter. And found that the above problems could be solved. The present invention has been completed from such a viewpoint.

[0007]

That is, the present invention relates to a method for heating a molten material at a slag port of a plasma arc type melting furnace. A heating step of heating the melt from the upper part of the slag gutter during the step of moving the melt until the step of moving the melt. Here, by performing temperature detection at the outlet of the slag gutter, the temperature of the melt is measured, and when the temperature of the melt reaches a predetermined temperature or lower, the heating in the heating step is performed so that the melt does not solidify. Temperature control can be performed. The present invention also relates to a melting furnace outlet structure at a slag port of a plasma arc type melting furnace, wherein the slag port extends from the slag port of the melting furnace to a melt discharge system through a slag gutter. A heating furnace for heating a molten material from an upper part of a slag gutter is provided. Here, a slag outlet burner is suitable as the heating means. Further, in the outlet structure of the melting furnace using non-oxide-based bricks as the refractory inside the melting furnace, the lower part of the slag outlet burner is installed to be inclined outward from the furnace core with respect to the slag gutter. Is preferred. Thereby, oxygen can be prevented from entering the furnace by the flame of the burner, and the problem of oxidative corrosion of the refractory in the furnace can be avoided.

By using the heating method or the outlet structure of the present invention, a blockage state near the slag opening due to solidification of the melt is avoided, and continuous slag discharge of the melt is enabled. And
It is possible to continuously and stably perform the melting process in the plasma arc type melting furnace, always monitor the clogging condition, and stop the operation when it is clogged to remove slag mass. There is no need for a process.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on illustrated embodiments. FIG. 1 is a diagram showing a melt outlet structure and an arrangement of peripheral devices according to an embodiment of the present invention, and a heating burner is used as a heating means. The plasma arc type melting furnace 2 of the present embodiment has a structure shown in FIG.
As shown in FIG. 1, a furnace body 2 having a cylindrical shape with a bottom is provided. On the lower side surface of the furnace body 2, a slag port 3 for extracting molten slag and exhaust gas is provided. Also,
On the upper part of the furnace main body 2, a main electrode of a plasma electrode connected to a DC power supply device (not shown) is provided so as to hang therefrom, and nitrogen gas is supplied to the main electrode from a nitrogen gas generator. The incineration ash of the input waste is heated and melted by high-temperature plasma.

The melting furnace 2 is composed of a refractory (brick, caster) and a water-cooled jacket that covers the outside of the refractory, and the water-cooled jacket is formed of iron shell (iron plate) and has a closed cross section. . A through-hole (through-hole) for the main electrode is formed in the upper center of the melting furnace 2, and an insulating sleeve and a blowing nozzle (wind box) for sealing gas (nitrogen gas) are provided in the through-hole. ing. When discharging the slag, the slag gutter 4 overflows at the position shown by the solid line in FIG. 1 and is sequentially discharged, but when discharging the molten metal, the slag gutter 4 extends to the position indicated by the dotted line around the shaft 8. After the furnace is tilted, the molten metal is discharged.

The outlet structure according to the present embodiment is adapted for the molten slag discharged from the melting furnace 2 along the drain gutter 4.
The upper part is provided with a burner 1 as a heating means. By providing a heating burner or the like above the molten slag flow path at the subsequent stage of the slag outlet, the molten slag flowing on the slag gutter 4 is heated by the flame of the burner. On the other hand, non-oxide bricks such as SiC bricks and carbon bricks are widely applied to the refractory constituting the inner wall surface in the melting furnace 2. In this case, when the flame heating is performed by the burner, a problem of oxidation corrosion of the brick due to penetration of oxygen may occur. That is, in the case of heating means using a burner, oxygen is also released.
A gas flow of a gas containing oxygen is created in the furnace, and adverse effects such as refractory (SiC, carbon, etc.) inside the furnace being oxidized and brittle may be considered. Therefore, when the outlet structure of the present invention is applied to a melting furnace, a mode in which the lower part of the slag outlet burner is inclined outward from the furnace core with respect to the slag gutter 4 or a molten slag It is preferable that the flame of the burner is fired in the direction in which the gas flows down. This can prevent oxygen from entering the melting furnace due to the flame of the burner, and can avoid the problem of oxidation of refractories in the furnace.

With respect to the inclination and the direction of the burner 1 with respect to the slag gutter 4, it is preferable that the flame is fired outward from the core as close as possible to the slag gutter 4 as much as possible. However,
Normally, the angle θ from the gutter 4 to the upper part of the burner 1 is preferably about 20 to 80 °, and more preferably 30 to 60 °, due to structural restrictions of the slag port. Generally, the slag gutter 4 has an angle larger than a right angle on the slag outlet 3 side with respect to the outer wall of the furnace 2, and has a structure in which molten slag flows easily. Therefore, even when the burner 1 is installed in the vertical direction (see FIG. 1B), the burner 1 has an angle larger than a right angle with respect to the slag gutter 4.

When the molten slag is discharged, the slag gutter 4 is located at a position as shown by the solid line in FIG. However, when the molten metal is slagged, the slag gutter can be varied around the axis 8 and the slag gutter can be inclined as shown by a dotted line. In order to further facilitate slag removal, a slag opening means (cleaner 5) may be provided. A cutter-like member (blade) for shaving and removing solidified slag is provided at the tip of the cleaner 5.
Usually, when the rod-shaped cleaner itself advances in the furnace direction while rotating, it simultaneously rotates and scrapes solidified substances (slag) attached like a drill.

According to the outlet structure of the present invention having such a heating means, during the step of moving the melt from the slag outlet to the melt discharge system via the slag gutter, the upper surface of the slag gutter is used. A heating step of heating the melt can be performed to heat the melt. At this time, the temperature of the melt is measured by detecting the temperature at the outlet of the slag gutter 4, and when the temperature of the melt reaches a predetermined temperature or lower, the heating in the heating step is performed so that the melt does not solidify. It is preferable to control the temperature.
The location where the temperature is measured is not particularly limited as long as it is in the process of moving the melt from the slag port to the melt discharge system through the slag gutter, but there is a lot of dust near the melting furnace 2, Difficult to measure. Therefore, the latter part of the slag gutter 4 where the temperature of the molten material has dropped due to cooling of the slag gutter 4 or the like is preferable. By providing a temperature detecting means such as a radiation thermometer near the outlet of the slag gutter 4, the temperature of the molten slag is measured and the heating means is controlled so as not to be solidified. For example, there is a method in which the burner 1 is ignited at a temperature immediately before solidification of the melt starts.

By performing the control based on such temperature detection, the amount of slag discharged from the ash is reduced, for example, due to a decrease in the amount of ash treatment, so that the temperature of the slag outlet is reduced and the molten slag flowing over the slag gutter is cooled and solidified. Even in such a case, the burner 1 can be automatically ignited, and the molten slag flowing on the slag gutter 4 can be heated by the burner flame and not solidified. As a control method,
When a temperature detector is installed near the outlet of the gutter, the temperature for automatic ignition may be, for example, in the range of 1200 to 1400 ° C. The reason why the measurement in the vicinity of the outlet of the slag gutter 4 is preferable is that it is necessary to maintain the temperature at which the slag gutter does not solidify while flowing through the slag gutter, and that the temperature is the lowest at the gutter outlet. About 1400 ° C). Also, from the viewpoint of the performance of the thermometer, the range close to the furnace is extremely high, so that sufficient temperature measurement cannot be performed in many cases.
As the temperature detector used here, a radiation thermometer, an infrared camera, and the like are preferably mentioned.

As described above, according to the present embodiment, generation of solidified material can be avoided by heating the melt in an appropriate temperature range, and a smooth flow can be ensured in the process of moving the melt after the slag outlet. Therefore, the slag port does not fall into a closed state due to solidified matter or the like, and the furnace can be continuously operated.

In the plasma arc type melting furnace 11 shown in FIG. 3, when incinerated ash of waste is supplied from the ash hopper 12 into the furnace main body, the supplied ash is heated by the high-temperature plasma 20 and melted to form slag. 21 and the molten metal 22 is present below it. The molten slag 21 is discharged from a slag outlet through a slag gutter, dropped on a conveyor, and collected by a slag discharge system. The melting furnace outlet structure used in the present embodiment is provided in a path for discharging molten slag, molten metal, and exhaust gas from the molten state in such a furnace, and is usually installed at a stage subsequent to the slag outlet. Things. Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made without departing from the spirit of the present invention. is there.

[0018]

As described above, when the heating method or the outlet structure according to the present invention is used, a closed state near the slag outlet due to solidification of the melt is avoided, and continuous slag discharge of the melt is enabled. And the melting process in the plasma arc melting furnace,
It is possible to carry out continuously and stably, and it becomes possible to operate the melting furnace continuously. Further, it is not necessary to always monitor the state of blockage, and to stop the operation when the blockage is blocked and to remove the slag lump.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a melting furnace outlet structure according to the present invention and an arrangement of devices around the melting furnace outlet structure.

FIG. 2 is a view schematically showing a conventional melting furnace outlet structure.

FIG. 3 is a configuration diagram schematically showing a plasma arc type melting furnace and a system associated therewith.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Burner (heating means) 2 Plasma melting furnace 3 Slag port 4 Slag gutter 5 Cleaner 6 Conveyor 7 Slag port cover 8 Exhaust gas treatment device 11 Melting furnace 12 Ash hopper 13 Power supply 14 Ash inlet 15 Cooling structure 16 Refractory 17 Sleeve 18 Main electrode 20 Plasma arc 21 Molten slag 22 Molten metal 23 Outlet 24 Outlet gutter 25 Outlet cleaner 26 Outlet cover

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Noma 1-8-1 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture Inside Mitsubishi Heavy Industries, Ltd. Yokohama Research Laboratory (72) Inventor Kazuhiko Tomiwaki 12-nishikicho, Naka-ku, Yokohama-shi, Kanagawa F-term (reference) in Ryohichi Engineering Co., Ltd.

Claims (5)

[Claims] 1. A method for heating a melt at a slag port of a plasma arc type melting furnace, wherein during the step of moving the melt from the slag port to a melt discharge system through a slag gutter, A method for heating a melt, comprising a heating step of heating the melt from an upper portion of the slag gutter. 2. The temperature of the molten material is measured by detecting the temperature near the outlet of the slag gutter, and when the temperature reaches a predetermined temperature or lower, a heating step is performed so that the molten material is not solidified. 2. The method for heating a melt according to claim 1, wherein the heating is performed in step (a). 3. A melting furnace outlet structure at a slag outlet of a plasma arc type melting furnace, wherein the slag is discharged from the slag outlet of the melting furnace to a melt discharge system through a slag gutter. A melting furnace outlet structure, wherein a heating means for heating the melt from an upper part of the gutter is provided. 4. The melting furnace outlet structure according to claim 3, wherein said heating means is a burner. 5. An outlet structure of a melting furnace using a non-oxide brick as a refractory inside the melting furnace, wherein a lower portion of the burner is installed so as to be inclined outward from a furnace core with respect to a discharge gutter. The melting furnace outlet structure according to claim 4, characterized in that: