JPH10176820A - Melting furnace starting-up method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a melting furnace starting-up method which is designed to reduce load of a waste gas treatment plant by reducing work load which digs a condensed substance in the furnace and protecting a furnace main body in the digging work of this condensed substance and reducing the generation amount of gas. SOLUTION: Charged incineration ashes are heated by the application of power to a melt with electrodes 2 provided in a melting furnace, and a lower molten metal forming the lower layer and a molten slag forming the upper layer out of the furnace are extracted separately. The starting-up method of the melting furnace is arranged to leave the molten slag S by a proper depth during the operation interruption time of the melting furnace. When restarting the operation, the top of the solidified slab S is slightly dug, thereby forming a recessed area 7. An electric conductive material 8 is provided in the recessed area 7 and the electrodes 2 are arranged to drop into contact with the electric conductive material 8 where the incineration ashes or ground slag S1 are supplied to the recessed area 7 and the electric conductive material 8 is covered therewith and then electrically energized with the electrodes 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a start-up method for restarting operation of a melting furnace for melting incineration ash generated in an incinerator.

[0002]

2. Description of the Related Art Incineration ash generated in an incinerator is melted by a melting furnace having a structure shown in FIG. 2 (FIG. 2 shows a startup state at the time of restarting operation. There.)

This melting furnace is of a so-called electric resistance type. A plurality of electrodes 2 are provided, are driven up and down in the furnace, and are supplied with electric power from outside the furnace. The plurality of lowered electrodes 2 conduct electricity through the melt, generate Joule heat, and melt the incineration ash supplied from the inlet 3. The molten material is separated into a lower molten metal and an upper molten slag due to a difference in specific gravity.

When the operation of the melting furnace is stopped, the slag discharge port 5 and the metal discharge port 6 are opened, and the molten slag and the molten metal are separately discharged outside the furnace. At this time, all the molten slag and molten metal are discharged outside the furnace as much as possible. However, since the viscosity of the molten slag increases as the temperature decreases, the molten slag cannot be completely discharged. For this reason, the molten slag is not completely discharged, and as a result, remains at the furnace bottom. Along with this molten slag, a small amount of molten metal also remains at the furnace bottom. The slag mixed with such a metal is herein referred to as a metal mixed slag. This metal-mixed slag solidifies over time.

When the operation is resumed, as shown in FIG. 2, a flat surface is formed by slightly digging the upper surface of the solidified metal-mixed slag S2 on the furnace bottom, and an electrically conductive material 8 made of a conductive material is laid on the flat surface. Then, the electrode 2 is lowered and brought into contact with the current-carrying material 8, and then the incineration ash A is charged into the furnace so as to cover the current-carrying material 8.

[0006] When the furnace is started, it is necessary to make the heat capacity of the furnace reach a predetermined value or more. That is, unless the inside of the furnace is filled with a predetermined amount or more of the molten material, it is not possible to perform a normal operation of continuously injecting and melting the incinerated ash. Therefore,
When the furnace is started, incineration ash A in an amount capable of producing the melt is charged.

The current-carrying material 8 in contact with the electrode 2 is energized to generate a minute arc between the current-carrying material particles, thereby melting the incinerated ash A in contact with the current-carrying material 8. Next, the molten slag is energized to generate Joule heat, and the incinerated ash A is sequentially melted by the heat. The gas (e.g., carbon monoxide CO) generated from the heated incineration ash A is discharged from the exhaust gas port 4 and then burned in an exhaust gas treatment facility (not shown) to be rendered harmless.

[0008]

However, in the above-mentioned conventional example, there are the following problems in starting up the furnace when restarting the operation of the furnace.

At the furnace bottom, a relatively shallow layer of solidified metal-mixed slag S2 is formed. Then, in order to form a plane on which the conductive material 8 is laid, it is necessary to dig this metal-mixed slag S2. However, since the metal-mixed slag S2 contains a metal, the slag S2 has a high hardness and is relatively difficult to dig. Further, since the metal-mixed slag S2 is a shallow layer formed on the furnace bottom, there is a possibility that the furnace main body 1 may be erroneously damaged when digging.

Further, when the furnace is started, only a shallow layer of solidified metal-mixed slag S2 is formed on the bottom of the furnace. Ash A needs to be charged into the furnace. However, when such a large amount of incineration ash A is heated, the amount of generated gas is larger than that during normal operation, and the load on the exhaust gas treatment equipment for burning this gas outside the furnace increases. Correspondingly, the processing capacity of the exhaust gas treatment equipment must be increased only at the time of startup, which leads to an increase in cost.

The present invention has been made to solve such a problem of the conventional example.

An object of the present invention is to reduce the work load for digging solidified material in a furnace, to protect the furnace main body when digging this solidified material, and to reduce the amount of generated gas to reduce the load on exhaust gas treatment equipment. It is an object of the present invention to provide a method for setting up a melting furnace which aims to reduce the temperature.

[0013]

In order to achieve this object, the present invention is to melt the incinerated ash supplied by energizing the melt in the furnace by means of an electrode disposed in the melting furnace, thereby forming a lower layer. In the method of starting the melting furnace, in which the molten metal to be formed and the molten slag forming the upper layer are separately taken out of the furnace, the molten slag is left in the furnace to an appropriate depth when the operation of the melting furnace is stopped, and when the operation is restarted. Then, a recess is formed by slightly dug the upper surface of the solidified slag, an energizing material is arranged in the recess, the electrode is lowered until it contacts the energizing material, and incineration ash or pulverized slag is supplied to the recess. After covering the current-carrying material with the electrodes, the electrode is energized with the current-carrying material.

In this method of starting a melting furnace, slag with low hardness is dug, so that the burden of digging work is smaller than in the conventional example of digging slag with high hardness mixed with metal. In addition, since the slag remains in the furnace at an appropriate depth, there is no risk of damaging the furnace body when digging a concave portion.

[0015] Further, the pulverized slag or incinerated ash arranged in the concave portion formed in the slag is heated and melted, and thereafter,
By the heat of the melt, the slag and metal left in the furnace at an appropriate depth are melted. Due to the large amount of melt obtained from slag and metal left in the furnace, first heating,
The amount of ground slag or incinerated ash to be melted is small. As a result, the amount of gas generated by the first heating is small. Since the gas in the solidified slag that has been previously melted has already been released, almost no gas is generated when the solidified slag is melted.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG.

FIG. 1 shows a melting furnace for explaining the melting furnace starting method of the present invention (FIG. 1 shows a starting state at the time of restarting operation).

This melting furnace comprises a furnace body 1 and a furnace body 1
A plurality of electrodes 2 driven up and down and supplied with power from outside the furnace, an incineration ash inlet 3 provided at the top of the furnace body 1, and Exhaust gas port 4 provided at the top, slag discharge port 5 provided through the middle part of the side wall of furnace body 1, and metal discharge port 6 provided through the side wall at the furnace bottom level. And

The exhaust gas port 4 is connected to an exhaust gas treatment facility (not shown) on the downstream side. This exhaust gas treatment facility burns a gas such as carbon monoxide CO to render it harmless.

The operation of the melting furnace, the stoppage of the operation, and the start-up when restarting the operation are performed as follows.

First, in the normal operation of the melting furnace, the lowered electrode 2 is energized through the melt, generates Joule heat, and melts the incinerated ash. The molten material is separated into a lower molten metal and an upper molten slag due to a difference in specific gravity. The molten slag overflows from an overflow port (not shown), so that the upper surface level is maintained at the rated level L.

When the operation is stopped, the slag discharge port 5 is opened to discharge the molten slag, and the molten metal is left in the furnace without being discharged. However, as the temperature of the molten slag decreases, the viscosity of the molten slag increases. After all,
The molten slag will remain in the furnace to an appropriate depth.

The molten slag and molten metal remaining in the furnace solidify over time. Here, these are referred to as solidified slag and solidified metal.

Next, when restarting the operation, the melting furnace is started up as shown in FIG. First, a recess 7 is formed by partially dug a part of the upper surface of the solidified slag S only at a position below the electrode 2. In the recess 7, a conductive material 8 made of, for example, carbon particles is arranged. Next, the electrode 2 is lowered until it comes into contact with the conductive material 8. Then, the slag S <b> 1 is supplied to the concave portion 7 so as to cover the conductive material 8. That is, the slag S1 dug out when forming the concave portion 7 is returned to the concave portion 7.

In the present embodiment, the crushed slag is provided in the concave portion 7. However, incineration ash may be provided together with or separately from the slag.

The electrode 2 comes into contact with the current-carrying material 8, and the current-carrying material 8 is energized to generate a minute arc. By the heat of the conductive material 8, the pulverized slag S1 is melted, and then the molten stag is energized to generate Joule heat, the solidified slag S is melted by the heat, and the metal M solidified by the heat of the melted slag. Melts.

Since a large amount of solidified slag and metal left in the furnace become a molten material, the crushed slag S1, which is heated by the electrode 2 in the initial stage of startup,
A small amount of incineration ash is sufficient. As a result, the amount of gas generated when the crushed slag S1 and the incinerated ash are heated is small. Since the gas in the solidified slag that has been previously melted has already been released, almost no gas is generated when the solidified slag is melted. As a result, the load on the exhaust gas treatment equipment is reduced.

[0028]

According to the method for starting a melting furnace of the present invention described above, slag is dug, so that the burden of digging work is smaller than in the conventional example of digging slag mixed with metal. Moreover, since the slag remaining in the furnace at an appropriate depth is dug, there is no risk of damaging the furnace main body, and the furnace main body can be protected.

Further, since the amount of melt obtained from slag and metal left in the furnace is large, the amount of ground slag or incinerated ash to be heated and melted at first is small, and as a result, The amount of generated gas is small. Therefore, the load on the exhaust gas treatment equipment can be reduced, thereby reducing the exhaust gas treatment capacity, thereby realizing cost reduction.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a melting furnace for explaining a melting furnace starting method of the present invention.

FIG. 2 is a longitudinal sectional view of a melting furnace for explaining a conventional melting furnace startup method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace main body 2 Electrode 3 Input port 4 Exhaust gas port 5 Slag discharge port 6 Metal discharge port 7 Concave part 8 Conductive material S Solidified slag S1 Crushed slag S2 Metal mixed slag M Solidified metal L Rated level A Incinerated ash

Claims (1)

[Claims] 1. An electric current is supplied to a melt in the furnace by an electrode disposed in the melting furnace to melt the incinerated ash that has been put in, and a molten metal serving as a lower layer and a molten slag serving as an upper layer are separately taken out of the furnace. In the method of starting the melting furnace, the molten slag is left in the furnace at an appropriate depth when the operation of the melting furnace is stopped, and when the operation is restarted, the upper surface of the solidified slag is slightly dug to form a recess. Then, a current-carrying material is arranged in the concave portion, the electrode is lowered until it comes into contact with the current-carrying material, incineration ash or pulverized slag is supplied to the concave portion to cover the current-carrying material, and then the electrode is energized by the electrode. A method for setting up a melting furnace, characterized in that: