JPH09105507A - Operating method for ash treating electric resistance melting furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to conduct the optimum melting operation and to largely improve the lives of electrodes by detecting the molten slag level in a furnace and the thickness of molten salt by a molten surface level gage installed in a perpendicular direction from a furnace cover, and controlling the operation of the furnace based on the slag level. SOLUTION: The electric resistance melting furnace comprises an ash inlet 1 connected to a hopper 9 of incinerated ash or scattered ash, an exhaust port 2, a molten slag exhaust port 3, a molten salt exhaust port 12 and elevating electrodes 4. The electrodes 4 are inserted through an incinerated ash layer 5, and dipped at the ends in a molten slag layer 6. A conduction detector 14 contained in a heat resistant insulating tube 13 is vertically moved up and down by a driver 17 to measure the level of the slag and the thickness of the molten salt layer according to the change of the detected current value. The power supplying amount of a power source facility, the ash charging amount and timing of the rotary valve 15 of the hopper 9 and the elevating of the electrodes 4 by an electrode elevator 16 are controlled based on the results of the measurements.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for operating an electric resistance melting furnace for ash treatment for melting incinerated ash and fly ash.

[0002]

2. Description of the Related Art Conventionally, waste such as municipal waste has been incinerated in an incineration facility, and the incinerated ash and dust produced have been landfilled. However, due to problems such as groundwater contamination due to elution of harmful heavy metals, etc. A melting treatment method using coke, kerosene, electric power, etc. has been proposed, and some of them are actually treated.

Among them, an electric resistance melting furnace for ash treatment has been proposed as a melting furnace for ash treatment mainly composed of dust. FIG. 4 is a schematic diagram of a conventional three-phase alternating current electrical resistance melting furnace for incineration ash, and FIG. 5 is a schematic diagram of a direct current electrical resistance melting furnace. In both figures, the electrical resistance melting furnace for ash treatment shows incineration ash or An ash input port 1 for fly ash, an exhaust port 2, a molten slag discharge port 3 and an electrode 4 are provided. In the case of a three-phase AC electric resistance melting furnace, the electrodes 4 have three electrodes inserted from the furnace ceiling through the incineration ash layer 5 and the tips are immersed in the molten slag layer 6 to form a DC electric resistance furnace. In this case, one electrode is inserted through the incineration ash layer 5 from the furnace ceiling, the tip is immersed in the molten slag layer 6, and the counter electrode 4 is provided on the furnace bottom. The molten slag layer 6 becomes an electric conductor and melts ash by Joule heat due to electric resistance. The incineration ash 5 is supplied so as to cover the molten slag layer 6 to suppress the amount of volatile substances such as heavy metals and salts. The molten metal 7, the molten slag 6, and the molten salt 8 are discharged from their respective outlets.

[0004]

However, in the conventional electric resistance melting furnace for ash treatment, salts such as NaCl and KCl deposited on the upper portion of the molten slag layer are formed on the surface layer, and the molten salt wears the electrode. There is a problem that it may cause a short circuit of the electrodes, or the power cost becomes high.

Therefore, the present invention provides an optimum and stable operation method by detecting the level of molten salt and molten slag in the electric resistance melting furnace for ash treatment.

[0006]

According to the present invention, by detecting a molten salt and a molten slag level in a furnace by an electric current detector installed vertically in a furnace lid of an electric resistance melting furnace for ash treatment, The ash supply amount and the power input amount are controlled to achieve optimum and stable operation.

[0007]

1 is a sectional view of an electric resistance melting furnace for ash treatment according to the present invention, and FIG. 2 is a sectional view showing a structure of an energization detector. The electric resistance melting furnace has a rotary valve and the like. It is provided with an ash inlet 1, an exhaust outlet 2, a molten slag outlet 3, a molten salt outlet 12, and an electrode 4 which moves up and down, which are connected to a hopper 9 for incinerated ash or fly ash. The electrode 4 is inserted through the incineration ash layer 5, the tip is immersed in the molten slag layer 6, the counter electrode 4 is provided on the furnace bottom, and both electrodes 4 are connected to the power supply equipment. . The molten slag layer 6 becomes an electric conductor and melts ash by Joule heat due to electric resistance. The incineration ash 5 is supplied so as to cover the molten slag layer 6 to suppress the amount of volatile substances such as heavy metals and salts.
The molten metal 7, the molten slag 6, and the molten salt 8 are discharged from their respective outlets.

FIG. 2 shows an energization detector in which the energization detection terminal 14 is housed inside the heat resistant insulation tube 13. By moving the energization detector up and down by the driving device 17, the level of the molten slag and the thickness of the molten salt layer are measured by the change in the detected current value, and based on the result, the amount of power input by the power supply facility,
The amount and timing of ash charging are controlled by the rotary valve 15 and the like of the hopper 9, and the elevation of the electrode is controlled by the electrode elevating device 16.

The electric resistance melting furnace for ash treatment to which the present invention can be applied can be applied not only to a vertical electrode type furnace but also to a horizontal electrode type furnace.

[0010]

EXAMPLES The operation of the present invention will be described.

After throwing in the waste, melting begins and a melt is produced,
A molten slag layer and a molten metal layer are formed. In this state, the energization detection terminal 14 installed on the furnace lid is lowered by the driving device 17 and immersed in the molten slag. If the energization terminal is located above the molten slag, that is, in the space, the energization detection terminal 14
The resistance between them is infinite, and the current flowing between the terminals is zero. However, when the energizing terminal reaches the molten slag,
As shown in, since the electric resistance value differs between the molten salt deposited on the surface of the slag and the molten slag, the energizing current amount changes. It is possible to detect the level of the molten slag and the thickness of the molten salt layer based on the change in the current value and the distance that the energizing terminal descends.

Incidentally, the electric resistance ratio between the molten salt and the molten slag is 1/200 to 1/3 of the molten salt with respect to the molten slag 1.
Since it is significantly different from about 00, it is sufficient to detect the difference.

The present invention grasps the molten slag level by the detector and controls the ash supply amount so that the slag level is always constant. Further, by controlling the output power according to the ash supply amount, optimum melting processing can be achieved. For example, the molten slag tap opening is used as an opening / closing mechanism, the molten slag level is detected, and the molten slag level is adjusted by opening / closing the tap opening to enable stable continuous discharge of molten slag, and It is possible to control the ash supply amount in order to keep the slag level constant, and it is also possible to control the required electric power amount according to the ash supply amount.

When a large amount of molten salt that causes wear of the electrodes and unstable charging is accumulated on the molten slag, for example, by supplying ash from outside the system, the molten slag and the molten salt are separated. It is possible to raise the level, move the molten salt to the position of the dedicated molten salt tap hole provided on the furnace wall, and forcibly and continuously discharge only the molten salt.

[0015]

According to the present invention, the ash supply amount and the output power amount can be automatically controlled by detecting and grasping the molten slag level and the thickness of the molten salt layer, and the optimum melting treatment operation can be performed. Further, since the molten salt that significantly wears the electrode can be forcibly discharged, the life of the electrode can be significantly improved.

[Brief description of the drawings]

1 is a sectional view of an electric resistance melting furnace for incineration ash according to the present invention.

FIG. 2 is a cross-sectional view showing the structure of an energization detector.

FIG. 3 is a graph showing the relationship between the levels of molten slag and molten salt in the furnace and changes in the amount of current passed by the current detector.

FIG. 4 is a cross-sectional view of a conventional three-phase AC electric resistance melting furnace for incineration ash.

FIG. 5 is a sectional view of a conventional DC electric resistance melting furnace for incineration ash.

[Explanation of symbols]

1 ash input port, 2 exhaust port, 3 molten slag discharge port, 4 electrode, 5 incinerated ash layer, 6 molten slag layer, 7 molten metal, 8 molten salt layer, 9 hopper, 10 furnace wall 11 furnace wall, 12 molten salt Discharge port, 13 Heat-resistant insulating tube, 14 Energization detection terminal, 15
Rotary valve, 16 electrode lifting device, 17 driving device, 18 energization detector

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical display location H05B 3/00 330 H05B 3/00 330Z (72) Inventor Yoshifumi Hasegawa 46, Nakahara, Tobata-ku, Kitakyushu 59 Nittetsu Plant Design Co., Ltd.

Claims (2)

[Claims] 1. A molten surface level meter installed vertically from the furnace lid of an electric resistance melting furnace for ash treatment detects the molten slag level and the thickness of the molten salt layer in the furnace and determines the molten slag level. A method for operating an electric resistance melting furnace for ash treatment, which comprises controlling the operation of the melting furnace based on the above. 2. A voltage is applied to a pair of terminals of the melt surface level meter, and the terminals are moved up and down to be immersed in the melt.
2. The method for operating an electric resistance melting furnace for ash treatment according to claim 1, wherein the level of the melt and the thickness of the molten salt layer are detected from different current values depending on the difference in the resistance of the melt.