JPS6247356B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for starting operation in an arc furnace for waste treatment in which waste is melted at high temperatures by arc heating.

In this invention, waste is a general term for a wide variety of wastes, including industrial waste such as sewage sludge, general waste such as municipal garbage, and the incineration residue of these wastes.

Recently, a waste treatment method has been proposed in which waste is melted at high temperatures by arc heating.
To carry out this method, an arc is struck between the molten base metal and the electrode in a closed arc furnace with a structure similar to that commonly used for steelmaking. Waste materials such as dried sewage sludge are put into the tank. The waste undergoes thermal decomposition in the high-temperature reducing atmosphere inside the furnace, and the organic matter in the waste is gasified, the inorganic matter becomes molten slag, some metals are gasified, and the rest are distributed into slag and base metal. . When the molten slag obtained by this method is cooled and solidified, its volume is greatly reduced compared to the original waste, no heavy metals are released, and it can be effectively used as aggregate for concrete. , is attracting attention as a promising waste treatment method. When starting a furnace using the above treatment method when constructing a new furnace or refurbishing the furnace refractories once every six months, first put a good conductor such as iron scrap into the furnace, energize the electrode, and melt it with an arc. After the base metal has been prepared, the waste can be added to the base metal, making it easy to generate an arc and start operation smoothly. However, when restarting the furnace after an emergency shutdown in a continuous operation furnace or after slag discharge in a batch operation furnace,
If slag covers the top surface of the base metal at the bottom of the furnace, this slag has poor conductivity unless it is in a high-temperature molten state, making it difficult to generate an arc. If the upper surface of the uncoated base metal is flat and solidified, it is similarly difficult to generate an arc.

This invention was made in view of the above points, and was developed in the case where slag coats a conductive material such as base metal existing at the bottom of the furnace in an arc furnace for waste treatment, or where the base metal that is not coated with slag The purpose of the present invention is to provide a method for starting the operation of an arc furnace for waste treatment, which can generate an arc reliably even when solidified, and can start operation of the furnace smoothly and without bothering human hands. be.

However, in this invention, after the electrode is lowered to a predetermined position and connected to a power source to enable arc discharge, it is detected that no arc is generated even after a predetermined period of time has elapsed, and the conductive material supply device is operated. A method for starting the operation of an arc furnace for waste treatment, characterized in that a predetermined amount of powder or granular conductive material is supplied into the furnace, and an arc is generated between the conductive material and the electrode.

An embodiment of the present invention will be described below with reference to the drawings.

In the figure, 1 is a closed-type arc furnace, 2 is a furnace shell thereof, and 3 is a furnace cover that is placed over this furnace shell. 4
is an electrode that penetrates the furnace lid 3, and is supported by an electrode support arm (not shown) that can be moved up and down. 5 is a slag drain, and the slag outlet 6 is filled with refractory bricks or stamp material. 7 is a waste inlet provided in the furnace lid 3, 8 is a waste hopper for storing waste W, and 9 is a screw conveyor. Reference numeral 10 denotes a gas discharge port provided in the furnace cover 3, which is connected to a generated gas processing device (not shown) comprising a gas scrubbing tower, a gas cooler, a blower, and the like. On the other hand, 11 is a powder or granular conductive material, such as graphite powder, iron oxide powder, iron powder, or pellets thereof. Reference numeral 12 denotes a conductive material supply device, which includes a hopper 13, a rotary leaf feeder 14 provided at the outlet of the hopper, an electric motor 15 for driving the rotary leaf feeder, and a chute 16 for charging the conductive material that communicates with the furnace. Become.
17 is a control panel for controlling the electric motor 15, and 18 is a current transformer for detecting arc current. Further, 19 is an arc furnace control panel.

In the apparatus having the above configuration, when the upper surface of the base metal 20 in a molten or solidified state at the bottom of the furnace is covered with slag 21, the operation of the furnace is started as follows. First, the electrode 4 is lowered to a position a predetermined distance from the upper surface of the slug 21,
The electrode 4 is connected to a power source to enable arc discharge. If the slag 21 is in a high-temperature molten state, it has conductivity, so an arc is generated between the electrode 4 and the base metal 20, and the operation of the furnace is started. slag 2
If the electrode 1 is not in a high-temperature melting state, no arc will occur, so when the electrode 4 becomes ready for discharge, the control panel 1 is activated by the signal S issued by the arc furnace control panel 19.
If the current detected by the current transformer 18 is below the specified value even after a predetermined period of time (several seconds to 10 seconds) has elapsed, the control panel 17 will activate the built-in timer device. Then, the electric motor 15 is rotated for a certain period of time. As a result, a predetermined amount of the conductive material 11 in the hopper 13 is supplied onto the slag 21 in the furnace, and an arc is generated between the conductive material 11 and the electrode 4, causing the slag 21 to partially undergo initial melting. Get started. When the slag melts, a stable arc is generated between the molten slag 21 or base metal 20 and the electrode 4, and the furnace starts operating. Note that one conductive material 11
If the slag 21 is not sufficiently melted by supplying only the slag 21 and the generation of the arc stops, the control panel 17 detects that the arc current is below the specified value after a certain period of time has elapsed after supplying the conductive material, as described above. Then, the conductive material 11 may be introduced into the furnace again.

Although the above embodiment describes the case where the base metal is covered with slag, the above embodiment also applies when the base metal is not covered with slag and the top surface of the base metal is flat and solidified. By supplying the conductive material 11 onto the base metal using a similar method and generating an arc between the conductive material 11 and the electrode 4, the solidified base metal can be melted and the operation of the furnace can be started smoothly. It is.

In the above embodiment, instead of activating the timer of the control panel 17 by the signal S issued by the arc furnace control panel 19 and operating the conductive material supply device if the arc current remains below the specified value even after the predetermined time has elapsed. If the lower end of the electrode came into contact with solidified slag or base metal before the arc current exceeded the specified value while the electrode was lowering, this could be caused by fluctuations in the load on the electrode lifting motor or slack in the electrode lifting wire. In the case of an electrode drive device in which the electrode, electrode support arm, etc. are suspended by a wire), the conductive material supply device may be operated based on this electrode contact detection signal.

In addition to an arc furnace having a base metal formed by melting scrap iron or the like as a conductive material in the bottom of the furnace as shown in the above embodiment, the present invention also relates to an arc furnace having a non-consumable electrode as a conductive material in the bottom of the furnace. It can also be applied to arc furnaces.

As explained above, according to the present invention, even when a conductive material such as a base metal is covered with slag, or when the base metal that is not covered with slag is solidified, it is possible to The supplied conductive material reliably generates an arc and allows the furnace to start operating smoothly. In addition, the supply of conductive material is performed by operating the conductive material supply device after detecting the absence of arcing, so there is no wasteful consumption of conductive material, and the furnace can be operated extremely easily and without the hassle of human labor. You can start.

[Brief explanation of the drawing]

The drawing is an equipment system diagram showing an example of an apparatus used to implement the method according to the present invention. 1... Arc furnace, 2... Furnace shell, 3... Furnace lid, 4
... Electrode, 11 ... Conductive material, 12 ... Conductive material supply device, 13 ... Hopper, 14 ... Rotary feeder, 5 ... Electric motor, 16 ... Chute, 1
7... Control panel, 18... Current transformer, 19... Arc furnace control panel, 20... Base metal, 21... Slag.

Claims (1)

[Claims] 1. In a closed-type arc furnace for waste treatment, in which the furnace shell is covered with a furnace lid and an electrode is provided that passes through the furnace lid, when the furnace starts operating, the electrode is lowered to a predetermined position and connected to the power source. After connecting to enable arc discharge, it detects that no arc has occurred even after a predetermined period of time has elapsed, and operates the conductive material supply device to supply a predetermined amount of powder or granular conductive material into the furnace. and generating an arc between the conductive material and the electrode.