JP2955961B2 - Waste incineration ash melting furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a furnace for melting main ash generated from a refuse incinerator.

[0002]

2. Description of the Related Art As an electric melting furnace for refuse incineration ash, there is an electric resistance type ash melting furnace utilizing resistance heating of slag shown in FIG.

[0003] 11 is a melting furnace body, 12 is a graphite electrode, which is held vertically movable. Reference numeral 13 denotes a power supply for supplying electric power for melting the ash, which outputs an alternating current. A large furnace may output three phases, and a small furnace may output single-phase alternating current. Reference numeral 14 denotes a port for charging the incinerated ash, and the ash is continuously or intermittently charged into the furnace. Numeral 15 is a molten metal which separates when the ash is melted, and has a large specific gravity and accumulates at the furnace bottom. Reference numeral 16 denotes a slag formed by melting ash, and has conductivity in a molten state. 17 is the ash covering the slag surface,
It is in an unmelted state. Reference numeral 18 denotes a tap for discharging molten metal or slag out of the furnace.

In such a configuration, the electrodes are arranged so as to be immersed in the slag, and the distance between the electrodes 12a-12b, 12b-1 is reduced.
An electric current flows through 2c and 12c-12a, and the slag between them becomes hot due to resistance heating. The high-temperature slag causes the ash covering the top to melt sequentially.

[0005]

In the above-mentioned method, since the slag is used as a means for generating heat, electric power is supplied solely by an AC power supply. The required ash melting furnace has the following problems. 1) Since the electrodes are submerged in the high-temperature slag, the electrodes are consumed greatly. Also, electrodes are required for the number of AC phases, which increases the cost of the electrodes. This increases operating costs. 2) Since the slag is heated unnecessarily, the average temperature of the slag increases, the efficiency for melting decreases, and the power consumption decreases.

[0006] 3) The life of the refractory brick used for the furnace body is shortened due to the increase in the average temperature of the slag. For this reason, the replacement work while the furnace is stopped also increases, resulting in a decrease in the utilization rate of the furnace and an increase in repair costs. SUMMARY OF THE INVENTION It is an object of the present invention to provide a melting furnace for refuse incineration ash which can solve the above problems.

[0007]

The refuse incineration ash melting furnace of the present invention is a melting furnace for melting refuse incineration ash by an electric resistance heating method. Is characterized in that the polarity of the upper graphite electrode in which the burial is buried is negative and the polarity of the furnace bottom electrode is positive, and electricity is supplied between these electrodes to heat and melt the refuse incineration ash.

[0008]

[Action] to reduce the number of graphite electrodes than conventional, and by utilizing the polarity effect, it is possible to reduce the consumption of graphite electrodes. Also, by maintaining the slag temperature at an appropriate value, it is possible to improve the power consumption unit and extend the life of the refractory brick. Hereinafter, details of the above operation will be described with reference to FIGS.

As shown in FIG. 2, a molten crucible is filled in a kind of crucible made of non-conductive refractory brick.
When the graphite electrodes are connected to polarities as shown in the figure and energized, after a certain period of time, the electrodes are consumed as shown in the figure.

This result indicates that the direct current heating has a polar effect on the consumption of the electrode, and it is recognized that the electrode is significantly consumed on the anode side. In the case of AC heating, the polarity is alternately changed, so that the consumption of the electrodes becomes equal between the two electrodes.

The present invention employs an energization method and electrode polarity utilizing this polarity effect in order to minimize the consumption of the graphite electrode, which is a major problem in ash melting furnaces.

Further, an advantage of the current supply method of the present invention is that slag can be uniformly heated, and as a result, the slag temperature does not need to be set to an unnecessary high temperature. This is an experiment in which a thick crucible made of mild steel shown in FIG. 3 was filled with molten slag, one graphite electrode was inserted into the slag, and DC heating was performed with the polarities shown in FIGS. Explained by the results.

(A) In the case where the graphite electrode has a negative polarity, the current flows almost uniformly from the electrode submerged in the slag, and the slag temperature increases almost uniformly with the energization time. The penetration position after the end of energization clearly indicates this.

On the other hand, when the graphite electrode shown in FIG. 2B has a positive polarity, the current is concentrated near the tip of the electrode, and only the slag in the vicinity of the electrode is intensively heated to a very high temperature. For this reason, penetration after the end of energization is also limited to the vicinity of the lower part. In such a heating mode, the temperature rise on the upper surface of the slag required for ash melting must be brought about by electromagnetic convection concentrated on the electrode tip,
Friction of the furnace wall with the refractory brick occurs, causing the brick to erode quickly. In addition, since the slag is locally heated to a high temperature, heat loss increases, and extra power is required.

Therefore, the melting furnace for refuse incineration ash of the present invention
With the above configuration, only one graphite electrode is required, and by giving a negative polarity of direct current, the consumption of the electrode can be suppressed to a very low level, and the slag can be uniformly heated without overheating. Therefore, there is an advantage that the power use efficiency is increased and the power consumption unit can be improved.

In addition, since the local heating of the slag and the convection are weakened, the interaction with the refractory brick is reduced, and the advantages of extending the life of the refractory brick can also be achieved.

[0017]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

Reference numeral 1 denotes a melting furnace body, and 2 denotes an upper graphite electrode having a negative polarity, which is vertically movable. Reference numeral 3 denotes a power supply for supplying electric power for melting ash, which outputs a direct current. Reference numeral 4 denotes a port for charging the incinerated ash, and the ash is continuously or intermittently charged into the furnace. Numeral 5 is a molten metal that separates when the ash is melted and has a large specific gravity, and accumulates at the furnace bottom. Reference numeral 6 denotes a slag formed by melting ash, and has conductivity in a molten state. 7 is the ash covering the slag surface,
It is in an unmelted state. Reference numeral 8 denotes a metal tap for discharging the molten metal 5 out of the furnace. The tap 8 has an opening / closing device (not shown) so that tapping and stopping can be performed. Reference numeral 9 denotes a slag tap for discharging the molten slag 6 out of the furnace. The molten slag 6 naturally overflows when it reaches a liquid level higher than the slag tap 9. Numeral 10 denotes a furnace bottom electrode having a positive polarity, which cools the outside of the furnace with water to prevent burning due to energization.

When DC power is supplied from the power source 3 and the melting of the ash 7 proceeds, the contained metal components are separated and accumulated as molten metal 5 at the furnace bottom. Therefore, the liquid level of the molten metal 5 gradually rises. On the other hand, most of the ash 7 accumulates above the molten metal 5 as molten slag 6, and when it reaches the slag outlet 9, overflows and the liquid level of the slag 6 becomes constant.

The graphite electrode 2 is adjusted so as to sink into the molten slag 6 to an appropriate depth. This can be realized, for example, by monitoring the voltage between the graphite electrode 2 and the furnace bottom electrode 10 and moving the graphite electrode up and down so that this voltage becomes constant.

When the liquid level of the molten metal 5 exceeds the upper limit (for example, the monitor voltage is detected to be lower than the set voltage range), the opening and closing device of the metal tap 8 is opened, and the molten metal 5 is removed. The metal is discharged outside the furnace, and the metal liquid level up to the tap 8 is lowered. In this state, the opening / closing device is closed to stop tapping. Thereafter, melting of the ash proceeds while repeating the above operation again.

In this way, the liquid levels of the molten metal 5 and the molten slag 6 can be continuously melted only during the operation of the furnace by moving within a predetermined appropriate fluctuation range. . In the above embodiment, the case where one upper graphite electrode is used has been described, but a plurality of upper graphite electrodes may be used.

[0023]

The refuse incineration ash melting furnace of the present invention is as described above. The number of graphite electrodes is reduced as compared with the conventional one, and the consumption of the graphite electrodes is reduced by utilizing the polarity effect. be able to. Also, by maintaining the slag temperature at an appropriate value, it is possible to improve the power consumption unit and extend the life of the refractory brick.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the overall configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram of an operation of a polar effect relating to electrode melting.

FIG. 3 is a diagram for explaining the effect of the polarity effect relating to slag heating.

FIG. 4 is an explanatory view of a conventional electric resistance type ash melting furnace.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Melting furnace body, 2 ... Top graphite electrode with negative polarity, 3 ... DC power supply, 4 ... Inlet for incineration ash, 5 ... Molten metal, 6 ... Molten slag, 7 ... Incineration ash, 8 Metal outlet
9: slag outlet, 10: furnace bottom electrode with positive polarity.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F23J 1/00 F23J 1/08

Claims (1)

(57) [Claims] 1. In a melting furnace for melting refuse incineration ash by an electric resistance heating method, a direct current is used as a power source for melting, and a vertically movable part is held in a molten slag so that the tip is buried to an appropriate depth. A refuse incineration ash melting furnace characterized in that the polarity of the upper graphite electrode is made negative and the polarity of the furnace bottom electrode is made positive, and electricity is supplied between these electrodes to heat and melt the refuse incineration ash.