JPH02101310A - Melting furnace - Google Patents

Abstract

PURPOSE:To prevent heavy metal compounds from vaporizing in a melting furnace for refuse containing heavy metal compounds such as sewage sludge, etc. by installing alternate current electrodes for melting and positive and negative direct current electrodes for electrolysis, and placing the negative direct current electrode along the center line of a slag port and slightly above the slag port. CONSTITUTION:Alternate current electrodes 15 for melting are installed in a melting chamber 13 of a melting furnace 11. A continuous annular positive direct current electrode 16 is mounted around the internal circumferential surface of the melting furnace 11 and slightly above the A.C. heating electrodes 15. A funnel shape negative direct current electrode 17 corresponding to the positive direct current electrode 16 is installed in the center of the melting furnace below the alternate current electrodes 15 and above a slag port 14, and its periphery is supported by an insulating refractory 18. By this constitution, a boundary layer A is formed between a molten layer 19a and an ambient temperature raw material layer 19 on the top so that heavy metal compounds can be prevented from vaporizing and sealed in molten slag. As a result, a separate heavy metal treatment is made unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a melting furnace for melting waste containing heavy metal compounds such as sewage sludge and municipal waste incineration ash.

BACKGROUND OF THE INVENTION FIG. 2 is a diagram for explaining a conventional comprehensive waste treatment system that combines incineration and melting. In Figure 2,
1 is an incinerator, and garbage 2 collected in a pit is transported to the incinerator 1 by a crane 3 and incinerated. Reference numeral 4 denotes a melting furnace, and the iron content of the incinerated ash is recovered by magnetic separation 1 to 15 before melting and recycled, and the load on the melting furnace 4 is reduced and the iron content is melted. By melting in the melting furnace 4, the molten slag becomes scientifically stable and its volume is significantly reduced compared to incineration ash. 6 is a flue, which exhausts incineration gas and the like.

Problems to be Solved by the Invention Various types of melting furnaces such as surface melting furnaces, coke ovens, and arc furnaces can be used as the melting furnace 4 of the integrated waste treatment system, but any of the 78 melting furnaces can be used to melt incinerated ash. When the material to be melted is heated to a high temperature, low boiling point substances such as lead, zinc, and cadmium are easily volatilized along with the combustion gas, and most of them are released into the exhaust gas and are dissolved in the molten slag. In order to treat the heavy metal compounds released into the exhaust gas, first, the exhaust gas containing the heavy metal compounds is cooled to below 300°C, and the volatilized heavy metal compounds are collected as particles in a dust collector. It must be collected and treated with cement or asphalt.

As described above, in the past, as a pollution control measure, the heavy metal compounds volatilized in the exhaust gas had to be treated in a process separate from the melting process, which posed the problem of requiring double treatment.

The present invention solves the above-mentioned conventional problems by encapsulating heavy metal compounds in the molten slag without volatilizing them even at high temperatures when melting the material to be melted, thereby eliminating the need for heavy metal treatment in a separate process. The purpose is to provide a melting furnace that can.

Means for Solving the Problems In order to solve the above problems, the melting furnace of the present invention includes an input port on the upper end side for inputting waste containing heavy metal compounds;
A melting furnace having a melting section for melting input waste and a slag port for flowing molten slag downward, an AC electrode for melting the waste, and an AC electrode for electrolyzing the heavy metal compound. A DC electrode consisting of both positive and negative electrodes is provided in the melting part, and the negative DC electrode is provided at a position slightly above the slug port along the center line of the slug port. It is.

Operation With the above configuration, waste containing heavy metal compounds is charged into the melting furnace through the input port, and when the waste is melted by passing electricity between the alternating current electrodes provided in the melting section, this becomes a molten layer.

Further, electricity is applied to the molten layer between the positive and negative DC electrodes to electrolyze the heavy metal compounds contained in the slag. At this time, positively charged heavy metal ions are concentrated near the negative DC electrode and are electrolyzed and precipitated by heavy metals, but the negative DC electrode is installed at a position slightly above the slag port along the center line of the slug port. Therefore, the molten slag flowing out from the slag port has a cylindrical shape with a molten layer containing a large amount of heavy metals as the center and a molten layer that does not contain heavy metals as the outer periphery.

This cools and solidifies from the outer surface, sealing the heavy metals inside and preventing heavy metals from evaporating again.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of a Nirekuro furnace as a melting furnace showing one embodiment of the present invention. In FIG. 1, a melting furnace 11 has an input port 12 at its upper end for inputting waste containing heavy metal compounds, and at an intermediate position between the upper and lower sides thereof.
It has a melting section 13 for melting input waste, and a slag port 14 for flowing out molten slag at the center of its lower end. This melting section 13 has an AC heating type f! 15 are provided. Slightly above this AC heating electrode 15, a straight current electrode 16, which is a DC electrolysis electrode, is provided in an annular manner continuously in the inner circumferential direction of the melting furnace 11. Further, the melting furnace 1 is located below the AC heating electrode 15 and above the slag port 14.
A negative DC pole 17 of a funnel-shaped DC electrolytic electrode is provided at the center of the electrode 1 in correspondence with the direct current electrode 16, and its outer periphery is supported by an insulated refractory part 18. 19
is a raw material layer, which is a layer of incineration ash containing heavy metal compounds, which is input from the input port 12. The boundary A between the raw material layer 19 and the molten layer 19a is located slightly above the direct flow electrode 16 than the AC heating electrode 15.

The operation of the above configuration will be described below.

When an AC voltage of 100 to 200 V is applied to the AC heating type I#115 and an AC current of 100 to 300 A is passed, the waste is melted by Joule heat, and the melting temperature is 1200 ° C to 13
A temperature of 00°C can be maintained. At this time, a boundary A is formed between the melt 119a and the raw material layer 19 at room temperature, and the melting furnace 11 and the upper part of the fishing rod are covered with this raw material layer 19, which plays the role of a filter, and the heavy metal compounds are volatilized by melting the waste. , Preventing volatilization 6 Normally, heavy metal compounds with low boiling points would concentrate near the boundary A at the bottom of the raw material layer 19 and repeat melting and solidification, but by using the positive and negative DC electrodes 16 and 17,
By applying a current of 10 to 100 A, the heavy metals are reduced from their oxide or chloride state and deposited as heavy metals on the surface of the negative DC electrode 17 located at the bottom. Further, due to the insulating refractory 18 covering the outer circumference of the negative DC electrode 17, the outer circumference of the insulating refractory 18 becomes a molten layer 19b that contains relatively no heavy metals.

Therefore, the molten slag flowing out from the slag port 14 has a molten layer 19c containing a large amount of heavy metals and a molten layer fj containing no heavy metals.
The melt layer 19b forms a columnar shape with inner and outer surfaces, and is gradually cooled and solidified from the outer surface. In this process, even if the surface temperature is high, the heavy metals gather near the center, and the outer molten layer 19b, which does not contain heavy metals, acts as a filter, preventing the heavy metals from re-volatilizing and being sealed inside. Leave it to cool and fix.

As shown in 2, the slag containing a large amount of heavy metals is cooled and fixed inside and does not come into direct contact with the atmosphere, so compared to conventional melting furnaces, the heavy metal treatment process is a separate process from the melting process as a pollution control measure. There is no need to provide one.

Effects of the Invention As described above, according to the present invention, an AC electrode for melting waste containing heavy metal compounds and a DC electrode consisting of both positive and negative electrodes for electrolyzing this heavy metal compound are provided in the melting part, By installing this negative DC electrode along the center line of the slag port and slightly above the slag port, it is possible to prevent re-volatilization of heavy metals, and compared to conventional melting furnaces, it is possible to prevent pollution. There is no need to provide a heavy metal treatment process as a separate process from the melting process, and therefore, the work and equipment involved can be omitted.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a melting furnace showing an embodiment of the present invention, and FIG. 2 is a diagram for explaining a conventional comprehensive waste treatment system that combines incineration and melting. DESCRIPTION OF SYMBOLS 11... Melting furnace, 12... Inlet, 13... Melting part, 14... Slag port, 15... AC heating electrode, 16... Direct current electrode, 17... Negative DC electrode, 18
... Insulating refractory, 19... Raw material layer, 19a...7
B melting layer, 19b...melting layer not containing heavy metals, 19c
...A molten layer containing heavy metals. Agent Yoshihiro Morimoto Figure 2 Figure 2 I-1/2- /4 /6- Sea ≧ 4;) Rishi inlet 38 Melting section slag port AC power 0 units, t, Oshido Masaaki Jimaru electric machine , 7---The negative current is extremely 18-11 body color barley resistance x A's/9'---Hara sashiso tqa--Gonyu layer tqb-m-weight is 10,000 ε included I ft'-・4 seal parables tqc
--5 units including 1st official Kinwei E

Claims (1)

[Claims] 1. In a melting furnace having an input port on the upper end side for inputting waste containing heavy metal compounds, a melting section for melting the input waste, and a slag port for flowing molten slag downward, An AC electrode for melting the material and a DC electrode consisting of both positive and negative electrodes for electrolyzing the heavy metal compound are provided in the melting section, and the negative DC electrode is connected to the slag along the center line of the slag port. A melting furnace characterized by being installed at a position slightly above the port.