JPS6121291B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of an upper electrode in a vertical zinc distillation and smelting furnace, which includes an upper electrode and a lower electrode.

In non-ferrous wire refining, electric distillation smelting furnaces are used for several metals, typified by zinc. Taking electrothermal distillation smelting of zinc as an example, sintered lumps of oxidized and roasted zinc sulfide ore and coke are charged from the top of a vertical distillation smelting furnace. Coke and zinc oxide react in the high temperature zone of the furnace, and the zinc oxide is reduced to zinc vapor. Zinc vapor is drawn from the middle of the furnace and condensed in a condenser. After the zinc has volatilized, the residue descends through the furnace and is discharged from the bottom of the furnace by a rotating scavenger tray. The furnace is equipped with an upper electrode and a lower electrode, and the required amount of heat is generated using the resistance of the charge. FIG. 1 shows a conventional electric distillation furnace 1 for smelting zinc. From the top of the furnace 1, a mixture 2 of zinc oxide sintered mass and coke is mixed in an approximately 2:1 ratio.
(weight ratio). As the charge descends through the furnace, it passes through a high temperature zone created by the current flow between the upper electrode 3 and the lower electrode 5, where the following reaction takes place: ZnO+C→Zn+CO ZnO+CO→Zn+CO ₂ CO ₂ +C →2CO The generated zinc vapor is led to the steam ring 9 by suction from a vacuum pump, etc., and then passed through a condenser and condensed. The residue from which the zinc has volatilized descends within the furnace and is discharged to the outside of the furnace by a rotating ore removal tray 7.

The conventional upper electrode 3 is constructed by, for example, 4 to 12 graphite electrodes arranged radially around the furnace. A large number of lower electrodes 5 are also arranged radially around the furnace in pairs with the upper electrodes. As for the lower electrode, we recognized that there is a build-up around the tip of the lower electrode that protrudes into the furnace, and as a result, the cross-sectional passage inside the furnace becomes extremely narrow, which prevents the smooth outflow of residue. It has been proposed by the applicant in this case to provide a single lower electrode in the center of the ore discharge pan.

It has been conventionally believed that it is essential for the upper electrode to have a plurality of electrodes arranged radially in view of the temperature distribution within the furnace. However, in operations using such upper electrodes, it is troublesome to handle a large number of electrodes, and when the electrodes are worn out, electricity must be stopped to reinsert the electrodes, resulting in a decrease in production per furnace. Because the upper electrode protrudes into the furnace, it is easily broken by contact with the descending charge, and if it breaks, electricity will flow through the furnace wall and wear out the refractory bricks on the furnace wall, causing the furnace repair cycle to be interrupted. This resulted in shortcomings such as shortening the . Recently, attempts have been made to increase the number of electrodes used in order to make the temperature distribution in the furnace more uniform, but as the number of electrodes increases, the above-mentioned drawbacks become more pronounced.

In order to solve the above-mentioned drawbacks and to make the temperature distribution in the furnace more uniform, the present invention attempts to completely change the conventional upper electrode concept and install a single upper electrode at the top of the furnace, and has succeeded. I paid it. In particular, by using Soederberg electrodes as electrodes, additional electrodes can be added to the upper end as the electrodes wear out, reducing the trouble associated with conventional electrode replacement work and minimizing furnace downtime. . Furthermore, it has been found that when the single top electrode is used in combination with the single bottom electrode described above, an even better effect of energizing the furnace can be achieved.

Thus, the present invention provides a vertical zinc distillation and smelting furnace comprising an upper electrode and a lower electrode and generating heat by resistance heating through the charge, in which the upper electrode is provided at the top of the furnace, preferably a Soederberg It is an object of the present invention to provide a zinc distillation smelting furnace characterized in that it is a single electrode type.

Hereinafter, a specific example of the present invention will be described using a zinc distillation furnace as an example.

FIG. 2 is a partial cross-sectional view from the front of a zinc distillation furnace equipped with the present invention. It is shown as being equipped with a single lower electrode 5. The attached equipment for the furnace body is omitted. A single upper electrode 3 is inserted vertically into the furnace top leaving an annular gap around it. A suitable number of charge feed ports 8, for example four, are provided in the annular area (FIG. 3). The charge is conveyed from the feed hopper via a suitable preheater to a cushion hopper 6 mounted, for example, on top of the furnace, and from there fed into the furnace via a feed leg 6' leading to a feed opening 8. Here, two electrodes are placed in front and behind the upper electrode 3.
A concrete example is shown in which two cushion hoppers 6 are installed, and two feed legs 6' from each cushion hopper each lead to a supply port 8 (only the front one is shown in the drawing, and the same cushion hopper is located behind the electrode 3). be). The charge feeding device is not limited to this, but may have any configuration capable of uniformly feeding the charge into the furnace, for example, feeding the charge through a feed chute that covers the entire annular cavity. May be supplied. Alternatively, feed ports may be provided along the perimeter of the furnace near the top of the furnace. Furthermore, the upper electrode 3
It is also possible to use in combination with the above-mentioned means an arrangement in which the tube is in an annular form and the charge is fed through its central hole.

Although the lower electrode 5 is shown as a single electrode,
This does not preclude the use of multiple peripheral electrode configurations inserted near the bottom of the furnace, or any other electrode configuration, as is conventional. For the single lower electrode 5, a copper wire ring 5' is attached around the upper end of the lower electrode 5 to disperse the current in order to improve the current flow inside the furnace and to avoid excess heat generation in the lower part of the furnace. is preferred. Conventionally, a contact method around the brush has been proposed for supplying current to the lower electrode, but as shown in FIG. Generally speaking, the method of holding the brush from above and below prevents accidents such as brush burnout, and
It was also found that stable power supply can be achieved.

By providing a single lower electrode 5 at the bottom of the furnace in combination with a single upper electrode 3 at the top of the furnace, the current distribution through the charge is uniformed and the temperature distribution within the furnace is optimized. Moreover, it goes without saying that by arranging a large number of rods in a radial manner, damages such as the occurrence of adhesion and breakage, which have conventionally been observed, can be eliminated. As a result of these, stable furnace operation over a long period of time becomes possible.

Details of the upper electrode structure are shown in FIG. Also shown is the charge feed facility. Upper electrode 3
is lowered as the electrode wears out by an electrode lifting device 15 and an electrode gripper 17, which are shown here as hydraulic cylinders. The electrodes are consumed by, for example, 5 cm per day, although this varies depending on the amount of current applied. Lowering of the electrode may be carried out continuously or intermittently. In addition to the hydraulic cylinder, any suitable means may be used, such as a method of lowering the electrode by temporarily loosening the electrode grip. In order to prevent the upper electrode 3 from swinging, an electrode holder 18 is provided between the electrode holder 17 and the furnace top. The electrode 3 is inserted through the seal 19 into the top of the furnace. Power is supplied through the water-cooled copper tube 20 and the electrode holder 18.

Although an artificial graphite electrode, a carbon electrode, etc. can be used as the upper electrode 3, it has been found that a Soederberg electrode is suitable for the purpose of the present invention. The Soederberg electrode is a container made of a cylindrical thin metal plate filled with coke or anthracite called Soeder paste and pitch or tar as a caking agent, and is heated by the heat in the furnace and the electricity flowing through the electrode. After naturally softening and melting, the volatile components are gasified, leaving behind carbon to form the electrode. If the electrode becomes short due to wear and tear, a new iron plate case can be welded on top of the old one and electrode material can be filled into it to add more. Soederberg electrodes cost approximately half as much as artificial graphite electrodes, do not require the trouble of replacing electrodes, and can fully demonstrate the required energizing effect.

When using a single, large-diameter upper electrode at the top of the furnace, there was initially concern that only a portion of the electrode would serve as the feeding point, and the current would concentrate there, worsening the temperature distribution inside the furnace. However, if the current is too high, the electrode will wear out quickly, and the contact with the charge will deteriorate, making it difficult for the current to flow.In the end, the electrode tip will maintain a constant shape and the current will flow from the entire surface of the tip. It was found that the upper electrode could be energized without any problems due to its recoverability.

Using the furnace shown in Figure 2 with a furnace height of approximately 10,000 mm and a furnace top inner diameter of 2,050 mm, and using a Soederberg electrode with a diameter of 800 mm, zinc was produced on a basis of 1,000 tons/month. Although the reactor had been closed for brick repairs, it was able to operate for almost several years without requiring any repairs. The temperature distribution inside the furnace was uniform, and good results were obtained in zinc production.

As described above, the present invention breaks down the concept of multiple radially inserted upper electrodes conventionally used in electric furnaces for smelting, and by disposing a single large-diameter electrode at the top. It solves the problems encountered in actual operations and makes a meaningful contribution to the industry.

[Brief explanation of the drawing]

FIG. 1 is a schematic partial sectional view showing a conventional electrothermal smelting furnace, FIG. 2 is a partial sectional view of a specific example of the smelting furnace according to the present invention, and FIG. 4 is a perspective view of the power supply device to the lower electrode, and FIG. 5 shows details of the upper electrode. 1: Furnace, 3: Upper electrode, 5: Lower electrode, 7: Ore discharge pan, 9: Steam ring, 8: Charge supply port, 6:
Cushion hopper, 6': Leg, 5': Copper wire ring,
10: Power supply ring, 12: Brush, 15: Electrode lifting device, 17: Electrode grip, 18: Electrode holder,
19: Seal, 20: Water-cooled copper tube.

Claims (1)

[Claims] 1. In a vertical zinc distillation smelting furnace that is equipped with an upper electrode and a lower electrode and generates heat by resistance heating through the charge, the upper electrode is a single electrode provided at the top of the furnace. Zinc distillation smelting furnace characterized by: 2. The zinc distillation smelting furnace according to claim 1, wherein the upper electrode is a Soederberg electrode. 3. The zinc distillation and smelting furnace according to claim 1, wherein the lower electrode is a single electrode provided below the furnace bottom.