MXPA98002845A - Method for cleaning the scene in an electric oven - Google Patents

Abstract

The invention relates to a method for cleaning slag, created in metallurgical processes of non-ferrous metals, in an electric furnace and particularly the method is related to a semi-continuous cleaning process. According to the novel method, the electric furnace is provided with at least two holes of slag bleeding, the lower hole is disposed on the same level as the bleeding hole in a conventional batch-operated furnace, and the second bleed hole is located above, either at the height of the input of the feed or only slightly underneath

Description

METHOD FOR CLEANING SCORING IN AN ELECTRIC OVEN TECHNICAL FIELD The present invention relates to a method for cleaning slag -created in metallurgical processes of non-ferrous metals in an electric furnace and, in particular, the method refers to a semi-continuous cleaning process.

BACKGROUND OF THE INVENTION In nickel and copper pyrometallurgical processes, the finely divided and dried nickel and / or copper sulphide concentrate is first conducted, for example, to an instant melting furnace, where in addition to the concentrate air, oxygen or a feed is fed. mix of them, and a fluxing agent such as sand. In the furnace the concentrate reacts with the other substances fed there and two layers are deposited on the bottom of the furnace; the lower layer being a mat containing most of the valuable metals, and an upper layer consisting of a layer of slag, which also contains a small amount of valuable metals.

The oxidized slag obtained from an instant melting furnace or from some other furnace in the first stage of the process contains valuable metals to such an extent that their treatment is continued, more generally in an electric furnace, where the slag is reduced by medium of a reducing agent, such as coke. In the electric furnace treatment, the valuable metals bound to the slag phase are reduced and separated to form a specific mat phase under the slag layer. Both the created mat and the reduced and disposable slag are removed through respective extraction holes. In addition to copper and nickel, valuable metals include precious metals and other non-ferrous metals, such as cobalt, present in small amounts in the slag.

In most cases the electric furnace used in slag treatment is operated as a batch process. Now the volume of the furnace, that is, the size of the batch, and the time required to process the batch during the various stages, restricts the capacity of the furnace. Hence, if for example the capacity of casting of concentrate is increased, it is also necessary to raise either the capacity of the electric furnace, for example by implementing two electric furnaces or replacing an electric furnace with a larger one, or shortening the reduction time and settlement of the lot, that is, by decreasing the speed of recovery.

Various methods have been developed to increase the capacity of electric furnaces operated in batches. The U.S. Patent No. 3,857,700 discloses a method wherein cleaning of the slag is improved by mechanical mixing. The U.S. Patent No. 4,110,107 describes a method wherein the coal used in the reduction is injected into the molten slag; and a method of conformance with U.S. Pat. No. 4,168,156 attempts to increase slag removal by feeding gas into the molten mass.

From the US Patent No. 3,666,440 a method of cleaning the sheath is known in which a continuously operated electric oven is used. In this type of kiln, the extraction orifice of the treated waste slag is disposed at the same level as the entrance of the oxidized slag to be fed to the kiln. The advantage of the furnace is that the slag is extracted as a spill from the furnace. Because the more completely reduced slag is located on the surface, it is advantageous for it to be discharged first. In a batch process, the slag bleeding orifice is located in the lower part of the slag layer, where the slag cleaning is finally carried out. On the other hand, the disadvantage of a continuous process is that during the course of time, most of the volume of the furnace remains unused, when the incoming slag flows out of the furnace through the fastest route. In the method according to U.S. Pat.

No. 3,666,440, this is to be avoided by means of a wall structure located towards the loading end and extending downwards as far as the sheath layer.

OBJECTIVES OF THE INVENTION In accordance with the present invention, for the purpose of increasing the capacity of a batch operated furnace, a slag cleaning method has now been developed which can be termed semi-continuous. The method aims to combine the advantages of batch and continuous methods and, at the same time, - minimize the disadvantages of both methods.

As is clear from the foregoing, in an electric furnace generally only one orifice of slag bleeding is used at one time; in a batch operated furnace is located in the lower part of the slag layer and in a continuously operated furnace it is located at the height of the feed inlet, in which case the reduced slag is discharged as a spill. Obviously at least one reservoir bleeding hole has always been built in the furnace, but these holes are not taken into account in the present invention.

According to the new method, the electric furnace is provided with at least two slag orifices for active use; the lower one is located above the level of the bleeding orifice of a conventional furnace operated in a batch mode, and the other hole is located higher, either above the level of the feed inlet or just a little lower. The terms extraction orifice, bleeding orifice and discharge orifice (slag) used in the text all refer to the same thing. The essentially novel features of the invention will become clearer from the appended claims.

By means of the method of the invention, the amount of the batch to be fed * inside an electric furnace it increases by 20 - 50% compared to a conventional batch process, but the total treatment time of the batch remains unchanged.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The so-called semi-continuous electric furnace according to the present invention can be operated in two alternative ways. When the highest slag bleeding hole is made in the upper part of the furnace, the washers are also provided on the same level; and if they are already provided in the furnace and lower holes and scrubbers, they are also maintained. If the furnace is a new electric furnace, extraction holes and scrubbers are provided for both batch and continuous removal.

The first method of operation of the so-called semi-continuous process is as follows: the cleaning of the slag in the electric furnace is initiated so that in a known manner the furnace that was completely drained of slag through the lower bleeding orifice starts to be filled by loading slag into the electric furnace in a normal way from an instant melting furnace or some other corresponding casting furnace, while the lower bleeding hole is closed. Some reducing agent such as coke is fed onto the slag surface. The furnace is filled to the maximum level of melted mass, this is up to the upper bleed hole provided on the feed inlet level, but then the feed is still continued without interruption, for example, for a time corresponding to 20-50% of the normal filling time of the oven. Now the spill begins through the top hole of the oven. It is naturally clear that at least the upper slag bleeding hole is made on the opposite side of the furnace with respect to the feed inlet. The sheepskin that flows through the bleeding orifice The upper one is slag that has been put in contact with a reducing agent from the beginning of the emptying, so that it has a long time to be reduced and settle, and has a low content of valuable metals. The spill must be stopped when the barrel fed into the furnace also begins to flow directly outward as a spill. The charge from the melting furnace to the electric furnace is stopped, and after that the electric furnace is processed in the form of a furnace operated in a batch mode, by reduction, settling and sulfurization in a normal manner. The final bleed of the clean slag takes place through the lower extraction hole, in the same way as in a normal batch process.

According to another method of operation of the so-called semi-continuous process, the upper slag extraction orifice completed with the scrubber is constructed below the maximum surface area of the melted mass of the kiln, for example, at a distance that is no more than 1/2, advantageously and approximately 1/3 of the height between the maximum surface of melted mass and the normal orifice of slag bleeding. At the beginning, the furnace is operated in the same way as indicated above, that is, the filling of a totally empty furnace starts charging slag in a normal way from an instant melting furnace or a corresponding melting furnace to the furnace electrical, while the lower bleeding hole remains closed. On the slag surface, some reducing material, such as coke, is fed. The furnace is filled to the top bleed hole, but the uninterrupted load is then continued, for example, for a period equivalent to 20-50% of the normal furnace filling time. Now spill begins through the upper hole in the oven. After an appropriate period of spillage, the top hole closes and the slag surface rises to the maximum. The kiln discharge starts after a processing time that is shorter than normal, first through the upper bleed hole, because it can be assumed that the slag surface layer consists of reduced slag and already processed. After an appropriate time, that is, a time consumed in a normal batch process, the bleeding of the slag ends through the hole * lower.

As can be seen in the description of the aforementioned methods of operation, it is now possible to work an electric furnace under a batch process regime as a semi-continuous process and, in this way, the capacity of the furnace can be greatly increased. The method according to the present invention is particularly useful when the production must be increased, because under advantageous conditions, the materializations described above are capable of processing even a double amount of slag compared to the process ^ T conventional batch. Respectively, by employing said method the new furnace unit can be designed to be smaller in dimensions than the furnaces of the prior art. fifteen twenty

Claims (9)

1. Novelty of the Invention 1. A method for the cleaning of the sheath created in metallurgical processes of non-ferrous metals in an electric furnace, characterized in that the cleaning of the slag in the electric furnace is carried out as a semi-continuous process .
2. 2. The method of claim 1, characterized in that the electric slag cleaning furnace is provided with at least two discharge orifices and respective scouring machines for slag bleeding and which are . ío located at different heights.
3. 3. The method of claims 1 and 2, characterized in that the lower orifice of slag bleeding is disposed on the same level as the lower surface of the slag.
4. 4. The method of claims 1 and 2, characterized in that the upper slag bleeding orifice is disposed at the height of the feed inlet.
5. 5. The method of claims 1 and 2, characterized in that the upper slag bleeding orifice is located at a distance that is, when measured from the top, no more than half the height between the feeding inlet and the lower orifice of slag bleeding.
6. 6. The method of claim 5, characterized in that the upper slag bleeding orifice is located at a distance that is, when measured from the top, no more than one third of the height between the inlet of the slag. Feeding and the lower orifice of slag bleeding.
7. 7. The method of claim 4, characterized in that the filling of the electric furnace with the slag charged from a melting furnace is continued, even after the electric furnace is filled to the maximum level of the melted mass, for a period corresponding to 20 - 50% of the normal furnace filling period, after which the filling is stopped and the slag batch is processed in the same way as in a batch process.
8. 8. The method of claim 5, characterized in that the filling of the electric furnace with the slag bled from a melting furnace is continued, even after the electric furnace is filled to the level of the upper bleed hole, for a period corresponding to 20 - 50% of the normal filling period of the furnace, after which the filling is stopped, the upper bleeding hole closes, the slag surface rises to the level of the maximum level of melted mass, and the slag batch it is processed in the same way as in a batch process.
9. 9. The method of claim 8, characterized in that the slag treated in the same manner as in a batch process is discharged from the furnace by first opening the upper bleeding orifice and only after that the lower bleeding orifice. Extract of the Description The invention relates to a method for cleaning slag, created in metallurgical processes of non-ferrous metals, in an electric furnace and particularly the method is related to a semi-continuous cleaning process. According to the novel method, the electric furnace is provided with at least two slag bleeding holes, the lower orifice is disposed on the same level as the bleeding orifice in a conventional batch-working furnace, and the second orifice Bleeding is located higher up, either at the height of the feed intake or only slightly below it.