LU86211A1 - PROCESS FOR RECOVERY OF METAL COMPONENTS CONTAINED IN DUST AND SLUDGE FROM STEEL PLANTS - Google Patents

Description

_: _ BL-3820 / vdw -1- "Process for the recovery of metallic components contained in dust and sludge from steel plants”

The present invention relates to a process 5 for recovering metallic components contained in dust and sludge from steel plants, according to which the dried or ground dust or sludge is continuously introduced into the bottom of an iron bath, at the same time, continuously, in said bath carbonaceous materials in sufficient quantities to maintain a carbon content of more than 1%, there are added to the bath trainers of a slag of basic character and means are provided heating to compensate for heat losses in said bath.

A process of this kind is described in the Luxembourg patent no. 81 330. The idea on which this patent is based consists in replacing the known calcination treatments by a complex reaction which involves, on the one hand, a rapid reduction effected by the carbon contained and constantly added to the bath. of iron and, on the other hand, one! selective volatilization of reduced zinc and a fusion of reduced iron. Reduced lead, which has a high fired evaporation temperature, is found in the bottom of the bath, in metallic form in the liquid state.

Έη now on the bath a layer of slag preferably having a basicity index close to 1.4, we manage to retain the sulfur contained in the treated dust and sludge. This constitutes a considerable advantage over conventional methods based on reductive calcination, the products of which are polluted by sulfur and therefore cannot be used directly without additional purification.

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The zinc fumes released are oxidized according to the formula Zn + CO2 - "> ZnO + CO in the gaseous phase to be evacuated and collected continuously, while part of the metallic bath or of the liquid slag which is formed during the treatment according to the invention which is the subject of the known patent and which contains sulfur. The cast metal is generally subjected to a granulation, preferably a water granulation. These granules can then be integrated into the charge of a blast furnace. The slag extracted can also be granulated.

The implementation of this process for recovering metallic components such as iron, lead and zinc is however subject to

the preliminary solution of the problem of the introduction of the materials to be treated, the fuel and slag formers in the metal bath. Indeed, these materials must be introduced into the bath itself, that is to say below its surface, failing which they will float and the targeted reactions will not take place. To solve this problem, the aforementioned Luxembourg patent recommends an installation for the implementation of the process which comprises a metallurgical container, a lance provided with a refractory lining whose head is located near the bottom of the metallurgical container and whose l The inlet is connected to a cellular metering device situated outside the container, as well as a discharge pipe which extends inside the container and which is connected to a dust collector. The materials to be treated, the fuel and the slag formers are introduced J

by the alveolar metering device in a pressurized gas j • 35 which entrains these products through the lance in j the metal bath. These gases pass through the cellular metering unit at a pressure sufficient to ensure intense bubbling of the bath, so that it suffices to adjust the rotation of the metering unit at a determined speed to inject a desired quantity of dust and products.

Unfortunately, it has been found that this installation does not yet ensure sufficient absorption of the materials to be treated and the dust in the mass of the metal bath. In fact, a non-negligible part of the dust and of the materials to be treated come out again with the gas bubbles out of the metal bath.

Therefore, the object of the present invention is to provide a new process of the kind described in the preamble with a new method of introducing dust, materials to be treated, fuel and slag formers and which prevents these materials from get out of the bath again. i i

To achieve this objective, the method 20 proposed by the present invention is essentially characterized in that the dust or sludge, carbonaceous materials and slag formers are injected below the surface of the bath in the form of wires filled with a diameter between 25 5 ran and 200 mm.

The sheath of the cored wires advantageously consists of cardboard with a thickness of between 0.5 and 10 mm and which is consumed on contact with the liquid bath.

Advantageously, a certain agitation is maintained in the bath by the injection of a neutral gas such as argon or nitrogen by means of one or more permeable elements provided in the bottom or in the wall. of the metal container! 35 pic.

»F γ" Λ -4- With the exception of the device for introducing the products into the metallurgical container, the installation for implementing the process according to the present invention may be the same as that proposed in the Luxembourg patent. cited above No. 81 330. The device intended for forming the cored wire may be a device known per se and which is located in the immediate vicinity of the installation.

This apparatus comprises means for forming filiform sections of a mixture comprising the dried and ground dust or sludge, carbonaceous materials and slag formers and around which films of cardboard are wound, for example helically. It is thus possible to produce cored wires of variable length which can be lowered, continuously or intermittently through an opening in the lid of the metallurgical container.

f 20 Reference is made to the aforementioned Luxembourg patent for additional information concerning the process and the installation for its implementation.

It should be noted that the method provided by the present invention for introducing the materials into the bath also has the advantage of better control of the amount of materials introduced into the bath. In addition, it is no longer necessary to replace the lance which becomes damaged after a certain time in contact with the metal bath.

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Claims (4)

1. Method for recovering metallic i components contained in dust and sludge from steel plants, according to which 5 the dust or sludge · dried and ground is continuously introduced into the bottom of an iron bath. carbonaceous materials in sufficient quantity to maintain a carbon content of more than 1% are continuously introduced into said bath at the same time, the formers of a slag with a basic character are added to the bath and provides heating means to compensate for the heat losses in said bath, characterized in that dust or sludge, carbonaceous materials and slag formers are injected below the surface of the bath in the form of wires filled with d '' a diameter between 5 and 200 mm. 2. Method according to claim 1, characterized in that the sheath of the cored wires consists of cardboard with a thickness of between 0.5 and 10 mm. 3. Method according to one of claims 1 or 2, characterized in that the cored wires are produced in an apparatus known per se being located in the immediate vicinity of the installation for carrying out the method. 4. Method according to any one of claims 1 to 3, characterized in that some agitation is maintained in the bath by the injection of a neutral gas such as argon or nitrogen via one or more permeable elements located at the bottom or in the wall of the metallurgical vessel. m