GB2232907A - Separation of metal from slag from furnaces - Google Patents

Abstract

The metal-containing slag is crushed (2) and sieved (3) in order to remove the fraction smaller than 7 mm., passing the latter to a first hopper (4). The rest is ground in grinders (5) to attain granulometries smaller than 40 mm. and it is sieved (6) again in order to separate another fraction smaller than 7 mm which is also passed to the first hopper (4). The slag larger than 7 mm. is sent to a first density separator (8) to separate out the metal which passes to a silo (9), with a purity of 90% metal. From the first density separator (8) a concentrate with a granulometry less than 7 mm. and 60 % metal content is sent to the first hopper (4). From the first hopper (4) the fine slag and metal passes to another density separator (10) with screen less than 0.5 mm and thus a metal of 0.5 to 0.7 mm with a fineness of 95 to 98 % and metal smaller than 0.5 mm. with a fineness of 98 % are obtained. <IMAGE>

Description

MECHANICAL PROCESS OF SEPARATION OF METALS IN SLAG COMING FROM SIDERURGICAL FURNACES OBJECT OF THE INVENTION The present invention, as is expressed in the title of this specification, refers to a mechanical process of separation of metals in slag coming from siderurgical furnaces.

As is well known, the slag that is produced in the different melting furnaces, electric ones as well as ones of any other type, contain in a larger or smaller amount, portions of ferric and non-ferric metalwhich have been drawn with it in the manufacturing process.

The enormous energy cost existing today and the possibility of recycling materials due to the new techniques, the lack of space for wastes and the Environmental Protection Laws make this process extremely interesting since it solves in itself several problems, in other words: - A poor casting of the furnace can be recovered in accordance with the invention, at a very economical cost.

- Up to 98 % of the material existing in the slag can be recovered.

- Dumps are reduced given that with this process the ground slag can be marketed as an aggregate for concrete as a base and sub-base for highways, as well as an additive (in most slag) for cement in the manufacture of the P.A.

type.

The fineness of the recovered metal and its quality are not reduced given that it is not exposed to any chemical treatment.

BACKGROUND OF THE INVENTION The recovery of the portions of metal that are drawn by the slag in siderurgical furnaces up to the moment and due to the low energy cost, as well as the existence of rather uncontrolled large dumps and without any Environmental Protection legislation was not interesting.

In accordance with the above, a poor casting was not recovered from the furnace, since it was costly, aside from the fact that any present process of recovery of slag entails a chemical treatment which lessens the quality of the recovered metal.

DESCRIPTION OF THE INVENTION The mechanical process of separation of metals that the invention proposes is based on the separation by difference of densities between the slag and the material to be recovered.

As long as said density has a difference higher than 6 %, we can assure the success of the separation.

We can divide the process in two steps: In the first place the metal is freed from its slag proceding with crushing in a crushing machine which ae ptfembly- - of the ones on the market called double effect ones in order to avoid wear, given that most slag from casting is abrasive.

Then there will be a prior sieving in order to remove the fraction between 0 and 7 mm. being collected in a hopper which we will call "sending to concentration." The rest of the material, is made to pass, according to the size upon coming out of the primary crusher, to one or several grinders, which may either be of the hammer or conical type and until a granulometry not higher than 40 mm is reached, where sieving will take place again in order to separate material with a granulometry of O to 7 mm., sending said 'material to the "sending to concentration hopper" and the rest to a hopper which we will call "sending to separation. n In this first step the freeing of the metal from the slag is attained, forming two types of material: the first between 0-7 mm. and the second higher than 7 mm. and up to 40 mm.

This range between 7 and 40 mm. can have its granulometry chosen for each type of slag, making prior grinding which are examined with a magnifying glass or microscope and deducing the ideal size in which the metal has been freed.

According to the granulometry chosen, one or another screen will be put in the density separation box or sieve which we will discuss hereinafter.

Once the freeing of the metal from its slag has been attained, a second stage is proceeded with in which the separation of the metal from the ground slag takes place. The ground material with a granulometry higher than 7 mm which is found in the corresponding hopper goes to the separation plant, made up of a density sieve, by means of a conveyor belt with feeding adjustable from the sieve itself, mixing with water with the help of a propeller preparation device, is washed and the mud if there is any is removed. Said preparation device acts in turn- as a density sieve feeder, providing a constant feeding, a very important constancy for good preparation. The adjustment of feeding is due to the fact that said adjustment is in relationship with the amount of metal that arrives with the slag. The operator can adjust the entry flow to the density sieve.

The sieve or density box of the ones which are called on the market "surging box" or REMEN, will have in the bottom part three purge type outlets.

In the front part of the box, by means of a small hopper, thè already separated material is sent to its corresponding silo. With this small hopper, we will obtain separated metal with a granulometry higher than 7 mm.

and a richness of 90 ,' of freed metal.

Through the outlets or purges a concentrate with a granulometry less than 7 mm. is obtained vlth 60 o,Ó of metal content.

We send this material to the hopper which we have called the concentral-,n hopper above, where in turn the slag ground between 0 and 7 mm. is located.

A density sieve similar to the previous one but much smaller with a screen smaller than 0.5 mm. is also fed from this hopper, with a feeder adjustable at will. Through the front small hopper of this sieve, metal is obtained of 0.5 to 7 mm. with a fineness between 95 and 98 %, and through the purgings a metal with a maximum granulometry with a fineness of 98 % is obtained.

The slag now free of metal goes to some propeller preparation devices from where it comes out totally dry towards the consecutive sieves where different groups of granulometries'are obtained for their subsequent use in construction.

Upon the separation process being totally mechanical, being the main element to attain the water recovery, the savings is manifest and it can be assured that the energy cost in the separation process is only 5 % of what is necessary for grinding.

In order to avoid water consumption, we can recycle it, taking advantage of this recycling to purify the water by means of a tank where the mud which is subsequently removed and taken to a preset place is drawn off. This mud can in some cases contain metal in fractions of microns, metal which by means of any type of shaketable of the ones that exist on the market can be recovered.

In order to facilitate the understanding of the features of the invention and forming an integral part of this specification, a sheet of drawings in whose sole figure with an illustrative and non-restrictive nature the following has been represented has been accompanied.

BRIEF DESCRIPTION OF THE DRAWINGS Sole figure.- It shows a diagram of the mechanical treatment of the slag-metal in accordance with the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Making reference to the numbering that is indicated on on the diagram of the figure, we can see that the mechanical process of separation of metals in the slag coming from siderurgical furnaces, that the invention envisages, includes the slag hopper 1 from which the material is led to the grinder 2 and sieve 3, withdrawing the fraction that goes through the mesh towards hopper 4. The material that does not go through the sieve 3 is ground in the mill until a granulometry no greater than 40 mm. is obtained. The material that goes through sieve 6 and that has a granulometry smaller than 7 mm is withdrawn again, leading it to the same hopper 4. The remaining material, with a granulometry between 7 and 40 mm goes to hopper 7.

The ground slag, with a granulometry higher than 7 mm and which is found in hopper 7 goes to the separator 8 in which the metal is separated from its slag by densities. By means of a small hopper the metal with a granulometry higher than 7 mm is sent towards the silo 9, while through the outlets or purges of this separator 8 a concentrate with a granulometry smaller than 7 mm. is obtained with a 60 % metal content, which is also sent to hopper 4 where the slag ground between 0 and 7 mm. is located.

The material of this hopper 4 is sent to another separator 10 with a screen smaller than 0.5 mm and from which, by means of the front small hopper a metal of 0.5 to 7 mm. is obtained and through the purges a metal with a maximum granulometry of 0.5 mm. is obtained, being collected in a silo 11.

The slag free of metal which is obtained in the separators 8 and 10, after its total drying goes through different sieves in order to obtain different granulometries for use thereof in construction, respectively collected in silos 12, 13 and 14.

The place chosen for the collecting of mud coming from the separators 8 and 10 is shown with reference 15.

Claims (9)

1. A process for separating metals from slag comprising initially grinding the slag; separating the ground slag with a granular size less than a first predetermined value by means of a sieve; collecting the separated slag in a first hopper; grinding the unseparated slag a second time so as to obtain a granular size no greater than a second predetermined value larger than the first predetermined value; separating the ground slag of less than the second predetermined size and collecting particles having a granular size less than the first predetermined value in the first hopper; collecting the remaining slag in a second hopper; separating metal from the ground slag contained in the second hopper by means of a first density separator; storing in a silo the metal separated from the slag contained in the second hopper, which metal has a granular size greater than the first predetermined amount; obtaining a mixture having granular particles of less than the first predetermined amount through purges or outlets of the first density separator and transferring the mixture to the first hopper; separating the slag contained in the first hopper by means of a second density separator; separating from the slag passed to the second density separator particles having a size smaller than a third predetermined value, which the predetermined value is less than the first predetermined value; separating through purges or outlets of the second density separator metal contained within the slag of a size between said second and third predetermined value; collecting the metal having a granular size of less than said third predetermined size in a silo and drying the separated metal free slag from the first and second density separator6, wherein the first, second and third predetermined values are determined according to the type of slag.

2. k process according to claim 1 wherein the dried metal free slag is separated according to different ranges of granular size for subsequent use in construction.

3. A process according to claim 1 or claim 2 comprising washing mud from the slag and collecting the mud from the first and second density separators.

4. An apparatus for separating metals from slag comprising means for initially grinding the slag: separator means for separating the ground slag with a granular size less than a first predetermined value; a first hopper for collecting the separated slag; means for grinding the unseparated slag a second time so as to obtain a granular size no greater than a second predetermined value larger than the first predetermined value; means for separating the ground slag of less than the second predetermined size: means for collecting particles having a granular size less than the first predetermined value in the first hopper; a second hopper for collecting the eema;.ning slag; first density separator means for separating the ground slag contained in the second hopper by density separator; means for storing in a silo metal separated from the slag contained in the second hopper a which metal has a granular size greater than the first predetermined amount: purge or outlet means in the first density separator for obtaining a mixture having granular particles of less than the first predetermined amount; means for transferring the mixture to the first hopper; a second density separator for separating the slag contained in the first hopper; means for separating from the slag passed to the second density separator particles having a size smaller than a third predetermined value, which the predetermined value is less than the first predetermined value: purge or outlet means in the second density separator for separating metal contained within the slag of a size between said second and third predetermined value; means for collecting the metal having a granular size of less than said third predetermined size in a silo; and means for drying the separated metal free slag from the first and second density separators: wherein the first1 second and third predetermined values are determined according to the type of slag.

5. An apparatus according to claim 4 comprising means for separating the dried metal free slag according to different ranges of granular size for subsequent use in construction.

6. An apparatus according to claim 4 or claim 5 comprising means for washing mud from the slag and collecting mud from the first and second density separators.

7. Mechanical process of separation of metals in slag coming from siderurgical furnaces characterized because initially a grinding and prior sieving is proceeded with in order to remove the fraction between 0 and 7 mm which passes to a hopper (4), while the rest of the material is led towards one or several mills (5) until a granulometry no greater than 40 mm. is obtained, sieving again in order to separate another fraction of 0 to 7 mm. that is collected in the same hopper 4 and the rest is sent to a second hopper (7); the arterial of this hopper (7) goes to a separator (8) where the metal is separated from its slag by densities, sending to a silo (9) the metal withdrawn with a small hopper, with a granulometry greater than 7 mm. and a richness of 90 % of freed metal; a concentrate with a granulometry less than 7 mm. is obtained through the purges or outlets of the separator (8) with a 60 % metal content, being sent to the hopper (4) with a granulometry between 0 and 7 mm; from this hopper (4) and by means of a feeder adjustable at will, it is sent to another densities separator (10) similar to the previous one but with a screen smaller than 0.5 mm. from where metal of 0.5 to 7 mm. with a fineness between 95 and 98 % is obtained and through the purges a metal with a granulometry less than 0.5 mm. and a fineness of 98 % is obtained; the metal free slag is sent to some propeller preparation devices from where it comes out dry and is distributed in different granulometries for the subsequent use thereof in construction.

8. A method according to claim 1 substantially as hereinbefore described.

9. Apparatus for separating metals from slags substantially as hereinbefore described with reference to the accompanying drawings.