WO1991008836A1

WO1991008836A1 - A method and an apparatus for crushing slags resulting from steel production

Info

Publication number: WO1991008836A1
Application number: PCT/DK1990/000317
Authority: WO
Inventors: Henning Kallestrup
Original assignee: Tarco Vej A/S
Priority date: 1989-12-07
Filing date: 1990-12-05
Publication date: 1991-06-27
Also published as: DK617889A; DK160915B; DK161680B; DK617889D0; DK161680C

Abstract

A method of continuously crushing and sieving slag resulting from production of steel, said method substantially including a preparatory coarse crushing (KG), a coarse sieving (SG) followed by a separation of the largest pieces of steel of the slag by a first separating step (U1) and a completing final sieving (SS) where the crushed slag is separated into fractions comprising their respective predetermined granular size. By the method the content of the slag of steel or iron is separated therefrom at a plurality of separating steps (U1, U2, U3, P1, P2, PS). The slag passes a plurality of crushing, sieving and separating steps in such a manner that each crushing step (KM; KF) is followed by a separating step (U2; P2) prior to the succeeding crushing or sieving step. The slag separated at any arbitrary separating step (U1, U2; P2) passes repeatedly both a steel particle separating step (P1, PS; P2), where the free steel particles are separated, and the crushing step (KM; KF) associated with said separating step. In this manner it is possible to separate an amount of the steel/iron content in the slags which compared to previously is unusually high with the effect that the slags are particularly suited for use in connection with production of road surfaces.

Description

Title: A Method and an Apparatus for Crushing Slags Resulting From Steel Production

Technical Field

The invention relates to a method of continuously crushing and sieving slag resulting from production of steel, said method substantially including a preparatory coarse crushing, a coarse sieving followed by a separation of the largest pieces of steel of the slag by a first separating step and a completing final sieving where the crushed slag is separated into fractions comprising their respective predetermined granular size, said method further including a plurality of separating steps where the content of the slag of steel or iron is separated therefrom.

Background Art Methods of the above type are known where the primary object is to produce a slag which in the ready state is to be used for road surfaces. During recent years the use of crushed slags for road surfaces has increased, said slags resulting from production of steel. The increasing use is particularly due to the advantages presented by road surfaces containing steel slag, viz. advantages such as high s trength , hi gh wearab i l i ty and c ons equent ly a long life. It is, however, of vital importance that the iron/steel content in the crushed slag is as low as possible and preferably less than 1% when said slag is mixed with bitumen for the production of road surfaces. A too high iron/steel content in the slag involves a risk of the road surface not being as strong as desired due to the iron/steel particles rusting. As a consequence thereof both the slag and the slag and bitumen compound are weakened, said problem particulary applying when the surface of the slag comprises too large iron/steel particles. In addition, it is desired to use as much of the original iron/steel content as possible, said content amounting to 3 to 4% in the slags resulting from the production of steel.

Disclosure of Invention

The object of the present invention is accordingly to provide a method of continuously crushing and sieving slags resulting from the production of steel, where a particularly high amount of the original steel/iron content in the slag is separated before the crushing, especially in order to reduce the remaining iron/steel content in the crushed slag to less than 1%.

The method according to the invention is characterised in that the slag passes a plurality of crushing, sieving and separating steps in such a manner that each crushing step is followed by a separating step prior to the succeeding crushing or sieving step, and furthermore such that each sieving step is followed by a separating step as far as the sieved slag fraction comprising the smallest granular size is concerned, and that the steel-containing slag at one or more separating steps repeatedly passes a steel particle separating step where the free steel particles are separated and pass a crushing step associated with said separating step for separation of free steel particles of a decreasing size compared to the preceding separating step before the remaining slag is advanced to the succeeding crushing, sieving and separating steps or to the final sieving.

In this manner each crushing of the slag into another and smaller granular size prevents the slag particle fraction containing the steel or iron particles from continuing to the next crushing step until said steel particle containing slags have passed the crushing step and the steel particle separating step in question several times, said next crushing step involving a crushing into yet another smaller granular size. In this manner it is ensured that the steel particles in the slag have now been separated as steel particles, said steel particles having caused said slag to be separated as steel-containing slag at the separating step in question. Subsequently, the remaining slag is allowed to pass and continue to the next crushing step. After the crushing at the next crushing step, slag particles are again present which are separated because remaining steel or iron particles are uncovered in or adjacent the surface of said slag during the crushing into the even smaller granular size. The cycle is repeated until the slag has passed the last separating step before the final sieving.

According to the invention, the separation of the steelcontaining slag and the free steel particles may be carried out by way of magnetism, and the slag may be substantially subjected to magnetic fields of varying strengths when it passes the succeeding separating steps. As a result, a particularly high amount of the iron/steel content in the slag is separated.

Furthermore according to the invention, the first separating step including separation of the coarsest pieces of steel/iron may be followed by an intermediate crushing step in turn followed by an associated second separating step, and the separated steel-containing slags resulting from the first and the second separating step may be brought together and pass a steel sieving step so as to separate the coarsest pieces of steel, whereafter the slag passes a first step separating the steel particles and returns to the intermediate crushing step. In this manner the coarsest steel pieces are separated in a particularly simple manner.

Moreover according to the invention, the second separating step may be followed by an intermediate sieving step, whereafter the slag fraction sieved at said intermediate sieving step passes a succeeding fine crushing step followed by the finely crushed slag fraction being carried through a second steel particle separating step, thereafter brought together with the slag fraction and together therewith carried to the intermediate sieving step, whereby a particularly simple embodiment is obtained of the two last crushing and sieving steps before the final sieving. In addition according to the invention, the sieved slag fractions of the smallest granular size resulting from the intermediate sieving step and from the coarse sieving step may both pass a third separating step before they are continued to the final sieving, and the steel-containing slag resulting from the third separating step may be brought together with the sieved slag fraction of the largest granular size resulting from the intermediate sieving step. In this manner the content of steel/iron particles in the crushed slag is controlled one more time before said slag continues to the completing final sieving. Furthermore according to the invention, one or more of the fractions resulting from the final sieving may, if desired, be returned to the final crushing step which the slag passes before the final sieving, preferably the fine crushing step. As a result no limits apply to the amount of each fraction desired to be produced because the fractions of a granular size larger than the fraction of the minimum granular size can be returned for another crushing until the desired proportion of the fractions has been obtained. Accordingly any amount of each fraction can be chosen.

In addition according to the invention the crushed slag may pass a drying step so as to reduce the moisture content of the slag to approximately 3 to 4% before the final sieving. When subjected to particularly unfavourable weather conditions involving a high moisture percentage or rain or snow, the resulting, crushed slag is prevented from clotting during the final sieving step, which might otherwise involve a production breakdown.

Moreover according to the invention the slag may during the crushing and sieving procedure pass, if desired, one or more moisturing steps so as to increase the moisture content of the crushed and sieved slag, whereby it is avoided that the slag pollutes the surroundings, especially under weather conditions involving intense heat and strong winds. The invention relates furthermore to an apparatus for continuously crushing and sieving slag resulting from production of steel and to be used when carrying out the method described above, said apparatus substantially comprising a coarse crushing station, a coarse sieving station and a succeeding separating station adapted to separate the coarsest pieces of steel of the slag, as well as a final sieving station adapted to separate the crushed slag into fractions. The apparatus according to the invention is characterised in that the apparatus comprises a plurality of crushing, sieving and separating stations between the first separating station and the final sieving station, said separating stations being adapted to separate the steel or iron content of the slag, where said stations are interconnected by means of conveyors, and where said crushing, sieving and separating stations are adapted such that the outlet of each crushing station is connected to the inlet of a separating station, and such that the outlet of each sieving station for the sieved slag fraction of the smallest granular size is connected to the inlet of a separating station, and that the outlet of any separating station for the separated steel-containing slag is connected to the inlet of a steel particle separating station adapted to separate the free steel particles and further connected to the inlet of the crushing station associated with the separating station in question. The resulting apparatus allows separation of a particularly high amount of the original iron/steel content in the slag. The apparatus according to the invention deals in particular with crushed slags to be used in connection with production of road surfaces. In addition, the apparatus allows reuse of a high amount of the original steel/- iron content in the slags for the production of steel.

According to the invention the outlet of the first separating station may be connected to the inlet of an intermediate crushing station, where the outlet of said intermediate crushing station is connected to the inlet of an associated second separating station, the outlets of both the first and the second separating station for the separated steel- containing slag may be connected to the inlet of a steel sieving station separating the coarsest pieces of steel, and the outlet of the steel sieving station for the sieved slag may be connected to the inlet of a first steel particle separating station, where the outlet of said steel particle separating station for the slag is connected to the inlet of the intermediate crushing station. In this manner it is rendered possible in a particularly simple manner to separate the coarsest pieces of steel in the slag during the separating step simultaneously separating steel/iron particles of a significantly smaller size.

Moreover according to the invention the outlet of the second separating station for the slag may be connected to the inlet of an intermediate sieving station, where the outlet for the sieved slag fraction of the largest granular size is connected to the inlet of a fine crushing station, where the outlet of said fine crushing station is connected to the inlet of a second steel particle separating station, and where the outlet of said steel particle separating station for the slag is connected to the inlet of the intermediate sieving station. As a result, the final crushing station of the apparatus is particularly advantageously structured.

In addition according to the invention the outlets of the intermediate sieving station and the coarse sieving station for the sieved slag fraction of the smallest granular size may both be connected to the inlet of a third separating station, where the outlet of said third separating station for the slag is connected to the inlet of the final sieving station, and where the outlet of said third separating station for the separated steel-containing slag is connected to the inlet of the fine crushing station. In this manner a particularly advantageous structure of the final separating station of the apparatus is obtained, said final separating station being followed by the crushed slag continuing to the completing final sieving.

Furthermore according to the invention the outlet of the final sieving station for each sieved fraction may be connected both to storage containers and to the inlet of the fine crushing station. As a result no limits apply to the amount of each fraction desired to be produced because the fractions of a granular size larger than the fraction of the minimum granular size can be returned for another crushing, if desired, until the desired proportion of the fractions has been obtained. Accordingly any amount of each fraction can be chosen.

Moreover the crushing stations may according to the invention comprise a cone or rotor crusher, which proved to be particularly advantageous. Another particular advantage is obtained by the separating stations comprising overlying magnetic conveyors or magnetic tumblers. According to the invention the outlet of the third separating station may be connected to the inlet of a drying station, where the outlet of said drying station is connected to the inlet of the final sieving station. As a result, the moisture content of the crushed slag can be reduced to approximately 3 to 4% with the effect that the slag is prevented from "clotting" during the completing final sieving, when said slag is being crushed under particularly unfavourable weather conditions involving rain, snow or high moisture percentages.

Finally the apparatus may according to the invention also comprise any desired number of moisturing stations substantially adapted to water the crushed slag so as to increase the moisture content of said slag. In this manner the moisture content in the crushed slag can be increased such that the slag does not pollute the surroundings under weather conditions involving intense heat or strong winds.

Brief Description of Drawing

The invention is explained in greater detail below with reference to the accompanying drawing showing a diagrammatic view of an embodiment of the crushing, sieving and separating stations of the apparatus, and further showing how the slag passes through the apparatus, the connecting arrows between the individual stations symbolizing conveyors advancing the slag from station to station.

Best Mode for Carrying Out the Invention

The drawing shows a diagrammatic view of an apparatus for continuously crushing and sieving slag resulting from the production of steel. The apparatus comprises a preparatory coarse crushing station K_G supplied with the slag and followed by a coarse sieving station S_G and a succeeding first separating station U₁. The first separating station U₁ is adapted to separate the coarsest pieces of steel in the slag. The apparatus comprises furthermore a completing sieving station Sg, in which the completely crushed slag is separated into fractions fed to storage containers, as well as a plurality of crushing, sieving and separating stations arranged between the first separating station U₁ and the completing sieving station S _S . All the stations are interconnected by means of conveyors symbolized by the connecting arrows in the drawing. The stations are explained in greater detail below.

The outlet K_GU o f the coarse crushing station is connected to the inlet S_Gl of the coarse sieving station, said inlet S_GI being fed with slags containing pieces of steel preferably of a granular size in the range 0 to 85 mm. The outlet S_GUG of the coarse sieving station for the slag fraction of the largest granular size is connected to the inlet U_1l of the first separating station U₁. The coarse crushing station Kp may for instance comprise any known type of jaw breakers optionally also including a safety release device. The coarse sieving station S _G may comprise any known type of coarse sieves, and the first separating station U₁ may for instance comprise a magnetic tumbler adjusted to a magnetic field intensity suitable for separating very large pieces of steel and steel-containing slag with a high steel content. The outlet U_1U of the first separating station U₁ for the remaining slag is connected to the inlet K_Ml of an intermediate crushing station, and the outlet K_GU of said intermediate crushing station K_M is connected to the inlet U_2l of a second separating station U₂. The intermediate crushing station K_M may comprise a known rotor or cone crusher, and the second separating station U₂ may comprise a known overlying magnetic conveyor adjusted to a comparatively weaker magnetic field intensity than in the first separating station U₁. The outlet U_1US of the separating station U₁ for the separated steel-containing slag is connected to the outlet U_{2U S} of the separating station U₂ for the steel-containing slag and furthermore connected to the inlet P_Sl of a steel sieving station P_S. The steel sieving station P _S separates the coarsest pieces of steel resulting from the production of steel and leaving said steel sieving station Ε _S through the outlet P_SUS thereof to a storage L'. The remaining steel-containing slag passes the outlet P_{S U} of the steel sieving station Ε _S , said outlet being connected to the inlet P_1l of a first steel particle separating station P₁. The first steel particle separating station P₁ comprises preferably a known type of overlying magnetic conveyors being adjusted to a suitable magnetic field intensity such that free steel/iron particles are separated from the steel-containing slag. The free steel/iron particles leave the station P₁ through the outlet P_1US thereof to a storage L". The remaining steel-containing slag unseparatable at the magnetic field intensity in the station P₁ is carried through the outlet P_1U of the station P₁, said outlet being connected to the inlet K_Ml of the intermediate crushing station K_M. In this manner the steel- containing slag passes the intermediate crushing station Ktø several times before it continues through the separating station U₂ and the steel particle separating station P₁, until it is finally crushed to such an extent that the free steel particles have been separated and the steel particles remaining in the slag cannot be separated until another crushing to a smaller granular size of the slag has been performed.

The outlet U_2U of the second separating station U₂ is connected to the inlet S_Ml of an intermediate sieving station S_M, said inlet in the embodiment shown being supplied with crushed slags of a granular size in the range 0 to 22 mm. The outlet S_MUG of the intermediate sieving station S_M for the slag fraction of the largest granular size, preferably in the range of 12 to 22 mm, is connected to the inlet K_Fl of a fine crushing station K_F. The outlet K_FU of the fine crushing station K_F is connected to the inlet P₂₁ of a steel particle separating station P₂. The station P ₂ comprises preferably an overlying magnetic conveyor performing a field intensity suitably adjusted such that the separated steel particles of the smallest size in the apparatus can pass through the outlet P_2US of the station P₂ to storage L"'. The outlet P_2U of the station P₂ for the remaining steel-containing slag is connected to the inlet S_Ml of the intermediate sieving station S_M. Subsequently, the remaining steel-containing slag passes through the steel sieving station S_M, and in case said slag has not been sufficiently crushed it continues to the fine crushing station K_F so as again to return to the steel particle separating station P₂ for separation of the optionally released remaining steel particles separated in the station P₂.

The outlet S_MUF of the intermediate sieving station S_M for the sieved slag fraction of the smallest granular size is connected to the inlet U_3l of a third separating station U₃, said inlet U_3l also being connected to the outlet S_GUF of the coarse sieving station S _G for the sieved slag fraction of the smallest granular size. The sieved slag fraction from the intermediate sieving station S_M is preferably of a granular size in the range 0 to 12 mm, and the sieved slag fraction from the coarse sieving station S_G is preferably of a granular size in the range of 0 to 8 mm. The third separating station U₃ comprises preferably both an overlying magnetic conveyor and a magnetic tumbler arranged in sequence and adjusted to varying magnetic field intensities. The overlying magnetic conveyor and the magnetic tumbler present a final control for separation of the remaining steel particle containing slag, which after separation is returned to the inlet K_Fl of the fine crushing station K_F through the outlet U_3US of the separating station U₃. The remaining steel-containing slag is subsequently crushed in the fine crushing station K_F with the result that the remaining free steel particles are separated in the steel particle separating station P₂ and the remaining slag is returned so as again to pass and be controlled by the third separating station U₃.

The slag supplied to the apparatus presents usually an original steel/iron content of 3 to 4%, and the apparatus according to the invention proved to allow separation of such a high steel/iron content into a crushed and sieved slag containing less than 1% of steel/iron. The latter feature is particularly advantageous when the crushed slag is to be used in connection with production of road surfaces. Problems are consequently avoided concerning a reduced strength of the road surface and a reduced life thereof due to a too high steel/iron content in the slags and especially due to a too high content of free steel/iron particles on the surfaces of the slags. In addition, it presents a great advantage that a maximum amount of the original steel/iron content in the slags can be reused for the production of steel. The apparatus according to the invention allows for instance production of approximately 60,000 ton of crushed slags per year, which in turn involves a significant amount of released iron/steel of about 1,800 ton per year.

According to a particularly advantageous embodiment, the outlet U_3U of the third separating station U₃ can be connected both to the inlet S_Sl of the completing sieving station S_S and to the inlet T_l of a drying station T. In this manner the completely crushed slag can be carried according to desire directly to the completing sieving station Ss or in advance be carried through the drying station T, where the crushed slag is dried to a moisture content of 3 to 4%, which is of importance when the produc tion is carried out under particularly unfavourable weather conditions involving rain, snow or a high moisture percentage. Accordingly, problems are avoided concerning the slag "clotting" during the completing sieving. The apparatus can be provided with one or more arbitrarily arranged moisturing stations, said stations, however, preferably being arranged after each crushing station and before the crushed slag passes the sieving station, cf. for instance the moisturing station B indicated by a dotted line. In this manner the surroundings are not polluted when the production is carried out under weather conditions involving intense heat and strong winds. Several moisturing stations can advantageously also be suitably arranged at other locations in the apparatus. By the completing sieving, the completely crushed slag is separated into a suitable number of fractions, such as of a granular size in the range of 0 to 2 mm, of 2 to 5 mm, of 5 to 8 mm, and of 8 to 12 mm. The outlet S_{SU R} of the completing sieving station S_S can, however, also be connected to the inlet K_{Fl R} of the fine crushing station K_F, whereby some of the completely sieved fractions can be returned, if desired, for another crushing. A particularly great advantage is obtained thereby when a production of a very large amount of slag of a predetermined granular size for instance is to be produced. In this manner it is possible at any time to adjust the amounts produced of the various fractions to the demand for the product in question. Accordingly, the demand for storage can also be considerably reduced. All the crushing, sieving, steel particle separating, drying and moisturing stations of the apparatus and all the conveyors interconnecting said stations are preferably provided with control means communicating with a central computerized control unit with the effect that the apparatus and consequently the production rate thereof can be utilized to a maximum.

The apparatus can comprise an arbitrary number of crushing. sieving and separating stations in response to the demand in question for the type of slags to be crushed and resulting from the production of steel.

Claims

C l a ims

1. A method of continuously crushing and sieving slag resulting from production of steel, said method substantially including a preparatory coarse crushing, a coarse sieving followed by a separation of the largest pieces of steel of the slag by a first separating step and a completing final sieving where the crushed slag is separated into fractions comprising their respective predetermined granular size, said method further including a plurality of separating steps where the content of the slag of steel or iron is separated therefrom, c h a r a c t e r i s e d in that the slag passes a plurality of crushing, sieving and separating steps (K_M, U₂, S_M, K_F, P₂, U₃) in such a manner that each crushing step (K_M; K_F) is followed by a separating step (U₂; P₂) prior to the succeeding crushing or sieving step, and furthermore such that each sieving step (S_G, S_M ) is followed by a separating step (U₃) as far as the sieved slag fraction comprising the smallest granular size is concerned, and that the steel-containing slag at one or more separating steps (U₁, U₂; U₃) repeatedly passes a steel particle separating step (P₁; P₂) where the free steel particles are separated and pass a crushing step (K_M ; K_F) associated with said separating step for separation of free steel particles of a decreasing size compared to the preceding separating step before the remaining slag is advanced to the succeeding crushing, sieving and separating steps or to the final sieving.

2. A method as claimed in claim 1, c h a r a c t e ri s e d in that the steel-containing slag and the free steel particles are separated by way of magnetism, and that the slag is substantially subjected to magnetic fields of a varying strength when it passes the succeeding separating steps (U₁, U₂, U₃).

3. A method as claimed in claim 1 or 2, c h a r a c t e r i s e d in that the first separating step (U₁) including separation of the coarsest pieces of steel/Iron is followed by an intermediate crushing step (K_M) in turn followed by an associated second separating step (U₂), and that the separated steel-containing slags resulting from the first and the second separating step (U₁, U₂) are brought together and pass a steel sieving step (P_S) so as to separate the coarsest pieces of steel, whereafter the slag passes a first step (P₁) separating the steel partides and returns to the intermediate crushing step (K_M).

4. A method as claimed in one or more of the preceding claims 1 to 3, c h a r a c t e r i s e d in that the second separating step (U₂) is followed by an intermediate sieving step (S_M), whereafter the slag fraction sieved at said intermediate sieving step passes a succeeding fine crushing step (Kp) followed by the finely crushed slag fraction being carried through a second steel particle separating step (P₂), thereafter brought together with the slag fraction and together therewith carried to the intermediate sieving step (S_M).

5. A method as claimed in one or more of the preceding claims 1 to 4, c h a r a c t e r i s e d in that the sieved slag fractions of the smallest granular size resulting from the intermediate sieving step (S_M) and from the coarse sieving step (S_G) both pass a third separating step (U₃) before they are continued to the final sieving (S_S), and that the steel-containing slag resulting from the third separating step (U₃) is brought together with the sieved slag fraction of the largest granular size resulting from the intermediate sieving step (S_M).

6. A method as claimed in one or more of the preceding claims 1 to 5, c h a r a c t e r i s e d in that one or more of the fractions resulting from the final sieving (S_S), if desired, are returned to the final crushing step (K_F) which the slag passes before the final sieving, preferably the fine crushing step.

7. A method as claimed in one or more of the preceding claims 1 to 6, c h a r a c t e r i s e d in that the crushed slag passes a drying step (T) so as to reduce the moisture content of the slag to approximately 3 to 4% before the final sieving (S_S).

8. A method as claimed in one or more of the preceding claims, c h a r a c t e r i s e d in that during the crushing and sieving procedure the slag passes, if desired, one or more moisturing steps (8) so as to increase the moisture content of the crushed and sieved slag.

9. An apparatus for continuously crushing and sieving slag resulting from production of steel and to be used when carrying out the method described in the preceding claims 1 to 8, said apparatus substantially comprising a coarse crushing station, a coarse sieving station and a succeeding separating station adapted to separate the coarsest pieces of steel of the slag, as well as a final sieving station adapted to separate the crushed slag into fractions, c h a r a c t e r i s e d in that the apparatus comprises a plurality of crushing, sieving and separating stations (K_M, K_F, S_M, U₂, U₃, P₂) between the first separating station (U₁) and the final sieving station (Ss), said separating stations (U₁, U₂, U₃, P₂) being adapted to separate the steel or iron content of the slag, where said stations (K_G, S_G, U₁, K_M, U₂, S_M, K_F, P₂, U₃, S_S) are interconnected by means of conveyors, and where said crushing, sieving and separating stations are adapted such that the outlet (K_MU ; K_FU) of each crushing station is connected to the inlet (U_2l; P_2l) of a separating station, and such that the outlet (S_GUF; S_MUF) of each sieving station for the sieved slag fraction of the smallest granular size is connected to the inlet (U_3l) of a separating station, and that the outlet (U_{1U S}, U_2US, U_{3U S}) of any separating station for the separated steel-containing slag is connected to the inlet (P_1l; P_2l) of a steel particle separating station (P₁; P₂) adapted to separate the free steel particles and further connected to the inlet (K_Gl; K_Fl) of the crushing station (K_M ; K_F) associated with the separating station (U₂; P₂) in question.

10. An apparatus as claimed in claim 9, c h a r a c t e r i s e d in that the outlet (U_1U ) of the first separating station (U₁) is connected to the inlet (K_Ml) of an intermediate crushing station (K_M), where the outlet (K_MU) of said intermediate crushing station (K_M) is connected to the inlet (U_2l) of an associated second separating station (U₂), that the outlets (U_{1U S}, U_2US) of both the first and the second separating station for the separated steel-containing slag are connected to the inlet (P_Sl) of a steel sieving station (P_S) separating the coarsest pieces of steel, and that the outlet (P_SU) of the steel sieving station (P_S) for the sieved slag is connected to the inlet (P_1l) of a first steel particle separating station (P₁), where the outlet (P_1U ) of said steel particle separating station (P₁) for the slag is connected to the inlet (K_Ml) of the intermediate crushing station (K_M).

11. An apparatus as claimed in claim 9 or 10, c h a r¬a c t e r i s e d in that the outlet (U_2U) of the second separating station (U₂) for the slag is connected to the inlet (S_{M l}) of an intermediate sieving station (S_M), where the outlet (S_MUG ) for the sieved slag fraction of the largest granular size is connected to the inlet (K_Fl) of a fine crushing station (K_F), where the outlet (K_FU) of said fine crushing station (K_F) is connected to the inlet (P_2l) of a second steel particle separating station (P₂), and where the outlet (P₂U) of said steel particle separating station (P₂) for the slag is connected to the inlet (S_{M I}) of the intermediate sieving station (S_M).

12. An apparatus as claimed in one or more of the preceding claims 9 to 11, c h a r a c t e r i s e d in that the outlets (S_MUF; S_{GU F}) of the intermediate sieving station (S_M) and the coarse sieving station (S_G) for the sieved slag fraction of the smallest granular size both are connected to the inlet (U_3l) of a third separating station (U₃), where the outlet (U_3U) of said third separating station (U₃) for the slag is connected to the inlet (S_Sl) of the final sieving station (S_S), and where the outlet (U_3US) of said third separating station (U3) for the separated steel-containing slag is connected to the inlet (K_Fl) of the fine crushing station (K_F).

13. An apparatus as claimed in one or more of the preceding claims 9 to 12, c h a r a c t e r i s e d in that the outlet (S_SUR) of the final sieving station (S_S) for each sieved fraction is connected both to storage containers and to the inlet (K_FlR) of the fine crushing station (K_F).

14. An apparatus as claimed in one or more of the preceding claims 9 to 13, c h a r a c t e r i s e d in that the crushing stations (Krø, Kp) comprise a cone or rotor crusher.

15. An apparatus as claimed in one or more of the preceding claims 9 to 14, c h a r a c t e r i s e d in that the separating stations (U₁, U₂, U₃ , P₁, P₂) comprise overlying magnetic conveyors or magnetic tumblers.

16. An apparatus as claimed in one or more of the preceding claims 9 to 15, c h a r a c t e r i s e d in that the outlet (U3U) of the third separating station (U₃) is connected to the inlet (T_l) of a drying station (T), where the outlet (T_U) of said drying station (T) is connected to the inlet (S_Sl) of the final sieving station (S_S).

17. An apparatus as claimed in one or more of the preceding claims 9 to 16, c h a r a c t e r i s e d in that the apparatus comprises any desired number of moisturing stations (B) substantially adapted to water the crushed slag so as to increase the moisture content of said slag.