Short title: Method for separating metal-containing parts from rubble-containing soil.

The present invention relates to a method for separating metal-containing parts from rubble- containing soil. In particular, the invention relates to a method for separating substantially all metal-containing parts from possibly chemically contaminated rubble-containing soil with a high sticky mass content, in particular high clay content. Contaminations in the soil may be, for example, packing substances or aromatic compounds.

Currently, the decreasing availability of various natural raw materials is a substantial problem. Due to the fact that these raw materials are becoming relatively scarce and more difficult to obtain, the prices of raw materials are rising. In the cement industry, for example, large quantities of limestone and marl are used as raw materials and these raw materials are increasingly difficult to obtain. The limestone and marl quarries are becoming exhausted or have become increasingly less accessible. This increases the cost for the natural raw materials limestone and marl. An additional problem is the fact that, as a result of various environmental levies and environmental laws, the dumping of contaminated soil is increasingly expensive and can only be permitted under strict rules.

DE3248493A1 discloses a device and method for re-obtaining valuable materials from the structural sector. Beside demolition remainder a released discharge flow of remainders from the structural sector may comprise for example as a result of re-development work, also rubble, domestic objects, furniture, packaged materials and a lot of other objects. Most of the times this discharge flow of remainders is transported away in containers. The discharge flow of remainders comprises a lot of valuable materials like wood, metal, stone, sand and combustible materials, which can be re-obtained. For this a separating device is provided which comprises a bunker to which the discharge flow of remainders can be supplied for subsequently separating by conveyer bands ed. along screen units, manual sorting stations, scissors, separators for ferrous containing metal parts, wind separators and separators for non ferrous metal parts, into several re-usable materials.

A drawback to the known separator device is that it is not suitable for the processing of other kinds of remainder discharge flows. For example digged-up highly chemically contaminated clay-containing soil which also contains a certain amount of rubble can not be processed with the separator device, because this would very soon lead to a silting up of several components of the separator device.

This is especially the case when the content of clay becomes very high. In addition it is by far not possible to guarantee that all the metal parts can be removed from the soil. As a consequence this is the reason why it is impossible to provide a temperature treatment to a part of the soil in a furnace, which results in that the chemical contaminations cannot be cleaned or converted into non-harmful materials. Further, it is not possible to re-obtain raw materials like limestone and marl in such a quality from the soil that it is allowed to re-use them in the cement industry.

At present there is still no good solution for the treatment of digged-up highly chemically contaminated clay-containing soil, which has as a direct consequence that it has to be dumped somewhere time after time having a lot of negative disadvantages as a consequence. Besides this, only accurately selected rubble-containing soil can be offered to the cement industry for further processing if it is from the beginning established that these materials are not chemically contaminated and that these are free from metal parts like copper, aluminum, etc.

It is an object of the invention to overcome at least one of the abovementioned drawbacks, at least partially, and/or to provide a usable alternative. In particular, it is an object of the invention to provide an efficient and reliable method for supplying an alternative raw material for the production of cement.

This object is achieved by a method for a separation process according to claim 1. The method according to the invention separates metal-containing parts from the rubble- containing soil. By removing the metal-containing parts from rubble-containing soil, the remaining rubble-containing soil can be used as an alternative raw material for the production of cement. According to the method, the limestone and marl which are used for the production of cement can at least partially be replaced by the resulting rubble-containing soil.

Advantageously, the method according to the invention is environmentally friendly due to the re-use of materials. In addition, it is possible to achieve a cost saving with respect to the natural raw materials limestone and marl by admixing the fractions of rubble-containing soil.

It is advantageous that, thanks to the re-use, the rubble-containing soil does not have to be taken to waste sites, despite some possible contaminations in the soil. During re-use of the rubble-containing soil for the production of cement, very high temperatures occur e.g. due to a temperature-treatment in a furnace, as a result of which the soil is cleaned of any contaminations or the latter are converted to harmless substances.

Contaminations in the rubble-containing soil are not so relevant for cement production; what is much more important is the fact that, as is the case with the method according to the invention, substantially all metal-containing parts in particular those metal-containing parts which are greater than 12 mm have been removed from the rubble-containing soil. The fact is that metal-containing parts are able to cause great damage to grinding mills and detectors and thus cause malfunctions during the production of cement. As a result of the reliable functioning of the method according to the invention, the risk of damage or malfunction is minimized.

Old rubble dumps can be used as a source of rubble-containing soil. Likewise, excavated soil containing remains of foundations can serve as a supply of rubble-containing soil. The rubble-containing soil comprises a variety of metals, such as Fe, Cu, Al, RVS, Zn, Pb, brass, etc., which originate from reinforcements in concrete building structures or old ducts, for example.

In a preferred embodiment of the method according to the invention, a screen device is used having at least one screen unit of the star screen type. The star screen has driven shafts which are provided with star-shaped screen bodies. It is typical of the fractions of rubble- containing soil supplied that the soil comprises many sticky masses, such as clay, in particular till more than 50 % sticky masses like said clay. As a result of the sticky masses, there is a considerable risk that a screen unit in the screen device will become blocked. Using star-shaped screen bodies with the method according to the invention prevents the screen unit from becoming blocked.

In a further advantageous embodiment according to the invention, at least one screen unit of the screen device employed comprises cleaning brushes. In particular with a fine screen unit, for example for sieving out fractions having a size up to at most 12 mm, the cleaning brushes can be used in order to prevent the screen unit from becoming blocked by sticky masses. As a result, the risk of a jam or another kind of malfunction is reduced and the reliability of the method according to the invention is increased further.

Preferably, the screen device for use with the method according to the invention comprises several screen units for splitting the fractions of rubble-containing soil into several discharge flows on the basis of size.

In one particular embodiment, the supplied fractions of rubble-containing soil are split into several discharge flows by the screen units, with fractions having a size up to at least 80 mm, but preferably at least 60 mm being sifted out in a first discharge flow. The fractions in the first discharge flow can be returned from the screen device to the crushing device. The

fractions of rubble-containing soil can be split further into several discharge flows, in particular at least a second, third and fourth discharge flow. Preferably, the smallest fractions, having a size of at most 20 mm, but preferably at most 12 mm, are discharged in the finest, for example the fourth discharge flow. The fractions in intermediate discharge flows, for example the second and third discharge flow are preferably subdivided in size between at least 12 mm and at most 60 mm, for example into fractions having a size which is between at least 12 mm and at most 35 mm, and at least 35 mm and at most 60 mm, respectively. By splitting the fractions of rubble-containing soil on the basis of size, the susceptibility to malfunction is reduced and the reliability of the method improved further.

In order to extract raw materials which can be re-used from the rubble-containing soil, it is important that with the method the metal-containing parts are removed from the discharge flow of fractions of rubble-containing soil in a reliable manner. To this end, in one particular embodiment, the method according to the invention comprises a step in which iron- containing fractions are removed from the crushing device, a screen feeder, the first discharge flow and/or the second discharge flow by means of a magnetic field. This is particularly advantageous because in a separating device for use with the method according to the invention, many iron-containing parts are thereby already separated at an early stage in the separating process in a simple manner. The iron-containing parts, such as reinforcing iron and ducts, as a result of their shape and toughness, could cause malfunctions in the grinding or screen device. By providing a magnetic field at several positions in the separating device, the iron-containing parts are removed at an early stage and the reliability of the separating process is increased.

Further preferred embodiments are defined in the other subclaims.

The invention will be explained in more detail with reference to the attached drawings, which show a practical embodiment of the invention, but should not be regarded as being limiting and in which:

Fig. 1 shows a diagrammatic top view of a separating device for carrying out the method according to the invention;

Fig. 2 shows a diagrammatic side view of a screen device in the separating device as shown in Fig. 1; and Fig. 3 shows a diagrammatic representation of a sensor separator in the separating device as shown in Fig. 1.

Fig. 1 shows a schematic top view of a separating device which is suitable for carrying out the method according to the invention. In the separating device, metal-containing parts are

removed from rubble-containing soil.

The rubble-containing soil is fed to a crushing device 10 from a dump by means of an excavator. The rubble-containing soil is often contaminated with various kinds of contaminations. In addition, the rubble-containing soil is often sticky and wet on account of the high loam content. The crushing device 10 has a bunker 11 for the supply of rubble- containing soil. At the bottom of the bunker 11 , contra-rotating crushing shafts 12 are provided having crushing and/or cutting bodies for crushing the rubble-containing soil into small fractions. The rubble-containing soil is pulled between the shafts and crushed and cut into small fractions. In addition, metal-containing parts are exposed through the crushing process, so that they can be removed in a relatively simple manner. The crushed fractions of rubble-containing soil are discharged from the crushing device via a discharge belt 13 and deposited on a screen feeder 25. The fractions of rubble-containing soil on the discharge belt 13 are exposed to a magnetic field. A permanent magnet 19 is arranged near the discharge belt 13 for removing iron-containing fractions.

The ground fractions of rubble-containing soil are fed to a screen device 20 comprising at least one screen unit 21 via the screen feeder 25. The screen feeder 25 is in this case designed as a conveyor belt. Above the screen feeder 25, an electromagnet 28 is positioned for removing iron-containing fractions. The screen feeder 25 opens into a bunker 26 of the screen device 20. In the bunker 26, a metering mechanism 27 is provided which contributes to a gradual supply of fractions of rubble-containing soil to the screen units 21 of the screen device 20. In the screen device,, the fractions are separated on the basis of fraction size. A first screen unit produces a first discharge flow 20.1. Preferably, the first screen unit 21 separates on the basis of a fraction size of at least 80 mm, but more preferably on the basis of a size of the fractions of at least 60 mm. The large fractions of rubble-containing soil in the first discharge flow 20.1 are returned to the crushing device 10.

The screen device 20 in this case furthermore has a second, a third and a fourth discharge flow 20.2, 20.3, 20.4 of fractions of rubble-containing soil. The fourth discharge flow 20.4 has a small fraction size preferably of up to at most 12 mm.

A magnetic separating unit 29.2, 29.3, 29.4 is positioned near each discharge flow in the screen device. The magnetic separating unit 29.2, 29.3, 29.4 comprises a high-gradient magnet, preferably a lanthanide magnet and more preferably a neodymium magnet. The magnet is placed in a reversing roller in a conveyor belt device in such a manner that iron- containing fractions follow a different path, separate from the other fractions, as they fall off the conveyor belt. Such an arrangement of a magnet in a reversing roller for separating purposes is also referred to as a top roll magnet. When the discharge flows have passed the

magnetic separators, the discharge flows are substantially free from iron-containing fractions.

The third discharge flow 20.3 comprises fractions of rubble-containing soil of at least 12 mm to at most 35 mm. The second discharge flow comprises fractions of rubble-containing soil of at least 35 mm up to at most 60 mm. The second and third discharge flow 20.2, 20.3 are fed to a sensor separator 30 together. The sensor separator 30 comprises a distributor 31 which is positioned upstream of a supply belt 32. The fractions of rubble-containing soil are distributed over the supply belt 32 by the distributor 31. Components of the distributor 31 which come into contact with the rubble-containing soil are provided with a PU coating. This coating advantageously prevents sticking of the fractions of rubble-containing soil to the parts of the distributor 31. Rubble-containing soil sticking to parts of the distributor 31 plays a part in particular with soil having a high loam content. A receptacle 34 is positioned at the end of the supply belt 32 of the sensor separator. The receptacle 34 is intended for holding metal- containing parts. Both iron-containing (in so far as they have not already been separated) and non-iron-containing parts are collected therein. Furthermore, the sensor separator 30 has a discharge flow 38 for the fractions of rubble-containing soil from which the metal- containing parts have substantially been removed.

In order to improve the reliability of the separating process further, the separating device for carrying out the method according to the invention has been extended, as illustrated in Fig. 1 , by the part of the separating device which falls within the frame formed by broken lines. The discharge flow 38 from the sensor separator 30 takes the fractions of rubble-containing soil to a metal detector 50. The metal detector 50 may be provided as a last checking stage in the separating device for carrying out the method according to the invention in order to improve the reliability of the separating process further. A magnetic separating unit 40 comprising a high-gradient magnet is placed upstream of the metal detector 50. In this case, the high-gradient magnet is a lanthanide magnet and preferably a neodymium magnet. The neodymium magnet is arranged inside a drum and has a high field strength of approximately 9500 Gauss, resulting in a high reliability in the separation of iron-containing parts. A vibratory feeder is arranged upstream of the magnetic separating unit, whose components which come into contact with the fractions of rubble-containing soil are provided with a PU coating, thus preventing the fractions from sticking. Due to the strong high-gradient magnet, it is possible to also separate stainless steel-containing fractions with the magnetic separating unit 40, since the stainless steel-containing fractions have become slightly magnetic by being ground in the crushing device 10. The iron- and stainless steel-containing fractions are discharged via a discharge belt 42. The remaining fractions of rubble-containing soil are passed through the metal detector 50. The metal detector 50 passes the fractions of rubble-containing soil on to a conveyor belt 51 as separating unit. The conveyor belt 51 , a so-called reversing belt, can be switched and move in two directions. The conveyor belt 51

usually carries away the fractions of rubble-containing soil further to a discharge belt 52, but when metal-containing parts are present, the direction of the conveyor belt 51 reverses and the fractions of rubble-containing soil are carried away to a collecting tray 54. The fractions of rubble-containing soil which are carried away over the discharge belt 52 have been cleared of metal-containing parts with a high degree of reliability and are suitable for being admixed as replacement raw material for limestone or marl in the production of cement.

Fig. 2 shows a screen device 20 suitable for use in the separating device for separating metal-containing parts from rubble-containing soil, as illustrated in Fig. 1. The screen device 20 comprises various screen units 21. In this case the screen units are of the star screen type. A screen unit 21 of the star screen type has shafts with star-shaped screen bodies. A star screen is particularly suitable as a screen unit for separating wet and sticky material, such as soil with a high clay content. The presence of the star-shaped bodies prevents the rubble-containing soil from sticking in the screen unit and thus the risk of blockages.

A plurality of screen units 21 are provided in the screen device for splitting the flow of fractions into several discharge flows on the basis of the size of the fractions.

The screen device 20 shown here is arranged so as to be mobile. On the bottom of the screen device 20, slides 22 are provided in order to make it possible to move the screen device in a simple manner. In an alternative embodiment, the mobile screen device 20 may be provided with wheels.

Furthermore, the screen device comprises a bunker 26 which is provided with a metering mechanism 27. The metering mechanism 27 comprises a distribution shaft having a threaded profile for the uniform supply of fractions of rubble-containing soil to the screen units 21.

In order to prevent the rubble-containing soil from sticking to the screen unit, the screen unit 21 may be provided with cleaning brushes. By means of the cleaning brushes, the relatively fine screen units in particular are prevented from becoming blocked. The screen unit 21 can be cleaned by regular brushing with the cleaning brushes, which is desirable, in particular with sticky soil.

Fig. 3 is a diagrammatic representation of a sensor separator 30 suitable for use in carrying out the method according to the invention. The sensor separator 30 is designed to handle a capacity of approximately 20 tons/hour. The sensor separator 30 comprises a supply belt 32 for supplying the fractions of rubble-containing soil. The fractions are supplied on the supply belt 32 via a distributor 31. The supply belt 32 has a length such that the fractions become

substantially stationary on the supply belt 32. The fractions are evenly distributed over the width of the supply belt 32 according to size in order to increase the reliability of the separating process. The fractions are exposed to an electromagnetic field 35. Using a sensor 36, which in this case is situated below the supply belt 32, it is possible to measure a disturbance in the electromagnetic field 35. When a metal-containing part is present in the electromagnetic field 35, such a disturbance will occur. Using the measured signal of the sensor, a blow nozzle 33 is activated via a processor 37 as soon as a metal-containing part passes the blow nozzle 33. Below the blow nozzle 33, a receptacle 34 is placed for the separate collection of metal-containing parts and other fractions. In this manner, the metal- containing part is separated from the other fractions of rubble-containing soil.

In addition to the embodiment of the method according to the invention shown, many variants are possible which are covered by the scope of protection as defined in the claims.

Thus, in an alternative embodiment of the method according to the invention, it is for example possible to lead the various discharge flows past one magnetic separator in the shape of an electromagnet.

It is also possible to arrange several crushing and/or screen devices or sensor separators in parallel in order to increase the capacity.

It is for example possible to use a mechanical structure as an alternative to the blow nozzles in the sensor separator, in which mechanical structure metal-containing parts are separated from the remaining fractions using a slide.

Thus, the method according to the invention is suitable for separating metal-containing parts from rubble-containing soil, resulting in alternative raw materials which can be used as additives for the production of cement. The rubble-containing soil can be cleaned in an efficient and reliable manner and used as replacement raw material for a part of the limestone and marl. Furthermore, the rubble-containing soil which has been cleaned of metal-containing parts by the method according to the invention can be used for other purposes, so that the rubble-containing soil does not have to be disposed of at a rubbish dump. This advantageously makes the method environmentally friendly and results in a cost saving.

Key

10 Crushing device 31 Distributor

11 Bunker 32 Supply belt

12 Crushing shafts 33 Blow nozzle

13 Discharge 34 Receptacle

19 Magnetic field 35 Electromagnetic field

20 Screen device 36 Sensor

20.1 First discharge flow 37 Processor

20.2 Second discharge flow 38 Discharge flow

20.3 Third discharge flow 40 Magnetic separating unit

20.4 Fourth discharge flow 41 Vibratory feeder

21 Screen unit 42 Discharge belt

25 Screen feeder ^v 50 Metal detector

26 Bunker 51 Conveyor belt

27 Metering mechanism 52 Discharge belt

28 Electromagnet 54 Collecting tray

29 Magnetic separating unit

30 Sensor separator