FR2696661A1 - Recycling procedure for demolition materials - includes subjecting to various riddling processes and densimetric grading to remove particles of wood and other light materials - Google Patents

Abstract

The procedure consists of sorting to remove non-stone materials, crushing and grading, and then storing separately the materials with different grain sizes.The different processes are carried out in a dry state, with the finest particles separated in a first riddling stage, after which at least a proportion of the remaining material is subjected to densimetric grading, using a current of air to remove wood and other lightweight materials before a second riddling stage. The densimetric grading is carried out by passing a continuous flow of the material over a vibrating table and then letting it fall through a current of air which is then passed through a dust extractor. The air can be re-used in a closed-circuit system.The procedure can be carried out in an installation which incorporates a first riddling post (13), a densimetric grading post (22) and a second riddling post (25), with a series of silos (15,17,27,29) for storing the materials of different granule sizes. USE/ADVANTAGE - Produces materials which can be used e.g. for road foundations or mixed with a stabiliser such as cement, gravel or bitumen for other purposes.

Description

PROCESS AND INSTALLATION FOR TREATING MATERIALS
DEMOLITION TO RECYCLE
The present invention relates to a process for treating demolition materials comprising stony materials with a view to recycling them in the form of reusable aggregates, in which a preliminary treatment phase is carried out in which non-stony materials and / or l are removed. 'the materials are crushed, then a sorting phase comprising at least two screening steps to divide the materials into different particle size components of aggregates which are stored separately.

The invention also relates to an installation for treating demolition materials to be recycled for the implementation of this process.

The materials from the demolition of buildings contain a majority of stony materials, which are reusable for various purposes depending on their nature and especially according to their content of impurities. The term stony materials means not only mineral or solid materials of natural origin, such as sand and gravel, stones, blocks, etc., but also derived materials such as cement, concrete, brick and glass. Reduced into aggregates classified into particle size components, these materials can be recomposed to be reused without transformation, for example in foundation layers of traffic lanes, or be stabilized by means of a binder in the form of cement concrete, a stabilized grave or bituminous mixes.

Such recycling encounters various technical or economic obstacles, mainly due to the fact that demolition materials contain, in addition to rubble and other stony materials, scrap metal, plaster, wood, earth, etc. . At present, installations capable of supplying recycled aggregates at a competitive price compared to natural aggregates generally only accept demolition products composed of unreinforced concrete, without wood or synthetic material (in particular insulating materials such as than expanded polystyrene). Consequently, a preliminary sorting and cleaning treatment is necessary and expensive. In addition, the removal of dust and other fine impurities (wood) is carried out by washing and decanting, which produces discharges of charged water in particular highly polluting heavy metals. Known dry-running installations give off a great deal of dust or include very expensive filters.

The subject of the present invention is a method and an installation making it possible to avoid the pollution problems mentioned above and to treat demolition materials at an acceptable cost, in order to draw therefrom reusable aggregates having a determined particle size.

For this purpose, the invention relates to a method of the type indicated above, characterized in that all the treatment is carried out dry, and in that, in the sorting phase, the finest particle size component is separated in a first screening step, then at least part of the rest of the materials are subjected to a densimetric sorting by an air stream to remove wood and / or other light materials before a second screening step.

In this way, the method according to the invention makes it possible to conserve, in the finest component of the aggregates produced, a high proportion of fine particles which are useful for future consumers and which would otherwise be eliminated by washing or by dedusting. prior. The importance of the fines content of the aggregates is well known for obtaining good compactness and / or good "workability" of the products obtained by recomposition of the various components of the aggregates. These fine particles may also contain particles of cement or other binders which are useful in the products to be manufactured. The process according to the invention is based in particular on the fact that impurities such as wood, rubber or of polystyrene do not pass through the finest screens, so that it is possible to extract them from the aggregates after having separated the fine fraction from them. Thus it is possible to separate said impurities by means of a densimetric table without at the same time removing large quantities of dust which should then be discarded.

Preferably, to carry out the densimetric sorting, a continuous flow of materials is spread out by means of a vibrating table and the said continuous flow is dropped through a stream of air which then passes through a dust collector. Said air stream is preferably in a closed circuit.

For the implementation of the process defined above, the invention provides a treatment installation comprising means of preliminary treatment, means of particle size sorting of materials, means of storing sorted materials, and means of taking up materials. stored, the installation being characterized in that the sorting means successively comprise a first screening station, a densimetric sorting station and a second screening station, in that the first screening station is arranged to separate one or more components constituting the fine fraction of the materials and to deliver the rejection of the screening at the densimetric sorting station, and in that the densimetric sorting station comprises a light material receiving bin, a heavy material receiving bin to be delivered to the second screening, a dust collector and means for passing a current of air above said tanks, then through the dust collector.

In an advantageous embodiment, the preliminary treatment means comprise a crusher, a metal extraction station, a preliminary screen and a conveyor loop arranged for transporting materials from the crusher to the metal extraction station and the latter. to the preliminary screen and to send back to the crusher materials retained by the preliminary screen. Said conveyor loop may include at least two inlets for the materials, respectively to the crusher and to the metal extraction station.

In an installation according to the invention, said fine fraction of the materials preferably comprises a particle size component from 0 to 5 mm. It can also include a particle size component of 5 to 20 mm.

Preferably, the densimetric sorting station comprises a vibrating table arranged to spread the materials and discharge them in a substantially continuous sheet above a separating wall, in a stream of air substantially perpendicular to said wall, so that the materials fall respectively on one side and on the other side of the separating wall in said receiving bins. The separating wall can be adjustable in position in the direction of the air flow.

In a preferred form of the installation, the storage means comprise at least four silos each receiving a particle size component, and the recovery means comprise metering devices, associated with the silos for taking therefrom predetermined quantities of each component, and a device mixer for mixing said quantities withdrawn.

Other characteristics and advantages of the present invention will appear in the following description of an exemplary embodiment, with reference to the accompanying drawings, in which - Figure 1 is a schematic plan view of an installation according to the invention, for recycle demolition materials into four particle size components capable of being recomposed to provide a reusable mixture having the desired particle size, and - Figure 2 is a schematic elevational view partially cut away of a densimetric sorting station forming part of the installation illustrated in figure 1.

The installation shown in FIG. 1 comprises an inlet hopper 1 into which demolition materials are discharged by vehicles from an access ramp 2. The raw materials are delivered to a crusher 3 after having passed on a prior screening device of a known type, making it possible to eliminate fine waste such as soil, in order to evacuate it by a conveyor 4 to a waste rock depot 5. These waste rock can have, for example, a particle size of 0- 8 mm. The crusher 3 can be an impact crusher, capable of receiving blocks up to 1 m3 and reducing them to a caliber less than 60 mm. The materials thus crushed in a granulometric spindle of 0-60 mm are evacuated by a conveyor 6 to a scrap extraction station 7, where all the steel waste is extracted by means of a magnet. the largest pieces or steel bars likely to be in the materials will have been removed before passing through the crusher.

At station 7, additional manual sorting can also be provided to remove non-magnetic metals or other materials. A conveyor 9 allows materials of grain size 0-X which may be less than or greater than 60 mm to be diverted to a stock 8, which do not need to be cleaned (for example concrete alone). At the exit from station 7, another conveyor 10 takes the materials to a preliminary screen, integrated into a first screening station 13.

Said preliminary screen retains the elements of a caliber greater than 60 mm to return them to the crusher 3 by a return conveyor 12. In this way, the elements 3, 6, 7, 10, 12 and 13 of the installation constitute a preliminary treatment loop, at the outlet of which there are dry materials having a particle size of 0-60 mm and composed of stony materials and various impurities, such as fragments of wood, plaster, synthetic materials, etc.

The screening station 13 is of traditional construction, with a 20 mm screen and a 5 mm screen. The 0-5 mm particle size component is removed by a conveyor 14 to a silo 15, while the 5-20 mm particle size component is removed by a conveyor 16 to a silo 17. As mentioned above, the fragments of lightweight materials such as wood, rubber, expanded polystyrene and other synthetic materials hardly pass through the 5 mm screen. On the other hand, we find a little of this waste in the 5-20 mm component. It is possible to remove them by means of a vacuum cleaner 18 placed on the conveyor 16.

The reject materials from the first screening station 13 are transferred by a conveyor 21 to a densimetric sorting station 22, where the rest of the light materials are separated to put them in a waste depot 23. Station 22 will be described in detail below with reference to FIG. 2. It essentially results in stony materials with a particle size 20-60, which are transferred by a conveyor 24 to a second screening station 25 provided with a 40 mm screen. From there, the 20-40 mm component is evacuated by a conveyor 26 to a silo 27, and the 40-60 mm component is evacuated by a conveyor 28 to a silo 29. We thus have, in silos 15, 17, 27 and 29, of four components of essentially stony materials, reusable in different types of construction. The four silos are aligned above a recomposition line comprising a weight metering device 30 at the exit of each silo, a belt conveyor 31 passing under the metering units 30 and a mixer 32 which feeds a loading station 33. In this way, it is possible to provide customers with different particle size mixtures suitable for different uses and usable in place of natural materials.

In the densimetric sorting station represented in FIG. 2, the generally continuous flow of the raw materials of caliber 20-60 mm is discharged as indicated by arrow A, on a vibrating table 34 slightly inclined, having the effect of spreading the materials and advancing them to pour them into a thin sheet, indicated by arrow B, in a densimetric sorting chamber 35 traversed by a current of air indicated by arrows C and delivered by a nozzle 36 supplied by a blower 37 In chamber 35, the heaviest materials and in particular stony materials fall directly into an outlet hopper 38 to be evacuated according to arrow D by the conveyor 24 (FIG. 1). On the other hand, lighter materials such as waste wood, plaster, insulating materials, etc., are deflected by the air flow C according to arrow E and fall to the bottom of another hopper 39, from which they are extracted by u n rotary valve 41 to be evacuated to the depot 23 (Figure 1). In the chamber 35, between the two hoppers 38 and 39, a separating wall 42 is provided, the position of which can be adjusted on a lower hinge 43 in order to adapt the densimetric sorting to the quality of the materials treated. Furthermore, the speed and the flow rate of the air stream C can be adjusted by means of an adjustment valve 44 at the inlet of the blower 37.

The air stream C, loaded with dust at the outlet of the sorting chamber 35, is recycled as schematically indicated by arrow F, in a dedusting cyclone 45, the outlet 46 of which is connected to the inlet of the blower 37. At the bottom of cyclone 45, the collected dust is extracted by means of a rotary valve 47 to be deposited or recycled in the installation. In general, the volume of this dust is low, since the fine fraction of the raw materials has been previously separated in the first screening station 13. On the other hand, as the air stream C is in a closed circuit, dusting does not need to be very thorough and can therefore be done by means of simple cyclone 45.

The present invention is not limited to the embodiment described above, but it extends to any modification or variant obvious to a person skilled in the art. In particular, it is not limited to sorting into four components, this number being able to be lower or higher depending on the case, provided that the finest component is separated by screening before the densimetric sorting.

Claims (10)

Claims 1. Process for the treatment of demolition materials comprising stony materials with a view to recycling them in the form of reusable aggregates, in which a preliminary treatment phase is carried out in which non-stony materials are removed and / or crushed the materials, then a sorting phase comprising at least two screening steps to divide the materials into different particle size components of aggregates which are stored separately, characterized in that all the treatment is carried out dry, and in that, in in the sorting phase, the finest particle size component is separated in a first screening step, then at least part of the rest of the materials are subjected to densimetric sorting by a stream of air to remove wood and / or d 'other light materials before a second screening step. 2. Method according to claim 1, characterized in that to carry out the densimetric sorting, a continuous flow of materials is spread out by means of a vibrating table and this continuous flow is dropped through a stream of air which then passes through a dust collector. 3. Method according to claim 2, characterized in that said air stream is in a closed circuit. 4. Installation for processing demolition materials to be recycled, for the implementation of the method according to claim 1, comprising means for preliminary treatment, means for grading material by size, means for storing sorted materials, and means recovery of stored materials, characterized in that the sorting means successively comprise a first screening station (13), a densimetric sorting station (22) and a second screening station (25), in that the first screening station screening (13) is arranged to separate one or more components constituting the fine fraction of the materials and to deliver the refusal of screening at the densimetric sorting station, and in that the densimetric sorting station (22) comprises a material receiving tank light (39), a container for receiving heavy materials (38) to be delivered to the second screening station, a dust collector (45) and means (36, 37) for passing a current of air above said tanks, then through the dust collector. 5. Installation according to claim 4, characterized in that the preliminary treatment means comprise a crusher (3), a metal extraction station (7), a preliminary screen (13) and a conveyor loop (6, 10 , 12) arranged to transport materials from the crusher to the metal extraction station and from the latter to the preliminary screen and to return to the crusher materials retained by the preliminary screen. 6. Installation according to claim 4, characterized in that said fine fraction of the materials comprises a particle size component from 0 to 5 mm. 7. Installation according to claim 6, characterized in that said fine fraction of the materials further comprises a particle size component of 5 to 20 mm. 8. Installation according to claim 4, characterized in that the densimetric sorting station (22) comprises a vibrating table (34) arranged to spread the materials and pour them into a substantially continuous sheet above a separating wall (42 ), in a stream of air substantially perpendicular to said wall, so that the materials fall respectively on one side and on the other side of the separating wall in said receiving tanks (38, 39). 9. Installation according to claim 8, characterized in that the separating wall (42) is adjustable in position in the direction of the air flow. 10. Installation according to one of the preceding claims, characterized in that the storage means comprise at least four silos (15, 17, 27, 29) each receiving a particle size component, and in that the recovery means comprise devices dosers (30), associated with the silos for withdrawing predetermined quantities from each component, and a mixing device (32) for mixing said withdrawn quantities.