EP1009533B1 - Method and plan for disintegrating crude material in lumps into granular material according to a particle size distribution - Google Patents

Description

The present invention relates to a method and an installation, especially with continuous operation, to reduce a raw material into pieces and obtain a grain material with a required particle size distribution as well that an application of the mixture of granular material obtained by setting work of such a process.

In the area of fragmentation, we are often led to produce, from a material in pieces, grains whose staging of dimensions respect a predetermined particle size distribution or zone in particular to allow the subsequent implementation of this material by various means of compacting by vibration, compacting or pressing, minimize the addition of any binder required during this implementation, and / or optimize the physical characteristics of the workpiece after forming according to criteria also predetermined.

A characteristic generally prevailing in the definition of this granulometric zone is the aptitude of fine grains to fill the most exactly possible the intergranular spaces of the size grains superior, this characteristic contributing to an optimization of the compactness of the workpiece, to a reduction in the consumption of any binder to fill the gaps, as well as better performance in terms of mechanical resistance and / or electrical or thermal conductivity.

Another feature often sought after for fractions coarse of this size range is to present resistance optimal for compression, so as not to be degraded during subsequent work and to reinforce the mechanical characteristics of the part worked after forming.

Currently, we do not control the characteristics of raw materials used and we do not control the particle size distribution grains directly from the fragmentation operations.

To obtain a dimensional distribution of the grains respecting the required size zone, it therefore appears essential to break down the particle size preparation process into two stages.

The first step is to divide the material into several grain size fractions using classification devices, to reduce possible surpluses of certain fractions by means of crushing or grinding, to recirculate the fragmented products on the classification apparatus, and for storing the various fractions thus produced in silos or hoppers buffers according to their granulometry.

The second step then consists in reconstituting a mixture different particle size fractions produced in the first step, in order to satisfy the required size zone, thanks to an extraction controlled materials under each silo by means of volumetric and / or weight dosing.

Although we know of installations using only a single fragmentation device for the simultaneous production of the different fractions, all of these operations, and more particularly the classification and mixing, require numerous and bulky equipment, especially when you want to limit the excess of non-reusable materials. In addition, they operate in a closed circuit and involve a recirculation of materials. They are therefore complex and costly.

Such installations are described in document WO-A-97 / 35.665 with a crusher operating by crushing in a layer of material. It should however be noted that this document was not public at the date of filing of the current.

It is also known from document US-A-5,375,779 a size reduction installation comprising a single mill whose products can possibly be directly used. However, it is a grinder whose operation is essentially monogranular. This installation is therefore dedicated to obtaining a material with terminals lower and upper grain sizes given, excluding the presence of fine and coarse pieces. In addition, the mechanical characteristics of the material obtained at the outlet of the mill does not present any particular interest.

The object of the invention is to propose a method and a installation for particle size reduction of a raw material into pieces in one grain material which overcomes the aforementioned drawbacks and allows the direct, especially continuous, production of a particle size distribution required without recirculation, without classification or remixing of all or part fragmented products.

Another object of the present invention is to provide a process and installation for particle size reduction of a raw material into pieces which allow direct use of the grain material obtained without having to modify its particle size distribution again according to the desired application.

Another object of the present invention is to provide a application of the mixture of grain material obtained allowing the manufacture objects having advantageous physical properties.

Other objects and advantages of the present invention will appear during the description which follows which is given only as indicative and which is not intended to limit it.

The present invention relates first of all to a method of particle size reduction of a raw material into pieces according to claim 1.

The process which is the subject of the invention uses a raw starting product whose pieces have, for example, dimensions less than or equal to 200 mm.

It has been found that the choice of crushing by crushing in material layer allows to select the parameters of the operation of grinding so that the grain product obtained satisfies the spindle particle size required from pieces of any size, and this in open circuit.

The expression crushing by crushing in a layer of material designates the grinding processes according to which a multigranular layer of product to be ground is compressed between two surfaces with pressure sufficient to cause fragmentation of grains which are reduced to grains smaller.

During the crushing process in layer crushing matter, the compressive force exerted is transmitted within the layer of grain to grain material through grain contact zones.

At the start of this process, the coarse grain size of the matter makes the intergranular spaces generally large, and that the contact surfaces between grains are limited, which generates a significant pressure and causes the most fragile grains to burst. The grains of smaller size thus generated then rearrange themselves in the spaces vacant intergranulars, gradually increasing contact surfaces between grains, and simultaneously reducing the local pressure in the areas of contact.

The process therefore contributes to reducing the volume intergranular voids by correlatively increasing the compactness of the layer of material, until the multiplication of the points of contact between grains lowers local pressures below the rupture threshold by overwriting of these.

It is thus observed that the active parts of the mill for the reduction may have little contact with the material. In effect, it grinds by itself under the effect of the pressure transmitted between the grains. It is therefore possible to treat abrasive materials by limiting the wear of the parts used.

Thanks to such a technique, it is also possible to obtain a relatively wide size range, for example 0-30 mm or more.

Such methods make it possible to obtain a distribution grain size which is substantially independent of the size initial of the songs used. To vary said distribution and / or to adapt it to the raw material used, it will suffice to play on the parameters adjusting the grinding such as, for example, the fragmentation force and / or the applied pressure.

The latter will depend, in particular, on the pressure of subsequent use of the material and will be greater than or at least equal to it to avoid grain deterioration in this step.

Apparatus known for the implementation of grinding by crushing in a layer of material are, for example, grinding mills, vertical ball or roller mills, ring mills, presses with cylinders and vibrating cone crushers.

It could be, in particular, a vertical cone crusher vibrating, i.e. a grinder in which the cone or the tank is placed vibration, the other element, tank or cone, of the mill being fixed or mobile. Various examples using some of these mills are developed in the after.

On this subject, the present invention also relates to a installation according to claim 2.

As mentioned above, thanks to the operating principle crushers in a layer of material, it has been found that the grain material obtained has particle size distributions directly usable, as determined, and the installation according to the invention therefore does not require a product recirculation or division device fragmented.

The installation according to the invention thus comprises, advantageously a single crusher by crushing in a layer of material. However, other preliminary operations, notably crushing could also be considered, using other devices provided for in upstream.

If the required size zone requires the presence of grains larger than the maximum grain size produced by the fragmentation device used, the installation could be possibly supplemented, upstream of the latter, with a classification which will generally be a screen and / or a grid, allowing to select different fractions of the raw material and, in particular, take from its pieces one or more large fractions missing in the material in grains. These large fractions will then avoid, thanks to a bypass, in all or part of the grinder.

Advantageously, these large fractions will consist of grains with dimensions greater than or equal to one millimeter.

The present invention advantageously relates to a application of the mixture of grain material obtained by the implementation of the process described above during manufacture, after compacting, pressing and / or compaction by vibration of said mixture, of objects having properties optimized mechanics.

Indeed, especially in the event of crushing by crushing layer of material, the break points between grains during fragmentation may be different depending on the nature and cohesion of the latter, it appears a selective fragmentation primarily affecting the grains fragile. Thus, the large grains of the fragmented product are preferably from the hardest constituents of the raw product.

In addition, as previously mentioned, the distribution particle size of the ground product has a satisfactory compactness, the vacant intergranular spaces being filled during treatment.

Thanks to such processes, and thanks to this choice, we therefore have, at the outlet of the mill and before any additional treatment, of a product already having advantageous mechanical characteristics.

They can thus be used, in particular, for manufacturing anodes for example, for the production of aluminum by electrolysis. Of such anodes are produced, in particular, by grinding coke.

• la figure 1 décrit un premier exemple de réalisation du procédé conforme à l'invention,
• la figure 2 décrit un second exemple de réalisation du procédé conforme à l'invention,
• la figure 3 décrit un troisième exemple de réalisation du procédé conforme à l'invention,
• la figure 4 décrit un quatrième exemple de réalisation du procédé conforme à l'invention.

The present invention will be better understood on reading the following description, accompanied by the appended drawings which form an integral part thereof and among which:

• FIG. 1 describes a first embodiment of the method according to the invention,
• FIG. 2 describes a second embodiment of the method according to the invention,
• FIG. 3 describes a third embodiment of the method according to the invention,
• Figure 4 describes a fourth embodiment of the method according to the invention.

According to the embodiment shown in FIG. 1, the installation according to the invention consists, for example, of a system feed of raw material 1, a grinder 2 and a system of storage 3 and truck loading 5.

The crusher 2 is, for example, a vibrating cone crusher of the type described in documents FR-2.702.970 and FR-2.735.402 in the name of applicant.

The truck storage and loading system can also be replaced by any other system such as a heaping device on the ground, bagging or other.

Furthermore, the crusher 2 can also directly feed a downstream device ensuring possible mixing with a binder and / or setting work of the mixture.

For some applications, the installation can be designed mobile, trailer or self-propelled, for example by assembly on a road or rail chassis.

Such an installation can be used, in particular for the production of road material with grain size which can be 0-30 mm.

As shown in Figures 2 to 4, according to a variant of realization, the gross product is previously divided into different fractions particle size, so that, as previously mentioned, some of the the coarsest fractions avoid, thanks to a bypass, in whole or in part the grinding stage and are mixed with the ground material in order to complete the coarse grain content necessary to satisfy the distribution particle size required.

More specifically, the installation, the diagram of which is shown in Figure 2 can be considered for example for the manufacture of certain hydraulic concrete.

Such an installation comprises, between the supply system 1 and the crusher 2, in particular, a screen 4 with two fabrics or grids which go allow to puncture two coarse fractions G1 and G2 in the material brute. These coarse fractions can be for example a 5-20 mm and a 20-40 mm respectively. They are stored in silos or hoppers 6 and 7.

An overflow device on one or more of its silos or hoppers 6 and 7, followed by a conveyor 8, for example with a belt, make it possible to return the excess of its fractions to the inlet of the mill 2 with the material gross M passing to the last mesh of the screen.

The mill 2 is here, for example, a ring mill of the type described in documents FR-90 / 14.004 and FR-2,679,792.

The fragmented material F, in particular in 0-10 mm, is taken up by a handling system 3, such as a bucket elevator, to be stored in a silo 5.

An extraction and metering system 9, constituted here for the example of a vibrating extractor, under each silo or hopper 5-7, allows to control the flow of fragmented products extracted, and that of additions correspondents of the two coarse fractions to complete the product fragmented to meet the required size range.

According to the variant illustrated in FIG. 3, the mixture of grains obtained after grinding can also be applied, in particular, to the preparation coke for the manufacture of anodes used in the production of aluminum by electrolysis.

In addition to using a bucket elevator 10 instead of a belt conveyor for feeding the raw material, it does not differ from the diagram in Figure 2 only by returning the entire most fraction coarse G2 at the entrance of the shredder 2 with removal of the corresponding silo and by the use of a vibrating cone crusher described above with reference to the figure 1.

Furthermore, the metering system 9 shown under the silos 5 and 6 is by weight, of the weight loss type, as commonly used in conventional installations.

For this application, the typical particle size of the various flows of material are of the order of 0-30 mm for raw coke, 15-30 mm for the fraction G2, 5-15 mm for fraction G1 and 0-15 mm containing a small quantity greater than 5 mm for the fragmented material F.

Figure 4 illustrates a simplified alternative of the example previous based on a simple volumetric assay of the fractions F and G1, when the precision of the weight system is not required.

In this case, the intermediate silo storage is no longer necessary and the volumetric flow rate of the G1 fraction is regulated as a proportion of the total flow measured on the rocker 11 of the recovery conveyor 12, by acting on the extraction system of the overflow dispenser 13.

The latter can be, as shown, a dispenser by variable frequency vibrating extractor.

The operating parameters of the shredder 2 are then regulated to ensure online control of the total flow on scale 11.

Naturally, the installations described above are not given as a non-limiting example. Other modes of implementation and / or other applications within the reach of ordinary skill in the art could have been envisaged without departing from the present invention.

Claims (6)

1. A method for granulometric reduction of a raw material in lumps wherein:

   the material in lumps, in whole or in part, is crushed into a layer of material, in order to obtain, upon completion of the operation, a grain material, with required size grain distribution, exhibiting high compactness and/or pressure mechanical strength, starting from any granulometry of said material in lumps,

   said grain material is directed downstream exclusively towards a common container, regardless of the size of the grains, in order to obtain, in a single pass, inside said container, a mixture of grain material, exhibiting said size grain distribution, for usage as such,

   the raw product is divided beforehand into different granulometric fractions, so that some of the roughest fractions avoid, thanks to a by-pass, the crushing stage in whole or in part, and are mixed with the crushed imaterial in order to top up the necessary contents of rough grains to meet the required size grain distribution.
2. An installation for the implementation of the method according to claim 1 for granulometric reduction of a raw material in lumps comprising at least:

   means (2) to crush said material in lumps, in whole or in part, in order to obtain, upon completion of the operation, a grain material, with required size grain distribution, exhibiting high compactness and/or pressure mechanical strength, starting from any granulometry of said material in lumps, whereas said means (2) intended for crushing said material in lumps are composed of a fragmentation device to crush said material into a layer of material,

   means (3) for directing said grains downstream exclusively towards a container (5) regardless of the size of the grains,

   a classification device (4), capable of selecting different fractions of the raw product, and means to withdraw among these different fractions of the raw product, one or several rough fractions and to top up said size grain distribution with said rough fraction(s) by causing said fractions to avoid, thanks to a by-pass, said means (2) in order to crush said raw material, in whole or in part.
3. An installation according to claim 2, wherein said classification device (4) is a screen.
4. An installation according to claim 2, wherein said classification device (4) is a grid.
5. An installation according to claim 2, foreseen mobile by assembly on a road or railway frame.
6. An application of the mixture of the grain material obtained by the implementation of the method according to claim 1, to the manufacture, after compacting, pressing and/or vibration settling of said mixture, of objects exhibiting optimised mechanical properties.

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