EP1072370B1 - Method and apparatus for treating material comprising in majority wet clay, in particular excavated earth of embankments - Google Patents

Abstract

An even layer (10) of material (6) is carried on a flat conveyor (2) to a treatment chamber (11), where at least one additive (23) is added evenly either before it enters the chamber or in the chamber itself. The material and additive are mixed and crushed by a rotor (15) with blades (17) turning in the opposite direction to that (F) of the conveyor. The treated material (26) is recovered

Description

The present invention relates to the field of materials clay with the presence of pebbles, especially spoil from earthwork. It relates more particularly to a method of treatment intended to mix a material of this type with one or several additives and it also concerns an installation specially designed for the implementation of said method, known from document EP-A-0 560 222.

All earthworks generate spoil which must either be reused or stored on site or disposed of for be stored or reused elsewhere. These spoils are from different composition depending on the location where the earthwork. Depending on the location and the depth of the earthworks, cuttings may contain a very large percentage of clay humid, even very humid depending on the proximity of the water table. We know that it may be preferable when reusing such spoil. earthmoving, add a powder-like adjuvant or binder, in particular so as to decrease the humidity. This addition adjuvant and mixing it with the cuttings in place is done on site proper with the help of equipment, for example a shaft mixer horizontal, which mixes the clay material and the additives previously distributed on the ground in the form of strips of a given width.

We understand that it is under these conditions very difficult to obtain a mixture which is perfectly homogeneous and controlled, especially due to the imprecision during the formation of the deposit of adjuvant, leading either to a superposition of the bands and therefore an excess of adjuvant either at a spacing between the strips and therefore a lack of adjuvant.

In addition, you must necessarily have the equipment on site adequate mixer and a suitable ground for its operation in good conditions.

In addition, processing on the site requires conditions acceptable climatic conditions. Rainy weather is unacceptable and causes the site to stop with its negative repercussions in terms financial and deadlines.

The goal set by the applicant is to propose a process which overcomes the drawbacks of current techniques with regard to concerns the re-use of earthmoving cuttings. This process is not however not limited to excavation but can see its applications to any material which mainly contains wet clay which we want to mix with at least one adjuvant.

This object is perfectly achieved by the method of the invention which concerns the treatment of a material mainly containing wet clay, especially earthmoving cuttings.

a) déposer une couche de hauteur sensiblement uniforme dudit matériau sur un élément d'entraínement, en déplacement dans une direction longitudinale donnée, qui forme au moins sur une portion donnée une surface plane et rigide ;

b) à introduire la couche ainsi formée dans une enceinte de traitement disposée au-dessus de l'élément d'entraínement,

c) à ajouter au matériau au moins un adjuvant en quantité déterminée et sensiblement également réparti transversalement soit sur la couche avant son introduction dans l'enceinte soit dans l'enceinte elle-même,

d) à soumettre, dans l'enceinte, le matériau et l'adjuvant à un traitement de mélange et de broyage par l'action d'un rotor à pales d'axe transversal, dont les pales tournant à contresens par rapport à la direction donnée affleurent sensiblement la surface de l'élément d'entraínement, au niveau de ladite portion qui forme une surface plane et rigide,

e) à récupérer, en sortie de l'enceinte, le mélange du matériau et de l'adjuvant.

Said method consists in:

a) depositing a layer of substantially uniform height of said material on a drive element, moving in a given longitudinal direction, which forms at least on a given portion a flat and rigid surface;

b) to introduce the layer thus formed into a treatment enclosure disposed above the drive element,

c) adding at least one adjuvant to the material in a determined quantity and substantially equally distributed transversely either on the layer before its introduction into the enclosure or in the enclosure itself,

d) subjecting, in the enclosure, the material and the adjuvant to a mixing and grinding treatment by the action of a rotor with blades of transverse axis, the blades of which rotate in opposite direction to the direction given substantially flush with the surface of the drive element, at the level of said portion which forms a flat and rigid surface,

e) recovering, at the outlet of the enclosure, the mixture of the material and the adjuvant.

It is the merit of the Applicant that to have put in evidence that the use of a plane and rigid drive element in the area of action of a rotor placed in an enclosure not only provides a homogeneous mixture of material mainly containing clay and adjuvant (s) but having also a particle size suitable for its subsequent use. In effect, the treatment and in particular the mixing of a material containing mainly wet clay poses technical problems specific to the texture of the material.

Thus, in the case of document US 4 125 332 which describes a process of mixing sand and bentonite, the sand being majority proportion, the specific mixing problems that arise proposes to solve the present invention does not arise. Indeed, materials mainly containing wet clay have a high density due in particular to their water content and have tendency to agglomerate and harden under the kneading effect of conventional mixing means such as rotors which makes it difficult mixing them with an adjuvant and grinding them.

In particular, in the case of the installation described in the above document, it would not be possible due to the use of a conveyor belt as a conveyor for mixing and grinding a material mainly containing wet clay. Indeed, a such material compacts in the hollow formed by the treadmill and it then it would not be possible either to mix it with an adjuvant or to mix it grind, in particular using a rotor placed above the carpet rolling.

Preferably, the addition of the adjuvant is carried out using a dispenser in an amount which depends on the height of the layer material and the frame rate of the element drive.

The choice and percentage of adjuvant is determined in depending on the end use which is envisaged for the product obtained. The same applies to the conditions of use of the rotor blades. whose action aims not only to achieve a homogeneous mixture of material and the adjuvant but also to refine the particle size of the material.

These are earthworks cuttings intended for backfill, the adjuvant used is in particular lime and the conditions for implementing the rotor are such that allow to obtain a treated material having a particle size maximum of 50mm.

For earthworks for form layer for roads, the conditions of implementation of the rotor are such that they make it possible to obtain a treated material having a maximum particle size of 30mm.

In a specific embodiment, the height of the layer formed on the drive element was of the order of 10 to 50 cm, the amount of adjuvant added to the layer before entering the enclosure was of the order of 0.1 to 5% by weight relative to the material, the rotor rotation speed was between 160 and 200 rpm with element moving speed between 200 and 1000 meters / hour.

In a particular variant of implementation of the method of the invention, water is added, preferably by spraying, before and / or after and / or when submitting, in the enclosure, the material and the adjuvant to a mixing and grinding treatment by the action of a rotor.

It is another object of the invention to propose a treatment plant specially designed for processing of the above process.

a) un élément d'entraínement équipé de moyens de déplacement dans une direction longitudinale, au moins une portion donnée de cet élément formant une surface plane et rigide,

b) une trémie apte à réaliser le stockage du matériau et son dépôt sur l'élément d'entraínement sous la forme d'une couche de hauteur sensiblement uniforme,

c) une enceinte disposée au-dessus de l'élément d'entraínement avec une ouverture d'entrée et une ouverture de sortie pour le passage sensiblement ajusté de la couche de matériau,

d) des moyens d'apport uniforme d'au moins un adjuvant,

e) un rotor à pales, d'axe transversal, monté à l'intérieur de l'enceinte, équipé de moyens d'entraínement en rotation à contresens de la direction de déplacement de l'élément plan et dont les pales affleurent sensiblement la surface de l'élément d'entraínement lors de leur rotation au niveau de la portion donnée formant une surface plane et rigide et

f) des moyens de récupération disposés au niveau de ou sous l'élément plan en aval de l'enceinte.

This material processing installation includes:

a) a drive element equipped with means for moving in a longitudinal direction, at least a given portion of this element forming a flat and rigid surface,

b) a hopper capable of storing the material and depositing it on the drive element in the form of a layer of substantially uniform height,

c) an enclosure arranged above the drive element with an inlet opening and an outlet opening for the substantially adjusted passage of the layer of material,

d) means of uniform supply of at least one adjuvant,

e) a rotor with blades, of transverse axis, mounted inside the enclosure, equipped with means for driving in rotation against the direction of movement of the planar element and the blades of which are substantially flush with the surface of the drive element during their rotation at the given portion forming a flat and rigid surface and

f) recovery means arranged at or under the planar element downstream of the enclosure.

In a preferred embodiment, the planar element drive consists of a tile chain, particularly effective in the case where the material to be treated consists of spoil from earthmoving with a high proportion of wet clay, having tendency to form compact and sticky blocks. The current invention is however not limited to the use of such a chain with tiles; it indeed possible, in the context of the present invention to use any other type of flat and rigid conveyor element or comprising a flat and rigid area such as for example a floor vibrating or a floor comprising a scraper ensuring the advancement load; in the latter case, the method of the invention is used implemented discontinuously.

The means of adding the adjuvant are, in a variant of embodiment, consisting of a metering device arranged transversely above of the element training plan, before the entry opening of the enclosure and able to distribute the adjuvant in the form of a layer of substantially uniform determined height.

According to a second alternative embodiment, the means of additive are constituted by a dispenser able to dispense the adjuvant inside the enclosure by a hole made nearby of the entrance opening thereof.

• la figure 1 est une représentation très schématique en coupe longitudinale de ladite installation ;
• la figure 2 représente plus particulièrement et de manière schématique le rotor utilisé dans ce mode de réalisation préféré ; et
• la figure 3 représente plus en détails la chaíne à tuiles utilisée dans le mode de réalisation préféré de la présente invention.

The present invention will be better understood on reading the description which will be given of a preferred embodiment of an installation for processing earthmoving cuttings, illustrated by the appended drawings in which:

• Figure 1 is a very schematic representation in longitudinal section of said installation;
• Figure 2 shows more particularly and schematically the rotor used in this preferred embodiment; and
• Figure 3 shows in more detail the tile chain used in the preferred embodiment of the present invention.

Earthworks cuttings can contain up to 80% wet or even very wet clay in the case where the water table is close to the ground where earthworks are carried out. The objective of the present invention is to create a site for treatment to which the materials from the earthworks to be stored in a building for drying natural then treated. The material thus treated is then stored for sale or delivered directly to the site by boat or truck. The treatment must allow to obtain that the material from earthworks either homogeneously mixed with one or several adjuvants, and has a given maximum particle size. The choice and proportion of adjuvant as well as its maximum particle size are determined by the processing conditions based on the intended use, for example taking into account the parameters provided for in the technical guide entitled "Realization of embankments and form layers "referenced D 9233-1 in the LCPC publications (Central Laboratory of Bridges and Roads).

A first outlet for the treated materials can consist in their use for embankments or for form layers for road. In this case, it can be silt or clay treated with as an additive to lime and / or hydraulic binders.

Another outlet may consist in the use of treated materials, in a substantially impermeable layer, for technical landfill centers. In this case, we use as bentonite adjuvant.

Figure 1 attached includes as a drive element comprising at least a given portion forming a flat surface and rigid, a tile chain 2, which is stretched between two wheels 3 and 3 ', a idler 3' upstream and a gear 3 downstream which is driven to move in the direction of arrow F by means not shown.

In the upstream part of the upper strand 4 of the chain 2 is disposed a hopper 5 for storage and supply of a material 6. The lateral uprights 7 of the hopper 5 come almost into contact with the upper strand 4 of the chain 2 with the exception of the amount 7 a , most downstream relative to the direction F of movement of the chain 2, the lower edge 8 is at a distance h from the upper strand 4 of the chain 2, which distance h is adjustable manually or automatically. The free space between the lower edge 8 of said lateral upright 7 a and the strand 4 constitutes the feed orifice 9 of the hopper 5, which allows the constitution of a substantially uniform layer 10 of the material 6 during the movement of the chain 2.

Towards the downstream part of the upper strand 4 of the chain 2 is provided a treatment enclosure 11. This enclosure 11 is disposed above the upper strand 4. It is closed by a cover 12 which has an inlet opening 13 and a outlet opening 14. Inside the enclosure 11 is mounted a rotor 15, rotating about an axis of rotation 16 mounted parallel to the tiles forming the upper strand 4 of the chain 2 and transverse to the direction of displacement F. The periphery of this rotor 15 is equipped with blades 17, mounted radially. The height of each blade 17 is determined so that the end edge 17 a of a given blade comes substantially flush with the upper strand 4 of the chain 2 during its rotation. The direction of drive of the rotor 15 is produced in the direction of the arrow G, which is in the opposite direction relative to the longitudinal direction F of movement of the chain 2.

In the particular case shown here, the drive element forms a flat and rigid surface not only at the level of the area of action of the rotor 15 but over its entire length. The strand upper 4 of the tile chain 2 forms a flat and rigid surface over its entire length, i.e. from the storage hopper and supply 5 to the rotor action area 15.

In the figure, two dispensers 18, 19 are shown. The first metering device 18 is arranged between the hopper 5 and the treatment chamber 11. It allows the spreading of a determined quantity of adjuvant on the layer 10 of material leaving the hopper 5 through its orifice supply 9.

The second metering device 19 allows the addition of adjuvant directly in enclosure 11. The head 20 of this second dispenser 19 opens out in a slot 21 made in the cowling 12 of the enclosure 11 to near the inlet opening 13 thereof.

In a variant not shown, the installation includes humidification means, in particular by spraying water on the material and / or the material and the adjuvant. These means which can be consist of any known humidification device and in particular of spraying can be arranged upstream of the rotor 15, which allows to moisten either the layer 10 of materials 6, or the layer adjuvant, downstream of the rotor which makes it possible to moisten the mixture of materials 6 and adjuvant or else at the level of the rotor 15 itself.

The operation of the installation 1 is as follows.

The materials 6, from earthworks, are stored in the hopper 5. Depending on their origin, said materials can be screened beforehand using the screen 22 shown schematically above the hopper 5. Due to the continuous movement of the tile chain 2 in the direction of arrow F, the materials which are in contact with the tiles of the upper strand 4 of the chain 2 are caused to move and form a substantially uniform layer 10, leaving the hopper 5 through the feed orifice 9, over a height h , the upper edge 8 of the transverse upright 7 a somehow forming a scraper.

The first dispenser 18 spreads on layer 10 at least one adjuvant 23 in the form of an additional layer 24. The assembly 25 formed by the layer 10 and the complementary layer 24 enters the enclosure 11 through the inlet orifice 13. Inside the enclosure 11, the material 6 and the adjuvant 23 are subjected to the action blades 17 of the rotor 15 which, due to the rotation of the rotor, 15 against the direction of the displacement of the assembly 25, a mixing of the two constituents capable of producing not only a homogeneous mixture of these but also a mechanical action grinding. The materials 6 and the adjuvant 23 are lifted by the blades 17 of rotor 15 then successively thrown against the face internal 12a of the cowling 12 and against the surface of the upper strand 4 of the tile chain 2. It is this action of plating against the face internal 12a of the cover 12 and against the rigid surface formed by the upper strand 4 of the tile chain 2 which makes it possible to complete effectively the action of grinding and kneading the blades 17 of the rotor 15.

After the treatment thus carried out inside the enclosure 11, there comes out of the outlet orifice 14 of said enclosure 11 a layer uniform of the treated material 26 consisting of the homogeneous mixture of material 6 and of adjuvant 23 both in its composition and in its grain size curve. This treated material 26 falls naturally of the upper strand 4 of the chain 2 beyond the toothed wheel 3 and is recovered by any appropriate means, conveyor belt, tank storage ...

In place of the first dispenser 18 or possibly in complement of it, it is possible to implement the second dispenser 19 to add adjuvant 23 or a second adjuvant 27 directly inside the enclosure 11.

It should be noted that the dimensions of the inlet 13 and outlet 14 openings of the enclosure 11 are preferably proportioned so that the incoming 25 and outgoing 26 layers act as seals so as to limit the projection of material and dust outside the enclosure by said openings 13, 14. The metering device (s) 18, 19 are provided with adjustment means known either for selecting the quantity of adjuvant to be deposited on the layer 10 or to be introduced in enclosure 11 to obtain the proportion which is desired according to the intended use. These adjustment means can be manual or automatic, taking into account in particular the speed of movement of the chain 2 and the height h of the layer 10 of material 6 from the hopper 5. This height h can also be adjusted by manual means or automatic, not shown, for example a shutter hatch sliding along the transverse upright 7 a .

The processing conditions take into account the parameters that are intended for the intended use, for example as they appear from the guide entitled "Realization of embankments and form layers ”referenced D 9233-1 in the publications of LCPC (Central Laboratory of Bridges and Roads).

To avoid any risk of deterioration of the upper strand 4 of the tile chain 2, the height of the blades 17 is determined so that the free end 17 a of each blade 17 passes at a distance of a few millimeters from said upper strand 4. The rotation blades makes it possible to carry out the mixing and grinding action on all of the material 6, including in the zone being in direct contact with the upper strand 4. The fact that the drive element has a flat surface and rigid at the level of the rotor action zone, this keeps the spacing between the free end 17 a of each blade 17 and the upper strand 4.

By using bentonite as an adjuvant, it is possible to obtain a treated material which is impermeable and equivalent to a clay of permeability 10 ^-9 , usable as an impermeable layer for technical landfills.

More conventionally, one or more additives are added to improve certain technical characteristics of the material. It can especially be lime in order to reduce moisture of the material or hydraulic binders in sight to increase the mechanical properties of the material with regard to concerns its distribution and its implementation.

The exact proportion of adjuvant to be added is most often determined by successive tests followed by the analysis of the parameters affected by the use, for example the humidity level of the treated mixture.

With reference to FIG. 2, the rotor 15 will be described more fully. The blades 17 of the rotor 15 consist of an arm 17 b at the end of which is fixed a tooth 17 c which can be easily changed when its end 17 d is worn. The end 17 d of the teeth 17 c corresponds to the end of the blades 17 a previously described. The rotor 15 comprises four series of arms 17 b distributed uniformly over the section of the rotor 15 along an axis perpendicular to the axis of rotation 16. Each series of arms 17 b forms a V as shown in FIG. 2, the tip of the V corresponding to half the length of the axis of rotation 16 of the rotor 15.

With reference to FIG. 3, the tiles of the tile chain 2 previously described will be described more fully. The tile chain 2 comprises a plurality of tiles 2 a hinged to each other so as to allow the drive of the tile chain 2 via a rack 2 b . Each tile 2a has a flat end 2 c and a curved end 2 d . The flat end 2 c of a tile 2 a fits under the curved end 2 d of the next tile 2 a so as to form a floor which forms a continuous, flat and rigid surface. The tiles 2 a are for example made of XC 38 steel and have a thickness of 38 mm. In a variant not shown, the two ends 2 e corresponding to the width of the tile 2 a have a vertical edge which makes it possible to treat a more fluid material capable of flowing on the floor formed by the tiles 2 a .

Claims (12)

1. Process for treatment of a material largely containing damp clay, particularly earthwork débris, consisting of:

   a) putting a layer (10) of more or less uniform height (h) of the said material (6) onto a drive unit (2), moving in a given longitudinal direction (F), at least a given portion of the said unit forming a flat and rigid surface,

   b) introducing the layer thus formed (10) into a mixing and crushing treatment enclosure (11) arranged above the drive unit (2),

   c) adding to the material (6) a particular quantity of at least one additive (23), and more or less equally spread transversely either onto the layer (10) before it is put into the enclosure (11) or into the mixing and crushing enclosure (11) itself, characterised in that it next consists of:

   d) subjecting the material (6) and the additive (23), in the enclosure (11), to the said mixing and crushing treatment by the action of a rotor (15) with blades (17) with a transverse shaft (16), the blades (17) of which, rotating in the opposite direction from the given direction (F), more or less sweep the surface of the drive unit (2), at the level of the said portion forming a flat and rigid surface; and

   e) recovering the treated material (26) as it leaves the enclosure (11).
2. Process according to Claim 1, characterised in that the material (6) is held in and fed from a hopper (5) arranged above the drive unit (2).
3. Process according to Claim 1, characterised in that a quantity of the additive (23) is added by means of a metering dispenser (18) to suit the height (h) of the layer 10) of material and the paying out speed of the drive unit (2).
4. Process according to one of the Claims 1 to 3, characterised in that, as the material is earthwork débris intended for filling or banking up, the additive used is lime and the conditions of use of the rotor are such that they enable a treated material (26) with a maximum granulation of 50 mm to be produced.
5. Process according to one of the Claims 1 to 3, characterised in that, as the material is earthwork débris for a shaped layer for highways, the conditions of use of the rotor are such that they enable a treated material (26) with a maximum granulation of 30 mm to be produced.
6. Process according to one of the Claims I to 5, characterised in that the height (h) of the layer (10) formed on the drive unit (2) is in the region of 10 to 50 cm, in that the amount of additive added to the layer before entering the enclosure is in the region of 0.1 to 5% by weight compared with the material, and in that the speed of rotation of the rotor is between 160 and 200 r.p.m. with a rate of travel of the drive unit between 200 and 1000 metres/hour.
7. Process according to any of the Claims 1 to 6, characterised in that water is added, preferably by spraying, before and/or after and/or at the time of subjecting the material (6) and the additive (23), in the enclosure, to a mixing and crushing treatment by the action of the said rotor (15).
8. Plant for treating a material largely containing damp clay, particularly earthwork débris, comprising:

   a) a drive unit (2) complete with means of moving in a longitudinal direction (F);

   b) a hopper (5) suitable for holding the material (6) and depositing it on a flat unit (2) in the form of a layer (10) of more or less uniform height (h);

   c) an enclosure (11) arranged above the drive unit (2) with an inlet opening (13) and an outlet opening (14) for more or less adjusted passing through of the layer (10) of material (6);

   d) means (18, 19) of uniformly adding at least one additive (23, 27);

   e) a rotor (15) with blades (17) and a transverse shaft (16), mounted inside the enclosure (11), fitted with means of rotary drive in the direction opposite to the direction of movement (F) of the flat unit, these blades (17) more or less sweeping the plane of the drive unit (2) when they turn, and

   f) means of recovery arranged at the level of or underneath the flat unit downstream of the enclosure,

   characterised by the fact that at least a given portion of the said drive unit forms a flat and rigid surface and by the fact that the blades (17) of the said rotor (15) more or less sweep the plane of the drive unit (2) when they turn at the level of the said portion forming a flat and rigid surface.
9. Plant according to Claim 8, characterised in that the drive unit consists of a plate chain.
10. Plant according to one of the Claims 8 or 9, characterised in that the means of adding the additive consist of a metering dispenser (18) arranged transversely above the flat drive unit (2), before the inlet opening (13) of the enclosure (11) and suitable for spreading the additive (23) in the form of a layer (24) of a particular more or less uniform height.
11. Plant according to one of the Claims 8 or 9, characterised in that the means of adding the additive consist of a metering dispenser (19) suitable for dispensing the additive (27) to the inside of the enclosure (11) through a port (21) made in the vicinity of its inlet opening.
12. Plant according to any one of the Claims 8 to 11, characterised in that it also has means of moistening the said material arranged upstream and/or downstream and/or at the level of the said rotor (15).

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