EP0461995B2 - Fiber product recycling in a production line from fibers mat - Google Patents

Description

The invention relates to production techniques mineral fiber mattress.

Industrially, these mattresses are obtained by a two-phase process, producing the fibers properly say by drawing and freezing a molten mineral material at first then, association of a very large number of fibers that come together to form a mattress. Between the two phases, glass fibers or rock are sprinkled with a binder which will be polymerized at the end of the second phase. Once the mattress is finished, it remains to finish the elaboration to constitute a ready product to work. In particular, we must cut the edges length of the ribbon so that they are clear. This operation produces a residue, the edges of the mattress, which want to reuse. Likewise, certain falls resulting from further processing of panels or rollers constitute by-products that it is interesting to be able to recycle. So far, the first operation, the recycling of the falls coming from the banks is carried out, when it occurs, shredding the scraps and returning the flakes upstream to where the mattress is created. This simple operation, however, has two disadvantages: on the one hand the flow rate of reintroduced falls in the mattress is not regular, and on the other hand, as it is impossible to introduce falls whose density differs too markedly from that of the mattress in which we introduce them, and that also the time which runs from the time the falls are cut downstream of the line and the time when they arrive upstream is very long, it is impossible to introduce the falls during a change in manufacturing as soon as the difference in densities of manufactured products exceeds a certain threshold. Likewise, with regard to the use of the scraps produced later when operating the mattress at during surfacing operations (possibly), cutting longitudinal, packaging and even shipping, it is very difficult and requires a lot of interventions human to prepare waste, store it individually after flaking then to take the decision to reintroduce them and finally execute it.

The object of the invention is to simplify and mechanize and to generalize the recycling of all scraps fibers produced during manufacturing and operation mineral fiber mattresses or at least reintroduce the maximum proportion tolerated by the quality to produce and increase this limit over techniques earlier.

The reintroduction of falls from fibrous mattresses is a traditional practice, both on the lines of production of rock fiber mattresses such as those produced according to the process described in patent EP-A-0059152 that on the fiber production lines of glass according for example to a process of the type described in patent EP-A-OO91866. It consists of reintroducing falls in the form of flakes during the formation of the fibrous mattress. In the first process mentioned above using only one source of fiber, the scraps have the form of flakes and are injected into the receiving hood, the flakes are aspirated at the same time as the fibers new on the conveyor which is a perforated mat where the first mattress is formed. In the other process that uses, in series, several fiber production units, two techniques were used, namely the introduction of flake-like falls above the conveyor, between two fiber production heads, either - according to the technique described in French patent FR 2,559,793 -directly in one or more of the receiving hoods. Apart from the requirement for formatting flakes of the falls, two other constraints are imposed, we impose on the one hand that the falls before putting under flakes, have a density, i.e. a density which deviates as much as possible from the density of the mattress that we produce from a limit value which depends on the nature and the use of the mattress. In addition, the amount of recycled fiber does not exceed a certain rate. It also depends on the quality you want respect in the product mattress. She herself reports to technical criteria, such as for example the use practice for which the product is intended or criteria for example, manufacturing a product of high or low end, etc ... Anyway this rate in most cases must remain below 12%. It should also be noted that the higher the density of recycled fiber differs from that of the mattress, lower is the accepted rate. So we see that the two values previously given are only for information, since they must be combined according to criteria very diverse technical or commercial.

As we have seen, waste can have two origins one, systematic, the rectified edges of the mattress, the other random, the waste produced during the exploitation of said mattress, exploitation which can provide waste under the most diverse conditions: most are due to production difficulties: it happens that we make unsaleable products for a reason or for another and more the product is developed or the more sophisticated the packaging, the greater the risk tall. So the so-called "surfaced" products, that is to say on the surfaces to which a facing has been pasted may have detachments, tears, appearance defects, etc. It is then impossible to sell or even use the panel or the roll produced. In this case as an alternative: either discard the finished product or properly recycle the essentials, that is to say the part fibrous. The first solution poses problems about the environment and that's why we try as much as possible to reuse the fibers of such unsaleable panels or rolls. Techniques various have been proposed to separate the facing of fibrous material and we assume that they have been implemented and we have here the bare panel or fiber roll. These are fibers - as well as fibers from edges of the mattress - we want to recycle. It's a process to perform this recycling as the invention offers.

Other known techniques such as those described in patents DE-A-22 23 683 or US-A-2 702,069 relate to the introduction of different nature in the manufacture of insulation masts.

According to the invention, the process for manufacturing the mineral fiber mattress includes steps following: fiber formation from a material in fusion, stretching, entrainment by a current gas ; the flow of fibers then being directed towards a conveyor that collects and drags them. Then, allogenic fibrous materials are added to the main flow of fibers, they were selected according to their density weighs, homogenized destructure and are driven at volumetric flow constant to be added to the main flow of fibers.

Preferably, the materials are formed flakes.

In addition, allogenic fibrous materials have been stored before their introduction into the stream main fibers, their storage is done in silos where, in each, the fibers have a density defined mean.

Allogenic fibrous materials are removed in stocks of different average densities in quantities such as the average density resulting is compatible with those of the fibers of the main stream. The invention therefore provides that weighings are carried out permanently at the exit of each silo. In the same silo, the materials allogenic fibrous are mixed according to their densities and their respective amounts and regardless of their origin.

In the manufacturing process according to the invention, between leaving the silos and entering the main flow of fibers, fibrous materials allogens are mixed and then destructured.

We also propose a device to put implementing the manufacturing process of the invention

Furthermore, for a given belt speed, it is the first comb roller which defines the volumetric flow. The second is settled so as to extract most of the materials fibrous reached him.

The process of the invention thus makes it possible to recycle as many products as possible, it allows therefore to almost completely eliminate pollution from the environment with mineral fibers from fibrous mattress, moreover this technique allows significantly lower production costs insofar as new fibers are replaced in the finished product by fibers which - otherwise - would have been lost.

La figure 1 schématise les techniques de l'art antérieur,

La figure 2 résume schématiquement l'ensemble des opérations préconisées par l'invention pour le recyclage des déchets sur une ligne de production de fibres minérales,

La figure 3 présente sous forme schématique la machine utilisée pour la préparation et le dosage des flocons.

The description and the figures which follow will make it possible to understand the operation of the invention and its advantages.

FIG. 1 schematizes the techniques of the prior art,

FIG. 2 schematically summarizes all the operations recommended by the invention for recycling waste on a production line for mineral fibers,

Figure 3 shows in schematic form the machine used for the preparation and dosing of the flakes.

In Figure 1, we see a manufacturing line a mattress of mineral fibers, in this case of glass fibers, here by the process using the centrifugation of a stream of liquid glass through holes in the wall of a container fast rotation. This process is described for example in patent EP-A-0091 866. In such a process usually several sources of fiber are used which successively deposit tablecloths which constitute, by their superposition, the fibrous mattress. In the figure, four are shown. We see diagrammatically in 1 the centrifuge device which projects a rain of fibers 2 which comes to settle on the conveyor, in this case a metal mat perforated 3. Through the carpet we suck air 4 so as to press the mattress 5 onto the carpet. Each centrifuge device 1 is isolated from the outside by a wall 6 which constitutes a suction hood. The fiber mat 5 is driven on a very long in the direction of arrow 7. This length is most often a hundred of meters. The system transporting the mattress is not shown. We also did not represent the device which in each extractor hood allows a liquid binder to be sprayed onto the fibers which is then dried and polymerized in the enclosure 8.

The mattress 5 will then be cut to constitute either rolls or panels. The shaping of the mattress for the realization of the finished product requires that the longitudinal edges used to be irregularities of the mattress are eliminated. Sure the production line, so we have to proceed systematic longitudinal cutting of selvedges. We see them at 9 in Figure 1. They are driven to a shredder 10 which transforms into flakes of fibers whose dimensions range from one to a few centimeters. These flakes, animated by the air supplied by a blower 11 are conventionally returned directly upstream, where the fiber mat is developing. There, we put them back in the mattress, either between the extractor hoods or either more homogeneous, according to the technique described in the FR 2,559,793, directly in the flow of fibers from each of the range hoods. On the Figure 1, it is this technique of introducing fibers in the extractor hood which is shown diagrammatically, the introduction is done at the level of each sheet of new fibers such as 2 by conduits 12, two in number in each of the extractor hoods. Between the blower 11 and the conduits 12 the recovered fibers so have to follow a long way 13 up to a distributor 14 which directs flows of recycled fibers identical on the four extractor hoods shown. They thus pass through the four pipes 15 before arriving at the distributors 16 which also divide the flow intended for each of the conduits 12.

In steady state, that is, when during long periods, we manufacture the same type of finished product, that is to say with the same density and the same binder, the flakes from the banks 9 are introduced without difficulty in the mattress 5.

However, it is obvious that the time which elapses between the production of a given mattress and the introduction of the scraps coming from this mattress into the extractor hoods is very long. Thus for example, on a line of the type of that of FIG. 1 with four fiber-drawing units at 15 tonnes per day and a mattress width of 1.2O m, we measure, in the case of the manufacture of a mattress with 6O kg / m ³ in 1O cm of thickness, a delay of the order of 20 minutes between the production of a mattress and the reintroduction of its selvedges into the fiber mattress produced subsequently. During a stabilized production, this delay has no consequences, however, if we change manufacturing, with a significant difference in the densities of the two mattresses which makes it impossible to recycle the old fibers, there is then no other solution than storing large quantities (in the example chosen, 14 m ³ ) while awaiting identical future production or the disposal of the falls concerned. The solution of recycling the fibers in the glass or slag melting furnace can also be considered, but it is expensive (the fibers must be remelted) and it can disturb certain parameters of the melting such as the redox balance of the bath.

But in traditional production lines we also wants to recycle scraps of fibrous materials produced offline, for example due to poor workmanship. When we want to recycle such products after having rid of allogenic elements like materials serving as facings for example, two cases arise, or they are compatible with the production of the moment (same binder and neighboring density) and then they can be added to the edges until constituting with them a defined fraction of the finished mattress, for example 10%, this limit proportion being a function of the desired quality and the density of the mattress produced. On the other hand when the materials are incompatible and you want reuse the scraps, the only possibility outside the recycling in the oven is storage pending again produce the material whose density and / or quality to be obtained will allow reincorporation of scraps stored.

Always on figure 1, we find the recycling circuit finished products. We see in 17 a shredder into which the panels 18 (or the rollers) are introduced stripped of their surface coating. The wind tunnel 19 propels the airborne flakes to the distributor 20 which - depending on the original density of the panel 18 (or roll) sends them through the pipeline 21 to the storage silo 23 - reserved for example for light products, the others being transferred through the conduit 22 to silo 24 reserved, in the example, for products the densest.

According to the type of mattress 5 (density, target quality) which is in production, we will draw on the stock of materials silo 23 or heavy materials of the silo 25. In the traditional process for adjusting the throughput of recycled products at the target value which depends quantities to be recycled and tolerable maximums, function themselves of the nature of the product in manufacture and of quantities of flakes from edges that have already been reintroduced, we use a discontinuous scale 25 which loads permanently flakes then that empties when the load reaches a defined weight fixed in advance. The entire load is then poured onto the conveyor belts 26 and 27 to finally join circuit 13 thanks to a wind tunnel not shown. The route followed by this second family of waste is then the same as that of waste from selvedges.

The waste recycling system which has just been described and which would allow, on a line devoted to a only type of manufacturing, to recycle as much waste as possible possible has, as we have seen, many drawbacks. Among these, some concern the recycling of the banks during campaign changes and have been explained at length above, they are very annoying because it happens one campaign lasts less than an hour, the others concern dosing and assimilation of waste from finished products. The first phase of the cycle, which begins with the introduction of panel 18 into the shredder 17 to complete with the storage of the flakes of light products in silo 23 and dense flakes in Silo 24 is generally going very well. This is the second part, between the sampling in the silos until the introduction in the distributor 14 which poses serious problems for dosing of waste.

Take as above, the example of a production a mattress based on dense products with a width of 1.2O m with the four centrifuges shown in Figure 1. In the example, cutting the banks produces 8% of waste which are continuously recycled using the pipeline 13. The production carried out is here intended for use final which tolerates for example 12% of waste. he should therefore have been possible to introduce a maximum of 4% of waste from silo 24. The theoretical flow to introduce is, given the more defined parameters high, 1.6 kilograms per minute. 25 scales work in the following way: one establishes at the exit silos an approximately stabilized flake flow at the desired rate and at regular time intervals, the exact desired charge is released and falls onto the mat rolling 26. In the example in question, it is a charge of 530 grams which falls every 20 seconds. Such a system thus provides good average flow but instant flow very variable. In fact, during transport later, the differences will slightly decrease, but we nevertheless sees an oscillation of the overall quantity of recycled flakes around the target value. As we have the imperative not to exceed, for commercial reasons in this case the value of 12%, we are forced to reduce the quantity of flakes recycled from silo 24, for example at 10% to be sure never exceed the maximum tolerance.

Traditional methods of recycling scrap from defective finished products are limited by the difficulties of assimilating flakes of allogenic origin in the mattress. Indeed, the flakes that have been stored in silos 23 and 24 will be extracted and transported and finally mixed as is with the flow of new fibers. So they stay in the same form in the finished mattress where they constitute heterogeneities of dimension notable.

FIG. 2 represents the process of the invention for prepare, select, store, dose while destructuring then finally distribute the waste as well those from the edges on the line than those from falls or workmanship, offline. Some elements are the same as those in Figure 1, especially everything which concerns the line itself, extractor hoods 28 to mattress 5 at the end of the line. The treatment longitudinal edges 9 uses shredders 10 and the blowers 11.

La rive, découpée par des scies, des disques ou des jets d'eau, s'engage dans un conduit horizontal suivi d'un conduit vertical ou oblique aboutissant au broyeur installé soit sous la ligne, soit de préférence dans la cave, ce qui facilite les opérations de maintenance et diminue le bruit. Il y a un broyeur par rive. La longueur minimum du conduit horizontal est de 5OO mm. Sa section sera, par exemple, 34O x 35O mm.

The shredders are fed here as follows:

The bank, cut by saws, discs or water jets, engages in a horizontal conduit followed by a vertical or oblique conduit leading to the crusher installed either under the line, or preferably in the cellar, which facilitates maintenance operations and reduces noise. There is one crusher per bank. The minimum length of the horizontal duct is 500 mm. Its section will, for example, 34O x 35O mm.

Upstream of the horizontal duct, a motorized caster comes to lay the shore flat while pinching it. This avoids bank breaks downstream of the cutting saw. The length of the vertical or oblique part is approximately 2.5 m (depending on the depth of the cellar).

Depending on the width of the product, the distance between the horizontal ducts is adjustable by means of two motors and two screw-nut assemblies.

The vertical conduits have at their upper end a cone which keeps the vertical part fixed, despite the variation in distance between the horizontal conduits.

As a shredder, hammer mills are used. The mill consists of a 45O mm rotor diameter a length of 4OO mm, it includes 90 hammers spread over three rows, its rotation speed is around 1500 revolutions per minute. The grid is made of steel manganese with dimensions 4O x 4O mm.

At the outlet of each shredder, a fan 11 ensures the evacuation of the flakes.

The characteristics of the fan are calculated in order to obtain a speed of 20 m / sec in pipes with diameters from 2OO to 250 mm, i.e. a flow rate 4 of approximately 3500 m ³ / h. The total pressure being calculated as a function of the pressure losses due to the installation of the pipes.

The materials used for the impeller and the scroll have good abrasion resistance.

At the outlet of the fans 11, there are here distributors 29 which are capable of orienting the flakes, either towards the duct 30 if, for example they are light, or towards the duct 31 if they are denser, they then join the main light 21 or heavy 22 circuit which directs them respectively to the silos 21 or 24. The circuit for scraps or finished products from poor workmanship 18: shredder 17, blower 19, distributor 20 then main pipes 21 or 22 is itself consisting of elements which are exactly the same as those which have just been described. It can be seen simply in FIG. 2 that the selvedge circuit has joined, after separation according to density, the circuit of falls and poor workmanship so as to constitute a single circuit, that of allogenic fibrous materials. Passage through silos such as 23 or 24 is therefore systematic. These silos are, for example, cylinders with a vertical axis with a capacity of 4 m ³ each. Each is surmounted by a capacitor (43, 44) which allows the separation of air and flakes. They are fitted with filters to remove dust before the air is recycled. In the figure only two silos have been shown, one 24 for dense products, the other 23 for light products. During the tests, the light products / heavy products border was placed at a density of 20 kg / m ³ . The distributors 20 or 29, on each of the flake supply circuits are switched according to the density of the flakes which feed them, either on the conduit 21 if their density is low, or on the conduit 22 if their density exceeds the limit fixed. This limit depends on the range of products manufactured on the lines (in the case of Figure 2, it can range from 8 to 110 kg / m ³ ) but it also depends on the respective quantities manufactured in the different densities, as well as it also depends on the proportion of additions of different density tolerated which is not the same according to the end uses of the product: a fiber intended to constitute a filler in a bitumen does not have the same requirements from this point of view as that which will constitute a roll intended for the insulation of roof spaces for example.

The number of silos shown in Figure 2 is two but it is obvious that a finer classification of the flakes to recycling can be interesting. We then multiply the number of silos which makes it possible to refine the adequacy between respective densities of recycled flakes and mattresses in production.

The rest of the recycled flake route, at the output from the silos (23, 24) is identical to that of the figure 1, there are successively the scales 25, the belts treadmill 26 and the main treadmill 27. The element essential new in the circuit is machine 32. It it is a machine called "ball breaker", its function is multiple. First of all the usual function of this type of machine which is to "break" tangles of fibers. Indeed during previous multiple manipulations, the flakes could be packed, compacted, nested and there try to restore them to their original configuration, their integration into the new fibers will be found all the better. We even want to go further: destructuring, "burst" the original flakes to facilitate their integration into the flow of new fibers and so in the mattress. A second function of this machine which is not usually required in breakers is to homogenize the flakes that have origins multiple: selvedges on the one hand and finished products on the other but also among these, flakes that have a different story from each other. A third completely new function is also fulfilled by this machine. The function is new because the problem posed here is not usual in workshops where such machines are installed, it is a question of making constant the flow at the outlet of the scales, flow which varies periodically, as we've seen. You have to "smooth" the variations cyclical so that excess flow over at the average flow compensates for the deficiencies. We obtain thus a constant volumetric flow.

The machine 32 is shown schematically in the figure 3. The product leaves the treadmill 33 which is shown in Figure 2, this raised the flakes above machine, left. The machine entry in 34 is presents as a trough whose bottom is constituted by the treadmill 35. The latter is driven at constant speed, the flakes will therefore deposit there periodically as delivered by the balance 25 in operation.

This conveyor belt 35 in turn feeds a strip conveyor 36 which constitutes the bottom of a level tank constant, in fact, it is equipped with an ultrasonic system not shown which allows material flakes allogeneic fibrous fibers which charge it to occupy a thickness constant. As soon as the chosen level is reached, the engine treadmill drive locks up and the fiber supply is immediately stopped. Of in this way, the flakes occupy in the tank 37 a defined height chosen so that the fibers are driven upward at a constant rate which corresponds to the average weighing of the balance 25. The drive upwards is carried out thanks to the spiked mat 38 in translation at constant speed. This speed can be adjusted by a manual control not shown.

At the top of the spiked carpet, the flakes reach the comb roller 39 which has four generators equipped with spikes and turns against the current, it hunts down the excess flakes, ensuring flow perfectly regular fibers. By the way, the teeth combs penetrate the flakes held by the carpet tips by causing the desired "destructuring". A second identical roller 40, which turns in the direction of flow, fulfills a neighboring function and extracts all fibers of the spiked apron and returns them on the inclined plane 41, towards the outlet 42 of the machine.

Below this exit is the conveyor belt 45 which supplies a fan not shown. This sends the regular flow of allogenic fibrous materials delivered by machine 32 to distributor 46 which feeds as many pipes as there are hoods 28. Before dispensing into each hood, again, distributors 47 separate the fiber stream recycled into two equal streams which feed two by two the extractor hoods where they will be mixed with the flow main fiber.

It is thus seen that the use of the machine 32 allows to deliver a constant and well defined volumetric flow since it corresponds to the weighing carried out by the balance 25.

The invention therefore makes it possible to supply the lines of production of rock fibers or glass fibers immediately after fiberizing machines with regular flow of destructured, open flakes. These two elements, regular feeding on the one hand, destructuring of each other’s flakes facilitate the incorporation of allogenic fibers in the flow new fibers. We can always choose, if it's required, the maximum compatible recycled fiber throughput with the quality criteria of the moment which are as we saw it depending on the nature of the products manufactured, their final destination and the nature of the fibers to be recycled.

The following examples will show how storage of non-native fibrous materials in silos where the average density is defined makes it possible to control the average density of fibers reintroduced into the flow main fiber.

Example 1

On a centrifuge glass fiber line comprising four fiberizing heads which produces 6O tonnes per day in 1.3O m of gross width, for a useful width of 1.2O m, we therefore have about 8% shoreline waste. The contribution of waste from finished products was zero that day. The line is equipped with two storage silos, silo A for light products and silo B for dense products. At the time of the example, the density limit between A and B was 30 kg / m ³ and the average density in silo A was: d AT = 2O kg / m 3 and in silo B: d B = 60 kg / m 3

The production chosen for the example was that of a very dense product d _f = 90 kg / m ³ . It turns out that given the market for which the product is intended and especially its conditions of use, only in compression, there is no problem of cohesion of the mattress and the proportion of light flakes tolerated is large. Empirically, it has been found that using the techniques of the invention, this proportion can reach 8% by volume with a product whose density is equal to that of the mattress in production, that is to say equal to d _f , but it can go up to 15% if its average density is 15 kg / m ³ . Between the two an interpolation is possible, that is to say that for example, if one wants to reintroduce flakes of average density 30 kg / m ³ , one can reintroduce 13.5% and if their density is 6O kg / m ³ , 11%. In the concrete case of the example, we chose the latter possibility and we therefore took all of the products to be recycled in silo B, the balance of which was adjusted to deliver an average of 275 kilos per hour. The machine 32 of FIG. 2 is adjusted so as to precisely ensure the constant volumetric flow rate of the quantity retained. By making this choice, the stock of waste contained in silo B is slightly reduced. In fact, the hourly quantity introduced (in silo B since its density, 90 kg / m ³ is greater than the fixed limit, 30 kg / m ³ ) corresponds to 8% of production while the quantity extracted is 11%. In addition, the average stock density is increasing. This parameter - management of waste stocks - is in addition to those already mentioned. It is one of the elements to consider before choosing the average density and the quantity to be reintroduced.

Example 2

The glass fiber production line according to the method of European patent EP A 0091 866 comprises six centrifuge heads with a production of 120 tonnes / day. The net width is 2.4O m and shore waste constitutes 4% of production. Storage takes place in three silos, A, B and C, the average densities of d _A = 12 kg / m ³ , d _B = 2O kg / m ³ and d _c = 50 kg / m ^{3, respectively} .

On the day of the example, the production was that of a mattress with a density of 30 kg / m ³ and the contributions of finished products to be recycled which had to be introduced into the silos consisted of a quantity of 2OO m ³ per day with a density of 10 kg / m ³ . For production management reasons, we want to keep the same average density here in silo B, so we will introduce into it all the falls from the banks (200 kg, or 6.7 m ³ per hour) and l 'we will introduce the same volume of finished product scraps of density 10 kg / m ³ . The rest of the scraps of finished products will be stored in silo A where the average density will drop slightly. The product manufactured on the day concerned accepted 8% by volume of scrap but with an average density close to that of the product in production. A flow of 8.9 m ³ / h (178 kg) was therefore taken from silo B and silo C, 4.4 m ³ / h (220 kg), these quantities will be mixed and introduced, after equal distribution, into the receiving hoods of the 6 fiber production units.

But we might as well have taken a volume c from silo C and a volume a from silo A such that: a + c = 13.3 13.3. 3O = 12 a + 50 c We can deduce a = 7 m 3 / h and c = 6.3 m 3 / h

We see that there are many possibilities in the choice of parameters which, thanks to the invention, are offered to the production manager.

The technique of the invention therefore not only allows to permanently reintroduce falls from edges of the mattress, while prior techniques forced to interrupt this reintroduction during production changes, but in addition it authorizes the recycling of waste whatever its source and whatever the nature of their fibers. The only constraint is that you need sufficient storage to wait until production is compatible with the nature of the fibers that we want to reintroduce.

Systematic recycling of fibers from finished product is particularly favorable to preservation of the environment.

Furthermore, by making it possible to reintroduce the maximum tolerable quantity of recycled fibers, we realize a significant saving on the cost of production. New fibers are replaced in the finished product made from fibers that would otherwise have been that cost nothing and have eliminated costs that would have resulted from their elimination. The additional cost is limited to that of the transformation of the finished product in flakes that can be stored in silos and some subsequent handling.

We can see that the progress made in the field of environmental protection recalls that of the years 8O when the industrialized countries recycled the glass bottles.

Claims (8)

1. Method of producing a mineral fibre mat comprising forming fibres from a molten material, drawing them, entraining them by means of a stream of gas, the stream of fibres subsequently being directed towards a conveyor which collects them and entrains them and in which foreign fibrous materials are added to the main stream of fibres, characterised in that the foreign fibrous materials which are introduced, especially those coming directly from the edges, are selected as a function of their density, weighed, homogenised, destructured and entrained at a constant volumetric rate in order to be added to the main stream of fibres.
2. Method of producing a mineral fibre mat according to claim 1, characterised in that the foreign fibrous materials have been stored prior to their introduction into the main stream of fibres.
3. Method of production according to claim 2, characterised in that storage is in silos and in that, in each silo, the fibres have a clearly defined average density.
4. Method of production according to claim 3, characterised in that the added fibrous materials are taken from stocks having different average densities, in quantities such that the resulting average density is compatible with that of the fibres of the main stream.
5. Method of production according to claim 4, characterised in that weighing is performed continuously at the output of each silo.
6. Method of producing a mineral fibre mat according to claim 3, characterised in that the foreign fibrous materials are mixed in the same silo as a function of their densities and their respective quantities and irrespective of their origin.
7. Device for implementing the method of producing a mineral fibre mat according to claim 1 comprising forming fibres from a molten material, drawing them, entraining them by means of a stream of gas, the stream of fibres subsequently being directed towards a conveyor which collects them and entrains them and in which foreign fibrous materials are added to the main stream of fibres, comprising in particular a blower (11, 19), a distributor (20), compactors (43, 44), silos (23, 24), scales (25), a distributor (46), characterised in that it comprises a machine (32) ensuring entrainment at a constant volumetric rate.
8. Device according to claim 7, characterised in that the machine (32) comprises a constant level tank (37), a spiked and ascending belt (38) and two comb rollers (39, 40) in the upper part.

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