EP0022035B1 - Process and device for depollution in an apparatus for manufacturing a fibrous mat - Google Patents

Description

The invention generally relates to a method and a device for depolluting or cleaning and purifying gases loaded with fibers, dust and gaseous effluents containing polymerizable materials, in an installation for manufacturing a fiber mat, by example of mineral fibers such as glass wool or rock wool, or vegetable fibers such as flax fibers, wood fibers, or any other material.

The mattresses of mineral or vegetable fibers are generally formed by projection of fibers, by means of a rotating die, on a conveyor belt contained in an elongated enclosure. A suction of air under the conveyor belt causes the fibers to settle on this belt, to form a mattress. At the same time as the fibers, a polymerizable binder is also sprayed onto the strip, to agglomerate the fibers into a mattress.

In the current technique, the suction of air under the conveyor belt, which is generally of the perforated type, is done by means of suction fans. To prevent particles of polymerizable binder from settling on the walls of the enclosure or of the ducts located under the conveyor belt and connected to the fans, spray bars for spraying a washing liquid at high pressure, generally water , are provided under the conveyor belt. However, it is found in practice that these measures are not sufficient, and that the polymerizable binder is deposited on the blades of the fan or fans, and solidifies there. This deposit causes a static and dynamic imbalance of the fan blades, which after a very short time can no longer function. It is then necessary to dismantle the fans and clean them with a chisel. The use of a high pressure washing liquid in the spray bars also results in very rapid wear of the spray nozzles, a risk of fouling and clogging of these nozzles, etc. Poor spraying of washing liquid immediately results in a deposit of polymerizable binder and dust on the walls of the ducts leading to the fans.

Such depollution methods are disclosed in particular in patent application FR-A-2 247 346 which describes a depollution process in an installation for manufacturing a fiber mat which are sprayed with droplets of polymerizable binder on a conveyor belt. , this method consisting in placing under vacuum by a fan a box located under the conveyor belt and associated with a washing chamber placed downstream of the box under vacuum. Spraying means are arranged in the duct defined below the conveyor belt by the box and the washing chamber in order to constitute curtains of water droplets on the passage of the fumes having passed through the mattress of fibers in formation and which are thus freed from the elements which they contain in suspension, these elements being constituted by the fibers and the binder with which they are responsible when they pass through the mat of fibers in formation. In contact with the washing water, coming from the sprayers, the fibers contained in the smoke collect water droplets and are deposited by gravity on the bottom of the washing chamber, the water to which part of the the pollutant load of the fumes being removed for further treatment.

The purpose of the present invention is precisely to avoid the drawbacks of the prior art, and for this purpose it proposes a depollution process in an installation for manufacturing a mattress of fibers, such as glass or rock wool, which are projected or deposited with particles or droplets of polymerizable binder on a perforated conveyor belt, consisting in associating with suction means air loaded with fiber dust and particles or droplets of binder through a conduit located under the conveyor belt, to means forming ramps for spraying a washing liquid such as water, arranged in the duct to form a runoff of liquid on all the walls of the ducts or dust removal means on which dust and the binder are likely to be deposited, and then to treat this washing liquid, characterized in that it consists in having, under the conveyor belt, series of Venturi with adjustable section neck housed in boxes and opening into the duct connected to the suction means, to have some of the spray sprays of washing liquid at low pressure consisting of nozzles cooperating with means for dispersing the jets of liquid in upstream of the Venturi, other spraying ramps for washing liquid also at low pressure being thus disposed downstream of the outlet of the Venturi, and to be provided at the outlet of the Venturi with means deflecting the fluid flowing through the Venturi towards the walls of the duct.

The invention also provides a depollution device in an installation for manufacturing a fiber mattress, enabling the method according to the invention to be carried out, characterized in that it comprises, under the conveyor belt for forming the fiber mattress , an enclosure whose upper part is closed by the conveyor belt and which contains a series of longitudinally aligned boxes, forming Venturi with adjustable section neck, arranged under the conveyor belt, spraying sprays of washing liquid at low pressure such as water, to form a runoff of liquid on the walls of the enclosure and boxes, the outlet of said enclosure being connected to air suction means, and means for adjusting the section from the Venturi pass.

• La figure 1 est une vue schématique en plan représentant l'implantation d'un dispositif de dépollution selon l'invention sous la bande transporteuse de formation d'un matelas de fibres.
• La figure 2 est une vue en coupe à plus grande échelle, selon la ligne II-II de la figure 1.

The invention will be better understood and other objects, characteristics, details and advantages thereof will appear more clearly during the explanatory description which follows, made with reference to the appended schematic drawings given solely by way of example illustrating a mode of the invention and in which:

• Figure 1 is a schematic plan view showing the installation of a pollution control device according to the invention under the conveyor belt for forming a fiber mat.
• FIG. 2 is a sectional view on a larger scale, along the line II-II of FIG. 1.

An installation for manufacturing a mattress of fibers, such as glass wool or rock wool, generally comprises, very schematically, a forming head 10 such as a rotary die, which projects fibers 11 on a conveyor belt 12 of the perforated type, on which a mattress 13 of fibers is formed. A polymerizable binder is also projected as indicated by the arrows 14, on the conveyor belt 12 with the fibers 11, to form the mattress 13. The enclosure containing the rotary die 10 and the means for spraying binder, has been shown very schematically at 14, and includes air inlets.

The air from the enclosure 15 is sucked through the conveyor belt 12 by suction fans, not shown, mounted at the end of the duct 16. This suction, which takes place over a certain length of conveyor belt 12, makes it possible to attract the fibers and the binder on the strip 12 to form the mattress 13.

It is understood that the air passing through the conveyor belt 12 and sucked through the conduit 16 towards the suction means, is loaded with fiber dust and polymerizable binder, which tend to deposit and stick immediately on all the walls that they may meet between the conveyor belt 12 and the suction means. The mixture of dust and binder stuck on these walls is extremely difficult to remove afterwards.

To solve this problem, the invention therefore proposes a series of means which will be described in detail in the following.

The invention firstly provides booms 17 for spraying a low-pressure washing liquid, such as water, under the conveyor belt 12. The booms 17 extend longitudinally and horizontally under this belt, and they are provided with spray nozzles 18, surmounted by cups 19 and 20, provided at two different heights. The nozzles 18 have a relatively large diameter, so that they cannot become clogged. They are also not subject to very rapid erosion, the liquid flowing in the pipes 17 being at low pressure.

The liquid leaving the nozzles 18 strikes the cups 19 and 20, and is sprayed on the walls of an enclosure 21 situated under the conveyor belt 12. This enclosure 21 is provided with inspection doors 22, allowing inspection and maintenance of the water spraying systems 17, 18, 19 and 20. A central wall 23 is removably attached to a rod extending just under the conveyor belt 12.

Under the aforementioned enclosure 21, there is another enclosure 24, the upper part of which is connected to the enclosure 21, and the lower part of which is connected to the duct 16 leading to the abovementioned suction fans.

In this enclosure 24 are disposed boxes 25, only one of which is shown in section in FIG. 2, and which are three in number, in FIG. 1, being longitudinally aligned end to end.

Each box 25 comprises two Venturi 26 which are transversely juxtaposed in the box. Each V-shaped venturi 26 is of elongated longitudinal shape, its neck 27 being constituted by an elongated rectangular slot. The section of the neck 27 is adjustable, by means of a plate 28 which is slidably mounted between two guide plates 29 of the box and the internal end of which more or less closes the slot constituting the neck 27 of the Venturi.

It will be noted that one of the walls 30 forming one of the longitudinal sides of the Venturi ends, under the neck 27, by a curved spoon-shaped part 31.

Each box 25 is mounted vertically mobile, in the enclosure 24, between an upper service position which is that shown in FIG. 2, and a lower position, not shown, in which the box 25 is brought opposite a door. 32 of the enclosure 24. In this lower position, the box 25 can be removed from the enclosure 24, to be cleaned or replaced.

Each box 25 can be supported by a rigid frame connected to handling cables 33 passing over pulleys 34 and arriving at winches 35, or else each box 25 can itself be directly connected to cables 33.

A central wall 36, similar to the aforementioned removable central wall 23, is hung under each box 36.

• le liquide de lavage à basse pression circulant dans les canalisations 17 est pulvérisé, au moyen des coupelles 19 et 20, sur les parois intérieures de l'enceinte 21 et sur les deux faces opposées de la paroi centrale 23. Ce liquide ruissèle sur ces parois et pénètre dans les caissons 25 (se trouvant dans leur position supérieure de service) en ruisselant sur les parois 30 formant les Venturi 26. Au niveau du col 27, se produit une atomisation assez poussée du fluide s'écoulant à travers les Venturi 26 et comprenant l'eau de ruissellement, et l'air chargé de poussière et de liant. Grâce à cette atomisation, on obtient un mélange intime d'eau de lavage, d'air, de poussière et de liant, les poussières rentrant par choc dans les gouttelettes d'eau.

The device which has just been described operates as follows:

• the low-pressure washing liquid circulating in the pipes 17 is sprayed, by means of cups 19 and 20, on the interior walls of the enclosure 21 and on the two opposite faces of the central wall 23. This liquid trickles onto these walls and penetrates into the boxes 25 (being in their upper service position) by flowing over the walls 30 forming the Venturi 26. At the level of the neck 27, there occurs a fairly extensive atomization of the fluid flowing through the Venturi 26 and including runoff, and air laden with dust and binder. Thanks to this atomization, an intimate mixture of washing water, air, dust and binder is obtained, the dust returning by impact into the water droplets.

The spoon-shaped part 31 placed at the output from the neck 27 of each Venturi 26, makes it possible to retransform by shock, the water mist resulting from the atomization, into large droplets. The mixture of liquid and air leaving the Venturi 26 is guided, by the parts 31, on the one hand on some of the internal walls of the enclosure 24, and on the other hand on one face of the central wall 36. spraying ramps for washing liquid at low pressure, shown at 37, are provided on the other walls of the enclosure 24, to prevent them from depositing and sticking of dust and binder.

The liquid and the air then flow through the conduit 16.

It can be seen that very good depollution of the air sucked in through the conveyor belt 12 is thus obtained, and that the air which reaches the blades of the fans no longer contains any binder and dust.

The washing liquid laden with dust and binder is treated, in a conventional manner, for the separation of dust and binders, and is then advantageously recycled in the spraying booms 17 and 37.

It will be noted that, advantageously, at least some of the walls of the means which have just been described, and which are capable of receiving a deposit of dust and binder, can be covered with an adhesive plastic sheet which makes it possible to clean very easily these walls. After a certain period of use, it suffices to remove these adhesive sheets and replace them with others.

It will also be noted that the method and the device according to the invention, which have just been described, still make it possible to obtain another extremely advantageous technical advantage.

Indeed, as a certain number of boxes 25 (three in number in the example shown in FIG. 1), are longitudinally aligned, under the conveyor belt 12, and substantially starting from the rotary die 10, it is possible, by adjusting correctly the sections of the necks 27 of the Venturi 26, obtaining over a certain length of conveyor belt 12, a pressure drop profile such that the mattress 13 of fibers formed on the belt 12 has a constant thickness and / or density. In the prior art, which does not allow this adjustment, the fibers tend to deposit on the strip 13 at the place where the suction is strongest, that is to say at the nearest place a suction fan. The method and the device according to the invention make it possible, on the contrary, to obtain a regular and uniform deposit of fibers, over the entire useful length of the forming strip 12.

Of course, the number of boxes 25 that can be provided longitudinally one after the other, is variable to a large extent. Likewise, each box 25 can comprise several Venturi transversely juxtaposed, their number not necessarily being two as in the example shown in FIG. 2.

Claims (11)

1. Method of cleansing in a plant for manufacturing a mattress (13) of fibres such as glass or rock wool which are projected or deposited together with particles or droplets of a polymerizable binder onto a perforated conveying belt (12), consisting in associating means for drawing the air loaded with fibre dust and with binder particles or droplets through a duct (16) located below the conveying belt, with means (17 ; 37) forming a rack for spraying a washing liquid such as water, arranged within the duct to provide a streaming of liquid over all the walls of the dust-removing ducts or means onto which the dust and the binder are likely to deposit, characterized in that it consists in disposing, underneath the conveying belt (12), series of venturis (26) with throats of adjustable crosssections, accommodated in boxes (25) and opening into the duct (16) connected to the suction means, disposing racks (17) for spraying a washing liquid at low pressure, provided with nozzles (18) co-operating with means (19, 20) for scattering the jets of liquid, upstream of the venturis (26), racks (37) for spraying a washing liquid also at low pressure being also arranged downstream of the outlets of the venturis ; and providing, at the outlet of the venturis (26), means (31) for deflecting the fluid flowing through the venturis by deviating it towards the walls of the duct.

2. Method according to claim 1, characterized in that it consists in providing, below the conveying belt (12), at least two adjacent rows of longitudinally aligned venturis (26).

3. Method according to one of the foregoing claims, characterized in that it consists in protecting at least some of the walls of said suction ducts and means by sheets of flexible plastics material unremovably secured for instance by means of an adhesive to these walls.

4. Cleansing device in a plant for manufacturing a mattress (13) of fibres (11), permitting the performance of the method described in one of the foregoing claims, characterized in that it comprises, underneath the conveying belt (12) for forming the fibre mattress (13), an enclosure (24) the upper part of which is closed by the conveying belt (12) and which contains a series of longitudinally aligned boxes (25) forming venturis (26) having throats with adjustable crosssections (27), disposed below the conveying belt, racks (17 ; 37) for spraying a washing liquid at low pressure, such as water, for providing a streaming of liquid over the walls of the enclosure and of the boxes, the outlet (16) of the enclosure being connected to air suction means, and means (28) for adjusting the cross-sections of the throats of the venturis (26).

5. Device according to claim 4, characterized in that the venturis (26) are of an elongated longitudinal shape with a substantially V-like cross-section, the throat (27) of each venturi consisting of a slot of substantially elongated rectangular shape of adjustable width.

6. Device according to claim 4 or 5, characterized in that the outlet of each venturi comprises a longitudinal plate with a curved cross-section (31) onto which is projected the flow of fluid exiting from the venturi (26).

7. Device according to one of the claims 4 to 6, characterized in that said boxes (25) are mounted for vertical displacement inside of the enclosure (24) between an upper working position wherein they are urged tightly against the upper horizontal wall of the enclosure and a lower rest position located on a level with inspection doors (32) provided in the wall of the enclosure (24) making it possible to move said boxes (25) out of the enclosure.

8. Device according to claim 7, characterized in that the boxes (25) are supported by rigid frames (33, 34, 35), for instance of the cable type, allowing to displace the boxes between their two aforesaid positions.

9. Device according to one of the claims 4 to 8, characterized by racks (17) for spraying washing liquid, extending longitudinally above the inlets of the venturis (26) and provided with sprinkling nozzles (18) at two different levels.

10. Device according to one of the claims 4 to 9, characterized in that at least one of the walls of the enclosure (24) comprises, downstream of the venturis, a rack (37) for spraying a washing liquid.

11. Device according to one of the claims 4 to 10, characterized in that it comprises several longitudinally juxtaposed boxes (25), each box comprising at least two transversely juxtaposed venturis (26).

Images