NO153529B - PROCEDURE AND APPARATUS FOR WASHING OF EXHAUSTS IN THE MANUFACTURE OF MINERAL FIBER MATTS. - Google Patents

Description

The present invention relates to the washing of exhaust gases in connection with the production of mineral fiber mats and further an apparatus for carrying out the method.

The production of mineral fiber mats or similar products includes a series of operations and in particular:

Formation of fibers,

their advancement towards a receiving element by means of gas flows,

gluing the fibers by means of a binder by bringing this latter in the form of a finely divided preparation to the flow paths of the fibers between the preparation and the receiver element,

mat formation on the receiving element, usually formed by a perforated carrier,

separation of the fibers and the carrier gas stream by passing these gases through the receiver element and evacuation and/or return of gases that are recovered downstream of the receiver element,

treatment of the fiber mat, coated with binder, to adhere the binder, optionally followed by a cooling step, and evacuation of gases from adhesion treatment of the binder and from the exhaust gases,

transferring the resulting mat into finished product form and collecting and evacuating saturated air from this transformation.

Regardless of the manufacturing method for the fibers and the type of binder used, the waste gases can neither be returned nor evacuated without at least a minimal treatment due to the pollution risk that exists.

Among the contaminant elements, those originating from the binder are particularly undesirable. In particular, these are fine droplets that were not retained in the fiber mat or they are gas products originating from the binder preparation. They are also degradation products that can be released when a binder is brought into contact with the fibers at high temperature.

Of course, in addition to these contamination elements are the fibers that are not retained on the receiving element or that are pulled up from the mat during the conversion steps.

These elements are unfavorable for several reasons. In particular, binder droplets contaminate and quickly vaporize the walls of the equipment and channels that transport the waste gases. Thus, they tend to form adhesive deposits that retain entrained fibers or fiber fragments. Reconditioning the installations therefore requires periodic removal of these deposits. In addition to the disruption this causes, these cleaning operations are labour-intensive. The result is a significant increase in production costs.

The first treatment carried out on the waste gases is usually a water atomisation in order to cool and initially to remove the bulk of polluting elements. In particular, with the help of this atomization, an attempt is made to remove as much binder as possible to prevent overgrowth of the installation, which is known to pose a significant problem in this type of production.

However, the effective application of this water atomization causes certain difficulties.

The first difficulty has to do with the extremely large amount of circulating gas present in these installations, and as a consequence the dimensions of the installation itself where these operations must be carried out.

In FR-PS 2 247 346 certain volumes of gas are indicated, characteristic of different types of fiber production. These 6 6 values are in the order of 0.1 x 10 to 1 x 10 m 3 /hour waste gas for the work that results in the formation of mats. As can be seen, it is difficult to achieve a fine, homogeneous dispersion on such large volumes using the traditional techniques in this area.

Another difficulty associated with the waste gases coming from the formation of fibers lies in the need to prevent the formation of deposits on the gas flow paths as soon as the gases have crossed the fiber receiver element. Thus, deposits that form directly under this receiver element can modify the cross-section for the gas flow path and, as a consequence, their progress through the mat that is formed. Such a modification affects the homogeneity of the fiber mat.

In order to prevent the deposition of such deposits, it is desirable to carry out the washing step very close to the receiving element, which constitutes a further difficulty because the fiber mat that is formed must not be reached by sprayed water during the washing step.

A third difficulty lies in the fact that the water used, which becomes saturated with polluting elements, cannot be discarded. Therefore, it is common to return it after it has been cleaned of a portion of entrained polluting elements. In order for the costs to be acceptable, the step or steps aimed at ridding the water of polluting elements must be relatively simple. E.g. could they involve a summary filtering or similar. At the end of this treatment, reclaimed water usually still contains a significant amount of substances in suspension and of stable or unstable undissolved products. The use of water in conventional atomizing apparatus therefore causes problems, especially with regard to clogging or erosion-corrosion.

Usually atomization of the water is carried out under pressure by passing the water through nozzles with small dimensions. For the desired use, this method has various shortcomings. Firstly, the amount of water that is distributed through each atomizing nozzle and the amount that is effectively treated by this atomization is very limited due to the very small size of the nozzle. Of course, it is possible to increase the number of nozzles accordingly, nevertheless it is difficult to achieve a perfect continuity and a good homogeneity of the layer of water droplets throughout the required space. In practice, even with a large number of nozzles of this type, it is not possible to effectively treat the entire gas flow, and as a consequence to prevent the formation of deposits on the walls of the chamber or channels. Secondly, because of the nozzle dimensions, frequent blockages occur, and this all the more so because returned water is more saturated with polluting elements. Therefore, even a good distribution of nozzles in the atomization area cannot guarantee continuous homogeneous atomization. These nozzle blockages also require frequent downtime for cleaning.

In an attempt to overcome the difficulties, the conventional nozzles were replaced with apparatus in which the water dispersion is no longer achieved by passing it under pressure through delivery pipes of small cross-section, but by spraying on a concavely curved element (a kind of spoon or spatula). The beam directed at this element formed a liquid layer which spread out and was blown up into a large number of droplets. This atomization method gave a significant increase of the outlet for each jet. The formation of very fine droplets is, however, only possible for relatively small outlets. Furthermore, there is rapid wear of the elements that ensure the water dispersion. Within a few hours, it loses its luster in the radiation path which is saturated with abrasive particles. Within a few days, an erosion-corrosion phenomenon then occurs under these conditions, which causes deformation of the dispersing element which then becomes less effective, the replacement of these elements must in typical cases be carried out after two weeks of continuous operation.

The object of the present invention is to improve the known technique and the invention thus relates to the initially stated method in which: fibers are produced and carried using gas streams to a receiving element where they are collected and separated from the carrier gas, finely divided liquid binder preparation is introduced into the gas the flow that carries the fibers upstream of the receiving element, fiber.--the mat is optionally treated, especially thermally, for adhesion of the binder and undergoes transformations that lead to the finished form,

in water is atomized in the flow path of the gases that have carried the fibers, downstream of the receiver element and/or in the flow path of the gas from the treatment step for adhesion of the binder and/or from the transformation step of the fiber mat, and this process

way is characterized by the fact that the water, which may possibly be recycled, purified water, is atomized by collision between compact jets.

The invention also includes an apparatus for carrying out the method as described below.

Atomization by impact of jets is known essentially for dispersing flammable liquids in combustion chambers in engines. In these applications, the outflow of liquid is relatively small, and the dispersion is achieved in a high-velocity gas (of the order of 30 m/second).

It has also been proposed to atomize water by jet collision in the throat of a venturi-type apparatus, an assembly which is intended to remove fine gases such as dust from jet furnaces after the latter has undergone an initial washing. In such applications, the dispersion is carried out in a gas, provided that it is kept at a high speed, and at a point where the passage cross-section is narrow.

The dispersion of water by beam collision according to the invention differs from these previous applications because of the environment in which this technique is used as well as because of the goals sought or, as described in more detail below, due to the conditions of use.

The studies that led to the invention showed that when two jets collide, it is possible to develop an extended layer of droplets compared to what is achieved by conventional means. A dispersion over large surfaces is achieved without discontinuity in the spatial distribution of the droplets. This represents a real advantage compared to the previously known atomization methods.

By working in the manner described according to the invention, even when the treatment is carried out in very large chambers, it is possible to use only a small number of dispersing apparatus. By suitable choice of parameters for the colliding beams and their location, the entire cross-section of the chambers in installations of the type in question is covered without difficulty.

Usually, the shape of the layer of droplets that develops does not exactly correspond to the shape of the chamber cross-section, and some of the water is thrown against the walls. The wall in the impact zone with the drops is thus "planed". In order to achieve this cleaning effect for the walls, however, it is not necessary that the impact be strong.

Furthermore, experience has shown that washing the waste gases using homogeneous water dispersions produced by impinging jets leads to very clean walls, even beyond the impingement zones.

To a certain extent, it is preferred to limit the impact force to prevent erosion on the walls. This is achieved by adjusting the shape and extent of the layer of droplets by modifying the operating conditions of the jets in the manner described below.

Various conditions determine the shape and extent of the layer of droplets that are dispersed.

If the two jets are identical at the point of impact, i.e. if they have the same dimension, velocity and discharge characteristics, the projection of the droplets obtained is practically in one plane. This plane is orthogonal to that for

the rays and form a plane of symmetry. Gravity and gases passing through the drop layer disturb this plane. However, for relatively low gas velocities and relatively high jet velocities such as those desired according to the invention, this disturbance is reduced. For practical purposes, the layer can be assumed to be flat.

In practice, it seems advantageous to have an initially flat layer that covers the largest cross-section, where the other radiation conditions are constant. Nevertheless, it is possible to use jets with different intensities (discharge velocities). Layers with the appearance of a more or less "disturbed" paraboloid are thus formed. Such an arrangement may seem advantageous when e.g. for a given liquid outlet, the dispersion is achieved in a chamber whose dimensions are relatively small, and when it is desired, to prevent the liquid layer from hitting the walls. In this case, one seeks to provide a deformed layer, drawn in the longitudinal direction of the chamber.

In all cases, the beams, even when they are different, have characteristics that remain in the same order of magnitude, so that a satisfactory dispersion is provided.

The general shape of the layer was determined experimentally as a function of the angle between the two beams. This study, carried out for two identical beams, shows

that the layer develops in a circular form when the converging rays are aligned, i.e. that they form an angle of 180° between them. If the angle decreases, the layer of droplets tends to take the form of a circular sector whose angle decreases in the same way as the angle between the rays decreases. In this latter case, the sector center corresponds to the collision point of the rays.

It is preferred that the atomizing apparatus (also called an injector) does not constitute an obstacle in the flow path for the gas. In other words, this apparatus is preferably arranged close to the chamber wall or the channel wall where it is placed. Under these conditions, there is a tendency to seek to achieve a layer in the form of a sector whose angle is close to 180° in order to cover the space up to the wall from which the atomization is carried out. It can also be advantageous to create a layer whose angle is greater than 180°, which also enables the wall on which the injector is fixed to be sprayed. If the equipment is placed close to a corner, a small layer angle may of course be preferable. In this case, the angle between the rays is reduced to a smaller value.

By following the description, examples of beam angles and the shape of the corresponding layers are given. In normal use, the angle between the beams is not less than 30° and preferably between 60 and 130°.

Of course, the layer is also provided with a certain thickness from the point of impact and on both sides of the rising plane. This thickness remains relatively small compared to the other dimensions. Usually it is no more than a few tenths of a centimeter. It is practically proportional to the outlet and is smaller as the angle of incidence for the rays is greater.

Because the general shape of the layer is mainly determined by the fact that the jets are identical and by the angle between them, the extent of the layer is a function of the outlet and the jet velocities.

As shown, it is preferred to have sufficiently large layers to prevent discontinuity in the distribution. It therefore seems desirable to create a layer with dimensions so that the entire cross-section is covered. This solution can be effectively customized. Nevertheless, the use of a single layer is not desirable in all cases.

A reason that may lead to the use of several layers comes from the fact that, as indicated above, the force of the water projection on the walls must preferably be limited. If, in order to cover the entire surface, a single layer was made which actually extended beyond the limits of the chamber (or channel), the water would be thrown against the walls with excessive force, which could be detrimental to the proper operation of the apparatus.

Another reason is related to the fact that for very large surfaces high-performance jets should be used, which is difficult to achieve in industrial installations.

In practice, the jet collision technique used according to the invention forms droplet layers of 45 m<2> usable surface area or more quite easily. For the reasons stated above, it is preferred to form layers whose dimensions are not the largest possible, and to use several injectors which provide a series of layers which overlap each other.

The amount of water that each pair of jets must provide depends mainly on the cross-section of the gas stream and the wall surfaces to be sprayed. With regard to the atomization according to the present invention, the amounts most often used are in between

3

10 and 80 m per hour.

Transformation of the jets into fine droplets is a function of the impact force and therefore of the jet velocities. The speed itself is a function of the pressure exerted to form the jets. In industrial installations and for significant quantities, it is difficult to exceed pressures in the order of 10 Pa. For the dispersion and proportioning sought to achieve the goal of the present invention, a pressure of the order of 3 to 6 x 10<5>Pa is satisfactory.

The size of the droplets is a function of the speed of the jets and therefore of the pressure. Experimentally, it has been determined that the higher the pressure, and as a consequence the greater the power of the jets, the greater the tendency to form fine droplets. However, this variation is relatively slow. In other words, large variations in pressure only lead to a slight modification of the droplet size. When the pressure is of the order of magnitude, or greater than 2.5 - 3 x 10^, a certain percentage of extremely fine droplets occur, i.e. where the dimensions are smaller than 0.01 mm. In a way, the presence of these very fine droplets can be beneficial for the washing, especially by ensuring a very strong contact between the water and the waste gases; however, the subsequent removal of these droplets prior to release of the gases may require additional separation.

The amounts of water used according to the invention are of the same order of magnitude as those used in the earlier apparatus. Due to the more regular distribution of the water in the gases, these quantities can possibly be reduced.

For atomization of water in the flow path of waste gases from installations for the production of fiber mats, it is usually considered that a volume of water in the order of

3 3 3

0.5 to 2 m per 10 ra gas gives satisfactory results. These values are obviously not imperative. They are a function of numerous factors and especially of the waste gases, especially their binder content and the nature of the binder, the temperature, but also the water quality. Thus, when it comes to the latter, it should be taken into account that it is usually returned after a more or less vigorous cleaning, the less the returning water is saturated, the more effective the treatment and the less water is needed.

The amount of water used can also be linked to the cross-section of the chamber or channel in which the dispersion is carried out. Advantageously, this quantity is between 2 and 20 m 3 per m 2 per hour. Expiration per unit area obviously depends on the discharge of waste gases that pass through this area.

According to another feature directly in connection with the quantities just described, according to the invention it seems advantageous to carry out the treatment at a point in the flow path of the exhaust gases where the average velocity for these is less than 10 m per second and even less than 5 m per second. This is only a hypothesis, but it seems that when the speed of the gas is lower and therefore the contact time with the droplets is greater, better exchange occurs between the gases and the dispersed water.

These preferred conditions of velocity are usually present, especially at the beginning of the flow path of the waste gases, whether this is in chambers located directly downstream of the fiber receiving element or it is from the emission of waste gases from other work steps carried out on the fiber mat. Because it is so much more advantageous, it is preferred to effect atomization of water as soon as possible to prevent deposits that may form upstream of the atomization. The atomization by beam collision is therefore preferably carried out just downstream of the fiber receiver surface and/or directly at the outlet of the chamber for processing and conditioning the fiber mat.

While it seems preferable to carry out the washing as quickly as possible in the path of the waste gases, it may also be advantageous to repeat this washing at different points in this flow path. Although the significant proportion of polluting elements present in the gases as a result of the quality of the washing by impinging jets is recovered by droplets from the first layer, a certain amount of water is entrained by the gases. This water, which is of greater quantity the finer the dispersion, tends to deposit on the walls along the flow path. If the gases are not saturated with moisture, deposits may form, albeit smaller than in the first part of the flow path, but nevertheless they can be problematic. For this purpose, secondary washes can be linked to the main wash, preferably carried out as the first in case of colliding jets.

The water that is sprayed against the walls runs along them

and is recovered under the chamber in which the atomization is carried out.

The atomized water that is entrained in the exhaust gases is separated from these before they are released into the atmosphere. Usually, a first separation is carried out in the atomization chamber.

The largest drops, or those formed from several drops, are separated from the gases without any special work and are recovered in the lower part of the apparatus where the water runs down the walls.

When it comes to the very fine drops that are carried along

of the gases, traditional methods for separating liquid and gas can be used.

The water that is recovered is beneficially returned. It can be subjected beforehand to cleaning procedures that are common in these environments. The minimal purification prior to return consists of decanting to remove at least a portion of the solids in suspension.

Other physical or chemical methods can complete the purification. In particular, a degassing of the water can be carried out.

Regardless of the cleaning method(s) carried out, it is advantageous that the returned water does not contain more than 4% dry matter.

As mentioned above, the invention also relates to an apparatus for carrying out the above-mentioned method and this apparatus comprises: an element for forming fibres, means for producing one or more gas streams which transport the fibres, means for introducing a finely dispersed liquid binder mixture in the gas stream carrying the fibers, a receiver element on which the fibers are collected in the form of a mat and separated from the gas stream,

possibly means for treatment, especially thermally, of the fiber mat and transformation of the mat to obtain it in its finished form,

chambers (or channels) (5, 9, 11, 17, 18, 22) which carry the gases passing downstream from the receiver element, and/or gases from treatment or conversion of the fiber mat, means for atomizing water in these chambers (or channels) in the flow path of the gases, and the apparatus is characterized by the means for atomizing the water comprising at least two pipes which are designed and directed so that compact, converging jets of water are formed which, upon collision, form an area of atomized water that lies across the flow path of the gases.

In the apparatus according to the invention, the means for atomizing water are made up of at least one injector comprising two converging jets.

The injector is placed in the chamber (or channel) which transports the exhaust gases, so that the layer of water produced extends across the direction of flow of the gases and preferably in a direction essentially orthogonal to this path.

The injector comprises two tubes whose axes are in the same plane. Mouthpieces for calibrating the emitted rays are attached to the "free" ends of these tubes.

The tubes and mouthpieces are preferably cylindrical in shape.

To provide identical rays that, like that

is described above, is the preferred case, the tubes and nozzles are of identical size and shape and the distance separating these from the point of convergence is the same for both jets.

Due to the power of the jets, the injector's pipe is subjected to a significant impact of force. In order to rigorously maintain the geometrical conditions that are initially defined, the tubes are preferably mounted stationary on a rigid plate.

This plate also serves as protection against erosion that can develop in the immediate vicinity of the injector when, due to its construction, the latter leads a large amount of water directly against the wall on which it is fixed.

j The injector is preferably located close to a wall in the chamber or channel. The gas flow is thus not disturbed. Preferably, the injector is attached to the wall so that only the pipes project into the gas flow path. It is even possible that the pipes

placed in a house, shielded from the wall, where only the rays pass through openings for this purpose.

Depending on the circumstances, one or more reflectors may be placed upstream of and near the injector to directionally correct the projection of water when the operation of at least one of the jets is temporarily disrupted.

Considering the outlet conditions stated above, injector nozzles according to the invention usually have an opening of more than 8 mm and more frequently between 8 mm and 17 mm.

As explained, each injector can provide a large surface layer capable of covering the entire cross-section of the chamber or channel. However, it is generally preferred to use several injectors where each forms a layer that covers part of the cross-section and where adjacent layers partially overlap each other.

Under the present conditions of dimensions for installations, it is advantageous to place an injector where each has a surface area of 2.5 m 2 .

In order to extend and/or complete the treatment according to the invention, it is possible to carry out several atomisations at intervals along the flow path of the gases.

For this purpose, injectors are placed at different levels in the chamber (or in the channel).

The installation also contains equipment for separating water carried away by the gases. These apparatuses are advantageously of the cyclone type. This separation can be facilitated by supporting the coalescence of droplets among themselves.

For the removal of the finest droplets, coalescence accelerators can be used,

Several separation systems can be used together, and a special combination consists of a cyclone followed by an ultrafiltration apparatus.

The water that is separated from the gases is usually sent to a decantation tank and/or to filters to remove at least part of the entrained solids. It is also possible to incorporate a decantation column into the installation.

Other equipment for treating the water can complete the whole thing.

The invention shall be described in greater detail below with reference to the accompanying drawings in which: Figure 1 is a schematic view of part of an apparatus for treating gases originating from a fiber manufacturing apparatus,

Figure 2 is a schematic perspective view of the washing zone downstream of the fiber collecting element,

Figure 3 is a schematic perspective view of a method for carrying out the gas washing according to the invention, applied to an apparatus for treating fiber mats such as

.?n oven,

figure 4 is a schematic view corresponding to that in figure showing another arrangement of the washing equipment,

figure 5 is a partial cross-section of the apparatus according to figure 4, which shows in detail the connections between the chamber for treating the mat and the means for washing the gases,

Figure 6 is a particular embodiment of an injector

I up f i nne l sen .

Figure 1 represents the apparatus in which the steps are carried out which result in the formation of fibers and of the mat. A series of chambers and channels through which the gas coming from the receiving surface is circulated is arranged during this installation.

The apparatus for the production of fibres, e.g. of the centrifuge type, is shown at 1. This apparatus provides a ring of fibers whose drawing is completed by a downwardly directed hot gas ring stream or jet. The combination of this jet and the induced air currents from the surrounding atmosphere is directed towards a hood with movable walls 2. A fiber-receiving surface 3 is arranged in the lower part of this hood along the entire width, e.g. consisting of a perforated conveyor belt.

A binder preparation is atomized in the fibres' flow path between the fiber production element and the receiving surface, the tube atomisation devices are shown at 4.

Below the receiving surface is a first chamber 5 with a pressure which is somewhat reduced in relation to the pressure in the cap. The gases pass from the hood through the fiber mat 6 and the receiver surface to the chamber 5.

Collisional beam injectors 7 are located on the walls

of the chamber 5 directly below the receiver element.

The different characteristics of the injectors 7 are chosen so that the layer of droplets extends over the entire cross-section of the chamber 5 and completely saturates the gas mass.

The chamber 5 is connected to a chamber 9 by means of a passage 8. The presence of the passage 8 with a smaller cross-section gives an acceleration of the gases and favors a redispersion of water flowing down from the walls of the chamber 5 and thus completes the washing effect.

The gases that enter the chamber 9 move more slowly, and large drops in suspension fall out, and the water is evacuated through a pipeline 10.

The washed gases are directed through a channel 11 towards a separation apparatus 12 of the cyclone type. Fine entrained droplets are deposited in this cyclone, and these are recovered in the lower part, while the purified gases escape through the upper part through a fan 13.

It is this fan which ensures the maintenance of a reduced pressure in the chamber 5 and the movement of the gases through - this part of the apparatus which is located downstream of the fiber receiver element.

When very fine droplets are present in the gases, it will possibly be advantageous to complete the separation by passing

the gases through an ultrafiltration apparatus shown at 14"

In the diagram described above, they are used

gases released to the atmosphere.

However, it is also possible, as described in FR-PS

2 247 346, 2 318 121 and 2 368 445, to recycle a part of the used gas. In this case, e.g. the recirculated gas at the outlet of the fan 13 and is recirculated to the chamber where the fiber production is carried out.

Water that is recovered at various points in the system is fed to the decanting vessel. The composition of the system of water pipes and water treatment devices is not shown in the figure.

A total apparatus usually comprises several fiber production apparatuses arranged along a common device for supplying material to be fibred. The transport belt 3 which makes up the receiving element is located in the longitudinal direction below the series of devices. In order to ensure circulation of the gases, it is usually desirable to arrange several units, as described above, comprising chamber 5, chamber 9, cyclone 12, ventilator 13, etc., this essentially to take into account the capacity of commercially available elements .

Figure 2 shows in greater detail the shape of the apparatus represented in Figure 1, at the washing level.

This presentation is limited to the elements in connection with a single chamber 5. This chamber 5 forms part of a series of corresponding chambers which extend along the production line.

Arrangement of the washing injector 7 is indicated on it. longitudinal wall of the chamber 5.

The four injectors 7 are arranged two by two in a symmetrical relationship and in the upper part of the chamber, i.e. close to the not shown conveyor belt.

The base of the chamber is sloped to facilitate the downward flow of water.

The chamber 5 and the adjacent lying chamber 9 are connected along the entire length. The connecting zone consists of passage 8.

The bottom of the chamber 9 is also beveled. The bottom bottom part consists of a collector 15 which receives the water and leads it to the pipeline 10.

Gases that cross the chamber 9 are led through the channel 11 and from there towards the separation apparatus, not shown.

The diagram in Figure 3 shows an apparatus including the chamber for evacuating and washing gases arising from an apparatus for treating fiber mat.

This equipment is e.g. an oven for curing the resin pix that make up the binder. There can also be a fitting for cooling by circulating air at room temperature. It can also be an apparatus for extracting formed dust particles, e.g. from cutting the fiber mat. In all or some of these treatments, a gas stream is formed which is saturated with polluting elements.

The treatment is carried out in a closed chamber 16 of which only a part is shown. The fiber mat 6 passes through this chamber. For the sake of simplicity, the treatment agents are not shown. E.g. in an oven, there are devices that provide a forced circulation of hot gases through the mat. Such an apparatus is specifically described in FR-PS 2 394 041.

The polluted gases formed during the treatment pass from the chamber 16 to a direction-changing chamber 17 which is located in the upper part of the chamber 16 and then to the washing chamber 18. To show this better, the front wall of the means that conduct the gases has been removed.

The positions of the two injectors 7 with converging jets are indicated in the upper transverse wall of the washing chamber 18. These injectors are arranged so that the layers of droplets are formed across the path of the gases. Optionally, deflectors such as the one shown in Figure 6 can prevent washing water from being thrown in the direction of the chamber 17.

Of course, the location and characteristics of the injectors used in such an apparatus are chosen by the user as a function of the specific conditions of the washing to be carried out.

The bottom of the washing chamber is made with an inclined wall 19 which directs deposited water towards the collector 20.

At the outlet of the washing chamber, a narrow cross-section 21 envelops and accelerates the gases which then expand to the connecting line 22. This line 22 leads to the separator 2 3 of the cyclone type.

Water that is separated in the cyclone 23 is removed through the collector 24.

In addition, the apparatus comprises a fan which is not shown and, depending on the circumstances, supplementary filtering devices.

In Figure 4, certain sides of the apparatus have been removed to better show the relative position of the various elements.

The apparatus according to figures 4 and 5 corresponds to the previous one, however, the gas outlet from the treatment chamber through the outlet holes 25 is this time placed on the side walls of the chamber 16.

Collars 26 enter the interior of the direction-changing chambers 17, placed on either side of the chamber 16. Each of these chambers 17 is connected to a washing chamber 18. The two chambers 18 are connected above the chamber 16. From these chambers, the washed gases escape out through the common channel 27.

On each washing chamber there are points 7 for two colliding jet injectors. In this apparatus, as in the previous one, the injectors are arranged so that the layer of droplets extends across the gas flow.

The dispersed water is made to flow along the inclined wall 19 which forms the bottom of the washing chamber and runs

down the walls of the chamber 17 and escapes through the collector 20. The flanges 26 separate running water from the inlet to the gas stream of the chamber 17.

Other arrangements for the discharge of the gases from the treatment chamber may be considered. In particular, it is possible for certain embodiments to release the geese at the bottom of the chamber. In this case, the washing device can be arranged in the manner described with reference to Figures 1

and 2.

Figure 5 shows in particular the downward inclined position of the claims 26 which are intended to prevent the supply of water to the chamber 16. Figure 6 shows a cross-section of an injector according to the invention.

The injector consists of two cylindrical tubes 2 8 which have calibrating nozzles 29 at the ends. The ends of the tubes 28 are threaded, and the nozzles are screwed on.

The pipes 2 8 are soldered to a plate 30 which forms a wall of the feed chamber 31. The wash water is led to this feed chamber through the pipe line 32. The entire assembly of the chamber 31, pipe line 32, pipe 2 8 and nozzle 2 9 is arranged in a strictly symmetrical manner , so that the formed beams are identical.

The plate 30 which carries the pipes 28 is fixed on a second protective plate 33 fixed to the wall 34 and prevents the latter from being ground off.

A gasket 36 ensures tightness between the plates 30 and 33. The means for fastening these plates together are not shown. They can e.g. screwed together.

The plate 30 carries a conical deflector 35 which "wraps" one of the injector tubes to prevent propagation of the opposing jet when the "wrapped" jet is accidentally disturbed.

As shown above, this arrangement is particularly useful when the injector is located near the fiber receiving element and when it is beneficial to protect the mat formed from possible contact with water.

When the collision between the jets is temporarily interrupted, the jet that is not "wrapped" strikes the deflector 35. Of course, the injector is arranged so that the deflector is on the side of the installation that requires protection.

Example_el_1_

The configuration of atomized layers of water was studied in preliminary samples.

A series of measurements of the opening angles for the layer

which had for of a circular sector was thus demonstrated to be a function of the angle between two identical rays.

The measured values were as follows:

The outlet values obtained for nozzles of 16 mm and

5 3

8x10 Pa amounted to 50m per hour.

5 For nozzles up to 16 mm and a pressure of approx. 6 x 10 Pa under an angle of 120° was the drop layer that formed over 90 m<2>.

Example 2

The washing according to the invention is used in a washing chamber and in the second following chamber, downstream of the fiber receiver conveyor in an installation for the production of fiber mats.

Previously, 13 spoon- or spatula-like atomizing elements were placed in the washing chamber and 16 in the next lying chamber.

These are replaced by two collision beam injectors on

the opposite walls of the washing chamber directly below the conveyor (75 cm below this) and two in the second following chamber which by means of channels led the gases towards a cyclone.

The cross-section of the washing chamber under the conveyor

was approx. 7.5 m.

The amount of gas passing through the wash chamber was

3 3

about. 54 x 10 m per hour.

The injectors placed in the washing chamber had nozzles with a diameter of 16 mm and the injectors placed in the next chamber had a diameter of 11 mm.

The water pressure was 5x10 Pa.

The beams are directed towards each other at an angle of 120°.

The water used was recycling water which contained in the order of 2.5% by weight of dry matter.

3

In the washing chamber, the outlet was ground to approx. 36 m per

hour for each injector. It was 18 m 3 per hour for each injector in the second following chamber and thus a total of approx. 108 m 3 per hour, i.e. a quantity comparable to what was previously used with the conventional nebulisers.

No difficulties occurred during a year of continuous operation. No interruption of operations was necessary. The injectors were never clogged. The wear on the nozzles was negligible. As for the diameter, it was less than a tenth of a millimeter.

The walls of the washing chamber, the next chamber and the channels were completely clean.

Example_<e>l_3

Following the results obtained and which are indicated in example 2, two total production lines for fiber mats were equipped with a system for washing with colliding jets.

One line comprised 8 centrifuge fiberization elements

which gave a total of 140 tonnes of fibers per day, and the reception of the exhaust gases under the conveyor belts was ensured by four washing chambers.

The total volume of gas that passed through these washing

3 3

chambers were of the order of 288 x 10 m per hour.

18 collision jet injectors are placed in the wash chambers and the next following chambers. The 18 injectors are identical. The angle of the rays was 120°. The diameter of the nozzles was 13 mm and the water pressure 5 3 5 x 10 Pa. Each injector provided approx. 26 m per hour, a total of 3

46 8 m per hour.

These 18 injectors were installed in this installation to replace 139 spoon-like atomizing devices.

After more than 6 months of continuous operation, an examination of the installation showed complete cleanliness of the entire circuit for the gases, especially the washing chambers, the channel, the cyclone separators and the fans. With the previous washing devices, a systematic stop was necessary every six weeks.

Claims (27)

1 t Procedure for washing exhaust gases in connection with the production of mineral fiber mats in which: fibers are produced and fed using gas streams to a receiver element where they are collected and separated from the carrier gas, finely divided liquid binder preparation is fed into the gas stream that carries the fibers upstream of the receiver element, the fiber mat is optionally treated , especially thermally, for adhesion of the binder and undergoes transformations leading to the finished form, water is atomized in the flow path of the gases that have carried the fibers, downstream of the receiver element; and/or in the flow path for the gas from the treatment step for adhesion of the binder and/or from the conversion step of the fiber mat, characterized in that the water, which may possibly be recycled, purified water, is atomized by collision between compact jets. 2. Method according to claim 1, characterized in that the jets are arranged so that the layer of water that is dispersed extends across the flow path for the gases. 3. Method according to claim 1 or 2, characterized in that the collision is effected between jets in one or more pairs of identical jets to produce one or more essentially planar layers of droplets. 4. Method according to any one of the preceding claims, characterized in that the pair of jets or pairs of jets are selected so that the layer or layers of dispersed water droplets cover the entire cross-section of the gas passage. 5. Method according to any one of the preceding claims, characterized in that the water dispersion is effected on flowing gas with an average speed of less than 10 m per second. second. 6. Method according to any one of the preceding claims, characterized in that the amount of water in which is dispersed is between 0.5 and 2 m 3 of water for a gas volume of 10 m . 7. Method according to any one of the preceding claims, characterized in that the angle between converging rays is greater than 30°. 8. Method according to claim 7, characterized in that the angle between the beams is between 80 and 130°. 9. Method according to any one of the preceding claims, characterized in that the dispersed water is fed under a pressure of between 3 and 6 x 10^ Pa. 10. Method according to any one of the preceding claims, characterized in that the outlet of in water which is dispersed in the chamber (or channel) per cross- average area unit and per hour is between 2 and 20 m 3 per hour 2 per m. 11. Method according to any one of the preceding claims, characterized in that the dispersion of water is effected immediately after the exhaust gases enter into the evacuation circuit. 12. Method according to any one of the preceding claims, characterized in that the dispersed water is first separated from the gases and subjected to one or more work steps in order to remove at least part of the products which is dispersed in the water and that the water is reused for new washing steps. 13. Method according to claim 14, characterized in that the water that is separated from the gases is filtered to remove at least a proportion of entrained solid products, the recycled water not containing more than 4% dry matter. 14. Apparatus for washing exhaust gases in connection with the production of a mineral fiber mat comprising: an element (1) for forming fibers, means for producing one or more gas streams which transport the fibers, means (4) for bringing a finely dispersed liquid binder mixture into the gas stream carrying the fibers, a receiver element (3) on which the fibers are collected in the form of a mat (6) and separated from the gas stream, optionally means for treatment, especially thermally, of the fiber mat and transformation of the mat to obtain the in its finished form, chambers (or channels) (5, 9, 11, 17, 18, 22) which carry the gases passing downstream from the receiver element, and/or gases from treatment or conversion of the fiber mat, means (7) for atomization of water in these chambers (or channels) in the flow path of the gases, characterized in that the means (7) for atomizing the water comprise at least two pipes (2 8) which are designed and directed so that compact, converging jets of water are formed as in collision forms an area of atomized water that lies across the flow path of the gases. 15. Apparatus according to claim 14, characterized in that the tubes (28) have nozzles (29) which calibrate the jets, and that the tubes (28) and the nozzles (29) have a circular cross-section. 16. Apparatus according to claim 14 or 15, characterized in that a pair of identical tubes (28) with nozzles (29) are arranged with converging axes, the distance separating the mouth of each nozzle from the convergence point for the axes being the same. 17. Apparatus according to any one of claims 14 to 16, characterized in that the tubes (28) are located on a plate (30) which is in turn attached to a wall in the chamber (5, 18) (or channel), whereby only the tube (28) and the nozzle (29) project from the wall into the interior of the chamber. 18. Apparatus according to any one of claims 14 to 17, characterized in that the pipes (28) and nozzles (29) are located in the shelter of the wall surface, so that they do not constitute any obstacle to the flow path of the gases. 19. Apparatus according to claim 17, characterized in that a deflector (35) arranged upstream of the pipes and nozzles constitutes an obstacle to random blowing of water against the gas flow. 20. Apparatus according to any one of claims 15 to 19, characterized in that the nozzle (29) has a mouth diameter of over 8 mm. 21. Apparatus according to any one of claims 14 to 20, characterized in that in order to form a layer of dispersed water, a pair of pipes is arranged for each surface cross-section of 2.5 m 2 . 22. Apparatus according to any one of claims 14 to 21, characterized in that several pairs of pipes are placed at the same level in the chamber (or channel) to form several partially adjacent water layers. 23. Apparatus according to any one of claims 14 to 22, characterized in that the means (7) for treating gases downstream of fiber receiver elements (3) are placed as close to this element as possible, but without the risk of wetting the fibers that make up the mat (6 ). 24. Apparatus according to any one of claims 14 to 23, characterized in that a zone of reduced cross-section (8, 21) is placed in the flow path of the gases downstream of the water dispersion zone in order to accelerate the gases. 25. Apparatus according to any one of claims 14 to 24, characterized in that it comprises a collector (15, 20) placed in the bottom part of the zone in which the dispersion is carried out, to receive and remove deposited water. 26. Apparatus according to any one of claims 14 to 25, characterized in that the downstream chambers (5, 18) (or channel) in which the water is dispersed contains a separation system (12, 23) for the finest droplets entrained by the gases . 27. Apparatus according to claim 26, characterized in that the separator (12, 23) consists of a cyclone.