CA1185431A

CA1185431A - Washing process and apparatus used in the manufacture of mineral fiber mat

Info

Publication number: CA1185431A
Application number: CA000400388A
Authority: CA
Inventors: Guy M. Baduel
Original assignee: Saint Gobain Isover SA France
Current assignee: Saint Gobain Isover SA France
Priority date: 1981-04-02
Filing date: 1982-04-02
Publication date: 1985-04-16
Also published as: ES8302609A1; FI821117L; YU43513B; ZA822114B; MX156142A; KR830010010A; YU72182A; IE52743B1; FR2503134A1; TR21600A; FR2503134B1; KR880002702B1; JPS57177322A; DK158613B; FI821117A0; ATE15025T1; JPH0247250B2; AR227584A1; NZ200123A; ES511043A0

Abstract

ABSTRACT

The invention relates to a process and apparatus for washing the effluent gases arising from the manufacture of fiber mat.

The washing according to the invention is achieved by water dispersion by means of a collision jet apparatus.
This dispersion is effected on the effluent gases starting from their entry into the evacuation circuit. With respect to an installation for the formation of the fibers and their reception, the collision jet injectors (7) are placed directly under the receiving element (6). The water dispersed in the gases is separated from the gases in 9, 12 and 14.

Description

W~SHING PROCESS AND APPAR~TUS USED IN T~
M~NUFACTUI~E OF MINERAL FIBE~ ~T
.
~CKGROUND AND_ STi.~TEMENT OF OBJECT8 ~he invention relates to the washing implemented in S the manufacture of mineral fiber mats, and more precise-ly, to the washing carried out on the path of the effluent gases issuing from this manufactureO

The manufacture of mineral fiber mat, or similar pro~
. ducts, comprises a series of operations, and especially:
- the formation of fibers, - their advancement to~ard a receiving element by means of gas current~, -- the sizing of the fibers by means of a binder, by projection of the latter, in the form of a finely divided composition, on the path of the fibers between their pro-duction and the receiving element, - the formation o~ the mat on the receiving element~
cus~omarily constituted by a perforated sopport, - the separation of the fihers and the carrier ga~
currents by passage of these gases across the receiving element, and the evacuation and/or the recycling of th~
gases recovered downstream of the receiving element, ~ the treatment of the fiber mat, coated with bi~der, to adhere this binder, possibly follow~d by a cooling stage, and the evacuation of the gases issuing from the adhesion treatment of the binder and from the cooling gases, - the transformation of the mat resulting in the fl-nished form of the product, and the collecting and evacu-ation of the saturated air arising ~rom thls transformation.

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~egardless of the mode of pruduction of the fiber~
and the type of binder used, the efluent gases can be ne~-ther recycled nor evacuated without minimal treatment be-cause of the polluting elements which they entrain.
.~
Among the polluting elements, those which come from the binder are particularly troublesome. In particular, these are fine droplets which were not retained in the fiber mat, or gaseous products escaping from the binder compo-sitions. They are also the degradation products which can be emitted when the binder is placed in contact with the fibers at high temperature.

Of course~ fibers not retained by the receiving element, or which are pulled up from the mat during the transforma-tions resulting in tbe finished product, are added to these ~, pollu~ing elements.

These elements are troublesome for several reasons.
In particular, the binder droplets and vapors rapidly soil the walls of the installations and ducts which convey the effluent gases. In effect, they tend to form adhesive deposits which retain the entrained fibers or fiber fragments. The reconditioning of the installation therefore requires the periodic removal of these deposits. In addition to the stoppages which they cause, the reconditioning operation~
are quite laborious. Tbe result i8 an appreciable iDcrea~e in production cost3.

The firqt treatment carried out on the ef1uent gases is ordinarily a water atomi~ation for the purpo~e of coollng _ ,1' .. . . .

.' ~L1~5~3~ ' and initially removlng the maximum amount of polluting ele~
ments. sy means of this atomization, in particular, ~n effort is made to remove as much binder a~ possible in order to prevent the fouling of the installation which is known to constitute a significant problem in this type of manu-facture.

~owever, the effective implementation of this water atomization causes some difficulties.

A first difficulty is associated with the extremely large quantity of gas ~irculating in these installations and, consequently, with the dimensions of the installation~
themselves in which these operations must be conducted.
In French patent ~o. ~,247,346 some values of gas volumes are indicated, characteristic of different modes of fiber production. These values are on the order of 0.1 ~ 106 to 1 x 106 m3/hr. of effluent gas for the operations re-sulting in the formation of mat. ~s will be seen, it ~s 7 difficult to obtain a fine, homogeneous dispersion on 3uch large volumes while using the traditional techniques in this domain.

A second difficulty, concerning the effluent gase~
arising from the formation of the fibers, comes from the need to prevent the formation of deposits on the path of the gases as soon as the gases have crossed over the fiber receiving element~ In effect, the deposits ~hich are formed directly under this receiving element can modify the passage sectLon of the gases and, consequently, the progres~ion of these gases across the mat being formed.
Such a modification interferes with the homogeneity of the ., ,, .. . . , . , . , . ~ . . , ~ . . .. . . .

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~iber mat, To prevent the formation of these deposi s, it i8 de sirable to effect the washing very close to the receiving e3ement which constitutes a supplemental constraint slnce the fiber mat ~ormed must not be reached by ~he water pro-je!cted during this washing operation.

A third difficulty comes from the fact that the ~ater used, which becomes saturated with polluting elements, can-not be discarded. Therefore, it is customary to recycle it, after it has been cleansed of a portion of the entralned polluting elements. In order for the ~ost to be acceptable, tbe operation (or the operations) aiming to rid the wat~r of its pollutents must be relatively simple. For example, it could involve a summary filtration or a similar opera-tion. At the end of this treatment the recycled water or~
dinarily still contains a substantial quantity of m~terials ~, in suspension and of stable or unstable dissolv~d products.
It:s use in the conventional atomizing apparatus thesefore poses problems, in particular, of obstruction or erosion-corrosion.

Conventionally, the atomization of the water is effected under pressure by passing the water through nozzles of small dimensions. For the use considered, this method suffers several disadvantages. Fir t, the quantity of water distributed through each atomizing nozzle and the e~panse C
effectively treated by this atomization are very limited because of the very dimension of the nozzle. Of course, it is possible to increase the number of nozzles accordinglyO
Neverth~less, It Is dl,f1colt to ttaln ~ p~rfeot contlnu-. ., . ~ . . , ~

S~3~ , i~y and a good homogeneity of the layer of water droplet~
throughout the entire space neces~ary. In practice, even with a greater number of nozzles of this type, it is not possible to effectively treat all of the gas stream and~
consequently, to prevent the formation of deposits o~l eh~
walls of the chamber or the ducts.

Secondly~ because of the nozzle dimensions, frequent blockings are produced, and this all the more because the recycled water is more saturated with polluting elements.
Therefore, even a good distribution of the nozzlas in the atomi~ing area could not guarantee a continually homogeneous atomization~ These nozzle blockings require, besides, frequent interventions for reconditioning.

In an efort to overcome the difficulties, the con-ventional nozzles were replaced by apparatus in which tbe water dispersion is no longer obtained by passage under J, pressue through small cross section delivery tubes, but by projection on a concave, curved element ~a sort of 5poon or spatula). The jet, directed on this element, form~ a liquid layer which widens and bursts into a multitude of droplets.

This mode of atomizing provides a considerable increa~e in the output from each jet. Howaver, the formation o~
very fine droplets is only possible for relatively low out-puts Furthermore, there is rapid wearing of the elemant providing the water dispersion. In a few hours it loses its poli~h in the path of water saturated with abrasive particles. Next, wlthin several days, a phenomenon of _ .. . . .

5~31 erosion corrosion under these conditions causes the deforma~ ; ~
tion of the dispersion element which then becomes le s efficient, The replacement of these elements, in the typical ca~e, must be undertaken after two weeks of continuous operation.

One object of the invention is to provide a water atomi-zation under conditions which prevent the formation of depos~ts on the walls of the chambers and the ducts used by the effluent gases of the manufacture of mineral fiber mat.

Another object of the invention, concerning the part 10 of the installation located directly under the fiber re-ceiving element, is to provide a cleaning of the walls i~ediately below the receiving element, witbout discontinuity, and without the atomizing water reaching this çlement.

Another object of the invention is to provide an extremely 15 homogeneous water dispersion in the chambers and ducts conveying these effluent gases, even ~hen they are of large dimensions.
, Another object of the invention is to provide a good efficiency of removal of the polluting products carried by the effluent gases.

Another object of the invention is to implement means enabling the atomization of water, even that saturated with abraslve particles, without the operation of said means being substantially modified after a prolonged usage.

Another object of the invention is to implement means enobllng atomization oE ~=ter acoldentally saturated tith .

, . , ., . . , . , 3~ 1 relatively voluminous corpuscles without ri~king blockag~
of the atomizing me~n~.

Another object of the invention is to be able to extena ~he application of the same washing means to all the efflu-ent gases arising from the manufacturing process described abo~e.

BRIEF SUMMARY OF THE INVE~TION
.

These objectives are attained by the invention of which ona object is a process for manufacturing mineral fiber mat, such as indicated above, and in which water is dispersed on the path of the e~fluent gases by collision of two jet~
directed ~oward each other.

The atomization by collision of jets is known essen-tially for dispersing combustible liquids in combustion 1~ chambers of motors. In these applications the output of liquid is relatively small and the dispersion is realized in a gas at high speed (of on the order of 30 m/s~.

It has also been proposed to atomize water by jet colli-sion in the neck of a venturi-type apparatus, this assembly being intended to remove the fine gas likedust from blast furnaces after the latter have sustained a first washing.
In such application, the dispersion ls effected in a gas, attempted to be maintained at high speed, and at a locatlon where the passage cross section i~ narsow.

The dispersion of water by jet colli~ion accordlng to the invention is distinguishable from the~e prio~ ap-. _ . , . . , . , . . , . . .. ~ .

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plications by the environment ~n whicb this technique is used~ as well as by the objectives pursued or, a~ i9 mors fully described below, by the condi~ions of implementation.

The studies which led to the invention showed that by the collision of two jets it is possible to develop an expanded layer of droplets in comparison to those produced by the conventional means. A dispersion on large surface~
i~ obtained, without discontinuity in the spatial distribu-tion of the droplets. $his represents a real advantage with respect to the prior modes of atomization.

By operating in the manner proposed by the invention~
even when the treatment is carried out in very large chambers, it is possible to use only a small number of dispersion apparatus. By a suitable choice of parameters for the col-lision jets and their location, the entire cross sect~on of the chambers, for ~he installations of the type considered, is covered ~ithout difficulty.

Ordinarily the form of the layer of droplets developed does not correspond exactly to that of the chamber section, and a portion of the water is projected on the walls.
The wall in the impact zone of the droplets is in thls way "scouredn. ~o obtain this cleaning action of the walls, however, it is not necessary for the impact to be forceful.

Furthermore~ experience shows that the washing of the effluent gases by means of homogeneous water dispersion produced by jet collision leads to very clean walls, even beyond the impact zones.

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To some degree it is pre~erable to limit the impact force to prevent the ero~ion of the walls~ This is obtained by adjusting the form and expanse of the layer of droplets by modifying the operating conditions of the jets ln the manner described herebelow.

Several conditions determine the form and expanse o u the layer of droplets dispersed.

If the two jets are identical at their meeting point, that is to say, if they have ~he same characteristics of dimension, speed and output, the projection of the droplet~
is achieved in practically one plane. This plane is ortho-gonal to that of the jets and forms a plane of symmetry.
Gravity and the gases which pass through the layer of droplets distort this plane. Howev2r, for relatively low gas speeds and relatively high jet speeds, such as those implemented according to the invention, this distortion is reduced.
~or practical purposes, it can be considered that the layer is level.

In practice, it seems advantageous to have an initially level layer which covers the largest section, the other conditions of the jets being constant. Nevertheless, it is possible to use jets of different intensities ~output-speed). Layers are thus formed having the appearance of a more or less distorted paraboloid. Such an arrangement could appear advantageous when, for example, fos a given output of liquid the disperslon is effected in a chamber of which the dimensions are relatively small, and when it is desirable to prevent the liquid layer from hitting the walls~ In this case a deformed layer i8 attempted to be -10- ! -. , ,...................... : .
-developed, drawn in th~ longitudinal directlon of the cha~-be~ O

In all cases the jets, even different ones, have ch~-racteristics which remain on the same scale in order that the dispersion is satisfactorily produced.

The general form of the layer was determined experi-mentally as a function of the angle between the twô jets.
This study, made for two identical jets, shows that the layer is developed in circular form when the convergent jets are aligned, that i5, form an angle of 180~ between them. If the angle decreases, the layer of droplets tends to take the form of a circular sector of which the angle decreases at the same time that the angle between the jets decreases. In this last clse the center of the sector corres-lS ponds to the impact point of the jets~ ` \

It is preferable that the atomizing apparatus ~alsocalled an injector) not create an obstacle in the path of the gas. In other words, this apparatus is preferably close to a wall of the chamber, or of the duct, in which it is placed. Under these conditions there is a tendency toward seeking to obtain layers in the form of a sector of which the angle is close to 180 In order to cover the space up to the wall from whicb the atomi~ation is effected. It can even be advantageous to form a layer of which the angle is greater than 180, which also enables the wall on which ~' the injector is fastened to be sprayed~ Of cour~e, i the apparatus is situated near a corner, a smaller angle of I

. ~ . . .

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the layer ~ould be preferable. In this case the angle oP
~he jets is reduced to a smaller valueO
.
Following the description, examples of jet angles and tbe form of the corresponding layers are ~iven. In general use the angle between the jets is not less than 30 and peeferably is comprised between 60 and 130.

Of course, the layer is also developed with a certain thickness from the point of impact and on both sides of the initial plane. This thickness remains relatively small in relation to the other dimensions. Ordinarily it does not exceed a few tenths of centimeters. It is practically proportionate to the output and is smaller as the angle of incidence of the jets is larger.

Since the general form of the layer is mainly determined by the fact ~hat the jets are identical and by the angle between them, the expanse of the layer is a functiQn of the output and of the speed of the jets.

As has been seen, it is preferable to have suffic1ently large layers to prevent discontinuity in the distributiona Therefore, it would appear desirable to create a layer of dimensions such that the entire section is covered. ~his solution can effectively be adopted. Neverthele3~ the use of a single layer is not desirable in all cases.

One reason which can lead to using several layers come~
from the fact that, as was indicated above, the force o~
the water projection on the walls must preferably be limitedu If, to cover the entire surface, a single layer was developed .. . . . . . . .

~5~3~ il which virtually e%tended far beyond the limit~ of the chamber (or the duct), the water would be projected on the wall~
with superfl~ous for~e which could be harniful to the propar operation of the apparatus.

hnother reason is associated with the fact that for very large surfaces high yield jets should be used, which would be difficult to implement in industrial installations.

In practice, by the technique of jet collision used according to the invention~ layers of droplets of ~5 m~
of useful surface or more can easily be formedO For the reasons noted above it i5 preferable to form layers of which the dimensions are not the largest possible, and to make use of several injectors producing a series of layers being partially covered over.

The quantity of water which each pair of jets must yield depends mainly on the section of the gaseous stream and the wall surfaces to be sprayed. For the implementation of the atomizing according to the invention the yields cur-rently used are comprised between 10 and 80 m3 per hour.

The bursting of the jets into fine droplets is a func-tion of the collision force and therefore of the speed of the jets.

The speed, itself, is a function of the pressure exerted to create the jets. In industrial installation~ and fo~
significant yields, it is difficult to exceed pressures of on the order of 106 Pa. For the dispersion and propo~-tionment sought for implementation according to the inventlon ... . .. .

~ ~5~3~L `

.
pressure of on the order of 3 to 6 x 105 Pa i8 satisfactoy~

rrhe si~e 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 pre~sure, and consequently the greater the Çorce of the jets, the greater the tendency is to form fine droplets. ~owever, ~his varia-tion is relatively slow. In other words, large varlations in pressure only lead to a slight modification in the slze of the drops. When pressure of on the order of, or greater ~han,-2.5 - 3 x 105 is used, a certain percentage of extremely -fine droplets appears, that is, of which the dimension~
are less than 0.01 mm. In a certain way the presence of these very fine droplets can be favorable to the washing operation, particularly by assuring a very forceful contact 1~ Of the water and the effluent gases; however, the subsequent removal of these droplets~ before the release of the gases, can require supplementary separaticn operations.

The quantities of water used according to the inven-tion are on the same scale as those used in the prior ap-paratus. Because of the more regular distribution of the water in the gases these quantities can possibly be reducedO

For the atomizat}on of~water on the path of ehe ef-fluent gases from installations for manufac~uring fiber mat, it is ordinarily considered that a volume of wate~
of on the order of 0.5 to 2 m3 for 103 m3 oE gas give~ sat1 factory results. These values are obviously not imperative.
They are a function of numerous factors, and especially of the effluent gases, in particular, thelr binder content and the nature of the blnder, their temperature, but also --1~-- I ..

, , ,,,, , ~, .. . . . .. . . . . . . . .

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the quality of the water. In effect, for the latter lt should be taken into account that it is normally recycled after a more or less fosceful purification. The less th~
recycled water is saturated, the more effective is the trea~-ment and the less the quantity of water necessary.

The quantity of ~7ater used can also be related to the sec~lon of the chamber or of the canalization in which the dispersion is effected. Advantageously this quantity comprises between 2 and 20 m3/m ~hr. The output per unit of surfaca 1~ obviously depends on the output of effluent gases pass~ng through this surface.

According to another aspect directly related to the quantities just described, according to the invention it seemed preferahle to carry out the treatment at a point on the path of the effluent gases where the average speed of the latter remains less than 10 m/s, and even less than ~ -5 m/s. This is only a hypothesis but, it appears that P7hen the speed of the gas is slower, and consequently the time of contact with the droplets is longer, better exchanges occur between the gases and the water dispersed~

These preferred conditions of speed are ordinarily present, particularly at the beginning of the path of the effluent gases, whether this be in the chamber placed di-rectly downstream of the fiber receiving element, or whether this be from the emisslon of the effluent gases arising from other operations conducted on the fiber mat. S$nce it i8 SO much more advantageous, ~t is preferable to effect the atomization of water as soon as posslble in order to prevent tne deposits whlch could form upstr~am of thi~

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.:
atomizationO The atomization by ~et collision is, there-fore, preferably realized just downstream of the fiber receiving surface and/or directly at the ex~t of the chambers for treating and conditioning the fiber matO

While it seems preferable to proceed to the washing as soon as possible on the pa~h of the effluent gases, it can also be advantageous to repeat this washing at various points on this path. In fact, even if as a result of the qualities of the washing by jet collision the essential part of the pollutents present in the gases is recovered by droplets of the first layer, a certain quantity of water is carried along by the gases. This water J more abundant - when the dispersion is finer, is liable to be deposited on the walls along the path. If the gas is not saturated with moisture, then deposi~s can be formed, certainly les~
than in the first part of the path, but which neverthele~s can be troublesome. For this reason secondary washing~ _ can be joined with the principal washing, advantageously effected as the first by jet collislon.

2~ The water projected on the walls runs along the latter and is recovered below the chamber in which the atomizing is carried out.

The atomized water entrained in the effluent gaseR
is separated from the latter before their release into the atmosphere. Ordinarily a first separation is effected ~n the atomizing chamber. -The lacge3t drops, or those which are formed from sev- -eral droplet~, become ~epacated from the gases without any !

... , . . . . .. , . . . . . .. ~, .

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particular operation and are recovered in the lower part of the ayparatus with the water running down on the wall~.

For the very fine dropletR which are carrled along by the ga~es a traditional method for liquid/gas separation can be used.

The water recovered is advantageously recycled. Itis subjected, in advance, to the purification procedures customary in this environment. The minimum purification before recycling consists of decantation to remove at lea~t part of the solids in suspensionO

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

Regardless of the purification treatment(s) carried out, it is preferable that the recycled water contain no more than 4~ dry matter.

An object o the lnvention is also to provide an apparatu~
or equipment for implementing the process described above.

These apparatus for the manufacture of a mat of mineral fibers generally comprise the following element~:
- an element for the formation of the fibers, - means producing one or several gas currents conveying the fiber~, - means for the projection of a l~quid binder compo-sition, finely dispersed in the ga~ current carrying thefibers, ;17 5~3~ `

.

- a receiving element on which the fibers are collected to form the mat, and are separated from the gas curr~nt, - possibly means for the treatment, particularly ther-mal, of the fiber mat coated with the binder composition, and means for the cooling of the mat and the transfor~a-tions resulting in the finished product, - chambers (or ducts) conveying the gases downstream of the receiving element and/or the gases issuing from the treatment of the fiber mat, from its cooling or from the gases emitted during the transformations resulting in the finished product, - means for atomizing ~dater in these chambers (or ducts) in the path of the effluent gase~.

In the apparatus (or installations) according to the invention the means for atomi~ing the water are constituted by at least one injector forming two converging jet~.
-This injectoe is placed in the chamber (or the duct) con- ~;
veying the effluent gases so that the layer of water produced extends transversel~ to the path of the gases and preferably in a direction appreciably orthogonal to this path~

The injector contains two blast pipes of which the axes are situated in a same plane. Nozzles for calibrating the jets emitted are attached to the "freen extremity of these blast pipes.

The blàst pipes and the nozzles are preferably of cylin-drical shape.

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..

. . _ 33~ :

, To produce identical jets, which, as we have ~eenO
is the preferred case, the blast pipes and the nozzles ar~
of identical size and shape, and the distance separating the nozzle from the point of convergence is the same ~or both jet~.

The blast p~pes of the injector, due to the power o the jets implemented, are subjected to significant force.
To rigorously maintain the geometric conditions initially defined, the blast pipes are advantageously mounted sta-tionarily on a rigid plate.

This plate also serves as protection against the ero-sion which can develop in the immediate vioinity of the injector when the latter, by its structure, guides a large quantity of water directly on the wall on which it is fastened.

The injector is advantageously placed near a wall of the chamber or of the duct The gas flow is thus prevented from being disturbed. Preferably, the injector is fastened on the wall so that only the blast pipes project ;nto the path of the gases. It is even possible for the blast pipe3 to be placed in a housing, sheltered from the wall, with only the jets passing through the orifices contrived for this purpo~e.

Depending on circumstances, one or several deflectors can be placed upstream of and close to the in~ector to rec- c~
tify the projection of water when the operatlon of at lea~t one of the jets iB momentarily disturbed, --19-- ~

.. ....

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Taking into account the output conditions which were noted above, the injector nozzles according tc the invent~on customarily have an opening greater than 8 mm and more of ten comprised between 8 ~ and 17 ~, As it has been seen, each injector can produce a large surface layer capable of covering the entire section of the cha~ber or of the canalization. However, it is generally preferable to use several injectors, each one for~ing a layer covering a portion of this section, the adjacent layers partially overlapping.
.
Under the present conditions for dimensions of the installations it is advantageous to place an injector there-abouts for each sur~ace cross section of 2.5 ~2, To prolong and/or complete the treatment according \_ to the invention it is possible to carry out several atQmi-zat~ons placed at inter'i;als along the path of the gases.

For this purpose injectors are placed at various levels of the chamber [or of the duct~.

The installation also contains apparatus for separating the water en~rained by the gases. These apparatu~ are ad-vantageously of the cyclone type. This separation can be facilitated by encouraging the fusion of the drops between themselve~.

Por the removal of the finest drops traditional coaiescence accelerators can be used.

;20 ~85~3~

Several separation systems can be used together, one particular combination being constituted by a cyclone followed by an ultrafiltration apparatus.
The water separated from the gases is ordinarily conducted to a decanting tank and/or on filters to remove at least a portion of the solids entrained. It is also possible for a degassing column to be included in the installation.
Other apparatus for the treatment of water can complete the assembly.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is described in greater detail below b~ making reference to the sheets of drawings in which:
- figure 1 is a schematic view of part of an installation for the treatment of gases arising from the formation oE fibers, - figure la is an enlarged sectional view of the lower left hand portion of the installation shown in Fig. l;
- figure lb is a sectional plan view taken along line lb lb of Fig. la and showing the atomization pattern of the collision jets;
- figure 2 is a schematic perspective view of the washing 7one downstream of the fiber collecting element, - figure 3 is a schematic perspective view of a mode of implementation of gas washing according to the~invention, applied to an apparatus for treating fiber mat, such as an oven, - figure 4 is a schematic view similar to that of figure 3 showing another arrangement of the washing means, - figure 5 is a partial transverse section of the apparatus of figure 4 detailing the connections between the chamber for treatment of the mat and the means for washing the gases, - figure 6 represents a particular embodiment of an injector according to the invention.

,.. .

sd/~ -21-3~

Figure 1 represents the apparatus in which the operatlons are conducted resulting in the formation of the fiber~D
and then of the mat. A series of chambers and ducts, through which the ~as aspirated across the receiving surface circulate~, ls located under this installatlon.

The apparatus for the formation of fibers, for example of the centrifuge type is shown at 1. This apparatus produce-~a ring of fibers, the attenuation of which is completed by a downwardly directed hot annular gaseous blast or current.
The combination of this blast and the induced air currents from the ambient atmosphere is directed toward a hood with movable walls 2. ~ fiber receiving surface 3 i5 located in the lower part of this hood, along the entire width, formed for example b~ a perforated conveyor belt~

A binder composition is atomized in the path of the fibers between the fiber forming element and the receiving surface. The atomizing means are represented at 4O
.
Under the recei~ing surface a first chamber 5 is located, its pressure slightly reduced in relation to the atmosphere of the hood. The gases pass from the hood through the fiber mat 6 and the receiving surface and into the chamber 5~

Collision jet injectors 7 are placed on the walls of the chamber 5 directly below the receiving element.
c~
The characteristics of the injectors 7 are chosen so that the layer of droplets extends across the entire wid~h of the chamber 5 and totally saturates the gas mass.

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The chamber 5 connec~s with a chamber 9 by a pa~s~ge 8. The pre~ence of p~ssage 8, having a smaller cros~ sectlon, provides an acceleration of the gases and favors a redisper sion of the ~ater running down from the walls of the chamber 5, thus cGmpleting the washing effect.

The gases entering the chamber 9 slow up and the large droplets in suspension are precipitated with the water belng evacuated through a conduit 10.

The washed gases are directed through a duct 11 t~ward a separatin~ apparatus 12 of the cyclone type. In this cyclone the fine droplets entrained are deposited and are recovered at the lower part, while the purified ~ases which exit at the upper part are aspirated through a blower 13.

It is this blower which assures the m~intenance of ~`- .
a reduced pressure in the chamber 5 and the progression of the gases through the portion of the apparatus situated downstream of the fiber receiving element.

Possibly, when very fine droplets are present in the gases, it will be advantageous to complete the separation by passing the gases through an ultrafiltration apparatus, represented at 14.

In the diagram described above~ the gases used are released into the atmosphere. It is also possible, as described ~a ~
in French ~ tent~ar~unhrhho~ No. 2,247,346, 2,318,121 and 2,368,445, to recycle a part of the gas used. In this ca~e, the recycled gas is taken, for example, at the exlt of tha blower 13 and returned to the chamber where the fiber forma~ion -23~

...... ...

~s~
i5 carried out.
The water recovered at various points of the system is conducted to decanters. The assembly of the system of water conduits and water treatment means is not shown on this figure A complete installation usual]y comprises several fiber ~orming apparatus, aligned along a fore-hearth introducing the fiberizing material. The conveyor belt 3 forming the receiving element is placed longitudinally under the series of apparatus. To assure the circulation of the gases~ it is ordinarily desirable to place several units, such 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.
The gas washing or scrubbing arrangement of the installation shown in ~ig. 1 is shown in greater detail in Figs. la, lb an~ 2. Although these views illustrate the details with respect to a single scrubbing chamber S, it should be understood that the chamber 5 represents only one of a series of similar chambers extending along the production line beneath the conveyor 3.
As shown in Figs. la and lb and schematically in Fig. 2, the injector assemblies 7 are mounted on the ver~ical walls of the scrubbing chamber 5 in the upper part of the chamber close to the conveyor 3. The injector assemblies include pairs of blast pipes and nozzles 7 mounted in symmetrical relation, each pair being disposed with their axes in a common vertical plane extending transverse to the conveyor.
The blast pipes and nozzles communicate with a feed chamber or manifold 31 into which pressurized water is introduced by means sd/~ -24-~5~3~

of the conduit 32. For convenience of assembly, the blast pipes may be mounted on a demountable plate 30 which serves as a portion of the chamber wall.
The collision of the jets of water issuing from the injectors creates a sheet or layer of water 37 extending essentially horizontally across the chamber 5, the plane of the water layer being essentially perpendicular to the plane of each pair of nozzles. The injectors are angularly disposed to the vertical chamber walls so that the atomized water layer issues principally outwardly from the injectors to produce the atomizatlon patterns shown schematically in Fig. lb. A
portion of the atomized water layer impinges on the walls of the chamber and runs down the walls as shown in Fig. la creating a cleansing of the walls in the process.
In order to prevent any splashing of the collision jets from reaching the fiber blanket on the conveyor as well as to prevent any possibility of the lowermost jet spraying the conveyor in the event of malfunction of the uppermost jet, conical deflector plates 35 are fastened on the walls of the chamber above each pair of blast pipes but clear of the atomized water layer 37.
As shown in Fig. 2, the chamber 5 and the adjacent chamber 9 are connected along their length, the connection zone being formed by the passage 8. The bottom of the chambers 5 and 9 slope continuously toward the collector 15 to funnel the collected water into the duct 10.
The diagram cf figure 3 shows the apparatus including the chambers for evacuation and washing of the gases coming from an apparatus for treating fiber mat.
.~
.. ~

sd ~ -25-35~3~L

This apparatus is, for example, an oven for the hardening of the resins forming the binder. It can also be an assembly for cooling by circulation of air at room temperature. It can also be an apparatus for the aspiration of dust particles formed, for example, from the cutting of the fiber mat. In all these treatments, or similar ones, a gas current saturated with polluting elements is formed.
The treatment is effected in a closed chamber 16, only a part of which is shown. The fiber mat 6 passes through in this chamber.
For reasons of simplification, the treatment means ~, sd/~ -25a-35~3~

are not shown. In an oven, for example, there are apparatu~
providing a forced circulation of hot gases across the ~at.
Such apparatus are described in particular in French patent ~ ~s~?~k~h~ No. 2,394,041.

The polluted gases which are formed during the treat-ment pass from the chamber 16 to a direction changin~ chamber 17 placed at the upper part of the chamber 16, then into the washing chamber 18. To enable a better represeDtation, the frontal wall of the means conducting the gases is removed.

The positions of two injectors 7 with converging jets are indicated on the upper cross wall of the washing chamber 18~ These injectors are arranged so that the layers of droplets are formed transversely to the trajectory of the gases. Possibly, deflectors such as the one shown in fig-ure 6 prevent any projection of washing water in the direc-tion of ~he chamber 17. J' Of course, the number, the position and the characteri-tics of the injectors used in such an appara~us are selected by the user as a function of the specific conditions of the washing to be effected.

The base of the washing chambes is formed by an inclined wall 19 conducting the water deposited toward the collec-tor 20.
~"
At the exit of the washing chamber a narrow cross section 21 contalns and accelerates the gases whlch then expand into the connection conduit 22. This conduit 22 leads to the separator 23 of the cyclone type.

. ,, ,, . , . , .. . , . , , .. , , . , j 3~
., The water ~eparated in the cyclone 23 is evacuated through the collector 24.

In addition, the installation usually comprises a blowex not shown, and, depending on circumstanc~s, complementary filtration mean~.

on figure 4 certain sides of the apparatus are removed to better show the relative placement of tbe various el~-ments.
. .
The apparatus of figure 4 and 5 is similar to the pre-ceding one, however, this time the gases e~it from the treat-ment chamber through exit apertures 25 situated on ~he side .
walls of the chamber 16 Sleeves 26 enter into the interior of the direction changing chambers 17, placed on each side of the cha~ber 16. Bach o~ these cha~bers 17 connects with a washing cham-ber 1~. The two chambers 18 are joined above the chamber ~ -16. From these chambers the washed gases escape through the common duct 27.
..
On each washing chamber there are placements 7 of ~wo collision jet injectors. In this apparatus, as in the pre-ceding one, the injectors are arranged so that the layer of droplets extends transversely to the gas current, The dispersed wa~er is caused to flow on the inclined wall 19, forming the base of the washing chamber, running down on the walls of the chamber 17 and 1s evacuated through the collector 20. The sleeves 26 separate the running water .. . . . . . . ...

~S9L3~ `

.

from the entrance of the gas c~rrents into the chamber 17.

Other arrangements for the exit of the gases from the treatment chamber can be considered~ In particula~, it i~ possible for certain embodiment~ to evacuate the ga3e8 at the base of the chamber. In thi~ case the washing assem-bly can be arranged in the manner described with regard to figures 1 and 2.

Figure 5 shows, in particular, the downwardly incl~ned position of the sleeves 26 which is intended to prevent any introduction of water in the chamber 16.

Figure h represents a cross section of an injeotor according to the invention.
\~
This injector comprises two cylindrical blast pipe8 ~' 28 bearing on their extremities the calibrating nozzles 29. The extremities of the blast pipes 28 is threaded and the nozzles are screwed therein.

The blast pipes 2~ are soldered on a plate 30 which forms a wall of the feed chamber 31. The washing water is led to this feed chamber through the conduit 32. The assembly of chamber 31, conduit 327 blast pipes 28 and nozzle~ 29 is arranged in a rigorously symmetrical manner so that the jets formed are identical. C

The plate 30 supporting the blast pipe~ 28 iB a~te~ed onto a second protection plate 33 fa~tened on the wall 34, for example, by soldering. It i8 formed by a thick plate, . .

,, " . , . , . . _ , .. . . . ....

~L~85~3~

which directl~ receive~ the impact from the part of the layer of water directed toward tbe chamber wall, and pro-tects the latter from abrasion.

A joint 36 assures the tightness bet~een the plates 30 and 33. The means for fastening these plates together are not shown. ~hey can for example be screwed together.

The plate 30 supports a conical deflector 35 which "envelopes" one of the injector blast plpes to prevent the propagation of the opposite iet when, accidentally, the "enveloped~ jet is momentarily disturbed.

~s it has been seen above, this arrangement i~ parti-cularly useful when the injector is situated in the vicinity of the fiber receiving element and when it is advisable to protect the mat being formed from a possible projection Of water.

When the impact of the jets is momentarily interrupted, the jet which is not enveloped impi~ges against the deflector 35. 0~ course, the injector is arranged 50 that the deflec-tor is situated on the side o the installation requiring protection.

Example 1 The configuration oi the atomized layers of water was studied in preliminary te~t3.

A seriea of measurements of the opening angle of th~

~L8S9~3~

layer having the form of a circular sector were thus e~tab~
lished as a function of the angle between the two ldenti~sl iet~ .

These measured values are the following:
angle between the jets gor 100 108D 120 open ng angle of the 4~o 8Q 120~ 150~ 180 21CG

The output values obtained for nozzles of 16 mm and 8.105 Pa reach S0 m3/hr.

For nozzles of 16 mm and a pressure of about 6.105 Pa, under an angle of 120, the layer of droplets formed is greater than 90 m2 , The washing according to the invention is used in a washing chamber and in the adjacent chamher, downstream of the fiber receiving conveyor of an installation for form-ing fiber mat.

Previously, 13 spoon or spatula-like atomizing element~
were placed in the washing chamber and 16 in the adjacent chamber.

These element.s are replaced by 2 collision jet injectors on the opposite walls of the washing chamber directly below the conveyor ~5 cm below the latter) and two in the ad~acent chamber which, by means of duct~, lead the gases toward a cyclone.

4~

The cross sectlon of the washing chamber under t~e conveyor i about 7.5 ~2.

The quantity of gas passing through the washing cha~-ber i5 about 54.103 m3/hr.

The injectors placed in the washing chamber have nozzles of 16 mm in diameter; those of the injectors placed in the adjacent chamber are of 11 mm in diameter.

The water pressure is 5.10 Pa.

The jets are directed toward each other following an angle of 120.

The water used is recycled water which contains on the order of 2.5~ by weight of dry matter.

In the washing chamber the output measured is about 36 m3/hr. fox each injector. It is 18 m3/hr. ~or each injector in the adjacent chamber, therefore, a total of about 108 m3/hr.; that is to say a quantity comparable to that previously used with the conventional atomizers.

No difficulties appeared during the course of a year of continuous operation. No interruption of operation was necessary. The injectors never became obstructed~ The wear of the nozzles was negligable. For the diameter~ it was less than a tenth of a ~illimetera v The wails of the washing chamber, the ad~acent chamber, and the ducts were perfectly clean.

,,, . .... . .. . . , -.. ~, . .... .

Following the results obtained and which were reported in Example 2, two entire production lines of fiber mat were equipped with a system for wa~hlng by jet collision.

On a line comprising 8 centrifuge fiberiz1ng elemen~s producing A total of about 140 tons of fiber per day, the reception o~ the effluent gases under the conveyor belt is assured by four washing cha~bers.

. . .
The total volume of gas passing in these washtng cham-bers is of on the order of 288O103 m3/hr.

18 collision jet injectors are placed in the washing chambers and in the adjacent chambers.
\
Tbe 18 injectors are identical~ The angle of the jets is 120. The diameter-of the nozzles is 13 mm and the water pressure 5.105 Pa. Each injector yields about 26 m3~hr., a total of 468 m3/hr~

These 18 injectors were introduced into this installation as a replacement for 139 spoon-like atomizing apparatus.

After more than 6 months of continuous operationO an examination of the installation showed the total cleanliness of the entire circuit taken by the ga~es, particularly th2 washing chambers, the ducts, the cyclone separators and the blowers. With the previous washing means systematic stoppages were nece~sary about every slx weeks.

.....

Claims

The embodiments of the invention in which an ex-clusive property or privilege is claimed are defined as follows:

1. A process for the manufacture of mineral fiber material comprising the steps of attenuating mineral fibers;
coating the fibers with a finely divided liquid binder composi-tion; entraining the coated fibers in a downwardly directed gaseous current in a forming hood having a foraminous conveyor in a lower region thereof movable transversely across the fiber-laden current; collecting fibers in the form of a blanket on the conveyor, directing the gaseous current passing through the conveyor into a gas receiving chamber below the conveyor having a width substantially equal to the width of the conveyor; providing a plurality of pairs of convergent jets of a scrubbing liquid in said gas receiving chamber to produce a substantially planar sheet of atomized scrubbing liquid coextensive with the cross-sectional area of said gas receiving chamber and disposed immediately beneath said conveyor and parallel thereto to intercept the gaseous current flowing downwardly therethrough; and accelerating the flow of the gaseous current following its passage through the atomized scrubbing liquid by directing said current into an off-take passage having a cross-sectional flow area sub-stantially smaller than that of said gas receiving chamber.

2. A process according to claim 1, characterized in that the jets are arranged so that the layer of water dispersed extends transversely to the path of the gases.

3. A process according to claim 2, characterized in that the jet collision is produced between pairs of identi-cal jets to develop a substantially planar layer of droplets.

4. A process according to claim 1, characterized in that the water dispersion is effected on the gases flowing at an average speed of less than 10 m/s.

5, A process according to claim 1, characterized in that the quantity of water dispersed comprises between 0.5 and 2 m3 of water for a volume of gas of 103m3.

6. A process according to claim 3, characterized in that the output of water for a pair of convergent jets comprises between 10 and 80 m3/hr.

7. A process according to claim 3, characterized in that the angle between the jets of each pair is greater than 30°.

8. A process according to claim 7, characterized in that the angle of the jets comprises between 80 and 130°.

9. A process according to claim 1, characterized in that the water dispersed is conducted at a pressure com-prising between 3 and 6.105 Pa.

10. A process according to claim 1, characterized in that the output of water dispersed per unit of sectional area and per hour comprises between 2 and 20 m3/hr. m2.

11. A process according to claim 1; characterized in that the dispersed water is next separated from the gases and is treated to remove at least a portion of the products with which the water is saturated from contact with the gases and the walls of the chamber, and that the water is re-used for a new washing operation.

12. A process according to claim 11, characterized in that the water separated from the gases is filtered to remove at least a portion of the solid products entrained, the re-used water containing no more than 4% dry matter.

13. Apparatus for manufacturing mineral fiber blanket comprising means for attenuating mineral fibers, means for developing a downwardly directed gaseous current with the attenuated fibers entrained therein, a forming hood for receiving the fiber-laden current and having side walls in upright planes at opposite sides of the current and also having spaced end walls, a foraminous conveyor movable in a path in the lower region of the hood between said side walls in position to move transversely across the fiber-laden current and thereby collect fibers in the form of a blanket moving with the conveyor while permitting the gas of the current to flow through the conveyor, gas receiving chamber means below the conveyor and having a gas flow area of width substantially equal to the width of the forming hood, a gas flow off-take passage communi-cating with the gas receiving chamber means in a region spaced below the conveyor and of small cross-sectional flow area as compared with that of the receiving chamber means, and mechanism for subjecting the gas of said current to liquid scrubbing action after passage through the forami-nous conveyor and before entry into said region of small cross-sectional flow area, said mechanism comprising a plurality of pairs of blast pipes for delivering a scrubbing liquid, the pairs of pipes being mounted in the receiving chamber at a level spaced above said gas flow off-take pas-sage, the blast pipes of each pair being positioned adjacent to a boundary wall of the gas receiving chamber means and being directed at an angle toward each other substantially in a common upright plane perpendicular to the adjoining wall of the gas receiving chamber means, said plurality of pairs of blast pipes being positioned to produce an atomized sheet of the scrubbing liquid extended across the gas receiving chamber means in a plane extended substantially throughout the area of the underside of the foraminous con-veyor exposed to the gas receiving chamber means.

14. An apparatus according to claim 13, character-ized in that the extremities of the blast pipes bear nozzles calibrating the jets, and in that the blast pipes and the nozzles have a circular cross section.

15. An apparatus according to claim 14, character-ized in that the blast pipes and the nozzles of a same pair are of identical size and shape, their axes are convergent, and the distances separating the orifice of each nozzle from the point of convergence of the axes are equal.

16. An apparatus according to claim 14, character-ized in that the blast pipes are mounted on a plate fastened on a wall of the chamber, only the blast pipes and the noz-zles projecting through the wall into the interior of the chamber.

17. An apparatus according to claim 14, character-ized in that the blast pipes and the nozzles are situated adjacent the surface of the wall so as not to form an obstacle to the path of the gases.

18. An apparatus according to claim 16, including a deflector disposed upstream of the injection blast pipes to form an obstacle to the accidental projection of water countercurrent to the gases.

19. An apparatus according to claim 14, character-ized in that the blast pipe nozzles have an orifice diameter greater than 8 mm.

20. An apparatus according to claim 13, character-ized in that a separating system is provided downstream of the region of small cross-sectional flow area to remove liquid entrained by the gases.

21. An apparatus according to claim 20, character-ized in that the separating system comprises a cyclone.