CA1056568A - Gas blast attenuation with recirculation of gas and cooling thereof - Google Patents

Abstract

Abstract of the Disclosure:

Methods and equipment are disclosed for production of mineral fibers, by attenuation, involving the use of a substan-tial volume of gas, in which water is also employed at least in a fiber binder, the methods and equipment providing for recircu-lation of most of the gases, and preferably also of the water employ-ed in the system. Both the gases and the water are purified and the pollutants are separated and are also treated to convert the pollutant constituents to a from not ecologically objectionable for disposal. The methods and equipment also minimize discharge of fluids and aural efflux from the plant.

Description

GAS sLAsT ATTENUATION WITH
RECIRCULA~ION OF GAS AND COOLING THEREOF

The present invention is concerned with a process, and the devices for implementing it, which assures the suppression of harmful factors and permits the elimination of at least the majority of the ecologically objectionable pollutant elements--noxious or undesirable due to their toxicity, their odor, and their opaqueness--contained in the gas or liquid wastes discarded by installations manufacturing mineral fibers, and which also assures reduction of the noise produced by these same installa-tions.

The invention is concerned with installations for the manufacturing of fiber blanket, mat padding, or boards of mineral fibers and especially glass, agglomerated by thermosetting or th~rmoplastic binders, which coat the fibers and/or bring about close binding between fibers in the finished product.

The binders commonly used in this type of manufactur-ing have a base consisting of pure or modified phenoplast or aminoplast resins, since these present advantageous character-istics for the manufacturing of agglomerated fibrous products.
They are thermohardenable, soluble or emulsifiable in water, they adhere well to the fibers, and are relatively low in cost.

Generally, these binding agents are used dissolved or dispersed in water to which certain ingredients are added, in order to form the binder which is sprayed on the fibers.

Under the effect of the heat to which they are subject-ed during the fiber products manufacturing processesl these binders release toxic volatile elements having a perceptible pungent odor even at very weak concentrations, such as phenol, formaldehyde, urea, ammonia, and decomposition products of organic mateeials. ~

~565~8 Other binders are used for certain applications due to their very low cost. Certain extracts of natural products are hardened by drying and cross linking, such as occurs with linseed oil upon oxidation. Others are thermoplastic, as for example bitumen. During the fiber binding process~ they are all, at least to some extent, increased in temperature and to a temperature sufficient to cause the release of volatile ele~
ments, noxious or otherwise undesirable, among other reasons, due to their odorO

In the text below, the word "binder" will be used to designate any one or all of the binding products mentioned above, whether they are used in liquid form, dissolved or sus-pended in water or in other liquid, or in an emulsion.

The invention relates to that part of the installa-tion for manufacturing agglomerated fibrous materials calledthe fiber collecting or forming section, which is situated imme-diately after the fiber production apparatus, and in which the following operations are carried out primarily:
--the conveying of the fibers from the fiber produc-tion apparatus to the mat or blanket forming equipment;
--the application of the binder to the fibers, the binder generally incorporating pollutant elements;
--the formation of the blanket on the fiber collect-ing device, for which purpose the collecting device generally consists of a perforated belt;
--the cooling of the fibers and of the gases used for attenuating or guiding the fibers, such cooling general-ly being accomplished by air induced by the gases;
--the separation of the fibers from the gases and induced air by suction of these fluids through the blanket being formed; and --the evacuation outside of the installation of all

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the elements not re~ained by the fiber blanket or the mat being made.

It is in the fiber collecting or forming section that large quantities of gases and water have contact with the bind~
er whîch contains the pollutant elements, and are contaminated according to a pollution process which is common to all known processes for the manufacture of blankets, mats, or boards o fibers agglomerated by a binder~ and which will nol~ be describ-ed.

a) The pollution of the gaseous effluents takes place according to the following process:

The binder is projected into the current made up of fibers and gases, coming from the fiber production apparatus, the binder being present in the form of clouds of fine droplets.
Some of this binaer is entrapped by the fibers, some is unavoid-ably deposited on the walls of the installation, and finally some is found in the gases or fumes in the form of fine droplets and in the form of vapor.

Thus two fluid contamination modes coexist, the one consisting of contamination by droplets of the binder and the other consisting of contamination by vapors of the binder. In the binder application, the binder atomization or dispersion devices used furnish particles or droplets within a very wide range of diameters. The finest droplets are not entrapped by the fibers and are drawn through the blanket being formed by the gaseous cuTrent, in which they are present in suspension.

The droplets of binder deposi~ed on the fibers du~ing the binder application are subjected to the kinetic effects of the gaseous current passing through the blanket being formed.
A large quantity o droplets is extracted from the fibers, mi-grates through the blanket, and is found in suspension in the ~ O S ~ ~ 6 8 exhausted gases.

Finally, the desire to obtain a homogeneous distribu-tion of the binder in the blanket makes it necessary to disperse the binder in the fiber and gaseous current in an area situated near the fiber production apparatus, where this current still has a well-defined geometric form but where i~s temperature may still be high enough so that some o the binder, or at least its most volatile components, are evaporated. These pollu~ant vapors mix with the gases and contaminate them.

In the text below, the word "fumes" will be used ~o designate the gaseous effluents which pass through the fiber blanket and are evacuated ou~side of the collecting unit, i.e., the gases used for attenuating or guiding the fibers, the fluids ;nduced by these gases, and the pollutant elements in the form of droplets or vapor suspended in these fluids. It is to be understood that various features of the invention, such as treat-ment steps and components of the apparatus, may be employed with "fumes" having a wide range of compositions and pollutants. It is preferred to treat all components of such fumes, but vari-ous features of the invention may also be employed with gasesoriginating in fiber production operations in which ~he gases have pollutant components, whether or not the pollutants have their origins in fiber binders.

b~ The functions performed by the water in a fiber collecting unit make a large degree of pollution inevitable in any installation in which binders are used.

In operation, water is used:
--tl~ to dilute and carry the binder when the latter is used in liquid form;
--t2) to wash or scrub the fumes, an operation which consists:

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--(2a~ of causing the largest possibl~ amount of pollutants contained in the fumes in the form of droplets or vapor to be captured by the droplets o the scrubbing water, thus causing the pollut~nt charge of the fumes to be transferred ~o the wash water;
--(2b) of capturing and entraining on the walls o the collecting unit ~he fibers suspended in khe fumes;
--~3) to ~ash the di~ferent parts of the collecting înstallation tperforated belt, ~ume flues, etc.~ in order to evacuate the bincler and the fibers deposited therein.

During these operations the wash water is charged with binder components which are soluble, insolubleJ or în the vapor state, and the concentration o pollutant elements may reach high values.

The oregoing description of the manner in which the fumes and the water are con~aminated i5 based on an interpreta-tion of measurements and observations made in actual manufactur-ing installations.

Data derived from such measurement and observation is herein given by way of information; but it will be understood that other data and explanations may be found and that the inven-tion is not limited by the data given.

In all installations for the manufacturing of agglomer-ated fibrous products, regardless of the fiberization process used, the effluent pollution described above involves consider-able quantities of effluents.

In installations equipped with devices for attenuating fibers by blowing, in which the material to be attenuated is transformed into fibers by means of high-energy jets, the quantities of fumes discharged into the atmosphere are--for the best known 5.

~LOS1~568 processes--on the order of magnitude of the following values:
--100 Nm3 per kilo of fibers for the process described in the Slayter U.S. Patent No. 2,133,~36;
--300 Nm3 per kilo of fibers for the AEROCOR process (Stalego U.S. Patent No. 2,489,243);
--70 Nm3 per kilo of fibers for the SUPERTEL process (Levecgue French Patent No. 1,124,489 and U.S. Patents Nos.

3,114,618 and 3,285,723);

which, for large production plants, leads to outputs ranging from 500,000 to 1,000,000 Nm3/hr. (In these values, Nm3 refers to the cubic meter volume at standard atmospheric pressure and room temperature.) In installations equipped with fiber attenuating de-vices, in which the material to be attenuated is transformed into fibers under the effect of mechanical forces--centrifugal for example--and where a gaseous current is only used as a med-ium (generally flowing in an essentially horizontal direction, see hereinafter described Figure 14, for example) for carrying the fibers produced towards the collecting device--the quantity of fumes given off is a little less, but nevertheless very impor-tant: for example, 30 Nm3 per kilo of fibers, for the process described in Powell U.S. Patent No. 2,577,431, which for a pro-duction plant results in outputs on the order of 300,000 to 400,000 Nm3/hr.

The quantities of polluted water are pretty much the same for all processes, and on the order of 1,000 m3/hr. or more for large industrial installations.

The volume of these quantlties of polluted effluent has led legislatures first to limit the concentration of phenol compounds in the effluents discarded in the atmosphere, and later to prohibit discarding of any pollutants, at least in certain countries.
;~3 * Trademark ~56568 Furthermore, limitations concernin~ the odors or the opaqueness o discharged effluents have been established in various countries.

In addition~ installations for the manufacture of agglomerated ~ibrous products also tend to pollute in another respect. In addition to toxic or p~mgent-smelling products, these installations discard substantial quantities o steam, on the ord~r o~ 20 to 30 metric tons per hour for large plants, which steam escapes rom s~acks in very opaque plumes.

Noise is another type of nuisance created by installa-tions for the manufacturing of agglomerated fibrous products.
In these installations, the noise is essentially emitted by two sound sources--the apparatus for producing the -Eibers and the fan for extracting the fumes.

Actually, all the equipment for producing fibers mount-ed in these installations uses jets o-E gases at high speed either for transforming the material to be drawn or attenuated into fibers or for directing the fibers produced. It is known that the acous-tic power level emitted by these jets considerably increases with the speed of the jets. This level may exceed 100 decibels adjacent to the fiber production apparatus, where the operators are required to work. This level is much higher than the level tolerated by industrial regulations in many countries.

Furthermore, the acoustic power developed by the fume extraction fan is transmitted along the flues connecting with the fume exhaust stack. The latter is ordinarily situated outside the buildings, where i* functîons as an antenna, and radiates this acoustic power into the surrounding environment. The in-convenience resulting for the vicinity has caused authorities in different countries to order the shut-down o certain install-ations.

~5f~5~8 The need ~o reduce or eliminate the pollution produced --and this at costs low enough not to overly influence the cost price of the finished product--is pressing. Numerous investiga-tions have been carried out on this problem, and certain solu-tions ha~e been developed.

The process accordi.ng to the invention is characteriz-ed by the fact that the fumes ~as hereinabove d~fine~) are par-tially recyclecl, so as to C~llSe them repeatedly to trav0rse the blanket or mat being ormed. The process according to the inven-tion is also characterized by the fact that the majority of theheat contrihutecl by the gases coming from the fiber production apparatus and the attenuated fibrous material is transferred to the wash water, by the fact that the wash water is cooled, by the fact that the fumes are washed in water after they have tra~ersed the blanket or mat and the fiber collecting de~ice in order to transfer ~o the water some of the pollutant products contained in these fumes, by the fact that the non-recycled part of the said fumes is puriied before evacuation into the atmo-sphere, by the fact that at least some o the wash water is re-cycled--a certain quantity of which has been subjected to a treat-ment for extracting at least a sizable fraction of the pollu-tant products contained in the wash water--and by the fact that the solid wastes are subjected to a purification treatment before final disposal.

The foregoing process effects cooling of the recircu-lation gases, wl~ich is important in making possible such recir-çulation. In combination with such cooling of the recirculating gases, it is preferred also to spray water on the current of - fibers an~ gases in the receiving chamber, in order to cool the fiber and gas current. Such water spraying, with resultant cool-ing of the current, toge~her with the cooling of the recirculat-ing gases provides for reduction of the temperature of the current l~S6~8 notw;thstantling ~he substantial absence of induction of ambien~
air by the attenuating blast.

According to a particularly important characteristic of the invention, the quantity of fumes discarded into the atmosphere is essentially equal to the quantity of gases flowing from the attenuating device, The invention is particularly concerned Wit}l recycling the majority oF the fumes in the installa~ion, an~l with treating and evacuatin~ only a small portion o the ~umes--it bein~ poss-ible for the recycled portion to reach at least 9S~ of the ~otalquantity of fumes ordinarily evacuated into the atmosphere. The quantity of fumes to be puri~ied before discarding may thus be less than 5~ of all of the fumes; which even makes it practicable to use costly puriication treatment, whose effectiveness is total--as for example burning--without prohibitive energy expen-ditures.

Another object of the invention is to render insoluble the thermohardenable resins contained in the water. These resins are rendered insoluble J according to the invention, by means of a heat treatment--preferably at a temperature greater than 100 C., and more advantageously ranging between approximately 150 and 240 C., and under pressure.

The application of the above process ~for rendering resins insoluble) to at least some of the cooling and washing water is advantageously used to render insoluble the dissolved binder components contained in the water~ in order to subsequent-ly be able--by means of known techniques--to extract insoluble materials and thus to maintain the concentrations o the pollu-tant constituents in the washing and cooling waters at a level compatible with the continuous re-u~ilization of these waters in the installation. The wash wafer thus circula~es in a closed :iOS6568 circuit and any extarnal rejection of pollutants with the wash water is eliminated.
Another ob~ect of the invention consists of a heat treatment ~o which the wash water is subjected--a treatment which consists of vaporizing it and of heating this vapor to a tempera-ture sufficient so that the pollutant constituents are trans-formed into non-pollutant constituents.
The invention also i5 concerned with means for sound insulation--adJusted to the particular conflguratlon~ shown--to the devices Eor conveying and guiding the recycled fumes, in order to reduce the nolse emi~ted by these devlces, and with a particular arrangement of the apparatus for evacua~ing the non-recycled fumes into the atmosphere, which reduces the noise emitted by this apparatus in the surrounding environment.
Broadly speaking, and in summary of the above, ~he present invention overcomes the problems of the prior art by providing a method for manufacture of fibers from thermoplastic~ ;
- material comprising attenuating fibers from the material and entraining the fibers in a gaseous current, delivering the current and the entrained fibers into a forming section hav~ng a foraminous flber collectlng device at a boundary of the forming section through which the gas of the current passes and on which the fibers collect to form a blanket, recirculating gas from the downstream side of the collecting device to and through the forming section and the collecting device, and cooling the re-circulating gas in the flow path between the collecting device and the forming section.
The above method may be carried out in equipment for manufacture of fibers by attenuation of thermoplastic material and entrainment of the fibers in a gaseous current, comprising a for~ing section having an lnlet for a current of the gas and the entrained attenuated fibers, a suction chamber, a foramlnous fiber collecting device dlviding the suction chamber from the dap/ ~

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forming section, a suction fan having i~s inlet in communication with the suction chamber and it~ outlet connected to provide for recirculation of gas ~rom the suction chamber through the forming section and through the foraminous fiber collecting device, and means for cooling the recirculating gas stream in the recirculation ~low path between the foraminous fiber collecting device and the forming section.
Other ob~ects and advantages of the invention, includ-ing in particular numerous specific advantages for the recycling of fumes, w-lll be given and explained more completely below.
The drawings illustra~e several preferred embodiments of the invention, all of the figures being at least in part diagrammatlc and in general showing elevational or vertical sectional views.
Figure 1 illustrates a conventional fiber collection installation of a -type to which the present invention is applica-able.
Figure 2 similarly shows an installation of the type represented in Figure 1, but in which the walls defining the ~O receiving chamber are extended up to the fiber production device.
Figure 3 shows a fiber collection installation of the general kind shown in Figures 1 and 2, but modified by the addition of equipment according to the present invention.

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:~ S 6 ~ ~ 8 Figure 4 shows another embodiment of an installation according to the invention.

Figure 5 shows another embodiment of a ume washing chamber which may be employed in various installations.

Figure 6 depicts the evolution of the efFiciency level for the insolubilization treatment based on treatment temperatures and times.

Figure 7 shows a set-up providing for treatment of wash waters by heating under pressure, as is contemplated by the invention.

Figure 8 shows a set-up in continuous operation for treating the waters.

Figure 9 shows a set-up providing for one of the solid waste heat treatments of the invention.

Figure 10 shows a set-up pro~iding another solid waste treatment process.

Figure 11 represents a complete fiber collection install-a~ion used for the manufacture o fiber glass boards, made accord-ing to the invention.

Figure 12 shows an embodiment of the invention as appli-ed to another fiber glass manufacturing process.

Figure 13 shows another embodiment of the invention adapted to a process or the manufacture of minera] fibers by blowing.

Figure 14 shows another embodiment of the in~ention adapted to a process for *he manufacture of mineral fibers, and especially o slag.

Figure 1 shows a fiber collection installation of known type to which the invention may be applied. This installa-tion comprises a fiber production device, represented by ll, of a known type such as is ordinarily used in installations for the manufacturing of agglomerated or bonded fibrous panels or boards, in which the material to be attenuated is subjected to the action of a centrifugal or aerodynamic force, or to a combination of the two. The aerodynamic force is applied to the material to be attenuated or to the fibers by means of gaseous jets which are generally at a high temperature and high speed. An example of such e~uipment is shown in Levecque U.S.
Patent No. 3,285,723. The fibers produced leave device 11, dispersed in a current 12 of fluids generally in the gaseous state formed by high-energy jets and the air or other gases which they induce from the surrounding medium, a current which envelops the fibers and directs them, in the form of a stream with fairly well-defined contours, towards the collection device.

The equipment further includes a zone for application of binder, placed in the path of the fiber and gas current, between the fiber production device ll and the collection device, in which atomizers 13 disperse the binder, in the state of a cloud made up of fine droplets, into the fiber and gas current, A large proportion of these droplets intercepts the fibers and clings to them, the remainder being present in suspension in the gases accompanying the fibers either in the form of droplets or in the form of vapors.

A fiber distribution device which may be any one of several known types, indicated diagrammatically at 14~ placed in the path of the fibers and the gases 12, either between the pro-duction device ll and the binder application zone or between the binder application zone and the forming section~ as is shown in Figure l, which by imparting an oscillating movement to the , ~ 56S~8 current of fibers and gas or by deforming this current, makes it possible to distribute the fibers on the collection surface so as to form a blanket whose weight per unit of area is essen-tially uniform.

The collection surface is provided by an endless per-forated belt 15 r on which the fibers accumulate to form the blanket 23.

A chamber 16, placed beneath the perforated belt, in the area where the fibers are deposited and the blanket or mat is formed, i.e. the area of the forming zone or sectionr and in which chamber a pressure reduction or negative pressure created by a fan 19, causes all of the gases accompanying the fibers along their path between production device 11 and per-forated belt 15 to traverse the blanket being formed.

Vertical walls 21, which extend from the perforated belt 15 to a level near the fiber production device 11 r and which mark off the area where the blanket is formedr define a section or chamber 22, surrounding the current of fibers and gas, open at its upper end, in an area near the fiber production device. This is commonly desighated as the forming "hood".

A fan 19, provides a negative pressure in chamber 16 sufficient to force all of the gases accompanying the fibers (as they are being deposited in the forming section) through the blanket being formed, and evacuates the fumes to the atmos-phere through stack 5.

It has already been mentioned that the quantitiesof fumes to be evacuated from a forming section of the type described above are considerable. In effect, in the fiber produc-tion devices of these installations, the drawing and attenuation of 13.

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the material to be Eiberized, or the guiding of this material, or the guiding of the fibers, is achie~ed by gaseous jets, which have a very high output and speed.

This speed, w~lich is generally greater than 100 meters per second, is desirable or the formation of the fibers but is much greater than the speed necessary--in order to form an appropriate blanket--as the fibers and gases arrive at the per~orat ed belt 15, which latter in general need not exceed 10 meters per second. In fact, it is necessary to substantially slow down the jets coming from the fiber production device. This is achie~-ed by transferring some of the momentum of these jets to the ambient fluid in which they flow. Portions of the ambient fluid are induced and accelerated in the direction of the jets~ and mixed with the jets. It is this mixture of jets from the fiber production device and the induced fluid which constitutes the gas current accompanying the fibers.

The induction of surrounding fluid by the jets coming from the fiber production device is a well-known phenomenon char-acteristic of any jet flowing in the open air, or in a chamber containing a fluid. Fluid mechanics teaches us in effect that such a jet induces important quantitîes of surrounding gas, and that these quantities of induced gas flow increase with the out-put of the jet and the length of its course in the ambient gas.
However, since the induction phenomenon is a progressive pheno-menon, the drop in speed of the inducing jet is only significantafter this jet has traveled a sufficient distance through the ambient gas.

In installations of the type described above, in order to provide a speed of the current of fibers and accompanying gases, upon arrival at the collection belt 15, equal to the value given above (on the order of or less than 10 meters per second), 14.

~ 0 ~ 8 the length of the path followed by this current from the fiber production device 11 to the belt 15 is generally greater than 2 or 3 meters, and the quantities of gases which the jets from the production device ll haYe induced in this distance, and which traverse the belt 15, are at least equal to 10 OT 20 times the quantity of gases constituting the jets issuing from the iber production device 11.

In addition to the slowing down which must be imparted to the current of fibers and accompanying gases, in order that the blanket be formed under good conditions J it is necessary that the 10w directions of the ibers and the gases be parallel and oriented in the general direction of flow from the fiber production device to belt 15.

In order to further explain the matter, the current or stream 12 of fibers and accompanying gases may be divided in segments, limited by sections perpendicular to the direction of flow, i.e., sections lying between lines M, N, 0, and P.

In any segment such as that marked off by section lines M and N for example, the stream maintains a well-determined direc-~0 tion and undergoes a well-determined loss of speed.

These two factors--direction and reduction in speed--~ill have the desi~ed characteristics in each segment, if the current or stream can uniformly induce along the periphery of the segment all the quantity of fluid necessary--this being pro-portional ~o the product of the fluid mass constituting thecurrent at the entrance at line M times the relative speed re-duction undergone by the current upon crossing the segment con^
sidered, for instance the segment MN.

This relati~e speed reduction is equal to the differ-ence between the speed of the current entering at line M, and 15.

~05~5~;8 the speed of the current leaving at line N, related to this firstspeed~

If foT each of the current segments between the fiber production de~ice and the collection belt the ambi~nt air or gases can supply the quantity of gases necessary ~or the direction and slowing down of the current to have the desired charac~eris-tics3 an induced surrounding gas flow will be established along the current of fibers and accompanying gases and in the direction from production device 11 to the collection belt lS. This flow is represented on Fi~ure 1 by lines 27.

In fiber forming and collecting installations of the type represented in Figure 1, all the gas induced by current 12 is formed by the atmospheric air entering chamber 22 through opening 28 which is of large dimensions near fiber production device 11.

Figure 2 shows a configuration of the fluid flow in a forming chamber when the surrounding medium cannot freely supply the jets coming from the attenuating device with all of the gases that they may induce; this configuration is given by way of example in order to clarify the description.

Figure 2 represents part of the collection installation containing a fiber production device 11, from which a current of fibe~s and gases 12 flows, a binder application device 13, a fiber distribution device 14, a collection belt 15, and a suc-tion chamber 16 into which fumes 29 flow a~ter they have travers-ed the blanket 23 being formed. All of these elements are iden-tical to those in Figure 1, However, in Figure 2, walls 21 defining receiving chamber 2~ are extended up to fiber production device 11, so as to extensively reduce the opening 28 through which chamber 22 communicates with ~he atmosphere, and consequently the quantity of atmospheric air entering this chamber.

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Thus, if in any segment of current 12, and especially segments such for example as ~, (situated in a zone near the fiber production device ll--i.e., near the ejection orifices of the guiding or attenuating jets for the material to be fiber-ized, or near the guiding jets of the fibers, and therefore inthe region where the s~eeds of these jets are the highest) the surrounding meclium cannot supply current 12 with all the gases that the current may induce~ the segments of current 12 situated downstream, sush for example as OP, tin which current 12 has a slower speed) will furnish the lacking quantity.

Gas currents 30, emanating from the downstream zones of the current or stream 12 itself, will rise along walls 21 towards the upstream zones at higher speeds, will be picked up by the current and will be reaccelerated in the general flow lS direction of this current. Thus, the eddies represented by 31 will appear and develo~ between the boundaries of current 12 and the walls 21 of the chamber. The intensity of these eddies increases with the quantity of fluid that the surrounding medium has not been able to furnish. Their direction of circulation is such that the fibers which they extract from the blanket 23 being formed and which they carry, are directed along walls 21 of the chamber towards the fiber distribution device 14, the binder application devices 13, or the fiber production device 11 .

If the quantity of atmospheric air entering the re-ceiving chamber of an installation of the type shown in Figures 1 and 2 is reduced to a value much less than the quantity of air that the current can induce, the intensities of eddies 31 may be sufficient so that the fibers that they carry cling to the fiber distribution and binder application devices, disturbing the smooth functioning of those devices. These eddies also have the effect of disorganizing the blanke~ 23 being formed, as is 17.

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indicated in Figure 2.
The industrial use of installations of this type shows that the phenomenon whereby the fibers are driven upwards may be acceptable as long as the quantity of air entering the cham-ber is no less than 60 or 70~ of the necessary quantity. Belowthis value, operation is no longer industrially practicable.
If it is desired to further reduce, or totally elimi-nate, the quantity of atmospheric air entering the chamber, the turbulence in the chamber would be such that the fibers could not be deposited on the collection belt.
One of the objects of the invention is to furnish a process making it possible to considerably reduce the quantity of atmospheric air entering the forming section, while preserv-ing the conditions suitable to the formation of the blanket.
This process consists of using as induced fluid, not the atmospheric air, but some of the fumes taken from the outlet of the exhaust fan, i.e., returning to or recycling in the form-ing section some of the fumes that are withdrawn from this section.
A set-up permitting the implementation of this process is represented in Figure 3. The upper part of receiving chamber 22 is closed by a cover 32 containing an orifice through which current 12 of fibers and accompanying gases coming from fiberi-zation device 11 penetrates forming section 22. The edge portion 33 of the cover 32 is tangential to current 12 and are of such a profile as to facilitate passage of the above-mentioned current.
For the sake of operating convenience, cover 32 may be placed at a distance ~ from fiberization device 11.
The set-up in Figure 3 consists of a washing chamber 17, placed downstream from the suction chamber 16 and generally 9~2 .'105~ 8 larger in section than the latter chamber, equipped with appara-~us in which fumes 29--i.e., the gases accompanying the fibers between produc~ion de~ice 11 and collection belt 15, and the - pollutants in suspension--are placed in contact with a washing fluid, in particular water. In this washing chamber 17, the fumes are separated from a portion of t}le elements that they contain in suspension--the latter elements essentially consist-ing o~ fibers and the binder with which they are charged upon passing through the zone where binder is applied and the ~iber blanket is formed. In contact with the washing water, the fibers contained in the ~umes retain droplets of water and subsequently have a tendency to be deposited by gravity on the bottom of cham-ber 17, this phenomenon being moreover accelerated by the abrupt reduction in speed of the fumes as a result of the variation in the flow section along their path of tra~el from chamber 16 to chamber 17. Some of the droplets or pollutant vapors are inter-cepted by the droplets of washing water, and are dissol~ed by this water. It is the functioning of these two operations to-gether which constitutes the washing of the fumes. The water 2~ which was used for washing, and to which at least some of the pollutant charge of the fumes was transferredl is discharged through orifice 24.

This set-up also contains a separation system 18, of the cyclone or electrostatic type, placed between washing chamb-er 17 and the suction fan 19, in which the fumes are at leastpartially stripped of the water droplets with which they are charged during the washing operation, and which it is important to eliminate before entering fan 19. The washing water extract-ed from the fumes in the liquid form is evacuated from the separa-tion system through orifice 25.

A collector 26 leads the washing water evacuated throughorifices 24 and 25 towards the treatment zone.

lg .

:1~5~;5~i8 As above mentioned, the current of fibers and qases passes the binder devices 13 and then fiber distribution device 14. The fibers are deposited on collection belt 15 and the fumes 29 pass through the fiber blanket 23 being formed, through chamber 16, through washing chamber 17, and through water sepa-rating unit 18, and are driven upwards by a fan 19 into flue 34. Some of these fumes are evacuated from the system through orifice 35. The rest are led through flue 34 towards forming section 22, in which they penetrate through an opening 36 placed in a zone situated near the fiber production device 11.

The quantity of gas entering the forming section through opening lying within the edge portion 33 is equal to the sum of the quantity of gas coming from production device 11 and the quantity of air induced by the latter as they pass in the open air, along the length H. The quantity of gas entering the chamber therefore increases with the length ~.

For the system to be in equilibrium, it is necessary that the quantity of fumes evacuated from the system through discharge orifice 35 be equal to the quantity of gas entering the system through orifice 33. The quantity of fumes to be evacuated will thus decrease when the distance H is reduced.

Figure 4 shows a particular embodiment according to the invention, in which distance H is zero, i.e., in which fiber-ization device ll--or at least the ejection orifices of the at~enuating and guiding jets--are situated in chamber or section 22. The quantity of fumes to be evacuated from the system will be very nearly egual to the quantity of fluids coming from pro-duction device 11~

The proportion of recycled fumes may thus reach values equal to at least 96-97~ in this embodiment.

20.

~, ~05~ 8 In the installations built according to the invention and represented in Figures 3 and 4, the recycled quantities of gases correspond to the quantities induced by the jets coming from device 11, and this flow of the fluids through the section 22 will take place in the direction of 1Ow of the attenuating jets, and therefore in the absence of disturbing eddies. The recycled fumes essentially follow the current lines represented by arrows 37.

One o:f the advantages of the invention is based on the Eact that1 by means of fan 19, currents 37 of recycled fumes may be provided with a speed that is slightly ~reater than that of currents 27 of atmospheric air which current 12 of fibers and gas induces in installations of the type represented in Figure 1. Thus currents 37 have enough momentum to overcome the possibility of causing counterflow or "blow-back" of the fibers back to the binder nozzles 13 and the distributor 14, as explained above in connection with Pigure 2.

One of the most important advantag~s of the process according to the invention lies in the fact that the ~uantity of fumes evacuated from the system may comprise only from 3 to

4% of the quantities ordinarily evacuated (the order of magni-tude of which has been given above), and in the fact that, with such a small quantity of fumes, it is practical ~o apply a highly effective purification treatment notwithstanding that such treat-ment is costly.

In operation, the invention provides for treating thefumes evacuated through orifice 35 by burning, an operation which consists of heating the fumes to a temperature sufficient to burn organic components, preferably greater than 600 C.--beyond which the pollutants of the fumes, and especially the phenol com-pounds, are transformed by combustion into non-pollutant elements, ~ ~ S ~ ~ ~ 8 such as CO2 and ll20. This treatment also has the advantage of destroying odors. As shown in Figure 3, the burning procedure takes place in device 38, of a known type, consisting of a com-bustion chamber 39, a burner 40 supplied with a combustible mixture, ` and provided with a grid or any other flame stabilization device 41. The treatment temperature may be reduced to a value ranging between 300 and 400 C. in the presence of a combustion catalyst.

The puri~ied fumes are discharged to the atmosphere through stack ~2. At the outlet of stack 42, the temperature of the fumes is high enough, and due to recycling their output is small enough, so that the steam contained in these fumes is not condensed before total dilution of the fumes in the atmo-sphere. Thus no cloudy plume appears at the outlet of stack 42.

Another advantage of the invention lies in ~he fact that since the fumes are recycled and subjected to a total puri-fication treatment, it is not necessary to subject them to a very complete preliminary washing, which makes it possible to reduce the dimensions and the in~estments with respect to washing device 17 and water separating device 18 placed upstream of the suction fan 19.

Installa~ions built according to the invention and represented in ~igures 3 and 4 consist of a forming section 22 surrounding the binder and fiber distribution devices 13 and 14 making access to the latter devices difficult. During opera-tion, it may be necessary to provide access to binder nozzle13 or fiber distribution device 14. In order to do this, it is necessary to open inspection windows which are desirably placed in the walls of the chamber in a zone situated near the iber production device 11.

I~ is also contemplated to maintain the pressure in the forming section 22 equal to or lower than atmospheric press-~5~5~8 ure, by a few millimeters of water column, in order to prevent the f~es from escaping from chamber 22 during the recycling of the fumes~ which still carry pollutants.

l~hen ~he inspection windows are closed, this also makes it possible to prevent any untimely escape due to sealing defects.
The pressure in section 22 is adjusted to the desired value by regula~ing ~he negati~e pressure created in chamber 16 by fan 19, in the exemplified embodiment represented in Figure 3.

Another process consists o removing the quantity of fumes to be evacuated, not from recycling 1ue 34, but ~as shown in Figure 4) directly from forming sectioll 22, via an opening 43 placed in the walls of the chamber in the zone where it is necessary to maintain ~he pressure at the desired value. The fumes are extracted from section 22 by means of a small auxiliary fan 44 and evacuated through flue 35~ Thus fan 19 is relied upon only to assure recycling of the fumes. This type of set-up facilitates more precisely establishing a pressure in the chamber 22 in the neighborhood of atmospheric pressure.

One of the characteristics of the invention consists of the fact that it is possible to regulate the flow of the atom-ized binder through nozzles 13 as a function of the quantity of binder components in suspension in the recycled fumes, which are deposited on the fiber blanket when these fumes pass through it.

In operation9 recycling causes the fumes to make re-peated and very frequent passes through the fiber blanket being formed and, although the retaining capability of this blanket is limited, because the speed of the fumes transversing it is low, the number of successi~e passes ~around 15 per minute3 is such that an appreciable quantity of binder components in sus-pension in the fumes is retained by the blanket. This makes l~S6Stil~
it possible to reduce to the same extent the quantity of binder atomized or dispersed by the application devices 13, which per-mits an increase in the binder efficiency on the o~der of 5~, an economic advanta~e not to be neglected.

In an installation such as that represented in Figure 1, it is necessary to maintain a specific temperature in the forming section 22, and thus to evacuate the heat supplied by the material to be drawn and by the attenuating or ~uiding ~luids.
In operation, since the binder used for bonding the fibers is usually ~hermohardenable~ under ~he effect of the he~, it under-goes a continuous evolution which progressively converts it from the liquid state, in which it is atomized, to the solid state.
If the temperature in section 22 is excessive, during formation of the blanket the binder may reach a state of evolution suffi-ciently advanced to alter its power to bind the fibers. Thisphenomenon is sometimes called pregelification, ana this may be prevented by cooling the forming section 22.

In an installation as represented in Figure l, this cooling is achieved by induction of atmospheric air, which is generally at a temperature lower than the minimum temperature desired in section 22. The quantities of heat brought into the chambeT by the material to be attenuated and by the attenuating or guiding fluias and which, depending upon the fiberization processes used, are on the order o 1,500 to 15,000 Kcal per kilo of material, are transmitted to the induced air and then to the fumes, which transfer a small quantity of the heat to the washing water and exhaust the rest into the atmosphere.

In the installations represented in Pigures 3 and 4, since the small volume of fumes evacuated ~o the atmosphere only eliminates a very small quantity of heat, the invention provides other means for cooling the forming section 22.

24.

~ 5 ~ S~ 8 The foregoing is accomplished by transferring the heat brough~ into section 22 by ~he material to be attenuated and by the attenuating or guiding fluids, at least partially to a heat transfer fluid such as water, by placing the current of fibers s and accompanying gas or the fumes in contact with t}liS heat trans-fer fluid. This fluid is discharged, after it has absorbed the heat brought into section 22, outside of this chamber, and it is cooled by means of any appropriate system situa~ed outside o~ the installation.

The heat exchange between the current of fibers and accompanying gas or the fumes and the cooling water takes place either by direct contact between fluids or through a heat-conduct-ing or heat transfer wall. It is known that the quantities of heat exchanged per unit of time by means of such heat transfer lS are proportional to the temperature differential between the fluid to be cooled and the cooling fluid, and also to the area of the contact surface.

The relatively high speeds of the gases or fumes, with respect to the dimensions of the installation, permit only short periods of time for the heat exchange to take place. It is there-fore necessary that the quantities of heat exchanged per unit of time be large if sufficient cooling is to be accomplished.

The invention provides processes and devices for achiev-ing this goal.

One of the processes consists of discharging, outside forming section 22, the calories brought in by the material to be attenuated and by the attenuating or guiding fluids, by cooling the fumes in chamber 16 and in washing chamber 173 where the ~olumes available make it possible to have large surface con-tact areas between the fumes and the cooling water. This large contact surface is obtained in several ways: either by dispersing 1~i65~8 the water in the form of ine dro~lets, or by making it flow in the form o a very thin film, or finally by making the fumes bubble in the water.

In the arrangement represented in Figure 3, for exam-ple, atomizers 45 disperse the cooling wa~er in the form of sheetsor curtains of fine droplets, these sheets being generally per-pendicular to the direction o:E flow oE fumes as indicated at 29. Once the fumes have traversed the fiber blanket being formed, they enter chamber 16 at a temperature on the order of from 80 to 100~ C. and are cooled by contac~ with the sheets of water to a temperature on the order of 30 C, The temperature of the water at the entrance to atomizers 45 is on the order of 15~
to 20 C., according to the capability of the cooling devices ser~ing to supply the atomizers. By contact with the fumes, the water is reheated to a temperature on the order of 3Q to 40 C., ac~ording to the flow rate through the atomizers 45.

The recycled part of the cooled fumes, after passing through separating device 18 and fan 19~ reenters forming section 22 where, by mixing with the gases from fiber production device 11, the recycled fumes cool these gases and the fibers in the same way as the atmospheric air in the device represented in Figure 1.

Another exemplary embodiment is represented in Figure 4, in which the water flows over baffles 46 in the form of very 2~ thin films. The current of fumes indicated at 29 flows along these partitions, licks over the films of water, and is cooled in contact with the water.

Another exemplary embodiment is shown in Figure 5. In this set-up~ the current of fumes indicated at 2g emerges through orifices 47 below the free surface of the water mass contained in vat 48 placed downstream from suction chamber 16, creatin~

26.

l~)Slt;5~8 in this mass an~l a~ the level of oriEices 47, an intense bubbling--generating gaseous bubbles whose liquid walls have a large water-fumes contact sur-face.

Another process consists of directly cooling the current 12 of fibers and gas by projecting water on it, and discharging this water outside of forming section 22 to thereby remove the heat brought in by the materials to be fiberized and the attenu-ating or guiding fluids. The projection of water on the current thus takes place in the zone where the contact surfaces cannot be very large since the available space is small, but where the temperature differential between the fluid to be cooled and the cooling fluid is large. For example in tl~e embodiment represented in Figure 3, atomizers 49, placed between fiber production device 11 and binder devices 139 project a cloud of fine droplets of water against the attenuated fibers and gases of the current to be cooled.

The droplets reach the current of gas and fibers in a zone where this current is at a high temperature, which may reach 600 C., and are immediately vaporizedJ thereby effecting cooling at high efficiency. The large quantities of hea~--on the order of 650 to 700 Kcal per kg of water--necessary to va~or-ize the droplets are taken from the current of fibers and gas, which consequently undergoes a very rapid cooling. This reduces the temperature of the current, at the level of binder devices 13, to a value on the order of 100 to 120 C. The vapor produced is evacuated with the fumes, through fiber blanket 23, into chamber 16 and washing chamber 17, where in contact with the curtain of water sprays emitted by atomizers 45, the vapor condenses, transferring its latent heat of vaporization to the cooling water coming from atomizers 45. This heat is thus discharged from the system along with the water from the atomizers 45.

~ ~ S 6 ~ ~ 8 The placement of the spray devices 49 for projecting the cooling water against current lZ, between fiber pro~uction device 11 and binder nozzles 13, is the preferred arrangement according to the invention, since in operation this arrangement has certain special advantages:

First o all, it is in ~his zone that the temperature diferential between the current to be cooled and the water is the ~reatest and where the }leat trans~er is consequently the highest, The binder is then sprayed on a current of cooled fibers and gases~ at a temperature that is su~ficiently low (100 to 120 C.) so that breaking down of the binder due to volatiliza-tion of constituents thereof is very limited or non-existent.

As a result, there is an increase in the binder effi-ciency of the order of 5%, and a çonsequent reduction in thepollution from the fumes.

Another embodiment is shown in Figure 4, in whirh devices 50 for spraying cooling water against the current of fibers and gas 12, is placed between binder device 13 and the collection belt 15. As in the embodiment shown in Figure 3, the cooling water in the form of vapor passes through the blanket 23 being formed. This water condenses, transferring its heat to the films of water flowing over partitions 46 of washing chamber 17.

This water is discharged externally of the installation by orifices 24 and 25 placed at low points in chambers 16 and 17 and in water separating unit 18, into device 51, in which the solid particles in suspension in the water, notably fibers, are separated.

Device 51 may be either a filter, with meshes, of a known rotating or vibrating type, or a decanter, or a centrifuge, 28.

1~565~8 also of known type, Th~ ~ater, -free of suspended solid parti~les, is collect-ed in a tank 52 and, in the embodiment of Figure 3, the water is then directed, by gravity or by means of a pump 53, into a cooling station 54. IJpon leaving this station, the cooled water may be discharged outside or reused in the system.

As shown in Figure 3, station 54 may include a cooling tower 106, of known type, in which water is cooled by contact with air. The cooling water is circulated through ~he s~ray cooling tower by means of a pump 107. The wa~er ~om tank 52 is brought into indirect heat excllange relation to the cooled water o~ the tower 54 by means o-~ the heat exchanger indicated at 105, from which the cooled water may be returned to the tank 52. Make-up water may be introduced as by the water supply connec-tion indicated at 111.

It is preferred to cool the washing water by indirect heat exchange with the cooling water ~or other cooling fluid) circulating through the cooling tower 106, because this completely avoids polluting the air with any remaining volatile pollutants in the wash water, although the content of such remaining pollu-tants in many installations is so very low ~for instance, less than 5~ of the quantity discharged by the gas offtake of a non-recycled installation such as shown in Figure 1) that it may be practicable to directly cool the wash water in the spray cooling tower 106.

An advantage provided by the invention, is that it is contemplated that no water in liquid state be discharged outside of the installation, so as not to contaminate the environment even by the small content of pollutants that the water still con-tains.

2~.

1~)56568 This implies that the water introduced through nozzles49 or 50 and the washing water circulate in a closed circuit within the installation.

On the installations represented in Figures 3, 4 and

5, the closed circuit made by the cooling and washing water is the following:

--The water leaving cooling station 54 is sent via pump 55 to cooling devices 49 and/or 50 situated in chamber 22, and also to the ~apor condensation devices and fume washing devices placed in chamber 17, which include either the atomizers 45 as shown in Figure 3, or the baffles with water film 46 as shown in Figure 4, or the water may be sent towards the tank 48 shown in Figure 5.

--The washing water and the condensed vapor, charged lS with pollutants, fibers, and binder components, flow through orifices 24 and 25 placed at low points in washing chamber 17 and water separator 18, into a collec~or 26 which leads them towards filtra-tion device Sl; this separates solid wastes 56 in suspension, fibers, and insoluble binder components from the washing water.

These wastes are collected on a conveyor 57. Since the filtered washing water only contains dissolved binder com-ponents and pollutants, it is sent by gravity or via pump 53 to-wards cooling station 54.

The applicants have observed that when the washing water circulates in a closed circuit, it is necessary to maintain the concentration of the materials dissolved or suspended in the filtered water below a certain value, this being on the order of 3 to 4%--computed in unit of mass of dry materials per unit of mass of water. Above this value, some of the materials dissolved or suspended in the washing water (essentially microfib-1~5~5~:;8 ers or micropartlclcs of binder not ca~tured by Eiltration device 51, and soluble binder components) are aeposited on different parts of the installation. The binder is polymerized, forming viscous or solid layers which progressively obstruct the washing water ejection orifices 45, 49 and 50 and also the orifices in collection belt 15 for the passage of fumes 29. As a result, there is a reduction in the quantity oE fumes evacuated from the hood and in the cooling of these fumes, soon leading to shut-down of the installation.

In order to maintain the concentration of materials carried in the water below the value which will obstruct spraying or fume e~acuation, i* is necessary to extract large quantities of materials -from the washing water. In operation~ a large pro-portion, on the order of 20 to 30~ of the binder sprayed on the fibers by nozzles 13 ends up in the washing water, in the manner already described. For large plants, this makes it unavoidable that 3,000 to 5,000 kilograms of binder per day (counted in dry material) will be introduced into the closed circuit for circula-tion of the washing water3 and it is necessary to extract from the water quantities of binder identical to those introduced in order to maintain the concentration at an equilibrium value.

Several extraction processes are possible:

One of these processes consists of treating at least some of the washing water in a centrifuge, which is capable of separating from the water solid particles in suspension that are much smaller than can be handled by filter 51. Thus, as seen in Figure 3, the water treated by centrifuge 58 may return to vat 52, as is shown on Figure 3, or more advantageously may be sent to cooling device 49.

Another process consists of treating the water by the addition of a flocculant, followed by separating the flocculated 31.

~ s~s~
material.

These t~o proces~es hav~ the disadvantage of essential-ly extracting from the water only the insoluble materials that it contains. The dissolved binder, l~hich constitutes the great-est part of of the materials to be extracted, is not affectedor is affectecl only slightly.

The invention provides several processes for extract-ing the binder dissolved in the washing water.

One process consists oE using the il~ered or centri-fuged was}lin~ water to dilute the binding agents upon preparationof the binders applied to the fibers by application device 13.
The filtered ~ater may be removed from any point whatsoever in the circuit downstream from cooling station 54, or more advantag-eously downstream from centrifuge 58, as shown in Figure 3, by means of valve 59.

Another process consists of using the washing water as a fluid for cooling current 12 of fibers and gas, in chamber 22. The washing water is thus projected against curren~ 12 by cooling device 49, as shown in Figure 3, or by 50 in Pigure 4.

These two processes have the advantage that they per-mit the reutilization of some of the binder contained in the washing wa~er, and it is contemplated by the invention to regu-late the quantity of binder dispersed by application device 13 as a function of the quantity of binder that the blanket 23 being formed retains from the water projected by devices 49 or 50, which permits an improvement in the binder efficiency; but these processes do not permit extracting from the washing water quan-tities of dissolved binder sufficient so that the concentration of this water is maintained below the desired value. It is or this reason that the invention provides two processes which make ~ 56~8 it possible ~o complete thc ~xtraction of large binder quantities dissolved in the l~ater circul~ting in the closed circuit.

One of these proc~sses consists of burning a small portion, on the order of 1 to 5~, of the washing water flowing into the circulation circuit, in an appropriate device 60. This device~ represented on ~igure 4, is of known type and contains:
--a burner 61 supplied with a combustible air-fuel mix-ture;
--an atomizer injector 62) in which the water to be treated arriving through pipe 63 is projecked in the form of pressurized droplets into the flame of burner 61, under the effec~
of atomization air 64; and --a reaction chamber 65 in which~ under the effect of the heat released by burner 61, the l~ashing water treatment is carried out. This consists first of all of vaporizing the wash-ing water and then of raising the vapor produced as well as the binder components provided by the water to a temperature on the order of 800 C.--which permits these binder and pollutant com-ponents to be transformed into non-pollutant elements such as CO2 and H2O.

The non-pollutant vapor escapes through stack 66 exter-nally of the installation, at a high temperature--thus preventing the ormation of a cloudy plume.

The point where the water to be treated is removed is gene~ally located between pump 55 and the devices 50 and 46, as is shown on Figure 4.

This process has the advantage of extracting and trans-forming into non-pollutant elements all the binder components contained in the treated washing water. It has the disadvan-tage of requiring a large expenditure o energy and thus of being very costly. The influence of the treatment cost on the price :~S65~8 of th~ fibrous products manufactured may be reduced by recovering some of the quantity of h~at Erom the hig}l-temperature vapor, in an exchanger producing superheated vapor for various uses.

Thc other process consists of subjecting to a heat treatment a small portion--on thc order of 1 to 5~--of the flow of washing water charged with dissol~ed binder circulating in the circuit, so as to insolubilize the binder, ollowed by sepa-rating the binder from the water by any appropriate ~neans of separation such as filtration, flocculation, centrifuging...

In operation, the applicants have observed that if the water usecl for cooling and washing of the fumes- -and thus, after filtration, containing the binder or dissolved binder com-ponents--is maintained at a given temperature for a given period of time, a proportion of the dissolved binder increasing with the temperature and the time would be transformed into insoluble particles and would subsequently be found in suspension in the water and could then be easily separated from the water.

The proportion of dissolved material--insolubilized by the treatment--characterizes the efficiency of the treatment.

The treatment temperature has a very important influ-ence on the efficiency. For example, it has been found that for a water containing 1% dissolved ~inder component, the treat-ment efficiency is:
40% if the water is main~ained at 40C. for eight days;
~5 40~ if the water is maintained at 70C. for three days;
40% if the water is maintained at 160C. for three minutes;
60% if the water is maintained at 180C. for three minutes;
95% if the water is maintained at 240C. for three minutes.

34.

~L0~i6568 Figure 6 shows tlle ~volution o~ the treatment eficien-cy as a function of the temperature and o the treatment time.

In large capacity plants manufacturing panels of agglo-merated fibers, since the quantities of water to be treated may reach 50 m3/h, in order to avoid ~he installation of treatment plants of considerable d;mensions, it is necessary to determine the shortest treatment times and thus to work at high tempera-tures, greater than 100 C. This means carrying out the treatment in a pressurized chamber, at a temperature maintained at approxi-mately 5 C. below the boiling temperature of water at the press-ure of the chamber, so that the water remains in the liquid phase throughout the duration of treatment. This solution also has the advantage of requiring only a small ~nergy expendlture which, with respect to the wastes, only corresponds to the increase in heat imparted to the water in order to raise its temperature.

Thus, with an identical quantity of dissolved binder extracted, this process is one-quarter as costly as the process by burning previously described.

One of the disadvantages ordinarily encountered when heating in a chamber water containing the binder or dissolved binder ~omponents, even in a wea~ concentration, is that an in-solubilized binder deposit foTms on the walls of the chamber which very quickly becomes thick enough to obstruct the e~acuation orifices of the chamber, or the chamber itself.

The applicants have observed that if the heat necess-ary for treatment is released in the water mass to be treated and the wall of the chamber is maintained thraughout the treat-ment at a temperature less than that of the~water mass treated, there is no formation of deposit on the wall, the insolubilized binder remaining in suspension in the water. This leads to heating the water, either by mixing with hot fluids such as steam that 1 0 5 6 56 ~
llas preferably been superheated, or with immersed burner combustion ga~es, or by m~ans localizing ~he energy in thc midst of the water mass such as an electric arc.

A wide range of operating conditions is possible, for example 6 to 40 bars for the absolute pressures, from 150 to 240 C. for the temperatures, and from 3 to lO minutes for the treatment duration.

The following conditions are the result oE a satisfac-tory compromis~ between the energy cost and the equipment main-10 tenance cost:
--temperature: 200 C, --pressure : 16 bars absolute --duration : 5 minutes --efficiency : from 70 to 80~.

This method of treatment may be applied to a discon-tinuous operation set-up or to a continuous operation set-up.

Figure 7 shows a discontinuous operation set-up for the application of this treatment process. The water to be treat-ed is introduced to chamber 68 through motorized valve 67. The quantity of water introduced, or the charge, represents 70 to 80% o-f the capacity of this chamber. The heating fluid or vapor--preferably superheated--then penetrates the chamber through injec-tor 69, whose outlet orifice is immersed. The quantity of vapor is regulated by motorized valve 70, controlled by regulator 71.

The treatment cycle takes place as follows.
Chamber 68 contains a water charge to be treated which is initially under atmospheric pressure.
The treatment pressure desired, for example 16 bars absolute, is recorded on regulator 71.

Valve 70 opens and the vapor flows through injector 36.

~ s~s~
69, mixes with the ~Yater to be treatetl ~ and upon condensing trans-mits all of its latent and sensible heat to the water. The tem-perature and the pressure in chamber 68 rise until reaching approxi-mately 200 C. and 16 bars absolute.

The introduction o-E vapor is then terminated. Injector 69 has been adjusted so that this temperaturc and pressure rise is rapid, occurring in less than one minute.

Thc water is ma;ntained at 200 C. and lfi bars absolute for two to four minutes.

At the end of this period of time, a pump 72 is put in operation in order to deliver through jacket 74 a new charge o~ water to be treated, into a vat 73. As it passes through the jacket the water to be treated--which is at a temperature of approximately 40 C. at the entrance--initiates the cooling of the treated water contained in chamber 68. The dimension of jacket 74 is adjusted so that the water to be treated reaches vat 73 at a temperature of approximately 80 C.

A supplementary cooling fluid circulates in the jacket 75 and completes the cooling of the treated water contained in chamber 68. This cooling is considered to be completed when the temperature of the treated water drops below 100 C., and pre-ferably 40 to 50 C. ~t this moment, a motorized valve 76 is progressively opened in order to decompress chamber 68.

The treated water flows towards a filtration station 51, or a flocculation9 decantation, or centrifu~ing device, which separates the binder insolubilized by the treatment from the treat-ed water.

The filtered water flows into ~at 52 and the extracted wastes 56 are delivered to a conveyor 57.

When chamber 68 is empty, valve 76 is closed and valve 1 0 5 ~ 56 8 67 is opened, thus permitting the preheated charge o~ water in vat 73 to flow by means of gravity into chamber 68. An exhaust 67a completes the installation.

A new cycle may be started again Figure 8 shows a continuous operation set-up for the application of the treatment process.

A pump 77, under the ~reatment press-~re, sends the water to be treated ko a mixer 78 in which an injector 79 is arranged, through which the heating 1uid consisting of steam is introducecl. This steam mixes with the water to be treated and, upon conaensing, transmits its total heat to this water.
The steam flow is regulated by motorized valve 80 controlled by regulator 81, in order to maintain the desired treatment tempera-ture at the outlet of mixer 78. Subsequent to leaving mixer 78 in which it has remained for 10 seconds, the water to be treated passes through a reactor 82~ where insolubilization of the binder takes place--the dimensions of which are adjusted so that the retention time of the water to be treated csrresponds to the dura-tion of treatment, ~or instance 2 to 4 minutes.

Subsequent to leaving the reactor, the water is cooled in an exchanger 83, to a temperature less than 100 C., and pre-ferably from 40 to 50 C. Some of this cooling is provided by the water to be treated, which is thus preheated in coil 84 from approximately 40 C. to approximately 80 C.

The rest of the cooling is provided by a cooling fluid circulating in coil 85.

Subsequent to leaving exchanger 83, the treated and cooled water is decompressed to atmospheric pressure through a pressure-reducing valve 86 which, controlled by a regulator 87, maintains the treatment pressure in the installation.

38.

~56~;t;8 The decompressed water ~lows towards a fil~ration device 51, or a flocculation-decantation or centri~uging device, which separates the binder insolubilized by the treatment from the treat-ed water. The filtered water flows towards vat 52 and the wastes 56--residues of the treatment--are delivered to a conveyor 57.

The set-up shown in Figur~ 8, of the continuous opera~
tion type, permits a more flexible and less costly treatment than that shown in Figure 7.

Another process consists of subjecting some of the washing water, containing the pollutant elements, to a bacterio-logical treatment in an aerated pond. In such a pond, the bac-terial organisms present are responsible for the enzymatic destruc-tion of the phenol products, in particular, present in the water.
By means of an operation corresponding to a total oxidation reac-tion, the treatment leads to the transformation of the phenolproducts, in particular~ into non-pollutant elements such as CO2 and H 0. In order for this reaction to be total, it is necessary by aerating the pond to supply the bacterial organisms and the oxidation reaction with the necessary oxygen.

The installations for the manufacturing of agglomerated fibrcus panels discharge a large quantity of waste varying in make-up, but always containing the binder or pollutant binder components.

It is irst of all the manufacturing wastes of the panels which are rejected by quality control. These wastes con-tain extensively dispersed pollutant elements, but are very vol-uminous. Then there are the wastes coming from the cooling and washing water filtration, which contain fibers and a very large concentration of binder and binder components. Up to the present, all of these wastes have ordinarily been stored in quarries.

This practice is objectionable because of resultant pollution.

The invention provides a process for transforming the wastes into non-pollutant elements. After a preliminary preparation, it consists of submitting the wastes to a heat treatment which, by burning, transforms the pollutant materials into non-pollutant elements such as CO2 and H2O.

Figure 9 shows a set-up permitting the application o the process.

Wastes 56 coming from thermal treatment and water filtration stations are carried by conveyor 57 and delivered into a comminuter 88, where they are mixed with waste agglomer-ated fibrous products 87 coming from the manufacturing process.

Upon leaving comminuter 88, the mixture is poured into an incinerator 90, by means of conveyor 89. The heat re~
leased by burner 91 increases the wastes to a temperature greater than 1,000 C. At this temperature, the binder and the binder components are transformed into non-pollutant elements such as H2O and CO2 and evacuated into the atmosphere with the com-bustion gases from burner 91, through stack 93. ThQ materialconstituting the fibers, softened by the heat, accumulates on the bottom of furnace 90, is evacuated from this furnace via drain 92 in the form of a viscous stream and cooled in vat 94 filled with water. The cooled material thus appears in the form of granules, which may be retransformed into fibers.

Figure 10 shows another set-up permitting the treat-ment of the wastes.

The mixture of wa~tes 56 and 87, leaving comminuter - 88, is deposited by conveyor 89 on a belt 94 which extends through furnace 95O By means of the heat released by the radiating burn-4~.
,~

~I~)S6568 ers or electric resistances 96, this furnace increases the wastesto a temperature on the order of 600 to 700 C. At this tempera-ture, the binder or binder components contained in the wastes are transformed into non-pollutant elements such as CO2 and H2O, evacuated through stack 97. The fibers constituting the majority of the was~es by ~olume are softened Imder the effect of tlle heat, are consolidated, and agglomerate by sintering in the ~orm of plates 9S having a volume that is a great deal less than the initial volume of the wastes. These plates may then be reinjected inko the fiber production circuit.

Another important characteristic of the invention is to reduce the noise emitted by the receiving installations with which the invention is concerned.

In these installations, the most important source of noise is the fiber production device, and more precisely the high-speed fluid jets that it emits. The noise level around the fiber production device, where the operators ar0 brought to work~ generally exceeds 100 decibels. The configuration of the zone surrounding the acoustic source in the open installa-tion, such as are represented in Figura 1, does not permit an effective insulation of the acoustic source with respect to the outside, because it is necessary to provide a free space of large dimensions for the passage of the induced air. On the installa-tions built according to the invention and represented in Figures 3 and 4, closing wall 32--which contains orifice 33 through which the current of fibers and gas 12 enters chamber 22--and walls 21 of chamber 22 are given a configuration permitting the install-ation of absorbent acoustic panels 99, inside chamber 22, and insulating acoustic panels 100 outside chamber 22.

The reduction in the noise level obtained by installing these panels, in the zones surrounding fiber production device 41.

~ ~ S 6 S~ ~

11~ is from 20 to 30 decibels--which considerably improves the working conditions of the opera~ors.

Another source of sound is the fume exhaust fan 19.
The acoustic power emitted by this fan is transmitted through the flues connecting with the stack which, situated outside the buildings housing the installation, radiate the sound into the surroundin~ en~ironment.

On the installations representecl in Figure 1, the large ~olumes to be evacuated through stack 35, and the problem of limiting the pressure drop in this stack, have led to the install-ation of a large diameter stack directly at the outlet of fan 19, so that almost all of the acoustic power emitted by this fan is radiated.

On the installations built according to the invention and represented by Figures 3 and 4~ the small volume of fumes evacuated makes it possible to place the point where the fumes are evacuated at a distance from fan 19. In Figure 3, it is situated on recyling flue 34 at a point separated from fan 19 by at least one bend and a flue length sufficient so that at - 20 least part of the acoustic power emitted by fan 19 is absorbed by conduit 34. In the arrangement of Figure 4 the offtake is also small and remote from the fan 19.

The reduction in the acoustic level in the zone surround-ing stack 35 may reach 10 decibels or more.

Figure 11 represents a set-up according ~o the inven-tion, which contains:
--A fiberization device 101 in which the melted material 102 is in~roduced to a unit revolving at a high speed; this has a certain number of orifices on its periphery, through which the material leaves under the action of the centrifugal force; the 42.

1~56St~8 resulting iber ~ilaments are then subjected to the action of a concentric annular jet of high-speed hot gases generally direct-ed downwards, which a~tenuates them into fine fibers;
--A fiber distribution device made up o an oscillat-ing tuyere 14 (for example as illustrated in U.S.A. Patent No.
- 3,134,145~, which surrounds current 12 o ibers ancl gas coming from the fiberization device;
--A cooling device containing atomizers 50 for project-ing cooling water on current 12. This device is placed between distribution apparatus 14 and binder application deYice 13;
--A blanket collection device 15, consisting o a per-forated belt;
--A forming section 22, o a parallelepiped shape, bordered in the bottom by the perforated belt 15, laterally by vertical walls 21, and at the top by a horizontal wall 32 at a distance o 200 mm. under fiberization device 101, and contain-ing a circular orifice 33 through which current 12 passes; ~he edges of this orifice are profiled so as to facilitate the entrance of current 12, and are tangential to this current; vertical walls 21 mark off the zone where the blanket is formed on perforated belt 15;
--A compar~ment 16, positioned below the perforated belt 15 in the zone where the blanket is formed, and having its pressure reduced by a fan 19;
--A suction and washing chamber 17, placed downstream from compartment 16, which contains atomizers 45 arrangsd so as to form sheets of water droplets upon the path of fumes indicat-ed at 29;
--Downstream from chamber 17, a water separator 18 of the cyclone type;
--A fan 19, which forces all of the gases accompanying the fibers to pass through the belt 15, and which drives the gases into flue 34;
43.

~056561~3 --~ recycling flue 34, whose downstream end empties~-thro-lgh opening 36 in the upper portion of chamber 22--into a zone surrounding fiber distribution device 14; quantities of recycled fumes on the order of 90 to 95% of those passing through perforated belt 15 are led into section 22 through opening 36, via recycling flue 34;
--A conduit 35 situated on flue 34 evacuates Erom S
to 10~ of the fumes passing through the belt 15 towards the burn-ing device 39; after passing throug}l the burning device, whère they are brought to a temperature greater than 600 C., the fumes are discharged into the atmosphere;
--Absorbent panels 9~ and insulating panels 100, placed on ~Yalls 21 and 32, in the zone near fiber production device 101;
--A sump 103, which collects the washing-cooling wat~rs chargad with fibers and with the binder and binder components, dissolved or in suspension, coming from orifices 24 and 25 plac-ed at low points in chamber 17 and cyclone 18;
--A pump 104, which delivers the water contained in the sump to a filtration device 51;
--A filtration device 51 of the vibrating type with a screen, which separàtes the insoluble wastes from the washing water;
--A vat 52 placed under filter 51, in which the filter-ed water is collected;
--An indirect heat exchanger 105, in which the water contained in vat 52 circulates and is returned to the vat 52 under the action of pump 53, and is cooled by releasing the heat absorbed by contact with fumes 29, as it passes through chambers 22 and 17 and compartment 16;
--A cooling tower 106, in which the cooling water from exchanger 105 circulates under the action of pump 107;
--A pump 55 which puts the water from vat 52 back into circulation and delivers it toward the spray cooling devices 44.

~ ~ 5 ~ 5 ~ ~
50 for the fiber and gas current, and toward the condensa~ion and washing spray devices 45 for the ~umes 29, and still further toward the binder preparation station 108, and the water treatment station 109;
--~ t~ater treatment station 109, in which the water to be treated is subjected to an increased pressure o~ 16 bars absolute via pump 77, subsequently p~ssing through an exchanger 83 in which it is heated up to ap~roximately 80 C.; upon leaving this exchanger, the water to be treated enters a mixer 78, where it is placed in contact with a flow o~ steam that has preferably been superheated, consequently increasing its temperature ~o 200 C.--at which it is maintained for two to four minutes in reactor 82 connected with the outlet of mixer 78; upon leaving reactor 82, the treated water is passed through the exchanger 83 and is cooled to a temperature of 40 to 50 and then decom-pressed to atmosphe~ic pressure via pressure-reducing valve 86 after which it is sent to a centrifuge 110 which separates ~he binder insolubilized by the treatment from the treated water;
the treated water is returned to vat 52;
--A fresh water supply line 111, delivering into vat 52, makes it possible to maintain the quantity of water in the installation constant;
--Conveyors 57 and 112, carrying the wastes from fil-tration station 51 and water treatment station 109, and also the waste materials from the manufacturing line, toward the waste treatment station 113; and --A waste treatment station 113, consisting of a fur-nace equipped with radiant gas tubes or electric resistances, in which the wastes are brought to a temperature on the order of 600 to 700 C., so as to burn the binder and the binder com-ponents, and to sinter the fibers in thin plates of reduced dimen-sions~ which may be reintroduced in the fiber production circuit.

45.

1~5~;568 Figure 12 represcnts another set-up according to the invention, which includes:
--A fiberization device in which the melted material, and especially glass, flows rom a crucible 114 in the form of ine primary streams 115 that solidify before coming into contact with pulling rollers 116~ which introduce the solid Eilaments or rods into a high-speed hot gaseous jet 117--orclinarily in a direction practically perpendicular to this jet. As a result lQ the ends o the rods are heated and softened, so that the jet can attenuate them into fibers and carry these fibers to the blanket or mat forming unit 15, in the form of a current 12 made up of fibers and gas. Figure 12 further includes:
--A cooling device containing atomizers S0, for pro-jecting cooling water on current 12;
--Binder application devices 13 for projecting the bind-er on current 12, situated downstream from the cooling device, in the direction o-f flow o current 12;
--A blanket formation unit 15, consisting of a per-forated belt; and --A forming section 22, having a parallelepiped shape, bordered at the bottom by perforated belt 15, laterally by vert-ical walls 21, at the top by wall 32, and in the rear by vertical wall 118 placed approximately 200 mm. from the ejection orifice of jet 117 and containing a rectangular orifice 33 through which the current 12 passes. The edges oE this orifice are proiled so as to facilitate the entrance of current 12, and are tangen-tial to this current. Vertical walls 21 border the zone where the blanket is formed on perforated belt 15.

Figure 12 further includes:
--A suction compartment 16 9 placed beneath perforated belt 15, in the zone where the blanket is formed;
--A washing chamber 17, placed beneath compartment 46.

~ ~ S ~5 6 ~
16, containing orifices 47 which open below the surface of a body of water 48, and through which fumes indicated at 29 flow; atom-izers 45 spray the washing water, and the wa~er overflows through pipe 24 for delivery to collector 26;
--Downstream from chamber 17, a water separator 18 of the cyclone type;
--A fan l~, which forces all of the gases accompanying the fibers to pass through the fiber collection device and to deliver the ~ases into fluc 3~;
--A recycling flue 34~ whose downstream end empties into chamber 22 through two openings in the t~o vertical walls ~1 situated one on each side of the fiberization apparatus, in a zone near this apparatus; quantities of recycled fumes, which may reach as high as 95% of the quantities passing through per-forated belt 15, are led into chamber ~2 through these openings;
--A conduit 43, communicating with chamber 22 in a zone situated in an upstream zone of *his chamber, which evac-uates the non-recycled fumes ~hrough fan 44 to the burning device 39;
--Absorbent panels 99 and insulating panels lO0, plac-ed on walls 21, 32 and 118 in the zone near the fiberization device;
--A sump 103, which collects the washing-cooling waters charged with fibers and wi*h the binder and binder components, dissolved or in suspension, coming from orifices 24 and 25 plac-ed a~ low points in chamber 17 and cyclone 18;
--A pump 104, which leads the water contained in the sump to a filtration device 51;
--A filtration device 51 of the vibrating type wlth a screen, which separates the insoluble wastes from the washing water;
--A vat 52 placed beneath filter 51~ this vat collect-ing the filtered water; and --A heat exchanger 105, in which the water contained 47.

;5~8 in vat 52 circulates und~r the action o pump 53 and is cooled by releasing the hea~ absorbed from the fumes 29, as they pass through chambers 22 and 17.

The installation that was just described also contains--as is shown--a water treatment station an~l a waste treatment station as described above with reference to Figure 11.

Figure 13 shows another set-up according to the inven-tion, which comprises the following.

A fiberization clevice, in which the molten material flows from forehearth 118 of a furnace through the orifice~ of one or several rows of tips provided on a bushing ll9, produces a large number of strands of material that flow into an attenuat-ing zone, where they pass between high-speed convergent, gaseous jets. Jet ejection devices 120 are situated very close to the glass fibers, and the jets are directed downwardly, in a direc-tion that is practically parallel to the direction of movement of the glass fibers. Usually, the jets consist of high-pressure steam. The fibers produced, the attenuating jets, and the surround-ing fluid that they induce constitute current 12.

Cooling spray devices S0 project cooling water on current 12.

Binder spraying devices 13 project the binder on curr-ent 12.

A fiber distribution deuice 14, such as is shown in Berthon et al U.S. Patent No. 3,020,585, is made up of two press-urized air injectors, for directing the fibers in the desired direction.

The rest of the installation represented in Figure 13 is similar to that shown in Figure 11.

~8.

~:)S~;S68 In an installation o~ the general arrangement of Fig-ure 13 the fiberization may alternatively be of the toration type as disclosed in copending Canadian application of Marcel Levecque and Jean A. Battigelli, Serial No. 196,120, fil~d March 27, 1974. Thus, in the general position of the devices indicated at 119 and 120 in Figure 13, and in place of such devices 119 and 120, one or more intersecting and interacting glass carrier jets and blasts may be arranged to provide Eor the production of a current 12 of gases and attenuated fibers.

Figure 14 shows another set-up accordiny to the inven-tion, which comprises the following.

A fiberization device is provided, in which material in the molten state and in the form of stream 121, is directed by high-speed jets coming from orifices 123, against the peri-phery of a rotor 122 turning at a high speed. Under the effect of the centrifugal force, revolving unit 122 transforms some of the material that it receives into fibers and sends the rest of the material to a second rotor 124, wbich transforms some of the material that it receives into fibers by means of a simi-lar process. The number of rotors such as 122 is generallylimited to two or three. By means of a ring provided with ori-fices 125 surrounding rotors such as 122 and 124, jets of fluid are emitted--also at a high speed--which act on the fibers pro-duced, to direct them towards the receiving unit. These jets consist of air or steam under high pressure. Generally, orifices 125 are also used to project the binder on the fibers. Current 12 is made up of the fibers, the guiding jets, and the surround-ing fluid that they induce.

Cooling spray devices 50, for projecting cooling water on current 12, are placed downstream from orifices 125, the 49.

~I~S6S61~3 binder being atomized via certain of these orifices. The rest of the installation represented in Figure 14 is similar to that shown in Figure 13.

50.

~3

Claims (35)

The property or privilege in which an exclusive right is claimed are defined as follows:

1. Equipment for the manufacture of fibers by gas blast attenuation of thermoplastic material comprising a forming sec-tion having an inlet for a current of the attenuating gas and the attenuated fibers, a suction chamber, a foraminous fiber collecting device dividing the suction chamber from the forming section, a suction fan having its inlet in communication with the suction chamber and its outlet connected to provide for recirc-ulation of gas from the suction chamber through the forming section and through the foraminous fiber collecting device, and means for cooling the recirculating gas stream in the recirculation flow path between the foraminous fiber collecting device and the forming section.

2. Equipment as defined in Claim 1 and further includ-ing means for spraying a liquid on the current of gas and fibers in the forming section, and means for separating liquid entrain-ed by the gas stream, the separating means being disposed in the recirculation flow path between the foraminous fiber collecting device and the receiving chamber.

3. Equipment as defined in Claim 2 and further includ-ing means for cooling the liquid separated from the gas stream and means for recirculating the cooled liquid to the liquid spray-ing means.

4. Equipment as defined in Claim 3 and further includ-ing means for separating entrained solids from the recirculated liquid at a point upstream of the return of the liquid to the spraying means.

5. Equipment for the manufacture of fibers by gas blast attenuation of thermoplastic material comprising a forming section having an inlet for a current of the attenuating gas and the attenuated fibers, means for applying binder to the fibers, a suction chamber, a foraminous fiber collecting device dividing the suction chamber from the forming section, a suction fan having its inlet in communication with the suction chamber and its outlet connected to provide for recirculation of gas from the suction chamber through the forming section and through the foraminous fiber collecting device, means for cooling and washing the recirculating gas stream comprising means providing for extensive gas to water intercontact at a point in the recirculation flow path between the foraminous fiber collecting device and the forming section, and means for cleaning the wash-ing water by separating binder entrained thereby.

6. Equipment for the manufacture of fibers by gas blast attenuation of thermoplastic material comprising a forming section having an inlet for a current of the attenuating gas and the attenuated fibers, a suction chamber, a foraminous fiber collecting device dividing the suction chamber from the forming section, means for spraying a liquid binder composition on the current of gas and fibers in the receiving chamber, a suction fan having its inlet in communication with the suction chamber and its outlet connected to provide for recirculation of gas from the suction chamber through the forming section and through the foraminous fiber collecting device, means for cooling and washing the recirculating gas stream comprising means providing for extensive gas to water intercontact at a point in the recirculation flow path between the foraminous fiber collecting device and the forming section, and means for cleaning the wash-ing water by separating binder entrained thereby.

7. Equipment as defined in claim 6 and further includ-ing means for spraying the cleaned washing water onto the current of gas and fibers in the forming section.

8. Equipment for the manufacture of fibers by gas blast attenuation of thermoplastic material comprising a forming section having an inlet for a current of the attenuating gas and the attenuated fibers, a suction chamber, a foraminous fiber collecting device dividing the suction chamber from the forming section, means for spraying a liquid binder composition on the current of gas and fibers in the forming section, a suction fan connected to withdraw gas from the suction chamber, means for separating entrained liquid binder-containing components from the gas withdrawn from the suction chamber, means for sepa-rating solids from the separated liquid binder-containing com-ponents, means for recirculating liquid components and reusing them in the sprayed binder composition, means for recirculating gas withdrawn from the suction chamber to the forming section and through the fiber collecting device after separation of entrained liquid binder-containing components, and means for cooling the recirculating gas in the recirculation flow path between the collecting device and the forming section.

9. Equipment as defined in Claim 8 and further in-cluding an offtake for recirculating gas extended from the recir-culating flow path at a point between the means for separation of the entrained liquid and the fiber collecting device.

10. Equipment for the manufacture of fibers by gas blast attenuation of thermoplastic material comprising a forming section having an inlet for a current of the attenuating gas and the attenuated fibers, a suction chamber, a foraminous fiber collecting device dividing the suction chamber from the forming section, means for spraying an aqueous liquid binder composition on the current of gas and fibers in the forming section, means for spraying water on the current of gas and fibers in the form-ing section, a suction fan connected to withdraw gas from the suction chamber and for recirculation of the withdrawn gas to and through the forming section and the collecting device, means for cooling the recirculating gas stream in the recirculation flow path between the collecting device and the forming section, means for separating binder-carrying water from the gas withdrawn from the suction chamber, means for separating binder components from such separated water, and means for recirculating the water to at least one of said spraying means.

11. Equipment as defined in Claim 10 in which the means for spraying water on the current of gas and fibers in the forming section is arranged to spray the water on the cur-rent upstream of the binder spray means.

12. Equipment for the manufacture of fibers by gas blast attenuation of thermoplastic material comprising a forming section having an inlet for a current of the attenuating gas and the attenuated fibers, a suction chamber, a foraminous fiber collecting device dividing the suction chamber from the forming section, means for spraying a liquid binder composition on the current of gas and fibers in the forming section, a suction fan having its inlet in communication with the suction chamber and its outlet connected to provide for recirculation of gas from the suction chamber through the forming section and through the foraminous fiber collecting device, means for cooling the recirculating gas stream in the recirculation flow path between the foraminous fiber collecting device and the forming section, and an offtake for discharging a portion of the recirculating gas extended from the recirculating flow path at a point between the cooling means and the fiber collecting device.

13. Equipment as defined in Claim 12 and further in-cluding means in said offtake for reheating the gas being dis-charged sufficiently to burn organic components entrained in the gas.

14. Equipment for the manufacture of fibers by gas blast attenuation of thermoplastic material comprising a forming section having an inlet for a current of the attenuating gas and the attenuated fibers, a suction chamber, a foraminous fiber collecting device dividing the suction chamber from the forming section, a suction fan having its inlet in communication with the suction chamber and its outlet connected to provide for recirculation of gas from the suction chamber through the forming section and through the foraminous fiber collecting device, and means for washing the recirculating gas stream comprising means providing for extensive gas to water intercontact at a point in the recirculation flow path between the foraminous fiber collecting device and the forming section.

15. Equipment as defined in Claim 14 in which the washing means comprises devices for spraying water on the re-circulating gas stream at a point in the recirculating flow path between the fiber collecting device and the suction fan.

16. Equipment as defined in Claim 14 in which the washing means comprises means for establishing flowing films of water over which the gas passes.

17. Equipment as defined in Claim 14 in which the washing means comprises a water bath in the bottom of the suc-tion chamber and baffle means providing flow channels directing the gas into and through said bath prior to delivery of the gas to the suction fan.

18. A method for manufacture of fibers by gas blast attenuation of thermoplastic material comprising delivering a current of the attenuating gas and the attenuated fibers into a forming section having a foraminous fiber collecting device at a boundary of the forming section through which the gas of said current passes and on which the fibers collect to form a blanket, recirculating gas from the downstream side of the collecting device to and through the forming section and the collecting device, and cooling the recirculating gas in the flow path between the collecting device and the forming section.

19. A method as defined in Claim 18 and further includ-ing diverting a portion of the cooled recirculating gas from the recirculation path.

20. A method as defined in Claim 19 and further includ-ing heating the diverted portion of the gas to a temperature above 300°C.

21. A method for manufacture of fibers by gas blast attenuation of thermoplastic material comprising delivering a current of the attenuating gas and the attenuated fibers into a forming section having a foraminous fiber collecting device at a boundary of the forming section through which the gas of said current passes and on which the fibers collect to form a blanket, spraying a resinous fiber binder on the current of gas and fibers in the forming section, recirculating gas from the downstream side of the collecting device to and through the forming section and the collecting device, cooling the recir-culating gas in the flow path between the collecting device and the forming chamber, diverting a portion of the cooled gas from the recirculation path, and heating the diverted portion of the gas to a temperature sufficient to burn organic components, and discharging the products of such burning to atmosphere.

22. A method as defined in Claim 21 and further includ-ing washing the recirculating gas with water at a point in the recirculation path downstream of the fiber collecting device but upstream of the point of diversion of a portion of the gas.

23. A method as defined in Claim 22 in which the wash-ing of the gas is effected downstream of cooling of the gas.

24. A method as defined in Claim 22, further including separating washing water from the recirculating stream upstream of the point of diversion of a portion of the gas, and separating entrained solids from the separated wash water.

25. A method for manufacture of fibers by gas blast attenuation of thermoplastic material comprising delivering a current of the attenuating gas and the attenuated fibers into a forming section having a foraminous fiber collecting device at a boundary of the forming section through which the gas of said current passes and on which the fibers collect to form a blanket, spraying water and a resionous fiber binder on the current of gas and fibers in the forming section, recir-culating gas from the downstream side of the collecting device to and through the forming section and the collecting device, cooling the recirculating gas in the flow path between the collecting device and the forming section, separating water with entrained solids from the recirculating gas stream, separating entrained solids from the separated water, and reusing the solids-freed water for spraying the current of gas and fibers in the forming section.

26. A method as defined in Claim 25 and further in-cluding cooling the water being reused for the spraying.

27. A method as defined in Claim 25 in which water and aqueous resinous binder are separately sprayed on the cur-rent of gas and fibers in the receiving chamber and in which the solids-freed water is reused in both the water and aqueous binder spraying.

28. A method for manufacture of fibers by gas blast attenuation of thermoplastic material comprising delivering a current of the attenuating gas and the attenuated fibers into a forming section having a foraminous fiber collecting device at a boundary of the forming section through which the gas of said current passes and on which the fibers collect to form a blanket, spraying water and a resinous fiber binder on the current of gas and fibers in the forming section, withdrawing gas from the downstream side of the fiber collecting device and recirculating the withdrawn gas to and through the forming section and the collecting device, cooling the recirculating gas in the flow path between the collecting device and the form-ing section, separating water with entrained solids from the withdrawn gas, separating solids from the separated water and reusing the solids-freed water for spraying the current of gas and fibers in the forming section.

29. A method as defined in Claim 28 and further includ-ing cooling the reused water upstream of the spraying.

30. A method for manufacture of fibers by gas blast attenuation of thermoplastic material comprising delivering a current of the attenuating gas and the attenuated fibers into a forming section having a foraminous fiber collecting device at a boundary of the forming section through which the gas of said current passes and on which the fibers collect to form a blanket, spraying water and a resinous binder on the current of gas and fibers in the forming section, recirculating gas from the downstream side of the collecting device to and through the forming section and the collecting device, spraying water on the recirculating gas stream in the flow path between the collecting device and the forming section, separating water and entrained solids from the recirculating gas stream, separat-ing solids from the separated water, cooling the solids-freed water and reusing the cooled water for spraying the current of gas and fibers in the forming section and for spraying the recirculating gas stream.

31. A method as defined in claim 30 in which water and resinous binder are separately sprayed on the current of gas and fibers in the forming section, the water being sprayed on the current upstream of the binder spray.

32. A method for manufacture of fibers by gas blast attenuation of thermoplastic material comprising delivering a current of the attenuating gas and the attenuated fibers into a forming section having a foraminous fiber collecting device at a boundary of the forming section through which the gas of said current passes and on which the fibers collect to form a blanket, spraying water and a resinous binder on the current of gas and fibers in the forming section, recirculating gas from the downstream side of the collecting device to and through the forming section and the collecting device, spraying water on the recirculating gas stream in the flow path between the collecting device and the forming section, separating water with entrained solids from the recirculating gas downstream of the water spraying of the gas stream, diverting a portion of the recirculating gas stream at a point downstream of the separation of water therefrom, heating the diverted portion to a temperature sufficient to burn entrained organic constituents, and discharging to the atmosphere the products of the burning.

33. Equipment for the manufacture of fibers by gas blast attenuation of thermoplastic material comprising a forming section having an inlet for a current of the attenuat-ing gas and the attenuated fibers, a suction chamber, a foraminous fiber collecting device dividing the suction chamber from the forming section, a suction fan having its inlet in communication with the suction chamber and its outlet connected to provide for recirculation of gas from the suction chamber through the forming section and through the foraminous fiber collecting device, means for cooling the recirculating gas stream in the recirculation flow path between the foraminous fiber collecting device and the forming section, and a gas offtake connected with the forming section and providing for exhausting a portion of the gases from the forming section, an exhaust fan in said offtake, and means for burning pollutants carried by the exhausted portion of the gases.

34. Equipment for the manufacture of fibers by attenuation of thermoplastic material and entrainment of the fibers in a gaseous current, comprising a forming section having an inlet for a current of the gas and the entrained attenuated fibers, a suction chamber, a foraminous fiber collecting device dividing the suction chamber from the forming section, a suction fan having its inlet in communication with the suction chamber and its outlet connected to provide for recirculation of gas from the suction chamber through the forming section and through the foraminous fiber collect-ing device, and means for cooling the recirculating gas stream in the recirculation flow path between the foraminous fiber collecting device and the forming section.

35. A method for manufacture of fibers from thermo-plastic material comprising attenuating fibers from the material and entraining the fibers in a gaseous current, delivering said current and the entrained fibers into a forming section having a foraminous fiber collecting device at a boundary of the forming section through which the gas of said current passes and on which the fibers collect to form a blanket, recirculating gas from the downstream side of the collecting device to and through the forming section and the collecting device, and cooling the recirculating gas in the flow path between the collecting device and the forming section.