CA1098270A - Control of rate of gas recirculation in anti- pollution system - Google Patents

Abstract

Abstract of the Disclosure:

System for suppression of pollution in fiber at-tenuating operations, especially in mineral fiber insulation blanket production. The system disclosed provides gas blast attenuation of the attenuable material in a fiber forming chamber and for recirculation of attenuating gases. There are disclosed various controls used in association with the gas recirculation system, provision being made for con-trolling the temperature,pressure and recirculation rate of the recirculating gases. Still further the system dis-closed includes provision for the spraying of water upon the recirculating gases, and there is disclosed means for recirculating the water and for controlling the temperature of the recirculating water.

Description

~8~7~

The present application is a division of our 5application Serial No. 267,424 filed December 8, 1976. -~

The present application and the companion appli-cation Serial No. 267,423, filed concurrently with parent application Serial No. 267,424, contain disclosure of the same subject matter, but this application and the companion application contain claims directed to the inventions of different inventive entities.

Systems for mineral fiber manufacturing incor~
porating means for suppression of pollution are d}sclosed in Canadian application Serial No. ~L0,777, filed October 154, 1974 and in corresponding French Patent 2,247,346~ Such systems are also disclosed in Canadian application Serial No. 245,255, filed February 9, 19~6. In these prior appli~
cations pollution suppression techniques are disclosed as applied to a variety of techniques for attenuation of fibers from thermoplastic materials, for instance mineral materials such as glass. The general arrangement of such systems is explained hereinafter. As is also explained hereinafter, the fiberizing techniques in general involve the use of gas blast attenuation.

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In a typical production plant or facility, the means for effecting gas blast attenuation of the fibers is located in or at an entrance into a forming section or ~-chamber, frequently defined by a hood having enclosing walls, and at one boundary wall, most commonly the bottom wall, a perforated or foraminous fiber collecting device is arranged.
This fiber collec~ing device is commonly formed by a forami-nous moving belt or conveyor, and the fibers are collected on the fiber collecting device in the form of a mat or blanket. -~

The collection of the fibers on the foraminous collecting device is ordinarily assisted or effected by the provision of a suction chamber or chambers behind or below the collecting device, an exhaust or suction fan being ~;
connected with the suction chamber to thereby assist in developing a current of the attenuating gas, carrying the attenuated fibers from the zone of attenuation through the ~-forming section to the collecting device. The fibers are thereby deposited as a mat or blanket on the surface of the collecting device and the gases pass through the collecting device into the suction chamber or chambers.
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It is also well known to spray binder material upon the fibers before they are layed up upon the collecting device, such binders commonly comprising an aqueous solution or suspension of heat hardenable binder resin material, and the formed blanket is later subjected to heating in

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a curing oven in order to cure or harden the resin and stabilize the formed blanket or mat. Examples of various binder materials frequently used are referred to hereinafter.

It i5 still further known to spray water upon 5 the fibers being formed, for instance at a point in the current of gases and fibers upstream of the point where the binder is sprayed upon the fibers.

In consequence of such binder and water sprays, the current of gas passîng through the foraminous collect- ;
ing device entrains substantial quantities of water and also constituents of the binder materials in the form of ~`
droplets of various sizes, or in gaseous form; and in addition the current of the gases also entrains substantial quantities of small fragments of the fibers. The foregoing constituents which are entrained by the current of the attenuating gas represent pollutants having a serious adverse effect upon the environment, and this is particularly true with respect to certain of the constituents which originate from the binder material which is sprayed upon the newly formed fibers.
Ordinarily, the thermoplastic minerals used for fiber forma-tion, such as glass, require the use of high temperatures and the attenuating gas at the point where the binder material is sprayed, is also at high temperature, and in consequence various components of the binder composit;on or material are volatilized and, if discharged into the atmosphere, may be highly objectionable from several environmental standpoints.

Having the foregoing in mind, the prior applications above identified make provision for suppression of pollu-tion of the kind referred to by employment o several tech-niques including the following~

First, a large proportion of the attenuating gas current is recirculated through a recirculation path extended from the downstream side of the collection device to and through the forming section, into which the attenuating gas blast and the fibers initially enter. In the recircu-lation path of the gases, the gases are washed or scrubbed by means of water sprays in order to assist in the separa~
tion of the entrained pollutants, and the sprayed gases are passed through a separator for instance a cyclone or ~`
centrifugal separator in order to remove as much of the moisture or spraying water as feasible and thereafter the gases are returned to the forming section in the region of the admission of the attenuating gas and the fibers being ;~
formed. The water sprayed on the recirculating gases is then collected and i5 subjected to various stages of screen~
2U ing and filtration in order to separate the pollutant con~
stituents from the water, and thereafter the water is reused for spraying the recirculating gases and also for preparation -of additional aqueous binder material to be sprayed upon the newly formed fibers in the forming section. Such treated water may also be used as a water spray in the forming sectionD -:

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Because additional quantities of gas are normally introduced into the forming section as a result of the gas blast attenuation of the fibers being formed, a portion of the recirculating gases is diverted and discharged from the recirculation path. The portion of the recirculating gases which is thus diverted and discharged~ is desirably subjected to the action of a high temperature burner in order to burn any residual organic constituents before said gases are discharged to atmosphere, and this further enhances the elimination of pollution.
::
In techniques of the kind referred to above, the use of the various means for suppression of pollution, es-pecially the recirculation of the current of the attenuating gas and also the separation of the pollutants from the re-circulating gas, as by means of a water spray, may at timestend to introduce undesirable fluctuations in the conditions under which the fibers are formed or attenuated, and the conditions under which the fiber blanket i5 formedO Because of the recirculation of a large part of the gases, it is desirable to more ~ompletely enclose the forming section, than has been customary where the suppression of pollution by recirculation of the gases is not contemplated. With the more tightly enclosed forming section and where recir-culation of gases is employed for the purpose of suppression of pollution, there may be tendencies for fluctuation of both the pressure and the temperature of the gas in the ~
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forming section. The pressure will vary in accordance with the quantity of the gases which are diverted and discharged from the recirculation flow path; and in addition, the tem~
perature will vary in accordance with a number of factors including not only the quantity of gas diversion and discharge from the recirculation flow path, but also the extent of -~
water spraying utilized for separation of pollutants from the recirculation gases, as well as the temperature of the water used for such water spraying. Still further, variation in atmospheric conditions, for example as between summer i and winter, may also influence the operating conditions with respect to both pressure and temperature. ~ ~
, ~. ~, ,,,~
.~: , Variable factors such as those just referred to tend to alter uniformity of fiber and fiber blanket produc~
tion, particularly in the fiber formation by gas blast attenua~
tion, since uniformity of the fibers depends in part upon - ~ ~-uniformity of the conditions of temperature and pressure.
In fact, if the temperature of the gaseous current and con~
sequently o~ the fiber blanket is too high, polymeri~ation of the binder will s~art prematurely, i.e., in the forming section, instead of awaiting feed of the blanket into the binder curing oven. This condition tends to reduce the mechanical properties of the products, particularly their resilience.

On the other hand if the temperature of the gases and consequently that of the blanket is too low, the moisture carried by the blanket increases, and this reduces the ef-ficiency of the curing oven, and can even lead to dimen-sional irregularities of the manufactured products.

Pressure variations tend to adversely influence the effectiveness of the devices used to reduce the pollution in the gases discharged through the stack. A negative pressure in the formation chamber, that is a pressure below atmospheric pressure will increase the quantity of the air penetrating into the forming section and conse~uently the quantity of gases to be diverted ~rom the recirculation path and discharged. This results in an increase in the quantity of pollutants ejected into the atmosphere. A posi~
tive pressure, on the other hand, leads to leakage or dis-charge from the formation chamber of gases not yet treated, thereby impairing the intended suppresslon of pollution.

With the foregoing in mind it is contemplated according to the present invention that controls be provided for maintaining substantial uniformity of the conditions prevailing in the zones of fiber attenuation and fiber blanket formation, particularly uniformity of pressure and tempera~
ture of the gases in these zones. In addition, it is further contemplated to regulate the volume of the gas in circula~
tion.

It i5 also contemplated according to the present invention that the controls for temperature and pressure be adjustable in order to establish the desired pressure and temperature levels.

Although, as above indicated, various controls, including both temperature and pressure controls~ are dis-closed herein, the aspects of the invention to which the claims of the present application are primarily directed, ~ : -comprise the method and apparatus providing for control of the rate of recirculation of the gases passing from the downstream side o the perforated fiber collecting surface into and through the forming section. :~

Several embodiments of control systems according ~o the invention are illustrated diagrammatically in the accompanying drawings in which:

Figure 1 is a schematic view of a fiber production installation having certain equipment associated therewith for suppression of pollutants, and illustrating one embodi-lS ment of pressure and temperature controls according to the ;~
present invention;

Figure 2 is a view similar to Figure 1 but illus-trating another embodiment of the pressure control system;

Figure 3 is a view similar to Figure 1 but illus-trating another embodiment of the temperature control system;

Figure 4 schematically illustrates still anotherembodiment of controls; and ~ , ~h ., .

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Figure 5 is a schematic view illustrating one form of system adapted to insolubilize pollutants carried by water used in the system.

Referring first to Figure 1, there is diagram~
S matically represented a fiber production and collection ~ .
installation including a fiber production device indicated at 11. This may take a variety of forms, such as a centri- ~
fuge, for instance as shown in the Levecque U.S. patent ` ~ ~;

3,285,723. It may also take the form of various other fiber~
ization techniques~ such as that disclosed in U.S. Patent 3,874,885 and the corresponding Canadian application 5erial :- -No. 196,120, filed March 27, 1974. In either event, and also in the event of using still other techniques for fiber~
ization, the technigue includes employment of attenuating .- ~
gases which carry the attenuating and attenuated fibers downwar~ly into and through the chamber or forming section 22 which is defined by the enclosing walls 21, the current :
: of the attenuating gas and fibers being indicated in the ::~
Figure 1 at 12. Although in Figure 1 the fiber production ~ device 11 is shown at the top and the collection device at the bottom, other relationships may be employed.

Although the fiber forming equipment may be located within the chamber 22, as shown in Figure 1 it is located ~.
just above the top wall 100 and delivers the current of the attenuating gas and the fibers downwardly into the chamber. :~

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If desired a centrally apertured closure 32 may be arranged around the current entering the chamber.

At the bottom of the chamber 22 a foraminous col~
lecting device diagrammatically indicated at 15 is provided, this collecting device advantageously taking the form of a perforated endless conveyor on which the ibers are deposited, so as to build up a mat as indicated at 23, which is carried by the conveyor out of the zone of the forming section, as is well understood in this art. A fiber distributing device diagrammatically indicated at 14 may also be employed to assist in laying down a unifvrm blanket upon the conveyor 15.

As is indicated by arrows applied to Figure 1, the attenuating blast entrains air or ga es and the resultant current passes downwardly through the foraminous collecting ;
device 15 and into the suction chamber indicated at 16 A suction fan 19 serves to provide forced circulation of the gas, and assists in establishing the current downwardly in the forming section so as to deposit the fibers on the collecting device 15 and draw the gas through this device and through the washing chamber indicated at 17 and the cyclone separator 18. The exhaust or suction fan delivers the gases into the duct 34 which, as clearly appears in Figure 1, is connected with the upper portion of the forming section or chamber 22, in the region in which the fibers are being introduced or attenuated. A recirculation of , -1 0 - . ~

the gases is thus provided in the manner fully described in Canadian application Serial No~ 210,777 referred to above.
As described in that same application, a water spray, originat-ing from nozzles 49 may be applied to the curren~ in the upper portion of the forming section, and, in addition, ~ :
a binder may be sprayed upon the current, for instance by ~ ~ :
nozzles indicated at 13. ~-~he gases being drawn downwardly through the form- : ~ -ing section, through the blanket 23 and the perforated col-lecting device 15, entrain substantial quantities of water and pollutants, and in order to remove pollutants the recir-culating flow is subjected to a washin~ action by water spray nozzles indicated at 45, as the gases pass into the : ~
scrubber 17. Some of the water and pollutants will then ~ ~-drain or flow by gravity through the opening indicated at 24 into a collection or draining system 26 and ultimately into a sump 52. Droplets of moisture and pollu~ants which ~
are not separated at this point flow with the recirculating ~ ~ :
gas into the cyclone separator 18, in which moisture droplets ~:
are separated and flow downwardly by gravity through the discharg~ 25 and then join the liquid in the sump 52. After separation of the liquids in this manner the gases are returned to the forming chamber as above described.

According to the prior application Serial No.
210,777 referred to above, the water entering the sump 52 from the collecting system 26, is subjected to a screening ~:

operation by means of ~he screen diagrammatically indicated at 51 thereby straining out various solids, as indicated at 56, which solids may be received in the trough 57 for subsequent disposal, fGr instance after processing in the manner reerred in the application first identified above.
The liquid in the sump 52 is desirably cooled, for instance -in the indirect heat transfer device indicated at 105, the liquid being delivered by the pump 53 through this heat transfer device, in heat exchange relation to a cooling liquid from the supply pipe 53a, for instance a normal water ~:
supply pipe. The cooled liquid is then returned to the sump 52.

Liquids may be withdrawn from the sump 52 by means of the pump 55 and delivered to the spray nozzles 49 and 45, as shown in Figure 1, and if desired some water may : ~:
be diverted through connection 108a and used in the formula-tion of additional aqueous binder spray material to be sprayed upon ~he fibers by nozzles 13, in the manner more fully explained in application Serial ~o. 210,777 referred to above.

Recirculating wash water which is sprayed upon the current of attenuating gases and fibers through the nozzles 49 will be subjected to considerable elevation in temperature, in consequence of which soluble organic consti-tuents carried in the wash water will be in part insolubilized,so that upon subsequent passage of this water through the filtration and separation equipment, such as diagrammatically indicated at 51, some separation of additional solids will occur. More extensive insolubilization of the pollutant organic constituents in the wash water may be effected by diverting a portion of the wash water from the recirculation flow path beyond the pump 55, as by means of the branch -lO9a, having a valve lO9b, as described hereinafter with reference to Figure 5.

In the embodiment shown in Figure 1, offtake 19a :~:
is provided for diverting and discharging a portion of the ~ :
recirculating gases~ This offtake delivers the diverted gases through a venturi separator of known type incluaing adjustable venturi device l9b for increasing the velocity of the gases; and the separator l9c, from which the gases are withdrawn at the top through the connection l9d under the influence of the blower l9e which discharges into the stack S. The additional liquids separated in the separator l9c are delivered through a connection l9f back to the sump 52.

In the embodiment of Figure 1 a bypass SB is also provided from the downstream side of the suction or circulat- ~
ing fan 19 to the stack, and this bypass desirably has a ~:
normally closed damper Dl therein. Similarly a normally open damper D2 is provided in the recirculation duct downst~eam of the point of connection of the bypass SB~ The dampers Dl and D2 are provided for the purpose o bypassing the gas flow to the stack for instance in the event of a malfunc tion in the venturi separator equipment which is contem-plated for normal use in this embodiment.

For pressure control in the embodiment of Figure l it is contemplated to employ a pressure sensor l9g in the recirculation flow path close to or in the forming section, this sensor being provided with a control connection diagram- `
matically indicated at l9h which is extended from the sencor to the motor for driving the blower l9e. When the pressure device l9g senses increase in the pressure, the control system operates to increase the speed of operation of the motor for the blower l9e, thereby resulting in diverting ~ ;~
and discharging a larger percentage of the recirculating gases. It is contemplated and preferred that this pressure sensor and the associated control system operate to maintain the pressure in the forming section substantially at atmos- ;
pheric pressure, thereby avoiding tendency for substantial leakage of gases from or into the forming section, notwith~
standing the operation of the recirculation system. In a system of the kind illustrated and described, the quantity of gases diverted and discharged will ordinarily approximate about 15% of the total of the gases entering the suction chamber 16, and in a typical installation the attenuating gases introduced by the fiber forming equipment and leaking into the suction chamber 16 also represent about 15~ of the total gases flowing through the system.

7~

The offtake l9a could be directly connected to the blower l9e, without the interposition of the venturi separator l9b-19c, and the pressure control system would still function in the manner described, but it is preferred to use a separator in this offtake in order to supplement the separation of pollutants effected by the scrubbing of the gas in the scrubber 17 and the separation of entrained ~
moisture in the separa~or 18. ~ :

Turning now to the matter of temperature control, attention is first called to the fact that a valve 53b is provided in the cooling water supply line 53a. This valve is placed under the control of a temperature sensor 53c which is also positioned in the recirculation flow path near to or in the upper portion of the forming section 22.
~.
This sensor has a control connection indicated diagrammatically at 53d which is extended to and connected with the water ;
supply valve 53b. The sense of this control is to increase the valve opening with increase in temperature in the recir~
culating gases and decrease the valve opening with decrease in temperature. By this system of control, the temperature of the water in the sump 52 is maintained substantially constant, so that the water used for spraying and scrubbing the gases in the scrubber 17, i.e., the water delivered to the spray nozzles 45, is also maintained substantially constant. This control of the water temperature will in :
turn control the temperature of the recirculating gases and, when operation of the system is established and stabi-lized, deviation of temperature of the recirculating gases from a predetermined median value will result in a compensat ing change in the temperature of the water used for scrubbing the gases, thereby compensating for gas temperature fluctua~

tion.
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The arrangement of Figure 1 thus provides for both temperature and pressure control, and thereby assures ~ ;
maintenance of uniform operating conditions in the zone of fiberization and blanket formation in the forming sec-tionO
'.';' . ~
It is contemplated that the controls be established in a manner maintaining a pressure within the forming sec~
tion very close to atmospheric pressure. Thus, the pres-sure sensor and the control system for adjusting the speed of operation of the blower or fan l9e will operate to divert ;
and discharge that quantity of the total recirculating gases which is represented by newly introduced attenuating gases and leakage of air. For accurate maintenance of the desired pressure, the offtake for diverting and discharging a portion of the gases from the recirculation flow path is desirably connected with the ducting downstream of the suction fan ~ . .
or flower 19, but upstream of the forming section. Maintenance - ;
of the pressure in the forming section at atmospheric pressure -~
is desirable in order to avoid leakage of gases from the - ~-~
forming section into the surrounding atmosphere~ and also ;~
to avoid leakage of air into the forming section.

, l~B~`~

Turning now to the embodiment illustrated in Figure 2, it is first noted that the fc~rming section and associated devices are illustrated in the same manner as in Figure 1, and that the various parts are identified by the same reference numerals. Moreover~ the embodiment of Figure 2 illustrates the same temperature control system, including the indirect heat exchange 105, the cooling water supply line 53a, and the supply controlling valve 53b which is operated under the influence of the temperature sensor 53c.

~owever, the pressure control system shown in Figure 2 is different from that shown in Figure 1. In Figure 2 an offtake l9j is connected with the recirculation flow path at a point between the fan 19 and the forming section, and this offtake l9j is directly connected with the stack S. The offtake l9j is provided with a control valve, for instance a butterfly type of valve indicated at Bl. In addition a similar butterfly control valve B2 is located ~ -in the ducting 34 extended from the blower 19 to the forming section. - -The two butterfly control valves Bl and B2 are both controlled by the pressure sensor l9g, a control connec-tion being provided as diagrammatically indicated at l9h~
The control valve Bl, being located in the offtake l9j, regulates the quantity of the gases diverted from the re circulation flow path. However, accuracy-of pressure control in the forming section requires also that the butterfly control valve B2 in the ducting be operated simultaneously with the valve Bl. The manner of operation of these valves under the influence of the sensor l9g is as follows. When the sensor l9g experiences an increase in pressure, the position of the valve B2 is shifted to decrease the opening for the recirculating gases, and at the same time the posi~
tion of the valve Bl is adjusted to increase its opening.
This results in tendency to equalize or stabilize the pressure of the recirculating gases in or entering the forming section.
Although, for maximum accuracy of pressure control, it is preferred to use both of valves Bl and B2, it is also possible to approximate the desired control by employment of valve B2 only.

In the embodiment of Figure 2, instead of employ- ;;~
ing a separator of the type indicated at 19b and l9c i~
Figure 1, the offtake l9j is connected directly to the stack S, as noted above. Where pollution restrictions are par~
ticularly stringent, a system such as shown in Figure 2 preferably further embodies a burner device indicated dia~
grammatically at 38, this device being provided with a burner 40 supplied with a combustible mixture and provided with a grid 41 or any other suitable flame stabilization device.
The portion of the gases or fumes diverted and discharged are passed through this burner device 38 and are subjected to high temperaturel preferably between about 600 and 700C, to thereby burn any organic constituents remaining before discharge of the diverted gases to atmosphere. A tempera~
ture of from about 300 to 400C may be used in the presence of a combustion catalyst.

The employment of the burner 38 in a system such ~ :
as diagrammatically illustrated in Figure 2 is effective to reduce the pollutants in the discharged gases to a very low value. : ~:

In Figure 2 there is also disclosed a control~;
for the flow or volume of the gases in the recirculation ^~
system. Thus, a flow sensor l9K is arranged in the con- ~ :
nection between the separator 18 and the suction fan 19, and this sensor is connected as indicated at l9L witb the motor for the suction fan 19. The sensor is connected with the motor in a manner to provide for decrease in the ~otor speed when the sensor experiences an increase in the ~low, and for an increase in motor speed when the sensor ex~eriences a decrease in flow. Although this flow control may ~ot always be required, it will serve to ~urther stabilize the operating conditions in the forming section.

Turning now to the embodiment illustrated i~ Figure :-3, it is notéd that here again the portio~ of the sys~m comprising the forming section and associated parts alr~;;~
the same as those described above in connection with ~igures 1 and 2.

In the system of Figure 3, however, there ~:s disclosed an alternative arrangement for cooling the water use~. ~o spray and cool the recirculating gases. In this emboldiment a spray cooling tower 126 is utilized for cooling the water :~

_19_ circulated through the sump 52. The water is withdrawn from the bottom of the su~p by the pump 53 which delivers the water through a spray nozzle into the cooling device :~.
126 for direct heat transfer to the air. The water is col-lected at the bottom of the tower as at 126a, and is then returned to the sump 52 as indicated. In this arrangement ~
the temperature is controlled by a sensor 53c having control ~:
connections 53d extended to the motor for the pump 53, there- .
by regulating circulation of the water through the spray ~ :
tower 126. When the temperature sensor 53c e~periences a drop in temperature below the desired median value, the speed of the pump 53 is returnedl thereby diminishing the ~ ~-water coolins effect of the tower 126. In consequence of this the water sprays 45 and 49 will deliver water at a somewhat higher temperature and will therefore not cool the recirculating gases to the same extent. ;~

This embodiment provides an exceedingly ~imple temperature regulation system and may be used in installa~
tions where the.~uantity of poll.utants.remaining.in the filtered water in the sump 52 is not very high, and will therefore not result in any extensive atmospheric pollution as a result of spraying the water in the tower 126. The system of Figure 3 also incorporates an offtake 35 for di-verting and discharging a portion of the recirculating gases.
As here shown the offtake is provided with a burner device 38 of arrangement similar to that described above in con~
nection with Figure 2.

~ s will be unders~ood, a system such as shown in Figure 3 may also incorporate a pressure control system for instance a system as disclosed in Figure 1 or Figure 2, and described above.

Likewise, although the apparatus in Figures 1 and 2 includes systems for both pressure and temperature control according to the invention, either one of these ~ ;
systems may be used alone.

In the embodiment of Figure 4, the forming section and various other parts shown in the preceding figures bear the same reference characters. Figure 4 shows a fiberiza~
tion installation similar to that described in application Serial No. 245,255 above referred to and comprising principal gaseous current or blast generators 154, 156 and 157 and also secondary or carrier jet generators 148, 150 and 152 placed in a forming section 22.
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As described in U.5. Patent 3,874,886, each secondary gaseous jet, by penetrating the principal current, creates a zone of interaction into ~7hich is led a stream of thermo-plastic material such as moIten glass, thereby effecting attenuation of the glass by the process known as toration.
The glass is supplied from the orifices in the bushings 142, 144 and 146, fed by the forehearths 136, 138 and 140 :

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It is preferable to use in combination with each principal current a plurality of secondary jets and a plu-rality of glass streams are led into each principal current, each being associated with a secondary jet, which provides groups of fiberization centers for each principal current generator. The fiberization centers formed by the various groups of generators deliver atténuated fibers into a guide 168, 170 or 172. The guides comprise channels directing the fibers downwardly, with relation to the fiberization zone, delivering the fibers onto the foraminous blanket forming device or conveyor 15 which is located at the bottom of forming section 221 The gases delivered from the blast generators and from the secondary jets flow with the fibers into the guides and form with the fluids which t~ey induce the currents of gas and fibers illustrated at 12.

The suction chambers 16 placed under the perforat- ;
ed conveyor 15 provide for lay down of the fibers in the conveyor. These suction chambers communicate with the cyclone separators 18 each connected to an exhaust fan 19 which- -`
drives the gases into the recycling duct 34 as described -~
in connection with the preceding figures. This duct compris~
es a portion of the gas recycling path; it is connected to an end of the fiber forming chamber 22, and with guiding partitions 132 provides uniform distribution of the recycled gases in the said chamber. -7~

The gases and fibers are cooled as soon as they leave the guides 168, 170 and 172 by water delivered from nozzles or sprayers 49 preferably arranged both above and below the currents 12 of the attenuated fibers and the gases.
S The spraying nozzles 13 are used for spraying the binder, the nozzles 13 being located downstream of the nozzles 49.

~ s speciried above, the gases entering the suction chambers contain resinous components from the binder, and moisture and small debris from fibers, and these constituents are extracted from the gases in the cyclone separators 18 This separation is enhanced by the previous washing of the gases by the water sprayers 45 placed inside the suction chambers 16. The water and the pol~l~uting elemen~.~ discharged through the tubes 25 accumulate in the sump 103. After this separation the gases are recycled to the fo~ming section or chamber 22. ~`

The general flow of the gases in the recycling path is illustrated by the arrows 29.- In the forming séction 22 the gaseous flow is established primarily by the evacuation fans 19 but is reinforced by the action of the principal current or klast and of the carrier jets in the fiberiæation centers. A portion of the recycled gases enters the upper ends of the guides and other portions are led toward the gas and fiber currents 12 beyond the discharge ends of the guides.

The water and the polluting elements recovered in the sump 103 are delivered by pump 104 and to the sump 52 which is provided with a filter or sieve 51. ~he gathered liquid in the sump is sent by means of the pump 53 through ~ :
the heat exchanger 105 to be cooled. The heat exchanye ~ ~ :
is effected in two stages by means of a fluid of heat car~
rier which circulates by pump 107 through the cooling system 106. This is comprised, for example, of a cooling tower in which water from a normal water supply source is cir~
culated by the pump 107 and is brought into contact with the atmospheric~air. The cooled liquid in the exchanger 105 is then sent to the sump 52. ;~

The liquid withdrawn from the sump 52 by the pump 55 can be reused as already pointed out in the description relating to Figure 1 and the withdrawn portion is eventually submitted to the insolubilization treatment of the polluting organic constituents.

Make-up water can be introduced into the system by way of the feed connection 111 delivering to the sump ~ .
52.
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A discharge duct 35 extended from the upper part of the forming section or chamber is used to discharge a portion of the gases from the said chamber under the influ~
ence of the fan 44. The gases thus emi.tted are let into .

; . . . .: ,;

a burning apparatus 39 in which the temperature is raised, as described for Figures 2 and 3, preferably to a value at least equal to 600~C. ~ere again, the quantity of gases directed and treated in the burning apparatus can be about 5~ of the total quant.ity of gas flowing through the perforated .~.
conveyor 15.

The pressure control in this installation is ef-fected by a pressure sensor l9g placed in the formation chamber and connected to the operating motor for the fan 44 by means of the control connection schematically illus-trated at l9h. The operation of this system is similar to that described for Figure 1. When the pressure sensor l9g detects a rise in pressure, the control system effects ~
an increase of the speed of the fan 44, which increases ~ :
the quantity of gas discharged through the duct 35.

For temperature control a valve 53b is used, placed in the path in which the cooling fluid circulates through the cooling system 106.

The valve 53b is connected, by means of a control connection schematically illustrated at 53d, to a tempera- :
ture sensor 53c placed in the forming chamber 22, preferably in its upper partO When the temperature sensor detects an increase in temperature of the gases in the forming cham-ber, the regulation system effects opening of the valve 53b, which initiates an increase of the circulation of the heat carrier liquid and increases the cooling action in the heat exchanger 105, and conversely when the temperature decreases in the forming chamber the cooling action is dimin-ished. This temperature control of the water coming from the sump 52 and sprayed by the sprayer nozzles 45 and 49 controls in turn the temperature of the recycled gases and consequently that of the forming section or chamber.
::
The pressure and temperature control devices il- ;
lustrated in Figures 1 and 2 as well as the discharge duct 19a or l9j for the non-cycled gases, and various of the separation devices such as electrofilters, can be used in the same general way in the installation shown in Figure

4 instead of oftake 35.

As hereinabove mentioned, and as fully explained in the prior application Serial No. 210,777 identified above, the recirculating wash water is desirably subjected to fur-ther purification, especially by treatment of the wash water at elevated temperature in order to ~onvert water soluble pollutant constituents to an insoluble form. This is de-sirably accomplished as proposed in said prior application Serial No. 210,777 either batch-wise or continuously and in either event the treatment may be carried out in a manner to withdraw a portion only of the water from the recirculation flow path and then return the treated portion to the sump 52. A continuous system for this purpose is illustrated --diagrammatically in Figure 5. In the bottom central portion .

:' ' " ~ ' ' ; . ~ :

of this figure the connection 109a is indicated. This con-nection as mentioned above constitutes a valved branch for diverting a portion of the water from the recirculation flow path. The water to be treated is delivered from this connection 109a to a mixer 78 in which an injector 79 is arranged, through which the heating fluid consisting of steam is introduced. This steam mixes with the water to be treated and, upon condensing, transmits heat to this water. The steam flow is regulated by motorized valve 80 controlled be regulator 81, in order to maintain the desired treatment temperature at the outlet of mixer 78. Subsequent to leaving mixer 78 in which it had 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 o~ the water to be treated corresponds to the duration of treatment, for instance 2 to 4 minutes at a temperature of 200C.

Subsequent to leaving the reactor, the water is cooled in an exchanger 83, to a temperature less than 100C~
and preferably from 40 to 50~ C. Some of this cooling is provided by the water to be treated, which is thus preheated in coil 84 for instance, from approximately 40C. to approx~
mately 80C. The rest of the cooling is provided by a cool-ing fluid circulating in coil 85.

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

The decompressed water flows towards the filtra ~:
tion device 51, or a flocculation-decantation or centri-fuging device, which separates the binder insolubilized . by the treatment of the treated water The filtered water returns to sump 52 and the solid wastes 56--residues of. ~ ;
the treatment--are delivered to the conveyor 57 EXAMPLES

Glass fibers were made in accordance with the techniques illustrated in Figure 1.
~ ~ .
Water was sprayed on the fibers through nozzles :
49 and binder resin material was sprayed on the fibers through nozzles 13.

The binder resin material was a 10~ aqueous solu-tion of the following (solids indicated by weight parts)~
Phenol formaldehyde 50 (water soluble resol type) Urea 40 Emulsified Mineral oil 7 Ammonium sulphate 3 2~

In sprayin~ the binder material on the fibers, the binder material was subjected to a temperature of about 300C., resulting in volatilization of some constituents of the binder materialD Such volatilized constituents were entrained by the circulating gases and were washed from the gases by the wash water in which these constituents were suspended or dissolved.

The wash water was found to contain 2.5~ of solids.
Of these solids about .2% was represented chiefly by broken ~-fi~ers and already insolubilized binder resin; and about 20 3% was represented by soluble constituents of the binder ~:
re~in material, chiefly pheno~ (1.5~) and formaldehyde ~.4%).

The soluble constituents just mentioned were sub~
jected to insolubilization by treatment at elevated tempera~
ture, in the general manner described above with reference to Figure 5~ Thus, a temperature of about 200C. was main-tained for an interval of a few minutes and the water was then cooled. After this treatment about 70% of the soluble constituents were insolubilized. The insolubilized constit-uents were then filtered from the water.

In consequence of the treatment of this example,the solids content of the wash water was brought down to about .7~, which is satisfactory for reuse in the system.

After separation of the wash water, most of the gases were recirculated to the fiberization zone. ~owever, a portion of the gases were withdrawn from the recirculation ~ -path and in accordance with Figure l were passed through a venturi separator and were discharged to the stack. The gases delivered to the venturi separator contained a residual ~ -quantity of the pollutants and the venturi separator removed from about 60% to 70% of the residual pollutants before discharge of the gases from the stack.

In another example, the ~peration was carried out in the same manner as described above, but instead of delivering the withdrawn gases through the venturi separator, ~ ~-the withdrawn ~ases were delivered through a burner chamber -prior to discharge from the stack as in the manner illus~
trated in Figure 2. In this case, the efficiency of the burner was close to 100%, i.e., it eliminated virtually all of the pollutants from the gas discharged to the atmos~
phere~

Numerous other fiber binders including melamine formaldehyde~ urea formaldehyde, dicyandiamide formaldehyde resins and also bitumen are useable in techniques as describ~
ed in the example above.

Claims (3)

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

1. Apparatus for manufacture of fibers comprising fiberizing means for effecting gas blast attenuation of thermoplastic material, a forming section having a foraminous fiber collecting device as a boundary thereof, means for establishing a current of the attenuating gas from the fi-berizing means through the foraminous collecting device and providing for formation of a fiber blanket on the collect-ing device, means for recirculating gas of said current in a recirculation path from the downstream side of the foraminous collecting device to the forming section, and means for separating pollutants from the recirculating gas, characterized by means acting to maintain the gas flow in the forming section substantially constant.

2. Apparatus in accordance with Claim 1 in which means acting to maintain the gas flow substantially constant comprises a gas flow sensing device in the recirculation path.

3. Apparatus in accordance with Claim 2 and further including means acting by said sensing device to regulate the rate of recirculation flow.