CA1111004A - Apparatus and method for refining asbestos dispersions - Google Patents
Apparatus and method for refining asbestos dispersionsInfo
- Publication number
- CA1111004A CA1111004A CA312,226A CA312226A CA1111004A CA 1111004 A CA1111004 A CA 1111004A CA 312226 A CA312226 A CA 312226A CA 1111004 A CA1111004 A CA 1111004A
- Authority
- CA
- Canada
- Prior art keywords
- tube
- contaminants
- screw
- filter tube
- slurry
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Filtration Of Liquid (AREA)
Abstract
APPARATUS AND METHOD FOR REFINING
ASBESTOS DISPERSIONS
Abstract of the Disclosure Apparatus for the refinement of colloidal asbestos dispersions comprises a horizontally dis-posed cylindrical tube having a plurality of closely spaced holes around the periphery thereof, a helical screw disposed within the tube, and a flanged jacket concentric with and spaced outwardly from the tube.
A slurry of unrefined dispersion is continuously fed into the tube to fill it. Refined slurry is drawn through the holes by a suction pump connected to the jacket while contaminants are retained in the tube and moved by the screw to the outlet end of the tube where they are compacted and removed as sludge through a spring loaded discharged door.
ASBESTOS DISPERSIONS
Abstract of the Disclosure Apparatus for the refinement of colloidal asbestos dispersions comprises a horizontally dis-posed cylindrical tube having a plurality of closely spaced holes around the periphery thereof, a helical screw disposed within the tube, and a flanged jacket concentric with and spaced outwardly from the tube.
A slurry of unrefined dispersion is continuously fed into the tube to fill it. Refined slurry is drawn through the holes by a suction pump connected to the jacket while contaminants are retained in the tube and moved by the screw to the outlet end of the tube where they are compacted and removed as sludge through a spring loaded discharged door.
Description
?4 Thi-s invention relates to a method and apparatus for the removal of contaminants from colloidally dispersed chrysotile asbestos fibers.
The invention more particularly relates to a method and apparatus for refining such dispersions in a continuous manner and much more efficiently than heretofore possible.
In the production of asbestos yarn as tau~ht, for example, by Novak and orzechowski :in U.S. Patent 3,453,818, issued July 8, 1969, the yarn is formed by extruding colloidally '.
., ' ' ' ::
dispersed asbestos fibers through extrusion nozzles in-to a coagulating liquid. The exit orifices of these extrusion nozzles can vary in both size and shape. For example, circular orifices can range from 0.020 inch to 0.125 inch.
Orifices of elliptical, triangular or rectangular shape may have minimum openings within the above mentioned range of 0.020 to 0.125 inch.
The difficulty-arises in that bagged asbestos as received for processing into yarn contains from 0.1% to 10.0%
of foreign material or contaminants such as rock, wood, rubber, clots, unopened bundles of asbestos, spicules, wire, and the like. The physical dimensions of such con-taminants are larger than the orifice or the slits of the extrusion nozzles. There-fore, if such particles are not removed, they will cause the nozzle orifices to become plugged, resulting in discontinuities in the formation of the yarn and interruption of yarn production.
Nozzle plugging necessitates removal of the nozzles for cleaning by probing, backflushing, washing, etc.
There are many known methods of refining asbestos dispersions, none of which are entirely satisfactory. In one such prior art method, the dilute colloidal asbestos slurry is centrifugally forced through slotted screens.
Another method comprises the forcing of the unrefined slurry through a filter screen having small holes with definitely prescribed spacing.
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The reason for the critical;ty oE the hole diameter and spacing is that the long asbestos fibers present in dispersions suitable for yarn making tend to more rapidly clog the screening l~oles. In any event, the contaminants themselves, along with a certain amount of asbestos fibers, tend to clog the Eilter holes.
Prior art refining devices, therefore, have utilized scrapers of various types whicll are moved across the '~r filtering screen surface periodically for the purpose of keeping the screen holes open.
Despite s~lcll attempts to keep the screen holes open, plugging still occurs. In fact, cleaning of known prior art refining devices may be required as often as once per hour iE excessively dirty fibers are introduced into the system. Even with fibers of normal average cleanliness, sufficient clogging occurs to require daily cleaning.
The apparatus and method of the present inven-tion overcomes many of the disadvantages of prior __ art refining systems. Broadly, the present invention contemplates physically separating undesirable particles, or contaminants, from an incoming slurry of colloidally dispersetl asbestos fibers, drawing off the refined ~ispersion for f~lrther processing, and conveying the con~aminants toward a discharge end of the device where they are compacted and automatically i ejected responsive to compaction pressure. The device is co~tinuous in operation and virtually self-cleaning, thereby having greater efficiency and being more economical to operate than prior art devices.
In summary of the above, therefore, the present invention may be broadly seen to provide a method of removing contaminants from a slurry of colloidally dispersed asbestos fi~ers, comprising the steps of: feeding the contaminated slurry into a cylindrical, horizontally disposed tube having helical screw means extending for the full length thereof, the outer periphery of the screw means being in close proximity with the inner surface of the tube; forcing the slurry with the asbestos fibers out of the tube through a plurality of - closely spaced openings in the wall of the tube, the openings being of a size and having a spacing so as to permit egress of the asbestos fibers but to retain the contaminants in the tube; simultaneously rotating the screw means to move the contaminants to the discharge end of the tube and compact them at the discharge end to remove excess slurry therefrom;
and then removing the compacted contaminants from the tube in response to compaction pressure The above method may be carried out in apparatus for removing contaminants from a slurry of colloidally dispersed asbestos fibers comprising: a horizontally disposed cylindrical jacket; a cylindrical perforated filter tube internally of the jacket and concentric therewith, the filter tube having an inlet end and an outlet end and being spaced from the jacket to form a chamber therebetween; a screw disposed for rotation within the filter tube, the screw extending to the extreme ' ' `
' '' . ', '' ' ~ :
. , .
outer end of -the tube; means for feeding slurry into the filter tube; suction means associated with the chamber so that refined dispersion is drawn through the perforations from the filter tube into the chamber while the contaminants are retained in the filter tube; means for rotating the screw to compact the contaminants at the discharge end of the filter tube; and means responsive to pressure of the compacted con~
taminants for discharging the compacted contaminants from the discharge end of the filter tube.
Other advantages will be apparent from the following description of the preferred embodiment of the apparatus and method and the accompanying drawings wherein:
Fig. 1 is an elevational view, partially in section, of the apparatus for carrying out the process of this invention;
Fig. 2 is an end view of the discharge end of the apparatus of Fig. l; and Fig. 3 and Fig. 4 are fragmentary sectional views showing preferred shapes of filtering holes.
Referring to Fig. 1, the refining apparatus comprises a horizontally disposed, preferably cylindrical jacket 10 supported by suitable framework 12. For assembly and main-tenance purposes, the jacket 10 may be formed in two halves, each provided with flanges 14 and fastened together by bolt and nut assemblies 16, The jacXet obviously may be other than cylindrical, the cross sectional contour not being critical.
A cylindrical perforated tube 1~ is disposed within the jacket 10 and radially spaced therefrom ~4.o form a chamber 20 closed at both ends by walls 22. The tube 18 is provided with a plurality of filter holes 24 around the entire periphery, the holes preferably being circular in cross section but alternately may be s~uare or rectangular. The holes may be of a necessary suitable size dependent on the size of the nozzles which will be used in a subsequent yarn making process and can range between 0.001 to 0.125 inch from edge to edge at the smallest part.
It has been found that there is less tendency for asbestos fibers to clog the holes if the holes are formed with at least a partial taper increasing in cross-sectional area toward the outside of the tube 18 as shown in Fig. 1.
Two possible embodiments of filter holes are shown in Fig. 3 and Fig. 4.
The filter tube 18 projects beyond jacket 10 at the inlet end 26 and communicates with a supply reservoir 28 having inlet means 30 and drain means 32.
The filter tube 18 also projects beyond jacket 10 at the outlet or discharge end 34 which is closed except for a spring biased discharge door 36 held normally in closed position by spring 38.
, Received within the tube 18 and extending the full length thereof is a screw 40 which may be driven through gear 42 at variable speeds by any suitable power source 41.
The outer periphery of the screw is preferably polished and chrome plated for hardness so as to prevent binding as it rotates within the filter tube and also to provide good scraping action along the full length of the tube.
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.. . . . : .
.
, While in the preferred embodiment the screw periphery should be in contact with the inner wall of the tube, it will be appreciated tha-t as a practical matter this condition will be difficult to achieve. However, any clearance which will be provided should be held to a maximum of about 0.025 inch to ensure positive removal of fibers and residue from the holes and to provide positive conveyance of debris to the discharge end of the tube as will be explained later.
As mentioned heretofore, the periphery of the screw conveyor may be chrome plated or, alternately may be case hardened or equipped with flexible, replaceable strips of hard rubber, Teflon*, polypropylene, polyethylene, alloy steel, or the like so as to provide good scraping characteristics.
It has been found that air and foam at times accumulate toward the discharge end of filter tube 18. To alleviate this condition, a vent tube 46 and a shut-off valve 47 may be provided, the vent -tube communicating with the filter tube 18 to bleed off foam and air from the compacting dispersion.
In operation, unrefined dispersion, containing about 0.1% to 4.0% solids, enters the device through inlet 30 and reservoir 28 in which a constant level head, well above the horizontal tube entrance, is maintained by any conventional means such as an overflow or a float control device (not shown). The head level must be high enough so that a vacuum seal may be maintained on the filter holes 24 as will become eviclent.
.~
* Trademark sd/~-~ -6-The unrefined dispersion, or slurry, is drawn into the tube 18 and fills it completely. A variable speed pump (not shown) connectcd to an outlet pipe 44 creates a suction in chamber 20 and pulls refined dispersion through the filter holes of tube 18 into the chamber 20 and from there removes it through outlet pipe 44 for further processing such as spinning into yarn.
Simultaneously, the screw 40 is rotated at the desired speed and conveys the debris and contaminants, which are too large to pass through filter holes 24, to the discharge end 34 of the tube. When the residue of contaminants becomes sufficiently compacted and de-watered, that is to a concentration of about 20% to ~0% solids, its viscosity permits it to be rotated by the action and strategic location of the screw. As additional residue accumulates, pressure is built up so as to force open the spring biased discharge door 36 through which the residue is continuously expelled to be properly collected and disposed of. It will be noted that preferably the screw will extend to the extreme outlet end of tube 18 to ensure that the screw thrust will overcome the friction between the residue and the tube wall and thus eject the residue.
sd/~ -7-, , ' :' ' ~ ~ ' ' The above described apparatus and method refines colloidal asbestos dispersions much more quickly and efficiently than prior art devices. Furthermore, it has been determined that the apparatus of this invention requires very little down time for cleaning purposes.
For example, it has been thought that the distance between filter holes was extremely critical and had to be greater than the length of the asbestos fibers in the slurry.
Utilizing the screw means of the present invention, the distance between filter holes may be reduced to about three-quarters of the length of the asbestos fibers. This spacing is adequate, because of the greater wiping action of the screw, to prevent "bridging" of fibers between adjacent holes and also allows about a 25% increase in effective filter area.
_ It should be noted that, if desired, the effective-- ness of the continuous cleaning of the filter holes can be monitored by means of a vacuum gage (not shown) installed in the suction line, or outlet pipe, 44. Clogged holes will result in an increased vacuum while the cleaning of holes will result in a decreased vacuum.
sd~ 8-
The invention more particularly relates to a method and apparatus for refining such dispersions in a continuous manner and much more efficiently than heretofore possible.
In the production of asbestos yarn as tau~ht, for example, by Novak and orzechowski :in U.S. Patent 3,453,818, issued July 8, 1969, the yarn is formed by extruding colloidally '.
., ' ' ' ::
dispersed asbestos fibers through extrusion nozzles in-to a coagulating liquid. The exit orifices of these extrusion nozzles can vary in both size and shape. For example, circular orifices can range from 0.020 inch to 0.125 inch.
Orifices of elliptical, triangular or rectangular shape may have minimum openings within the above mentioned range of 0.020 to 0.125 inch.
The difficulty-arises in that bagged asbestos as received for processing into yarn contains from 0.1% to 10.0%
of foreign material or contaminants such as rock, wood, rubber, clots, unopened bundles of asbestos, spicules, wire, and the like. The physical dimensions of such con-taminants are larger than the orifice or the slits of the extrusion nozzles. There-fore, if such particles are not removed, they will cause the nozzle orifices to become plugged, resulting in discontinuities in the formation of the yarn and interruption of yarn production.
Nozzle plugging necessitates removal of the nozzles for cleaning by probing, backflushing, washing, etc.
There are many known methods of refining asbestos dispersions, none of which are entirely satisfactory. In one such prior art method, the dilute colloidal asbestos slurry is centrifugally forced through slotted screens.
Another method comprises the forcing of the unrefined slurry through a filter screen having small holes with definitely prescribed spacing.
sd~ , -2-'' - : - , , :
. ' ' , :.~ :
,:
.. ...
The reason for the critical;ty oE the hole diameter and spacing is that the long asbestos fibers present in dispersions suitable for yarn making tend to more rapidly clog the screening l~oles. In any event, the contaminants themselves, along with a certain amount of asbestos fibers, tend to clog the Eilter holes.
Prior art refining devices, therefore, have utilized scrapers of various types whicll are moved across the '~r filtering screen surface periodically for the purpose of keeping the screen holes open.
Despite s~lcll attempts to keep the screen holes open, plugging still occurs. In fact, cleaning of known prior art refining devices may be required as often as once per hour iE excessively dirty fibers are introduced into the system. Even with fibers of normal average cleanliness, sufficient clogging occurs to require daily cleaning.
The apparatus and method of the present inven-tion overcomes many of the disadvantages of prior __ art refining systems. Broadly, the present invention contemplates physically separating undesirable particles, or contaminants, from an incoming slurry of colloidally dispersetl asbestos fibers, drawing off the refined ~ispersion for f~lrther processing, and conveying the con~aminants toward a discharge end of the device where they are compacted and automatically i ejected responsive to compaction pressure. The device is co~tinuous in operation and virtually self-cleaning, thereby having greater efficiency and being more economical to operate than prior art devices.
In summary of the above, therefore, the present invention may be broadly seen to provide a method of removing contaminants from a slurry of colloidally dispersed asbestos fi~ers, comprising the steps of: feeding the contaminated slurry into a cylindrical, horizontally disposed tube having helical screw means extending for the full length thereof, the outer periphery of the screw means being in close proximity with the inner surface of the tube; forcing the slurry with the asbestos fibers out of the tube through a plurality of - closely spaced openings in the wall of the tube, the openings being of a size and having a spacing so as to permit egress of the asbestos fibers but to retain the contaminants in the tube; simultaneously rotating the screw means to move the contaminants to the discharge end of the tube and compact them at the discharge end to remove excess slurry therefrom;
and then removing the compacted contaminants from the tube in response to compaction pressure The above method may be carried out in apparatus for removing contaminants from a slurry of colloidally dispersed asbestos fibers comprising: a horizontally disposed cylindrical jacket; a cylindrical perforated filter tube internally of the jacket and concentric therewith, the filter tube having an inlet end and an outlet end and being spaced from the jacket to form a chamber therebetween; a screw disposed for rotation within the filter tube, the screw extending to the extreme ' ' `
' '' . ', '' ' ~ :
. , .
outer end of -the tube; means for feeding slurry into the filter tube; suction means associated with the chamber so that refined dispersion is drawn through the perforations from the filter tube into the chamber while the contaminants are retained in the filter tube; means for rotating the screw to compact the contaminants at the discharge end of the filter tube; and means responsive to pressure of the compacted con~
taminants for discharging the compacted contaminants from the discharge end of the filter tube.
Other advantages will be apparent from the following description of the preferred embodiment of the apparatus and method and the accompanying drawings wherein:
Fig. 1 is an elevational view, partially in section, of the apparatus for carrying out the process of this invention;
Fig. 2 is an end view of the discharge end of the apparatus of Fig. l; and Fig. 3 and Fig. 4 are fragmentary sectional views showing preferred shapes of filtering holes.
Referring to Fig. 1, the refining apparatus comprises a horizontally disposed, preferably cylindrical jacket 10 supported by suitable framework 12. For assembly and main-tenance purposes, the jacket 10 may be formed in two halves, each provided with flanges 14 and fastened together by bolt and nut assemblies 16, The jacXet obviously may be other than cylindrical, the cross sectional contour not being critical.
A cylindrical perforated tube 1~ is disposed within the jacket 10 and radially spaced therefrom ~4.o form a chamber 20 closed at both ends by walls 22. The tube 18 is provided with a plurality of filter holes 24 around the entire periphery, the holes preferably being circular in cross section but alternately may be s~uare or rectangular. The holes may be of a necessary suitable size dependent on the size of the nozzles which will be used in a subsequent yarn making process and can range between 0.001 to 0.125 inch from edge to edge at the smallest part.
It has been found that there is less tendency for asbestos fibers to clog the holes if the holes are formed with at least a partial taper increasing in cross-sectional area toward the outside of the tube 18 as shown in Fig. 1.
Two possible embodiments of filter holes are shown in Fig. 3 and Fig. 4.
The filter tube 18 projects beyond jacket 10 at the inlet end 26 and communicates with a supply reservoir 28 having inlet means 30 and drain means 32.
The filter tube 18 also projects beyond jacket 10 at the outlet or discharge end 34 which is closed except for a spring biased discharge door 36 held normally in closed position by spring 38.
, Received within the tube 18 and extending the full length thereof is a screw 40 which may be driven through gear 42 at variable speeds by any suitable power source 41.
The outer periphery of the screw is preferably polished and chrome plated for hardness so as to prevent binding as it rotates within the filter tube and also to provide good scraping action along the full length of the tube.
sd/,~ S , ~ , .
.. . . . : .
.
, While in the preferred embodiment the screw periphery should be in contact with the inner wall of the tube, it will be appreciated tha-t as a practical matter this condition will be difficult to achieve. However, any clearance which will be provided should be held to a maximum of about 0.025 inch to ensure positive removal of fibers and residue from the holes and to provide positive conveyance of debris to the discharge end of the tube as will be explained later.
As mentioned heretofore, the periphery of the screw conveyor may be chrome plated or, alternately may be case hardened or equipped with flexible, replaceable strips of hard rubber, Teflon*, polypropylene, polyethylene, alloy steel, or the like so as to provide good scraping characteristics.
It has been found that air and foam at times accumulate toward the discharge end of filter tube 18. To alleviate this condition, a vent tube 46 and a shut-off valve 47 may be provided, the vent -tube communicating with the filter tube 18 to bleed off foam and air from the compacting dispersion.
In operation, unrefined dispersion, containing about 0.1% to 4.0% solids, enters the device through inlet 30 and reservoir 28 in which a constant level head, well above the horizontal tube entrance, is maintained by any conventional means such as an overflow or a float control device (not shown). The head level must be high enough so that a vacuum seal may be maintained on the filter holes 24 as will become eviclent.
.~
* Trademark sd/~-~ -6-The unrefined dispersion, or slurry, is drawn into the tube 18 and fills it completely. A variable speed pump (not shown) connectcd to an outlet pipe 44 creates a suction in chamber 20 and pulls refined dispersion through the filter holes of tube 18 into the chamber 20 and from there removes it through outlet pipe 44 for further processing such as spinning into yarn.
Simultaneously, the screw 40 is rotated at the desired speed and conveys the debris and contaminants, which are too large to pass through filter holes 24, to the discharge end 34 of the tube. When the residue of contaminants becomes sufficiently compacted and de-watered, that is to a concentration of about 20% to ~0% solids, its viscosity permits it to be rotated by the action and strategic location of the screw. As additional residue accumulates, pressure is built up so as to force open the spring biased discharge door 36 through which the residue is continuously expelled to be properly collected and disposed of. It will be noted that preferably the screw will extend to the extreme outlet end of tube 18 to ensure that the screw thrust will overcome the friction between the residue and the tube wall and thus eject the residue.
sd/~ -7-, , ' :' ' ~ ~ ' ' The above described apparatus and method refines colloidal asbestos dispersions much more quickly and efficiently than prior art devices. Furthermore, it has been determined that the apparatus of this invention requires very little down time for cleaning purposes.
For example, it has been thought that the distance between filter holes was extremely critical and had to be greater than the length of the asbestos fibers in the slurry.
Utilizing the screw means of the present invention, the distance between filter holes may be reduced to about three-quarters of the length of the asbestos fibers. This spacing is adequate, because of the greater wiping action of the screw, to prevent "bridging" of fibers between adjacent holes and also allows about a 25% increase in effective filter area.
_ It should be noted that, if desired, the effective-- ness of the continuous cleaning of the filter holes can be monitored by means of a vacuum gage (not shown) installed in the suction line, or outlet pipe, 44. Clogged holes will result in an increased vacuum while the cleaning of holes will result in a decreased vacuum.
sd~ 8-
Claims (6)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Apparatus for removing contaminants from a slurry of colloidally dispersed asbestos fibers comprising: a horizontally disposed cylindrical jacket; a cylindrical perforated filter tube internally of said jacket and con-centric therewith, the filter tube having an inlet end and an outlet end and being spaced from the jacket to form a chamber therebetween; a screw disposed for rotation within the filter tube, said screw extending to the extreme outer end of said tube; means for feeding slurry into the filter tube; suction means associated with the chamber so that refined dispersion is drawn through the perforations from the filter tube into the chamber while the contaminants are retained in the filter tube; means for rotating the screw to compact the contaminants at the discharge end of the filter tube; and means responsive to pressure of the compacted contaminants for discharging said compacted contaminants from the discharge end of the filter tube.
2. Apparatus according to Claim 1, wherein the outer periphery of the screw is in sliding fit relationship with the filter tube.
3. Apparatus according to Claim 1, wherein the outer periphery of the screw is spaced from the filter tube by an amount in the range of about 0.002 inch to 0.025 inch.
4. Apparatus according to Claim 1, and including a vent tube communicating with the filter tube to bleed off air and foam from the residue being compacted.
5. Apparatus according to Claim 1, wherein the pressure responsive means comprises a spring biased discharge door.
6. A method of removing contaminants from a slurry of colloidally dispersed asbestos fibers, comprising the steps of: feeding the contaminated slurry into a cylindrical, horizontally disposed tube having helical screw means extend-ing for the full length thereof, the outer periphery of the screw means being in close proximity with the inner surface of the tube; forcing the slurry with the asbestos fibers out of the tube through a plurality of closely spaced openings in the wall of the tube, the openings being of a size and having a spacing so as to permit egress of said asbestos fibers but to retain the contaminants in the tube; simultaneously rotating the screw means to move the contaminants to the discharge end of the tube and compact them at said discharge end to remove excess slurry therefrom; and then removing said compacted contaminants from said tube in response to compaction pressure.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA312,226A CA1111004A (en) | 1978-09-27 | 1978-09-27 | Apparatus and method for refining asbestos dispersions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA312,226A CA1111004A (en) | 1978-09-27 | 1978-09-27 | Apparatus and method for refining asbestos dispersions |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1111004A true CA1111004A (en) | 1981-10-20 |
Family
ID=4112472
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA312,226A Expired CA1111004A (en) | 1978-09-27 | 1978-09-27 | Apparatus and method for refining asbestos dispersions |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1111004A (en) |
-
1978
- 1978-09-27 CA CA312,226A patent/CA1111004A/en not_active Expired
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |