US2386713A - Asbestos treatment - Google Patents

Description

oct. 9, 1945.

L. c. PHARo ASBESTOS TREATMENT Filed Nov. 2.1, 1942 4 sheets-sheet 1l /N VEA/Tof? LEE 6 PHAR@ ATTORNEY.

Oct. 9, 1945. L c.\ PHARO ASBESTOS TREATMENT 4 Sheets-Sheet 2 Filed Nov. 2l, 1942 /N VEN fof? LEE C. 0f/,4R0

' rToRn/EY.

oct. 9, 1945. l

l.. c. PHARo ASBESTOS TREATMENT Filed Nov. 21. 1942 4 Shegts-Sheet 5 /N VEA/TOR LEE C. PHA/Q0 TToR/VEY i Patented Oct. 9, 1945 n' UNITED s'rArEs PATENT oFFicE 2,386,713 ASBESTOS TREATMENT Lee C. Pharo, Thetford Mines,

J ohnsons Company, Quebec, Canada a'ssignor to Mines, West,

Quebec, Canada, Thetford Application November 21', i942, serial No. 466,522 In Great Britain February 10, 1942 9 Claims.

Introduction by underground mining. The highest grade of the mineral, known as crude asbestos is removed from the ore by hand; Crude forms only about one-eighth of the yield of a Canadian chrysotile asbestos mine, the remainder being milled fiber, which must be recovered by mechanical means and with the treatment ofwhich this application staple length of the masses, incomplete berizing and other unsatisfactory conditions.

The present invention, therefore, relates to the solution of this problem and to a method in which asbestos fiber is treated to remove impurities, thereby enhancing its textile qualities, and to api paratus employed in carrying it out.

Objects Having regard to the foregoing, it is a`principal object of the present invention to provide a method of treatment wherebyasbestos ber f may be rendered satisfactory for uses for which is primarily concerned. In the recovery of milled fiber, ,the ore must first be crushed. This involves several mechanical operations by which the rock is nally reduced to approximately-2% inches. It is then dried to remove inherent moisture. y y Milling includes 'further crushing,` inal series of steps in which the rock is finally `reduced to about 1/2 inch. As an incident to each of these steps, free fiber is removed to prevent injuryr in it has heretofore been thought necessary to use ber of a higher grade. l f

It is a further'object of theinvention to provide a satisfactory method of cleaning asbestos fiber t0 fulfill the previous' object.`

A more specic object is to provide for washing asbestos masses and subsequently freeing the individual fibers from the masses to render the washed product suitable for textile use. y

It is a further object to provide a method for improving the textile qualities of asbestos recov` A ered by mechanical methods.

subsequent operations. The milled fiber is then bagged. v p s When the milled product is sold tothe textile manufacturer, its price is considerably lower than' 'that of crude fiber. The reason for the discrepancy in price is that in subsequent textile opera,- tions muchless cotton need be'added to crude asbestos than to milled fiber. necessary in all cases-to give satisfactory textile qualities toltheyarn. 2 l

p The present invention results from the applicants observation of a reason underlying the inferior textile qualities of milled ber. The milling process, he found; results in an accumulation Some cotton is of dust upon the .fibers,'the dust acting as arlubricant to the individual fibers causing them to slip one over the other, thus preventing their forming a satisfactory yarn. From this observation camev the thought of cleaning the ber t'o rid it of the entrained dust. But, asbestos is a peculiar material which cannot be treated similarly to other fibers. treatment have resulted in the matting together of inseparablemasses of fiber, a 'decrease in the For instance, previous attempts/.at Wet Y It is a still further object of the invention to provide convenient apparatus for carrying out the process of the invention.

The invention These objects and others are accomplished according to a preferred embodiment of the invention, in a process in which milled asbestos is washed and'scrubbed to rid it of dust, dried and flberized to yield a commercialV product. having substantially ,the textllecharacteristics of crude fiber. vThe fiber, from which the rock has been removed by a usual milling method is first subjectedto the wash-ing step inwhich the "dust is effectively removed. In the washing process in `commercially applicable equipment, agitation of a particular nature is employed in order to achieve the desired cleansing action withoutr tangling or ropingl the fibers, which is an expected incident to treating asbestos in water.

The fibers, freed of impurities, are then treated to remove the-greater part of the water and compacted into thin sheets suitable fordrying. 'I'he sheets arev dried. After drying, the sheets are treated in a step whichprovides for `their thorough working so that'theasbestos is berized v further without injury t0 the fibers. The fiberized asbestosis then subjected to a special uiiing operation in which it is blown against a resistance apparatus shown in Figure 3.

` acceptable product. This conception hasfup to now, resulted in the general rejection of proposais for wet concentration as opposed to the usual methods. u f v Detailed descriptionl The invention will understood more specically by reference to the following detailed description illustrated by the accompanying drawings showing preferred equipment used in carrying. out a specic' and in which:

Figures 1 and 2 are diagrammatic illustrations showing the equipment Vemployed in carrying out the preferred process. v

Figure 1a is a diagrammatic illustration of an alternative piece of equipment for compacting the washed ber.

Figure 3 is a side elevation on a larger-scale of the washing apparatus. Figure i-is a vertical cross section through the `ll'igure 5 is a pian view of the apparatus shown in Figures 3 and .4.

Figure 8 is a side elevation partly in sectionV showing the uing apparatus according to this preferred form of the invention.

.assuma t .supply pipe Ila also leading from the supply line embodiment of the invention I8. `The pipe Ila is controlled by a valve IIb.

'I'he bottom'l! includes a circular opening 29. In this openinygfis tted forvertical movement a discharge pipe 30. .The pipe. is snugly tted to the opening by a gland 3l so that leakage is minimized. The top of the pipe 30 is connected by means of a bracket 32 to a slider bar 33. To the upper end of the bar 33 is fastened a rack 24. IThe bar is siideable in `a guideway -38 mounted in a frame 38 suspended over the apparatus A. Also mounted'in the frame 38 is a horizontal shaft 40 Aoperated by a hand wheel 4|. `(Jn the inner end of the shaft 40 is a pin- `ion gear 42 adapted to engage the rack 34. In this way the pipe 30 may be raised and lowered by operating the hand wheel 4l. The tank is also provided with a drain pipe 45 controlled by a valve 46. A cylindrical baiiie'may be employed about the top of the pipe 30 s'o as -to prevent asbestos from entering prematurely the -top of the pipe. Y

- The dewatering apparatus B is made up of I ...a'vibrating screen 5I) having sides II 'a discharge Figure 'l is a plan view of the apparatus shown in Figure 8.

Figure 8 is a fragmentary cross section along l the line 99 of Figure 6 illustrating the manner of attachment of the resistance'screen.

Referring in more detail to the drawings, A represents an apparatus for washing the ber after the ore has been crushed; B is equipment for partially dewatering the masses of ber leaving the washing apparatus A; C is a lter used for compacting and dewatering the bers; D is an alternative compacting apparatus whichmay be ,used in place of theulter C; E is a drying apparatus for drying the ber leaving the lter C: F is a mechanism for. partially disintegrating the sheets of compacted ber leaving the' apparatus E; Gfis a berizing apparatus for fiberizing the compacted sheets lai'ter drying; H is a threshing device for further disintegrating the masses: I is a fiumng o`r teasing apparatus for liberating the bers before use in textile operations: J is a bagging room. y

Washing apparatus The washingapparatus A is made up of a large circular tank or bath having sides I| and a bottom I2. `Encircling the bottom of the tank, adjacent to the side is a water supply pipe Il having openings or jets I8 through which the water is injected into the tank. Pipes I4, Ile and I1 connect the pipe II to amain I8 leading from a suitable source of water supply. The line I8 is'controlled by a valve I9. 'Enckcling' the bottom of A an air supply pipe 20 provided with `iets 2| through which air is funnel 52 for the 'water from the screen, and a discharge spout 53 for the wet ber leaving the screen. Masses of ber reach the device B by means of a chute 49 arranged between'these two mechanisms.

1 Filter Mounted on the frame are brackets 8l equipped'to receive bearings 81 capable of vertical adjustment. In thebearings 81 are journailed the ends of a horizontal shaft carrying the filter cylinder 10. The cylinder is made up of a plurality of separate sections 1I communicating at their inner ends with a valve system l2;

-The surface of the cylinder is provided with a screen or other suitable filter medium 84. A suitable source of exhaust'pressure is connected withthe valve system 82 so that suction is appliedito the surface of the cylinder separately at the individual sections as Awill be un-A derstood by one familiar with the art. vT'he arrangement is such that suction is applied-to the sections :lust as they emerge from the water fand ceases to be applied in the region where asbestos is removed from the surface of the cylinder as will be described. l

Extending about the filter and about mure-oir and tensioning rollsl 85 and 88 are a number of continuous parallel/string I a.web adapted to remove the asbestos masses supplied to the tank at marginal points thereof for the purposes of agitation as will be described.

'I'he pipe 28 is connected by pipes 28, 2l and by a supply line 28ieading'from a compressed air supply. The line 26 is controlled by a valve 21.

For the purpose of giving the water inthe tank a circular movement 'there is also provided a water receive the ber from the from the lter as the ycylinder rotates. A suit'- is provided for rotating the cylinder 10.

An alternative form of device'suitable for com- Ipacting and de-watering the washed vasbestos is A indicated as D. 'I'his device includes a spout |80 to 4receive the ber from the spout 5I. Below the spout I 60 are lfour cooperating ringer rolls l' |45 and |48, |41 and |48. Between the pairs of rolls |45 and |48,l |41 and |48 there is a cylindrical perforated plate or screen `|1II adapted to spout |80." The pair of rolls |41, |48 is rotatable counter-clockwise leading from the dewatering device.

s or bands 81 forming.

` upwards from the rolls. A

provided tooperate the conveyer at any Pipe (in'the gure) and the pair |45 and |46 clockwise, by any suitable mechanism (not shown). Rotation of the rolls rotates the plate |10. Compressed air nozzles 55 receiving compressed air from a suitable source are arranged to blow on the upper side' of the screen |10 through the perforations and thus to remove the fiber sheet which is formed on the screen as it is conveyed plate |56 is arranged to receive the sheet from the screen. The asbestos may be recovered-from the plate |56 byl hand or by a suitable mechanism.

Drying apparatus The drying apparatus indicated in the drawings consists of an enclosure or housing .90 within which the' air is capable Aof being conditioned and heated. An endless conveyer 9| is provided for carrying containers vfor the asbestos masses continuously through the oven. A`drive"92 is desired speed.

The separating apparatus vF consists of a pair of rolls 95 and 96 respectively. The bottom rolls operate faster than the top ones, whereby the sheets of berare pulled apart into smaller sheets with no substantial reduction of the fibers.

The apparatus G consists'of a series of pairs of rolls operating at the same or at slightly different speeds. Alternative pairs of rolls 91 and 90 are grooved in different directions. In other words, in one pair the surface grooves run axially and in the otherv they run circumferentially. An apparatus of this type is Patent No. 2,219,071-, October 22, 1940.'

The device H is a threshing machine of a conventional type in which projections |03 on a drum cooperate with projections |02 on a` stationary )member |04 providing a threshing action.

Fluing apparatus The device-I consists of a spiral tubular cas'- ing H0 made preferably of suitable sheet matcrial. This casing includesa floor a ceiling ||2 and side walls H5. In bodiment shown, the casing I|0 is provided with an entrancev Intermediate these openings the casing is looped in a spiral.

The floor is surfaced with a coars'e mesh wire screen |20. This screen is held in place by brackets |22 secured to the-11oor by nuts and bolts |25. IThe ceiling ||2 is similarly surfaced with la screen |30 held in place by and nuts and bolts |35.-

Adjacent the entrance HB isa pair of air supply pipes Ilucontrolled by ya valve (not shown). These pipes are connected with. a suitable source of air supply capable of giving an air pressure at the outlet ofthe pipes of about 100 lbs. per square inch. In this particular apparatus the is of internal diameterv of about Va inch.l

One of the sides ||5 is provided with openings giving access tothe inside o f the casing; 'Ihese openings are provided with sliding doors |5| f1tting snugly in suitable guideways |55.

The process A process of'treating theasbestos in this pre- |6 and a discharge opening ||1.

. employed y vthe discharge Where it pass ||9 to the next step in supplied several times -is removed.

the particular em-A gling a bracket |32.

' dry, has a tendency to cake or used in making bricks.

ferred apparatus according to one embodiment of theinvention will now be described. L

The asbestos is first concentrated or milled by usual methods. Generally the rock separated from the asbestos by dry methods during which Washing The tank is rst filled with water. The pipe 30 is adjusted so that its top end or entrance is at a height to bring the water to a desired depth without overiiowing, for instance as indicated in Figure 4.

Masses of asbestos are then suitably fed into the water. These masses are allowed to soak for a period sufficient to soften the dust adhering to the fibers. Then, the compressed air supply is turned on, causing air bubbles to rise from the jets 2|. This results in agitation of the water in a circular motion from the lower margin o f the tank upwards Aand then inwards towards the outlet pipe 30. lThe water feed is continued so that a slight overflow takes place allowing dirty water to escape. Several water and air inlets are at various points about the circumference of the tank, so that the pressure is more or less uniform at various points. The agitation is continued for aL period until the Water becomes fairly clear. Then the pipev 30 is lowered gradually and the asbestos allowed vto escape through s on down the chute the treatment. Alternatively, thel water may be removed and fresh water before the asbestos itself Supplying water through the pipe |5a causes a circularmovement of the asbestos about the tank which has been found beneficial in the treatmen The restricted outlet afforded by the pipe 30 minimizes the premature escape of asbestos, without objectionable blocking which might take place where a screen or device is employed.

The manner of washing the fiber is important. Agitation of the'contents of the tank as described, prevents swirling. of the water in eddies or any other turbulent motion which might cause tantangling must be meticulously avoided` or the fiber would tend to coil up into masses which cannot be out injury to the fiber. This is one of the diiiiculties always experienced up to `now in to as roping The particular type of agitation, preferably by injecting compressed air through the vwater and floating fiber, results in a substantially non-turbulent scrubbing action in which the individual fibers and masses of fiber are rubbed together andthe entrained dust or sludge, as it becomes when wet, is removed. Unless this sludge is removed, the iiber once wet, on being allowed to mat, the -film of a bond between them dust on the fibers forming the clays not unlike Portland cement or some of Dewatering and sheeting The masses of fiber pass on to thel vibrating screen. Vibration of 'the screen 50 water to flow into the hopper 5'! while the asbestos, partially dewatered, passes on down the chute 53 into the f'llter.

` The masses reaching the filter are immersed disentangled withthe wet f treatment of asbestos and is sometimes referred causes thel f cylinder by suction. The

i y operation.

. a position where it is blown valve setting up high f dividual bers is vice is employed the fiber should be discharged through the rotating screen I 'HL As the sheet mass of asbestos ber against the upper rolls by the lower ones. asbestos comes outl on the other side of the rolls compacted onto the screen in the form og a thin sheet which adheres to the screen to be carried to by the compressed air nozzles from the screen onto the plate 56.

The compacting of the- 4fiber into thin sheets without forming an inseparable tangled' mass is particular manner of compacting and dewaterlng V.the mass is important.

'I'he compacted masses are then dried. `This may be performed in any convenient lmanner in the apparatus E. The thin masses resulting from the compacting and dewatering operations are placed intrays suspended from the conveyer 9| and are moved slowly through the heating chamare compacted and dry quite rapidly. Fiber liberation-flberizing The'l masses'are then action oi' the rolls 95 and 96 of the apparatus F.

They are then conveyed to the iiberizing apparatus G where they are berized according to the meth Flumng The compressed air is turned on by the control pressure 'at the entrance The asbestos'masses which have partially berized n 1s thought that theu partially broken up by the spout |60 onto the surface ci' the i top pairs .of rolls and the screen which is lforced and are immediately taken up by the air stream and forced through the casing their passage through the casing they impinge on partial and the the screens and ties as contemplated by the 60 -sage formed inthe casing. `Hence breakage of in minimized. 4In the present discharge l I 1 is very iluil'y.

general practice is to pass them through prelim inary textile operations before they are actuall: Spun.

so as to liberate the fibers without breaking them.

is particularly true of the sheets coming from the drier E. In these sheets the fibers lare laid at various angles to each other remembered that the ability to ilberize and duit the masses of ber depends lAdvantailes procedures outlined oii'er great advantages asbestos art. Milled and therefore AmountY lost in :treatment The resulting fiber Theiiber resulting from this process has excellent spinning qualities. The major portion of impurities such as sand and dust which might impair its textile qualities are effectively` and thoroughly removed;V any freel iron content is reduced.`1 The treatment is such that the4 fibers are not injured nor are they entangled or otherwise held together to prevent their being subjectedto textile operations. In fact, the fiber vleaving the fiuillng apparatus can be made into yarn having substantially equal spinning qualities to that made from a similar staple crude ber, that is. it can be spun with the small addition of cotton used in crude fiber.v In view of vthe current conception that milled ber cannot be used for spinning without the addition of a large quantity of cotton, this is a new and unexpected development in .theasbestos art.

Examples In order that thev effectiveness of the present method of asbestos treatment may be further explained actual examples will be given. It is to be understood that these examples are not to be taken as limiting.

Example! then passed' through the fiberizing -machine as herein -described under spring pressure and fluffed atan air pressure of approximately 100 lbs. per square inch in a fluffer corresponding substantially to I. After fiufiing, the masses were pooledperiodically and bagged. The aggregate amount of asbestos fed to the tarik Il' and the amount eventually bagged is shown in the following table,- the remainder being the loss in treatment.

Table.v Amount of asbestos fed 13 tons .700 lbs. Amount recovered from process-- 11 tons 160 lbs.

2 tolls 540 lbs,

The loss is made" up principally of dust and a small proportion of other losses such ias tramp iron and spiculs of flberized asbestos. The spicules were collected and re-used.

Eixample II 'v boxes'.' measurins 24% by 14% inches and '3tlg` inches in depth. The boxes, posed one above the other, are numbered from the top down 1, 2, 3- and 4.` The bottoms of- Iboxes Nos. 1, 2 and 3 are made of metallic screen of the following specifications: Box No. lz l/L inch opening, diameter of wire,0.105 inch. Box No. 2:

y4mesh wire, 0.063 inch.' Box No.\3: 10-mesh wire, 0.047 inch. Box No. 4 is a receptacle forl the nes which fall through the three other boxes. The nest 'of four boxes or trays rests on a table to which van eccentric with a throw of i; inchl gives a movement of 11% inchtravel. To make a test, 16 ounces of asbestos is put on the top tray which is covered. The machine is run at the rate of 300 R. lP. M. at the shaft of the eccentric, and by means of an'automatic device, this is kept going for exactly two minutes, giving the nest a horizontal shaking movement. At the end of this timeA the asbestos which remains on each tra'y is weighed. This gives the grades of the asbestos fiber; the longest fiber' naturally stays on the top tray, `whereas the shorter fiber, accordingto its length, remains on screens 2 and 3 ,orv drops into the pan or lowest tray. The more fiber retained on the first screen and the less fiber in the pan, the higher the grade and therefore the greater its value. If for instance a customer buys spinning fiber of the specification 4-7-4-1, it means that in a sample of 16 ounces, representing the average of the lot shipped, 4 ounces will remain on the top screen, 'l on the second, 4 on the third and finally 1 ounce will go through all the screens into the pan. He will evidently pay more for this material than for paper stock testing 0-0-10-6. This indicates that out of 16 ounces tested, nothing isy retained on the firstv two screens, 10 ounces remain on the third and 6 ounces go through the latter into the pan. It is evident that the figures ofthe test represent the proportion in ounces of the different lengths of ,fiber in a pound of asbestos. e s

During the mill-run, a sample of each grade is taken every half-hour, both at the grading screens and at the point of bagging. As exact uniformity of grading cannot be secured, owing to the variable nature of the material coming from the pit, an allowance is made in the requirements of the test, the mill test showing a higher :percentage in the upper test boxes than called for by market tests. As a general rule', the pur- Fiber treated according to lchaser is delivered a fiber running higher on test than specified in his contract.

Several pounds of asbestos treated according to Example I were run through the standard testing machine and the results assayed. Subsequently, several samples of No. 2 crude fiber were .put'into the machine and the results assayed.

The results were as follows, in terms of the per'- centage of the starting fiber. which remained on the first and second boxes of the testing machine. Percent No. 2 crude, about 91 Example I, about' "-.92

'Ihe treated fiber thus exhibited slightly better test results than the No.- 2 crude, according to the Quebec Standard test which isthe accepted trade measurement of grade.

Example III on its spinningqusimes, ail, the treatedy fiber of Example I was sold-to the textile trade 'at a price of '$330.00 (Canadian, May 1942) per ton, approximately $300.00 U. B. funds (May which are super- 6, y 1942) or at the equivalent price of No. 2 crude ber. Excellent reports were received as `to its textile' qualities.

Example IV Sample lots of the ber treated in accordance with Example I were subjected to opening This is a preliminary treatment before textile use. The shrinkage was about 11.9% by weight. This compares with the normal shrinkage for opening No. z'crudeii-ber of about 12%.

` Example V A batch of asbestos orewas milledby dry methods. 'I'he milled ber was subjected to treatl It winbe understood that, without departing from the spirit of the invention or the scope of the claims, various modifications may be made in the specific expedients described. The latter are illustrative only-and not offered in a restricting sense,\it being desired that only such limitations shall be placed thereon as may be required by the state of the prior art.

The sub-titles used throughout-the specication l are merely to simplify reference thereto and should otherwise be disregarded.

I claim:

1. A process of treating milled asbestos ber, y

comprising, scrubbing masses of the fiberwith water eiectively to remove entrained dust without roping` the fibers, compactingsaid masses into sheets, drying the sheets, berizing the sheets by subjecting themto flexure in various directo preliminary textile operations in which it was mixed with` about 6%- cbtton. The mixture oi' crude fiber and cotton was made into yarn B.

`The yarns A and B were spun on a spinning machine. The yarn A was observed to have substantially equal textile qualities to yarn B.

The procedures and results described make it evident that milled bertreated by the present process is the equivalent in textile qualities of No. 2 crude ber. The potential textile qualities of the milled ber are improved. Dust up to'the amount of about 17% by weight of the aber and' which would normally impair the textile qualities is removed. The flber length is preserved since the batches of the lmilled in the examples retain a ber length substantially equivalent to No. 2 crude as determined by the Quebec Standard test. "In other Words, the treatment is successful in removing the undesirable content ofr the milled ber masses Without having the expected undesirable effect of causing c inseparable matted masses, which could not'beV disintegrated without reducing the ber length.

` In brief, the'ber lengthis maintained substantially at'the potential for the particular milled ber being treated.v f

The treated milled ber textile qualities of No. 2 crude ber and sells at about the saine prices Only about 5 to about 7% cotton need be added tothe treated fiber for spinning. Previously, milled ber required'up to about 18 of 20% of cottonA to impart satisfactory spinning qualities to the roving.

The invention has been described specifically as applied to milled ber. It willbe understood that in its broader aspects, the process might be applied to cleaning and otherwise improving ber which has not'actually been milled. Also, some y, of the process stepsas specically described may t be modified by the substitution of equivalents, provided, of course, they fall within the scope of the following claimsfj Water has been specified as the washing medium as this is vthe most con-` venient liquidknown forthe purpose. Any other suitable washing medium could be used without altering the spirit of the invention.

, Whilechrysotile asbestos has been dealt withy in this speciilcation because this is the type of asbestos occurring in Canada it lwill be understood that various othe'x` types of asbestos may also be treated by this method, for instance amphibole, crocydolite, etc. 'I'he term asbestos is,

therefore, used in a generic sense.

has substantially the ber referred to y tions while partially supported,'and liberating the fibers from the partially berized sheets by the action upon them of compressed air without substantially reducing the staplelength thereof, whereby there is produced a cleaned ber having substantially thepotential textile qualities of the starting ber.

2. A method of treating asbestos ber `containing dust, comprising, washing masses of the sheets to flexure alternatively in transverse directions while supported between opposed surfaces whereby the sheetsare-completely berized,I

" and blowing the sheets with high pressure air against a resistance element to liberate the bers.-

4. An apparatusfor washing asbestos ilbers, comprising in combination, a substantially cylindrical tank having sides and a ioor and adapted l to contain water, a centrally arranged discharge opening in said floor, a discharge pipe adapted t0 fit in said opening for vertical movement, means for moving said discharge pipe in a vertical direction whereby it may be set to maintain the water in the tank'at apredetcrminedlevel and may be lowered to allow water and asbestos to escape from the tank, a water supply pipe encircling the' bottom of the ltank substantially at the margins thereof,*a plurality of discharge openings inl said pipe constituting ljets arranged to supply water in a substantially vertical direction at a number of points' about the margin of the tank, an air pipe encircling the bottom of the tank adjacent the margins thereof, openings in said air pipe constituting jets for the injection of air adjacent the bottom of the tank in a substantially vertical direction thereby to cause non-turbulent circulation oi.' the water away from said openings upwards and inwards towards the center of the tank, means for supplying water to the water pipe and 'means for supplying air tothe airpipe, means for controlling the water supply, and means for controlling the air supply.

5. An apparatus as claimed in claim 4 wherein means is provided for injecting water into the tank adjacent the margins thereof in a substaninto thin sheets, subjecting 2,386,713 caused circulation of the water about the tank inI a horizontal direction.

6. In a process of treating asbestos obtained by dry milling asbestos ore wherein the rock is crushed and the asbestos fibers oi spinning grade are removed therefrom containing dust in amount to impair their v ing said ilbers with water and\washing out the dust without roping` the bers, dewatering the washed substantially dust-free mass, drying the textile qualities,l the steps of wash.

same, working the dried mass totlberize the same,

and uiling the berized mass to separate the bers from each other without substantially reducing is produced -a cleaned -ber having substantially ghi; potential textile qualities of the starting the staple length thereof, whereby there v LEE c. PHARo.

Certificate of Correction Patent N o. 2,386,713. October 9, 1945'. LEE C. PHARO It is hereby certied that error appears in the above numbered patent requiring correction as follows: In the heading to the printed specification, line 7, foreign filing date, for In Great Britain February 10, 1942 read In Canada February 10, 1942; and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Oce.

Signed and sealed this 23rd day of September, A. D. 1947.

[SEAL] THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents.

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