US3162381A - Apparatus for delaminating laminar minerals - Google Patents

Description

Dec. 22, 1964 M. l. COHN ETAL APPARATUS FOR DELAMINATING LAMINAR MINERALS Original Filed Dec. 22, 1958 4 Sheets-Sheet 1 L'EeRINEIIrNEgAL CONASARATOR wATER sLuRRY PUSTEsD/REVE Y 'SEPARATOR FEED TANK plpp j GRAVITY 2 3 4 FEED /2 w PREssuRE cRusl-IER PUMP a VALVE -DRE 34 f4@ j@ 36) f scREEN DEADDLDMERATDR E DRYER cENTRlFueE GLAgsRlFIER FINISHED PRoDucT F I G. l

QQNTNEEIAL MlcA WATER sLuRRY PREssuRE AToR ANR A VE SEPARATOR coucENTR FEED T pgp Pump e v L GRAVITY KZ \3 4/ FEED Q /34 DVERsnzE REcYcLE scREEN GRUSHER cLAsslHER -DRE /40 /35 /36 'L''snrw DEADDLDMERATDR DRYER A cENTRlFuDE F I G. 2

INVENTORS MORRIS l. COHN ROY D. PERDUE @ii/Mm mm@ ATTORNEYS Dec. 22, 1964 M. l. col-IN ETAI. 3,162,381

APPARATUS FOR DELAMINATING LAMINAR MINERALS Original Filed Dec. 22, 1958 4 Sheets-Sheet 2 INVENTORS MORRIS l. COHN ROY D. PERDUE D BY "ga/W www ATTORNEYS Dec. 22, 1964 M coHN ETAL 3,162,381

j FIG. 7

INVENTORS BY www. Saug@ l ATTORNEYS Dec. 22, 1964 M. coHN ETAL APPARATUS Foa DELAMINATING LAMINAR MINERALS 4 Sheets-Sheet 4 Original Filed Deo. 22, 1958 INM.

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INVENTORS MORRIS l. COHN ROY D. PERDUE ATTORNEYS 3,162,381 Patented Dec. 22, 1964 sassi t claims. (ci. zii-to) The present invention relates to a method of and apparatus for grinding and delaminating mica, especially mica derived from mica schist ores.

Mica is found in nature in the form of schist, pegmatite, alaskite and other deposits. Some schist deposits contain as much as 60% or higher mica by weight. Pegmatite ores, now being commercially Worked, seldom yield higher than 10% mica from the total rock mined. The former are soft, consist of small particles of mica dispersed throughout the rock and are easily worked by open pit mining techniques.` The latter occur in hard rock `as veins and are inherently more diiiicut to mine. Schist deposits therefore are attractive sources of mica if the delaminated ground product derived therefrom could meet the specifications of the mica consuming industries. However, prior to the present invention, no commercially successful method has been found to grind schist mica to obtain a mica product which is acceptable commercially in spite of the fact that many attempts have been made to do so.

Mica occurs in nature as clusters of laminated sheets called blocks or books. In schist, these books are quite small, perhaps 1A to 1A; inch across and smaller and are dispersed throughout the rock. On the other hand, mica books from conventional pegmative veins may run several inches in one or more dimensions. Mica derived from pegmatite deposits can be delaminated and ground by several well known wet land dry processes to yield fine particles having a plate-like structure. It is this plate-like or iiaky shape thatr mainly accounts for the utility of ground mica. Mica derived from alaskite deposits (in the mining of feldspar) also lends itself to conventional delaminating and grinding techniques yielding line iiakes. On the other hand, schist mica and micaV from other sources containing a large percentage of fines have always been diiiicut to delaminate and grind to sufficient lineness while still preserving a plate-like particle shape. In other words, it is ditiicut to delaminate the small books of mica in schist and other mica products containing the same and reduce the delaminated sheets to Hakes of proper iineness without destroying the plate-like structure of the mica. With most conventional grinding techniques, the ground particles obtained from schist mica and other mica containing a large percentage of lines are not suiliciently aky and consequently the resulting product is commerciallyunsatisfactory. It is believed that the reason for this is that the smal! books are ground as such into smaller books without delamination occurring.

The paint industry, wallboard-joint cement manufacturers, and other high tonnage consumers of ground mica have established particle size and bulk density specifications, among others, `in order to control the quality of the mica being used in their products. It has been found that the bulk density, i.e. the actual weight of ground mica contained in a given flufed or riiiled volume thereof (pounds per cubic foot), correlates Well with the ilakiness and iineness of the individual particles. The more flakes present in a sample, i.e. the greater the degree ot' delamination, the greater the percentage of voids and thus the lower the bulk density. The lower the bulk density and the finer the Hakes, the higher the quality of the product. The bulk densities of undelaminated mica ground and unground and of ground mica, the platelike shape of which has been destroyed, are relatively high.

The best and more costly ground mica products obtained from dry and wet grinding methods have bulk densities of 10 to 14 lbs. per cubic foot. Of these products, the finer grinds having particles of dimensions less than 44 microns (minus 325 mesh) command the higher selling prices.

No commercially satisfactory, instantaneous and continuous method of grinding a true schist mica and other mica products containing a large percentage of nes to low bulk densities 10-14 pounds per cubic foot and lower) and ine particle size has been known prior to this invention. Batch type wet mulling as practiced in water ground mica manufacture will delaminate schist mica, but this method is unattractive because of the long time cycles and high overall cost.

An object of the present invention is t0 provide for the rst time an economical, commercially feasible, instantaneous and continuous apparatus for delaminating and grinding schist mica and other mica products containing a high percentage of ines into tine, flaky particles `without destroying the plate-like structure of the mica, to produce a tine, iaky mica product having a sufiiciently low bulk density and sufficient ilakincss and ineness to meet the most exacting standards of the mica consuming industries. While primarily designed for schist mica, the delaminating and grinding method of the present invention provides an economical, instantaneous and continuous methodfor grinding conventional scrap or book mica derived from pegrnatite, alaskite and other mica deposits or from mica trimmings and splittings to the necessary particles size and bulk density specifications required for the more costly ground mica products.

A further object of this invention is to provide a cornmercially feasible, economical, instantaneous and continuous apparatus for delaminating and grinding mica, which in addition to having the advantages above referred to, can accommodate, as feed, mica books of tine size which heretofore had tobe discarded.

yA. still `further object is to provide an improved apparatus for delaminating and grinding mica.

Another object of the invention is to delaminate mica by forcing a liquid `slurry of mica particles under high pressure to flow at a high velocity through a highly restricted opening and separating thetne particles of the delaminated mica from the larger particles vand recycling the larger particles through said opening.

According to the present invention a high fluid pres- K sure is applied on a liquid slurry of mica books orblocks to force it to flow at a high velocity through a highly restricted opening in thenature of a fraction of ali inch formed by closely spaced hard surfaces designed to imy slurry on the valve and valveA seat.1"=

embodiment,'the restricted opening comprises a valver opening and the slurry under high pressure is directed.

against the valve to force it slightly away from its seat against the force of resilient means such as a spring or the like yieldingly Vurging it toward its seat, whereby Vthe slurry under pressurey is forced at an extremelyhigh velocity throughthe highly restricted opening between l the valve and Aits seat and against the impact surface. The direction of ow of the slurry through the valve opening is at an 'angleto the direction .of flow to the valve, and the opening -is preferably annular inV shape.

Preferably, thegvalveis rotated to prevent the slurry from wearing a channel in vthe valve seat and to cause the wear effects of. the slurry onr the valve and. valve seat to be more uniform 4whereby theusefulflife of the valve and valve seat beforeroverhaul andrepair becomes necessary issubstantially,increased.- n Y v The fluidA pressure can be 'generated sure pump such as. a piston pumpoperating on th slurry.

The valvefmounted onl the pumpdischarge, can berainyV oneof several designs such as that used forthe high pressure homogenizing of milk. I v Y The impact'surface can be provided byan impactring around the annular valve `openingandyvithin a fraction of an inch therefrom, Vas is customary with valves of this design. The ring forms with the/outside of the valve ,a passage of restricted crossv sectiony extending at anVY angle to the' valve openingy and through whichl the slurry flows after impacting against theV ring.

A valve assembly such as "'thattknown :as Vva Gaulin Single Stage Homogenizing,ValveAssembly is suitable.,

However, valves of similar'and modied designproviding like action c an beused within the scope of thisiinvention'.

Fluid pressure can be generated by, any meanswhichwill develop. suiciently high pressures. multiple piston pump is hereinaftery cited as a convenient method, butvvertical head pipes,- accumulators, pumps of alternate designV and the like could also. be lemployed as f @45 particularly suitable because of pressure sources.

`An aqueous slurry is l A thelowcost and availability of water and because the usual steps employed in removingnon-micaceousminerals from the ore Ynormally require water.Y However, any

liquid which doesrnot detrimentally. aifect the mica VcanV be used'. Y

The invention will be more clearly understood the following descriptionl in conjunction with the accompanying drawings,y inwhich: q Y FIG. 1 is allow diagram of themethod of the present Y invention with the various units designated as boxes.

FIG. 3` is a diagrammatic View of themica slurry tank and theY pump andkvalve assembly of'FIG. l. Y

being recycled back to the slurry feed tank. v

FIG. 4 is anenlarged .view of the valve oi:"-FIG,`3...-` L..

FIG.l 5 Vis a .view takenalong the line 5.-.-5-of FIG, 4.

FIG; 6tis a View taken along the 1ine-'6-v-6of FIG. 4. Y

v FIG; k7 is a viewv like FIG.` 4 showing `the yeffector) the parts of the abrasive action of the micaslurry aftenthep' valve assembly has been in Vuse .for some time."

by a suitable pref-vv The use of al Before explaining in detail the present invention it is to be understood that the invention is not limited in its application to thefdetails andA :arrangements,illustrated and described herein, since the invention is capableiof other embodiments and of being'practiced or carried out in various ways. Also, the terminology employed and the theories described herein arerfor the purposes of descrip- Vtion yand explanation and not of limitation and it is not intended to limit the invention claimed herein beyond the requirements of the prior art. Y

'With reference to the drawings, the mica ore (schist, pegmatite or alaskite or other f mica deposits) is rst crushed into small particles in a conventional ore crushing mechanism 1. Garnet and heavy minerals, if present, are then removed from the crushed oreY in a mechanism 2 conventionally used for that purpose. Silica and other remaining non-micaecous minerals are then removed from ythe mica in a conventionalV froth otation unit or :othermica concentrator utilizingwater and suitable flotation reagents, if necessary. The mica and water discharge from flotation unit 3 flow tofthe mica slurry feedV tank 4 to which additionalwater is added to obtain the desired 1concentration of micaV in yvvatenz The mica and Water arey agitated. in tank 4 by agitator 5 to produce a uniform aqueous .mica slurry which is fed. by gravity or va ypump to the inlet-Tof liquid piston Vpump 10 ofthe pressure `pumpand valve assemblylZ.V The slurry is sucked` from inlet 7 through suction ball check-valve 13 of pump ltlitin'to the pump -cylinder- 14 by the suction FIGB is a' view/taken along the' line s s.Qf"FIG.. 7. Y i 'FIG'. 9 isa view'taken alongthe line 9 9 of FIG, -7,.-

' `FIGJ 10 is afsection invelevationV of anotheriembodi``v ment of a valveassernbly for carrying outthe'method of the presenti invention andy havingY a `mechanismf-'for rotating'the valve'surface.: withliwhich. the mica slurry y comes: incontact to reduce harmfulfwearreffects-iof the'i stroke of piston 16 and isrforced through discharge ball check valve. 18 to andy through the high pressure pump outlet 20V into-the highpressure inlet passage or chamber 22 of the valve assembly 23rand.` against valve 24,(which is urged toward valve seat 26 by a heavy spring 33. The high pressure exertedon the valve 24 by the slurry in the conned passage 22 forces the valve slightly away (a fraction of anginch) from its seat 26, whereby: the slurry undery pressure flows at an extremely high velocity through theV highly restricted valve opening ZSVagainst an annular" impact ring 30. extending around'the valve.V y The` slurry then flows through the narrowpassage 29- between the ring 30 and the adjacent outer peripheral walls of the valve and seat. Delamination andgrinding are'achi'eved "by the shearing eiect on the mica particles of the closely spaced valve seat 26 and valve face- 31 forming 7opening y ZSfand of the closely-rr spaced impact ring 30 y'and' outer shattering and impact of the ,particles against the yimpact ring 30 and; valve face 31. The variouschanges in direction/ ofhflow of Ythe slurry from 22 to -28 andfrom-ZS to` 2791 Aalso*'contribute toV the delaminating and. grinding l phenomena. It is believed Vthatthe liquid media conl effectiveness the `deVlaminating-andV Vtributesyto ...th l grinding forces. i

and'hit the impact ring edgewise. Thisbelie'f is supported. by thefact` that initiallywith anew impact'ringthe im'f Y pact surface.immediatelytopposite the-discharge of the yopening develops la. very# iinely'etched` hair-line groove *l and by the fact that thefpostagestamp`shaped mica particles. in the nishediproduct havetwoldimensions (plan-ar- .dimensions) which are greater thanlthe'size' dofvthr yopen- .V and the widthfof the-hairline groove. i f

'The slurryv containingfthe .delaminated groundfmica Vhows/from pressure pump and valveassembly 12 'toa` second `pressurepump-and valveassembly.3,2` of lthe same VItis alsobelieved that therestricted valve ope'ningZSy y for removal of water from the centrifuge cake.

construction as l2 and in which the mica is further delaminated and ground. The delaminated mica flows from 32 to a conventional screen or classier 34 in which the mica particles which are coarser than desired in the iinal end product are removed. The second pump and valve assembly 32 can be omitted in which case the mica slurry flows from 12 directly to 34. The mica slurry containing tine mica llakes flows from 34 to a conventional centrifuge 36 where the bulk of the water is removed and the coarse particles may be recycled back to the slurry feed tank 4. The mica particles are then dried in a conventional dryer 3S and the dried mica is passed to a conventional deagglomerator 4d in which any agglomerates formed during centrifuging and drying are broken up. The iinished product is discharged from the deagglomerator 40 and comprises fine mica iakes of low bulk density and top quality.

The iiow described above is continuous and the delamination and grinding of the mica occurs instantaneously as it passes through aperture 28, strikes ring 30 and passes through passage 29. ln the particular valve assembly 23 shown in the drawings, the diameter a (see FIG. 4) of the bore forming valve inlet 22 is 0.1877 inch, the diameter b of the valve 24 is 0.375 inch, the distance c between the impact ring 30 and the outer peripheral surfaces of the valve 24 and seat 26 is .032 inch, the distance d between the valve face 31 and the valve seat 26 (width of opening 28) is between .001 and .005 inch, the width c of the impact ring 30 is .2848 inch and the thickness f of valve seat 26 (distance of travel of slurry While between the valve and seat) is .0935 inch. The spring 33 is of suiicient weight and is compressed suiiciently to exert, when dow through the assembly is O, a closing force on the valve which is slightly less than the force exerted on the valve by the liquid slurry which is under apressure ot about 6,000 pounds per square inch so that, during ilow of slurry through the valve assembly, the valve 2d is forced a fraction of an inch away from the seat 26 by -a slight compression of spring 33 to form the annular opening 28 through which the slurry flows at a velocity of about 540 feet per second from high pressure area 22 to the low pressure (substantially atmospheric) areay outside the valve. The above mentioned specific dimensions, pressure and velocity are given by way of example only and it is not intended that the invention be limited thereto.

lt is advantageous to recycle the coarse mica particles separated from the iines at screen 34 from the screen back to the slurry feed tank d as shown in FIG. 2.

The slurry feed tank 4 can be any tank iitted with an agitator designed to keep the mica books in uniform suspension. The screen or classifier 34 can be any or" a variety of rotating or vibrating screens capable of handling slurries or any other type ot' wet classifier such as' arake classifier. The centrifuge 36 can bera'periorate bowl type fitted with a suitable iilter media or a solid bowl type. The dryer 38 can be of conventional design The deagfrlomeratorl dil can be any kind of device, such as a hammer mill, which will break up the dried mica. This f mica sometimes cakes into hard lumps as it passes through ,t the dryer and normally needs only a slight impact to reduce the lumps yand restore the mica to loose particles.

Although an annular valve opening 28 is shown in the drawings and is preferred, a fixed or adjustable aperture of any kind and shape can be used in conjunction with ,an impact surface in front of the aperture discharge.

As indicated above, the individual sheets of mica within the books are separated and reduced to iine particle size by shearing, turbulence, shattering, impact and cavitation forces as the slurry of `books is forced under pressure through the restrictedop'ening 2S of the valve at extremely high velocities and is impacted against the ring tlfand'fiows throughpassage 29. The effectiveness of this phenomenon in producing tine, flaky, plate-like particles has been found to depend on the following variables:

Variable Weight percent concentration oi mica in the slurry. Particle size range oi the mica books, or the average particle size of the books.

3 Pressure developed by the pump or head device.

4 The number of timos that the slurry is subjected to the phenomenon, hereinafter' called the number of passes.

5 The removal of une particles as soon as they have been produced and recycling of the coarser particles back to the slurry feed tank.

1. CONCENTRATION 2. PARTlCLE SZE RANGE OR AVERAGE PARTCLE SlZE Holding `the other variables constant, the larger the average particle size, the lower the bulk density of the resulting product. While an absence of exceedingly tine books has been found to give a better product, the method of the present invention can be used no matter how tine the average particle size may be by adjusting the concentration downward (see Example l below and discussion of Variable No. l above) and by recycling the coarser particles removed at screen 3d (see Example 5 and discussion of Variable No. 5 below). Particles are limited in maximum size only by the capabilities of the pumping or pressure produc-ing device and the internal dimensions of the valve. In practice, a particle just passing a 20 mesh screen can be easily handled. lf a piston pump is used, the larger the pump, the larger the particles which can be handled. The effect of varying particle size is demonstrated by Example 2 below.

3. SLURRY PRESSURE Holding the other variables constant, the higher the slurry pressure, the lower the bulk density of the resulting product. Pressures as high as 12,000pounds per square inch have been used uccessfully. The maximum pressure dictated only by the limitations and capabilities of currently available equipment. Some pumps presently available can develop 20,000 pounds per square inch and higher. As a practical matter, the upper limit is consistent with goed product quality without undue equipment maintenance and wear and the lower limit is not the lowest pressure at which the phenomenon can be detected, but rather represents a point below which other variables must be adjustedy to such a point as to make the process lose its commercial advantage. About 250 pounds per square inch may be considered as a practical lower limit, although with certain soit mica deposits some delamination may occur at pressures as low as about pounds per square inch. Griginally, pressures from about 1,500 pounds per square inch to 6,000 pounds per square inch were studied and more recently, pressures from about 500 and 600 pounds per square inch to 6,000 pounds per square inch have been used successfully and are presently the most practical, All pressures referred to hereinbefore and hereinafter are gage pressures. The effect of varying pressure is demonstrated by Example 3 below.

n of less-than about 0.10 inch-*is .preferred f 7 4. NUMBER oF PAssEs Holding all other variables constant, the greater the number of passes, the lower the bulk density of the resulting product. The etect of increasing the number of passes is demonstrated by Example 4 below.

5. REMovAL oF FINE PARHCLES AND RECYCLING CoARsER PARTICLES It has been found that by passing the slurry through the valve, removing the desired fine mica flakes by Wet screening or the like, recycling the oversize material and adding raw mica and water to restore the concentration, a lower bulk density and higher conversion to tine flaky particles can be obtained'thanV without recycling of the oversize material.

The size d ofthe valve'opening 28 depends upon the compression of the spring 33 and the tluid pressure on the slurry. Opening sizesrin thenature of between ,about .001 and .005 inch (less .than '.010 inch) are typical., y The lower lirnitisV dictated only by practical considerations. Opening sizes greater than about .090. Vinch require such a high pumping rate or such a small dimension a (FIG. 4) to achieve adequate velocities through opening 28 that they are not commerciallylpractical. In fact, opening sizes greater than about .050 inch are diiiicult to use, although with certain soft mica deposits and under certain conditions, some delamination may l'occurr'with opening sizes as large as about 0.10 inch. The'velocity of the `slurry through the opening 2S depends on the size of the opening, the uidpressure, the force exerted by the spring`33, the capacity of the pump (volumetricI delivery) and the magnitude of Vdi-y mension a. Velocities in the nature of about 540 feet per second and greater, including sonic velocities, can be used. Maximum velocities. are dictated only by practical considerations and limitations of available equipment. Velocities between about 300 feet Vpersecond and 1,000 feet per second are preferred.' With most mica concentrates the .delarninating yphenomena, decreasesV rapidly below about 250 feet per second, although with certain soft mica deposits,ldelamination may occur at velocities as low as' about 1001feet .per second. Y

The rate of feed of slurry to, the pressure pump 10 is not critical and `can be as low'as 15 gallons per hour and as high asV 3,000 YVgallons per hour and more de pending on the capacitiesof the pump 10 and valve 23. Slurry pressures and velocities developed at the valve are regulated by `the compression of kspring 33. By compressing therspring more, a higher pressure is developed to force the` slurrypthrough the spring loaded valve, `the opening 28 becomes more restricted andthe slurry velocity increases. .The maximum spring force is dictated Y by maximum pressures and velocities which in turn are dictated by limitations-ofV currently available equipment.

The minimum spring force dictated only bythe mini? mum pressures, velocities and valve opening sizes Vat which Y substantial delamination occurs.v

Although aspring`33 visV shown urging the valve 24` toward closed position,1, any other resilientvyieldable means can rb e'rused such-as .a' pneumatic orhydraulic y inotorv or blockvof elastic material such Vasl a hardrubber material.

` The distance the impact" ring 30 from? the adjacent peripheralsurfaces of the valve andV seatisim'portant. The smaller-.fit is, the better the results. However, it

mustfb'e large enough to"accommodate the discharge from` n opening k2.8.4 'Ihe vdelaminating effect .decreases rapidly atV distances Ygreater' than about 0.25 inch.V A distance c Y Ermpls -I v y 1el rangeY of 'eicienciesl and performance which` can V b btained vby va'ryimgftheV aboveY/ ariableszl to Share.'

manifold. "The following examples are meant to supp'ort the preceding statements'and in` no fway are intended to limit the scope of the invention.

TheV mica feed for the following examples, with the 5i yexception of Example, was obtainedV from the Gassetts Schist located in Chester, .Vermont The schist was crushed and ground in 1 to pass a. 20'mesh screen. The garnets and Yheavy minerals werey removed -in -2. The mica was separated from Vsilica-and' other non-V lomicaceousminerals by froth flotation-'in 3. A particle size analysis of the resulting mica concentrate is vas fol-V lows:

Mesh: V y Percent Minus 20 plus 30 v 0.62 Minus 30 plus 40 Q. 3.78 Minus 40 plus 60v A 15.8 Minus 60 plus 100 Y l19.0 Minus 1001plus 200 L 31.9r Minus 200 plus 325y y14.9 yMinus 325011 pan 14.0

, 100.0 A 13u11; ansityzfis-smbsper n.ft.

Ineach example, the whole or a fraction; (as indicated) KIof the mica discharged from froth flotation apparatus 3 was passed to 4 Where an aqueous 'slurry of proper concentration..(asindicatedin the examples): was made.

and then ilowed through thevarious units as Vdescribed above and shown in flow diagrams 1 and 2. In Examples 1 to 4,'flow' was accordingr tojFIG. 1 exceptv thatin runl 1 'o'f Example 4 the pressurerpumpand valve assembly 35- 32 was'. omitted. iIn' Example 5,' steps 2 and 5, theflow was according Vto FIG. 2, whereas in. step 1 the -il'ow was according to FIG. l with the exception that +325 meshY particles separated Vfrom the slurry in 34 were recycled Yfrom 34 to 4. In Example 6, ow was according Vto VFIG. 1'. 1 l i EXAMPLE 1,-EFFECT Y f Y OF SLURRY Feedto 4: -60 plus 200 mesh fraction o mica concentr atc discharged from 3. and described above v Rate of slurry, feed te 12: 15 gallons per hour Fluid pressure in 12. nd 32: 6,000 pounds per square inch Number of passes: -2 (Two pressure pump and valve assemblies 12 and 32 .in series as'shown in Fig. 1) y I l Removal of ne particles between passes: None Concentration Bulk Density oMica in of Minus 325 Run No. Water Slurry, Mesh Fraction,

Y Percent Bylbs/Cu. Ft.,

Weight Removed from EXAMPLE 2.-`EFFECT OF VARYING AVERAGE PARTICLE f SIZE OF MICA yFEED g Pressure in 12 and 32: '6,000 pounds per square inch Number of passes: 2 f Removaljof fine particles between passes: None Concentration: 10% -by weight. j 1 .A Y

Same rate o`f slurry feed asExample 1 I BulkLDcnsity Y of Minus 325 Run-No. FeedDescription; A Mesh/Fraction,

I lbs/CuFt," Rempvedfrom- 40,.'

' 1.-- Fraction of micaV concentrate discharged v 16.4v frbm`8minu's100mesh onlyf.; -v 2 Fraction of mica concentrateN discharged 12,1 Y Y, from 3, plus 10D mesh only. y .Y

A0l? VARYING CONCENTRATION EXAh/IPLE 3.-EFFECT ONJARYING PRESSURE IN 12 Feed: Sehist mica concentrate as discharged from mica concentrator 3 Rate of slurry feed: Same as Example 1 Number of passes: 2

Removal of fine particles between passes: None Concentration: 5% by weight i Bulk Density EXAMPLE 1r-EFFECT OF VARYING NUMBER OF PASSES Feed: Schist mica concentrate as discharged from mica concen'trator .3

Rate of slurry feed z Same as Example 1 Removal of fine particles between passes None Concentration 5% by weight Pressure 6,000 pounds per square inch Number o Passes Run No.

Nr-l

EXAMPLE s nnrrovAL or FINE PAR'rrcLEs (-325 MESH) WITH nEcYcLrNG 0E coARsER PARcrrcLEs (+325 MESH) Feed Schist concentrate as discharged from mica concentrator 3 Rateof slurry feed Same as Example 1 Concentration b v weight Pressure 6,000 pounds per square inch N0rE.-Conversion of approximately 25% of total material handled per pass to 325 mesh low density mica is obtained after stabilization.

The initial 200 parts of feed to 1 2 was all raw feed. 133.5 parts 'of the discharge from 32 was 325 mesh and continued on to 150. 66.5 parts were +325 mesh and were recycled back to 4f and 133.5 parts of raw feed were added to bring the total feed back to 200 parts. Sutilcient water was added to provide a 20% concentration. Thchew feed was fed to l2 and then directly to 34 as shown in FlG. 2. 62.3 parte were 325 mesh and were passed on to 40. 137 parts were +325 mesh and were recycled. This increase in the amount of +325 mesh discharged from 12 was duc to the fact that only one pass was used in step 2 and the fact that the new feed with the recycled mica contained more coarse particles than thc original feed. 62.3 parts of lraw feed were added to the recycled feed to bring the total back to 200 parts and enough water was added to obtain a 20% by weight concentration and the new feed of step No. 3 was fed to l2. Thereafter, the amount of 325 mesh particles produced stayed at about of the feed and the amount of recycled +325 mesh particles stayed at about 75% of thetotal feed. Thus, conditions became stabilized after the first step and bulk densities 'of between 12 and 13 pounds per cubic foot were continuously obtained (discharged from llt?) from raw feed having a bulk density of 48-52 pounds per cubic foot continuously fed to EXAMPLE` 6 A sample of conventional mica scrap (not schist) having a particle size analysis as follows was used in another run (fed to 4) under the following conditions:

Mesh: Percent On 20 Trace Minus 20 plus 30 Trace Minus 30 plus 40 1 2.8 Minus 40 plus 60 44.0 Minus 60 plus 100 43.3 Minus plus 200 6.0 Minus 200 plus 325 1.6 Minus 325 on pan 2.3

1 Bull: density 20.0 lbs/cu. ft.

Rate of aqueous slurry feed: Same as in Example l Pressure in 32: 6,000 pounds per square inch Pressure in l2: 2,000 pounds per square inch Number of passes: 2 (12 and 32) Removal of une particles between passes: None Concentration: 10% by weight in water Bulk density of minus 325 mesh fraction removed from d0: 9.55 lbs/cu. ft.

Percent converted to 7325 mesh: 38.6%

ln accordance with the present invention, mica having bulli densities less than about 7 or 8 pounds per cubic foot and as lov. as about 3 and 4 pounds per cubic foot and having a incness of much less than 325 mesh can be produced efficiently, economically and continuously. Mica having such low bulk densities has never before been produced.

Dcnsitics of about 3 and 4 pounds per cubic foot were obtained with theuse of the conditions of Example l but with 4 passes, a rate. of slurry feed to 12 of 120 gallons per hour, a fluid prcsurc of 3000 pounds per square inch and a concentration of 1% and with a North Carolina mica scrap having the following particle size analysis as feed:

Mesh Percent Plus 20 mesh 1.5 Minus 20 plus 30 13.3 Minus 30 plus 40 8.1 Minus 40 plus 60 23.0 Minus 60 plus 100 26.8 Minus 100 37.3

1 ruiten buik density 2`s-so ibs; per cu. ft.

The abrasive action of thev mica slurry on the surfaces 26 and 31 or the valve seat and valve respectively produces the following wear effects on suon surfaces after the valve assembly has been operated for a period of time.

Referring to` FIGS. 7 and 8, at the ring shaped arca 34a on the valve face 31 where the mica slurry changes direction and is simultaneously accelerated by the decreased cross sectional arca as it enters the restricted opening 28, a ring shaped area of wear 34a slowly develops. This ring shaped area develops into a ring shaped groove 34a which destroys or alters the working surface 31 of the `valve and thereby prevents the Yachievement of a proper uniform clearance d between the surfaces 26 and 31. As a result the quality and uniformity of the rcsulting delaminatcd mica deteriorates. Simultaneously as the ring shaped groove 34a develops on valve face 31 an area of wear develops on thervalve seat 'surface 26. This area of wear is either in thc form of a tine line 35 or wide channel 35, as shown in FlG. 9. The former is typical of softer valve material; the latter is typical of harder valve material such as tungsten carbide. The mica slurry flow tends to channel through these channular arcas of wear 35 and 36, thereby reducing velocity and shear effects on the mica particles and making presy can be used.

. l l sure control' and the achievement of properk slurry velocities diicultor impossible. nation'fand grinding and consequentlycauses the quality and uniformity ofthe resulting delaminated micaV to de-Y teriorate. K

To remedy these wear effects it is necessary yto remove the valveseat 26 Vvand valve 24 from thevalve assembly 23 and have 4the surfaces 26 and 31 relapped and polished by conventional. machine Shop practice. Y

It hasbeen foundthat the formation'of channels 35 and 36 can be substantialy reducedfor eliminatedand that thegroove 34 will develop more uniformly by rotating the` valvek about its Ylongitudinal axis.

A device in which the valve is so rotated and which is ysuiiiciently rugged indesign to operate satisfactorily at Vproduction rates of severaltons per hour` of ltin-e, delaminated mica from a coarse and abrasive mineral slurry,'

is shown in FIG;v 10. VThefvalve 37 has the same cross sectional shape. and'dimensionV as valve 24 in FIGS. 3 to 6 and is rotated by a rotatingshaftl 3ft to one endrof which the valve 37 is anchored by means or a press or interference lit of the end of the valve in a recess'in the end ofV the shaft.

This prevents proper delami- The shaft 38 is supported by two radial-package type bearings 41 and 42 equipped vwith dust and grease seals4 andenters the fluid chamber 43 through a stuffing box 44; The radial bearings 41 and 42 are Vpress iitted intoV the radial bearing supports 45 and 46; The stniling'box Vferrecl through nut 65 `and the spring rod 64 to plate 61h` er l adjusted by means of compression adjustment plug 62. The plug 62 is threaded in a supporting wall 63 and has a hollowV passage in which spring rod 64 is loosely tted.

l V'Olne end of rod '164 is threaded into hub 61d and the rod isy loosely tted in an aperture iny plate 61a. v y

Rotatin'g'lthe plug 62in one direction so that it moves axially to thefleft as viewed'in FIG. 10 increases the spring force exerted on the valve 37. Rotatingrthe plug in the other direction so `that it moves axially to the right decreases the spring force exerted on the valve 37. Continued movement to the right of plug 62 is nally transto-release the spring force on the valve 37 so that the unit can be disassembled.

The slight axial movement of shaft '38 and valve 37 betweenclos'ed position of the valve and maximum open position isV notv enough to interfere'with the pulley drive 50, 52 and 53.V

The parts of thevalveassembly subject to themost.

'severe conditions, -i.e. the valve 37, the valve seat 39 and PIG. l is designed so that these parts are of minimum Y the impact ring 54, are best made of the hardest obtainable materialssuch as tungstencarbide. Because o f the high cost of these materials, theV `apparatus shown ,in

size and can be replaced necessary. f

The dimensions'mfb, Vc, d, eand finthevalve assembly of FIG. 10 are substantially the same as' the'correspond- 44 prevents leakage loftvvater and mineral particles alongY the outer periphery of' shaft 38 by means ofy several rings of packing 47, a pression nut 49. p

Rotating motion is'imparted to theshaft 38 by means of a pulley 50 which is keyed to the shaft' 3S.. The

pulley 50'is driven by a motorl'; pulley V752 and V-belt 53.V

The cylindrical valve seat 39`jhas the same cross sectional shape and dimensions as valve seat 26 in FIGS; 3 to 6vand is supported in position by a cylindricaljvalve seatholder 40 into which yan end thereof'lis `anchored by means of a press or interference lit.

and 46a respectively which havethe same cross sectional shape and internal diameter as high pressure inlet'passage or chamber 22 in FIGS. 3 yto,6 andinto which mica slurry under pressure is pumped from pump lil,A 1

The impact ring 54 has thesame shape and dimensions as impact ring in FIGS. 3 to 6 and is held by means of a press lit in theimpact ring holderSS which in turn 'is supportedy and properly positioned byV aV Wall 56, whichis supported by the wall 69l of 'chamber43.l The peripheral portion of Wall 56adjacent outlet 68 of therchamber 43 is Y bevelled at 43u10 permit the mica slurry to ilow from the chamberV 43 on both sides ofwall 56`into outletj.

` The valv'e ,37, is urged axially towardthe valveseat i' packing follower 48-and a packing com-V Valve seatholder 46 is supported in an aperture in the end wallr 70 .ofe fluid vchamber 43. The valve seat 39`and valve'seatholder 40 are hollow and have axially aligned internal bores39a r.p.m. aresatisfact'ory. However 7600-800-r.p.m. is aY preferred range and can'be achieved through the proper selection of motor `5l. Aand the pulleys 50'and 52. v

surface 67 of valve seat 39 by the'actio'n ofa'co'rripresf'.,

sion spring acting on the end of shaft 38infan4axial f direction through a thrust' bearingv assembly 61;. Thev rthrust bearing assembly 61 permits the, shaftV 38 to rotate while being urged tothe left, as'shown in FIG.Y l0,l by the stationary spring 60. Y-

Thrust bearing assembly 61 comprises a yplate ,l 61a which is urged tothe left as viewed in FIG. 10' byrs'pring f 60. Plate 61a .actsV onplate lb'rthrough ball bearings 61a` and through the engagement of plate ,61a Withhubj, 61d ofplatei61b, to urge plate 61h to the left. Plate` 61hl Y acts on shaft 38thl urge it to thevle'ftl through ball bearings V61e and plate 611 atlxed to the end of the shaft. The

plates and ballfbearings of thrust bearing assembly 61 are housed within'afreefloatin'g housing 61g Vwhich'is prevented from-rotation fbutrwhichfis free to'rnove longitudinally. Any conventional thrust bearing assembly The amount o ing dimensions in the valve assembly' infFIGS; 3 to 6, it being understood that the-l invention is lnot limitedV to ksuch dimensions.

'The rotating motion of the yValve surface 66 .withfrespect to both the valve seatsurface 67 andthe impact surface of rimpact-.ring 54 causes theslurry therebetween to impart a constant lapping and polishing action on such surfaces which prevents the' formation of channels 35, 36

inV surface 67 as shown in FIG. 9. The surface 67 and the portion of suiface 66 facing surface '67 wear uniiormly and the equipment canbe operated until the Y groove 34a (FIG. 8) becomes so deep as to cause striking of the ungrooved peripheral portion'. of surface 66 against surface 67. When the surface begin to strike, the

valve can be disassembled and ythesurfaces 66 and 67 can4 be relapped and polished by conventional machine shop practice.'` Y I *l Valve37 can be rotatedras slowly as 0.5 revolution per minute (rpm.) and, as fast as. 3540 rpm. or more.

Speeds l' of-conventional motors, asfor example 1750 The rotary motion imparted to valve face 66 may be Flow through `the valveVv assembly ofFIG.` 10vshould be adequate to assure .a1 layer of slurry between the surfaces 66 and 67, which layer of slurry Vprovides a constant lapping raction on the surfaces and prevents thesurfacesv fromrubbingagainsteach other.v For example, with a valve seat 39jhavirigA an internal diameter aof 0.250'inch a` flow of aboutfour,gallonsper-ninute (gpm.) yor more is adequate. y

The fluid chamber 43 cani-bve formedby acylindrical 'Wall 69 or a series of ilat `wal1:s,.such asa box, and is closed at the endslby plate or wallf70, which ,supportsA the valve j sea-t holder 40, andthe stuffingbox 44.`

39a in the valve seat holder 40 and valve seat 39l respectivelyrjagainst-the,rotating valve ,37 to forcel surface 66 1 Y With reference ,to FIG. 10,'1`mineral slurry under pres-v C sure 'from the pump 10 passesthroughrthe bores 40a and l away from surfaee67 against the force exertedl on the valve by spring 60, to'-,th`ereby provide restricted 'opening a betweensurfacesl '661A and'67 throughlwhichv opening n Vthe slurry-flows at-'a high'velocity `againstthe impact ring 54, intof fluid 'chambenkt and out yof fluid chamber The method of the present invention can be used to delaminate and grind any mineral which occurs in the form of laminated layers such as seracite, talc and other socalled platy minerals.

Talc having a bulli density of 15 pounds per cubic foot and less, i.e., as low as six pounds per cubic foot, has been produced with the use of the method of the present invention.

Although its chief advantages are achieved in delaminating and grinding mica and other platy or layer-like minerals, it can also be used to grind minerals of all kinds.

This application is a continuation-impart of our application Serial Number 758,930, led September 4, 1958, now abandoned, and is a divisional application of our copending application Serial Number 782,992, iled December 22, 1958, now abandoned.

We claim:

1. An apparatus for continuously delaminating and grinding laminar mineral particles of the group consisting of mica and talc particles comprising means for forming a liquid slurry of mica particles, a spring loaded valve, a pump for pumping said slurry against said valve under a pressure suticient to force said spring loaded valve to open a fraction of an inch and force the slurry to low through the valve opening at a high velocity, a classifier for classifying the delaminated and ground mica discharged from said valve opening to remove coarse mica particles and means for recycling said coarse particles back through said pump.

2. An apparatus according to claim 1, including an impact member adjacent the discharge end of said valve opening and against which said slurry impacts as it is discharged from said valve opening.

3. An apparatus for continuously delaminating and grinding laminar mineral particles, said apparatus comprising means for forming a liquid slurry of said particles, a spring loaded valve, a pump for pumping said slurry against said valve under a pressure sucient to force said spring loaded valve to open a fraction of an inch and force the slurry to flow through the valve opening at a high velocity, a classier for classifying the delaminated and ground particles discharged from said valve opening to remove coarse particles and means for recycling said coarse particles back through said pump.

4. An apparatus according to claim 3, including an impact member adjacent the discharge end of said valve opening and against which said slurry impacts as it is discharged from said valve opening.

References Cited by the Examiner UNITED STATES PATENTS 1,756,198 4/30 Hurrell. 1,934,637 11/33 Rafton 241-21 2,204,063 6/40 Atwood 241-4 2,490,129 12/49 Heyman 241-4 2,547,336 4/51 McDaniel et al 241-4 2,549,880 4/51 Bardet. 2,778,713 1/57 NOda 23-110 2,936,218 5/60 McNeill 23--110 3,009,570 11/61 Lancaster 241-4 FOREIGN PATENTS 451,223 9/48 Canada.

1,045,335 6/53 France.

ANDREW R. JUHASZ, Primary Examiner.

ROBERT A. OLEARY, JOHN C. CHRSTIE,

Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,162 ,381 December 22 1964 Morris I. Cohn et a1.

It is hereby certified that'error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1 linesl Z3 47 and 49 for "difficut" each occurrence, read difficult line 36, for "pegmative" read pegmatite column 2, line 44, for "particles" read particle column 4, line 17, for "non-micaecous" read e non-micaceous column 8, in the first table, under the heading "Percent", line 4 thereof, for "-119.0" read 19.0 same table, footnote thereof, for "lBulk density" read Bulk density column 10, in the firstl table, under the heading "Percent", line 3 thereof, for "12.8" read 2.8 same table, footnote thereof, for "lBulk density" read Bulk density same column 10, in the second table, under the heading "Percent" line Z thereof for "13.3" read 3.3 same table, footnote, thereof, for "Initial bulk" read Inita bu1k column 11, 1ine 11, for "substantialy" read substantially column 12, line 41, for "surface" read surfaces Signed and sealed this 18th day of May 1965.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims (1)

1. AN APPARATUS FOR CONTINUOUSLY DELAMINATING AND GRINDING LAMINAR MINERAL PARTICLES OF THE GROUP CONSISTING OF MICA AND TALC PARTICLES COMPRISING MEANS FOR FORMING A LIQUID SLURY OF MICA PARTICLES, A SPRING LOADED VALVE, A PUMP FOR PUMPING SAID SLURRY AGAINST SAID VALVE UNDER A PRESSURE SUFFICIENT TO FORCE SAID SPRING LOADED VALVE TO OPEN A FRACTION OF AN INCH AND FORCE THE SLURRY TO FLOW THROUGH THE VALVE OPENING AT A HIGH VELOCITY, A CLASIFIER FOR CLASSIFYING THE DELAMINATED AND GROUND MICA DISCHARGED FROM SAID VALVE OPENING TO REMOVE COARSE MICA PARTICLES AND MEANS FOR RECYCLING SAID COARSE PARTICLES BACK THROUGH SAID PUMP.

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