US3592396A - Grinding and apparatus therefor - Google Patents

Grinding and apparatus therefor Download PDF

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Publication number
US3592396A
US3592396A US869413*A US3592396DA US3592396A US 3592396 A US3592396 A US 3592396A US 3592396D A US3592396D A US 3592396DA US 3592396 A US3592396 A US 3592396A
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Prior art keywords
grinding
grinding media
unit
continuous
media
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English (en)
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Andrew Szegvari
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UNION PROCESS INTERNATIONAL Inc AN OH CORP
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Individual
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Assigned to UNION PROCESS INTERNATIONAL, INC. AN OH CORP. reassignment UNION PROCESS INTERNATIONAL, INC. AN OH CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: ARNO, SZEGVARI, ADMINISTRATOR, DBN/WWA OF THE ESTATE OF ANDREW SZEGVARI, DEC`D
Assigned to SZEGVARI, ARNO ADMINISTRATOR DE BONIS NON OF THE ESTATE OF ANDREW SZEGVARI, DEC'D. reassignment SZEGVARI, ARNO ADMINISTRATOR DE BONIS NON OF THE ESTATE OF ANDREW SZEGVARI, DEC'D. LETTERS OF ADMINISTRATION (SEE DOCUMENT FOR DETAILS). EFFECTIVE MARCH 27, 1981. Assignors: SZEGVARI, ANDREW, DEC'D.
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/07—Stirrers characterised by their mounting on the shaft
    • B01F27/072—Stirrers characterised by their mounting on the shaft characterised by the disposition of the stirrers with respect to the rotating axis
    • B01F27/0726—Stirrers characterised by their mounting on the shaft characterised by the disposition of the stirrers with respect to the rotating axis having stirring elements connected to the stirrer shaft each by a single radial rod, other than open frameworks
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/11—Stirrers characterised by the configuration of the stirrers
    • B01F27/112—Stirrers characterised by the configuration of the stirrers with arms, paddles, vanes or blades
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/80—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F33/00—Other mixers; Mixing plants; Combinations of mixers
    • B01F33/25—Mixers with loose mixing elements, e.g. loose balls in a receptacle
    • B01F33/251—Mixers with loose mixing elements, e.g. loose balls in a receptacle using balls as loose mixing element
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
    • B02C17/16—Mills in which a fixed container houses stirring means tumbling the charge
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C17/00—Disintegrating by tumbling mills, i.e. mills having a container charged with the material to be disintegrated with or without special disintegrating members such as pebbles or balls
    • B02C17/16—Mills in which a fixed container houses stirring means tumbling the charge
    • B02C17/163—Stirring means

Definitions

  • the invention relates to apparatus for the grinding of solids suspended in a liquid by contact with grinding media which are activated by agitating means.
  • the grinding media may be balls of different sizes as is known in the art, or pebbles of French flint, as disclosed in Szegvari U.S. Pat. Nos. 2,764,359 and 3,149,789 which describe apparatus known in the industry as attritors; or the grinding media may be smaller particles such as the sand or the like employed in the so-called sand mills," such as disclosed in Hochberg U.S. Pats. Nos.
  • the operation involving the diminution starts with the combining of solids to be diminuted with liquids.
  • This :initial processing step is usually referred to as premixing and takes place in vessels equipped with a mechanically driven agitator in the absence of grinding media.
  • the acting forces are derived from liquid shear.
  • the nature of liquid shear is such that it is mechanically limited, that is, in a given apparatus its action is limited to a certain amount of dynes per square centimeters of acting area which cannot be exceeded. As a result, the action or liquid shear is limited regardless of duration.
  • the statistical effect of interaction between a system of activated grinding media and the feed to be diminuted depends first on the size of the interacting grinding media, and second, on the size relationship of these grinding media and the material to be diminuted, and third, on whether the interaction is carried out on a batch or continuous basis.
  • the width" or range of the distribution curve is narrower in batch-type operations (FIG. 4) and much wider, or flatter, in continuous operations because the probability of something happening, which is different from the average, is much smaller in the closed-circuit batch operation, where there is chance processwise of each cubic inch being like every other cubic inch, which is nothing else but the condition to have a narrow" or sharp distribution curve.
  • the processing drawback of this statistical procedure is that it takes time; much longer than necessary to obtain the flatterdistribution curves of a continuous statistical process.
  • Elimination of the larger! or coarsest particles That is reduction of the area of the distribution curve under the large end A.
  • the action of large grinding medium and coarse feed would eliminate the large particles without producing fines.
  • a large grinding medium on a fine feed would have no required effect on the absent large particles; on the other hand, it does not have any statistical chance to produce fineness effectively.
  • a small grinding medium on a coarse feed has very little statistical chance to eliminate the large particles but it will effectively made small particles from the small fraction, thus resulting in a very wide distribution curve.
  • a small grinding medium on a fine feed will effectively produce the largest amount of small particles.
  • premix is meant the mixing of the solids and liquid previous to feeding. them. into the continuous diminuting apparatus. Some diminution may occur during the premixing. While premixing is essential for continuous diminution units, this is not the case with batch operations where the solids and liquid can be fed without "premixing.
  • FIG. 1 is a distribution curve in which fineness measured in Hegman gauge is plotted on the vertical axis and time is plotted on the horizontal axis.
  • the Hegman gauge is used commercially in the paint and other industries, and ranges from Hegman to Hegman 8. The larger numbers indicate greater fineness.
  • FIG. 2 is a family of graphs, wit the vertical axis measuring premixing time in minutes required to arrive at a certain Hegman fineness (using activated grinding media), and the horizontal axis indicating the grindability" of the particular slurry in some practical units thus indicating the grindability of-the particular dispersion in a practical yardstick.
  • the ordinarily well-known grinding time in conventional ball mills expressed in hours.
  • FIG. 3 is a flow sheet of various processing operations which are within the scope of the invention.
  • FIG. 4 is a representation, largely schematic, of apparatus for carrying out Process D of FIG. 3;
  • FIG. 5 is a representation, largely schematic, of apparatus for carrying out Process E of FIG. 3;
  • FIGS. 6a to 6d are distribution curves.
  • FIG. 6a is a representative distribution curve of the particle sizes ofa solid powder.
  • FIG. 6b shows in dotted lines the effect of diminution using relatively large grinding media (the solid line showing is the original FIG. 6a).
  • FIG. 60 shows in solid lines the effect of diminution with relatively small grinding media, the solid line showing is the original curve of FIG. 6a.
  • FIG. 6a' shows the curve of FIG. 6a to the right, and to the left shows the effect of a batch and a continuous operation carried out to the same particle size.
  • FIG. 1 shows the fineness expressed in Hegman gauge grades, as a grinding progresses, which applies generally to the effect of activated grinding media on solids in liquids.
  • the horizontal axis is scaled so as to indicate full grinding time of l O0,"regardless of how long the grinding continues. This applies to all materials and equipment.
  • the percentage means simply the percentage of the full grinding time expressed in the same time scale.
  • the graph shows the extremely rapid rise in the amount of fine particles obtained during the first few percent ofthe elapsed total grinding time.
  • FIG. 2 indicates that when premixing in a batch-type premixer, containing activated grinding media such as described for use in Process D below, one can obtain 3 to 5 Hegman grade fineness in a relatively few minutes, mostly less than 10 minutes, with any slurry with usual average grindability, such as finished in a conventional ball mill within two days.
  • FIG. 3 shows a series of operations schematically in each of which a slurry of solid material in a liquid is subjected to two or more grinding steps by activated grinding media, in the first of which larger grinding media are employed and in the second of which smaller grinding media are employed.
  • PROCESS A This is a general process illustrated schematically, in which any two types of grinding equipment containing activated grinding media are used with the grinding media in the first vessel of larger size than those in the second vessel.
  • the suspension produced in the first vessel is conveyed continuously or intermittently to the second vessel.
  • Process A is selected as presently appearing to have the greatest commercial possibilities
  • Processes C and D are particularly adapted for use in the fine grinding of pigments for paints, inks, etc., and other processes may be particularly adapted for the grinding of other solids including drugs and inorganic materials.
  • PROCESS B Process using a premixing device containing activated grinding media which discharges into continuous grinding equipment, with or without an intermediate converter.
  • PROCESS C Process using a premixing device containing activated grinding media which is continuously charged with metered amounts of solid and liquid. The premixer is discharged continuously into continuous grinding equipment.
  • PROCESS D Solid and liquid components of a slurry are combined conventionally and fed into a batch pregrinding device containing activated grinding media and by way of the instrumentality ofa converting mechanism feeding into a continuously grinding unit.
  • An example for this process is the large-scale production of the so-called white base of the paint industry consisting essentially of a titanium dioxide pigment suspended in the properly formulated slurry.
  • the pigment as illustrated in FIG. 4, which may be of a size of about 325 mesh, will, for example, be fed once a day with the suspending medium to a premixer l which'may be a 600-gallon tank.
  • These pregrinders may each have a capacity of about 40 gallons and will grind the pigment to an average Hegman gauge of 4 to 5.
  • the finished premix is metered automatically and continuously by way of the controlling monitor 3 and pump 6 into the continuous grinding unit 7 which contains grinding media in the size range between [/64 and l/8 inch.
  • This unit 7 may be of the type illustrated and described in Szegvari US. Pat. No. 3,149,789.
  • the solids are ground to an average Hegman fineness greater than 7.
  • PROCESS E As illustrated in FIG. 5, the solid and liquid components of the slurry are charged into the batch premixer 10 containing activated grinding media, and pumped intermittently by pump 11 into an intermediate premix accumulator 12.
  • the size of this accumulator is such that it can provide continuous feeding through a metering pump 13 to the continuous grinding device 14, requiring at least two overlapping periods of the premixer 10.
  • the device 14 may be of the type described in Szegvari US. Pat. No. 3,149,789.
  • the premixer 10 may be, for example, of 40-gallon capacity, and using balls 3/8 inch in diameter will produce a premix of a size of about Hegman gauge 2%1/2 to 4%1/2 every l0 minutes.
  • smaller grinding media will be used in the range of H64 inch to H8 inch and the processed slurry will be ground to a Hegman gauge of 7%1/2 to 8.
  • PROCESS F Slurry premixed in any type of premixing device is metered into a continuous grinding device from which a product issues into a second continuous grinding device.
  • These continuous grinding devices contain grinding media in the range between US inch and H64 inch; the first grinding device having grinding media in the range between l/8 inch and 3/32 inch and the second continuous grinding device having grinding media in the range between 3/32 inch and H16 inch.
  • the first and second grinding devices may have additional differences, namely, the rpm. of the first grinding device may be between the range of I and 600 r.p.m., while in the second grinding device, the r.p.m. may be in the range between 150 and 1,000 r.p.m.
  • Apparatus such as described in Szegvari US. Pat. No. 3,149,789 may be used for each of these continuous grinding units. This process is adapted for the fine grinding of powders, drugs, etc. to an average particle size in the range of l to 2 microns.
  • PROCESS G This process is similar to Process F, with the exception that the components of the liquid slurry are charged into a premixing device containing activated grinding media, which device completes the premix in requested time intervals; and the slurry is passed through a converter C by continuous flow into the continuous grinding device.
  • a premixing device containing activated grinding media, which device completes the premix in requested time intervals; and the slurry is passed through a converter C by continuous flow into the continuous grinding device.
  • Such apparatus is used in the processing of ferrites, starting with a material between 200 and 325 mesh and finishing at the average particle size of 1 micron.
  • a preferred type of premixer contains activated grinding media. It may be such a premixer as is described in the following and known as an attritor premixer. In many respects this premixer resembles the grinding device disclosed in Szegvari US.
  • Pat. No. 2,764,359 but generally it will not contain as many grinding media as used in a commercial grinding operation.
  • the grinding media will usually be of a size of at least between A inch and inch.
  • the top of the tank will conveniently be equipped with an apron to facilitate manual loading with solid and liquid feed material and it will be equipped with a discharge conduit suitable for continuous or intermittent discharge of the slurry to a flow converter or a continuous grinder or other equipment as required.
  • Discharge opening is provided for the discharge of the premixed slurry and the grinding media. Exposed parts of the drive are protected from contamination by ingredients floating in the air as a result of the loading process. All apparatus details which serve the purpose of finishing the grinding to ultimate fineness, such as cooling means and specific tank-handling equipment are omitted.
  • a converter is used for the purpose of changing intermittent discharge from the premixing devices containing activated grinding media into a continuous flow to feed continuous grinding apparatus.
  • FIGS. 5 indicates the use of an intermediate premix flow converter, the regulation of which is manually controlled, following the preferred type of premixer, an attritor premixer, just described.
  • FIG. 4 shows an apparatus where a large quantity of solid and liquid, for instance, the entire supply used in one shift, is combined in a container of sufficient size; the size of the container might be between 200 and 800 gallons.
  • These containers are equipped with a conventional agitator to assist in the distribution of solids in the liquids and to keep the distributed solids from excessive sedimentation. No grinding media are used.
  • the control of the flow which involves charging the twin premixers containing activated grinding media, and the subsequent intermittent discharging of each of these premixers into the continuous grinding equipment, is controlled by an electric monitoring device which acts on the four valves to control the intermittent charging and the discharging of the' twin system.
  • the controls of the monitor are effected by conventional timing and level control apparatus.
  • Apparatus for grinding a solid to a size of a few microns in a liquid which contains substantially spherical grinding media and means for activating the same which apparatus comprises two units each equipped with grinding media and means for activating the same, the equipment of the first unit being adapted for batch operation and equipped with substantially larger grinding media than those with which the second unit is equipped and the equipment of the second unit being adapted for continuous grinding and equipped with substantially smaller grinding media than those with which the first unit is equipped, and means for conveying the solid and liquid resulting from grinding in the first unit into the bottom of the second 'unit.
  • the apparatus of claim 1 in which the first unit comprises two pieces of apparatus each operated on a batch basis and the second unit is connected to be fed alternately from said two units, and there is a premixer in which the solid is suspended in the liquid, and means is provided to discharge from the premixer alternately to the two pieces of the first unit.
  • the apparatus of claim 1 in which the first unit comprises two pieces of apparatus each operated on a batch basis and the second unit is connected to be fed alternately from said two pieces.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Crushing And Grinding (AREA)
US869413*A 1964-10-30 1969-07-14 Grinding and apparatus therefor Expired - Lifetime US3592396A (en)

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US40771664A 1964-10-30 1964-10-30
US53493466A 1966-01-19 1966-01-19
US86941369A 1969-07-14 1969-07-14

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120282470A1 (en) * 2004-09-21 2012-11-08 Al-Shafei Mansour A Ground particulate spent claus catalyst product
FR3018807A1 (fr) * 2014-03-20 2015-09-25 Herakles Procede d'obtention de charges de cristaux d'hexanitrohexaazaisowurtzitane (cl20) de granulometrie monomodale submicronique, lesdites charges et leur utilisation comme charges d'ensemencement

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US241653A (en) * 1881-05-17 Drying apparatus
US1361205A (en) * 1916-10-02 1920-12-07 Allis Chalmers Mfg Co Combination mill and process of efficient operation thereof
US2168093A (en) * 1936-08-27 1939-08-01 Sullivan Machinery Co Size-reducing mill
US2764359A (en) * 1950-05-24 1956-09-25 Szegvari Andrew Treatment of liquid systems and apparatus therefor
US3154255A (en) * 1961-03-01 1964-10-27 Amberley Co Method of reclaiming cellulsoe fibers from thermoplastic coated cellulosic webs
US3215353A (en) * 1963-05-20 1965-11-02 Draiswerke Gmbh Grinding method for interruptedly and continuously working mills and apparatus for practicing said method
US3275250A (en) * 1963-10-14 1966-09-27 Hercules Inc Process for making fine particles of nitrocellulose

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US241653A (en) * 1881-05-17 Drying apparatus
US1361205A (en) * 1916-10-02 1920-12-07 Allis Chalmers Mfg Co Combination mill and process of efficient operation thereof
US2168093A (en) * 1936-08-27 1939-08-01 Sullivan Machinery Co Size-reducing mill
US2764359A (en) * 1950-05-24 1956-09-25 Szegvari Andrew Treatment of liquid systems and apparatus therefor
US3154255A (en) * 1961-03-01 1964-10-27 Amberley Co Method of reclaiming cellulsoe fibers from thermoplastic coated cellulosic webs
US3215353A (en) * 1963-05-20 1965-11-02 Draiswerke Gmbh Grinding method for interruptedly and continuously working mills and apparatus for practicing said method
US3275250A (en) * 1963-10-14 1966-09-27 Hercules Inc Process for making fine particles of nitrocellulose

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120282470A1 (en) * 2004-09-21 2012-11-08 Al-Shafei Mansour A Ground particulate spent claus catalyst product
US10301216B2 (en) * 2004-09-21 2019-05-28 Saudi Arabian Oil Company Ground particulate spent Claus catalyst product
FR3018807A1 (fr) * 2014-03-20 2015-09-25 Herakles Procede d'obtention de charges de cristaux d'hexanitrohexaazaisowurtzitane (cl20) de granulometrie monomodale submicronique, lesdites charges et leur utilisation comme charges d'ensemencement

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Owner name: UNION PROCESS INTERNATIONAL, INC. 1925 AKRON-PENIN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:ARNO, SZEGVARI, ADMINISTRATOR, DBN/WWA OF THE ESTATE OF ANDREW SZEGVARI, DEC`D;REEL/FRAME:004303/0006

Effective date: 19840306

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Owner name: SZEGVARI, ARNO ADMINISTRATOR DE BONIS NON OF THE E

Free format text: LETTERS OF ADMINISTRATION;ASSIGNOR:SZEGVARI, ANDREW, DEC D.;REEL/FRAME:004300/0101

Effective date: 19840628