US3624796A - Grinding of minerals - Google Patents

Grinding of minerals Download PDF

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Publication number
US3624796A
US3624796A US35668A US3624796DA US3624796A US 3624796 A US3624796 A US 3624796A US 35668 A US35668 A US 35668A US 3624796D A US3624796D A US 3624796DA US 3624796 A US3624796 A US 3624796A
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United States
Prior art keywords
mixture
process according
particulate grinding
grinding medium
cooling
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Expired - Lifetime
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US35668A
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English (en)
Inventor
Ronald Eric Brociner
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Imerys Minerals Ltd
Original Assignee
English Clays Lovering Pochin Co Ltd
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Application filed by English Clays Lovering Pochin Co Ltd filed Critical English Clays Lovering Pochin Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
    • B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
    • B02C19/00—Other disintegrating devices or methods
    • B02C19/18—Use of auxiliary physical effects, e.g. ultrasonics, irradiation, for disintegrating
    • B02C19/186—Use of cold or heat for disintegrating

Definitions

  • This invention relates to the grinding of materials and, more particularly but not exclusively, is concerned with the grinding of minerals.
  • a process for grinding a material which process comprises forming a dry, or substantially dry, mixture of the material to be ground and a particulate grinding medium, wherein the particulate grinding medium consists of particles ranging in size from 150 microns to one-fourth of an inch equivalent spherical diameter and wherein the weight ratio of particulate grinding medium to material is in the range of from 2:1 to 5:1, agitating said mixture for a time sufficient to reduce the material to the desired particle size, cooling the agitated mixture, and thereafter separating the ground material from the particulate grinding medium.
  • an apparatus for carrying out the process of the invention comprises a vessel provided with an internal impeller including a rotatable shaft on which is mounted means for agitating a mixture of a material to be ground and a particulate grinding medium when the apparatus is in use, and means for cooling the mixture of material to be ground and particulate grinding medium.
  • the materials which are treated by the process of the present invention will either be naturally particulate or will normally be coarsely ground or crushed before being ground to a fine particle size by the process of the invention; generally, particles larger than 2.0 mm. will require coarse grinding or crushing before being treated by the process of this invention.
  • Processes according to the present invention are particularly useful for the grinding of minerals, for example clays and chalks.
  • substantially dry there is meant herein that the material to be ground is sufficiently dry to flow as a powder; generally this will mean that the material will contain not more than 5 percent by weight of water but in the case of fine clays, for example, there may be present up to percent by weight of water.
  • the cooling of the mixture of material to be ground and particulate grinding medium is effected simultaneously with the agitation of the mixture, for example by passing a cooling fluid through the mixture whilst the latter is being agitated.
  • the particulate grinding medium preferably consists of particles ranging in size from 500 microns to one'eighth of an inch, the particles having a substantially Gaussian distribution of particles size between these limits, and is advantageously formed of quartz, flint, calcined china clay, small beads of glass, or a ceramic material, for example beads of sintered alumina.
  • the particulate grinding medium will have a hardness in the range of from 5 to 9 on the Moh scale, and a specific gravity of at least 2.0.
  • the mixture of material to be ground and particulate grinding medium is cooled because attrition grinding generates a considerable amount of heat which, in the absence or substantially complete absence of water, can cause a rapid rise in temperature and this agglomeration of the fine particles.
  • the mixture of material to be ground and particulate grinding medium can be cooled by means of a gas, e.g., air or carbon dioxide, which is injected into the mixture.
  • the mixture can be cooled by injecting dry ice," ice or water into the grinding vessel in order to cool the contents thereof by evaporation, in the latter case at a rate sufficient to keep the material and particulate grinding medium cool by evaporation but no so great as to cause the material to contain more than 5 percent by weight of water at the completion of the grinding.
  • a suitable rate will be in the range of from 0.5 to 5.0 cc. of water per minute per kilogram of material.
  • the ground material can be separated from the particulate grinding medium by screening the mixture on a sieve of a mesh size which will retain the particulate grinding medium and pass the ground material.
  • the mixture can be fluidized in an upward flowing current of gas which will carry the ground material upwards out of the fluidized mixture leaving the particulate grinding medium behind.
  • the apparatus for carrying out the process of the invention is advantageously provided with a foraminous base, the apertures of which are sufficiently small to retain the smallest particles of the particulate grinding medium when no fluidizing gas is flowing therethrough.
  • the width or diameter of the apertures will be in the range of from 50-500 microns.
  • the impeller used in the apparatus of the invention can be constructed from, for example, stainless steel, glass or a plastics material resistant to high temperatures, or from a metal with a coating of glass or a plastics material resistant to high temperatures.
  • the agitating means mounted on the rotatable shaft can be, for example, a number of bars secured to and projecting from the shaft, a number of toothed discs, or a slotted cage.
  • the means for cooling the mixture of material to be ground and particulate grinding material can be, for example, a device for feeding a cooling fluid, generally a cooling gas, to the interior of the vessel.
  • a suitable device is, for example, an annular chamber surrounding the vessel and communicating with the interior of the vessel through a plurality of ports in the sidewall of the vessel.
  • a cylindrical vessel 1 provided with a central impeller 2 which comprises a rotatable shaft 3 to which is secured a boss 4. Projecting from the boss 4 there are a plurality of round bars 5.
  • the boss 4 and the round bars 5 are constructed from a plastics material, e. g., poly(methyl methacrylate).
  • the shaft 3 runs in bearings 10 and 11, and the impeller is driven by an electric motor 6 through a belt drive 7, and through pulleys 8 and 9 which can be changed to provide different speeds of rotation of the impeller.
  • the cylindrical vessel 1 has attached to its sidewall an annular chamber 12 which communicates with the interior of the grinding vessel through a plurality of ports 13. A cooling gas is supplied to the annular chamber 12 through a conduit 14 and the flow of gas is regulated by a valve (not shown).
  • EXAMPLE 1 500 g. of a dry, coarse china clay were introduced into a grinding vessel, constructed according to the design described above with reference to the accompanying drawing, together with 1,500 g. of a particulate grinding medium consisting of particles ranging in size from one-eighth of an inch to 2,000 microns and comprising flint and quartz in approximately equal proportions.
  • the particles of the particulate grinding medium had a hardness of 7 on the Mob scale and a specific gravity of 2.6.
  • the grinding vessel was formed from poly(methyl methacrylate) and had an internal diameter of 6 inches; and the impeller was formed from the same material and had four transverse round bars for agitating the mixture of clay and grinding medium, the overall length of the bars being inches.
  • the speed of rotation of the impeller was 1 100 r.p.m.
  • the impeller was rotated in the mixture of clay and grinding medium for 30 minutes during which time 55 hp.-hr. (41 kw.- hr. of energy per ton of dry clay were dissipated in the mixture.
  • cool air was supplied to the annular chamber 12 at a rate such as to maintain the temperature of the mixture at 82 C. 180 F.) or below in order to reduce the formation of agglomerates and avoid distortion of the EXAMPLE 2
  • 500 g. of a dry paper filler grade china clay were introduced into a grinding vessel similar to that used in example 1 but having an impeller with twelve round bars for agitating the mixture of clay and grinding material.
  • the sand particles had a hardness of 7 on the Moh scale and a specific gravity of 2.6.
  • the impeller was rotated in the mixture of clay and grinding medium for 40 minutes during which time 74 hp.-hr. (55 kw.- hr.) of energy per ton of dry clay were dissipated in the mixture.
  • the temperature of the mixture was maintained at 82 C. 180 F.) or below by supplying a current of cool air to the annular chamber.
  • the clay was separated from the grinding medium by fluidizing the mixture in an upcurrent of cool air so that the particles of ground clay were elutriated out of the fluidized bed whereafter they were separated from the air in a cyclone.
  • EXAMPLE 3 500 g. of dry, crushed coke were introduced into a grinding vessel together with 2,000 g. of the same grinding medium as was used in example 2.
  • the grinding vessel was constructed according to the design described above with reference to the accompanying drawing but was made from brass and had an internal diameter of 5 inches.
  • the impeller was made from stainless steel and had four round bars for agitating the mixture, the overall length of the bars being 5 inches. The speed of rotation of the impeller was l,l00 r.p.m.
  • the impeller was rotated in the mixture of crushed coke and grinding medium for minutes during which time 203 hp.- hr. (151 kw.-hr.) of energy per ton of coke were dissipated in the mixture.
  • carbon dioxide gas was introduced into the annular chamber to cool the mixture to 100 C. (212? F.) or below and also to reduce the risk of combustion of the fine coke.
  • carbon dioxide gas it is possible to use dry ice which is advantageously crushed to a particle size comparable to that of the particulate grinding medium and the particles fed to the grinding vessel continuously as the grinding progresses.
  • the ground coke was separated from the grinding medium by fluidizing the mixture in an upcurrent of cool air.
  • the coke was elutriated out of the fluidized bed and was separated from the air in a cyclone.
  • the coke initially had a particle size distribution such that 75 percent by-weight consisted of particles smaller than 0. l5 mm. (100 mesh B.S. sieve) and 93 percent by weight of particles larger than 53 microns (30 mesh B.S. sieve). After treatment the ground coke had a particle size distribution such that 31 percent by weight consisted of particles larger than 53 microns, 62 percent by weight of particles larger than 10 microns and 7 percent by weight of particles smaller than 1 micron.
  • the improvement which comprises forming a mixture of the material to be ground and a particulate grinding medium wherein the particulate grinding medium consists of particles ranging in size from microns to one-fourth of an inch equivalent spherical diameter and wherein the weight ratio of particulate grinding medium to material is in the range from 2:1 to 5:1, agitating said mixture for a time sufficient to reduce the material to the desired particle size, cooling the agitated mixture to prevent the temperature of the particles of the material from rising during the agitation thereof to a level at which they tend to agglomerate, and thereafter separating the ground material from the particulate grinding medium.
  • cooling fluid is water or a mixture of water and a gas and wherein the water is passed through said mixture at a rate which lies in the range of from 0.5 to 5.0 cc. per minute per kilogram of said material in said mixture.
  • said particulate grinding medium consists of particles ranging in size from 500 microns to one-eighth of an inch.
  • said particulate grinding medium comprises quartz, flint, calcined clay, glass or a ceramic material.

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  • Health & Medical Sciences (AREA)
  • Toxicology (AREA)
  • Engineering & Computer Science (AREA)
  • Food Science & Technology (AREA)
  • Crushing And Grinding (AREA)
  • Dental Preparations (AREA)
  • Food-Manufacturing Devices (AREA)
US35668A 1969-05-15 1970-05-08 Grinding of minerals Expired - Lifetime US3624796A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB2493069 1969-05-15

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DE (1) DE2023995C2 (de)
GB (1) GB1310222A (de)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3833178A (en) * 1970-02-06 1974-09-03 E Beck Method of comminuting synthetic-resin articles
EP0757922A3 (de) * 1995-08-08 1997-03-19 Hoechst Aktiengesellschaft Autogenes Mahlen von Siliziumnitrid
US6520837B2 (en) 1998-07-17 2003-02-18 Reiner Weichert Method and apparatus for ultrafine grinding and/or mixing of solid particles
US20060269662A1 (en) * 2005-05-27 2006-11-30 Xerox Corporation Imaging systems and method that form a layer on an imaging member
CN115518764A (zh) * 2022-10-12 2022-12-27 深圳市尚水智能设备有限公司 一种立式研磨机的进料控制方法及立式研磨机

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA1242680A (en) * 1984-07-26 1988-10-04 Geoffrey J. Lyman Comminution of coal, ores and industrial minerals and rocks
GB2190016B (en) * 1985-08-01 1989-07-26 Ecc Int Ltd Communition of material
US5593097A (en) * 1994-06-10 1997-01-14 Eastman Kodak Company Micro media mill and method of its use

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2565420A (en) * 1946-07-15 1951-08-21 Agrashell Inc Grinding of organic materials
US2764359A (en) * 1950-05-24 1956-09-25 Szegvari Andrew Treatment of liquid systems and apparatus therefor
US2893216A (en) * 1956-02-01 1959-07-07 Gen Dynamics Corp Method of refrigerating a finelydivided material

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1288890B (de) * 1964-04-10 1969-02-06 Draiswerke Gmbh Verfahren und Vorrichtung zum trockenen Feinstzerkleinern von Feststoffen

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2565420A (en) * 1946-07-15 1951-08-21 Agrashell Inc Grinding of organic materials
US2764359A (en) * 1950-05-24 1956-09-25 Szegvari Andrew Treatment of liquid systems and apparatus therefor
US2893216A (en) * 1956-02-01 1959-07-07 Gen Dynamics Corp Method of refrigerating a finelydivided material

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3833178A (en) * 1970-02-06 1974-09-03 E Beck Method of comminuting synthetic-resin articles
EP0757922A3 (de) * 1995-08-08 1997-03-19 Hoechst Aktiengesellschaft Autogenes Mahlen von Siliziumnitrid
US6520837B2 (en) 1998-07-17 2003-02-18 Reiner Weichert Method and apparatus for ultrafine grinding and/or mixing of solid particles
US20060269662A1 (en) * 2005-05-27 2006-11-30 Xerox Corporation Imaging systems and method that form a layer on an imaging member
US7410743B2 (en) * 2005-05-27 2008-08-12 Xerox Corporation Imaging systems and method that form a layer on an imaging member
CN115518764A (zh) * 2022-10-12 2022-12-27 深圳市尚水智能设备有限公司 一种立式研磨机的进料控制方法及立式研磨机

Also Published As

Publication number Publication date
GB1310222A (en) 1973-03-14
DE2023995C2 (de) 1985-11-14
DE2023995A1 (de) 1970-11-19

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