US5083712A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of producing fine particles
Assignee: Rio Tinto Alcan International Ltd
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Filing: 1990-12-03
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Granted: 1992-01-28
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Expires: 2010-12-03
Abstract
Abstract A method of reducing the particle size of solid particles is applicable to the production of very fine particles of a wide variety of solids, including alumina hydrate, and comprises milling a liquid suspension of solid particles in an agitated media mill, pumping the milled suspension through a particle size classification device to separate the slurry into a coarse fraction and a fine fraction, the particles of the coarse fraction having a greater median particle size than the particles of the fine fraction, recycling the coarse fraction from the particle size classification device to the input of the mill, and recycling the fine fraction by pumping it to the classification device, wherein recycling of both coarse and fine fractions are continued until solid particles of the desired reduced particle size are produced. Preferably a single classification device and a single mill can be used, and particles having a median particle size of 0.3 microns or less and a relatively narrow paricle size distribution can be produced, even using a hydrocyclone as the classification device.
Inventors
- 👤 Herbert F. Askew
- 👤 Stephen C. Brown
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:44
CPC Classifications
C; C09; C09C; C09C1/00; C09C1/40; C09C1/407; A; A62; A62D; A62D1/00; A62D1/0007; A62D1/0014; B; B02; B02C; B02C21/00; B02C23/00; B02C23/08; B02C23/10; B02C23/12; B02C23/18; B02C23/36; C01; C01F; C01F7/00; C01F7/02; C01F7/021; C01F7/023; C01F7/46; C01P; C01P2004/00; C01P2004/51; C01P2004/52; C01P2004/60; C01P2004/61; C01P2004/62; C01P2006/00; C01P2006/12
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
140 words
A continuous method of producing solid particles of material of reduced median particle size no greater than 2 microns, which method comprises: milling in a milling stage a liquid suspension of solid particles of said material, feeding the milled suspension to a suspension blending stage, classifying in a classifying stage the blended suspension to separate the blended suspension into a coarse fraction and a fine fraction, the particles of the coarse fraction having a greater median particle size than the particles of the fine fraction, recycling the coarse fraction back to the milling stage, recycling the fine fraction back to the suspension blending stage, and continuing recycling of both coarse and fine fractions with only a minor amount of the fine fraction being taken off as product solid particles of said desired reduced particle size no greater than 2 microns.
Claim 2
Dependent Claim
140 words
A continuous method of producing solid particles of material of reduced median particle size no greater than 2 microns, which method comprises: milling in a milling stage a liquid suspension of solid particles of said material, feeding the milled suspension to a suspension blending stage, classifying in a classifying stage the blended suspension to separate the blended suspension into a coarse fraction and a fine fraction, the particles of the coarse fraction having a greater median particle size than the particles of the fine fraction, recycling the coarse fraction back to the milling stage, recycling the fine fraction back to the suspension blending stage, and continuing recycling of both coarse and fine fractions with only a minor amount of the fine fraction being taken off as product solid particles of said desired reduced particle size no greater than 2 microns.
Claim 3
Dependent Claim
47 words
A method according to claim 1 in the form of a semicontinuous process wherein recycling of both coarse and fine fractions are continued with essentially no product being drawn off until solid particles of the desired reduced particle size are produced and thereafter drawing off the product.
Claim 4
Dependent Claim
28 words
A method according to claim 1 wherein recycling of both coarse and fine fractions are continued until product solid particles of a polydispersity not exceeding 0.35 are produced.
Claim 5
Dependent Claim
28 words
A method according to claim 2 wherein recycling of both coarse and fine fractions are continued until product solid particles of a polydispersity not exceeding 0.35 are produced.
Claim 6
Dependent Claim
18 words
A method according to claim 1 in which the particle size classification is carried out in a hydrocyclone.
Claim 7
Dependent Claim
48 words
A method according to claim 5, in which the milled suspension and fine fraction are pumped to the suspension blending stage for intermittent periods such that over a period of time the flow from the coarse fraction of the classification stage balances the flow through the milling stage.
Claim 8
Dependent Claim
18 words
A method according to claim 6, wherein the slurry contain from 35 to 50% by weight of solid.
Claim 9
Dependent Claim
17 words
A method according to claim 5, in which the slurry contains from 5 by weight of solid.
Claim 10
Dependent Claim
15 words
A method as claimed in claim 5, in which a single milling stage is used.
Claim 11
Dependent Claim
22 words
A method according to claim 1 in which the milled suspension and fine fraction are pumped continuously to the suspension blending stage.
Claim 12
Dependent Claim
19 words
A method according to claim 10, in which the slurry contains from 35 to 50% by weight of solid.
Claim 13
Dependent Claim
48 words
A method according to claim 1, in which the milled suspension and fine fraction are pumped to the suspension blending stage for intermittent periods such that over a period of time the flow of the coarse fraction from the classification stage balances the flow through the milling stage.
Claim 14
Dependent Claim
18 words
A method according to claim 12, wherein the slurry contains from 5 to 65% by weight of solid.
Claim 15
Dependent Claim
48 words
A method according to claim 1, in which the milled suspension discharged from the milling stage and the fine fraction discharged from the classification stage are both conducted to a receptacle for blending and the contents of the receptacle are pumped to the inlet of the classification stage.
Claim 16
Dependent Claim
60 words
A method according to claim 1, in which the milled suspension discharged from the milling is conducted to a reservoir for blending, the fine fraction discharged from the classification stage is conducted to a receptacle, the contents of the receptacle are conducted to the reservoir, and the contents of the reservoir are pumped to the input of the classification stage.
Claim 17
Dependent Claim
83 words
A method according to claim 1, in which the milled suspension discharged from the milling stage is pumped to the classification stage by a pump intermediate the milling stage and the classification stage, the suspension is aspirated through the milling stage by said pump, the fine fraction discharged from the classification stage is conducted to a receptacle and the contents of the receptacle are aspirated to a blending stage intermediate the milling stage and the pump to be recycled through the classification stage.
Claim 18
Dependent Claim
87 words
A method according to claim 1, in which the milled suspension discharged from the milling stage is pumped to the classification stage by a first pump intermediate the milling stage and the classification stage, the suspension is aspirated through the milling stage by the first pump, the fine fraction discharged by the classification stage is conducted to a receptacle and the contents of the receptacle are pumped by a second pump to a blending stage intermediate the first pump and the classification stage to be recycled therethrough.
Claim 19
Dependent Claim
19 words
A method according to claim 1, in which the slurry contains from 5 to 65% by weight of solid.
Claim 20
Dependent Claim
19 words
A method according to claim 18, in which the slurry contains from 35 to 50% by weight of solid.
Claim 21
Dependent Claim
15 words
A method as claimed in claim 1, in which a single classification stage is used.
Claim 22
Dependent Claim
15 words
A method as claimed in claim 1, in which a single milling stage is used.
Claim 23
Dependent Claim
26 words
A method according to claim 1, in which the milled suspension is subjected to ion exchange to reduce the content of any soluble ionic species therein.
Claim 24
Dependent Claim
25 words
A method according to claim 1, in which the milled suspension is subjected to ion exchange to reduce the content of any soluble soda therein.
Claim 25
Dependent Claim
28 words
A method according to claim 1, in which a viscosity modifier is added to the suspension in an amount of up to 10% by weight of the particles.
Claim 26
Dependent Claim
14 words
A method according to claim 1, in which the milled suspension is spray dried.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1995-01-27 | 1995-07-29 | 1996-01-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-01-27 | 1999-07-29 | 2000-01-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-01-27 | 2003-07-29 | 2004-01-28 | $7700.00 | Window Closed / Lapsed |