US4943378A
Expired / Lapsed
US
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Flocculation processes
Assignee: Ciba Specialty Chemicals Water Treatments Ltd
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Filing: 1989-03-15
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Granted: 1990-07-24
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Expires: 2009-03-15
Abstract
Abstract When flocculating an aqueous suspension of suspended solids using a high molecular weight synthetic polymeric flocculant the shear stability of the flocs is increased if the polymeric material includes polymeric particles of below 10 μm dry size. The flocculated solids can therefore be subjected to shear without increasing the amount of discrete suspended solids in the aqueous medium and generally they are suspended to shear by shearing the aqueous medium containing them, either before dewatering, generally on a centrifuge, piston press or belt press, or by continuously agitating them, for instance in a chemical reaction medium. The polymeric material is generally formed by mixing into water polymeric particles made by reverse phase or emulsion polymerization in the presence of added cross linking agent. Alternatively particles insolubilized by insoluble monomer may be used. A reverse phase dispersion of water soluble polymer may be used if the particles remain undissolved, e.g. if they are added in the absence of an oil in water emulsifying agent.
Inventors
- 👤 Peter Flesher
- 👤 David Farrar
- 👤 John R. Field
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 18:17
CPC Classifications
C; C02; C02F; C02F1/00; C02F1/52; C02F1/5227; C02F1/54; D; D21; D21H; D21H21/00; D21H21/06; D21H21/10; D21H17/00; D21H17/20; D21H17/33; D21H17/34; D21H17/37; D21H17/41; D21H17/42; D21H17/43; D21H17/44; D21H17/45; D21H17/455
Claims Analysis
Total Claims: 25
Claim 1
Independent Claim
111 words
A process for dewatering an aqueous suspension of suspended solids comprising adding to the suspension a flocculating amount of a synthetic polymeric flocculant material to form thereby an aqueous medium containing flocculated solids and dewatering the aqueous medium and in which the said polymeric material has a specific viscosity (measured by a capillary viscometer at 34° C. on 0.5% solution deionised water) above 10 and comprises, cross linked water insoluble water swellable polymeric particles that have a dry size of below 10 μm, the polymeric material is added in a floc stabilising amount, and the dewatering is effected under shear by a process selected from centrifugation, belt pressing and piston pressing.
Claim 2
Dependent Claim
111 words
A process for dewatering an aqueous suspension of suspended solids comprising adding to the suspension a flocculating amount of a synthetic polymeric flocculant material to form thereby an aqueous medium containing flocculated solids and dewatering the aqueous medium and in which the said polymeric material has a specific viscosity (measured by a capillary viscometer at 34° C. on 0.5% solution deionised water) above 10 and comprises, cross linked water insoluble water swellable polymeric particles that have a dry size of below 10 μm, the polymeric material is added in a floc stabilising amount, and the dewatering is effected under shear by a process selected from centrifugation, belt pressing and piston pressing.
Claim 3
Dependent Claim
16 words
A process according to claim 1 in which the dewatering under shear is conducted by centrifugation.
Claim 4
Dependent Claim
36 words
A process according to claim 1 in which the suspension comprises sewage and the said polymeric flocculant material is a cationic polymer obtained by reverse phase polymerisation of ethylenically unsaturated monomers comprising monoethylenically unsaturated cationic monomer.
Claim 5
Dependent Claim
15 words
A process according to claim 1 in which the suspension is a municipal sewage sludge.
Claim 6
Dependent Claim
49 words
A process according to claim 1 comprising feeding the suspension into a dewatering centrifuge, adding the said polymeric flocculant material to the suspension before the suspension enters the centrifuge and effecting the dewatering of the resultant flocculated suspension under shear by centrifugation of the flocculated suspension in the centrifuge.
Claim 7
Dependent Claim
35 words
A process according to claim 1 in which the particles have been formed by polymerisation in the presence of added cross-linking agent of a monomer or monomer blend that is soluble in the aqueous suspension.
Claim 8
Dependent Claim
35 words
A process according to claim 6 in which the cross linking agent is a diethylenically unsaturated monomer and the amount of cross linking agent is from 1 to 100 ppm based on the polymerisable monomers
Claim 9
Dependent Claim
50 words
A process according to claim 6 in which the polymeric material has ionic regain greater than 15% and is cationic, wherein said ionic regain is calculated as (X-Y)/x×100 where x is the ionicity measured after applying standard shear and y is the ionicity of the polymer before applying standard shear.
Claim 10
Dependent Claim
51 words
A process according to claim 6 in which the polymeric material has ionic regain of 25 to 70% and is cationic, wherein said ionic regain is calculated as (X-Y)/x×100 where x is the ionicity measured after applying standard shear and y is the ionicity of the polymer before applying standard shear.
Claim 11
Dependent Claim
71 words
A process according to claim 6 in which the polymeric material has ionic regain of 25 to 70% and is a cationic copolymer of acrylamide with at least 5 mole percent dialkylaminoalkyl acrylate (including acid addition and quaternary ammonium salts thereof), wherein said ionic regain is calculated as (X-Y)/x×100 where x is the ionicity measured after applying standard shear and y is the ionicity of the polymer before applying standard shear.
Claim 12
Dependent Claim
52 words
Process according to claim 6 in which the polymer has intrinsic viscosity of 100-ionic regain/a where a is from 6 to 14, wherein said ionic regain is calculated as (X-Y)/x×100 where x is the ionicity measured after applying standard shear and y is the ionicity of the polymer before applying standard shear.
Claim 13
Dependent Claim
20 words
A process according to claim 1 in which the particles have been formed by emulsion polymerisation or reverse phase polymerisation.
Claim 14
Dependent Claim
45 words
A process according to claim 1 in which the polymeric material is made by mixing an aqueous solution of linear water soluble polymer having specific viscosity above 10 with a dissolved cross linking agent whilst stirring with sufficient force to form a homogeneous aqueous composition.
Claim 15
Dependent Claim
21 words
A process according to claim 13 in which the cross linking agent is a counterionic polymer having specific viscosity above 10.
Claim 16
Dependent Claim
32 words
A process according to claim 1 in which the polymeric material is selected from materials that have intrinsic viscosity above 4 and materials that can have intrinsic viscosity above 4 after shearing.
Claim 17
Dependent Claim
48 words
A process according to claim 1 in which a 1% aqueous composition of the polymeric material that is added to the suspension gives, when cast as a film on a glass plate and dried, a discontinuous film of discrete swellable particles having a size of below 10 μm.
Claim 18
Dependent Claim
34 words
A process according to claim 1 in which the amount of polymeric material is from 50 to 150% of the amount that gives maximum floc size after application of shear to the aqueous medium.
Claim 19
Dependent Claim
123 words
A process according to claim 1 and which comprises providing a homogeneous dilute aqueous composition of a reverse phase polymerised, non film-forming, acrylamide copolymer with dialkylaminoalkyl (meth) acrylate acid salt or quaternary salt having a dry particle size below 2 μm, ionic regain above 15 and intrinsic viscosity=100-ionic regain/a where a is from 6 to 14, wherein said ionic regain is calculated as (X-Y)/x×100 where x is the ionicity measured after applying standard shear and y is the ionicity of the polymer before applying standard shear, adding this composition to sewage sludge in an amount of 50 to 150% of the amount required for maximum floc size after shearing, subjecting the blended mixture to dewatering on a centrifuge, piston press or belt press.
Claim 20
Dependent Claim
93 words
A process according to claim 1 in which the polymeric flocculant is a polymer formed from one or more ehtylenically unsaturated monomers selected from the group consisting of acrylamide, methacrylamide, N-vinyl methyl acetamide, N-vinyl methyl formamide, vinyl acetate, vinyl pyrollidone, (meth) acrylic esters, styrene acrylonitrile, water soluble forms of carboxylic or sulphonic acids selected from (meth) acrylic acid, itaconic acid and 2-acrylamido methyl propane sulphonic acid, sulpho methylated acrylamide, allyl sulphonate, sodium vinyl sulphonate, dialkylaminoalkyl (meth) acrylates and their quaternary or acid salts, and dialkylaminoalkyl (meth) acrylamides and their quaternary or acid salts.
Claim 21
Dependent Claim
67 words
A process according to claim 1 in which the polymeric material is a polymer formed by polymerisation of a monomer selected from the group consisting of water soluble acrylic acid salt, water soluble 2-acrylamido methyl propane sulphonic acid salt, dialkylaminoalkyl (meth) acrylates and their quaternary or acid salts, and dialkylaminoalkyl (meth) acrylamides and their quaternary or acid salts, and blends of any of said monomers with acrylamide.
Claim 22
Dependent Claim
111 words
A process for dewatering a suspension that comprises municipal sewage, the process comprising feeding the suspension into a dewatering centrifuge, adding to the suspension a floc stabilising amount of a synthetic cationic polymeric flocculant that is in the form of cross linked water insoluble water swellable polymeric particles having a dry size below 10 μm and that has been made as such particles by polymerisation of ethylenically unsaturated monomer comprising monoethylenically unsaturated cationic monomer and that has a specific viscosity (measured by a capillary flow viscometer at 34° C. on a 0.5% solution in deionised water) above 100, and dewatering the resultant flocculated suspension by centrifugation under shear in the centrifuge.
Claim 23
Dependent Claim
111 words
A process for dewatering a suspension that comprises municipal sewage, the process comprising feeding the suspension into a dewatering centrifuge, adding to the suspension a floc stabilising amount of a synthetic cationic polymeric flocculant that is in the form of cross linked water insoluble water swellable polymeric particles having a dry size below 10 μm and that has been made as such particles by polymerisation of ethylenically unsaturated monomer comprising monoethylenically unsaturated cationic monomer and that has a specific viscosity (measured by a capillary flow viscometer at 34° C. on a 0.5% solution in deionised water) above 100, and dewatering the resultant flocculated suspension by centrifugation under shear in the centrifuge.
Claim 24
Dependent Claim
216 words
A process comprising flocculating an aqueous suspension of suspended solids by adding to the suspension a flocculating amount of a synthetic polymeric flocculant material to form thereby an aqueous medium containing flocculated suspended solids in which the said polymeric flocculant material has a specific viscosity (measured by a capillary flow viscometer at 34° C. on a 0.5% solution in deionised water) above 10, and is formed by polymerisation of a monomer selected from the group consisting of water soluble acrylic acid salt, water soluble 2-acrylamido methyl propane sulphonic acid salt, dialkylaminoalkyl (meth) acrylates and their quaternary or acid addition salts, and dialkylaminoalkyl (meth) acrylamides and their quaternary or acid addition salts, and blends of any such monomer with acrylamide and has been made by polymerisation in the presence of added diethylenically unsaturated cross linking agent in an amount of from 1 to 100 ppm and is in the form of polymeric particles that are water insoluble but water swellable and that have a dry size of below 10 μm, the amount of the polymeric material added to the suspension is from 50 to 150% of the amount that gives maximum floc size after the application of shear to the aqueous medium, and dewatering the aqueous medium under shear on a centrifuge, piston press or belt press.
Claim 25
Dependent Claim
216 words
A process comprising flocculating an aqueous suspension of suspended solids by adding to the suspension a flocculating amount of a synthetic polymeric flocculant material to form thereby an aqueous medium containing flocculated suspended solids in which the said polymeric flocculant material has a specific viscosity (measured by a capillary flow viscometer at 34° C. on a 0.5% solution in deionised water) above 10, and is formed by polymerisation of a monomer selected from the group consisting of water soluble acrylic acid salt, water soluble 2-acrylamido methyl propane sulphonic acid salt, dialkylaminoalkyl (meth) acrylates and their quaternary or acid addition salts, and dialkylaminoalkyl (meth) acrylamides and their quaternary or acid addition salts, and blends of any such monomer with acrylamide and has been made by polymerisation in the presence of added diethylenically unsaturated cross linking agent in an amount of from 1 to 100 ppm and is in the form of polymeric particles that are water insoluble but water swellable and that have a dry size of below 10 μm, the amount of the polymeric material added to the suspension is from 50 to 150% of the amount that gives maximum floc size after the application of shear to the aqueous medium, and dewatering the aqueous medium under shear on a centrifuge, piston press or belt press.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-07-23 | 1994-01-22 | 1994-07-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-07-23 | 1998-01-22 | 1998-07-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-07-23 | 2002-01-22 | 2002-07-24 | $7700.00 | Window Closed / Lapsed |