[go: up one dir, main page]

EP0859744A1 - Concentration de solides dans le procede bayer - Google Patents

Concentration de solides dans le procede bayer

Info

Publication number
EP0859744A1
EP0859744A1 EP96937034A EP96937034A EP0859744A1 EP 0859744 A1 EP0859744 A1 EP 0859744A1 EP 96937034 A EP96937034 A EP 96937034A EP 96937034 A EP96937034 A EP 96937034A EP 0859744 A1 EP0859744 A1 EP 0859744A1
Authority
EP
European Patent Office
Prior art keywords
solids
polymer
stream
bayer
polymers
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP96937034A
Other languages
German (de)
English (en)
Inventor
Greg Flieg
Robert W. Cole
Ronald Thomason
Patrick Bair
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.)
Cytec Technology Corp
Original Assignee
Cytec Technology Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Cytec Technology Corp filed Critical Cytec Technology Corp
Publication of EP0859744A1 publication Critical patent/EP0859744A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
    • C01F7/00—Compounds of aluminium
    • C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
    • C01F7/04—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom
    • C01F7/06—Preparation of alkali metal aluminates; Aluminium oxide or hydroxide therefrom by treating aluminous minerals or waste-like raw materials with alkali hydroxide, e.g. leaching of bauxite according to the Bayer process
    • C01F7/0646—Separation of the insoluble residue, e.g. of red mud
    • C01F7/0653—Separation of the insoluble residue, e.g. of red mud characterised by the flocculant added to the slurry

Definitions

  • the present invention is directed to a process of alumina manufacture via the Bayer process. More particularly, it is concerned with improvements in the Bayer alumina process by the removal of suspended solids by contacting process streams with a polymer which contains hydroxamic acid groups or salts thereof, flocculating said suspended solids, and subjecting the resultant flocculated solids to centrifugation.
  • the almost universally used process for the manufacture of alumina is the Bayer process.
  • raw bauxite ore is pulverized to a finely divided state.
  • the pulverized ore is then fed to a slurry mixer where a slurry is prepared using water, spent liquor and added caustic.
  • This bauxite slurry is then diluted and sent through a series of digesters where, at about 300 * - 800" F. and 100-2000 p.s.i., most of the total available alumina is extracted from ore which may contain both trihydrate and monohydrate forms of alumina.
  • the effluent from the digesters passes through a series of flash tanks wherein heat and condensate are recovered as the digested slurry is cooled to about 230 * F and brought to atmospheric pressure.
  • the aluminate Iiquor leaving the flashing operation contains about 1-20% solids, which consist of the insoluble residues that remain after reaction between the bauxite ore and basic material used to digest the ore and the insoluble products which precipitate during digestion.
  • all percentages are by weight, based on total weight, unless otherwise stated.
  • the coarser solid particles are generally removed with a "sand trap" cyclone
  • the slurry is normally fed to the center well of a primary mud settler where it is treated with a flocculant such as a polyacrylamide polymer, polyacrylate polymer, hydroxamated polymer, flour and/or starch.
  • a flocculant such as a polyacrylamide polymer, polyacrylate polymer, hydroxamated polymer, flour and/or starch.
  • clarified sodium aluminate solution referred to as "green” or "pregnant” Iiquor
  • the settled solids (“red mud") are withdrawn as underflow from the bottom of the primary mud settler and passed through a countercurrent washing circuit, generally comprised of a series of washers, for recovery of sodium aluminate and soda.
  • Aluminate liquor overflowing the primary settler still contains typically 50 to 200 milligrams of suspended solids per liter.
  • This Iiquor is then generally further clarified by filtration to give a filtrate with less than about 10 milligrams suspended solids per liter of Iiquor.
  • the level of suspended solids should be sufficiently low to provide an alumina product from the precipitation step which meets all of the industry standards.
  • Alumina, in relatively pure form is then precipitated from the filtrate as alumina trihydrate crystals.
  • the remaining liquid phase or spent Iiquor is returned to the initial digestion step and employed as a digestant of additional ore after being reconstituted with additional caustic.
  • 56092116 (7/25/81) is disclosed starch cationized with a quaternary ammonium salt for use as a coagulant;
  • U.S. Pat. No. 4,083,925 promotes separation from alkali metal aluminate liquor by contacting it with anionic polyacrylamide under special conditions within the mud settler;
  • East German (DE) Pat. No. 2552804 (8/11/77) subjects starch to treatment with sodium tetraborate and a magnesium salt to provide improved flocculating properties with lower levels of starch;
  • Russian Pat. No. 507526 (4/06/76) reports that cationic flocculants of the formula (R— AR— CH ?
  • Fiocculation of the solids aids in the settling process by tending to agglomerate smaller particles into larger ones, which tend to settle faster. Fiocculation also aids in the filtering process because larger agglomerates are easier to filter than smaller ones, and less likely to plug the filtering means.
  • Red mud is generally obtained as the underflow from a settler. It consists mainly of extremely fine, difficult-to-filter, insoluble residue that remains after the caustic-soluble components have been extracted.
  • the red mud underflow from a primary settler passes through a countercurrent washing circuit, generally comprised of a series of washers, for recovery of sodium aluminate and soda.
  • Current practice is to dispose of the last washer underflow stream and other red mud streams by pumping them as a relatively dilute slurry to holding ponds and lakes constructed for that purpose. The practical limit of such a slurry is 25 to 40 percent solids; 40 percent solids content is usual.
  • the dikes of mud lakes must be maintained, and there is always the risk of a break and spill of the mud into a nearby stream or waterway.
  • the large amounts of water going to the impoundment along with the suspended mud may contain caustic and solubilized alumina, which are lost from the process and present a large economic penalty.
  • Centrifugation is a well-known process for achieving solid-liquid separations, but has not been typically used to dewater red mud. It is known to those skilled in the art that centrifugation of red mud is only marginally effective f r increasing the solids.
  • the processes of the present invention are designed to increase red mud solids and to recover the dissolved components, such as aluminate and soda, contained therein.
  • the improvement forming the basis of the present invention lies in the centrifugation of suspended solids-containing streams, particularly those containing red mud solids, that have been flocculated using polymers that contain hydroxamic acid groups. Centrifugation of solids that were not flocculated with polymers, or that were flocculated with polymers that did not contain hydroxamic acid groups, has been found to be less effective than current commercial procedures.
  • a process for improving the dewatering of suspended solids, particularly red mud, of the Bayer process whereby a polymer containing hydroxamic acid groups or salts thereof is added to the Bayer process stream in order to effectively remove suspended solids therefrom, and the resulting flocculated solids are dewatered by centrifugation.
  • the polymer to be employed in the present invention can vary rather broadly in type. It should be sufficiently stable to be effective under the process conditions used, e.g., high temperatures and strong caustic conditions, typically, 185 * - 225" F., and 80-400 grams per liter total alkali content (expressed as sodium carbonate equivalent).
  • any water-soluble hydroxamic acid or salt group-containing polymer may be used in the process of the present invention.
  • the useful polymers can best be exemplified by those containing pendant groups of the Formula (1): O
  • R is hydrogen or a cation.
  • polymers are well known in the art and can be derived from polymers containing pendant ester, amide, anhydride, nitrile, etc., groups by the reaction thereof with hydroxyiamine or its salt, or by polymerization of a monomer which contains a hydroxamic acid or salt group. Hydroxamated polymers derived from polymers containing amide groups e.g. polyacrylamide are preferred.
  • Exemplary of the polymers which may be hydroxamated for use in the process of the present invention are acrylic, methacrylic, crotonic etc., acid ester polymers such as polymers produced from the polymerization of methyl acrylate, ethyl acrylate, t-butyl acrylate, methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, dimethyl aminoethyl methacrylate, dimethyl aminoethyl acrylate, methyl crotonate, etc., polymers of maleic anhydride and esters thereof, and the like; nitrile polymers such as those produced from acrylonitrile etc; amide polymers such as those produce ⁇ from acrylamide, methacrylamide and the like.
  • Hydroxamated polymers are well known to those skilled in the art and are specifically disclosed, as are methods for their production, in U.K. Patent Application 2171 127 and U.S. Pat. Nos. 3,345,344; 4,480,067, 4,532,046; 4,536,296; 4,587,306; 4,767,540; 4,902,751 ; and 5,128,420; all of which are hereby inco ⁇ orated herein by reference.
  • these hydroxamated polymers may be produced by reacting the polymer containing a pendant reactive group, in solution, with a hydroxyiamine or its salt at a temperature ranging from about 10 * C to 100 * C, preferably below 50 * C, for several hours, and more preferably, at a pH over about 10. From about 1-90% of the available pendant reactive groups of the polymer may be replaced by hydroxamic groups in accordance with said procedures.
  • a hydroxyiamine or its salt it is known that a polymer latex or emulsion may be reacted directly with a hydroxyiamine or its salt.
  • the latex may be, e.g., a copolymer of acrylamide and methyl acrylate or a copolymer of acrylic acid and methyl acrylate.
  • the hydroxyiamine or its salt reacts primarily with the ester groups to form hydroxamic acid groups.
  • aqueous solutions of polymers derived from inverse emulsions and inverse microemuisions herein referred to also as emulsions and microemulsions function efficiently in the process of the present invention.
  • emulsions and microemulsions are made of, for example, aqueous polyacrylamide, or acrylamide/acrylic acid copolymers dispersed in oil and reacted directly with a hydroxyiamine or its salt to give very high molecular weight polymers containing hydroxamic acid groups.
  • Dilute aqueous solutions bf these polymers, useful in the instant invention are derived from emulsions and microemulsions by "breaking"; e.g. adding the emulsions and microemulsions to water, optionally adding surfactant, and agitating to dissolve the polymer.
  • the degree of hydroxamation i.e., the concentration of Formula I units in the polymers useful herein, may range from about 1 to about 90 mole percent, preferably from about 5 to about 75 mole percent and, most preferably, from about 10 to about 50 mole percent.
  • the degree of hydroxamation may be determined by nuclear magnetic resonance spectroscopy techniques well known to those skilled in the art.
  • Suitable hydroxyiamine salts include the sulfates, sulfites, phosphates, perchlorates, hydrochlorides, acetates propionates and the like.
  • the pH of the solution is adjusted to be in the range of about 3 to about 14, preferably over about 7, more preferably over about 10, by means of acid or base addition to the solution.
  • Any water-soluble polymer may be used in the present process which, after hydroxamation, performs to settle suspended soiids.
  • homopolymers, copolymers, te ⁇ olymers, etc. of the above exemplified monomers may be used.
  • Suitable comonomers which, by copolymerization, may form, for example, up to about 95 mole percent of the polymers useful herein can include acrylic acid, sodium acrylate, methacrylic acid, maleic anhydride, vinyl acetate, vinyl pyrrolidone, butadiene, styrene as well as others of the above enumerated esters, amides and/or nitriles and the like as is known in the art and is set forth in the above-inco ⁇ orated patents as long as such copolymers, te ⁇ olymers etc., are water- soluble after hydroxamation.
  • the weight average molecular weight of the polymers useful in the process of the present invention range from about 1 X 10 4 to about 1 X 10 ⁇ , preferably from about 3 X 10 s to about 5 X 10 7 .
  • Weight average molecular weight may be determined by light scattering techniques well known to those skilled in the art.
  • the polymers used in the present invention are employed by adding them, usually in the form of a dilute aqueous solution, to any digested bauxite ore process stream containing solubilized alumina and suspended solids dispersed throughout, in an amount at least sufficient to settle said suspended solids.
  • the polymers are added to settler underflow streams, washer train underflow streams, and/or digester blow-off streams.
  • the process stream may undergo other chemical treatment e.g. acidification before, during or after the time that the polymer is added. Generally, for best results, at least about 0.1 milligrams (mg) of the hydroxamated polymer is added per liter of process stream.
  • hydroxamated polymers with other water-soluble polymers e.g polyacrylates, acrylate/amide copolymers, starch, dextran, etc. are effective and may be preferred.
  • a 1% solution of a polymer containing pendant hydroxamic acid or salt groups could be blended with a 1 % solution of polyacrylic acid or its salt and the resultant mixture used to flocculate red mud, or the polymers could be blended while still in the emulsion form.
  • Mixtures of hydroxamated polymers with other chemical agents useful in the Bayer process e.g surfactants may also be effective.
  • centrifugation is well known to those skilled in the art and a detailed description may be found in e.g Ullman's Encyclopedia of Industrial Chemistry, Volume B2, pp. 11-1 to 11-27, which is hereby incorporated herein by reference.
  • Any centrifuge including filter centrifuges, screen centrifuges, sedimentation centrifuges, decanting centrifuges, etc. may be used in the present invention. Sedimentation and decanting centrifuges are preferred, and classifying decanter centrifuges are most preferred.
  • Feed volume depends on the size of the centrifuge and type of centrifuge. For a horizontal classifying decanter centrifuge with a bowl diameter of about 20 inches and a length of about 80 inches, a feed volume of about 4 to about 250 gallons per minute may be used, preferably about 20 to about 100 gallons per minute, most preferably about 30 to about 90 gallons per minute. Feed solids may range from about 0.01% to about 45%, preferably from about 15% to about 30%.
  • the G- force is generally in the range of about 500 to about 3000 X G, preferably in the range of about 1000 to about 1500 X G.
  • the differential between the scroll and the bowl is generally less than 150 revolutions per minute (rpm), preferably from about 1 to about 100 rpm, more preferably from about 10 to about 50 ⁇ m, most preferably from about 30 to about 40 rpm.
  • Water-soluble polymers containing pendant hydroxamic acid or salt groups may be mixed with the Bayer process stream, preferably the settler underflow or digester blow-off, in a holding tank prior to being introduced to the centrifuge, or pumped into the process stream feed line, or added via a feed tube directly inside the centrifuge.
  • the polymer is added in the form of a dilute solution, e.g. from about 0.01 % to about 3%, directly inside the centrifuge.
  • a dilute solution e.g. from about 0.01 % to about 3%
  • the flocculated solids are centrifuged to produce centrifuged solids (cake) and aqueous liquid (centrate).
  • the operation of the centrifuge is optimized according to principles well known in the art.
  • the settler underflow streams are preferably primary settler underflow streams.
  • the washer train underflow streams may be streams from any washer in the washer train, preferably the last washer underflow stream.
  • the cake solids (the weight percent water-insoluble material) of the cake, or centrifuged solids, is higher than the feed solids, preferably greater than about 40%, more preferably greater than about 50%, most preferably greater than about 60%. Although is it generally preferred for the cake solids to be as high as possible, plugging of the centrifuge may occur at very high solids levels e.g. 90%. For obvious reasons plugging of the centrifuge is to be avoided. In practice, the desired solids level is generally dependent on whatever handling characteristics are desired in the centrifuged solids.
  • the processes of the instant invention are particularly useful for concentrating, or dewatering, red mud, typically from settler underflow streams, and/or blow-off discharge.
  • the centrate which is comprised of the aqueous liquid, or aluminate Iiquor, to be as clear as possible; i.e., to have as low a concentration of suspended solids as possible to avoid contamination of the final product.
  • the solids level (the weight percent water-insoluble material) in the aqueous liquid is less than the feed solids, preferably 1% or less, more preferably 0.5% or less, even more preferably 0.2% or less, and most preferably 0.1 % or less.
  • the solids level in the centrate is frequently expressed as the centrate clarity, as specified in the examples.
  • the centrifugation of flocculated solids to achieve both highly dewatered red mud and clear aqueous Iiquor is most often optimized in the context of other plant operations.
  • the degree of red mud dewatering and the clarity of the aqueous liquor may be adjusted up or down to achieve other desirable outcomes such as lower power consumption, reduced waste disposal costs, increased rates of production, increased product purity, reduced consumption of raw materials, etc.
  • Fiocculation and centrifugation may be used in place of, or in addition to, or in combination with, the usual means of solids/liquids separation employed in the Bayer process e.g settlers, decanters, thickeners, classifiers, and filters.
  • settlers may be reduced or avoided by flocculating and centrifuging blow-off discharge directly-.
  • a consecutive or intermittent series of centrifuges may also be employed, with the output of one as the input for another.
  • the solids content (cake solids) of centrifuged solids is determined by weighing a sample of centrifuged solids, washing the solids with deionized water, and drying the sample to constant weight in a forced air oven maintained at about 105 * C.
  • the cake solids are expressed in wt. % as (dried weight / initial weight) X 100.
  • Centrate (aqueous Iiquor) clarity or wt % water-insoluble material in the aqueous liquid, is determined by weighing a centrate sample, filtering the centrate through a previously weighed 45 micron polypropylene or glass filter, washing the solids with water, and drying the filter to constant weight in a forced air oven maintained at about 105" C. Values for centrate clarity are expressed in wt. % as [(dried filter weight - initial filter weight) / (centrate weight)] X 100.
  • Polymer D is obtained commercially; it contains about 90 mole % ammonium acrylate and about 10 mole % acrylamide and has a molecular weight of about 15,000,000.
  • Polymer A is prepared as follows: 100 Parts of 18 % aqueous solution of polyacrylamide (molecular weight of about 500,000) is combined with 3 parts of sodium thiosulfate stabilizer, 54 parts of 30 % aqueous hydroxyiamine sulfate, and 35 parts 50 % aqueous sodium hydroxide in a suitable vessel. The mixture is stirred at a temperature of about 30-
  • Polymer B is prepared as follows: 65 Parts of 30 % aqueous hydroxyiamine sulfate, 25 parts of sodium thiosulfate stabilizer, 142 parts water and 160 parts 50 % aqueous sodium hydroxide are mixed in a suitable vessel to give a solution. This solution is added to a mixture of 141 parts aliphatic oil, 1 part of an ethoxylated amine surfactant, and 438 parts of a polyacrylamide microdispersion having a molecular weight of about 15,000,000 and containing 25 % polymer solids, with the temperature being maintained below about 35"C for about 24 hours or more. The resulting hydroxamated polymer microdispersion contains about 11% polymer solids and the degree of hydroxamation is about 14 mole %.
  • Polymer C is prepared as follows: 70 parts of a 1% solution of a polymer prepared as in Example B is blended with 30 parts of a 1 % polymer solution of a commercially available sodium polyacrylate having a molecular weight of about 10,000,000.
  • the Bayer process stream used in these examples is underflow from a red mud settler.
  • the underflow slurry is fed with a variable speed pump to a horizontal classifying decanter centrifuge having a bowl diameter of about 20 inches and a length of about 80 inches.
  • the G force is between about 1000 X G and about 1600 X G.
  • the differential speed is about 15 to about 35 revolutions per minute (rpm).
  • the polymer as a -0.5% solution, is fed directly into the feed chamber of the centrifuge via a feed tube.
  • the dosage of the polymer, in units of grams of real polymer per dry ton (g/DT) of centrifuged solids, is shown in Table 1. Centrifugation of red mud without the use of polymer gives an unacceptably cloudy filtrate.
  • Table 1 also shows the identity of the polymers used, prepared as in Examples A, B and C, the wt. % solids of the red mud slurry, the feed rate of the red mud slurry (in units of gallons per minute, gpm), the cake solids (wt. % solids in the centrifuged red mud solids) and the centrate clarity (wt. % filterable solids in the aqueous iiquor).
  • the results demonstrate that the hydroxamated polymers provide high centrifuge cake solids and clear centrate.
  • the Bayer process stream used in these Examples is primary settler overflow having a feed solids of about 0.015%.
  • the conditions used are the same as in Examples 1-12, wit.' appropriate adjustment for the lower solids content of the slurry.
  • values of cake solids are obtained that are substantially equivalent to those in Table 1 ; values of centrate clarity less than 0.015% are obtained.
  • the Bayer process stream used in these Examples is last washer underflow having a feed solids of about 30%.
  • the conditions used are the same as in Examples 1-12, with appropriate adjustment for the higher solids content of the slurry.
  • polymers prepared as in Examples A, B, and C values of cake solids and centrate clarity are obtained that are substantially equivalent to those in Table 1.
  • the red mud slurry used in these Examples is blow-off discharge.
  • the feed solids of the slurry is about 2% and the feed rate of the slurry is shown in Table 2
  • the slurry is fed with a variable speed pump to a horizontal classifying decanter centrifuge having a bowl diameter of about 20 inches and a length of about 80 inches.
  • the G force is about 1200 X G.
  • the differential speed is about 10 rpm.
  • Polymers A and B are obtained as above, diluted to 1 % solution, and fed directly into the feed chamber of the centrifuge via a feed tube.
  • the dosage of the polymer is as shown in Table 2.
  • the centrate clarity both with and without polymer is shown in Table 2.

Landscapes

  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Separation Of Suspended Particles By Flocculating Agents (AREA)
  • Treatment Of Sludge (AREA)

Abstract

Procédés permettant d'améliorer l'efficacité de la séparation solides/liquides dans le procédé Bayer. Selon ces procédés les solides sont floculés avec des polymères hydroxamatés puis centrifugés.
EP96937034A 1995-11-07 1996-10-29 Concentration de solides dans le procede bayer Withdrawn EP0859744A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US630095P 1995-11-07 1995-11-07
US630P 1995-11-07
PCT/US1996/017247 WO1997017292A1 (fr) 1995-11-07 1996-10-29 Concentration de solides dans le procede bayer

Publications (1)

Publication Number Publication Date
EP0859744A1 true EP0859744A1 (fr) 1998-08-26

Family

ID=21720235

Family Applications (1)

Application Number Title Priority Date Filing Date
EP96937034A Withdrawn EP0859744A1 (fr) 1995-11-07 1996-10-29 Concentration de solides dans le procede bayer

Country Status (5)

Country Link
EP (1) EP0859744A1 (fr)
CN (1) CN1201439A (fr)
AU (1) AU712311B2 (fr)
BR (1) BR9611355A (fr)
WO (1) WO1997017292A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1850938B1 (fr) 2005-02-25 2017-08-16 Cytec Technology Corp. Emulsions eau dans l'huile dans l'eau de polymeres hydroxamates et leurs methodes d'utilisation
WO2013152796A1 (fr) * 2012-04-12 2013-10-17 Krsys Gmbh Procédé et dispositif d'obtention de produit valorisable à partir d'un résidu de bauxite
JP7755991B2 (ja) * 2020-12-28 2025-10-17 花王株式会社 変性セルロース繊維ケークの製造方法

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR924112A (fr) * 1946-02-27 1947-07-28 Alais & Froges & Camarque Cie Perfectionnement à la fabrication de l'alumine par le procédé bayer
US4767540A (en) * 1987-02-11 1988-08-30 American Cyanamid Company Polymers containing hydroxamic acid groups for reduction of suspended solids in bayer process streams
CA1330865C (fr) * 1989-01-31 1994-07-26 George Dennison Fulford Procede de production d'alumine a partir de bauxite
DE69211224T3 (de) * 1991-05-23 2001-02-22 Cytec Technology Corp., Wilmington Microdispersionen von Polymeren mit Hydroxamsäuregruppen

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9717292A1 *

Also Published As

Publication number Publication date
WO1997017292A1 (fr) 1997-05-15
AU712311B2 (en) 1999-11-04
CN1201439A (zh) 1998-12-09
AU7479896A (en) 1997-05-29
BR9611355A (pt) 1999-03-30

Similar Documents

Publication Publication Date Title
US5853677A (en) Concentration of solids by flocculating in the Bayer process
AU689350B2 (en) Blends of hydroxamated polymer emulsions with polyacrylate emulsions
EP1597301B1 (fr) Polymeres de poids moleculaire eleve contenant des groupes lateraux d'acide salicylique permettant de clarifier des liqueurs de procede bayer
US5665244A (en) Reduction of impurities in bayer process alumina trihydrate
US5951955A (en) Concentration of solids in the Bayer process
AU699929B2 (en) Removing suspended solids by addition of hydroxamated polymers in the Bayer Process
EP1363716B1 (fr) Procede de clarification de liqueurs bayer a l'aide de polymeres contenant de l'acide salicylique
AU2002232607A1 (en) Method of clarifying bayer process liquors using salicylic acid containing polymers
US6599489B2 (en) Aluminum trihydrate crystals and improved method for the production thereof
US5286391A (en) Red mud flocculation
EP1368390A1 (fr) Polymeres de poids moleculaire eleve contenant des groupes d'acide salicylique lateraux
AU2002231152A1 (en) High molecular weight polymers containing pendant salicylic acid groups
AU712311B2 (en) Concentration of solids in the bayer process
CA2234917A1 (fr) Concentration de solides dans le procede bayer
AU691595B2 (en) Use of anionic flocculants and hydroxamated polymers as Bayer Process red mud flocculents
CA2234765A1 (fr) Reduction des impuretes dans le trihydrate d'alumine produit par procede bayer

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19980417

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE

17Q First examination report despatched

Effective date: 19981008

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE APPLICATION IS DEEMED TO BE WITHDRAWN

18D Application deemed to be withdrawn

Effective date: 20000404