IE76299B1 - Trihydrate clarification aid for the bayer process - Google Patents
Trihydrate clarification aid for the bayer processInfo
- Publication number
- IE76299B1 IE76299B1 IE930677A IE930677A IE76299B1 IE 76299 B1 IE76299 B1 IE 76299B1 IE 930677 A IE930677 A IE 930677A IE 930677 A IE930677 A IE 930677A IE 76299 B1 IE76299 B1 IE 76299B1
- Authority
- IE
- Ireland
- Prior art keywords
- alumina trihydrate
- slurry
- polymer
- mer units
- thickener feed
- Prior art date
Links
- 150000004684 trihydrates Chemical class 0.000 title claims abstract description 98
- 238000005352 clarification Methods 0.000 title claims abstract description 26
- 238000004131 Bayer process Methods 0.000 title claims abstract description 21
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 103
- 229920000642 polymer Polymers 0.000 claims abstract description 98
- 239000002002 slurry Substances 0.000 claims abstract description 80
- 125000000129 anionic group Chemical group 0.000 claims abstract description 21
- 239000002562 thickening agent Substances 0.000 claims description 40
- 239000007787 solid Substances 0.000 claims description 36
- 238000000034 method Methods 0.000 claims description 30
- 239000006228 supernatant Substances 0.000 claims description 22
- NEAQRZUHTPSBBM-UHFFFAOYSA-N 2-hydroxy-3,3-dimethyl-7-nitro-4h-isoquinolin-1-one Chemical compound C1=C([N+]([O-])=O)C=C2C(=O)N(O)C(C)(C)CC2=C1 NEAQRZUHTPSBBM-UHFFFAOYSA-N 0.000 claims description 21
- 239000013078 crystal Substances 0.000 claims description 16
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 13
- 239000003518 caustics Substances 0.000 claims description 12
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 11
- ANBBXQWFNXMHLD-UHFFFAOYSA-N aluminum;sodium;oxygen(2-) Chemical compound [O-2].[O-2].[Na+].[Al+3] ANBBXQWFNXMHLD-UHFFFAOYSA-N 0.000 claims description 11
- 229910001388 sodium aluminate Inorganic materials 0.000 claims description 11
- 229910052739 hydrogen Inorganic materials 0.000 claims description 9
- 239000001257 hydrogen Substances 0.000 claims description 9
- 239000000047 product Substances 0.000 claims description 9
- 229910001570 bauxite Inorganic materials 0.000 claims description 7
- 239000002244 precipitate Substances 0.000 claims description 7
- 238000001556 precipitation Methods 0.000 claims description 7
- 239000008346 aqueous phase Substances 0.000 claims description 5
- 230000015572 biosynthetic process Effects 0.000 claims description 5
- 239000000470 constituent Substances 0.000 claims description 5
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 3
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 150000001768 cations Chemical group 0.000 claims description 3
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims description 3
- 125000001424 substituent group Chemical group 0.000 claims description 3
- RREGISFBPQOLTM-UHFFFAOYSA-N alumane;trihydrate Chemical compound O.O.O.[AlH3] RREGISFBPQOLTM-UHFFFAOYSA-N 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 abstract description 3
- 239000000243 solution Substances 0.000 description 24
- 238000001914 filtration Methods 0.000 description 8
- 239000002245 particle Substances 0.000 description 8
- 239000007864 aqueous solution Substances 0.000 description 7
- 238000000926 separation method Methods 0.000 description 7
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 6
- SMZOUWXMTYCWNB-UHFFFAOYSA-N 2-(2-methoxy-5-methylphenyl)ethanamine Chemical compound COC1=CC=C(C)C=C1CCN SMZOUWXMTYCWNB-UHFFFAOYSA-N 0.000 description 5
- 239000002253 acid Substances 0.000 description 5
- 230000029087 digestion Effects 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 150000003839 salts Chemical class 0.000 description 5
- HRPVXLWXLXDGHG-UHFFFAOYSA-N Acrylamide Chemical compound NC(=O)C=C HRPVXLWXLXDGHG-UHFFFAOYSA-N 0.000 description 4
- NIXOWILDQLNWCW-UHFFFAOYSA-M Acrylate Chemical compound [O-]C(=O)C=C NIXOWILDQLNWCW-UHFFFAOYSA-M 0.000 description 4
- 150000004645 aluminates Chemical class 0.000 description 4
- -1 crotonic acid ester Chemical class 0.000 description 3
- 150000002148 esters Chemical group 0.000 description 3
- 125000002496 methyl group Chemical group [H]C([H])([H])* 0.000 description 3
- 238000006116 polymerization reaction Methods 0.000 description 3
- 239000002243 precursor Substances 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- KAKZBPTYRLMSJV-UHFFFAOYSA-N Butadiene Chemical compound C=CC=C KAKZBPTYRLMSJV-UHFFFAOYSA-N 0.000 description 2
- 229920002307 Dextran Polymers 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- AVXURJPOCDRRFD-UHFFFAOYSA-N Hydroxylamine Chemical compound ON AVXURJPOCDRRFD-UHFFFAOYSA-N 0.000 description 2
- CERQOIWHTDAKMF-UHFFFAOYSA-N Methacrylic acid Chemical compound CC(=C)C(O)=O CERQOIWHTDAKMF-UHFFFAOYSA-N 0.000 description 2
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical compound C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 description 2
- 239000012670 alkaline solution Substances 0.000 description 2
- 125000000217 alkyl group Chemical group 0.000 description 2
- 150000001733 carboxylic acid esters Chemical class 0.000 description 2
- 125000002091 cationic group Chemical group 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 229920001577 copolymer Polymers 0.000 description 2
- 229960002086 dextran Drugs 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 239000010419 fine particle Substances 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000004816 latex Substances 0.000 description 2
- 229920000126 latex Polymers 0.000 description 2
- 239000000178 monomer Substances 0.000 description 2
- 229920001897 terpolymer Polymers 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- GVPKQBSVGAYFOD-UHFFFAOYSA-N 4-carbamoylpent-4-ene-2-sulfonic acid Chemical compound OS(=O)(=O)C(C)CC(=C)C(N)=O GVPKQBSVGAYFOD-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 229920002126 Acrylic acid copolymer Polymers 0.000 description 1
- NLHHRLWOUZZQLW-UHFFFAOYSA-N Acrylonitrile Chemical compound C=CC#N NLHHRLWOUZZQLW-UHFFFAOYSA-N 0.000 description 1
- 229910018626 Al(OH) Inorganic materials 0.000 description 1
- 101150000595 CLMP gene Proteins 0.000 description 1
- 101100382322 Drosophila melanogaster Acam gene Proteins 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- XBDQKXXYIPTUBI-UHFFFAOYSA-M Propionate Chemical compound CCC([O-])=O XBDQKXXYIPTUBI-UHFFFAOYSA-M 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- LSNNMFCWUKXFEE-UHFFFAOYSA-N Sulfurous acid Chemical compound OS(O)=O LSNNMFCWUKXFEE-UHFFFAOYSA-N 0.000 description 1
- XTXRWKRVRITETP-UHFFFAOYSA-N Vinyl acetate Chemical compound CC(=O)OC=C XTXRWKRVRITETP-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 229920006322 acrylamide copolymer Polymers 0.000 description 1
- 125000005396 acrylic acid ester group Chemical group 0.000 description 1
- 238000013019 agitation Methods 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 125000003368 amide group Chemical group 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 150000008064 anhydrides Chemical group 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 239000011362 coarse particle Substances 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000002178 crystalline material Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 229960000633 dextran sulfate Drugs 0.000 description 1
- 239000003866 digestant Substances 0.000 description 1
- 125000000118 dimethyl group Chemical group [H]C([H])([H])* 0.000 description 1
- 230000003292 diminished effect Effects 0.000 description 1
- 229920001971 elastomer Polymers 0.000 description 1
- 125000004185 ester group Chemical group 0.000 description 1
- 125000001495 ethyl group Chemical group [H]C([H])([H])C([H])([H])* 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 238000005189 flocculation Methods 0.000 description 1
- 230000016615 flocculation Effects 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 150000004676 glycans Chemical class 0.000 description 1
- 229920001519 homopolymer Polymers 0.000 description 1
- 150000002443 hydroxylamines Chemical class 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- FPYJFEHAWHCUMM-UHFFFAOYSA-N maleic anhydride Chemical compound O=C1OC(=O)C=C1 FPYJFEHAWHCUMM-UHFFFAOYSA-N 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- FQPSGWSUVKBHSU-UHFFFAOYSA-N methacrylamide Chemical compound CC(=C)C(N)=O FQPSGWSUVKBHSU-UHFFFAOYSA-N 0.000 description 1
- 125000005397 methacrylic acid ester group Chemical group 0.000 description 1
- MCVVUJPXSBQTRZ-ONEGZZNKSA-N methyl (e)-but-2-enoate Chemical compound COC(=O)\C=C\C MCVVUJPXSBQTRZ-ONEGZZNKSA-N 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- HQVFKSDWNYVAQD-UHFFFAOYSA-N n-hydroxyprop-2-enamide Chemical compound ONC(=O)C=C HQVFKSDWNYVAQD-UHFFFAOYSA-N 0.000 description 1
- 125000002560 nitrile group Chemical group 0.000 description 1
- 150000002825 nitriles Chemical class 0.000 description 1
- VLTRZXGMWDSKGL-UHFFFAOYSA-M perchlorate Inorganic materials [O-]Cl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-M 0.000 description 1
- VLTRZXGMWDSKGL-UHFFFAOYSA-N perchloric acid Chemical compound OCl(=O)(=O)=O VLTRZXGMWDSKGL-UHFFFAOYSA-N 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 229920002401 polyacrylamide Polymers 0.000 description 1
- 229920001282 polysaccharide Polymers 0.000 description 1
- 239000005017 polysaccharide Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 125000000999 tert-butyl group Chemical group [H]C([H])([H])C(*)(C([H])([H])[H])C([H])([H])[H] 0.000 description 1
- LDHQCZJRKDOVOX-UHFFFAOYSA-N trans-crotonic acid Natural products CC=CC(O)=O LDHQCZJRKDOVOX-UHFFFAOYSA-N 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 0.000 description 1
- 229920003169 water-soluble polymer Polymers 0.000 description 1
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
- C01F7/14—Aluminium oxide or hydroxide from alkali metal aluminates
- C01F7/144—Aluminium oxide or hydroxide from alkali metal aluminates from aqueous aluminate solutions by precipitation due to cooling, e.g. as part of the Bayer process
- C01F7/148—Separation of the obtained hydroxide, e.g. by filtration or dewatering
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Inorganic Chemistry (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
In a Bayer process for the production of alumina, the clarification of the alumina trihydrate slurry is improved by adding to the slurry an anionic water-soluble hydroxamated polymer e.g. in an amount 0.01 - 20 mg/l of slurry.
Description
TRIHYDRATE CLARIFICATION AID FOR THE BAYER PROCESS -5 The present invention is in the technical field of trihydrate clarification,, the settling of alumina trihydrate particles, in the Bayer process for the recovery of alumina from bauxite ore.
In the Bayer process for the production of alumina, bauxite ore is pulverized, slurried in θ water, and then digested with caustic at elevated temperatures and pressures. The caustic solution dissolves oxides of aluminum, forming an aqueous sodium aluminate solution. The caustic insoluble constituents of bauxite ore arc then sep arated from the aqueous phase containing the dissolved sodium aluminate Solid alumina trihydratc product is precipitated out of the solution and collected as product. 1$ in. more detail, the pulverized bauxite ore is fed to a slurry mixer where a water slurry is prepared. The slurry makeup water is typically spent liquor (described below) and. added caustic. This bauxite ore slurry is then diluted and passed through a digester or a series of digesters where about 98% of the total available alumina is released from the orc as caustic-soluble sodium aluminate. The digested slurry is then cooled to about 110 °c (about 230°F), typically employing a series of flash tanks wherein heat and condensate are recovered. The aluminate liquor leaving the Hashing operation contains from about 1 to about 20 weight percent solids, which solids consist of the insoluble residue that remains after, or is precipitated during, digestion. The coarser solid particles may be removed from the aluminate liquor with a 'sand trap” cyclone. The finer solid particles are generally separated from the liquor first by settling θ and then by filtration, if necessary. The slurry of aluminate liquor and finer solids is normally first fed io She center well Thctdarified sodium aluminate liquor is seeded with alumina trihydrate crystals to induce precipitation of alumina in the form of alumina trihydrate, Al(OH)r The alumina trihydrate particles or crystals are then separated from the concentrated caustic liquor, and the remaining liquid phase, the spent liquor, is returned to the initial digestion step and employed as a digestant after reconstitution with caustic.
The treatment of the liquor collected after the primary settlement to remove any residual suspended solids before alumina trihydrate is recovered is referred to as a secondary clarification stage.
In another section of the Bayer circuit, the settled solids of the primary settler ('‘red mud) are withdrawn from the bottom of the settler and passed through a countercurrent washing circuit for recovery of sodium slumisate and soda. As noted above, the red mud docs not include any coarser particles removed prior to feeding the slurry to the primary or mud settler.
In the recovery of s&roana trihydrate as product in the Bayer process, or for use as precipitation seed, the alumina trihydrate crystals are generally separated from the liquor in which they are formed by settling and/or filtration. Coarse particles settle easily, but fine particles settle slowly and to some extent are lost product or, if recovered by filtration, blind the filters. The fine particles of alumina trihydrate which do not settle easily often flow over the top of the alumina trihydrate settler and are sent hade to digestion with the spent liquor. That alumina trihydrate is then digested, and precipitated again an a second cycle through the Bayer process, unnecessarily expending energy and reducing the alumina extraction capacity of the spent liquor.
Canadian Patent No. 825,234, October 1969, uses dextran, dextran sulfate and compositions therewith containing anionic salts to improve the flocculation and filtration of alumina trihydrate from alkaline solutions thereof. U.S. Patent No. 5,041,269, August 1991, Moody et at, uses a flocculant for the recovery of alumina irihydratc crystals comprising a combination of dextran, or certain other polysaccharides, together with an anionic flocculant polymer including acrylic monomer.
It is an object of the present invention to provide a more effective separation of alumina trihydrate particles from aqueous alkaline media, particularly the fine alumina trihydrate particles, and particularly the separation thereof from the alkaline liquor in which they are formed in the Bayer process. It as an object of the present invention to provide a method whereby the suspended solids retained in the supernatant after settling of the alumina trihydrate θ from the 'alkaline liquor of the Bayer process are diminished. Et is an· object of the present invention to provide a more effective Bayer process wherein the separation of alumina trihydrate from the alkaline liquor isimproved by an improved clarification of the supernatant that forms above the settling, or settled, alumina trihydrate solids. These and other objects of the present invention are described in more detail below.
The present invention provides a method for the improved clarification of a Bayer process alumina trihydrate slurry comprising adding a water-soluble anionic hydroxamated polymer to a Bayer process alumina trihydrate thickener feed slurry in an amount effective to improve the clarification of the slurry upon settlement, and a Bayer process including that method.
In the Bayer process digestion, the aqueous alkaline solution acquires a sodium aluminate content. After primary settlement and secondary clarification the concentrated aluminate liquor (a supersaturated solution) is seeded with alumina trihydrate crystals to induce precipitation. The precipitate settles and is then separated from the spent liquor and further treated.
The precipitated alumina in the form of alumina trihydrate is difficult to separate from the concentrated caustic liquor. The finer crystalline material tends to settle slowly and gives poor supernatant clarities, which results in product or precipitation seed losses. Further, where recovery of She precipitate includes a filtration step, tine material causes filter blinding. The addition of the hydroxamated polymer improves the supernatant clarity, reducing the amount of suspended solids, which are typically very fine suspended solids, in the supernatant upon settlement The improved supernatant clarity minimizes alumina trihydrate losses and improves the subsequent supernatant filtration by reducing falter blinding, or eliminates the need for such subsequent supernatant filtration. It is also believed that the hydroxamated polymer clarification aid will improve-the alumina-caustic liquor separation on a vacuum filter by forming a more porous filter cake.
The liquor from which the alumina trihydrate crystals arc to be separated in a -commercial Bayer process is commonly referred to as the alumina trihydrate thickener feed, or alumina trihydrate thickener feed slurry. It is the feed to the Bayer circuit station at which the alumina tri,hydrate crystals, after formation, arc to be concentrated, or thickened, by settlement, after which the supernatant sad the alumina trihydrate crystals are separated, la a broader sense, an duoiina4rihydrate thickener feed, shiny is an alkaline aqueous slurry in which she solids are predominantly alumina trihydrate crystals, prior to separation of solids and the aqueous phase by settlement and the like.
The alumina trihydrate precipitate is usually recovered after settlement by filtration and washing of the settled, phase after supernatant removal, although it may be subjected to Ί settlement alone with removal of the supernatant. The recovered trihydrate crystals may then be treated by the usual processes, Including calcination, which drives off the water and is sufficient ¢0 bum off any organic residues, Including the residues of the hydroxamated polymer. The supernatant (spent liquor) is recycled sn the conventional manner to the digestion stage.
A commercial alumina trihydrate thickener feed is most commonly a caustic liquor having a pH from about KO to above 14, a temperature between about 75 ”F and about 190 Ύ (from about 24 *C to about 88 C) and an alumina trihydrate solids content of from about 5 to about WO grams per liter of alumina trihydrate thickener feed slurry.
The alumina trihydrate thickener feed slurry to which the hydroxamated polymer Is θ added may have a concentration of dissolved organic components up to about 30 g/liter of slurry, and such a slurry typically has a concentration of dissolved organic components In the range of from about 0.1 io about 5 or 10 g/liter of slurry. The solids content of the alumina trihydrate thickener feed slurry outside of the alumina trihydrate solids generally is no more than about 50 mg (.05 grams), and the concentration of solids other than alumina trihydrate solids generally does not exceed a weight ratio of about 1:100 other solids to alumina trihydrate solids. The alumina trihydrate crystals therefore comprise at least about 99 weight percent of the total solids in the alumina trihydrate thickener feed slurry to which the hydroxamated polymer is added.
The alkalinity of the alumina trihydrate thickener feed slurry can range from about 5 to about 400 g/liter of slurry, expressed as sodium carbonate. The alkalinity of alumina trihydrate thickener feed slurries typically are in the range of from about 50 to about 400 g/liter of slurry expressed as sodium carbonate, and often are within the range of from about 200 to about 400 g/liter of slurry expressed as sodium carbonate.
The process is generally carried out with the alumina trihydrate slurry at a of at least about 50 ®C and after/within the range of from about 60 *C to about 30 °C.
The addition of the hydroxamated polymer is made after precipitation has been induced and preferably while at least a significant portion of the alumina trihydrate solids remain suspended in the liquor, but it is possible to add it after some separation of alumina trihydrate solids has occurred as long as it as added before the final separation of alumina trihydrate residuals.
The hydroxamated polymer should be added to the alumina trihydrate thickener feed slurry in an^amount effective to improve the clarification of the supernatant upon settlement. An improvement in supernatant clarification is, of course, in comparison to supernatant clarification for the same process parameters in the absence of the hydroxamated polymer.
The effective amount of hydroxamated polymer can depend on the concentration of alumina trihydrate solids in the slurry, other slurry conditions, and the hydroxamated polymer’s anionic charge density and molecular weight. The amount of the hydroxamated polymer added is usually in the range of from about 0.01 to about 20 mg/1 iter of slurry, preferably from about 0.05 to about 10 mg/Iiter of slurry, and more preferably from about 0.1 to about 5 mg/iiter of slurry. Commonly less than about 0.5 mg/liter of slurry of polymer can be used.
The effective amount of hydroxamated polymer can be from about 0.0005 to about 1 pound of hydroxamated polymer per ton of alumina trihydrate solids in the slurry, and In more preferred embodiment from about 0.005 to about 0.1 pound of hydroxamated polymer per ton of alumina irihydratc solids an the slutty. About 0.1 pound per ton is the maximum needed under most conditions; and more than. 1 pound per ion will often be unnecessary.
The hydoxamic polymer should be sufficiently stable under the process conditions used, the temperatures and caustic 'Conditions described above.
Any water soluble hydroxara/’c polymer may be used, but the hydroxarnic polymer is commonly a polymer containing mer units with hydroxamic acid or salt pendant groups of the Formula I R’ -(- C - C -)I Formula I C = O I R - N - O - R wherein R is hydrogen or a cation, and R’ and R are independently hydrogen or a substituent to carbon other than hydrogen, for instance a lower alkyl such as methyl.
The hydroxamic polymers, or hydroxamated polymers, arc well known in the art and can be prepared by post-polymerization dcrivatization from polymers containing pendant reactive groups, such as pendant ester groups, pendant amide groups, pendant anhydride groups, pendant nitrile groups and She like by the reaction thereof with hydroxylamine or its salt at a temperature within the range of from about 20 *C to about WO *C for several hours. From about ll to about 90 mole percent of the available pendant reactive groups of the precursor polymer may be replaced by hydroxamic groups in accordance with such procedures. Such post-polymerization dcrivatization may be carried out in a polymer solution or in a polymer-containing latex, including both water-continuous laticcs and water-in oil laticcs (wherein the polymer is substantially associated with the dispersed aqueous phase). When two or more species of pendant reactive groups are present in the precursor polymer, the reaction with hydroxyl amine may favor one or more of such species over the others). Tne molecular weight of the hydroxamated polymer is dependent upon the molecular weight of the precursor polymer.
Hydroxamic acid or salt-containing polymers of very high molecular weights can be prepared by using a water-sn-oil latex of, for example, polyacrylamide or copolymers of acrylamide with acrylic acid or other suitable comonomers .
Exemplary of ihe polymers which may be hydroxamated for use in the present process include acrylic acid ester polymers, methacrylic acid ester polymers, crotonic acid ester polymers, and the like carboxylic acid ester polymers, such as polymers produced from the polymerization of methyl (meth)acrylate, ethyl (meth)acrylate, t-butyl (mcth)acrylate, cyclohcxyl (meth)acrylatc, dimethyl aminocihyl (mcth)acry!ates dimethyl aminoethyl (meth)acrylate, methyl crotonate, and the Sake type of carboxylic acid ester containing mer units, generally wherein the ester moiety is derived from a C,.,2 alcohol, and preferably wherein the ester moiety is derived from a C3jJ alcohol. The polymers which may he hydroxamaied for use an the present process also include polymers of maleic anhydride and esters thereof, pendant nitrile containing polymers such as those produced from acrylonitrile, pendant amide containing polymers such as those produced from acrylamide, methacrylamide and the like. The hydroxamic acid or salt-containing polymer may be derived from homopolymers, copolymers, terpolymers, or polymers of more varied mer units. Hydroxamic polymers are well known to those of ordinary skill in She art and are specifically disclosed, together with methods for their preparation, in U.S. Patent Nos. 3,345,344,4,480,067,4,532,046, 4,536,296, and 4,587,306, and U.K. Patent Application 2171127, hereby incorporated hereinto by reference. Suitable hydroxylamine salts include the sulfate, sulfite, phosphate, perchlorate, hydrochloride, acetate, propionate, and the like.
The hydroxamic acid or salt-containing polymer for use in the present process should generally have a weight average molecular weight within the range of from about 10,000 to about 50,000,000. The hydroxamated polymer preferably has a weight average molecular weight of at least about 1 million, preferably with an IV of from about 5 to about 40 dl/g.
The degree of hydroxamation, that is, the concentration of mer units (polymer segments containing two adjacent backbone carbons) of the Formula 1 above, may vary from about 1 to about 90 mole percent, and preferably is within the range of from about 5 to about 75 mole percent and most preferably from about W to about 50 mole percent.
Since the alumina trihydrate thickener feed slurry is alkaline, the hydroxamated polymer q in preferred embodiment Is predominantly anionic, although It can also contain nonionic or even a minor amount of cationic mer units, provided that the amount of any such cationic mer units is sufficiently small so that the polymer retains an overall anionic nature and its water solubliiy. The anionic mers other than the hydroxamic mer units (referred to herein as the ’anionic mer units” unless expressly Indicated otherwise) are generally carboxylic acids or sulphonic acids, and are usually derived from acrylic acid (AA) but can be derived from methacrylic acid (MAA) or a sulfoalkyl acrylamide, such as 2-sulfopropylacrylamide, or the other anionic monomers noted above. The Hydroxamated polymer generally is comprised of from about 1 to about 99 mole percent, and preferably from about 15 to 90 mole percent, anionic mer units with the balance being hydroxamic mer units, optionally together with nonionic mer units. More preferably the hydroxamated polymer as comprised of from about 25 to about 75 mole percent anionic mer units, the balance being hydroxamic mer units, optionally together with nonionic mer units. In even more preferred embodiment, the hydroxamated polymer is comprised of from about 25 to about 75 mole percent anionic mer units, from about 10 to about 40 mole percent hydroxamic mer units and from about 10 to about 40 mole percent nonionic mer units.
The nonionic mer units are usually the polar (mcth)acrylamlde mer units (AcAm or tnetfaAcAm), but others may be used, for instance, mer units derived from vinyl acetate, vinyl pynoiidonc, butadiene, styrene, aikanolactyiamides such as mcthylol acrylamide and others.
Test Method The test method employed for evaluating Bayer process trihydrate clarification with and without a trihydrate clarification aid is as follows. A quantity of alumina trihydrate thickener feed sufficient for the desired, number of comparative test runs is obtained fresh from a commercial Bayer circuit, and for each test run a 1000 ml sample thereof ( “test sample”) is charged to a WOO ml graduated cylinder. The test samples are each plunged ten times to re-suspend the alumina trihydrate particles, then dosed with the trihydrate clarification aid being used, if any, and again plunged ten times to disperse the trihydrate clarification aid in titc alumina trihydrate thickener feed shiny. The plunging is accomplished using a stainless steel rod with a perforated steel disk or rubber stopper attached to the end. The slurry is then left standing, without agitation, for a settlement time period of 30 minutes immediately following the final plunging. At the end of the 30 minute settlement period, a sample of the supernate liquor is collected, and the turbidity of such supernate sample is determined with a turbidity meter. TheAirbidity of the supernate is inversely related to clarification efficiency. The alumina trihydrate thickener feed slurries so obtained fresh from a commercial Bayer circuit will contain from about 5 to about W0 grams of alumina trihydrate crystal per 1 iter of slurry, and no more than about 50 mg of other solids per liter of slurry.
Example 1 The Test Method described above was employed to demonstrate the trihydrate clarification aid performance of a representative hydroxamated polymer according to the present invention. The polymer was an anionic, water-soluble terpolymer comprised of acrylic acid, acrylamide, and acrylhydroxamic mer units in the approximate mole ratios of 2:1:1, derived from the hydroxamation of a high molecular weight acrylic acid/acrylamide copolymer. The weight average molecular weight of the hydroxamated polymer was about 10,000,000. The polymer dosage employed was 0.2 mg of poly^ci actives per liter of the slurry, and polymer being added as s, dilute aqueous solution. A blank or control in which no trihydrate clarification θ aid was used was also run as a comparison. The test results, in terms of supernatant turbidity (WNTU), are set forth below in Table 1.
Clarification Aid none Hydroxamated Polymer Table 1 Dosage of Clarification Aid (mg/litcrl none 0.2 Supernatant Turbidity (NTin 108 Π8 The hydroxamated polymer employed in the present invention is, as noted above, a water soluble polymer. The water solubility characteristics of the hydroxamated polymer preferably is defined in terms of the fluidity of its aqueous solutions. By water soluble is meant herein, and generally, that an aqueous solution of the polymer, at the polymer actives concentration at which it Is charged io the aluminum trihydrate thickener feed slurry, is reasonably fluid, and preferably has a viscosity of no more than about 5 000 to 20,000 cps Brookfield, at a pH of between about 6 and about 14, and ambient room temperature (from about.23-to.about.26 *C.) The addition of the hydroxamated polymer in She form of a dilute aqueous solution facilitates a rapid dispersion of the polymer an the slurry. Such aqueous solutions of the hydroxamated polymer should not be overly viscous, but they also should not be so dilute that unnecessary volume of water is added to the alumina trihydrate slurry. For most hydroxamated polymers, an aqueous solution containing from about 0.01 ic about 0.5 weight percent of polymer actives is generally reasonable. To further facilitate the rapid dispersion of the hydroxamated polymer in the slurry, in preferred embodiment the polymer is added to the alumina trihydrate thickener feed slurry as an alkaline aqueous solution, for instance having a pH of at least about 9, and more preferably at least about 10, up io about a pH of about 14.
The present invention provides a method for the improved clarification of a Bayer process alumina trihydrate slurry comprising adding to a Bayer process alumina trihydrate thickener feed slurry an anionic water-soluble hydroxamated polymer in an amount effective to improve the clarification of the slurry upon settlement. The present invention also provides an improved Bayer process for the production of alumina wherein bauxite ore Is pulverized, slurried in water, and then digested with caustic at elevated temperatures and pressures, forming an aqueous sodium aluminate solution containing caustic-insoluble constituents, wherein the caustic-insoluble constituents are then substantially separated from the aqueous phase of the aqueous sodium aluminate solution, and the sodium aluminate solution ss then seeded with crystals of alumina trihydrate whereby a solid alumina trihydrate product is precipitated out of the solution, subjected to settlement (whereupon a supernatant Is formed) and collected ss product or recycled as precipitation seed. Such improved process is characterized by adding to the solution after formation of the alumina trihydrate precipitate, and prior to the complete formation of the supernatant, a water-soluble anionic hydroxamated polymer in an amount effective to improve the clarification of the supernatant upon the settlement of the alumina trihydrate precipitate.
In preferred embodiment, the alumina trihydrate thickener feed slurry or the solution has an alumina irihydratc solids content of from about 5 to about 100 grams per liter of alumina irihydratc thickener feed slurry or the solution. In preferred embodiment, the alumina irihydratc crystals of the alumina irihydratc thickener feed slurry or the solution comprise at least about 99 weight percent of the total solids in the alumina trihydrate thickener feed slurry or the solution.
In preferred embodiment, the alumina trihydrate thickener feed slurry or the solution has an alkalinity of from about 5 io about 400 g/liter of the slurry or the solution, expressed as sodium carbonate. In. preferred embodiment, the hydroxamated polymer is added to the alumina trihydrate thickener feed slurry or the solution when the alumina trihydrate thickener feed slurry or the solution is at a temperature within the range of from about 60 *C to about 80 eC.
In preferred embodiment, the amount of the hydroxamated polymer added to the alumina trihydrate thickener feed slurry or the solution is in the range of mom about 0.01 to about 20 mg per liter of the slurry or She solution. In preferred embodiment, the amount of the hydroxamated polymer added to the alumina trihydrate thickener feed slurry or the solution is In the range of from about 0.05 to about SO mg per liter of the slurry or the solution. In preferred embodiment, the amount of the hydroxamated polymer added to the alumina trihydrate thickener feed slurry or the solution Is in the range of from about 0.0005 to about 1 pound of the hydroxamated polymer per ion of alumina trihydrate solids in the slurry or the solution·, that is, from about 0.0005 to about 1 kg per 2240 kg. in preferred embodiment, the water soluble hydroxamic polymer is a polymer containing mer units of ihe Formula Ϊ R' + C- C + I Formula I C = O I R - N - O - R wherein R is hydrogen or a cation, and R and R are independently hydrogen or a substituent to carbon other than hydrogen, for instance a Lower alkyl such as methyl.
In preferred embodiment, the hydroxamated polymer has a weight average molecular weight within the range of from about 10,000 to about 50,000,000. In preferred embodiment, the hydroxamated polymer has a weight average molecular weight of at least about 1 million. In preferred embodiment, the hydroxamated polymer has an Intrinsic Viscosity of from about 5 io about 40 dl/g. In preferred embodiment, the hydroxamated polymer is comprised of from about 25 to about 75 mole percent anionic mer units other than hydroxamic mer units, the balance being hydroxamic mer units, optionally together with nonionic mer units. In preferred embodiment, the hydroxamated polymer is comprised of from about 25 to about 75 mole percent anionic mer units other than hydroxamic mer units, from about 10 to about 40 mole percent hydroxamic mer units and from about 10 to about 40 mole percent nonionic mer units.
Claims (16)
1. A method for the clarification of a Bayer process alumina trihydrate slurry comprising adding to a Bayer process alumina trihydrate thickener feed slurry an anionic water-soluble hydroxamated polymer.
2. A method according to claim 1 wherein said alumina trihydrate thickener feed slurry has an alumina trihydrate solids content of from about 5 to about 100 grams per liter of alumina trihydrate thickener feed slurry.
3. A method according to claim 1 or claim 2 wherein the alumina trihydrate crystals of said alumina trihydrate thickener feed slurry comprise at least about 99 weight percent of the total solids in said alumina trihydrate thickener feed slurry.
4. A method according to claim 1, claim 2 or claim 3 wherein said alumina trihydrate thickener feed slurry has an alkalinity of from about 5 to about 400 g/liter of said slurry, expressed as sodium carbonate.
5. A method according to any one of the preceding claims wherein said hydroxamated polymer is added to said alumina trihydrate thickener feed slurry when said alumina trihydrate thickener feed slurry is at a temperature within the range of from about 60°C to about 80°C.
6. . A method according to any one of the preceding claims wherein the amount of said hydroxamated polymer added to said alumina trihydrate thickener feed slurry is in the range of from about 0.01 to about 20 mg per liter of said slurry.
7. A method according to claim 6 wherein the amount of said hydroxamated polymer added to said alumina trihydrate thickener feed slurry is in the 10 range of from about 0.05 to about 10 mg per liter of said slurry.
8. A method according to any one of the preceding claims wherein the amount of said hydroxamated polymer added to said alumina trihydrate 15 thickener feed slurry is in the range of from about 0.0005 to 1 kg of said hydroxamated polvper per 2240 kg of alumina trihydrate solids in said slurry.
9. A method according to any one of the 20 preceding claims wherein said water soluble hydroxamic polymer is a polymer containing mer units of the Formula I R' I 4- c — c 4i 25 Formula I C = O R _ N -0 — R wherein R is hydrogen or a cation, and R' and R are independently hydrogen or a substituent to carbon other than hydrogen.
10. The method according to any one of the preceding claims wherein said hydroxamated polymer has a weight average molecular weight within the range of from about 10,000 to about 50,000,000.
11. A method according to claim 10 wherein said hydroxamated polymer has a weight average molecular weight of at least about 1 million.
12. A method according to any one of the preceding claims wherein said hydroxamated polymer has an Intrinsic Viscosity of from about 5 to about 40 dl/g.
13. A method according to any one of the preceding claims wherein said hydroxamated polymer is comprised of from about 25 to about 75 mole percent anionic mer units other than hydroxamic mer units, the balance being hydroxamic mer units, optionally together with nonionic mer units.
14. A method according to any one of claims 1 to 12 wherein said hydroxamated polymer is comprised of from about 25 to about 75 mole percent anionic mer units other than hydroxamic mer units, from about 10 to about 40 mole percent hydroxamic mer units and from about 10 to about 40 mole percent nonionic mer units.
15. A method according to any one of the preceding claims wherein bauxite ore is pulverized, slurried in water, and then digested with caustic at elevated temperatures and pressures, forming an aqueous sodium aluminate solution containing caustic-insoluble constituents, wherein said caustic-insoluble constituents are then substantially separated from the aqueous phase of said aqueous sodium aluminate solution, and wherein sodium aluminate solution is then seeded with crystals of alumina trihydrate whereby a solid alumina trihydrate product is precipitated out of said solution and subjected to settlement, whereupon a supernatant is formed, and said aluminum trihydrate precipitate is collected as product or recycled as precipitation seed, adding to said solution the said hydroxamated polymer after at least the formation of said alumina trihydrate precipitate, and prior to the complete formation of said supernatant.
16. Methods according to claim 1 substantially as herein described and exemplified.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US94429092A | 1992-09-14 | 1992-09-14 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| IE930677A1 IE930677A1 (en) | 1994-03-23 |
| IE76299B1 true IE76299B1 (en) | 1997-10-08 |
Family
ID=25481143
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| IE930677A IE76299B1 (en) | 1992-09-14 | 1993-09-13 | Trihydrate clarification aid for the bayer process |
Country Status (4)
| Country | Link |
|---|---|
| AU (1) | AU667390B2 (en) |
| CA (1) | CA2105333A1 (en) |
| GB (1) | GB2270519B (en) |
| IE (1) | IE76299B1 (en) |
Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE69308777T2 (en) * | 1992-12-14 | 1997-07-31 | Nalco Chemical Co | Change of trihydrate crystals in the Bayer process |
| AU669284B2 (en) * | 1993-06-02 | 1996-05-30 | Nalco Chemical Company | Use of hydroxamic acid containing polymers to improve filtration of settler overflow in Kelly filters in the Bayer process |
| US5601726A (en) * | 1994-06-06 | 1997-02-11 | Cytec Technology Corp. | Hydroxameted polymers in the bayer process to reduce solids |
| US5539046A (en) * | 1994-11-04 | 1996-07-23 | Cytec Technology Corp. | Blends of hydroxamated polymer emulsions with polyacrylate emulsions |
| CN1201440A (en) * | 1995-11-07 | 1998-12-09 | Cytec技术有限公司 | Reduction of impurities in bayer process alumina trihydrate |
| UA89663C2 (en) | 2005-02-25 | 2010-02-25 | Сайтек Текнолоджи Корп. | method for flocculation and composition COMPRISING water-in-oil-in-water emulsions |
| EP3199218B1 (en) | 2009-09-15 | 2019-11-06 | Suncor Energy Inc. | Process for drying oil sand mature fine tailings |
| CA2701317C (en) | 2009-09-15 | 2016-08-23 | Suncor Energy Inc. | Process for flocculating and dewatering oil sand mature fine tailings |
| AU2009354586A1 (en) | 2009-10-30 | 2012-05-24 | Suncor Energy Inc. | Depositing and farming methods for drying oil sand mature fine tailings |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| 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 |
-
1993
- 1993-09-01 CA CA002105333A patent/CA2105333A1/en not_active Abandoned
- 1993-09-02 GB GB9318210A patent/GB2270519B/en not_active Expired - Fee Related
- 1993-09-03 AU AU46114/93A patent/AU667390B2/en not_active Withdrawn - After Issue
- 1993-09-13 IE IE930677A patent/IE76299B1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| GB9318210D0 (en) | 1993-10-20 |
| GB2270519A (en) | 1994-03-16 |
| AU4611493A (en) | 1994-03-24 |
| AU667390B2 (en) | 1996-03-21 |
| IE930677A1 (en) | 1994-03-23 |
| CA2105333A1 (en) | 1994-03-15 |
| GB2270519B (en) | 1996-03-20 |
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| MM4A | Patent lapsed | ||
| FC9A | Application refused sect. 31(1) |