WO1990009349A1 - Recuperation d'agents a partir de liqueurs obtenues par le procede bayer - Google Patents

Recuperation d'agents a partir de liqueurs obtenues par le procede bayer Download PDF

Info

Publication number
WO1990009349A1
WO1990009349A1 PCT/AU1990/000047 AU9000047W WO9009349A1 WO 1990009349 A1 WO1990009349 A1 WO 1990009349A1 AU 9000047 W AU9000047 W AU 9000047W WO 9009349 A1 WO9009349 A1 WO 9009349A1
Authority
WO
WIPO (PCT)
Prior art keywords
liquor
organic
bayer
cationic
organic contaminants
Prior art date
Application number
PCT/AU1990/000047
Other languages
English (en)
Inventor
Mark Keeney
Original Assignee
Industrial Minerals Research & Development Pty. Ltd.
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 Industrial Minerals Research & Development Pty. Ltd. filed Critical Industrial Minerals Research & Development Pty. Ltd.
Publication of WO1990009349A1 publication Critical patent/WO1990009349A1/fr

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
    • C01F7/46—Purification of aluminium oxide, aluminium hydroxide or aluminates
    • C01F7/47—Purification of aluminium oxide, aluminium hydroxide or aluminates of aluminates, e.g. removal of compounds of Si, Fe, Ga or of organic compounds from Bayer process liquors
    • C01F7/473—Removal of organic compounds, e.g. sodium oxalate

Definitions

  • This invention relates to an improvement in methods associated with the Bayer Alumina Process for reducing humate type impurities in Bayer process liquors.
  • the Bayer Alumina Process is widely used to process bauxite to produce alumina for aluminium production. It involves the digestion of bauxite in a strong base, gener ⁇ ally caustic soda or lime, to produce a soluble aluminate that is crystallised and calcined to produce alumina.
  • bauxites typically contain organic contaminants, such as humates, which are also liberated during digestion. As these compounds have detrimental ' effects on further processing, their removal from Bayer process liquors is essential.
  • the present invention provides an improvement in the method of treating Bayer process liquors to remove organic contaminants in which the Bayer liquor is extracted with a cationic extraction agent preferably a cationic polymer- and the liquor is then treated in a hydrocyclone under centrifugal forces to separate the liquor into treated liquor with reduced organic contaminants and an organic layer containing organic contaminants and the cationic extraction agent.
  • a cationic extraction agent preferably a cationic polymer-
  • the process uses a small hydrocyclone of the type normally used to separate stable oil-in-water emulsions, particularly in the petroleum industry.
  • the hydrocyclone separates the dispersed polymer from the Bayer process liquor by centrifugal force based upon the large specific gravity differences between the polymer and the process liquor.
  • the hydrocyclone can be used on its own, as a replacement for the settling step, or as a "scrubber" after separation of the bulk of the polymer in a settling tank, to recover all traces of the polymer from the process liquor.
  • a preferred form of hydrocyclone is the VORTOIL liquid-liquid separator primarily used in oil/water separation.
  • the "organic layer” is separated from the process liquor in a settling tank after organic extraction has occurred.
  • the overflow from the settling tank is sent directly to a stripping tank where an alkali metal salt is added to precipitate alkali metal humate salts and regenerate the cationic polymer.
  • the polymer used for organic extraction is extremely hygroscopic and there is always a considerable amount of Bayer liquor entrained in the separated "organic layer".
  • the amount of entrained process liquor can vary from 25-50 weight %.
  • the present invention provides a method of treating Bayer process liquors to remove organic contaminants in which the Bayer liquor is extracted with a cationic extraction agent and the treated mixture is separated into an organic phase comprising organic contaminants and cationic extraction agent and a contaminant free Bayer process liquor phase, wherein the organic phase is then treated with a strong alkaline solution, preferably greater than 30wt. % NaOH to form a solid which can be separated from any remaining Bayer process liquor entrained in the organic phase.
  • a strong alkaline solution preferably greater than 30wt. % NaOH
  • the viscous "organic layer" separated from the Bayer liquor is first 5 treated with a clean caustic solution of greater than 30 weight % NaOH (i.e., a resin-wash step), and preferably in the range 40 to 50 weight % NaOH to avoid material handling problems whilst minimising reagent costs before being sent to the strip tank, the organic-loaded polymer completely 10 solidifies and the entrained Bayer liquor is readily washed away.
  • alumina refineries it is likely that the wash-liquor used would be the 50 weight % NaOH solution used for caustic make-up in the plant.
  • resin is to vigourou ⁇ ly agitate the "organic layer" in the hot, caustic wash-liquor.
  • a two-stage, counter-current resin-wash process • 20 may offer distinct advantages over a single stage wash for recover of the soluble alumina values.
  • the ability to use a strong, caustic-solution treatment as a resin-wash in order to alter the handling characteristics of the "organic layer” is predicated upon 25 the extreme insolubility in caustic of the water-soluble polymers used as extractants in the process. It is precisely this caustic-insolubility of the polymers which makes the process possible in the first place, since the polymer must be recovered from the caustic Bayer liquor. However, the 30 caustic level of the Bayer process liquors is insufficient for the polymer to precipitate in a completely solid form. We have found that the "organic layer" begins to solubili ⁇ e if the caustic level of the solution begins to drop much below that of Bayer liquor.
  • poly-DADMAC The preferred polymer used in the prior organic removal process extracts organic anions from the process liquor by an anion exchange technique
  • Poly-DADMAC has quaternary ammonium functionality nearly identical to that of highly cross-linked, strong base anion exchange resins.
  • the polymer precipitates from the process liquor it functions as an anion exchange resin with the chloride anion of the polymer exchanging with specific organic anions in the process liquor.
  • the water-soluble polymer used in the -prior process simply coagulates into a soft mass (i.e., "organic layer"). By efficiently separating this organic mass from the process liquor, Bayer organics are removed from the system.
  • the present invention provides an improvement in the method of removal of organic contaminants from Bayer process liquors in which the Bayer liquor is extracted with a cationic extraction agent and the liquor is separated into a first liquor having a reduced contaminant level and a second liquor rich in contaminants and the cationic agent and subsequently contacting the second liquor with an inorganic polyelectrolyte to precipatate the organic contaminants and enable the cationic agent to be recovered for re-use.
  • an inorganic polyelectrolyte preferably polyaluminium chloride
  • alkali metal salts for stripping the DADMAC polymer (an anionic polyelectrolyte) of extracted organics.
  • PAC polyaluminium chloride
  • the present invention also provides a means whereby excess (“parasitic”) water introduced at the resin-washing, stripping and organic precipitate washing stages can be removed prior to re-use of the DADMAC polymer.
  • the regenerated DADMAC stream containing approximately 20% DADMAC polymer, is contacted with strong 50 weight %.caustic solution intended for use as make-up caustic in the digestion stage.
  • This process results in absorption of "parasitic water” by the caustic solution and thus reduces the water content of the DADMAC polymer solution from 80% to &0%.
  • the 40% DADMAC solution so obtained forms a separate phase from the diluted caustic solution it can be recovered as overflow in a settling process and re-used for organic contaminant removal.
  • the diluted caustic solution is used in the resin-wash and then passes to the digestion stage as caustic make-up.
  • FIG. 1 shows a schematic of a process flowsheet incorporating the present invention.
  • Feed bauxite is first solubilised in steam, heated autoclaves in a digestion process involving strong caustic solution.
  • the humate containing Bayer liquors are treated with a cationic polymer, the preferred polymer being poly-DADMAC, to remove humates.
  • Poly-DADMAC is added at a dosage dictated by process conditions, but a typical dosage would be 100 g poly-DADMAC per litre of Bayer liquor.
  • Poly-DADMAC is water soluble and may be added as a 20% poly-DADMAC solution to the organic extraction stage.
  • the Bayer liquor consists of two phases, one being an organic phase containing cationic extraction agent (poly-DADMAC) and humates, the other being an aqueous phase containing treated Bayer liquor which must be separated before the aqueous phase can pass to crystallisation.
  • poly-DADMAC organic phase containing cationic extraction agent
  • humates aqueous phase containing treated Bayer liquor which must be separated before the aqueous phase can pass to crystallisation.
  • separation takes place in a hydrocyclone which accomplishes a separation using centrifugal forces and which is based on the large specific gravity differences between the polymer and the treated Bayer liquor.
  • a preferred form of hydrocyclone is the VORTOIL liquid-liquid separator (not shown), primarily used in oil/water separation. If desired, primary separation may be achieved in a settling tank, with final "polishing" being accomplished in the hydrocyclone.
  • the loaded organic stream 1 recovered from the hydrocyclone which contains poly-DADMAC and humate passes to a resin-wash stage 2 wherein the organic phase is vigorously agitated and contacted with a caustic solution of at least 30 weight %, and preferably 40 to 50 weight % sodium hydroxide to avoid material handling problems while minimising caustic consumption.
  • a caustic solution of at least 30 weight %, and preferably 40 to 50 weight % sodium hydroxide to avoid material handling problems while minimising caustic consumption.
  • Caustic solution stream 15 from water removal stage 17 is employed for the resin wash process which results in the solidification of the organic phase, thus facilitating separation of organic resin from the caustic solution.
  • the process is preferably to be accomplished in two stage countercurrent washing mode as it is essential that full solidification of organic occurs if polymer losses are to be avoided and effective sold/liquid separation is to be achieved. It is also critical that the caustic level of the "wash” solution be maintained at least at that of the Bayer liquor from the autoclaves in order that resolubilisation of the organic "resin" be avoided.
  • the resin-wash treatment also has the advantage that Bayer liquors entrained in the organic may be readily washe free.
  • DADMAC-humate solids stream 3 passes to strip process stage 5 to which aqueous precipitant stream 16 containing 20 weight % polyaluminium chloride (PAC) is added. PAC is made up in precipitant make-up tank 11 with process water and make up PAC 10.
  • PAC polyaluminium chloride
  • Sufficient PAC that is 0.9 parts PAC to one part DADMAC-humate solids, is added to resolubilise the DADMAC polymer.
  • the humate solids form an insoluble salt with PAC and may be removed by centrifugation or other suitable means in solid/liquid separation stage 6.
  • the recovered humate solids are thoroughly washed with process water stream 8 in wash stage 7 to remove adhering poly-DADMAC and are then discarded.
  • the wash water is recycled to the precipitant make-up tank 12. It is to be noted that the efficiency of the stripping stage 5 depends upon the chemical composition of the PAC utilised.
  • Maxwell Chemical product which can be used to recover 95% of the DADMAC when utilised as described above, has a significantly higher sulphate content, 7 weight %, than the other products tested.
  • Alternative PAC products tested from AKZO Chemicals and Cyanamid contain 0.03 weight % and 0.05 weight % sulphate respectively. The low sulphate products were found to induce redissolution of PAC-humate solids when added at the same dosages as the Maxwell Chemicals product and are therefore not as effective.
  • Regenerated 20% poly-DADMAC solution passes from the said solid/liquid separation stage 6 to a reagent storage tank 11 from which it passes to water removal stage 17.
  • water removal stage 17 50 weight % caustic stream 13 intended for caustic make-up in the digestion stage, is contacted with the 20% poly-DADMAC solution.
  • 40% DADMAC may be recovered by settling as it forms an organic phase which is immiscible with the diluted 10.
  • Caustic solution 15 is used in the resin-wash stage 2 and then passes to the digestion stage as caustic make-up.
  • the present invention provides three improvements to the method of removing organic contaminants which enable a greater economic recovery of the cationic extraction agent.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Inorganic Chemistry (AREA)
  • Extraction Or Liquid Replacement (AREA)

Abstract

L'invention concerne des améliorations relatives à un procédé d'échange d'ions dans un liquide basique, selon lequel de la liqueur de Bayer est traitée à l'aide d'un agent d'extraction cationique, se présentant de préférence sous la forme d'un polymère (poly-DADMAC), afin d'extraire une quantité significative des contaminants organiques (des sels ou esters d'acide humique) de la liqueur. On sépare la couche chargée de contaminants de la liqueur traitée (laquelle est renvoyée au système) à l'aide d'un hydrocyclone, on la traite à l'aide d'une solution alcaline forte afin de solidifier ladite couche organique, puis on l'extrait selon une technique de précipitation de polyélectrolyte inorganique afin de régénérer le polymère.
PCT/AU1990/000047 1989-02-10 1990-02-09 Recuperation d'agents a partir de liqueurs obtenues par le procede bayer WO1990009349A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
AUPJ2643 1989-02-10
AUPJ264389 1989-02-10

Publications (1)

Publication Number Publication Date
WO1990009349A1 true WO1990009349A1 (fr) 1990-08-23

Family

ID=3773700

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/AU1990/000047 WO1990009349A1 (fr) 1989-02-10 1990-02-09 Recuperation d'agents a partir de liqueurs obtenues par le procede bayer

Country Status (1)

Country Link
WO (1) WO1990009349A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10793444B2 (en) 2017-09-26 2020-10-06 Ecolab Usa Inc. Methods and compositions for bauxite beneficiation

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU5505380A (en) * 1979-01-31 1980-08-07 Alcan Research And Development Limited Removing oxolate from bayer liquor
AU8307887A (en) * 1986-12-24 1988-06-30 Commonwealth Scientific And Industrial Research Organisation Removal of humates from bayer process liquors

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU5505380A (en) * 1979-01-31 1980-08-07 Alcan Research And Development Limited Removing oxolate from bayer liquor
AU8307887A (en) * 1986-12-24 1988-06-30 Commonwealth Scientific And Industrial Research Organisation Removal of humates from bayer process liquors

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10793444B2 (en) 2017-09-26 2020-10-06 Ecolab Usa Inc. Methods and compositions for bauxite beneficiation

Similar Documents

Publication Publication Date Title
EP0186312B1 (fr) Purification de liqueurs du procédé Bayer
US4275042A (en) Removal of oxalate from Bayer process liquor
US2806766A (en) Process of purifying caustic aluminate liquors
US5284634A (en) Purification of Bayer process liquors using cationic polymeric quaternary ammonium salts
US4101629A (en) Purification of solutions circulating in the bayer cycle
US20230011640A1 (en) Methods for recovering organic salts from industrial process streams
US6726845B1 (en) Dextran starch and flocculant combination for improving red mud clarification
US4083925A (en) Method for removing ferrous iron from alkali metal aluminate liquor
US6110377A (en) Process for recovering the sodium contained in industrial alkaline waste
US4902425A (en) Removal of humates from bayer process liquors
EP1089797B1 (fr) Combinaison de dextrane, d'amidon et de floculant servant a ameliorer la clarification de la boue rouge
US4496524A (en) Process for the removal of sodium oxalate compounds from Bayer spent liquor
CA1097483A (fr) Procede d'extraction de l'hydroxyde d'aluminium precipite d'une solution d'aluminate de sodium
CA2784292C (fr) Procedes et compositions servant a l'elimination des impuretes dans un liquide ionique charge d'impuretes
WO1990009349A1 (fr) Recuperation d'agents a partir de liqueurs obtenues par le procede bayer
US4581207A (en) Recovery of aluminum from spent liquor
AU2007233571A1 (en) Method for controlling the precipitation of alumina
CA1277479C (fr) Methode d'epuration de l'alumine
EP0127262A1 (fr) Epuration de liquides utilisés selon le "procédé Bayer"
US5547647A (en) Production of alumina
JP3316863B2 (ja) 赤泥の分離方法
AU601252B2 (en) Removal of humates from bayer process liquors
Scarsella Impurities Control in Bayer Circuit
US4472361A (en) Method of recovering alumina values from a starting solid mixture comprising AlCl3 and NaCl
CN114787397A (zh) 一种净化拜耳工艺流的方法和设备

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): AU CA US

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH DE DK ES FR GB IT LU NL SE

NENP Non-entry into the national phase

Ref country code: CA