US3738411A - Treatment of aluminate digester liquor - Google Patents

Treatment of aluminate digester liquor Download PDF

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Publication number
US3738411A
US3738411A US00059954A US3738411DA US3738411A US 3738411 A US3738411 A US 3738411A US 00059954 A US00059954 A US 00059954A US 3738411D A US3738411D A US 3738411DA US 3738411 A US3738411 A US 3738411A
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liquor
digester
heat exchanger
dilute
alumina
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US00059954A
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F Lazar
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    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S159/00—Concentrating evaporators
    • Y10S159/34—Caustic

Definitions

  • ABSTRACT Aluminum-containing minerals, such as bauxite, are digested in sodium aluminate liquor, wherein the digestion liquor leaves the digester at a temperature above 150C and is conducted, without flashing, in a heat exchanger in a countercurrent flow with respect to the feed liquor for the digester so that the temperature difference between the two liquors is less than 10C.
  • kxNa O concentration of caustic Na O (e.g., above 220 g/l caustic Na O) to be designated hereinafter in the specification and the claims as kxNa O in the digesting liquor is advantageous for the digestion, since higher caustic concentrations allow the application of lower temperatures and reduced pressure, further specific pressure may also be lowered compared to the process in which the digesting liquor has a lower concentration of kx Na O.
  • Evaporation of the dilute liquor is absolutely necessary, for a digesting liquor with a concentration lower than 170 g/l kxNa O is uneconomical due to a deterioration in digestion efficiency.
  • Another method of eliminating the evaporation of the liquor may be carried out by diluting the digester liquor only to a degree which will ensure that after decomposition and precipitation of the aluminum hydroxyde, a concentration of 180 g/l of kxNa O will obtain. This solution is however uneconomical partly because of the less satisfactory settling of the red mud and partly because of a lowering of the decomposition efficiency.
  • the method for the processing of digester liquor slurry obtained in the continuous digestion of alumina containing minerals, especially of bauxite, with sodium aluminate liquor according to the present invention is characterized by leading the liquor leaving the digester at a temperature above 150C without expansion in indirect countercurrent heat exchange with respect to the dilute liquor used for digestion through heat exchangers or through series connected heat exchangers preferably so that the temperature difference between the dilute liquor exiting from the heat exchanger and of the feed digester liquor slurry entering the heat exchanger should be less than 10C and evaporating the heated dilute liquor in one or several steps by expansion (flashing).
  • the sodium aluminate liquor used for the digestion of bauxite is a liquor which is obtained by the dilution of the digester liquor and separation of the red mud by decomposition.
  • the digester liquor is diluted to a value suitably of about to g/l of kxNa O.
  • the dilute liquor to be evaporated and used for digestion is preferably led at pressure values of 5 to 60 atm. through the heat exchanger, thereafter the flashing of the heated dilute liquor leaving the heat exchangers is effected in several steps.
  • the super-heated steam formed by the flashing of the dilute liquor is used for pre-heating the starting mixture.
  • the apparatus for the implementation of the method according to the present invention is characterized by the used of at least one heat exchanger between the digester and the flashing (expansion) equipment said heat exchanger being fitted on one end with a conveyor pump to feed the dilute liquor to be evaporated and at the opposite end of the heat exchanger with a pipe for feeding the digester liquor, and with automatic temperature and pressure control devices.
  • heat exchanger preferably a shell tube heat exchanger is used which withstands operation pressures up to 100 atm., or heat exchangers with laminar plates or of helical construction withstanding operation pressures pressures between 15 and 50 atm.
  • a desilicated digester liquor for most effective heat exchange it is advantageous to have on the one hand a desilicated digester liquor and on the other hand solids of small particle sizes in the digester liquor.
  • the diameter of the particles is between of about 1 to about 45 microns.
  • the dilute liquor to be evaporated is transported by means of piston or centrifugal pumps capable of producing over-pressures of 5 to 60 atm. into the heat exchanger, while at the opposite side of the heat exchanger the pressure of the digester liquor may be used for transporting it.
  • the digester liquor slurry leaving the digesters 17 and 18 at a temperature above 150C and under pressure is led through one of the chambers la, 2a and 3a of the series connected heat exchangers 1, 2 and 3, while in the other chambers 11), 2b and 3b of the series connected heat exchangers dilute liquor flows in countercurrent.
  • the dilute liquor originates from tank 6 which is designed to store the decomposed dilute liquor and is transported by means of pump 5 into the heat exchanger series.
  • the series connected heat exchangers 1, 2 and 3 part of the heat content of the digester liquor slurry is transmitted to the dilute liquor preferably in such a way that the temperature difference between the dilute liquor leaving from the series connected heat exchangers and the introduced digester liquor slurry should be less than 10C.
  • the desired temperature difference can be adjusted by means of a temperature regulator 7, and a pneumatic valve 8.
  • Automatically controlled pressure regulators 19 and 20 serve to ensure the heat transfer.
  • the dilute liquor which leaves the heat exchangers at a temperature higher than its boiling point and under pressure is led through flash vessels 9, 10 and 11 in which it is stepwise expanded and finally through pipe 12 into a holding tank, for the concentrated liquor which is kept under atmospheric pressure for use in the treatment of bauxite.
  • the caustic is mixed with the bauxite and the resulting slurry 13 is introduced through preheaters 14-16 into the digesters.
  • the digester liquor slurry which leaves the part 3a of the heat exchanger 3 and has been cooled to below its boiling point is led through pipe 4 into a dilution tank (not shown) which is also under atmospheric pressure.
  • the red mud is separated from the slurry, the aluminate is precipitated and separated by filtration and the canstic liquid is introduced into the tank 6.
  • the overheated vapors which leave the flash vessels 9, l0 and 11 are led as heating steam into preheaters 16, 15 and 14, respectively, of the initial liquor.
  • the starting bauxite slurry arriving through pipe 13 is heated in these preheaters.
  • Example 2 is intended as a comparison with the known process.
  • Example 1 3.1 metric ton of moist bauxite per metric ton of alumina is mixed with 12 or digesting liquor per metric ton of alumina, said digesting liquor having a concentration of 180 g/l of kxNa O. in this way the quantity of the liquor increases after mixing to 12.57 m per metric ton of alumina, while its concentration drops to 172 g/l of kxNa O.
  • This starting mixture is treated in a digester at a temperature of 240C and under pressure of 40 to 60 atm.
  • the digester liquor obtained in this way is led into a surface heat exchanger in which the liquor is cooled without flashing in.
  • the digester liquor is diluted to g/l of kxNa O concentration by means of the red mud liquor.
  • the quantity of wash water used for dilution is 3.4 m per metric ton of alumina.
  • the smaller quantity of wash water which can be used for the washing of the red mud may raise in this case the loss of caustic which can be washed out from the red mud, therefore at the end of the settling-washing line the mud is filtered to compensate for the caustic losses.
  • the concentration of the spent liquor obtained after decomposition increases as a result of the removal of the hydrate crystal water to g/l of kxNa O, whereby in the dilute liquor flash equipment of the digester plant by means of flashing of 3.4 m of dilute liquor per metric ton of alumina a digester liquor with a kxNa O concentration of 180 g/] is obtained.
  • the method according to the present invention eliminates the application of a separate liquor evaporator unit.
  • Example 2 3.1 metric ton of bauxite per metric ton of alumina is digested with 12 m digesting liquor of a kxNa O con centration of 180 g/l. After mixing of the bauxite with the digesting liquor the quantity of the liquor is increased by the moisture content of the bauxite to 12.57 m per metric ton of alumina, while at the same time the concentration of the liquor drops to 172 g/l of kxNa O. The starting mixture is heated in the digester to 240C under a pressure of 40 to 60 atm. Under these conditions the alumina content of the bauxite dissolves in the liquor.
  • the digester liquor under pressure is led through a flash line having 10 stages where it is ex panded to atmospheric pressure and the flashed steam is used for heating the liquor prepared for digestion.
  • the digester liquor which has been cooled in this way to 107C is led then into the dilution tank.
  • the digester liquor is concentrated in this way to 236 g/l of kxNa O.
  • the degree of water removal amounts to 3.4 m per metric ton of alumina, the volume is reduced to 9.17 m per metric ton of alumina. 1n the course of dilution the digester liquor is diluted with red mud water to 140 g/l of kxNa O, but is concentrated during decomposition to g/l of kxNa O.
  • the water requirement of dilution amounts to 6.3 m per ton of alumina.
  • a quantity of water of 2.90 m per metric ton of alumina is evaporated in the liquor evaporator whereby a digestion liquor of a concentration of 180 g/l of kJcNa O is obtained.
  • the water removal of 6.3 2.9 3.4 in per metric ton of alumina required for the water balance of the cycle is ensured by the flashing of the digester liquor.
  • aluminacontaining minerals wherein the aluminum content of the mineral is extracted in a reaction zone with a caustic solvent under elevated temperature to form a hot liquid slurry
  • the improvement which comprises transferring heat without expansion in an indirect heat exchanger from the hot liquid slurry after it leaves the reaction zone in countercurrent to a dilute caustic liquor, and concentrating the thus heated dilute caustic liquor by flashing, wherein said dilute liquor is obtained by separating the solids content and precipitating at least a major portion of the dissolved aluminum content of said liquid slurry after it leaves the heat exchanger.
US00059954A 1969-08-05 1970-07-31 Treatment of aluminate digester liquor Expired - Lifetime US3738411A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
AT752169A AT291197B (de) 1969-08-05 1969-08-05 Verfahren zur Verarbeitung der Autoklavenlauge, die bei dem kontinuierlichen Aufschluß von Aluminiumoxyd enthaltenden Mineralien, besonders von Bauxit, mit Natriumaluminatlauge erhalten wird

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US3738411A true US3738411A (en) 1973-06-12

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US (1) US3738411A (de)
AT (1) AT291197B (de)
AU (1) AU458474B2 (de)
DE (1) DE2038706C3 (de)
FR (1) FR2056990B1 (de)
HU (1) HU163357B (de)
RO (1) RO55560A (de)
SE (1) SE360638B (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4112047A (en) * 1977-06-08 1978-09-05 Kaiser Aluminum & Chemical Corporation Pretreatment system for goethitic bauxites
US4441958A (en) * 1981-01-27 1984-04-10 Giampaolo Teucci Forced-circulation evaporator plant
US5027891A (en) * 1988-03-30 1991-07-02 Alcan International Limited Method for transferring heat between process liquor streams
US6555076B1 (en) * 1998-10-01 2003-04-29 Gea Kestner Bauxite ore digestion in the bayer process
US7214290B2 (en) 2002-09-04 2007-05-08 Shaw Liquid Solutions Llc. Treatment of spent caustic refinery effluents
US20100120095A1 (en) * 2006-12-18 2010-05-13 Stroiazzo-Mougin Bernard A J Electromagnetic bioaccelerator

Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2459302A (en) * 1942-12-10 1949-01-18 American Viscose Corp Concentration of salts having minimum solubilities at temperatures above those of the initial solutions
DE851900C (de) * 1949-06-28 1952-10-09 Konrad Mattern Verfahren zum Eindampfen von Sulfit-Ablaugen oder sonstigen gipshaltigen Loesungen
US2806766A (en) * 1952-11-28 1957-09-17 Kaiser Aluminium Chem Corp Process of purifying caustic aluminate liquors
US2824058A (en) * 1953-12-14 1958-02-18 Sterling Drug Inc Method for the continuous self-sustaining flameless oxidation of combustible materials
US2852343A (en) * 1954-09-30 1958-09-16 Kaiser Aluminium Chem Corp Process for treating aluminous ores
US3332470A (en) * 1966-01-25 1967-07-25 Chicago Bridge & Iron Co Method for concentrating solutions
CA780291A (en) * 1968-03-12 J. Tusche Klaus Method and apparatus for the continuous extraction of bauxite
US3497317A (en) * 1964-12-22 1970-02-24 Vaw Ver Aluminium Werke Ag Method for continuous extraction of bauxite in a tubular reactor

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA780291A (en) * 1968-03-12 J. Tusche Klaus Method and apparatus for the continuous extraction of bauxite
US2459302A (en) * 1942-12-10 1949-01-18 American Viscose Corp Concentration of salts having minimum solubilities at temperatures above those of the initial solutions
DE851900C (de) * 1949-06-28 1952-10-09 Konrad Mattern Verfahren zum Eindampfen von Sulfit-Ablaugen oder sonstigen gipshaltigen Loesungen
US2806766A (en) * 1952-11-28 1957-09-17 Kaiser Aluminium Chem Corp Process of purifying caustic aluminate liquors
US2824058A (en) * 1953-12-14 1958-02-18 Sterling Drug Inc Method for the continuous self-sustaining flameless oxidation of combustible materials
US2852343A (en) * 1954-09-30 1958-09-16 Kaiser Aluminium Chem Corp Process for treating aluminous ores
US3497317A (en) * 1964-12-22 1970-02-24 Vaw Ver Aluminium Werke Ag Method for continuous extraction of bauxite in a tubular reactor
US3332470A (en) * 1966-01-25 1967-07-25 Chicago Bridge & Iron Co Method for concentrating solutions

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4112047A (en) * 1977-06-08 1978-09-05 Kaiser Aluminum & Chemical Corporation Pretreatment system for goethitic bauxites
US4441958A (en) * 1981-01-27 1984-04-10 Giampaolo Teucci Forced-circulation evaporator plant
US5027891A (en) * 1988-03-30 1991-07-02 Alcan International Limited Method for transferring heat between process liquor streams
US6555076B1 (en) * 1998-10-01 2003-04-29 Gea Kestner Bauxite ore digestion in the bayer process
US7214290B2 (en) 2002-09-04 2007-05-08 Shaw Liquid Solutions Llc. Treatment of spent caustic refinery effluents
US20070251650A1 (en) * 2002-09-04 2007-11-01 Duesel Bernard F Jr Treatment of spent caustic refinery effluents
US20100120095A1 (en) * 2006-12-18 2010-05-13 Stroiazzo-Mougin Bernard A J Electromagnetic bioaccelerator
US8969074B2 (en) * 2006-12-18 2015-03-03 Bio Fuel Systems, S.L. Electromagnetic bioaccelerator

Also Published As

Publication number Publication date
SE360638B (de) 1973-10-01
FR2056990B1 (de) 1975-01-10
HU163357B (de) 1973-07-28
DE2038706A1 (de) 1971-02-18
DE2038706B2 (de) 1973-05-30
FR2056990A1 (de) 1971-05-07
RO55560A (de) 1973-09-20
AU1827770A (en) 1972-02-03
AU458474B2 (en) 1975-02-13
DE2038706C3 (de) 1979-01-25
AT291197B (de) 1971-07-12

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