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WO1988007975A1 - Process for reducing the impurities in lyes in the bayer process - Google Patents

Process for reducing the impurities in lyes in the bayer process Download PDF

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Publication number
WO1988007975A1
WO1988007975A1 PCT/CH1988/000076 CH8800076W WO8807975A1 WO 1988007975 A1 WO1988007975 A1 WO 1988007975A1 CH 8800076 W CH8800076 W CH 8800076W WO 8807975 A1 WO8807975 A1 WO 8807975A1
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WO
WIPO (PCT)
Prior art keywords
alkali
membrane
anion
electrodialysis
bayer process
Prior art date
Application number
PCT/CH1988/000076
Other languages
German (de)
French (fr)
Inventor
Gregory P. Brown
Otto Tschamper
Original Assignee
Schweizerische Aluminium Ag
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Filing date
Publication date
Application filed by Schweizerische Aluminium Ag filed Critical Schweizerische Aluminium Ag
Priority to BR888806904A priority Critical patent/BR8806904A/en
Publication of WO1988007975A1 publication Critical patent/WO1988007975A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
    • B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
    • B01D61/44—Ion-selective electrodialysis
    • B01D61/445—Ion-selective electrodialysis with bipolar membranes; Water splitting
    • 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
    • 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

  • the invention relates to a process for reducing the dissolved inorganic and organic impurities in aqueous alkalis in the Bayer process for the production of aluminum hydroxide.
  • the raw materials used in the Bayer process essentially bauxite and caustic soda, contain organic and inorganic undesirable substances which are introduced into the Bayer process in particular during the dissolution of the bauxite and subsequently in a variety of ways affect this adversely.
  • the substances are acidic compounds such as Chlorides, phosphates, sulfates, vanadates, fluorides and / or organic salts or acids, in particular oxalates and humic acids.
  • the impurities accumulate at various points up to critical values, provided they are not removed from the process.
  • Process-related as well as economic problems are associated with the impurities. Cumulatively enriched, since they are obtained in the form of sodium salts, they lead to a reduction in the causticity and the proportion of free lye, which has the consequence that the lye productivity and thus the process economy decrease.
  • the process control is hindered by deposits of the undesirable substances on tanks, pipes, heat exchangers and other devices, so that cleaning steps have to be carried out in order to restore the intended production output. Under certain circumstances, the cleaning steps can be quite complex, for example by rinsing acid must be carried out when the deposits reach layer thicknesses that can only be removed inadequately by mechanical means or the deposits are in inadequate places.
  • the process economy is further reduced by the impurities in that they increase the alkali viscosity and thus the pump costs increase.
  • the settling process of the hydroxide and its separation is negatively influenced.
  • the inventors have therefore set themselves the task of presenting a process which is suitable for economically reducing the inorganic and organic dissolved impurities in aqueous alkalis in the Bayer process for the production of aluminum hydroxide and their concentrations in such a manner to keep low limits that they have practically no influence on the Bayer process.
  • the object is achieved by a process in which the lye of an electrodialysis using at least one anion-selective and / or at least one cation-permeable membrane and at least one bipolar, water-dissociating membrane to form an alkali lye component, which is the Circulation liquor of the Bayer process is added and subjected to an impurity component which is removed from the process and discarded.
  • the contamination level nente essentially contains the anionic acid residues of the contaminants from the contaminated alkali.
  • the invention is based on the use of a bipolar membrane in the electrodialysis of the alkali metal hydroxide solution from the Bayer process.
  • the generally written reaction takes place
  • MX + H2O HX + MOH, where M is alkali and X is the acid residue.
  • the salt thus forms as impurity and water, which is dissociated by the bipolar electrode.
  • Alkali alkali and the corresponding acid, by the in the corresponding Ze . II areas react by the selective membranes enriched cations or anions with the dissociation products of the water. For example, the following reactions can take place individually or simultaneously:
  • FIG. 1 the division of a contaminated lye stream in a cleaned caustic solution and a stream with impurities
  • FIGS. 2 to 6 different arrangements of electrodialysis cells
  • FIG. 7 the use of the electrodialysis cell (s) in the Bayer process cycle.
  • the alkali lye stream P v loaded with impurities and originating from the Bayer process is electrodialysis using at least one anion and / or at least one cation permeable membrane and at least one bipolar membrane to dissociate the water qualified membrane subjected.
  • a lye stream P r which is depleted of impurities and a separate current V which contains the impurities are obtained.
  • FIGS. 2 to 6 show examples of possible arrangements of electrodialysis units according to the invention. Furthermore, arrows indicate by way of example and schematically in which cell areas the contaminated alkali hydroxide solution P v can be introduced and from which cell areas corresponding reaction products P r , V can be taken or where the / the current (s) of the cleaned ones Alkali P r and the current (s) of the impurities V occur.
  • FIG. 7 shows in a highly simplified version the circulation of the lye in the Bayer process and the use of electrodialysis E-
  • electrodialysis can also be used in other places of the circulatory process.
  • the aforementioned locations are particularly preferred, since the necessary equipment can be installed at these points without significant operational changes and, on the other hand, the lye to be cleaned is diluted, which benefits the life of the membranes.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Geology (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Inorganic Chemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Water Supply & Treatment (AREA)
  • Urology & Nephrology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Separation Using Semi-Permeable Membranes (AREA)
  • Water Treatment By Electricity Or Magnetism (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Abstract

In processes for reducing the dissolved inorganic and organic impurities in aqueous lyes in the Bayer process for the manufacture of aluminium hydroxide, the additives used entail cost-intensive process controls and increased lye consumption, thereby raising production costs without necessarily ensuring product quality. These drawbacks may be eliminated by subjecting the impure lye Pv to electrodialysis using at least one anion-permeable membrane and/or one cation-permeable membrane and at least one bipolar water-dissociating membrane with formation of an alkaline lye component Pr which is added to the circulating lye in the Bayer process, and an impurity component V which is removed from the process and discarded.

Description

Verfahren zur Verringerunq von Verunreinigungen in Laugen beim Bayer-Prozess Process for reducing contaminants in alkalis during the Bayer process
Die Erfindung betrifft ein Verfahren zur Verringerung der gelösten anorganischen und organischen Verunreinigungen in wässrigen Laugen beim Bayer-Prozess zur Herstellung von Aluminiumhydroxid.The invention relates to a process for reducing the dissolved inorganic and organic impurities in aqueous alkalis in the Bayer process for the production of aluminum hydroxide.
Die beim Bayer-Prozess verwendeten Rohstoffe, im wesentli¬ chen Bauxit und Natronlauge, enthalten organische und anor¬ ganische unerwünschte Substanzen, welche insbesondere wäh¬ rend der Auflösung des Bauxits in den Bayer-Prozess einge- führt werden und in der Folge in vielfältiger Weise diesen nachteilig beeinflussen. Die Substanzen sind saure Verbin¬ dungen wie z.B. Chloride, Phosphate, Sulfate, Vanadate, Fluoride und/oder organische Salze oder Säuren, insbeson¬ dere Oxalate und Huminsäuren.The raw materials used in the Bayer process, essentially bauxite and caustic soda, contain organic and inorganic undesirable substances which are introduced into the Bayer process in particular during the dissolution of the bauxite and subsequently in a variety of ways affect this adversely. The substances are acidic compounds such as Chlorides, phosphates, sulfates, vanadates, fluorides and / or organic salts or acids, in particular oxalates and humic acids.
Da die Alkalilauge im Bayer-Prozess in verschiedenen Stufen auf verschieden hohen Konzentrationen im Kreislauf geführt wird, reichern sich die Verunreinigungen an verschiedenen Stellen bis zu kritischen Werten an, sofern sie nicht aus dem Prozess genommen werden. Mit den Verunreinigungen sind verfahrenstechnische als auch wirtschaftliche Probleme ver¬ bunden. Kumulativ angereichert führen sie, da sie in Form von Natriumsalzen anfallen, zu einer Reduktion der Kausti- zität und des Anteils an freier Lauge, was zur Folge hat, dass die Laugenproduktivität und damit die Prozesswirt¬ schaftlichkeit sinkt. Ferner wird die Prozessführung durch Ablagerungen der unerwünschten Stoffe an Tanks, Rohren, Wärmetauschern und sonstigen Einrichtungen behindert, so dass Reinigungsschritte durchgeführt werden müssen, um die vorgesehene Produktionsleistung wieder herzustellen. Unter Umständen können die Reinigungsschritte recht aufwendig sein, z.B. indem Säurespülungen durchge- führt werden müssen, wenn die Ablagerungen Schichtdicken erreichen, die mit mechanischen Mitteln nur unzulänglich entfernt werden können oder die Ablagerungen sich an unzu¬ länglichen Orten befinden.Since the alkali hydroxide solution is circulated at different levels in the Bayer process at different levels, the impurities accumulate at various points up to critical values, provided they are not removed from the process. Process-related as well as economic problems are associated with the impurities. Cumulatively enriched, since they are obtained in the form of sodium salts, they lead to a reduction in the causticity and the proportion of free lye, which has the consequence that the lye productivity and thus the process economy decrease. Furthermore, the process control is hindered by deposits of the undesirable substances on tanks, pipes, heat exchangers and other devices, so that cleaning steps have to be carried out in order to restore the intended production output. Under certain circumstances, the cleaning steps can be quite complex, for example by rinsing acid must be carried out when the deposits reach layer thicknesses that can only be removed inadequately by mechanical means or the deposits are in inadequate places.
Die Prozesswirtschaffclichkeit wird ferner durch die Verun¬ reinigungen dadurch reduziert, dass diese die Laugenvisko¬ sität erhöhen und damit die Pumpkosten steigen. Zusätzlich wird der Absetzvorgang des Hydroxids und dessen Abtrennung negativ beeinflusst.The process economy is further reduced by the impurities in that they increase the alkali viscosity and thus the pump costs increase. In addition, the settling process of the hydroxide and its separation is negatively influenced.
Neben den oben genannten, allen Verunreinigungen gemeinsam anzulastenden Nachteilen gibt es noch eine Vielzahl weite¬ rer Nachteile, die einzelnen Verunreinigungen zugewiesen werden. So färben die organischen Verunreinigungen, meist in Form von langkettigen Huminsäuren oder deren Derivate bzw. Reaktionsprodukte, das Aluminiumhydroxid gräulich ein. Von besonderer Bedeutung ist das während der Zer¬ setzungsphase des Bauxits durch Lösen und Zersetzung von Humin- und anderen organischen Säuren gebildete Oxalat. Dies kann sich bis zur Uebersättigung anreichern und beim Ausscheiden die Prozesswirtschaftlichkeit negativ beein¬ flussen, indem es die Kristallisation des Aluminiumhydrats erschwert und zusätzlich nachteiligen Einfluss auf die physikalischen Eigenschaften der Kristallagglomerate aus¬ übt.In addition to the above-mentioned disadvantages to be attributed to all impurities together, there are also a number of further disadvantages which are assigned to individual impurities. The organic impurities, usually in the form of long-chain humic acids or their derivatives or reaction products, give the aluminum hydroxide a gray color. Of particular importance is the oxalate formed during the decomposition phase of the bauxite by dissolving and decomposing humic and other organic acids. This can accumulate to the point of supersaturation and adversely affect the process economy when excreted, by making the crystallization of the aluminum hydrate more difficult and additionally exerting an adverse influence on the physical properties of the crystal agglomerates.
Zur Veränderung kritischer Schwellenwerte der Verunreini¬ gungen und zur Kontrolle ihrer Konzentrationen in den im Kreislauf geführten Laugen sind eine Vielzahl von Verfahren bekannt. Nach der US-PS 4 335 082 werden die Prozesslaugen mit Natriumhypochlorit oder anderen Oxidationsmitteln be¬ handelt, um die organischen Stoffe zu zersetzen. In der DE-OS 2 415 872 wird die Zugabe von Kalziumverbindungen vorgeschlagen, um die Huminsäuren als unlösliche Kalzium¬ verbindungen zu fällen. In ähnlicher Weise werden nach den US-PS'en 4 046 855 und 4 101 629 Fällungsreaktionen mit Magnesium- bzw. Bariumverbindungen vorgeschlagen. Die letztgenannten Verfahren können auch zur Oxalatentfernung eingesetzt werden, da die Lauge destabilisiert ist, wenn die Huminstoffe entfernt sind und dadurch das Oxalat als Natriumoxalat ausfällt. Zur Oxalatentfernung wurde ferner nach der US-PS 3 649 185 eine Erhöhung der Laugenkonzentra¬ tion durch weiteren Zusatz von kaustischer Soda vorgeschla¬ gen, wodurch das Oxalat ausfällt. In analoger Weise können auch die anorganischen Verunreinigungen ausgesalzt werden. Die Aussalzung durch Verdampfungskristallisation wurde ebenfalls früher angewendet und hat heute nur noch histori¬ sche Bedeutung.A large number of methods are known for changing critical threshold values of the impurities and for checking their concentrations in the circulating lyes. According to US Pat. No. 4,335,082, the process liquors are treated with sodium hypochlorite or other oxidizing agents in order to decompose the organic substances. DE-OS 2 415 872 proposes the addition of calcium compounds in order to precipitate the humic acids as insoluble calcium compounds. Similarly, according to US Pat. Nos. 4,046,855 and 4,101,629, precipitation reactions are also carried out Magnesium or barium compounds proposed. The latter methods can also be used for oxalate removal, since the alkali is destabilized when the humic substances have been removed and the oxalate thus precipitates out as sodium oxalate. According to US Pat. No. 3,649,185, an increase in the alkali concentration by further addition of caustic soda was also proposed for the oxalate removal, as a result of which the oxalate precipitates. The inorganic impurities can also be salted out in an analogous manner. Salting out by evaporation crystallization was also used earlier and is only of historical importance today.
Die vorgeschlagenen Verfahren sind relativ aufwendig in der Verfahrensführung, verwenden teure Zusätze oder machen ein¬ en erhöhten Laugenverbrauch notwendig, was in jedem Fall die Produktionskosten in die Höhe treibt und nicht in jedem Fall eine gute Produktqualität gewährleistet.The proposed processes are relatively complex to carry out, use expensive additives or require an increased amount of alkali, which in any case drives up the production costs and does not guarantee good product quality in every case.
Die Erfinder haben sich daher die Aufgabe gestellt, ein Verfahren vorzulegen, welches geeignet ist, die anorgani¬ schen und organischen gelösten Verunreinigungen in wässri- gen Laugen beim Bayer-Prozess zur Herstellung von Alumi¬ niumhydroxid in wirtschaftlicher Weise zu verringern und deren Konzentrationen in derart geringen Grenzen zu halten, dass sie praktisch ohne Einfluss auf den Bayer-Prozess sind.The inventors have therefore set themselves the task of presenting a process which is suitable for economically reducing the inorganic and organic dissolved impurities in aqueous alkalis in the Bayer process for the production of aluminum hydroxide and their concentrations in such a manner to keep low limits that they have practically no influence on the Bayer process.
Erfindungsgemäss wird die gestellte Aufgabe durch ein Ver- fahren gelöst, bei dem die Lauge einer Elektrodialyse unter Verwendung von mindestens einer anionen- und/oder minde¬ stens einer kationenpermselektiven Membran und mindestens einer bipolaren, das Wasser dissozierenden Membran unter Bildung einer Alkalilaugenkomponente, welche der Kreislauf- lauge des Bayer-Prozesses zugeschlagen wird, und einer Ver¬ unreinigungskomponente, welche aus dem Prozess entfernt und verworfen wird, unterworfen wird. Die Verunreinigungsko po- nente enthält im wesentlichen die anionischen Säurereste der Verunreinigungen aus der verunreinigten Lauge.According to the invention, the object is achieved by a process in which the lye of an electrodialysis using at least one anion-selective and / or at least one cation-permeable membrane and at least one bipolar, water-dissociating membrane to form an alkali lye component, which is the Circulation liquor of the Bayer process is added and subjected to an impurity component which is removed from the process and discarded. The contamination level nente essentially contains the anionic acid residues of the contaminants from the contaminated alkali.
Vorteilhafte Weiterbildungen des erfindungsgemässen Verfah- rens sind durch die Merkmale der Ansprüche 2 bis 8 gekenn¬ zeichnet.Advantageous developments of the method according to the invention are characterized by the features of claims 2 to 8.
Die Erfindung basiert auf die Anwendung einer bipolaren Membran bei der Elektrodialyse der Alkalilauge aus dem Bayer-Prozess. Es spielt sich dabei die allgemein geschrie¬ bene ReaktionThe invention is based on the use of a bipolar membrane in the electrodialysis of the alkali metal hydroxide solution from the Bayer process. The generally written reaction takes place
MX + H2O = HX + MOH ab, wobei M Alkali und X der Säurerest bedeuten. Somit bil¬ det sich aus dem Salz als Verunreinigung und Wasser, wel- ches durch die bipolare Elektrode dissoziert wird. Alkali¬ lauge und die entsprechende Säure, indem die in den ent¬ sprechenden Ze.llbereichen durch die selektiven Membranen angereicherten Kationen bzw. Anionen mit den Dissoziations¬ produkten des Wassers reagieren. Z.B. können folgende Reak- tionen einzeln oder gleichzeitig ablaufen:MX + H2O = HX + MOH, where M is alkali and X is the acid residue. The salt thus forms as impurity and water, which is dissociated by the bipolar electrode. Alkali alkali and the corresponding acid, by the in the corresponding Ze . II areas react by the selective membranes enriched cations or anions with the dissociation products of the water. For example, the following reactions can take place individually or simultaneously:
Figure imgf000006_0001
Na2c2°4 +2H2O =2NaOH + H2C2O4 NaCl + H2O ' = NaOH + HC1 a2S04 + 2H2O = 2NaOH + H2SO
Figure imgf000006_0001
Na 2 c 2 ° 4 + 2H2O = 2NaOH + H2C2O4 NaCl + H2O ' = NaOH + HC1 a2S04 + 2H2O = 2NaOH + H2SO
NaF + H2O = NaOH + HFNaF + H2O = NaOH + HF
Die Anwendung des erfindungsgemässen Verfahrens ist insbe¬ sondere dann von Vorteil, wenn aus den Verunreinigungen gasförmige Reaktionsprodukte entstehen, die sich selbsttä¬ tig aus dem weiteren Bayer-Prozess entfernen. Dies ist im besonderen Masse bei der obigen ersten Gleichung der Fall. Weitere Merkmale und Einzelheiten der Erfindung ergeben sich aus der Zeichnung. Diese zeigt schematisch inThe use of the method according to the invention is particularly advantageous when gaseous reaction products are formed from the impurities and are automatically removed from the further Bayer process. This is particularly the case with the first equation above. Further features and details of the invention emerge from the drawing. This shows schematically in
Fig. 1 die Aufteilung eines verunreinigten Laugenstroms in einen gereinigten Laugenstorm und einen Strom mit Verunreinigungen, Figuren 2 bis 6 verschiedene Anordnungen von Elektrodialy- sezellen und Fig. 7 den Einsatz der Elektrodialysezelle(n) im Bayer- Prozesskreislauf.Fig. 1 the division of a contaminated lye stream in a cleaned caustic solution and a stream with impurities, FIGS. 2 to 6 different arrangements of electrodialysis cells and FIG. 7 the use of the electrodialysis cell (s) in the Bayer process cycle.
Gemäss Fig. 1 wird der mit Verunreinigungen beladene, aus dem Bayer-Prozess stammende Alkalilaugenstrom Pv einer Elektrodialyse unter Verwendung vom mindestens einer Anio- nen- und/oder mindestens einer kationenpermselektiven Mem¬ bran und mindestens einer bipolaren, das Wasser zu disso- zieren befähigte Membran unterworfen. Nach der Elektrodia- lysezelle E erhält man einen an Verunreinigungen verarmten Laugenstrom Pr und einen separaten Strom V, der die Verun¬ reinigungen enthält. Durch mehrmaliges Durchlaufen des Lau¬ genstroms Pr durch die Elektrolysezelle E bzw. bei Einwir¬ kung einer grδsseren Anzahl von Einheiten von in Reihe ge¬ schalteter Elektrolysezellen auf den Alkalilaugenstrom Pv ist es möglich, eine gereinigte Lauge Pr zu erhalten, deren Verunreinigungen keinen Einfluss mehr auf die nachfolgenden Verfahrensstufen des Bayer-Prozesses haben.1, the alkali lye stream P v loaded with impurities and originating from the Bayer process is electrodialysis using at least one anion and / or at least one cation permeable membrane and at least one bipolar membrane to dissociate the water qualified membrane subjected. After the electrodialysis cell E, a lye stream P r which is depleted of impurities and a separate current V which contains the impurities are obtained. By running the lye stream P r through the electrolysis cell E several times or when a larger number of units of electrolysis cells connected in series acts on the alkali lye stream P v , it is possible to obtain a purified lye P r , the impurities thereof no longer have any influence on the subsequent procedural stages of the Bayer process.
Die Figuren 2 bis 6 zeigen beispielhaft mögliche Anordnun- gen von Elektrodialyseeinheiten gemäss der Erfindung. Fer¬ ner ist mit Pfeilen beispielhaft und schematisch angedeu¬ tet, in welchen Zellbereichen die verunreinigte Alkalilauge Pv eingeführt werden kann und aus welchen Zellbereichen entsprechende Reaktionsprodukte Pr, V entnommen werden kδn- nen bzw. wo der/die Strom/Ströme der gereinigten Lauge Pr und der/die Strom/Ströme der Verunreinigungen V anfallen.FIGS. 2 to 6 show examples of possible arrangements of electrodialysis units according to the invention. Furthermore, arrows indicate by way of example and schematically in which cell areas the contaminated alkali hydroxide solution P v can be introduced and from which cell areas corresponding reaction products P r , V can be taken or where the / the current (s) of the cleaned ones Alkali P r and the current (s) of the impurities V occur.
Fig. 7 zeigt in stark vereinfachter Ausführung den Kreis¬ lauf der Lauge im Bayer-Prozess und den Einsatz der Elek- trodialyse E-| entweder nach der Rotschlammwaschung und/oder den Einsatz der Elektrodialyse E2 nach der Waschung des Impfstoffes. Selbstverständlich kann die Elektrodialyse auch an anderen Orten des Kreislaufprozesses eingesetzt werden. Es hat sich aber gezeigt, dass die vorgenannten Orte besonders bevorzugt sind, da die notwendigen Gerät¬ schaften ohne wesentliche betriebliche Veränderungen an diesen Stellen installiert werden können und andererseits die zu reinigende Lauge verdünnt vorliegt, was der Lebens¬ dauer der Membranen zugute kommt. FIG. 7 shows in a highly simplified version the circulation of the lye in the Bayer process and the use of electrodialysis E- | either after washing red mud and / or using electrodialysis E2 after washing the vaccine. Of course, electrodialysis can also be used in other places of the circulatory process. However, it has been shown that the aforementioned locations are particularly preferred, since the necessary equipment can be installed at these points without significant operational changes and, on the other hand, the lye to be cleaned is diluted, which benefits the life of the membranes.

Claims

Patentansprüche Claims
1. Verfahren zur Verringerung der gelösten anorganischen und organischen Verunreinigungen in wässrigen Laugen beim Bayer-Prozess zur Herstellung von Aluminiumhydro¬ xid,1. Process for reducing the dissolved inorganic and organic contaminants in aqueous alkalis in the Bayer process for the production of aluminum hydroxide,
dadurch gekennzeichnet,characterized,
dass die Lauge einer Elektrodialyse unter Verwendung von mindestens einer anionen- und/oder mindestens ka- tionenpermselektiven Membran und mindestens einer bipo¬ laren, das Wasser dissozierende Membran unter Bildung einer Alkalilaugenkomponente, welche der Kreislauflauge des Bayer-Prozesses zugeschlagen wird, und einer Verun¬ reinigungskomponente, welche aus dem Prozess entfernt und verworfen wird, unterworfen wird.that the alkali of an electrodialysis using at least one anion and / or at least cation permselective membrane and at least one bipolar, water dissociating membrane to form an alkali lye component, which is added to the circulation liquor of the Bayer process, and a contaminant cleaning component, which is removed from the process and discarded, is subjected.
2. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Elektrodialyse unter Verwendung mindestens zweier in Reihe geschalteter, aus entweder einer kationen- oder anionenpermselektiver Membran und einer bipolaren Membran bestehender Einheiten durchgeführt wird, wobei dem/den von einer ionenselektiven Membran und einer gleich wie diese geladenen Teilelektrode einer bipola¬ ren Elektrode gebildete(r) Zellbereich(en) die verun¬ reinigte Lauge zugeführt wird.2. The method according to claim 1, characterized in that the electrodialysis is carried out using at least two units connected in series, consisting of either a cation-selective or anion-permeable membrane and a bipolar membrane, the one or the same of an ion-selective membrane and one this charged partial electrode of a bipolar electrode-formed cell region (s) which the contaminated alkali is fed to.
3. Verfahren nach Anspruch 2, dadurch gekenneichnet, dass zusätzlich in dem/den aus Anode und/oder Kathode und jeweils benachbarte Membran gebildete(r) Zellbereich(en die verunreinigte Lauge zugeführt wird. 3. The method according to claim 2, characterized in that the contaminated alkali is additionally supplied in the cell region (s) formed from the anode and / or cathode and in each case adjacent membrane (s).
4. Verfahren nach Anspruch 2 oder 3, dadurch gekennzeich¬ net, dass die Elektrodialyse unter Verwendung minde¬ stens zweier in Reihe geschalteter aus einer anionen- permselektiver Membran und einer bipolaren Membran be¬ stehender Einheiten durchgeführt wird, wobei dem/den von einer anionenselektriven Membran und einer anioni¬ schen Teilelektrode einer bipolaren Elektrode gebilde¬ tetr) Zellbereich(en) die verunreinigte Lauge zugeführt wird.4. The method according to claim 2 or 3, characterized gekennzeich¬ net that the electrodialysis is carried out using at least two series-connected units consisting of an anion-permselective membrane and a bipolar membrane units, the one being carried out by an anion electrode Membrane and an anionic partial electrode of a bipolar electrode (formed) cell area (s) which are supplied with contaminated alkali.
5. Verfahren nach Anspruch 1, dadurch gekennzeichnet, dass die Lauge einer Elektrodialyse unter Verwendung einer aus einer der Anode benachbarten kationenpermselektiven und einer anionenpermselektiven Membran und einer dazwischen liegender bipolaren Elektrode bestehenden Einheit oder mehrere derartige Einheiten unterworfen wird, wobei den von der Anode und der Kathode und den benachbarten ionenpermselektiven Membranen gebildeten Zellbereichen und/oder dem/den von den Anionen- und kationenpermselektiven Membranen gebildeten Zellbe- reich(en) die verunreinigte Lauge zugeführt wird.5. The method according to claim 1, characterized in that the alkali is subjected to an electrodialysis using a unit consisting of one of the anode adjacent cation permselective and an anion permselective membrane and an intermediate bipolar electrode, or several such units, the anode and the The contaminated alkali is supplied to the cathode and the adjacent cell regions formed by the ion permeable membranes and / or the cell area (s) formed by the anion and cation permeable membranes.
6. Verfahren nach Anspruch 5, dadurch gekennzeichnet, dass zusätzlich zwischen der anionenpermselektiven Membran und der Kathode eine kationenpermselektive Membran eingefügt ist.6. The method according to claim 5, characterized in that a cation permeable membrane is additionally inserted between the anion permeable membrane and the cathode.
7. Verfahren nach einem der Ansprüche 1 bis 6, dadurch ge¬ kennzeichnet, dass die Verunreinigungen enthaltende Lauge mindestens teilweise die im Kreislauf des Bayer- Prozesses geführte, nach dem Waschen des Impfstoffs an¬ fallende Lauge ist. Verfahren nach einem der Anspüche 1 bis 7, dadurch ge¬ kennzeichnet, dass die Verunreinigungen enthaltende Lauge mindestens teilweise die im Kreislauf des Bayer- Prozesses geführte, nach dem Waschen des Rotschlamms anfallende Lauge ist. 7. The method according to any one of claims 1 to 6, characterized ge indicates that the alkali containing contaminants is at least partially the alkali which is carried in the cycle of the Bayer process and is obtained after washing the vaccine. Method according to one of Claims 1 to 7, characterized in that the alkali containing contaminants is at least partially the alkali which is circulated in the Bayer process and is obtained after washing the red mud.
PCT/CH1988/000076 1987-04-15 1988-04-11 Process for reducing the impurities in lyes in the bayer process WO1988007975A1 (en)

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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0310553A1 (en) * 1987-10-01 1989-04-05 Alusuisse-Lonza Services Ag Process for the reduction of lye impurities in the Bayer process
WO1990006167A1 (en) * 1988-12-01 1990-06-14 Allied-Signal Inc. Method for purification of bases from materials comprising base and salt
WO1990012637A3 (en) * 1989-03-15 1991-01-10 Pulp Paper Res Inst Electrodialytic water splitting process for the treatment of aqueous electrolytes
US5135626A (en) * 1988-12-01 1992-08-04 Allied-Signal Inc. Method for purification of bases from materials comprising base and salt
FR2729305A1 (en) * 1995-01-18 1996-07-19 Atochem Elf Sa REGENERATION OF STRONG ORGANIC ACIDS BY BIPOLAR MEMBRANES
EP0792896A3 (en) * 1996-02-10 1998-02-25 Hüls Aktiengesellschaft Process for separating lye from condensation resins
EP0834346A2 (en) * 1996-10-03 1998-04-08 Sachem, Inc. Process for purifying hydroxide compounds
EP0834345A2 (en) * 1996-10-03 1998-04-08 Sachem, Inc. Electrochemical process for purifying hydroxide compounds
WO2000034224A1 (en) * 1998-12-07 2000-06-15 Basf Aktiengesellschaft Methods for producing or purifying onium hydroxides by means of electrodialysis

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* Cited by examiner, † Cited by third party
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CN104016388B (en) * 2014-06-12 2016-03-30 合肥工业大学 A method for separating alkaline feed liquid in alumina production
CN110510714A (en) * 2019-08-26 2019-11-29 北京廷润膜技术开发股份有限公司 A kind of electrodialysis plant and the method using electrodialysis plant separation alkali and salt
CN113044863B (en) * 2021-04-25 2022-06-21 百色学院 A kind of method for improving the decomposition rate of seeds in alumina production

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4219396A (en) * 1979-08-03 1980-08-26 Allied Chemical Corporation Electrodialytic process
US4238305A (en) * 1979-10-29 1980-12-09 Allied Chemical Corporation Electrodialytic process for the conversion of impure soda values to sodium hydroxide and carbon dioxide
US4592817A (en) * 1984-12-03 1986-06-03 Allied Corporation Electrodialytic water splitting process for gaseous products

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4219396A (en) * 1979-08-03 1980-08-26 Allied Chemical Corporation Electrodialytic process
US4238305A (en) * 1979-10-29 1980-12-09 Allied Chemical Corporation Electrodialytic process for the conversion of impure soda values to sodium hydroxide and carbon dioxide
US4592817A (en) * 1984-12-03 1986-06-03 Allied Corporation Electrodialytic water splitting process for gaseous products

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0310553A1 (en) * 1987-10-01 1989-04-05 Alusuisse-Lonza Services Ag Process for the reduction of lye impurities in the Bayer process
WO1990006167A1 (en) * 1988-12-01 1990-06-14 Allied-Signal Inc. Method for purification of bases from materials comprising base and salt
US5135626A (en) * 1988-12-01 1992-08-04 Allied-Signal Inc. Method for purification of bases from materials comprising base and salt
AU632521B2 (en) * 1988-12-01 1993-01-07 Graver Water Systems, Inc. Method for purification of bases from materials comprising base and salt
WO1990012637A3 (en) * 1989-03-15 1991-01-10 Pulp Paper Res Inst Electrodialytic water splitting process for the treatment of aqueous electrolytes
US5993629A (en) * 1995-01-18 1999-11-30 Elf Atochem S.A. Regenerating of acids, particularly of strong organic acids, using bipolar membranes
WO1996022154A3 (en) * 1995-01-18 1996-10-10 Atochem Elf Sa Regenerating acids, particularly strong organic acids, using bipolar membranes
FR2729305A1 (en) * 1995-01-18 1996-07-19 Atochem Elf Sa REGENERATION OF STRONG ORGANIC ACIDS BY BIPOLAR MEMBRANES
EP0792896A3 (en) * 1996-02-10 1998-02-25 Hüls Aktiengesellschaft Process for separating lye from condensation resins
EP0834346A2 (en) * 1996-10-03 1998-04-08 Sachem, Inc. Process for purifying hydroxide compounds
EP0834345A2 (en) * 1996-10-03 1998-04-08 Sachem, Inc. Electrochemical process for purifying hydroxide compounds
EP0834346A3 (en) * 1996-10-03 1998-11-11 Sachem, Inc. Process for purifying hydroxide compounds
EP0834345A3 (en) * 1996-10-03 1998-11-11 Sachem, Inc. Electrochemical process for purifying hydroxide compounds
WO2000034224A1 (en) * 1998-12-07 2000-06-15 Basf Aktiengesellschaft Methods for producing or purifying onium hydroxides by means of electrodialysis
US6527932B1 (en) 1998-12-07 2003-03-04 Basf Aktiengesellschaft Methods for producing or purifying onium hydroxides by means of electrodialysis
CN100339355C (en) * 1998-12-07 2007-09-26 Basf公司 Method for producing or purifying onium hydroxides by means of electrodialysis

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AU1543388A (en) 1988-11-04
HUT52005A (en) 1990-06-28
AU610158B2 (en) 1991-05-16
EP0309509A1 (en) 1989-04-05
ES2006407A6 (en) 1989-04-16
BR8806904A (en) 1989-10-31
CN88102321A (en) 1988-11-02

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