DE2043986A1 - Process for the digestion of bauxites containing diaspore - Google Patents

Description

pROF.DR.DRJ.REITSTÖTTER

DR.-ING. W. BUNTE

DR. KG LÖSCH DS MUNICH 13, BAUERSTR. 22nd

PROCESS FOR DIGESTION OF BAlJXITEE CONTAINING DIASPORUS

The most important aluminum minerals found in the bauxites Hind: Ilydrargylüt, Böhmit and Diaapor. In In some bauxite species, only one aluminum can be found, in which most bauxites are found, but all three in less or larger amount.

Among the individual festivities of the Bayex process - the amount of aluminum in the alkaline solution a the bauxite, Hodann au «separating dea Al (Off) -j

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from the sodium aluminate liquor separated from the insoluble parts - only changes the decomposition operation to a substantial degree depending on whether it is the decomposition of hydrargyllite, content or diaspore.

Among the above aluminum mineral, it is hydrargyllite at the lowest temperatures löalieh. In the industrial In practice, the hydrargy content is generally at a temperature of 100 to 10 ^ ° C on gea chi on fi on. In practice, bohmite only works at temperatures above

above 160 C in solution; In the case of boehmite processing containing bauxites, the digestion generally takes place at temperatures above 200.degree.

The diaspora content of the bauxites is even heavier unlockable than the boehmite. In order to «dissolve the diasporfi to promote, the bauxite lye (sludge) lime is added; (3 to 5 # the bauxite weight), but aelbat in this case the digestion is carried out at a temperature above 220 ° C.

In industrial practice this is largely the last Years of trying to use higher digestion temperatures to be observed e.g. even those who do not become a Diaopor containing bauxites old boehmite content often at 240

ο
bia 250 open-minded.

Instead of the old discontinuous extraction process the continuous process is already widespread today. According to this method, the the digesting sodium aluminate liquor, from bauxite and Any pulp formed from lime is continuously fed into the first section of the several containers coupled one after the other (Autoclave) introduced existing digestion series. The added substance is continuously fed into the one after the other the switched container and finally leaves the digestion system. The aitfxiinchileßende is in the containers Cloudy on the consummation temperature mentioned, and.inn for the

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further operations cooled down. The amount of fed Turbidity is regulated accordingly that in the row of containers sufficient time for the digestion process to be carried out a should be available. '-

There will be pure warming instead of the individual limbs the tank series also uses heat exchangers that The so-called pipe flow systems are recently under development there are essentially only aii3 heat exchangers.

The processing of the diaspore-containing bauxites also takes place in such a continuous Aufuchluflay atoms. '

The method according to the invention offers one possibility Ability to digest the diaspore containing bauxites to produce more economical wines than before -

According to us ο purely ancestors are containing the diaspore Bauxite with a two-stage continuous Aul'-closing technology, opened up in a continuous digestion system consisting of »two sections, lin first section of the Auflasssyatein, the aiui several successively connected autoclaves and / or Warmeaun1.au shear is made up of the «digesting sodium hydroxide solution, from the diaspore containing kauxite and even ■ tuell made of lime slurry continuously fed. The turbidity is in the individual autoclaves (heat exchangers) warmed up, so their temperature increases in the successively connected autoclaves (heat exchangers) gradually to, finally reached the digestion temperature. The composition (the ratio of the catching Lye and bauxite) and the men ^ n of fed clay Turbidity should be regulated in such a way that in this first section of the digestion system the diaspora content of the bauxite.) in the autoclave operating at the digestion temperature (Heat exchangers) is unlocked. The first -.Section ', of the closure system leaving, so-called on

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closed turbidity becomes without cooling in the first, soy ;. "Mixer" unit of the, from successively connected autoclaves and / or heat exchangers existing second sections of the continuous consisting of ο two Ah-iohnitten Auischlußsy stems introduced.

In the same mixer unit, the one from unlocking Nat ri umal umi nat lye --- / As from Börmit, or Böhmit ur.i Hydrargyllite containing ·· ^ bauxite formed turbidity continuously fed in. The two TrM flows are mixed in the mixer unit, and the one created in this way

fc turbidity is continuously generated by the Units of the second section of the digestion system consisting of two sections, then from the last unit is fed into a cooling system where the Cloudy cools down for further operations. The composition (the ratio of bauxite and dor aufohließendou Sodium aluini η at lye) and the amount of in the mixer unit of the second section of the digestion system, Boehmite »or bauxite containing boehmite and hydrargyllite · NatriuraaluiTiinatlauge Turbidity is said to have been goregulated in such a way that that the boehmite or boehmite and hydrargyl jit content of the bauxite is unlocked, and that from the last unit of the second section one has already been opened ne slurry is passed for cooling.

In the first section of the two-sections digestion system which consists of the disintegrating sodium aluminate liquor from which diaspore bauxite and possibly containing lime slurry is heated to the containing the digestion of bauxite, diaspore usual temperature of 220 to 27O ⁰ C.

The boehmite or boehmite and hydrarg.yl are added to the mixer unit of the second section of the digestion system lit containing bauxite pulp on the digestion temperature of the first section warmed up, or boi lower? Temperature introduced. In the two-tone section, the AufMohluß-

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Ayatema increases the temperature of the pulp by heating it up the Aufechlufltemperabur the harvesting section a increased, or ea the temperature of the pulp is adjusted to a lower value by moderate heating, possibly without heating than the outflow temperature of the eraten Aoachnittea. Ea iat appropriate diö in the second section dea Continuous exploration system consisting of two sections fed in, boehmite, or boehmite and hydrargyllite containing bauxite slurry in a continuous autoclave and / or preheat heat exchange series.

The application of the procedure means in the case of a for example on twelve autoclaves and / or heat exchanger units existing, continuous Aufachlußreihe divided into two sections, that the first Digestion section consisting of nine autoclaves and / or heat exchanger units, the second section, on the other hand, consists of three autoclave and / or heat exchanger units. The ouch Diaapor-containing bauxite, from digesting sodium aluminate liquor and possibly turbidity formed from lime continuously into the first unit of the nine autoclaves and / or existing heat exchangers fed in. The turbidity flows from the first unit further into the 2 "3rd, ... 9th. Unit. In the 1st, 2nd,.,. 7th unit the pulp is heated and its temperature reaches the digestion temperature in the 7th unit. The 8th The 9th and 9th unit ensures that the dwell time of the pulp at the digestion temperature is extended, and thereby the diaspora content of the bauxite is digested »The 9th unit turns the digested pulp into the first unit of the second section of the exposure series, i.e. in the .10. Unit of the series forwarded. In the 10. In addition to the disrupted turbidity, there is also an Boehmite, or bauxite containing boehmite and hydrargyllite and turbidity formed from the disintegrating sodium aluminate liquor at the same temperature as the ixiifgeachlooaene TrU--

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be continuously incorporated.

The 10th unit has a special role, Oa in this daa mixing of the whitened turbidity with the boehmite, or Bb'hmit and Hydrargyilifc containing Bauxite sodium aluminum / sodium hydroxide cloudiness occurs. Auu the 10th, So-called mixer unit is formed from the two Ti'übeafcrömen Mixture continued continuously in the 11th and 12th unit.

In the 10th unit arrested in dJo, pu'f the same Temperature like the preheated pulp, Tribestrom containing bb'hmite or boehmite and hydrargyllite the breakdown begins already in the course of the prewar- " mena, the process continues in the 10th and 11th units and ends in the 12th unit, also the pulp which has already been digested is passed on to the cooling.

The expediency of applying the inventive two-stage open-up technology shows when the Löalichkeitaverhae dea Diaapor3 and Boehmita or hydrargyllite and accordingly the decomposition ratios used in the two decomposition sections are taken into account will.

In practice the. Alumina industry daa measure of the solubility of the individual ^{AluminiuBHBiDiex:} iilien expressed in the concept of so-called Laugenlö3ungen with llolVerhältnisses (oC).. This means the quotient of the mol number deo in the caustic and AlgO-ji in the sodium umiriatlauge

caustic well _? 0 moles

Al ₂ O ₃ number of moles

(Daa caustic Na ₃ O means the MaOIl content present in the free state and _{bound to Al 2} O ₃ , expressed in Na ,, 0.)

Then measure of the solubility of each mineraliaohon Phanen i'if; of the concentration and the temperature of the

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Sodium aluminate lye dependent. Comparing the solubility values of diaspore and boehmite in a sodium aluminate liquor of the same temperature and concentration, it is found that diaspore is much less soluble than boehmite, that is, diaspore can be digested at higher values of the alkali. _{For example, in industrial practice, about 242 g / ^ liter of Al 2} OJ are soluble in a sodium aluminate solution of 250 g / liter of caustic Na ₂ O concentration at 230 ° C. in the course of processing a diaspore containing bauxite, ie the molar ratio after digestion in the lye is about 1.7 »in the course of processing a boehmite-containing bauxite, on the other hand, in a lye of 250 g / liter caustic Na ₂ O concentration, at 230 ° about 274 g / liter Al ₂ OJ are soluble, ie the molar ratio after the digestion in this case is about 1.5 (at the digestion temperature of 230 ° C., the hydrargyllite can be regarded as identical to the boehailite from the standpoint of the degree of solubility).

We can say that the solution has the following composition: caustic Na ₂ O = 250 g / liter, Al ₂ O-, = about 242 g / liter («x = about 1.7), at 230 ⁰ C temperature from the industrial point of view Practice is saturated with regard to the diaspora, at the same time the practical saturation occurs for the boehmite phase only at Al ₃ OJ = about 274.0 g / liter (<*. = About I »5). (The theoretical saturation corresponds to a higher ΑΙρΟ -, - value and a lower ot value, but in industrial practice the3 cannot be achieved.)

It follows from the above that in the containment in the course of taking place at 230 ⁰ O temperature digestion of diaspore bauxite obtained sodium aluminate of 25O g / liter caustic NaPO concentration at the same temperature of 230 ⁰ C is still 274-242 = 32 g Al ₂ Dissolve O ₃ per liter when this _{amount of Al 2} 0-j is in the form of aine boehmite or boehmite and hydrargyllite phase containing bauxite in the sodium aluminate liquor saturated on Dl-aepor

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is introduced.

In the method according to the invention this is possible exploited the technological conditions dea er; Hon Sections of the two-section continuAnj. The borrowed Aufachlußreihe correspond to your Aufach] uß do.j Diaspora, and in the second section I also realize the conditions the digestion of boehmite.

In the sodium aluminate lye of 250 g / liter of caustic NagO concentrate clay, for example, about 103 g / liter of Al ₂ O ₃ are present before digestion; t («* .- value before digestion about 4). DIEA means that the digestion cycle about 242 during the ^ workup of containing bauxite Dia3por Oich while "- 103 = 139 g / liter Al ₃ O ₃ dissolve If this value with the second in the inventive portion resolvable Al ₀ Landmarks, value _V. on 32 g / liter in comparison

32 is set so it can be said that about γ ^ χ 100 -2'i dea from the dianpor containing bauxite digested AlpO-, can be brought into solution in the second section. If the AlgO ^ value (32 g / liter) which can be resolved in the second section is compared with the Al 1, Oγ value which can be resolved in both sections, the result is

X 100 = 18.7 #

A decisive factor in the economy of the digestion process is how much Al ₂ O ₃ can be dissolved in the unit volume of the sodium aluminate liquor during the digestion cycle.

In the process according to the invention, in comparison to the traditional one-step process, the steam consumption of the digestion processes and - although to a lesser extent - the capacity of the digestion system also increases as _{the amount of dissolvable Al 2} O _{3 increases.}

With our method there is thus a & wa 20 ^ -ige To achieve a reduction in steam consumption for the digestion and a substantial increase in the capacity of the

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Information series, if apart from the processing of the diaspore containing Bauxite also boehmite or boehmite and hydrargyllite containing bauxites are to be processed, and theeae the latter bauxites are available separately. Based on the above, it is therefore for the bauxites containing Dia3por Processing companies are also expressly advantageous Boehmite or boehmite and hydrargyllite containing bauxites to work up according to the method described, since in this Fall the digestion of boehmite or boehmite and hydrargyllite containing bauxites have significantly lower steam costs, as well as the specific costs the digestion device is lower.

In the mixer unit of the second section uneereo In the process, however, not only boehmite or bauxite containing boehmite and hydrargyllite can be introduced, besides these, the bauxite can also contain diaspore. in the second section, however, the diaspore is no longer open. close, 30 only the feed comes in the second section of bauxites with a low diaspora content in question, with the extremely favorable steam consumption of the two-stage Taking into account the digestion process, the disintegration losses caused by the diaspore can be disregarded can.

In industrial practice it happens that a bauxite is to be worked up which, among the aluminum minerals, mainly contains boehmite or boehmite and hydrargyllite, but in small amounts (1 to ^v fh Al ₃ O ^), also diaspore. Such bauxites are often processed according to the decomposition technology corresponding to boehmite. Z.J3 _e at 230 ⁰ C temperature, the digestion takes place with a digestion eye, which contains 2 ^ 0 to 3 27O g / liter of kauntinchea Na ₂ O and whose molar ratio ( oc) is 4, where the ratio of Lau-50 and of the bauxite in the zimohließenderi turbidity 30 is adjusted so that the molar ratio of the barrel, "after the digestion about 1.45 bin lsi? no «oll and that

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No lime becomes cloudy: added. With this digestion technology, the diaspora content of the bauxite; of course not open-minded and ended up in the Rotachlamm. In the case of bauxites with a low Dianρor content, the application of the AufschluBtechnnlogle used for boehmite can nevertheless be appropriate, since the triggering of the hydrargyllite and boehmifc content with significantly lower Daiipfconsumption and smaller autoclave capacity from ions i3t alπ if the triggering of the Dia3porehalts would have to be carried out. (If would also unlock the Diasporgehalt in the above example at 230 ° C temperature, ao should be set in such a way the ratio of the liquor and bauxite in the slurry aufzuschließenden that the Molverhält.nis after digestion about 1 7 to 1, 8 and lime would also have to be added to the sludge.)

If a bauxite-sodium aluminate liquor triibe with such a low diaspore content is also introduced into the first and second digestion section of the present two-stage digestion process, the economic advantage is that the digestion yield increases in relation to the one-stage technology carried out with boailite. In the first section of the digestion, as a result of the digestion conditions of the diaspora, the diaspora content of the bauxite is also unlocked by appropriate adjustment of the lye-bauxite ratio and possibly by adding lime. In the case of the bauxite introduced in the second section of the digestion _; Of course, only its hydrargyllite and boehmite content is digested. ;

Assuming that in the first section of the digestion ^: about 70 # of the processed grain is included, in this way a menu of about 70% of the amount of Diaapor with the Al ^ O ^ -content is reported Me at the ancestor's understanding aiii cheek.

The increase in the disclosure statistics fco was initiated by Hi 1Tο

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dea two-step process carried out in such a way that the steam requirement for the digestion remained the same as for the one-stage digestion technology, and only a low one Investment in new facility was necessary.

If the aweiten section a Hydrargyllit, or principally Hydrargyllit (small amounts of boehmite, possibly Diaapor) containing bauxite are available, so ea is expedient escaping from the first portion of the Aufschlußayatems, digested sludge from 220 to 27O ⁰ C in the mixer unit of the the second portion to direct de3 on "chiußaysteras after such a cooling carried out, that the temperature which is also fed, or Hydrargyllit hauptaächlicht Hydrargyllit containing bauxite - should amount of sodium aluminate liquor and pulp, the digested pulp after the Vermiachen 100 to 150 ⁰ C. In this way, the temperature range of the digestion of the hydrargyllite would be established in the second section, the digestion system consisting of two sections, and the hydrargyllite content of the bauxite fed into the mixer unit would be unlocked. The hydrargyllite dissolves in the temperature range between 100 and IJ) O ⁰ C iat, assured that its solubility in this temperature range is greater than the solubility of the diasporn in the temperature range between 220 and 270 ⁰ C.

In this case, according to the invention, in the first Section of the continuous flow system consisting of two sections, which consists of several autoclaves and / or heat exchangers connected in series, continuously one from the digesting sodium aluminate liquor, from bauxite containing diaapor and possibly au3 Lime formed turbidity fed in.

The turbidity is in the individual autoclaves (heat exchangers) heated and so their temperature increases in the successively connected autoclaves (heat exchangers) gradually until the reflux temperature is reached.

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The composition of the injected turbidity (Verbaltnia dor digesting lye and the bauxite), their amount should be regulated in such a way that in the first section dos Digestion aysteins in those operated at digestion temperature Autoclaves (heat exchangers) the diaspore content Bauxite is unlocked. The first section of the • Aufschlussaystema leaving, 3og. unlocked turbidity is cooled down and in the first, & og. Mixer unit of the • / wide section of the autoclave connected one after the other (Containers) existing continuous, two-stage digestion system. In the same mixer unit is a

fc from digesting sodium aluminate liquor and hydrargyllite or mainly: bauxite containing hydrargyllite The pulp formed is fed in continuously, possibly after it has been preheated. The the two streams of turbidity mixed, and that formed in this way Turbidity is continuously created by the successive units of the second section of the digestion 3yateina directed, then from the last unit - possibly after cooling down - directed to further operation.

The composition of the feed into the mixer unit of the second section of the digestion system, Hydrargyllite or mainly hydrargyllite-containing bauxite-sodium aluminate liquor pulp (ratio of bauxite

W and the disintegrating sodium aluminate lye) and its amount should be regulated in such a way that the hydrargyllite content of the bauxite is disrupted.

In the first section of the two-sections Aufachlußsyetems the AU3 containing diaspore bauxite, AU3 aufschlioßender sodium aluminate and possibly existing lime sludge is heated to the containing the digestion of bauxite, diaspore conventional temperature 220-270 ⁰ C.

The first section of the Aufchi ußsy st one opened pulp of 220 bio 270 ⁰ C temperature

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to be cooled to the extent that the temperature should be of from the disrupted in the mixer unit and formed from the bauxite slurry mixture 100 to 15O ⁰ C.

The individual parameters of the present two-stage digestion technology can be selected according to the properties and nature of the operation. 'May for example be changed, the amount ratio of the fed in the first and second portion of bauxite in the feed in the first and second portion of sludge, the ratio of bauxite and liquor "the concentration of the liquor, etc. mean This elasticity of technology over their application a very great advantage.

Furthermore, an example for the application of the method according to the invention is described. The enclosed ~ The figure below is the circuit diagram of this application, In which the heated autoclaves labeled 1 to 7 .., with the heat-holding autoclaves 8 and 9 »with the mixer autoclave 10 and with the heat-holding autoclaves 11 and 12 are connected in series. The heated autoclave row 13 to 16 is also switched on in the mixer autoclave 10. In the The pulp to be digested in the first stage enters the system through line 17, the pulp to be digested in the second stage Cloudy through line 18 and into the. both Slurry which has been broken down in stages leaves the system through line 19.

In the first unit 1 of the first section (autoclaves 1 to 9) of a ^{two-stage, continuous series of digestions, consisting of 12 pieces, provided with stirrers, connected in series and operated at 230 0} C, a continuous series of digestions is carried out every hour from 144.4 rs? Digestion liquor, 44.4 t of dlaspor-containing bauxite and 1.6 t of lime slurry were fed. Composition dos bauxite: 56.0 * Al-pO-j, 4.0 # SiO ₂ , 3, O # TiO ₂ , 22.0 # Oj, 1.016 CaOj aiülirückatarftisJT, ^} other substances:

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0.5 '/ »; adherent moisture: 10.0 $, 80 # de3 auslöfiba- ταη AljjO ^ -content was diaspore, 10 # boehmite and 1OJ & hydrargyl-

Composition of the digesting runet 275.0 g / liter Na ₂ O, 113.0 g / liter Al ₂ O ₃₁ molar ratio 4.0, active CaO content of the lime: 90 #. The pulp is heated indirectly with steam in the harvested autoclaves 1 to 7. 7 in the autoclave the temperature reaches 230 ⁰ C. during which the slurry through the autoclave 8 and 9 is passed, the digestion of the Hydrargyllit-, boehmite and Diaaporgehalt ends of Bauxite is triggered, the temperature of the slurry in the autoclave is 9 227 ° C .

From the autoclave 9, the turbidity stream (153/2 m "/ hour lye and 17.4 t / hour Rotachlamm, molar ratio of the lye phase 1.7) is passed into the autoclave 10, into which an amount of turbidity is continuously fed every hour 2 m ^ digesting lye and bauxite containing 7.9 t boehmite and which was previously heated to 220 ° C. by indirect steam heating in the row of autoclaves 13 to 16 connected in series with 4 stirrers. Composition of the bauxite: 52, 0 * Al ₂ O ₅ , 5.0% SiO ₂ , 3.0 # TiO ₂ , 23.0 * Fe ₃ O ₃ , 0.5 * CaO; <"'! Uh loss 16.0 * j other substances 0.5 *; adherent moisture 15.0 *. 90 * of the deployable Al ₃ O ₃ gel pouch is made from boehmite, 10 $ from flydrargyllite. Composition of the digesting liquor: 150.0 g / liter caustic Να ,, Ο, pi, 7 g / liter Al ₃ O ₃ , molar ratio 4.0.

The two streams of pulp are mined in the mixer autoclave and the temperature of the vegetable pulp is increased to 230 ° C by indirect steam heating. The sludge moves continuously through the autoclaves 11 and 12, in the meantime the AI ^ O .-- (! It is kept. The autoclave 12 leaves the autoclave 12 and Ii oh an au: -j 10 '), 6 - m " ³ sodium almninatlaiige and auo 24.3 f. Robiinhlamm bentohondor Trübentrowi of 227 ⁰ C Te: npo-

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temperature that is cooled down by expansion cooling for further operations. The concentration of the lye phase is as follows: 224 _t 0 g / liter caustic Na ₂ O * molar ratio 1.5. Amount of dissolved AIpO .: 28.3 t / hour,

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Claims (6)

- i6 - PATENTAL APPLICATIONS 1. Process for the digestion of diaspore-containing bauxites according to the Bayer process, using a two-stage, continuous technology, characterized in that the Aufachlußayatem is formed in two sections, with a slurry consisting of diaspore-containing bauxite and sodium aluminate liquor in the eraten section fed in wlYd, this is ^{warmed to a temperature exceeding 220 0} G, and the pulp is ensured a long residence time at this temperature, so that the diaspore content of the bauxite is increased. P is closed, then the opened Trübestroiar ", and so on first section is passed into the second section of the continuous digestion system, where this with a turbidity stream consisting of boehmite or boehmite and hydrargyllite containing bauxite and also sodium aluminate liquor is mixed and the pulp produced in this way is passed through the second section, where this is secured so much residence time that the boehmlt or boehmite and Hydrargyllite content of the bauxite fed into the second section is digested. 2. The method according to claim 1, characterized that in the first section of the continuous digestion system a diaspore containing ™ Bauxite, consisting of lime and sodium aluminate lye Is led cloudy. 3. The method according to claim 1 or 2, characterized in that the from aluminate liquor as well Turbidity stream consisting of boehmite or boehmite and hydrargyllite containing bauxite before the introduction into the second section is preheated ·. 4. The method according to claim 1 or 3, characterized in that the digestion systems in the second section the turbidity stream is warmed up 5.% ne variation of the method according to claim 1 1098U / 1902 2ÜA3986 or 2, characterized in that the the first section of the systeraa-demanding turbidity after cooling in the second section the opening system where the ae with a sodium aluminate liquor and consisting of bauxite mainly containing hydrargyllite Turbidity stream is mixed, the cooling being regulated in such a way that the temperature of the after The turbidity formed by mixing between 100 and 150 ° C should lie. 6. Procedure na £ h ^ Af * sprTlcbT ~ 5 »thereby g e k * e η η ζ e i ^> - tTet that the one made from sodium aluminate lye Hydrargyllite-containing bauxite existing turbidity flow prior to feeding into the second section is preheated. 7 _# . Process according to any one of the preceding claims, characterized in that the bauxite fed into the second section of the continuous digestion system also contains diaapor in addition to boehmite and / or hydrargyllite. 109814/1902 Blank page