Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
3~
PROC~SS FOR PRODUCI~G A~UMI~A AND ~ERRIC OLIDE
~ROM ALU~IU~ CARRIERS WI~ HIGH IRON A~D SILICO~
CONTE~T
q~he invention ~elate~ to a new proce~ for
producing alumina a~d ~erric o~ide from aluminium
carrier~ with high iron and si`1icon content~ More
p~rticularly~ the invention concerns a method ~or
producing alumi~a and ~erric oxide from aluminium .
carrler~ pre~erably ~rom low-grade bau~ite~ claye~
red mud, etc. in a purity~ which make~ ~urthsr
~anu~acturing w~thout addltional puri~icatio~ po~sibleO
- It is well known that high-quality bau~ite~
lO. raquired for the Bayer process are only restrictedl~
a~ailablo and their ~upply i~ decreasing year bg
year, On the other hand, alu~ini~m- and iron-contain-
ing waste ~atter~, e~g~ red mud9 colliary rock~9
coal a~h, etc~ are produced in an increasin.g amountD
~here l~ there~ore, a high demand ~or economlc
method~ by which aluminium and/or iron can be
racorered ~rom the~e and other low-grade carrier~9
e,g, low-~rad0 baux~te~, clay mineral~ and ~latee,D
~he:re are numerou~ methodZ3 known in the art
20 to rcco~er alumir~ium or iron ~rom low-grade carrîer~8
~ener~ aluminlum ie reoovered ~rom carrier~ having
~mall or reduced iro~ co~cen tratiorl, while for .re~
covering iron, carrier~ enriched iIl iron are
gerlerally employedO The phy~ic~1 method~ u~e~ r
25 the eeparation of di~ `e~ent type~ o:~ row m~teri.al~
A 2123~-75
~L76~301
- 2 -
e.g. washin~, flotation, separation by ~pecific
gravity9 etcO ~enerally cannot produce the re-
quired ~elective separatio~. Thi~ i9 a difficult
problem, ~ince for in~tance the additional puri~i-
cation o~ aluminium alloy~ produced from aluminiumcarrier~ with a hi~h iron and ~ilicon concentra-
tion i~ rather complicated and cannot be p.er~ormed
economically. Similarly~ the treatment of aluminium
carriers with a high ~ilicon content with sul~urou~
or sulfuric acid i~ not economic eitherO
~ he pyrolytic methods also provide rather
poor re~ults, when carried ou.t on low-grade aluminium
carriers. It has beeri a-ttempted -to subject aluminium~
containing raw materials to chemical deironization
by sulfuric acid, hydrochloric acid, ammonium salts
thereof or chlorine ga~. In this way, however, a
~ubstantial amoun~ o~ alumina i~ also dissolved,
the separation is difficul-t, and hence high los~es
in aluminium are re~ulted.
Since the energy demand of the electroly~i~
of` aluminium chloride i~ con~iderably less than
that of' the electroly~i~ of alumi~a, oe~eral method~
have been developed f`or the conver~i.on of` alumina
into aluminium chloride by chlorinat:ion and for the
production o~ aluminium f'rom aluminium chloride~
Such proce~es are for example di~closed in the
Hungaria~ Patent Specifications ~o~ 160 229 and
f ~i
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-- 3 --
162 348. ~hese methods~ however~ involve serious
problem~ in the operation5 require special
equipment~ and the purity o~ the aluminium
obtained ie also not ~atisfactory~
~ccording to another method di~clo~ed in
the Hungarian Patent Specification 150 459 low~
grade aluminium carrier~ are calcined at 650 C~
ground and treated with a 20 % aqueous hydrochlorid
acid solution. In this way aluminium, calcium, iron,
etc. are dissolvedO ~he solution i~ then ~iltered,
deironized with a ~trongly basic ion ~xchange resin~
the aluminium chloride solution is evaporated and
iron i3 eluted ~rom the resin with a slightly acidic
aqueous ~olution. By this method iron and silicon
can be ~eparated from aluminium~ The method can,
however9 not be employed f~or manufac-turing bauxites,
since under the given conditions aluminium oxide~
are very poorly ~oluble, the purity of the obtained
alumina io not ~atisfactory and -the problem o~ the
recovery of' the mother liquor~ has not been ~olved.
~hi~ proces~ is, therefore, very expen~:Lve and the
filtration of the ~olution with concentrated hydro-
chlorlc acid require~ extreme precaution~ and i~
very ~low.
It can be e~tabli~hed that there i~ no method
known in the art for an economic recovery of
alumina and ferric o~ide ~rom low-grade aluminiu~
~ 9.76~3~
carriers in an appropriate purity.
The present invention provides a process for obtaining alumina and
ferric oxide from a material which contains aluminium~ iron and silicon,
which process comprises:
~ a) treati.ng the material at 90 to 130 QC with from one to two
volumes of aqueous hydrochloric acid containing from 200 to ~20 g./li-t. of
hydrochloric acid, thereby obtaining a solution of ferric chloride and a
deironized product
~ b) contacting the solution o:E ferric chloride with an anion
exchange resin which obsorbs ferric chloride and hydrochloric acid~ sub-
sequently eluting ferric chloride and hydrochloric from the resin, returning
hydrochloric acid to the process for treatment of further material and sub-
jecting the ferric chloride to pyrolytic decomposition at about 850 C to
obtain ferric oxide,
(c) adding concentrated sulfuric acid to the deironized product
in an aboutstoichiometric amount, calculated for the soluble oxides and
heating the mixture to about 140 to 160 C to obtain an aluminium sulfate
solution
~d) separating the sulfuric acid and aluminium sulfate solution,
returning separated sulfuric acid to the process for treatment of further
cleironized product and subjectlng the aluminium sulfate to pyrolytic de-
composition to o~tain '6-~1203.
In tlle process according to the invcntion bauxites havi.ng a low
module and/or contal.ning laterite, siderite and red mud, colliary rocks,
coal ash and clays can for example be used as starting materials. Mineral
row materials and
~ ~ 7
-- 5 ~
hydrochloric acid ~olution are contacted in
a mu-tual proportion of 1:1 to 1:2. Iron di~solved
in the form o~ ~erric chloride is eliminated by
strongly ba~i~ anion excha~ge resin~, pre~erabl~
containing trime-thyl amine (dimethylethanol amine)
or pyridine active group~. The anion exchange
resin can be employed also as a membrane or cloth
in a batch-type or continuou~ proces~ Iron can
be ab30rbed from a ~iltered ~olution but ~ati~-
Eactory re~ult~ are obtained al~o by leading the~lurry containing ferric chloride in counter-
flow with the elutin~ aqueou~ solution, alon~ the
ion exchange cloth or membraneO( To -the deironized
residue concentrated ~ulfuric acid ie added in an
about ~tochiometric amount calculated for the
soluble ogide~, the mixture i~ heated up to 140
to 160 C with stirring, and hydrochloric acid
~et free during ~ul~atization is recycled into
the deironization procee~ as an azeotropic mixture.
The exces~ of sulPuric acid, which i~ di3tilled
of~ at 300 to 400 C during the auto-thermic reaction
i~ aloo recycled into the eul.Eati.eation ~tep.
The nearly acid-free, heat-treated ~ulfate mixture,
which ha~ loet its cry~tal water and ha~ been
di~ir~tegrated into a .~inely divided, powder~
product i~ di~olved in water and the undi~solved,
deh~drated oilicate~ and titanate~ are ~iltered o~f,
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-- 6 --
optionally in the pre3ence o~ f'locculating
agents. I~ de3ired, the ~iltrate can be ~ubjected
to a ~urther deironization, which can be carried
out by extraction or ion exchange~
'~he ~erric chloride and aluminium sul~ate
~olutions obtained durin~ the procedure are
evaporated, whereupon they are subjected to
thermal decomposition at about 850 C. ~he hydro-
chloric acid and sulfuric trioxide formed are re-
cycled into the corre~ponding, earlier stages of
~he proces~ and~ apart f'rom minor lo~Ye~, hydro-
chloric acid and 3ul~uric acid are kept in a closed
cyclic proce~. Pyrolysi~ resul-t~ in the formation
of ferric o~ide and a major amount o~ ~-alumina
in a ~ati.sfactory purity, with a good ef~iciency,
~ hough the proce~s according to the inven-
tion includes some technological step~ known in
the art 9 these are combined with each other and
with furthsr, entirely new reac-tion steps in a
speci~ic way, which make~ the u-tilization o~
low~grade, aluminium contain:ing miner~l raw
material~ ~or producing alumina and ~erric oxide
pos~ible. By the in~tant proce~s alumina and
ferric o~ide are directly obtained in a quality,
which is suitable ~or f'urther man~c~uring. It
~hould ~urther be empha~ized tha-t by the proces~
according to ~he invention aluminium and iron,
i ,
.., . I
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7 --
which mutuàlly contaminate each other, can
aimultaneously be i~olated in a ~ati~actory
purity by an economic technology~ This i~ a
highly une~pected re~ult 3 since none of the
prior art processe~ could garantee the ~ame or
similar results.
Further detail~ o.f the invention are
illu~trated by the following, no~-li~iti~g ~amples.
E~ le 1
Deironizatio~ o~ bauxite and pr~e~tion o~
~erric oxide
___ ____
26 ton~ o~ bau2ite having a grain size o~
about 30 mm~ are ground to a grain si~e of about
300 microna in a wet ball millO ~auxite contain~
50 % A1203, 22 ~o ~e203 a~d 6 % SiO2. 17 ~. of
water are added to the bauxite and the granulate
is heated up to 65 ~C in a heat exchangerO To the
bau~ite ~lurry 32.4 ~. o~ a 34 % (420 go/lit~)
hydrochloric acid solution are added ? and the
bauxite i~ digested i.n ~even ~tage~, for 1.5 houra~
Duri~g thi~ treatment about 90 ~0 o~ the iron
content o~ the starting ma-terial ia di~olved~
which corre~pond~ to 5 ton~ of ~erric o~ide, i~e.
about 10 tons of Feal3. To hal~ of the volume of
the digeated slurry 500 g./tons o~ Sedosan
flocculating agent are added in an amount o~
500 g~/tons 9 and the ~lurry i~ ae-ttled down i~
i~ a ~our-stage "Dorr" sedimentator~ It is then
~IL7~3~
~iltered through ~ive acid-resistant cylindric
filter, having an area of 20 m . eachg and i~
washedq The ~eC13 ~olution i9 evapora-ted to a
conce~tration of 200 g./lit. Fe3~ and -the
concentrate i~ decompo~ed at 520 C in a
pyrolysator to give 4.5 torlY of ~e203 i~ a purity
o~ about 90 % and azeotropic hydrochloric acid.
Hydrochloric acid i9 ~upplemented with fre~h acid
and i9 then recycled into the manufacturing proce~s~
The deironi~ed bauxite can advantageousl~ be
processed by the ~ayer method, ~ince during it~
further -treatment red mud i9 not formed.
a~
D~i70r~z- tlDn o~ the bBU~itg ~3~E~
~ ohlorio aci.d b.Y anion e~c~
Half o-~ the ~olume o~ dige~ted bauxite
slurry obtained in E~ample 1~ which con-tains
28 g./lit. of Fe3+ and 220 g./lit. of hydrochloric
acid in -the aqueou~ pha~e, i~ introduced into a
dialy~ator~
r~he dialysator is 0quipped with an anion
selective cloth containing dimetharlolamine groups,
and the bauxite ~lurry contairling hydrochloric
acid and water are led in counter flow along the
two opposite side~ of the cloth~ r~he slurry and
the aqueous phaae are u~ed in a volume ratio o~
1:1. Iron i~ dialysed from th0 slurry into the
~i
L3~
g
aqueou~ pha~e a~ FeC13~ The pores o~ the cloth
are clogged by the slurry, therefore, it i~
practically unpermeable for the aqueou~ phase~
Hence, -the Fe3~ concentration o~ the bauxite
31urry i9 decra~ed below 1 g~/lito~ while it~
aluminium content remain~ practically unchanged~
~he ~eC13 ~olution obtained i9 converted into
ferric oxide a~ de~cribed in Example 1.
Exam~e 3
The~ ration of alumina ~uitable ~or
in~ a~drou~ AlCl and ~erric o~ide ~rom
3 ~-- _
low-eE~ e
...
As a starting material 28 ton~ o~ low-grade
bauxite containing 46 % A1203, 15 % ~e203 and 18.6 %
SiO2 are used~ The row material i5 broken and
wet milled up to a grain ~ize of about 300 micron~
The bauxite i~ digested with 65 ~. of a 200
g./lit. aqueous hydrochloric acid solution
(azeotropic mixture). Dige~tion i9 carried out
in containers (duplicator~) in ~even ~tage~, for
two hour~. The input temperature i~ about 60 to
85 C and the output temperature i9 about 105 to
130 C.
'~he bauxite slurr~ i~ settled in a Dorr
~edimentator whereupo~ it i~ ~iltered through
~ilter cylinder~ and i~ sub~equently wa~hed. The
solution contain~ abou-t 20 g./lit D 0~ iron and
,~
~7~3~
-- 10 --
about 200 g~/lit~ of hydrochloric acid. l'he
solu-tion is deironized on a.n ion exchange column
~illed with a resin Yarion AT 660~ containing
trimethylamine active moietie~. ~he ~peci~ic load
of the column i9 10 ~ o hourO When the solution
leaving the colum~ corltain3 2 g./lit. o~ ~e3~, the
ion exchange procedure i~ stopped a~d the re~in
i9 wa~hed to iron-free with water corresponding
to twice of its volume~ ~fter this regeneration
the column can be u~ed again for deironization.
~he eluted ferric chloride solution is evaporated
to a concentration o~ about 1000 g.~lit. of ~eC13
and therea~ter it ig thermally decomposed ~o Fe203.
The hydrochloric acid obtai~ed during e~aporation
and pyroly~is is coriverted into concentrated hydro-
chloric acid in ab~orbers used also in the prepara
tion o~ h~drochloric acid.
The filter cake contai~s about 13.3 t.
hl203, 0~58 t. ~e2Q39 -34 t. CaO and 0016 t~ MgOo
q'o dissolve the ~oluble oxides a calculated amount
(42 t~) of conce~trated sul~uri~ acid i~ ndded to the
cake, in acid re~istant autocla~e~, where the
~ubsta.nce i9 heated ~or about 30 minute~ in two
stages. ~rom t,he ~lurry water is evaporated and
the autothermic procedure of the alumi~ium sulfate
formation is ~tarted, as a result o~ which the
~lurry is heated approximately up -to 160 C J Before
,. ~
7~3~
~olidification the slurry i~ introduced into
an oil-heated pipe mill, where the o~ides are
digested at about 400 C and the ~lurry
~o~idifie~. The sul~uric acid, which i~ released
duri~g the heating, i9 distilled of~ and, a~ter
conden~ation, can be used up again.
The powdery product obtained i9 dissolved
i~ 52.2 ~. of water, keeping the solid to liquid
ratio at about 1:2. The mi~ture i3 concentrated in
Dorr evaporators a~d the in~oluble residue, which
contains siliGates and tita~ium oxides a~ major
compone~t~ filtered off and wa~hed at 70 C.
~he filter cake, after dryingy can be u~ed for
ceme~t production or a~ a titanium oxide 30urce.
If alumina i~ to be prepared in a high
purity, the 3ulfate-containing solution can be
~urther puri~ied by an anio~ exchange re~in. In
thi~ ca~e the aluminium sulfate ~olution, contain-
ing about 400 g./lit. of aluminium sulfate and
about 12 g./lit~ of ferric sulfate a~ impuri-ty,
i~ adju~ted to pH 1.5 to 4 and i~ pas~ed through
a colum~ ~illed with ~arion AP (an anion exchange
re~:in containing pyridine active group~ Under
these condi-tion~ the impuritie~, including iron
are efficiently ad~orbed on the ~tronely ba~ic
anion exchange resinO The solution leaving the
column contain~ at most 0.5 g./lit. of iron~ 'rhe
; 12 - ~76~3~
ion e~change resin can be regenerated with an
aqueou~ sulf~ric acid ~olution containing 100 go/lit~
o~ sul~uric acid.
The purified, aluminium sul~ate-containing
~olution i~ evaporated, dehydrated and i3 treated
at 340 C~ At thi~ temperature the a:Luminium
~ul~ate disintegrates in-to a white powder, which
is subjected to thermal decompo~ition at 800 to
1000 C 9 12~5 ton~ o~ a product ~ubs-tantiallg
consisting of ~-alumina and about 35 ton~ of S03
ga~ are obtainedO ~he ga~ i~ introduced i~-to a
sul~uric acid absorber and i~ recycled to the
~ul~ating step.
The alwmina obtained can be u~ed for the
preparation of AlC13 very well3 ~i~ce at a
temperature of 450 to 500 C it can be chlori~atecl
with a practically theoretical (lOO ~) yield.
Pr~e~tion of ferric oxide and alumina
~0 fr~ m red mud
~he red mud u~ed a~ a raw ma-terial contain~
17 9 % A1203~ 34.6 ~0 Fe203, 5.1 % TiO2~ l~. 2
3.8 % ~aO and 6.2 Na2Q. For l ton of a dry red
mud having the above compo~ition 985 kg. o~ HCl
(100 %) can be calculated, and there~ore~ the red
mud i~ treated with 2~35 ~. of an aqueou~ hydro~
chloric acid ~olution, having a concentration o~
~, . .
~t7~30
- 13 -
420 g./lit. in an autoclaYe 7 at 130 C for 2
hours. During this treatment 166 kg. of A1203
and 337 kg. o~ ~e203 are dis~olved. The slurry
i~ admixed wi-th Varion AT re~in in a ratlo o~
3-1, and the re~in, on which iron i~ ad~orbed,
i~ separated from the ~lurry by filtration with
vibration~ Iron i~ eluted from the re~i~ with
water, the ~eC13 solution i9 evapora-ted and i~
converted into ferric o~ide by thermal decompo~i-
tion~ The released hydrochloric acid and the hydro-
chloric acid~containing ~olution filtered off ~rom
the deironiæed ~lurry in the presence of Sedo~an
~locculati~g agent~ are subjected to fractionated
evaporation~ In thi~ way an azeotropic hydrochloric
acid solution i~ obtained~ which i~ recycled into
the deironization ~tep. '~he evaporation residue,
~ub~tantially con~isting of AlC13 0 6~20 i9 purified
and can be marketed as AlC13 of "technical purity"
or can be 3ubjected to thermal decompo~ition in a
pyroly~ator, to yield A1203. In the whole procedure
an about 8 ~ lo~ ~n hydrochloric acid can be
ob~erved, due -to the Na20 and CaO content of -the
red mud.
'rhe major advantages of the proce~ according
to the invention can be ~ummarized a~ ~ollow~:
- '~he inven-tion provides a procea~ for the
utilization of low~grade aluminium and iron
~L~76~3~
carriers, ~uch ag laterite and siderite-contain-
ing bauxite~ 9 or bauxite~ having a high silicon
concentration~ red mud~ clay~, etc. Up to -the
pre~ent there ha~ been known no economic proce~s
to recover the aluminium and/or iron con-tent of
~uch low-grade carrier~.
- Startin~ ~rom the above raw ma-terials a
practically silicon- and iron-~ree alumina can be
prepared in a 80 % purity~ Since the product
e~sentially con~ists o~ ~-alumina~ it is very
active and can be u~ed a~ a ~tarting material in
chlorometallurgical proce~ses, ~uch a~ chlorina-
tion at 450 to 500 C with a mixture o~ C0 gas and
chlorinating ga~, under atmospheric pre~ure.
- In addition to alumina, the proce~
according to the invention yield~ a further
product containing 90 to 99 % of ~e203. Thi~
product i~ ~ubstantially free of pho~phorus and
sulphur, and is therefore equally ~uitable for
metallurgioal and other indu~trial purpo~es, e.g~
~or the production of ~erromagnet~, pigments, etc.
- ~y the proces~ of the present invention
the de~ired product~ are obtained with an e~cellent
yield (over 90 %) and highly ~electively~
~ The proce3~, not like the Bayer proce~,
can be accompli3hed without the formation o~ large
amount~ of unde~lrable ~olid and liquid wa~te
,, J.~
~6~3
5 --
mat t er3 0
- Hydrochloric acid and ~ulfuric acid
are used in a clo~ed cyclic proce~s 9 only the
~mall 1093e~3 should be ~upplemented 9 and the
5 proce~ there:Eore very economic,,
,~
