CA1076366A - Aluminium extraction process - Google Patents

Aluminium extraction process

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Publication number
CA1076366A
CA1076366A CA251,274A CA251274A CA1076366A CA 1076366 A CA1076366 A CA 1076366A CA 251274 A CA251274 A CA 251274A CA 1076366 A CA1076366 A CA 1076366A
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Canada
Prior art keywords
aluminium
carbonisation
containing mineral
organic material
carbon
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CA251,274A
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French (fr)
Inventor
Edward M.A. Willhoft
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Individual
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Individual
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Priority to CA251,274A priority Critical patent/CA1076366A/en
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Abstract

ABSTRACT

The invention provides a process for recovering aluminium values from aluminium-containing minerals, such as oxides of aluminium and aluminosilicates.
The process involves heating an intimate mixture of an aluminium-containing mineral and a solid carbonisable organic material, preferably a fibrous cellulosic material, so as to carbonise the organic material, and chlorinating the solid residue from the carbonisation step. The solid residue contains carbon in very finely divided form distributed throughout the aluminium-containing mineral, The surface area and reactivity of this carbon is much higher than that of powdered coal and the chlorination reaction thus takes place in a most efficient manner.

Description

~763~i6 This invention relates to a process for recovering aluminium values from aluminium-containing minerals.
Aluminium is widely distributed about the surface of the earth, mainly in the form of clays from which it S has hitherto not proved economic to extract the metal or its compounds. It is known to -form aluminium chloride by sintering a mixture of bauxite, which is a hydra-ted oxide of aluminium, and powdered coal at a high temperature and then passing gaseous chlorine over the mixture. This tO process has been applied industrially, but is limited by the relatively low yield of aluminium chloride and the high cost of the starting materials.
'I`he present invention enables aluminium values to be recovered from aluminium-containing minerals, and in particular from materials containing minerals which have hitherto been regarded as industrial waste products.
The present invention provides a process for recovering ~lunlinium values from an aluminium-containing mineral, which process comprises heating a dried paper sludge,
2~ said dried paper sludgecontaining a carbonisable organic material in the form of organic fibres in intimate association with an aluminium-containing mineral selected from the group consisting of an oxide of aluminium and an aluminosilicate in finely divided form, to a temperature 2~ of 500 to 1000C to carbonise the organic fibers, chlorinating the solid residue from the carbonisation step, and recovering a chlorination product containing aluminium and chlorine.
The invention may be applied to a wide range of ~0 aluminium-containing minerals in which aluminium is in combination with oxygen and/or silica.

7 t;~61~

- Thus the invention may be applied -to oxides of aluminium, for example hydrated oxides such as bauxite, and alumino-silicates, for example aluminium-containing glasses and clay minerals such as kaolinite (sometimes referred to as china clay), montmorillonite, bentonite, halloysite, allophane and mica. The aluminium-containing mineral is ~`inely divided in order to make possible intimate mixing with the carbonisable organic fibres, particle sizes down to 20 microns, especially down to 10 microns, are preferred.
The mineral can, if desired, be calcined before the carbonisation step.
The organic material should be one that can be ~arbonised without complete volatilisaion although some production of volatile material can be tolerated and may 1~ indeed be desirable in that it can help to distribute fine particles of carbon throughout the aluminium-containing mineral. The carbonisable organic material is in fibrous form so that, upon carbonisation, a very finely divided form of carbon is obtained in intimate contact with the aluminium-containing mineral.
The process of the invention utilises dried paper sludge as carbonisable organic material. Paper sludge is the effluent from paper making processes and consists of a dilute slurry of organic fibres of vegetable origin, 2~ usually cellulosic fibres, and of non-fibrous fillers or loading agents. The organic fibres in the sludge are extremely fine, since they have passed through the paper-making wire, and upon carbonisation provide very finely divided carbon. The fillers or loading agents can con-tain a high proportion of aluminium-containing minerals, for example clays such as bentonite and china clay. Paper ., ~ , . .

7~;3~;~

sludge thus can contain a carbonisable organic mineral, in the form of organic fibres, and also an aluminium-con-taining mineral, and a paper sludge containing both may be used directly in the process of the invention. Additional carbonisable material, such as shredded waste paper, and/or an aluminium-containing mineral may be added to a paper sludge and incorporated therein by simple mixing techniques. Paper sludge can contain as much as 10% by weight of solid material, but usually the proportion is typically around 500 ppm to 100 ppm in the effluent as it leaves the paper mill. The sludge is preferably allowed to settle, concentra-ted, for example to 20 to 25% by weight solids content, and then dried ~o 90 to 95% by weight solids content for use in the process o~` the present invention.
In the next stage of the process, the paper sludge or other mixture of aluminium-containing mineral and carbonisable organic material is heated to carbonise the organic material present. The mixture can be shaped, for example by pelletising or briquetting, before the carbonisation. The carbonisation can be carried out entirely in a non-oxidising atmosphere which may for example be nitrogen or carbon dioxide or i-t is possible to supply a limited amount of oxygen or gas containing molecular oxygen in order to burn some of the organic material and supply heat for the carbonisation reaction. Clearly in the latter case it is necessary to use sufficient organic material to allow for that which is burnt while leaving a suitable amount to undergo carbonisation. The temperature of carbonisation will of course depend upon the organic material being used, but is usually in the range of from 500C to 1000 C, and preferably from 750 C -to 900C. The 636~
organic material is converted upon carbonisation to finely divided carbon which is distributed throughout the aluminium-containing mineral and provides for a high interfacial area of contact between the aluminium-containing mineral and the carbon. l`he surface area and reactivity of this carbon is many times greater than that of the powdered coal which has hitherto been used.
The solid residue from the carbonisation reaction is then ch.lorinated, for example by passing chlorine gas (which need not be pure and can contain, for example, hydrogen chloride, hydrocarbons and chlorinated hydrocarbons) through the carbonised material at an elevated temperature. The temper-ature of` reaction may be up to about 1500C but is preferably ~ htly lower than the carbonisation temperature,for example 1~ in the range of from 500 C to 800 C. The main produc-ts of the chlorination reaction are gaseous at the reaction temper-ature and consist of the product containing aluminium and chlorine, oxides of carbon and phosgene together with unreacted chlorine, and minor amounts of impurities including silicon ~0 tetrachloride and ferric chloride. The chlorination products can differ at different chlorination temperatures for example greater amounts of silicon tetrachloride are produced at the higher chlorination temperatures. The chlorination reaction may be carried out in any suitable apparatus, for example a ~5 rotary kiln, fluidised bed, or indirect-fired system.
The chemical form of the chlorination product containing aluminium and chlorine can depend upon the conditions of -the chlorination reaction. The most usual chlorination product is aluminium chloride, but other products could result, such as aluminium oxychloride, aluminium hydroxychloride and mixed ~L~763~6 ehlorides such as sodium aluminium ehloride or potassium aluminium chloride.
The reactions taking place during the chlorination step involve simultaneous oxidation and reduetion. Two possible reaetion sehemes when using an aluminium-containing mineral such as a clay and producing aluminium chloride can be summarised as follows:
(~) A1203 ~ 3C + 3C12 = 2AlC13 ~ 3CO
and (B) 2A12 3 2 3 2 The first of these (A) can be termed the "carbon monoxide"
rout~, while the seeond (B) ean be the "earbon dioxide"
rou~. Whieh rou-te is the better to be followed will depend upon the circumstances of a given situation since much ean depend upon choice and form of starting materials and upon energy requirements. The choice of route will affect the theoretieal quantities of starting materials required for stoiehiometric eonversion of -the aluminium values in the aluminium-eontaining mineral into aluminium chloride. In ~0 enlculating the relative proportions of the starting ma-terials aeeount must also be taken of the fact tha-t the organic material usually suffers a large weight loss upon earbonisation, whereas the aluminium-containing mineral is comparatively unaffeeted. For example, eellulose suffers an approximately ~5 5-fold reduction in weight upon carbonisation. When taking these factors into consideration it is ealculated -that -the theoretical quantities (parts by weight) of -the starting materials and product for the differen-t routes are as follows ~vhen using cellulose and china clay:-~L~763~6 Cellulose (dry weight) China Clay Aluminium ChlorideRoute (A) 1 1.45 0.89 Route (B) 1 2.9 1.79 It is possible to employ an excess of the organic material over tl~e stoichiometric requirements. When this is done the c~cess carbon remaining after carbonisation and chlorination rem<lins in the solid residue of the chlorination reaction and is in highly active form, having become activated during -the chlorination and also by moisture (either mois-ture introduced by recycling products of combustion or carbonisation, or bound moisture released by a clay during the final stages of carbon-i~ation). Such active carbon may usefully be recovered.
~ lulllinium chloride may be separated from other products vt` the chlorination reaction by dissolving in ethanol, passing the resultant solution through a bed of active charcoal and recovering the purified aluminium chloride from the ethanolic solution. Alternatively it may be separated from the other products by fractional distilla-tion or sublimation of the condensed vapours emerging from the reaction zone.
Aluminium chloride produced by the process of the present invention has a variety of uses as a ca-talyst in organic chemistry, particularly in polymerisation reactions and organic syntheses. It is also a useful intermedia-te in the production ot` aluminium, for example by the TOTH and ALCOA processes, and may have pharmaceutical applications.
The solid residue from the chlorination reaction is depleted in aluminium ions and may therefore find application as a solid adsorbent and as an ion exchange material. I-t might also find use as an ingredient of cemen-t. Active carbon contained therein can be separately recovered if desired.
The invention is illustrated by the following Example:

~76366 c ) ~: X ~ M P L E
Paper sludge containing china clay and cellulose fihres in a ~eight ratio of 1:5 is dried to a moisture content o~
about 5% b~ wei~ht. The dried paper sludge is then fed into a tu~ular he~ting chamber formed from passive alumina and situated inside an electrically heated furnace. The tube may be coated with metal to reduce oxygen di~usion into the reaction æone or could be constructed of quartæ ox graphite.
~fter introduction of the drièd ma~erial, one end of the tub~ is ~itted wlth an inlet for gas introduction and the other end with an outlet for the products of the carbonisation and chlorina~ion reac~ions. The temperature o the ~urnace is gradually raised to $00C and maintained at 800C for one hour, while passing a stream of nitrogen through the tube, lS Volatile mater.ial produced by the carbonisation of the ce].lu~ose ~ibres is condensed and discarded. The temperature is the~
gradually lowered to 550C and chlorine passed through the tube at approximately 1 litre per minute until chlorination is complete. The rate of reaction may be controlled by varying the temperature. The volatile products of the chlorination reaction are bubbled through ethanol and passed through a bed of active carbon. Finally the ethanol is separated from the puri~ied aluminium chloride by fractional distillation.

~3 ~

Claims (3)

The embodiments of the invention, in which as exclusive privilege or property is claimed, are defined as follows.
1. In a process for preparing a product containing aluminium and chlorine by chlorinating a mixture of an aluminium-containing mineral and carbon and recovering a a product containing aluminium and chlorine, the improvement wherein a dried paper sludge, said dried paper sludge contain-ing a carbonisable organic material in the form of organic fibres in intimate association with an aluminium-containing mineral selected from the group consisting of an oxide of aluminium and an alumino-silicate in finely divided form, is heated to a temperature of 500 to 1000°C to carbonise the organic fibres, the solid residue from the carbonisation step is chlorinated, and a product containing aluminium and chlorine is recovered.
2. A process according to claim 1 wherein the aluminium-containing mineral is selected from bauxite, kaolinite and mica.
3. A process according to claim 6 wherein the amount of carbonisable organic material is in excess of the amount required to provide for stoichiometric conversion of the aluminium values in the aluminium-containing mineral to aluminium chloride after the carbonisation and chlorination reactions.
CA251,274A 1976-04-28 1976-04-28 Aluminium extraction process Expired CA1076366A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA251,274A CA1076366A (en) 1976-04-28 1976-04-28 Aluminium extraction process

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CA251,274A CA1076366A (en) 1976-04-28 1976-04-28 Aluminium extraction process

Publications (1)

Publication Number Publication Date
CA1076366A true CA1076366A (en) 1980-04-29

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Family Applications (1)

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