AN IMPROVED PROCESS FOR THE PRODUCTION OF ALUMINIUM
Year: 1882

page_text: LETTERS PATENT to James Morris, D.Sc. of Uddingston, in the County of
Lanark, North Britain, Analytical Chemist, for an invention of "AN IMPROVED
PROCESS FOR THE PRODUCTION OF ALUMINIUM."
PROVISIONAL SPECIFICATION left by the said James Morris at the Office
of the Commissioners of Patents on the 4th March 1882.
JAMES MORRIS, D.Sc. of Uddingston, in the county of Lanark, North Britain,
Analytical Chemist, "AN IMPROVED PROCESS FOR THE PRODUCTION OF ALUMINIUM,"
This Invention relates to an improved process to be employed for the production
of metallic aluminium from alumina, or from chlorides, sulphates, or other
compounds of alumina; the object of the Invention being to produce the metal by
much less expensive means than hitherto adopted.
The improved process consists essentially in heating an intimate mixture of
alumina and carbon or carbonaceous matter to the temperature of ignition within
a close vessel, such as a tube, retort, or cruicable, and subjecting the mixture to the
action of carbonic acid gas, whereby carbonic oxide is formed and the alumina is
reduced in whole or in part to metallic aluminium.
In carrying out the Invention I use a very intimate mixture of alumina and
carbon prepared as follows. A soluble salt of aluminium, preferably the chloride,
is mixed in solution with powdered charcoal, to which may be added soot, tar,
sugar, or other substance singly or in combination, which on ignition yields
charcoal, and this is evaporated till it forms a stiff plastic mass when it is broken
up or formed into pellets. The broken pieces or pellets are then ignited in a
covered vessel, and kept at a red heat, to expel the moisture and volatile matters,
until alumina and carbon alone remain. The intimate mixture of alumina and
carbon thus produced, is according to my Invention, ignited either within the same
or within a separate vessel in an atmosphere of carbonic acid gas which has been
freed from moisture. For this purpose wrought-iron tubes may be employed,
through which the carbonic acid gas in excess may be made to pass over or through
the mixture of alumina and carbon. The excess of carbonic acid gas mixed with
CD1

page_text: the carbonic oxide formed in the reaction may be collected at the outlet of the
tube, and passed through an adjoining tube in which also alumina and carbon
pellets are ignited, or it may be otherwise utilised.
The carbonic acid gas used may be produced by any ordinary means, such as by
the action of hydrochloric acid on carbonate of lime, or by the combustion of
carbon, or of a gas or substance containing carbon, in air. In the latter case the
nitrogen of the air would be allowed to pass with the carbonic acid gas through
the tubes or vessels containing the alumina and carbon, its presence having no
effect on the re-action which takes place.
It is preferred to use the alumina and carbon in such proportions that all, or
nearly all, the carbon shall be used up before the whole of the alumina is reduced,
so that the metal produced may be left in the powdered alumina, and may come
less in direct contact with the vessel in which the reaction occurs. The relativo
masses of the substances thus also tend to yield a metal containing less carbon in
combination; and to further effect this last-mentioned purpose the mixed metal
and alumina may be heated for a variable length of time either under or above the
fusing, point of the metal, and in doing this the same precautions may be observed
as hereinafter described in the fusion of the metal to effect its separation from the
alumina. The unreduced alumina may be used in subsequent operations, while the
length of time and degree of temperature, to which the mixture is subjected may
be varied, the completion of the reaction may be inferred by the carbonic acid
passing through the tube or vessel without the formation of carbonic oxide.
The metallic aluminium produced by this process may not in general be
chemically pure. It may be freed from unreduced alumina and any excess of free
carbon, by fusion, or by mechanical separation, or by both. The fusion of the
metal may be effected within the tube or vessel within which the alumina is
reduced to the metallic state, or in separate vessels, and with or without fluxes;
and when the metal is in a state of fine sub division, the fusion may be made in an
atmosphere of hydrogen or carbonic oxide, or in any other gaseous atmosphere
which will prevent oxidation.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said James Morris in the Great Seal Patent Office on the 1st September
1882.
JAMES MORRIS, D.Sc. of Uddingston, in the County of Lanark, North-Britain,
Analytical Chemist,
« ΑΝ
IMPROVED PROCESS FOR THE PRODUCTION OF
ALUMINIUM"
My said Invention relates to an improved process to be employed for the pro-
duction of metallic aluminium from alumina, or from clorides, sulphates, or other
compounds of alumina, the object of the Invention being to produce the metal by
much less expensive means than hitherto adopted.
The improved process consists essentially in heating an intimate mixture of
alumina and carbon to the temperature of ignition within a close vessel, such as a
tube or retort, and subjecting the mixture to the action of carbonic acid gas,
whereby carbonic oxide is formed, and the alumina is reduced in whole or in part
to metallic aluminium.
The intimate mixture of alumina and carbon may be prepared in any known
manner, but is by preference prepared and treated as hercin-after described, and
the mixture of alumina and carbon is according to my Invention placed in a
covered or close vessel, and ignited in a current of carbonic acid gas which has been
freed from moisture. For this purpose, wrought iron tubes or retorts may be
employed through which the carbonic acid gas is made to pass over or through the
mixture of alumina and carbon.
In carrying out or performing my said Invention, I use a very intimate mixture
of alumina and carbon prepared as follows. A soluble salt of aluminium, preferably
the chloride, is mixed in solution with powdered charcoal, to which lamp-black
may be added. I find one part charcoal to one and a half parts by weight of lamp-
black to do well, and this is evaporated till it forms a stiff plastic mass, which is
formed into pellets. In evaporating this solution of chloride of aluminium, the
chlorine escapes as hydrochloric acid and alumina is left, and the latter is thus to a
large extent precipitated within the pores of the carbon.
The two chief points to be remembered in the preparation of the pellets for my
process are, that the alumina and carbon shall be brought into very intimate contact
or admixture with each other, and, that the pellets shall have a porous texture, to
permit of their easy permeability by the carbonic acid gas. Thus it is chiefly from
physical considerations that I use a mixture of charcoal and lamp-black; the lamp-
black allowing a very complete impregnation into its pores, while the charcoal
from its coarser texture maintains the porosity of the pellets. For a like reason
the relative proportions of the charcoal and lamp-black may be varied. Thus the
more finely the charcoal is ground, the less lamp-black may be proportionally used,
and vice versa. For the same reason, lamp-black containing any considerable
quantity of turry matter should not be used. In forming the pellets, whether
rolled by hand, or formed by mechanical means, the mass should be sufficiently
moist to hold properly together, but an excess of moisture is to be avoided.
The relative proportions of alumina and carbon may be varied within certain
limits, but from the nature of the process a quantity of carbon considerably greater
than that indicated by theory must be used. In practice I use one part by weight
of alumina to one and a quarter of carbon. The alumina is weighed and reckoned
as oxide, not hydroxide, but no allowance is made for absorbed moisture, either in
the alumina, or carbon, or lamp-black. At present I obtain the chloride of
aluminium by dissolving alumina in strong hydro-chloric acid and diluting with

page_text: water. When some other compound of aluminium forms the starting point of the
process, a corresponding quantity of the other compound may be used. The more
carefully the regulation of the heat is attended to, the less will be the excess of
carbon required, but a considerable excess must be used in all cases.
After the pellets are formed they are exposed to the air to dry, which operation
may be accelerated by a gentle heat. The pellets thus prepared still contain a
small amount of chloride of aluminium, and to get rid of this they may with
advantage be placed in tubes or other close vessels, and exposed to the action of a
current of steam, a heat being externally applied to the vessels, sufficient to prevent
any condensation of the steam, otherwise the pellets will be again reduced to a
pasty mass. By this operation an evolution of hydrochloric acid is produced, and
the steaming has also a good effect in softening the pellets. The pellets now
consist of hydrate of alumina, carbon, and moisture, and after driving off the
combined water and free moisture they are ready for the reduction. To effect the
preparation for the reduction, they may be ignited in the same or other tubes or
retorts, or other close vessels, simply under exclusion of air, or in a current of
hydrogen or other neutral gas or mixture of gas or the carbonic acid gas for the
reduction may be at once led in. In the latter case, no reduction will of course
take place till the combined water and free moisture are expelled, but the amount
of carbon so burnt off without effect will be inconsiderable. The reduction of the
alumina to the metallic state is effected by the stream of carbonic acid gas which
is led into the tube or retort containing the mixture of carbon and alumina. The
carbonic acid is reduced by the carbon to carbonic oxide, and this latter gas in the
nascent state is re-oxidised to carbonic acid, by combining with the oxygen of the
alumina, the alumina being by this process reduced to aluminium. Only a portion
of the carbonic oxide is however thus re-oxidised, a considerable quantity of it
escaping as such from the tubes or retorts.
The steaming of the pellets to drive off the hydrochloric acid, the ignition to
expel all the water, and the reduction itself may all be conducted in one and the
same vessel, and without removing the pellets from it at any of the different stages.
Wrought iron tubes may be with advantage employed, and they may, by means of
clay or other luting, or by sprinkling powdered borax over them, or by other
suitable means be protected from the action of the fire. For the better regulation
of the heat, the tubes or vessels are preferably fired by gaseous fuel.
The tubes or other vessels may be, of course, of varying size and shape, but as it
is preferable to have all the individual pellets kept as nearly as possible at one and
the same temperature, they are preferably used of moderate side; And when tubes
are used, they should be of rather small diameter in proportion to their length.
To further effect the equalization of the temperature the carbonic acid gas may be
heated before passing into the reducing vessels. The pellets should also be of
moderate size.
The average temperature during the reduction should be kept so high that the
outside of the iron tubes, when unprotected by clay or other thick and non-trans-
parent lute, appears in the dark of a moderate red. The degree of temperature
may be of quite moderate red at the earlier stages of the operation, but may be
somewhat increased as the reduction proceeds..
The progress of the reduction may be further observed by the amount of carbonic
oxide escaping from the reducing vessels. The temperature, the current of carbonic
acid, and the other conditions, should be so regulated that a slow but steady
evolution of carbonic oxide is maintained throughout the operation. This evolution
of carbonic oxide will of course get gradually weaker as the carbon is consumed,
even though the temperature be somewhat increased.
The carbonic acid gas used may be produced by any ordinary means, such as by
the action of bydrochloric acid on carbonate of lime, or by the combustion of
carbon, or a substance containing carbon in air; further by the burning of lime-
stone or chalk into lime, or the carbonic acid formed in the combustion of the fuel
used for heating the retorts, or other vessels used in the process of manufacture, or

page_text: the carbonic acid in the waste gases of lime kilns may be used. When the carbonie
acid produced by the combustion of carbon, by the burning of lime, or by similar
methods is used, it will be mixed with the nitrogen of the air, which will take
no part in the reduction but simply pass through the reducing vessels; And in
such cases, care must be taken that none of the oxygen of the air is left in the
gases. The carbonic acid gas, whether or not mixed with nitrogen, should be
freed from moisture by passing through oil of vitriol or other suitable dehydrating
agent, and should also be freed from any other injurious impurities.
When carbonic acid mixed with nitrogen is used, a relatively greater quantity
of the mixed gases should be passed through the retorts, than when carbonic acid
is used alone. The presence or absence of nitrogen in the gases employed, will
affect the indications of the carbonic oxide produced. When there is no nitrogen,
or only a comparatively small quantity of nitrogen in the gases employed, the
carbonic oxide produced during the reduction will burn so long as a light is applied
to the outlet or exit end of the reducing vessel, which exit should be made of
small diameter. When on the other hand the carbonic acid is mixed with a large
proportion of nitrogen, more accurate methods of estimating the relative amount
of carbonic oxide in the escaping gases, may be employed. In any case an analysis
of a mixture of nitrogen, carbonic acid, and carbonic oxide can be rapidly mado,
the carbonic acid being rapidly absorbed by caustic potash solution, the carbonic
oxide by a hydrochloric acid solution of subchloride of copper, while the nitrogen
is absorbed by neither re-agent. When the carbonic acid is produced by the com-
bustion of carbon or like incans, carbonic oxide inay also be present. It will exert
no injurious influence, but its possible presence must be kept in mind when
observing the composition of the gases escaping from the reducing vessels.
Although the amount of carbonic oxide evolved, may be in general taken as
indicative of the progress of the operation, yet the heating of the tubes or other
reducing vessels should not be pushed till the evolution of this gas entirely ceases,
or even becomes very weak, as through some slight difference in their texture,
some pellets lose all their carbon before others, and if an objectionable amount of
carbon should remain in some of them, they may be preserved, and when sufficiently
numerous be again subjected to the reduction. I have found that the minimum
time required, even with vessels of very moderate dimensions, is rarely under
thirty hours, the alumina and carbon being used in the proportions named.
The two ends of the tubes protruding beyond the furnace, should have wire or
loosely fitting clay plugs. That is to say, no pellets should be in any part of the
tubes not exposed to the full effect of the fire, for if they be cooler than the rest,
they may still give off carbonic oxide after the central pellets have lost all their
carbon, and the metal in the latter (central) part may be even burnt back to
earth.
The metal is produced in a more or less spongy mass, and may be freed by
fusion (assisted by any suitable mechanical means) from unreduced alumina and
any unconsumed carbon, and then run into ingots. The metal produced by this
method, whether in the form of metallic sponge or ingots, may not in general be
chemically pure. The metal may be freed from combined carbon, or from other
impurities, by a method analogous to that known as the Bessemer process, as
employed in the manufacture of steel, or any other suitable known process may be
used for purifying the metal.
The fusion is preferably made in separate vessels, and cryolite, chloride of
sodium, and any other suitable flux or fluxes may be used, as required. When
there is fear of serious oxidation, or otherwise loss of metal from its being some-
what finely divided, the fusion, or at least a preliminary sintering together of
the metal may be made in an atmosphere of hydrogen or other neutral gas or
gases.
I do not claim any method for the fusion of the spongy metal so obtained into
ingots, nor for freeing it from any chemical or mechanical impurities.
The thorough intermixture of the alumina and carbon is an organic part of the

page_text: process, and an evaporation of the soluble salt in presence of the carbon, or some
other process giving a very thorough intermixture of the alumina and carbon is
necessary for the attainment of a satisfactory result. The method of intermixture
described is neither scientifically nor technically new in itself, but is new as
forming a part of this process for reducing the aluminium.
Having thus particularly described the nature of my said Invention, and the
manner of performing the same, I wish it to be understood that I do not confine
myself to the precise details of the process described, but what I consider novel
and original, and therefore claim as the Invention secured to me by the herein-
before in part recited Letters Patent is,―
First. The process herein described of producing aluminium from alumina, or
compounds of alumina, such process consisting in subjecting an intimate mixture
of alumina and carbon within a close heated vessel to the action of carbonic acid
gas, substantially as, or in the manner herein set forth.
Second. As means for producing aluminium from alumina, or compounds of
alumina, the mode of forming a very intimate mixture of alumina and carbon and
reducing such mixture to the metallic state by means of carbonic acid gas,
substantially as or in the manner herein set forth.
In Witness Whereof, I the said James Morris, have hereunto set my hand and
Seal, this Twenty-third day of August in the year of our Lord One
thousand eight hundred and eighty two.
Witness
WALLACE FAIRWEATHER C.E.
96 Buchanan Street
Glasgow.
JAMES MORRIS. D.Sc. (Tüb.) (L.S.)