Improvements in Electric Smelting of Aluminous and other Refractory Ores or Compounds.
Year: 1892

page_text: Date of Application, 28th Nov., 1892
Complete Specification Left, 24th Aug., 1893--Accepted, 30th Sept., 1893
PROVISIONAL SPECIFICATION.
Improvements in Electric Smelting of Aluminous and other
Refractory Ores or Compounds.
1, THOMAS LEOPOLD WILLSON, of Leaksville, in the County of Rockingham,.
and State of North Carolina, United States of America, Electrician, do hereby
declare the nature of this invention to be as follows:-
This invention relates to the reduction of aluminium and other difficultly
reducible metals from refractory ores or compounds thereof by the process of
electric smelting in the presence of a reducing agent.
Processes of smelting by electric heat are well known. In such processes an
electric furnace is employed constructed to convert the energy of an electric
current into heat energy, either by interposing the resistance of a poor conductor
or by the formation of an electric arc. The alumina or other metallic oxide or ore
is fused and vaporized by the heat thus generated, and is brought into contact with
a reducing agent within the furnace, preferably carbon or hydro-carbon, whereby
the oxygen is dissociated from the metal, thereby reducing the latter to the metallic
state. Ordinarily a base metal is present in the furnace to alloy with the aluminium
or other metal as it is reduced from the ore.
My present invention aims to improve and perfect such processes of reduction by
quickening and cheapening the process. According to my invention I bring the
metallic compound in a state of extremely fine sub-division into most intimate
contact with the reducing agent before subjecting it to the electric smelting process..
By my process, the alumina or other metallic compound, and the carbon or other
reducing agent, are brought into the closest atomic proximity that is possible by
mechanical means.
My invention consists essentially in subjecting to the heating action of an electric
current a metallic compound in a fine state of subdivision or pulverization and
impregnated with a suitable reducing agent so that substantially each particle of
the compound to be reduced carries with it the agent for its own reduction, by the
latter either permeating it or coating it, or being otherwise attached to it.
More specifically, my invention consists in the employment of finely subdivided or
pulverized and preferably porous alumina, or other metallic oxide, ore or compound,
which is impregnated with a reducing agent by saturating it therewith, while the
reducing agent is in liquid condition. The reducing agent is preferably a hydro-
carbon, and is applied by steeping the oxide or metallic compound therein until
sufficient of the hydro-carbon has been absorbed thereby to enable an effective
reduction to be performed. The oxide or compound is preferably stirred into the
liquid hydro-carbon or other reducing agent until the liquid is all absorbed into the
metallic compound, which may then be dried by heating or evaporation, leaving it
impregnated or saturated with the reducing agent.
A metallic compound or ore treated with a reducing agent in any of the ways
thus suggested is subjected to electric smelting according to any of the well known
electric smelting processes.
In an incandescent electric furnace, it should be mixed
with the broken or pulverized resistance material, preferably carbon, employed in
such furnaces to convert the electric energy into heat so that upon the passage of
the current through the mixture, the current will be conducted by this resistance
material, and by reason of the poor conductivity thereof, it will be largely converted
into heat, the heat thus developed being distributed throughout the mass traversed
by the current, so that the intermixed impregnated metallic compound on
being heated thereby will undergo a reaction, its oxygen entering into a new

page_text: combination with the reducing agent, and its aluminium or other metal being set
free. In the case of aluminium, an alloying metal may be provided in the furnace
to take up the freed aluminium.
In an electric are furnace of ordinary construction comprising a carbon crucible
or hearth connected to one electric terminal, and, a carbon pencil projecting into it
and joined to the opposite terminal, the impregnated metallic compound is introduced
either before or after the setting of the furnace in operation, and may either be
introduced in bulk at the outset, or continuously or at intervals from time to time
during the running. The heat of the electric are acts upon the portions of metallic.
compound within its range, and induces a reaction between the metallic oxide or
other compound and the impregnated reducing agent, the latter combining with the
oxygen and setting the metal free. In the reduction of aluminium in an electric
furnace it is usual to provide a base metal in the furnace, which being kept molten
by the heat, takes up the aluminium as it is freed by forming an alloy therewith.
If a base metal be not present, the product of the reduction will be carbide, of
aluminium.
My invention is not limited to any particular reducing agent, but comprehends
any substance whatever that is available for the reduction of oxygen compounds
by combining with the oxygen thereof. Carbon or hydro-carbons are ordinarily
preferable, but I have successfully used common salt (sodium chloride) as a
reducing agent.
In practicing my invention as applied to the production of aluminium alloys by
reduction of alumina in an electric arc furnace I proceed as follows:-
I employ by preference precipitated alumina thoroughly dried. In this form the
alumina is in an exceedingly fine state of subdivision or pulverization, and is in a
permeable or porous condition. As the reducing agent, I employ coal tar, or heavy
hydro-carbon oil, or paraffine. Assuming that tar is used, 1 place it in a caldron
and heat it to a boiling temperature, and while maintaining this temperature I
gradually stir in the precipitated alumina until the tar is all absorbed into the
alumina. 1 find that twenty-two pounds of alumina will thus absorb one gallon of
tar. The tar-impregnated alumina is thoroughly dried by increasing the heat so as
to drive off as much as possible of the moisture or volatile constituents contained
in the tar, the mass being continually stirred from the time of boiling until it
becomes dry. The tar-impregnated alumina then appears as a very fine black or
nearly black powder. place a small quantity of the base, metal for the alloy,
preferably granulated copper, in the bottom of the crucible of the furnace, and
lower the carbon electrode into it until it touches the copper. The crucible being
covered over, a current is passed through the furnace and the carbon electrode is
lifted slightly out of contact with the granulated metal, thereby forming an arc,
and in the subsequent treatment the carbon pencil is kept lifted sufficiently to
maintain this arc. 1 now introduce through the rent opening in the top of the
furnace a suitable quantity of the tar-impregnated alumina, which falls down beside
the carbon pencil and into the arc, where it is immediately heated thereby, to an
exceedingly high temperature. The first effect of the heat is to drive off the
moisture and volatile elements of the hydro-carbon still contained in the tar-
impregnated alumina. This action is shown by the black smoke that immediately
issues from the vent opening. Immediately thereafter a series of violent explosions
cccur within the furnace. Presumably these are due to the formation of carbon
monoxide or dioxide caused by the combination of the carbon from the tar with
the oxygen of the alumina, a combination which apparently takes place with great
rapidity at the inconceivably high-temperature existing within the furnace. The
aluminium which is thus freed is immediately alloyed with the copper which under
the high temperature in the furnace exists in the condition of a molten bath in a
state of violent ebullition, with its vapors streaming through the arc.
The feeding in of the tar impregnated alumina is kept up as long as it is desired
to operate the process, granulated copper being also added from time to time,
preferably in alternation with the impregnated alumina. The resulting aluminiuin

page_text: bronze may also be tapped off from the furnace from time to time without stopping
the operation.
J
By practicing this process, I have obtained a greatly increased output of
aluminium reduced, as compared with any other electric process of reduction.
"
The use of tar as a reducing agent is advantageous because of its cheapness,
but other hydro-carbons are equally applicable. In using paraffine or any heavy
hydro-carbon, I proceed in the same manner as described with tar, the hydro-
carbon being boiled and the alumina stirred into it. In using the lighter hydro-
carbons which are sufficiently fluid at ordinary temperatures, the boiling is
unnecessary. I have used ordinary kerosene oil as the reducing agent by simply
mixing it with the alumina so that the alumina absorbs or becomes saturated with
the oil. and then feeding the oil-impregnated alumina immediately into the furnace.
In the case of alumina in a less porous condition than precipitated alumina, the
liquid reducing agent may not penetrate the substance of the alumina to any
considerable extent, or may in fact be applied only to the exterior thereof; but in
such case, if the alumina shall have been reduced by grinding to an impalpable
powder, or otherwise sufficiently subdivided or pulverized, and then introduced and
soaked into the liquid reducing agent, the coatings of reducing agent thus applied
around and between the minute particles of alumina will constitute an impregnation
thereof with reducing agent in the sense of my invention, and to equivalent effect
to the permeating of porous alumina with the reducing agent.
My invention is not limited in its application to the reduction of aluminium, but
is equally applicable to other difficultly reducible nietals or ores.
Dated the 28th day of November 1892.
J. C. MEW.BURN,..
55 & 56, Chancery Lane, London, Chartered Patent Agent. I
COMPLETE SPECIFICATION.
Improvements in Electric Smelting of Aluminous, and other
Refractory Ores or Compounds.
.. J
1, THOMAS LEOPOLD WILLSON, of Leaksville, in the County of Rockingham,
and State of North Carolina, United States of America, Electrician, do hereby
declare the nature of this invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement :-
This invention relates to 'the reduction of aluminium and other difficultly
reducible metals from refractory ores or compounds thereof, by the process of
electric smelting in the presence of a reducing agent.
:
Processes of smelting by electric heat are well known. In such processes an
electric furnace is employed constructed to convert the energy of an electric current
into heat energy, either by interposing the resistance of a poor conductor or by the
formation of an electric arc. The alumina or other metallic oxide or ore is fused
and vaporized by the heat thus generated, and is brought into contact with a
reducing agent within the furnace, preferably carbon or hydro-carbon, whereby the
oxygen is dissociated from the metal, thereby reducing the latter to the metallic
state. Ordinarily a base metal is present in the furnace to alloy with the aluminium
or other metal as it is reduced from the ore.
My present invention aims to provide and perfect such processes of reduction by
quickening and cheapening the process. According to my invention I bring the
metallic compound in a state of extremely fine subdivision into most intimate
contact with the reducing agent before subjecting it to the electric smelting process.
By my process, the alumina or other metallic compound, and the carbon or other
reducing agent, are brought into the closest atomic proximity that is possible-by
mechanical means.
;;
My invention consists essentially in subjecting to the heating action of an electric
4

page_text: current a metallic compound in a fine state of subdivision or pulverization and
impregnated with a suitable reducing agent so that substantially each particle of
the compound to be reduced carries with it the agent for its own reduction, by the
latter either permeating it or coating it, or being otherwise attached to it.
More specifically, my invention consists in the employment of finely subdivided
or pulverized and preferably porous alumina, or other metallic oxide, ore or
compound, which is impregnated with a reducing agent by saturating it therewith,
while the reducing agent is in liquid condition. The reducing agent is preferably
a hydro-carbon, and is applied by steeping the oxide or metallic compound therein
until sufficient of the hydro-carbon has been absorbed thereby to enable an effective
reduction to be performed. The oxide or compound is preferably stirred into the
liquid hydro-carbon or other reducing agent until the liquid is all absorbed into the
metallic compound, which may then be dried by heating or evaporation, leaving it
impregnated or saturated with the reducing agent. In the case of a hydro-carbon
which is not liquid at ordinary temperatures it is liquefied by heating before
stirring in the metallic compound. Paraffine and coal-tar may thus be employed,
being heated to a boiling temperature and the metallic compound stirred into
the bath until as much has been introduced as will suffice to fully absorb the hydro-
.carbon.
A metallic compound or ore treated with a reducing agent in any of the ways
thus suggested is subjected to electric smelting according to any of the well known
electric smelting processes. In an incandescent electric furnace, it should be mixed
with the broken or pulverized resistance material, preferably carbon, employed in
such furnaces to convert the electric energy into heat so that upon the passage of
the current through the mixture, the current will be conducted by this resistance
material, and by reason of the poor conductivity thereof, it will be largely converted
into heat, the heat thus developed being distributed throughout the mass traversed
by the current, so that the intermixed impregnated metallic compound on being
heated thereby will undergo a reaction, its oxygen entering into a new combination
with the reducing agent, and its aluminium or other metal being set free. In the
case of aluminium, an alloying metal may be provided in the furnace to take up the
freed aluminium.
In an electric arc furnace of ordinary construction comprising a carbon crucible
or hearth connected to one electric terminal, and a carbon pencil projecting into
it and joined to the opposite terminal, the impregnated metallic compound is
introduced either before or after the setting of the furnace in operation, and may
either be introduced in bulk at the outset, or continuously or at intervals from time
to time during the running. The heat of the electric arc acts upon the portions of
metallic compound within its range, and induces a reaction between the metallic
oxide or other compound and the impregnated reducing agent, the latter combining
with the oxygen and setting the metal free. In the reduction of aluminium in an
electric furnace it is usual to provide a base metal in the furnace, which being kept
molten by the heat, takes up the aluminium as it is freed by forming an alloy
therewith. If a base metal be not present, the product of the reduction will be
carbide of aluminium.
My invention is not limited to any particular reducing agent, but comprehends
any substance whatever that is available for the reduction of oxygen compounds by
combining with the oxygen thereof. Carbon or hydro-carbons are ordinarily
preferable, but I have successfully used common salt (sodium chloride) as a
reducing agent, and doubtless many other substances are in greater or less degree
suitable as substitutes for carbon or hydro-carbons. When sodium chloride is used
in reducing alumina, it is decomposed by the heat, the chlorine escapes, and the
sodium attacks the oxygen of the alumina, forming soda, and setting free the
aluminium in metallic form.
In practicing my invention as applied to the production of aluminium alloys by
reduction of alumina in an electric arc furnace I proceed as follows:-
1 employ by preference precipitated alumina thoroughly dried. In this form the

page_text: alumina is in an exceedingly fine state of subdivision or pulverization, and is in a
permeable or porous condition. As the reducing agent, I employ coal tar, or heavy.
hydro-carbon oil, or paraffine, or coal-tar pitch. Assuming that tar or pitch is
used, I place it in a caldron and heat it to a boiling temperature, and while
maintaining this temperature I gradually stir in the precipitated alumina until the
tár is all absorbed into the alumina. I find that twenty-two pounds of alumina will
thus absorb one gallon of tar. The tar-impregnated alumina is thoroughly dried
by increasing the heat so as to drive off as much as possible of the moisture or
volatile constituents contained in the tar, the mass being continually stirred from
the time of boiling until it becomes dry. The tar-impregnated alumina then
appears as a very fine black or uearly black powder which is a non-conductor of:
electricity. I place a small quantity of the base metal for the alloy, preferably
granulated copper, in the bottom of the crucible of the furnace, and lower the
carbon electrode into it until it touches the copper. The crucible being covered-
over, a current is passed through the furnace and the carbon electrode is lifted
slightly out of contact with the granulated metal, thereby forming an are, and in-
the subsequent treatment the carbon pencil is kept lifted sufficiently to maintain
this are.
I now introduce through the vent opening in the top of the furnace a
suitable quantity of the tar-impregnated alumina, which falls down beside the
carbon pencil and into the arc, where it is immediately heated thereby to an
exceedingly high temperature. The first effect of the heat is to drive off the
moisture and volatile elements of the hydro-carbon still contained in the. tar-
impregnated alumina. This action is shown by the black smoke that immediately
issues from the vent opening. Immediately thereafter a series of violent explosions
occur within the furnace. Presumably these are due to the formation of carbon
monoxide or dioxide caused by the combination of the carbon from the tar with the
oxygen of the alumina, a combination which apparently takes place with great.
rapidity at the inconceivably high temperature existing within the furnace.
aluminium which is thus freed is immediately alloyed with the copper which
under the high temperature in the furnace exists in the condition of a molten bath
in a state of violent ebullition, with its vapors streaming through the arc.
The
The feeding in of the tar-impregnated alumina is kept up as long as it is desired
to operate the process, granulated copper being also added from time to time,..
preferably in alternation with the impregnated alumina. The resulting aluminium
bronze may also be tapped off from the furnace from time to time without stopping.
the operation.
By practicing this process, I have obtained a greatly increased output of
aluminiuin reduced, as compared with any other electric process of reduction.
With the same current and under the same electro-motive force I have obtained
over twice the product of reduced aluminium in a given length of time that I have
been able to obtain by any other process of electric smelting of alumina. In
practicing electro-thermic reduction in an arc furnace I employ no granulated or
pulverized carbon within the furnace, nor is any other reducing agent introduced
than that contained in the tar-impregnated alumina. The reactions in my process
are more rapid and violent than in any other electric-smelting process, thereby
resulting in the reduction of a greater quantity of aluminium for a given expenditure
of electrical energy. I attribute this important economic advantage of my process
to the fact that the alumina and the reducing agent are brought into the closest.
atomic proximity that is possible by mechanical means-that is to say, by any
means short of effecting a new chemical combination. Thus each particle of
alumina contains inseparably within itself the elements necessary for its own
reduction. In this important respect my improved process differs from all
processes of electric smelting or reduction heretofore practiced or suggested.
The use of tar or pitch as a reducing agent is advantageous because of its
cheapness, but other hydro-carbons are equally applicable. In using paraffine or
any heavy hydro-carbon, I proceed in the same manner as describe.l with tar, the
hydro-carbon being boiled and the alumina stirred into it. In using the lighter

page_text: hydro-carbons which are sufficiently fluid at ordinary temperatures, the boiling is
unnecessary. I have used ordinary kerosene oil as the reducing agent by simply
mixing it with the alumina so that the alumina absorbs or becomes saturated with
the oil, and then feeding the oil-impregnated alumina immediately into the
furnace.
In the impregnation of the alumina with a hydro-carbon the latter, I believe,
permeates the pores of the minute particles of alumina, and by subsequent heating
or drying the hydro-carbon is more or less distilled, the lighter hydro-carbons
being cracked off and leaving a residue of precipitated carbon and of heavy
hydro-carbons within and upon the particles of alumina. The reducing agent thus
applied to the alumina is hence partly disseminated within it porous structure and
partly applied as an exterior coating.
In the case of alumina in a less porous condition than precipitated alumina, the
liquid reducing agent may not penetrate the substance of the alumina to any
considerable extent, or may in fact be applied only. to the exterior thereof; but
in such case, if the alumina shall have been reduced by grinding to an impalpable
powder, or otherwise sufficiently subdivided or pulverized, and then introduced and
soaked into the liquid reducing agent, the coatings of reducing agent thus applied
around and between the minute particles of alumina will constitute an impregnation
thereof with reducing agent in the sense of my invention, and to equivalent effect
to the permeating of porous alumina with the reducing agent.
My invention is not limited in its application to the reduction of aluminium, but
is equally applicable to other difficultly reducible metals or ores.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
3
1. The process of reduction of a pulverized metallic compound which consists in
so impregnating or treating it with a reducing agent that substantially each
particle shall carry with it the agent for its reduction, and subjecting the compound
so treated to the heating action of an electric current, in substance as specified.
2. The process of reduction of a pulverized metallic compound, which consists in
first impregnating it with a reducing agent by saturating it therewith while the
latter is in liquid condition and then subjecting the impregnated compound to the
heating action of an electric current, in substance as specified.
3. The process of reduction of a pulverized metallic oxide, which consists in
first impregnating it with a reducing agent in the nature of a hydro-carbon which is
liquid when heated, by introducing the oxide into a heated bath of the reducing
agent until sufficient of the latter has been absorbed by the metallic compound,
then drying the latter by heat, and finally subjecting the impregnated compound to
the heating action of an electric current, in substance as specified.
4. The process of reduction of a pulverized metallic oxide, which consists in
introducing it into boiling coal-tar or pitch, drying it by heat to expel the volatile
constituents of the tar or pitch, and then subjecting the impregnated oxide to
electric smelting in substance as specified.
Dated this 21st day of August 1893
J. C. MEWBURN,
55, Chancery Lane, London, Chartered Patent Agent.