An Improved Method or Process of Extracting Metals from Pulverized or Finely Divided Ores or Compounds.
Year: 1897

page_text: Date of Application, 7th Dec., 1897-Accepted, 22nd Jan., 1898
An Improved Method or Process of Extracting Metals from
Pulverized or Finely Divided Ores or Compounds.
We, JOHN RUDOLPHS and JOHN LANDIN, of 40, Drottninggatan, Stockholm,
Sweden, Engineers, 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 an improved method or process of extracting metals
from their oxide-ores or other oxygen-compounds by dry reduction in heat.
Our improved method or process consists in first mixing the metalliferous raw
materials, in a pulverized or finely divided state, with pulverized or
finely divided carbon and such solid, or liquid, nitrogenous and hydro-
carbon-containing materials in a finely-divided state as, on subsequent
moderate heating to about from 300 to 500 degrees Centigrade, will
cause the mixture to change its aggregate state and form a uniformly caked
inass. As examples of the latter substances may be mentioned blood-charcoal
or other kinds of carbon which are rich in nitrogen, or products of distillation
obtained from such carbons, ferrous or ferric cyanic compounds (mixed with
materials containing hydrocarbon), dried and ground blood, leather or horn, etc.
The mixture thus obtained is subsequently heated in the shape either of lumps
or of pieces of definite shape (briquettes, for instance), preferably after being
previously compressed and while under pressure, so as to cause it to change its
aggregate state and assume the form of a uniformly caked mass, the oxygen-
compounds of the metal being thus surrounded by a dense vitreous envelope.
This mass (with or without previous and more intense heating) is used as a
charge in the furnace where the extraction of the metal is to take place. Where
the character of the metalliferous raw-material so demands in order that a
fusible slag may be formed from the impurities contained, there is added to the
mixture, previous to its preparatory heating for effecting its aggregate change,
some suitable flux (lime, for instance) for ores rich in silicic acid, etc.
With ores containing impurities having deleterious effects on the properties of
the metal, such substances are also added as will combine with the said impurities
and thus remove them from the metal, for instance, with phosphorous ores, car-
bonate of soda, etc. The products of distillation escaping during the heating
operation are condensed and collected to be again utilized as a flux for fresh
mixtures of the metalliferous raw-material with carbon.
Having thus generally outlined the invention, we will now proceed to describe
the methods followed in obtaining specific metals, a beginning being made with
iron, which can in this manner be produced in a malleable state, or with a
higher or lower percentage of carbon, at will.
Particularly suited for use in the extraction of iron by this method, is so-
called separated ore, which already during the separating process must be in a
finely divided state, and also bog-ore. As an example, ore of the former kind may be
taken. For the sake of simplicity it may also be assumed that the ore belongs

page_text: to that class of ores whose constituents of rock are capable of forming a liquid
slag without the addition of either basic or sour or acid substances. The reverse
being the case, the necessary fluxes would have to be added as required according
to the results of an analysis made in accordance with well-known principles in
each individual case, the materials thus added likewise being in a finely-divided,
solid or liquid (i.e. molten) state. To an ore of the description previously men-
tioned containing, for instance, 65 per cent. of iron corresponding to 89.7 per
cent. of magnetic oxide of iron, there may, for the production of iron containing
about 2 per cent. of carbon, advantageously be added, for each 1000 kilograms of
ore, 180 kilograms of finely divided anthracite, 30 kilograms of coal-tar and
15 kilograms of dry-blood, z.e. dried and ground blood. In place of anthracite,
coals richer in nitrogen may be used, a smaller quantity of dry-blood being then
required. Another mixture by which good results may be obtained, is composed
of 1000 kilograms of ore of the kind before mentioned, 180 kilograms of finely-
divided anthracite or coke, 35 kilograms of coal-tar and 7 kilograms of finely-
divided ferrocyanide of potassium (prussiate of potash). On being mixed the
materials are suitably formed into briquettes in a press, and in the compressed
state they are heated to about 400 degrees Centigrade, at which temperature the
mixture changes its aggregate state, a uniformly caked mass being obtained.
This caked mass, preferably while hot, is subsequently charged into a smelting.
furnace where the reduction of iron takes place. If it is desired to produce iron
with less than 2 per cent. of carbon, the coal added as above mentioned is reduced
in quantity, and when iron of a higher percentage of carbon is desired, the
quantity of coal thus added is increased. The added material containing nitrogen
and hydrocarbons form, during the heating operation, products of distillation,
which latter are condensed and again utilized in place of tar as additions for fresh
quantities of iron ore, the proportion of dry-blood or ferrocyanide of potassium
being then reduced according to the percentage of nitrogen in the products of
distillation obtained.
Another metal in the extraction of which our improved process may be advan-
tageously employed, is aluminium. According to the methods hitherto adopted
for extracting this metal in an electric furnace, a pulverized mixture of the
raw materials has been introduced between the electrodes in the furnace. The
aluminous raw materials used have been alumina (usually bauxite) generally
in conjunction with fluorides (cryolite, etc.) as a flux. Electrolysis of fluoride of
alkali is then assumed to take place, in such a manner that alkali metal is
separated and acts to separate metallic aluminium from fluoride of aluminium
while the fluoride reacts on alumina, re-forming fluoride of aluminium, etc.,
alumina besides being reduced at the carbon anode. According to the improved
method herein referred to, the aluminous raw-material is mixed with finely-
divided carbon and a material containing nitrogen and hydrocarbons, for instance,
blood-charcoal and coal-tar rich in nitrogen. With bauxite, the mixture is
so proportioned as to make its percentage of carbon correspond to the oxygen
contained in the aluminous raw-material. It has been found that a suitable
mixture is formed by adding 25 kilograms of finely-divided anthracite, 10
kilograms of coal-tar and 5 kilograms of dry-blood to each 100 kilograms of
finely-divided alumina. After thoroughly mixing the ingredients mentioned, the
mixture is pressed into briquettes, strips or strings and subsequently heated, the
products of distillation being collected as before described with regard to iron,
and the caked mass obtained being introduced between the electrodes in an
electric furnace where metallic aluminium is extracted.
In extracting zinc from zinc-spar (carbonate of zinc) or roasted zinc-blende, an
analogous method is followed. The pulverized ore is mixed, for instance, with
finely-divided anthracite, tar and dry-blood in the proportions given for
aluminium, while the total percentage of carbon is adjusted so as to be sufficient
for the extraction of the zinc. The mixture is subsequently compressed and
heated, as before stated for iron and aluminium, and the caked briquettes, strips

page_text: or strings are heated between carbon electrodes in the electric furnace or in any
other convenient manner for the extraction of the zinc.
A similar procedure is adopted also in extracting tin from tin ore, copper from
oxides or roasted copper ores, wolfram from tungstate of lime, etc.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. The extraction of metals from their pulverized or finely-divided oxide-ores
or oxygen-compounds by a method or process in which the said ores or oxygen-
compounds are mixed with finely-divided carbon and with such materials con-
taining nitrogen and hydrocarbons as, on subsequent moderate heating, will
cause the mixture to change its aggregate state and form into a uniformly caked
mass, the said mixture in a compressed state or other suitable condition being
heated, preferably. under pressure, so as to form a mass of the character men-
tioned, which (with or without previous and more intense heating) is reduced
in the furnace where the extraction of the metal is to take place.
'
2. The modification of our invention in which to the mixture of metalliferous
raw-material, carbon and materials containing nitrogen and hydrocarbons, previous
to their being heated to change their aggregate state, there is added such fluxes
in a finely-divided state as will form a liquid slag, in case the metalliferous raw
material alone is incapable of forming such slag, and, where the character of the
raw-material so demands, substances adapted to remove deleterious impurities
from the metal, substantially as hereinbefore described.
3. In the extraction of metals from ores or compounds by our improved method
or process, condensing and collecting the products of distillation escaping while
the mixture of raw-materials is being heated, for the purpose of again utilizing
the said condensed products as additions to fresh mixtures of metalliferous raw-
material and carbon.
DAL 1
D1007
D. YOUNG & Co.,
11 & 12, Southampton Buildings, London, W.C.,
Agents for the Applicants.