A New or Improved Process for Concentrating Iron Ore.
Year: 1890

page_text: COMPLETE SPECIFICATION.
A New or Improved Process for Concentrating Iron Ore.
I, REGINALD HADDAN, of the firm of Herbert & Co., Patent Agents, of
18, Buckingham Street, Strand, W.C., London, Civil Engineer, do hereby declare
the nature of this invention a communication to me from abroad by Gurdon
Conkling, of Glens Falls, in the State of New York, United States of America,
Manufacturer, 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 a new process for concentrating ore containing iron, said
process being pointed out in the following Specification and claim. The accompanying
drawing represents in Figure 1, a longitudinal vertical section of a magnetic separator
which may be used in carrying out a certain part of the process, and Figure 2, is a
plan or top view of another magnetic separator which may be used in carrying out
another part of the invention.
If a man comes in possession of a mine, his first question is can I work this mine
with a
profit? If he finds that he can, he works the mine, but if he finds that he will
lose rather than profit, ho will let the mine lay idle. The object of this invention is
to reduce the cost of concentrating iron ore to such an extent, that iron mines which
heretofore could not be worked without loss, can be worked with a profit.
It is a well known fact that iron ores differ very much in their granular formation
and in their richness of iron. The granular formation of some ores is such that cubes
of, say, a quarter of an inch and under, contain comparatively pure ore, while with
other ores the granular formation is such that the cubes formed of pure ore are equal
to the twentieth or even the thirtieth part of an inch. It is also a well known fact
that the cost of crushing ore depends upon the fineness to which the ore is to be
crushed and furthermore the longer the crushing operation is continned, the larger
becomes the quantity of powdered or flowered ore produced by the crushing operation
and that this powdered ore entails a great loss in the percentage of pure ore obtained
by the process of concentration. For instance, the cost of crushing iron ore to half
an inch is, say, 10 cents. per ton, the cost of crushing the same ore to a quarter of an
inch is 20 cents per ton, and the cost of crushing the same to one-eighth of an inch
is 45 cents per ton and at the same time in carrying on the crushing operation to an
eighth of an inch a large quantity of powdered ore is produced, which is extremely
difficult to save and the consequence is a loss in money and in ore.
In carrying out my process with an iron ore, the granular formation of which is
such that cubes of say a quarter of an inch and under are formed of pure ore I pro-
ceed as follows: 1 first crush the ore to a quarter inch (such fineness being necessary
because in being crushed the lumps of ore do not split upon exact lines of granular
formation above stated) and then 1 expose the crushed mass to the action of strong
magnets, so that not only fragments which consist of puro iron ore will be attracted
but also all the fragments which are composed of a large percentage of gangue and a
small percentage of iron ore and consequently the gangue which passes away as
tailings in the process of concentrating contains very little iron ore. In carrying
out this part of the process an apparatus may be used, such as illustrated in
Figure of the drawing, in which the letter A designates the endless belt which
extends over rollers B B¹, and is placed in an inclined position. F is a magnet
which is situated in the interior of the belt A close upon its upper branch. E is
a trough over which the crashed ore mixed with water is fed to the belt A, and
S is a spray pipe for washing the particles of ore which are attracted by the
magnet. The belt moves in the direction of arrow 1 and the particles which are
attracted by the magnet are carried by the belt A over the pulley B and are collected
in the receiver L. The particles which are not attracted by the magnet, run down
over the pulley B' and are collected in the receiver K. The mass which has been

page_text: attracted by the magnets and collected in the receiver L is composed of particles from
a quarter of an inch down and many of the larger particles contained in this mass are
composed of iron ore and gangue still attached and not having been mechanically
separated in the crushing process, and in order to eliminate this gangue from the
mass I submit the same to a second crushing operation and the re-crushed mass
is then exposed to the action of magnets. The mass to be treated in this second
crushing operation is considerably smaller than the mass which is to be treated in the
first crushing operation and it can be crushed to say one-eighth of an inch in a com-
paratively short time. But in order to reduce the mass which is to be re-crushed
still further I select screens the meshes of which will permit cubes of say an eighth
of an inch or under to pass through, while they refuse the lumps of larger size and [
pass the entire mass from the receiver I, to these screens. The coarser particles
refused by the screens are then re-crushed to say one-eighth of an inch and again
submitted to the action of magnets.
From this explanation it is apparent that the bulk of the mass which has to be
re-crushed is much smaller than the bulk of the mass which must be treated in the
first crushing operation and if it should be attempted to crush the entire mass in
the first crushing operation to an eighth of an inch, the cost of the crushing opera-
tion would be more than doubled and at the same time a large quantity of
powdered ore would be produced and the consequence would be a loss in money
and in iron ore which in many cases would be fatal to the working of a mine
from an economical point of view.
The oporation of re-crushing the particles refused by the screens can be effected
in a comparatively short time and very little if any powdered ore is produced
since the mass which is to be re-crushed consists of particles of a quarter of an inch
and under, each particle containing a greater or less amount of iron ore and the bulk
of this entire mass is small, say one-eighth of the bulk of the mass which must
be treated in the first crushing operation.
For the purpose of exposing the re-crushed mass to the action of magnets,
I can use with advantage an apparatus such as shown in Figure 2, of the drawing.
This apparatus consists of a main belt A and the secondary belt which extends
at right angles over the main belt A and in the interior of which close to its
lower branch are situated the magnets F F. The mass to be separated is fed to
the main belt A through the hopper E and the magnetic particles which are
attracted by the magnets F are carried away by the belt C in the direction of
arrow 1 while the gangue which remains on the belt A is carried away in the
direction of arrow 2.
From the foregoing example it will be readily understood that before the concen-
trating process is applied to a given quantity of iron ore, it is first necessary to find
out the largest natural granular formation of the ore in order to be able to determine
the finoness to which the oro is to be crushed in the first and afterwards in the second
crushing operation.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
The process of concentrating iron ore which consists in first coarsely crushing the
ore to a size required by its natural granular formation without reducing any con-
siderable proportion of the ore to dust, then concentrating the ore by the action of
magnets, then screening this concentrate to separate the richer ore, then re-crushing
the ore refused by the screen and finally concentrating the re-crushed ore by the
action of magnets, substantially as described.
HERBERT & Co.,
18, Buckingham Street, Strand, London, W.C., Agents to Applicant.