Process and Apparatus for Classing Pulverised Ores by Air Currents.
Year: 1892

page_text: Date of Application, 6th Oct., 1892
Complete Specification Left, 22nd Mar., 1893-Accepted, 20th May, 1893
PROVISIONAL SPECIFICATION.
A Process and Apparatus for Classing Pulverised Ores by Air
Currents.
We, GUSTAV HENOCH, of Gotha, in the Empire of Germany, Mining Engineer,
and EDMOND MAURICE COMTE EXELMANS, of No. 62 Avenue du Bois de
Boulogne, Paris, France, do hereby declare the nature of this invention to be as
follows:-
ores.
Various attempts have been made to employ air instead of water for classing
The apparatus suggested for this purpose have been based on those used
for cleaning grain by directing wind across the grain falling from a hopper. As a
result of observation and study devoted to the application of a like principle to
the separation and concentration of ores, we have come to the conclusion that two
conditions are essential to success.
We have proved that first of all it is necessary to class by bulk ores previously
crushed, that is to say to subject to the wind apparatus only such granules as have
We have then found that it was necessary to
as nearly as possible the same size.
repeat several times, that is to say, to multiply the action of the wind upon the
same quantity of ore, in order to correct the irregularities presented by pulverised
ore in respect of the shapes of its granules or of their agglomeration as they issue
from the distributing hopper.
Such are the conditions which are fully met by our system of classing in the dry
way which forms the subject of our present invention.
According to our system, the ores after having been dried (should that be neces-
sary in consequence of the moisture with which they are generally charged), are
crushed, then separated according to the sizes of the granules by suitable sifting
apparatus such as the cylindrical screen used for wheat.
The granules then fall into a hopper which leads them to the wind classing
apparatus.
is
This classing apparatus, the principal object of our invention is based on the
principle mentioned above, repeated action of the wind, and, for this purpose
divided into several superposed chambers, each consisting of cases or compartments
which are of hopper form with slits at the bottom so that the contents of the
compartments of one chamber can descend through the chamber below.
The granules of ore all horizontally driven by the wind as they descend from the
feed hopper begin to separate according to their density or specific weight into the
compartments of the first chamber, but, instead of remaining there, they fall
successively from chamber to chamber, thus being several times subjected to the
action of horizontal wind currents, and it is not until the granules reach the lowest
chamber that they are definitely classed.
Our invention therefore is based on the principle of the falling of the ore in
a cascade subject to the repeated action of the wind in the various storeys of the
apparatus.
By treating ores as above described great concentration is rapidly effected, and
all the advantages resulting from the use of air instead of water are obtained.
Thus concentration can be effected in a manner which admits of the precious
deposits being continually watched, and which provides against the floating away
of the finer particles.
Moreover, by the wind system of concentration there is no danger of any

page_text: granules being entangled in gangues of clay or kaolin, and as the concentration
can be carried on in places where there is no water, it can be effected on the spot
where the ore is obtained, the cost of transport of crude ore being thus largely
economised.
Dated this fith day of Oarabar 1805
ABEL & IMRAY,
Agents for the Applicants.
COMPLETE SPECIFICATION.
A Process and Apparatus for Classing Pulverised Ores by Air
Currents.
We, GUSTAV HENOCH of Gotha in the Empire of Germany, Mining Engineer,
and EDMOND MAURICE COMTE EXELMANS, of No. 62 Avenue du Bois de
Boulogne, Paris, France, 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 :-
ores.
Various attempts have been made to employ air instead of water for classing
The apparatus suggested for this purpose have been based on those used
for cleaning grain by directing wind across the grain falling from a hopper. As a
result of observation and study devoted to the application of a like principle to
the separation and concentration of ores, we have come to the conclusion that two
conditions are essential to success.
We have proved that first of all it is necessary to class by bulk ores previously
brushed, that is to say to subject to the wind apparatus only such granules as have
as nearly as possible the same size. We have then found that it was necessary to
repeat several times, that is to say, to multiply the action of the wind upon the
same quantity of ore, in order to correct the irregularities presented by pulverised
ore in respect of the shapes of its granules or of their agglomeration as they issue
from the distributing hopper.
Such are the conditions which are fully met by our system of classing in the dry
way, which forms the subject of our present invention.
According to our system, the ores after having been dried (should that be
necessary in consequence of the moisture with which they are generally charged),
are crushed, then separated according to the sizes of the granules by suitable sifting
apparatus such as the cylindrical screen used for wheat. The granules then fall
into a hopper which leads them to the wind classing apparatus. This classing
apparatus, the principal object of our invention is based on the principle mentioned
above, repeated action of the wind, and, for this purpose it is divided into several
superposed chambers each consisting of cases or compartments which discharge
those of one chamber into those of another. The granules of ore all horizontally
driven by the wind begin to separate according to their density or specific weight
into the compartments of the first chamber, but instead of remaining there they
fall successively from chamber to chamber thus being several times subjected to the
action of the wind. It is not until the granules reach the lowest chamber that they
are definitely classed. Our invention therefore is based on the principle of the
falling of the ore in a cascade subject to the repeated action of the wind in the
various storeys of the apparatus.
The construction and operation of apparatus according to our system will be
understood on reference to the accompanying drawing.
In Sheet 1, Fig. 1 is an elevation, Fig. 2 is a vertical section and Fig. 3 is a plan
shewing a complete set of our apparatus.
M is the sifter, which may be of any known kind capable of sorting the ore
according to several sizes or qualities, for instance six. The sifter is placed above
classing apparatus A' A' A³ on our system which as shewn are arranged vertically
side by side so as to receive the different sizes 1, 2, 3 of the ore granules which are

page_text: conveyed by the several travelling aprons P1 P2 P³ to the hopper T' T² T" of the
dry classing machines.
In Sheet II, Fig. 4 is a longitudinal section and Fig. 5 is a transverse section of one
of these machines.
It consists substantially of a long casing A which may be about 5 metres
long and 30 c.m. broad, divided as mentioned above into several chambers B B B
each of which is subdivided into compartments C C C having their sides
inclined like funnels with slits at the bottom to allow the ore to fall through into
the compartment below. The air at a pressure suited to the character of the ore,
is supplied by a fan D or, if necessary, by a blower, and is directed into the
casing A in several currents separated by partitions of the space F. The pressure
or velocity of the air currents in the several passages is regulated by the register G
shewn separately in Fig. 6, consisting of several plates or grids with graduated
apertures so as to vary the wind force according to the effect required in each
chamber. In some cases a plate damper may be employed to throttle more or less
the air passage.
According to the preceding explanation the action of the apparatus may be
readily understood. The one falling from the hopper T, its discharge from which
is facilitated by the revolving roller S, is caught in the first chamber by the air
current below the hopper and thus each granule is driven to a distance corresponding
with its density, the heaviest falling in front and the lightest behind. But instead
of remaining in the first compartments, in which they are already partially classed,
the granules fall from these into the compartments of the chamber below, meeting
in their fall the second air current which farther separates them. The separation
is completed by the third and fourth air currents in the two lowest chambers, and
finally the granules in the cases of the lowest chamber which are open at the bottom
or may be closed by spring doors which are opened automatically by the weight of
a certain charge.
To give an idea of the efficacy of our classing apparatus, we give an example of
the results of trials made with the apparatus on two kinds of ore, the one of silver,
the other of gold and silver. These results are shewn in the two following tables
which explain themselves.
In the boxes 1, 2, 3,
4, 5, 6 there are 79.4%
of the silver and a reduc-
tion of the mass to 10%
In the boxes 1, 2, 3,
4, 5 6 and 7 there are
90-9% of the silver and
reduction of the mass to
16.9%

page_text: By the above figures it is seen that a great enrichment of the ore and simul-
taneously a considerable reduction of the mass are obtained, an advantage besides
those resulting from the use of air instead of water, which are the following.
1. By this system the classing can be effected anywhere even in countries void of
water.
2. The dry treatment is preferable to the moist because it allows watching of the
deposited products, particularly precious metals such as gold and silver. It avoids
the inconvenience of the levigating process which allows of the very fine particles
floating and becoming lost.
3. By the dry method, mud is avoided and the pasting of the granules in the
gangues when they consist of clay or kaolin.
4. Finally the classing by the air allows the enrichment to be effected on the
spot, that is to say at the mine thus economising the transport of the ore to the
refining establishment.
These advantages will be especially appreciated in applying our system to the
cleansing and classing of gold bearing ores and sands, phosphates &c.
Having now particularly described and ascertained the nature of our inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The herein described process for classing crushed dried and sized ores by
subjecting them to the repeated action of air currents so as to separate the granules
according to their densities.
2. The apparatus for conducting the said process, consisting of a casing divided
into several superposed chambers, themselves divided into several compartments
which discharge from one to another and finally into those of the lowest chamber,
substantially as described.
Dated this 22nd day of March 1902