IMPROVEMENTS IN TREATING CERTAIN URES AND IN OBTAINING PRODUCTS THEREFKUM.
Year: 1869

page_text: LETTERS PATENT to James Henderson, of Bishopton, in the County
of Renfrew, Scotland, Chemist, for the Invention of "IMPROVEMENTS
IN TREATING CERTAIN URES AND IN OBTAINING PRODUCTS THEREFKUM.
PROVISIONAL SPECIFICATION left by the said James Henderson at the
Office of the Commissioners of Patents, with his Petition, on the
13th November 1869.
I, JAMES HENDERSON, of Bishopton, in the County of Renfrew,
Scotland, Chemist, do hereby declare the nature of the said Invention for
"IMPROVEMENTS IN TREATING CERTAIN OBES AND IN OBTAINING PRODUCTS THERE-
FROM," to be as follows:-
Before the majority of ores are subjected to the process of calcination
they are usually crushed and passed through a sieve (generally about
8 holes to the inch), they therefore consist of a mixture of different
sized particles.

page_text: I have found that when it is simply designed to calcine an ore in an
ordinary furnace to expel the sulphur the fine particles are reduced to
the state of oxide long before the larger particles, and that the fine oxide
dust then adheres to and coats the surface of the larger particles and
prevents the access. of air, and thus retards the process of oxidation.
This difficulty is still further increased when upright furnaces such as
Girstenhoffer's, and still further when revolving furnaces are used. In
the case of the Girstenhoffer furnace, where a steady stream is fed on to the
upper bars, the largest particles, which necessarily require the longest
calcination, are soonest delivered from the furnace, the smallest particles
remaining longest in the furnace.
The theory of the working of a Girstenhoffer is that the ore as fed
into the furnace will gradually pile itself up on the flat surface of the
triangular obstructing bars and then suddenly slip onto the next bar;
in practice this is not the case, the ore, though crushed to pass through
a uniform size of sieve, consists of a large number of different sized
particles, and the result is, as is seen in piling up a heap of gravel and
sand, the sand will reach to a sharp pyramidical form in the centre,
whilst the gravel, according to its size, will form a more or less tailed out
base. So in the working of a Girstenhoffer furnace with different sized
particles running in in a constant stream the large particles, which
actually require the longest calcination, reach the outlet of the furnace
first, while the fine portions, which are more rapidly decomposed, remain
longest in the furnace.
In like manner when such mixed sizes of oro are attempted to be cal-
cined in inclined revolving furnaces with a constant stream of such orc
passing through, I have found that the largest particles pass soonest
through although they require the longest time. These facts of great
importance when applied to the simple climination of sulphur from ores,
have much greater force when it is desired to effect a double decomposition,
as is the case when burnt cupreous ores are decomposed by calcining with
common salt or suitable chloride to render the copper soluble. As in this
process the decompositions can only be effected by the contact of the
particles of the ore and the chloride, and by uniform exposure to the air,
and as the chloride required to effect the decompositions does not
usually form more than 10 to 20 per cent. of the ore with which it is
mixed, it follows that the same particle of ore ought to be brought
in contact with a particle of chloride repeatedly. It is not, however,

page_text: advisable in working to reduce the ore to too fine a powder, as in calcina-
tion in an ordinary furnace with flame and draft playing over it a large
portion of the ore goes into the flues as dust, and the same thing happens
in Girstenhoffer's furnaces to a much greater extent; and if the burnt
cupreous pyrites be reduced to too fine a powder and decomposed-with
salt the after washing out of the soluble copper is effected with great
difficulty.
To effect these decompositions regularly, expeditiously, and perfectly, I
proceed as follows:-I prefer to grind or reduce the ore by itself in an
ordinary Cornish crushing mill, and pass the whole through a sieve cor-
responding to 8 meshes to the inch. The sieve ordinarily in use is a
revolving sieve constructed of thick wires with long rectangular spaces.
I propose to retain these strong sieves as at present, as those constructed
of small wires and divided into squares would not stand the wear and
tear of the rough particles that are returned to the mill. The coarse
powder that has passed through the sieve of 10 holes I then pass
through an ordinary sizing machine, which may consist of a revolving
sieve divided into compartments with different sized sieves or meshes
like an ordinary flour bolting machine, or a series of trays having the
requisite number and size of sieve bottoms, the coarsest uppermost, and
to all of which a shaking, shogging, or knocking motion is imparted,
as is commonly in use for sifting and cleaning grain.
When the ores to be worked are a mixture of salt and burnt cupreous
pyrites I prefer that the top sieve should be one of 10 holes to the lineal
inch or 100 to the square inch, and that all the coarse irregular sized
picces that do not pass through be returned to the mill and re-crushed
generally from 15 to 20 per cent is thus returned. At a suitable distance
below the 10-hole sieve I place one of 20 holes, and below that one of
30 holes, and under that again one of 50 holes. The result is that there
is delivered, into the spout to receive what does not pass through the
meshes, from the 20-hole sieve about 41 per cent., from the 30-hole sieve
about 24 per cent., from the 50-holo sieve about 15 per cent., and in fine
powder that passes the 50-hole sieve about 20 per cent.
The proportions will vary much according to the ore, but the necessity
still exists for separating the particles into their various sizes. Other
sieves of different sized meshes to the above may be substituted when
found to suit the nature of the ore better, and I do not confine myself to
any particular size or arrangement of sieves so long as a classification

page_text: of the particles of the ore is effected. The larger the number of different
sized sieves employed it is obvious that the classification will be more
complete; in practice, however, I believe an arrangement of sieves such
as I have described above will answer all useful purposes. I have found
in practice that when common salt was mixed and crushed with the ore,
if the salt used was in the state of rock. salt, a pretty uniform distribution
was effected through all the sizes of orc, but when crystallized salt was
used the distribution was not nearly so equal. The most certain way to
obtain a proper proportion would be to crush the salt separately, and
size, it by passing it through the corresponding sieves. In many cases,
especially when the proportion of salt used is small and the mixture has
to be calcined in a close or open reverberatory furnace, the salt may bo
crushed or ground to a very fine powder.
Taking, for example, the sized sieves that I havo described it will be
seen that those particles that pass through a 10-hole sieve must have
nearly 25 times the cubic contents of those that pass the 50-hole sieve.
The decomposition that it is purposed to effect can only be effected by
the contact of the particles of the salt and ore and their uniform exposure
to heat and air, and the object in view is to obtain the whole of the
copper in a state of soluble chloride. This process may be carried too far
and a subchloride be formed. It is self-evident that to effect the decom-
positions thoroughly and efficiently the particles should be as nearly
the same size as practicable, and it is absurd to expect such results
from particles when mixed indiscriminately together varying so greatly
in size.
Having classified the crushed ore into its various sizes I find that the
different classes of granular ore, viz., those that are delivered from the
20, 30, and 50 hole sieves, can be worked with the greatest regularity
and exactness in revolving furnaces or in upright furnaces with obstruct-
ing bars, or in ordinary reverberatory furnaces, close or open.. I prefer
to calcine the dust or fine ore that passes through the 50-hole sieve in
a close reverberatory furnace, as from its extreme state of division
it is easily carried away by the draught in an upright furnace or a
revolver.
Each separate sized ore should have a separate furnace. The finer
the ore is the quicker the decompositions are effected, and generally
In great saving of time and much better results are effected by sizing
the are

page_text: When the calcined ore has to be washed to extract the soluble copper
and other soluble salts the various sizes may either be mixed, washed
separately, or placed in layers. If the proportion of fine ore be too great
and interfere with tho washing of the other sizes of ore the excess can be
washed separately in agitators.
By classifying the crushed green pyrites in a similar manner and
calcining with the requisite proportion of common salt the conversion
of the salt into sulphate of soda, and the copper into solublo chloride will
be simultaneously effected.
When the ore to be treated is very rich in sulphur an addition of oxide
of iron or burnt cuprcous pyrites is desirable.
Ores used in these processes should be as free as practicable from silica.
The Spanish or Portuguese raw and burnt ores are very suitable and I
prefer to use them.
SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said James Henderson in the Great Seal Patent Office
on the 13th May 1870.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, JAMES
HENDERSON, of Bishopton, in the County of Renfrew, Scotland, Chemist,
send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Thirteenth day of November, in the year
of our Lord One thousand eight hundred and sixty-nine, in the thirty-
third year of Her reign, did, for Herself, Her heirs and successors, give
and grant unto me, the said James Henderson, Her special licence that I,
the said James Henderson, my executors, administrators, and assigns, or
such others as I, the said James Henderson, my executors, administrators,
and assigns, should at any time agree with, and no others, from time
to time and at all times thereafter during the term therein expressed,
should and lawfully might make use, exercise, and vend, within the United
Kingdom of Great Britain and Ireland, the Channel Islands, and Isle
of Man, an Invention for "IMPROVEMENTS IN TREATING CERTAIN ORES AND IN
OBTAINING PRODUCTS THEREFROM," upon the condition (amongst others) that
I, the said James Henderson, my executors or administrators, by an
instrument in writing under my, or their; or one of their hands and

page_text: seals, should particularly describe and ascertain the nature of the said
Invention, and in what manner the same was to be performed, and
cause the same to be filed in the Great Scal Patent Office within six
calendar months next and immediately after the date of the said Letters
Patent.
NOW KNOW YE, that I, the said James Henderson, do hereby declare
the nature of my said Invention, and in what manner the same is to be
performed, to be particularly described and ascertained in and by the
following statement thereof, that is to say:-
Before the majority of ores are subjected to the process of calcination
they are usually crushed and passed through a sieve (generally about
8 holes to the inch), they therefore consist of a mixture of different sized
particles..
I have found that when it is simply desired to calcinc an ore in an
ordinary furnace to expel the sulphur the fine particles are reduced to
the state of oxide long before the larger particles, and that the fine oxide
dust then adheres to and coats the surface of the larger particles and
prevents the access of air, and thus retards the process of oxidation.
This difficulty is still further increased when upright furnaces such as
Gerstenhoffer's, and still further when revolving furnaces are used. In
the case of the Gerstenhoffer furnace, where a steady stream is fed on to
the upper bars the largest particles, which necessarily require the longest
calcination, are soonest delivered from the furnace, the smallest particles
remaining longest in the furnace.
The theory of the working of a Gerstenhoffer is that the ore as fed
into the furnace will gradually pile itself up on the flat surface of the
triangular obstructing bars, and then suddenly slip on to the next bar;
in practice this is not the case, the ore, though crushed to pass through
a uniform size of sieve, consists of a large number of different sized
particles, and the result is, as is seen in piling up a heap of gravel and
sand, the sand will reach to a sharp pyramidical form in the centre,
whilst the gravel, according to its size, will form a more or less tailed
out base. So in the working of a Gerstenhoffer furnace with different
sized particles running in a constant stream the large particles, which
actually require the longest calcination, reach the outlet of the furnace
first, while the fine portions, which are more rapidly decomposed,
remain longest in the furnace.

page_text: In like manner when such mixed sizes of ore are attempted to be
calcined in inclined revolving furnaces with a constant stream of such
ore passing through I have found that the largest particles pass soonest
through, although they require the longest time. These facts, of great
iniportance when applied to the simple elimination of sulphur from ores,
have much greater force when it is desired to effect a double decom-
position, as is the case when burnt cupreous ores are decomposed by
calcining with common salt or suitable chloride to render the copper
soluble. As in this process the decompositions can only be effected by
the contact of the particles of the ore and the chloride and by uniform
exposure to the air, and as the chloride required to effect the decom-
position does not usually form more than 10 to 20% of the ore with
which it is mixed, it follows that the same particle of orc ought to be
brought in contact with a particle of chloride repeatedly. It is not
however advisable in working to reduce the orc to too fine a powder, as
in calcination in an ordinary furnace with flame and draught playing.
over it a large portion of the ore goes into the flues as dust, and the same
thing happens in Gerstenhoffer's furnaces to a much greater extent;
and if the burnt cupreous pyrites be reduced to too fine
powder and
decomposed with salt the after washing out of soluble copper is effected
with great difficulty.
To effect these decompositions regularly, expeditiously, and perfectly,
I proceed as follows:-I prefer to grind or reduce the ore by itself in an
ordinary Cornish crushing mill, and pass the whole through a sieve
corresponding to 8 meshes to the inch. The sieve ordinarily in use is a
revolving sieve constructed of thick wires with long rectangular spaces.
I propose to retain these strong sieves as at present, as those constructed
of small wires and divided into squares would not stand the wear and
tear of the rough particles that are returned to the mill. The coarse
powder that has passed through the sieve of 8 holes I then pass through
an ordinary sizing machine, which may consist of a revolving sieve divided,
into compartments with different sized sieves or meshes like an ordinary.
flour bolting machine, or a series of trays having the requisite number:
and size of sieve bottoms, the coarsest uppermost, and to all of which a.
shaking, shogging, or knocking motion is imparted, as is commonly.in.
use for sifting and cleaning grain.
When the ores to be worked are a mixture of salt and burnt cupreous
T
15

page_text: inch, or 100 to the square inch, and that all the coarse irregular sized
pieces that do not pass through be returned to the mill and re-crushed;
generally from 15 to 20 per cent. is thus returned. At a suitable
distance below the 10-hole sieve I place one of 20 holes, and below that
one of 30 holes, and under that again one of 50 holes. The result is
that there is delivered into the spout to receive what does not pass
through the meshes, from the 20-hole sieve about 41%, from the 30-holo
sieve about 24%, from the 50-hole sieve 15%, and in fine powder that
passes the 50-hole sieve about 20%.
The proportions will vary much according to the ore, but the necessity
still exists for separating the particles into their various sizes. Other
sieves of different sized meshes to the above may be substituted when
found to suit the nature of the ore better, and I do not confine myself to
any particular size or arrangement of sieves so long as a classification of
the particles of the orc is effected. The larger the number of different
sized sieves employed it is obvious that the classification will be more
complete; in practice, however, I believe an arrangement of sieves such
as I have described above or a similar arrangement of revolving sieves
will answer all useful purposes. I have found in practice that when
common salt was mixed and crushed with the ore, if the salt used was in
the state of rock salt, a pretty uniform distribution was effected through
all the sizes of ore, but when crystallized salt was used the distribution
was not nearly so equal. The most certain way to obtain a proper
proportion would be to crush the salt separately, and size it by passing
through the corresponding sieves. In many cases, especially when the
proportion of salt used is small and the mixture has to be calcined in a
close or open reverberatory furnace, the salt may be crushed or ground
to a very fine powder, or may even be dissolved partially or wholly and
mixed with the crushed or uncrushed ore.
Taking, for example, the sized sieves that I have described it will be
seen that those particles that pass through a 10-hole sieve must have
nearly 25 times the cubic contents of those that pass the 50-hole şieve.
The decomposition that it is purposed to effect can only be effected by
the contact of the particles of salt and ore and their uniform exposure
to heat and air, and the object in view is to obtain the whole of the
copper in a state of soluble chloride. This process may be carried too
far and a sub-chloride be formed. It is self evident that to effect the
decomposition thoroughly and efficiently the particles should be as

page_text: nearly the same size as practicable, and it is absurd to expect such
results from particles when mixed indiscriminately together varying so
greatly in size.
:
Having classified the crushed ore into its various sizes I find that the
different classes of granular ore, viz., those that are delivered from the
20, 30, and 50 hole sieves, can be worked with the greatest regularity
and exactness in revolving furnaces, or in upright furnaces with
obstructing bars, or in ordinary reverberatory furnaces close or open.
I prefer to calcine the dust or fine ore that passes through the 50-hole
sieve in a close reverberatory furnace, as from its extremo state of
division it is casily carried away by the draught in an upright furnace or
a revolver. Each separate sized ore should have a separate furnace.
The finer the orc is the quicker the decompositions are effected, and
generally a great saving of time and much better results are effected by
sizing the orcs.
When the calcined ore has to be washed to extract the soluble copper
and other soluble salts the various sizes may cither be mixed, washed
separately, or placed in layers. If the proportion of fine ore be too great
and interfere with the washing of the other sizes of ore the excess can be
washed separately in agitators.
By classifying tlic crushed green pyrites in a similar manner and
calcining with the requisite proportion of common salt the conversion of
the salt into sulphate of soda, and the copper into soluble chloride, will
be simultaneously effected.
When the ore to be treated is very rich in sulphur an addition of
oxide of iron or burnt cuprcous pyrites is desirable.
Orcs used in theso processes should be as free as practicable from
silica. The Spanish or Portuguese raw and burnt ores are very suitable,
and I prefer to use them.
These improvements are applicable to all ores from which it is desirable
to climinate the sulphur or arsenic, and I recommend the careful sizing
of crushed ores prior to all attempts at calcination. In like manner to
obtain the best and most perfect results in reducing oxides to the metallic
state (whether the reducing agent is applied in the solid or gaseous
state) I prefer to obtain the oxides to be reduced in particles of a
uniform size as near as practicable.

page_text: In any process for the conversion of one compound into another by
the mixture of a third, and where such decomposition is produced by
heating in a dry state with or without exposure to currents of heated
air, I have found that the best and most perfect results aro obtained
by carefully sizing the particles of the substance to be so operated
upon,
And having now described the nature of my said Invention, and in
what manner the same is to be performed, I desire to claim as my
Invention, and consider to be novel in this my Specification, subdividing
particles of crushed ore into given sizes and subjecting them to the
action of heat separately in a furnace, so that the whole of them are
operated upon or calcined to the same degree, in order to obtain a better
result than heretofore produced, in the manner herein-before described.
And, secondly. I claim the calcination, reduction, or decomposition of
the several sizes or particles of ore separately, substantially, as described.
In witness whereof, I, the said James Henderson, have hereunto set
my hand and scal, this Eleventh day of May One thousand
cight hundred and seventy.