IMPROVE- MENTS IN THE TREATMENT OF REFRACTORY GOLD AND SILVER ORES AND IN APPARATUS THEREFOR
Year: 1887

page_text: Date of Application, 26th Nov., 1887
Complete Specification Left, 22nd Sept., 1888
Complete Specification Accepted, 26th Feb., 1889
and in Apparatus therefor.
I HENRY HUTCHINSON of 90 Cannon Street in the City of London Metallurgical
and Chemical Engineer do hereby declare the nature of his Invention for IMPROVE-
MENTS IN THE TREATMENT OF REFRACTORY GOLD AND SILVER ORES AND IN APPARATUS
THEREFOR to be as follows:
•
This invention has for its object the treatment (by a combination of what is known
as the Dry and Wet Method) of refractory Gold and Silver ores.
Hitherto it has been found impossible to treat what is known as rebellious or
refractory Gold & Silver bearing ores by wet or hydro-metallurgical methods when
such gold or silver is associated with the elements Sulphur, Arsenic, Antimony, or
Tellurium and long experience has proved in practice that in preparing such refractory
gold and sometimes silver ores, for their successful after treatment by the methods
now in use, such as amalgamation and chlorination-a preliminary roasting or calci-
nation has been found necessary, to free such ores from the aforesaid rebellious
elements.
It has been stated by other inventors (Newberry & Vautin) that chlorine under
pressure is the only successful methods of solving the difficult problem of extracting
gold from rebellious gold-bearing ores, but such methods in practice have hitherto
failed,, and such inventors have in every case had resort to a preliminary roasting
or calcination to free the gold preparatory to chlorination to make such inventions
the claimed success.
To accomplish the aforesaid calcination or roasting process more successfully than
has hitherto been done, I construct my calcining furnace in the following way―
Namely.-
To a suitable gas generator I construct a vertical heating chamber and of the
required size, in which I place one or more iron, earthenware or fireclay tubes around
which the burning generator gas is made to play and heats such tubes to the desired
temperature.

page_text: I then send a gentle current of air through the aforesaid highly-heated tubes into
what I call the calcining, oxidising, or chloridizing zone of such furnace.
At the top or sides of this calcining chamber I arrange a suitable vertical hopper,
through which the finely pulverised ores to be calcined (with or without Salt) is
dropped by removing a suitable stopper.
I also arrange in the aforesaid calcining or chloridizing zone or chamber suitable
baffle-plates or shelves, on to which the calcined or chloridized ores falls on their way
to what I call the dust settling or ore chamber-in these chambers I place suitable
division walls to stop or baffle the floating particles of calcined or chloridised ore-
these division walls I use for heat regenerators and build them on the regenerative
principle, and I am thus enabled to utilise such regenerators for the purpose of
heating the air, gas, steam or water required in Metallurgical operations.
I also place in these chambers one or more suitable firebrick shelves to receive the
falling calcined ores.
I also place at the end of the aforesaid dust chambers a suitable damper or dampers
to enable me to close the connexion to and from the chimney and thus direct the
current of heated gases over the top of the aforesaid dust chambers, and under and
through a suitably constructed flue and over such flue I place suitable iron-plates,
through which pass the waste-heated gases. Such plates or drying floor, 1 use to dry
the pulverised ores or salt required by this invention.
I also place other suitable dampers in the gas mains from the gas generators which
dampers I use to divert the combustible gases from the gas generator directly to the
drying floor by which means I am enabled to empty the contents of the dust chambers
through suitable doors placed at the lower part of such chambers-whilst the
burning gases are passing under the drying-floor to the chimney and thus by this
means admitting free access to the dust-chamber, without interfering with the drying
operations.
I use the aforesaid calcining and chloridizing furnace in the following manner-
The finely pulverised gold and silver ores to be freed from Sulphur, Arsenic,
Antimony, or Tellurium are thoroughly dried on the drying floor the said ores (with
or without salt) are then dropped through the hopper-in doing so such ores are
instantly struck by a current of highly-heated air and generator gas-expelling the
aforesaid rebellious elements.
The calcined ore then finds its way to the settling chamber where such calcined ore
may be further exposed to prolonged heating in an atmosphere of highly heated air
and gases. The calcined ore may then be withdrawn, allowed to cool (if found
necessary) and will be found to be in a suitable condition for the treatment by amalga-
mation and chlorination or by other well known processes.
HENRY
HUTCHINSON,
Metallurgical & Chemical Engineor,
90, Cannon Street, London.

page_text: and in Apparatus therefor.
1, HENRY HUTCHINSON of 90 Cannon Street, in the City of London, Metallurgical
and Chemical Engineer, 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 has for its object the dry treatment of refractory gold and silver ores
for the purpose of rendering them capable of being successfully treated by wet methods
for the extraction of the gold or silver or both contained therein.
Hitherto it has been found impossible to successfully treat what are known as
rebellious or refractory (hereinafter called refractory) gold and silver bearing ores by
wet or hydro-metallurgical methods when the gold or silver or both have been
associated or combined with sulphur, arsenic, antimony, or tellurium, and long
practical experience has proved that in preparing such refractory gold and silver ores
for their successful subsequent treatment by the methods now in use, such as amalga-
mation and chlorination, a preliminary roasting or calcination is necessary to free such
ores from the before mentioned elements.
It has been stated by some inventors (Newberry and Vautin) that the employment
of chlorine under pressure is the only successful method of solving the difficult problem
of extracting gold from refractory gold bearing ores but so far as I know that method
has not heretofore proved successful in practice and resort has been had to a
preliminary roasting or calcining operation to free the gold, preparatory to chlori-
nation, to render this method of using chlorine successful.
According to my invention I effect the calcination or roasting of the ore to be
treated in a more successful manner than heretofore by subjecting it whilst in a finely
divided and suspended condition to the oxidizing action of a blast of highly heated air,
mixed or not with steam or water vapour. For carrying out this operation I employ
a calcining furnace of special construction. In this furnace which is connected with a
gas generator of any suitable construction there is formed a vertical heating chamber
in which is or are placed one or more tubes of suitable refractory material such as
iron, earthenware, or fireclay around which the burning generator gas mixed with air
is caused to pass and impart to the tubes the desired high temperature.
At
A current of air is caused to flow through the highly heated tubes into a vertical
calcining chamber which may be called the calcining, oxidising or chloridizing zone
of the furnace but for brevity is hereinafter referred to as the calcining chamber.
the top or sides of this calcining chamber is arranged a suitable hopper and tube
through which the ore to be calcined which is in a finely pulverized condition and
may be mixed with common salt when the òre is silver ore and is to be chloridized is
dropped by removing a suitable plug or stopper.
Within the calcining chamber there are arranged suitable baffle plates or shelves on
to which the ore whilst being calcined successively falls on its way to a dust of settling

page_text: or ore chamber (hereinafter called the settling chamber). This settling chamber is
constructed with divisions or walls to stop or baffle the floating particles of calcined or
chloridized ore and these divisions or walls which divide the chamber into a series of
compartments may be made of considerable thickness and constructed in such a
manner that when heated by the products of combustion and heated' ore they will act
as reservoirs of heat to equalize the temperature of the said chamber after the manner
of the brickwork in regenerative stoves. The divisions or walls may be employed for
heating the air, water or steam required in carrying out the calcining or roasting
operation. Within the dust or settling chamber may be arranged one or more
suitable firebrick shelves to receive the falling particles of calcined ores etc.
A suitable damper or dampers is or are placed at the further end of the settling
chamber for the purpose of closing the flue leading to the chimney and causing the
current of heated gases and products of combustion to pass over the top of the settling
chamber and through a suitably constructed flue, over which is placed a drying floor
constructed of suitable material such as iron plates.
This drying floor serves io dry the pulverized ore, or the salt required in carrying
out the calcining or roasting operation. Suitable valves or dampers arranged in the
gas flues leading from the gas generator, may be used when necessary for causing the
combustiblo gas to pass direct from the gas generator to the flue beneath the drying
floor where it is mixed with air for its combustion. By the construction described
the contents of the settling chamber may be removed through suitably arranged
openings in the floor of the chamber without stopping or interfering with the com-
bustion of the gases under the drying floor or with the exit of the products of
combustion to the chimney. Free access may thus be obtained to the settling chamber
without interfering with the drying operations.
In the accompanying sheet of illustrative drawings.
Fig. 1 is a longitudinal vertical section of a calcining furnace constructed
according to this invention for heating refractory ores of the kind hereinbefore
mentioned.
Figs. 2 and 3 are sectional detail views illustrating a modified construction of part
of the furnace.
Referring to Fig. 1 A is a gas port in communication with a gas main or flue
leading from a gas generator, of any suitable construction and B, B, are ports for
admitting air to effect the combustion of the gas. These gas and air ports are formed
in the lower part of a vertical heating chamber in which is arranged a series of
refractory air heating tubes D through which air is caused to pass from an air inlet
port E and air chamber E to the caleining chamber. The air tubes are heated
externally by the combustion of the generator gas in the heating chamber through
the opposite walls of which the said tubes pass. The chamber F is provided with a
series of baffle plates or inclined shelves G. These plates cause the ore treated to fall
in a zig-zag course through the calcining chamber. H is a hopper through which
dried pulverised ore is fed to the said calcining chamber or zone. I is a tube through
which pulverised ore may be blown by a steam or other suitable blower into the
calcining chamber direct from a pulveriser or grinding apparatus without being
subsequently handled. J, J, are poking holes through which bars may be inserted
for stirring up the ore when necessary to prevent lodgement thereof. K is a tube
through which finely divided common salt may be blown for delivered to the lower
part of the calcining chamber. When the ores treated are to be chloridized, the sult
is introduced in such a manner as to meet a descending shower of the partly de-
sulphurised and sulphated ore. LL are blast pipes or blowers for the introduction of
air to the chambers C and E. M is an opening for the direct passage of gas from
the heating chamber C to the lower part of the calcining chamber F and seitling
chamber ; it is normally closed by a sliding damper that may be drawn out when
it is desired to heat the floor of the settling chamber F¹ direct or when this chamber
is to be used as a calcining chamber.
N. N. are openings in the side of the settling chamber; they are normally closed
by doors.

page_text: 00 are discharging holes in the floor of the said chamber.
P is a flue leading from another furnace A' for heating the bottom of the settling
chamber to assist calcination operations therein when desired.
Qis a damper for controlling a passage between the settling chamber and a flue R
that passes beneath a drying floor S. By means of the damper and flue R the
waste heated gases and products of combustion may be utilized for drying ores and
other substances placed on the drying floor. T is a continuation of the flue R leading
to a chimney. W W are divisions or walls extending downward from the top of the
settling chamber and WW1 are division walls extending upward from the floor
thereof. These walls cause the hot gases and products of combustion to pass in a
zig-zag direction through the settling chamber on their way to the chimney and thus
facilitate the precipitation of any particles of powdered ore that may be carried forward
by the force of the draught. The walls "W' may be formed with air ways and
ports for the admission of air to the settling chamber, as shewn at W or pipes
may be imbedded within the walls as indicated at V V. Through such pipes air
or steam for use in the calcining chamber F may be passed the heat of the walls
being utilized for heating the same. X is a sight hole and Y is a valve for controlling.
the communication between the settling chamber and the flue T' leading to tho
chimney.
In Figs. 2 and 3 the air heating and combustion chamber C in lieu of containing
tubes Das in Fig 1 contains a number of vertical fire brick walls or divisions D
of refractory material arranged at a short distance apart as shewn. A' is a gas main
from a gas generator; and B B air supply ports. D' is a blast pipe for the introduc-
tion of air to the chamber C for use in the calcining chamber F the sides of which aro
formed with inclined surfaces F. F is an opening normally closed by a door.
G is a flue communicating with the settling chamber and H a charging hopper as
before.
His a distributor fixed below the hopper opening for distributing the ore to the
calcining chamber. In Fig. 1 it is of cylindrical form and in Fig. 2 of wedge form.
The operation of the furnace is as follows:-The calcining chamber or zone is first
heated to a suitable temperature by the combustion of the generator gas and then the
ore to be treated, containing sulphur arsenic antimony or tellurium is introduced
therein through the hopper H in a finely pulverized and dried condition. The ore in
its descent through the caleining chamber is constantly subjected to a current of
highly heated air and generator gas which have the effect of completely expelling
the said rebellious elements from the ore, the zig-zag motion imparted to the ore
by the baffle plates Gaiding the operation by retarding the rate of descent and
distributing the oro so that the whole of it may be acted upon by the heated air.
The calcined ore passes to the settling chamber where it may be submitted to a
further heating operation in the presence of the escaping gases and excess of air,
and in the case where common salt (na cl) is introduced through the pipe K for
chloridizing the ore, it will be further subjected to the action of hydrochloric acid
and chlorine produced by the decomposition of the salt. The calcined ore may then
be withdrawn through the opening or openings 0 and if necessary allowed to cool
before being further treated. The ore will then be found to be in a suitable
condition for further treatment by amalgamation, chlorination, bromination, by
solution of hyposulphites, or by other well known processes for the extraction of
the gold or silver or both contained therein.
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:-
1. Treating rebellious or refractory gold and silver bearing ores for the purpose
set forth by subjecting the same whilst falling or passing in a finely divided
condition through a suitable chamber to the direct action of currents of heated air
substantially in the manner described.

page_text: 2. In the process of treating rebellious or refractory gold and silver bearing ores
as referred to in the preceding claim the use of a blower constructed and arranged
to convey the pulverised or disintegrated ore direct from a pulveriser or disintegrator
to the calcining chamber substantially as hereinbefore described.
3. My improved furnace constructed arranged and operating substantially as
hereinbefore described with reference to and shewn in fig. 1 of the drawings
annexed whether the division walls in the settling chamber be formed with or
without conduits for heating air water or steam.
4. The modified construction of furnace substantially as hereinbofore described with
reference to and shown in figs. 2 and 3 of the drawings annexed.
Dated this 22nd day of September 1888.
HENRY HUTCHINSON.
W. Lloyd Wise,
Per J. G. S.,
Applicant's Agent.
HENRY HUTCHINSON.
W. Lloyd Wise,
Per J. G. S.,
Applicant's Agent.