An Improved Furnace for the Treatment of Refractory Ores.
Year: 1891

page_text: Date of Application, 8th June, 1891
Complete Specification Left, 8th Apr., 1892-Accepted, 30th Apr., 1892
PROVISIONAL SPECIFICATION.
An Improved Furnace for the Treatment of Refractory Ores.
I, CHARLES JAMES FAUVEL of 15, George Street, Mansion House, in the
City of London, Assayer and Mining Engineer, do hereby declare the nature of
this invention to be as follows:-
This invention relates to the preliminary treatment of refractory ores of the
precious metals and it consists esentially of an improved furnace whereby the
operation of oxidizing the impurities associated with the ore may be effected
entirely out of contact with the furnace gases so that the ore will not be exposed
to the chemical action of the said gases or be contaminated by the formation of
any carbonaceous deposit therefrom but after undergoing the process of oxidizing
will be delivered in what is technically known as a
sweet "condition.
The furnace is also applicable for chloridizing the silver contained in the ore
for which purpose it is only necessary to add the requisite amount of salt to
the ore.
This improved oxidizing and ore sweetening furnace comprises a furnace of
suitable construction and a tower fitted with a series of inclined bafHes or shoots so
arranged that the pulverised ore supplied at the top of the tower will slide down
the shoots and be delivered from one to the other throughout the whole series and
finally to the first of a series of settling chambers at the bottom of the tower.
These shoots are heated by specially arranged flues running beneath each shoot
and connected by vertical flues at opposite ends with the heating flues of the
shoots above and below so that the products of combustion from the furnace are
caused to follow a zig-zag course through the whole series of flues from the lowest
upwards. The flue of the uppermost shoot communicates with a downflue passing
centrally down the tower to the heating flues in connection with the settling
chambers, the last of these flues leading direct to the chimney so that the furnace
gases do not at any point come into contact with the ore or with the oxidizing
medium.
Above the furnace proper is a heating chamber divided by baffles or partitions
into flues in which atmospheric air admitted through suitable dampers (or oxygen
gas generated in a retort and supplied to the heating chamber) is raised to the
proper temperature. The heated air or oxygen passes from the heating chamber
through suitable flues through the settling chambers to the tower where it meets
the falling orc, passes up through the same carrying away in its ascent the
refractory elements liberated by the intense heat and the direct action of the
heated air or oxygen.
At the top of the tower the oxidizing current passes to a
downflue disposed alongside the downflue for the products of combustion and leading
to a second series of settling chambers all like those of the first series having
inclined sides heated by flues beneath through which the products of combustion
pass, as above mentioned, on their way to the chimney.
The first settling chamber immediately beneath the tower is provided with a
discharge pipe with regulating valve, the pipe being scaled against the inflow of
cold air by dipping into a trough of running water into which the heated particles
of ore are allowed to fall. The sudden cooling of the ore breaks up the
particles and the little explosions produced by the sudden generation of steam frees
the noble metals from any adherent oxides of the base metals or other substances
which would be detrimental to the subsequent amalgamating operation and which
are carried off by the running water. The second of the first series of settling
chambers is for catching any particles of ore that may not settle in the first,
and the second series of settling chambers which are quite independent of the

page_text: first are for intercepting any particles which may be carried off by the oxidizing
current.
In order to ensure a sufficient draught in the chimney to draw the furnace gases
through the whole of the flues above described, a special draught furnace would be
provided near the foot of the chimney and alongside this a gas retort for the
generation of illuminating gas or of oxygen gas when required, in case the air
heating chamber before described should for any reason be out of service.
Dated this 8th day of June 1891
COMPLETE SPECIFICATION.
An Improved Furnace for the Treatment of Refractory Ores.
J, CHARLES JAMES FAUVEL, of 15 George Street, Mansion House, in the
City of London, Assayer and Mining 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 relates to the treatment of refractory ores containing precious
and other metals, and it consists essentially of an improved furnace whereby the
operation of oxidizing the impurities associated with or forming part of the ore
may be effected by a current of hot air entirely out of contact with the furnace
gases so that the ore will not be exposed to the chemical action of the said guses
or be contaminated by the formation of any carbonaceous deposit therefrom, but,
after undergoing the process of oxidizing, will be delivered in what is technically
known as a "sweet" condition.
To accomplish this oxidisement and sweetening it is essential that the current
of air which is to effect the oxidation should not be robbed of its oxygen to
support the combustion of the fire and accordingly the oxidizing current is
separately heated and the passages are so arranged that neither the ore nor the
oxidizing current can at any time come in contact with the products of combustion
of the fuel, whilst the flues for the latter are so arranged as to ensure the
utilization in a rational manner and to the utmost possible extent of the available
heat.
The furnace is also applicable for chloridizing the silver contained in the ore
for which purpose it is only necessary to add the requisite amount of chlorinating
medium to the ore.
This improved oxidizing and ore "sweetening" furnace is illustrated in the
accompanying drawings, forming part of this Specification, and will be described
with reference thereto.
Figure 1 is a longitudinal sectional elevation of the entire furnace.
Figure 2 is a vertical section on line a-a Figure 1.
Figure 3 is a central detail section looking in the reverse direction to Figure 1.
It comprises a fireplace A of suitable construction, an air-heating chamber B,
an oxidizing tower C, settling chambers D, E, E1, E2, and a chimney F, with their
various flues, shoots and other adjuncts constructed and arranged for effecting the
oxidizing operation as hereafter described with reference to the drawings in which
the feathered arrows indicate the course followed by the products of combustion
whilst the featherless arrows indicate the course of the oxidizing current.
The fireplace A is so constructed as to burn any fuel, air holes being provided
in the side walls to admit air and ensure perfect combustion. It is preferably
built in duplicate to give a greater command of heat at starting or whenever
required.
The oxidizing tower C in which the oxidation of the sulphides etc., is accom-
plished is a rectangular brick structure about forty feet high, fitted internally with a

page_text: These
series of inclined fireclay slabs G each slab extending the full width of the
oxidizing chamber and projecting alternately from the opposite walls by which
they are supported as shewn in Figure 1 so that the pulverized ore supplied at the
top of the tower must slide down these slabs in succession, the slabs being so
arranged with regard to each other that the ore will be delivered by each slab on
to the highest part of the next below and so on from one to another throughout
the whole series so that the whole superficial area of the slabs is utilized as beating
surface for the ore which is finally received in the first settling chamber D at the
bottom of the tower. It is beneath the inclined slab d forming one side of this
settling chamber that the greatest heat is developed, this being the point at which
the gases from the furnace enter the flues H H of the oxidizing tower.
flues H extend beneath each of the inclined slabs G and communicate with vertical
Hlues in the end walls of the tower which are so interrupted by cross-par-
titions that the furnace gases will be caused to follow a zig-zag course such as
indicated by the feathered arrows so as to pass through all the flues H in succession
from the lowest upwards, the highest flue H. finally leading into the upper end of
a central downcast flue K leading into a cross-flue L situated beneath the other
inclined slab of the settling chamber D and communicating by a side passage at
the opposite end with a flue M leading direct to the chimney F. None of these
flues has any connection with the interior of the oxidizing tower so that the furnace
gases cannot come in contact with the ore or the oxidizing current, whilst the
course of the furnace gases as well as that of the oxidizing current being upwards,
and inverse to that of the falling ore, the latter is subjected to a gradually
increasing temperature, the maximum degree of heat being attained at the com-
pletion of the operation. In this way the heat is developed and utilised in the
most rational manner for progressively effecting and finally completing the oxidation
of the ore.
Each flue H is enclosed at the underside by a fireclay slab which is also
available as heating surface for the oxidizing current which, in ascending through
the oxidizing tower, strikes against these underside slabs and takes up heat there-
from. The pulverized ore is supplied at the top of the oxidizing tower, by an
automatic feeder (preferably consisting of a fluted cylinder working in a hopper N)
which distributes the ore in the form of a thin stream extending across the whole
width of the tower and falls upon the hot sloping surfaces G rolling down them in
a constant stream, the particles being raised to a state of incandescence by contact
with the slabs. During their passage down the inclined slabs, and in falling from
one to the next, the ore particles encounter an abundant upward stream of hot air
supplied from the air heater B. The air heater is situated above the fire place A
and is divided by baffles and provided with air inlets furnished with dampers
to regulate the air supply to suit the ore under treatment. The air having been
heated to the proper temperature passes out of the heater through lateral and
cross flues B B B, as indicated by the featherless arrows, into the upper part of
the first settling chamber D and flows up through the oxidising tower meeting the
incandescent particles of falling ore, checking their descent and scattering them in
such a way that no particle can escape the complete oxidation and removal of its
associated sulphur, arsenic, antimony or tellurium compounds. Moreover, the
stream of heated air on entering the first settling chamber D not only helps by its
own temperature, and by perfecting the oxidation at that point, to raise the
temperature of the ore to the highest degree just where the greatest heating effect
is needed but the air is in the purest possible condition on meeting the ore at the
moment when it approaches the completion of its oxidation, so that the culminating
points of the heating and oxidation coincide.
The oxidizing current carries off the fumes and passes off at the top of the
tower into a downcast flue O leading to the series of settling and condensing
chambers EE' E2 wherein any solid particles that may be carried off along with the
oxidizing current are caught and wherein the sulphurous and other fumes are
condensed by contact with the cooled surfaces of metal tanks P, through which a

page_text: constant circulation of cold water is maintained, the air and vapors passing on into
the chimney F and being thus freed of noxious properties, before being allowed to
escape.
Reverting now to the product of the oxidizing process, the oxidised and
"sweetenedore is discharged from the settling chamber D through a discharge
pipe Q (provided with a regulating valve ) into a quick running stream R of cold
water contained in a trough into which the pipe Q dips whereby the pipe is sealed
against the admission of cold air.
It is necessary to keep the water in a turbulent state otherwise the bubbles of
steam may cause the particles to float on the surface of the water, instead of being
immediately immersed. The constant agitation of the water and the complete
immersion of the glowing particles may be conveniently effected by the introduction
in the pipe Q of jets of cold water at S which meet the falling stream of particles
and increase the force with which they descend into the trough.
The sudden cooling of the glowing particles of ore thereby effected, and the
disruptive effect produced by the flashing of the water into steam cause the
breaking up of the particles and of any glaze-like coating or adherent oxides of
the base metals, which are carried off by the running water, thus freeing the noble
metals of impurities which would be detrimental to the subsequent amalgamating
or other metal saving operation.
The particles are transported by the running stream to a series of settlers,
amalgamators or other means of arresting and collecting the heavier and valuable
metals contained in the ore.
As by this quenching operation the ore is reduced to an almost impalpable
powder very fine crushing is not necessary and therefore the output of the crushing
mill can be increased. Moreover, the particles are so minute that there is no
longer any room for atoms of gold or other metal to be locked up in them and the
skin of oxide having been removed, as above mentioned, the gold is clean and in a
condition specially adapted for amalgamation.
The settling chambers EEE are provided with discharge spouts e closed by
valves, at which the particles intercepted and the sulphurous and other vapors
which have been condensed may be periodically discharged into trucks below.
In order to ensure a sufficient draught in the chimney to draw the air through
the air heater and through the oxidizing tower and condensing chambers, and
likewise to draw the furnace gases through the flues above described, special
draught furnaces T would be provided, communicating directly with the chimney,
and over them, air-heating chambers U, connected by a flue with chamber D, for
the supply of hot air thereto, should the supply from the air heater B before
described be insufficient. Retorts for the generation of oxygen or chlorine gas,
may be arranged in or above the furnaces T for supplementing or replacing as the
case may be the oxygen of the hot-air supply when required.
Having now particularly described and ascertained the nature of the said
invention and in what manner the same is to be performed I declare that what
I claim is :-
:-
1. A furnace for the treatment of refractory ores, comprising an oxidizing tower
wherein a series of inclined slabs and flues in connection therewith are so arranged
that the slabs are heated progressively in the downward direction by an upwardly-
flowing current of furnace gases passing through the flues beneath the slabs, and
wherein the falling stream of ore is gradually heated and subjected to the
oxidizing and sweetening" action by falling over and down said series of heated
slabs and by meeting a current of air or gas heated in a heater separate from the
furnace and flowing continuously upwards through the falling stream from bottom
to top of the oxidizing tower, substantially as specified.
2. The combination, with the oxidizing tower and its adjuncts arranged for
operation as described, of a discharge passage leading from the settling chamber
at the foot of the tower and sealed by dipping into water, as described.

page_text: 3. The combination with the oxidising tower and its adjuncts arranged for
operation as described of the jets and stream of water for suddenly cooling and
splitting up the roasted ore, cleansing the precious metals contained therein and
carrying the whole off as described.
4. The combination, with the oxidizing tower and its adjuncts arranged for
operation as described, of the series of settling and condensing chambers for
intercepting the vapors and particles carried over by the oxidizing current, as
specified.
5. The herein described oxidizing and sweet-roasting furnace constructed and
arranged for operation, substantially as specified.
Dated this 8th day of April 1892.
By A. M. & Wm. Clark,
53, Chancery Lane, London, Chartered Patent Agents.