An Improved Process or Means for Extracting Precious Metals from their Ores.
Year: 1889

page_text: Date of Application, 6th Dec., 1889-Accepted, 11th Jan., 1890
COMPLETE SPECIFICATION.
An Improved Process or Means for Extracting Precious Metals from
their Ores.
We, DONALD DENNES of 23 Rona Road, Hampstead in the County of Middlesex,
Mechanical Engineer and Tом KIRKE ROSE of 94 Camberwell Grove in the
County of Surrey, Metallurgist 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 :-
Our Invention has for its object to extract gold and other precious metals from
their ores in a more rapid and efficient manner than heretofore. According to our
Invention the ore containing the precious metal (gold for example in which
connection we will describe it) after being crushed or reduced to the required degree
of fineness (which will depend upon the nature of the ore to be treated) is fed into
a furnace to be roasted or oxidized in which furnace the ore is preferably subjected to
the action of water gas (hydrogen) or any other suitable heating gas and air. The
ore when sufficiently roasted or oxidized is passed from the furnace into a vessel.
preferably mounted on hollow trunnions so as to be capable of rotating. Water is
admitted to this vessel and to this is added any suitable reagent such as Bromine or
Chlorine. When Chlorine is used Chlorine gas is generated by Chloride of lime and
sulphuric acid in the vessel containing a charge of the ore which vessel is then rotated
(whereby the contents are agitated and mixed together) for a sufficient length of time
to allow the metal contained in the ore to be dissolved or chlorinated thus forming a
solution of chloride of the metal the time required to effect the chlorination varying
from say about 2 to 4 hours according to the nature of the ore. Before discharging
the ore from this vessel it is necessary to extract therefrom any excess of chlorine or
other gas which is effected by admitting air or the like under pressure into the vessel
through one of the hollow trunnions so as to drive the excess of gas out of the vessel
through the other hollow trunnion after which the contents of the vessel are discharged
into a leaching vessel in which the separation of the liquid from the solid matter is
effected. This vessel is provided with filtering material through which the liquid
portion of the contents is forced by means of compressed air or vapour in combination
or not with water under pressure. If compressed air or vapour only be used for
expelling the liquid through the filtering material (preferably consisting of graded
sand or gravel which has been roasted) water may be added occasionally to the mass
until the whole of the chloride of gold is washed out. The solution of chloride of
gold thus obtained is then treated in another vessel containing a filter bed (preferably
of graded sand which has been roasted) on a perforated false bottom through which
the chloride of gold in solution is forced by means of compressed air or the like any
particles of grit which may have entered this vessel with the liquid from the leaching
vessel being arrested by the filtering material. The liquid which passes through the
filtering material in this vessel is conducted by a suitable passage into an elevated
tank from which it descends to gold precipitating filter presses wherein the gold is
collected. These presses contain an insoluble sulphide such for example as sulphide
of copper or of iron through which the solution of the precious metal is caused to
percolate. We prefer to cause the solution of chloride of gold to pass upwards
through the sulphide and to cover the said sulphide with canvas or equivalent
material so as to cause the liquid to percolate slowly through the Sulphide that the
gold may be more effectually precipitated.
The accompanying drawing illustrate the apparatus which we prefer to use in
carrying out our improved process which apparatus constitutes the subject matter of
our application for Letters Patent bearing the same date as this, but we do not
restrict ourselves to the use of this precise apparatus as other suitable apparatus may
be employed.

page_text: A represents a crushing machine by which the ore is first reduced and from which
it passes by the shoot a to the action of a Cornish crusher B by which it is further
reduced.
The crushed ore is delivered from the mill B through a sieve into a hopper b
which conducts it into a muffle furnace C in which it is subjected to the action of
water-gas in combination with air. The sulphides contained in the ore are thus
decomposed after which the ore is discharged from the furnace into a hopper c which
conducts it into the vessel D containing water to which is added chloride of lime and
sulphuric acid in the required proportions for effecting the chlorination of the gold.
Any excess of chlorine which may be generated in this vessel may be discharged
therefrom through one of the hollow trunnions on which the vessel rotates by means
of compressed air admitted through the other hollow trunnion. The gas thus expelled
from this vessel may be conducted into a vessel containing lime water or other
suitable absorbent of the gas for subsequent use.
The chlorinated gold ore is discharged from the vessel D into a leaching vat or
vessel F containing filtering material through which the liquid portion is forced by
means of compressed air or other vapour (in combination or not with water under
pressure) into a clarifying vessel G which also contains filtering material through
which the liquid chloride of gold is forced by means of compressed air.
The chloride of gold passes thence upwards through a pipe into a tank H from
which it descends into a gold precipitation press I and if desired from this press into
one or more similar presses. The chloride of gold solution enters these presses from
the bottom and percolates upwards through insoluble sulphide therein which is
preferably covered with canvas to retard its passage through the sulphide so that
the gold shall remain in contact with the sulphide to effect its more perfect
precipitation.
When the sulphide in the filter presses has become sufficiently rich with the
precipitated gold it is removed from the press and may be refined in any suitable or
well known manner.
Having now particularly described and ascertained the nature of our said Inven-
tion and in what manner the same is to be performed we declare that what we
claim is.-
Obtaining gold and other precious metals from their ores by the improved
process described consisting in submitting crushed or reduced ore to the successive
operations of roasting or oxidizing by gas chlorination or the like, leaching by
pressure, clarifying by pressure and precipitation substantially as hereinbefore
described.