Improvements in Machinery or Apparatus for Extracting Precious Metals from their Ores.
Year: 1889

page_text: Date of Application, 6th Dec., 1889-Accepted, 1st Mar., 1890
COMPLETE SPECIFICATION.
Improvements in Machinery or Apparatus for Extracting Precious
Metals from their Ores.
We DONALD DENNES of 23 Rona Road Hampstead in the County of Middlesex
Mechanical Engineer and TOM 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 provide machinery or apparatus for extracting
precious metals from their ores in a more rapid and efficient manner than
heretofore.
We will describe our Invention with reference to the accompaying drawings for
extracting gold from its ores from which its application to the extraction of other
metals will be clearly understood. Figure 1 of the drawings represents in elevation
the whole apparatus arranged in the order in which the several parts operate
throughout the process. Figures 2 and 3 are sections of the various parts of the
apparatus shewing their internal construction.
The ore to be treated is first partially reduced in any suitable crushing machine
such for example as a Blake's crusher as shewn at A. Figure 1 after which the
partially reduced ore may be further reduced in what is known as a Cornish roller
mill B (which in its action produces a minimum per centage of flour and slime) but
any other suitable reducing or grinding apparatus may be employed.
The ore having been sufficiently reduced and sieved to the required degree of
fineness is conducted from the hopper 6 by the shoot 1 into a muffle furnace C in
which it is roasted or oxidized:
The crushed ore passing from the shoot 1 falls into a passage 3 Fig. 3 in a nozzle 4
fitted in one side of the muffle furnace C. The said passage 3 communicates with the
central passage 4 in the nozzle in the rear of which is inserted another nozzle 6 which
is connected to a fan blower d Fig. 1 or other air forcing device.
The powdered ore enters the passage 4 in a small regular stream and is driven by a
stream of compressed air or the like admitted through the nozzle 6 into the muffle
where it is met by a jet of water gas (hydrogen) or other heating gas which enters
the muffle by the nozzle 7 connected with the gas holder 8 (Figure 1). The air
entering by the nozzle 6 provides the necessary oxygen to support combustion of the
gas thus causing intense heat which effects the decomposition of the sulphides
contained in the ore. The muffle is made of non-heat conducting material and is
provided at the bottom with a discharge nozzle 9 through which the oxidized powdered
ore passes into the chlorinating vessel D. In treating ores containing much sulphur
or such ores as are rich in sulphides the powdered ore may be passed through two or
more of these oxidizing or roasting furnaces or muffles in succession.
The ore as it passes from the muffle may be admitted directly into the chlorinating
vessel or it may first fall into the hopper c (Figure 1) from which it is fed as required
into the chlorinating vessel. This vessel consists of a cylinder or barrel D preferably
of cast iron lined with lead and provided with hollow axes or trunnions 11 on which
the vessel is free to rotate in bearings 12 on a suitable frame or support.
These trunnions 11 are lined with lead and are each fitted with a gland or stuffing
box 13 through which are passed lead pipes 14. 15 one of which lead pipes (14) is
bent up vertically inside the vessel to within a short distance of the inner side thereof
whilst the other pipe 15 is straight and only just enters the cylinder. These pipes are
each provided with a cock or valve 16 for opening and closing as required the passage
through them. The crushed ore is introduced into this vessel through the man hole 17
and is moistened with water. Sulphuric acid and chloride of lime (to produce chlorine

page_text: gas) or bromine or other suitable reagent is then added and when the vessel is
sufficiently charged it is closed by a closely fitting cover 18 kept in position by a
screw 19.
The vessel is now made to revolve for a sufficient time to thoroughly mix the
contents and cause the gold contained in the ore to be dissolved and chlorinated thus
forming chloride of gold in solution. The time usually required to effect the
chlorination is from about 2 to 4 hours. The vessel D should be lined with lead and
cased in the interior with wood 20 which slopes from both ends towards the centre of
the length of the vessel where the discharge passage or manhole 17 is situated,
whereby the material is prevented from accumulating in the angles formed between
the heads or ends and the side of the vessel. When the chlorination is completed
the rotation of the vessel is discontinued but before the contents are discharged it is
necessary to get rid of any excess of chlorine gas contained in the vessel for which
purpose the pipe 15 is connected to an air compresser or air forcing device by which
air under pressure is admitted or forced into the vessel to drive the free gas through
the pipe 14 which is connected by a discharge pipe communicating with the atmo-
sphere or with a vessel containing lime-water or other suitable absorbent for the gas.
When the excess of gas has been discharged from the chlorinating vessel the cover 18
is removed from the manhole 17 and the contents of the vessel discharged there-
through into the feeding hopper of the leaching vessel E wherein the liquid is
separated from the solid matter. This vessel is of a conical form the wider end
theroof being at the bottom and like the vessel D it should be lined with lead. The
hopper 21 into which the material passes from the vessel D is attached to the upper
part of the vessel E and is provided with a valve 22 at the bottom which may be
opened and closed as required by means of a lever 23 and rod 24. The bottom E³
of the vessel E is detachable from the part E and is supported on the plunger 25 of
a hydraulic ram F by which it is maintained in contact with the part É a packing of
india rubber 26 being interposed at the meeting surfaces to ensure a liquid tight
joint.
The removable bottom E' contains a bed of filtering material supported on a
perforated false bottom 28 and covered with canvas or like material which is secured
to the upper edge of a rim 38 on the removeable bottom which rim when the bottom
is in position enters the lower end of the conical portion E of the vessel as shewn in
Figure 2.
When the vessel is charged with the material from the vessel D compressed air or
the like from the compresser & is admitted through the pipe 29 which air by acting
on the surface of the material as a piston forces the liquid portion of the contents
through the filtering material 27 and the perforations in the false bottom 28. The
liquid material thus forced through the filter passes from the vessel by discharge
pipe 29 to which there is connected a flexible pipe 30 by which the liquid is conducted
into a clarifying vessel G.
Water may be occasionally introduced into the vessel E to wash the whole of the
chloride of gold from the mass or as we prefer we connect to the upper part of the
vessel E a pipe 31 through which water under pressure may be admitted to
the vessel in combination with the compressed air or the like so that a continuous
action may be maintained until the whole of the chloride of gold is extracted from
the mass.
When this operation is completed and it is required to discharge the refuse
material from the vessel the moveable bottom E2 with the filter bed 27 is lowered
until the wheels 32 thereon rest on the track 35. A stud 36 on the said bottom then
engages a hook 37 formed on the end of the piston rod 39 of a steam or other motive
fluid cylinder 40 by means of which the bottom E' may be drawn along the track 35
from beneath the vessel E. As the bottoin is moving from beneath the vessel the
refuse material resting on the filter bed will be scraped therefrom by the lower edge
of the vessel E whilst owing to the conical form of this vessel the whole of its
contents will readily discharge therefrom and fall into a hopper or other receptacle
below. The bottom E2 with the filter bed may then, by reversing the motion of the
piston in the cylinder 40, be returned to beneath the conical part of the vessel E and

page_text: then raised into contact with the lower end thereo
means of the
desired in place of the hydraulic ram F a screw operated by a worm and worm wheel
or any other suitable mechanical device may be employed for raising and lowering
the bottom E³.
The liquid forced from the leaching vessel is conducted by the flexible pipe 30
into the upper part 41 of the clarifying vessel G wbich is separated from the lower
part 42 by a partition fitted with a valve 43 through which valve the liquid from
the upper part is admitted to the lower part as required. The valve is opened and
closed by means of a lever 44 which may be sufficiently weighted to maintain a
water-tight joint so long as the quantity of the liquid in the upper part 41 does not
exceed a certain amount but which will when this quantity is exceeded allow the
valve to open automatically and admit the excess of liquid to pass into the lower
part 42 in which is a filter bed 45 supported on a perforated false bottom 46 in a
similar manner to that in the leaching vessel E. Compressed air gas or other vapour
under pressure is admitted to the lower compartment 42 by the pipe 47 which air
acting on the surface of the liquid forces it through the filtering material and up a
pipe 48 into a lead lined tank H any mud grit or the like which may have entered
the vessel with the solution of chloride of gold being arrested by the filtering
material 45. The solution of chloride of gold is conveyed from the tank 49 by the
pipe 50 to a gold precipitating filter press I and then if desired to one or more
similar presses as shewn in Figure 1.
We
The precipitating filter press contains an insoluble sulphide of iron or of copper but
preferably an insoluble sulphide of copper prepared in the following manner :-
dissolve sulphate of copper in water and we also dissolve caustic soda in water and
mix therewith flour of sulphur. The temperature of this mixture is then raised to
about 300° Fahrenheit to dissolve the sulphur. When the sulphur has dissolved, a
quantity of the mixture is added to the solution of copper sulphate sufficient to
precipitate or throw down the copper sulphide which may then be collected and
filtered the solid matter left being then ready to be placed in the precipitating press.
Sulphide of iron may be prepared in a similar manner.
The chloride of gold from the tank H is admitted by the pipe 50 to the precipi-
tating filter press I through the bottom thereof and passes upwards through the
sulphide 51 which we cover with canvas 52 or like material so as to cause the liquid
to percolate slowly through the sulphide, thereby retaining the solution of gold in
contact with the said sulphide for as long a period as convenient in order to more
effectually precipitate the gold. The liquid from which the gold has been thus
separated passes from the filter through the pipe 53. The canvas or like material
which covers the insoluble sulphide is held in position by being engaged at its edges
between the lower part 54 and the upper part 55 of the press, the said upper part
being held to the lower part by means of a screw 56, an intervening elastic packing 57
being interposed between the parts to ensure a liquid tight joint.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed we declare that what we
claim is :-
1. The general construction and combination of apparatus for extracting precious
metals from their ores substantially as hereinbefore described and illustrated by the
accompanying drawings.
2. In a chlorination or like process for obtaining precious metals from their ores
the use of a muffle furnace provided with nozzles through one of which the ore to be
roasted or oxidized is fed into the muffle in combination with air; water-gas or other
inflammable gas being introduced through another of the nozzles to meet the air
whereby the combustion of the gas is effected and the ore is roasted or oxidized
substantially as herein before described with reference to the accompanying drawings.
3. In a chlorination or like process for extracting precious metals from their ores,
the use of a metal cylinder or drum in which the ores are chlorinated or the like the
said cylinder or drum being provided with hollow axes or trunnions and lined with

page_text: lead and having inside the lead lining a casing of wood inclining from the opposite
ends to the centre of the length of the cylinder where the charging and discharging
opening or manhole is situated substantially as and for the purpose herein before
described with reference to the accompanying drawings.
4. In a chlorination or like process for extracting precious metals from their ores
a conical bleaching vessel containing a removable filter bed through which the liquid
portion of the chlorinated ore is forced by means of compressed air or other vapour
in combination or not with water under pressure substantially as hereinbefore described
with reference to the accompanying drawings.
5. The combination with the subject matter of the last preceding claiming clause
of means for moving the bottom of the leaching vessel containing the filter bed to
and from beneath the conical portion thereof substantially as and for the purpose
herein before described with reference to the accompanying drawings.
6. In a chlorination or like process for separating precious metals from their ores
a precipitating filter press containing an insoluble sulphide through which the
solution containing the precious metal is caused to percolate from beneath upwards
substantially as herein before described with reference to the accompanying drawings.
7. For separating precious metals from solutions containing them a precipitation
filter press containing an insoluble sulphide covered with canvas or like material
substantially as and for the purpose hereinbefore described and illustrated in the
accompanying drawings.
Dated this 6th day of December 1889
J. H. JOHNSON & Co.,
Agents.