Improvements in or relating to the Extraction of Metals from:Ores or Slimes and Apparatus therefor.
Year: 1899

page_text: Date of Application, 8th Dec., 1899-Accepted, 10th Feb., 1900.
COMPLETE SPECIFICATION.
Improvements in or relating to the Extraction of Metals from:Ores or
Slimes and Apparatus therefor.
J .
422
عدد ..
We, SAMUEL HENRY JOHNSON, Metallurgical and Chemical Engineer, of the
Engineering Works, Stratford, in the County of Essex, HENRY LIVINGSTONE
SULMAN, Metallurgical Chemist and Assayer, of 60, Gracechurch Street, in the
County of Middlesex, and S. H. JOHNSON & COMPANY, LIMITED, Metallurgical and
Chemical Engineers, of the Engineering Works, Stratford, in the County of
Essex, 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 extraction of metals from ores or slimes and
apparatus therefor, and has for its object the removal of gold and other metals
from finely divided minerals or from slimes by chemical treatment in the wet
process. The invention has particular reference to processes employing filter
presses for leaching the finely divided ores or slimes, and is applicable for instance
to such a process as is described in the Specification of British Letters Patent
No. 19389 of 1891.
Finely divided precipitated ores, such for example as the settled slimes which
precipitate from battery tailings, contain a large amount of water, the propor-
tion in some cases being about 5 parts by volume of dry solid to 15 parts by
volume of water. In treating such material with chemical solutions; such for
instance as a solution of cyanide of potassium, the water present obviously tends
to dilute the solution used and consequently a greater waste of the chemicals
must occur in the extraction of the metal than would be the case if the water
were not present. By the employment of filter presses a considerable proportion
of the water in the material may be expressed. It is found that by this pre-
liminary filter pressing, 20 parts by volume of settled slime yield about 8 parts
by volume-of filter pressed cake and 12 parts by volume of filtrate, thus leaving
behind in the cake 5 parts by volume of dry solid and 3 parts of water.
An important feature of this invention is the elimination of the water which
remains in the pressed material in such a manner as to avoid the expense of
driving off such water by heat, thus permitting of the treatment of wet- or
battery-crushed ores and ore products with the same economy as can be effected
with dry materials. This is accomplished by displacing the water remaining in
the cakes after the preliminary filter pressing, by means of a cyanide or other
chemical solution of normal strength. If precautions are taken in the pressing
so that the cakes produced are uniformly permeable the whole of the remaining
water may be displaced by our process with only a very slight admixture of the
chemical solution used. Owing to the fact that the displaced water contains a
small amount of the solvent solution it will in the case of gold slimes contain
some gold and it is desirable in order to recover this gold without diluting the
bulk of the main body of solvent liquor; to employ a small set of zinc boxes

page_text: #
zinc cones or other convenient apparatus, the overflow from which may be allowed
to run to waste. The main volume of the working solvent liquor is treated in
another precipitating apparatus as herein after described.
For the purpose of correctly gauging the volume of liquid displaced from the
cakes a graduated tank is employed and when the effluent displaced from the
cakes in the filter press is equal to the volume of water that those cakes originally
contained the amount of such volume being determined in any particular case
by a preliminary assay-the process of displacement is considered to be complete.
By thus removing a volume of liquid equal to the volume of the water contained
in the cakes after the preliminary compression, it follows that no practical alter-
ation will take place in the volume of the main bulk of solvent liquor subse-
quently employed in extracting the metal from the pressed material.
The cakes from which the moisture has been displaced by means of normal
solvent liquor, in the filter pressing operations above described, are then mechani-
cally broken up and agitated with a sufficient quantity of normal solvent solution
to bring them into a sufficiently liquid condition to admit of their being readily
treated with the solvents, but the mixture should not be made so liquid that the
solid matter in suspension would readily settle therefrom. The amount of liquid
required would be from once to twice the volume of the cake or more, depending
upon the relative facilities of different ores for remaining in suspension in the
liquid; the object being that there shall be sufficient mobility in the liquid to
admit of speedy solution of the precious metals, and at the same time, that there
shall not be any tendency for the solids to settle out of the liquid in the chambers
of the filter press during the period of charging or in the other operations, as such
settlement would tend to produce cakes which would not be uniformly permeable,
a condition which should be carefully guarded against. The best state of dilution
may be easily determined upon, for any particular ore, by anyone of experience
and skill in such matters.
To ensure the rapid solution of the metals and also that the solids shall be
suspended in the liquor so as to form a homogeneous magma suitable for working
properly in the filter presses an improved mixing apparatus is employed which is
hereinafter more fully described. It is to be understood, however, that this par-
ticular form of mixing apparatus is not absolutely essential to the carrying out of
our process, other convenient apparatus may be employed.
After the material has been thoroughly mixed with the additional quantity of
normal solvent solution it is treated in leaching filter presses and a large pro-
portion of the liquid which now contains the metal in solution is squeezed out
and allowed to flow directly to the zinc boxes or other apparatus where the gold
or other metal is precipitated. After leaving this apparatus the liquid is returned
to the strong liquor tank. Some of the metal bearing solution will remain in the
cakes in the filter press and this is now displaced by means of water, the volume
displaced being gauged as in the first part of the process so that dilution of the
solvent liquid is avoided. The displaced liquid is treated in the precipitating
apparatus and is then returned to the strong liquor tank. The washing is con-
tinued for the purpose of finally removing all traces of gold in solution from the
cakes, and these washings are collected and are passed through a separate precipi-
tating apparatus from which the liquid may be allowed to run to waste.
It will be seen that the process according to this invention may be summarised
by stating that after a preliminary treatment of the material in a filter press
the water remaining in the cakes is displaced by a normal solvent solution,
the material being then further mixed with the solvent solution and
again treated in a filter press by means of which the metal-bearing liquid is
removed partly by expressing and finally by displacing it with water, the whole
of these operations being conducted so that an approximately constant volume of
the solvent solution is maintained.
In the accompanying drawings which illustrate diagrammatically one construc-
tion of apparatus according to this invention for carrying out the improved process.

page_text: Figure 2 is a side elevation, and
Figure 3 a central vertical section of the mixing apparatus to a larger scale.
Like letters indicate like parts throughout the drawings.
A and A¹ are settling tanks through which the liquid containing the finely
divided ore may flow continously, the slimes being deposited by gravitation.
From the settling tanks the slime passes by means of a pipe A² to a forcing
receiver B, which is supplied with compressed air through a pipe C³ communicat-
ing with compressed air reservoirs C and C2, these reservoirs being supplied
from an air compressor C. Preferably, the forcing receiver is arranged so that
when the pressure of air is removed the receiver automatically refills with semi-
liquid slimes by gravitation from the settling tanks A and A¹. D and D¹ are filter
presses used for the elimination of the water from the slime, which is supplied to
them through the pipe D², being forced up through the pipes B' and D² by com-
pressed air.
The greater part of the water in the slime is expressed in the filter presses D
and D' and passes through a pipe D³ to a tank E and thence to waste by a pipe E¹.
The residual water in the cakes is then displaced or "pushed out" by means of
solvent solution of normal strength which is pumped from a liquor tank F
through a pipe F by a pump G. The delivery pipe G¹ of the pump G com-
municates with the bottom of the compressed air reservoir C¹ and another pipe G²
leads from the same portion of that reservoir to the filter presses D and D¹.
The tank E is preferably gauged so that a calculated quantity of water may be
displaced by the solvent solution and when this operation has been performed
as the displaced water may contain a small quantity of the solvent it is passed
through a pipe E2 to a small set of zinc boxes H, or other convenient precipitat-
ing devices. After leaving the zinc boxes the liquid may be allowed to run to
waste. Beneath the filter presses D and D₁ is a shoot J, into which the com
pressed cakes fall and are conveyed to a mixing apparatus K, hereinafter more
fully described. The material, while in the mixer , has an additional quantity
of normal solvent solution added to it, this solution being pumped by a pump K
through pipes K2 from the liquor tank F. It is found that a convenient quan-
tity of the solvent is an amount which is approximately equal to the volume of
water mechanically expressed from the slime in the filter presses 1) and D¹.
After being thoroughly mixed with the solvent in the apparatus K the mate-
This forcing
rial passes through a pipe K³ to a second forcing receiver L.
receiver L is supplied with compressed air from the reservoirs C¹C through a
pipe C and the material is forced up through the pipes L' and L2 to a second
set of filter presses M and M¹. In these presses M and M¹ the material is first
compressed to extract the more easily removable solvent solution-now the metal
bearing liquid and then the remaining portion of the liquid is displaced by
means of water which is forced into the presses M M through a pipe M2 by means
of compressed air from the reservoir C. The water is supplied to the reservoir C2
by means of a pump N, the delivery pipe N¹ of which communicates with the
bottom of the reservoir.
The expressed metal bearing liquid is passed to a separate set of zinc boxes H¹,
or other convenient precipitating devices, through a pipe M³, from whence it
passes by a pipe H2 to the liquor tank F. The displaced metal bearing liquid
passes through a pipe M to a graduated tank O, and thence through a pipe O¹
to the precipitating devices H.
After the calculated volume of solvent has been displaced by the water under
pressure, more water is forced through the cakes in the presses M M¹, in order
to remove the last traces of metal bearing liquid. This liquid also passes into
the tank 0, but owing to its weak condition is not allowed to pass to the preci-
5 pitating devices H¹ but is passed through a pipe 02 to the small zinc boxes H,
from whence the liquid may be allowed to run to waste.

page_text: It will be noticed that the air reservoirs C¹ and C2 communicate by a pipe. 05
and thus the air pressure upon the solvent solution and the washing water is
equalized.
and
Figure 3 illustrates in vertical section an improved form of mixing device which
is found to be extremely efficient; the general principle upon which, this device
works is similar to that described in the Specification of British, Letters, l'atent
No. 5377/92, and the present mixer constitutes an improvement, upon the
imachines therein mentioned.
.:
The improved mixing-apparatus comprises a vessel K having a neck, K¹ and
provided with a vertical shaft K2 suitably journalled at the bottom of the vessel.
This shaft K2 carries a vane K³ which is formed with two discs Khaving
between them ribs K5 which are curved, or partly radial and partly curved so
that they act upon the liquid in the tank in a way, similar to the action of a
centrifugal pump. The shaft, Kis driven by a small engine K which is
mounted upon the neck of the vessel K. Surrounding the shaft K2 within the
vessel K is a trunk pipe K which does not rotate, and at the top of this conduct-
ing or trunk pipe A a hopper K8 is provided, the mouth of which is only
slightly smaller than the contracted neck, K' of the vessel K.... The top of the
neck K is shaped as at K and this shaped portion tends to cause the flow of
liquid delivered from the centrifugal vane K to converge towards and overflow
the rim of the hopper K8 in the form of a cascade. The object, of causing the
liquid to enter the hopper in this cascade is to secure the efficient oxidation of
the liquid, when such as desirable, by atmospheric, aeration... This effect is
further increased by providing the top of the hopper K8 with a rim or band K10
which is perforated or provided with slots, such slots being preferably made with-
out removing the metal, merely slitting it so as to form small flaps... Through
these perforations or slots the liquid under agitation is delivered in cascade form
into the hopper K8.
In order to enable the mixing apparatus to work efficiently, even when it is
not quite full, the circulating or trunk pipe K7 is arranged so that it is capable
of sliding up for a short distance upon the shaft K... This allows the liquid to flow
into the vane K3³ between the trunk pipe K' and the top. of the vane thus securing
a thorough circulation and agitation at the bottom of the vessel K. The-move-
ment of the trunk pipe K7 is effected by means of a cord or equivalent. K" which
passes over two pulleys K and is fixed to a support or spider K3 at the top
portion of the trunk pipe K. The other end of the cord is..fastened to a
screw K which can be screwed in or out of its support K15 by means of a hand
wheel K16.
'..'.
f
The function of the trunk pipe K is to cause the liquid to circulate in a ver-
tical direction and the pipe K merely forms a feed conduit to the centrifugal
vane K3 at the bottom of the tank. It will be readily seen that with such a
vane in the lower part of the vessel no deposition of fine sands can take place
during the mixing operations.
When bromide of cyanogen is used, or in other cases where oxidation "'is' unde
sirable, the hopper K8 and the cascading arrangement Ko may be omitted:
. In the apparatus various cocks or valves are placed to control the respective
pipes, but these form no part of the present invention and are omitted from the
drawings for the sake of clearness.
As herein before stated it is to be distinctly understood that the apparatus
described, although forming a convenient means for carrying out this invention,
is not essential thereto but may be varied in many ways while still carrying out
the improved process.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed, we declare that what
we claim is:-
1. A process for the treatment of ores or slimes in which a solvent solution is

page_text: used for displacing the residual water in pressed slime cakes for the purpose
described.
2. A process for the treatment of ores or slimes in which a portion of the
water is first removed by pressure and the remainder displaced by an equal
volume of a solvent solution.
3. A process for the treatment of ores or slimes containing metals in which the
residual water in pressed cakes is displaced by a normal solvent solution in a
filter press the material being then further mixed with an additional quantity of
the solvent solution and again treated in a filter press wherein the metal bearing
solvent solution is removed and water substituted therefor substantially as
described.
4. A process for the treatment of ores or slimes containing metals consisting in
displacing the residual water in pressed cakes by a normal solvent solution in
a filter press, treating the cakes with additional normal solvent in a mixing
anparatus with or without aeration, expressing the metal bearing solution in a
filter press, displacing the remaining portion of such solution with water and
returning the solution after the metal has been extracted from it to the main
body of solvent solution, all the operations being performed so that an approxi-
mately constant volume of the normal solvent solution is maintained substan-
tially as described.
5. In the treatment of ores or slimes containing metals, mixing or mixing and
aerating apparatus comprising a centrifugal vane and a non-rotatable trunk-
pipe capable of vertical adjustment with or without a cascade aerating device sub-
stantially as described.
6. The complete apparatus for the treatment of ores or slimes containing metals
substantially as described or illustrated in the accompanying drawings.
Dated this 8th day of December 1899
BOULT, WADE & KILBURN,
Agents for the Applicants.