Improvements in the Treatment of Slimes, or Finely Divided Ore, Containing Precious Metals.
Year: 1893

page_text: Date of Application, 9th Mar., 1893
Complete Specification Left, 9th Jan., 1894-Accepted, 17th Feb., 1894
PROVISIONAL SPECIFICATION.
Improvements in the Treatment of Slimes, or Finely Divided Ore,
Containing Precious Metals.
I, CHARLES RALEIGH, of Johannesburg, in the South African Republic, Milling
Engineer, do hereby declare the nature of this invention to be as follows:-
-
This invention relates to the treatment of slimes, or ore in a state of fine
subdivision, containing precious metals, the extraction of which is about to be
effected with the aid of chlorine, cyanide of potassium, or other lixiviating or
leaching solution.
It is found that when treating tailings direct from a stamp battery or other
crushing or pulverizing mill, the process of lixiviation or leaching is seriously
interfered with owing to the slimes or finely divided ore caking or packing and
preventing thorough percolation of the solvent solution. The application of a
suction pump to the bottom of the vats or filters with a view to drawing off the
leaching solution does not obviate this difficulty, inasmuch as the solution selects
favourable paths or passages instead of permeating the whole mass.
My invention consists in part in keeping the mass of slimes or tailings in a state
of vibratory or pulsatory movement, such movement being imparted to the mass of
slimes or tailings by means of water, air, or gas, pumped or forced into and out of
the vat or filter, the inlet therefor being under or over the filter bed, or at the side
or bottom of the vat, filter or other receptacle; its position being such that
thorough circulation takes place, either in a vertical, horizontal, curvilinear, or
circular direction. The leaching solution employed may however take the place of
the water jet, and oxygen gas may with advantage be used to accelerate the solvent
action on the gold and silver. In order to increase the density of the leaching
solution, and to prevent the grains of ore from settling, it is advantageous to add
mud, and to mix the same with the material under treatment; or to employ muddy
water or muddy solution, so that the density of the vehicle in which the finely
divided ore is suspended is approximately equal to that of the matter in suspension.
In this manner, settling or packing of the slimes or finely divided ore is prevented.
The treatment of the slimes or finely divided ore is as follows:-
:-
A vat, filter, or other suitable receptacle is provided, and the material under
treatment, the mud (if any) and the leaching solution are added together. Mean-
while the pulsator, jigger or pump (hereinafter described) is started, and a stream
of chemical solution is continuously or intermittingly injected and ejected; means
being provided for controlling the injection and ejection in such a manner that the
liquid, air or gas injected is in excess of that ejected, or the amount injected may
be less than that ejected or withdrawn.
The effect of the continuous or intermittent injection and withdrawal of the
chemical liquid is to cause the mass of slimes or finely divided ore to pulsate,
vibrate, or oscillate, the flux and reflux of the leaching solution enabling the latter
to thoroughly permeate the fine grains of ore, and to rapidly extract the gold' and
silver therefrom, the particles being meanwhile held in suspension. To assist the
pulsatory movement of the fine grains of ore, a mechanical jigger may be employed
in addition to the pump or pulsator; but I prefer to effect the pulsation or jigging
of the material under treatment in the manner previously described.
When the gold, silver or other precious metals have been thoroughly lixiviated
or leached, the pump or pulsating appliance is regulated to inject less than to eject;
the result being that the leaching solution is gradually withdrawn, the withdrawal

page_text: and consequent drying of the slimes, etc., proceeding gradually from the top to the
bottom of the vat or filter.
The whole or part of the leaching solution having been withdrawn, the pump or
pulsator is set to inject and eject clean water, or a very weak solution of the
necessary leaching solvent. The injection, being now greater than the ejection,
the clean water or weak solution gradually permeates the whole mass of slimes or
finely divided ore, washing it thoroughly in its course.
The action of the pump or
pulsator is then reversed, and the washing water or weak solution withdrawn from
the material under treatment, leaving it dry and ready for removal.
When treating sands or larger particles of ore mixed with slimes containing gold
or silver, I find it advantageous to work as follows:-
The vat is loosely filled with tailings, the pulsator pump started, and caused to
violently inject water, which breaks up and divides the tailings in its upward
passage.
When sufficient water has been injected, the pulsator pump injects air, which,
rising from the bottom of the vat, agitates the tailings, and in its upward course
carries with it all the slimes, leaving the sand at the lower portion of the filter
perfectly clean and systematically graded; the heavier or coarser sand lying next
to the filter bottom, the lighter or finer sand occupying a higher position, above
which are the slimes held in suspension by the water and prevented from settling
by the breaking of the air bubbles as they rise to the surface.
When the tailings are sufficiently washed and freed from slimes, more water is
injected, which, rising, carries the slimes through the slime outlet at the top of
the vat; this being continued till the water comes from the tailings free from acid
or slimes.
From the slime outlet, a pipe conveys the slimes together with the wash water to
the slime filter, hereinafter more particularly referred to.
The vat now contains only clean sand, which can rapidly be treated by injection of
strong solution of cyanide, or other lixiviating liquid, followed by pulsating or jigging
with air in the manner previous described. It is, however, advantageous, when
jigging or pulsating with air, to reverse the action of the pulsator pump, and to
eject instead of to inject; fresh passages being provided for the passage of the air
when the pulsator pump is again set to inject.
Owing to the favourable and systematic grading of the sands, the total absence
of slimes, and the introduction of air, the extraction of the precious metals is
rapidly effected; and the lixiviating liquid being rapidly withdrawn, the sand is
left dry and ready for washing with clean water, which is injected, agitated with
air, and subsequently withdrawn, leaving the sand not only free from gold, silver,
or cyanide solution, but in a dry condition.
The sand can now either be dug out in the usual way, or fresh water can be
injected, and violent pulsation or jigging carried on, while a trap-door at the
bottom or side of the filter or vat is opened to allow the contents to flow out in a
semi-liquid state, assisted if necessary by a revolving worm.
A filter constructed specially for the treatment of slimes is arranged in a
manner similar to that appertaining to the tailings filter; but the slimes are
admitted by preference at the bottom of the vat, just above the filter bed.
The separation of the slimes from the liquid is carried out as follows:-
The slimes having been allowed to run in at the bottom of the vat above the
filter bed, the pulsator pump is started, the partial withdrawal of the liquid causing
the slimes to rapidly settle, the remainder of the water being drawn off at the top
of the slimes, instead of, as is usually the case, the whole of the liquid being with-
drawn through the bottom of the filter.
A solution of cyanide or other lixiviating liquid is now injected, and followed
by pulsating with air, till the whole of the previous metals are extracted. The
withdrawal of the cyanide solution at the bottom and top of the vat, followed by
a thorough washing, completes the process; the slimes being discharged by a worm
or other mechanical device.

page_text: At the commencement of the process, instead of extracting and discharging the
slimes in the first washing in the tailings vat, the gold and silver may be first
extracted, and the slimes run into the slime filter, merely to separate the solid from
the liquid. Or the slimes may be run into a centrifugal dryer, consisting of a
circular globe-shaped pan having its sides or circumference arranged as a filter;
the pan being mounted on a vertical or horizontal shaft, revolving at a high rate
of speed.
'
By centrifugal force, the slimes fly from the centre to the periphery of the pan,
A little heavy
the liquid passing through and leaving the slimes in a dry state.
sand is previously added to the slimes, and scrapers are arranged to prevent the
clogging of the filtering surfaces.
The pump or pulsator may comprise an ordinary pump, driven in any convenient
manner; the valves being however arranged or regulated in such a manner that
only a part of the liquid withdrawn is discharged, the balance being returned or
pumped back to the vats. The proportion so returned may be readily varied and
adjusted.
Air chambers may be interposed between the pump or pulsator and the vats or
filters, direct contact between the leaching solution and the pump being avoided.
Dated the 9th day of March 1893:
G. G. M HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.
COMPLETE SPECIFICATION.
Improvements in the Treatment of Slimes, or Finely Divided Ore,
Containing Precious Metals.
I, CHARLES RALEIGH, of Johannesburg, in the South African Republic, Milling
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 slimes, or ore in a state of fine
subdivision, containing precious metals, the extraction of which is about to be
effected with the aid of chlorine, cyanide of potassium or other lixiviating or
leaching solution.
It is found that when treating (according to the ordinary method) tailings direct
from a stamp-battery or other crushing or pulverizing mill, the process of
lixiviation or leaching is seriously interfered with owing to the slimes or finely
divided ore caking or packing and preventing thorough percolation of the solvent
solution. The application of a suction pump to the bottom of the vats or filters
with a view to drawing off the leaching solution does not obviate this difficulty,
inasmuch as the solution selects favourable paths or passages instead of permeating
the whole mass.
My invention consists in part in keeping the mass of slimes or tailings in a state
of vibratory or pulsatory movement, such movement being imparted to the mass of
slimes or tailings by means of water, air, or gas, pumped or forced into and out of
the vat or filter, the inlet therefor being under or over the filter bed, or at the side
or bottom of the vat, filter or other receptacle; its position being such that
thorough circulation takes place, either in a vertical, horizontal, curvilinear, or
circular direction. The leaching solution employed may however take the place of
the water jet, and oxygen gas may with advantage be used to accelerate the solvent
action on the gold or silver. In order to increase the density of the leaching
solution, and to prevent the grains of ore from settling, it is sometimes advantageous
when working under my improved method to add mud, and to, mix the same with
the material under treatment; or to employ muddy water or muddy solution, so

page_text: that the density of the vehicle in which the finely divided ore is suspended is
approximately equal to that of the matter in suspension. In this manner, settling
or packing of the slimes or finely divided ore is prevented.
The treatment of the slimes or finely divided ore is as follows:-
A vat, filter, or other suitable receptacle is provided, and the material under
treatment, the mud (if any), and the leaching solution are added together. Mean-
while the pulsator, jigger or pump (hereinafter described) is started, and a stream
of chemical solution is continuously or intermittingly injected and ejected; means
being provided for controlling the injection and ejection in such a manner that the
liquid, air, or gas injected is in excess of that ejected, or the amount injected may
be less than that ejected or withdrawn.
The effect of the continuous or intermittent injection and withdrawal of the
chemical liquid is to cause the mass of slimes or finely divided ore to pulsate,
vibrate, or oscillate, the flux and reflux of the leaching solution enabling the latter
to thoroughly permeate the fine grains of ore, and to rapidly extract the gold and
silver therefrom, the particles being meanwhile held in suspension. To assist the
pulsatory movement of the fine grains of ore, a mechanical jigger may be employed
in addition to the pump or pulsator; but I prefer to effect the pulsation or jigging
of the material under treatment in the manner previously described.
When the gold, silver or other precious metals have been thoroughly lixiviated
or leached, the pump or pulsating appliance is regulated to inject less than to eject;
the result being that the leaching solution is. gradually withdrawn, the withdrawal
of the solution and consequent drying of the slimes, &c., proceeding gradually from
the top to the bottom of the vat or filter, and leaving the concentrates, sand and
slimes in regularly disposed strata.
The whole or part of the leaching solution having been withdrawn, the pump or
pulsator is set to inject and. eject clean water, or a very weak solution of the
necessary leaching solvent. The injection being now greater than the ejection, the
clean water or weak solution gradually permeates the whole mass of stratified slimes
and finely divided ore, washing it thoroughly in its course.
The action of the pump
or pulsator is then reversed, and the washing water or weak solution withdrawn from
the material under treatment, leaving it dry and ready for removal.
When treating sands or large particles of ore mixed with slimes containing gold
or silver, I find it advantageous to work as follows:-
-
The vat is loosely filled with tailings, the pulsator pump started, and caused to
violently inject water, which breaks up and divides the tailings in its upward
passage.
When sufficient water has been injected, the pulsator pump injects air, which,
rising from the bottom of the vat, agitates the tailings, and in its upward course
carries with it all the slimes, leaving the sand at the lower portion of the filter
perfectly clean and systematically graded, the concentrates or heavier or coarser
sand lying next to the filter bottom, the lighter or finer sand occupying a higher
position, above which are the slimes held in suspension by the water and prevented
from settling by the breaking of the air bubbles as they rise to the surface.
When the tailings are sufficiently washed and freed from slimes, more water is
injected, which, rising, carries the slimes through the slime outlet at the top of the
vät; this being continued till the water comes from the tailings free from acid
or slimes.
From the slime outlet, a pipe conveys the slimes together with the wash-water to
the slime filter, hereinafter more particularly referred to.
The vat now contains only clean sand, which can be rapidly treated by injection
of strong solution of cyanide, or other lixiviating liquid, followed by pulsating or
jigging with air in the manner previously described. It is, however, advantageous,
when withdrawing fluid, to reverse the action of the pulsator pump, and to inject
fluid fresh passages being provided for the fluid when the pulsator pump is again
set to eject. Alternately with water or solution, air may be injected and ejected..
Owing to the favourable and systematic grading of the sands, the total absence

page_text: of slimes, and the introduction of air, the extraction of the precious metals is
rapidly effected; and the lixiviating liquid being rapidly withdrawn, the sand is
left dry and ready for washing with clean water, which is injected, agitated with
air, and subsequently withdrawn, leaving the sand not only free from gold, silver,
or cyanide solution, but in a dry condition.
The sand can now be dug out in the usual way and separated from the concen-
trates, which may be retreated. Or, fresh water can be injected, and violent
pulsation or jigging carried on, while a trap-door at the bottom or side of the
filter or vat is opened to allow the contents to flow out in a semi-liquid state assisted
if necessary by a revolving worm.
A filter constructed specially for the treatment of slimes is arranged in a manner
similar to that appertaining to the tailings filter; but the slimes are admitted by
preference at the bottom of the vat, just above the filter bed.
The separation of the slimes from the liquid is carried out as follows:-
The slimes having been allowed to run in at the bottom of the vat above the
filter bed, the pulsator pump is started, the partial withdrawal of the liquid causing
the slimes to rapidly settle, the remainder of the water being drawn off at the top
of the slimes, instead of, as is usually the case, the whole of the liquid being with-
drawn through the bottom of the filter.
A solution of cyanide or other lixiviating liquid is now injected, and followed by
pulsating with air, till the whole of the precious metals are extracted. The with-
drawal of the cyanide solution at the bottom and top of the vat, followed by a
thorough washing, completes the process; the slimes being discharged by a worm
or other mechanical device.
At the commencement of the process, instead of extracting and discharging the
slimes in the first washing in the tailings vat, the gold and silver may be first
extracted, and the slimes run into the slime filter, merely to separate the solid from
the liquid. Or the slimes may be run into a centrifugal dryer, consisting of a
circular globe-shaped pan having its sides or circumference arranged as a filter; the
pan being mounted on a shaft revolving at a high speed.
By centrifugal force, the slimes fly from the centre to the periphery of the pan,
the liquid passing through and leaving the slimes in a dry state. A little heavy
sand may be previously added to the slimes, and scrapers are arranged to prevent
the clogging of the filtering surfaces.
The pump or pulsator may comprise an ordinary pump, driven in any convenient
way; the valves being however arranged or regulated in such a manner that only
a part of the liquid withdrawn is discharged, the balance being returned or
pumped back to the vats. The proportion so returned may be readily varied and
adjusted.
Air chambers may be interposed between the pump or pulsator and the vats
or filters, direct contact between the leaching solution and the pump being
thereby avoided.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I claim :--
1. In leaching finely divided ore, the employment of a pump, pulsator, jigger or
other suitable apparatus for pulsating, vibrating or jigging the material under
treatment in order to prevent settling or packing of the slimes, thus facilitating the
rapid extraction of the precious metals, substantially as herein described.
2. In leaching finely divided ore in the manner herein described, injecting oxygen
gas for the purpose set forth.
3. In leaching finely divided ore, the addition of clay or mud to the liquid in
order to increase its density, thereby preventing the settling or subsiding of the
slimes, substantially as herein described.
4. In treating finely divided ore, causing the concentrates, sand and slimes to lie
in regular layers one above another, thus forming a regulated filter bed adapted to

page_text: facilitate the action of the leaching solution on the material under treatment,
substantially as herein described.
5. In treating finely divided ore, separating the slimes from the tailings,
substantially as herein described, before the tailings are subjected to the action of
the leaching solution.
6. In leaching finely divided ore, separating solid from liquid matter by first
withdrawing liquid from the bottom of the filter and then allowing liquid to run off
at the top of the filter, substantially as herein described.
7. In leaching finely divided ore, cleaning or keeping porous the filter bottom by
alternate injection and ejection, substantially as herein described.
Dated the 9th day of January 1894.
G. G. M. HARDINGHAM,
191, Fleet Street, London, E.C., Chartered Patent Agent.