Note: Descriptions are shown in the official language in which they were submitted.
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ASSAYING METHOD
FIELD OF THE INVENTION
THIS invention relates to assaying, and particularly, but not exclusively, to
assaying
gold and/or platinum group metals (PGM's), in an ore sample.
BACKGROUND TO THE INVENTION
It is common practice in gold or platinum mining and exploration operations to
assay
the ore in order to quantify the amount of gold and/or PGM's (platinum,
palladium,
rhodium, osmium, iridium and ruthenium) present.
The conventional assaying process is commonly known as "fire assay". The
process
involves weighing an amount of a comminuted ore, and mixing it with a lead
oxide
bearing flux or nickel flux. The mixture is then placed in a crucible and
heated to
elevated temperatures usually around 1100 to 1250 degrees Celsius for a period
of
about 60 to 90 minutes.
During this process the mixture melts, the lead oxide is reduced to lead metal
or nickel
sulfide is formed and the lead or nickel sulfide acts to collect the PGM's
and/or gold
due to their chemical affinity.
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The molten slag and collector material is poured in to a mould where it is
allowed to
cool. The lead or nickel sulfide settles to the bottom of the mould. Once the
mould is
cooled, the lead or nickel sulfide is separated from the slag using mechanical
techniques. The procedure is labour intensive. Once the collector material has
been
separated from the slag, it is placed in a cupel which is pre-heated at 1000
to 1300
degrees Celsius to allow the lead to be absorbed by the cupel. The result is a
tiny prill
left at the base of the cupel. The PGM's and gold content in the prill can
then be
determined using a number of analytical techniques.
1o Apart from the time consuming process described above, it has been found
that during
the loading and removal of reaction vessels or crucibles from a fire assay
furnace
considerable energy losses occur resulting in further delays in the assaying
process.
Regarding the fluxes used in fire assay processes, conventional components of
fluxes
include borax (hydrated sodium borate), sodium carbonate, litharge (lead
monoxide),
silica, carbon, fluospar, red lead Pb304) potassium nitrate, and iron.
OBJECT OF THE INVENTION
The object of the present invention is to provide a new method of collecting
metals in a
mineral sample in an assaying process.
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A further object of the present invention is to provide a methods and means
for
concentrating a metal collected in a collector and/or co-collector material.
A further object of the invention is the provision of methods and means for
separating
a metal collected in an assaying process, from a molten slag.
A further object of the invention is to provide a handling mechanism and
method
which is suitable for use in an assaying process.
Yet a further object of the invention is to provide a novel reaction flux for
assaying
which it is believed will have advantages over conventional fluxes.
A further object of the invention is to provide a handling mechanism and
method
suitable for loading and removing crucibles, reaction vessels or the like into
and
removing the same from a furnace.
SUMMARY OF THE INVENTION
According to the present invention, a method for assaying a mineral sample for
determining the concentration of selected metals in the sample, comprises the
steps of:
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providing a comminuted mineral sample;
mixing such sample with a flux;
preheating a reaction vessel to a temperature which approximates the
melting point of the flux;
introducing the mixture of the mineral sample and flux into the crucible,
whereby the mixture is transformed to a molten state to capture the
metal to be assayed in a collector material;
and separating slag from the collector material.
Further according to this aspect of the invention, heat energy is added to the
reaction
vessel and mixture once the latter has been introduced into the reaction
vessel to cause
fusion of the mixture.
In one embodiment of the invention, the collector material will be lead or
other
material capable of being oxidized, and a further method of the invention
provides for
the step of oxidizing such collector material to reduce the volume thereof, or
a
collector material. In such a method, the re-oxidized collector material will
thus be
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recaptured by slag of the flux. This method may be applied to conventional
assaying
processes wherein the reaction vessel is not preheated.
In the above aspect of the invention, the collector material is oxidized by
introducing
oxygen, or an oxygen producing material, into the reaction vessel. Preferably,
the
5 oxygen will be introduced into the collector material by means of a lance or
the like.
In an alternative arrangement the reaction vessel can be provided with a low
level
outlet and oxygen introduced into the reaction vessel through the low level
outlet
thereof for re-oxidizing collector material. Thereafter, the collector
material can be
to drained through the low level outlet further analysis.
Also according to this aspect of the invention, the method may include the
step of
introducing a separate collector for the material to be assayed into the
reaction vessel,
such as silver or gold.
In an alternative arrangement the method of the invention may include the step
of
separating the collector material from the slag formed during the fusion
process, and
thereafter contacting the collector material with oxygen or oxygen forming
material to
oxidize the collector material or a portion thereof. In this arrangement it is
preferable
that a stream of oxygen gas will be blown onto, or into the collector material
for
oxidization purposes. Thus in the cases where collector material includes
lead, such
lead will be oxidized to lead oxide which will be released as a vapor.
Collector
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material such as silver which is not capable of being oxidized readily, will
remain for
assaying purposes.
In a further example oxygen may be introduced into the separation vessel from
a
supply source via a collection mould which sealingly engages the separation
vessel
below the outlet duct therefrom.
Also according to this aspect of the invention, the method includes the step
of
disengaging the collection mould from the separation vessel to permit the
collected
io material to drain into such collection mould. Pressure in the collection
mould thus
serves to close the outlet duct until the collection mould is disengaged from
the
separation vessel.
Once the collected material has been discharged into the collection mould, the
material
will be caused to fuse and to form a prill, and such prill can be deposited on
a suitable
transportation means for further processing.
Also included within the scope of the invention, is a apparatus suitable for
use in the
above method comprising a separation vessel, having a low level outlet duct,
and a
collection mould disposed below the outlet duct and adapted sealingly to
engage the
separation vessel, an inlet for oxygen or other gas in the collection mould to
enable
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oxygen/gas to be ducted through the interior of the collection mould and the
low level
outlet duct, into the separation vessel.
Also according to this aspect of the invention, the apparatus includes lifter
means
whereby the collection mould can be lifted into engagement with the separation
vessel,
and lowered to a position removed from the separation vessel.
Preferably, the separation vessel will include a downwardly directed tube
formation
extending from the outlet duct, and against which the collection mould
sealingly
engages.
The invention further provides a method of separating the collector material
from the
slag, comprising the steps of providing a collector material which is of
greater density
and/or lower viscosity than the slag, providing a separating vessel which is
provided
with a outlet duct, and draining the collector material through such outlet
duct, the
arrangement being one wherein the dimensions of the outlet duct are such that
the
collector material passes therethrough, while the slag is arrested at the
duct.
Preferably the outlet duct will be disposed at the lower extremity of the
vessel.
The invention is also directed separately to the separating vessel described
above and
in one embodiment thereof, the vessel is of a generally conical shape in cross-
section,
with the outlet duct being disposed at the lowermost pinnacle of the cone
shape.
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Where the collector material is lead, the outlet duct could for example be of
a circular
cross-section having a diameter of between 0.5mm and 2.0mm, preferably around
1.0mm.
In an alternative arrangement, such a method of separating collector material
from slag
comprises the steps of providing a separating vessel which defines an interior
concavity which terminates in a lower portion for receiving the collector
material, and
which defines an outlet duct in a position spaced from such lower portion, and
comprising the further steps of rotating the reaction and separating vessel
transversely
1o so that collector material in the lower-most portion, flows to the zone of
the outlet
duct; and draining such collector material through the outlet duct. As
previously
mentioned the proportions of the outlet duct will be such that the collector
material is
capable of passing therethrough, while the slag is arrested.
With the above alternative method the vessel thus has a lower portion for
receiving
collector material and an outlet duct spaced from such lower portion, the
outlet duct
being such that the collector material is capable of passing therethrough,
while the slag
is arrested, and a concavity in the zone of the outlet duct for receiving the
collector
material when the reaction and separating vessel is rotated angularly to cause
the
collector material to flow to the zone of the outlet duct.
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According to a different aspect of the invention a handling mechanism for
transporting
an article such as a reaction vessel or crucible into a furnace is provided
comprising
carrier means, the carrier means being movable between a first position in
which it is
displaced from the furnace and a second position in which it mates with an
aperture in
the furnace; and drive means for moving the carrier means between the first
and
second positions.
The handling mechanism described above is particularly suitable for use in the
fire
assaying methods of the invention. Accordingly, the article may comprise at
least a
crucible containing a mineral sample and a flux therein.
Preferably, the aperture is located in a base portion of the furnace and the
carrier
means is suitable for mating with the aperture when in the second position,
effectively
to close the aperture. Further, the handling mechanism according to the
invention may
include a loading device for transporting an article to the carrier means when
the
carrier means is in the second position. The loading device is preferably a
robotic
arm. The drive means is preferably a pneumatic reciprocating ram.
Alternatively, the
drive means may be a lever or a cam mechanism.
The invention further provides a furnace for use with the handling mechanism
described above, the furnace having at least one aperture suitable for mating
with the
carrier means.
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Separately included within the scope of the invention, is a process for heat
treating an
article for example in an assaying process comprising the steps of:
- providing a furnace as described above;
5 - moving the carrier means to the first position;
- loading the carrier with an aticle;
- moving the carrier means to the second position such that the article is
carried into the furnace; and
- removing the article from the furnace after the required residence time,
10 by moving the carrier means to the first position.
According to yet a further aspect of the invention, a flux suitable for use in
the fire
assay methods of the invention includes a collector material adapted to
combine with
material in a mineral sample which is to be collected, and potassium
hydroxide. For
most applications, the flux will include between 5 % and 60%, preferably 7.5 %
potassium hydroxide by weight.
Further according to this aspect of the invention, the flux includes one or
more
additional compounds selected from the alkaline earth metal group of
compounds.
Preferably, such alkaline earth metal group compounds will be hydroxides. Thus
in
one arrangement the flux may include between 5 % and 60 %, preferably 7.5 % by
weight of calcium hydroxide.
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Also according to the invention, the flux may include one or more additional
compounds from the alkaline metal group, preferably hydroxides. For example,
the
flux may include between 10% and 19% sodium hydroxide, by weight.
In order more clearly to illustrate the invention, some embodiments thereof
are
described hereunder, purely by way of example, with reference to the
accompanying
drawings wherein:
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 is a flow diagram of a method of assaying in accordance with the
invention;
Figures 2 to 3 are schematic sectioned elevations of a reaction and separating
vessel which is employed in the method of the invention,
illustrating various steps in such method;
Figure 4
and Figure 5 are schematic sectioned elevations of a reaction and separating
vessel which is employed in a method of assaying in accordance
with the invention illustrating various steps in such method;
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Figure 6
and Figure 7 are schematic sectioned elevations of a reaction and separating
vessel which is employed in a method of assaying in accordance
with the invention illustrating various steps in such method;
Figure 8
and Figure 9 are schematic sectioned elevations of a reaction and separating
vessel which is employed in a method of assaying in accordance
with the invention illustrating various steps in such method; and
Figure 10
and Figure 11 are schematic elevations of a handling mechanism for introducing
and removing reaction vessels into and from a heating furnace.
DESCRIPTION OF DRAWINGS AND EXAMPLES OF THE INVENTION
Referring to the drawings, a method of assaying in accordance with the
invention
comprises the steps set out in Figure 1. These steps comprise providing a
mineral
sample shown at 10, normally in dry powdered form, and mixing (11) a
predetermined
weight of such sample with a predetermined quantity of a suitable known flux
which
contains lead oxide, nickel or on other material which is adapted to form a
collector
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material for the analyte/metal mineral which is to be assayed. The method of
the
invention is in particular but not exclusively adapted for assaying gold or
PGM's.
The mixture prepared as above, is next introduced into a reaction vessel (13).
It is a
feature of the invention that the reaction vessel will be pre-heated (12) to a
temperature
in the region of the fusion temperature of the mixture, in a suitable furnace
or the like.
Such furnace could for example be gas fired, electric or an induction furnace.
Upon
introduction of the mixture into the reaction vessel, further heat energy is
supplied to
the reaction vessel as shown at 14 to maintain it at the fusion level of the
mixture.
Upon fusion of the mixture, a collector material, such as lead or nickel
sulfide, is
formed at 15 and acts to collect the gold and PGM's through chemical affinity.
The
collector material can thereafter be separated from the slag as described
below, for
analysis.
One aspect of the invention, provides for the collector material to be reduced
in
volume (16), and if necessary, to be concentrated by a co-collector material
(17) in
order to enhance the assaying process. Such reduction in volume is illustrated
in
Figure 2 and comprises the step of introducing oxygen 23 into the collector
material
24, Figure 2, for example by means of a lance 21 which projects into the
reaction
vessel shown at 19, Figure 2. The oxygen 23 thus reacts with the lead 24, or
other
collector material, which is capable of being oxidized, and oxidizes the lead
to lead
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oxide which is recaptured in the slag 25. With this method, a small amount of
lead 24
can be retained for assaying (18), or else, concentrated in a co-collector
such as silver
or gold which is more amenable to analysis, for example, by means of spark
spectrometry. The invention thus envisages that a separate co-collector
material could
be added to the mixture prior to fusion or thereafter.
As an alternative to the use of the lance 21, the molten collector material 24
can first
be separated from the molten slag 19 and deposited in a cupel in molten form,
and at
that stage contacted with a rich source of oxygen, whereby the collector
material 24 is
oxidized or partially oxidized. As previously mentioned, the collector
material 24 can
comprise lead which is readily oxidized in such conditions, together with
silver as a
co-collector which is not readily oxidized. During the oxidation process, the
silver
will thus remain to form a prill which contains the metal to be assayed. Such
a prill
will for example lend itself to analysis by gas release cromatographic
analysis. Thus,
this source of oxygen can again for example be in the nature of a lance 21
used for
blowing oxygen gas onto or into the collector material 24, or alternatively,
an oxygen
producing salt can be introduced into the collector material 24.
Alternatively with reference to Figures 9 and 10 oxygen can be introduced
through the
low level outlet 20 of the reaction vessel 19 via a collector vessel 131 and a
tubular
extension 121 of the reaction vessel 19.
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The invention further provides for a methods of separating the molten
collector/co-
collector material 24 together with the gold or PGM's contained therein, from
the
molten slag 19.
5 Example 1 of a separating vessel:
One method comprises the provision of a separating vessel 19 illustrated in
Figures 2
and 3.
1o The vessel 19 is of a generally conical profile with the termination 19a of
the cone
facing downwardly. An outlet duct 20 is provided co-axially with the lower
termination 19a of the cone 19, and is adapted in use to drain the collector
material 24
from the vessel 19 into a suitable vessel or mould 26, Figure 3. The invention
envisages that the collector material 24 will be of a greater density and/or a
lower
15 viscosity than the molten slag 25 and the proportions of the outlet duct 20
will be such
that only the collector material 24 is capable of flowing through the duct 20.
Thus in
the case of lead, the lead will readily drain through the outlet duct 20,
while the molten
slag 25 will be arrested at the outlet duct 20 and incapable of passing
therethrough as a
result of the lower density and viscosity thereof, as shown in Figure 3. It
has been
found that an outlet duct 20 of generally circular cross-section with a
diameter of
between 0.5mm and 2.0mm preferably around 1.0mm, will be suitable.
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It will be appreciated that the size of the aperture could be rendered
adjustable to suit
requirements, for example by providing a suitable valve, not shown, or stopper
for
such outlet duct 20. One such arrangement is shown in Figure 2 wherein the
oxygen
lance 23 terminates in a plug formation 22 which is axially movable between a
position
wherein it engages the lower end 19a of the vessel 19 to seal the outlet duct
20, and a
position wherein the plug 22 is displaced from the lower end 19a of the vessel
19 to
open the outlet duct 20. With such an arrangement therefor, the separating
vessel 19
can also be utilized as a reaction vessel by closing the outlet duct 20 until
separation of
the collector material 24 and the slag 25 is required. Thus during fusion of
the
1o mixture 15, Figure 1, and the step of oxidizing the collector material 16,
Figure 1, the
plug 22 will be in its closed position. Subsequently, it will be opened to
effect
separation between the collector material 24 and the slag 25 as described
above.
Example 2 of a separating a vessel:
In this example with reference to Figures 4 to 7, a reaction and separating
vessel 19
comprises a body member which defines an interior concavity 32 which includes
a
lowermost portion 32a for receiving a collector material 24 during an assaying
procedure. Thus, during the process of causing fusion of a mixture of a flux
material
and a mineral sample, a collector material 24 in the form of lead or nickel
sulfide or
silver or the like is formed and serves to capture gold and PMG's present in
the
mineral sample. The collector material 24 being of greater density settles in
the
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lowermost zone 32a of the reaction and separating vessel, while a slag 25
which
includes gangue, overlies the collector material 24. As disclosed above,
oxygen may
be introduced into the collector material 24 to oxidize all, or a portion
thereof, which
is then reabsorbed in the slag 25.
The reaction and separating vessel 29 of the present disclosure is
characterized in the
provision of an outlet duct 20 which is located outside the lowermost zone 32a
of the
concavity 32, which receives the collector material 24. In the arrangements
illustrated, the outlet duct 20 is located in the side wall of the vessel 29,
but the
invention is not limited to such a location and clearly other positions could
also be
functional.
It is a feature of the invention that the collector material 24, or the
remainder thereof
after oxidization, is separated from the slag 25 by rotating the reaction and
separating
vessel 29 transversely, so that the collector material 24 flows to the zone of
the outlet
duct 20, and is received in the outlet duct concavity 30. From the outlet duct
concavity 30, the greater density and/or lower viscosity of the collector
material 24
permits such material to be drained through the outlet duct 20, whereas the
slag 25 is
arrested and cannot flow through the duct 20. As disclosed above, the
proportions of a
circular outlet duct 20 could be between 0.5mm to 2.0mm, preferably 1.0mm in
diameter.
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Preferably, the outlet duct 20 will include a concavity 30 into which the
collector
material 24 will flow prior to, or upon, being drained through the duct 20. If
required, a groove or pathway, not shown, could also be provided on the inner
surface
of the vessel 29 to direct the collector material 24 from the lowermost
portion 32a of
the vessel 29 to the outlet concavity 30.
In the arrangement illustrated in Figures 4 and 5; the vessel 29 is rotated
through
approximately 90 degrees in order to position the outlet duct 20 at a lower-
most
position of the rotated vessel 29 for purposes of draining the collector
material 24
1o therefrom. In the arrangement illustrated, the outlet duct 20 is disposed
in a side wall
of the vessel 29, but clearly this position can vary in accordance with the
requirements, and could for example be disposed in a roof portion of the
vessel. It
will be understood that the position of the outlet duct 20 will determine the
angle
through which the vessel 29 should be rotated in order to cause the collector
material
24 to flow to such outlet duct 20 for drainage purposes.
In the arrangement shown in Figures 4 and 5, the outlet duct concavity 30 is
formed
by an outward bulge 29a of the side wall of the vessel 29.
In an alternative arrangement shown in Figures 6 and 7, the outlet duct
concavity 30
is formed by an inwardly directed shoulder 29b of the inner wall of the vessel
29.
With this arrangement, the vessel will be rotated through an angle which is
greater
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than 90 degrees in order to position the vessel 29 so that the outlet duct
concavity 30 is
disposed lower-most. In such a position, the slag 25, or at least a portion
thereof, will
overflow from the vessel 29 as shown in Figure 7, and can be collected
separately.
Thus the arrangement will be such that all the slag 25 is decanted in such
position,
while the collector material 24 is drained through the duct 20.
In both examples described above, Figures 4 and 5 and Figures 6 and 7, the
outlet duct
20 may be provided with valve or stopper means for selectively draining
collector
material 24 from the vessel.
Example 3 of a separating vessel
Referring to Figures 8 and 9 separating means for use in the assay method in
accordance with the invention comprises a separation vessel 19 which is
generally
conically shaped and which terminates in a low level outlet duct 20. Below the
outlet
duct 20, a short length of ceramic tube 121 depends downwardly from their
separation
vessel 19.
The apparatus further includes a collection mould 131 which is disposed co-
axially
below the ceramic tube 121, and which is movably by means of a lifter 141 such
as a
hydraulic ram from a position removed from the ceramic tube as shown in Figure
8; to
a position wherein it sealingly engages the ceramic tube, Figure 9. The
collection
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mould 131 further includes a inlet 15 for oxygen 161 in the side wall thereof.
With
this arrangement, it is therefore possible to introduce oxygen 161 from a
supply
source, not shown into the separation vessel 10 via the interior of the
collection mould
14 and through the outlet duct 11 from the separation vessel 10.
5
In an assaying method using the above apparatus, a mixture of a comminuted
mineral
sample, and a assaying flux will be introduced into a separation vessel. The
flux will
for example include lead oxide which will form slag and lead in a reaction
process, the
latter combining with the gold and/or PMG's as a result of chemical affinity.
At this
10 stage, heat is supplied to the separation vessel and/or material therein.
The separation
vessel may also be preheated as disclosed above. At this stage, the collection
mould
131 will be engaged with the ceramic tube 121 oxygen 161ducted and introduced
into
the separation vessel 19 via the interior of the collection mould 13 land
outlet duct 20
while the molten slag and lead is added to the separation vessel 19. Once
sufficient
15 time has elapsed, the oxygen supply is shut-off. At this stage the
collector material
such as lead has been re-oxidized to red oxide for absorption in the molten
slag.
Pressure in the collection mould 131 will however at this stage limit
discharge of
material through the outlet duct 20 of the separation vessel 19. The next step
of the
20 process comprises lowering the collection mould 13 from the separation
vessel 19 by
means of the hydraulic ram 141, causing collected material 24 to drain through
the
outlet duct 20 into the collection mould 131. The diameter of the outlet duct
20 is
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such that the relatively dense and low viscosity collected material 24 will
pass through
the duct 20, while the slag 28 will be arrested within the vessel 19. The
collection
mould 131 which is relatively insulated from the heat of the separation vessel
19 by
means of the ceramic tube 121 will be relatively cool and the collected
material 24 will
rapidly solidify in the collection mould 131, to form a prill of material.
Thereafter the
collection mould 131 can be tilted to discharge the prill 24 onto suitable
conveying
means, not shown, for further processing. At this stage also the separation
vessel 19
can be tilted to discharge remaining slat 25 in the vessel 19 which is
immediately
available for re-use.
A further aspect of the invention comprises a handling mechanism whereby
reaction
vessels, crucibles, etc., which are used in a fire assay method can be loaded
into and out
of a furnace efficiently without undue loss of energy.
Such handling mechanism 110 consists of carrier means in the form of a number
of
level platforms 116 of refractory material, each of which are driven by a
reciprocating
ram 117, typically a pneumatic cylinder. Each platform 116 is movable between
a
first position in which it is displaced from the furnace 114 (shown in Figure
2) and a
second position in which it mates with a corresponding aperture 118 in the
furnace
112 (shown in Figure 1).
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The apertures 118 are located in a base portion of the furnace 114 and each
platform
116 is suitably dimensioned for mating with a complementary aperture 118 when
the
platform 116 is in the second position, effectively to close the aperture 118.
A loading device in the form of a robotic arm 120 is provided for
loading/unloading the
crucible 112 onto/from the platform 116 when the platform 116 is in the first
position.
In use, a crucible 112 containing at least a mineral sample and flux is
prepared for heat
treatment in the furnace 114. One of the platforms 116 is moved into the first
position,
in which it is displaced from its complementary aperture 118 in the base
portion of the
furnace 114. The robotic arm 120 loads a crucible 112 onto the platform 116.
The
reciprocating ram 117 moves the platform 116 into the second position, and the
crucible
112 is received into the furnace 114 through the aperture 118. The platform
116 mates
with the aperture 118 so as effectively to close the aperture 118.
After the required residence time, the reciprocating ram 117 retracts,
displacing the
platform 116 away from the furnace 114, into the first position. When in the
first
position, the crucible 112 containing molten flux is removed from the platform
116
with the robotic arm 120. Once the crucible has been removed, the platform is
moved
back into the second position, to prevent heat escaping from the furnace 114
through
the aperture 118.
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It is envisaged that the handling mechanism will be useful in a fire assaying
method in
that sample carrying crucibles can be heated consecutively and on a continuous
basis as
opposed to a batch basis, to prevent heat escaping from the furnace when the
crucibles
are removed. Because the crucibles are not heated on a batch basis, the
apparatus and
method according to the invention has a further advantage in that the
crucibles do not
cool substantially, which reduces the time required to preheat the crucibles
prior to
assaying.
Yet a further aspect of the invention comprises the provision of a novel flux
which has
1o been found to provide a particularly rapid reaction time is provided.??
In one example of a flux in accordance with the invention, suitable for
assaying of gold
ores and Platinum Group element ores could typically have the following
composition:
Potassium hydroxide 7.5%
Calcium hydroxide 7.5%
Sodium hydroxide 10%
Borax 31%
Litharge 30%
Sodium carbonate 7.0%
Silica 6.5%
Carbon 0.5%
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24
the above percentages being by weight.
In practice, the above composition will be used in quantities of approximately
200
grams for purposes of assaying gold ores and Platinum Group metal ores. For
mine
tailings quantities up to 500 grams might be used.
It has been found that the composition above, dramatically increases the rate
of fusion
of the flux during fire assay.
1o It has also been found that the action of the potassium hydroxide is
further enhanced
by the addition of sodium hydroxide. It has been found that a synergistic
effect is
created by the use of these two alkaline metal hydroxides.
The exact composition of the flux will vary in accordance with the types of
ores to be
1s assayed. Thus for example, the quantity of potassium hydroxide could vary
between
5% and 60%, calcium hydroxide between 51% and 60%, and sodium hydroxide
between 10% and 19%. In addition the flux composition could include fluorspar,
red
lead, potassium nitrate, and iron.
20 The advantages of the various aspects of the invention will be understood
by persons
skilled in the art. The processes of the invention readily lend themselves to
mechanization and computerization. It will also be understood that the
accuracy of the
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assaying process will be enhanced, and the time period required therefor,
greatly
reduced.
Doubtless variations of the invention in detail exist without departing from
the
5 principles set out in the consistory clauses. The invention is directed
separately to a
method of assaying as described above, as well as to a method of reducing the
volume
of a collector material, and/or concentrating in a co-collector material for
the metal to
be assayed, and also to a method and means for separating a collector/ co-
collector
material from a molten slag.
