Note: Descriptions are shown in the official language in which they were submitted.
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SYSTEM AND PROCESS FOR THE CONTINUOUS RECOVERY OF METALS
BACKGROUND OF THE INVENTION
This invention relates to mining and metallurgical refining and more
particularly to
systems and processes for solvent extraction and electroextraction of metals.
To this end, there are generally two main processes available for precious
metal
concentration and recovery: zinc precipitation, and electrowinning. Zinc
precipitation involves
crushing and grinding ore containing the precious metal (e.g., gold), and then
combining the
ground ore with a water and caustic cyanide solution. The resulting mud-like
pulp is moved to a
settling tank where the coarser gold-laden solids move to the bottom via
gravity, and a lighter
first pregnant solution of water, gold, and cyanide moves to the top and is
removed for further
processing. The gold-laden solids are agitated and aerated in a separate
agitated leach process
where oxygen reacts to leach the gold into the caustic water and cyanide
forming a second
pregnant solution. The second pregnant solution passes through a drum filter
which further
separates remaining solids. The first and second pregnant solutions are
combined with zinc to
precipitate out the dissolved gold. The resulting precipitated gold
concentrate may then be
smelted to produce refined gold bar.
Electrowinning typically involves extracting a precious metal such as gold
from an
electrolyte. First, activated carbon is combined with a pregnant solution in a
batch process step.
The activated carbon adsorbs the precious metal contained within the pregnant
solution, and
becomes "loaded" with the precious metal. The loaded carbon is then descaled
by sequentially
washing it in three batch process steps to remove ore residue. First, the
loaded carbon is moved
to a washing tank and then the tank is filled with a dilute acid solution. The
washing tank is then
drained and the used dilute acid solution is pumped away and disposed of. The
same washing
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tank is then filled with water to rinse remaining acid from the loaded carbon.
The water becomes
slightly acidic during this process. In a similar fashion to the dilute acid,
the used slightly acidic
rinse water is also drained from the washing tank, pumped away, and disposed
of. Lastly, the
tank is filled with a caustic solution, and the activated carbon is washed in
the caustic solution.
The used caustic solution is then drained from the tank, pumped away, and
disposed of. An
optional final water rinse step may be performed by again, filling the washing
tank with rinse
water or pH-neutral solution, rinsing caustic residue from the loaded carbon,
and then draining
the tank of the used rinse water/solution so that it may be pumped away for
disposal.
After washing, the loaded carbon is removed from the washing tank and then
added to a
strip solution comprising water, a caustic substance, and cyanide to form a
strip solution/loaded
carbon slurry. The strip solution/loaded carbon slurry goes through an elution
process where
high temperatures and pressures are used to "re-leach" gold from the loaded
carbon into the
caustic strip solution to form an electrolyte solution. The electrolyte
solution is then moved to a
batch electrolytic cell where wire (e.g., reticulated) or plate cathodes
collect deposited gold
concentrate during electrolysis. After the batch electrowinning process, the
cathodes are
manually removed from the cell for cleaning, so that gold concentrate
deposited thereon can be
removed from the cathodes and readied for smelting. After cleaning, the
cathodes are then
manually replaced within the electrolytic cell, and the entire sequence of
batch washing, elution,
and electrowinning processes is repeated. Some cathodes (e.g., wire cathodes,
due to their small
interstices) are not re-useable and must be recycled after processing, thereby
increasing
overhead/operational costs.
FIG. 27 schematically illustrates a conventional metal recovery process 9000
as described
above. Activated or reactivated carbon 9560 is suspended within a pregnant
solution in a
conventional batch carbon loading step 9700. The pregnant solution is
generally formed by
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percolating a dilute cyanide solution through a heap leach pad of crushed
mineral-laden ore (e.g.,
by way of a drip or spray irrigation having a concentration of about 0.5 to 1
pound of sodium
cyanide, potassium cyanide, or calcium cyanide per ton of solution). Once the
active carbon
adsorbs the desired material (e.g., gold, silver, platinum, lead, copper,
aluminum, platinum,
uranium, cobalt, manganese) from the pregnant solution, it becomes "loaded"
carbon 9570 and
enters a batch acid wash process 9100 configured for descaling the loaded
carbon 9570 as
previously discussed.
FIG. 28 shows one example of a conventional batch acid washing system 9100'.
Loaded
carbon 9570 enters an acid wash vessel 9120 which receives dilute acid from a
dilute acid tank
9140 via a pump 9132. Dilute acid overflow is captured by a sump pump 9150
which moves the
overflow to a neutralizing tank 9160. Contents of the neutralizing tank 9160
may be moved to a
secondary holding tank via a pump 9136. The conventional batch acid wash
process 9100
continues by draining the acid wash vessel 9120 of dilute acid solution, and
then filling the
vessel 9120 with an aqueous rinse solution. Overflow of aqueous rinse solution
is captured by
sump pump 9150 which moves the overflow to a neutralizing tank 9160 and/or a
holding tank.
The process 9100 may continue by draining the vessel 9120 of aqueous rinse
solution, and then
filling the vessel 9120 with a caustic rinsing agent. Overflow of the caustic
rinse may likewise
be captured by sump pump 9150 and moved to a neutralizing tank 9160 and/or a
holding tank
(not shown).
After the loaded carbon 9570 is descaled, it leaves the batch acid washing
process 9100
(via carbon transfer pump 9134) and enters a conventional batch (e.g. Zadra
strip) elution
process 9200. As shown in FIG. 29, a conventional batch elution process 9200
typically
involves feeding descaled loaded carbon 9500 and/or loaded carbon directly
from an adsorption
system 9700 into a strip vessel 9240. Strip vessel 9240 is generally a large
cylindrical tank of
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material suitable for holding reagents at an elevated pressure and temperature
(e.g., 138 degrees
C ¨ 148 degrees C). The descaled loaded carbon 9500 is maintained within the
strip vessel 9240
at high temperatures and pressure in the presence of a caustic aqueous strip
solution comprising
cyanide. After a period of time, spent carbon 9550 is removed from the strip
vessel 9240 (e.g.,
via carbon transfer pump 9232), and is moved to a carbon handling system or
carbon
regeneration system 9300' or process 9300. Hot electrolyte solution 9421 is
formed within the
strip vessel 9240 as material previously adsorbed onto the loaded carbon
leaches into the strip
solution. The hot electrolyte solution 9421 is also removed from the strip
vessel 9240 and passes
through a heating skid 9250 or equivalent heat exchanger for cooling before
entering a
conventional batch electrowinning system 9400' or process 9400. Cooling of hot
electrolyte
solution 9421 to form a lower temperature electrolyte solution 9530 is
generally necessary to
reduce the risk of flashing within a conventional batch electrolytic metal
recovery cell 9420. The
heating skid 9250 also serves to recycle energy by warming cooler barren
solution 9540 which
exits the electrolytic metal recovery cell 9420 (e.g., at about 66 degrees C)
and/or barren solution
9237 which exits the barren solution storing tank 9220 before re-entering the
strip vessel 9240 to
serve once again as a strip solution re-leaching agent. Warming of the cooler
barren solution
9237, 9540 to form a hot barren solution 9239 may also be done using a heater
in addition to, or
in lieu of said heating skid 9250. One or more pumps 9234, 9236 are generally
used to transfer
barren solution back to the strip vessel 9240. Additional reagent from a
reagent handling system
and/or more pregnant solution may be added to barren solution tank 9220 as
needed.
As shown in FIG. 30, electrolyte solution 9530 enters a conventional batch
electrolytic
metal recovery cell 9420 which operates in batch cycles. A series of parallel
plate cathodes are
placed within close proximity and the electrolyte solution 9530 is pumped in
and agitated around
the cathodes. Body portions of the cell 9420 carry an opposing charge with
respect to the
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cathodes, and by virtue of electrolysis, ions contained in the electrolyte
solution 9530 are
subsequently deposited on the cathodes as a cathode sludge concentrate of the
recovery metal or
as a solid cathode plating. In operation, cathodes are typically removed
simultaneously from the
cell 9420 in a batch process step in order to collect the recovered metal. In
instances where plate
cathodes are used, the cathode may be flexed to delaminate and remove the hard
cathode plating
from the cathode. In other instances where higher deposition wire mesh (i.e.,
"reticulated")
cathodes are employed, the concentrate is separated from the cathode in a
subsequent process
and the cathodes are then recycled. Sludge concentrate may collect at the
bottom of the cell
9420 and may be removed periodically. An electrowinning pump box 9440 and pump
9430 may
be employed to temporarily store spent electrolyte (i.e., barren solution)
which is removed from
the cell 9420 between batches.
Problems associated with the abovementioned conventional acid wash systems
9100' and
processes 9100 are numerous. For instance, the systems utilize independent ,
non-continuous,
"batch" process steps which require constant manpower, downtime, and energy
(e.g, continually
draining and refilling the same acid wash vessel 9120 with different rinsing
agents). Moreover,
such conventional batch acid wash processes 9100 typically discard expensive
acid, caustic,
and/or other reagents after each use. This increases overhead (e.g.,
purchasing costs, disposal
costs) and creates unnecessary harm to the environment. Furthermore, every
time a conventional
acid wash vessel 9120 is drained and re-filled with a different rinsing
solution, carbon (and
precious minerals/metals attached thereto) may not be recovered due to system
inefficiencies
caused by heat, friction, increased pump residence time and exposure, an
increased number of
pipe elbows and valves, and the frequent discarding of spent rinsing solution
which may still
contain small amounts of loaded carbon and precious metal. In other instances
(not shown), if
separate vessels are used for each rinse step of the acid wash process, as
many as four tanks and
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ten pumps may be required. This increases both initial plant overhead costs
and overall plant
footprint.
Problems associated with the described conventional batch elution process 9200
are also
numerous. For instance, the process 9200 employs batch process steps which
require constant
manpower and energy (e.g., continually draining and refilling the strip vessel
9240 with new
strip solution, hot barren solution 9239, and loaded carbon 9500 each time
more electrolyte
solution 9530 is needed for electrowinning 9400). This increases overhead
costs (e.g., labor,
maintenance), complicates production scheduling, and may cause harm to the
environment.
Furthermore, conventional metal recovery systems 9000' are bulky and require
large plant layout
footprints as demonstrated by FIG. 23, when compared to a system 100' for the
continuous
recovery of metals according to the invention (FIG. 22) which will be
described hereinafter.
Moreover, conventional elution systems have limited operating flow rates,
temperatures, and
pressures which drive up radiation losses and power consumption. Additionally,
the
electroextraction of metals using the conventional "batch" electrowinning
processes 9400
described above requires intervals of non-production downtime of the
electrowinning cell 9420
and significant physical labor, which may contribute to premature cathode wear
and wasted
electrolyte solution 9530.
The process of using zinc to precipitate precious metals out of pregnant
solutions is also
costly, may be less efficient for large-scale operations, works for only
certain metals, and may
result in less precious metal recovery.
OBJECTS OF THE INVENTION
It is, therefore, an object of the invention to provide an improved metal
recovery system
which is configured for continuous carbon loading/adsorption, continuous
washing and stripping
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of loaded carbon, continuous electrolyte formation, continuous electrowinning,
and continuous
regeneration/re-activation, thereby avoiding the aforementioned problems
associated with
conventional batch metal recovery processes.
Another object of the invention is to improve the efficiency of a metal
recovery process
(e.g., by minimizing radiation losses, reducing power consumption, minimizing
reagent
consumption, and preventing carbon breakdown and electrolyte loss).
Yet another object of the invention is to prevent or minimize carbon loss and
reagent
waste.
Another object of the invention is to maximize total metal recovery.
Another object of the invention is to provide a metal recovery system which is
configured
to cost less and have a smaller footprint area than conventional metal
recovery systems.
Another object of the invention is to provide a system and process for the
recovery of
metals which is configured to operate at higher flow rates, temperatures,
and/or pressures than
conventional processes.
Yet even another object of the invention is to reduce the percentage by weight
of
unrecovered metal present in spent electrolyte/barren solution.
These and other objects of the invention will be apparent from the drawings
and
description herein. Although every object of the invention is believed to be
attained by at least
one embodiment of the invention, there is not necessarily any one embodiment
of the invention
that achieves all of the objects of the invention.
SUMMARY OF THE INVENTION
A system for the continuous recovery of metals is provided. The system
comprises, in
accordance with some embodiments of the invention, at least one of a
continuous acid wash
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system configured for receiving a continuous, uninterrupted inflow of loaded
carbonaceous
particulate and delivering a continuous, uninterrupted outflow of descaled
loaded carbonaceous
particulate; a continuous elution system configured for receiving a
continuous, uninterrupted
inflow of a strip solution containing a descaled loaded carbonaceous
particulate and delivering a
continuous, uninterrupted outflow of electrolyte solution; and a continuous
electrowinning
system configured for receiving a continuous, uninterrupted inflow of
electrolyte solution,
delivering a continuous uninterrupted outflow of a barren solution, and
continuously and
uninterruptedly forming a cathode sludge concentrate. Each of the continuous
acid wash system,
the continuous elution system, and the continuous electrowinning system are
generally
configured to operate simultaneously without periodic interruptions which are
common with
conventional batch metal recovery processes.
In some embodiments, the system may comprise an integrated carbon regeneration
system operatively connected to the continuous elution system. A continuous
carbon
loading/adsorpsion system may be operatively connected to and upstream of the
continuous acid
wash system. The continuous acid wash system may be operatively connected to
the continuous
elution system; for example, via a holding tank between said continuous acid
wash system and
said continuous elution system. One or more pumps may be provided to
facilitate the
transportation of slurry and solids within the system. In preferred
embodiments, the continuous
elution system is operatively connected to the continuous electrowinning
system and comprises
one or more screens or filters configured to prevent carbonaceous particulate
from passing to the
continuous electrowinning system.
The continuous acid wash system may comprise a chamber adapted for retaining a
fluidization medium; an inlet adapted for receiving a feed containing loaded
carbonaceous
particulate; a fluidized bed distribution panel or other means adapted for
fluidizing the loaded
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carbonaceous particulate in the presence of said fluidization medium; an
opening adapted to pass
loaded carbonaceous particulate and fluidization medium from the chamber; and
a screen
adapted to filter loaded carbonaceous particulate from a fluidization medium.
The continuous
elution system may comprise a splash vessel, a continuous elution vessel, and
a flash vessel,
wherein the splash vessel is operatively connected to the continuous elution
vessel in series, the
continuous elution vessel is operatively connected to the flash vessel in
series, and the splash
vessel is operatively connected to the flash vessel in parallel. The
continuous electrowinning
system comprises an electrolytic cell having a cell body configured to
maintain electrolyte
solution at a high pressure and/or temperature; at least one anode; at least
one cathode; an inlet
configured for receiving a continuous, uninterrupted influent stream of
electrolyte solution; a
first outlet configured for discharging a continuous, uninterrupted effluent
stream of spent
electrolyte solution; a second outlet configured for removing cathode sludge
concentrate; and a
residence chamber configured to continuously transfer electrolyte solution
from said inlet to said
first outlet and increase residence time of said electrolyte solution between
said at least one
anode and said at least one cathode. The residence chamber may comprise one or
more channels
which are configured to provide a forced flow of electrolyte solution therein
which is strong
enough to continuously dislodge and/or transport cathode sludge concentrate
along said one or
more channels and eventually out of said residence chamber.
The continuous elution vessel may comprise an influent manifold and an
effluent
manifold which communicate with the first outlet and inlet of the electrolytic
cell, respectively,
and may further comprise a fluidized bed and/or one or more internal baffles
which are
configured to torture flow paths and increase a residence time of loaded
carbonaceous particulate
therein. A valve configured to flash solution leaving the continuous elution
vessel and entering
the flash vessel may also be provided.
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The continuous acid wash system may comprise at least one of an acid solution,
an
aqueous solution, and a caustic solution. The continuous elution system may
comprise a solution
containing at least one of a carbonaceous particulate loaded with a precious
metal, an electrolyte
solution, spent carbonaceous particulate, a caustic, an aqueous component, and
cyanide. The
continuous electrowinning system may comprise an electrolyte solution or
cathode sludge
concentrate. Each of the continuous acid wash system, the continuous elution
system, and the
continuous electrowinning system may be configured to increase a residence
time, pressure, or
temperature of solutions or slurries contained therein and may comprise a
screen or filter
element.
In some embodiments, the continuous acid wash system may comprise multiple
washing
vessels, each washing vessel comprising a chamber adapted for retaining a
fluidization medium;
an inlet adapted for receiving a feed containing a loaded carbonaceous
particulate; a fluidized
bed distribution panel or other means adapted for fluidizing and cleaning the
loaded
carbonaceous particulate with said fluidization medium; an opening adapted to
pass loaded
carbonaceous particulate and fluidization medium from the chamber; and a
screen adapted to
filter loaded carbonaceous particulate from fluidization medium. For instance,
in some
embodiments, the continuous acid wash system may comprise an acid wash tank
containing an
acidic fluidization medium, an aqueous rinse tank containing a substantially
pH-neutral aqueous
solution, and a caustic rinse tank containing an alkaline fluidization medium.
In some embodiments, the continuous acid wash system may comprise one or more
recirculation tanks for collecting spent fluidization medium, and one or more
weirs, channels,
valves, or drains for capturing spent fluidization medium. The continuous
electrowinning system
may be configured for continuous and uninterrupted collection and removal of
said cathode
sludge concentrate and may comprise one or more channels defined between a
cathode, an
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anode, and an insulator. The one or more channels may comprise portions of a
helix, spiral, coil,
compound curve, 3D-spline curve, figure-8, or serpentine shape and the cathode
and anode may
be formed as sleeves or tubes which are separated by said insulator. In some
embodiments, the
carbon regeneration system is operatively connected to both the continuous
elution system and
the continuous carbon loading/adsorpsion system, and the continuous carbon
loading/adsorpsion
system is operatively connected to said continuous acid wash system.
A process for the continuous recovery of a metal is also disclosed. The
process,
comprises, in accordance with some embodiments, continuously feeding a
continuous wash
system with particulate loaded with a metal; continuously washing said loaded
particulate within
the continuous wash system to descale the loaded particulate; continuously
removing descaled
loaded particulate from said continuous wash system; continuously loading a
continuous elution
system with said descaled loaded particulate; continuously removing
electrolyte solution from
said continuous elution system; continuously feeding a continuous
electrowinning system with
said electrolyte solution; continuously removing spent electrolyte solution
from said continuous
electrowinning system; and, continuously delivering said spent electrolyte
solution to said
continuous elution system; wherein each of the continuous wash system, the
continuous elution
system, and the continuous electrowinning system are configured to allow the
above steps to be
performed simultaneously, without the periodic interruptions required for
conventional batch
processes.
The process may further comprise continuously removing spent particulate from
the
continuous elution system; continuously feeding said spent particulate to a
carbon regeneration
system; continuously removing cathode sludge concentrate from the continuous
electrowinning
system; and/or forming said loaded particulate by continuously adsorbing metal
onto said
particulate in a continuous carbon loading/adsorption system which is similar
to or identical to
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said continuous wash system. The particulate may be one of a carbonaceous
particulate, a
polymeric adsorbent, or an ion-exchange resin.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 schematically illustrate a system and method for the continuous
recovery
of metals according to some embodiments;
FIG. 3 is a flowchart of a three-sequence continuous acid wash operation
according to
some embodiments;
FIGS. 4 and 5 outline steps of a continuous acid washing process according to
some
embodiments;
FIGS. 6 and 7 depict a washing tank which may be used in the acid wash process
shown
in FIGS. 1-5;
FIG. 8 shows an acid wash system comprising a plurality of the washing tanks
depicted
in FIGS. 6 and 7;
FIGS. 9 and 12 schematically illustrate a system and method of continuous
elution
according to some embodiments;
FIG. 10 is an isometric view of a continuous elution system according to some
embodiments;
FIG. 11 shows a side cutaway view of the continuous elution system of FIG. 10;
FIGS. 13 and 19 schematically illustrate a system and method of continuous
electrowinning according to some embodiments;
FIG. 14 shows a top plan view of a continuous electrowinning system according
to some
embodiments;
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FIGS. 15 and 16 are vertical and isometric cutaway views, respectively, of a
continuous
electrowinning system taken on line XV-XV in FIG. 14;
FIG. 17 is a detailed view of FIG. 15, showing the particulars of an inlet
according to
some embodiments;
FIG. 18 is a transverse cutaway view of an electrowinning cell along line
XVIII-XVIII in
FIG. 14;
FIG. 20 shows a process for regenerating/reactivating spent carbon according
to some
embodiments;
FIGS 21 and 22 show a system for the continuous recovery of metals;
FIG. 23 shows a conventional batch system for the recovery of metals;
FIG. 24 shows an alternative to the washing tank shown in FIGS. 6-8 or an
apparatus to
be used for continuous carbon loading/adsorption;
FIG. 25 shows a detailed isometric view of the chamber shown in FIG. 24;
FIG. 26 is a cutaway view of the chamber shown in FIG. 25;
FIG. 27 shows a conventional system for the recovery of metals.
FIG. 28 shows a conventional acid wash process;
FIG. 29 shows a conventional batch elution process; and,
FIG. 30 shows a conventional batch electrowinning process.
DETAILED DESCRIPTION OF THE INVENTION
As shown in FIGS. 1 and 2, a plant system 100' or process 100 for the
continuous
recovery of a metal from mined ore may comprise, in accordance with some
embodiments of the
invention, a continuous acid wash system 10' or process 10, a continuous
elution system 20' or
process 20, a continuous electrowinning system 40' or process 40, a continuous
carbon
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regeneration system 30' or process 30, and a continuous carbon
loading/adsorption system 70' or
process 70. Activated/reactivated carbon 56 (which may be derived for example,
from coconut
shells or charcoal), or alternatively, an equivalent particulate substance
such as loaded polymeric
adsorbent or loaded ion-exchange resin, is subjected to a continuous carbon
adsorption process
70 where it spends a time of residence suspended in a pregnant solution which
contains a
dissolved target recovery metal such as gold, silver, copper, aluminum,
platinum, uranium,
chromium, zinc, cobalt, manganese, or lead. The continuous carbon
loading/adsorption system
70' or process 70 may comprise, for example, an apparatus as shown in FIGS. 6
and 7 or FIGS.
24-26 which serves to fluidize the activated/reactivated carbon 56 within the
pregnant solution.
Once the carbon 56 becomes loaded with the target recovery metal, it undergoes
a continuous
acid wash process 10. Descaled loaded carbon 50 leaving the continuous acid
wash process 10
enters a holding tank 60 filled with a strip solution containing one or more
reagents (e.g., water,
caustic, and cyanide) to form a slurry 51 of strip solution and descaled
loaded carbon 50. The
slurry 51 enters a continuous elution process 20 where the temperature and/or
the pressure of the
slurry 51 is increased and the target recovery metal previously adsorbed by
the carbon is re-
leached into the strip solution thereby forming an electrolyte solution 53
which may be used for a
continuous electrowinning process 40. Barren solution (i.e., spent
electrolyte) 54 leaving the
continuous electrowinning process 40 is returned to the continuous elution
process 20 and/or the
holding tank 60 for re-use. A solids fraction 55 of spent carbon, depleted of
its target recovery
metal via the continuous elution process 20, moves to a carbon regeneration
process 30 for
reactivation before being re-used in the continuous carbon loading/adsorption
process 70.
As shown in FIGS. 2-5, a continuous acid wash process 10 may generally
comprise the
steps of: feeding 1004 loaded carbon 57 into a continuous acid wash system
10', fluidizing 1006
incoming loaded carbon 57 in a dilute acid solution within a first acid wash
tank 12, extracting
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1008 loaded carbon from the acid wash tank 12, screening 1010 the extracted
loaded carbon to
remove the dilute acid solution, capturing 1012 dilute acid solution 57c
separated from the
loaded carbon, optionally processing 1014 the captured dilute acid solution
57c (e.g., filtering,
additives, pH adjust), and recycling the dilute acid solution 57c by feeding
1016 the dilute acid
solution 57c back into the acid wash tank 12. Acid-rinsed loaded carbon 57a
which has
undergone an acid bath in acid wash tank 12 is fed 1018 into a second aqueous
rinse tank 14
containing water or another pH-neutral aqueous rinse solution 57d, and then
fluidized 1020 in
said aqueous rinse tank 14. The process 10 further comprises extracting 1022
rinsed loaded
carbon 57b from the aqueous rinse tank 14, screening 1024 the extracted rinsed
loaded carbon
57b to remove aqueous rinse solution 57d, capturing 1026 separated aqueous
rinse solution 57d
separated from the rinsed loaded carbon 57b, optionally processing 1028 the
captured aqueous
rinse solution 57d (e.g., filtering, additives, pH adjust), and recycling the
aqueous rinse solution
57d by feeding 1030 the aqueous rinse solution 57d back into the aqueous rinse
tank 14. Rinsed
loaded carbon 57b which has undergone washing in aqueous rinse tank 14 is fed
1032 into a
third caustic rinse tank 16 containing a caustic rinse solution 57e, and is
then fluidized 1034 in
said caustic rinse tank 16. The continuous acid wash process 10 further
comprises extracting
1036 descaled loaded carbon 50 from the caustic rinse tank 16, screening 1038
the extracted
descaled loaded carbon 50 to remove caustic rinse solution 57e, capturing 1040
caustic rinse
solution 57e separated from the descaled loaded carbon 50, optionally
processing 1042 the
captured caustic rinse solution 57e (e.g., by filtering, providing additives,
or adjusting pH), and
recycling the caustic rinse solution 57e by feeding 1044 the solution 57e back
into the caustic
rinse tank 16. The continuous acid wash process 10 may comprise the step of
providing one or
more pumps 13a, 13b for re-circulating the rinsing solutions in each of the
aforementioned tanks
12, 14, 16. Optionally, a fourth aqueous rinse cycle (not shown) may be
provided, and one of
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ordinary skill in the art would acknowledge that any one or more of the
aforementioned washing
steps may be repeated or alternated.
Turning now to FIGS. 6 and 7, an acid wash tank 200 for cleaning and descaling
a loaded
particulate material may be employed for any portion of the continuous acid
wash process 10.
The loaded particulate material washed within said acid wash tank 200 may be
of any particle
size, shape, and density which can be fluidized by or suspended within a
cleaning fluidization
medium. The acid wash tank 200 is advantageously configured to descale active
carbon
particulate which has been loaded with a target metal, in preparation for
creating an electrolyte
for electrowinning. In such instances, the acid wash tank 200 may be filled
with a fluidization
medium comprising acid. Similar tanks 200', 200" may be used with fluidization
mediums
comprising water or caustic soda. Moreover, similar tanks may be used in yet
other processes
such as a continuous carbon loading/absorption process 70, wherein the
particulate comprises
activated/reactivated carbon 56, and the fluidization medium comprises a
pregnant solution
formed by percolating cyanide and/or other reagents through a heap leach pad
of crushed ore
containing a target metal or mineral.
According to some embodiments, acid wash tank 200 may comprise an acid wash
tank
having a first chamber 220, a first fluidized bed distribution panel 221, a
first inlet 222, a first
recirculation inlet 223a, a first recirculation outlet 223b, a first weir 224,
a first screen 226, a first
overflow outlet 227, a first discharge outlet 228, a first recirculation tank
229, a bottom wall 260,
an inner tubular wall 266, an outer tubular wall 268, and a first channel 282
defined between the
inner tubular wall 266 and outer tubular wall 268 adjacent the first weir 224.
The first screen
226 serves to filter an incoming feed by separating its liquid fraction (e.g.,
spent pregnant
solution, fluidization medium, or transport fluid) from its solid particulate
fraction (metal-laden
loaded or reloaded carbon). The liquid fraction drained from the particulate
is maintained in the
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first recirculation tank 229 and may be removed through first recirculation
outlet 223b. The first
recirculation outlet 223b may be sealed during operation, coupled to a holding
tank, coupled to a
drain, coupled to a sump pump, or otherwise configured to feed an upstream or
downstream
process.
In some embodiments, as shown in FIG. 8, a continuous acid wash system 10' may
comprise one or more separate washing tanks 200, 200', 200" connected in
series in order to
provide flexibility in customizing plant layout and/or reduce overall
footprint. In some
instances, the tanks 200, 200', 200" may comprise similar or identical design
characteristics, each
containing different fluidization mediums. For example, in some embodiments, a
first tank 200
may comprise an acid wash tank containing a strong or dilute acid solution
57c, whereas second
200' and third 200" tanks may comprise aqueous and caustic rinsing tanks
containing aqueous
57d and caustic 57e rinsing agents, respectively. While not required, tanks
200, 200', and 200"
may be constructed as "universal" or "interchangeable" tanks. Moreover, tanks
200, 200', 200"
may be configured with tubular (e.g., cylindrical pipe or prismatic extrusion)
shapes as shown in
order to reduce manufacturing costs. Any one or more of tanks 200, 200', and
200" may be
replaced with a tank of dissimilar scale or a tank 2000 as shown in FIGS. 24-
26, which will be
described hereinafter.
A first fluidization medium comprising a dilute acid or anti-scaling agent
solution may
occupy the first acid wash tank 200. In some embodiments, the first
fluidization medium may
comprise a solution of 1-10% vol/vol mineral acid, such as nitric acid or
hydrochloric acid
configured to dissolve carbonate scale. In use, incoming loaded/reloaded
carbon 57 moves over
the first screen 226 and flows into the first chamber 220 of the first acid
wash tank 200 via the
first inlet 222. Fluid which may be present with the incoming loaded/reloaded
carbon 57 is
drained and enters the first recirculation tank 229. The screened loaded
carbon subsequently
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falls downwardly along the first screen 226 and towards the first fluidized
bed distribution panel
221 and is fluidized by the first fluidization medium. The first fluidization
medium enters the
first recirculation inlet 223a and passes through distribution panel 221.
Clarified first
fluidization medium rises above the highest suspended level of loaded carbon
within the first
acid wash tank 200 and pours over the first weir 224 and into the first
channel 282. Thereafter,
clarified first fluidization medium exits the first acid wash tank 200 via
outlet 227 and optionally
feeds the first recirculation inlet 223a and first fluidized bed distribution
panel 221. One or more
pumps 13a may be provided between outlet 227 and inlet 223a.
A slurry of acid-rinsed loaded carbon 57a and residual first fluidization
medium exits the
first acid wash tank 200 through the first discharge opening 228 and enters a
second aqueous
rinse tank 200' through a second inlet 232. The acid-rinsed loaded carbon 57a
may be conveyed
to the tank 200' using only gravitational forces, or the acid-rinsed loaded
carbon 57a may be
conveyed to the tank 200' using one or more slurry pumps (not shown). A second
fluidization
medium such as a substantially pH-neutral aqueous scrubbing solution or a hot
water may
occupy the second aqueous rinse tank 200'. In use, the acid-rinsed loaded
carbon 57a and first
fluidization medium moves over a second screen 236 or equivalent filter and
then flows into the
second chamber 230 for pre-soak. The second screen 236 serves to separate
residual first
fluidization medium liquid from the acid-rinsed loaded carbon 57a, wherein
drained first
fluidization medium is maintained in a second recirculation tank 239 and may
be removed
through second recirculation outlet. The second recirculation outlet 233b may
be coupled to a
holding tank, a filtering apparatus, or an upstream or downstream process. For
instance, as
schematically indicated by the dotted line path of dilute acid solution 57c',
the second
recirculation outlet 233b may be operatively connected to the first
recirculation inlet 223a to
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fluidize loaded/reloaded carbon 57 within the first washing tank 200. Though
not shown, one or
more pumps may be disposed between the outlet 233b and inlet 223a.
After passing over the second screen 236, acid-rinsed loaded carbon 57a
subsequently
falls towards a second fluidized bed distribution panel 231 and is fluidized
within the second
chamber 230 by a flow of second fluidization medium entering the second
recirculation inlet
233a and passing upwards through panel 231. Clarified second fluidization
medium free of
loaded carbon particulate rises above a suspended level of acid-washed loaded
carbon and pours
over a second weir 234 and into a second channel 284, where it exits the
second aqueous rinse
tank 200' via outlet 237 and optionally feeds the second recirculation inlet
233a and second
fluidized bed distribution panel 231 as schematically illustrated by dotted
line path taken by
aqueous rinse solution 57d.
A slurry of rinsed loaded carbon 57b and second fluidization medium exits the
second
washing tank 200' through second discharge opening 238 and enters a third
washing tank 200"
through a third inlet 242. The rinsed loaded carbon 57b may be conveyed to the
third caustic
rinse tank 200" using only gravitational forces, or the rinsed loaded carbon
57b may be conveyed
to the tank 200" using one or more pumps (not shown). A third fluidization
medium such as a
caustic rinse solution may occupy the third washing tank 200". For example,
the third
fluidization medium may comprise an amount of sodium hydroxide (NaOH) or
potassium
hydroxide (KOH) between 0.5% and 5% wt, for instance 1% wt. The third
fluidization medium
may comprise other reagents, for instance 1-10% wt sodium cyanide (NaCN). The
third
fluidization medium may be heated (e.g., 20-100 degrees C). In use, a slurry
of rinsed loaded
carbon 57b and second fluidization medium flows over a third screen 246 or
equivalent filter and
into the third chamber 240. The third screen 246 serves to filter the slurry
by separating its
second fluidization medium liquid fraction from its rinsed loaded carbon 57b
solid fraction. The
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separated second fluidization medium is maintained in a third recirculation
tank 249. The
second fluidization medium may be removed from the tank 249 via a third
recirculation outlet
243b which may be coupled to a holding tank, filtering apparatus, or one or
more upstream or
downstream processes. For instance, as schematically indicated by path taken
by aqueous rinse
solution 57d', the third recirculation outlet 243b may be operatively
connected to the second
recirculation inlet 233a in order to help fluidize particulate within the
second washing tank 200'.
Though not shown, one or more pumps may be disposed between the outlet 243b
and inlet 233a.
In some instances, outlet 243b and inlet 233a may be operatively connected to
a plant water
system.
After passing over third screen 246, twice-rinsed loaded carbon particulate
subsequently
falls towards a third fluidized bed distribution panel 241 and is fluidized
within the third
chamber 240 by a flow of third fluidization medium entering the third
recirculation inlet 243a
and passing through the panel 241. Clarified third fluidization medium rises
above the highest
level of suspension of the loaded carbon fluidized within the tank 200" and
pours over a third
weir 244 and into a third channel 286, where it exits the caustic rinse tank
200" via outlet 247
and optionally feeds the third recirculation inlet 243a as indicated by the
dotted line path taken
by caustic rinse solution 57e.
A slurry of caustic-rinsed, descaled loaded carbon 50 and third fluidization
medium exits
the third caustic rinse tank 200" through third discharge opening 248 and may
be subsequently
screened or filtered for further processing. After leaving the tank 200", de-
scaled loaded carbon
50 within the slurry may be separated from the third fluidization medium
liquid fraction by a
screen or filter (not shown) and then added to a strip solution of water,
caustic, and cyanide in a
holding tank 60 for use in downstream continuous elution 20 and electrowinning
40 processes.
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The continuous acid wash system 10' shown and described, when used, reduces or
eliminates the need to continually purchase and replace lost quantities of
carbon particulate,
water, caustic, acid, and/or other anti-scaling agents. System 10' also
significantly reduces the
amount of spent solution and carbon requiring disposal and reduces the
potential for
environmental harm.
It should be known that the particular features and suggested uses of the
continuous acid
wash system 10' described herein are exemplary in nature and should not limit
the scope of the
invention. For example, fluidized bed portions 221, 231, 241 may be replaced
with, or used in
combination with one or more mechanical or forced air agitators (not shown) to
suspend loaded
carbon particulate in fluidization medium. Moreover, the number of chambers
220, 230, 240 per
system 10' may be greater or less than what is shown. In some embodiments, the
relative sizes,
dimensions and/or volumes of chambers 220, 230, 240 may vary. In other
embodiments, the
chambers 220, 230, 240 may be dimensioned and proportioned similarly.
Additionally, one or
more tanks 200, 200', 200" may be placed in parallel with others in order to
increase throughput.
For example, a third caustic rinse tank 200" of a system 10' may be directly
or indirectly coupled
to a plurality of upstream aqueous rinse tanks 200'. Multiple tanks 200 may
replace any one of
the single tanks 200, 200', 200" in system 10' by splitting inlets 222, 223a;
232, 233a; 242, 243a
and/or outlets 223b, 227; 233b, 237; 243b, 247. Moreover, any one chamber 220,
230, 240 may
be compartmentalized into multiple chambers. As previously stated, the system
10' or portions
thereof may be used to continuously load activated carbon in a continuous
carbon
loading/adsorption process 70. For example, infeed particulate may comprise
activated or
reactivated carbon and the first, second, and third fluidization mediums may
comprise a pregnant
solution (e.g., sodium cyanide (NaCN) solution containing a dissolved precious
metal).
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FIG. 9 illustrates a continuous elution process 20 according to some
embodiments. A
feed slurry 51 of strip solution and descaled loaded carbon 50 is moved to a
splash vessel 22 via
gravity or one or more pumps 23. The splash vessel 22 increases the
temperature and/or pressure
of incoming slurry 51 and delivers the hot pressurized slurry 51a to a
continuous elution vessel
24. In the continuous elution vessel 24, target metal previously adsorbed onto
the loaded carbon
is leached into the strip solution to form an electrolyte solution 53. The
electrolyte solution 53 is
filtered by one or more screens to remove spent carbon and non-stripped loaded
carbon from the
electrolyte solution 53, before it is moved to a continuous electrowinning
process 40. Electrolyte
solution 53 may be conveyed to the continuous electrowinning process via an
effluent manifold
28b provided on the continuous elution vessel 24. Spent slurry 51c of strip
solution and spent
carbon is flashed by a valve 29 and enters into a flash vessel 25 where steam
is captured and
returned to the splash vessel 22 via a steam return 21 to help heat and
pressurize the splash vessel
22 in an efficient manner. The resulting concentrated spent slurry 51d is
separated into solid 55
and liquid 52 fractions using a dewatering screen 26. The liquid fraction 52
of concentrated
spent slurry 51d may be returned to holding tank 60, and the solids fraction
55 of the
concentrated spent slurry 51d (i.e., spent de-watered carbon) may be sent to a
carbon
regeneration process 30 for reactivation. Barren solution 54 returning from a
continuous
electrowinning process 40 is generally heated with an immersion heater 27 and
then sent back to
the continuous elution vessel 24 via one or more pumps 23 and an influent
manifold 28a.
FIG. 10 shows a continuous elution system 20' according to some embodiments.
The
continuous elution system 20' generally comprises a first splash vessel 22, a
second continuous
elution vessel 24, and a third flash vessel 25 connected in series via piping
sections, and a steam
return 21 extending between the splash 22 and flash 25 vessels in parallel.
One or more pumps
23 may be provided at various portions of the system 20' in order to
facilitate flows to, from, and
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between the vessels 22, 24, 25, other parts of the system 20', and/or other
portions 10', 30', 40'
within a system 100' for the continuous recovery of metals.
As shown in FIG. 11, the continuous elution vessel 24 comprises a fluidized
bed
distribution panel 320 which separates a residence chamber 340 from a
fluidizing chamber 350.
One or more baffles 318 may be provided within the residence chamber 340 in
various
configurations (e.g., number, angle, spacing, geometry), in order to increase
the residence time of
incoming hot pressurized slurry 51a within the continuous elution vessel 24.
The one or more
baffles 318 may be parallel and staggered to create a serpentine flow path 5
lb of hot pressurized
slurry 51a. The baffles 318 may be parallel, non-parallel, staggered at a
single predetermined
angle, or disposed in alternating fashion with each baffle oriented in a
different predetermined
angle. It should be understood that other baffle patterns and arrangements may
be used without
limitation, and that the shapes, porosities, and/or textures of baffles 318
may differ from what is
shown. For example, any one or more of the baffles 318 may comprise folds,
bends, curves,
corrugations, openings, lattice structures, or the like.
Slurry flowing within the continuous elution vessel 24 may contain incoming
hot
pressurized slurry 51a and barren solution 54 leaving a continuous
electrowinning system 40' or
process 40. Fluidizing chamber 350 may be fed by an influent manifold 28a
connected to the
continuous elution vessel 24 via one or more influent ports 326 having
influent port mounts 322.
Alternatively, the influent manifold 28a may instead be connected directly to
the one or more
sidewalls 310 of the continuous elution vessel 24. A stream of barren solution
54 flows into the
continuous elution vessel 24 via the influent manifold 28a. The stream enters
and fills the
fluidizing chamber 350 and flows through fluidized bed 320 to help fluidize
and suspend carbon
particulate within the residence chamber 340 as it travels along the
serpentine flow path 5 lb.
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An effluent manifold 28b is also provided to the continuous elution vessel 24
to extract
an electrolyte solution 53 from the residence chamber 340 and deliver said
electrolyte solution
53 to a continuous electrowinning system 40' or process 40. Effluent manifold
28b comprises
one or more effluent manifold ports, which may be provided with effluent
manifold port mounts
for ease of connection to the continuous elution vessel 24. Similarly to the
influent manifold
28a, the effluent manifold 28b may be connected directly to the one or more
sidewalls 310 of the
continuous elution vessel 24, or may be connected to the vessel 24 via one or
more effluent ports
316 having effluent port mounts 312.
While in the residence chamber 340 of the continuous elution vessel 24, loaded
carbon is
exposed to strip solution reagents under high temperature and high pressure
conditions. The
reagents in the strip solution act to strip the loaded carbon of its
previously adsorbed metal
contents (e.g., gold), and "re-leach" it into the solution to form an
electrolyte solution. One or
more screens or filters 324 may be provided between the residence chamber 340
and the effluent
manifold 28b in order to extract a clarified stream of electrolyte solution 53
from the continuous
elution vessel 24 and/or prevent carbon particulate from passing downstream of
the effluent
manifold 28b. In some embodiments, as shown, the placement of said screens or
filters 324 may
be at the interface between the effluent ports and the one or more sidewalls
310 of the continuous
elution vessel 24. However, the screens or filters 324 may be provided in
other locations without
limitation, for instance: within the effluent manifold 28b, within the
continuous elution vessel 24,
at the interface between the effluent manifold 28b and mounts 312, or
downstream of said
effluent manifold 28b. It should be known that one or more seals or gaskets
(not shown) may be
placed between the influent 28a or effluent 28b manifolds and the continuous
elution vessel 24.
Fluidized carbon and solution within residence chamber 340 continues to move
along the
serpentine flow path 5 lb until it is either removed through effluent manifold
28b to be used as
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electrolyte, or passes through outlet 328. The outlet 328 may comprise an
outlet mount 330
and/or an outlet seal 329 for connecting to a valve 29. The valve 29 may be of
any sort known in
the art, such as a ball or cone valve without limitation, and one would
appreciate that the valve
may be separately coupled to, or formed integrally with either one or both of
the continuous
elution vessel 24 and the flash vessel 25. Moreover, additional piping
sections may be added
between the second outlet 328 and the valve 29 if the distance between the
continuous elution
vessel 24 and the flash vessel 25 is large.
The stream of hot pressurized spent slurry 51c exiting the continuous elution
vessel 24
"flashes" as it passes through the valve 29. The resulting mixture of gas
vapors, fluids, and
solids enters the lower pressure flash vessel 25, where heated steam is
diverted back to the splash
vessel 22 via steam return piping 21. Unvaporized spent solution and spent
carbon leave the
flash vessel 25 in a stream of concentrated spent slurry 51d. The concentrated
spent slurry 51d
may comprise a barren solution liquid fraction 52, and a solids fraction 55 of
spent carbon
substantially-free of previously-adsorbed precious metal (e.g., gold). As
previously mentioned,
the stream of concentrated spent slurry 51d may be subsequently screened or
filtered by a
dewatering screen 26.
In the embodiment shown, a liquid fraction 52 of the concentrated spent slurry
51d is
separated from the solid fraction 55 by dewatering screen 26 and returned to
the holding tank 60
for re-use as strip solution. One or more pumps (not shown) may be provided to
move the liquid
fraction 52 to the holding tank 60. The solids fraction 55 of dewatered spent
carbon is sent to a
carbon regeneration process 30 comprising a regeneration kiln 35 or other
means for reactivating
the carbon. Dewatering screen 26 may be provided as a two-stage screen,
wherein a first stage
removes a majority of the liquid fraction 52 from the spent carbon solids
fraction 55, and a
second stage removes residual caustic and/or cyanide from the solids fraction
55 of spent carbon
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before it enters a regeneration kiln 35 or wash vessel. Accordingly, equipment
in the carbon
regeneration system 30' is not damaged.
FIG. 12 schematically illustrates a continuous elution process 20 according to
some
embodiments. First, a slurry 51 of descaled loaded carbon 50 and a caustic
strip solution
comprising water and cyanide is produced 1048. The slurry 51 may be formed and
stored in a
holding tank 60. The slurry 51 is then pumped 1050 into the splash vessel 22
which is
configured to elevate the temperature and/or pressure of the descaled loaded
carbon/strip solution
slurry 51. After increasing the temperature and/or pressure 1052 of the slurry
51 in the splash
vessel 22, a hot pressurized slurry 51a of loaded carbon/strip solution is
formed and moved 1054
from the splash vessel 22 to the continuous elution vessel 24. The hot
pressurized slurry 51a is
kept within the vessel 24 for an increased residence time 1056, for instance,
by providing a
fluidized bed 320 alone or in combination with a plurality of baffles 318 in
order to elongate the
physical travel path of the hot pressurized slurry 51a between the inlet 304
of the vessel 24 and
the outlet 328. The physical travel path may be for instance, a serpentine
flow path 5 lb as
shown.
During its time of residence within the continuous elution vessel 24, the
loaded carbon in
the hot pressurized slurry 51a is stripped of its adsorbed precious metal by
reagents in the caustic
strip solution. Accordingly, the caustic strip solution dissolves the precious
metal into itself
thereby forming an electrolyte solution 53. The electrolyte solution 53 is
screened to remove
carbon particulate therefrom and is extracted 1064 from the continuous elution
vessel 24.
Subsequently, the electrolyte solution 53 is fed 1066 to a continuous
electrowinning system 40'
(e.g., into a continuous electrolytic metal extraction cell 42) for precious
metal recovery. During
the electrowinning process 1068 (see FIG. 19), barren solution 54 is
continuously removed 1070
from the continuous electrowinning system 40' and pumped 1072 back into the
continuous
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elution vessel 24 either directly, or indirectly (e.g., via a barren solution
holding tank (not
shown) or immersion heater 27).
Solution and carbon are continuously removed from the continuous elution
vessel 24, and
the liquid fraction of the solution "flashed" or at least partially vaporized
1058 with a valve 29
before entering the flash vessel 25. The process 20 further comprises
recovering 1060 heated
steam from the rapid evaporation of exiting spent slurry 51c, and piping 1062
the steam back to
the splash vessel 22 in order to efficiently increase 1052 the temperature
and/or pressure of the
first vessel 22. Concentrated spent slurry 51d is removed 1074 from the flash
vessel 25, and then
dewatered 1076 to separate the spent liquid fraction 52 from the spent solids
fraction 55. The
solids fraction 55 comprises dewatered carbon which is sent 1078 to a carbon
regeneration
system 30', and the spent liquid fraction 52 of the concentrated spent slurry
51d is sent 1080 to
the holding tank 60 for re-use.
It should be known that the particular features and suggested uses of the
continuous
elution systems 20' and processes 20 shown and described herein are exemplary
in nature and
should not limit the scope of the invention. For example, fluidized bed 320
may be replaced
with, or used in combination with one or more mechanical agitators (not shown)
to suspend
loaded carbon particulate. Moreover, the number of baffles 318 in the
continuous elution vessel
24 may be greater or less than what is shown, in order to provide the
residence times and flow
rates required for a particular process. Additionally, one or more additional
vessels 22, 24, 25
may be added to a continuous elution system 20' and placed in series or
parallel with other
vessels 22, 24, 25 to increase throughput. For example, two or three
continuous elution vessels
24 may be directly or indirectly coupled to each other in parallel, and placed
in series between a
single splash vessel 22 and a single flash vessel 25.
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FIG. 13 shows a continuous electrowinning process 40 according to some
embodiments.
The process 40 comprises continuously providing an electrolyte solution 53,
continuously
feeding the electrolyte solution 53 to a continuous electrolytic metal
extraction cell 42, extracting
cathode sludge concentrate 53f from the cell 42 in a sludge removal stream
53g, continuously
extracting barren solution 54 from the cell 42 and using said barren solution
54 to feed a
continuous elution vessel 24 within a continuous elution process 20.
As shown in FIGS. 14-18, the continuous electrowinning system 40' largely
comprises a
continuous electrolytic metal extraction cell 42 comprising a cell body 406
having a first end
440, a second end 480, one or more sidewalls 482 extending therebetween, a
base 404 having
one or more mounts 402, at least one inlet 410 for receiving a continuous
influent stream of a
precious metal-containing electrolyte solution 53, at least one first outlet
420 for providing
continuous egress of a spent electrolyte stream 53d and barren solution 54
contained therein, and
at least one second outlet 430 for providing egress of cathode sludge
concentrate 53f collected
within the cell 42. The second outlet 430 may be configured for continuous
egress of collected
cathode sludge concentrate 53f, or the second outlet 430 may be configured for
intermittent
egress of said collected cathode sludge concentrate 53f. Within the cell body
406 is provided a
first chamber 405, a second chamber 407, a third chamber 408, and a residence
chamber 460
comprising one or more elongated channels 462. The channels 462 are configured
to increase
residence time of the electrolyte solution 53 and provide a forced flow
electrolyte stream 53b of
electrolyte solution 53 therein which is strong enough to dislodge and/or
displace cathodic
sludge concentrate which forms and builds up within the channels 462. The one
or more
channels 462 may comprise, for example, a portion of a helix, double-helix,
coil, spiral,
serpentine, spline, compound curve, and may extend in curvilinear paths. In
some embodiments,
as shown, the residence chamber 460 may be concentrically situated between the
first chamber
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405 and the third chamber 408. The first chamber 405 may be configured to be
devoid of
electrolyte and/or cathodic sludge concentrate during operation, and may
generally serve as a
space-filler bounded between first end 440, inner anode 477, and baffle 450.
The space filling
first chamber 405 generally provides channels 462 within the residence chamber
460 with a
larger radius, thereby increasing the overall effective length and total
surface area of the channels
462 exposed to forced flow electrolyte streams 53b contained therewithin. The
third chamber
408 serves to temporarily hold and/or transport spent electrolyte streams 53d
from within the cell
42 to one or more first outlets 420. In some embodiments, to reduce material
costs, the first end
440 may be configured as an annular panel having a central opening exposing
the first chamber
405, rather than as a solid continuous circular panel as shown. The one or
more first outlets 420
may be provided at an upper portion of the cell 42 where overflow is likely to
be more clarified
and free from cathode sludge concentrate.
Each channel 462 may be defined between at least one anode 474, at least one
cathode
472, and one or more insulators 476 extending therebetween. In the particular
embodiment
shown, one or more anodes 474 and one or more cathodes 472 are provided as
sleeve portions
which alternate concentrically between an outer anode 479 and an inner anode
477 with each
sleeve portion having a different radius. The anodes 474 and cathodes 472 are
radially separated
and maintain a uniform spacing by one or more spacing protuberances 473
projecting from said
one or more cathodes 472. It should be understood, that while not shown, the
one or more
protuberances 473 may alternatively extend from the anodes 474 alone, or may
extend from both
anodes 474 and cathodes 472 without limitation. However, by providing
protuberances 473 on
the one or more cathodes 472, a small amount of extra cathodic surface area is
provided for
precipitating cathodic sludge concentrate out of the forced flow electrolyte
stream 53b during
electrolysis. The one or more insulators 476 prevent short circuit between the
negatively
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charged anodes 474 and positively charged cathodes 472 and may serve as
flexible, tolerance-
compensating gaskets which delineate the cross-sectional boundary of each
channel 462 and
build/concentrate the forced flow electrolyte stream 53b within each channel
462.
As shown in FIG. 18, each anode 474 may communicate with one or more anode
terminals 442. Anode terminals 442 may comprise, for example and without
limitation, a
fastener 442a such as a pin or screw, a clamping member 442b such as a nut,
flange, or head, a
terminal lead 442c connected to a ground or power source, a conductive washer
442d or other
clamping member, an insulative bushing 442e to prevent electrical currents
from passing to
surrounding portions of the cell 42, a thread or equivalent securing feature
442f provided on said
fastener 442a, a conductive support 442h comprising a complimentary thread or
equivalent
securing feature 442g for communicating with said thread or equivalent
securing feature 442f,
and a receiving portion 442i provided within the conductive support 442h for
engaging and
supporting one or more anodes 474. In the particular embodiment shown, anodes
474 are
generally tubular cylindrical sleeves and therefore, receiving portions 442i
may be provided as
small straight or generally arcuate slits. However, other equivalent
interfaces are envisaged,
particularly for non-cylindrical or non-tubular anodes 474 and cathodes 472.
For example,
instead of slits, receiving portion 442i may comprise a plurality of
conductive clamps, spring
clips, or pegs extending from the support 442h which straddle and secure an
anode 474 thereto.
In some embodiments, the continuous electrowinning system 40' may be provided
with a
cylindrical cell body 406, a flat circular upper first end 440, and a
generally frustoconical lower
second end 480. The frustoconical shape of the lower second end 480 generally
aids in
channeling collected heavy cathode sludge concentrate 53f to the second outlet
430 for removal.
The first end 440 may be secured to the cell body 406 via an annular flange
445 which may be
electrically neutral or positively charged with the rest of cathodic cell body
406. The first end
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440 may comprise a series of sandwiched panels, such as one or more ground or
electrically-
neutral panels 447, one or more anodic panels 444, and one or more insulative
panels 446. In
some embodiments the one or more insulative panels 446 may comprise a gasket,
such as a
polytetrafluoroethylene (PTFE) insulating gasket. One or more fasteners 441 or
adhesives may
be provided to secure the first end 440 to the body 406 and/or to secure
sandwiched panels 444,
446, 447 together. For example, a series of fasteners 441 may be provided
around a perimeter of
the first end 440 to secure the first end 440 to the flange 445. The fasteners
441 may be
insulated, for example, with a sheath, coating, bushing, or washer of non-
conductive material
such as high molecular weight polyethylene (HMWPE), polyvinylidene fluoride
(PVDF),
polypropylene, or polyvinylchloride (PVC). Moreover, the fasteners 441 may
serve the dual
purpose of securing the first end 440 to the body 406 and also securing
sandwiched panels 444,
446, 447 together.
In use, an influent stream of electrolyte solution 53 at a higher-than-ambient
pressure and
temperature continuously enters the cell 42 via inlet 410. The electrolyte
solution 53 may
contain metal ions of copper, gold, silver, platinum, lead, zinc, cobalt,
manganese, aluminum, or
uranium, without limitation. The continuous electrowinning system 40' is
preferably maintained
at a higher-than-ambient temperature (e.g., around 88 degrees Celsius) and/or
pressure. The
influent stream of electrolyte solution 53 may come from an upstream
electrolyte holding tank
(not shown), a continuous elution system 20', or a combination thereof. In
some embodiments,
the inlet 410 may be formed from a portion of a pipe or tubing having one or
more sidewalls 412
and may further comprise an inlet mount 414 having a flange, seal, valve, pipe
fitting, or
equivalent connector for integration with the continuous elution system 20'.
Inlet 410 comprises
one or more openings 413 (e.g., through said one or more sidewalls 412), which
are configured
to feed said one or more channels 462 of the residence chamber 460 with
incoming electrolyte
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solution 53. Though not shown, a plurality of openings 413 may be provided per
channel 462. In
the event multiple channels 462 and a single inlet 410 is employed as shown,
the influent stream
of electrolyte solution 53 may be split into a plurality of dispersed influent
streams 53a, each
entering different channels 462. Alternatively, while not shown, a separate
inlet 410 may be
provided for each channel 462. The openings 413 may be configured to provide
uniform or non-
uniform flow rates across each channel 462 or provide similar electrolyte
residence times for
each channel 462. As clearly shown in FIG. 17, one or more insulators 417
(e.g., an insulation
pad) may be placed between one or more sidewalls 412 of the inlet 410 and the
first end 440 of
the cell body 460. The one or more insulators 417 may encircle the one or more
openings 413 to
ensure that incoming electrolyte solution 53 from dispersed influent streams
53a does not form,
plate, or sludge within the openings 413, particularly adjacent cathodes 472.
In some embodiments, channels 462 may be configured to allow the dispersed
influent
streams 53a of electrolyte solution 53 to flow forcedly through the channels
462 in a forced flow
electrolyte stream 53b which follows a uniform helical or spiral path as
shown. However, while
not shown, the channels 462 may also be configured to direct the dispersed
influent streams 53a
along straight paths, serpentine paths, compound curve paths, or complex 3D-
spline curve paths
so long as they can support a forced flow electrolyte stream 53b therein and
provide a sufficient
residence time of electrolyte between an anode 474 and cathode 472.
Channels 462 may shrink or grow in circumference or change in overall or cross-
sectional shape and/or size as they extend within the residence chamber 460;
however, it is
preferred that channels 462 remain uniform in cross-section, direction, and/or
anode-cathode
spacing throughout their entire length. While not shown, since channels 462
located at greater
radial distances from the center of the cell 42 are longer and will generally
have higher residence
times than inner channels 462, the number of turns of inner channels 462
(e.g., channels adjacent
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inner anode 477 and first chamber 405) may be adjusted to be greater than the
number of turns
for outer channels 462 (e.g., channels more proximate the outer anode 479 and
third chamber
408). In other words, while not shown, inner portions of residence chamber 460
may be greater
in height than outer portions of residence chamber 460, in order to lengthen
the effective length
of inner channels 462 (adjacent the first chamber 405). Portions of baffle 450
adjacent the
residence chamber 460 and third chamber 408 are generally open so as to allow
channels 462 to
continuously deliver spent electrolyte streams 53d to the third chamber 408
and collected
cathode sludge concentrate 53f formed in the channels 462 to the second
chamber 407.
As shown in FIG. 16, baffle 450 may comprise an anodic layer 452, a middle
electrically-
neutral insulator 454 to support said one or more anodes 474 and cathodes 472,
and a support
structure 456 for supporting the insulator 454 and anodic layer 452. The
insulator 454 may be
made of a chemically-robust material such as ultra-high molecular weight
polyethylene
(UHMWPE) and may be cruciform in shape as shown. A plurality of receiving
portions 458
such as notches may be provided to the insulator 454 to hold, space, insulate,
and support the one
or more anodes 474 and cathodes 472; however, other holding means such as
pegs, spring clips,
or clamps may be provided. The insulator 454 may be connected to the support
structure 456
with one or more fasteners, adhesives, or other connecting means, and the
support structure 456
may be connected to the body 406 by conventional means such as bolting,
forming, adhering,
welding, or supporting on a flange or shelf. The anodic layer 452 may serve to
close off the first
chamber 405 and prevent electrolyte 53 in the forced flow electrolyte stream
53b from entering
said first chamber 405. In some embodiments, the support structure 456 may be
a lattice
structure such as a mesh screen or supporting member such as a crossbar which
spans a width of
the cell body 406. Support structure 456 is generally configured not to
inhibit electrolyte
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flowing from the channels 462 to the third chamber 408, or inhibit the passage
of cathode sludge
concentrate 53f to the second chamber 407.
As electrolyte solution 53 forcibly flows through the one or more channels 462
in the
residence chamber 460, a large electric potential is placed between the one or
more anodes 474
and one or more cathodes 472 in order to effectively "plate-out" sludge
concentrate onto the one
or more cathodes 472. However, by varying operating parameters such as
residence time,
electric current, electrolyte flow rate, temperature, pressure, electrolyte
concentration/composition, and/or smoothness/material/coating of each
cathode(s) 472, the
channels 462 may be configured such that cathodic sludge concentrate initially
forms on or
adjacent to the one or more cathodes 472, but will not actually bond or
"plate" to the cathodes
472 and will instead flush down the channels 462 and/or become suspended in
the forced flow
electrolyte streams 53b. Any sludge concentrate that may settle to bottom of a
channel 462 may
also be washed down and eventually swept out of the channels 462 and into
second chamber 407
by the forced flow electrolyte streams 53b. Sludge concentrate may be flushed
out of the one or
more channels 462 by virtue of: gravitational forces acting on inclined
surfaces, high flow rates
of forced flow electrolyte streams 53b passing through the one or more
channels 462, increased
turbulence within each channel 462, and/or by virtue of small cross-sectional
areas provided to
each channel 462.
After the forced flow electrolyte streams 53b pass through the one or more
channels 462,
the outflow 53c of the residence chamber 460 will generally comprise a liquid
carrier component
of barren solution 54 which is substantially-free of dissolved precious metal,
and a solid
precipitate component comprising cathodic sludge concentrate which has been
discharged from
the channels 462 by the forced flow electrolyte stream 53b. The heavier solids
may follow a
sludge precipitate stream 53e before settling in a mass of collected cathode
sludge concentrate
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53f within the second chamber 407 adjacent the second end 480. Barren solution
54 travels via
spent electrolyte stream 53d into the third chamber 408 and continuously
leaves the cell 42
through outlet 420. In embodiments where the cell body 406 is cathodic, some
residual plating
or cathodic sludge concentrate formation may occur within the third chamber
408 (for example,
on or around inner portions of cathodic sidewall(s) 482). However, any cathode
sludge
concentrate 53f formed within the third chamber 408 will typically settle and
eventually end up
in second chamber 407 with the rest of the collected cathode sludge
concentrate 53f.
The first outlet 420 may be formed from a portion of a pipe or tubing having
one or more
sidewalls 422 and may further comprise a first outlet mount 424 having a
flange, seal, valve,
pipe fitting, or equivalent connector for integration with a continuous
elution system 20'. When
in use, an effluent stream of barren solution 54 continuously leaves the cell
body 406 through
said first outlet 420 at which point it may enter a barren solution holding
tank (not shown), be
discarded, return to a continuous elution system 20', or undergo further
processing.
Captured cathode sludge concentrate 53f may be removed from the cell 42
intermittently
or continuously via second outlet 430. The underflow, or sludge removal stream
53g of cathode
sludge concentrate 53f may proceed to a holding tank, be pumped away for
further refining, or
may be dumped into a container and transported to a smelter. In some
embodiments, the second
outlet 430 may be formed from a portion of a pipe or tube having one or more
sidewalls 432 and
may further comprise a second outlet mount 434 having a flange, seal, valve,
pipe fitting, nozzle,
tap, or equivalent connector for integration with a holding tank or smelting
apparatus.
The cross-section of residence chamber 460 may vary, so long as one or more
channels
462 therein are formed between at least one anode 474 and at least one cathode
472 which are
separated from each other by one or more insulators 476. Channels may extend
linearly
(resembling an elongated pipe), helically, in a cascade of connected,
horizontally-arranged, and
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vertically-displaced "figure-8s", or in any continuous path in 3-D space which
is configured to
provide a "forced flow" of electrolyte solution. In order to assist with
outgassing of air which
could get caught in the channels 462 and also prevent the backup of
precipitated sludge
concentrate within the channels, it is preferred that the continuous path the
channels follow in 3-
D space be free of sharp bends, abrupt turns, overhangs, high spots, and/or
tightly wound corners
which may be prone to air capture and clogging. In some embodiments, a
residence chamber
460 may comprise one or more channels 462 therein which simply extend as long
straight pipe
sections tilted at an angle with respect to horizontal.
FIG. 19 schematically illustrates a continuous electrowinning process 40
according to
some embodiments. The process 40 comprises providing 1082 an electrolyte
solution 53 having
an elevated temperature or pressure with respect to ambient conditions. The
electrolyte solution
53 may be produced from a continuous elution process 20 and may comprise
water, cyanide,
caustic, and a dissolved metal (e.g., gold, copper, silver, platinum,
aluminum, lead, zinc, cobalt,
manganese, or uranium) therein. The electrolyte solution 53 is continuously
fed 1084 (e.g., at a
predetermined flow rate) into a continuous electrolytic metal recovery cell 42
which is preferably
maintained 1086 at a higher-than-ambient temperature and/or pressure. In some
embodiments,
the cell 42 may comprise a series of nested anode sleeves 474 and cathode
sleeves 472, wherein
adjacent sleeves have a different electrical potential or charge. In a
preferred embodiment, the
sleeves are spaced concentrically and radially evenly with respect to each
other so that any two
neighboring sleeves hold an opposite charge 1088. One or more insulators 476
may be placed
between the anodes 474 and cathodes 472 to define a plurality of channels 462
(e.g., helical
channels) and simultaneously prevent arcing between the anodes and cathodes.
The process 40
further comprises subjecting 1090 the electrolyte solution 53 to a longer
residence time within a
continuous electrolytic metal recovery cell 42. This may be achieved by
providing one or more
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elongated channels 462 between the anode 474 and cathode 472 sleeves, which
extend in
smooth, continuous, and uninterrupted helical paths. It should be known that
residence time may
also be increased by alternatively employing long tubular straight channels.
Electrolyte solution
53 maintained within the channels 462 is forced through the channels 462 and
walls thereof by
small pressure differentials between the inlet 110 and the first 120 outlet
and/or small pressure
differentials between the inlet 110 and the second 130 outlet. As the
electrolyte solution 53
moves through the channels 462, cathodic sludge concentrate precipitates out
of the electrolyte
solution 53 until the solution becomes weaker in concentration and eventually
substantially-free
of precious material 1092. Precipitating concentrate from the sludge
precipitate stream 53e is
continuously collected 1094 within second chamber 407, and collected cathode
sludge
concentrate 53f may be extracted 1098 continuously or intermittently or a
combination thereof.
A stream of barren solution 54 (which is substantially devoid of precious
metal) is continuously
extracted 1096 from the cell 42 via outlet 420, and may be fed to a continuous
elution vessel 24
within a continuous elution process 20.
FIG. 20 shows a carbon regeneration process 30 according to some embodiments.
A
solids fraction 55 of concentrated spent slurry 51d comprising spent de-
watered carbon is sifted
with a screen 32 to separate out spent carbon fines 55b. The spent carbon
fines 55b are placed in
a carbon fines holding tank 34. The remaining course spent carbon 55a is sent
to a regeneration
kiln 35 (or other means for regeneration such as a chemical, steam, or
biological process). Hot
reactivated carbon 55c is removed from the regeneration kiln 35 and quenched
in a carbon
quench tank 36. A slurry of cooled regenerated carbon and fluid moves to a
dewatering screen
37 via pump 33. After passing through dewatering screen 37, dewatered
activated/reactivated
carbon 56 is moved to a continuous carbon loading/adsorption process 70. The
fluid underflow,
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which comprises cool reactivated carbon slurry 55d, is moved to the carbon
fines holding tank
34.
FIG. 21 shows a continuous metal recovery system 100' according to some
embodiments
of the invention comprising a continuous acid wash system 10', a continuous
elution system 20',
a continuous electrowinning system 40', and a carbon regeneration system 30'.
FIGS. 22 and 23
serve to compare scale plant layouts and overall footprints. FIG. 22 shows the
system 100' for
the continuous recovery of metals according to FIG. 21 and FIG. 23 comprises a
conventional
system 9000' for the batch recovery of metals using "batch" process steps. As
can be seen from
FIGS. 22 and 23, the system 100' according to the invention is smaller in size
than the
conventional system 9000' depicted in FIG. 23. In addition to smaller size,
system 100' is also
more efficient and environmentally-friendly.
FIG. 24 shows an alternative to the washing tanks 200, 200', 200" shown in
FIGS. 6-8. In
the embodiment shown, an acid wash tank 2000 is provided, which may replace
acid wash tank
200. Acid wash tank 2000 comprises a wash chamber 2020 having a fluidized bed
panel 2021
spanning the length of the wash chamber 2020 with pore sizes smaller than the
mean particle size
of loaded/reloaded carbon, one or more adjustable mounts 2007, 2009 which may
be individually
raised, lowered, or pivoted on a rack or linkage (not shown for clarity) to
change the inclination
angle of the chamber 2020 with respect to a skid 2002, a recirculation inlet
2023a provided
below the fluidized bed panel 2021, and a recirculation outlet 2023b provided
above the
fluidized bed panel 2021. Recirculation outlet 2023b comprises one or more
overflow outlets
2027, each provided with at least one washable/replaceable recycle screen
2008, which maintains
loaded/reloaded carbon 57 within the chamber 2020 and filters exiting dilute
acid solution 57c.
Recycle screens 2008 may be conveniently provided between bolted flange
members of the
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overflow outlets 2027 and may comprise built-in peripheral gaskets. FIGS. 25
and 26 show
more detailed views of the chamber 2020 shown in FIG. 24.
Recirculation inlet 2023a may comprise one or more adjustable nozzles 2011
which serve
to fluidize loaded/reloaded carbon 57. The nozzles 2011 may be individually or
collectively
angularly adjusted and "set" to a fixed angle, in order to: compensate for
various inclinations of
the chamber 2020, prevent buildup of loaded/reloaded carbon 57, and counteract
backflow
within the chamber 2020 caused by eddy currents surrounding interior baffles
2018. Chamber
2020 may, as shown, be constructed in clamshell form, with a number of
fasteners 2004
connecting upper and lower clamshell portions together. One or more additional
gaskets may be
employed between the upper and lower clamshell portions to form a seal, or the
fluidized bed
panel 2021 itself may be provided with peripheral gasketing material
properties to provide a seal
between the upper and lower clamshell portions.
A first filter 2001 is provided at an inlet 2022 to the acid wash tank 2000.
The first filter
2001 comprises a housing 2003 which serves to collects influent
loaded/reloaded carbon slurry
57', a first screen 2026 which serves to separate loaded/reloaded carbon 57
from carrier fluid 57f
present in the slurry 57', a first filter outlet 2006 which serves to transfer
strained
loaded/reloaded carbon 57 from within the upper housing 2003 to the wash
chamber 2020, a
recirculation tank 2029 which collects carrier fluid 57f separated from the
liquid fraction of the
influent slurry 57', and one or more clamps 2005 which removably attach the
housing 2003 to the
recirculation tank 2029 with the first screen 2026 extending therebetween,
thereby allowing
periodic cleaning and/or replacing of the first screen 2026. Recirculation
tank 2029 may be
configured to continuously redistribute carrier fluid 57f to a holding tank
(not shown) or may
simply comprise a valve for batch removal of the collected carrier fluid 57f.
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A second filter 2024, similar to the first filter 2001, is provided adjacent a
first channel
2082 extending from the fluidized bed panel 2021 to an outside portion of the
wash chamber
2020. First channel 2082 is configured to provide egress of acid-rinsed loaded
carbon 57a
resting on/around/above fluidized bed panel 2021 after it has undergone a
predetermined
residence time of acid washing within the chamber 2020. The acid-rinsed loaded
carbon 57a is
filtered by a second screen 2036, and the strained solids fraction of the acid-
rinsed loaded carbon
57a exits a discharge outlet 2028. The acid-rinsed loaded carbon exiting the
discharge outlet
2028 may be captured and contained by a holding tank 2060 and subsequently
transported (via
pump 2030) to a downstream process (e.g., aqueous rinse cycle). Alternatively,
the acid-rinsed
loaded carbon exiting the discharge outlet 2028 may directly enter a
downstream process (e.g.,
pour into another aqueous rinse tank 200' without an intermediate holding tank
2060 and pump
2023). Holding tank 2060 advantageously serves as a buffer which maintains a
level of process
control and prevents too much carbon feed to downstream processes.
In use, replenished dilute acid solution 57c' (obtained by filtering acid-
rinsed loaded
carbon 57a with second screen 2036) enters recirculation tank 2039 and is
pumped to chamber
2020 via a pump 2030. The replenished dilute acid solution 57c' enters the
recirculation inlet
2023a and then passes upwards through fluidized bed panel 2021 via nozzles
2011. The
replenished dilute acid solution 57c' suspends incoming loaded/reloaded carbon
57, and moves
the loaded/reloaded carbon 57 through the chamber 2020 and around baffles 2011
for a
predetermined residence time. The replenished dilute acid solution 57c' passes
through recycle
screens 2008 and filtered dilute acid solution 57c re-enters the recirculation
tank 2039 via
recirculation outlet 2033b. Residence time of the loaded/reloaded carbon 57
may be increased or
decreased by adjusting the inclination angle of the chamber 2020 and/or
adjusting the angular
orientation of nozzles 2011. For a fixed, non-variable metal extraction
process, the inclination
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angle of chamber 2020 and angular positions of nozzles may be preset by the
manufacturer and
permanently fixed in the optimum configuration to yield the most efficient
residence time for
said process.
EXAMPLE 1
A water-based, loaded carbon slurry 57 comprising approximately 30-300 oz/ton
gold
and approximately 30% wt/wt, activated coconut shell carbon is delivered to a
continuous acid
wash system 10'. First, inorganic components, namely calcium and magnesium
carbonate, are
removed from the loaded carbon by fluidizing a bed of loaded active carbon
with a dilute
aqueous acid solution comprising approximately 1-5 wt% hydrogen chloride (HC1)
and/or nitric
acid (HNO3) in an acid wash tank 12, 200. The loaded active carbon is
continuously transferred
from the acid wash tank to an aqueous rinse tank 14, 200' where the loaded
active carbon is
fluidized and cleaned with water. The loaded carbon is subsequently
continuously transferred
from the aqueous rinse tank 14, 200' to a caustic rinse tank 16, 200". The pH
of the loaded active
carbon delivered to the caustic rinse tank is raised above 10 by a caustic
solution comprising
approximately 1-3 wt% sodium hydroxide.
The basic descaled loaded carbon 50 is fed continuously to a splash vessel 22
within a
continuous elution system 20' via a transfer medium of caustic strip solution
comprising
approximately 1 wt% caustic (NaOH) and 0.1 wt% cyanide (NaCN). The splash
vessel 22 is
generally held at an operating temperature between approximately 100 and 200
degrees
Fahrenheit ( F), and at a pressure of approximately atmospheric level. The
loaded carbon is
transferred from the splash vessel 22 to the continuous elution vessel 24,
where the gold is
removed from the carbon (i.e., gold dissolution). The continuous elution
vessel 24 operates at
roughly 300 degrees Fahrenheit ( F), which temperature is achievable by
elevating the strip
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solution pressure to roughly 70 psi (gauge). The continuous elution vessel 24
continuously
discharges into a lower pressure flash vessel 25. A drop in pressure between
the continuous
elution vessel 24 and flash vessel 25 causes rapid flash vaporization of a
portion of the effluent
caustic strip solution. Steam generated is channeled to the splash vessel 22,
thereby
simultaneously heating the splash vessel 22 and cooling the flash vessel 25.
Spent carbon, (e.g.,
comprising less than 1 oz/ton gold), is continuously moved out of the
continuous elution system
20' and into a regeneration process 30.
The approximately 300 F pressurized caustic strip solution is filtered by one
or more
screens or filters 324 to remove barren carbon particulate and form
electrolyte solution 53, which
is then passed through a continuous electrolytic metal extraction (i.e.,
electrowinning) cell 42.
The electrolyte solution 53 is forced (via the increased pressure provided by
the continuous
elution vessel 24) through at least one channel 462 having a fixed helical
path between a
cylindrical sleeve anode 474 and a cylindrical sleeve cathode 472. A voltage
between
approximately 2 and 4 volts is passed between the anode 474 through the
electrolyte solution 53
and the cathode 472, thereby depositing cathode sludge concentrate 53f on
surfaces of the
cathode 472. The velocity of the electrolyte solution 53 creates a forced flow
electrolyte stream
53b within the channel 462 which continuously washes the collected cathode
sludge concentrate
53f which may form and collect on the cathode's surfaces to the conical bottom
of the cell 42,
where it may be removed at the operator's leisure or continuously via a
control valve.
A contractor or other entity may provide a system 100' or process 100 for the
continuous
recover of metals in part or in whole as shown and described. For instance,
the contractor may
receive a bid request for a project related to designing a continuous metal
recovery system 100'
or process 100, or the contractor may offer to design such a system 100' or a
process 100 for a
client. The contractor may then provide, for example, any one or more of the
devices or features
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thereof shown and/or described in the embodiments discussed above. The
contractor may
provide such devices by selling those devices or by offering to sell those
devices. The contractor
may provide various embodiments that are sized, shaped, and/or otherwise
configured to meet
the design criteria of a particular client or customer. The contractor may
subcontract the
fabrication, delivery, sale, or installation of a component of the devices or
of other devices used
to provide such devices. The contractor may also survey a site and design or
designate one or
more storage areas for stacking the material used to manufacture the devices.
The contractor
may also maintain, modify, or upgrade the provided devices. The contractor may
provide such
maintenance or modifications by subcontracting such services or by directly
providing those
services or components needed for said maintenance or modifications, and in
some cases, the
contractor may modify an existing metal recovery process 9000 or system 9000'
with a "retrofit
kit" to arrive at a modified process or system comprising one or more method
steps, devices, or
features of the systems 100' and processes 100 discussed herein.
Although the invention has been described in terms of particular embodiments
and
applications, one of ordinary skill in the art, in light of this teaching, can
generate additional
embodiments and modifications without departing from the spirit of or
exceeding the scope of
the claimed invention. For example, particulates and carriers other than
carbon (e.g., polymers
or ion exchange resins) may be used with the disclosed systems and processes.
Moreover,
reagents other than water, cyanide, and caustic may be used to wash, descale,
or strip the
particulates. Furthermore, the disclosed systems and processes may be used to
recover numerous
types of materials including, but not limited to copper, gold, silver,
platinum, uranium, lead, zinc,
aluminum, chromium, cobalt, manganese, rare-earth and alkali metals, etc.
Accordingly, it is to
be understood that the drawings and descriptions herein are proffered by way
of example to
facilitate comprehension of the invention and should not be construed to limit
the scope thereof.
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Reference numeral identifiers
57c, 57c' Dilute acid solution
Continuous acid wash process 57d, 57d' Aqueous rinse solution
10' Continuous acid wash system 57e Caustic rinse solution
12 Acid wash tank57f Carrier fluid
13 Pump 60 Holding tank
14 Aqueous rinse tank 70 Continuous carbon
loading/adsorption process
16 Caustic rinse tank 70' Continuous carbon
loading/adsorption system
Continuous elution process 100 Process for the continuous
recovery of metals
20' Continuous elution system 100' System for the continuous
recovery of metals
21 Steam return 200 Acid wash tank
22 Splash vessel 200' Aqueous rinse tank
23 Pump 200" Caustic rinse tank
24 Continuous elution vessel 220 First chamber
Flash vessel 221 First fluidized bed panel
26 Dewatering screen 222 First inlet
27 Immersion heater 223a First recirculation inlet
28a Influent manifold 223b First recirculation outlet
28b Effluent manifold 224 First weir
29 Valve 226 First screen
Carbon regeneration process 227 First overflow outlet
30' Carbon regeneration system 228 First discharge outlet
32 Screen 229 First recirculation tank
33 Pump 230 Second chamber
34 Carbon fines holding tank 231 Second fluidized bed panel
Regeneration kiln 232 Second inlet
36 Carbon quench tank 233a Second recirculation inlet
37 Dewatering screen 233b Second recirculation outlet
Continuous electrowinning process 234 Second weir
40' Continuous electrowinning system 236 Second screen
42 Continuous electrolytic metal extraction cell 237 Second overflow
outlet
Descaled loaded carbon (or caustic/basic sluny thereof) 238 Second
discharge outlet
51 Slurry of strip solution and descaled loaded carbon 239 Second
recirculation tank
51a Heated and/or pressurized slurry 240 Third chamber
51b Serpentine flow path of slurry 241 Third fluidized bed panel
242 Third inlet
51c Spent slurry
51d Concentrated spent slurry 243a Third recirculation inlet
52 Liquid fraction of concentrated spent slurry 243b Third recirculation
outlet
53 Electrolyte solution 244 Third weir
53a Dispersed influent stream 246 Third screen
53b Forced flow electrolyte stream 247 Third overflow outlet
53c Residence chamber outflow 248 Third discharge outlet
249 Third recirculation tank
53d Spent electrolyte stream
53e Sludge precipitate stream 251 Acid overflow
53f Cathode sludge concentrate 253 Drained acid return
53g Sludge removal stream 254 Rinse water overflow
54 Barren solution (i.e., spent electrolyte) 256 Drained rinse water
return
257 Caustic rinse overflow
Solids fraction of concentrated spent slurry (e.g., de-water
260 Bottom wall
55a Course spent carbon
55b Spent carbon fines 266 Inner tubular wall
55c Hot reactivated carbon 268 Outer tubular wall
55d Cool reactivated carbon slurry 282 First channel
56 Activated/reactivated carbon 284 Second channel
57' Loaded/reloaded carbon slurry 286 Third channel
57 Loaded/reloaded carbon
57a Acid-rinsed loaded carbon
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454 Anode/Cathode insulator
57b Rinsed loaded carbon 456 Anode/Cathode insulator support
301 Inlet seal 458 One or more receiving portions
302 Inlet mount 460 Residence chamber
304 Inlet 462 One or more channels
306 First end 472 Cathode
308 Second end 473 One or more protuberances
310 One or more sidewalls 474 Anode
312 Effluent port mount 476 One or more insulators
314 Mounting member 477 Inner anode
316 Effluent port 479 Outer anode
318 One or more baffles 480 Second end
320 Fluidized bed panel 482 One or more sidewalls
322 Influent port mount 1000 Process for the continuous
recovery of metals
324 Filter (e.g., disk screen) 1002-1046 Continuous acid wash steps
326 Influent port 1048-1080 Continuous elution steps
328 Outlet 1082-1100 Continuous electrowinning
steps
329 Outlet seal 2000 Acid wash tank
330 Outlet mount 2001 First filter
340 Residence chamber 2002 Skid
350 Fluidizing chamber 2003 Housing
402 Mount 2004 Fastener
404 Base 2005 Clamp
405 First chamber 2006 First filter outlet
406 Cell body 2007 First adjustable mount
407 Second chamber 2008 Recycle screen
408 Third chamber 2009 Second adjustable mount
410 Inlet 2011 Nozzle
412 One or more inlet sidewalls 2018 Baffle
413 One or more openings 2020 Chamber
414 Inlet mount 2021 Fluidized bed panel
417 One or more insulators 2022 Inlet
420 First outlet 2023 Pump
422 One or more first outlet sidewalls 2023a Recirculation inlet
424 First outlet mount 2023b Recirculation outlet
430 Second outlet 2024 Second filter
432 One or more second outlet sidewalls 2026 First screen
434 Second outlet mount 2027 Overflow outlet
440 First end 2028 Discharge outlet
441 Fastener 2029 Recirculation tank
442 Anode terminal 2033b Recirculation outlet
442a Fastener 2036 Second screen
442b Clamp 2039 Recirculation tank
442c Terminal lead 2060 Holding tank
442d Conductive washer 2082 First channel
442e Insulative bushing
442f Thread or equivalent securing feature
442g Complimentary thread or securing feature
442h Conductive support
442i Receiving portion
444 Anodic panel
445 Cathodic flange
446 Insulative panel
447 Anodic panel
450 Baffle
452 Anodic panel
CA 02831936 2013-09-30
WO 2012/135826
PCT/US2012/031845
9000 Conventional batch metal recovery process
9000' Conventional batch metal recovery system
9100 Conventional batch acid wash process
9100' Conventional batch acid wash system
9120 Acid wash vessel
9132 Pump
9134 Carbon transfer pump
9136 Pump
9140 Dilute acid tank
9150 Sump pump
9160 Neutralizing tank
9200 Conventional batch (Zadra strip) elution process
9200' Conventional batch (Zadra strip) elution system
9220 Barren solution tank
9232 Carbon transfer pump
9234 Barren solution backup pump
9236 Barren solution pump
9237 Barren solution
9239 Hot barren solution
9240 Strip vessel
9250 Heating skid or equivalent heat exchanger
9300 Carbon regeneration process
9400 Conventional batch electowinning process
9400' Conventional batch electowinning system
9420 Batch electrolytic metal recovery cell (e.g., removable plate cathodes)
9421 Hot electrolyte solution
9430 Pump
9440 Electrowinning pump box
9500 Descaled loaded carbon
9530 Electrolyte solution
9540 Barren solution
9550 Spent carbon
9560 Activated/reactivated carbon
9570 Loaded or reloaded carbon
9700 Conventional batch carbon loading process
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