U.S. patent application number 14/009130 was filed with the patent office on 2014-05-29 for system and process for the continuous recovery of metals.
This patent application is currently assigned to FLSmidth A/S. The applicant listed for this patent is Cameron Barton. Invention is credited to Cameron Barton.
Application Number | 20140144788 14/009130 |
Document ID | / |
Family ID | 46931971 |
Filed Date | 2014-05-29 |
United States Patent
Application |
20140144788 |
Kind Code |
A1 |
Barton; Cameron |
May 29, 2014 |
SYSTEM AND PROCESS FOR THE CONTINUOUS RECOVERY OF METALS
Abstract
A system [100'] and process [100] for the continuous recovery of
metals is disclosed. The system [100'] comprises a continuous acid
wash system [10'], a holding tank [60], a continuous elution system
[20'], a continuous electrowinning system [40'], a carbon
regeneration system [30'], and a continuous carbon
loading/adsorption system [70']. The systems and methods disclosed
overcome the disadvantages associated with current systems and
processes which utilize batch process steps and equipment designed
for batch processes. The systems [10', 20', 30'] are each
configured to receive a continuous inflow of a solution or slurry
and deliver a continuous outflow of a solution or slurry, without
interruptions which are common with conventional metal recovery
systems [9000'].
Inventors: |
Barton; Cameron; (Salt Lake
City, UT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Barton; Cameron |
Salt Lake City |
UT |
US |
|
|
Assignee: |
FLSmidth A/S
Valby
DK
|
Family ID: |
46931971 |
Appl. No.: |
14/009130 |
Filed: |
April 2, 2012 |
PCT Filed: |
April 2, 2012 |
PCT NO: |
PCT/US12/31845 |
371 Date: |
October 1, 2013 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
61470570 |
Apr 1, 2011 |
|
|
|
Current U.S.
Class: |
205/704 ;
204/234 |
Current CPC
Class: |
C22B 3/04 20130101; C25C
1/00 20130101; C22B 3/02 20130101; Y02P 10/20 20151101; Y02P 10/234
20151101 |
Class at
Publication: |
205/704 ;
204/234 |
International
Class: |
C25C 1/00 20060101
C25C001/00 |
Claims
1. A system [100'] for the continuous recovery of metals comprising
at least one of the following: a continuous acid wash system [10']
configured for receiving a continuous, uninterrupted inflow of
loaded carbonaceous particulate [57] and delivering a continuous,
uninterrupted outflow of descaled loaded carbonaceous particulate
[50]; a continuous elution system [20'] configured for receiving a
continuous, uninterrupted inflow of a strip solution [51]
containing a descaled loaded carbonaceous particulate [50] and
delivering a continuous, uninterrupted outflow of electrolyte
solution [53]; and, a continuous electrowinning system [40']
configured for receiving a continuous, uninterrupted inflow of
electrolyte solution [53], delivering a continuous uninterrupted
outflow of a barren solution [54], and continuously and
uninterruptedly forming a cathode sludge concentrate [53f]; wherein
each of the continuous acid wash system [10'], the continuous
elution system [20'], and the continuous electrowinning system
[40'] are configured to operate simultaneously without
interruptions common with conventional batch metal recovery
processes.
2. The system [100'] according to claim 1, further comprising a
carbon regeneration system [30'] operatively connected to said
continuous elution system [40'].
3. The system [100'] according to claim 1, further comprising a
continuous carbon loading/activation system [70'] operatively
connected to said continuous acid wash system [10'].
4. The system [100'] according to claim 1, further comprising a
holding tank [60] operatively connected between said continuous
acid wash system [10'] and said continuous elution system
[20'].
5. The system [100'] according to claim 1, comprising all three of
said continuous acid wash system [10'], said continuous elution
system [20'], and said continuous electrowinning system [40'].
6. The system [100'] according to claim 1, further comprising one
or more pumps [13, 23, 33].
7. The system [100'] according to claim 1, wherein said continuous
elution system [20'] is operatively connected to the continuous
electrowinning system [40'].
8. The system [100'] according to claim 7, wherein continuous
elution system [20'] further comprises one or more screens or
filters [324] configured to prevent carbonaceous particulate from
passing to the continuous electrowinning system [40'].
9. The system [100'] according to claim 1, wherein the continuous
acid wash system [10'] further comprises a chamber [220] adapted
for retaining a fluidization medium; an inlet [222] adapted for
receiving a feed containing loaded carbonaceous particulate [57]; a
fluidized bed distribution panel [220] or other means adapted for
fluidizing the loaded carbonaceous particulate [220] in the
presence of said fluidization medium; an outlet [228] adapted to
pass loaded carbonaceous particulate and fluidization medium from
the chamber; and a screen [226] adapted to filter loaded
carbonaceous particulate from a fluidization medium; wherein the
continuous elution system [20'] comprises a splash vessel [22], a
continuous elution vessel [24], and a flash vessel [25], wherein
the splash vessel [22] is operatively connected to the continuous
elution vessel [24] in series, the continuous elution vessel [24]
is operatively connected to the flash vessel [25] in series, and
the splash vessel [22] is operatively connected to the flash vessel
[25] in parallel; and, wherein the continuous electrowinning system
[40'] comprises a continuous electrolytic metal recovery cell [42]
having a cell body [406] configured to maintain electrolyte
solution [53] at a high pressure and/or temperature; at least one
anode [474]; at least one cathode [472]; an inlet [410] configured
for receiving a continuous, uninterrupted influent stream of
electrolyte solution [53]; a first outlet [420] configured for
discharging a continuous, uninterrupted effluent stream of barren
solution [54]; a second outlet [430] configured for removing
cathode sludge concentrate [53f]; and a residence chamber [460]
configured to continuously transfer electrolyte solution [53] from
said inlet [410] to said first outlet [420] and increase residence
time of said electrolyte solution between said at least one anode
[474] and said at least one cathode [472], the residence chamber
[460] comprising one or more channels [462] which are configured to
provide a forced flow of electrolyte solution [53] therein which is
strong enough to continuously dislodge and/or transport cathode
sludge concentrate along said one or more channels [462] and
eventually out of said residence chamber [460].
10. The system [100'] according to claim 1, wherein said continuous
acid wash system [10'] further comprises at least one of a dilute
acid solution [57c], an aqueous rinse solution [57d], and a caustic
rinse solution [57e]; wherein the continuous elution system [20']
further comprises 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; and wherein the continuous
electrowinning system [40'] further comprises an electrolyte
solution.
11. The system [100'] according to claim 1, wherein the continuous
acid wash system [10'], the continuous elution system [20'], and
the continuous electrowinning system [40'] are each configured to
increase a pressure and/or temperature of a solution or slurry
contained therein.
12. The system [100'] according to claim 1, wherein a carbon
regeneration system [30'] is operatively connected to said
continuous elution system [20'], a continuous carbon
loading/activation system [70'] is operatively connected to said
continuous acid wash system [10'], and the carbon regeneration
system [30'] is operatively connected to said carbon
loading/activation system [70'].
13. The system [100'] according to claim 1, wherein said continuous
acid wash system [10'] is operatively connected to the continuous
elution system [20'].
14. A process [100] for the continuous recovery of a metal
comprising: continuously feeding [1004] a continuous wash system
[10'] with particulate [57] loaded with a metal; continuously
washing [1006, 1020, 1034] said loaded particulate [57] within the
continuous wash system [10'] to descale the loaded particulate;
continuously removing [1046] descaled loaded particulate [50] from
said continuous wash system; continuously loading [1050] a
continuous elution system [20'] with said descaled loaded
particulate [50]; continuously removing [1064] electrolyte solution
[53] from said continuous elution system [20']; continuously
feeding [1066, 1082, 1084] a continuous electrowinning system [40']
with said electrolyte solution [53]; continuously removing [1070,
1096] barren solution [54] from said continuous electrowinning
system [40']; and, continuously delivering [1072] said spent
electrolyte solution to said continuous elution system [20'];
wherein each of the continuous wash system [10'], the continuous
elution system [20'], and the continuous electrowinning system
[40'] are operably connected and configured to allow the above
steps to be performed simultaneously.
15. The process [100] according to claim 14, further comprising
forming said loaded particulate by continuously adsorbing metal
onto said particulate in a continuous loading/adsorption system
[70'] identical to said continuous wash system [10'].
16. The process [100] according to claim 15, wherein said
particulate is one of a carbonaceous particulate, a polymeric
adsorbent, or an ion-exchange resin.
17. The process [100] according to claim 14, further comprising
continuously removing cathode sludge concentrate [53f] from the
continuous electrowinning system [40'].
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates to mining and metallurgical refining
and more particularly to systems and processes for solvent
extraction and electroextraction of metals.
[0002] 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.
[0003] 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 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.
[0004] 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.
[0005] 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 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.
[0006] 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).
[0007] 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 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.
[0008] 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 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.
[0009] 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 ten pumps
may be required. This increases both initial plant overhead costs
and overall plant footprint.
[0010] 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.
[0011] 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
[0012] 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 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.
[0013] 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).
[0014] Yet another object of the invention is to prevent or
minimize carbon loss and reagent waste.
[0015] Another object of the invention is to maximize total metal
recovery.
[0016] 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.
[0017] 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.
[0018] Yet even another object of the invention is to reduce the
percentage by weight of unrecovered metal present in spent
electrolyte/barren solution.
[0019] 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
[0020] 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 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.
[0021] 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.
[0022] 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 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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 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.
[0027] 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.
[0028] 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 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
[0029] FIGS. 1 and 2 schematically illustrate a system and method
for the continuous recovery of metals according to some
embodiments;
[0030] FIG. 3 is a flowchart of a three-sequence continuous acid
wash operation according to some embodiments;
[0031] FIGS. 4 and 5 outline steps of a continuous acid washing
process according to some embodiments;
[0032] FIGS. 6 and 7 depict a washing tank which may be used in the
acid wash process shown in FIGS. 1-5;
[0033] FIG. 8 shows an acid wash system comprising a plurality of
the washing tanks depicted in FIGS. 6 and 7;
[0034] FIGS. 9 and 12 schematically illustrate a system and method
of continuous elution according to some embodiments;
[0035] FIG. 10 is an isometric view of a continuous elution system
according to some embodiments;
[0036] 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;
[0037] FIG. 14 shows a top plan view of a continuous electrowinning
system according to some embodiments;
[0038] FIGS. 15 and 16 are vertical and isometric cutaway views,
respectively, of a continuous electrowinning system taken on line
XV-XV in FIG. 14;
[0039] FIG. 17 is a detailed view of FIG. 15, showing the
particulars of an inlet according to some embodiments;
[0040] FIG. 18 is a transverse cutaway view of an electrowinning
cell along line XVIII-XVIII in FIG. 14;
[0041] FIG. 20 shows a process for regenerating/reactivating spent
carbon according to some embodiments;
[0042] FIGS. 21 and 22 show a system for the continuous recovery of
metals;
[0043] FIG. 23 shows a conventional batch system for the recovery
of metals;
[0044] 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;
[0045] FIG. 25 shows a detailed isometric view of the chamber shown
in FIG. 24;
[0046] FIG. 26 is a cutaway view of the chamber shown in FIG.
25;
[0047] FIG. 27 shows a conventional system for the recovery of
metals.
[0048] FIG. 28 shows a conventional acid wash process;
[0049] FIG. 29 shows a conventional batch elution process; and,
[0050] FIG. 30 shows a conventional batch electrowinning
process.
DETAILED DESCRIPTION OF THE INVENTION
[0051] 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 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.
[0052] 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 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
ordinary skill in the art would acknowledge that any one or more of
the aforementioned washing steps may be repeated or alternated.
[0053] 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.
[0054] 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 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.
[0055] 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.
[0056] 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 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.
[0057] 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 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.
[0058] 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.
[0059] 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 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.
[0060] 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.
[0061] 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.
[0062] 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.
[0063] 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).
[0064] 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.
[0065] 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 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.
[0066] 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 51b 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.
[0067] 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
51b.
[0068] 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.
[0069] 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.
[0070] Fluidized carbon and solution within residence chamber 340
continues to move along the serpentine flow path 51b until it is
either removed through effluent manifold 28b to be used as
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.
[0071] 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.
[0072] 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 before it
enters a regeneration kiln 35 or wash vessel. Accordingly,
equipment in the carbon regeneration system 30' is not damaged.
[0073] 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 51b as shown.
[0074] 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 elution vessel 24 either directly, or indirectly
(e.g., via a barren solution holding tank (not shown) or immersion
heater 27).
[0075] 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.
[0076] 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.
[0077] 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.
[0078] 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 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.
[0079] 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 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.
[0080] 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.
[0081] 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 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.
[0082] 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 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.
[0083] 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.
[0084] 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 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.
[0085] 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
flowing from the channels 462 to the third chamber 408, or inhibit
the passage of cathode sludge concentrate 53f to the second chamber
407.
[0086] 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.
[0087] 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 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.
[0088] 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.
[0089] 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.
[0090] 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 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.
[0091] 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 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.
[0092] 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, which comprises
cool reactivated carbon slurry 55d, is moved to the carbon fines
holding tank 34.
[0093] 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.
[0094] 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 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.
[0095] 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.
[0096] 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.
[0097] 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.
[0098] 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 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
[0099] 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 (HCl)
and/or nitric acid (HNO.sub.3) 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.
[0100] 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 (.degree. 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 (.degree. F.), which temperature is
achievable by elevating the strip 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.
[0101] The approximately 300.degree. 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.
[0102] 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 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.
[0103] 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.
TABLE-US-00001 Reference numeral identifiers 10 Continuous acid
wash process 10' Continuous acid wash system 12 Acid wash tank 13
Pump 14 Aqueous rinse tank 16 Caustic rinse tank 20 Continuous
elution process 20' Continuous elution system 21 Steam return 22
Splash vessel 23 Pump 24 Continuous elution vessel 25 Flash vessel
26 Dewatering screen 27 Immersion heater 28a Influent manifold 28b
Effluent manifold 29 Valve 30 Carbon regeneration process 30'
Carbon regeneration system 32 Screen 33 Pump 34 Carbon fines
holding tank 35 Regeneration kiln 36 Carbon quench tank 37
Dewatering screen 40 Continuous electrowinning process 40'
Continuous electrowinning system 42 Continuous electrolytic metal
extraction cell 50 Descaled loaded carbon (or caustic/basic slurry
thereof) 51 Slurry of strip solution and descaled loaded carbon 51a
Heated and/or pressurized slurry 51b Serpentine flow path of slurry
51c Spent slurry 51d Concentrated spent slurry 52 Liquid fraction
of concentrated spent slurry 53 Electrolyte solution 53a Dispersed
influent stream 53b Forced flow electrolyte stream 53c Residence
chamber outflow 53d Spent electrolyte stream 53e Sludge precipitate
stream 53f Cathode sludge concentrate 53g Sludge removal stream 54
Barren solution (i.e., spent electrolyte) 55 Solids fraction of
concentrated spent slurry (e.g., de-water 55a Course spent carbon
55b Spent carbon fines 55c Hot reactivated carbon 55d Cool
reactivated carbon slurry 56 Activated/reactivated carbon 57'
Loaded/reloaded carbon slurry 57 Loaded/reloaded carbon 57a
Acid-rinsed loaded carbon 57b Rinsed loaded carbon 57c, 57c' Dilute
acid solution 57d, 57d' Aqueous rinse solution 57e Caustic rinse
solution 57f Carrier fluid 60 Holding tank 70 Continuous carbon
loading/adsorption process 70' Continuous carbon loading/adsorption
system 100 Process for the continuous recovery of metals 100'
System for the continuous recovery of metals 200 Acid wash tank
200' Aqueous rinse tank 200'' Caustic rinse tank 220 First chamber
221 First fluidized bed panel 222 First inlet 223a First
recirculation inlet 223b First recirculation outlet 224 First weir
226 First screen 227 First overflow outlet 228 First discharge
outlet 229 First recirculation tank 230 Second chamber 231 Second
fluidized bed panel 232 Second inlet 233a Second recirculation
inlet 233b Second recirculation outlet 234 Second weir 236 Second
screen 237 Second overflow outlet 238 Second discharge outlet 239
Second recirculation tank 240 Third chamber 241 Third fluidized bed
panel 242 Third inlet 243a Third recirculation inlet 243b Third
recirculation outlet 244 Third weir 246 Third screen 247 Third
overflow outlet 248 Third discharge outlet 249 Third recirculation
tank 251 Acid overflow 253 Drained acid return 254 Rinse water
overflow 256 Drained rinse water return 257 Caustic rinse overflow
260 Bottom wall 266 Inner tubular wall 268 Outer tubular wall 282
First channel 284 Second channel 286 Third channel 301 Inlet seal
302 Inlet mount 304 Inlet 306 First end 308 Second end 310 One or
more sidewalls 312 Effluent port mount 314 Mounting member 316
Effluent port 318 One or more baffles 320 Fluidized bed panel 322
Influent port mount 324 Filter (e.g., disk screen) 326 Influent
port 328 Outlet 329 Outlet seal 330 Outlet mount 340 Residence
chamber 350 Fluidizing chamber 402 Mount 404 Base 405 First chamber
406 Cell body 407 Second chamber 408 Third chamber 410 Inlet 412
One or more inlet sidewalls 413 One or more openings 414 Inlet
mount 417 One or more insulators 420 First outlet 422 One or more
first outlet sidewalls 424 First outlet mount 430 Second outlet 432
One or more second outlet sidewalls 434 Second outlet mount 440
First end 441 Fastener 442 Anode terminal 442a Fastener 442b Clamp
442c Terminal lead 442d Conductive washer 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 454 Anode/Cathode
insulator 456 Anode/Cathode insulator support 458 One or more
receiving portions 460 Residence chamber 462 One or more channels
472 Cathode 473 One or more protuberances 474 Anode 476 One or more
insulators 477 Inner anode 479 Outer anode 480 Second end 482 One
or more sidewalls 1000 Process for the continuous recovery of
metals 1002-1046 Continuous acid wash steps 1048-1080 Continuous
elution steps 1082-1100 Continuous electrowinning steps 2000 Acid
wash tank 2001 First filter 2002 Skid 2003 Housing 2004 Fastener
2005 Clamp 2006 First filter outlet 2007 First adjustable mount
2008 Recycle screen 2009 Second adjustable mount 2011 Nozzle 2018
Baffle 2020 Chamber 2021 Fluidized bed panel 2022 Inlet 2023 Pump
2023a Recirculation inlet 2023b Recirculation outlet 2024 Second
filter 2026 First screen 2027 Overflow outlet 2028 Discharge outlet
2029 Recirculation tank 2033b Recirculation outlet 2036 Second
screen 2039 Recirculation tank 2060 Holding tank 2082 First channel
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
* * * * *