U.S. patent application number 11/287779 was filed with the patent office on 2007-05-31 for methods for processing crushed solids with a liquid within a vessel.
This patent application is currently assigned to Russell Technologies, LLC. Invention is credited to James J. Moore, Matthew F. Russell, Robert L. Russell.
Application Number | 20070119277 11/287779 |
Document ID | / |
Family ID | 38086145 |
Filed Date | 2007-05-31 |
United States Patent
Application |
20070119277 |
Kind Code |
A1 |
Russell; Matthew F. ; et
al. |
May 31, 2007 |
Methods for processing crushed solids with a liquid within a
vessel
Abstract
A method is provided in which solids, such as run-of-mine ore,
are crushed and reacted with a liquid within a mass flow reactor as
a substantially continuous process. The reaction can include
dissolving at least one material out of the crushed solids and into
solution with the liquid. Solid and liquid materials migrate
through and are extracted from the mass flow reactor substantially
under the influence of gravity alone and without the use of other
relevant driving means or forces. The respective flows of solid and
liquid materials through the mass flow reactor can be controlled so
as to maintain generally constant levels of each therein. At least
some of the reaction can occur under a predetermined hydrostatic
head of the liquid. Further processing of the solid and liquid
materials can be performed, including isolation of at least one
material of interest extracted from the crushed solids.
Inventors: |
Russell; Matthew F.;
(Spokane, WA) ; Russell; Robert L.; (Kellogg,
ID) ; Moore; James J.; (Gilbert, AZ) |
Correspondence
Address: |
John S. Reid;Reidlaw LLC
1926 S. Valleyview Lane
Spokane
WA
99212-0157
US
|
Assignee: |
Russell Technologies, LLC
|
Family ID: |
38086145 |
Appl. No.: |
11/287779 |
Filed: |
November 28, 2005 |
Current U.S.
Class: |
75/712 ;
75/743 |
Current CPC
Class: |
C22B 3/22 20130101; Y02P
10/20 20151101; C22B 3/02 20130101; C22B 3/04 20130101; C22B 3/00
20130101 |
Class at
Publication: |
075/712 ;
075/743 |
International
Class: |
C22B 15/00 20060101
C22B015/00 |
Claims
1. A method of processing solids with a liquid, comprising:
providing a vessel; crushing the solids to not less than a
predetermined median particle size, thus defining crushed solids;
reacting the crushed solids with the liquid within the vessel, thus
deriving a pregnant leach solution and post-reaction solids,
wherein at least some of the reacting occurs under a predetermined
hydrostatic head; migrating the pregnant leach solution and the
post-reaction solids through the vessel substantially under the
influence of gravity alone; and extracting the pregnant leach
solution and the post-reaction solids from the vessel.
2. The method of claim 1, wherein the crushed solids define a
permeability with respect to the liquid within the vessel, the
method further comprising: controlling the permeability by way of
at least one of: chemically flocculating fine particles of the
crushed solids to form larger particles of the crushed solids
within the vessel; agglomerating fine particles of the crushed
solids to larger particles of the crushed solids prior to the
reacting within the vessel; or removing fine particles of the
crushed solids by way of at least one of dry screening, wet
screening, or cyclonic separation of the crushed solids prior to
the reacting within the vessel.
3. The method of claim 1, wherein the predetermined hydrostatic
head is not less than 65 feet of the liquid.
4. The method of claim 1, wherein the reacting includes leaching at
least one material out of the crushed solids and into solution with
the liquid, thus deriving the pregnant leach solution and the
post-reaction solids.
5. The method of claim 4, wherein the at least one material leached
out of the crushed solids includes gold, silver, a platinum group
metal, gallium, germanium, lead, copper, zinc, uranium, cobalt,
nickel, a refractory metal, molybdenum, a light metal, sulfur,
crude oil, caregens, or a rare earth element.
6. The method of claim 1, wherein the liquid includes an aqueous
solution of acid or acids, an aqueous solution of acid or acids
including an oxidizing agent, sulfuric acid, a solution including
sulfuric acid, an aqueous solution of an alkali or alkali's, an
aqueous solution of an alkali or alkalis including an oxidizing
agent, an aqueous solution of cyanide including an oxidizing agent,
an aqueous solution of sodium or calcium hypochlorite, an aqueous
solution of ferrous or ferric sulfate, an aqueous solution of
ferrous or ferric sulfate including an oxidizing agent, an aqueous
solution including a bacterial catalyst, an aqueous solution of
chlorine, an aqueous solution of hydrogen peroxide, a solution of
ammonium thiosulfate, or an aqueous solution of air and sulfur
dioxide and copper.
7. The method of claim 1, wherein the solids include one of
gold-bearing ore, silver-bearing ore, ore bearing at least one
platinum group metal, ore bearing rare earth elements, ore bearing
gallium, ore bearing germanium, ore bearing light metals, ore
bearing copper, ore bearing zinc, ore bearing molybdenum, ore
bearing lead, ore bearing uranium, ore bearing cobalt, ore bearing
nickel, ore bearing refractory metal, contaminated soil, solids
containing coal, solids containing oil sands, and solids containing
oil shales.
8. The method of claim 1, and further comprising adding the liquid
into the vessel at a first flow rate, wherein the pregnant leach
solution is extracted from the vessel at a second flow rate, and
wherein the adding the liquid and the extracting the pregnant leach
solution are performed simultaneously for a predetermined period of
time.
9. The method of claim 8, wherein the first and second flow rates
are at least one of essentially equal or essentially constant for
the predetermined period of time.
10. The method of claim 8, wherein the predetermined period of time
is not less than 3 hours.
11. The method of claim 1, and further comprising adding the
crushed solids into the vessel at a first flow rate, wherein the
post-reaction solids are extracted from the vessel at a second flow
rate, and wherein the adding the crushed solids and the extracting
the post-reaction solids are performed simultaneously for a
predetermined period of time.
12. The method of claim 11, wherein the first and second flow rates
are at least one of essentially equal or essentially constant for
at least the predetermined period of time.
13. The method of claim 11, wherein the predetermined period of
time is not less than 3 hours.
14. The method of claim 1, wherein the post-reaction solids are
extracted from the vessel proximate a bottom of the vessel.
15. The method of claim 1, wherein the post-reaction solids are
extracted from the vessel substantially under the influence of
gravity alone.
16. The method of claim 1, wherein the pregnant leach solution is
extracted from the vessel substantially under the influence of
gravity alone.
17. The method of claim 1, and further comprising separating at
least some of the post-reaction solids into at least two distinct
groups, wherein each group corresponds to a predetermined median
particle size of post-reaction solid.
18. The method of claim 1, and further comprising removing pregnant
leach solution from at least some of the post-reaction solids.
19. The method of claim 18, including centrifuging at least some of
the post-reaction solids to remove at least some of the pregnant
leach solution.
20. The method of claim 18, including passing at least some of the
post-reaction solids along a screen to remove at least some of the
pregnant leach solution.
21. The method of claim 18, including leaching at least some of the
post-reaction solids in a barren solution wash, thus deriving an
aqueous leachate.
22. The method of claim 21, wherein the vessel is a first vessel,
the method further comprising: providing a second vessel;
performing the leaching of at least some of the post-reaction
solids in the barren solution wash within the second vessel, thus
deriving the aqueous leachate and post-leaching solids; and
extracting the aqueous leachate and the post-leaching solids from
the second vessel.
23. The method of claim 1, and further comprising extracting at
least one material from the pregnant leach solution.
24. The method of claim 23, wherein the at least one material
includes gold, silver, a platinum group metal, gallium, germanium,
molybdenum, lead, copper, zinc, uranium, cobalt, nickel, a
refractory metal, a light metal, crude oil, sulfur, or a rare earth
element.
25. The method of claim 23, wherein the extracting includes at
least one of using a solvent extraction , chemical precipitation,
or electrolytic precipitation.
26. The method of claim 1, and further comprising controlling at
least one of pH, Eh, temperature, a gas concentration, or a liquid
concentration within the vessel during the reacting the crushed
solids with the liquid.
27. The method of claim 1, wherein the vessel is a first vessel and
the liquid is a first liquid and the pregnant leach solution is a
first leach solution and the post-reaction solids are first
post-reaction solids, the method further comprising: providing a
second vessel; and reacting at least some of the post-reaction
solids with a second liquid within the second vessel, thus deriving
a second pregnant leach solution and second post-reaction
solids.
28. The method of claim 1, and further comprising injecting a gas
into the vessel during at least some of the reacting the crushed
solids with the liquid.
29. The method of claim 28, wherein the gas is defined by an
oxidizing gas.
30. The method of claim 1, wherein the crushed solids within the
vessel define a permeability with respect to the liquid, the method
further comprising: providing at least one essentially inert solid
within the vessel during the reacting so as to increase the
permeability of the crushed solids with respect to the liquid.
31. A method of processing mine ore with a lixiviant, comprising:
providing a reaction vessel defining solids outlet openings and
liquid outlet openings; crushing the mine ore to not greater than a
predetermined size, thus defining crushed ore; reacting the crushed
ore with the lixiviant within the reaction vessel, thus deriving a
pregnant leach solution and post-reaction solids; extracting at
least some of the pregnant leach solution from the reaction vessel
via the liquid outlet openings substantially under the influence of
gravity alone; and extracting the post-reaction solids and at least
some of the pregnant leach solution from the reaction vessel via
the solids outlet openings substantially under the influence of
gravity alone.
32. The method of claim 31, wherein the predetermined size is such
that at least 80 percent of the crushed ore is not greater than 6
inches in size.
33. The method of claim 31, and further comprising removing solids
of less than 0.15 millimeters from the crushed ore prior to the
reacting the crushed ore with the lixiviant within the reaction
vessel, the removed solids defining fine solids.
34. The method of claim 33, and further comprising removing at
least one material from the fine solids by way of leaching the fine
solids.
35. The method of claim 31, wherein: the reacting includes
dissolving at least one material out of the crushed ore and into
solution with the lixiviant, thus deriving the pregnant leach
solution; and the at least one material includes gold, silver, a
platinum group metal, gallium, lead, germanium, copper, molybdenum,
zinc, uranium, cobalt, nickel, a refractory metal, a light metal,
sulfur, crude oil, or a rare earth element.
36. The method of claim 31, wherein the lixiviant includes an
aqueous solution of acid or acids, an aqueous solution of acid or
acids including an oxidizing agent, sulfuric acid, a solution
including sulfuric acid, an aqueous solution of a base or bases, an
aqueous solution of a base or bases including an oxidizing agent,
an aqueous solution of cyanide including an oxidizing agent, an
aqueous solution of sodium or calcium hypochlorite, an aqueous
solution of ferrous or ferric sulfate, an aqueous solution of
ferrous or ferric sulfate including an oxidizing agent, an aqueous
solution including a bacterial catalyst, an aqueous solution of
chlorine, an aqueous solution of hydrogen peroxide, a solution of
ammonium thiosulfate, a lixiviant for leaching uranium, or an
aqueous solution of air and sulfur dioxide and copper.
37. The method of claim 31, wherein the crushed ore includes
gold-bearing ore, silver-bearing ore, ore bearing at least one
platinum group metal, ore bearing rare earth elements, ore bearing
gallium, ore bearing germanium, ore bearing light metals, ore
bearing copper, ore bearing zinc, ore bearing molybdenum, ore
bearing lead, ore bearing uranium, ore bearing cobalt, ore bearing
nickel, ore bearing refractory metals, solids containing coal,
solids containing oil sands, or solids containing oil shales.
38. The method of claim 31, and further comprising introducing the
lixiviant into the reaction vessel at a first flow rate, wherein
the pregnant leach solution is extracted from the reaction vessel
at a second flow rate, and wherein the first and second flow rates
are simultaneous.
39. The method of claim 38, wherein the first and second flow rates
are essentially equal, essentially constant, or essentially equal
and constant.
40. The method of claim 31, and further comprising introducing the
crushed ore into the reaction vessel at a first flow rate, wherein
the post-reaction solids are extracted from the reaction vessel at
a second flow rate, and wherein the first and second flow rates are
simultaneous.
41. The method of claim 40, wherein the first and second flow rates
are essentially equal, essentially constant, or essentially equal
and constant.
42. The method of claim 31, and further comprising separating at
least two predetermined sizes of solids from at least some of the
post-reaction solids.
43. The method of claim 31, and further comprising removing
pregnant leach solution from at least some of the post-reaction
solids, wherein the removing the pregnant leach solution includes
at least one of: centrifuging at least some of the post-reaction
solids; passing at least some of the post-reaction solids through a
filter; passing at least some of the post-reaction solids along a
screen; or leaching at least some of the post-reaction solids in
barren solution wash, thus deriving an aqueous leachate.
44. The method of claim 31, and further comprising separating at
least one dissolved material out of the pregnant leach solution,
wherein the at least one dissolved material includes gold, silver,
a platinum group metal, gallium, germanium, copper, zinc, uranium,
cobalt, molybdenum, nickel, lead, a refractory metal, a light
metal, crude oil, caregens, or a rare earth element.
45. The method of claim 31, and further comprising controlling at
least one of temperature, pH, Eh, a gas concentration, or liquid
concentration, within the reaction vessel during the reacting the
crushed ore with the lixiviant.
Description
BACKGROUND
[0001] Many applications are known wherein a liquid is reacted with
a particulated or crushed solid ("solids") to enhance one or the
other of the liquid or the solids (or both) for commercial benefit.
One common application is to react a liquid "lixiviant" with a
solid to extract a soluble compound from the solid by way of
percolating or washing the solid with the liquid. (Accordingly, a
"lixiviant" is a liquid used for this purpose.) This process is
commonly described as "leaching", and is known to various fields of
endeavor. Typical examples include extracting valuable metals from
ores containing the metals by contacting the ores with a lixiviant.
The extracted metals will then be in solution with the lixiviant,
and can be later removed from the lixiviant by known chemical
processes, such as chemical precipitation, to render a relatively
pure form of the extracted metals, or a form that can be
subsequently processed to render a relatively pure form of the
extracted metals. One example is to wash ore containing gold with a
lixiviant containing cyanide to remove the gold from the ore. Other
examples include washing oil shales with a solvent to extract
petroleum from the shales, and washing coal with a
sulfur-extracting liquid to remove sulfur from the coal. Yet
another example includes contacting contaminated soil with a
liquid-borne biological agent (or agents) to thereby decontaminate
the soil.
[0002] In all of these processes the volumes of solids to be
treated are typically considerable--on the order of tens to
thousands of metric tons per day. In the case of ore leaching (to
remove valuable metals from ores containing the metals), the most
common process is to pile the ore into a "heap" on a leach pad, and
then to introduce a lixiviant onto the top of the heap. After the
lixiviant has passed through the ore heap via gravity, the
lixiviant is collected and processed to remove the extracted metals
from the lixiviant. The spent ore is then discarded (as for example
by moving it to a spent ore pile), and new unprocessed ore is then
placed on the leach pad, and the process repeated. Such leach pads
often occupy areas covering many acres, and in some cases square
miles. Due to the nature of the lixiviants used, and the metals
being extracted from the ores, leach pads are typically subject to
significant environmental controls to reduce the possibility of
potential contamination of soil surrounding the leach pad. Further,
the ore leaching process via ore heaps and leach pads is a slow
process. Common leach times (i.e., the time between when the ore
heap is initially formed and the lixiviant added to the ore heap,
and the time when the ore is considered "spent" and is removed from
the leach pad) are on the order of months. A six month leach time
is not uncommon.
[0003] Other prior leaching methods and apparatus include: (1)
batch tank leaching, (2) agitated vat leaching, (3) counter-current
tank leaching, (4) permanent pad heap leaching (described briefly
above), (5) re-usable pad heap leaching, and (6) bio-heap leaching.
A common description for each of these methods and apparatus is a
"leach circuit".
[0004] The specific shortcomings of the prior art are as
follows.
[0005] For agitated vat leaching, the basic operational concept is
to provide an elevated contact rate of lixiviant and other
additives to the surfaces of the ore particles by (a) increasing
the surfaces of the ore which can be accessed by the lixiviant by
grinding the ore to a particle size that exposes the desired metal
or mineral value, (b) vigorously agitating the ore and lixiviant so
as to provide an elevated level of contact between unconsumed
reaction agents, and (c) to readily remove reaction outputs so as
to maintain in majority concentration the unconsumed reaction
agents.
[0006] The shortcomings of such a process include: (1) significant
capital and operational costs are associated with grinding the ore
to a small particle size and vigorously agitating such a dense
media as an ore slurry; (2) the processing time required for the
desired recovery level--as short as 24 hours in the typical
case--in conjunction with the size limitations for a vessel which
will afford reasonably good economic access of the agitation
mechanical to the ore slurry, necessitates a large number of
containment vessels, which in turn necessitates a plant of
commensurate size to contain and support the operation of the
containment vessels, all of which requires significant capital and
real estate to construct; (3) small particle sizes typically
present challenges for disposal of spent ore since special
impoundments are typically required to de-water and stabilize it as
permanent fill; (4) because of the relatively high capital and
operating costs of such a leach process, the method is not
economical for very low grade ores or ores which require leach
times in excess of 24 hours to achieve economic recovery; (5) batch
processing contains an inherent limitation in that there is wasted
economic time between batch operations; and (6) because of the
complexity of such a mechanically intensive process, design and
construction times for the plant are relatively long (as compared
to heap leaching, for example).
[0007] Heap leaching is an alternative to vat leaching and attempts
to address the limitations of vat leaching with respect to low
grade ores and ores that require longer leach recovery times (e.g.,
using certain oxides and certain sulfides). The basic operational
concept of heap leaching is to trade-off leach recovery time for
leach circuit processing size or volume by (1) secondary or
tertiary crushing of the ore instead of grinding to a fine grain
size, (2) agglomerating the ore into relatively uniform ore spheres
to increase permeability of lixiviant and increase contact
effectiveness rather than agitating the ore, (3) stacking in broad,
relatively shallow piles on an impermeable layer instead of
batching in expensive vessels, (4) sprinkling lixiviant on the ore,
letting it trickle down under the action of gravity alone through
the ore, and collecting the pregnant solution from perforated pipes
on the bottom of the heap rather than submerging the ore within a
vat or tank, (5) blowing air into the heap (as in the case of
bio-heap leaching), and (6) removing the ore continuously from the
pad as in the case of re-usable pads to make heap leaching a more
continuous rather than a batch process.
[0008] Although heap leaching extends leaching technology to lower
grade and harder-to-leach ores that are not economically done with
vat leaching because of the implied processing volume required,
heap leaching is less effective in extracting metals and the like
from the ores, primarily due to the absence of submersion of the
ore in the lixiviant and agitation of the ore (as in agitated vat
leaching). Of particular concern in the use of a trickle-type
application of lixiviant to a stack or pile of ore on a leach pad
is channeling of the lixiviant, leaving significant portions of the
leach pile without sufficient lixiviant to extract the theoretical
maximum recoverable metals using the heap.
[0009] Another inherent shortcoming of heap leach is the inability
to control environmental inputs such as temperature and oxygenation
of the heap, which are critical factors in bio-heap leaching where
the effectiveness of the bacteria is closely dependent on these
variables.
[0010] Perhaps the greatest shortcoming of heap leaching is the
capital and operating costs associated with large volumes of
material, especially in the case of re-usable pads. Whereas in vat
leaching the ore is transported in a slurry in pipe conduits, heap
leaching, because of the large geometric extents of leach pads and
complexity of stacking a stable heap, has been performed almost
exclusively with conventional overland conveyors and specialized
spreading and reclaim conveyors, which imply high capital and
operating costs as compared to the compact plant piping of vat
leaching.
[0011] What is needed then is an economical, efficient method
and/or apparatus to react solids and liquids with one another that
achieves the benefits to be derived from similar prior art
apparatus and methods, but which avoid the shortcomings and
detriments individually associated therewith.
SUMMARY
[0012] One embodiment provides for a method of processing selected
solids with a selected liquid, the method including the steps of
providing a vessel, and crushing the solids to not less than a
predetermined median particle size. The crushed solids define, or
are referred to herein, as crushed solids. The method also includes
the step of reacting the crushed solids with the liquid within the
vessel, such that a pregnant leach solution and post-reaction
solids are derived. At least some of the reacting of the
aforementioned step occurs under conditions of a predetermined
hydrostatic head. The method further includes the step of migrating
the pregnant leach solution and the post-reaction solids through
the vessel substantially under the influence of gravity alone.
Furthermore, the method includes the step of extracting the
pregnant leach solution and the post reaction solids from the
vessel.
[0013] Another embodiment provides for a method of processing a
mine ore with a lixiviant, the method including the step of
providing a reaction vessel, wherein the vessel defines solids
outlet openings and liquid outlet openings. The method also
includes the step of crushing the mine ore to not greater than a
predetermined size, such that crushed ore is defined or derived.
The method further includes the steps of reacting the crushed ore
with the lixiviant within the reaction vessel, thus deriving a
pregnant leach solution and post-reaction solids, and extracting at
least some of the pregnant leach solution from the reaction vessel
via the liquid outlet openings substantially under the influence of
gravity alone. The method includes extracting the post-reaction
solids and at least some of the pregnant leach solution from the
reaction vessel via the solids outlet openings substantially under
the influence of gravity alone.
[0014] These and other aspects and embodiments will now be
described in detail with reference to the accompanying drawings,
wherein:
DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a block diagrammatic view depicting a system that
can be used to perform a method according to one embodiment of the
invention.
[0016] FIG. 2 is block diagrammatic view depicting details of the
system of FIG. 1.
[0017] FIG. 3A is flowchart depicting a method according to one
embodiment of the invention.
[0018] FIG. 3B is a continuation of the flowchart of FIG. 3A.
[0019] FIG. 3C is a continuation of the flowchart of FIG. 3A.
DETAILED DESCRIPTION
[0020] In representative embodiments, the present teachings provide
methods and apparatus for processing solids such as run-of-mine
ore, in a substantially continuous manner, so that one or more
materials of interest can be extracted or isolated from the ore and
further processed to a condition deliverable to the market
place.
[0021] The following terms are defined as used herein:
[0022] Run-of-Mine Ore: Refers to matter comprising at least one
material of interest that is to be extracted or separated from the
balance of the matter. Run-of-mine ore (or, interchangeably, ore)
is in essentially the same condition as when it was removed from
its natural or native source and, typically (but not exclusively),
defines a substantially solid, chunk-like consistency and includes
individual particles of substantially varying size. Non-limiting
examples of materials of interest within such ore include gold,
silver, platinum group metals, gallium, lead, germanium, refractory
metals, molybdenum, copper, zinc, uranium, cobalt, nickel, light
metals, crude oil, caregens, rare earth elements, etc. Other ores,
comprising other respective materials of interest, can also be
used. Examples of a native source for run-of-mine ore include, but
are not limited to, a shaft mine, an open pit mine, a strip mine,
etc.
[0023] Lixiviant: This refers to any of a number of chemical
compounds, typically (but not necessarily) in a liquid state, which
chemically reacts with run-of-mine ore so as to dissolve, or
"leach", one or more materials out of the ore and into solution
with the lixiviant. Non-limiting examples of lixiviant include an
aqueous solution of acid or acids, an aqueous solution of acid or
acids including an oxidizing agent, an aqueous solution of an
alkali or alkali's, sulfuric acid, a solution including sulfuric
acid, an aqueous solution of an alkali or alkalis' including an
oxidizing agent, an aqueous solution of cyanide including an
oxidizing agent, an aqueous solution of sodium or calcium
hypochlorite, an aqueous solution of ferrous or ferric sulfate, an
aqueous solution of ferrous or ferric sulfate including an
oxidizing agent, an aqueous solution including a bacterial
catalyst, an aqueous solution of chlorine, an aqueous solution of
hydrogen peroxide, a solution of ammonium thiosulfate, or an
aqueous solution of air and sulfur dioxide and copper. Other
suitable lixiviants can also be used. Various embodiments allow the
use of a lixiviant (or lixiviants) of typically greater
concentration than those used in known heap leaching operations.
Furthermore, the concentration (and/or other characteristics) of a
lixiviant can be controlled to tighter tolerances, if desired,
during continuous mode operation of various embodiments, as
compared to known heap leaching operations.
[0024] Pregnant Leach Solution (PLS): This refers to a liquid
comprising a lixiviant--in some overall degree of chemical
depletion or expenditure--and one or more materials dissolved into
solution therewith. Thus, pregnant leach solution typically results
from a chemical reaction between a solid material, such as crushed
run-of-mine ore, and a pristine (new, fresh, or regenerated)
lixiviant.
[0025] Post-Reaction Solids (PRS): This term refers to solids,
typically in a crushed form, which have reacted with a lixiviant
such that at least some amount of one or more materials are
dissolved out of the solids. As used herein, post-reaction solids
are usually defined by crushed run-of-mine ore that has reacted, to
some degree, with a lixiviant as generally defined above. That is,
such post-reaction solids are typically defined by crushed ore
matter that has been depleted, to some extent, of one or more
materials previously present in its original (pre-reaction)
condition. In some cases, post-reaction solids (PRS) will include
some quantity (i.e., trace or residual amounts, etc.) of pregnant
leach solution (PLS) until and/or unless further treatments or
processing steps are performed to remove (e.g., leach) such PLS
borne by the PRS.
[0026] Barren Solution: Generally, this term refers to lixiviant
that has been previously used within a leach process (i.e., was
once a pregnant leach solution) and has been processed or otherwise
sufficiently reconstituted (i.e., recycled) so as to be useful in
one or more embodiments. Non-limiting examples of such recycling
steps can include removal of the materials dissolved into solution
with the PLS, reconstitution by gas injection or addition of new
acid, etc. In one example, a barren solution is derived that can be
used within a wash process in order to leach (soak, or free)
another liquid out of a solid material, thus defining an aqueous
leachate. In another example, a barren solution is defined by
sufficiently recycling PLS so as to derive a lixiviant in
substantially new condition, and which can be used as such.
[0027] Turning now to FIG. 1, a block diagrammatic view depicts a
system 100 that can be used to perform one or more methods in
accordance with the present teachings. While the system 100 depicts
particular elements used in accordance with one embodiment, it is
to be understood that other elements (not shown) can be used,
and/or selected ones of those elements shown FIG. 1 can be omitted,
in accordance with other embodiments. Thus, the system 100 as
depicted in FIG. 1, is but one of any number of systems that can be
used in accordance with the present teachings.
[0028] The system 100 includes a supply of run-of-mine ore (ore)
102. The supply of ore 102 is typically piled in a covered or
uncovered fashion to wait further processing, as described
hereinafter.
[0029] The system 100 includes a crusher 104. The crusher 104 can
be defined by any suitable means for crushing the ore 102 to a
predetermined median (or, optionally, a mean, not-less-than, or
not-to-exceed) size. In one embodiment, the crusher 104 is defined
by a jaw mill. In other respective embodiments, the crusher 104 is
defined by a gyratory type or SAG mill. One of ordinary skill in
the mining engineering arts is aware of numerous such crushers 104
for suitably crushing run-of-mine ore 102, in accordance with the
specific type of ore 102 and/or the desired median crushed size,
and further elaboration is not required for purposes herein. In any
case, the crusher 104 is suitably selected and used to crush the
run-of-mine ore 102, thus deriving (i.e., defining) a supply (or
stream) of crushed solids (i.e., crushed ore) 106.
[0030] The system 100 includes a supply of lixiviant 108. The
lixiviant 108 can be defined by any suitable such lixiviant as
defined above. The lixiviant 108 is reacted with the crushed solids
106 in order to derive one or more desired by-products (or effects)
of the reaction such as, for example, a pregnant leach solution as
defined above. For example, the lixiviant 108 can be suitably
defined so as to react with the crushed solids 106 such that gold
is leached out of the crushed solids 106 and into solution with the
lixiviant 108. Other suitable lixiviants (i.e., liquids, etc.) 108
can also be used in accordance with the particular type of crushed
solids 106, the desired reaction to occur therewith, etc. One of
ordinary skill in the mining or chemical arts is aware of numerous
such lixiviants 108 and their respective uses.
[0031] The system 100 of FIG. 1 also includes a slurry preparation
tank 107. The slurry preparation tank (hereinafter, slurry prep
tank) 107 can be defined by a tank or box-like structure and can
(optionally) be lined with a hard coating or other suitable wear-
or corrosion-resistant material. In one embodiment, the slurry prep
tank 107 is formed of steel and is lined with ceramic tile. Other
embodiments of the slurry prep tank 107, respectively formed from
other suitable materials, can also be defined and used. The slurry
prep tank 107 is configured to receive respectively controlled
flows of the crushed ore 106 and the lixiviant 108. In another
embodiment (not shown), the slurry prep tank is also configured to
receive a flow of a suitable flocculant. The slurry prep tank 107
serves as a mixing chamber wherein the crushed ore 106 and
lixiviant 108 (and flocculant, if used) are combined so as to
define a wetted material (or slurry) stream 109. In another
embodiment of the system 100 (not shown), the slurry prep tank 107
is provided in conjunction with suitable piping or other material
conduits so that flow of the crushed ore 106 can be optionally
bypassed around the slurry prep tank 107, while the flow of
lixiviant 108 into the slurry prep tank is curtailed. In yet
another embodiment of the system 100 (not shown), the slurry prep
tank 107 itself is omitted altogether.
[0032] The system 100 of FIG. 1 further includes a mass flow
reactor 110. The mass flow reactor (MFR) 110 is also referred to
herein as a vessel. One or more embodiments of mass flow reactor
110 suitable for use in accordance with the present teachings
is/are described in detail in U.S. patent application Ser. No.
10/447,801, titled METHODS AND APPARATUS FOR PROCESSING MIXTURES OF
LIQUIDS AND SOLIDS, as filed with the United States Patent and
Trademark Office on May 29, 2003 and as incorporated herein by
reference in its entirety. The MFR 110 provides a vessel-like
structure within which the crushed solids 106 are reacted with the
lixiviant 108. The crushed solids 106 and the lixiviant 108 can be
received by the MFR 110 as respectively separate flows or as, or in
combination with, the slurry stream 109, in accordance with the
desired mode of operation. As depicted in FIG. 1, it is presumed
that reaction of the crushed solids 106 with the lixiviant 108
results in the derivation of post-reaction solids and pregnant
leach solution, respectively. Other solids/liquids reactions,
resulting in other solid and/or liquid by-products, can also be
performed within the MFR 110.
[0033] The mass flow reactor 110 of FIG. 1 is configured to permit
the post-reaction solids and the pregnant leach solution to migrate
through the MFR 110 and to be extracted there from substantially
under the influence of gravity alone as a stream of post-reaction
solids 112 and a stream of pregnant leach solution 114,
respectively. In this way, the mass flow reactor 110 is distinct,
for example, from an agitated vat or other type of ore-handling
apparatus wherein driven paddles, augers and/or overall rotary
motion are used (whether in conjunction with gravity or not) to
forcibly induce ore (or other materials) to migrate from an entry
point to an exit point. Further operational aspects of the mass
flow reactor 110 will be discussed in detail hereinafter.
[0034] The system 100 of FIG. 1 includes a heat exchanger 115. The
heat exchanger 115 receives the flow of PLS 114 from the mass flow
reactor 110. The heat exchanger 115 can be defined by any suitable
form such as, for example, a plate-and-frame design, a serpentine
tube design, a multi-tube single-pass design, etc. One of skill in
the mechanical engineering arts is aware of numerous heat exchanger
115 designs and their general use and further elaboration is not
needed for purpose here. In one example, the heat exchanger 115
recovers heat from the PLS 114 and routes it (interconnecting means
not shown) for pre-heating the lixiviant 108 prior to introduction
into the slurry prep tank 107 and/or the MFR 110. In another
example, such recovered heat is simply expelled to atmosphere via a
suitably coupled cooling tower (not shown). In yet another example,
heat recovered from the heat exchanger 115 is used to pre-heat
water or another fluid for use in an electrical generation plant
(not shown). In any of these examples, the pregnant leach solution
114 is cooled to define a cooled PLS stream 117. In yet another
example, the heat exchanger 115 is used to heat the PLS 114 to a
temperature greater than that as it is received from MFR 110, prior
to subsequent processing of the (heated) PLS 114. In such a case,
the pregnant leach solution is heated to define a heated PLS stream
117. In yet another embodiment of the system 100 (not shown), the
heat exchanger 115 is optionally bypassed or otherwise inoperative,
or the heat exchanger 115 itself is omitted altogether.
[0035] The system 100 includes pregnant leach solution process (PLS
process) 116. The PLS process 116 can be defined by any suitable
process (or combination of sub-processes) configured to receive the
pregnant leach solution stream 114 from the mass flow reactor 110,
the cooled/heated PLS stream 117 from the heat exchanger 115,
and/or the PLS stream 134 (described hereinafter) and to separate
(i.e., extract) one or more materials out of the residual pregnant
leach solution. For example, a suitable PLS process 116 can be
defined and used that causes gold to precipitate out of solution
with the remaining PLS liquid advancing to the next stage.
Non-limiting examples of process steps performed by the pregnant
leach solution process 116 include any suitable one, or combination
of, heating or cooling, clarification, filtration, bulk
precipitation, pH modulation, solvent extraction, electrowinning,
mercuric retorting, smelting, carbon column absorption, magnetic
separation, cyclonic separation, etc. One of ordinary skill in the
mining engineering arts is aware of numerous, well-established
methods and materials for extracting particular materials out of
pregnant leach solution and specific definition and elaboration is
not required.
[0036] In any case, the pregnant leach solution process 116
includes suitable process steps resulting in the extraction and
isolation of one or more minerals, metals, and/or other materials
118 in a condition suitable for provision to the market, or further
processing, if desired. Also, the PLS process 116 can be defined
and operated so as to reconstitute (i.e., recycle) the lixiviant
within the PLS stream 114, 117 and/or 134, or some fraction
thereof, so that a renewed lixiviant stream (or supply) 148 is
derived. As depicted in FIG. 1, the renewed lixiviant 148 is routed
back to and combined with the supply or source of lixiviant 108. In
another embodiment (not shown), the PLS process 116 is defined and
operated so as to derive a stream (or supply) of barren solution
(not shown). Other embodiments of the pregnant leach solution
process 116 can also be defined and used.
[0037] The system 100 of FIG. 1 also includes a screen process 120.
The screen process 120 can include any suitable mesh-like apparatus
such as, for example, a mesh conveyer belt, a vibratory screen
assembly, etc. Other suitable screen process 120 apparatus can also
be used. The screen process (or screen) 120 is configured to
receive and support the post-reaction solids 112 such that
post-reaction solids 112 of less than a predetermined size are
separated from the balance of the PRS stream 112. In one
embodiment, the screen process 120 is configured so that
post-reaction solids of less than 5/8 inch, defining fine solids
(or "fines"), are separated from the balance of the post-reaction
solids 112. Other configurations for separating other sizes of
post-reaction solids 112 (i.e., solid matter) can also be defined
and used. Thus, typical operation of the screen process 120 derives
a stream (or supply) of relatively coarse post-reaction solids 122,
and a stream (or supply) of fine solids 124.
[0038] As depicted in FIG. 1, the coarse solids 122 are routed onto
other processing 126, which can include any desirable step or
combination of steps for handling the relatively coarse solids 122.
Such other processing 126 step or steps can include, for example,
detoxification and/or disposal of the coarse post-reaction solids
122, further extraction of another material of interest therefrom,
processing and/or market preparation of "cleaned" coal or oil shale
(e.g., coal or oil shale from which sulfur has been "washed" or
leached within the MFR 110), etc. One of skill in the mining arts
is aware of numerous subsequent steps that can be performed after
screen separation of fines from coarse solids, and further
elaboration is not needed for purposes herein.
[0039] The system 100 of FIG. 1 further includes a centrifuge
process 128. The centrifuge process 128 includes any suitable
apparatus configured to receive the fine post-reaction solids
(fines) 124 and to additionally separate pregnant leach solution
(i.e., PLS 114) there from by way of centrifugal force (i.e., rapid
rotation within a drum), thus deriving a stream (or supply) of
pregnant leach solution 130. The pregnant leach solution 130 can be
routed if needed to a clarifying process 132, described in detail
hereinafter. Also, the centrifuge process 128 derives a stream (or
supply) of generally dried (i.e., "dewatered") post-reaction solids
136. One of ordinary skill in the mining arts is aware of various
suitable centrifuge processes and apparatus, and further
elaboration is not required.
[0040] The system 100 also includes a barren solution (or water)
wash 140. Typically, the barren solution wash 140 can be used to
leach additional PLS (i.e., PLS 114) out of the (dried, or
"dewatered") fine solids 136. For example, some fine solids 136
include surface geometry, absorption characteristics, or other
considerations that economically justify use of the barren solution
wash 140 in order to recover additional material of interest (i.e.,
cyanide complexed gold, etc.) therefrom. In one embodiment, the
barren solution wash is provided by way of a vessel substantially
mechanically equivalent to the mass flow reactor 110. However
defined and used, the barren solution (or water) wash 140 derives a
stream (or supply) of aqueous leachate 142 borne by the (dried)
fine solids as they exit the barren solution wash 140. In a sense,
the fine solids 136 have been "rewetted" by way of soaking
(leaching) within the barren solution wash 140 in the interest of
recovering additional material of interest therefrom (e.g.,
dissolved copper, etc.). In some cases, the barren solution or
water wash 140 is not used at all.
[0041] The system 100 also includes another centrifuge 144. The
centrifuge 144 can be defined by any suitable apparatus configured
to receive the stream of "rewetted" fine solids from the barren
solution wash 140 and to separate the aqueous leachate 142
therefrom by way of centrifugal force. In this way, the centrifuge
144 derives a stream (or supply) of liquid aqueous leachate 146 and
a stream (or supply) of re-dried (or "dewatered") fine solids 145.
As also depicted in FIG. 1, re-dried fines solids 145 are
optionally routed onto other processing 138, which can include any
desirable step or combination of steps for handling the re-dried
fines solids 145. Such other processing 138 step (or steps) can
include, for example, detoxification and/or disposal of the
re-dried fines 145, further extraction of another material of
interest therefrom, cyclonic (or other) separation of different
sizes (or classes) of fines material 145, etc. One of skill in the
mining arts is aware of numerous subsequent steps that can be
performed after centrifuge separation of liquid from fines, and
further elaboration is not needed for purposes herein.
[0042] The system 100 includes a clarifying process 132. The
clarifying process 132 can be defined by, or include, any suitable
apparatus or processing step (or steps), if any, as desired or
required, to remove solids from or otherwise handle the stream of
pregnant leach solution 130 generated by the centrifuge process
128, and/or the aqueous leachate 146 generated by the centrifuge
144. For example, in a case where the PLS 130 contains 5000 ppm
solids, reacted lixiviant and material of interest therein (e.g.,
dissolved copper, etc.), the clarifying process 132 can be suitably
defined to remove a substantial fraction of the solids therefrom.
In any case, the clarifying process 132 derives a stream (or
supply) of pregnant leach solution 134 to be routed on to the PLS
process 116 described above. In another embodiment of the system
100 (not shown), the clarifying process 132 is bypassed or omitted
altogether. In yet another embodiment (not shown), the clarify
process 132 can be suitably interconnected to the heat exchanger
115 so as to be heated or cooled thereby.
[0043] The system 100 of FIG. 1 depicts particular system elements
(i.e., process apparatus) coupled in particular cooperative
relationships. However, it is to be understood that other systems
(not shown) can also be defined and used in accordance with various
corresponding embodiments. Further exemplary operation of the
system 100 will be described hereinafter. While the system 100 of
FIG. 1 is described above in terms of processing run-of-mine ore
(i.e., 102), it is to be understood that another system (not
shown), including a mass flow reactor (e.g., MFR 110, etc.), can
also be defined and used for decontaminating soil and the like. One
of ordinary skill in the mining or industrial arts and/or
geological sciences will recognize that the MFR 110 can provide a
basis for any number of substantially continuous processes
involving reactions between solid and liquid materials.
[0044] FIG. 2 is a block diagrammatic view depicting selected
details of the system 100 of FIG. 1. As depicted in FIG. 2, the
mass flow reactor (i.e., vessel) 110 is coupled to receive the
stream of crushed solids (i.e., crushed ore) 106 directly--that is,
the slurry prep tank 107 of FIG. 1 is not included. Furthermore,
the mass flow reactor 110 is coupled in fluid communication with
the supply of lixiviants 108. As depicted in FIG. 2, the MFR 110
receives the crushed solids 106 via at least one point (or opening)
150 proximate an open top of the MFR 110. However, in another
embodiment (not shown), the MFR 110 is configured to receive the
crushed solids 106 via at least one point (or opening)
elevationally lower with respect to the MFR 110. It is to be
understood that the system 100 is suitably equipped to regulate the
flow of crushed solids 106 into the mass flow reactor 110 over some
predetermined range, including complete shut off (zero flow).
[0045] The mass flow reactor 110 is also configured to receive the
lixiviant 108 at a plurality of liquid entry points (or openings)
152 elevationally distributed within the MFR 110. While not
specifically depicted in FIG. 2, it is understood that the mass
flow reactor 110 is suitably equipped (e.g., via valves, pressure
regulators, electronic and/or pneumatic controls, etc.) so as to
throttle, or regulate, the flow of lixiviant 108 (i.e., liquid)
through each of the liquid entry points 152 over some predetermined
range, including complete shut off. The flow of lixiviant 108 can
be independently controlled through each liquid entry point 152,
suitably ganged so as to throttle each liquid entry point 152 flow
in unison with the others, etc.
[0046] The MFR 110 is also configured to permit the extraction of
post-reaction solids 112 from one or more solids exit points (or
openings) 154. Typically, at least one such solids exit point 154
is coincident with, or substantially proximate to, a bottom center
"B" as defined by the mass flow reactor 110. Other respective
suitable locations defined by the MFR 110 can also be used for
locating the solids exits points 154. In any event, the mass flow
reactor 110 is suitably equipped so as to throttle the flow of
post-reaction solids 112 through each of the solids exit points 154
over some predetermined range, including complete shut off. The
flow of post-reaction solids 112 can be independently controlled
through each solids exit point 154, coupled (ganged) so as to
throttle each exit point 156 flow in unison with the others,
etc.
[0047] The MFR 110 is further configured to permit the extraction
of pregnant leach solution 114 at a plurality of liquid exit points
(or openings) 156 elevationally distributed within the MFR 110. It
is to be understood that the mass flow reactor 110 is also suitably
equipped so as to throttle (regulate) the flow of lixiviant
pregnant leach solution 114 (i.e., liquid) through each of the
liquid exit points 156 over some predetermined range, including
complete shut off. The flow of PLS 114 can be independently
controlled though each liquid exit point 156, ganged such that each
liquid exit point 156 flow is throttled in unison with the others,
etc.
[0048] It is important to note that the mass flow reactor 110 as
depicted by FIG. 2 is configured such that post-reaction solids 112
and pregnant leach solution 114 (as well as, to some respective
extents, crushed solids 106 and lixiviant 108) are induced to
migrate (or flow) thorough the MFR 110 substantially under the
influence of gravity alone, in the prevailing direction indicated
by the arrow "G". It is to be further understood, of course, that
post-reaction solids 112 and pregnant leach solution 114 also
migrate toward their respective solids exit points 154 and liquid
exit points 156, in various directions which deviate from the
prevailing direction "G" in order for material (e.g., PRS 112 and
PLS 114) extraction from the MFR 110 to be performed. However, such
extraction of the post-reaction solids 112 and the pregnant leach
solution 114 is also performed substantially under the influence of
gravity alone. As used herein, "substantially under the influence
of gravity alone" refers to migration or motion of respective
materials through the mass flow reactor 110 without the use of
other mechanical driving means or influences--for example, the mass
flow reactor 110 is devoid of any driven paddles or augers,
downward and/or upward liquid jetting, or vibration, shaking,
rocking or rotation of the MFR 110, and wherein gravity accounts
for not less than ninety percent of the overall migration-inducing
force when the mass flow reactor 110 is operated with a gaseous
pressure (other than ambient atmospheric) present over the liquid
and/or solids materials being processed within the MFR 110 (e.g.,
see location "U" in FIG. 2). This makes operation of the mass flow
reactor 110 distinct from other types of vessels or processing
conduits known in mining or the related arts.
[0049] The mass flow reactor 110 of FIG. 2 is also configured so as
to define an internal cavity of volume "V", and a maximum possible
(or working) depth "L" of liquid there in. In this way, it is
possible to establish a predetermined hydrostatic head gradient by
providing and/or maintaining the corresponding depth "L" of liquid
(i.e., lixiviant 108 and PLS 114) within the MFR 110. In one
exemplary embodiment, the MFR 110 is configured such that a stratum
corresponding to a hydrostatic head "H" in excess of 65 feet of the
liquid is present, and can be maintained, within the mass flow
reactor 110. Other configurations of MFR 110 corresponding to other
(potential) magnitudes of hydrostatic head can also be used. In any
case, the mass flow reactor 110 can be suitably configured to
provide a zone (or stratum) where at least some of the reaction of
the crushed solids 106 with the lixiviant 108 can take place under
a predetermined hydrostatic head "H" of the liquid. As depicted in
FIG. 2, the MFR 110 can be generally open to ambient atmospheric
pressure at an elevationally upper end "U". In another embodiment
(not shown), the MFR 110 is configured such that a non-atmospheric
pressure (i.e., a relative vacuum or over-atmospheric pressure) is
present over the liquid within the MFR 110, wherein such
pressure--be it atmospheric or not--can be provided by way of any
suitably selected gas (e.g., air, O.sub.2, N.sub.2, NO.sub.x,
CO.sub.2, etc.).
[0050] As depicted in FIG. 2, the mass flow reactor 110 is coupled
in fluid communication with a supply of gas 158. The MFR 110
receives the gas 158 by way of at least one gas entry point (or
opening) 160. Such gas entry point or points 160 can be selectively
located and/or distributed within the MFR 110 as desired or
required. Non-limiting examples of the gas 158 include an
oxygen/air mixture, a sulfur dioxide/air mixture, air, pure oxygen,
a gaseous oxidizing agent, or any of these or another suitable gas
or gasses dissolved in a liquid or lixiviant that is injected into
the reactor 110 via entry port(s) 160, etc. Other suitable gases
158 can also be defined and used in. For example, the gas 158 can
be an oxygen/air mixture of predetermined ratio that is provided to
the MFR 110 for purpose of oxidizing sulfur compounds present
within or liberated from the crushed solids 106 so that such
oxidized sulfur compounds are more readily handled at some
subsequent process (not shown) external to the mass flow reactor
110. Furthermore, the mass flow reactor 110 in the upper end "U"
(or area proximate thereto) can be suitably equipped with ducting
or piping, fume collection hoods, fans, etc. (not shown), so that
gases (e.g., the gas 158, a gaseous by-product or by-products of
reaction, etc.) can be captured/collected and routed away from the
MFR 110 for containment, processing, etc. In any case, one of
ordinary skill in the mining arts is aware of numerous processes in
which one or more gases can be injected into a reaction zone for
one or more purposes, and further elaboration is not required.
[0051] The mass flow reactor 110 of FIG. 2 can also be coupled to a
supply of flocculant 170 that can be controllably introduced into
the MFR 110 at one or more flocculant entry points (or openings)
172. The flocculant 170 can be defined by any suitable agent used
to cause relatively fine particles of the crushed solids 106 to
adhere to one another, thus defining a plurality of larger solids
entities. In an alternative embodiment, the flocculant 170 is
defined by any suitable agent that causes such fine particles of
the crushed solids 106 to adhere to relatively larger particles (or
chunks) of the crushed solids 106 (agglomeration). In this way, an
overall permeability of the crushed solids 106 with respect to the
lixiviant (liquid) 108 within the MFR 110 can be suitably affected
so as to increase contact between the two. In any case, the
flocculant 170 can be provided to the MFR 110 when such
flocculation or agglomeration is desired. One of ordinary skill in
the mining arts is familiar with the selection and use of
flocculants 170 as applied to processing ore "fines", and further
elaboration is not required here.
[0052] In another embodiment (not shown), a supply of inert solids
is provided and selectively used so as to affect and/or stabilize
one or more physical characteristics during reaction of solids with
liquid(s) within a mass flow reactor (e.g., the MFR 110, etc.) such
as, for example, increasing or decreasing heat conductivity,
increasing or decreasing heat absorption, increasing or decreasing
heat capacity, etc. Non-limiting examples of such inert solids (not
shown) include steel spheres, etc.
[0053] FIG. 3A is flowchart 200 depicting a method in accordance
with one embodiment of the present teachings. The method of the
flowchart 200 is described hereinafter in reference to system 100
of FIGS. 1 and 2 in the interest of understanding. However, it is
to be understood that the method of the flowchart 200 can also be
performed using other systems and/or elements (not shown) within
the scope of the present teachings. While the flowchart 200 depicts
particular method steps and order of execution, it is to be
understood that other embodiments that include other respective
steps and/or orders of execution can also be used. Thus, the method
of the flowchart 200 is exemplary of any number of other such
methods within the present scope.
[0054] In step 202 (FIG. 3A), run-of-mine ore is crushed to a
suitable median size. For purposes of example, it is assumed that
gold-bearing, run-of-mine ore 102 (FIG. 1) is crushed using a
suitable crusher 104 so as to derive (define) crushed solids (i.e.,
crushed ore) 106 having a median size of approximately 0.375 inches
in diameter. Other median sizes and/or sizing schemes for the
crushed solids 106 can also be used.
[0055] In step 204 (FIG. 3A), crushed solids 106 (FIG. 2) are
provided directly into the mass flow reactor 110 by way of solids
entry point 150 so as to fill the MFR 110 to a predetermined
operating depth (i.e., vertical pile dimension) "S". Thus, the
slurry prep tank 107 (FIG. 1) is assumed to be bypassed or
otherwise unused. For purposes of the ongoing example, it is
assumed that the MFR 110 is filed with crushed solids 106 to a
depth "S" of eighty feet. Other operating depths of the crushed
solids 106 within the MFR 110 can also be used. It is further
assumed that the cavity volume "V" defined by the mass flow reactor
110 is such that 82,700 tons of crushed solids 106 are present when
the exemplary depth "S" of eighty feet is achieved. It is important
to note that at this time, no material is being extracted from the
MFR 110. Once the desired depth "S" of crushed solids 106 is
established in the MFR 110, the flow thereof is ceased at least for
the time being. Also at this time or anytime while filling, any
initial amount of flocculant 160 that is desired can be provided
into the MFR 110.
[0056] In step 206 (FIG. 3A), a predetermined liquid lixiviant 108
(FIG. 2) is provided into the mass flow reactor 110 by way of
controlled flow through one or more of the liquid entry points 152.
For purposes of example, it is assumed that a predetermined
operating depth "L" of ninety feet of the lixiviant 108 (i.e.,
liquid) is established in the MFR 110. Other operating depths "L"
can also be used. It is further assumed that the lixiviant 108 is
defined by an aqueous solution including cyanide. As in step 204
(FIG. 3A) above, no material is being extracted from the MFR 110
(FIG. 2) at this time. Once the desired liquid depth "L" of
lixiviant 108 is established in the MFR 110, the flow thereof is
ceased for the time being.
[0057] In step 208 (FIG. 3A), the crushed solids 106 (FIG. 2) are
reacted with the lixiviant 108 within the MFR 110 for a
predetermined period of time, or dwell, so as to permit at least
one material of interest to be dissolved out of the crushed solids
106 and into solution with the lixiviant 108. Thus, the derivation
of post-reaction solids 112 and pregnant leach solution 114 is
underway. Also, if desired or required, the gas 158 can be
controllably introduced into the mass flow reactor 110. This dwell
time (i.e., period of reaction without any extraction of
post-reactions solids 112 or pregnant leach solution 114) can be
performed for any predetermined period of time such as, for
purposes of example, five hours, etc.
[0058] In step 210 (FIG. 3A), the post-reaction solids 112 (FIG. 2)
and the pregnant leach solution 114 (as well as substantially
not-yet-reacted lixiviant 108 and crushed solids 106) begin to
migrate through the mass flow reactor 110 in the prevailing
direction "G", by way of gravity alone. In this initial instance,
such migration is generally due to settling of material due to the
liquid-bath conditions present in the MFR 110.
[0059] In step 212 (FIG. 3A), which in fact can occur just prior
to, or almost simultaneously with, step 210 above, the extraction
of post-reaction solids 112 (FIG. 2) via one or more of the solids
exits points 154 begins. The extraction of pregnant leach solution
114 by way of one or more of the liquid exit points 156 is also
begun. The extraction of the post-reaction solids 112 is generally
performed in a controlled fashion so that the volumetric (or mass)
flow of the post-reaction solids 112 follows a predetermined
pattern or scheme, defining a solids extraction flow rate. In turn,
the extraction of pregnant leach solution 114 is also performed in
a predetermined controlled-flow manner, defining a liquid
extraction flow rate. Such solids and liquids extraction flow rates
can be, respectively, substantially constant, increase or decrease
linearly or non-linearly over time, etc. In short, any desired flow
rate characteristic can be independently employed in regard to the
extraction of post-reaction solids 112, and any desired flow rate
characteristic can be employed, up to the maximum permeability
rate, in regard to the extraction of pregnant leach solution 114.
In any case, the extraction of PRS 112 and PLS 114 is performed
substantially under the influence of gravity alone as previously
described above.
[0060] Also in step 212 (FIG. 3A), the introduction (or addition)
of crushed solids 106 (FIG. 2) into the MFR 110 is performed at a
rate in accordance with the extraction of post-reaction solids 112.
Furthermore, lixiviant 108 is added to the MFR 110 at a rate
corresponding to the extraction of pregnant leach solution 114.
Thus, at this time, crushed solids 106 are added to, and
post-reaction solids 112 are extracted from, the mass flow reactor
110 in a simultaneous fashion such that a "mass flow" or migration
(substantially under the influence of gravity alone) of solid
material through the MFR 110 is established and maintained for a
predetermined period of time. For purposes of the ongoing example,
this simultaneous flow of crushed solids 106 and post-reaction
solids 112 is maintained for a period of at least of at least 3
days. Typically, the crushed solids 106 and the post-reaction
solids 112 are extracted at substantially equal and/or constant
rates, such that the predetermined depth "S" of solids (e.g.,
eighty feet, etc.) within the MFR 110 is generally maintained
constant during this "simultaneous flow" period. Furthermore,
lixiviant 108 is added to, and pregnant leach solution 114 (as well
as any trace and/or incidental amount of PLS borne by the PRS 112)
is extracted from, the MFR 110 in a simultaneous fashion, such that
a gravity-driven mass flow or migration of liquid material through
the MFR 110 is established and maintained for a period of time. For
purposes of the ongoing example, this simultaneous flow of
lixiviant 108 and pregnant leach solution 114 (as well as any
residual amount of PLS borne by the PRS 112) is maintained for a
period of at least 3 days. Generally, the respective flow rates of
the lixiviant 108 and the pregnant leach solution 114 are
controlled at substantially equal and/or constant rates, such that
the predetermined liquid depth "L" (e.g., ninety feet, etc.) is
maintained essentially constant within the MFR 110 during the time
of simultaneous flows.
[0061] It is important to note that the respectively controlled
flow rates of solids (i.e., crushed solids 106 and PRS 112) and
liquids (i.e., lixiviant 108 and PLS 114) through the mass flow
reactor 110 results in the reacting, or processing, of ore or other
solid materials in a manner that is substantially
continuous--rather than batch-like--in overall process operation.
This means that once the desired depths (i.e., quantities) of
solids "S" and liquid "L" are established in the MFR 110 (e.g., as
in steps 204 and 206 above), such respective depths (or mass
quantities, etc.) can be maintained essentially constant within the
mass flow reactor 110, if desired, by way of appropriate solids and
liquid flow control in to and out of (that is, through) the MFR
110. Once established, such continuous processing can be
perpetuated for essentially any predetermined period of time
(hours, days, weeks, months, etc.).
[0062] In step 214 (FIG. 3B), the post-reaction solids 112 (FIG. 1)
are routed to a screen process 120. Therein, post-reaction solids
112 of less than a predetermined size are separated from the
balance of the post-reaction solids 112, thus defining a stream (or
supply) of relatively coarse post-reaction solids 122, and a stream
(or supply) of fine post-reactions solids (or "fines") 124. For
purposes of example, it is assumed that the screen process 120 is
defined and provided such that the fines 124 are comprised of
individual particles less than five-eights inch in size. Other
sizing (or classifying) schemes can also be used in separating
fines 124 from coarse post-reaction solids 122. The coarse
post-reaction solids 122 (FIG. 1) are then routed to suitable other
processing 126 such as, for example, detoxification, disposal,
heaping for later processing, etc.
[0063] In step 216 (FIG. 3B), the stream of fine post-reactions
solids 124 (FIG. 1) are received by a centrifuge process 128 where
additional pregnant leach solution (i.e., PLS 114) is extracted
from the fines 124 resulting in a stream (or supply) of pregnant
leach solution 130. In another embodiment, (not shown), other
equipment such as filters could be used instead of the centrifuge
process 128. Fine post-reaction solids exit the centrifuge process
128 and define a stream (or supply) of dried fines 136. While such
are referred to as "dried", it is to be understood that relatively
small quantities of PLS 114 may still be present on, or absorbed
within, the dried fines 136. This aspect of the dried fines 136
will be considered in further detail below.
[0064] In step 218 (FIG. 3B), the stream of pregnant leach solution
130 (FIG. 1) is received by a clarifying process 132. The
clarifying process 132 removes solids from the PLS 130, by a
gravity type clarifier, a cyclonic type clarifier, by filters, or
by any suitable known means, so as to derive a relatively
low-solids stream (or supply) of pregnant leach solution 134. In
this way, subsequent PLS 134 processing can be performed with
greater efficiency and/or efficacy as most of the solids in the
solution have been removed. In some embodiments, the clarifying
process 132 is omitted altogether, and the stream (or supply) of
PLS 130 directly defines the stream (or supply) of PLS 134 by way
of, for example, carbon columns treating dilute gold solutions.
[0065] In step 220 (FIG. 3B), the dried fines 136 (FIG. 1) are
(optionally) routed to a barren solution (or water) wash 140. The
barren solution wash 140 is essentially a barren solution filled
vessel in which the dried fines 136 are soaked for some period of
time so as to further extract (i.e., leach) relatively small or
trace amounts of pregnant leach solution (i.e., PLS 114) from the
dried fines 136. Typically, the barren solution wash 140 is used
only when the material of interest (i.e., gold, platinum, etc.)
dissolved into the pregnant leach solution (i.e., PLS 114) is of
sufficient value to economically warrant such extra processing.
When used, the barren solution wash 140 derives a stream (or
supply) of aqueous leachate 142 borne by the "rewetted" fine
solids. For purposes of ongoing example, it is assumed that at
least some of the dried fines 136 are routed to the barren solution
wash 140, where additional gold-bearing pregnant leach solution 114
is leached out of the dried fines 136 and into solution with the
barren solution, thus defining the aqueous leachate 142. It is also
assumed that the fines bearing the aqueous leachate 142 are routed
to other processing 138, where the aqueous leachate 142 is
separated from the fines (e.g., by way of centrifugal separation
144, a filter arrangement (not shown), etc.) and thereafter
combined with the PLS stream 134 for additional processing at step
222 below. In turn, it is further assumed that any non-washed fine
solids 136 are sent to respective other processing 138 and are
discarded, etc. In those embodiments (not shown in FIG. 3B) where
the barren solution wash 140 is not used, the dried fines 136 are
simply routed to other processing 138 for detoxification, disposal,
etc., as desired.
[0066] In step 222 (FIG. 3C), the respective streams (or supplies)
of pregnant leach solution 114 (FIG. 1) and 134 are received at a
pregnant leach solution process 116. Thus, with respect to the PLS
stream 114, the heat exchanger 115 (FIG. 1) is assumed to be
bypassed or otherwise unused. Therein, any suitable process step or
combination of steps and/or apparatus is/are used to extract at
least a majority of the material of interest from the aggregate
pregnant leach solution (114 and 134 of FIG. 1). For purposes of
ongoing example, it is assumed that dissolved gold is recovered
from the aggregate PLS by way of adsorption, elution,
electrowinning and retorting--processes known to one of ordinary
skill in the mining engineering arts. The recovered material of
interest (e.g., gold, etc.) is then sent on to step 224 (FIG. 3C)
below. The residual liquid of processing the pregnant leach
solution (114 and 134 of FIG. 1) is assumed to be processed as
desired by way of regeneration, destruction, containment and
disposal, etc.
[0067] In step 224 (FIG. 3C), the recovered material of interest
from step 222 above is finally processed as needed so as to be
delivered to the market place. For purposes of example, it is
assumed that retorted gold is smelted by known techniques to
produce gold bullion. Other process steps can also be employed, as
needed or desired, in accordance with the goal at hand. In this
way, the steps 222 and/or 224 are typically performed so as to
isolate at least one material of interest, as originally present in
the run-of-mine ore 102 (FIG. 1), in a form that can be provided to
(i.e., sold within) the market. At this point, the exemplary method
of the flowchart 200 is presumed to be completely described.
[0068] In the interest of understanding, at least some of the
characteristics and advantages of the present teachings are
summarized as follows:
[0069] a) The reaction of crushed solids with lixiviant (or other
liquid) can be performed within a vessel, otherwise referred to as
a mass flow reactor, as a substantially continuous process;
[0070] b) Solid and liquid materials migrate through, and are
extracted from, a mass flow reactor substantially under the
influence of gravity alone and without the use of other relevant
mechanical means or forces such as, for example, driven paddles,
augers, downward and/or upward liquid jetting, or vibrating,
rocking, shaking, and/or rotating the mass flow reactor, and
wherein gravity is not less than ninety percent of the
migration-inducing force when gaseous pressure is present over the
materials within the mass flow reactor;
[0071] c) At least some of the reaction of crushed solids with
liquid within a mass flow reactor can be performed under conditions
of a predetermined hydrostatic head of the liquid;
[0072] d) A flocculant can be used, if desired, to affect the
permeability of crushed solids with respect to liquid within a mass
flow reactor. In this way, liquid-on-solid contact, and the
corresponding reaction between solids and liquids, can be suitably
increased;
[0073] e) A gas can be injected into a mass flow reactor so as to
oxidize or otherwise chemically affect compounds present during the
reaction of crushed solids with liquid.
[0074] f) One or more physical and/or chemical variables can be
suitably controlled within the mass flow reactor during processing,
by any respectively suitable known means. Non-limiting examples of
such variables include pH, Eh (i.e., electron potential in
solution), temperature, viscosity, the concentration of a gas, the
concentration of a liquid, etc.
[0075] g) A suitable inert solid can be used, if desired, to
affect--increase, decrease or stabilize--one or more
characteristics within a mass flow reactor during a reaction
between solids and a liquid or liquids. Non-limiting examples of
such characteristics include heat conductivity, heat absorption,
etc.
[0076] It is anticipated that the invention will be embodied in
other specific forms, not specifically described, that do not
depart from its spirit or essential characteristics. The described
embodiments are to be considered in all respects only as
illustrative and not restrictive, the scope of the invention being
defined by the appended claims and equivalents thereof.
* * * * *