United States Patent [19]
Sherman et al.
[11] Patent Number:
[45] Date of Patent:
4,629,502
Dec. 16, 1986
[54] PRESSURIZED REACTION OF
REFRACfORY ORES WITH HEAT
RECOVERY
[75] Inventors: Michael I. Sherman; Carl L. Elmore,
both of Glens Falls, N.Y.; Robert J.
Brison, Golden, Colo.
OTHER PUBLICATIONS
Habashi, "Pressure Hydrometallurgy: Key to Better
and Nonpolluting Process", EIMJ, Feb. 1971, pp.
96-100.
Habashi, "Pressure Hydrometallurgy: Key to Better
and Nonpolluting Process," EIMJ, May 1971, pp.
88-94.
Linke, W. F., "Solubilities of Inorganic and Metal-Or-
[73]
[21]
[22]
[51]
[52]
[58]
[56]
Assignee: Kamyr, Inc., Glens Falls, N.Y.
Appl. No.: 664,733
Filed: Oct. 25, 1984
Int. CI.4 COIG 7/00; C22B 11/04
U.S. CI 75/118 R; 75/0.5 A;
75/0.5 AA; 75/0.5 BA; 75/2; 75/115; 75/101
R; 75/105; 423/25; 423/27; 423/29; 423/30;
423/31; 423/41;423/45; 423/47
Field of Search 423/27,29,30,31,
423/25, 109, 150,41,45,47; 75/0.5 A, 0.5 AA,
2, 0.5 BA, 3, 105, 101 R, 118 R, 119, 120
References Cited
U.S. PATENT DOCUMENTS
3,879,272 4/1975 Atwood et aI 75/117
4,071,611 1/1978 Chilson 423/41
4,097,271 6/1978 Milner et aI 75/104
4,108,639 8/1978 Lake et aI 75/101 R
4,256,705 3/1981 Heinen et aI 423/27
4,423,010 12/1983 Maurel 423/87
4,438,076 3/1984 Pietsch et aI 75/99
4,501,721 2/1985 Sherman et aI 423/29
FOREIGN PATENT DOCUMENTS
3126234 3/1983 Fed. Rep. of Germany .
7811844/1978 South Africa.
ganic Compounds (Seidel)", 4th Ed., 1958, vol. 1, p.
250, and vol. 2, pp. 1228-1230.
Tronev, Von V. G., and Bondin, M., "On the Dissolution
of Precious Metals at High Pressure; 11, Dissolution
of Gold in Cyanide Under Air Pressure," Comptes
Rendus (Doklady) de l'Academie des Scienes del
I'URSS (1937), vol. 16, No.5, pp. 281-284.
Headley, N. and Tabachnick, H., "Chemistry of Cyanidation,
Mineral Dressing Notes," American Cyanamid
Company, Dec. 1968.
Finkelstein, N. P., "The Chemistry of the Extraction of
Gold From Its Ores," Chap. 10 in Gold Metallurgy in
South Africa, 1972, See p. 309.
Davidson, R., Brown, G. A., Schmidt, C. G. et al., "The
Inventive Cyanidation of Gold-Plant Gravity Concentrates,"
J.S. Mr. Inst. Min. Metall., 1978, pp. 146-165.
Pietsch, H. B., Turke, W., Rathje, G. H., "Research on
Pressure Leaching of Ores Containing Precious Metals,"
Erzmetall, Jun. 1983, pp. 261-165.
Muir, C. W. A., Hendriks, L. P., and Gussman, H. W.,
"The Treatment of Refractory Gold-Bearing Flotation
Concentrates Using Pressure Leaching Techniques,"
Precious Metals: Mining Extraction, and Processing,
1984, pp. 309-322.
Primary Examiner-John Doll
Assistant Examiner-Robert L. Stoll
Attorney, Agent, or Firm-Nixon and Vanderhye
[57] ABSTRACf
Metal is removed from particlized metal bearing refractory
ores in an efficient manner utilizing pressure metallurgy
with heat recovery. The particlized ore is mixed
with a heated liquid, and preferably a flocculant and
fibers, to form a slurry. The ore in the slurry is oxidized
at superatmospheric pressure, and elevated temperatures
(e.g. around 300° F.). The oxidized ore is washed
to remove acids, and like products of oxidation, and the
washed ore is subsequently subjected to conventional
leaching processes to effect an actual metal recovery.
Heat recovery is practiced by utilizing spent wash
water as part of the slurrying liquid, and using two or
more liquid-interconnected vessels in effecting the oxidization.
11 Claims, 1 Drawing Figure
u.s. Patent Dec. 16, 1986 4,629,502
~
~\
~\~
~ --~ ~
~
~
~ ~
~
~\
It -- ~
~8
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a schematic of exemplary apparatus for
practicing an exemplary method according to the present
invention.
4,629,502
1
PRESSURIZED REACTION OF REFRACfORY
ORES WITH HEAT RECOVERY
2
No. 503,178, it is highly desirable to add flocculant
and/or fibers to the slurry during mixing. The flocculant
and fibers hold the particlized ore in a stable network
in the slurry. The flocculant may be a natural or
BACKGROUND AND SUMMARY OF THE 5 synthetic polymer such as a synthetic polymer of ani-
INVENTION onic, cationic, or nonionic type. The fibers may be cel-
In copending application Ser. No. 503,178 fIled June lulosic, fiberglass, or ceramic fibers (or mixtures
10, 1983, now U.S. Pat. No. 4,501,721 (the disclosure of thereof), and preferably the fibers make up about
which is hereby incorporated by reference herein), a 0.01-10% by weight of the slurry.
method was provided for removing predetermined con- 10 According to another aspect ofthe present invention,
stituents from a particlized mineral material, such as a method of removing metal from a particlized metal
removing precious metals from a metal bearing ore. The bearing ore is provided which comprises the following
invention disclosed therein is extremely useful for re- steps:
moving metals from many types of ores, however it is (a) mixing the particlized refractory ore with a heated
not particularly applicable to recovery of materials 15 liquid to form a heated liquid slurry.
from refractory ores. (b) Continuously passing the slurry to a top portion of
Refractory ores are those in which metal cannot be the first vessel, and flowing the slurry downwardly in
easily leached since it is held by chemical bonds or the frrst vessel.
locked inside mineral particles. Often, the metal is (c) Introducing heated liquid containing an oxidizing
bound with sulphur. A typical refractory ore is gold ore 20 agent into the bottom of the frrst vessel to flow counterin
which the gold is disseminated in iron sulfide. Other currently to the slurry flowing downwardly in the frrst
refractory ores are those containing aluminum (i.e. vessel.
bauxite), and some nickel, cobalt, zinc, uranium, copper (d) Removing treated slurry from the bottom of the
ores (i.e. chalcopyrite), and the like. Pressure hydromet- frrst vessel and passing it to a top portion of the second
allurgy has been successfully employed for effecting 25 vessel so that it flows generally downwardly in the
metal recovery from refractory ores. However conven- second vessel.
tional pressure hydrometallurgical processes are energy (e) Removing liquid from adjacent the top of the frrst
intensive since a large amount ofheat is wasted in grind- . ul . .
. f th . t tall hin d h vessel, and crrc atmg that liquid to the bottom of the
mg 0 e ore pnor 0 ac u . eac g, an suc .pro- second vessel to flow in the second vessel generally
cesses often consume substantial amounts of chemIcals, 30 t tl t th 1 fl' d dl .
h suc as II·me fior the neutral"lZatlon 0 f sulphun'c aCI'd cthoun ercudrren yI 0 e s urry OWIng ownwar y m
which is formed when the metal-sulphur bonds are e secon v~sse: . .
broken in the refractory ore. (f) RemOVIng liqUid from the second vessel adjacent
According to the present invention, a pressure hydro- the top there?f.
metallurgical processes is provided which has numer- 35 (g) Removmg treat~d s~urry from the. bottom of ~he
ous advantages over prior art processes for ultimately second vessel ~d passmg It to a top portion of the: third
effecting metal removing from refractory ores. Accord- v~ssel so that It flows generally downwardly m the
ing to the present invention on continuous process is third vessel. . .
practiced, with careful heat recovery steps being imple- .(h) Introducmg ~ash water mto the bottom of the
mented, so that the energy requirements are very sub- 40 third vessel so th~t It flows generally co~tercurrently
stantially reduced compared to conventional pressure to ~he slurry. flowmg down~ar~ly there~.
agitation and like processes. Also, according to the (I). Removmg spent wash liqUid from adjacent the top
present invention continuous washing is effected of the portion of the third vessel; and
refractory ore after the metal-sulphur bonds have been .m removing washed slurry from .the bott~m of the
broken, so that no lime-or like chemical-need be 45 third vessel and subsequently effectmg leaching treatconsumed
to neutralize the sulphuric acid and the like ment thereof so as to remove metal from the metal
produced during oxidation, and in order to even allow bearing refractory ore.
acid recovery. In the practice of this particular method, it is desir-
According to one aspect of the method according to able to add oxygen (or like oxidizing agent) to the liquid
the present invention, a method ofremoving metal from 50 removed from the frrst vessel before introduction into
a particlized metal bearing refractory ore (one in which the second vessel, and to add oxygen to and heat the
the metal is bound chemically, usually with sulphur) is liquid removed from the second vessel, and then introprovided.
The method comprises the following steps: duce it as the countercurrent flowing liquid at the bot-
(a) Mixing the particlized refractory ore with a tom of the frrst vessel. The temperature of the liquid
heated liquid to form a heated liquid slurry. 55 introduced at the bottom of the frrst vessel is preferably
(b) Continuously passing the slurry in a flow path. generally about 330· F. Flocculant and fibers prferably
(c) Oxidizing constituents of the ore in the slurry are added to the slurry during mixing.
while in said flow path, at super atmospheric pressure It is the primary object of the present invention to
and temperature above 2120 F. provide an effective, energy efficient, and economical
(d) Washing the ore in the slurry with a wash liquid 60 method facilitating the recovery of metal from refracto
remove products of oxidation therefrom. tory ores. This and other objects of the invention will
(e) Recovering heat from the slurry, including as part become clear from an inspection ofthe detailed descripof
step (d); and tion of the invention, and from the appended claims.
(f) subsequently effecting leaching of the washed,
oxidized, particlized refractory ore, to effect recovery 65
of metal therefrom.
In the practice of the invention, as in the practice of
the method disclosed in said copending application Ser.
4,629,502
4
In order to facilitate good heat recovery, and energy
efficiency, the liquid withdrawn from the top of the
second vessel 30 into line 40 is ultimately introduced as
the counter-currently flowing liquid at the bottom 22 of
5 the first vessel 18. An oxidizing agent (e.g. oxygen gas)
is added to the liquid in tank 41, and the liquid is heated-
as by indirect steam heating-in conventional heater
43, before passing into conduit 44 to be introduced into
the bottom 22 of the vessel 18, at a temperature of about
10 3300 F. Typically approximately 40 pounds of steam per
ton of ore is used in the heater 43.
To further facilitate heat recovery, the liquid from
line 25 and tank 26 is pumped into the line 34 to be used
as the countercurrently flowing liquid in the second
vessel 30.
From the bottom of the second vessel 30, the treated
slurry (at about 2590 F.) is pumped by pump 46 into line
47 and is subsequently introduced in to a top portion of
the third vertical pressure vessel 48 (e.g. at 50). Vessel
48 is maintained at super atmospheric pressure and elevated
temperature, including by pressure regulating
means 52. Vessel 48 is a wash tower, and wash water
(preferably with caustic, and at a temperature of about
900 F.) is introduced through line 54 into the bottom 55
of the vessel 48 to flow upwardly in the vessel 48 countercurrently
to the generally downward flow of slurry
that has been introduced through line 47. Spent wash
liquid (e.g. at about 2280 F.) is removed at 56, adjacent
the top ofthe vessel 48, and again suitable screens or the
like may be utilized to effect this liquid removal. The
spend wash liquid passes in line 57 to tank 58, in which
the level is controlled by level sensor 59 and solenoid
operator valve 60.
The spent wash liquid in line 57 and tank 58 includes
the products of the oxidation of the ore. Typically, this
would primarily be sulphuric acid since the metal-sulphur
bonds have been broken by the oxidation. A first
part of the spent wash liquid is preferably circulated in
line 60, under the influence of pump 61, to be combined
with makeup water (e.g. at about 900 F.) from line 62 to
supply the liquid in line 14 for mixing with the particlized
ore in tank 10. This greatly facilitates heat recovery
since the spent wash liquid typically would have a
high temperature (e.g. about 2280 F.). A second portion
of the spent wash liquid passes in line 64 utilmately to a
station 65 at which it is disposed of, or acid recovery is
practiced.
The oxidized, washed, particlized ore slurry (at about
9,. F.) that is removed through line 70 from the bottom
of the wash tower 48 is subsequently passed to a leaching
tower or otherwise subjected to leaching processes
for the ultimate recovery of the metal therefrom. Any
suitable conventional leaching process may be utilized,
and there is no necessity for further grinding of the ore
before passing it to the leaching processes. The particle
size for the ore as introduced to the tank 10 is preferably
the particle size that is most suited for the subsequent
leaching processs. The utilization of tlocculant and
fibers allows a large variety ofdifferent sizes ofparticles
to be effectively handled (as explained in said copending
application Ser. No. 503,178, now U.S. Pat. No,
4,501,721), including fmes of 200 mesh or smaller up to
particle sizes up to about! inch in diameter.
It will be seen that in the practice of the present invention,
no significant amount of chemicals-aside
from oxidizing agents-are consumed since it is not
necessary to neutralize the sulphuric acid produced as a
3
DETAILED DESCRIPTION OF THE DRAWING
The apparatus illustrated in FIG. 1 includes apparatus
for mixing a heated liquid slurry, oxidizing the particlized
metal bearing refractory ore in the slurry, continuously
washing the ore to remove products of oxidation
(primary sulphuric acid), and practicing heat recovery
during the entire procedure.
In a tank 10 having a mixer 12 associated therewith,
crushed (i.e. particlized) refractory ore (e.g. iron sulfide,
bauxite, etc.) is mixed with heated liquid (e.g. 2150
F.) from line 14, to form a slurry. Preferably a flocculant,
such as a synthentic polymer anionic, cationic, or
nonionic types of synthetic polymer, from flocculant
tank 16, and fibers from tank 18 are also added to the 15
tank 10. The fibers preferably comprise cellulosic, fiberglass,
or ceramic fibers, or mixtures thereof, but fibers
having potentially adverse environmental effects (such
as asbestos) are preferably avoided. Fibers typically
comprise 0.01-10% by weight of the slurry, and suffi- 20
cient flocculant and fibers are provided to lock the
particlized ore in a stable network in the slurry to
thereby facilitate even, efficient, and successful continuous
treatment. 25
From tank 10, the slurry is passed in a flow path
through line 16 under the influence of pump 18 to a first
vertical pressure vessel 18. Vessel 18 comprises an oxygen
reactor. The slurry (e.g. at about 1830 F.) is introduced
into the vessel 18 at a top portion 20 thereof to 30
flow generally downwardly in the vessel 18. Vessel 18
is maintained at super atmospheric pressure, including
by pressure regulating means 21, and at a temperature
above 2120 F. The temperatures ofthe liquids and slurry
at different points discussed herein are typical tempera- 35
tures at which the various method steps according to
the invention may be practiced, although the temperatures
may vary widely depending on the particular ore,
subsequent treatment stages, and like factors.
Oxidation of the ore, to effect breaking of the metal- 40
sulphur bonds and the like, is effected in part by introducing
a heated liquid containing oxidizing elements
into the bottom of the vessel 18 at 22, to flow upwardly
in the vessel countercurrent to the downwardly flowing
slurry. Typically the oxidizing component of the liquid 45
will be oxygen, although chlorine, chlorine dioxide, or
other oxidizing agents may be used.
Spent treatment liquid (e.g. at about 2560 F.) is removed
from the vessel 18 adjacent the top thereof, at
24. A "stilling well" may be provided at the top of the 50
vessel 18, or suitable screens may be provided thereat,
to facilitate liquid removal. The liquid passes into conduit
25, and preferably additional oxidizing agent (such
as oxygen gas) is added to the liquid at vessel 26.
The treated slurry from the bottom of the first vessel 55
18 is pumped by pump 28 in conduit 29 (e.g. at about
3300 F.) to a top portion of a second vessel 30, being
introduced at a top portion (32) of the vessel 30 so that
the slurry flows generally downwardly in vessel 30.
Countercurrently flowing liquid (e.g. at about 2500 F.) 60
is introduced through conduit 34 into the bottom 35 of
the second vessel 30 to flow upwardly in vessel 30 countercurrent
to the flow of slurry therein, and spent treatment
liquid (e.g. at about 3160 F.) is removed at point 36
adjacent the top of the second vessel 30, again utilizing 65
screens, a "stilling well", or the like. The second vessel
30 is also maintained at superatmospheric pressure and
elevated temperature, as by means 38.
4,629,502
5 6
reaction product of the oxidation. In fact, the sulphuric 2. A method as recited in claim 1 wherein the floccuacid
can be recovered, as a by-product of the process. lant is selected from the group consisting essentially of
It will be further seen that according to the present synthetic polymers of anionic, cationic and nonionic
invention because of the continuous nature of the pro- types.
cess and the careful attention to heat recovery, rela- 5 3. A method as recited in claim 2 wherein the fibers
tively little energy is consumed. For instance, for an are selected from the group consisting essentially of
iron sulphide content of 40 pounds per ton of ore, there cellulosic fibers, fiberglass fibers, ceramic fibers and
typically would be an exothermic action (as a result of mixtures thereof.
oxidation) of about 4,626 BTUsl1b iron sulfide. The 4. A method as recited in claim 3 wherein the fibers
heat of this exothermic reaction is recovered in the 10 comprise about 0.01%-10% by weight, of the slurry.
practice of the method according to the invention. For S. A method as recited in claim 1 wherein the fibers
instance, for a refractory ore having an iron sulphide comprise about 0.01%-10% by weight, of the slurry.
content of 40 pounds per ton, utilizing conventional 6. A method as recited in claim 5 wherein the fibers
pressure agitation followed by one stage of CCD, are selected from the group consisting essentially of
245,300 BTUs of steam are required per ton of ore. For 15 cellulosic fibers, fiberglass fibers, ceramic fibers and
conventional pressure agitation followed by two stages mixtures thereof.
CCD, 91,800 BTUs of steam are required per ton of ore. 7. A method as recited in claim 1 wherein steps (b)
By practicing the present invention, however, only and (c) are practiced by passing the heated liquid slurry
about 40,400 BTUs of steam per ton of ore are required, generally downwardly in a flow path and flowing heata
very substantial energy saving. 20 ing liquid at superatmospheric pressure countercur-
It will thus be seen that according to the present rently to the flow path of the slurry.
invention an effective, efficient, and economical method 8. A method as recited in claim 7 wherein step (d) is
has been provided for facilitating the recovery ofmetals practiced by flowing the oxidized particlized ore slurry
from metal bearing refractory ores. While the invention generally downwardly countercurrent to a flow of
has been herein shown and described in what is pres- 25 wash water.
ently conceived to be the most practical and preferred 9. A method as recited in claim 8 utilizing first, secembodiment
thereof, it will be apparent to those of ond, and third generally vertical pressure vessels, each
ordinary skill in the art that many modifications may be vessel having a slurry inlet at a top portion thereof, a
made thereof within the scope of the invention, which slurry outlet at a bottom portion thereof, a countercurscope
is to be accorded the broadest interpretation of 30 rent .flowing liquid inlet at the bottom thereof and a
the appended claims so as to encompass all equivalent spent liquid removal conduit at the top portion thereof;
methods and procedures. and wherein step (e) is further practiced by passing
What is claimed is: liquid removed from the top of the second vessel to be
1. A method of recovering gold from a particlized introduced as countercurrent flowing liquid at the botgold
bearing refractory ore, comprising the steps of 35 tom of the first vessel, and heating the liquid and adding
continuously: oxygen thereto before introducing it at the bottom of
(a) Mixing the particlized refractory gold ore with a the first vessel; and passing liquid removed from the top
liquid heated above ambient temperature to form a of the first vessel to be introduced as countercurrent
heated liquid slurry, and mixing the particlized ore flowing liquid at the bottom of the second vessel; and
with a flocculating material and fibers so as to lock 40 wherein the slurry from step (a) is introduced at the top
the particlized ore in a stable network in the slurry; of the first vessel, the slurry removed from the bottom
(b) continously passing the slurry in a flow path; of the first vessel is introduced at the top of the second
(c) oxidizing oxidizable constituents of the ore in the vessel, the slurry removed from the bottom of the secslurry,
to break metal-sulphur bonds, while in said ond vessel is passed to the top of the third vessel, and
flow path, at super-atmospheric pressure and tem- 45 the slurry from the bottom of the third vessel is passed
perature above 212" F.; to step (t).
(d) washing the ore in the slurry with a wash water to 10. A method as recited in claim 1 wherein only a part
remove products of oxidation, including sulphuric of the spent wash water removed is passed, along with
acid, therefrom; makeup water, to provide the heated liquid in step (a),
(e) recovering heat from the slurry, including by 50 and the rest of the spent wash water removed is passed
removing spent wash water from the slurry and to an acid recovery or disposal station.
utilizing the spent wash water as heated liquid in 11. A method as recited in claim 1 wherein the partistep
(a); and clized refractory ore in step (a) has the particle size
(t) subsequently effecting cyanide leaching of the desired for the practice of step (t) so that no grinding of
washed, oxidized, particlized refractory gold ore, 55 the ore is necessary prior to the practice of step (t).
to effect recovery of gold therefrom. * * * * *
60
65