4,629,502 Pressurized reaction of refractory ores with heat recovery

Patent Number/Link:

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

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~ ~

It -- ~

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

PRESSURIZED REACTION OF REFRACfORY

ORES WITH HEAT RECOVERY

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

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

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

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

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. * * * * *