4,557,905 Leaching and washing a flocculated slurry having a fiber content

Patent Number/Link:

United States Patent [19]

Sherman et al.

[11]

[45]

Patent Number:

Date of Patent:

4,557,905

* Dec. 10, 1985

FOREIGN PATENT DOCUMENTS

2085856 5/1982 United Kingdom .

OTHER PUBLICATIONS

Heinen et al. "Enhancing Percolation Rates in Heap

[21] Appl. No.: 649,921

[22] Filed: Sep. 13, 1984

[54] LEACHING AND WASHING A

FLOCCULATED SLURRY HAVING A FIBER

CONTENT

[57] ABSTRACT

Particlized mineral material, such as gold ore, silver ore,

or coal, is subjected to a leaching process in a manner to

maximize treatment effectiveness even when the partic1ized

mineral material contains small fines. The material

is slurried with a flocculating material and fibers,

such as cellulosic fibers, fiberglass fibers, or ceramic

fibers, and a liquid, and then is passed to the top of a

leaching reactor. The slurry is continuously passed

downwardly in the reactor while the leaching liquid,

such as a cyanide solution, is passed counter-current to

the slurry. Leaching liquid is removed from the top of

the leaching reactor by a stilling well, and then passed

through a carbon adsorber and reintroduced into the

reactor. Leached slurry is passed to a continuous washing

station, with spent wash liquid from the top of the

washing station being utilized as a slurrying liquid for

the particlized mineral material.

Leaching of Gold-Silver Ores" International Bureau of

Mines., 1979.

Perry, "Refining Zinc Silicate Ore by Special Leaching

Technique" Chemical Engineering, 10/10/66 pp.

182-184.

Mager "Technical and Commercial Aspects of the Refining

of Leaching Residues from Zinc Electrolysis",

Erznetall, May 1976, pp. 224-229 [Eng. Abs.].

Shoemaker et al. "Recovery of Gold and Silver from

Ores" paper to International Precious Metals Institute,

10/23/80.

Sederov "Intensification of Zinc Pulp Settling and Solution

Clarifying Through the Use of F10cculants",

Yearbook of the Institute of Non-Ferrous Metallurgy,

1978, pp. 22-37. [Eng. Abs.].

Habashi, "Pressure Hydrometallurgy: Key to Better

and Nonpolluting Processes "; E/MJ, pp. 96-100 (2/71)

and 88-94 (5171).

Primary Examiner-John Doll

Assistant Examiner-Bob Stoll

Attorney, Agent, or Firm-Cushman, Darby & Cushman

21 Claims, 3 Drawing Figures

Michael I. Sherman; Carl L. Elmore,

both of Glens Falls, N.Y.; Robert J.

Brison, Golden, Colo.

Kamyr, Inc., Glens Falls, N.Y.

The portion of the term of this patent

subsequent to Feb. 26, 2002 has been

disclaimed.

Inventors:

Assignee:

Notice:

[75]

[73]

[ * ]

Related U.S. Application Data

[62] Division of Ser. No. 503,178, Jun. 10, 1983, Pat. No.

4,501,721.

[51] Int. Cl.4 COIG 7/00

[52] U.S. Cl 423/27; 423/29;

423/109; 423/150; 423/578 A; 75/2; 75/3;

75/101 R; 75/105; 75/117; 75/119; 75/118 R;

75/120; 75/121

[58] Field of Search 423/25, 27, 29, 109,

423/150,578 A; 75/0.5 A, 2,3, 101 R, 117, 118

R, 105, 119, 120, 121

[56] References Cited

U.S. PATENT DOCUMENTS

2,479,930 8/1948 Herkenhoff et al. 423/29

3,151,972 10/1964 Streib 75/1

3,788,841 1/1974 Agarwal et al. 75/103

4,071,611 1/1978 Chilson et al. 423/41

4,174,997 11/1979 Richter 162/19

4,256,705 3/1981 Heinen et al. 423/27

4,256,706 3/1981 Heinen et al. 423/29

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4,557,905

LEACHING AND WASHING A FLOCCULATED

SLURRY HAVING A FIBER CONTENT

This is a division ofapplication Ser. No. 503,178, filed 5

June to, 1983, now U.S. Pat. No. 4,501,721.

BACKGROUND AND SUMMARY OF THE

INVENTION

The leaching of constituents from particlized mineral 10

materials is practiced utilizing a wide variety of materials

and equipment. Leaching procedures are particularly

useful for the recovery of metals from particulized

mineral ores, such as gold and silver ores. The dominant

process for the extraction of such metals from ores is 15

leaching with alkaline cyanide solution and oxygen, and

this basic procedure has changed relatively little since

the issuance of the first patent thereon in 1887. Despite

extensive use of cyanide leaching, however, it has a

number of drawbacks associated therewith, including 20

the practical necessity of either grinding the ore fine for

continuous agitation leaching or utilizing batch leading

methods on coarser material, significant pollution loads,

and minimal adaptability.

According to the present invention a method for the 25

leaching of particlized mineral materials to remove

constituents therefrom is provided which has enhanced

effectiveness compared to prior art procedures. The

method according to the invention is particularly applicable

to the removal of metals from metal bearing ores, 30

such as gold and silver ores, but also is adaptable to

other processes, such as the removal of the pyritic,

organic, and sulfate sulfur compounds present in a solid

carbonaceous fuel of the coal or coke type.

The method according to the invention effects the 35

treatment of a slurry of particlized mineral material in a

continuous manner, with no large pressure losses and

with good metal removal efficiency. The process is

capable of treating particlized mineral materials in a

continuous manner even where there is a relatively 40

large percentage of small fines (e.g. 200 mesh or below),

without channelling and with excellent uniformity of

flow. The process according to the invention is easily

adaptable to high temperature and/or high pressure

conditions, and may be closed to the atmosphere 45

thereby reducing the pollution potential associated

therewith. The process also generally requires less

grinding equipment and energy and less pumping, agitating,

and like energy expenditures compared to prior

art continuous leaching processes, can handle ores of a 50

wide variety of sizes, and can handle soft materials-

such coke or coal.

Further, by practicing the invention substantially the

same results can be achieved as by leaching with carbon

added to the "pulp" being leached, without the neces- 55

sity of adding carbon. This is in part because the retention

time for the dissolved metal (e.g. gold) in contact

with ore is very short due to countercurrent flow in the

reactor vessel of the invention.

The invention also comprises a novel slurry of parti- 60

clized mineral material, and a method of removing metals

from a pregnant leaching solution utilizing a conventional

carbon adsorber device.

According to one aspect of the present invention, a

particlized mineral material, such as gold or silver ore, 65

is slurried with a liquid. The material is passed downwardly

in a generally vertically upstanding leaching

reactor vessel, and leaching liquid is passed counter-

currently (Le. upwardly) to the continuously downwardly

passing slurry. Treated slurry is continuously

removed from a bottom portion of the vessel, while

pregnant leaching liquid (with leached constituents, e.g.

gold or silver) is continuously removed from the top of

the vessel, as by utilizing a stilling well. The leached

slurry is continuously washed, preferably in a single

stage or in a two stage wash procedure utilizing a vessel

or vessels comparable to the leaching reactor. For two

stage washing, the spent wash liquid from the first stage

of the washing is utilized as the liquid for slurrying the

particulized mineral material.

In order to lock the ore particles in a stable network

for treatment in the continuous process according to the

invention, a flocculating agent and fibers are added to

the liquid and particulized mineral material during slurrying

thereof. Any suitable conventional flocculant,

such as synthetic polymers, may be utilized, and the

fibers may be selected from cellulosic fibers (e.g. wood

pulp fibers), fiberglass fibers, or ceramic fibers.

The utilization of flocculants and fibers is not restricted

to the practice of a continuous process. Rather

the formation of a slurry utilizing those materials is also

applicable to batch leaching and washing operations,

and the like.

The cyanide solution leaching liquid, containing metals

removed from particlized ores, is treated in a particular

manner to facilitate removal of the metal therefrom.

The pregnant leaching solution-that removed

from the top of the leaching reactor vessel described

above-is passed through a carbon adsorbing device.

Fresh carbon is added periodically to the top of the

device and loaded carbon removed from the bottom,

and effiuent from the carbon adsorption device is recycled

to the washing or leaching stage.

It is the primary object of the present invention to

provide for the effective removal of predetermined

constituents from a particlized mineral material. This

and other objects of the invention will become clear

from an inspection of the detailed description of the

invention, and from the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow sheet illustrating the practice of a

method according to the present invention for the treatment

of gold or silver ore;

FIG. 2 is a schematic illustration of exemplary apparatus

utilizable for the practice of a method according

to the present invention; and

FIG. 3 is a detail cross-sectional schematic view of an

alternative form that a leaching reactor vessel could

take for the practice of a method according to the present

invention.

DETAILED DESCRIPTION OF THE

DRAWINGS

A flow sheet illustrating practice of an exemplary

method according to the present invention is provided

as FIG. 1 of the drawings. While the invention will be

primarily described with respect to the removal of gold

or silver from gold and silver ores, it is to be understood

that the invention has broader applicability, and is applicable

to a wide variety of particlized mineral materials

to be treated with a leaching liquid. For instance, the

invention is utilizable with a wide variety of metal bearing

ores (such as copper and zinc ores), as well as for the

removal of pyritic, organic and sulfate sulfur compounds

from coal or the like.

4,557,905

According to the invention as illustrated in FIG. 1,

the ore is first crushed or ground and then slurried, with

flocculants and fibers added to the slurry to lock ore

particles in a stable network. The slurry is passed to a

leach tank for counter-current flow treatment with a 5

leaching liquid. The pregnant solution is passed to a

station for metal recovery, while the leached slurry is

passed to wash tanks, with the residue passed to a tailings

pond, or like disposal area.

FIG. 2 schematically illustrates equipment that may 10

be utilizable for the practice of the novel aspects of the

process illustrated by the flow sheet of FIG. 1. The

particlized ore is passed by conveyor 10 or the like to

the slurrying tank 11, which may include a conventional

mixing means 12. A slurrying liquid is added to the tank 15

11 from line 13, the liquid in line 13 preferably comprising

water and/or the spent wash liquid from one or

more washing stages to be hereinafter described.

Also added to the slurry tank 11 is a flocculant from

source 14, and fibers from source 15. The flocculant and 20

fibers may be any suitable flocculant or fibers that are

capable of locking ore particles, including fines, in the

slurry in a stable network so that they may be subsequently

subjected to the leaching treatment. Typical

flocculants comprise synthetic polymers of anionic, 25

cationic or nonionic types, and typical fibers comprise

cellulosic fibers, fiberglass fibers, ceramic fibers, and

combinations thereof.

The slurry from tank 11 is passed through line 17 to

the top of a substantially vertically elongated leaching 30

reactor vessel 18. The vessel may be of a type as disclosed

in U.S. Pat. Nos. 4,061,193 or 4,174,997, having

a "stilling well" structure 19 at the top thereof above

the slurry introducing point 20 of a slurry introduction

tube 21, and having a rotating liquid introducing device 35

22 at the bottom thereof, preferably commonly rotatable

with slurry discharge structure 23.

The slurry flows continuously downwardly in vessel

18, and is ultimately discharged through line 24 at a

bottom portion of the vessel 18. Leaching liquid is intro- 40

duced through line 25-as from source 26-so that it

flows to the distributor 22, and then flows upwardly in

vessel 18-counter-currently to the slurry flow therein.

The fibers and flocculant in the ore slurry lock the ore

particles in a stable network so that leaching can occur 45

without channelling, and with a minimal pressure drop

over the vessel 18. Thus fines of 200 mesh, or smaller,

can be handled without substantial difficulty. Additionally,

ores having particle sizes up to ~ inch mesh, or

even larger, may be handled at the same time that the 50

fines are being handled.

The leached slurry withdrawn in line 24 passes to a

washing station. At the washing station, preferably a

single washer 27 is provided, although a first washer

(27) and a second washer 28 (or more) may be provided. 55

The vessels 27, 28 are substantially identical to the vessel

18, but generally of smaller size, and include a stilling

well arrangement 29, 29' at the top thereof, and a

rotating liquid introducing structure 30, 30' at the bottom

thereof. Where two vessels are utilized, clean wash 60

water enters vessel 28 through line 31, passes through

liquid distributor 30' counter-current to the slurry flow

in vessel 28, and spent wash liquid is withdrawn from

the stilling well 29' through line 32, to be used as feed

wash liquid for the first wash vessel 27. Spent wash 65

liquid in vessel 27 withdrawn from stilling well 29

through conduit 33 preferably is passed to the slurrying

tank 11, providing a liquid feed to line 13. The washed

slurry is withdrawn from second wash tank 28 through

line 34, and is passed to a tailings pond, or like disposal

site.

Where only a single wash vessel 27 is utilized, line 31

is connected to structure 30, and line 32 to the tailings

pond or the like.

An alternative form the leaching reactor 18 of FIG. 2

may take is illustrated in FIG. 3, with functionally related

components in the two embodiments illustrated by

the same reference numeral, only the reference numeral

being preceded by a "I" in FIG. 3. The form of vessel

118 may, of course, be utilized for the wash vessels 27,

28, also.

For the vessel 118, the slurry feed and the treatment

liquid feed are preferably provided in concentric tubes

125, 117. The tube 117 is connected to rotating slurry·

introducing device 121, which introduces slurry at level

120 below the overflow launder or stilling well 119

provided at the top of the vessel 118.

The liquid introduction pipe 125 is operatively connected

to the liquid distributing device 122 at the bottom

of the vessel 118, with paddles or like slurry discharge

mechanism 123 provided on the bottom of the

vessel 122. Note that in this embodiment the structures

121,122 are rotated by acommon shaft 37 connected up

to a conventional drive motor 38. A discharge control

valve 39 may be provided in the line 24 so that the

vessel 118 may be utilized for batch operations, as well

as for continuous operations, and to control the rate of

solids removal.

Returning to FIG. 2, a method for facilitating removal

of the metals from the pregnant leaching solution

withdrawn from the stilling well 19 will now be described.

Pregnant leaching solution is withdrawn from stilling

well 19 through line 42, and passes to the carbon adsorbing

device 43, ultimately passing to line 25.

Operatively connected to the device 43 via line 44 is

the storage tank 45, which is adapted to store strong

leaching solution therein. The invention is particularly

applicable to the leaching of gold and silver ores, in

which case the leaching liquid from source 26 comprises

a caustic cyanide solution, such as sodium cyanide,

and the solution in tank 45 is· supplied from a

source 46 of hot caustic cyanide solution. Fresh carbon

is periodically added to the top of device 43 via line 47

and loaded carbon is withdrawn from the bottom

through line 44 and dumped into tank 45.

From tank 45, caustic and carbon are periodically

passed by pump 49 through valve 50 to metal removal

station 51. From metal removal station 51 carbon is

passed to carbon reactivation station 52 to supply fresh

carbon, through line 47, to device 43 as needed.

Operation

An exemplary method of operation of the apparatus

of FIG. 2, in the practice of an exemplary method according

to the present invention, will now be described.

Particlized gold ore is fed by conveyor 10 to tank 11,

to which liquid from line 13, polyall flocculant from line

14, and cellulosic fibers from line 15 are added. Sufficient

fibers are added so that they comprise between

about 0.01 percent and 10 percent, by weight, of the

total slurry, preferably about 0.05-0.75%.

The slurry is continuously mixed in tank 11, and then

is continuously pumped through line 17 to enter tube 21

of the vessel 18, and continuously passed downwardly

therein. Sodium cyanide leaching liquid is introduced

4,557,905

synthetic polymers of anionic, cationic, and non-ionic

types.

6. A· method of removing metal from particlized

metal bearing ore, utilizing a treatment vessel, compris5

ing the steps:

(a) mixing the ore with a liquid to form a liquid slurry,

and with a floccuating material so as to hold the

ore in a stable network;

(b) continuously passing the slurry downwardly in

the vessel;

leaching the metal from the ore, upwardly in the

vessel, counter-current to the slurry passage, to

remove metal from the ore of the slurry;

(d) continuously removing the treated slurry from a

bottom portion of the vessel; and

(d) continuously removing pregnant leaching liquid,

with removed metal therein, from a top portion of

the vessel.

7. A method as recited in claim 6 comprising the

further step (t) of continuously washing the slurry removed

in step (d).

8. A method as recited in claim 7 wherein step (t) is

practiced utilizing a washing vessel, and by passing

wash liquid upwardly in the vessel counter-current to

slurry moving downwardly in the vessel, with spent

wash liquid removed from a top portion of the vessel

and washed slurry removed from a bottom portion of

the vessel.

9. A method as recited in claim 6 wherein step (a) is

further practiced by adding fibers to the particlized ore

and slurrying liquid so as to facilitate locking the particlized

ore in this stable network.

10. A method as recited in claim 9 wherein the flocculent

is selected from the group consisting essentially of

synthetic polymers of anionic, cationic, and non-ionic

types; and wherein the fibers are selected from the

group consisting essentially of cellulosic fibers, fiberglass

fibers, ceramic fibers, and mixtures thereof; and

wherein the fibers comprise about 0.01%-10%, by

weight, of the slurry.

11. A method as recited in claim 6 wherein the leaching

liquid in step (c) is a cyanide solution.

12. A method as recited in claim 11 comprising the

further step of: (g) continuously passing pregnant liquid

withdrawn in step (e) through a carbon adsorbing device,

and reintroducing the liquid into the vessel as

leaching liquid for step (c).

13. A method as recited in claim 6 wherein step (a) is

further practiced by adding fibers to the particlized

mineral material and slurrying liquid so as to facilitate

locking the particlized mineral material in a stable network.

14. A method as recited in claim 6 wherein the flocculent

is selected from the group consisting essentially of

synthetic polymers of anionic, cationic, and non-ionic

types.

15. A method of removing metal from particlized

60 metal bearing ore, utilizing a treatment vessel, comprising

the steps:

(a) mixing the ore with a liquid to form a liquid slurry,

and with fibers so as to facilitate locking of the ore

in a stable network;

(b) continuously passing the slurry downwardly in

the vessel;

leaching the metal from the ore upwardly in the

through line 25 and distributing device 22 to continuously

flow counter-current to the slurry in vessel 18,

and pregnant leaching liquid is removed from the stilling

well 19-without the necessity for utilizing screens-

in line 42.

The pregnant solution in line 42 passes through the

carbon adsorber device 43, and then is recirculated

through line 25 to the device 22. Fresh carbon is supplied

to, and loaded carbon removed from, device 43 as

necessary.

Leached slurry is discharged by device 23 from the

bottom of the vessel 18 into line 24, and passes to the top

of washing stage 27. The slurry flows downwardly

through washing stage 27, and then may be fed to the

top of vessel 28, and ultimately passes through dis- 15

charge 34 to a disposal site. Wash water introduced in

line 31 to vessel 28 flows counter-currently to the

slurry, and the spent wash liquid withdrawn from line

33 is pumped to the slurry in tank 11.

Utilizmg the equipment illustrated in FIGS. 2 and 3, 20

it is easy to adapt the process to high temperature and

high pressures, thus providing versatility in the processes

which may be practiced, and in the available

leaching liquids. Also, the process can be closed to the 25

atmosphere thereby minimizing discharges of pollutants

into the atmosphere. Because little agitation of the

slurry is necessary (only that small amount provided in

tank 11), energy requirements are minimized, and the

process is readily adaptable to the handling of "soft" 30

particlized mineral materials, such as coal. Further, the

process can be operated in a continuous manner even

when a relatively high percentage of fines, including

small fmes, are present, and may be practiced with particles

up to about! inch in diameter. 35

While the invention has been herein shown and described

in what is presently conceived to be the most

practical and preferred embodiment thereof, it will be

apparent to those of ordinary skill in the art that many

modifications may be made thereof within the scope of 40

the invention, which scope is to be accorded the broadest

interpretation of the appended claims so as to encompass

all equivalent methods and products.

What is claimed is:

1. A method of treating particlized metal bearing ore 45

to effect removal of the metal therefrom, comprising

the steps of:

(a) forming a slurry from the particlized ore, liquid, a

flocculating agent, and fibers, the flocculating

agent and fibers causing the particlized mineral 50

material to be locked in a stable network;

(b) subjecting the slurry to treatment with a leaching

liquid; and

treatment of the slurry.

2. A method as recited in claim 1 wherein the fibers

are selected from the group consisting essentially of

cellulosic fibers, fiberglass fibers, ceramic fibers, and

mixtures thereof, the fibers comprising about 0.01 percent

to 10 percent, by weight, of the slurry.

3. A method as recited in claim 2 wherein the flocculant

is selected from the group consisting essentially of

synthetic polymers of anionic, cationic, and non-ionic

types.

4. A method as recited in claim 1 wherein the leach- 65

ing liquid in step (b) is a cyanide solution.

5. A method as recited in claim 1 wherein the flocculant

is selected from the gra.up consisting essentially of

(e) continuously removing pregnant leaching liquid,

with removed sulfur compounds therein, from a

top portion of the vessel.

18. A method as recited in claim 17 comprising the

5 further step (f) of continuously washing the slurry removed

in step (d).

'19. A method as recited in claim 17 wherein the flocculent

is selected from the group consisting essentially

of synthetic polymers of anionic, cationic, and non-ionic

types; and wherein the fibers are selected from the

group consisting essentially of cellulosic fibers, fiberglass

fibers, ceramic fibers, and mixtures thereof; and

wherein the fibers comprise about 0.01 %-10%, by

weight, of the slurry.

20. A method of treating particlized coal or coke to

. effect removal of sulfur compounds therefrom, comprising

the steps of:

(a) forming a slurry from the particlized coal or coke,

liquid, a flocculating agent, and fibers, the flocculating

agent and fibers causing the particlized coal

or coke to be locked in a stable network;

(b) subjecting the slurry to treatment with a leaching

liquid; and

liquid after treatment of the slurry.

21. A method as recited in claim 20 wherein the fibers

are selected from. the group consisting essentially of

cellulosic fibers, fiberglass fibers, ceramic fibers, and

mixtures thereof, the fibers comprising about 0.01 percent

to 10 percent, by weight, of the slurry.

* * * * *

4,557,905

vessel, counter-current to the slurry passage, to

remove metal from the ore of the slurry;

(d) continuously removing the treated slurry from a

bottom portion of the vessel; and

(e) continuously removing pregnant leaching liquid,

with removed metal therein, from a top portion of

the vessel.

16. A method as recited in claim 15 comprising the 10

further step (f) of continuously washing the slurry removed

in step (d).

17. A method of removing sulfur compounds from

particlized coke or coal, utilizing a treatment vessel,

15 comprising the steps:

(a) mixing the coke or coal with a liquid to form a

liquid slurry, and with fibers and a flocculating

material so as to hold the coke or coal in a stable

network;

(b) continuously passing the slurry downwardly in

the vessel;

leaching sulfur compounds from the particlized 25

coke or coal upwardly in the vessel, counter-current

to the slurry passage, to remove sulfur from

the particlized coke or coal of the slurry;

(d) continuously removing the treated slurry from a 30

bottom portion of the vessel; and