4,039,324 Fluidized hydrogen reduction process for the recovery of copper

Patent Number/Link:

United States Patent [19]

Stephens, Jr. et ale

[11]

[45]

4,039,324

Aug. 2, 1977

17 Claims, 1 Drawing Figure

U.S. PATENT DOCUMENTS

2,758,021 8/1956 Drapeau, Jr. et al. 75/26 X

2,783,141 2/1957 Foley 75/26

3,918,962 11/1975 Dubeck et aI 75/.5 B

Primary Examiner-M. J. Andrews

[57] ABSTRACf

Copper is recovered from copper salts, e.g. cuprous

chloride, by means ofa process comprising reducing the

copper salts with hydrogen in a fluidized bed in the

presence of chemically inert, generally spherical, relatively

smooth, non-pOrous particles in order to restrain

sintering of the reduced copper.

[54]

(75]

(73]

[21]

[22]

[51]

[52]

[58]

FLUIDIZED HYDROGEN REDUCTION

PROCESS FOR THE RECOVERY OF

COPPER

Inventors: Frank M. Stephens, Jr., Lakewood;

James C. Blair, Wheat Ridge, both of

Colo.

Assignee: Cyprus Metallurgical Processes

Corporation, Los Angeles, Calif.

Appl. No.: 631,832

Filed: Nov. 14, 1975

Int. Ct,2 .. C22B 15/00

U.S. Ct 75/72; 75/26

Field of Search 75/72, 26, 0.5 B, 91

[56] References Cited

Hel

FLUID BED

REACTOR

SAND

SAND HGAS

I SCRUBBER ~l HCI, H2, N2

CU2CI2 HCI

SAND r CU2C12 CU2CI2 SAND

SAND

FEED FEED

~ FLUID BED

LEACH

REACTOR

VESSEL

, I

SAND l SEPARATOR II H2 GAS

Cu N2 GAS

c..en

('D a

......

......:I

\aow

4,039,324

CU2CI2 + H2 +'" 2Cu + 2HCI

Excess hydrogen is preferably employed to insure the

complete reduction of the cuprous chloride, the amount

being in conformance with thermodynamic equilibrium.

The velocity of the fluidized gas is dependent upon

the overall processing conditions, and is such as to

maintain the bed in a proper fluidized state. The fluidizing

gas may be sufficiently preheated in order to maintain

the desired reaction temperature.

The primary novelty of the present invention is the

utilization of inert particles in the fluidized bed in order

to control the agglomeration or sintering of the metal

being produced. Uncontrolled agglomeration will tend

to defluidize the bed and disrupt the process. It is therefore

imperative for a successful fluidized bed process to

prevent excessive agglomeration and subsequent defluidization.

This problem is prevented by the present

process by employing a sufficient amount of inert particles

to physically prevent agglomeration to the degree

that defluidization results.

The particles used for this process are preferably

chemically inert with respect to the reactants in the

fluidized bed reactor. Adverse chemical reactions

would obviously be detrimental to the process, as well

as consume the particles necessary to maintain the fluidization.

Additionally, the particles useful for this process preferably

possess relatively small surface areas, and are

therefore preferably generally spherical. It is observed

that as the surface area of the particles increases, the

tendency of the reduced metal values to cake onto the

particles increases.

Furthermore, it is apparent that the particles must

have a melting point in excess of the reduction temperature.

In addition to these characteristics, it is highly preferable

for the particles to possess a minimum amount of

surface imperfection. It is observed that surface imperfections,

i.e., cracks, sharp edges, indentations, ridges

values include the copper oxides and copper salts, particularly

including cupric chloride and cuprous chloride.

The types of fluidized bed processes employed with

5 this invention are dependent upon engineering preference.

Numerous patents and articles exist describing the

various available fluidized bed processes, and the many

which would be suitable for use with this invention will

be apparent to the artisan. A good general discussion of

10 such processes is provided in Perry, Chemical Engineers'

Handbook, Fourth Edition, pages 20-42 to 20-52.

Similarly, the apparati employed with the process of

the present invention is a matter of engineering design

dependent upon the particular elements being processed,

the fluidizing agent, and other factors known to

those skilled in the art. Again, the· article cited above

from Perry's Chemical Engineers' Handbook, and the

references cited therein, discuss generally the various

pieces of equipment available for fluidized bed processes.

The fluidizing agent for the reactor comprises the

reducing gas, hydrogen, along with sufficient inert gas,

such as nitrogen, to maintain the bed in a fluidized state.

The amount of hydrogen required is dependent upon

the desired reaction. For the reduction of cuprous

chloride hydrogen is employed in the stoichiometric

amount required by the following equation:

FLUIDIZED HYDROGEN REDUCfION PROCESS

FOR THE RECOVERY OF COPPER

BACKGROUND OF THE INVENTION

SUMMARY OF THE INVENTION

The reduction of copper salts to elemental copper by

means of hydrogen reduction in a fluidized bed is facili- 55

tated by performing the reduction in the presence of

sufficient inert particles in order to restrain sintering of

the reduced copper. The particles are preferably chemically

inert, range in size from about -6 to about -100

mesh at space velocities of about 1 to 5 feet per second, 60

and within this range are relatively generally spherical

and non-porous and possess relatively smooth surfaces.

DESCRIPTION OF THE PREFERRED

EMBODIMENTS

The process of the present invention is useful in the

fluidized bed reduction of copper values which tend to

agglomerate or sinter upon reduction. These copper

1. Field of the Invention

This invention is concerned with improved processes

for recovering copper from copper salts by means of

hydrogen reduction in a fluidized bed.

2. The Prior Art

Many processes are of record relating to the recovery

of metals by means of fluidized bed hydrogen reduction,

including a number dealing specifically with copper.

For example, U.S. Pat. No. 1,671,003 to Baghdasarian

discloses a process of extracting copper (and other met- 15

als) from its sulfide by chlorinating the ore to produce a

copper chloride, and reducing the copper chloride to

elemental copper by hydrogen reduction. U.S. Pat.

Nos. 3,251,684 and 3,552,498 are additional examples of

patents which employ hydrogen reduction to reduce 20

copper cations to their elemental state.

A common technique for reducing metals to their

elemental state by means of hydrogen reduction is to

perform the hydrogen reduction in a fluidized bed.

Numerous patents recite various techniques and ap- 25

parati for conducting fluidized bed operations, including

U.S. Pat. Nos. 2,529,366, 2,638,414 and 2,853,361.

However, despite these numerous teachings a detrimental

phenomenon has been observed in the fluidized bed

reduction of cuprous chloride to elemental copper. 30

Within certain processing parameters, the reduced copper

tends to sinter and agglomerate, resulting in disruption

of the fluidized state of the bed. This phenomenon

has not been recognized in the prior art, although

Gransden and Sheasby observed a similar phenomenon 35

with respect to the fluidized reduction of iron in their

article entitled "The Sticking of Iron Ore During Reduction

by Hydrogen in a Fluidized Bed", published in

the Canadian Metallurgical Quarterly, Vol. 13, No.4

(1974). This article discloses that sticking of particles in 40

the fluidized bed reduction of iron ore at temperatures

in excess of 600° C occurs whenever clean iron surfaces

impinge. As the temperature of reduction increases, the

tendency for iron nucleation also increases. The authors

discovered that coating the iron ore particles with a 45

silica film inhibits the iron nucleation and permits iron

ore reduction up to temperatures approximately 840° C.

While this solution may be feasible under some circumstances,

applicants have discovered a process for

preventing sintering of the reduced copper without the 50

necessity of any surface coatings.

4,039,324

Space Maximum Minimum Preferred

Velocity Particle Particle Size Range

(ft./sec.) Size (Mesh) Size (Mesh) (Mesh)

1 24 150 -35+65

2.5 16 65 -20+35

5 9 48 -14+28

The amount of particles employed with the product

feed is dependent upon the particle size and density and

generally is preferably from about 0.7 to about 10, more

preferably from about 1 to 5, and most preferably from

about 2 to about 3 times the weight of the copper feed

material.

The term "restrained sintering" as used throughout

the specification and claims herein is intended to mean

the preventing of the agglomeration of the reduced

product to such a degree that defluidization of the bed

results. Some agglomeration of the reduced metal values

is required, as the product must assume some solid

form. However, the copper values to which the process

of the present invention applies would, if unrestrained,

agglomerate to such a degree that the bed could not be

maintained in a fluidized state. The actual size to which

the particles may be permitted to grow is dependent

upon. the particular design of the equipment and the

processing characteristics of the particular bed process.

Upon completion of the fluidized bed reaction,· the

solid products and particles are removed and further

processed in order to separate the particles from the

reduced metal. Much of the product may be separated

from the particles by means of screening due to the fact

that the product agglomerates will be slightly larger

than the inert particles. Additionally, the reduced metal

values may be melted, permitting the inert particles to

physically separate. Standard mechanical techniques

may also,be employed.

One particular embodiment of the process of the present

invention concerns the reduction of cuprous chloride

to elemental copper by means of hydrogen reduction

in a fluidized bed reactor. The reduced copper has

a high tendency to sinter in such a reaction to the extent

that a fluidized bed cannot be maintained. The FIGURE

illustrates a general process flow diagram for this

particular embodiment. Ottawa sand is illustrated as the

preferred type of particles employed to restrain sintering.

Referring to the FIGURE, it is observed that the

cuprous chloride feed material is mixed with the sand in

a ratio as hereinabove described. This combination is

then injected into the reactor at a point near the bottom

of the reactor. A mixture of gas and nitrogen is injected

into the bottom of the reactor and dispersed through a

diffusion plate under sufficient pressure to produce a

velocity sufficient to maintain the fluidized nature of the

bed. Hydrogen is preferably employed itl at least about

the stoichiometric amount required, more preferably

from about 120% to about 300%, and most preferably .

from about 150% to about 200% of the stoichiometric

amount required to insure complete reduction of the

cuprous chloride. Excess hydrogen is recovered and

recycled, hence employment of such an excess does not

present a.waste problem.

The process is conducted in a continuous fashion,

with the products being continuously recovered. As is

illustrated inthe FIGURE, the overhead stream from

left from chips, pockets, scars,cavities and the like,

provide the copper values with locations upon which

they tend to reduce. Additional copper values tend to

collect in these areas and on the reduced copper surfaces,

and ultimately the particle becomes wholly or 5

partially coated with copper. This obviously pegates

the usefulness of the particle. In this same vein, the

particles preferably have relatively· low "apparent"

porosity, "apparent" referring to the volume of openpore

space per unit total volume as opposed to sealed 10

pore space.

It is to be understood that these preferred properties

of the particles, e.g. their being chemically inert, generally

spherical, and relatively smooth and non-porous, to

a certain extent are relative and must be considered as a 15

matter of degree. In other words, a certain type of particle

may be completely chemically inert and non-porous

but may be of a configuration not generally spherical.

The use of such a particle will produce a noteworthy

improvement as compared to using no particles at all to 20

maintain fluidization in the same reaction, but would

not prove to be as effective as a particle possessing all

three of these qualities. Likewise, a particle may possess

some degree of porosity and/or some chemical activity

and still prove to be somewhat advantageous in main- 25

taining a fluidized bed and permitting the desired reaction

to proceed, but again such a particle would not be

as effective as a particle possessing all three of the desired

qualities.

Additional qualities of acceptable particles include 30

the ability to be separated from the product mixtures

upon completion of the process, cost of the particles,

and the ability to recycle spent particles with little or no

regeneration processing.

With these various considerations in mind, it has been 35

observed that the type of particles most preferred for

use with the process of the present invention is sand.

Sand is chemically inert to the copper reduction processes,

non-porous, has a high melting point, and many

naturally occurring sand beds comprise generally spher- 40

ical particles. Sand is relatively inexpensive and is easily

separated from the metal products and recycled to the

initial stages of the process.

Other types of acceptable particles include various

ceramic and porcelain products. These products are 45

chemically inert, non-porous and can be produced with

a spherical configuration. Most possess high melting

points and can be easily separated from the product

mixture.

Examples of particles which are somewhat less effec- 50

tive than the above-set forth types, but which nevertheless

produce improvement in the reduction reactions

include fused magnesium oxide, aluminum oxide and

fused aluminum oxide. Fused magnesium oxide is generally

of low porosity and is chemically inert, but pos- 55

sesses rough surfaces which tend to adsorb the reduced

copper, thereby causing some sintering of the reduced

metal. The fused aluminum oxide produces a result

similar to the fused magesium oxide. Aluminum oxide is

chemically inert and generally spherical, but overly 60

porous. This type of particle therefore adsorbs an inordinate

amount of the reduced copper product.

The size of the particles useful with the present invention

is dependent on several factors, including the particle

density and primarily the space velocity within the 65

reactor. It is suffi;:ient that the particles be sized such

that the bed may be maintained betweenincipient fluidization

and entrainment. The followingtableproyides

maximum, minimum and preferred

sand for the given space velocities:

particle sizes for

EXAMPLE 8

EXAMPLE'7

EXAMPLE 6

:This example employed,conditions'~imilar to those of

Example 5;' however, the particles were fused aluminum

oxide. Th~ test was run for 13.2 hours, and 1470 grams

of feed entered the react()r. Good copper agglomerates

were formed; however, a portion of the agglomerates

contained some of the aluminum oxide.

EXAMPLE 5

Magnesium oxide grains were used as a bed material

for reducing the cuproris chloride, the mixture being

one part cuprous chloride to two parts magnesium oxide.

The reaction temperature was maintained at about

445° C, the test was run for 10 hours with a total of 920

grams of feed entering the reactor.' Properly sized copper

agglomerates were formed; however, some copper

penetration of the magnesium oxide grains occurred.

'EXAMPLE 4

This test employed conditions similar to those of

Example,2; however, the particle type was a crushed

graphite of minus 20 plus 48 mesh. Copper uniformly

reduced on the carbon; creating,a sticky condition and

causing the bed to defluidize. The carbon particlespossessed

an irregular surface area and were highly porous.

Again, the conditions of Example 5 were repeated,

with the particle type being a reduction grade alumina.

The reactor temperature averaged about 450° C. The

test was conducted for 12.4 hours and 1572 grams of

feed entered the reactor. Relatively small copper ag-

35 glomerates were formed, and some of these appeared to

be based on the aluminum oxide substrates.

This example was also run in a manner similar to that

40 of Example 5, with the average temperature being maintained

at about 450° C, the test time being 12.2 hours

and the feed containing 1652 grams of cuprous chloride.

Periclase of a minus 20 plus 48 mesh were used as the

particles. Copper agglomerates were formed, although

the recovered product contained a substantial amount

of magnesium oxide, causing a more difficult product

separation problem.

As Examples 5 through 8 illustrate, particles other

50 than sand are suitable as long as they substantially meet

the requirements hereinabove set forth. However, as

these particles increasingly vary from these requirements,

the improvement in the reduction reaction decreases.

What is claimed is:

1. In a process for recovering elemental copper and

copper-bearing materials selected from the group consisting

of copper oxides and copper salts by means of

reducing the copper-bearing materials with hydrogen in

60 a fluidized bed reactor, the improvement comprising:

performing the reduction in the presence of sufficient

chemically inert, relatively smooth, generally

spherical particles in order to restrain sintering of

the reduced copper.

2. The process of claim 1 wherein the copper-bearing

material is cuprous chloride.

3. The process of claim 1 wherein the copper-bearing

material is cupric chloride.

4,039,324

EXAMPLES

EXAMPLE 2

EXAMPLE 3

Sodium chloride particles were mixed with the cuprous

chloride and injected into the reactor, with the

reaction temperature being maintained from about

520°-550° C. The cuprous chloride was not reduced, 45

and further inspection showed the formation of a eutectic

due to the chemical activity of sodium chloride. The

fact that the particles must be chemically inert is

thereby emphasized.

This test was conducted the same as Example 2; however,

the ratio of sand to cuprous chloride was changed 65

to one part sand to two parts cuprous chloride. This

ratio proved to be too low under these conditions, as the

bed would not maintain a fluidized condition.

This test used silica sand particles in a ratio of two

parts by weight sand to one part cuprous chloride feed.

The particle size was minus 20 plus 48 mesh, the feed

rate was about 5 grams per minute and the reactor space 55

velocity was maintained at about 1.50 feet per second.

The reaction temperature was about 440° C. The bed

maintained fluidization throughout the reaction, and the

product assayed 78.7% copper, indicating only a small

amount of sand in the product stream.

The following examples were carried out in a continuous

4-inch fluidized bed reactor equipped with a hydrogen

gas scrubbing and recycle system, and in each

example cuprous chloride was the feed material. The

fluidizing gas consisted of preheated hydrogen which

was injected into the reactor at the bottom of the bed

through orifices in the diffusion plate.

EXAMPLE 1

the reactor comprises hydrogen chloride, ancl unreacted

fluidizing gases, and this mixture is scrubbed to separate

the hydrogen chloride from the fluidizing gases. The

unreacted fluidizing gases are recovered and recycled,

while the separated hydrogen chloride solution is used 5

to cleanses and particles of any copper which may have

reduced on them. Copper agglomerates, with some

entrained sand, are continuously recovered from the

reactor and sent to the product separation stage. In the 10

product separation stage the sand is remo:ved from the

elemental copper, cleansed with hydrogen chloride to

produce cuprous chloride, hydrogen and clean' sand;

and each of these products is recycled to the initial

stages of the process. The resulting elemental copper 15

can then be refined and cast as desired.

The temperature of the reaction is preferably maintained

from about 200° to about 1,0000, more preferably

from about 400° to about 6000, and most preferably

from about 450° to about 550° C. If the reaction temper- 20

ature is too low, the rate of reaction decreases. If the

reaction exceeds about'600° C, a fraction of the cuprous

chloride reactant tends to volatilize, resulting in the

production of very fine copper. These fines are difficult

to handle and separate from the fluidized gases. 25

The hydrogen fluidizing agent introduced into the

reactor is preheated in order to maintain the' desired

temperature of reaction, and one source of preheat can

be the reactor overhead product stream.

* * * * *

rosities in order to restrain sintering of the reduced

copper.

11. The process of claim 10 wherein the copper-bearing

feed material is cuprous cbloride.

12. The process of claim 10 wherein the copper-bearing

feed material is cupric chloride.

13. The process of claim 10 wherein the particles

comprise sand.

14. In a process for recovering elemental copper from

10 cuprous chloride by means of reducing the cuprous

chloride with hydrogen in a fluidized bed reactor, the

improvement comprising:

performing the reduction in the presence of from

about 0.7 to about 10 times based on the weight of

cuprous chloride feed material of sand ranging. in

size from about minus 20 to about plus 48 mesh, the

sand particles possessing a relatively smooth surface

area and being generally spherical in shape in

order to restrain sintering of the reduced copper. '

15. The process of claim 14 wherein the temperature

of the reaction is maintained from about 400° C to about

600° C.

16. The process of claim 14 wherein the ratio based on

weight ofsand to cuprous chloride feed material is from

about 1 to about 5.

17. The process of claim 14 wherein at least the stoi.

chiometric amount of hydrogen is employed in the

reduction process.

4,039,324

4. The process of claim 1 wherein the reaction temperature

is maintained from about 400° C to about 600°

5. The process of claim 1 wherein the particles have a

relatively low apparent porosity.

6. The process of claim 1 wherein the particles comprise

sand.

7. The process of claim 1 wherein the melting point of

the particles is greater than the maximum temperature

in the reactor.

8. The process of claim 1 wherein the particles range

in size from about 9 to about 150 mesh within a space

velocity range of about I to about 5 feet per second.

9. The process of claim 1 wherein the amount of

particles is from about 0.7 to about 10 times by weight 15

of the amount of the feed material.

10. In a process for recovering elemental copper from

copper-bearing materials selected from the group consisting

of copper oxides and copper salts by means of

reducing the copper-bearing materials with hydrogen in 20

a fluidized bed reactor, the improvement comprising:

performing the reduction at a temperature of from

about 400° C to about 600° C in the presence of

from about 0.7 to about 10 times by weight based on

the amount of copper-bearing feed material ofparti- 25

cles ranging in size from about 9 to about 150 mesh,

the particles being characterized as being chemically

inert with respect to the reactants in the reactor,

and having relatively smooth, generally spherical

surface areas with relatively low apparent po- 30

UNITED STATES PATENT OFFICE

CERTIFICATE OF CORRECTION

Patent No. 4,039,324 August 2, 1977 _--'%.-+-l.Jc..J....:4-~=:L- _

Inventor(s) Frank M. Stephens, Jr. and James C. Blair

It is certified that error appears in the above-identified patent

and that said Letters Patent are hereby corrected as shown below:

Column 5, line 6, "cleanses and" should read

--cleanse the--.

In Claim 1, Column 6, line 56 "and" should read

--frorn--.

IS£AL)

~igncd and ~calcd this

Sixth Day 0 f June 1978

Attest:

RUTH Co MASON

Attesting Officer

DONALD W. BANN£R

Commissioner of Patents and Trademarks