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
Cu
I SCRUBBER ~l HCI, H2, N2
j
CU2CI2 HCI
SAND r CU2C12 CU2CI2 SAND
SAND
+
FEED FEED
~ FLUID BED
LEACH
REACTOR
VESSEL
J
, I
SAND l SEPARATOR II H2 GAS
Cu N2 GAS
c..en
~
~
('D a
~
~
......
\0
......:I
......:I
~
\aow
\0
\a
W
~
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
65
2
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:
1
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
3
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
4
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.
6
'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.
30
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
5
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.
* * * * *
5
8
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
7
4. The process of claim 1 wherein the reaction temperature
is maintained from about 400° C to about 600°
C.
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
35
40
45
50
55
60
65
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