United States Patent [19]
Henrickson
[11] 3,942,765
[45] Mar. 9, 1976
Primary Examiner-Robert W. Jenkins
Attorney, Agent, or Firm-Sheridan, Ross & Fields
[52] U.S. CI 259/4 R
[51 ] Int. CI............................................. BOlf 15/00
[58] Field of Search 259/4, 18, 36; 138/38,
138/42; 48/180 R, 180 M, 180 B; 239/476;
. 23/252 R
[54] STATIC MIXING APPARATUS
[75] Inventor: Angus V. Henrickson, Golden, Colo.
[73] Assignee: Hazen Research, Inc., Golden, Colo.
[22] Filed: Sept. 3, 1974
[21] App!. No.: 502,871
There is provided an improved static mixing apparatus
which comprises in combination a tubular body and a
static mixing element preferably coextensive in length
with the tubular body and disposed therein in fluid
flow intercepting relation. The static mixing element is
characterized by a plurality of alternately oppositely
extending first triangular elements from a common
center line whereby the laterally extending first triangular
elements are in axially staggered relation, and a
plurality of second triangular members each having
one apex on the common center line and each having
a side in common with a first triangular element, and
each of the second triangular elements lying in a plane
angularly related to the first triangular element with
which it has a side in common.
The second triangular elements lie in sectors about the
common center line. These devices are particularly
useful for mixing a plurality of materials in the same
or different states, miscible or immiscible, soluble or
insoluble, and reactive or nonreactive.
16 Claims, 9 Drawing Figures
[57] ABSTRACT
References Cited
UNITED STATES PATENTS
6/1934 Durkee 138/38
6/1952 Heyl 259/4
2/1953 Rogers : 239/476
11/1953 Morrow 138/38
9/1958 Lynn 138/38
8/1965 Mosey 259/4
[56]
1,961,744
2,601,018
2,628,864
2,660,198
2,852,042
·3,203,371
u.s. Patent March 9, 1976 3,942,765
54
f.
f.
f.
·1 "
"I"
~
16" r.~/8 srI. '\'~J 201l
26 ~[,
20g:::-r-'/ 20f.
20e \17 38d
,fl71 20d
20c" 38b
38c . 20b
, 380
~ORGA:~: Fig_;4
AQUEOUS
86)(
Fig_7
I--.."..=---l.--j---l---.,,----, 60
3,942,765
BRIEF DESCRIPTION OF THE DRAWINGS
DETAILED DESCRIPTION OF THE DRAWINGS
2
oppositely extending first triangular elements are in
axially staggered relation. There is also provided a
plurality of second triangular members each having an
apex on the common center line and each having a side
5 in common with at least a portion of a side of a first
triangular element, each of the second triangular elements
lying in a plane angularly related to the plane of
the first triangular element with which it has a side in
least in part in common. In a preferred embodiment of
10 the present invention, the first triangular elements all
lie in a common plane. The second triangular elements
each lie in a plane which is at right angles to the plane
of the first triangular member with which it has a side in
common. Conveniently, although not essentially, the
15 triangular elements are right triangles, for example 30°
right triangles.
1
BRIEF STATEMENT OF THE INVENTION
STATIC MIXING APPARATUS
BACKGROUND OF THE INVENTION AND PRIOR
ART
The concept of mixing materials by utilizing "static"
or motionless mixing has been known for sometime. In
the past 4 years, two designs have been available on the
market one of which consists of a series of helical elements
in a tube or pipe, and the other of which utilizes
a complex series of tubular channels. Both of these
structures divide and recombine a stream in geometric
progression, and within a relatively short distance, feed
stock material is thoroughly and predictably mixed.
("Automation", February 1972 "Motionless Mixers").
The helical element type of device is clearly disclosed
in U.S. Pat. No. 3,286,992 to Armeniades et al. dated
Nov. 22, 1966. These devices are called motionless
mixers because they have no moving parts. Relative The present invention may be better understood by
movement of the fluid with respect to the motionless 20 having reference to the annexed drawings wherein;
mixing elements is, however, achieved by the flow of FIG. 1 is a cross sectional view of a motionless mixing
fluid within the conduit. apparatus of the present invention employing a pre-
Other efforts at blending various materials include ferred motionless element therein.
the patent to Heyl et al. No. 2,601,018 wherein the FIGS. 2a and 2b are perspective views of the motionblending
tube contains a single perforated sheet metal 25 less mixing element shown in FIG. 1.
spiral member substantially throughout its length, the FIG. 3 is a top plan view of the motionless mixing
perforated surface ofthe spiral member extending from member shown in FIG. 2.
wall to wall of the blending tube. Rogers in U.S. Pat. FIG. 4 is an end view on an enhirged scale of the
No. 2,628,864 is disclosing an aerosol paint spraying apparatus shown in FIG. 1.
device taught the use within the spray tube of a spiral 30 FIG. 5 is a top plan view on an enlarged scale of a
form member formed either of twisted wire or a helical portion of the mixing element shown in FIG. 3.
ribbon of metal. Andrews et al. in U,S. Pat. No. FIG. 6 is a side elevation ofthe portion shown in FIG.
2,710,250 taught the mixing of fluids with a series of 5.
orifice members in a conduit. Grubb et al. U.S. Pat. No. FIG. 7 is a schematic illustration of a single stage
2,863,649 taught an apparatus for mixing on a small 35 solvent extraction unit employing a motionless mixing
scale of compositions having a short period of coexis- apparatus in accordance with the present invention.
tence when mixed and utilizing a rotating mixing rod FIG. 8 shows a portion of a blank from which the
having a small wire spirally wound around it and in- preferred motionless mixing elements may be formed
cluding at regularly spaced intervals spiral notches. by bending along the diverging diagonals of successive
Another device is taught in the patent to Thomas et al. 40 oppositely extending rectangular member according to
U.S. Pat. No. 3,089,683 wherein an elongated tubular a predetermined pattern.
body is provided with a series of diffusers which create
a turbulent flow of the liquids thereby ensuring a complete
mixture of the liquids prior to ejection through Referring now more particularly to FIG. 1, there is
the outlet. U.S. Pat. No. 3,203,371 to Mosey teaches a 45 here shown a tubular member 10 having an inlet end 12
machine for whipping of confectionary filling utilizing and an outlet end 14. The tubular member 10 may be
in the nozzle thereof a baffle which comprises a strip of formed of any suitable material which will not be afchrome
steel twisted into a helical form and having a fected by or reactive with the materials or anyone of
plurality of transverse slits to provide a multplicity of them being mixed. In some cases, therefore, the tubular
teeth or tongues which extend more or less radially 50 member may be formed of plastic, or glass, or a section
from the axis of the helical bent strip. of iron or cast iron pipe, or clay, as may be described.
The present invention is distinguished from these The cross section is desirably circular although a rectprior
art devices in that the motionless mixing element angular cross section may as well be used. The materiis
a singular structure of far simpler geometric configu- als to be mixed are conveniently introduced through a
ration then that heretofore proposed and therefore 55 Y-fitting at the inlet end as will be illustrated in FIG. 7.
much less costly in either fabrication or disassembly The mixing element 16 is positioned within the tubular
and cleaning than prior art structures. member in fluid flow intercepting relation.
Referring now to FIGS. 2a, 2b, 3, 4, 5 and 6, FIGS. 2a
and 2b show in perspective the mixing element gener-
Briefly stated, therefore, the present invention is in a 60 ally indicated by the numeral 16. For convenience, a
motionless mixing apparatus which comprises in com- center line 18 is shown and provides a reference from
bination a tubular body and a motionless mixing ele- which conveniently to describe the illustrated embodiment
disposed within the tubular body in fluid flow ment of the present invention. The center line 18 lies in
intercepting relation therein. The mixing element com- a plane. What will be designated for convenience as
prises an elongated member having a plurality of alter- 65 first triangles 20 also lie in the same plane. The first
nately oppositely extending first triangular elements triangles 20 alternately oppositely extend from the
from a common center line which forms a side of each center line 18. Thus, first triangles 20a, 20b, 20c and
said first triangular elements whereby the alternately 20d alternately extend first to the left then to the right,
3,942,765
4
shown in FIG. 4 being from the outlet end. The pattern
of disposing the second triangle members 38a, 38b, 38c
and 38d with respect to their respective contiguous first
triangular members 20a, 20b, 20c and 20d, and as
shown in FIGS. 5 and 6 is that the second triangular
member 38a is bent upwardly with respect to its contiguous
first triangular member 20a, the second triangular
member 38b is bent downwardly with respect to its
contiguous first triangular member 20d; the second
triangular member 38c is bent upwardly with respect to
its contiguous first triangular member 20c, and the
second triangular member 38d is bent downwardly with
respect to its contiguous first triangular member 20d.
Again regarding the device from the outlet end, in this
first group of four first triangular members 20, the
pattern of bending to form the second triangular members
38 is up-down-up-down. Thus, as one proceeds
axially toward the inlet end of the device, the bending
pattern is helical in a clockwise direction. With the next
20 set offour first triangle members 20e, 20f, 20g and 20h,
the bending pattern to form the second triangular
members 38e, 38f, 38g and 38h is just the opposite, i.e.,
counterclockwise and follows the pattern down-updown-
up.
The length of the motionless mixing element 16 is, in
the preferred embodiment, therefore, desirably divided
into segments of equal length wherein the bending
pattern alternates between·up and down ina clockwise
manner when viewed from the outlet end followed by a
bending pattern in the next adjacent segment in a counter-
clockwise fashion, followed by a bending pattern in
the next succeeding segment in a clockwise manner,
etc. The length of the individual segments as above
described is immaterial, and whereas in the preferred
embodiment, each segment is composed of four succeeding
first triangular members 20, the segment may
be composed of any even number of first triangular
members 20 in sequence with the bending pattern following
first upward then downward then upward, etc.
40 bending.
While reference has been had to "bending" in describing
mixing element 16, this is only occasioned by
reason that it has been found most convenient to form
the motionless mixing elements 16 from a flat piece of
metal, e.g., stainless steel sheet from a blank which
appears as shown in FIG. 8. The blank 58 shown in
FIG. 8 is conveniently slotted along alternately laterally
extending lines 60. With the centerline 18 extending
along the blank 58, it can readily be seen that the cen-
50 terline 18, the slit lines 60 andthe lower marginal edge
, 62 ofthe blank 58 define a series of rectangles lying
below the centerline 18. Likewise, the upper marginal
edge 64 of the blank 58 in combination with the centerline
18 and the radiating lines 60 define a series of
rectangular members. Since the lines 60 alternately
extend to the below and then above, the rectangular
members so defined are in alternating oppositely extending
staggered and overlapped relation. When the
rectangular members are bent along the diagonals 66
shown in dotted lines and converging upon the centerline
18, the bending being in the pattern above described
for each of the succeeding segments, the first
triangular members 20 and the second triangular members
38 are readily and conveniently formed. Bending
is desirably to an angular relationship with the first
triangular member 20 of 90°. When viewed from the
outlet end as shown in FIG. 4, it will be seen that there
is no clear path for the fluid to take as it proceeds from
3
then to the left and then to the right, for example,of
center line 18. This pattern persists for the length of the
mixing element 16, and illustrates what is meant by the
language "alternately oppositely extending first triangular
elements from a common center line 18." Consid- 5
ering, for the moment, the first triangle 20a, it will be
observed that it is composed of a base line 26, a radial
.line 28 and a hypotenuse 30, the first triangle 20a being
a right triangle. The base line 26 coincides with the
center line 18. Considering the first triangle 20b, it is 10
composed of a base line 32, a radial line 34, and a
hypotenuse 36. The base line 32 of the first triangle 20b
also coincides with the centerline 18. In the preferred
embodiment illustrated in FIGS. 2-6, the base line 32
of the first triangle 20b also coincides with a portion of 15
the base line 26 of the first triangle 20a. The extent of
the overlap or coincidence of the base line 32 with the
base line 26 is a matter of choice and, as shown in the
preferred embodiment is approximately one half the
length of the respective base lines 26 and 32. This
illustrates what is meant by the language "axially staggered
and overlapping relation." It should be understood
that while an overlap to the extent of one half of
the base line of contiguous first triangles is a preferred
arrangement, it is by no means an essential arrange- 25
ment, and the extent of overlapping may be zero or up
to 75%, with a 50% overlap being preferred.
In addition to the first triangles 20, there is provided
a plurality of second triangular members 38 which
members are disposed out of the plane of the first tri- 30
angular members 20. Consider, therefore, second triangular
members 38a, 38b, 38c and 38d. Each of these
triangles 38a, 38b, 38c and 38d has an apex on the
common center line 18, and each of the second triangular
members 38a, 38b, 38c and 38d, has a side in 35
common with a first triangular element 20. Consider,
therefore, second triangular members 38a. It has an
apex 44 lying on the common centerline 18. Also, it has
a side 46 which is in common with the side 30 of the
first triangular member 20 a and in the embodiment
shown, in coextensive therewith. It has been found
convenient, and therefore illustrated in the preferred
embodiment that the second triangular members 38
should also be right triangles as are the first triangles
20. Thus the side 46 of the second triangular member 45
38a is indeed a hypotenuse and coincides with the
hypotenuse 30 of the first triangular member 20a. The
sides 48 and 50 of the second triangular member 38a
intersect at a 90° angle, and again, although not essentially,
the right triangle 38a is a 30, 60, 90° right triangle
as is the right triangle 20a.
As shown in FIGS. 2a and 2b, the right triangle 38a is
bent out of the plane of the right triangle 20a and extends
upwardly as it appears in FIGS. 5 and 6. In like
but opposite and staggered manner, the triangle 38b is 55
bent downwardly along the hypotenuse 36 ofthe first
triangular member 20b. Thus, the right triangle 38b is
bounded by the hypotenuse 52, the radial line 54 extending
from the centerline 18, and the side 56. The
triangles 38a and 38b are angularly related to the 60
planes of their respective contiguous first triangular
members 20a and 20b, that angle being in the preferred
embodiment shown in FIGS. 2-6 a 90° angle.
Considering the first triangle members 20a, 20b, 20c
and 20d, these first triangles 20 in the order named are 65
proceeding serially and axially in the direction toward
what I shall for convenience denominate "the inlet",
the vantage point of viewing the mixing element as
3,942,765
6
seconds. The fluid velocity in the settler 86 is approximately
0.28 feet per second and retention time 143
seconds. The volume· of solvent in the mixer 70 and
settler 86 is approximately 4000 gallons.
For comparative purposes, a conventional tank mixer-
settler system which will handle 1000 gallons per
minute of aqueous flow requires 2 minutes retention in
the mixer and 0.5 square feet of settler area per gallon
per minute of total flow. Assuming a solvent aqueous
ratio of 1.5 to 1 in the mixer and solvent depth of 8
inches in the settler, the volume of solvent in one stage
will be approximately 10,000 gallons. This difference
can be realized for a large size solvent extraction plant.
The capital cost for a system such as that shown in FIG.
7 has been extimated to be approximately 75% of the
conventional type mixer-settler system.
The conditions of extraction vary, of course, with
different systems and the mixer portion of the apparatus
may be relatively shorter or longer depending upon
20 these conditions, e.g. phase separation rate, solvent
power of organic phase with respect to the solute, ionexchange
rate between phases, etc. It should also be
noted that while, for convenience in description, referencehas
been made to an inlet end and an outlet end of
the motionless mixing element, fluid flow may be in
either direction relative to the mixing elements of the
present invention with equivalent results.
The invention has been described in detail with particular
reference to a referred embodiment thereof, but
30. it will be understood that variations and modifications
can be effected within the spirit and scope of the invention
as described hereinabove and within the scope of
the claims appearing below.
What is claimed is:
1.A motionlessrnixing apparatus comprising in combination:
a. a tubular body;
b. a motionless mixing element disposed within said
tubular body in fluid flow intercepting relation,
said mixing element comprising:
1. an elongated member having a plurality of alternately
.oppositely extending first triangular elements
from a common centerline which forms a
side of each said first triangular element, each of
said first triangular elements lying on one side of
said common centerline having a side in common
with a portion of the sides of two oppositely extending
first triangular elements lying on the
other side of said common centerline, whereby
said laterally extending first triangular elements
are in axially staggered and overlapping relation,
and .
2. a plurality of second triangular members each
having one apex on said common centerline and
each having a side in common with a first triangular
element, each of said second triangular elements
lying in a plane angularly related to the
first triangular element with which it has a side in
common.
60 2. A motionless mixing apparatus in accordance with
claim 1 wherein the second triangular members each
lie in a plane at right angles to the plane of the first
triangular member with which it has a side in common.
3. A motionless mixing apparatus in accordance with
claim 1 in which the first triangular elements are right
triangles.
4. A motionless mixing apparatus in accordance with
claim 3 in which the first triangular elements are 30°
5
the inlet to the outlet all quadrants are substantially
blocked by upstanding or depending second triangular
members 38. While a circular cross section has been
shown for the tubular member 10, and there is necessarily
some free space between the sides 50 and 56, for 5
example and the tubular member 10, this is not regarded
as material in the light of the convenience and
inexpensive mode of fabrication the motionless mixing
elements 16 in the preferred embodiment illustrated
and as described above. The tubular member 10 might 10
as well be provided with a square or rectangular cross
section. .
This apparatus has been tested and has demonstrated
superior mixing characteristics in liquid-liquid extraction
system, wherein, two immiscible phases are inti- 15
mately dispersed to permit transfer of a soluble constituent
from the aqueous phase to the organic phase.
FIG. 7 shows as apparatus incorporating a mixer in
accordance with the present invention. Thus, there is
shown in FIG. 7 in schematic and diagrammatic fashion
a mixer tube 70 which although it cannot be seen in
FIG. 7 contains an elongated mixing element such as
that shown in FIGS. 2-6. The inlet end n is attached to
one leg of a Y-fitting 74, one arm of which is connected
to a source of organic medium pumped therethrough 25
by means of a pump 76 and controlled by means of a
.flow meter 78, and wherein the other arm is connected
to an aqueous medium source pumped thereto by
means of a pump 80 through a flow meter 82.
By the time the immiscible organic and aqueous phases
have traversed the length ofthe tube 70 and emerge
at the outlet end 84, the degree of subdivision of the
organic phase in the aqueous phase is quite fine. The
dispersion or emulsion, as the case may be, enters the
settler portion 86, the fluid flows in to aT-shaped set- 35
tling tube of relatively large diameter with the laterally
extending arms in a vertical position. The organic
phase containing the solute being lighter than the water
rises to the top and is exhausted through the line 90.
The aqueous phase is exhausted through line 92. Be- 40
cause the fluid velocity in the mixer 70 can be set to
give uniform droplet size, coalescence is fast and requires
a shorter retention time. After the mixing section
70, the mixed solvent and aqueous phases are
discharged into the enlarged section of pipe 86 so that 45
turbulance is reduced to a minimum and the phases are
given an opportunity to separate. The length of the
settler 86 which is required is dependent on the phase
separation characteristic of the two fluids and is a function
of the specific gravity, viscosity and surface or 50
interfacial tension.
An apparatus of the type shown in FIG. 7 has been
used in the solvent extraction of copper from a dilute
aqueous copper sulphate solution with kerosene solution
of 2-hydroxybenzophenoxime whereby copper is 55
exchanged into the organic phase. Comparative studies
were made using the mixing device of the present invention
in a system as shown in FIG. 7, and using a
conventional tank mixer-settler system.
It has been determined that a single stage of the extraction
circuit shown in FIG. 7 which handles 1000
gallons dilute aqueous copper sulphate (1 to 2 gms. per
liter) and 1500 gallons ofthe organic phase per minute
requires a mixer 70 which is 14 inches in diameter and
approximately 80 feet long. The settler 86 is then ap- 65
proximately 5 feet in diameter and approximately 40
feet long. This provides a fluid velocity of about 5.2
feet per second in the mixer 70 and a mixing time of 15
3,942,765
7
right triangles.
5. A motionless mixing apparatus in accordance with
claim 4 in which the 30° angle of the first triangular
members includes the side common to the common
centerline. 5
6. A motionless mixing apparatus in accordance with
claim 1 in which the first and second triangular elements
are right triangles.
7. A motionless mixing apparatus in accordance with
claim 6 wherein the common side between a first tri- 10
angular member and its second triangular member is
the hypotenuse of each.
8. A motionless mixing apparatus in accordance with
claim 6 in which the first and second triangular elements
are 30° right triangles. 15
9. A motionless mixing apparatus in accordance with
claim 8 in which the 30° angle of the first triangular
members includes the side common to the common
centerline.
10. A motionless mixing apparatus in accordance 20
with claim 1 wherein the second triangular members on
axially succeeding first triangular members occupy a
position in serial sectors about said common centerline.
11. A motionless mixing apparatus in accordance
with claim 10 in which the sectors are each 90°. 25
12. A "motionless mixing apparatus in accordance
with claim 1 wherein the first and second triangular
members are formed by folding staggered bilaterally
extending rectangular sections along a diagonal thereof 30
whereby the apices of successive first triangular members
alternately oppositely extending from said common
centerline also successively proceed along the
common centerline.
13. A motionless mixing apparatus in accordance 35
with claim 1 in which the first triangular members all lie
in a common plane.
14. A motionless mixing apparatus in accordance
with claim 1 in which the motionless mixing element is
formed from stainless steel sheet. 40
15. In a motionless mixing apparatus having a tubular
fluid conduit and stationary mixing means disposed in
said tubular fluid conduit, the improvement which
45
50
55
60
65
8
comprises: a single stationary mixing element coextensive
with said conduit comprising
a. an elongated member having a plurality of alternately
oppositely extending first triangular elements
from a common centerline which forms a
side of each said first triangular element, each of
said first triangular element, each of said first triangular
elements lying on one side of said common
centerline having a side in common with a portion
of the sides of two oppositely extending first triangular
elements lying on the other side of said common
centerline, whereby said laterally extending
first triangular elements are in axially staggered
and overlapping relation, and
b. a plurality of second triangular members each
having one apex on said common centerline and
each having a side in common with a first triangular
element, each of said second triangular elements
lying in a plane angularly related to the first triangular
element with which it has a side in common.
16. A motionless mixing apparatus comprising in
combination:
a. a tubular body;
b. a motionless mixing element disposed within said
tubular body in fluid flow intercepting relation,
said mixing element comprising:
I. an elongated member having a plurality of alternately
oppositely extending first triangular elements
from a common centerline which coincides
with a side of each of said first triangular
elements, whereby said alternately oppositely
extending first triangular elements"are in axially
staggered relation; and
2. a plurality of second triangular members each
having one apex on said common centerline and
each having a side in common with at least a
portion of a side of a first triangular element,
each of said second triangular elements lying in a
plane angularly related to the plane of the first
triangular element with which it has a side at
least in part in common.
* * * * *
gn:n�itx��0�ce:none'>pebble lime which reacts with the sulfur trioxide pro- 35
duced by the pyrolysis to form calcium sulfate. The ammonia
and water produced by the pyrolysis are also
passed through the lime column before being recycled
to the weak base leaching step. Calcium sulfate so produced
can then be either prepared for marketing or dis- 40
carded as a waste.
The liquid content separated in the first separation
step of FIG. 2 optionally may be processed by adding
a weak base, such as ammonia, thereby precipitating
potassium sulfate. The liquid may then be boiled in a 45
lime boil step in the presence of lime [Ca(OHhl. preferably
in excess of stoichiometric amounts at atmospheric
pressure, a reaction time of from about fifteen
minutes to about one and one-half hours. The product
of the lime boil step is then separated by conventional 50
means such as centrifuge, filter, thickener tanks, vacuum
distillation or crystallization, and the like. The liquid
portion then can be recycled to use in the leaching
step and the solid precipitated sulfate converted to 55
commercial products such as sulfuric acid, elemental
sulfur and the like.
Referring to FIG. 3 in more detail, the product
formed in the silica removal step optionally may be filtered
and the liquid solution containing aluminum hy- 60
droxide transferred to the precipitation step. The solid
content filtered is sodium aluminum silicate with or
without a sulfate ion depending upon the concentration
of silicon and sulfate in the solution.
After removal of silica (precipitated as sodium alumi- 65
num silicate) the resultant liquid is cooled to precipitate
crystalline aluminum hydroxide, which is then separated
from the liquid. Advantageously the liquid is
5
3,890,426
6
* * * * *
This invention has been described in detail with par- 9. The method of claim 1 wherein the alkali metal hyticular
reference to preferred embodiments thereof, it droxides of Step (d) are selected from the group conshould
be understood that variations and modifications sisting of sodium hydroxide and potassium hydroxide.
can be effected within the spirit and scope of the inven- 10. The method of claim 1 in which the precipitation
tion as described hereinbefore and as defined in the ap- 5 of silica of Step (f) is performed by heating the liquid
pended claims. to a temperature of about 90°C for at least one hour at
What is claimed is: atmospheric pressure.
1. A method for recovering aluminum hydroxide 11. The method of claim 1 in which the precipitation
from ore containing alunite comprising the steps of: of silica of Step (0 is performed by heating the liquid
a. roasting the ore to remove the water of hydration, 10 at a pressure of from about 0.5 atmosphere to about 7
b. leaching the roasted ore from Step (a) with a weak atmospheres at a temperature of from about 90°C to
base at a pH of from about 8 to about 12 to dissolve about 200°C and for at least fifteen minutes.
sulfate and alkali metals, 12. The method of claim 1 in which the precipitation
c. separating the liquid and solid portions of the of silica in Step (f) is accelerated by seeding with soslurry
resulting from Step (b), said liquid portion 15 dium aluminum silicates.
containing dissolved sulfate and alkali metals, 13. The method of claim 1 in which the precipitation
d. digesting the solid portion from Step (c) with an of aluminum hydroxide in Step (h) is performed by
aqueous mixture of alkali metal hydroxides at a cooling the liquid until crystalline aluminum hydroxide
concentration and at a temperature sufficient to is formed.
extract the aluminum content from said solid por- 20 14. The method of claim 1 further including accelertion,
ating the precipitation of aluminum hydroxide in Step
e. separating the liquid and solid portions of the (h) by seeding the liquid with aluminum hydroxide
slurry resulting from Step (d), crystals.
f. precipitating silica from the liquid portion resulting IS. The method of claim 1 including the additional
from Step (e), 25 step of washing the precipitation product of Step (i)
g. separating the liquid and solid portions resulting with water.
from Step (f), 16. The method of claim 1 including the additional
h. precipitating aluminum hydroxide from the liquid step of washing the precipitation product of Step (i)
portion resulting from Step (g), with an acid having a pH of about 4.5.
i. separating the aluminum hydroxide precipitate 30 17. The method of claim 1 including the additional
from the liquid portion resulting from Step (h). step of calcining the aluminum hydroxide precipitation
2. The method of claim 1 wherein Step (a) is per- product of Step (i).
formed at a temperature of from about 400°C to about 18. The method of claim 1 including the additional
850°C. step of crushing the ore containing alunite to a particle
3. The method of claim 1 wherein Step (a) is per- 35 size having a greatest distance between parallel oppoformed
at a temperature of from about 500°C to about site exterior surfaces of about one inch or less prior to
650°C. Step (a).
4. The method of claim 1 wherein the weak base of 19. The method of claim 1 including the additional
Step (b) is selected from the group consisting of ammo- step of reducing the size of the product of Step (a) to
nium hydroxide and alkali metal hydroxides. 40 a particle size of about 8 mesh or less before proceed-
S. The method of claim 1 in which Step (b) is per- ing to Step (b).
formed at a temperature of from about 20°C to about 20. The method of claim 1 including the additional
120°C and for a time of at least five minutes. step of recovering Si02 from the solid content sepa-
6. The method of claim 1 in which the sulfate sepa- rated in Step (e).
rated in Step (c) is converted to sulfuric acid. 45 21. The method of claim 1 including the additional
7. The method of claim 1 in which the sulfate sepa- step of filtering the solution formed in Step (f) to yield
rated in Step (c) is converted to elemental sulfur. sodium aluminum silicate solids and sodium aluminum
8. The method of claim 1 in which potassium sulfate sulfate solids.
is recovered from the liquid content of Step (c).
50
55
60
65
ize:��btf��0�y:"Times New Roman","serif";mso-fareast-font-family: HiddenHorzOCR'>second oxidation zone.
* >I< >I< * *
About 7% of the molybdenum contained in the calcines
is also solubilized in the sulfurous acid leach.
The leached residue is separated from the leach solution
by filtration and after drying is ready for packaging 5
for sale. The leach solution joins the solutions from the
scrubbers on the flash roaster and re-roaster.
The effectiveness of the above-described process is
graphically illustrated by the high recovery of rhenium
and molybdenum achieved. it provides for the recovery 10
of up to 95% of rhenium and high recovery ofmolybdenum
in molybdenite with a minimum of process time
and a minimum of oxygen and added heat. The economic
advantages of these features are apparent. The
process is adaptable to either a batch or continuous op- is
eration.
It is an attractive side advantage of the. process that
a small volume of exhaust gas containing a high percentage
by volume of sulfur dioxide is produced. The
process is normally operated with an exhaust gas volume
discharge rate of 1,350 cubic feet per minute
(CFM) with up to 220% excess oxygen and 30-50% by
volume of sulfur dioxide in the exhaust gas. This high
volume percentage of sulfur dioxide makes its recovery
economically feasible for various commercial uses. In
contrast, present-day processes utilizing air for cooling
and for supplying oxygen are of necessity operated with
an exhaust volume discharge rate of 40,000 CFM, 16
volume percent excess oxygen and 1-2 volume percent
of sulfur dioxide. This volume percentage of sulfur dioxide
in the exhaust gas is so low that its recovery is not
economically feasible because it involves processing
such large volumes of gas. As a result the sulfur dioxide
is exhausted to the atmosphere creating a serious pollution
problem in heavily populated areas. The process of 35
this invention eliminates this problem.
The reduced volume of exhaust gas also results in a
much higher concentration of rhenium oxide in the exhaust
gas than is obtained in conventional processes.
As a result, recovery of substantially all of the rhenium
is far more feasible and economical than in present processes
using air with resultant large volumes of exhaust
gas to be processed for recovery of the rhenium oxide.
Reduction of the volume of gas processed through
the system by a factor of about 30resultsin a dr1!§jic: 45
reduction in the size of equipment require-d~ith~jgnificant
savings in equipment cost and floor space.
What is claimed is:
n. A method for recovering rhenium and molybdic
mdde from molybdenite concentrate which comprises:
a. pre-heating particles of said concentrate in an oxygen-
free atmosphere to a temperature not in excess
of about 750"C to raise the temperature of the particles
to promote flash oxidation of the molybdenite
when the particles are introduced into a flash
oxidation zone,
b. causing said pre-heated particles to fall through a
first oxidizing zone of heated oxygen with said particles
and heated oxygen moving countercurrent to
each other to disperse said pre-heated molybdenite
particles in said heated oxygen to provide maximum
particle surface contact with heated oxygen
for effective oxidation, said first oxidation zone
being heated substantially by the exothermic heat
of the reactions occurring in said first oxidation 65