U.S. patent number 3,893,654 [Application Number 05/342,032] was granted by the patent office on 1975-07-08 for mixing apparatus.
Invention is credited to Kenji Asano, Harunobu Miura.
United States Patent |
3,893,654 |
Miura , et al. |
July 8, 1975 |
Mixing apparatus
Abstract
A mixing element for insertion into a conduit for supplying a
stream of the liquid mixture comprises a pair of rectangular
members having a common transverse axis, and a pair of generally
triangular members each leading normal to the rectangular members
from one half of the longitudinal edge of one of said rectangular
members and having its transverse edge abutting upon the other half
of the longitudinal edge of the other of said rectangular members
and having quasi-conical bodies abutting the rectangular members
and the conduit walls. A mixing apparatus is further disclosed
which comprises a conduit of uniform square or rectangular cross
section, and a desired number of the above mixing elements disposed
therein in the manner described in the specification. The apparatus
is not equipped with any mechanically driven agitator and has many
advantages such as in manufacture and service thereof.
Inventors: |
Miura; Harunobu
(Nishinomiya-shi, Hyogo-ken, JA), Asano; Kenji
(Fukuokashi, JA) |
Family
ID: |
12224369 |
Appl.
No.: |
05/342,032 |
Filed: |
March 16, 1973 |
Foreign Application Priority Data
|
|
|
|
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Mar 18, 1972 [JA] |
|
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47-027558 |
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Current U.S.
Class: |
366/337 |
Current CPC
Class: |
B01F
5/0641 (20130101) |
Current International
Class: |
B01F
5/06 (20060101); B01F 015/02 () |
Field of
Search: |
;259/4,18,36
;138/38 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hornsby; Harvey C.
Attorney, Agent or Firm: Browdy and Neimark
Claims
What is claimed is:
1. A mixing apparatus for mixing a substance comprising:
an elongated hollow conduit having a substantially rectangular
cross section, and having four sides each of said four sides having
a substantially flat inner surface;
a plurality of mixing elements contained within said hollow
conduit, each mixing element comprising:
first and second rectangular members, disposed on a common
transverse axis and having first and second longitudinal edges and
first and second lateral edges,
first and second generally triangular members each leading normal
to said first and second rectangular members,
said first generally triangular member leading from one half of
said first longitudinal edge of said first rectangular member and
having one edge thereof abutting one half of said first
longitudinal edge of said second rectangular member, and
said second generally triangular member leading from the other half
of said first longitudinal edge of said second rectangular member,
and having one edge thereof abutting the other half of said first
longitudinal edge of said first rectangular member;
said mixing elements being placed in said hollow conduit, such
that, said second longitudinal edge of said first rectangular
member abuts said flat inner surface of one of said sides of said
conduit, and said first lateral edge of said first rectangular
member abuts said flat inner surface of one of the sides adjacent
said one of said sides and said second lateral edge of said first
rectangular member abuts said flat inner surface of the other of
said sides adjacent said one of said sides, and said second
longitudinal edge of said second rectangular member abuts said flat
inner surface of the side opposite said one of said sides, and said
first lateral edge of said second rectangular member abuts said
flat inner surface of said one side adjacent said one of said sides
and said second lateral edge of said second rectangular member
abuts said flat inner surface of the other of said sides adjacent
said one of said sides;
a first quasi-conical body having an apex substantially coinciding
with the end, away from said transverse axis, of said one half of
said first longitudinal edge of said first rectangular member, said
quasi-conical member being disposed on the opposite side of said
first rectangular member from said first triangular member, and
abutting said flat inner surface of said one of said sides of said
conduit and also abutting said flat inner surface of said one side
adjacent said one of said sides;
a second quasi-conical body having an apex substantially coinciding
with the end, away from said transverse axis, of said other half of
said first longitudinal edge of said second triangular member, said
quasi-conical member being disposed on the same side of said second
rectangular member as said second triangular member, and abutting
said flat inner surface of the side opposite said one of said sides
and also abutting said flat inner surface of said other of said
sides adjacent said one of said sides; and
said quasi-conical bodies acting to prevent viscosity resistance
which would normally be generated in the space occupied by said
quasi-conical bodies thereby aiding the substance to smoothly flow
through said conduit.
2. A mixing apparatus in accordance with claim 1, wherein said
first and second rectangular members are normal to each other.
3. A mixing apparatus according to claim 1 wherein said mixing
elements are spaced in said conduit in a reversed disposition to
any of the adjacent elements.
4. A mixing apparatus in accordance with claim 3 wherein said
conduit is of uniform square cross section; and including at least
four of said mixing elements, each being spaced in said conduit
angularly at right angles from the immediately preceding element
upon the line passing the centers of said triangular members.
Description
BACKGROUND OF THE INVENTION
a. Field of the Invention
This invention relates to the mixing of flowing streams of liquids,
and more particularly, to a mixing apparatus having no rotor for
mechanical agitation but having a structure wherein the stream of
liquids is repeatedly divided and joined as it flows.
B. Description of the Prior Art
Hitherto, liquids have generally been blended or mixed in a tank or
tube which is agitated by a mechanically driven impeller. Such a
mechanically driven mixing apparatus has many defects in that it
inevitably vibrates and leaks liquids and, therefore, it is in
frequent need of repair and is difficult to maintain. Further,
since such a mixing apparatus is often set up as one unit of a
continuous process in a large scale chemical plant, such defects
affect not only the operation of itself but also the process
control of the entire plant.
Therefore, there have been developed static mixing apparatus which
have no mechanically driven impeller and which can be directly
disposed in the pipeline. Static mixing apparatus are, however,
generally equipped with more intricate mixing elements than the
mechanically driven mixers, and, therefore, they have less
effective space for flowing passage, resulting in economical
disadvantage not only in manufacturing but also in operation due to
the energy loss by the pressure drop of the stream. It is also
difficult to maintain the same. On the other hand, if a static
mixing apparatus is equipped with relatively simple elements, such
as a pipe equipped only with divider or deflector plates, the
essential mixing effect is not attained sufficiently, although it
is easy to manufacture and maintain.
SUMMARY OF THE INVENTION
A primary object of this invention is to provide a mixing apparatus
not having the above mentioned disadvantages of the prior art, but
which is more economical to manufacture and easier to service.
Another object of this invention is to provide a unitary mixing
element which can be disposed in the supply line of flowing liquids
in order to insure thorough and uniform homogenization of
liquids.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a front view of a mixing apparatus according to the
invention.
FIG. 2 is a side view of the same.
FIG. 3 is a plan view also thereof.
FIG. 4 and FIG. 5 are respectively a front view and a plan view of
a unitary mixing element according to the invention which element
comprises a pair of rectangular members 2 and 3, and a pair of
triangular members 4 and 5.
FIGS. 6, 7 and 8 diagrammatically illustrate the unitary mixing
element according to the invention.
FIGS. 9 and 10 illustrate the relation between the dead spaces and
the liquid stream in mixing apparatus of the prior art.
FIGS. 11 and 12 illustrate the comparison in the dividing
efficiency between mixing apparatus of the prior art and the
present invention.
FIGS. 13, 14 and 15 illustrate the dividing effect caused by the
deflector, namely, the rectangular plate of the unitary mixing
element. In these drawings, e, f, g and h indicate the direction
normal to the flowing direction. E, F and G indicate respectively
the divider plate, the flowing passage and the passing-through
passage.
FIGS. 16 and 17 illustrate the flowing-up action and the straight
flowing action of the liquid stream.
FIG. 18 shows a further embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Preferred embodiments of this invention will be described
hereinafter with reference to the accompanying drawings.
As is shown in FIGS. 1, 2 and 3, a mixing apparatus according to
the present invention comprises a conduit of uniform square or
rectangular cross section, having four sides 1a, 1b, 1c, 1d, each
of which has a substantially flat inner surface, for supplying a
stream of the mixture of liquids, and a number of mixing elements
disposed therein in a specific manner described hereinafter.
As is shown in FIGS. 6, 7 and 8, each of said mixing elements is
composed of a pair of units each comprising a rectangular member
(namely, deflector plate) and a generally isosceles triangular
member (namely, divider plate) leading normal to said rectangular
member from one half of the longer edge thereof. As is shown in
FIG. 6, a pair of said units is assembled into a mixing element in
such a manner that one rectangular member is positioned on the
center of the longitudinal edge of the other rectangular member in
crossing relationship and that the rectangular members have a
common central transverse axis 20. Thus, the mixing element
comprises a pair of rectangular members, a first rectangular member
2 having a first longitudinal edge 21, a second longitudinal edge
22, a first lateral edge 23 and a second lateral edge 24, and a
second rectangular member 3 having a first longitudinal edge 25
(FIG. 8), a second longitudinal edge 26, a first lateral edge 27
(FIG. 5) and a second lateral edge 28, having a common transverse
axis 20, and a pair of generally triangular members 4, 5 each
leading normal 20 to one of the rectangular members from one half
of the longitudinal edge thereof and having its transverse edge
abutting upon the other half of the longitudinal edge of the other
of said rectangular members 2, 3. Generally triangular member 5
leads normal to first rectangular member 2 from one half of the
first longitudinal edge 21 of the first rectangular member 2 and
has one edge 30 abutting the first longitudinal edge 25 of the
second rectangular member 3. Generally triangular member 4 leads
normal to second rectangular member 3 from one half of the first
longitudinal edge 25 of the second rectangular member 3 and has one
edge 31 thereof abutting the first longitudinal edge 21 of the
first rectangular member 2. Said rectangular members are preferably
assembled normal to each other. In this preferred embodiment, the
triangular members 4, 5 are right-angled triangles.
The conduit 1 may be provided with a desired number of the mixing
elements. In an embodiment of this invention, at least two mixing
elements are disposed in the conduit 1 in such a manner that the
mixing element is spaced therein in a reversed disposition to any
of the adjacent elements i.e., the common transverse axis 20 of
adjacent elements are rotated 90.degree. with respect to each
other. In another embodiment, at least four mixing elements are
disposed in the conduit 1 in such a manner that each of said mixing
elements is spaced angularly at right angles from the preceding
element upon the line passing the centers of the triangular members
4, 5. Therefore, within each element, in which the two triangular
members 4, 5 meet at their apex, the line passing through the apex
and joining the center of the base of each triangular member of
each mixing element, is always parallel to the longitudinal axis of
the conduit 1.
If the materials to be mixed or blended contain a fluid material or
high viscosity, a powder or a solid material, the flowing stream is
often caused to hold up due to the viscosity resistance generated
at the corner among the rear portions of the rectangular members
and the inner wall of the conduit 1. For the purpose of preventing
hold-up of the flowing stream, quasi-trigonal pyramids or
quasi-cones 11 and 12 may be provided at said corners as shown in
FIG. 18; as shown in FIG. 8.
In FIG. 18 it can be seen that a first quasi-conical body 11 has an
apex 33 at the end of the one half of longitudinal edge 21 of the
first rectangular member 2 from which leads triangular member 5.
The mixing element fits into the conduit with the first lateral
edges 23, 27 of respectively the first and second rectangular
members 2, 3 abutting the inner surface of one of the sides 1a of
the conduit 1. In addition, the second lateral edges 24, 28 of the
first and second rectangular members 2, 3 abut the inner surface of
side 1c of the conduit. The quasi-conical body 11, also abuts the
same surface 1a which the first lateral edge 23 of the first
rectangular member 2 abuts and it further abuts the inner surface
of 1d which is also abutted by the second longitudinal edge 22 of
the first rectangular member 2.
The second quasi-conical body 12 has an apex 34 at the end of the
other half of the longitudinal edge 25 from the half of
longitudinal edge 25 from which leads triangular member 4.
Quasi-conical body 12 abuts the inner surface of the conduit side
1c which surface is also abutted by the second lateral edge 28 of
the second rectangular member and further body 12 abuts the inner
surface of conduit side 1a, which surface is also abutted by the
second longitudinal edge 26 of the second rectangular member 3.
Operation of the mixing apparatus according to this invention will
be described in detail hereinafter.
Liquid stream 10 to be mixed or blended is divided into upper and
lower smaller partial streams by the divider plate of the first
mixing stage at the up-stream side, and thereafter, each partial
stream is again divided into two partial streams by the divider
plate of the mixing stage 7, therefore, the initial liquid stream
is resultantly into four partial streams. Such division occurs at
the divider plate of the mixing stage 8 into 16 partial streams and
at the divider plate of the mixing stage 9 into thirty two partial
streams and so forth, thereby intimately mixing the materials. The
stream divided by each divider plate is guided by the deflector
plates to thereby trace a vertical and horizontal zigzag course,
and is repeatedly divided and combined, thereby attaining a
prominant mixing effect. Further, since the liquid stream takes a
zigzag course and passes through, flows over and is compressed by
the deflector plates 2, 3 and divider plates 4, 5 with an increased
velocity, the mixing effect more prominantly increases.
When the substances to be mixed have a high viscosity or contain a
powder or solid material, quasi-conical bodies 11 are disposed at
the corners between the deflector plates 2, 3 and the inner wall of
the conduit 1 for the purpose of preventing the hold-up of the
flowing stream and to thereby pass the substances smoothly through
the conduit 1. In this case, the quasi-conical bodies constitute
"dead spaces" in the conduit 1, however, the occupation ratio of
the quasi-conical bodies in the conduit 1 may be as low as 2
percent. Therefore, the disposition of the quasi-conical bodies is
considered to be highly effective in uniformly mixing and
dispersing the substances.
Now, the mixing efficiency of the mixing apparatus according to the
present invention will be described in detail hereinafter in
comparison with those of the prior art.
The representative line or static mixing apparatus of the prior art
include the following:
A. "mixing device" u.s. pat. No. 3,286,992; CL.259-4
B. "mixing apparatus" u.s. pat. No. 3,051,453; CL.259-4
C. "a method for mixing fluids and an apparatus thereof" u.s. pat.
No. 3,239,197; CL.259-4 and U.S. Pat. No. 3,195,865; CL.259-4
These prior art patents are indicated hereinafter as (A), (B), and
(C). These have been developed in the U.S.A. and are similar to the
present invention in that they also are not equipped with any
mechanical driving means or rotary agitator.
The device of the prior art patent (A) comprises a circular
conduit, and unit elements each comprising spiral blades jointed
normal to each other. Therefore, the device (A) is completely
different in its construction from that of the present invention.
Further, since, in the prior art patent (A), the functions of the
divider and deflector plates are not distinguished, the action and
effect obtained by such distinct classification as in the present
invention cannot be obtained.
As is shown in FIG. 1, in the apparatus according to this
invention, the stream passes through all of the spaces in the
conduit 1. On the other hand, as is shown in FIGS. 9 and 10, the
apparatus of the prior art (B) or (C) has much dead space in its
conduit due to the blocks disposed therein. Especially, in the
apparatus of the prior art (C), the dead spaces occupy a volume
larger than the effectively usable space therein, and therefore, it
is not considered to be particularly economical either from the
manufacturing cost standpoint or from the operation cost
standpoint. Accordingly, it should be noted that the present
invention is distinguishable from the prior art in that there is
substantially no dead space in the conduit.
Now, referring to the dividing effect on the flowing stream, FIG.
11 shows a diagram of the dividing action by the apparatus of the
prior art patent (B) and (C), and FIG. 12 shows that of the present
invention. In FIGS. 11 and 12, the obliquely lined portions
indicate the stream of a material to be mixed. FIG. 12 shows a
progressive modification of the sectional configuration of flowing
streams. It is understood from FIGS. 12 and 15 that the flowing
streams are complicatedly modified due to a converting action
thereon accompanied by the displacement of streams indicated in c
and d of FIG. 12, and modification of the flowing passage shown in
"G" of FIG. 15. This was also experimentally understood. Such
complicated modification of the flowing streams can be readily
understood in that the modification of the obliquely lined portion
a - b - c - d in FIG. 12 is very different from that shown in FIG.
11. In FIG. 11, the black portions indicate the dead spaces, while
they don't appear in FIG. 12. As is readily understood, in the
prior art, the dividing action indicated as a - b - c - d in FIG.
11 is repeated, while in the present invention, the dividing action
indicated as a - b - c - d in FIG. 12 is also repeated.
The displacing action on the flowing streams indicated in c - d of
FIG. 12 does not appear in the prior art patents B or C. This means
that local mixing effect is obtained according to the present
invention. Such displacement of the flowing streams is shown in
more detail in FIGS. 13, 14 and 15. As is shown in FIGS. 13, 14 and
15, the displacing action is attained in the modification of the
flowing pass F - G or G - F in FIG. 15.
If desired, a fin member may be disposed in the portion indicated
by FIG. 16 so that the stream passes more smoothly therethrough. In
FIG. 17, the stream flows over the fin member and passes through a
narrow passage, and it is contracted smoothly without any
appreciable pressure drop. Such a member is not disclosed in the
prior art patents (B) and (C).
In a line or static mixing apparatus, it is important to prevent
"short-pass" of the flowing stream in order to increase the local
mixing effect, which can be attained by changing the flowing
pattern wherein the flowing stream is shortly passed through the
conduit into a pattern wherein the velocity of the flowing stream
is increased in a direction normal to the longitudinal axis of the
conduit. As is shown in FIGS. 9 and 10, in the apparatus of the
prior art patents (B) or (C), the flowing stream tends to pass
shortly through the conduit, resulting in an insufficient mixing
effect, On the other hand, in the apparatus according to the
present invention, the flowing direction of the stream can be
smoothly changed without causing any appreciable pressure drop. The
deflector plates of the mixing element of this invention are very
effective in preventing the stream from shortly passing through the
conduit, since they always face the flowing stream and have wall
faces to guide the same. Further, the flowing direction of the
stream is smoothly changed at right angles by the passage shown in
F - G or G - F of FIG. 15, thereby increasing the velocity of the
stream in a direction other than longitudinal axis to prevent the
"short pass" of the stream. Therefore, the present invention is
distinguishable from the prior art in view of the above mentioned
effect.
The advantage in operation cost obtained according to this
invention is described quantitatively hereinafter, by comparison
with the apparatus of the prior art.
If a mixing apparatus of a circular conduit has,
coefficient of friction; f
radius of the conduit; D
average velocity of the liquid stream; U
density of the liquid; .rho.
the consumption of power per volume; P.sub.v g.sub.c is calculated
as, ##EQU1## wherein g.sub.c indicates the gravimetric factor,
P.sub.v is indicated, for example by kg-m/sec.m.sup. 3. If the
stream is in laminar flow, coefficient of friction is ##EQU2## f:
the coefficient of friction of only the conduit ##EQU3## .mu. :
viscosity of liquid When a rotary mixing apparatus for liquid of a
high viscosity has consumption power Pg.sub.c, length of the blade
d, revolutions per minute n, the following experimental equations
are obtained:
if it is a helical ribbon mixer, ##EQU4##
if it is an anchor blades mixer, ##EQU5## By dividing Pg.sub.c by
the volume of the mixing tube V, we obtain consumption power per
volume, ##EQU6## Further, homogenization period is deemed to be
mixing duration M, the coefficient which can be usable in "SCALE
UP" of system can be obtained as the product of mixing duration
.theta..sub.M and .sqroot.P.sub.v g.sub.c /.mu..
In a usual rotary mixing apparatus for high viscosity, said
coefficient is, ##EQU7##
On the other hand, in the apparatus according to this invention,
since P.sub.v g.sub.c depends mainly upon the value of f, and .rho.
is in proportion with pressure loss .DELTA.P, f and .DELTA.P are
important factors.
A static mixing apparatus commercially sold by CHENICS Corp.
has,
f = (5 - 6 ) f.sub.o
According to the research of the present invention, a system in a
worse condition than said mixing apparatus of CHENICS Corp. has a
coefficient of SCALE UP, if,
f = 2.25 f.sub.o, ##EQU8## Therefore, it is more advantageous than
the usual rotary mixing apparatus described hereinbefore. However,
such advantage is determined by the scale of coefficient of
friction f and, therefore, even if the construction is unique, it
is meaningless unless the value of f is small.
A usual rotary mixing apparatus has, ##EQU9##
a static mixing apparatus has, ##EQU10##
Therefore, assuming that .theta..sub.M and viscosity of liquid .mu.
are respectively identical in both apparatus, we obtain, ##EQU11##
Since we obtain said equation from the data that coefficient f is
assumed to be 2.25 times larger than f.sub.o when the mixer is
empty, pressure loss can be allowed as low as 4 .times. 2.25 = 9,
about 10 times.
In the mixing apparatus according to the present invention,
pressure loss remains between 3 and 10 times in laminar flow and,
therefore, it is very economical. However, as is readily understood
from the description of Chemte - Ing. - Techn. 43, No. 6, page 348
(1971), Brunemann, etc., the mixing apparatus according to the
prior art (C) has a coefficiant of friction more than 10 times f as
follows:
f = (50 - 60 ) f.sub.o
Further, ISGMIXER (according to U.S. Pat. No. 3,404,869) which
gives rise to displacement of liquids by means of a number of
tortuous tubes, has a coefficient f = 300 f.sub.o accordingly,
these static mixing apparatus of the prior art are inferior to the
rotary mixing apparatus with respect to operation cost.
As described hereinbefore, the mixing apparatus according to this
invention is superior in operation cost to those of the prior
art.
The foregoing description of the specific embodiments will so fully
reveal the general nature of the invention that others can, by
applying current knowledge, readily modify and/or adapt for various
applications such specific embodiments without departing from the
generic concept, and, therefore, such adaptations and modifications
should and are intended to be comprehended within the meaning and
range of equivalents of the disclosed embodiments. It is to be
understood that the phraseology or terminology employed herein is
for the purpose of description and not of limitation.
* * * * *