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Патент USA US3029998

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April 17, 1962
J. o. HORN ETAL
3,029,986
BLENDING APPARATUS FOR FREE-FLQWING GRANULAR MATERIALS
Filed March 21, 1960
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IN VEN TORS
JOHN D. HORN
DAYTON R. REEM
ar%m
AT ORNEY
United} States Patent 0 ”
ice I
3,029,986
Patented Apr. 17, 1962
2
1
' Mounted in the chamber 10 enclosed by upper wall
3,029,986
16a and lower wall 16b and substantially coaxial there
with is fenestrated tube 18 spaced above outlet 14 to
BLENDING APPARATUS FOR FREE-FLOWING
GRANULAR MATERIALS
John D. Horn and Dayton R. Reem, Victoria, Tex., as
signors to Union Carbide Corporation, a corporation
of New York
Filed Mar. 21, 1960, Ser. No. 16,397
4 Claims. (Cl. 222—478)
This invention relates to apparatus for blending tree
?owing granular materials.
provide a su?icient clearance between the lower end of
fenestrated tube 18 and the outlet 14 to permit unim
peded flow of granular material therethrough.
Posi
tioned around fenestrated tube 18 is a ba?le 20 shown
as a divergent cone, whose peripheral edge cooperates
with lower wall 16b to de?ne an annular clearance
10 through which an amount of granular material can flow
unimpeded. The ba?le 20 is suitably supported by the
More particularly, it relates to apparatus comprising
fenestrated tube 18 but can be supported by the bin
a hopper providing blended flow of centrally and periph
walls by means of lateral members.
erally disposed free-?owing granular material at the
It is ~the principle of the present invention to achieve
hopper outlet.
15 blending of free ?owing granular materials disposed in
The need for adequate blending apparatus for granu
‘ a hopper by causing material in the center of the hopper
lar productshas long been recognized in the art, par
to be intermixed ‘with material at the walls of the hop
ticularly for the blending of granular products such as
per in controlled proportions. j‘Proportioning isachieved
synthetic resins and plastics, and the like, to achieve a
by controlling the rate of flow ‘of the central and periph
uniform blend or mixture. Many of these products when 20 eral portions of the stored‘material during discharge
produced vary on one side or the other of a set standard,
from the hopper. The ?ow of centrally disposed granu
and must be intimately blended with other similar com
ponents in order to minimize variations.
lar material in the blending action of' the apparatus of
this invention is ‘exclusively through the fenestrated tube
To produce an acceptably uniform blend in blending
18. The ?ow of peripherally disposed ‘granular mate
bins, it is necessary to intimately commingle all the 25 rial is' exclusively through the annular clearance de?ned
component resins. Suitable equipment must positively
by lower wall 16b and baf?e 20. The ratio of the cen
interrnix all the contents of the bin regardless of their
tral and peripheral flows is the crux of the present in
vention. We have found that if the rate of ?ow Ft of
‘material to the outlet 14 from the fenestrated tube 18
has been that the resin ?owing down the bin tends to 30 is X, the rate of ?ow F0 to the outlet 14 through the an
?ow faster down the center, over the outlet, thus caus
nular clearance must be at least 0.4X to achieve a fairly
respective proportions within the bin.
Heretofore, a disadvantage of bin blending systems
ing slower mixing through non-uniform ?ow. The pref
homogeneous blend and is preferably 2X for achieving
the most homogeneous blends. Ratios of 4.5X and
erential ?ow of resin in the center of the bin creates
stagnant pockets of resin against the bin walls.
- higher can also be used'but with a slight sacri?ce in de
It is an object, therefore, of the present invention to 35 gree of homogeneity'being realized in the resulting blend.
provide blending apparatus which by, providing con
‘The rate 'of flow of peripherally disposed material F0 is
trolled and proportional ?ow from central and periph
independent of the width of the clearance between baffle
eral portions of the bin makes highly uniform blends of
‘20 and-lower wall 16b within wide limits. The rate
free-?owing granular materials.
of ?ow of centrally disposed material Ft from fenestrated
Another object is to provide a storage bin modi?ed ,to 40 tube 18 is dependent upon a number of factors or vari
prevent coning or funnelling of material to the bin out
ables e.g. diameter of the tube, number of openings,
let whereby material entering the bin is blended with the
vertical spacing of the openings, lateral spacing of, the
other contents of the bin upon discharge therefrom with- ‘
openings, size of the openings relative to the size of the.
out signi?cant reduction in bin capacity or discharge
rate.
Still another object is to provide apparatus which,
when used in conjunction with recycling equipment,
blends variable quantities of free ?owing granular mate
pellets of ‘granulated material, shape of the openings
45 and head of material in the bin or hopper.
rials of varying pellet sizes to near homogeneity at a
variety of recycle rates.
' ,
These and other objects are accomplished in accord
These var
ious factors will be considered individually below but
it should be borne in mind that all the above mentioned
factors are interdependent and interrelated; variation in
one variable eg a decrease in the number of openings
50 can necessitate similar or opposite adjustments in other
ance with the present invention by the use of a blending
apparatus comprising a hopper having a centrally posi
tioned fenestrated tube and a baffle means which de?nes
variables eg increase in size of openings, and/ or greater
spacing of openings and/ or decrease in pellet size of the
granulated material.
,
.
Total resin flow is limited by the capacity of thecon
an annular clearance with the hopper wall whereby total 55 veyor used in conjunction with the apparatus. ‘If the flow
?ow of material to the hopper outlet FT is the sum of '
down ‘the tube, ?xed by the number and size of the open
?ows through the fenestrated tube Pt and the annular
ings of the tube and other factors mentioned above, is
clearance Fe.
termed F, and total ?ow is FT the flow through the an
The invention can be better understood from the at
nular clearance F6 is determined according to the equa
tached drawing wherein the single FIGURE is a sectional 60 tion
view, partly in elevation, of a preferred embodiment of
the apparatus shown in conjunction with a conveyor
Fenestrated tube 18 is an elongated member provided
with a plurality of‘ entrance means 26, sized to permit
prises chamber 10 preferably of substantially circular 65 easy ingress of free-?owing granular material disposed "
thereabout ‘without bridging. The size of entrance
‘horizontal cross-section which is representative of a
means 26 is determined by the particular granular mate- .
silo, hopper, bin, tank or like storage structure for free
rial sought to be blended. In general the size of the
?owing granular material. The chamber 10 is provided
opening
should be at least about ten times the size of
with inlet 12 at the top, an outlet 14 at the bottom and
extending therebetween a wall comprising a substantially 70 the individual pellets of the granulated material. The
shape of entrance means 26 is not critical provided free '
means.
Referring to the ?gure the apparatus in detail com- ’
cylindrical upper wall 16a and‘a substantially conical
lower wall 16b.
'
?ow of pellets is not impeded. Ease of fabrication will
3
3,029,988
4
obviously make certain shapes e.g. circular or oval pref
tribution level of 0.480% by weight. In 5 hours of
circulating with the conventional system, poor distribu
tion was indicated by high peaks being attained during
erable. The entrance means 26 should be equidistantly
spaced along substantially the entire length of the fene
strated tube 18 not covered by batlle 20 to insure sam
the ?rst 21/2 hours, followed by a leveling off to values
pling of all layers or portions of material in the bin.
Similarly, to insure adequate and representative sam
between 0.05 to 2.75%, which was well below the de
sired value of 0.480%. This demonstrates the spotty
pling the entrance means 26 should be regularly laterally
spaced. As shown in the ?gure fenestrated tube 18 is
and inadequate blending achieved with the conventional
method.
provided with a great number of entrance means 26 ver
Example 2
tically equidistantly spaced and laterally spaced around
10
the tube. The variables in design of fenestrated tube 18
should be adjusted to permit easy and rapid ?ow of cen
trally disposed material from outlet 14.
Three tests were made with the blender of this in
vention to determine the effect of tube flow rate with
different numbers of holes in the tube. Conditions of
the three tests were alike in that each employed (1) a
The ba?le 20 is made of rigid material and need not
be any particular size. The purpose of the baffle 20 15 recycle rate of 60,000 pounds per hour, (2) maximum
homogeneity level of 1% by weight, (3) a cone diameter
is to cooperate with lower wall 16b to de?ne an annular
of six feet, and (4) a sample frequency of ten minutes.
space conforming to the above given requirements. The
Results were as follows:
ba?le 20 is suitably positioned at a point in the bin
below substantially all of the entrance means 26 of
fenestrated tube 18. A small ba?le is to be preferred
No. of Ratl0—
Percent Distribution at Hour Intervals
holes of
Tube:
'
over a large one because the loss of storage volume
1.375” Annular
die. in
Clear1
2
3
4
5
6
7
8
consequent on the use of a ba?le is thereby kept to a
tube
once
minimum. The slope of the upper surface of ba?le 20
preferably forms an angle of 60° with the horizontal
80 ____ _0.415 0.45
3.1 1.25
1.5
1.2
1.3 1.25
1.1
which renders the battle 20 self-cleansing. A sloped 25 150.....
1.22 0.55 0.20 2.25
1.0
1.0
1.8 1.05
1.25
182"-..
2.02 0.60 0.70 0.75 0.65 0.70 0.65 0.55
0.75
surface on the ba?le is desirable in order to provide
self-cleaning properties and complete emptying of the
bin. It is also desirable that the ba?ie be adjustably
It is seen that higher ratios give, faster blending with
fewer peaks of concentration; that is, a greater homoge
to provide for changing of the annular clearance.
30 neity is attained.
In the drawing, the apparatus of the invention is shown
Example 3
in conjunction with a conveying means, suitably a pneu~
The
results
of
the
blending
test of Example 2 were
matic conveyor 28 and ducts 30 which carry granular
correlated
with
melt
index
as
a
representative property.
material from the outlet 14 past sampling point 32 to inlet
12 for recycle where desired for more homogeneous 35 The contaminant was assumed to have a melt index of
20.0 (the highest that might ordinarily be encountered),
blending using only one bin.
the
remainder of the resin had a melt index of 2.0
The data of the following examples illustrate the results
and the upper speci?cation limit on melt index of the
achieved with the apparatus of the present invention and
blend was 2.5.
the superiority thereof over unmodi?ed hopper blend
Results are given below:
mounted on the fenestrated tube or within the bin so as
ing devices.
The apparatus used in these tests comprised a hopper
having a diameter of twelve feet, a height of 35 feet and
a capacity of 100,000 pounds of free ?owing granular
40
No. of Ratio~
holes of Tube:
1.375” Annular
resin. The fenestrated tube was an eight inch diameter
pipe about 33 feet long closed at the top and provided
with four rows of entrance means laterally spaced 90°
die. in
Clear-
tube
ance
S0_____150_____
182“---
apart and equidistantly spaced vertically. On top of the
0.415
1.22
2.02
Melt Index 1 at Hourly Intervals
1
2
3
4
5
6
7
2.08
2.1
2.11
2. 56
2.05
2.14
2.22
2.4
2.14
2.3
2.18
2.11
2.22
2.22
2.12
2.21
2.32
2.12
2. -3
2.18
2.1
resin was placed a layer of resin colored with household
dye. Material was conveyed from the outlet to the inlet
lMelt index is given as
of the bin by a pneumatic conveyor having a 60,000
Test Method 1238-521‘.
pounds per hour capacity. Samples were taken fre 50
What is claimed is:
quently during the blending time. Total weight of the
preting the test results, it is important to remember that
placing all the di?erent color resin at the top of the
bin exceeds the worst blending condition likely to occur
in actual use.
Example 1
A. To 100,000 pounds of resin having a Ma" particle
size in a bin equipped with fenestrated tube having 182
2.2
2.24
2.1
deeigram/minute as determined by ASTM
1. Apparatus for blending free-?owing granular mate
sample was determined, then weight of the colored resin
pellets to determine the weight percent thereof present.
The closer the Weight percent was to the maximum theo
retical value the more uniform was the blend. In inter
8
rial comprising a hopper having a wall which converges
toward and terminates in an outlet, and supported in said
55
hopper spaced above said outlet, a substantially vertically
positioned fenestrated tube with a diameter X and having
a plurality of entrance means therein and a self-cleansing
> divergent ba?ie mounted below substantially all of said
entrance means and constructed and arranged to co
60 operate with said wall to de?ne an annular clearance
with a diameter of at least 0.4X whereby the cross-sec
tional areas of said fenestrated tube and said annular
clearance are proportioned so that the rate of flow of
holes 1% inches in diameter and a cone having a diam
material disposed in said hopper to said outlet from said
eter of 6 feet were added, at the top of the bin, 876 65 annular clearance is at least 0.4 times as great as the rate
pounds of colored resin, representing 0.876% by weight.
of ?ow of material from said fenestrated tube.
This blend was mixed for 12 hours. After 3 hours of
2. Apparatus for blending free-?owing granular mate
circulating through the blender of this invention, a stable
rial comprising a hopper having a wall which converges
colored resin distribution level of about 0.750% by weight
toward and terminates in an outlet, and supported in said
was reached.
70 hopper spaced above said outlet, a substantially vertically
B. For comparison, a conventional blending opera
positioned fenestrated tube with a diameter X and having
tion was carried out by adding to the top of a bin 480
a plurality of entrance means therein and a self-cleansing
pounds of colored resin. The resin in this bin was
divergent ba?le mounted below substantially all of said
mixed for 5 ‘hours with resin from four other bins, the
entrance means and constructed and arranged to co
whole totaling 100,000 pounds, with an optimum dis 75 operate
with said wall to de?ne an annular clearance with
3,029,986
6
operate with said wall to de?ne an annular clearance
with a diameter of about 2X whereby the cross-sectional
areas of said fenestrated tube and said annular clearance
are proportioned so that the rate of flow of material dis
posed in said hopper to said outlet from said annular
clearance is about 2 times as great as the rate of ?ow of
a diameter of from 0.4X to about 4.5X whereby the
cross-sectional areas of said tenestrated tube and said
annular clearance are proportioned so that the rate of
?ow of material disposed in said hopper to said outlet
from said annular clearance is from 0.4 to about 4.5
times as great as the rate of ?ow of material from said
material from said fenestrated tube.
4. The apparatus claimed in claim 3 wherein said
fenestrated tube.
3. Apparatus for blending free-?owing granular mate
fenestrated tube has a plurality of entrance means spaced
rial comprising a hopper having a wall which converges
toward and terminates in an outlet, and supported in said 10 substantially equidistantly along its length and laterally.
hopper spaced above said outlet, a substantially vertically
References Cited in the file of this patent
positioned fenestrated tube with a diameter X and having
UNITED STATES PATENTS
a plurality of entrance means therein and a self-cleansing
divergent ba?ie mounted below substantially all of said
entrance means and constructed and arranged to co
15
1,819,756
1,991,720
Reed ________________ __ Aug. 18, 1931
Barreda et al __________ _._ Feb. 19, 1935
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