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Патент USA US2567476

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Sept. 11, 1951
2,567,474
e. R. FlTTS ET AL
I
COUNTER CURRENT SOLVENT EXTRACTOR
Filed July 2, 1947
_ INVENTOR.
GEORGE R.F|TTs
ill
BY FRED 6. Low
Patented Sept. 11, 1951
2,567,474
UNITED STATES PATENT OFFICE
CbUNTERCURREIifZifIZiENT EXTRACTOR
George R. Fitts, York, Pa., and Frederick G. Low,
Newark, Del., assignors, by direct and mesne as
signments, to Read Standard Corporation, a
corporation of Delaware
Application July '2, 1947, Serial N0. 758,520
5 Claims. (0!. 23-270)
1
This invention relates to a method and appara
tus for continuous counter-current solvent ex
traction of solid materials.
It is an object of the present invention to pro
vide a novel procedure and apparatus of greater
e?iciency than those disclosed in the prior art
for extracting soluble matter from solid materials
containing such matter.
solvent, it not only carried back a substantial part
of the solvent but also interferred with the free
flow of solvent from one extracting section to
the next. An important object of the present
invention, therefore, is to provide a novel pro
cedure and apparatus wherein not only is “re
verse infusion” of solvent minimized but dam
ming of the flow of solvent is eliminated per
mitting free ?ow of solvent from one extracting
section to the next.
A further object of the invention is to provide
solvent extraction apparatus of the type described
embodying the counter-current ?ow of solvent
These and other objects, including improving
and solvent material,that is so improved in struc
generally on the procedures and structures pre
ture and mode of operation as to be capable of
viously employed in similar solvent extraction
more rapid and ef?cient extraction than prior
operations, will appear more fully from the fol
devices.
15 lowing description and the accompanying draw
It has been previously proposed to employ a
ing illustrating a preferred embodiment of the
tank having a series of adjacent extracting sec
invention. In the drawing
tions in the form of trough-shaped tubs, with
Figure 1 is a central vertical longitudinal sec
a paddle Wheel in each for moving the material
tional view of the improved apparatus;
to be extracted through its respective section and
Figure 2 is a sectional view of the invention
over the common edge of a pair of adjacent sec
taken on the line 2-2 of Figure 1;
tions into the next succeeding section, and caus
' Figure 3 is an enlarged view of the ba?le and
ing solvent to flow from one section to the next
portions of‘the adjacent extracting-sections of
succeeding section in a direction counter-current
the improved apparatus; and
with respect to the direction of movement of the 25
Figure 4 is a sectional view taken on the line
material being extracted. In this previous
4—4 of Figure 3.
method and apparatus, the level of the solvent
The preferred embodiment of the invention,
has been maintained a substantial distance above
as shown in the drawing, comprises a tank l0
the common or spill edge of a pair of adjacent
provided with a plurality of adjacent trough
sections to assure a continuous flow of‘ solvent. 30 shaped tubs or extracting sections II which ex
It is apparent that in such method and apparatus
tend across the entire width of the tank It and
a substantial portion of the material to be ex
are arranged parallel one with respect to the
tracted is carried over from one extracting sec
other. The adjacent upper ends of each pair of
tion or tub to the next succeeding one while still
adjacent tubs are formed with a common spill
immersed 'in the solvent, resulting in the carry 85 edge over which material to be extracted is passed
ing back of solvent having a greater concentra
from one tub II to the next, the series of tubs
tion of dissolved matter into and mixing it with
ll forming the bottom wall of an extraction
the solvent having a lesser concentration of dis
chamber l2.
solved matter. Since this occurs continually in
The tank In is provided with a top wall [3
each extracting section, the cumulative e?ect is
which also forms the top wall of the extraction
to materially prolong the extracting time.
chamber I2. The top wall 13 is preferably pro
It is, therefore, a more speci?c object of the
vided with a plurality of inspection openings H
invention to provide a novel procedure and ap
normally closed by the covers I5.
paratus in which carry back of solvent having
Mounted in each of the tubs I I is a paddle wheel
a greater concentration of dissolved matter and
mixing of it with solvent having a lesser con 45 ll, extending the full width of the extraction
centration of dissolved matter is very materially
chamber 12 and comprising a hub l8 which may
reduced by raising the material to be extracted
be in the form of a drum of any suitable shape
entirely out of contact with the solvent for sub—
in cross section, but preferably round as shown
stantially completely draining it before it is
in the drawings, and a plurality of preferably,
moved into the next succeeding extraction 50 though not necessarily, curved perforated blades
section.
Ill, The blades I9 extend the full width of the
In apparatus employing successive extraction
extraction chamber [2 and are spaced at equal
sections it has been previously proposed to form
a dam of material being extracted on or near
the common spill edge of a pair of adjacent ex
tracting sections tending to prevent “reverse in
fusion” of the solvent, however, since the major
portion of the damwas beneaththe level ofvv the
distances about the hub l8 to which they vare ‘se
Strengthening
ribs 20 either formed with or suitably secured to
the blades I9 extend a distance circumferentially
55 cured in any suitable manner.
2,567,474
4
flow of solvent from one trough shaped tub to
The hubs I8 are secured to and arranged to
rotate with shafts 2I which extend through and
are journaled in the sides of the tank I0. On
the next, and the sealing strips 3| which as pre
viously explained connect the upper ends of ad
the extensions of ‘the shafts 12I ‘at one side of
the tank“). are mounted Worm wheels 22 mesh
ijacentrtubs, iform'a bottom ‘wall for‘the passages,
'as best‘shown in‘FiguresB and 4,‘preventing sol
ing with worms 23 on the main driving shaft
24 which is operated from a suitable source ‘of
vent from ?owing from the extraction chamber
‘I2 into the bottom of tank Ill.
power (not shown).
.
The solvent introduced through pipe 29, thus
?ows through the perforated strips 34 from one
The material from which soluble matter is to
be extracted is introduced into an end tub tI-I “of 10 tub "to the -next "maintaining the level of the
solvent, ‘indicated at X in Figure 1, at substan
the extraction chamber I2‘in‘any‘suitablefman
tlallythe "level'of ‘the perforations in the strips
As shown in the drawings, the material
ner.
‘34. “The crests vor spill edges of the baffles 30
passes from the spout 25, which preferably ex
tends the width of the tub II, .throughg-arrota'ryy ' being substantially above the level X of the
metering device I6 and then through an opening
solvent, it is apparent that the solid material is
carried upwardly by the paddle wheel blades I!
26 in the top wall I3 of chamber I2. "It'isfof
out of contact with the solvent and drops over
course, desirable to arrange the spout or spouts
the spill "edge *of ‘the ‘ba?les v3|) into the ‘next
251in1su‘ch-mannerl as‘to'obtainlan' even distribu
succeeding tub, ‘the ‘direction {of vmovement of
tion :‘of the ‘material across the width ‘of tub
II. The blades I I9,‘which rotate in'vthe direction 20 the solid material through=the<extraction cham
of the arrows ‘as shown iniFigure 1,-advance the
ber II’2‘being countercurrent with respect tofthe
material‘in segregatedfmassesvfrom oneitub ‘ “to
direction'ofr?ow of ‘the'solvent. 'Sincethe per
the ' next r'suc'ceeding Itub, ?nally fdelivering 'the
forated'metal strips 34 are 'at'an elevation at
residue onto theLlower Ien'd'v of“ an? endless conveyor
least as high as the bottom portion of the drums
21 mounted in the=conveyor housing 28 which 25 I8, it is evident that the ‘level of the ‘solvent
communicates with the end of the extraction
Willjbe maintained at least as’high as ‘the bot
chamber I2 opposite that end into which the
tom-portion-oflthe drums -I8,’thereby prevent
material is introduced.
ing light particles of'material‘from ?oating on
The':solvent employed- in the extraction process
the'surfa'ce ofthe solvent ‘into the next section
is Introducedthrough a‘pipe or pipes .29 into the 30 and assuring'positive'submersion of all ‘the ma
end tub II opposite‘the'ipoint of introduction of
terial lin'the-‘solvent in each of the series'o'f
the ‘material to be ‘extracted, however, it will be
tubs II.
apparent'that if desired the solvent may be in
The end~tub >I-I opposite the‘solvent'inlet pipe
troduced into the conveyor housing ‘28, from
29 is provided with'a- strainer'orv screen 35 which
whichit-will flow overithe edge of andvinto the 35 permits “passage of “the micella - or solvent ‘with
adjacent tub' I'I.
its dissolved ‘matter into the micella receiving
The'common spill edgeof adjacent tubs II is
chamber '36,v formed “by ‘an ‘extended portion of
preferably though'rnot necessarily formed ‘as a
the tank I0. The vmicella ‘or solvent with-its
separable member orba?le ‘30 seated on a sealing
dissolve’d‘matter‘is withdrawn'from the chamber
strip'orzplate 3| connecting the adjacent upper 40 36‘through pipe ‘31 "and-‘may ~then be delivered
ends of the arcuate ‘shaped wall portions 32 of
to ‘a suitable recovery plant where ‘the soluble
adjacent tubs‘ I l. ‘Considered in cross section, the
matter and solvent maybe separated and "col
arcuate shaped wall portions 32-? are in the form
of a minor-arc described about'the’axis of'the
paddle wheels I‘! so'that during rotation of'the
paddle “wheels, the ends of the blades I9 will ?t
closely‘a'gainst the inner surface of the arcuate
shaped wall portions ‘3 2-.
Incross section, the bailies 30 are preferably
triangular-‘in shape, the sidefaces of which are
preferably formed on the same radius asthe wall
lected in known ‘manner.
The bla‘des'lll .curve :back ‘from the drums‘IB
of the pad'dle‘wheels I’Iin a generally tangential
direction so that'the material ‘falls away from
the blades, as they ascend from the con?nes ‘of
the "tubs I I, and 'drops'into "the'next succeeding
tub.
‘In operation'the material‘ to be‘ extracted drops
from‘therotary valveIB into 'theispace between
two successive "blades I9Iof‘ the paddle wheel H.
The trailing blade pushes the material down into
is obvious that ‘the ba?ies 39 may be other than
the solventaroun'd' the‘ bottom of .the.tub I I,‘ then
triangular in cross section and the ‘side faces need
elevates the segregated mass of material through
65
not necessarily be arcuate, since the ends of the
the solventand T?nally raises the entire segre
blades I9 may be provided with ?exible flaps
gated mass of material out of contactwith the
portions 32, so that they form continuations of
the arcuate surfacesof the wall portions'32. It
that will maintain a close lit with the side faces
of the ba?les 30, or if the space between the ends
of the blades I9 and the side faces of the‘ ba?les
solvent, ‘whereupon this segregated mass of ma
terial .is substantially completely drained.
The
is not so great as to permit an’ appreciable amount 60 solvent that is drained from the material passes
of-~material to pass therebetween, such flaps are
not necessary. Each of-the baffles 30 is'provided
in its basewith recesses 33 and perforated metal
strips 34 are secured in any suitable mamier, as
by welding, in the recesses ‘33, and are Prefer
ably curved to followthe contour of the wall
portions-32 and the side faces of the baffles 30.
through-the perforations .of the trailingblade. I9
back into the sametub II, while vthe thoroughly
drained material drops from the trailing blade I9
over I the spill edge. of the .ba?le-43Il into ‘the.’ next
succeedingtub I I. This positive submersion-of
the ‘material and > substantially » :complete - drain
agelis: repeat-edinw-each of the ‘series of tubs’ I I,
the drained material ?nally passing onto theeon
The recesses 33 and perforated strips34 are dis
veyor-:2‘I.
posed at a level substantially below the levelrof
the axes of the paddle 'wheels I'Tbut not below 70 'Since theisegregated‘vmasses- of material are
substantially ":completely .drained' of solvent - ‘be
the level of the lowermost portion of the drums
fore ifbeing‘delivered fromzone tub to ‘the ‘next
I8,"while the'cre'st'or spill edge of the ba?les'30
succeeding? tub?carrying r back-rzofsolvent: having
are‘arranged at approximately the same level
a'rhigher; concentration ;of.rlissolved'imatter into
as‘ the'le'vel 'of the axes of-the paddle-wheels
IT. The recesses 33 provide passages 'lforithe 75 solvent havinga rlowerlconcentnationtofl dissolved
2,567,474
5
6
matter is very materially reduced as compared
solvent, moving it through said troughs, raising
to prior apparatus.
it above said passageways and depositing it over
said common top edge portions into the next suc
It is, of course, apparent that the material
being extracted still retains a certain amount
of the solvent-solute mixture when it passes over
the baf?es 33 from one tub to the next. In the
description and claims it will be understood that
by substantially complete drainage is meant that
no substantial further amount of solvent-solute
3. In countercurrent solvent extraction appa
ratus in which material to be treated is intro
duced adjacent one end of the apparatus and
solvent adjacent the other, a series of adjacent
mixture is not expressed from the material but
a baffle seated on each of said plates and pro
ceeding trough.
extracting troughs comprising walls of arcuate
mixture will freely drip from the material being 10 con?guration in cross section, a plate connecting
the adjacent upper edges of said arcuate walls,
extracted. In other words, the solvent-solute
vided with passageways for the ?ow of solvent
therethrough from one trough to the next adja
gravity from each entire segregated mass or"
material before being introduced into the next 15 cent trough and conveying means rotating in
said troughs for ?rst moving the material through
succeeding extraction section.
the solvent in said troughs and then out of con
The solvent-solute mixture retained by the
tact with the solvent and over said ba?‘les into
material being extracted is diluted in the next
the next succeeding trough.
succeeding extraction section with solvent con
taining a lower percentae of solute, the extrac 20 4. In countercurrent solvent extraction appa
ratus in which material to be treated is intro
tion process is repeated and again the material
duced adjacent one end of the apparatus and
is drained before being passed on to the next
solvent adjacent the other, a series of adjacent
extraction section. This process is repeated
extracting troughs comprising walls of arcuate
through the necessary number of extraction sec
tions until the solvent-solute content of the ma 25 con?guration in cross section, a plate connect
ing the adjacent upper edges of said arcuate
terial being extracted reaches the minimum of
walls, a baffle seated on each of said plates, the
residual solute.
side walls of said baffles being formed on the
Our improved method and novel apparatus for
same radius of curvature as the radius of our
extracting soluble matter from solid materials
containing the same are capable of more rapid 30 vature of said arcuate walls to form continua
tions thereof, said ba?les having passageways
and ef?cient extraction than previously known
is permitted to substantially completely drain by
methods and apparatus.
We claim:
1. In a countercurrent solvent extraction appa
ratus, a series of troughs arranged side by side
and forming the bottom of an extraction cham
ber, each pair of adjacent troughs having their
adjacent walls meeting in a common top edge
formed in the base portion thereof adjacent‘ said
plates for the flow of solvent therethrough from
one trough to the next adjacent trough and
conveying means rotating in said troughs above
and below the level of said passageways for mov
ing the material through said troughs counter to
the direction of ?ow of the solvent and above
said passageways for depositing it over said baf
portion, said adjacent walls having passageways
?es into the next succeeding trough.
formed in said common top edge portion and
5. In countercurrent solvent extraction appa
above the bottom of said troughs providing for
ratus in which material to be treated is intro
the ?ow of solvent therethrough from one trough
duced adjacent one end of the apparatus and
to the next to maintain the solvent at the level
solvent adjacent the other, a series of adjacent
of said passageways and conveying means rotat
ing in said troughs above and below the level 45 extracting troughs comprising walls of arcuate con?guration in cross section, a plate connecting
of said passageways for moving the material
the adjacent upper edges of said arcuate walls,
through said troughs counter to the direction of
a bafile seated on each of said plates, said baffles
flow of the solvent and above said passageways
for depositing it over said common top edge por
having recesses provided in the bases thereof pen
tions into the next succeeding trough.
etrating said baf?es, perforated strips mounted
in the recesses of said baffles and providing for
the ?ow of solvent therethrough from one trough
to the next adjacent trough, said 'ba?les and per
forated strips being formed on the same radius
ber, said troughs being of arcuate con?guration
in cross section, each pair of adjacent troughs 55 of curvature as the radius of curvature of said
arcuate walls and rotating paddle wheels in said
having their adjacent walls meeting in a common
vtroughs for moving said material through said
top edge portion, said adjacent walls having pas
solvent counter to the direction of ?ow of the
sageways formed in said common top edge por
solvent and above said perforated strips for de
tion and above the bottom of said troughs pro
viding for the ?ow of solvent therethrough from 60 positing it over said baffles into the next succeed
ing trough.
one trough to the next to maintain the solvent
GEORGE R. FITTS.
at the level of said passageways, means for mov
FREDERICK G. LOW.
ing material through said extraction chamber
in a direction opposed to the direction of ?ow
of said solvent, said means including a rotatable
REFERENCES CITED
hub extending the full length of each trough
The following references are of record in the
2. In a countercurrent solvent extraction appa
ratus, a series of troughs arranged side by side
and forming the bottom of an extraction cham
with the lowermost peripheral portion of each
?le of this patent:
of said hubs being below said passageways and
UNITED STATES PATENTS
the uppermost peripheral portion of each of
said hubs being above said common top edge 70 Number
Name
Date
portion, perforated blades extending outwardly
471,995
Gschwind ______ __‘__ Mar. 29, 1892
from said hubs and having their free ends move
in a path in juxtaposition to the arcuate interior
surface of said troughs, said blades on rotation
1,628,787
2,227,605
2,405,105
Kennedy _________ __ May 17, 1927
Swallen et al ______ __ Jan. 7, 1941
Kennedy _________ __ July 30, 1946
submerging the material below the level of the 75
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