U.S. patent number RE33,444 [Application Number 07/230,878] was granted by the patent office on 1990-11-20 for fluid treating for removal of components or for transfer of heat, momentum-apparatus and method.
Invention is credited to Bernard J. Lerner.
United States Patent |
RE33,444 |
Lerner |
November 20, 1990 |
Fluid treating for removal of components or for transfer of heat,
momentum-apparatus and method
Abstract
Apparatus for treating fluids flowing at high velocity, for mass
and heat transfer, for gas-liquid contacting and for contaminant
particulate, mist or fume separation, including a plurality of
perforated or unperforated cylinders arrayed staggered in rows
perpendicular to the direction of flow of the fluid. The elements
are spatially separated from each other. Diagonal by-pass flow
through the array is blocked by a partition extending from each
element generally parallel to the direction of flow of fluid
bisecting the space between a pair of elements of an adjacent row
with the elements of the pair symmetrically spaced with respect to
the partition. Also, a method of removing contaminants from gas by
passing the gas through this array between and injecting a liquid
into the array. Capture of the contaminants by the drops is
effected because of the difference in acceleration of each as the
contaminated gas passes in and out of the gap between each cylinder
and its adjacent partitions. Also, mass interchange between a gas
transmitted upwardly through the array and liquid injected into the
gas. Stable dynamic bubbling within perforated cylinders of the
array takes place producing the interchange. After the gas passes
through an array, it is expanded so that its velocity is reduced
and it sheds drops of liquid.
Inventors: |
Lerner; Bernard J. (Pittsburgh,
PA) |
Family
ID: |
26924651 |
Appl.
No.: |
07/230,878 |
Filed: |
August 11, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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569270 |
Jan 9, 1984 |
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Reissue of: |
842203 |
Mar 21, 1986 |
04732585 |
Mar 22, 1988 |
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Current U.S.
Class: |
95/221; 165/159;
165/172; 210/150; 261/108; 261/114.1; 261/153; 261/154; 261/94;
261/DIG.9; 366/338; 55/443; 55/444; 96/357 |
Current CPC
Class: |
B01D
45/08 (20130101); B01D 45/10 (20130101); B01D
53/18 (20130101); F28F 13/06 (20130101) |
Current International
Class: |
B01D
45/00 (20060101); B01D 45/10 (20060101); B01D
45/08 (20060101); B01D 53/18 (20060101); F28F
13/00 (20060101); F28F 13/06 (20060101); B01D
047/14 () |
Field of
Search: |
;261/94,96,108,109,114.1,121.1,122-124,153-155,DIG.9
;55/80,83,84,97,90,226,259,443,444,257.1 ;210/150,758 ;366/336-340
;165/159,172 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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241225 |
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Oct 1962 |
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AU |
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531515 |
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Jan 1922 |
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FR |
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52-96973 |
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Aug 1977 |
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JP |
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562593 |
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Jul 1944 |
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GB |
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897417 |
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May 1962 |
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GB |
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1594524 |
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Jul 1981 |
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GB |
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Primary Examiner: Chiesa; Richard L.
Attorney, Agent or Firm: Diamond; Hymen
Parent Case Text
REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of application Ser. No.
06/569,270, filed Jan. 9, 1984 for FLUID TREATING, and now
abandoned.
Claims
I claim:
1. Apparatus for treating fluids for liquid-gas contacting, for
removing particulate, mist or fumes from fluids, or for
transferring heat or mass between fluids, the said fluids flowing
predominantly in a predetermined direction, the said apparatus
including separate cylindrical elements arrayed in a plurality or
rows, each said element being impermeable to the flowing fluids,
.Iadd.the elements in .Iaddend.said rows being transverse to said
predetermined direction, and the elements of adjacent rows being
staggered with .[.reference.]. .Iadd.respect .Iaddend.to each
other, the elements of each row being spatially separated from each
other and from the elements of adjacent rows, so that an open flow
space would normally surround each element, whereby there would
normally undesirably be by-pass channels permitting by-pass flow
for the fluids between the elements along the rows .[.at an
angle.]. .Iadd.diagonally .Iaddend.to said predetermined direction;
the said apparatus being characterized by that said elements have
non-reentrant surfaces on their upstream side with respect to the
direction of flow of said fluid and further characterized by that
said by-pass flow of said fluid is prevented by partitions bridging
between at least a plurality of pairs of certain of said elements,
the elements of each said .[.bridging.]. .Iadd.bridged
.Iaddend.pair being in alternate rows, and the elements of
intervening rows being positioned generally symmetrically with
respect to said partitions, said partitions being substantially in
contact with the surfaces of the elements which they bridge along
the length of said elements to interpose substantially complete
obstruction to said by-pass flow, .Iadd.there being no row from the
surfaces of whose said elements more than one said partition
extends, .Iaddend.said partitions being positioned
.[.transversely.]. .Iadd.generally parallel .Iaddend.to said
predetermined direction and being so shaped so as to minimize the
pressure drop in the fluids flowing through said apparatus.
2. The apparatus of claim 1 wherein each partition passes between a
pair of elements of an intervening row and the thickness of said
each partition is small compared to the minimum distance between
the outer surfaces of said pair of elements which surfaces bound
the space through which said each partition passes.
3. The apparatus of claim 2 wherein the thickness is 5 to 25%
.[.and preferably 5 to 15%.]. of the minimum distance.
4. Apparatus for treating fluids, for liquid-gas contacting for
removing particulate, mist or fumes from fluids, or for
transferring heat or mass between fluids, the said fluids flowing
predominantly in a predetermined direction, the said apparatus
including separate cylindrical elements arrayed in a plurality of
rows, the elements of each row spatially separate from each other
and from the elements of adjacent rows so that open flow space
would normally completely surround each element, each said element
being imperforate to the flowing fluids, said .Iadd.elements in
said .Iaddend.rows being transverse to said predetermined
direction, the elements of adjacent rows being staggered with
respect to each other, the said apparatus being characterized by
elements whose surfaces are non-reentrant on their upstream side
with respect to the direction of flow of said fluid and by the
suppression of by-pass flow diagonally of said rows, by partitions,
the said partitions being interposed between at least a plurality
of pairs of elements, the said elements of each said pair being in
alternate rows, each said partition being substantially in contact
with the surfaces of the element between which it extends along the
length of said elements to prevent said diagonal by-pass flow,
.Iadd.there being no row from the surfaces of whose said elements
more than one said partition extends, .Iaddend.each said partition
being generally parallel to said direction and being shaped so as
to minimize the pressure drop in said fluid flowing through said
apparatus.
5. Apparatus for treating fluids for liquid-gas contacting, for
removal of particulate, mist or fumes from fluids, or for
transferring heat or mass between fluids, the said fluids flowing
predominantly in predetermined directions, the said apparatus
including separate cylindrical elements, each said element being
permeable to fluid flow throughout its entire active surface, said
elements being arrayed in a plurality of rows in which said
elements are spatially separated from each other and the elements
of each row are spatially separated from the elements of adjacent
rows so that an open flow space would normally surround each
element, whereby there would normally undesirably be by-pass
channels for the fluid along the rows at an angle to said
directions, resulting in by-pass flow at said angle; .Iadd.the
elements in .Iaddend.each said row being generally perpendicular to
said predetermined directions, the said elements of adjacent rows
being staggered with respect to each other, the said apparatus
being characterized by that said by-pass flow is prevented by
partitions bridging between at least a plurality of pairs of
certain of said elements, the elements of each said bridged pair
being in alternate rows, and the elements of the intervening rows
being positioned generally symmetrically with respect to said
partitions, each said partition being substantially in contact with
the outer .[.surface.]. .Iadd.surfaces .Iaddend.of the elements
which it bridges along the length of said .[.each element.].
.Iadd.bridged elements .Iaddend.without penetrating through said
.Iadd.bridged .Iaddend.elements to interpose substantially complete
obstruction to flow of fluids in said by-pass channels, .Iadd.there
being no row from the surfaces of whose said elements more than one
said partition extends, .Iaddend.said partitions being generally
parallel to said predetermined .[.direction.]. .Iadd.directions
.Iaddend.and being shaped so as to minimize the pressure drop in
the .[.fluid.]. .Iadd.fluids .Iaddend.flowing through said
apparatus.
6. The apparatus of claim 5 wherein each partition passes between a
pair of elements of an intervening row and the thickness of said
each partition is small compared to the minimum distance between
the outer surfaces of said pair of elements, which surfaces bound
the space through which said each partition passes.
7. The apparatus of claim 6 wherein the thickness is 5 to 25%
.[.and preferably 5 to 15%.]. of the minimum distance.
8. Apparatus for removing particulate from a gas, the said
apparatus including a plurality of separate cylindrical elements,
each element being perforated throughout its entire active surface,
said elements being arrayed in rows spatially separated from each
other with each element in each row spatially separated from the
other elements of said each row so that open flow space would
normally surround .Iadd.each .Iaddend.said element, the elements of
adjacent rows being staggered with respect to each other, a
partition bridging between a plurality of pairs of certain of said
elements, the elements of each said bridged pair being in alternate
rows and being interposed between pairs of elements of the rows
intervening between said alternate rows, each said partition being
substantially in contact with the surfaces of the elements which it
bridges along the length of said .[.each element.]. .Iadd.bridged
elements .Iaddend.to prevent diagonal flow through said rows,
.Iadd.there being no row from the surfaces of whose said elements
more than one said partition extends, .Iaddend.whereby constricted
flow channels are formed between each partition and the elements of
the intervening rows between which it is interposed, means for
transmitting said gas through said elements in a direction
generally perpendicular to .Iadd.the elements in .Iaddend.said
rows, and means for injecting a liquid into said gas producing
liquid drops in said gas, the said elements and partitions being so
spaced with respect to each other that said constricted flow
channels function as venturi passages and a multple venturi effect
acts on said gas, particulate and liquid drops as they pass through
said constricted flow channels and they are accelerated to higher
velocities, the velocity of said particulate in said constricted
channels being higher than the velocity of the drops of said
liquid, whereby said drops capture said particulate.
9. The method of removing particulate from a gas with apparatus
including a plurality of cylindrical elements, each said element
being imperforate to said gas, .Iadd.said elements being
.Iaddend.arrayed in rows with the elements of adjacent rows
staggered with respect to each other.[.,.]. .Iadd.and .Iaddend.with
each element physically separate from the elements of its row and
.Iadd.from the elements in .Iaddend.adjacent rows, and with
partitions extending between the elements of alternate rows, each
said partition being substantially in contact with the surfaces of
the elements between which it extends along the length of said
.[.each element to prevent.]. .Iadd.elements between which it
extends, said partitions preventing .Iaddend.diagonal by-pass flow
through said rows, each of said partitions being interposed between
a pair of elements of rows intermediate said alternate rows,
.Iadd.there being no row from the surfaces of whose said elements
more than one said partition extends, .Iaddend.each element
.Iadd.of a said pair .Iaddend.and its adjacent partitions defining
channels for the flow of gas, each channel being bounded by the
continuous curvilinear surface of a said .[.cylindrical.].
.Iadd.each .Iaddend.element .Iadd.of a said pair .Iaddend.and a
said adjacent partition, .Iadd.each said channel
.Iaddend.decreasing gradually in width from a first distance
constituting a part of the distance between a pair of adjacent of
said adjacent partitions to a second substantially smaller distance
between said each element .Iadd.of said pair .Iaddend.and one of
said adjacent partitions and then gradually increasing in width
from said smaller distance to a distance constituting a part of the
distance between said adjacent partitions, the said first distance
and the said second distance being so related .[.to.]. .Iadd.that
.Iaddend.an effective venturi effect for a gas flowing through said
each channel is present; the said method comprising injecting a
liquid into said gas to produce drops of liquid in said gas,
.[.passing.]. said liquid drops, gas and particulate forming a
fluid.Iadd., passing said fluid .Iaddend.through said channels
defined by said rows of elements and their associated partitions
generally transverse to said rows thereby to accelerate said drops
of the liquid.[., .]. .Iadd.passing through .Iaddend.said each
channel from the region of said first distance through the region
of said second distance, at a lower rate than the particulate
.Iadd.passing from the region of said first distance through the
region of said second distance .Iaddend.is accelerated, whereby
said liquid drops are at a lower velocity than said particulate and
said particulate collides with said drops and is captured by its
collision with said drops.
10. Gas liquid contacting apparatus for transferring components
.[.in.]. .Iadd.between .Iaddend.a liquid .[.to.]. .Iadd.and a
.Iaddend.gas, the said apparatus including a unit having
(a) a plurality of separate cylindrical elements, each said element
being perforate throughout its entire active surface, the elements
being arrayed in rows, the elements in each row being spatially
separated from each other and from the elements of adjacent rows so
that open flow space would normally completely surround each
element, and
(b) partitions bridging pairs of certain of said elements, the
elements of each said bridged pairs being in alternate rows, each
partition being substantially in contact with the outer surfaces of
the elements which it bridges along the length of said each bridged
.[.elements.]. .Iadd.element .Iaddend.without penetrating through
said .Iadd.each .Iaddend.bridged .[.elements to suppress.].
.Iadd.element, there being no row from the surfaces of whose said
elements more than one said partition extends, said partitions
suppressing .Iaddend.diagonal by-pass flow through said rows, means
for transmitting a gas through said unit in a direction generally
transverse to said rows, and means, downstream of the most
downstream row of said unit with respect to the flow of said gas,
for transmitting a liquid to said unit in countercurrent
relationship to said gas, said gas having a flow velocity within a
range such that said transmitted liquid is held up within said
elements in a stable pool and said gas bubbles through said
pool.
11. The method of liquid-gas contacting for mass interchange with
an array of generally horizontal cylindrical elements, each element
being perforated throughout its entire active surface, said
elements being disposed in rows in said array with the elements in
alternate rows staggered with respect to the elements of the
intervening rows, each element being physically disconnected from
the elements of its row and from the elements of adjacent rows,
.Iadd.and with .Iaddend.partitions extending between pairs of
elements in alternate rows, each said partition being substantially
in contact with the outer surface of the elements between which it
extends along the length of said .[.each element.]. .Iadd.elements
.Iaddend.between which it extends, without penetrating through said
last-named elements, .[.to suppress.]. .Iadd.there being no row
from the surfaces of whose said elements more than one said
partition extends, said partitions suppressing .Iaddend.diagonal
by-pass flow of fluids through said array, the said method
comprising conducting a gas and a liquid between which mass
interchange is to take place generally vertically through said
array with said gas flowing generally vertically upwardly, said gas
flowing at a velocity such as to produce stable dynamic pools of
the liquid within said elements, interacting the gas and liquid by
bubbling the gas through said pools to produce the mass interchange
between the content of said gas and said liquid, and conducting the
thus interacted gas and the thus interacted liquid separately away
from said array.
12. The method of claim 11 wherein the velocity of the gas emerging
from said array is reduced so that reentrained liquid is removed
from said gas and the thus removed liquid is conducted away.
13. A bubbler for mass transfer between a generally vertically
flowing gas and a liquid in the stream of said gas to interact with
each other, the said bubbler including a container having a top
plate and also having therein a plurality of generally horizontal
separate tubular elements, the walls of each element being
perforated, the said elements being disposed in a vertical array of
rows with the elements in alternate rows staggered, with respect to
the elements in intervening rows, each element being physically
disconnected from the elements in its row and from the elements in
adjacent rows so that normally each element would be surrounded by
an open flow space, a plurality of generally vertical partitions,
each partition extending between at least certain of corresponding
pairs of elements in alternate rows and passing between the
staggered elements of the intervening row, said each partition
being so positionally related to the elements between which it
extends as to block diagonal by-pass flow of fluid along the
elements from which it extends, the said top plate of said
container extending beyond said array, and at least one downcomer
extending from said top plate in communication with its outer
surface to drain liquid deposited on said surface.
14. The bubbler of claim 13 wherein each partition is joined to the
elememts between which it extends.
15. A tower for mass transfer between a gas and a liquid, the said
tower including a plurality of bubblers arrayed in series generally
vertically within said tower, each said bubbler including
(a) a container having a top .Iadd.plate .Iaddend.extending
generally horizontally beyond the boundaries of said container,
(b) a plurality of generally horizontal separate tubular elements
within said container, the wall of each said element being
perforated, the said elements being disposed in a vertical array of
rows with the elements in alternate rows staggered with respect to
the elements in intervening rows, each element being physically
disconnected from the elements in its row and from the elements in
adjacent rows so that normally each element would be surrounded by
an open flow space,
(c) a plurality of generally vertical partitions, each partition
extending between a pair of elements in alternate rows and passing
between staggered elements of the intervening row, each partition
being so positionally related to the said elements between which it
extends as to obstruct diagonal flow along the last named elements,
and
(d) at least one downcomer extending from said .[.cover.].
.Iadd.top .Iaddend.plate externally of said array,
means.Iadd., .Iaddend.connected to said tower.Iadd., .Iaddend.for
conducting a gas vertically upwardly through said serially arrayed
bubblers in said tower, and means within said tower for injecting a
liquid into said gas to interact with said gas, the said downcomer
of each bubbler conducting liquid collected on the .Iadd.top
.Iaddend.plate of said each bubbler and conducting said liquid to
the bubbler just below said each bubbler for recirculation.
16. The method of mixing at least a first fluid and a second fluid
with apparatus including a plurality of separate cylindrical
elements arrayed in rows with each row spatially separated from the
rows adjacent to said each row and each element in each row
spatially separated from the elements adjacent to said each element
in said each row, the elements in each row being staggered with
respect to the elements in rows adjacent to said each row, said
apparatus also including partitions extending between the elements
of alternate rows, each said partition being substantially in
contact with the outer surfaces of the elements between which said
each partition extends along the length of said .[.each element.].
.Iadd.elements between which said each of said partitions extends
.Iaddend.without penetrating through said elements.Iadd., there
being no row from the surfaces of whose said elements more than one
said partition extends.Iaddend.; the said method including
transmitting said first fluid through said array, transmitting said
second fluid through said array, said transmitted first and second
fluids forming a main stream, and mixing said fluids
(a) by separating the main stream of said fluids into pairs of
separate substreams, each pair of substreams being produced by the
interposition in said main stream of each partition and the
elements immediately downstream and upstream of said each partition
in the row intervening between the alternate rows between whose
elements said last-named each partition extends, and
(b) by the recombination of each said pair of substreams downstream
of said each partition and said downstream intervening
elements.
17. The method of claim 16 wherein the first fluid is initially
injected as a first stream into the array and thereafter the second
fluid is injected into said first stream to form the main stream
with said first stream.
18. The method of removing contaminants from a gas with apparatus
including a plurality of sets of cylindrical elements, each set
being arrayed in a row so that the elements are arrayed in a matrix
with the elements in alternate rows staggered and partitions
bridging between at least certain of the elements in alternate
rows, each of said partitions being substantially in contact with
the outer surface of the elements between which said each partition
bridges along the length of said .[.each element.]. .Iadd.bridged
elements .Iaddend.without passing through said elements.Iadd.,
there being no row from the surfaces of whose said elements more
than one said partition extends.Iaddend.; the said method
comprising transmitting the gas in a stream generally perpendicular
to the .[.of elements.]. .Iadd.axes of the elements in the
.Iaddend.rows, injecting a liquid as a spray into said stream,
.Iadd.repeatedly increasing and decreasing the velocity of said
stream including said gas and the drops of said spray as said
stream passes through the matrix .Iaddend.by means of a plurality
of communicating venturi channels formed between each said
partition and the elements of the row .Iadd.intervening between the
elements of said alternate rows .Iaddend.between which said each
partition passes, each said channel being bounded by the surface of
said each partition on one side and the curvilinear surface of one
of said elements .Iadd.intervening between the elements of the
alternate rows .Iaddend.between which said each partition passes on
the opposite side, .[.repeatedly increasing and decreasing the
velocity of said stream including said gas and the drops of said
spray as said stream passes through the matrix.]. thus repeatedly
introducing differences between the velocity of said drops and the
velocity of the contaminants in said gas and enhancing the capture
of said contaminants by said drops, and capturing the drops
containing the contaminants on the elements, the velocity of said
stream being both increased and decreased gradually at a rate
determined by the boundary of said each said channel thereby
introducing gradually varying differences, in accordance with said
rate, between the velocity of said drops and the velocity of the
contaminants in said gas and effectuating the capture of said
contaminants by said drops.
19. Apparatus for removing particulate from a gas including a
plurality of cylindrical elements disposed in rows in an array
through which said contaminant-containing gas is to be conducted
with the elements of adjacent rows staggered with respect to each
other, with each said element physically separate from the elements
of its rows and from the elements of adjacent rows.Iadd.,
.Iaddend.and with partitions, each extending between a first pair
of elements in alternate rows, each said partition being
substantially in contact with the outer surfaces of the elements
between which it extends along the .[.length.]. .Iadd.lengths
.Iaddend.of said .[.each element.]. .Iadd.elements between which it
extends .Iaddend.without penetrating through .[.the.]. .Iadd.said
last-named .Iaddend.elements .[.to prevent.]. .Iadd.there being no
row from the surfaces of whose said elements more than one said
partition extends, said partitions preventing .Iaddend.diagonal
by-pass flow of said gas through said array, each said partition
being interposed between a second pair of elements of .[.rows.].
.Iadd.a row .Iaddend.intermediate the associated rows of the
elements between which said .Iadd.last-named .Iaddend.each said
partition .[.is interposed.]. .Iadd.extends.Iaddend., means for
injecting a liquid into said gas to be conducted through said array
.Iadd., .Iaddend..[.so that.]. said gas, said particulate, and
drops of said liquid forming a fluid .[.are.]. to flow through said
array, each element of said second pair and its adjacent partitions
forming channels for the flow of said fluid, each said channel
being bounded by the curvilinear surface of an element of said
second pair on one side and by .[.one of.]. .Iadd.a .Iaddend.said
.[.partitions.]. .Iadd.partition .Iaddend.adjacent to said
last-named element on the opposite side, each said channel
decreasing in width gradually as determined by its said boundaries
between a first distance upstream with respect to the direction of
flow of said fluid, and a second substantially smaller distance
downstream from said first distance with respect to the direction
of flow of said fluid and then increasing in width gradually, as
determined by the boundaries of said channel between said second
distance and a third substantially larger distance, said first and
third distance each being the maximum distance between the surface
of the partition which forms a boundary .Iadd.of .Iaddend.said
channel and said curvilinear surface of said adjacent element which
forms the opposite boundary of said channel, and said second
distance being the shortest distance between said curvilinear
surface and said last-named partition, the said first and third
distances and the said second distance being so related that an
effective venturi effect exists for said fluid through said each
channel, whereby as said fluid passes through said channel, it is
.[.gradually.]. accelerated gradually at a rate determined by the
boundaries of said channel as it passes through said channel
towards the region of said second distance and is decelerated
gradually as determined by said boundaries of said channel as it
passes out through said channel away from the region of said
minimum distance so that during acceleration said drops are
accelerated at a lower rate than said particulate and during
deceleration said drops are decelerated at a lower rate than said
particulate so that differences of velocity are induced between
said particulate and said drops and said drops capture said
particulate. .Iadd.20. A mist eliminator for eliminating mist from
a mist-laden gas flowing in a generally horizontal direction; said
mist eliminator including separate elongated cylindrical elements
each positioned with its long axis generally vertically in a
plurality of rows forming an array into which said fluid is to be
injected, each said element being non-reentrant on its upstream
side with respect to the direction of flow of said gas, the
elements of adjacent rows being staggered with respect to each
other, the elements in each row being spatially separate from each
other and from the elements of adjacent rows so that an open flow
space would normally surround each element, whereby there would
normally undesirably be bypass channels permitting bypass flow for
said gas at an angle to the horizontal direction in which said gas
is injected into said array; the said mist eliminator being
characterized by that said bypass flow of said gas is suppressed by
partitions bridging between at least a plurality of pairs of
certain of said elements, the elements of each of said bridged pair
being in alternate rows of said array, and the elements in the
intervening rows being positioned generally symmetrically with
respect to said partitions, said partitions being substantially in
contact with the elements which they bridge along the lengths of
said elements to interpose substantially complete obstruction to
said bypass flow, there being no row from the surfaces of whose
said elements more than one said partition extends, said partitions
being positioned generally parallel to the direction of flow of
said gas as it is injected in said array and being so shaped as to
minimize the pressure drop of the gas flowing
through said mist eliminator. .Iaddend. .Iadd.21. The mist
eliminator of claim 20 wherein the cylindrical elements are
impermeable to the gas. .Iaddend.
Description
.Iadd.This application is a reissue of application Ser. No.
842,203, filed Mar. 21, 1986, now U.S. Pat. No. 4,732,585.
.Iaddend.
BACKGROUND OF THE INVENTION
This invention relates to the processing or treatment of fluids in
such operation as mass transfer, heat transfer in heat exchangers,
liquid-gas contacting, and separation of contaminant particulate,
mist and fumes from gases. This invention has particular
relationship to such treatment of fluids with an array of sets of
elements in rows with elements in any row being staggered with
respect to the elements in adjacent rows.
An array of such elements may be used as a separate unit, or a
plurality of arrays may be disposed in series in a tower which
serves for mass transfer between a gas and a liquid. The word
"element" as used in this application means an element, usually an
elongated element, of any transverse cross-sectional shape. The
word "element" includes within its meaning cylindrical elements
which are hollow or solid such as tubes or rods. Cylindrical
elements have advantages in the treatment of fluids. The word
"cylindrical" is used here in its broad sense. A cylinder is
defined as a three-dimensional surface formed by tracing a plane
continuous closed curve with a line perpendicular to the plane of
the curve.
Staggered tubular arrays have been used for various industrial
purposes. For example, in cross-flow heat exchangers, fluid to be
heated or cooled flows perpendicularly to a staggered-tube array in
which the tubes are arranged in a triangular pitch or
rotated-square array. Typical values of tube pitch for common
heat-exchanger tube layouts are given on pages 10-26 of Chapter 10,
"Thermal Design of Heat-Transfer Equipment", in Perry's Chemical
Engineers' Handbook, 5th Edition, McGraw-Hill (New York). Similar
staggered tube or rod arrays have also been employed for gas
cleaning and mass transfer.
Gas demisting and particulate-removal applications of arrays of
cylindrical impingement rods of elliptical and streamlined
transverse cross-section are described in British Pat. Nos.,
Talboys 562,593, General Dynamics 897,417 and Lerner 1,594,524.
British Pat. No. 644,391 describes a particulate filter comprising
a staggered array of elements of streamlined transverse
cross-sectional shape fabricated from perforated sheet or gauze.
Talboys discloses an array of spaced parallel tubes for removing
dust and impurities from air in which the tubes are perforated or
foraminous and are covered with sleeves of woven cloth which are
kept wetted with oil. These tubes are of cylindrical or elliptical
transverse cross-section. General Dynamics discloses a
mist-eliminator array of impingement rods of streamlined transverse
cross-section covered with a water-absorbant material. Lerner
describes the application of a staggered array of fibrous cylinders
for gas absorption, mist and particulate removal. Andersen, in U.S.
Pat. No. 3,447,287, discloses an incinerator scrubber containing a
horizontal array of staggered rows of porous refractory cylindrical
impingement piers oriented perpendicularly to the path of gas flow.
Ekman, in U.S. Pat. No. 3,795,486, describes a wet scrubber
comprising a horizontal array of rod-like elements for absorbing
sulfur oxides. Staggered arrays of other types are shown in Heenan
& Froude, French Pat. No. 531,515. The instant invention
concerns itself with, and is applicable to, the arrays disclosed in
the above-described patents and literature which are typical of the
prior art.
In most, if not all, of the above-described applications of
staggered arrays of elements, the elements in the rows are
spatially separated from each other and from the elements of the
adjacent rows so that open flow space completely surrounds each
element. A disadvantage of the prior-art staggered arrays is that
they are not fully effective or efficient in the treatment or
processing of the fluids which are passed through them. Heretofore,
the cause of this deficiency in effectiveness and efficiency has
not been realized or known. Staggered element arrays are usually so
arranged that from the fluid approach point, or direction
perpendicular to the array, the fluid "sees" nothing but element
surface, i.e., there is no open, unobstructed flow area on a
projected view. The conventional wisdom on which such an
arrangement is based is that all fluid will impinge on, flow
around, and contact each element. While this is the desired and
desirable objective, it has not been realized in the prior-art open
array arrangement of elements.
It is an object of this invention to overcome the disadvantages of
the above-described prior art and to provide treatment or
processing apparatus for fluids, including a staggered array of
elements, in whose use the treatment shall be effectively and
efficiently carried out.
SUMMARY OF THE INVENTION
This invention arises from the discovery that in prior-art arrays,
there are open by-pass paths for the fluids to be treated between
the elements. These by-pass paths are along the diagonals of the
array, i.e., they are at an acute angle to the downstream direction
of fluid flow. These by-pass paths offer minimum flow resistance to
the fluids as compared to the alternate paths in which the fluid is
incident on the elements and a significant portion of the total
fluid bypasses through these open diagonal channels. In Heenan
& Froude, the by-pass paths are blocked by elements such as are
shown in its FIG. 6. However, this is achieved by closely spacing
channel-shaped elements in high-flow resistance relationship. Not
only is any potential by-pass flow blocked, but the flow as a whole
is blocked so that the pressure drop in a fluid passing through the
array is high, imposing an economic penalty which is not
acceptable. This is particularly true for fluids flowing at a high
velocity, e.g., gases at 500 to 2,000 feet/minute, so that high
flow-resistance apparatus such as those disclosed by Heenan &
Froude, at best, are economically limited to applications where the
velocities are in the low ranges, substantially below 500 feet per
minute for gases.
In accordance with this invention, the by-pass flow is suppressed
by partitions extending from or between the elements of a staggered
array for treating or processing a fluid. .[.As has been stated,.].
.Iadd.To .Iaddend.achieve the desired low resistance, each
partition is positioned so that its surfaces are generally parallel
to the direction of flow. These surfaces may be planar or
curvilinear, for example, corrugated; planar surfaces are
preferred. Each partition is also thin compared to the spacing
between the outer surfaces of the elements between which the
partition passes. Typically, the partition thickness is between 5
and 25% of this spacing and is preferably 5 to 15%. The partitions
extend substantially along the whole length of the elements. A
partition may extend from each of the elements of the array or from
a sufficient number of elements of the array to reduce the by-pass
flow sufficiently to render the array effective and efficient in
processing or treating the fluid. The reference in a claim of this
application to the presence of partitions between pairs of elements
of a straggered array means that the partitions need not be present
between all pairs of elements, but only between a sufficient number
of pairs for effective treatment of the fluid. Each partition
usually bridges between two elements of alternate rows of the array
but where there are only two rows the partitions extend from the
elements of only one row. A row is defined as a line or an array of
elements generally perpendicular or transverse to the direction of
flow of the fluid. It is desirable that each partition should be
positioned so that the elements of the intervening row between
which it passes are symmetrically spaced, i.e., the distances
between the longitudinal center plane of a partition and the
centers of the elements between which it passes should be
substantially equal. This symmetry is desirable so that the minimum
flow areas in the direction of the flow on each side of the
partition are substantially equal. If these areas are unequal, the
greater area will conduct more fluid-flow and the processing of the
fluid is not uniform. Where there are more than two rows, each
partition extends between elements in alternate rows. Each
partition need not be joined, for example by welding, to the
elements which it bridges; however, it may be joined to one or both
of these elements, but the partitions must be so arranged, or so
positionally or spatially related to the elements as to suppress
diagonal flow effectively. For example, in the case of heat
transfer, it is desirable that the partition be joined to both
elements which it bridges. Each partition may also be independently
supported from the structure which houses or supports the array.
The heart of this invention is in the provision of partitions to
suppress the diagonal flow effectively and any arrangement of
partitions which follows the teachings of this invention to
suppress diagonal flow is within the scope of equivalents of this
invention.
While the elements in the rows of the array may have transverse
cross-sectional shapes of different form, for example, such as are
disclosed in Heenan & Froude, staggered arrays with cylindrical
elements have the marked advantage that they impose lower
fluid-flow pressure drop. In addition, arrays with cylindrical
elements are more frequently encountered than arrays of other
types. In industrial operations such as heat transfer, the elements
of the arrays are inherently cylindrical tubes.
A surprising phenomenon, with potential for great utility, has been
discovered in conducting research with apparatus including an array
of rows of perforated horizontal tubes in which partitions are
interposed in accordance with this invention. The word "perforated"
is used here and throughout this application in its general meaning
to including tubes with perforations of any type. The tubes may be
composed of foraminous material such as wire mesh, or they may be
composed of other appropriate porous material.Iadd.; .Iaddend..[.a
semi-colon.]. they .[.maybe.]. .Iadd.may be .Iaddend.perforated
tubes composed of metal or plastic. It has been found that when gas
and liquid are conducted through such an array with the gas flowing
vertically upwardly, at at least a predetermined velocity, a
dynamically stable pool of the liquid is formed within each tube.
It has been discovered that the gas bubbles through this pool.
Based on this phenomenon, apparatus and a method have been created
in accordance with this invention for mass transfer between a gas
and a liquid.
The liquid accumulates predominantly within the perforated tubes of
an array according to this invention because of the pressure
differential induced across the tubes by the gas upflow through the
array. In addition, liquid is retained within the tubes because of
direct frictional drag exerted by the gas on the liquid and
momentum exchange between the gas and the liquid Earlier work on
the bubbler is described in the parent of this application and
carried over into this application. With the apparatus with which
this earlier work was carried out, it was observed that at 790 feet
per minute gas velocity, liquid partially filled the perforated
tubes and light, intermittent bubbling began in the top tubes and
extended rapidly to the other tubes. Above 1,450 f.p.m., the
bubbling action in the tubes decreased and entrainment of spray
became heavy. These observations define the operating range of gas
velocities which yield dynamically stable bubbling contact within
the perforated tubes for an air-water system, as between 790 f.p.m.
and 1,450 f.p.m. For other gases and liquids, the range would be
different.
It is important to note that the gas velocities, 790 f.p.m. to
1,450 f.p.m. are "superficial" gas velocities, i.e., velocities
based on the empty, transverse, free cross-sectional area of the
array or module with which the work was carried out and through
which the air and water flow took place. It is also important to
note that, for Example III, described in the parent application and
in this application, the bubbler module had a transverse
cross-section of 9 inches by 11 inches and that the column through
which the fluids passed into and out of the array had the same
dimensions and the array occupied the full cross-sectional area of
the channel. The heavy liquid entrainment in the upwardly flowing
gas, observed at the high gas velocities, was considered a limiting
factor. This entrainment was confined to the 9-inch by 11-inch
channel and had no escape route other than up or down.
In the early work, the water entrainment was permitted to reflux
countercurrent to air flow in the same confined transverse
cross-sectional area through which the air flowed upwardly. At high
velocities the liquid accumulated on the walls of the channel at so
high a rate that it could not drain off as rapidly as it
accumulated and flooding occurred. In accordance with an aspect of
this invention, the liquid carry-over is provided with escape
routes out of the gas flow path which induces the carry-over. This
is accomplished by providing a containing shell having a transverse
cross-sectional area greater than the transverse cross-sectional
area of the modular bubbler array. The modular bubbler array, in
which the bubbling takes place predominantly within the tubes,
according to this aspect of the invention, is essentially a walled
housing open at both ends, supported from (or appended to) a
horizontal plate or tray of substantially greater transverse area
than the housing of the array. In its practice, this aspect of the
invention may be applied to an individual array or module or to a
tower in which modules are arranged serially in a generally
vertical array and the mass interchange takes place in successive
modules.
In the practice of this aspect of the invention, the flow area
above the array or module is greater than the flow area within the
module. The velocity of the gas expanding into this upper area
decreases, causing liquid to drop out of the gas stream.
Additionally, the radial vector of the gas expansion direction
conveys the liquid carry-over radially outwardly. The liquid which
drops out of the conveying gas stream is collected on the
horizontal surface of the sheet external to the confined array,
and, in a tower in which the modules are vertically arranged in
series, is conducted by downcomers to a lower module, or in case a
single module or the lowermost module of a series in a tower, to a
storage sump. This aspect of the invention lends itself readily to
an efficient multi-stage liquid-gas contactor. A significant
advantage of this aspect of the invention is a gas velocity range
which is several times that allowed in conventional sieve or
bubble-cap tray columns or towers.
In accordance with this aspect of the invention, there is provided,
in addition to the module described above of an array of perforated
tubes with partitions for suppressing diagonal flow, a tower
including a vertical array or stack of such modules. The transverse
cross-sectional dimension of the tower is substantially greater
than the dimensions of the transverse cross-section of the
container of the array. The tower has a lower inlet and an upper
outlet for gas and within the tower there may be liquid spray
nozzles. The liquid spray nozzles may be above all or some of the
modules to spray the liquid countercurrent to the gas or below all
or some modules to spray the liquid cocurrent with the gas or both
above and below all or some of the modules.
The spray nozzles between bubbler modules of a series vertical
modular bubbler array may be omitted and the liquid may be supplied
by a spray above the upper contact module. In accordance with a
further aspect of this invention, the spray nozzles are omitted
entirely and the liquid for liquid-gas interchange is fed into a
series vertical array of modular bubblers in a stream above the
upper bubbler. The liquid flows downwardly in a stream. As it
encounters each modular bubbler in the vertical series array in its
turn, the gas bubbles through the liquid predominantly within the
tubes of the bubbler.
The arrays in accordance with this invention have an advantage in
addition to the advantage that they suppress by-pass flow. The
eddies formed in the wake of the fluid flowing between each element
and the partitions on each side of it, enhance the rate for mass
transfer to and from the wetted surfaces of the partitions and the
elements. The enhancement is partially achieved by a modified
venturi effect which occurs in the fluid as it passes between the
partitions and adjacent elements as will now be described.
In addition to the discover of the bubbling-flow liquid-gas
contactor in which the liquid bubbles predominantly within the
tubes, it has also been discovered that the array of this invention
has unique properties when used as a modified venturi scrubber for
particulate removal. In this aspect of the invention, the
cylindrical tubes of the array may be either perforated or solid,
and the preferred fluid flow is concurrent liquid and gas flow. The
gas rate may vary in the range of 1000 to 20,000 feet per minute,
and the liquid/gas ratio range is the same as those employed in
more conventional venturis. In both laboratory and field test work,
it has surprisingly been discovered that the efficiency of a
venturi particulate scrubber employing the array of this invention
as the venturi throat section, as described in Example II, below,
yields greater particulate removal efficiencies than a conventional
venturi operating at equal gas pressure drop, i.e., equal energy
consumptions. As far as is known, this appears to be the first
instance of a modification or "obstruction" of venturi throat flow
that offers a positive efficiency/energy consumption benefit ratio
as compared to the conventional unobstructed simple venturi
throat.
Another advantage of the use of the array of this invention as a
venturi contactor is that the venturi flow constrictions are
contained within the array itself. That is, it is not necessary to
have a converging approach section or diverging exhaust section,
which are difficult and expensive to fabricate. By distributing the
gas flow over multiple parallel flow acceleration paths and causing
a number of repeated venturi flow accelerations and deccelerations
in the course of a single traverse, the array of this invention
achieves at low energy inputs the particulate-removal efficiencies
of conventional high-energy venturis.
In other aspects of this invention which do not require bubble
contacting in the interior of the tubular elements, the elements of
the modules may be solid or tubular with the external surface
covered with filamentary materials such as cloth. This form of the
elements has advantages in applications such as mist elmination or
particulate removal, in that inertial removal mechanisms are
combined with filtration in effecting particle or drop removal in
flow through the array. Solid tubular elements may also be used in
applications involving scaling or plugging deposits which would
close off foraminous or filamentary elements. In general, the
apparatus is effective for a wide range of fluid velocities of from
500 to 2500 feet per minute for conventional particulate and mist
removal and/or mass transfer applications, and from 1000 to 20,000
feet per minute in the modified venturi aspect for the removal of
aerosols, fume and very fine particulates.
BRIEF DESCRIPTION OF THE DRAWINGS
For a better understanding of this invention, both as to its
organization and as to its method of operation, together with
additional objects and advantages thereof, reference is made to the
following description, taken in connection with the accompanying
drawings, in which:
FIG. 1 is a plan view of a staggered array of fluid-treating or
processing apparatus showing an embodiment of this invention;
FIG. 2 is a plan view of a staggered array of fuid-treating
apparatus showing a modification of this invention;
FIG. 3 is a diagrammatic fragmental view showing the manner in
which the rate of mass transfer is increased in the practice of
this invention;
FIG. 4 is a graph which, in connection with FIG. 3, aids in the
understanding of the manner in which the rate of mass transfer is
increased in the practice of this invention;
FIG. 5 is a diagrammatic .Iadd.plan .Iaddend.view .Iadd.as seen
from vertically above .Iaddend.showing test apparatus used in
investigating the treatment of fluids in the practice of this
invention;
FIG. 6 is a diagrammatic view showing apparatus for removing
fly-ash from a liquid in the practice of this invention;
FIG. 7 is a fragmentary diagrammatic view in section taken along
line VII--VII of FIG. 6 showing enlarged the array 195 which serves
to produce the capture of particulate from the air;
FIG. 8 is a view in side elevation of a perforated-tube
bubbler-scrubber in accordance with this invention;
FIG. 9 is a view in section taken along line IX--IX of FIG. 8;
FIG. 10 is a plan view of a dynamic bubbler module in accordance
with an aspect of this invention;
FIG. 11 is a view in side elevation taken in the direction XI--XI
of FIG. 10;
FIG. 12 is a view in side elevation, partly diagrammatic showing a
tower for mass transfer in accordance with an aspect of this
invention; and
FIG. 13 is a fragmental isometric view showing how the parts of the
tower of FIG. 12 are interconnected with each module.
The dimensions shown in, or described in connection with, FIGS. 1,
2, 5, .[.6,.]. .Iadd.7, .Iaddend.10, 11 and 12 are included only
for the purpose of aiding those skilled in the art in practicing
this invention and not with any intention of in any way limiting
this invention.
DETAILED DESCRIPTION OF EMBODIMENTS
The apparatus shown in FIG. 1 includes a staggered array 21 of
cylinders 23. Typically, each cylinder 23 includes a shell 24
supporting a cylindrical-layer 26 of knitted mesh typically of
polypropylene or stainless steel. Typically, the length of the
cylinders 23 may be between 1/2-foot and 5-feet. The array 21
includes a plurality of rows 25 and 27 of the cylinders 23, the
rows 25 alternating with the rows 27. The cylinders 23 of rows 25
are staggered with respect to the cylinders of the rows 27. The
cylinders 23 are generally uniformly spaced or distributed over the
array, i.e., the spacing between the centers of adjacent cylinders
23 in each row 25 and 27 are substantially equal and the spacings
between the lines through the centers of the cylinders of adjacent
rows 25 and 27 are substantially the same and the lines between the
centers of cylinders in alternate rows 25 and 27 substantially
bisect the lines between the centers of the adjacent cylinders 23
of the intervening rows 27 or 25. Partitions 29 extend or bridge
between the cylinders 23 of alternate rows 25--25 and 27--27.
Typically, the partitions 29 are composed of thin sheets of metal
or plastic, typically polypropylene. The partitions 29 extend
substantially along the whole length or heighth of the cylinders
23. Each partition 29 has a thickness which is small compared to
the minimum distance or spacing between the outer surfaces of the
pair of cylinders of the row intervening between the alternate rows
whose cylinders the partition bridges. Typically, the thickness of
the partition is about 5 to 25% and preferably 5 to 15% of the
spacing. The spacing which is compared to the thickness is the
minimum spacing S of the surfaces of the cylinders 23 which face
the partition.
The array 21 is mounted in a duct partially of plastic or metal.
The duct is of generally rectangular transverse cross-section and
has side walls 31 and top and bottom walls (not shown).
Semi-cylinders 33 of rows 25 abut the side walls 31. The side walls
serve as partitions between the semi-cylinders 33.
The fluid being processed flows through the duct and the array 21
in the direction of the arrow 35 generally perpendicularly to the
rows 25 and 27. With the cylinders 23 in the rows 25 and 27 spaced
as shown in FIG. 1, the fluid sees a solid wall formed of the
cylindrical surfaces. Typically, the fluid may be air or other gas
containing a contaminant which it is desired to remove. The
contaminant may be a hazardous gas or particulate matter.
Typically, liquid, usually water, is sprayed into the gas by
appropriately positioned spray nozzles 37.
The partitions 29 are interposed in the diagonal bypass paths 39
which exist between adjacent cylinders 23 along the successive
rows; e.g., between cylinders 23a-23b of rows 25 and 23c-.[.23d.].
.Iadd.23h .Iaddend.of rows 27. The partitions suppress by-pass
flow. The partitions have plane surfaces generally parallel to the
direction 35. It is desirable that each partition 29 be generally
centered along the line between the centers of the cylinders 23
between which it extends. Under such circumstances, the adjacent
cylinders 23 between which the partition passes are positioned
symmetrically with respect to each partition. For example,
cylinders .[.23c.]. .Iadd.23a .Iaddend.and 23d are positioned
symmetrically with respect to partition 29a.
The contaminated gas flows through and around the cylinders 23 as
shown by the arrows 31, 43 and 45. Because of the symmetric spatial
relationship of the partitions 29 and the cylinders 23, the streams
which emerge from and pass around an upstream cylinder 23e are
merged into common streams 47 and 49 flowing generally
symmetrically with respect to the baffle 29b downstream from
cylinder 23e. These streams 47 and 49 pass through and around the
cylinder 23f downstream from cylinder 23e. This cylinder 23f being
the most downstream cylinder of the array 21, the streams 53 and 55
merge into a unitary stream 59. The cylinders 23 and the partitions
29 effectuate the capture of the contaminants by the liquid from
the gas and drain it together with captured liquid into a container
(not shown). Because of the generally uniform distribution and the
generally symmetric positioning, with respect to the partitions, of
the cylinder 23, the processing of the fluid is uniform throughout
the extent of the array perpendicular to the direction 35.
FIG. 2 shows an array 61 including two rows 63 and 65 of hollow
cylindrical members 67 and 69. The cylindrical members 67 and 69
are typically formed of perforated metal or plastic tubing. The
array 61 is mounted in a duct of metal or plastic. In one row 63,
the members include a cylinder 67 flanked on each side by
semi-cylinders 69 which abut the side walls 71 of the duct. The
other row 65 includes the cylinders 67. Typically, the cylinders 67
and 69 are about 1 to 6 feet in length. The cylinders 67 in the row
65 are staggered with respect to the cylinders 67 and 69. A
partition 73 extends from cylinder 67 of row 63 between cylinders
67 of row 65. Typically the partition 73 is composed of metal or
plastic. The side walls 71 serve as partitions for the
semi-cylinders 69. The partitions 73 and side walls 71 extend along
the length of the members 67 and 69. The uniform spatial
distribution of the members 67 and 69 and the symmetry of the
cylinders 67 with respect to partition 73, described in connection
with FIG. 1, is present in the array of FIG. 2. Fluid to be treated
flows into the duct and the array 61 in the direction of the arrows
75 perpendicular to the rows 63 and 65.
In addition to improved effectiveness and efficiency by suppression
of diagonal by-pass flow of the processed fluid, this invention
yields unexpected and surprising benefits. In a study of the effect
of single stationary objects placed in the fluid stream on mass
transfer rates to the walls of a coaxial cylindrical tube,
Koncar-Kjurdjevic and Dudukovic, American Institute of Chemical
Engineers Journal, Vol. 23, p. 125 (1977) and ibid, Vol. 25, pp.
895-899 (1979), found that the wake of the stationary object
(sphere or concentric disk) produced two maxima in mass transfer,
as measured by the Sherwood number, Sh. ##EQU1## where k=mass
transfer coefficient,
d=hydraulic radius of flow channel, and
D=diffusion coefficient.
The Sherwood number is a measure of the mass transfer to the
surface from the fluid or from the surface to the fluid. It was
found that the first local maximum resulted from two effects: the
narrowing of the effective cross-section available for flow and
velocity component perpendicular to the wall which is imparted to
the fluid as it flows through the constriction. The second local
maximum was the result of wake formation and its interaction with
the boundary layer of fluid at the wall. Owing to the instability
and separation of the wake behind the object causing the initial
flow constriction, the intensity of turbulent pulsations increases
in the wake causing fluid elements to penetrate into the diffusion
sublayer on the wall, which leads to a rapid increase of the local
Sherwood number.
These investigators, Koncar-Djurdjevic et al., found that the ratio
of the downstream Sherwood number with the sphere or disk
obstruction in the coaxial tube to the Sherwood number in the empty
tube was, on average, greater than 1.0, and in most cases, more
than 2.0. The wake effect therefore doubles normal transfer rates
to (and from) the walls. Heat, mass and momentum transfer in the
turbulent fluid flow regime are all governed by a common mechanism:
the motion of turbulent eddies. To the extent that turbulent fluid
eddy motion can be mathematically described, either by theoretical
or experimental means, heat and mass transfer coefficients and
frictional (momentum) losses may be derived. These fundamental
relationships comprise the "analogy" between heat, mass and
momentum transfer. A full review of the theoretical and
experimental development of the analogy between heat, mass and
momentum transfer is given by W. S. Norman, "Absorption,
Distillation and Cooling Towers", John Wiley & Sons, New York,
1961, pp. 35-41. Because they are controlled by a common mechanism
of eddy transfer in turbulent fluid flow, heat and mass transfer
rate coefficients may be calculated, one from the other. The
relationship is usually stated in terms of the dimensionless
groups, the Sherwood number, Sh, for mass transfer and the Stanton
number, St, for heat transfer.
A doubling of the Sherwood number by an eddy-inducing device would
also result in a similar increment in the Stanton number for heat
transfer. Thus, the array of this invention which incorporates the
wake effect, enhances transfer rates for heat and mass by factors
greater than 1.0, that is, for more than the contact area added by
the bridge walls. Thus, heat exchanger arrays, partitioned
according to this invention, will have, on average, twice the
transfer coefficient of a unit having the same area entirely in
straight wall surface with parallel fluid flow.
The above-described improvements in mass transfer is illustrated in
FIGS. 3 and 4. FIG. 3 shows an assembly including a tube or disk
151 positioned between walls 153 and 155. Fluid 157 is conducted
through this assembly. Between the member 151 and the walls, the
fluid path is constricted. The fluid 157 is squeezed into the
constricted region 159 and its velocity is increased. After the
fluid leaves the constricted regions 159, its velocity is reduced
and eddies 161 form in its wake. The eddies 161 have a component of
velocity perpendicular to the walls 153 and 155 and this component
causes penetration of the layers 163 of fluid along the walls
effecting mass or heat transfer.
In FIG. 4, the ratio, Sh/Sh.sub.o, is plotted vertically as a
function of the distance from the entrance to the assembly which is
plotted horizontally. Sh is the Sherwood number of a system
including the disk 151 and the walls 153 and 155 and Sh.sub.o is
the Sherwood number for a system which does not include the disk
51. The resulting curve shows a maximum, corresponding to the
squeeze effect and a second, higher maximum corresponding to the
wake effect as labeled.
The flow through the baffled array of this invention is not
identical to the case of flow through a tube past a coaxial sphere
or disk, but it is a very close analog. In plan cross-section,
i.e., cross-section parallel to the plan view, the array of this
invention is comprised of a multiple set of parallel flow passages,
[analogous to the passages between 151 and 153 and 155 and 151
(FIG. 3)] each having the same plan section as the coaxial sphere
in a tube studied by Koncar-Kjurdjevic and Dudukovic. The wake
effect and the walled benefits thereof are multiplied both
laterally by the number of walled passages and in the fluid flow
direction by the number of transverse "target" elements.
In the array of this invention, the bridging parallel partitions
(29 FIG. 1 etc.) define the walls confining the flow of fluid
impinging on the transverse "target" cylinders. While for both the
conventional open (unpartitioned) array and the array of this
invention, converging fluid flow is obtained as the fluid flows
past the first row of transverse cylinders, in the open array the
wake energy is dissipated as turbulent frictional losses. With the
bridging partitions of this invention confining the flow through a
set of two, three or more rows, (two rows 151--153, 151-155 and the
third row outwardly at each cylinder) the wake energy is controlled
so that eddies normal to the wall are obtained for each successive
wake generation by a transverse element or element section. This
raises the average transfer coefficient beyond that of the single
obstruction because of the multiple, in series, repeated wake
generations.
The array of this invention also serves as a fluid mixer. The
nature of the array of this invention is such that the fluid stream
is repeatedly split and remixed with fluid flowing in alternate
flow streams as it passes in the general flow direction through the
array. Thus, fluid entering between two cylinders in the first row
is split into two streams by the second row cylinders and the
respective first-third row partitions (29 FIG. 1 etc.). However, as
fluid leaves the third row of cylinders, a different set of
partition walls become effective as flow confining walls, and the
two separated streams mix with two other adjacent streams. Not only
is this effective for periodic mixing and redistribution in heat
transfer as fluid flows through the array, but the array itself
serves as an excellent static mixing device. Different gases, for
example, ethylene oxide and air, or different liquids, for example,
paint and solvent, may be injected upstream of the array of
cylinders and thoroughly mixed as they pass through the array. In
this case the fluids, gases or liquids are injected into the array
21 of FIG. 1 in the direction of the arrows 35. Usually one gas or
liquid injected initially and the other or others are injected into
the stream of the one injected initially. Where none of the liquids
is water, the spray 37 may be omitted. The fluids may also be
injected simultaneously in separate streams.
EXAMPLE I
The fluid treatment of Example I was carried out with the staggered
array 162 shown in FIG. 5. This array includes four rows 164, 165,
167 and 169 of vertical plastic pipe 171 and 173 staggered in a
triangular pitch. Each pipe 171 and 173 has an outside diameter of
1 5/16 inches. The spacing between the centers of the pipes in
alternate rows 164 and 167 and 165 and 169 is 33/4 inches. The
length of the pipes is 191/4 inches. The distance between the
centers of the pipes along the row is 21/8 inches. There were 51/2
pipes per row. The pipes 173 of the third and fourth rows 167 and
169 which were to be positioned downstream with respect to the flow
of fluid were wrapped with a single layer 175 of thin fiberglass
cloth (Hollingsworth and Vose Company, "Fibernetics" .TM. "Hovomat"
.TM.) to facilitate liquid filming in accordance with the teaching
of British patent, General Dynamics No. 897,417.
The array 162 was used for demisting air flowing through a
horizontal duct 177 having a 12-inch by 12-inch flow
cross-sectional area. Air was blown through the test duct in the
direction of the arrow 179 by means of a No. 15 Cincinnati
centrifugal forced-draft blower (not shown) equipped with a 7.5
horsepower motor. The duct 177 and the array 162 were located
approximately 6 feet downstream of the blower. Mist was generated
by means of a Beta Fog Nozzle Company Type TF6FCN spray nozzle 181
located 11 inches upstream from the test assembly. The spray nozzle
181 was operated at 100 psig to generate a well-atomized spray. At
100 psig, the nozzle flow rate was 2.2 gallons per minute, and the
nozzle was pointed upstream into the air flow so that only the
finer mist particles carried back to the array 162 which served as
mist eliminator.
The array 162 was inserted in the duct 177 with the pipes 171 and
173 in the vertical position, and perpendicular to the air flow
direction 179. The piping array was tested for pressure drop and
mist elimination at varying air velocities. Air velocity was
measured by means of pitot tube 183 and traverses and pressure drop
across the test module by means of an inclined manometer 185. Mist
penetration was visually observed by means of the Tyndall effect,
using a light beam 187 normal to exit gas flow with the room
darkened.
With the test array sans the partitions as taught by this
invention, a fine mist penetration was immediately observed by
Tyndall effect at the lowest measurable air velocity of 423
feet/minute. This fine mist loading visibly and continuously
increased as the air velocity was increased to 1042 feet/minute.
Large-drop penetration of 0.01-0.1-inch diameter size drops was not
observed until the 700-800 feet/minute range of gas velocity. This
large-drop loading also increased with air velocity increase from
750 to 1042 feet/minute. The array 162 therefore was ineffective in
removing fine mist at all measured velocities down to 423
feet/minute, and was ineffective for large-drop mist removal above
about 750 feet/minute.
The array 162 .Iadd.without the partitions 189 .Iaddend.was then
modified to accord with the teachings of this invention.
Polypropylene partitions 189, 23/8 inches wide and 1/8-inch thick,
were mounted between alternate pipes 171 and 173. The partitions
189 were centered on the center lines between the pipes 171 and 173
and extended along the length of the pipes. The array in accordance
with this invention was then positioned in the duct 177 and
operated as a mist eliminator at air velocities between 455 and
1140 feet/minute. Tyndall beam observation of the exhaust air
showed no trace of visible fine mist penetration over the full
range of velocities tested. Larger droplet regeneration did not
begin until an air velocity of 1042 feet/minute and did not become
significant until 1140 feet/minute, at which point the test was
terminated.
The success of the partitioned array in preventing fine mist
droplet penetration shown by the conventional unpartitioned array
clearly demonstrates the superiority of the partition array of this
invention. The elimination of diagonal channel gas bypassing by the
partitions in accordance with this invention not only prevents fine
mist penetration, but also elevates the air velocity at which large
liquid drops first carry over. The pressure drop for the
"partitioned" array was 1.35-inches water column at 1042
feet/minute air flow, as against 0.75-inches water column at the
same air velocity for the unpartitioned array. Because gas pressure
drop in the turbulent-flow regime is approximately proportional to
the square of gas velocity, the ratio of pressure drops indicates
that approximately 34 percent of the gas flow in the unpartitioned
array bypasses along open diagonals at 1042 feet/minute. The
incremental pressure drop obtained for the array of this invention
as compared to an open unbaffled array results both from the
elimination of the by-pass flow and the increase in wake turbulence
intensity behind the transverse elements. These two effects are
interdependent, inasmuch as blocking diagonal by-pass flow would
increase the normal linear gas velocity approaching the second and
consecutive rows of transverse wake-generating elements, thus
causing increased wake turbulence eddying intensity. The influence
of wake eddy turbulence on augmenting both drop agglomeration and
impingement on the wall can be seen in the results from the above
tests. It should be noted that because the liquid mist load on the
test cell is a function of linear gas velocity, the large-drop
reentrainment point corresponds to an abnormally high liquid load
and is a liquid drainage rate limit, not an inherent efficiency
limitation of the device. Because the liquid does not drain down
the wall of the baffles 189 at the rate that it is deposited on the
baffles, there is a surplus of liquid in the lower areas of the
baffles. This liquid is reentrained by the gas and produces the
drops. The true mist removal effective velocity limit of the
apparatus of this invention is therefore greater than 1042
feet/minute.
EXAMPLE II
In this example, apparatus in accordance with this invention was
used for fly-ash removal from air by wet scrubbing. In this case
the array according to this invention is used as a modified venturi
scrubber. The apparatus 191 for carrying out this treatment is
shown in FIGS. 6 and 7. This apparatus 191 includes a vertical duct
193 having a 67/8-inch square flow cross-sectional area. A
staggered triangular array 195 (FIG. 7) is interposed in this duct
with a two-feet long, clear duct-run section above and below the
array which constitutes a modified venturi. The top of the vertical
square duct runs transitions to a 13-inch square .[.inch.]. air
inlet section 196.
This array 195 (FIG. 7) includes 1/2-inch diameter schedule 40
steel pipe 197 positioned horizontally in the array. The length of
the pipe is slightly less than 67/8 inches. The first and third row
upstream-to-downstream includes five pipes in each row; the second
and fourth rows upstream-to-downstream includes a half pipe at each
end and four pipes in between. The center-to-center pitch
perpendicular to the axis of the duct, i.e., to the direction of
fluid flow, is 13/8 inches and the center-to-center pitch generally
parallel to the axis of the duct is 11/8 inches. The array 195 is
provided with partitions 202 between the pipes of the alternate
rows. The partitions are of 16 guage steel and are spot welded to
the first and third and second and fourth rows of pipe centers.
Fly-ash supplied from hopper 199 was introduced into the air inlet
transition 196 by means of a variable-speed screw feeder 201 at a
controlled rate. At the start of the operation, a quantity of
fly-ash was deposited in the hopper 199. The fly-ash rate was
determined by weighing the fly-ash hopper containing fly-ash and
feeder assembly 199-201 before and after a timed interval. The
difference is the weight of fly-ash derived from the hopper which
was fed into the apparatus. Water was introduced above the baffle
array unit 195 through an impingement-jet spray nozzle 203 at a
rate metered by means of a Brooks rotameter. Water was supplied by
means of a Dayton centrifugal pump 205, recycling water from a
slurry collection tank 207. The slurry collection tank was the
bottom portion of a 24-inch diameter cyclone separator 209 placed
downstream of the vertical test section and connected to receive
the slurry from duct 193. The clean air exhaust from the cyclone
separator 209 flowed through a 12-inch diameter duct .Iadd.211
.Iaddend.to the suction side of a Size 15 Cincinnati blower 213,
equipped with a 7.5 HP, 3475 RPM motor. Filters 217 were interposed
in the liquid recycle circuit. Air flow was controlled by means of
a slide damper 215 on the fan suction. The blower 213 produced
negative pressure in the duct so that air was induced to flow into
the duct 193 vertically downwardly.
To determine the effectiveness of the modified venturi apparatus
according to this invention in removing particulate from gas, the
feeder 201 was set to feed fly-ash at a rate of 165.0 grams/minute
and the blower 213 was set to feed the air, at 4300 feet/minute
face velocity. Pressure drop across the array 195 was 7-inches
water column. Water was sprayed into the air stream above the array
at a rate of 7.6 gallons per minute. Pre-weighted filter cartridges
217 mounted on the recycle liquor circuit were used to filter out
the fly-ash captured by the liquid and collected in the cyclone
209. The liquid recycle lines and sump 207 were rinsed with fresh
water after the test, and the slurry filtered through the cartridge
filters. The cartridges were dried and weighed after each run. The
cartridge filters contained the fly-ash captured by the drops of
water from the air sucked through the duct 193. This air initially
contained the fly-ash. The total weight of fly-ash collected from
the liquor system was then compared with the difference in fly-ash
weight of the dry feeder and tank. Two consecutive runs made under
the same conditions gave an average weight recovery of 98.2%.
Inasmuch as the fly-ash samples used in these tests were collected
in an electrostatic precipitator at a Duquesne Light Company
coal-fired power plant in Pittsburgh, the fly-ash is representative
of that normally emitted by a coal-fired utility. The efficiency
level of 98.2% obtained in these tests for the removal of this ash
from the air is typical of performance of a venturi scrubber
operating at much higher pressure drop (and velocities) on fly-ash.
The energy efficiency of this invention for particulate removal is
thus seen to be uniquely high.
The scrubber of this aspect of the invention is essentially a
modified venturi scrubber. The high efficiency achieved by this
invention for particulate removal, may be explained as follows:
Water in the form of mist or spray is introduced upstream of the
array 195. The gas containing solid particulates and water droplets
is accelerated to a high velocity as it enters the constricted
areas 198 between the first row of transverse pipes 197. This is
essentially a modified venturi effect. The gas and the contained
fine particulate undergoes a rapid increase in velocity in the
constricted regions 200 between the pipes and the partitions 202,
but the water droplets, because of their larger mass, gain velocity
more slowly. Because of the difference in velocity, there are
collisions between the fly-ash particles and water droplets, with
the result that the fly-ash particles are captured by the water
droplets. This is not a complete process and (uncollided) water
drops and uncaptured particulates pass on downstream of the first
row of the array.
Immediately downstream of the first-row flow area constriction, the
flow area enlarges, the gas is decelerated, and the above-described
process is reversed, with the gas and contained particles losing
velocity more rapidly than the water droplets. In addition, a
portion of the gas flows in random turbulent eddies in the
downstream wake of the pipes 197, possessing high-velocity vector
components normal to the adjacent partition. The vector components
normal to the partition cause penetration through the fluid
boundary layers at the partition, enhancing impingement and fluid
transport normal to the partition. The second row of pipes 197
again forms a gas-accelerating constricted flow area, and the above
venturi process repeats itself.
Additional advantages in gas-liquid contacting may be secured by
use of transverse pipes 197 that are foraminous or perforated. For
example, the cylindrical mesh elements of Lerner disclosed in
British Pat. No. 1,594,524, or the porous ceramic elements of
Andersen, U.S. Pat. No. 3,447,287, or the perforated tubes of
British Pat. No. 644,391, may be employed as transverse pipes. Heat
addition to, or removal from, a fluid can also be accomplished in
the array of this invention in which the transverse elements 197
are tubular heating or cooling exhanger pipes.
EXAMPLE III
The efficacy of this invention for use in gas-liquid contacting was
investigated. The simplest form of array, a 2-row transverse
element array, such as is shown in FIG. 2, was employed. While it
is preferable in the arrays of this invention that the bridging
partitions run between alternate rows of transverse elements, in a
simple 2-row assembly, transverse elements cannot all be bridged to
downstream elements. In this case, alternate rows having two
transverse elements in line may be bridged, and front-row elements
without downstream partners may nevertheless be equipped with
partition walls, securing the same flow advantages for the
assembly. The apparatus 221 for carrying out this investigation is
shown in FIGS. 8 and 9. This apparatus includes upper and lower
vertical duct sections 223 and 225 of generally rectangular
transverse cross-section. The upper section 223 is provided with
flanges 227 and 229 at the top and bottom. The lower section 225 is
provided with a flang 231 at the top. A mist eliminator 233 is
mounted and secured to the flange 227. A staggered array 235 in
accordance with this invention is secured between the flanges 229
and 231. Spray nozzles 232 and 233 are mounted in the sections 223
and 225 above and below the array 235. The lower section 225 is
provided with a horizontal tee 241 through which air is injected by
a blower 243. The air is distributed by a buffle 245 in the lower
section 225 opposite the tee 241.
The array 235 includes two rows 247 and 249 of 27/8 inch O.D.
hollow, perforated, cylindrical elements 251 and 253 with centers
on a triangular pitch. The elements 251 and 253 in each row are
spaced 41/2 inches center-to-center. The elements and the partition
255 are about 1 foot long. The tubing of which the elements are
composed is commercial polypropylene rigid perforated tubing
supplied by Conwed Corporation, Product No. RN5640, with
1/4-inch.times.1/8-inch rectangular openings and an open area of
about 54%. Cylindrical elements 251 and 253 are located in a 9-inch
wide assembly, which necessitated half cylinder elements 253 at the
walls. The walls thus served as both containing outside walls as
well as parallel partitions, inasmuch as the walls passed through
the centerline of the outside semi-cylinders 253 in the first row.
The second row was comprised of two cylinders, and a 1/4-inch thick
partition 255 was inserted equidistant from these cylinders, and
splitting the first row center cylinder. The array 235 has a
cross-sectional rectangular flow area of 9 inches.times.11 inches;
the duct sections 223 and 225 have a flow area which is 12
inches.times.12 inches square.
Tests were conducted with air flowing vertically upwardly and
liquid spraying countercurrent downwardly from above the array or
cocurrent upwardly from below the array or in both directions. Air
was supplied through the tee 241 in the 12-inch square vertical
duct section 225 by a Cincinnati Size 15 centrifugal blower 243,
equipped with a 7.5 HP motor. Liquid drained from the section 225
to a small tank 252 and was recycled by means of an Oberdorfer
centrifugal pump 254 to one of the two spray nozzles 232 or 233
located 12 inches above and below the array 235. The top nozzle 232
was used for countercurrent liquid spray testing, and the bottom
233 for cocurrent liquid spray. Air flow was controlled by a slide
damper (not shown) on the suction side of the blower 243. Air
velocities were determined by pitot tube (not shown)
measurements.
The objective of the investigation was to determine if the
partition-buffle/sieve cylinder array 235 could be made to yield
dynamic liquid retention in the cylinders 251, 253 and if, and,
under what conditions, gas-bubbling would occur in the cylinders.
Stable bubbling within the cylinders 251, 253 was achieved over
linear gas velocities from 700 to 1450 feet/minute, for both
countercurrent and cocurrent liquid spray condition, with
equilibrium liquid drainage. For example, in one run, water spray
was introduced below the array 235, cocurrent with air flow at a
rate of 1.6 GPM. The air velocity through the module was varied in
steps from 540 feet/minute to 1800 feet/minute, while observing the
flow mechanisms and measuring pressure drop. At 540 feet/minute, no
bubbling was observed, and liquid holdup was minimal. At 720
feet/minute air velocity, liquid filled the tubes, and light,
intermittent bubbling began within the top cylinders 251. Bubbling
increased and remained vigorous and stable with all cylinders as
the air velocity was increased to 1294 feet/minute. At this point,
pressure drop across the array 235 was only 0.55 inches water
column, and equilibrium liquid drainage was being maintained. As
the air velocity was increased to 1450 feet/minute, the
differential pressure across the top row 247 of cylinders was
sufficient to initiate heavy entrainment, so that the liquid in the
cylinders began to spray upwardly and bubbling action in these
cylinders decreased. As gas velocity was increased above this
magnitude, the array 235 flooded, i.e., the liquid could no longer
drain against gas friction at the rate it was being introduced, and
the column of air and liquid went into violet discontinuous plug
flow of gas. This test was repeated for liquid flows of 2.7, 3.45,
4.2, 5.6, 6.0 and 6.45 GPM cocurrent. There were negligible effects
of liquid load variation on the gas velocity required to initiate
good bubbling action in the cylinders on the pressure drop, or on
the gas velocity flood point.
The tests were repeated over the same liquid flow rate range and
with the liquid countercurrent to gas flow from the spray nozzle
232 above the array 235. Although pressure drop was 0.25-0.5 inches
water column higher, the bubbling action as a function of gas flow
and flooding limits obtained with cocurrent flow were approximately
the same. A third set of runs made with both cocurrent and
countercurrent nozzles, equally splitting the liquid flow, gave
results similar to the separate countercurrent and cocurrent
liquid-gas flow condition.
The most impressive feature of the flow behavior was the
visually-observed vigorous and stable liquid-gas bubbling and
frothing action predominantly within the cylinder obtained at gas
flow velocities many times higher than those used in conventional
liquid-gas contacting devices such as bubble-cap trays or
sieve-plates. In the form tested, the appartus of this invention is
equivalent to a two-stage set of sieve trays rolled into
cylindrical form. The resulting sieve-tube partitioned array (with
the flow-parallel partitions) affords a uniquely new liquid-gas
contacting device capable of operating at vigorous and stable
contacting conditions, under very low pressure drops at ranges of
linear gas velocity which were previously regarded as unattainable.
Such apparatus has broad application to distillation and absorption
equipment of very compact and economic sizes.
In carrying out the work described above in connection with FIGS. 8
and 9, it was realized that the effectiveness of this apparatus is
limited by the liquid entrainment caused by the restricted flow of
the gas and liquid after these fluids leave the array. FIGS. 10
through 13 show apparatus for materially improving the mass
transfer by eliminating this deficiency.
FIGS. 10 and 11 show a bubbler tubular array unit or bubbler module
301 in accordance with this aspect of the invention. The module 301
includes a housing 303 of rectangular transverse cross-section open
at the top and bottom. As shown by the dimensions, housing 303 is
square. A plate or tray 305 extends from the top of the housing
301. Within the housing 303 a plurality of perforated tubes 307 are
mounted. The tubes are arrayed in rows 309 and 311. The tubes 307
in each row 309 and 311 are staggered with respect to the tubes in
adjacent rows 311 or 309. The housing 303 is generally vertical and
the tubes 307 are generally horizontal. As in the case with the
other modifications of this invention, partitions 313 extend
between the tubes 307 of alternate rows. The partitions 313 are
mounted generally vertically and are so positionally related to the
tubes 307 as to suppress diagonal flow through the array.
Specifically, in the module 301, the partitions 313 are joined, for
example, by welding or by an adhesive to the tubes 307 between
which they extend. The partitions 313 extend substantially along
the whole length of the tubes 307. The tubes 307 of the rows 309 or
311 intervening between the alternate rows 311 or 309 between which
each partition 313 passes are mounted generally symmetrical with
respect to the partition, i.e., each partition bisects the shortest
distance between the tubes between which it passes. The thickness
of each partition is small compared to this shortest distance and
it is shaped to minimize the resistance to the gas which flows
upwardly through the housing. A plurality of downcomers 315 are
suspended from the plate 305, each in communication with the top of
the plate through an opening 317. A hydraulic seal cup 319
suspended from the downcomer 315 is in communication with the lower
end of the downcomer 315. In the alternative the downcomer may be
sealed against the gas by an overflow weir segment on the tray
below.
As described, the elements of the array of the module 301 are
perforated tubes or wire mesh or of foraminous material. The
partitions 313 and the housing 303 are typically composed of
polypropylene.
FIG. 12 shows a tower 321 for mass transfer. The tower 321 includes
an outer circularly cylindrical shell composed of a plurality of
sections 323, 325, 327 and 328. The lower section 323 includes an
inlet fitting 329 for the gas to be treated and has a flange 331 at
the top. At the bottom there is a sump 332. The section 325 has
flanges 333 and 335 at the bottom and top and flange 327 has
flanges 337 and 339 at the bottom and top. Section 328 has a
section 341 at the bottom and is closed at the top. Section 328
also has an outlet fitting 343 for the treated gas.
A bubbler module 301 is suspended in the lower section 323. The
flange 305 of the module 301 is secured by bolts between the flange
331 of the section 323 and the lower flange 333 of the section 325
(FIG. 13). Gaskets (not shown) are interposed between each flange
331 and 333 and the flange 305. A nozzle 351 is suspended from the
box 303. The nozzle produces spray upwardly.
A bubbler module 301 is also suspended from section 325. This
module is suspended in the same way as the module in section 323.
The flange 305 of this module 301 is secured between the flange 335
of the section 325 and the flange 337 of the section 327 with
gaskets. A spray nozzle 353 is suspended from the box 303 of this
module. The spray 353 selectively produces sprays upwardly and/or
downwardly.
A mist eliminator 355 is suspended from section 327. This mist
eliminator 355 is similar to the module 301, except that the inside
transverse cross-section of its housing 357 is 10 inches square.
The reason for this increase in cross-section is to reduce the
velocity of the gas flow through the mist eliminator so that it
functions effectively to remove the mist. The mist eliminator has a
plate 361 at the top. The housing 357 is open ended and within the
housing a plurality of tubes 359 are arrayed in rows 362 and 363
with the tubes in alternate rows staggered. Partitions 365 extend
between alternate rows along the whole lengths of the tubes and
each is joined to the tubes 359 between which it extends. As in the
case of module 301 (FIGS. 10, 11), the partition 365 and the box
357 may be composed of polypropylene and the tubes 359 of
perforated polypropylene tubing such as "VEXAR". The mist
eliminator 355 is suspended by its plate 361 which is secured
between the upper flange 339 of section 327 and the flange 341 of
section 328. The mist eliminator 355 has no downcomers like the
downcomers 315 and its plate has no holes like the holes 317. A
spray nozzle 367 is suspended from the box 357. The spray nozzle
367 produces spray downwardly, but not upwardly.
Only two sections 323 and 325 containing bubbler modules 301 are
shown. In the practice of this invention, there may be any required
number of such sections.
In the use of the tower 321, the gas whose contaminants or other
content is to be separated is injected through fitting 329 and
flows upwardly through the sections 323, 325 and 327. Liquid spray
is introduced into the gas as required by the nozzles 351, 353 and
367. Depending upon the control of the nozzles, the spray may flow
cocurrent or countercurrent to the gas. The gas is supplied at high
enough velocity to produce stable dynamic pools in the tubes 307 of
the modules 301 and in the tubes 362 of the mist eliminator 355.
The gas bubbles through the liquid pools within the tubes of
modules 301 and mass interchange takes place. The treated gas which
leaves the lowermost module 301 expands into the space above the
plate 305 and its velocity is reduced. Liquid drops which have been
entrained in the array drop out on the plate 305 coalesce and the
resulting liquid runs into downcomers 315. The downcomers deposit
the liquid into cup 319. The overflow from the cups is deposited in
sump 332. The gas treated by bubbler module 301 in section 325 also
expands above the flange 305. The collected liquid entrainment from
plate 305 of the module in section 325 overflows cup 319. This
overflow is deposited partly into the array of the lowermost module
where it is reentrained by the upflowing gas. In part, this liquid
is deposited on plate 305 and runs out of downcomers 315 of the
lower-most module and then through cups 319 into sump 332.
The operation of a tower with perforated (VEXAR) tubes 307 in the
modules 301 in accordance with this invention was compared with the
operation of a tower with imperforate tubes. The operation of the
tower with the imperforate tubes was unsatisfactory, while the
performance of the tower with the perforate tubes was highly
satisfactory.
The internal hollow perforated tube bubbler embodiment of this
invention shown in FIG. 12 may be employed as a multi-stage
gas-liquid contacting column for mass-transfer applications, such
as distillation, gas absorption, stripping and the like, at gas
velocity ranges heretofore unachievable. In addition to the
bubbling contact action taking place predominantly within the
tubes, a greater degree of droplet or spray contact is obtained in
the disengaging space between trays than is normally found in
conventional sieve and bubble-cap plate columns. This is caused by
the higher gas velocities allowed by the arrays of this invention,
which induces a greater rate and degree of entrained liquid spray
off the tray.
In a multi-stage contacting tower (FIG. 12) analogous to a
distillation tower, any of the numerous conventional liquid
downcomer and overflow weir arrangements may be employed to secure
liquid countercurrent flow through the column, as well as crossflow
across each contact stage. Such downcomer and weir arrangements are
described in standard texts such as "Distillation" by Matthew Van
Winkle, McGraw-Hill Book Company. The contact stages where
gas-liquid contacting takes place are the bubbler arrays as
described above. The trays or plates includes in the bubbler arrays
may be secured within the tower by means of flanging individual
sections of the column as described with reference to FIG. 12 or,
in cases where an integral tower shell is required as for pressure
or vacuum applications, by more conventional means such as internal
support rings, seal rings, and the like.
It is also within the scope of equivalents of this invention to
have more than one bubbler tube assembly and housing contained on a
contact tray. It is also with the scope of equivalents of this
invention to introduce the liquid into the bubbler by a number of
different means. When the bubbler assembly is appended below the
tray, one such means is to allow overflow of the liquid into the
top row of the array either from the plane of the tray or from an
overflow weir on the tray. When the bubbler assembly is mounted on
top of the horizontal plate, liquid may be introduced into the
bubbler array through openings located in the vertical walls of the
bubbler array housing, in which case the housing walls also
function as partial overflow weirs. The openings in the vertical
housing walls allowing liquid to flow into the bubbler array from
the horizontal plate may correspond to the centerlines of a row of
tubes, preferably the bottom row. In this case, the liquid flows
from the horizontal plate to the inner portion of the bottom tubes
and is aspirated upwards by the gas venturi action as it discharges
from within the tubes.
Where multiple bubbler assemblies are mounted on a tray, cross-flow
tray gradients in liquid hydraulic flow and concentration may be
secured by conventional weir arrangements well known to the art.
For example, where two bubbler assemblies are located on a tray,
and the downcomers from the tray above to the tray below are
located at opposite sides or sections of the tray, then one or more
overflow weirs placed normal to the direction of liquid crossflow
on the tray may serve to provide a desired tray gradient. In the
present invention, the on-tray gradient weirs may be placed either
between bubbler assemblies or appended to their housing walls.
While preferred embodiments of this invention have been disclosed
herein, many modifications thereof are feasible. This invention is
not to be restricted, except insofar as is necessitated by the
spirit of the prior art.
* * * * *