Note: Descriptions are shown in the official language in which they were submitted.
-2- 10~4239
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THIS INVENTION relates to the treatment of fluid.
In particular it relates to a method of treating a fluid,
and to apparatus for the treatment of a fluid.
According to the invention a method of treating a fluid
comprises:
feeding into a length of passage a stream of fluid of a
single phase and having a composition which varies in a known
fashion with respect to a specified property thereof over
a cross-section of the tream transver~e to the direction
of movement of the stream;
moving the stream along the length of passage by
passlng it through an impeller or propeller located in
the length of passage downstream of the feeding without
destroying the variatlon in composition of the stream; and
before the variation in composition of the stream has
disappeared and after the ~luid has passed through the
lmpeller or propeller, separating at least some parts of
the stream having different compositions from one another
i while withdrawing them from the passage.
~ The specified property may be ph~sical or chemical.
; Thus partæ of the stream of different composition wlll be
different from one another with respect to that property.
By "single phase" is meant that the fluid is a gas, or it
i8 a liquid comprising fully miscible components having
no lnterfaces.
The length of passage may be circular or preferably
annular in cross-section, the composition of the stream
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1~74;~39
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varying in a circumferential direction from a single
minimum to a single maximum, the minimum and maximum being
located at diametrically opposed positions, and the
passage may form, or form part of, an endless c~rcuit
along which the stream moves, at least part of the stream
circulating around the circuit more than once.
The fluid of the str~am may follow one or more different
helix-like paths as it flows around the circuit, the axis
o~ each helix-like path being transverse to the direction of
movement of the stream along the passage and each complete
loop of each helix-like path extending the full length of
the circuit. There may be two helix-like paths, extending
circumferentially in opposite circumferential directions,
relative to the periphery of the passage presented by a
cross-section through the passage transverse to the direction
of flow along the passage from the minimum to the maximum
and each pas~ing more than once around the circuit, the
one path ~ccupying substantially one half of the passage
and the other path occupying the other half of the passage.
The method may include diverting the flow of at lelast part
of the stream, in the passage, to encourage flow of the
fluid along said helix-like paths.
The circuit may be defined by an inner cylindrical
housing located within and extending along the interior of
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074239
--4--
an outer cylindrical housing, opposite ends of the inner
housing opening into opposite ends of the outer housing,
the helix-like paths having axes which extend in opposite
circumferential directions relative to the housing from
the minimum to the max~mum.
The variation in composition may be substantially
continuous, or it may be substantially step-wise.
The impeller or propeller may b~ an axial flow impeller
or propeller.
The method may include changing the temperature of the
fluid in the stream prior to separating said parts of the
stream from one another and after feeding the stream into
the length of passage. Changing the temperature of the
fluid in the stream may be by means of a foraminous heat
exchange element extending across the passage.
:
Fluid may be removed from the stream by means of
;~ an isotope separator which alters the isotopic composition
of the stream, and fluid may be removed from or ad!~ed to
the stream by ducts opening out of and into the passage
respectively.
The method may include using partitions extending in
the direction of flow along part of the passage to separate
parts of the stream from one another, thereby to combat
.:,
! disappearance of the variation in composition of the stream.
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1~74239
When the methsd is applied to isotope separation
and the passage forms or forms part of an endless circu~t
along which the ~tream moves, the fluid fed into or added
to the stream is preferably added to that part of the stream
having the closest isotop~c composition to that of the
fluid which is added.
When the stream is moved along the passage by means of
an axial flow impeller or propeller, the stream of fluid will
be rotated bodily by a certain angle as it passes through
the impeller or propeller. The method may thus include -
deflecting the stream in a circumferential direction to
compensate for the rotation of the stream relative to the
passage which has been caused by means of the compressor.
Further according to the invention apparatus for the
treatment of a fluid comprises:
means defining a circuit which includes a passage;
; at least one inlet into the circuit and at least one
outlet from the circuit
an impeller or propeller located in the passa~e for
ca~slng flow of a fluid stream of a single phase along the
clrcuit and for circulating at least one part of the
stream more than once around the circult, ~aid ~nlet and
said outlet and sa~d impeller or propeller being arranged
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so that said part of parts each follow a helix-like path
around the circuit, the axis of each helix-like path
being transverse to the direction o~ movement of the
stream along the passage and each complete loop of each helix-
like path extending the full length of the circuit.
The passage may be annular, there being a main inlet
into one sector of the passage and a main outlet from a
circumferentially spaced sector o~ the p~ssage, to c~use
fluid enterin~ the main inlet to divide into two parts
which follow different helix-like paths around the
circuit to the main outlet~ The circuit may be
defined by an inner cylindrical housing extending along
the interior of an outer cylindrical housing, opposite ends
of the inner housing opening into opposite ends of the
outer housing.
The apparatus may include deflecting means for
diverting fluid flowing along the circuit to cause said
part or parts to follow said path or paths, and the
apparatus may include one or more partitions extending along
part of the passage in the direction of flow. S
7~Z39
--7
- The impeller or propeller may be an axial flow
imepller or propeller.
, :
The apparatus may include a foraminous heat exchange
element in and extending across the passage for changing
the temperature of the fluid stream as it flows along
the circuit, and it may include an isotope
separator in the circuit for performing an isotope
separation on the fluid stream as it flows
; along the circuit.
7'
The apparatus may have~ a plura~ity of subsidiary
inlets into the circuit which are spaced relative to
one another and a plurality of subsidiary outlets from the
circuit whlch are spaced relative to one another.
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In the detailed description of the invention
which follows hereunder~ the invention is described
and illustrated for convenience mainly with reference
to to a process of isotopic separation with a cut of
1/5, i.e. the iraction of the feed stream which
leaves the separating elements as an enriched
stream is 1/5 on a mass flow basis, and the enriched
stream is 1/4 of the depleted stream leaving
the element on a mass flow basis. The example is for
a case where the enriched and depleted streams
leaving such element are at the same
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pressure. The example may apply either to a process
in which a stream of fluid consisting only of a
process gas (such as UF6 to be enriched with
respect to U235) is treated, or to a process in
which a stream of fluid comprising a mixture of a
process gas and a carrier gas such as H2 or
helium is treated However, all references
hereafter to the isotopic composition and mass
flow of a stream of gas are to the isotopic
composition and mass flow of the process gas
in the stream.
- The ~nvention will now be described, by way
of exa~ple, with reference to the accompanying
drawin~s.
., .
In the drawings:
Figure lA shows a schematic flow diagram of part of a
cascade arrangement suitable for a cut of 1/5;
Figure 1 shows an axial sectional side elevation of
apparatus for the treatment of fluid in accordance with
the invention;
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1074239
Figure 2 shows a flow diagram of the apparatus of Figure l;
- Figure 3A:to 3H show diagrammatically flows through various
:: cross-sections of the apparatus of Figure 1.
'
Figure 4 shows a flow diagram for apparatus similar to that of
5 Figure 1 but adapted to have a lesser degree of circulation
than that of Figure 1,
Figures 5A to 5D show views similar to those of Figures
3A to 3H, for the flow diagram of Figure 4:
Figure 6 shows a flow diagram for apparatus similar to that
Figure 1 but adapted to have a greater degree of circulation
than the apparatus of Figure l;
Figures 7A to 7P show views corresponding to those of Figures
3A to 3H~ for the 10w aiagram of Figure 6;
,
Figure 8 shows a part sectional side elevation of another
apparatus ~or the treatment of fluid in accordance with the
invention in the direction of line VIII - VIII in Figure 9;
`:
Flgure 9 shows a part sectional end elevation of the
apparatus of Figure 8, in the direction of line IX- IX in
Figure 8; and
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1~7~239
~ Figure lO shows part of the apparatus of Figures 8 and
9 in detail, in the direction of line X - X in Figure 9.
~, .
In Figure lA reference numeral 1 generally designates
part of a block forming part of a cascade arrangement, the
cascade arrangement being made up of a plurality of blocks
interconnected in series. Each block comprises a plurality d
substantial~y identical stages 2, each stage 2
in turn comprising an isotope se~arator 3, a
heat exchanger 4 and a compressor 5 adapted to circulate
a stream of gas in series through the heat exchanger 4
and separator 3. The stages ~ are interconnected by means
defining feed streams 6, enriched streams 7, and depleted
streams 8. Each feed stream 6 ent-ring a stage 2
is made up of streams 7 and 8 from two further different
stages 2,and passes via the associated compressor 5 and heat
exchanger 4 into the associated separator 3 where it is
divided into further streams 7 and 8. The further streams in
turn lead to two further stages 2. In Figure lA, the part
of the block is shown comprising three groups 9 of four stages
2 each. Each group receives as a feed four enriched streams
7 from the preceding group and a depleted stream 8 from the
succeeding group 9. The stages can be regarded as
being connected in series with the enriched streams
7 flowing counter current to the depleted streams 8 along
2S the cascade. Thus each stage is shown receiving as
part of its feed the depleted stream
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- - : : ::
74239
8 from the succeeding stage, and as part of its feed
the enriched stream from the stage which is four behind
it in the series, the series being regarded as progressing
forwardly, together with the degree of enrichment of
the streams, along the cascade. Each stream 7 is 1/4 of
the stream 8 leaving the same stage on a mass flow basis;
and the streams 7 and 8 combining to form each stream 6
have about the same isotopic composition. The cascade
arrangement has an inlet feed stream, a final outlet enriched
stream and a final outlet depleted stream (not shown), and
the rate at which fluids are fed into and withdrawn from the
cascade via these streams is controlled to obtain desired mass
flow rates and isotopic compositions throughout the cascade
arrangement. The interconnection of the stages 2 described
above is for internal stages which are in the interior of
the block, remote from its boundaries. At the boundaries
of the block, i.e. the interfaces between the block and
adjacent blocks, the block will have terminal stages whose
interconnections to other stages may be different, as
dictated by the construction of the cascade, from the
interconnections of the stages 2 described.
In Figure 1 of the drawings, reference numeral 10 generally
designates apparatus in accordance with the invention and
suitable for the isotopic separation of gases. The apparatus
10 comprises an inner housing 12 and an outer housing 14
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1~74239
around the inner housing 12. The housing 12 is hollow-
cylindrical and open-ended, having a narrow portion 12.1
and a broad portion 12.2 interconnected by a tapering portion
12.3. Likewise, the outer housing 14 is hollow-cylindrical
having a narrow portion 14.1 and a broad portion 14.2 inter-
connected by a tapering portion 14.3. The ends of the outer
housing are closed. The narrow portion 12.1 is located in the
narrow portion 14.1; the broad portion 12.2 in the broad
portion 14.2; and the tapering portion 12.3 in the tapering
portion 14.3.
The housing 12 defines a passage 16 having a narrow
portion 16.1 opening into the narrow portion 14.1 of the
housing 14; and a broad portion 16.2 opening into the broad
portion 14.2 of the housing 14. The housings 12, 14 are
coaxial and the open ends of the housing 12 are spaced
axially inwardly from the closed ends of the housing 14. The
housings 12, 14 defined an annular passage 18 therebetween,
having a narrow portion 18.1 in communication with the
narrow portion 16.1 of the passage 16; and a broad portion
18.2 in communication with the broad portion 16.2 of the
passage 16. The passages 16, 18 together thus define an
endless passage or circuit, having an inner tubular part
formed by the passage 16, and an outer annular part, within
which the inner part is located, defined by the passage 18.
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1C~74239
An axial flow impeIler ~n the form of an axial
flow compressor 20, having a shaft 20.1 and a plurality
of blades 20.2, is~ provided in the passage 16. The
shaft 20.1 is coaxial with the passages 16, 18 and
projects- inwardly, from the exterior of the housing 14,
into the narrow portion 16.1 of the passage 16. The
blades 20.2 are located in the narrow portion 16.1 of
the passage 16.
A heat exchanger comprising a foraminous heat exchange
element 22 is located in the passage 16. The heat exchanger
. 22 extends across the broad portion 16.2 of the passage 16,
adjacent the tapering portion 12.3 of the housing 12.
A separator 24 including a plurality of isotopic
gas separation elements 26 is located in the broad portion ~
16.2 of the passage 16, the heat exchanger 22 being between :
the separator 24 and the impeller 20. The elements 26 each
have an inlet 26.1 in communication with the passage 16 and
directed towards the narrow portion 16.1 of the passage 16;
a main outlet 26.2 in communication with the circuit and
directed towards the closed end of the broad portion 14.2
of the housing 14; and at leas~ one subsidiary outlet between
the main outlet and the inlet. The elements are, for the :
purpose of Figures 1 to 7, of a type which has a cut of 1/5 i.e.
they separate a feed stream into an enriched stream and a
depleted stream, the enriched stream being 1/4 of the
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74239
depleted stream on a mass flow basis. Two partitions 28,
30~located respectively between the heat exchanger 22 and
separator 24, and at thè free end of the broad portion 16.2 of
the passage 16, isolate a compartment 32 in the passage 16 from
the rest of the circuit. The inlets 26.1 and main outlets 26.2
of the elements 26 are respectively from and into the
circuit outside the compartment 32; and the subsidiary
outlets are into the compartment 32. The compartment 32 has
an axially located outlet duct 34 which extends axially out- -
wardly from the compartment 32 and out through the end of
the broad portion 14.2 of the housing 14. It will be appre-
ciated that the subsidiary outlet of each element 26 may
instead of being a discrete outlet, comprise a permeable
surface on the element, depending on the isotope separation
process which is considered.
A main inlet 36 in the form of a pipe enters the broad
portion 18.2 of the passage 18 and is directed in the passage
18 in an axial direction towards the narrow portion 18.1 of
the passage. A main outlet 38 in the form of a pipe leaves
the broad portion 18.2 of the passage and is directed into
the passage 18 in the opposite axial direction to the inlet
36. The inlet 36 and outlet 38 are at diametrically
opposed positions along the circumference of the passage 18.
A further inlet in the form of a duct 40 having four
subsidiary ducts 40.1, 40.2, 40.3 and 40.4 extends circum-
ferentially around the housing 14.
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1C~74239
The duct 40 has a plurality of flow connectionsfrom its subsidiary ducts 40.1 to 40.4 into the annular
passage 18, arranged circumferentially around the
annular passage 18. The location of these flow connections,
two of which are shown in figure 1, indicated by reference
numeral 42, will be described in more detail hereunder.
The duct 34 is likewise internally divided by
partitions into four subsidiary ducts 34.1, 34.2, 34.3
and 34.4, which open via flow connections into the
compartment 32. Here again, the arrangement of the
flow connections will be described in more detail .
hereunder.
Deflecting means is provided in the annular passage
18, adapted to deflect the flow of a fluid along the
passage 18. The function of the deflecting means will
be described in more detail hereunder. The deflecting
means comprises a plurality of the deflecting elements,
conveniently in the form of curved deflector plates
(not shown) in the passage 18. The plates extend between
the housings 14 and 12, and, when viewed edge-on in a
radially inward direction, extend at an angle to the
longitudinal dimension, i.e. the polar axis, of the
apparatus 10. The plates are located in a circumferentially
extending r~ng at 44, immediately upstream of the main
inlet 36.
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1074239
The operation of the apparatus will now be described
also with reference to Figure 2 in which reference
numeral 46 generally designates a flow diagram of the
apparatus of Figure l; and to Figures 3A to 3H, in
which reference numeral 48 generally designates various
cross-sections of the apparatus 10 of Figure 1. Unless
otherwise specified, like reference numerals refer to
like parts.
: .
The apparatus 10 forms a module adapted to accommodate
a group of stages forming part of a block in a cascade
arrangement for an isotopic separation process for `
gases, there being a number of similar modules, interconnected
in series. An isotopic gas mixture comprising a first
component, and a second component which is isotopically
different from the first component, is moved along the
series. In each module an isotopic separation takes
place, whereby the gas mixture is separated into two
streams, i.e. a stream which is enriched with respect
to a desired component, for example the first component;
and a stream which is depleted with respect to said
desired component. Each module receives as a feed the
enriched stream from a previous module of the series,
and the depleted stream from a succeeding module in the
series. The enriched stream from the previous module
is generally designated 50, and passes along the duct
40. The said stream 50 is divided into four substreams 50.1,
50.2, 50.3 and 50.4. These substreams have different
" 17
1(~74Z39 ~ `
isotopic compositions, i.e. their concentration or de~ree
of enrichment with respect to the desired component,
defined as the ratio on a mass bas~s between the desired
(first) component and the other (secondl component, is
different. They pass respectively along the subsidiary ducts
40.1, 40.2, 40.3 and 40.4. The depleted stream from the
succeeding module is indicated by reference numeral 52.
The depleted stream 52 enters the passage 18 of the
apparatus 10 via main inlet 36. The subsidiary duct 40.1 has
a single flow connection 42 into the passage 18, and this
flow connection is immediately downstream of an axially
aligned with the inlet 36. The substream 50.1 has substan-
tially the same isotopic composition as the stream 52. If
desired mixing means, such as for example a nozzle, baffle
or the like, may be provided at the connection 42 to promote
mixing between the streams 52 and 50.1. Such mixing means may
be provided for each connection 42 described hereunder.
The combined stream formed from the substream 50.1 and
the stream 52 flows axially along the passage 18 towards
; te narrow end 14.1 of the housing 14. This flow takes
place substantially along a sector of the passage 18, and
the combined stream enters the compressor 20, where it
flows along a sector of the compressor 20 in the passage 16,
indicated by reference numeral 54 in Figures 2 and 3A. The
flow of the said stream 50.1, 52 along said sectors of the
passage 18 and the passa~e 16 through the compressor 20, is
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such that there is little mixing with streams flowing
alongside it. Said stream 50.1, 52 thus forms a sector of
the annular stream making up the total flow along the
passage 18, and a sector of the annular or circular stream
making up the total flow along the passage 16. When the
combined stream 50.1, 52 passes through the compressor 20
the sector of the total stream passing along the passage
16 occupied by said combined stream will be displaced in a
circumferential direction, being the circumferential
direction in which the blades 20.2 of the compressor 20
rotate. The sector 54 of the compressor 20 will thus follow
a helical path along the length of the compressor. There will
however be no substantial mixing of this stream with streams
in ad~acent sectors. The stream 50.1,52 in its sector 54,
flows along the passage 16 and enters a sector of the heat
exchanger 22. Its temperature is changed by a desired degree
as it passes through the heat exchanger 22, and it
passes into the elements 26 of a corresponding sector of
the compartment 32, via the inlets 26.1 to the separation
elements 26. The sectors in the heat exchanger 22 and
compartment 32 (i.e. the separator 24) are indicated in
Figures 2 and 3E by reference numeral 54.1. These sectors
54.1 need not be axially aligned with the sector 54 where
it leaves the compressor 20, as the possibility of cir-
cular swirl in a circumferential direction of the total
stream along the passage 16 ~etween the compressor 20 and
heat exchanger 22 is contemplated.
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1~74239
-~~ The combined stream 50.1, 52 undergoes an isotopic
separation process in the elements 26 making up the sector
54.1 of the separator 24.
In the sector 54.1 of the separator 24 the combined
stream 50.1, 52 is separated into an enriched stream 56.1
and a depleted stream 58.1, the elements 26 having a cut of
1/5 with respect to the process gas. The depleted stream
58.1 passes out of the main outlets 26.2 of the elements 26
making up said sector 54.1. The enriched stream passes
out of the subsidiary outlets of said elements 26 and into
the compartment 32. In the compartment 32 the enriched
stream 56.1 passes into the subsidiary duct 34.1 of the
duct 34, and thence it passes on to the next module of the
series.
The depleted stream 58.1 passes into the passage 18 and
flows axially along a sector of the passage 18 to the ring
of deflector plates at 44. It strikes one or more of
said deflector plates and is split into two substreams 58.1
which pass axially along the passage 18 and on opposite sides
of the inlet 36. The subsidiary duct 40.2 has a pair of flow
connections 42 into the passage 18, located where the
substreams 58.1 pass along the passage 18. The substreams 58.1
are joined via these flow connections 42 by the substream 50.2
from the subsidiary duct 40.2. The substreams 50.2, 58.1
have substantially the same isotopic composition. The combined
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~1~74Z39
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substreams 50.2, 58.1 pass axially along the passage 18
into the narrow portion 14.1 of the housing 14 on
opposite sides of the combined stream 50.1, 52. Said
combined substreams 50.2, 58.1 enter a pair of sectors
60 in the passage 16 at the compressor 20, on opposite sides
of the sector 54. It will be appreciated that, for ease of
representation, the sectors 60 are shown as a single sector in
Figure 2.
The combined substreams 50.2, 58.1, as described for the
combined stream 50.1, 52, pass along the passage 16 away
from its narrow portion 16.1, through the heat exchanger
22 and into the separator 24. The sectors of the heat
exchanger 22 and separator 24 through or into which these
combined substreams pass are designated 60.1. Once again, in
Figure 2, this pair of sectors is indicated as a single
sector for the heat exchanger 22 and separator 24. Each
combined substream 50.2, 58.1 enters the elements 26 of
one of the sectors 60.1 of the separator 24, via their
inlets 26.1.
In said sectors 60.1 of the separator 24 the combined
substreams 50.2, 58.1 are each separated into an enriched
substream 56.2 and a depleted substream 58.2. The enriched
substreams 56.2 pass through the subsidiary outlets of the
elements 26 in said sectors 60.1 into the compartment 32,
thence via flow connections into the subsidiary duct 34.2 of
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11~74Z39
the outlet duct 34, to form an enriched stream 56.2,
and thence on to the succeeding module of the series.
The depleted substreams 58.2 pass through the outlets
26.2 of the elements 26 in said sectors 60.1, and into
the passage 18, on opposite sides of the stream 58.1.
The substreams 58.2 pass along the passage 18 on opposite
sides of the stream 58.1 and are deflected by the deflector
plates at 44 so that they pass further along the passage 18
on the sides of the combined substreams 58.1, 50.2 remote
from the comhined stream 50.1, 52. Where the substreams
58.2 pass radially inwardly of the duct 40 they receive
the enriched stream 50.3 from the subsidiary duct 40.3,
via a pair of flow connections 42. The enriched stream
50.3 has substantially the same isotopic composition as the
substreams 58.2.
The combined substreams 50.3, 58.2 pass axially along
the passage 18 away from the deflector plates at 44 and
towards the narrow portion 18.1 of said passage. Said combined
substreams 50.3, 58.2 are located respectively on the sides
of the combined substreams 50.2, 58.1 remote from the
combined stream 50.1, 52. The combined substreams 50.3,
58.2 enter a pair of sectors 62 in the passage 16 at the
compressor 20, on the sides of the sectors 60 remote from
the sector 54. Once again, the sector 62 is shown as a
single sector in Figure 2.
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The combined substreams 50.3, 58.2, as descxibed
for the combined stream 5Q.1, 52 pass along the passage
16 away from its narrow portion 16.1, through the heat
exhanger 22 and into the separator 24. The sectors of
the heat exchanger 22 and separator 24 through or into
: which the combined substreams 50.3, 58.2 pass are
designated 62.1. Once again, in Figure 2, this pair of
sectors is indicated as a single sector for the heat
exchanger 22 and separator 24. Each combined substream
50.3, 58.2 enters the elements 26 of one of these
sectors 62.1 of the separator 24, via the inlets 26.1
thereof.
In said sectors 62.1 of the separator 24, the combined
substreams 50.3, 58.2 are each separated into an enriched
substream 56.3 and a depleted substream 58.3. The enriched
substreams 56.3 pass through the subsidiary outlets of the
elements 26 in said sectors 62.1 into the compartment 32,
thence via flow connections into the subsidiary duct 34.3 of
the outlet duct 34 and thence on to the succeeding module of
the series.
The depleted substreams 58.3 pass through the outlets
26.2 of the elements 26 in said sectors 62.1, into the passage
18, respectively on the sides of the substreams 58.2,
remote from the stream 58.1.
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1~74Z39
.
The substreams 58.3 pass along the passage 18
respectively on the sides of the substreams 58.2,
remote from the stream 58.1; and the substreams 58.3
are deflected by the deflector plates at 44 so that
they pass further along the passage 18 on the sides of
the combined substreams 58.2, 50.3 remote from the
combined substreams 58.1, 50.2. Said substreams 58.3,
after they pass over the deflector plates at 44 are
located adjacent each other to form a single stream
58.3. Where the stream 58.3 passes radially inwardly
of the duct 40 it receives the enriched stream 50.4
from the subsidiary duct 40.4, via the flow connection
42. The enriched stream 50.4 has substantially the
same isotopic composition as the combined stream 58.3.
The combined stream 50.4, 58.3, as described for the
; combined stream 50.1, 52, flows axially along the passage 18
towards the narrow end 14.1 of the housing 14. The combined
stream 50.4, 58.3 enters the compressor 20, where it flows
along a sector 64, between the sectors 62. Said combined
stream 50.4, 58.3 then passes along the passage 16 away
from its narrow portion 16.1, through the heat exchanger
22 and into the separator 24. The sectors of the heat
exchanger 22 and separator 24 through or into which the
combined stream 50.4, 58.3 passes are designated 64.1.
In said sector 64.1 of the separator 24 the c~mbined stream
` 50.4, 58.3 S separated into an enriched substream 56.4 and a
,~
, .
-24-
. ~ ~,
. --
,,: . ' - ' ~
.. . .
~, . . .
:. , ~ . .
.
1(:174239
depleted substream 58.4. The enriched substream
56.4 passes throu~h the subsidiary outlets of the
elements 26 in the sector 64.1 into the compartment
32, thence via a flow connection into the su~sidiary
duct 34.4 of the outlet duct 34, and thence on to
the succeeding module of the series.
The depleted stream 58.4 passes through the
outlets 26.2 of the elements 26 in said sector
64.1, and into the passage 18 between the substreams
58.3. The stream 58.4 passes a short distance
along the broad portion of the passage 18, and
then passes into the main outlet 38 along which it
passes to the preceding module in the series.
It will be appreciated that the stream 58.4 passing
along the outlet 38 has the same function in the preceding
module in the series~as the stream 52 entering the
apparatus 10 through the inlet 36. Likewise streams 56.1
to 56.4, which pass as substreams along the subsidiary ducts
34.1 to 34.4 of the duct 34, are treated in the same way and
have the same function in the succeeding module of the
series, as the substreams 50.1 to 50.4 entering the
apparatus 10 through the subsidiary ducts 40.1 to 40.4 of the
duct 40.
When the combined stream 50.1, 52, the combined sub-
streams 50.2, 58.1, the combined substreams 50.3, 58.2 and
1074239
the combined stream 50.4, 58.3 pass along the passages
16, 18 in an axial direction alongside one another,
they move along said passages with substantially no
mixing except a small amount of diffusion at their
interfaces. There is also no substantial mixing when
said streams and substreams pass through the compressor
20. It will thus be appreciated that, in the apparatus
10, the various streams and substreams are fed into the
passage 18, in the zone of said passage at which are
located the inlet 36, the duct 40 and the deflector
plates at 44, so that the composition of the total
stream flowing along the passage 18 varies in desired
fashion over its axial cross-section transverse to the
direction of movement of said total stream along the
passage. There is in fact a change in composition in
opposite circumferential directions from the main inlet
36 to the main outlet 38. Said change in composition is with
respect to the isotopic composition of the gas as expressed
by the concentration of the first or desired component. The
total stream flowing along the passages 18 and 16 is caused
to move along said circuit by the compressor 20, the
variation in composition over its cross-section remaining
substantially unchanged. Each time the total stream passes
through the heat exchanger 22, heat is withdrawn from it;
and each time it passes respectively through the separator
24 and under the duct 40, material is removed from and
added to it. The concentration of the desired component
-26-
- . ~ . . . : : -: - : .
- ' ' ~ ' ,
. . ~ : ~ . . .
1~74239
increases steadily in a ci,r:cum~erential direct~on from a
minimum at the main outlet 38 to a maximum at the main inlet
36. The composi,tion o,f the total stream in the passages 18, 16
thus varies in a circum~erential directi~on, the minimum being
diametrically opposed to the maximum, with respect to
the isotopic composition of the gas.
It will be appreciated that, immediately downstream of the
deflector plates at 44 and the flow connections 42, the
variation in composition of the total stream passing along
the passage 18 will be somewhat stepwise, there being step-
like differences in composition between the combined stream
50.1, 52 and the combined substreams 50.2, 58.1; between
the combined substreams 50.2, 58.1 and the combined
substreams 50.3, 58.2; and between the combined substreams
50.3, 58.2 and the combined stream 50.4, 58.3. The step
character of this variation will decrease as mixing by
diffusion takes place at the interfaces between the streams and
substreams as they pass along the passage 18 and passage 16.
The step character will be most pronounced between the stream 52
and the substreams 58.1 and will decrease between adjacent
streams in a circumferential direction so that the step
difference in composition between the stream 58.4 and
the substreams 58.3 will be the least pronounced. The
additions of the streams 50.1 to 50.4 via the duct 40
tend to retard the disappearance of the step-like
differences. Thus, as said streams and substreams pass
iC~74Z39
along the circuit from the inlet 36 to the outlet 38,
variation will become less steplike and will tend more to a
continuous variation from the minimum towards the maximum.
When the total stream passes through the compressor 20, it
will be rotated in the direction of rotation of the compres-
sor blades 20.2, but the minimum and maximum will remain
diametrically opposed to each other, and the variation of
the composition of the stream will remain substantially
unchanged.
As the total stream passes through the compressor
in the passage 16 it is compressed; as it passes
through the heat exchanger 22 its temperature is changed;
and as it passes through the elements 26 fluid is removed
from it by the elements, to form the enriched streams 56.1
to 56.4. The depleted streams and substreams 58.1 to 58.4
passing out of the various sectors of the separator 24 into
the passage 18 thus have different isotopic compositions
from the various combined streams and substreams entering
the same sectors of the separator 24 from the passage 16.
The total stream passing through the separator into the
passage 18 can thus be regarded as having its composition
changed with respect to the concentration of desired com-
ponent, by having fluid removed therefrom when it passes
through the separator 24. Furthermore, it will be appre-
ciated that fluid is added to the total stream flowing along
the passage 18 via the inlet 36 and the duct 40; and fluid
is removed from the passage 18 via the main outlet 38.
28
:
. . :
.
, :
-
.
.' .: - - '' .: ~ . -
' - ' : - : ': ' ' ': -
- . . - :. :
1074239
Fluid flow along the passage 18 is diverted by the
deflector plates at 44 in the passage 18. As the total
stream passes over the deflector plates at 44, the
isotopic composition thereof has its variation over its
cross-section maintained while withdrawal and addition
of fluid respectively via the ducts 38 and 36 take
place. The total stream flowing along the passages
changes its direction of flow at both ends of the
apparatus 10, where it passes from the passage 18 into
the passage 16, and where it passes from the passage 16
into the passage 18. It thus flows along a circuit.
Fluid flow along the circuit can be described
as starting through the main inlet 36, the flow being
added to via the flow connection 42 from the subsidiary
duct 40.1. The combined stream 50.1, 52 moves along the
circuit to the separator 24, where it is depleted by the
elements 26. The remainder of said stream, i.e. the
depleted stream 58.1, continues to flow along the circuit
until it reaches the deflector plates at 44. It is then
diverted into two parts, i.e. the substreams 58.1, which
continue to flow around the circuit. They are added to from
the duct 40.2 via the flow connections at 42 and the
combined substreams 58.1, 50.2 once again flow along the
circuit to the separator 24 where they are further
depleted. The depleted substreams 58.2 follow a similar
cycle around the circuit, being added to at the flow connec-
tions 42 by the stream 50.3 from the subsidiary
-29-
- :-: .
- , . . . .-
~ 1074239
duct 40.3. Combined substreams 50.3, 58.2 then flow along
to the separator 24 where they are further depleted to
provide the depleted stream 58.3. The stream 58.3 is added
to via the flow connection at 42 by the stream 50.4 from
the subsidiary duct 40.4. The combined stream 50.4,
58.3 makes a final circuit of the apparatus to the sepa-
rator 24 where it is finally depleted. The depleted stream
58.4 then passes out of the main outlet 38. From the
aforegoing it will be appreciated that the stream 52
entering through the main inlet 36 makes a circuit of the
apparatus 10 through the sectors 54, 54.1 after which
it is split into two streams. These streams follow
helical paths around the circuit made up by the passages 18,
16, the paths moving circumferentially oppositely away
from each other and passing respectively in turn through
the pairs of sectors 60, 60.1, and the pairs of
sectors 62, 62.1. This is most clearly seen in Figure
3. The paths move away from each other until they finally
converge and become a single path in the sectors 64, 64.1
before passing out of the main outlet 38. The paths, in
said circumferential direction, are such that the axes
of their helices extend oppositely along two halves of
a circle along arrows 65 (Figure 3A) from the inlet 36
to the outlet 38.
It will be appreciated that, at the inlet to the
passage 16 at the compressor 20, the total stream flowing
. . -: . :
.
-`` 1074Z39
into the passage 16 can be regarded as a plurality of
different streams of fluid having different compositions
entering the passage 16. They are moved along the
passage by the compressor 20 and are separated physically
from one another in the separator 24. They may be
regarded as being reintroduced into the circuit when
they pass, depleted, out of the separator 24 into the
passage 18. The stream 58.4 is finally separated
physically from the other streams~58.1, 58.2 and 58.3)
where it is removed from the circuit via the outlet 38.
If reference is again made to Figure lA, and it is
compared with Figures 2 and 3, the following correspondence
becomes apparent:
The module exemplified by the apparatus 10 of
Figure 1 is capable of, inter alia, accommodating four
stages 2, i.e. one of the groups 9, shown in Figure lA;
the stages 2 of a group 9 of Figure lA are shown
in Figures 2 and 3 as the sets of sectors 54, 54.1; 60,
60.1; 62, 62,1; and 64, 64.1 respectively;
the enriched streams 7 of Figure lA can be regarded
as the enriched substreams 56.1 to 56.4 of Figures 2
and 3;
': . . : ' ' ~ ,,
. ' "'' ' ." - ' ' ''' ' ' ' ' ~ ' -
- ,
- 1074Z39
the depleted streams 8 of Figure lA can ~e regarded as
the depleted substreams 58.1 to 58.4 of Figures 2 and 3; and
there is further correspondence, in the stages 2,
between the compressors 5 (Figure lA) and the compressor
20 (Figures l to 3); and between the heat exchangers 4
(Figure lA) and the heat exchanger 22 (Figures l to 3).
Thus the module lO of Figures l to 3 when used as shown in
Figures 2 and 3 accommodates a group 9 of stages 2
(Figure lA). Thus a single compressor 20 and heat exchanger
22 (Figure l) are used instead of the four compressors 5 and
four heat exchangers 4 of a group 9 of Figure lA. Further-
more, a single assembly of elements 26, as embodied by the
separator 24, is used instead of the four individual
separators 3 of Figure lA. In this regard it will be
appreciated that, to obtain the correspondence between
the Figures lA and l, 2 and 3, elements 26 are contemplated
for use in all the modules lO of the cascade arrangement,
which elements 26 have a cut of 1/5 with respect to the
process gas.
In the illustrations in Figures l, 2 and 3, the stream
52, with the various additions thereto and therefrom, can
be regarded as making four passes through the apparatus,
respectively through the sectors 54, 54.1, the sectors
60, 60.1, the sectors 62, 62.1, and the sectors 64, 64.1.
,
74239
In Figure 4, reference numeral 66 generally desig-
nates a flow diagram for apparatus similar to that of
Figure 1, but adapted to have a lesser degree of circula-
tion than that of Figure 1. In Figure 5 reference numeral
68 generally designates views corresponding to those of
Figures 3A to 3H for the apparatus having the flow
diagram of Figure 4.
An enriched stream 70 from the preceding module but
one in the series enters the apparatus for Figure 4 in the
form of a pair of substreams 70.1, 70.2, through the duct
40 which will have two subsidiary ducts 40.1, 40.2. There
will thus be two flow connections at 42, one for the duct
40.1 downstream of the inlet 36, and the other for the
duct 40.2 at a diametrically opposed position into the
passage 18 downstream of the outlet 38. A depleted stream
from the succeeding module in the series enters in the
form of a stream 72 through the inlet 36. The stream 72
makes two passes through the apparatus, instead of the
four shown in Figure 2. The first pass is through a
sector 74 of the compressor 20, and sectors 74.1 of the
heat exchanger 22 and separator 24. The stream 72 is
combined, prior to said pass through the sectors 74, 74.1,
with the substream 70.1 from the subsidiary duct 40.1.
After the combined stream 70.1, 72 passes through the
separator 24 and, as described hereunder, becomes a
depleted stream 78.1, it is deflected once at 44 by the
deflector plates to the diametrically opposite side of
the passage 18.
-33-
.. . . . . . . .
..
, . , ~ - . : : . .. ~- , .: .
1C~74Z39
The combined stream 70.1, 72 in the sector 74.1 of
the separator 24 is divided into an enriched stream 76.1
which passes to the succeeding module but one in the
series via the subsidiary duct 34.1 of the outlet duct 34,
and a depleted stream 78.1. In the elements 26 of the
sector 74.1 (and the sector 80.1 discussed hereunder)
there is a cut of 1/5 with respect to process gas. The
duct 34 comprises a pair of subsidiary ducts 34.1, 34.2
leading to the succeeding module but one in the series.
The depleted stream 78.1, as described above, in passing
over the deflector plates at 44 is diverted to a diametri-
cally opposed position in the passage 18. This stream
78.1 is added to by the substream 70,2 from the subsidiary
duct 40.2 and makes a second pass along the circuit
through the compressor 20, heat exchanger 22 and separator
24. It passes through the sector 80 of the compressor 20
and the sectors 80.1 of the heat exchanger 22 and separator
24. In the sector 80.1 of the separator 24 isotopic
separation takes place into an enriched stream 76.2 which
passes out through subsidiary duct 34.2 and a depleted
stream 78.2. The depleted stream 78.2 passes via the
outlet 38 to the preceding module in the series, and the
enriched stream 76.2 passes on to the succeeding module
but one in the series. Thus, the sectors 74, 74.1 and
80, 80.1 are substantially 180 sectors; whereas in the
case of Figures 2 and 3 the sectors 54, 54.1 and 64, 64.1
are 90 sectors, the sectors 60,60.1 and 62,62.1 being
45 sectors.
34
- -, ` ,.: ~ :
, ' '~
1074239
In Figure 6 reference numeral 82 generally designates
a flow diagram for apparatus similar to that of Figure 1
but adapted to have a greater degree of circulation than
the apparatus 10 of Figure 1. In Figure 7, reference
numeral 84 generally designates views corresponding those
of Figures 3A to 3H for the flow diagram of Figure 6.
The construction and function of the apparatus 10
which the flow diagrams of Figure 6 and Yigure 7 represent,
are similar in principle to those of the apparatus for
Figures 1, 2 and 3. The main difference is that the
deflector plates at 44 are arranged so that a depleted
stream 86 from the succeeding module in the series makes :
eight passes through the compressor 20, heat exchanger 22
and separator 24, before it exits through the main outlet :
38. The duct 40 has eight subsidiary ducts 40.1 to 40.8
and the duct 34 has eight subsidiary ducts 34.1 to 34.8.
Subsidiary ducts 40.1 to 40.4 of the duct 40 carry four
streams 88.1 to 88.4 from the preceding module in the
series, and the subsidiary ducts 34.1 to 34.4 of the duct
34 carry four enriched streams to the succeeding module in
the series. The subsidiary ducts 34.5 to 34.8 of the duct
34 are connected directly to the subsidiary ducts 40.5 to
40.8 of the duct 40. This connection is shown diagram-
matically in Figure 1 in broken lines at 89.
. - . ............................. , ~
:- . .: :
, ' ' ' ' ' . ` .'`. -~ ~'` ''...... , -':
1~74Z39
The sequence of flow is as follows:
(a) The stream 86 enters the passage 18 through the inlet
36. The stream 86 is added to by a stream 90.1 from the
subsidiary duct 40.5 of the duct 40. The stream 90.1 has
substantially the same isotopic composition as the stream
86. The combined stream 86, 90.1 circulates along the
circuit defined by the passages 18, 16 in the direction
described with reference to Figures 1, 2 and 3, and enters
the compressor 20. It passes through a 45 sector 92 of
the compressor 20, and through two 45~ sectors 92.1
respectively of the heat exchanger 22 and separator 24.
The combined stream 90.1, 86 in the elements 26 of the
sector 92.1 of the separator 24 is divided into an
enriched stream 94.1 which passes from said elements 26
into the compartment 32 and then from said sector 92.1 of
the compartment 32 via a flow connection into the sub-
sidiary duct 34.1; and a depleted stream 96.1 which
passes from the main outlets 26.2 of said elements 26 into
the passage 18.
(b) The depleted stream 96.1 is divided into a pair of
substreams by the deflector plates at 44, which flow along
the passage 18 towards its narrow portion 18.1 on opposite
sides of the inlet 36 and ~ stream 86. Said substreams
96.1 pass under the duct 40, where they receive parts of
a stream 90.2 from the subsidiary duct 40.6 via the flow
connections 42. The combined substreams 90,2, 96.1
circulate along the circuit on opposite sides of the
36
- 1C~74Z3~
combined stream 90.1, 86 and pass through a pair of 22~
sectors 98 in the compressor 20, and pairs of 22%
sectors 98.1 in the heat exchanger 22 and separator 24
respectively. The sectors 98 are on opposite sides of
the sector 92; and the sectors 98.1 are on opposite sides
of the sector 92.1 in the heat exchanger 22 and separator
24. In the elements 26 of the sectors 98.1 of the
separator 24 isotopic separation takes place and said
combined substreams 90.2, 96.1 are divided into enriched
substreams 94.2 which pass from the subsidiary outlets :
of the elements 26 into the compartment 32 and then
through flow connections from the sectors 98.1 of the
compartment into the subsidiary duct 34.2 of the duct 34;
and depleted substreams 96.2 which pass from the main
outlets 26.2 of the elements 26 into the passage 18.
(c) The depleted substreams 96.2 pass along the passage
18 on opposite sides of the depleted stream 96.1 until they
reach the deflector plates at 44, where they are deflected
so that they pass further along the passage 18 towards the
narrow portion 18.1 of the passage 18 on the sides of the
substreams 96.1 remote from the stream 86. ~here the
substreams 96.2 pass under the duct 40 they receive via
flow connections 42 from the subsidiary duct 40.7 parts of
a stream 90.3 at substantially the same isotopic composi-
tion. Combined substreams 90.3, 96.2 pass along the
circuit on the sides of the combined substreams 90.2,
96.1 remote from the combined stream 90.1, 86. Said
:
~74Z39
combined substreams 90.3, 96.2 enter further 22~ sectors
100 in the compressor 20 on the sides of the sectors 98
remote from the sector 92. The combined substreams 96.2,
90.3 then pass through pairs of 22~ sectors 100.1 in the
heat exchanger 22 and the separator 24 respectively. The
sectors 100.1 in the heat exchanger and separator are
on the sides of the sectors 98.1 remote from the sector
92.1. In the elements 26 of the sectors 100.1 of the
separator 24 an isotopic separation takes place and said
combined substreams 90.3, 96.2 are divided into enriched
substreams 94.3 which pass from the subsidiary outlets of
the element 26 into the compartment 32 and then through
flow connections from the sectors 100.1 of the compart-
ment 32 into the subsidiary duct 34.3 of the duct 34;
and depleted substreams 96.3 which pass from the main
outlets 26.2 of the elements 26 into the passage 18, on
the sides of the substreams 96.2 remote from the stream
96.1.
(d) The depleted substreams 96.3 flow along the passage
18 towards its narrow portion 18.1 on the sides of the
depleted substreams 96.2 remote from the depleted stream
96.1. The depleted substreams 96.3 are deflected by the
deflector plates at 44 so that they continue to flow
along the passage 18 alongside the depleted substreams
96.2. Where the substreams 96.3 pass under the duct 40
they receive, via flow connections 42 from the subsidiary
duct 40.8, parts of a stream 90.4 at substantially the
1~74~39
same isotopic composition. The combined substreams 90.4,
96.3 circulate along the circuit along the sides of the
combined substreams 96.2, 90.3 remote from the combined
substreams 96.1, 90.2 and pass through a pair of 22~ sectors
102 in the compressor 20, and pairs of 22~ sectors 102.1
respectively in the heat exchanger 22 and separator 24. In
the elements 26 of the sectors 102.1 of the separator 24 an
isotopic separation takes place and said combined substreams
90.4, 96.3 are divided into enriched substreams 94.4 and
depleted substreams 96.4. The enriched substreams 94.4 pass
through the subsidiary outlets of said elements into the
compartment 32 and from the sectors 102.1 of the compartment
32 via flow connections into the subsidiary duct 34.4 of the
duct 34. The depleted substreams 96.4 pass into the passage
18 via the main outlets 26.2 of the elements 26, on the sides
of the depleted substreams 96.3 remote from the depleted
substreams 96.2. The depleted substreams 96.4 flow along
the passage 18 to the deflector plates at 44 where they are
deflected to pass further along the passage 18 along the sides
of the depleted substreams 96.3 remote from the depleted
substreams 96.2.
(e) Where the depleted substreams 96.4 pass under the duct
40 they receive, via flow connections 42 from the subsidiary
duct 40.1 of the duct 40, parts of the stream 88.1, at
39
.
:. . . : :
: . .. : ., , ~ . - : -. . .
1~74. -39
,
substantially the same isotopic composition, from the
preceding module in the series. The combined substreams 96.4,
88.1 circulate along the circuit along the sides of the
combined substreams 96.3, 90.4 remote from the combined
substreams 96.2, 90.3. Combined substreams 96.4, 88.1
pass through a pair of 22~ sectors 104 in the compressor
20, alongside the sectors 102. They then pass through
a pair of 22% sectors 104.1 in the heat exchanger 22 and
into a pair of 22~ sectors 104.1 in the separator 24. In
the elements 26 of the sectors 104.1 of the separator 24 an
isotopic separation takes place and said combined substreams
96.4, 88.1 are divided into enriched substreams 90.1 and
depleted substreams 96.5. The enriched substreams 90.1 pass
from the subsidiary outlets of the elements 26 into the compart-
ment 32 and thence from the sectors 104.1 of the compartment
32 via flow connections into the subsidiary duct 34.5 of
the duct 34. Depleted substreams 96.5 pass from the main
outlets 26.2 of the elements 26 into the passage 18 alongside
the depleted substreams 96.4, on the sides of the depleted
substreams 96.4 remote from the depleted substreams 96.3.
The depleted substreams 96.5 then pass along the passage 18
along the sides of the depleted substreams 96.4 remote from
the depleted substreams 96.3 to the deflector plates at 44.
At the deflector plates the depleted substreams 96.5 are
deflected, so that they continue to pass along the passage
18 alongside the depleted substreams 96.4.
(f) Where the depleted substreams 96.5 pass under the duct
40 they receive, via flow connections 42 from the subsidiary
-40-
~`
.
1074239
duct 40.2, parts of a stream 88.2 from the preceding module
of the series, at substantially the same isotopic composition.
The combined substreams 96.5, 88.2 flow along the passage 18,
to the compressor 20. The combined substreams 88.2, 96.5
pass through a pair of 22~ sectors 106 in the compressor 20,
alongside the sectors 104. Combined substreams 96.5, 88.2
then pass along the passage 16 through 22% sectors 106.1
in the heat exchanger 22 alongside the sectors 104.1, and then
into 22~ sectors 106.1 of the separator 24 alongside the
sectors 104.1. In the elements 26 of the sectors 106.1 of the
separator 24 an isotopic separation takes place and said -
combined substreams 96.5, 88.2 are divided into a pair of
enriched substreams 90.2 and a pair of depleted substreams 96.6.
The enriched substreams 90.2 pass through the subsidiary
outlets of the elements 26 into the compartment 32,
and then through flow connections from the sectors 106.1 of the
compartment 32 into the subsidiary duct 34.6 of the duct
34. The depleted substreams 96.6 pass into the passage 18
and along the passage 18 alongside the depleted substreams
96.5 and on the sides thereof remote from the depleted
substreams 96.4. At the deflector plates at 44 the
depleted substreams 96.6 are deflected to continue to pass
along the passage 18 alongside the depleted substreams 96.5.
(g) Where the depleted substreams 96.6 pass under the duct 40
they receive, via flow connections 42 from the subsidiary
duct 40.3, parts of a stream 88.3 of gas from the preceding
.
- . .
- .
: . ~ .. . .
.- , ~: .
-
' . . , .~ , .
1~74Z3g
module in the series, at substantially the same isotopic
composition. The combined substreams 96.6, 88.3 pass
along the passage 18 to the compressor 20. Said combined
substreams 96.6, 88.3 pass through a pair of 22~
sectors 108 of the impeller 20, alongside the sectors
106. Combined substreams 96.6, 88.3 then pass through
a pair of 22~ sectors 108.1 of the heat exchanger 22
alongside the sectors 106.1 thereof, and into a pair of
22~ sectors 108.1 of the separator 24 alongside its
sectors 106.1. In the elements 26 of the sectors
108.1 of the separator 24 an isotopic separation takes place
and said combined substreams 96.6, 88.3 are divided into a
pair of enriched substreams 90.3, and a pair of depleted
substreams 96.7. The enriched substreams 90.3 pass from
the subsidiary outlets of the elements 26 into the compart-
ment 32 and then through flow connections from said
sectors 108.1 of the compartment 32 into the subsidiary
duct 34.7 of the duct 34. The depleted substreams 96.7 pass
into and flow along the passage 18 alongside the depleted
substreams 96.6 on the sides thereof remote from the
depleted substreams 96.5 to the deflector plates
at 44. The deflector plates deflect the depleted
substreams 96.7 so that they continue to flow along the
passage 18 alongside the depleted substreams 96.6.
42
1074Z39
(h) Where the substreams 96.7 pass under the duct 40
they receive via flow connections 42 from the subsidiary
duct 40.4 parts of a stream 88.4 from the preceding
module of the series, at substantially the same isotopic
composition. The combined substreams 88.4, 96.7 then
flow along the passage 18 towards the compressor
20. It will be apparent that, once the depleted substreams
96.7 pass over the deflector plates at 44, they are
combined in a single depleted stream which flows along
the passage 18 alongside and between the depleted
substreams 96.6. The combined stream 88.4, 96.7
passes through a 45 sector 110 in the compressor 20.
Said combined substream 96.7, 88.4 then passes through
a 45 sector llO.l in the heat exchanger 22 and enters
a 45 sector 110.1 in the separator 24. The sector llO
is between the sectors 108 and the sectors 110.1 are
respectively between the pairs of sectors 108.1 in the
heat exchanger 22 and separator 24. In the elements 26
of the sector llO.1 of the separator 24 isotopic separation
takes place and said combined stream 96.7, 88.4 is
divided into an enriched stream 90.4 and a depleted
stream 96.8. The enriched stream 90.4 passes through
the subsidiary outlets of the elements 26 into the
compartment 32 and then through a flow connection from
the sector 110.1 of the compartment 32 into the subsidiary
duct 34.8 of the duct 34. The depleted stream 96.8
passes from the main outlets 26.2 of the elements 26 in
the sector 110.1 of the separator 24 into the passage
-43-
- ~ . -
'' . - ' - , - . ~ ,, " ' ' ~ ' ' .
' -: . .
74Z39
18 between the depleted substreams 96.7. Said depleted
substream 96.8 passes along a single sector of the
passage 18 between the depleted substreams 96.7, and
passes out of the main outlet 38.
It will be appreciated that, as in Figures 2 and
4, the pairs of sectors 98. 100, 102, 104, 106, 108, and
the pairs of sectors 98.1, 100.1, 102.1, 104.1, 106.1 and
108.1 are shown for clarity in Figure 6 as a single sector.
The various isotopic compositions of the streams flowing
through the apparatus for the flow diagram 82 are arranged
so that the enriched streams 90.1 to 90.4 have substantial-
ly the same isotopic composition respectively as the stream
86 and the depleted streams 96.1 to 96.3. The flow of the
streams 90.1 to 90.4 from the subsidiary ducts 34.5 to
34.8 and into the subsidiary ducts 40.5 to 40.8 amounts to
an internal circulation regarding the apparatus 82. The
enriched streams 94.1 to 94.4 correspond to the streams
88.1 to 88.4 and pass on to a succeeding module in the series.
The depleted stream 96.8 corresponds to the stream 86, and
passes on to a preceding module in the series.
As with Figures 2 and 3, all the elements 26 of
Figure 1 described with reference to Figures 4 to 7 have a
cut of 1/5 with respect to the process gas.
44
~ :~07~Z39
Correspondence between Figures 4 and 5 and Figure
lA is as follows:
The module 10 of Figure 1, for Figures 4 and 5,
accommodates two stages 2 (Figure lA) i.eO a group of half
as many stages 2 as each of the groups 9 of Figure lA (or
half such a group 9);
t'he two stages 2 (Figures lA) forming the group
of Figures 4 and 5 are shown in Figures 4 and 5 respective-
ly as the sets of sectors 74, 74.1; and 80, 80.1;
the feed streams 6 of Figure lA can be regarded
as the streams 70.1, 72; and 70.2, 78.1 of Figures 4 and 5;
the enriched streams 7 of Figure lA can be
regarded as the enriched substreams 76.1, 76.2 of Figures
4 and 5; and
the depleted streams 8 of Figures lA can be
regarded as the depleted substreams 78.1, 78.2 of Figure 4.
If reference is made to Figure lA, it will also
be seen that a module 10 for Figures 4 and 5 must receive
its feed streams 70.1, 70.2 from the preceding module but
one in the series; and its enriched streams 76.1, 76.2
must pass on to the succeeding module but one in the series.
~?
~ ~ .
-~ 1074Z39
Correspondence between Figures 6 and 7 and
Figure lA is as follows:
The module 10 of Figure 1, for Figures 6 and 7,
accommodates eight stages 2 of Figure lA, i.e. it accommo-
dates a group of twice as many stages as a group 9 (or two
such groups 9) of Figure lA;
the eight stages 2 forming the group of Figures 6
and 7 are shown in Figures 6 and 7 as the sets of sectors
92, 92.1; 98, 98.1; 100, 100.1; 102, 102.1; 104, 104.1;
106, 106.1; 108, 108.1; and 110, 110.1;
, .
`~he feed streams 6 of Figure lA can be regarded
as the streams 86, 90.1; 96.1, 90.2; 96.2, 90.3; 96.3,
90.4 96.4, 88.1; 96.5, 88.2; 96.6, 88.3; and 96.7,
88.4 of Figures 6 and 7;
the enriched streams 7 of Figure lA can be
regarded as the enriched substreams 94.1 to 94.4 and 90.1
to 90.4 of Figures 6 and 7; and
the depleted streams 8 of Figure lA can be regarded
as the depleted substreams 96.1 to 96.8 of Figure 6.
As with Figures 2 and 3, there is in Figures 1 and
4 to 7 correspondence in the stages 2 between the compres-
sors 5 (Figure lA) and the compressor 20 (Figures 1 and 4
46
- ............................................ . .
. , . . - , . -
- ''- ' '"~
- 1074Z39
to 7); and between the heat exchangers 4 (Figure lA) and
the heat exchangers 22 (Figures 1 and 4 to 7). Thus the
module 10 of Figure 1, when used as shown in Figures 4 and
5 accommodates half a group 9 (or a group half the size of
said group 9) of stages 2 (Figure lA). A single compres-
sor 20 and heat exchanger 22 (Figure 1) are thus used
instead of two compressors 5 and heat exchangers 4 (Figure
lA). Similarly the module 10 when used as
shown in Figures 6 and 7 accommodates two groups 9
(or a group twice the size of a group 9) of stages 2
(Figure lA). The single compressor 20 and heat exchanger
22 thus replaces eight compressors 5 and heat exchangers 4
of Figure lA.
Furthermore, with reference respectively to
Figures 4 and 5 and to Figures 6 and 7, a single separator
24 may be used instead of the plurality of separators 3 of
Figure lA.
The invention has been illustrated with specific
reference to apparatus for the isotopic separation of gases.
The apparatus 10 forms a module in a cascade-type series of
similar apparatus. A single apparatus 10 has been shown in
Figure 1, and it is contemplated that the modules 10 will
remain substantially unchanged throughout the cascade
arrangement. Thus, in each module the overall dimensions
-47-
. .:
..... . .
.
'' - , , , ' - :
~ ~L074239
and relative locations of the housings 12, 14, the compres-
sor 20, the heat exchanger 22, the separator 24 and compart-
ment 32, the inlet 36 and outlet 38 and the ducts 34, 40
will remain substantially unchanged. However, as there is
progression along the series of modules of the cascade,
from the inlet feed stream of the cascade towards either
the final outlet enriched stream or the final outlet
depleted stream, mass flow rates in forward and reverse
directions along the cascade will diminish. Thus several
sets of modules 10 may be required to handle the total mass
flow rates of a group 9 of four stages in a block near the
feed stream of the cascade. In an intermediate position in
the cascade, a single module 10 may be able to handle the
total mass flow of a group 9 of four stages; and near the
final outlet enriched or depleted stream of the cascade, a
single module 10 may be able to handle more than the total
mass flow of a group 9 of four stages.
As shown in Figures 2 and 3, a module 10 can
accommodate a group 9 of four stages in a block 1 of a
cascade arrangement, which group 9 receives four enriched
streams (50.1 to 50.4) from the preceding module or group,
and which receives a single depleted stream (52) from the
succeeding module or group in the series. This demonstrates
a possible intermediate module in the cascade arrangement.
In Figures 4 and 5, on the other hand, flow
diagrams are shown for a module 10 receiving two enriched
streams 70.1 and 70.2 from the preceding module but one,
48
.
--
: . - - . ~, : ., . . : . .. . - - .
. . . -:
.: .. - . . . - - - : .
74239
and a depleted stream 72 from the succeeding module.
Figures 4 and 5 may thus be for a module near
the beginning of the cascade arrangement, where the
apparatus 10 is able to handle about half the total
mass flow of a group 9 of four stages. There may thus
be two sets of apparatus 10, forming a group 9 (Figure
lA) of stages, to handle the total mass flow. The
enriched streams (four) from the preceding group of
stages will flow into said two modules lO; and the
depleted stream (one) from the succeeding group 9 of
stages will flow into one of the said two modules lO.
The module lO of Figure l, with reference to Figures
lA, 4 and 5, thus accommodates half a group 9.
In Figures 6 and 7, the flow diagrams are shown
for a position near the end of the cascade arrangement.
The apparatus lO of Figure 1, at this position, may be
able to handle double the total mass flow. The apparatus
10 thus, for Figures 6 and 7, accommodates two groups 9
(Figure lA) in the cascade arrangement. In fact the
sectors 92, 98, 100 and 102, together with the sectors
92.1, 98.1, 100.1 and 102.1 accommodate a higher group
9 in the module 10, and the sectors 104, 106, 108 and
110, with the sectors 104.1, 106.1, 108.1 and llO.l ac-
commodate a lower group 9 in the module lO. Thus, said
lower group receives four enriched streams (88.1 to 88.4)
49
~, .
:.
- , , , -
- ``` 1~7~239
from the preceding group of stages in the cascade
arrangement (in a different module 101 and a depleted
stream (96.4) which is in the form of two substreams
from said higher group; and its enriched outlet streams
(90.1 to 90.4) pass on to said higher group while the
depleted outlet stream 96.8 passes on to said preceding
group. Correspondingly, the said higher group receives
enriched streams ~90.1 to 90.4) from said lower group,
and a depleted stream (86) from the succeeding group
(in another module) in the series; and its enriched
outlet streams (94.1 to 94.4) pass on to said succeeding
group in the series, while its depleted outlet stream
(96.4) passes on to said lower group.
Thus as one progresses along the cascade arrange-
ment from its inlet feed stream to its final outlet
enriched or depleted stream:
(a) At and near the beginning enriched streams moving
forward along the cascade arrangement will pass
from a module to the succeeding module but one,
each group 9 of four stages 2 being accommodated
by as many modules 10 as are required to handle
the total mass flow. (Figures 4 and 5).
.: . : , . : :
: . , . .. . ..... . , -
- .: .. : . ~ . . - :
1074239
(b) As progress is made along the cascade arrangement
the number of modules required to accommodate a
group of stages will decrease until a single
module (Figures 2 and 3) is required ~o handle the :~
total mass flow; and
(c) Towards the end of the cascade arrangement, two or
more groups can be accommodated by a single module
10. (Figures 6 and 7).
~, 51
- , .: . : . .. .
- - :
. ~ : - : :
- ~, . : '. ',' ,' - : :
. . ,, . : . . . . - : - . ...
- :- ::
:'. ' . . ., - . . . - , :, . ' ' .' -
74239
In Figures 8 and 9 another apparatus for
treatment of fluid in accordance with the invention
is shown. Unless otherwise specified, the same
reference numerals are used in Fi~ures 8 and 9 as
s are used in Fi~ure 1.
Thus~ reference numeral 10 generally desiqnates
the~ apparatus, which comprises an inner housing 12
and an outer housing 14 around the inner housina 12.
Inside the inner housin~ 12 is provided a substantially
cylindrical core member 112, and the outer housing 14
ls enclosed by a cylindrical vessel or tank 114.
The housing 12 and core mem~er 112 are coaxial and
define between them the passa~e 16, which is annular.
The housings 12, 14 in turn define between th~m the
passage 18, which is also annular. Opposite ends of
the passage 16 open radially into opposite ends of the
passage 18. The passages 16, 18 thus define an endless
passage or circuit, having an inner annular part formed
by the passage 16, and an outer annular part, within
which the inner part is located, defined bY
the passage 18.
. The axial flow compressor 20 is located in the passage
16, at one end 114.1 of the tank 114. The compressor
20 has shaft 20 1 and blades 20.2. The shaft 20.1
is coaxial with the passages 16, 18 and projects
--5~
~ - lQ74239
. . .
inwardly, form the exterior of the tank 114, at said end 114.1.
The foraminous heat exchange element 22 is located
in the passage 18, at the opposite end 114.2 of the tank 114,
where the passage 16 opens radially outwardly into the
passage 18. The heat exchanger 22 is annular.
The separator 24 is li~ewise annular and is bcated
in the passage 18, extending from the heat exchanger 22
towards the end 114.1 of the tank, being truncated-conical
in shape and tapering to~ards the heat exchanger 22. The
isotopic gas separation elements 26 corresponding to ~e
elements 26 of Figure 1, are located in the separator 24.
The part of the passage 18, deslgnated 18.1,
between the heat exchanger 22 and separator 24 is located
radially outwardly of the separator 24, between the separator and
the housing 14. The part of the passage 18, designated 18.2,
on the opposite side of the separator 24 from the heat ~changer
22 i8 located radially inwardly of the separator 24,
between the separator 24 and the housing 12.
The elements 26 of the separator 24 have their
inlets 26.1 in communication with the passage 18 and
directed through the partition 28 into the part 18.1
of the passage 18. ~he main outlets 26.2 of the
separation elements 26 communicate via the partition
30 into the part 18.2 of the passage 18 between the
~3
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. -
: .' . . ~ ' '
: ' , - . , : , , , ~ ' .:
'' ' ' : ' . '
-
` ` 1074Z39 ~.
.
separator 24 and the housing 12.
The compartment 32 which defines the separator
24 has its outlet duct 34 in ~he form of an annular
compartment extending around the housing 14 at the end
114,1 of the tank 114. The subsidiary outlets of the
gas separation elements open into the duct 34. The
duct 34 has twelve e~ually circumferentially spaced
radially outwardly projecting outlets 116.
The main inlet 36 enters the passage 18 at
end 114.1 of the tank 114 axially outwardly
of the ring of outlets 116. Diametrically
opposite the inlet 36 is provided the main outlet
38, which likewise communicates with the passage 18.
The further inlet duct 40 is annular, and
extends around the shaft 20.1 of the compressor
20, axially outwardly of the comnressor 20, The
duct 40 is defined between a spi~ot formation
118 projecting coaxially outwardly from the end
114.1 of the tank 114. The spigot formation 118 is
bolted to said end of the tank 114, having an end
cover 118.1 from which the shaft 20,1 projects
,. axially outwardly, sealing means 118.2 being
provided at said end cover.118.1
s~
- .. . . : . -~ .. . . . - .
.. . . . , . , .- .. . .
.. , : : .. . . - ,. ~ . :,. .:
: ' . - . , ' . , . ,. - .: . ~: ,
. - - - :. . . . - -
.
.
74239
Bearings 120 are provided for the shaft 20.1
respectively in the spigot formation 118 and in a
mounting formation 122 provided at the end of the
core member 112 adjacent the compressor 20.
An axial flow compressor 124 having blades 124.1
mounted on the shaft 20.1 is provided in the duct 40.
The ~uct 40 has t~elve inlets 126 which are equally
circumferentially spaced and comprise passages in the
spigot formation 118, the passages 126 opening radially
outwardly. The duct 40 opens axially into the passage
16 where the passage 18 communicates radially with
the passage 16 at the end 114.1 of the tank 114.
The end of the CQre membe-: 112 at the end 114.2
of the tank 114 is conne~ted to a manhole cover 128
lS by a bellows formation 130 which permits expansion
and contraction. A diffusor 13l is provided at the
outlet of the compressor 20.
With particular reference to Figure 9, the
passage 16, heat exchanger 22, separator 24 and
passage 18 are divided into axially extending
compartments by a plurality of radial, axially
extending circumferentially spaced partitions
132- There are 48 partitions 132 shown, 48 keing
typi~ally a suitable number for use with a separator 24
having a cut in the region of about 1/20.
5~
_ ~_
' ''' ' ' ' : ' ' ~ '
-
' ' :
` 1074239
Deflecting means is provided on the partitions, .
adapted to deflect fluid passing along the circuit
defined by the passages 16, 18 in a circumferential
direction relative to said passages. The deflecting
means is provided in the passage 18 at 134. By way of
example, the schematic representation in Figure 10 shows
the deflecting means in'the form of breaks at 138 in the
partitio~s 132, where deflector plates 140, forming part of l
said partitions 132, are inclined circumferentially .
relative to the remainder of said partitions, thereby
pèrmitting flow from one compartment between a pair of the
partitions 132 to another compartment between a different
pair of the partitions 132.
The function of the module 10 of Figures 8 and 9
ls substantially the same as that of the module of Figure L
The enriched stream from the previous module or modules
ln the series, and/or gas which is recirculated from the
outlets 116, passes along the duct 40, being in the form
of twelve sub-streams entering the duct 40 via ~e
inlets 126. Said enriched stream passes through the com- :
pressor 124 and enters the passage 16 upstream of
the compressor 20.
The depleted stream from the succeeding module
10 in the series enters the passage 18 via the main
inlet 36. ~his depleted stream passes radially
inwardly into the passage 18 and thence into the
S6
_~ .
- ~
107~239
passage 16 and into the compressor 20. Said depleted stream
from the cucceeding module passes axially along ~e passage
16 to the end of the passage at theend 114.2 of the housing
114, occupying its sector of the ~ssage 16. It pass~s
through the heat exchanger 22 into the part 18.1 of the
passage 18, thence into the separator 24 and thence
the depleted part thereof passes into the part 18.2
of the passage 18, in the direction of the arrows shown, and
the enriched part thereof passes into the duct 34.
~0 It will be appreciated that the sector occupied
by the depleted stream from the succeeding module entering
through the main inlet 36 may be d~fined by several
compartments between partitions 132. At the deflector
plates 140 at 134 in the passage 18, said depleted stream
is dlvided into two parts, which continue to flow along
the circuit in their appropriate sectors on oppositesides
of the first sector occupied by the depleted stream entering
through the main inlet 36. In this regard it will be
appreciated that the partitions 132 will not be parallel
to the polar axis of the module 10 along their full lengths.
They ~11 be shaped so that they are inclined to ~id axis,
so that the compartments defined between the partitions
discharge into the appropriate sector or sectors of the
. .
.
- . ~ - .
,
~074239
compressor 20. This arrangement of the partitions is
compensate for the bodily rotation of ~e stream of gas
by the compressor, as it passes through the compressor,
about said axis. ~he said two parts of the depleted
stream continue in their flow along their helix-like
paths in opposite directions circumferentially around
the module 10, as described with reference to ~igure 1,
until they eventually come together again and issue from
the main outlet 38 in the form of the depleted stream
from the module 10 which passes to ~e previcus module
in the series.
_~ .
-
'' ' ,. ...... . - ' ' . .
, , - ...
1074239
From a comparison of Figures 8 and 9 with
Figure 1, it will be appreciated that the inlets 126
into the duct 40 correspond with the subsidiary
ducts 40.1 to 40.4 of Figure 1, and the outlets 116
from the oùtlet duct 34 correspond with the subsidiary
ducts 34.1 to 34,4 of Figure 1. The parts of the
enriched stream from the pre~ious module which enter
the ~uct 40 via the inlets 126 are arranged so that
they are expelled by the compressor 124 into the inlet
of the compressor 20 at positions where their
lsotopic composition is the same as that of the
flow from the duct 18 into the inlet of
the compressor 20.
/
It will thus be appreciated that the module 10 of
Figure 1 may also be provided with partitions similar
to the partitions 132 shown in Figures 8 and 9. The
partitions divide the circuit into a plurality of
compartments extending along the circuit. These
compartments may, but need not necessarily,
correspond to the sectors occupied in the circuit
by the various streams and comhined streams
flowlng along the circuit.
The feature of the partitions 132 reduces mixing by
diffusion or turbulence at the interfaces of said streams
as they flow along the clrcuit. The more partitions 132
there are, the less mixing takes place. Thus, in
.. ..
1074Z39 -
general,as may partitions will be provided as possible,
the total number being limited by practical convenience
in construction, and economic considerations.
In general, the s'eeper the concentration gradientin
a circumferential direction in the circuit defined by the
passages 16 and 18 tXe more important are the partitions 1~2,
said partitions, as described above, serving to prevent
mlxing and to prevent disappearance of the concentration
gradient. Thus for a module comprising only a few stages,
e.g. 2 stages as shown in Figure 5, partitions, although
desirable, may not be necessary. For modules which comprise
a large number of stages, e.g. 10 which may typically
be encountered for cuts of about 1/10 or less, partitions
become progressively more important.
In the case of Figure 1, when there are no
partitions, the heat exchanger 22 and the tapering
portion of the passage 16 preferably have a centrally
located axially extending cylindrical core member 112
(hroken lines) extending from the shaft 20.1 to the
compartment 32, corresponding to the core member 112 of
Figures 8 and 9. This core member tends to prevent
mixing of streams flowing along the passage 16 with
streams at diametrically opposed positions.
~0
- , - --
.
.- . : .
- - ~ : . - . . ~ ,:
74Z3~
The examples with reference to Figures 1 to 7
have been described with reference to elements 26
in which the cut is 1/5 and in which enriched
streams and depleted streams are at the same pressure.
In cases where each stage 2 (Figure lA) has an
enriched stream 7 at a different pressure from that
of its depleted stream, it is contemPlated that the
streams having the lower pressure will be pas!;ed
through an additional compressor before being
added to the other streams, to equalise the pressure
- of the streams, after which the~ pass through the
common compressor 20 and heat exchanger 22 (Figure 1).
Thus, for example,an additional compressor may be
provide~ in the duct 40 of Fiaure 1 when the streams
50 (Figure 2) are at a lower pressure than the streams
52 and 58; or the addltional compressor ma~ ~e
provided in the portion 16.2 of the passage 16
when said streams S0 are at a higher pressure than the
streams 52 and 58. In the case of Figures 8 and 9,
the additional compressor is shown at 124, for circumstances
similar to the case where the streams 50 are at
a lower pressure than the streams 52 and 58.
Furthermore, it will be appreciated that the
module 10 need not be used to accommodate an integral
number of groups of stages, or a group or groups
comprising an integral number of stages. Thus it
6J
. 5~~
.
' ''
239
is contemplated that the module may be used to
accommodate any number of groups or portions thereof,
- comprising any number of stages or portions thereof.
Appropriate ~low connections will be ~ovided, as
necessary. Thus the method and apparatus are not
limited to specific cuts of e.g. a 1/3, a 1/4 or
a 1/5, and any desire~ cut down to 1/20 or less may
be used.
It will also be appreciated that the
deflector plates need not necessarily deflect flow from a
given compartment into the adjacent or any other specific
compartment. In practice the deflector plates can
divert the flow from a compartment by any arbitrary amount,
the deflection being sufficient to deflect the flow into
the adjacent sector, bearing in mind that the sectors need
not correspond with compartments between partitions 132.
The amount of diversion by the deflector plates will
in fact depend on mass flow balance considerations in the
module 10, i.e. on the magnitudes of the depleted
streams flowing between modules.
, -
b~ .
-5~ , ' .
.: ' ' ~ , - '. -
~ ~V74239
The invention has as an additional advanta~e the
fact that standardization of modules is possible.
Furthermore, in isotope separation, compression (passin~
the stream through a compressor to move the stream) and heat
exchange (e.g. coolin~ the stream after compressioil)
may be required whenever the stream has passed through
isotopic separation elements. A further advantage of the
invention is thus that each module 10 has a single
compressor 20 and heat exchangex 22, for internal
circulation, regardless of the number of separate
streams of gas moving forward or countercurrent along
the cascade arrangement and passing through the module. When
necessary, each module also only has a single compressor 124
to eaualize pressures between enriched streams entering
the module and internal circulating streams. The use
of a large number of compressors and heat exchanaers
(at least one for each stage shown in Fi~ure lA) is
thus avoided, and use of a relatively small number of
identical compressors and heat exchangers is thus made
possible. Where partitions are provided, the only
parts of the circuit in the module where the various
streams and substreams will be in contact with each
other will be in the portion of the circuit occupied
by the compressor 20 and the portion of the circuit
where the deflector plates 140 are located. In the
case of Figures 8 and 9 there will also be contact
~3
~ ~74Z39
where the compressor 124 is located, with respect to
the enriched streams from the previous module. The
partitions 132 thus serve to reduce mixing of
adjacent streams and sub-streams, while the advantages
of having a single compressor 20, a single compressor
124 where provided, a single heat exchanger 22 and a single
separator 24 for each module 10 are retained.
Use of the method and module in accordance
with the invention, for cuts in the region of
1/20 in the enrichment of uranium hexa-
fluoride (UF6) with respect to U235 , is
expected to lead to a reduction in plant cost
of in the region of at least 20~ and possibly
up to 50% or more. Loss of efficiency owing to
mixing by diffusion where gas stre~ns and
sub-streams are in contact is believed to be
under 10~ when compared with conventional
cascade arrangements, and the cost of extra
modules to make up this loss will be substantially
more than compensated for by the savings occasioned
by the use of standardized and relatively large
modules.
6~
- . : . , . .. i '
' ' - ~ ., - '' '.-
