NO145496B - PROCEDURE FOR TREATMENT OF GAS MIXTURE, AND APPARATUS FOR CARRYING OUT THE PROCEDURE - Google Patents

Description

The present invention relates to a method for the separation of gas mixtures, in particular isotope mixtures, in which gas is led through a cascade of several stages, each of which contains a separator, as well as a device for carrying out the method.

The above-mentioned method is characterized by the fact that the gases that come out of the separators from several stages in the cascade are led to a single compressor, since at least the gases that are taken out from some separators have different compositions,

that the gases are combined into a single gas stream, the composition of which in a manner known per se through a cross section of the gas stream varies from a minimum with regard to the concentration of one of the separated gases to a maximum

of this concentration, that the gas flow is led through the compressor during which the differences in the composition of the gas flow remain unchanged, and that the gas flow is divided into several sub-flows, at least some of which have a different composition, and these sub-flows are led through the further stages of the cascade.

Preferred embodiments appear from the subsequent subclaims 2-10.

The invention further comprises a device which is characterized as a cascade of several stages, each of which has a separator, a compressor, a device for extracting gases with different compositions from several separators which are arranged in the cascade's different stages and for supplying gases to the compressor , as the device combines the gases into a single gas stream whose composition varies in a manner known per se through a section of the gas stream that runs across the direction of flow from a minimum with regard to the concentration of the gas to be separated to a maximum of this concentration, and a device for dividing the gas flow coming out of the compressor into several sub-flows, at least some of which have different compositions, and for guiding these sub-flows through further stages of the cascade.

Preferred embodiments of the device can be seen from the subsequent subclaims 12-19.

In the following detailed description of the invention, this is described and illustrated for simplicity with "reference to a process for isotope separation with a separation of 1/5, i.e. that the fraction of the feed stream that is fed out of the separating elements as an enriched stream constitutes 1/5 on a mass current basis, and the enriched stream is 1/4 of the depleted stream leaving the element, on a mass current basis. The example relates to the case where the enriched and depleted streams exiting such an element have the same pressure.

The example can be applied to a process in which a stream of fluid consisting only of a process gas (such as UF, which is to be enriched

235

with regard to U ) is processed or a process gas in which a stream of fluid comprises a mixture of a process gas and a carrier gas such as hydrogen or helium is processed. However, in all subsequent references to an isotopic composition and mass flow of a stream of gas refer to the isotopic composition and mass flow of the process gas in the stream.

The invention shall be described by way of example and with reference to the attached drawings: Fig. IA schematically shows a flow chart for part of a cascade framework suitable for 1/5 fractionation,

fig. 1 shows an axial partial side section of the apparatus for treating a fluid according to the present invention,

fig. 2 shows a flow diagram for the apparatus according to fig. 1,

fig. 3A - 3H show schematic flows through different cross-sections of the apparatus according to fig. 1,

fig. 4 shows a flow diagram for a diagram of an apparatus similar to that shown in fig. 1, but adapted to have a lower degree of circulation than the apparatus according to fig. 1,

fig. 5A - 5D show sections corresponding to those shown in fig. 3A - 3H

for the flow diagram according to fig. 4,

fig. 6 shows a flow diagram for an apparatus similar to that shown in fig. 1, but adapted to have a greater degree of circulation than the apparatus according to fig. 1,

fig. 7A - 7P show corresponding sections to those shown in fig. 3A - 3H for the flow diagram according to fig. 6,

fig. 8 shows a partially cut side view of another apparatus for treating a fluid according to the present invention in the direction of the line VIII - VIII in fig. 9,

fig. 9 shows a partially cut-away elevation of the apparatus in fig. 8 in the direction of the line IX - IX in fig. 8, and

fig. 10 shows part of the apparatus in fig. 8 and 9 in detail, seen in the direction line X - X in fig. 9.

In fig. IA, the reference number 1 generally denotes a part of a block which forms part of a cascade arrangement/as the cascade arrangement is made up of a number of blocks which are connected in series. Each block comprises a number of substantially identical stages 2 and each stage 2 in turn comprises an isotope separator 3, a heat exchanger 4 and a compressor 5 adapted to circulate a gas stream in series through the heat exchanger 4 and the separator 3. The stages 2 are connected by means of the feed streams 6, enriched streams 7 and depleted streams 8. Each feed stream 6 introduced in stage 2 is made up of the streams 7 and 8 from two further different stages 2 and fed via an associated compressor 5 and heat exchanger 4 to the associated separator 3 where it is divided into further streams 7 and 8. The further streams are in turn fed to two further stages 2. In fig. IA is part of the block shown to comprise three groups

9 of four steps 2 each. Each group receives as input

four enriched streams 7 from the preceding group and one depleted stream 8 from the following group 9. The stages can be considered to be connected in series with enriched streams 7 flowing counter-currently to the depleted streams 8 along the cascade. Each stage is thus shown to receive as part of its input a depleted stream 8 from the succeeding stage, and as part of its input the enriched stream from the stage four behind in the series, the series being considered to advance, together with the degree of enrichment for the currents along the cascade. Each stream 7 is 1/4 of the stream 8 leaving the same stage on a mass current basis. Streams 7 and 8 combine to form each stream 6 which has approximately the same isotopic composition.

The cascade arrangement has an inlet feed stream, a final enriched outlet stream and a final depleted stream (not shown) and the rate^at which fluid is entrained into or withdrawn from the cascade via these streams is controlled to achieve the desired mass flow rates and isotopic compositions through the cascade- the event. The internal connections in step 2, described above, are for the internal steps that are within the block far from its boundaries. At the block's boundaries, i.e. at the interface between the block and adjacent blocks, the block will have a final step whose connection to other steps may be different from the connections for the described step 2, depending on the construction of the cascade.

In Fig. 1, the reference number 10 denotes an apparatus according to the invention which is suitable for isotope separation of gases. The apparatus 10 comprises an inner housing 12 and an outer housing 14 which encloses the inner housing 12. The housing 12 is hollow cylindrical and open-ended and has a narrow part 12.1 and a wide part 12.2 connected with a sloping part 12.3. Likewise, the outer housing 14 is hollow cylindrical with a narrow part 14.1 and a wide part 14.2 connected by a sloping part 14.3. The ends of the outer housing are closed. The narrow part 12.1 is located in the narrow part 14.1, the wide part 12.2 in the wide part 14.2 and the sloping part 12.3 in the sloping part 14.3.

The housing 12 defines a channel 16 with a narrow part 16.1 which opens into the narrow part 14.1 of the housing 14, as well as a wide part 16.2 which opens into the wide part 14.2 of the housing 14. The housings 12, 14 are coaxial and the open ends of the housing 12 are separated axially inwards from the closed ends of the housing 14. The housings 12,'14 define between them an annular channel 18 with a narrow part 18.1 which communicates with the narrow part 16.1 in the channel 16,

and a wide part 18.2 which communicates with the wide part 16.2

in the channel 16. The channels 16, 18 together with the thus defined endless channel or circuit, with an inner tube-shaped part formed by the channel 16 and an outer ring-shaped part, in which the. inner part is located, defined, by channel 18.

An axial vane wheel in the form of an axial compressor 20 provided with a shaft 20.1 and a number of turbine blades 20.2 is arranged in the channel 16. The shaft 20.1 is coaxial with the channels

16, 18 and extends inwards from the outside of the housing 14 in

in the narrow part 16.1 in the channel 16. The turbine blades 20.2 are arranged in the narrow part 16.1 in the channel 16.

A heat exchanger comprising a perforated heat exchange element 2 2 is arranged in the channel 16. The heat exchanger 22 extends over the wide part 16.2 in the channel 16, adjacent to the tapered part 12.3 in the housing 12.

A separator 24 including a number of isotope-gas separation elements 26 is arranged in the wide part 16.2 of the channel 16,'

and the heat exchanger 22 is thus arranged between the separator 24 and the impeller 20. The elements 26 are each provided with an inlet 26.1 which communicates with the channel 16 and is directed towards the narrow part 16.1 of the channel 16. A main outlet 26.2 communicates with the circuit and is directed towards it closed end of the wide part 14.2 in the housing 14, and towards at least one further outlet between the main outlet and the inlet. The elements are, shown in fig.

1 - 7, of the type which has a fractionation of 1/5, i.e. they separate the feed stream into an enriched stream and a depleted stream, the enriched stream making up 1/4 of the depleted stream, calculated on a mass stream basis. Two separating devices 28, 30 are respectively arranged between the heat exchanger 22 and the separator 24, and at the free end of the wide part 16.2 in the channel 16

and thus isolates a chamber 32 in the channel 16 from the rest of the circuit. The inlets 26.1 and the main outlets 26.2 of the elements 26 are respectively from and to the circuit outside the chamber 32, while the further outlets lead into the chamber 32. The chamber 32 has an axially arranged outlet channel 34 which extends axially from the chamber 32 and out through the end of the wide part 14.2 in the housing 14. It will be understood that the further outlet in each element 26 may, instead of being a simply defined outlet, comprise a permeable surface on the element, depending on the isotope separation process that comes into consideration.

A main inlet 36 in the form of a rudder leads into the wide part 18.2 of the channel 18 and is directed into the channel 18 in an axial direction towards the narrow part 18.1 of the channel. A main outlet 38

in the form of a rudder is arranged in the wide part 18.2 of the channel and

is directed towards the channel 18 in the opposite axial direction of the inlet 36. The inlet 36 and the outlet 38 are arranged at diametrically opposite positions along the circumference of the channel 18.

A further inlet in the form of a channel 40 provided with four secondary channels 40.1, 40.2, 40.3 and 40.4. extends

around the periphery of the house 14.

The channel 40 has a number of flow connections from the secondary channels 40.1 - 40.4 into the annular channel 18, which are arranged along the periphery of the annular channel 18. The location of these flow connections, two of which are shown in fig. 1, marked with the reference number 42, will be described in more detail in what follows.

The channel 34 is likewise internally divided by means of separating devices into four secondary channels 34.1, 34.2, 34.3 and 34.4. which opens via the flow connections into the chamber 32. The arrangement regarding the flow connections will be described in more detail below.

Deflection devices are arranged in the annular channel 18

and is adapted to deflect the fluid flow along channel 18. The effect of these deflection devices will be described

in more detail below. The deflection devices comprise a number of deflection elements, preferably in the form of curved deflection plates (not shown) in the channel 18. The plates extend between the housings 14 and 12 and, when viewed from an edge, in a radially inward directiona, extend at an angle to to the longitudinal dimension, i.e. the polar axis of the apparatus 10. The plates are located along a peripheral ring at 44, immediately upstream of the main inlet 36.

The operation of the apparatus will now be described with reference to

fig. 2, wherein reference numeral 46 generally denotes a flow diagram of the apparatus of FIG. 1, as well as to figures 3A - 3H in which the reference numbers 48 generally denote different cross-sections of the apparatus 10 in fig. 1. Unless otherwise stated, like reference numbers refer to like parts.

The apparatus 10 forms a module adapted to house a group of stages forming part of a block in a cascade arrangement for an isotope separation process for gases, and there are a number of similar modules connected in series. An isotopic gas mixture comprising a first component and a second component that differs isotopically from the first component is moved along the series.

In each module, an isotope separation takes place, whereby the gas mixture is divided into two streams, i.e. a stream that is enriched with regard to the desired component, e.g. the first component and a current which is depleted with respect to the desired component.

Each module receives as input the enriched current from a preceding module in series and the depleted current from a subsequent module in the series. The enriched stream from a preceding module is generally denoted by 50 and is fed along the channel 40. The stream 50 is divided into four sub-streams 50.1, 50.2, 50.3 and 50.4. These undercurrents have different isotopic compositions,

ie their concentration or degree of enrichment with respect to the desired component, defined as the ratio on a mass basis between the desired (first) component and the second component are different. These streams are respectively fed along the secondary channels 40.1, 40.2, 40.3 and 40.4. The depleted current from the subsequent module is generally denoted by reference number 52.

The depleted stream 52 is introduced into the channel 18 in the device 10

via the main inlet 36. The secondary channel 40.1 has a single flow connection 42 into the channel 18 and this flow connection is immediately downstream of and axially coincident with the inlet 36. The underflow 50.1 has essentially the same isotopic composition as the flow 42. If desired, can mixing devices, for example a nozzle, guide plate etc. is arranged at connection 42 to promote mixing between the two streams 52 and 50.1. Such mixing devices can be arranged for each connection 42, as described below.

The combined flow formed by underflow 50.1 and the flow 52 flows axially along the channel 18 towards the narrow end 14.1 in the housing 14. This flow essentially takes place along a sector in the channel 18 and the combined flow is fed into the compressor 20, where it flows along a sector of the compressor 20 and into the duct 16, indicated by reference number 54 in Figures 2 and 3A.

The flow of the current 50.1, 52 along the sectors in the channel 18 and 16 through the compressor 20 is such that there is little mixing with the currents flowing along it. The current 50.1, 52 thus forms a sector of an annular current which constitutes the total current through the channel 18, and a sector of the annular or circular current which constitutes the total current along the channel 16. When the combined current 50.1, 52 is fed through the compressor 20 the sector of the total flow which is fed along the channel 16 will be moved in a peripheral direction which is the peripheral direction in which the blades 20.2 in the compressor 20 rotate. The sector 54 in the compressor 20 will thus follow a helical path in the longitudinal direction of the compressor. However, there will be no significant mixing of this flow with flows in adjacent sectors. The stream 50.1, 52 in the sector 54 flows along the channel 16 and is fed into a sector of the heat exchanger 22. Its temperature changes to the desired degree when it is fed through the heat exchanger 22, after which the stream is fed into the elements 26 in the corresponding sector of the chamber 32>via the inlet 26.1 to the separator elements 26.

The sectors in the heat exchanger 22 and the chamber 32 (ie the separator 24) are indicated in fig. 2 and 3E with reference number 54.1. These sectors 54.1 do not need to be axially aligned with sector 54 when it leaves the compressor 20y as a result of which the possibility of a circular vortex in the peripheral direction in the total flow along the channel 16 between the compressor 20 and the heat exchanger 22 is expected.

In the combined stream 50.1, 52, an isotope separation process takes place in the elements 26 which make up the sector 54.1 in the separator 24.

In the sector 54.1 of the separator 24, the combined stream 50.1, 52 is separated into an enriched stream 65.1 and a depleted stream 58.1, the elements 26 having a fractionation capability of 1/5 with respect to the process gas. The depleted gas 58.1 is fed out of the main outlet 26.2 by the elements 26 which make up the sector 54.1. The enriched stream is fed out of the secondary outlets of the elements 26 into the chamber 32. In the chamber 32, the enriched stream 65.1 will be fed into the secondary channel 34.1 in the channel 34 and then fed to the next module in the series.

The depleted stream 58.1 is fed into the channel 18 and flows axially along a sector of the channel 18 to the ring of diverter plates at 44. It hits one or more of these diverter plates and is divided into two substreams 58^1 which are fed axially along the channel 18 and to the opposite sides of the inlet 36. The secondary channel: 40.2 has a pair of flow connections 42 to the channel 18, located where the underflows 58.1 pass along the channel 18. The underflows 58.1 are united via these flow connections 42 with the underflow 50.2 from the secondary channel 40.2. The underflows 50.2, 58.1 have essentially the same isotopic composition. The combined underflows 50.2, 58.1 are fed axially along the channel 18 into the narrow part 14.1 in the housing 14 at opposite sides of the combined flow 50.1, 52. These combined underflows 50.2, 58.1 enter a pair of the sectors 60 in the channel 16 at the compressor 20 on opposite sides of the sector 54. It will be understood that for the sake of a simple representation, these sectors 60 are shown as a single sector in fig. 2.

The combined substreams 50.2, 58.1, as described for the combined stream 50.1, 52, are fed along the channel 16 away from its narrow part 16.1, through the heat exchanger 22 and into the separator 24. The sectors in the heat exchanger 22 and the separator 24

through or into which these undercurrents are fed is denoted by 60.1. In this case too, these sector pairs are indicated as a single sector, in fig. 2, for the heat exchanger 22 and the separator 24. Each combined underflow 50.2, 58.1 is fed into the elements 26 in one of the sectors 60.1 of the separator 24 via their inlet 26.1.

In the sectors 60.1 of the separator 24, the combined substreams 50.2, 58.1 will each be divided into an enriched substream 56.2 and a depleted substream 58.2. The enriched substreams 56.2 are fed through the secondary outlets for the elements 26 in the sectors 60.1 into the chamber 32, and then via the flow connections into the secondary channel 34.2 in the outlet channel 34, to provide an enriched stream 56.2 and then to the subsequent module in the series.

The depleted underflows 58.2 are fed through the outlets 26.2 in the elements 26 in the sector 60.1 and into the channel 18 on opposite sides of the flow 58.1.

The undercurrents 58.2 are fed along the channel 18 on opposite sides

of the flow 58.1 and are deflected by the deflection plates at 44 so that they are fed further along the channel 18 on the sides of the combined underflows 58.1, 50.2 away from the combined flow 50.1, 52. Where the underflows 58.2 are fed radially inwards by the channel 40, they receive the enriched flow 50.3 from the secondary channel 40.3 via a pair of flow connections 42. The enriched stream 50.3 has essentially the same isotopic composition as the sub-streams 58.2.

The combined undercurrents 50.3, 58, 2 are fed axially along the channel 18 away from the deflection plates at 44 and towards the narrow part 18.1 in the channel. The combined sub-streams 50.3, 58.2

are each located respectively next to the combined substreams 50.2, 58.1 remote from the combined stream 50.1, 52. The combined substreams 50.3, 58.2 are fed into a pair of the sectors 62 into the duct 16 at the compressor 20 on the side of the sectors 60 remote from the sector 54. Also in this case, the sector 62 is shown as a simple sector in fig. 2.

The combined substreams 50.3, 58.2, as described for the combined stream 50.1, 52 are fed along the channel 26 away from its narrow part 16.1 through the heat exchanger 22 and into the separator 24. The sectors in the heat exchanger :22 and the separator 24 as the combined substreams 50.3, 52 lines through or into are denoted by 62.1. In fig. 2, these sector pairs are also indicated as a single sector for the heat exchanger 22 and the separator 24. Each underflow 50.3, 58.2 is fed into the elements 26 in one of these sectors 62.1 in the separator 24 via its inlet 26.1.

In the sectors 62.1 in the separator 24, the combined substreams 50.3, 58.2 are separated into an enriched substream 56.3 and a depleted stream 58.3. The enriched underflows 56.3 are fed through the secondary outlets of the elements 26 in the sectors 62.1 and into the chamber 32 and then via the flow connections into the secondary channel 34.3 in the outlet channel 34 and then to the following module in the series•

The depleted underflows 58.3 are fed through the outlets 26.2

in the elements 26 of the sectors 62.1 and into the channel 18, respectively at the sides of the sub-streams 58.2 distant from the stream-j58.1.

The undercurrents 58.3 are respectively fed along the channel 18 next to the undercurrents 58.2, away from the current 58.1 and the undercurrents 58.3 are deflected by means of the deflection plates at 44 so that they pass further along the channel 18 along the sides of the combined undercurrents 58.2, 50.3 away from the combined undercurrents 58.3 , 50.2. The underflows 58.3 will, after they are quickly over the deflection plates at 44, be located next to each other to give a single flow 58.3. Where the stream 58.3 is fed radially inwards over the channel 40, it receives an enriched stream 50.4 from the secondary channel 40.4 via the flow connection 42. The enriched stream 50.4 has essentially 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 channel 18 towards the narrow end 14.1 in the housing 14. The combined stream 50.4, 58.3 is fed into the compressor 20 where it flows along a sector 64, between the sectors 62. The combined stream 50.4, 58.3 is then fed along the channel 16 away from its narrow part 16.1 and through the heat exchanger 22 and into the separator 24. The sectors in the heat exchanger 2 2 and the separator 24 that the combined stream 50.4, 58.3 feed into or through is denoted by 64.1.

In the sector 64.1 of the separator 24, the combined stream 50.4, 53.3 is separated into an enriched substream 56.4 and a depleted substream 58.4. The enriched underflow 56.4 is fed through the secondary outlets in the elements 26 in the sector 64.1 and into the chamber 32 and then via the flow connections into the secondary channel 34.4

in the outlet channel 34 and then to the subsequent module in the series.

The depleted stream 58.4 is fed through the outlets 26.2 in the elements 26 in the sector 64.1 and into the channel 18 between the substreams 58.3. The stream 58.4 is fed a short distance along the wide part of the channel 18 and is then fed into the main outlet 38 through which it flows to the preceding module in the series.

It will be understood that the current 58.4 which is fed through the outlet

38 has the same function in the preceding module in the series as the current 52 which is fed into the apparatus 10 through the inlet 36. Similarly, the streams 56.1 - 56.4' which are fed as subcurrents along the secondary channels 34.1 - 34.4 are treated in the same way and have the same function in the subsequent module in the series as the subcurrents 50.1 - 50.4 which are introduced into the device IO through the secondary channels 40.1, - 40.4 in the channel 40.

When the combined stream 50.1, 52; the combined sub-streams 50.2, 58.1) the combined sub-streams 50.3, 58.2 and the combined stream 50.4, 58.3 are fed along the channels 16, 18 in the axial direction next to each other, they will move along the channels essentially without any mixing except for some diffusion at their interfaces. There is also no significant mixing when the streams and substreams are fed through the compressor 20. It will thus be understood that in the apparatus 10 the various streams and substreams are fed into the channel 18, into the zone in the channel which is located at the inlet 36,

at the channel 40 and the deflection plates at 44, so that the composition of the total current flowing along the channel 18 varies in the desired manner oyer its entire axial cross-section across the direction of movement of the total current along the channel. There is in reality a change in composition in opposite peripheral directions from the main inlet 36 to the main

outlet 38. This change in composition is, with respect to the isotopic composition of the gas, expressed as the concentration of the first or desired component. The total current flowing along the channels 18 and 16 is moved along the circuit by means of the compressor 20 and the variation in composition above it. cross section remains essentially unchanged. Each time the total flow is fed through the heat exchanger 22, heat is emitted from this and each time it is fed respectively through the separator 24

and below the channel 40, material is removed and added to the stream. The concentration of the desired component increases uniformly in the peripheral direction from a minimum at the main outlet 38 to a maximum at the main outlet 36. The composition of the total flow in the channels 18, 16 thus varies in the peripheral direction and the minimum is diametrically opposite to the maximum, with regard to the isotopic composition of the gas .

It will be understood that immediately downstream of the deflector plates at 44 and the flow connections 42, the variation in the composition of the total flow that is carried along the channel 18 will be somewhat gradual, as there is a stepwise difference in the composition between the combined flow 50.1, 52 and the combined subflows 50.2 , 58.1, and 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-by-step character in this variation will decrease as a result of mixing by diffusion taking place in the interfaces between the streams and the sub-streams when they are fed along the channel 18 and the channel 16. The step-by-step character will be most pronounced between the stream 52 and the sub-streams 58.1 and will decrease between adjacent streams in the peripheral direction so that the gradual difference in composition between the stream 58.4 and the sub-streams 58.3 will be the least pronounced. The additions of streams 50.1 - 50.4 via channel 40 will tend to delay the disappearance of this step-like difference. Thus, when the currents and undercurrents are fed along the circuit from the inlet 36 to the outlet 38, the variations will become less step-like and will tend to vary more continuously from the minimum towards the maximum. When the total flow is fed through the compressor 20, it will be rotated in the direction of rotation of the compressor blades 20.2, but the minimum and maximum will remain diametrically opposed to each other and the variation in the composition of the flow will be essentially unchanged.

When the total flow is fed through the compressor 20 in the channel

16 it is compressed and when it is passed through the heat exchanger 22 its temperature changes, and when it is passed through the elements

26 fluid is removed from it by means of these elements ten 1 å

give the enriched streams 56.1 - 56.4. The depleted substreams 58.1 - 58.4 that are fed out of the different sectors in the separator 24 and into the channel 18 thus have a different isotope composition from the various combined streams and substreams that are fed into the same sectors of the separator 24 from the channel 16. total flow that is fed through the separator into

in the channel 18 can thus be regarded as having its composition changed with respect to the concentration of the desired component by fluid being removed from this when it is fed through the separator

tore 24. Furthermore, it will be understood that fluid is added to the total flow that flows through the channel 18 via the inlet 36 and the channel 40 and fluid is removed from the channel 18 via the main outlet 38.

The fluid flowing along the channel 18 is deflected by the deflection plates at 44 in the channel 18. When the total flow is fed over the deflection plates at 44, the isotopic composition of the current will retain its variation over the cross-section, while the extraction and addition of fluid takes place via the channels 38 and 36, respectively.

The total current flowing along the channels changes its flow direction at both ends of the device 10 where it passes from channel 18 into channel 16 and where it passes from channel 16 into channel 18. It thus flows along a circuit.

Fluid that flows along the circuit can be described as coming from the main inlet 36, the flow being added via the flow connection 42 from the secondary channel 40.1 The combined flows 50.1, 52 are moved along the circuit to the separator 24, where it is depleted with the help of the elements 26. the remaining part of the stream, i.e. the depleted stream 58.1> continues to flow along the circuit until it reaches the deflector plates at 44. There it is deflected in two parts, i.e. in the undercurrents 58.1, which continue to flow around the circuit. They are also added from the channel 40.2 via the flow connections 42 and the combined underflows 58.1, 50.2 flow again along the circuit to the separator 42 where they are further depleted. The depleted undercurrents 58.2 follow a corresponding cycle around the circuit, being added at the flow connections 42 by means of the currents 50.3 from the secondary channel 40.3. The combined sub-streams 50.3, 58.2 then flow along the separator 24 where they are further depleted to give the depleted stream 58.3. The current 58.3 is supplied via the current connections at 42 by the current 50.4 from the secondary channel 40.4. The combined current 40.4, 58.3 makes a final circuit in the device to the separator 24 where they are finally depleted. The depleted stream 58.4 is then fed out of the main outlet 38. From what has been mentioned above, it will be understood that the stream 52 which is fed in through the main inlet 36 makes a circuit in the apparatus 10 through the sectors 54, 54.ljafter which it is divided into two streams. These currents follow a helical path around the circuit formed by the channels 18, 16, as the paths move diametrically opposite to each other and pass respectively in order through the sector pairs 60, 60.1, and the sector pairs 62, 62.1.

This can best be seen from fig. 3. The lanes are moved apart

until finally they converge and become a single path in the sectors 64, 64.1 for which they are fed out of the main outlet 38. The paths in the peripheral direction are such that the axes of their screws extend oppositely along tp halves of a circle along the arrow 65 (Fig. 3A) from inlet 36 to outlet 38.

It will be understood that at the inlet to the channel 16 at the compressor 20, the total flow into the channel 16 can be regarded as a number of different flows of fluids with different compositions that are introduced into the channel 16. They are moved along the channel by means of the compressor 20 and are physically separated from each other in the separator 24. They can be considered to be reintroduced into the circuit when they are fed, depleted, out of the separator 24 and into the channel 18. The stream 58.4 is finally physically separated from the other streams (58.1, 58.2 and 58.3) when it is removed from the circuit via outlet 38.

If fig. IA is compared with figures 2 and 3, the following agreement will appear: The module exemplified by the apparatus 10 in fig. 1 is i.a. capable of containing four stages 2, i.e. one of the groups 9 shown in fig.

IA,

steps 2 in group .9 in fig. IA is shown in figures 2 and 3 as respectively a set of sectors 54, 54.15 60, 60.1; 62, 62.1;

and 64 , 64 .1,

the enriched streams 7 in fig. IA can be regarded as enriched substreams 56.1 - 56.4 in figures 2 and 3,

the depleted streams 8 in fig. IA can be considered as depleted substreams 58.1 - 58.4 in figures 2 and 3, and

a further correspondence in the stages 2 between the compressors 5 (fig. IA) and the compressor 20 (figs. 1 - 3), and between the heat exchangers 4 (fig. IA) and the heat exchanger 22 (fig. 1 - 3). Thus, when the module 10 in figures 1-3 is used as shown in fig. 2 and 3, it occupies a group 9 of the steps 2 (figure IA). Thus, a single compressor 20 and a heat exchanger 22 (fig. 1) are used instead of four compressors 5 and four heat exchangers 4 in a group 9 in fig. IA. Furthermore, a simple combination of the elements 26, as shown by the separator 24, is used instead of four individual separators 3 in fig. IA. in this respect, it will be understood that in order to achieve coherence between figures IA, and 1, 2 and 3, the elements 26 are intended for use in all modules 10 in cascade arrangement, which elements 26

has a fractionation rate of 1/5 with respect to the process gas.

In the illustration in fig. 1, 2 and 3, the stream 52 with the various inputs and withdrawals therefrom can be considered as making four passes through the apparatus, respectively through sectors 54, 54.1, sectors 60, 60.1, sectors 62, 62.1 and sectors 64, 64.1.

In fig. 4, the reference numeral 66 generally denotes a flow diagram for the apparatus corresponding to that according to FIG. 1, but adapted to have a smaller degree of circulation than that in fig. 1.

In fig. 5, the reference number 68 denotes a general section corresponding to those in fig. 3A - 3H for the apparatus with the flow diagram according to fig. 4.

An enriched stream 70 from the preceding module minus one in the series is introduced into the apparatus according to fig. 4 in the form of a pair of undercurrents 70.1, 70.2 through the channel 40 which is provided with two secondary channels 40.1, 40.2. There will thus be two flow connections at 42, one for channel 40.1 downstream of inlet 36 and a second for channel 40.2 in a diametrically opposite position into channel 18 downstream of outlet 38. A depleted stream from the following module in the series is introduced in the form of a current 72 through the inlet 36. The current 72 makes two passes through the apparatus instead of four as shown in fig. 2. The first pass is through sector 74 in the compressor

20 and the sector 74.1 in the heat exchanger 22 and the separator 24. The stream 72 is combined, for the passage through the sectors

74, 74.1, with the undercurrent 70.1 from the secondary channel 40.1. After the combined stream 70.1, 72 passes through the separator 24 and, as described below, becomes a depleted stream 78.1, it is diverted once at 44 by the deflection plates to the diametrically opposite side of the channel 18.

The combined stream 70.1, 72 in the sector 74.1 in the separator

24 is divided into an enriched stream 76.1 which is fed to the following module minus one in the series via the secondary channel 34.1

at the outlet channel 34, as well as a depleted stream 78.1. In the elements 26 in sector 74.1 (and sector 80.1, discussed in the following) a fractionation of 1/5 takes place with respect to the process gas. The channel 34 comprises a pair of secondary channels 34.1, 34.2 leading to the following module minus one in the series. The depleted stream 78.1, as described above, is fed over the deflection plates at 44 and deflected to a diametrically opposite position in the channel 18. This stream 78.1 is fed to the underflow 70.2 from the secondary channel 40.2 and makes another passage through the circuit through the compressor 20, heat exchange

cleaner 22 and the separator 24. It passes through the sector 80

in the compressor 20 and the sectors 80.1 in the heat exchanger 22 and the separator 24. In the sector 80.1 and the separator 24, isotope separation takes place into an enriched stream 76.2 which is fed out through the secondary channel 34.2 and a depleted stream 78.2. The depleted stream 78.2 is fed via outlet 38 to the previous module in the series and the enriched stream 76.2 is fed to the following module minus one in the series'. Thus sectors 74, 74.1 and 80, 80.1 are essentially 180° sectors, while in the case of figures 2 and 3 sectors 54, 54.1 and 64, 64.1

are 90° sectors and sectors 60, 60.1 and 62, 62.1 are 45° sectors. 1 fig. 6, the reference numeral 82 generally denotes a flow diagram for an apparatus corresponding to that in FIG. 1, but is adapted to have a greater degree of circulation than apparatus 10 in fig. 1. In fig. 7, the reference numeral 84 denotes a general section corresponding to those in figures 3A - 3H for the flow diagram according to fig. 6.

The construction and function of the apparatus 10, which the flow diagrams of Figures 6 and 7 represent, is similar in principle to that of the apparatus according to Figures 1,

2 and 3. The essential difference is that the deflection plate at

44 is arranged so that a depleted stream 68 from the subsequent module in the series makes eight passes through the compressor 20, the heat exchanger 22 and the separator 24 before it is carried out through the main outlet 38. The channel 40 has eight secondary channels 40.1 - 40.8 and the channel 34 has eight secondary channels 34.1 -

34.8. The secondary channels 40.1 - 40.4 of the channel 40 feed four streams 88.1 - 88.4 from the preceding module in the series} and the secondary channels 34.1 - 34.4 of the channel 34 feed four enriched streams to the subsequent module in the series» The secondary channels 34.5 - 34.8 of the channel 34 are connected directly with the secondary channels 40.5 - 40.8 of the channel 40. This interconnection is shown schematically in fig. 1 with dashed lines at 89.

The str5mning sequence is:

(a) The stream 86 is fed into the channel 18 through the inlet

36. The stream 86 is fed to the stream 90.1 from the secondary channel 40.5 of the channel 40. The stream 90.1 has essentially the same isotopic composition as the stream 86. The combined stream 86, 90.1 circulates along the circuit as defined by the channels 18, 16 in the direction as described with reference to figures 1, 2 and 3 and is fed into the compressor 20. It is fed through a 45° sector 92 in the compressor 20 and through two 45° sectors 92.1 in the heat exchanger 22 and the separator 24 respectively. The combined stream 90.1, 68 in the elements 26 of the sector 92.1 in the separator 24 is divided into an enriched stream 94.1 which is fed from the elements 26 to the chamber 32 and then from the sector 92.1 in the chamber 32 via a flow connection into the secondary channel 34.1, and a depleted stream 96.1 which is fed from the main outlets 26.2 in the elements 26 and into channel 18.

(b) The depleted stream 96.1 is divided into a pair of substreams by the deflection plates at 44, which flow along the channel 18 towards its narrow part 18.1 on opposite sides of the inlet 36 and the stream 86. The substreams 96.1 are fed under the channel 40 where they receive part of a stream 90.2 from the secondary channel 40.6 via the flow connections 42. The combined substreams 90.2, 96.1 circulate along the circuit on opposite sides of the combined stream 90.1, 86 and are fed through a pair of 22 1/2° sectors 98 in the compressor 22 and a pair of 22 1/2 ° sectors 98.1

in the heat exchanger 22 and the separator 24, respectively. The sectors 98 are on the opposite side of the sector 92, and the sectors 98.1 are on the opposite side of the sector 92.1 in the heat exchanger 2 2 and the separator 24. In the elements 26 of the sectors 98.1 in the separato

pure 24, isotope separation takes place and the combined substreams 90.2, 96.1 are divided into an enriched substream 94.2 which is fed from the secondary outlets of the elements 26 into the chamber 32 and then through the flow connections from the sectors 98.1 in the chamber 32 and then through the flow connections from the sectors 98.1 in the chamber and into the secondary channel 34.2

in the channel 34, and in depleted underflows 96.2 which are fed from the main outlets 26.2 of the elements 26 and into the channel 18.

(c) The depleted underflows 96.2 are fed along the channel 18

on opposite sides of the depleted stream 96.1 until they reach the deflecting plates at 44, where they are deflected so that they are fed further along the channel 18 towards the narrow part 18.1 in the channel 18 and on the sides of the undercurrents 96.1 remote from the current 86. Where the undercurrents 96.2 are fed under the channel 40, they receive via the flow connections 42 from the secondary channel 40.7 a part of the stream 90.3 with essentially the same isotopic composition. The combined sub-streams 90.3, 96.2 are fed along the circuit next to the combined sub-streams 90.2, 96.1 separated from the combined stream 90.1, 86.

The combined sub-streams 96.2, 90.3 are introduced further

22 1/2° sectors 100.in the compressor 20 on the sides of the sectors

98 separated from the sector 92. The combined substreams 96.2, 90.3 are then fed through a pair of 22 1/2° sectors 100.1 in the heat exchanger 22 and the separator 24, respectively. The sectors 100.1

in the heat exchanger and the separator are at the sides of the sectors 98.1 distant from the sector 92.1. In the elements 26 of the sectors lOO.1 of the separator 24, an isotope separation takes place and the combined substreams 90.3, 96.2 are divided into an enriched substream 94.3 which is fed from the secondary outlets of the elements 26 into the chamber 32 and then through the flow connections from the sectors 100.1 in the chamber 32 of the secondary channel 34.3 of the channel 34, as well as depleted undercurrents 96.3 which are fed from the main outlet 26.2 of the elements 26 and into the channel 18 next to the undercurrents 96.2 distant from the current 96.1.

(d) The depleted substreams 96.3 flow along the channel 18 towards its narrow part 18.1 on the sides of the depleted substreams 96.2 remote from the depleted stream 96.1. The depleted undercurrents 96.3 are deflected by the deflection plates at 44 so that they continue to flow along the channel 18 along the depleted undercurrents 96.2. Where the undercurrents 96.3 are fed under the channel 40, they receive via the flow connections 42 from the secondary channel 40.8 a part of the current 90.4 with essentially the same isotopic composition. The combined sub-flows 90.4, 96.3 circulate along the circuit adjacent to the combined sub-flows 96.2, 90.3 remote from the combined sub-flows

96.1, 90. 2) and is fed through a pair of 22 1/2° sectors 102 in the compressor 20 and a pair of 22 1/2° sectors 102.1 in the heat exchanger 22 and the separator 24, respectively. In the elements 26 in the sectors 102.1 of the separator 24 find a isotope separation takes place and the combined substreams 90.4, 96.3 are divided into enriched substreams 94.4 and depleted substreams 96.4. The enriched substreams 94.4 are fed through the secondary outlets from these elements into the chamber 32 and from the sectors 102.1 in the chamber 32

via the flow connections into the secondary channel 34.4 in the channel 34. The depleted subflows 96.4. is fed into the channel 18 via the main outlets 26.2 of the elements 26 next to the depleted substreams 96.3 distant from the depleted substreams 96.2.

The depleted underflows 96.4 flow along channel 18 to the deflection plates at 44 where they are deflected to further

is fed along the channel 18 next to the depleted underflows 96.3; distant from the depleted sub-streams 96.3, distant from the depleted sub-streams 96.2. (e) Where the depleted underflows 96.4 are fed under the channel 40, they receive via the flow connections 4 2 from the secondary channel 40.1 of the channel 40, parts of the flow 88.1 from the previous module in the series with essentially the same isotopic composition. The combined substreams 96.4, 88.1 circulate along the circuit adjacent to the combined substreams 96.3, 90.4 remote from the combined substreams 96.2, 90.3. The combined substreams 96.4, 88.1 are fed through a pair of 22 1/2° sectors 104 in the compressor 20 along the sectors 102. They are then fed through a pair of 2 2 1/2° sectors 104.1 in the heat exchanger 22 and into a pair of 22 1/2 ° sectors 104.1 in the separator 24.

In the elements 26 in the sectors 104.1 of the separator 24, an isotope separation takes place and the combined substreams 96.4,

88.1 is divided into enriched substreams 90.1 and depleted substreams 96.5. The enriched underflows 90.1 are fed from the secondary outlets of the elements 26 into the chamber 32 and then from the sectors 104.1 of the chamber 32 via the flow connections into the secondary channel 34.5 of the channel 34. Depleted

undercurrents 96.5 are fed from the main outlets 26.2 of the elements 26 into the channel 18 along the depleted undercurrents 96.4 next to the depleted undercurrents 96.4 distant from the depleted undercurrents 96.3. The depleted undercurrents 96.5 are then fed along the channel 18 adjacent to the depleted undercurrents 96.4 remote from the depleted undercurrents 96.3 to the deflection plates at 44. At the deflection plates the depleted undercurrents 96.5 are deflected so that they continue to travel along the channel 18 adjacent to the depleted substreams 96.4.

(f) Where the depleted substreams 96.5 are lined below

the channel 40 receives, via the flow connections 42 from the secondary channel 40. 2, parts of a stream 88.2 from the previous module in series with essentially the same isotopic composition. The combined substreams 96.5, 88.2 flow along the channel 18 to the compressor 20. The combined substreams 88.2, 96.5 are fed through a pair of 2 2 1/2° sectors 106 into the compressor 20 along the sectors 104. The combined substreams 96.5, 88.2 are then fed along the channel 16 through the 22 1/2° sector 106.1 and into the heat exchanger 22 next to the sectors 104.1, and then into the 2 2 1/2° sector 106.1 in the separator 24 along the sectors 104.1. In the elements 26 of the sectors 106.1 in the separa-. tore 24, an isotope separation takes place and the aforementioned combined substreams 96.5, 88.2 are divided into two pairs of enriched substreams 90.2 and a pair of depleted substreams 96.6. The enriched underflows 92.2 are fed through the secondary outlets of the elements 26 into the chamber 32 and then through the flow connections from the sectors 106.1 in the chamber 32 into the secondary channel 34.6 of the channel 34. The depleted underflows 96.6 are fed into the channel 18 and along the channel 18 next to the depleted substreams 96.5 and next to this far from the depleted substreams 96.4. At the deflection plates at 44, the depleted substreams 96.6 are deflected to continue along the channel 18 adjacent to the depleted substreams 96.5.

(g) Where the depleted substreams 96.6 are fed under the channel 40, they receive via the flow connections 42 from the secondary channel 40.3 part of a stream 88.3 of gas from a preceding module in the series, with essentially the same isotopic composition

sentence.. The combined substreams 96.6, 88.3 are fed along the channel 18 to the compressor 20. The combined substreams 96.6, 88.3 are fed through a pair of 22 1/2° sectors 108 to the turbine wheel 20 adjacent to the sectors 106. Combined substreams 96.6, 88.3 is fed through a pair of 22 1/2° sectors 108.1 in the heat exchanger 22 next to the sectors 106.1 in this and

into a pair of 22 1/2° sectors 108.1 in the separator 24 along its sectors 106.1. In the elements 26 of the sectors 108.1 of the separator 24, an isotope separation takes place and the 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 underflows 90.3 are fed from the secondary outlets of the elements 26 into the chamber 32 and then through the flow connections from the sectors 108.1 in the chamber 32 into the secondary channel 34.7 of the channel 34. The depleted underflows 96.7 are fed into and flow along the channel 18, along and alongside the depleted undercurrents 96.6) removed from the depleted undercurrents 96.5 to the deflection plates at 44. The deflection plates deflect the depleted undercurrents 96.6 so that they continue to flow along the channel 18 adjacent to the depleted undercurrents 96.6.

(h) Where the substreams 96.7 are fed under the channel 40, they receive via the flow connections 42 from the secondary channel 40.4

a portion of a stream 88.4, with substantially the same isotopic composition, from the preceding module in the series" The combined substreams 88.4, 96.7 then flow along the channel 18 towards the compressor 20. It will be obvious that when the depleted substream 96.7 is fed above the deflection plates at 44, they are combined into a single depleted stream which flows along the channel 18 adjacent to and between the depleted substreams 96.6. The combined stream 88.4, 96.7 is fed through a 45° sector 110 into the compressor 20. The combined substreams 96.7, 88.4 are then fed through a 45° sector 110.1 in the heat exchanger 22 and then fed into a 45° sector 110.1

in the separator 24. The sector 110 between the sectors 108 and the sectors 110.1 is respectively between the sector pairs 108.1 in the heat» exchanger 22 and the separator 24. In the elements 26 of the sector 110.1 of the separator 24 an isotope separation takes place and the combined streams 96.7, 88.4 are divided in an enriched stream

90.4 and a depleted current 96.8. The enriched stream 90.4 is fed through the secondary outlets of the elements 26 into the chamber 32 and then through a flow connection from the sector 110.1 to the chamber 32 and into the secondary channel 34.8 of the channel 34. The depleted stream 96.8 is fed from the main outlet 26.2 of the elements 26 in the sector 110.1 of the separator 24 into the channel 18 between the depleted undercurrents 96.7. The depleted underflows 96.8 are fed along a single sector in the channel 18 between the depleted underflows 96.7 and are fed out of the main outlet 38.

It will be understood that, as in figures 2 and 4, the sector pairs 98, 100, 102, 104, 106, 108 and the sector pairs 98.1, 100.1, 102.1, 104.1, 106.1 and 108.1 for the sake of simplicity in fig. 6 is shown as a single sector. The different isotopic compositions in the streams flowing through the device for flow chart 82

are arranged so that the enriched streams 90.1 - 90.4 essentially have the same isotopic composition as the streams 86 and the depleted streams 96.1 - 96.3, respectively. The flow of the streams 90.1 - 90.4 from the secondary channels 34.5 - 34.8 and into the secondary channels 40.5 - 40.8 constitutes the internal circulation for the apparatus 82. The enriched streams 94.1 - 94.4 correspond to the streams 88.1'.- 88.4 and are fed to a subsequent module in the series. The depleted streams 96.8 correspond to the stream 86 and are fed to a preceding module in the series.

As in figures 2 and 3, all the elements 26 in fig. 1 described with reference to fig. 4-7 with a fractionation degree of 1/5 with respect to the process gas.

The coherence between figures 4 and 5 and fig. The IA is as follows:

Module 10 in fig. 1, for figures 4 and 5 occupy two steps 2

(fig. IA), i.e. a group with half as many stages 2 as each of the groups 9 in fig. IA (or half of such group 9);

the steps 2 (fig. IA) which make up the group in fig. 4 and 5 are shown in fig. 4 and 5 respectively as the sector sets 74, 74.1 and 80, 80.1;

the input currents 6 in fig. IA can be considered as the currents 70.1, 72 and 70.2, 78.1 in Figures 4 and 5;

the enriched streams in fig. IA can be considered as the enriched substreams 76.1, 76.2 in fig. 4 and 5; and

the depleted streams 8 in fig. IA can be considered as the depleted streams 78.1, 78.2 in fig. 4.

With reference to fig. IA it can also be seen that the module 10

in fig. 4 and 5 must receive their feed streams 70.1, 70.2 from the preceding module minus one in the series and its enriched streams 76.1, 76.2 must be fed to the following module minus one in the series.

The connection between fig. 6 and 7 and fig. IA is as follows: The module 10 in fig. 1 for fig. 6 and 7 comprise eight stages 2 of fig. IA, i.e. it occupies a group with twice as many steps as a group 9 (or two such groups 9) in fig. IA;

the eight steps 2 that make up the group in fig. 6 and 7 are shown in fig. 6 and 7 as the sector sets 92, 92.1; 98, 98.1, 100, 100.1; 102, 102.1; 104, 104.1; 106, 106.1; 108, 108.1 and HO, 110.1;

the input currents 6 in fig. IA can be considered 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 in fig. 6 and 7;

the enriched streams 7 in fig. IA can be considered as the enriched substreams 94.1 - 94.4 and 90.1 - 90.4 in fig. 6 and 7; and

the depleted streams 8 in fig. IA can be considered as the depleted streams 96.1 - 96.8 in fig. 6.

As for fig. 2 and 3 it is in fig. 1 and 4 - 7 conformity

in stages 2 between the compressors 5 (fig. IA) and the compressor 20 (figs. 1 and 4 - 7), and between the heat exchangers 4 (fig. IA)

and the heat exchangers 22 (fig. 1 and 4 - 7). Thus when the module IO in fig. 1 is used as shown in fig. 4 and 5, it occupies half a group 9 (or a group with half the stem movement of the group 9) in steps 2 (Fig. 1A). A single compressor 20 and the heat exchanger 22 (Fig. 1) are thus used instead of two compressors

sors 5 and heat exchangers 4 (fig. IA). In the same way, when mo-

the dowel 10 is used as shown in fig. 6 and 7, it occupies two groups 9 (or a group with twice the size of group

pen 9) of steps 2 (Fig. IA). The one compressor 20 and heat exchanger 22 thus replace eight compressors 5 and heat exchangers 4 in fig. IA.

Further with reference to fig. 4 and 5 and fig. 6 and 7, a single separator 24 can be used instead of a number of separators 3 in fig. IA.

The invention is illustrated with particular reference to a

apparatus for isotope separation of gases. The apparatus 10 forms a module in a cascade-type series of similar apparatus. A simple device 10 is shown in fig. 1 and it is assumed that modu-

len 10 will essentially remain unchanged in a cascade arrangement. Thus, in each module the general dimensions and relative positions of the housings 12, 14, the compressor 20, the heat exchanger 22, the separator 24 and the chamber 32, the inlet 36 and the outlet 38 and the channels 34, 40 will remain essentially unchanged.

However, when there is a development along the module series in the cascade, from the introduced supply stream to the cascade towards either the final outlet of the enriched stream or the final outlet of the depleted stream; the mass flow rates in the forward or reverse direction along the cascade will decrease.

Thus, several sets of modules 10 will be necessary to

act the total mass flow of a group 9 of four stages in a block close to the supply flow 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 of enriched or depleted stream in the cascade, a single module 10 may be able to handle more than the total mass stream of a group 9 of four stages.

As shown in fig. 2 and 3, a module 10 can hold a group 9 off

four steps in a block 1 of the cascade arrangement, which group 9 receives four enriched streams (50.1-50.4) from a preceding module or group and which receives a single depleted stream (52) from the following module or group in the series. This shows a possible intermediate module in the cascade arrangement.

In fig. 4 and 5, on the other hand, the flow diagrams are shown

for a module 10 which receives two enriched streams 70.1 and 70.2

from a preceding module minus 1, and a depleted current 72 from a subsequent module. Figs 4 and 5 can thus be for a module near the beginning of the cascade arrangement where the device 10 is able to handle approx. half of the total mass current for a group 9 of four stages. There can thus be two sets of the apparatus 10 which form a group 9 (fig. 1A) of steps to handle the total mass flow. The enriched streams (4) from the preceding group of stages will flow into the two modules 10, and the depleted stream (a) from the subsequent group 9

of stages will flow into one of the aforementioned two modules 10. The module 10 in fig. 1 with reference to fig. IA, 4 and 5 will thus occupy half of group 9.

In fig. 6 and 7 show flow diagrams for a position

near the end of the cascade event. The apparatus 10 in fig. 1,

at this position, may be able to handle twice the total mass flow. The device 10.can thus,

in fig. 6 and 7, occupy two groups 9 (fig. IA) in the cascade arrangement. In reality, sectors 92, 98, 100 and 102

together with the sectors 92.1, 98.1, 100.1 and 102.1 occupy a hby-

are group 9 in module 10, and sectors 104, 106, 108 and 110 together with sectors 104.1, 106.1, 108.1 and 110.1 occupy a lower group 9 in module 10. Thus, the lower group will receive four enriched streams (88.1 - 88.4) from the preceding group of steps in the cascade arrangement (in one other module IO)

and a depleted stream (96.4) in the form of two substreams from the said higher group, and its enriched effluent streams (90.1 - 90.4) are fed further to the said higher group, while the depleted effluent streams 96.8 are fed to the aforementioned preceding group. In a similar way, the aforementioned hbyere group

receive enriched streams (90.1 - 90.4) from the lower group and a depleted stream (86) from a subsequent group (in another module) in the series, and its enriched outlet streams (94.1 - 94.4) are fed to said subsequent group in the series' ,

while its depleted outlet strbm (96.4) is fed to the lower group.

Thus, in advancing along the cascade arrangement from its supplied food stream to its final outlet of enriched or depleted stream: (a) At and near the beginning, enriched stems moving forward along the cascade arrangement will pass from a mo-

dul to the following module minus one, and each group 9

of four stage 2 is occupied in as many modules 10 as are necessary to handle the total mass flow. (Fig. 4 and 5).

(b) Further in the cascade arrangement, the number of modules required to hold a group of steps will decrease until a single mo-

dul (fig. 2 and 3) is necessary to handle the total mass flow, and

(c) Towards the end of the cascade event, two or

several groups are accommodated in a single module 10. (Fig. 6 and 7).

In fig. 8 and 9 show another device for treating a fluid according to the invention. If nothing else is indicated, the same reference numbers are used in fig. 8 and 9 as those used in fig. 1.

Thus, the reference numeral 10 will generally denote an apparatus comprising an inner housing 12 and an outer housing 14 which encloses the inner housing 12. Within the inner housing 12 is indicated a substantially cylindrical core element 112 and the outer housing 14 is enclosed in a cylindrical vessel or tank 114.

The housing 12 and the core member 112 are coaxial and define between them a channel 16, which is annular. The housings 12, 14 will in turn define the channel 18 which is also annular. Opposite ends of the channel 16 open radially into the opposite ends of the channel 18. The channels 16, 18 thus define an endless channel or circuit with an inner annular portion formed by the channel 16 and an outer annular portion, in which the inner portion is arranged, defined by channel 18.

The axial flow compressor 20 is arranged in the channel 16 at one end 114.1 of the tank 114. The compressor 20 has a shaft 20.1 and vanes 20.2. The shaft 20.1 is coaxial with the channels 16, 18 and extends inwards from the outside of the tank 114 at the end 114.1.

A heat exchanger element 22 provided with holes is arranged in the channel 18 on the opposite end 114.2 of the tank 114, where the channel 16 opens radially outwards and into the channel 18. The heat exchanger 22 is annular.

The separator 24 is likewise annular and arranged in the channel 18 and extends from the heat exchanger 22 towards the end 114.1

of the tank and has a truncated cone shape with a slope towards the heat exchanger 22. The isotope gas separation elements 26 correspond to the elements 26 in fig. 1 and is arranged in the separator 24.

The part of the channel 18 designated by 18.1 between the heat exchanger 2 2 and the separator 24 is arranged radially beyond the separator 24, between the separator and the housing 14. The part of the channel 18, designated 18.2 on the opposite side of the separator 24 from the heat exchanger 22 is arranged radially inward from the separator 24, between the separator 24 and the housing 12.

The elements 26 in the separator 24 have their inlets 26.1 which communicate with the channel 18 and directly through the separating device 28 into the part 18.1 in the channel 18. The main outlets 26.2 for the separating elements 26 communicate via the separating device .30

with the part 18.2 in the channel 18 between the separator 24 and the housing 12.

The chamber 32 defining the separator 24 has an outlet channel 34 in the form of an annular chamber extending around the housing 14 at the end 114.1 of the tank 114. The secondary outlets for the gas separation elements open into the channel 34. The channel 34 is provided with twelve circumference equally spaced, radially outwardly projecting outlet 116.

The main inlet 36 leads into the channel 18 at the end 114.1 i

the tank 114 axially outwards from the ring of outlets 116. Diametrically opposite to the inlet 36, a main outlet 38 is arranged which likewise communicates with the channel 18.

Further inlet channel 40 is annular and extends around the shaft 20.1 of the compressor 20 and axially outwards in relation to the compressor 20. The channel 40 is defined between a stud formation 118 which extends coaxially from the end 114.1 of the tank 114. The stud formation 118 is bolted to said end of the tank 114 and is provided with an end cover 118.1 through which the shaft 20.1 extends axially above, sealing devices 118.2 are arranged in the end cover 118.1.

The layers 120 are arranged for the shaft 20.1 respectively in the pin formation 118 and in a mounting part 122 arranged at the end of the core element 112 adjacent to the compressor 20.

The axial compressor 124 is provided with blades 124.1 mounted

on the shaft 20.1 and is arranged in the channel 40. The channel 40

has twelve inlets 126 which are equally spaced around the periphery and form channels in the pin formation 118, the channels 126 opening radially outward. The channel 40 opens axially into the channel 16 where the channel 18 communicates radially with the channel 16 at the end 114.1 of the tank 114.

The end of the core element 112 at the end 114.2 of the tank 114

is connected to a manhole cover 128 by a bellows formation 130 which enables expansion and contraction. A diffuser 131 is arranged at the outlet of the compressor 20.

Reference is made in particular to fig. 9 where it can be seen that the channel 16, the heat exchanger 22, the separator 24 and the channel 18 are divided into axially extending chambers by means of a number of radially, axially extending along the circumference separated separation devices 132. There are shown 48 pieces of separation devices 132, 48 are ty- whip a suitable number for use in a separator 24 with a fractionation in the range of 1/20.

Decoy devices are arranged at the separating devices and

is adapted to deflect the fluid which is fed along the circuit defined by the channels 16, 18 in a peripheral direction in relation to the said channels. De-buoying devices are also provided in

the channel 18 at 134. As an example, in the schematic drawing in fig. 10 shows deflection devices in the form of brakes at 138 in the separation devices 132, where deflection plates 140 form part of the separation devices 132 and which lean along the circumference in relation to the rest of the separation device; thereby allowing flow from a chamber between a pair of separators 132 to another chamber between another pair of separators 132.

The operation of the module 10 according to fig. 8 and 9 is essentially the same as for the module according to fig.l. The enriched stream from a previous module or modules in the series, and/or gas that recycles from the outlets 116 is fed along the channel 40 in the form of twelve substreams that are fed into the channel 40

via the inlets 126. The enriched streams are fed through the compressor 124 and are fed into the channel 16 upstream in relation to the compressor 20.

The depleted stream from the following module 10 in the series is fed into the channel 18 via the main inlet 36. This depleted stream is fed radially inwards into the channel 18 and then into the channel 16 and into the compressor 20. The depleted stream from the following module is fed axially along channel 16

to the end of the channel at the end 114.2 of the housing 114 and occupies that sector of the passage 116. It is then fed through the heat exchanger 22 and into the section 18.1 of the channel 18, and then into the separator 24 and then the depleted part thereof is fed into the section 18.2 of the channel 18 in the direction shown with

arrow, while the enriched part thereof is fed into the channel 34.

It will be understood that the sector, which is occupied by the depleted stream from the subsequent module which is introduced through the main inlet 36, can be defined by different chambers between the separation devices 132. At the deflection plates 140 at 134 in the channel 18, the depleted stream will be divided into two parts which continue to flow along the circuit in their respective sectors on opposite sides of the first sector occupied by the depleted stream fed through the main inlet 36. In this regard, it will be understood that the separators 132 will not be parallel to the polar axis of the module 10 along their full length. They will be so shaped that they lean towards the aforementioned axis so that the chambers defined between the separation devices open into the appropriate sector or sectors of the compressor 20. This arrangement of the partitions is intended to compensate for a rotation of the gas flow around the aforementioned axis , caused by the compressor when the gas stream is fed through it. The two parts of the depleted gas flow continue their flow along their screw-like paths in opposite peripheral directions around the module 10, as described with reference to fig. 1, until they eventually come together again and are fed out of the main outlet 38 in the form of the depleted stream from module 10 and fed to the preceding module in the series.

From a comparison of Figs. 8 and 9 with fig. 1 it will be seen

that the inlets 126 of the channel 40 correspond to the secondary channels 40.1 - 40.4 in fig. 1, and that the outlets 116 from the outlet channel 34 correspond to the secondary channels 34.1 - 34.4 in fig. 1. The parts of the enriched gas stream from the previous module that are introduced into the channel 40 via the inlets 126 are arranged so that they are ejected from the compressor 124 and into the inlet of the compressor 20 at the positions where their isotopic composition is the same as that of the flow from the channel 18 into the inlet for the compressor 20.

It will thus be understood that the module 10 according to fig. 1 can also be provided with separation devices corresponding to the separation devices 132 shown in fig. 8 and 9. The separation devices divide the circuit into a number of chambers which extend along the circuit. These chambers may, but need not necessarily correspond to the sectors occupied in the circuit by the various currents and combined currents flowing along the circuit.

The feature of the separating devices 132 reduces mixing by diffusion or turbulence at the interfaces between the aforementioned streams when they flow along the circuit. The more separation devices 132 there are; the less mixing takes place. Thus, in general, as many separating devices as possible can be arranged, the total number being limited by practical considerations in the construction and by economic considerations.

In general, the steeper the concentration gradient in the circumferential direction in the circuit defined by channels 16 and 18; the more important the separating devices 132 become, as these separating devices, as described above, serve to prevent mixing and prevent the concentration gradient from being reduced. Thus for a module comprising only a few steps, for example two steps, as shown in fig. 5, the separating devices, even if they are desirable, will not be necessary. For.-modules which comprise a large number of steps, for example 10 which will be usual for fractions of approx. 1/10 or less, the separating devices become more and more important.

In the case according to fig. 1 where there are no separation devices, the heat exchanger 22 and the chamfered part of the channel 16 preferably have a centrally located axially extending cylindrical core element 112 (dashed lines) which extends from the shaft 20.1 to the chamber 32, and which corresponds to the core element 112 in fig. 8 and 9. This core element tends to prevent mixing of the currents flowing along the channel 16 with the currents on diametrically opposite sides.

The examples with reference to fig. 1 - 7 are described with reference to the elements 26 which have a fractionation degree of 1/5 and where the enriched streams and depleted streams have the same pressure. For the cases where each stage 2 (fig. IA) has an enriched stream 7 at a different pressure in relation to the depleted stream, it is intended that the streams at the lower pressures must be fed through an additional compressor before they are added to the other streams thereby to equalize the pressure in the streams, after which they are fed through the common compressor 20 and the heat exchanger 22 (fig. 1). For example, a further compressor can thus be arranged in the channel 40 in fig. 1 where the streams 50 (Fig. 2) are at a lower pressure than the streams 52 and 58, or a further compressor can be arranged in the part 16.2 in the channel 16 where the streams 50 are at a higher pressure than the streams 52 and 58. For the case according to fig. 8 and 9, the additional compressor is shown at 124 for corresponding cases where the streams 50 are at a lower pressure than the streams 52 and 58.

Furthermore, it will be understood that the module 10 does not need to

occupy an integer number of groups of steps or a group or groups comprising an integer number of steps. It is thus intended that a module can be used to accommodate any number of groups or parts thereof, including any number of steps or parts thereof. Suitable power connections will be provided as required. Thus, the method and the apparatus are not limited to particular degrees of fractionation, for example 1/3, 1/4 or 1/5, and any degree of fractionation down to 1/20 or less can be used.

It will also be understood that the deflection plates do not necessarily need to deflect the flow from a given chamber into the next adjacent or other specifically indicated chambers. In practice, the deflection plates can deflect the current from a chamber to any arbitrary degree, the deflection must be sufficient to deflect the current up to an adjacent sector, it being remembered that the sectors need not correspond to the chambers between the separation devices 132. The degree of deflection of the deflection plates will in reality depend on mass current balance considerations in the module 10, i.e. the control of the depleted currents that flow between the modules.

The invention has a further advantage in the fact that standardization of the modules is possible. Furthermore, in isotope separation, compression (passing the stream through a compressor to move the stream) and heat exchange (eg cooling the stream after compression) will be necessary each time the stream has passed the isotope separation elements. A further advantage of the invention is that each module 10 has a single compressor 20 and heat exchanger 22 for internal circulation, regardless of the number of separate gas streams which are moved forward or counter-flow along the cascade arrangement and which are fed through the module. When necessary, each module can also have a simple compressor 124 to equalize the pressures between enriched gas streams fed into the module and the internally circulating streams. The use of a large number of compressors and heat exchangers (at least one for each stage shown in Fig. IA) is thus avoided; and the use of a relatively small number of identical compressors and heat exchangers is thus made possible. When separating devices are arranged, the only parts of the circuit in the module, where the different currents and sub-currents will be in contact with each other, will be in the part of the circuit occupied by the compressor 20 and in the part of the circuit where the deflecting plates 140 are arranged. For the case shown in fig.

8 and 9 there will also be contact where the compressor 124 is arranged with respect to the enriched streams from the previous module. The separating devices 132 thus serve to reduce the mixing of adjacent streams and sub-streams, while maintaining the advantages of having a simple compressor 20, a

kel compressor 124, when one is provided, a single heat exchanger 22 and a single separator 24 for each module 10.

Application of the method and module according to the invention

for fractionation in the range 1/20 when enriching uranium hexa-

235

fluoride (UFg) with consideration of U is expected to lead to a reduction in installation costs of at least 20% and possibly up to 50% or more. Loss of efficiency as a result of mixing by diffusion where the gas streams and substreams are in contact is assumed to be below 10%, compared to conventional cascade devices, and the costs for extra modules to make up for this loss will be more than compensated for by savings, as a result of the use of standardized and relatively large modules.

Claims (19)

1. Procedure for the separation of gas mixtures, in particular isotope mixtures, in which gas is led through a cascade of several stages, each of which contains a separator, characterized in that the gases coming out of the separators (26) from several stages in the cascade are led to a single compressor (20) since at least the gases that are taken out from some separators (26) have different compositions, that the gases are combined into a single gas stream, whose composition, in a manner known per se through a cross section of the gas stream, varies from a minimum with regard to the concentration of one of the separated gases to a maximum of this concentration, that the gas flow is led through the compressor (20) during which the differences in the composition of the gas flow remain unchanged, and that the gas flow is divided into several sub-flows, of which at least some have a different composition, and these sub-flows are led through the further stages of the cascade. 2. Method according to claim 1, characterized in that the combination of the gases to form the only gas stream occurs in such a way that the composition in the circumferential direction is different, so that a concentration gradient exists along a line that extends parallel to the circumference of the stream in the cross-sectional plane, under which , the concentration minimum and maximum are spaced apart in the circumferential direction. 3. Method according to claim 2, characterized in that the combination of the gases during the formation of an annular gas flow takes place in such a way that the minimum and maximum of the concentration lie diametrically opposite each other. 4. Method according to one of claims 1 to 3, characterized in that when using a compressor (20) with an axial impeller with several radial vanes (20.2) arranged at a distance from each other in the circumferential direction, the gas flow moves over the vanes in the compressor axis_ (20.1 ) direction. 5. Method according to one of claims 1 to 4, characterized in that the temperature of the gas in the flow changes after the combination of the gases and before the division of the gas flow into sub-flows. 6. Method according to claim 5, characterized in that the gas flow for temperature change is led through a porous heat exchanger element (22). 7. Method according to one of claims 1 to 6, characterized in that the gas flow is led through a channel which at least forms part of an endless flow circuit, during which at least part of the gas flow runs through the flow circuit more than once. 8. Method according to claim 7, characterized in that the gas flow in the flow circuit follows one or more different helical paths, during which the axis of each helical path runs across the direction of movement of the gas flow in the channel (16) and each complete winding of each helical path path extends over the entire flow circuit's total length. 9. Method according to claim 8, characterized in that the gas flow is guided along two helical paths, which extend from minimum to maximum with respect to the circumference of the channel (16) in the opposite circumferential direction, under which the circumference is formed by a cross section of the channel of the flow direction and under which each path extends more than once around the flow circuit. 10. Method according to claim 8 or 9, characterized in that at least part of the gas flow in the channel (16) is branched off to favor a flow of the gas flow along the helical path or the helical paths. 11. Device for carrying out the method according to one of claims 1 to 10, characterized by a cascade of several steps, each of which has a separator, a compressor (20), a device (18) for extracting gases with different compositions from several separators (26) which is arranged in the different stages of the cascade and for the supply of gases to the compressor (20), as the device (18) combines the gases into a single gas stream whose composition varies in a manner known per se through a section of gas the flow that goes across the direction of flow from a minimum with regard to the concentration of the gas to be separated to a maximum of this concentration, and a device (24} 34) for dividing the gas flow coming out of the compressor into several partial flows, of which at least some have different compositions, and for passing these partial streams through further stages of the cascade. 12. Device according to claim 11, characterized in that a channel (16) is arranged which forms part of an endless flow circuit, which has at least one inlet (36) and at least one outlet (38), the inlet (36), the outlet (38) and the compressor (20) are arranged in such a way that the compressor causes a movement of the gas flow through the flow circuit and a more than one-time circulation of at least part of the gas flow in the flow circuit along at least one helical path and along the channel (16), and as the axis of the helical path runs across the direction of movement of the gas flow in the channel and each complete turn of the helical path extends over the full length of the flow circuit. ' 13. Device according to claim 12, characterized in that the compressor (20) has an axial impeller with several vanes (20.2) protruding radially from it, which are spaced apart in the circumferential direction and are capable of moving the gas flow in the channel's (16) longitudinal direction. 14. Device according to claim 12 or 13, characterized in that the flow channel (16) is annular, that the main inlet (36) is arranged in a sector of the channel and the main outlet (38) in a circumferentially spaced channel sector, so that the gas entering through the main inlet (36) is divided into two partial flows, which follow different helical paths from the main inlet to the main outlet , which extend in the circumferential direction opposite to the channel circumference, which is defined through a section of the channel across the direction of flow. 15. Device according to claim 14, characterized in that several auxiliary inlets (42, 126) spaced apart and several auxiliary outlets (34, 116) likewise spaced apart are arranged in the flow circuit. 16. Device according to claim 13 or 14, characterized in that the flow circuit is formed between an inner cylindrical housing (12) and an outer cylindrical housing (14), under which opposite ends of the inner housing (12) open into opposite ends of the outer house (14).. 17. Device according to one of claims 12 to 16, characterized in that there are deflection devices (140) for deflection of the gas along the flow circuit to support the flow of the partial flow along the helical path or the helical paths. 18. Device according to one of claims 12 to 17, characterized in that it has one or more dividing walls (132) which extend along the channel in the direction of flow. 19. Device according to one of claims 12 to 18, characterized in that it has a flow-permeable heat exchanger element (22) which extends inside the channel (16) across it.