HIGH LENGTH ISOTOPES SEPARATION COLUMN AND METHOD FOR ASSEMBLY

Abstract

The present invention relates to the field of distillation of isotopes obtained by distillation columns. An object of the present invention is to describe an innovative distillation column which provides significant improvements to the prior art. In particular, the distillation column will be a modular innovatively conceived column having any needed height.

Claims

1. A distillation column (100) for isotopic separation comprising at least a bottom reboiler (4), a top condenser (3) and a central column section, said central column section comprising at least one or more central modular element(s) (5 . . . 5.sub.n), said modular element(s) being connected to the wall of a supporting structure by means of connecting means, characterized in that one or a plurality of modules (5) comprise at least one or more bellows for compensating the thermal expansion or contraction of said module(s) due to the large swing between room and process operating temperature, by contraction or expansion of the bellows along the total height of the column, such as to maintain the total height of the internal column between its top and the bottom support unchanged, thus preserving the integrity of the columns during commissioning and operation, the modular column having any needed height.

2. The distillation column (100) for isotopic separation according to claim 1, wherein said module(s) (5 . . . 5.sub.n) comprise at least one insulation vessel element (22 . . . 22.sub.n) and at least one internal modular column element (23 . . . 23.sub.n) enclosed within said insulation vessel element (22 . . . 22.sub.n), said insulation vessel being modular and said column apt to support very large swings between room and process operating temperature.

3. The distillation column (100) for isotopic separation according to the preceding claims, wherein said distillation column can operate at cryogenic temperature being a cryogenic modular distillation column.

4. The distillation column (100) for isotopic separation according to claim 1, wherein one or more of said external insulation vessel element(s) (22) comprise bellows (26), that is a section of the vessel (22) is replaced by one or more bellows (26) to compensate for the thermal expansion or contraction induced by the smaller variations in the environmental temperature.

5. The distillation column (100) for isotopic separation according to the preceding claims, wherein said at least one external vessel element (22) and said at least one internal column element (23) are connected in one or no point by means of a fixed connection and in one or more points by means of sliding joints, sliding rest posts, chain links, or other means that permit adjustments of the positioning of the internal column elements with respect to the external vessel element in the axial directions, the parts of the at least one vessel (22) and internal column element (23) not connected by fixed means so being free to slide in the axial direction to compensate locally, within the height of the module (5), for thermal expansion or contraction of any of their parts.

6. The distillation column (100) for isotopic separation according to the preceding claims, wherein the volume (27) between the thermal insulation vessel (22) and internal the column element (23) is either operated under vacuum with the column element (23) wrapped by multi-layer insulation or being filled with special insulating material as apt for the operation of the column as a cryogenic distillation column, so that heat transmission is minimized and impact of temperature variation of the internal modular elements (23) on the external vessel elements (23) is minimized.

7. The distillation column (100) for isotopic separation according to the preceding claims, wherein the bellows are introduced also on service pipes that are placed in the space (27) between the internal column (23) and the external insulation vessel (22), outside the internal column and inside the external insulation vessel.

8. The distillation column (100) for isotopic separation according to the preceding claims, wherein said modular column (1) comprises an economizing heat exchangers for lowering the cost of isotopic separation process by recovering the enthalpy spent and gained at the reboiler and the condenser.

9. The distillation column (100) for isotopic separation according to the preceding claims, wherein at least an insulation vessel (22) contains multiple distillation column elements (23), and these columns are connected either in parallel or in series.

10. The distillation column (100) for isotopic separation according to the preceding claims, wherein the modular distillation column (100) has a minimum number of stages, ranging from several thousands to several hundreds of thousands, necessary for separation of the isotopes of argon and xenon, given that for an effective separation the minimal number of stages is in the order of the inverse of the difference between unity (the number one) and the relative volatility of isotopes of interest, said minimal number of stages therefore being of the order of several thousands for the argon isotopes and of the order of several tens of thousands for the xenon isotopes.

11. A method for assembly of the cryogenic distillation column according to the preceding claims, wherein a first module (5 . . . 5.sub.n) comprises column elements (22 . . . 22.sub.n) and surrounding insulation vessel elements (23 . . . 23.sub.n) jointly pre-assembled into modules (5 . . . 5.sub.n), said modules (5 . . . 5.sub.n) having an individual height ranging from a few meters to a few tens of meters, such as to be easily transported from the construction site, the modules then being sequentially assembled in place by being piled and connected in sequence, one onto the other within the mine shaft or supporting structure.

12. The method for assembly of the cryogenic distillation column (100) for isotopic separation according to the preceding claims wherein said modular elements are first accommodated in their final position and then connected together either by welding the final section of each module (5.sub.n-1) with the following one (5.sub.n) or by connecting the two sections through flanges.

13. The method for assembly of the cryogenic distillation column (100) for isotopic separation according to the preceding claims, wherein the module (5 . . . 5.sub.n) are coupled with structural supports (28) which are connected to a platform (29) secured to structural plates (30) fixed to walls of a shaft or of a mine shaft, directly or through other structural elements, either by means of rock bolts (31) or other type of connections to the walls of the shaft or to the rocks surroundings the wall of the shaft, including through tenon joints fixed into mortises recessed into the walls of the shaft or rocks.

14. The method for assembly the cryogenic distillation column (100) for isotopic separation according to the preceding claims, wherein the module (5 . . . 5.sub.n) is coupled with structural supports (28) which are connected to a platform (29) secured to any external support frame such as a very tall tower.

15. The method for assembly the cryogenic distillation column (100) for isotopic separation according to the preceding claims, wherein the refrigerant fluid is substituted by an inert noble element, such as argon, krypton, or xenon to extend the range of process operating temperatures.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0069] This and more advantages obtained thanks to the here described innovative cryogenic modular column for isotopes distillation will be further described hereinafter with reference to non-limitative examples, which are provided for explanatory, non-limitative purposes in the accompanying drawings. These drawings illustrate different aspects and embodiments of this invention and, where appropriate, the structures, components, materials and/or similar elements are indicated in the different figures with similar reference numbers.

[0070] FIG. 1 illustrates a preferred embodiment of the modular distillation column installed within a mine shaft/supporting structure and supported by the lateral walls of the mine shaft/supporting structure according to the present invention;

[0071] FIG. 2 illustrates a preferred embodiment of the modular distillation column with the inclusion of an economizing heat recovery loop according to the present invention;

[0072] FIG. 3 illustrates a preferred embodiment of the individual modules of the column with reference to their connection and realization.

DETAILED DESCRIPTION OF THE INVENTION

[0073] While the invention is susceptible to various modifications and alternative constructions, some of the illustrated embodiments are shown in the drawings and will be described below in detail.

[0074] It must be understood, however, that there is no intention to limit the invention to the specific illustrated embodiments, but, on the contrary, the invention intends to cover all the modifications, alternative constructions and equivalents that fall within the scope of the invention as defined in the claims.

[0075] The use of such as, etc., or indicates non-exclusive alternatives without limitations, unless otherwise indicated.

[0076] The use of includes means includes, but is not limited to, unless otherwise indicated.

[0077] FIG. 1 illustrates a simplified preferred embodiment of the innovative modular distillation column 100 comprising a support system 7 installed in a mine shaft 2 delimited by the surrounding rocks 1. In this embodiment the complete distillation modular column 100 comprises a condenser 3 and a reboiler 4 and one or a plurality of central modules 5, . . . 5n. The central modules 5 are advantageously each equipped with one or more bellows 6 to compensate for the thermal expansion or contraction of the modular column 100 in the vertical direction due to the large swing between room and process operating temperature With this innovative construction, thanks to the bellows comprised in the modules, the final height of the column between the top and bottom supports always remains the same, irrespective of any large swings in temperature between room and process operating temperature, this because when one or more modules of the column are expanded by an increase in temperature, the variation in height is compensated by the contraction of bellows comprised in said module (or also in other modules), and when the modules are contracted by a decrease in temperature, the variation in height is compensated by expansion of the bellows, thus in a very advantageous maintaining the same height of the column and preserving its integrity across different operating conditions, all while, in a very innovative and advantageous way, allowing construction of columns of any needed height, even taller than 100 meters.

[0078] Some or all the vertical modules 5 are connected to the walls of the shaft. In one embodiment, the vertical modules 5 are attached to the walls of the shaft by a mechanical supporting system 7 comprising, for example, brackets or structural supports (shown in FIG. 3) which in turn are fixed to the shaft walls by rock bolts 31 or other type of connections to the walls of the shaft or to the rocks surroundings the wall of the shaft, including through tenon joints fixed into mortises recessed into the walls of the shaft or rocks.

[0079] Please note that in FIG. 1 it is represented a simplified embodiment of the present invention where the modular elements 5 are directly connected to the walls of the shaft.

[0080] In a further embodiment, the vertical modules 5 are mounted on platforms 29 providing local access to the column 100, which in turn are attached to the walls of the shaft by mechanical brackets, which in turn are fixed to the shaft walls by rock bolts 31 or other means as discussed above. The walls of the shaft may be bare rocks or may be covered with a layer of concrete, reinforced concrete or brick or other means suitable for that purpose.

[0081] In one embodiment, also the condenser and/or the reboiler are fixed to the walls of the shaft by mechanical brackets, which in turn are fixed to the shaft walls by rock bolts or other means.

[0082] In one embodiment, also the condenser and/or the reboiler are mounted on platforms, providing local access, which in turn are attached to the walls of the shaft by mechanical brackets, which in turn are fixed to the shaft walls by rock bolts or other means. In one embodiment, also the condenser and/or the reboiler contain a section with one or more bellows to compensate for thermal expansion or contraction of the column in the vertical direction.

[0083] The addition of a system of economizing heat exchangers can lower the costs of operation by recovering the enthalpy spent and gained at the reboiler and at the condenser. According to FIG. 2, in one embodiment, the distillation is carried out at cryogenic temperature and the thermal exchange fluid serving as a refrigerant fluid at the condenser and as heating fluid at the reboiler is nitrogen or a noble element such as argon or xenon. The thermal exchange fluid is fed as a liquid to the top condenser heat exchanger 11; the cooling power required by the top condenser heat exchanger 11 to condense the vapor stream of the fluid undergoing separation by distillation in the distillation column is provided by the phase transition of the thermal exchange fluid into a gas; the thermal exchange fluid gaseous stream exhausted by the top condenser heat exchanger 11 is compressed at high pressure by a gas compressor 12 and sent to the input of the bottom reboiler heat exchanger 13; the heating power required by the bottom reboiler heat exchanger 11 to boil the liquid stream of the fluid undergoing separation by distillation in the distillation column is provided by the phase transition of the thermal exchange fluid from a gas into a liquid; the thermal exchange fluid liquid stream resulting from the bottom condenser heat exchanger 13 is pumped via a cryogenic pump 14 towards the top condenser heat exchanger, such as to close the loop.

[0084] According to FIG. 3, in one embodiment, the individual modules 5 of the column 100 comprise at least one external thermal insulation vessel 22; and at least one internal column elements 23 wrapped in multi-layer insulation (not shown in FIG. 3) except for the final section dedicated to the welding to the other modules 5 (that section will be covered with multi-layer insulation in place after performing the welding, as described below); the gap volume 27 between the thermal insulation vessel 22 and the volume 24 of the internal column 23 is kept under vacuum; not shown are the structural supports connecting the thermal insulation vessel to the internal column.

[0085] Each of said modules or modular elements 5 . . . 5.sub.n, in particular comprise at least an insulation vessel comprising vessel elements 22 . . . 22.sub.n enclosing internal column elements 23 . . . 23.sub.n.

[0086] Please note that one insulation vessel 22 may comprise one or more internal column element 23, forming independent columns which can work together or independently from each other.

[0087] In a preferred embodiment of the present invention the internal volume 24 of the internal column 23 is the process volume, and it is filled with structured packing and/or distillation plates (interleaved, when necessary, with liquid distribution plates). A section of the thermal insulation vessel 22 is advantageously replaced by one or more bellows 26 to accommodate for thermal expansion or contraction; in the present embodiment a section of the internal column 23 is also replaced by a bellow 25 to compensate for thermal expansion or contraction. Please note that the bellows 25 play a crucial function for the internal central distillation column 23, which is subjected to the highest thermal excursions and therefore to the biggest expansion or contraction cycles, due to the large swing in temperature expected between the room and process operating temperature. Bellows 26 may be introduced also on the external insulation vessel 22 (as here represented), or not.

[0088] In this regard it is noted that the volume 27 between the external thermal insulation vessel 22 and the internal distillation column 23 can be utilized to run service pipes, such as the two lines composing the closed loop of the thermal exchange fluid, running from the top to the bottom of the column, shown in FIG. 2, and also to house the column feed lines and sensors as necessary. In one preferred embodiment the bellows are introduced also on service pipes (here not represented) that are placed in the space 27 between the internal column 23 and the external insulation vessel 22, outside the internal column and inside the external insulation vessel.

[0089] The thermal insulation vessel 22 is coupled with structural supports 28, which are in turn connected to a platform 29, which is in turn secured to structural plates or supports 30, fixed to the walls of the mine shaft by rock bolts 31 or other type of connections to the walls of the shaft or to the rocks surroundings the wall of the shaft, including through tenon joints fixed into mortises recessed into the walls of the shaft or rocks.

[0090] In another embodiment the modular element 5 are directly connected to plates fixed to the mine shaft by rock bolts.

[0091] With the lowest modular element 5.sub.n already in place, the module 5.sub.n-1 which is to be sited next to the lowest one is lowered into the shaft 21 and positioned so that the internal column section 23.sub.n_1 of the top module 5.sub.n-1 can be welded to the internal column section 23.sub.n of the lowest module 5.sub.n, the weld spots identified by dots 33. (FIG. 3 represents a simplified embodiment, so there are shown only the modules 5.sub.n, 5 as examples.)

[0092] At this point, the multi-layer insulation (not represented), in use to reduce the transmission of heat via radiation, is wrapped around the section of the interior column not yet covered by the insulation vessel.

[0093] An external sleeve 32 was previously positioned around the external diameter of the bottom external thermal insulation vessel and is then raised in position and welded to the bottom 22.sub.n and next to the bottom 22.sub.n-1 external thermal insulation vessel elements, to close the cryostat section with weld spots 34.

[0094] All the other interposed or subsequent modular elements 5.sub.1 . . . 5.sub.n-2 will be fixed in the same or a similar method, in reverse order from 5.sub.n-2 to 5.sub.1, till reaching the desired operative height of the modular column 100.

[0095] Please note that the modules could be fixed together also by other adapted methods or means, this being merely a not significant variation to the present invention; in the present embodiment welding has been considered the most secure way to fix those modules 5.sub.n, 5.sub.n-1, 5.sub.n-2, . . . 5.sub.2, 5.sub.1, 5 in view of the significant mechanical stress to which the modular elements of the column 100 are anticipated to be subjected.

[0096] In any case please notice that is very easy and practical to couple together the modular elements 5.sub.1 . . . 5.sub.n and in the same way it will be easy and practical to disassemble some modular elements if necessary, for maintenance, in case of damages, etc., this also being an advantage of the present invention as all the other here before described.

[0097] As specified, a very important and innovative aspect described by the present invention, which in fact permits to build and develop a column so tall as to obtain all the advantages described above, is the introduction al least of modules 5 . . . 5.sub.n, one or more of said modules comprising at least one more bellows that can compensate for thermal expansion or contraction of the modules by contraction or expansion of the bellows.

[0098] In a preferred embodiment in particular said modules comprise modular vessel 22 and modular elements 23 of at least one distillation column, at least one of said modular elements 23 comprising one or more bellows.

[0099] Said at least one external vessel element 22 and said at least one internal column element 23 are connected in one or no point by means of a fixed connection and in one or more points by means of sliding joints, sliding rest posts, chain links, or other means that permit adjustments of the positioning of the internal column elements with respect to the external vessel element in the axial directions, the parts of the at least one vessel 22 and internal column element 23 not connected by fixed means so being free to slide in the axial direction to compensate locally, within the height of the module 5 for thermal expansion or contraction of any of their parts.

[0100] These and further objects of the present invention are achieved by means of the modular distillation column comprising the features of the annexed claims, which form an integral part of the present description.

[0101] So modifications in height or diameter of the modular elements, in the fixing means to the shaft, functional elements of the distillation modular column, number of fixing means, type of fixing means between the modules, are all to be considered only non-significant modifications of some realizations embodiment of the present invention and have to be considered covered by the object of the present invention as described above and better explicated with reference to the annexed claims.

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