NZ759130B2 - High length isotopes separation column and method for assembly - Google Patents

Abstract

The present invention relates to the field of distillation of isotopes obtained by distillation columns. An object of the present invention is a modular fractional continuous cryogenic distillation column (100) built out of several modules connected in series, installed within and adapted to be supported by a mine shaft (2) or adapted structure. It is desirable that extremely tall columns with many equilibrium stages are able to support the required very large up-flowing vapor stream and down-flowing liquid stream without incurring in the problematic condition of "flooding" of the column, which inhibits the very effective equilibrium between the vapor and liquid phases required for efficient isotopic separation. Proposed is a method of constructing a large internal structure surrounded by an external structure, allowing on the one hand a quick assembly on site answering to the stress of verticality of the column, and also allowing a pre- assembly at a workshop before transport on site. The procedure uses modules, each made from a section of an inner structure (1) enclosed in a section of an outer structure (5) and assembled on side to make a column of the required height. The inner and outer structures are fitted together by inserting each inner structure into an outer one, after which the two structures are fixed together to form a module. Supports (7) already installed along the final vertical direction of positioning of the column permit the construction of the column already in the final vertical direction and in the final position where it will be commissioned and operated, by mounting in series the modules of the column on said supports. 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 in the vertical direction due to the large swing between room and process operating temperature. Thanks to the bellows, 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.

Claims (12)

1. 26 A cryogenic distillation column (100) for isotopic separation comprising: at least one reboiler (4) disposed along a bottom, a condenser (3) disposed along a top, and a central distillation column section, said central distillation column section adapted to be connected to a wall of a supporting structure by means of connecting means between said central distillation column section comprising: at least one external insulation vessel element (22...22n), and at least one internal modular column element (23…23n) enclosed within said at least one external modular thermal insulation vessel element (22…22n), said at least one external modular thermal insulation vessel element (22...22n) conferring thermal insulation to said at least one internal modular column element (23…23n), an external sleeve positioned around an external diameter of a bottom external thermal insulation vessel of said at least one external modular thermal insulation vessel element (22…22n), wherein the external sleeve is adapted to be raised in position to be welded to the bottom external thermal insulation vessel and to a next external modular thermal insulation vessel element (22…22n) of the bottom external thermal insulation vessel, to close a cryostat section with weld spots (34), andat least one internal modular column element(s) (23….23n) being insulated, except for a final section thereof dedicated to be coupled to a next internal modular column element of the at least one internal modular column element (23…23n), wherein the final section is adapted to be covered with the multi-layer insulation in place, after the performing the welding, each of the at least one external modular thermal insulation vessel element (22…22n) and the at least one internal modular column element (23…23n) comprises one or more bellows, arranged therealong for compensating for thermal expansion along a height of the each of the at least one external modular thermal insulation vessel element (22…22n) and the at least one internal modular column element (23…23n) by contraction or expansion of the one or more bellows along a total height of the cryogenic distillation column.

2. The distillation column (100) for isotopic separation according to claim 1, wherein said at least one external thermal modular insulation vessel element (22) and said at least one internal modular column element (23) are connected in one or more points by means of sliding joints, sliding rest posts, chain links to permit adjustments of the positioning of the 27 at least one internal modular column element (23) with respect to the external modular thermal insulation vessel element (22) in the axial directions, parts of the at least one external thermal insulation vessel element (22) and the at least one internal modular 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 the parts therof.

3. The cryogenic distillation column (100) for isotopic separation according to claim 2, wherein volume (27) between the at least one external modular thermal insulation vessel element(s) (22) and the at least one internal modular column element (23) is either operated under vacuum with the column element (23) insuylated by wrapping by a multi-layer insulation or being filled with insulating material to minimize heat transmission and impact of temperature variation of the at least one internal modular column elements (23) on the at least one external modular vessel elements (22).

4. The cryogenic distillation column (100) for isotopic separation according to claim 3, further comprising service pipes, and bellows (26) introduced on the service pipes, wherein the bellows (26) are placed in a space (27) between the at least one internal modular column element(s) (23) and the at least one external modular thermal insulation vessel element(s) (22), outside the at least one internal modular column element(s) (23) and inside the at least one external modular thermal insulation vessel element(s) (22).

5. The cryogenic distillation column (100) for isotopic separation according to claim 1, further comprising an economizing heat exchangers operatively coupled to the reboiler (4) and the condenser (3) for lowering a cost of isotopic separation process by recovering the enthalpy spent and gained at the reboiler (4) and the condenser (3).

6. The cryogenic distillation column (100) for isotopic separation according to claim 1, wherein at least one of the external thermal insulation vessel element (22) contains multiple internal modular column elements (23), connected either in parallel or in series.

7. The cryogenic distillation column (100) for isotopic separation according to claim 1 further comprising a minimum number of stages, for separation of isotopes of argon and xenon, given that for an effective separation the minimal number of stages is inverse of a difference between unity (the number one) and the relative volatility of isotopes .

8. A method for assembly of the cryogenic distillation column according to the preceding claims, the method comprising: 28 providing at least one or more central module element(s) (5) comprising at least one or more external thermal insulation vessel (23...23n) surrounding at least one or more internal column elements (23...23n) jointly pre-assembled into the central modules elements (5...5n), having an individual height ranging from a meter to tens of meters, enabling said central module to be transported from a construction site, the modules then being sequentially assembled in place by being piled and connected in sequence, one onto the other within a mine shaft or a supporting structure, wherein sequentially assembling comprises: coupling two adjacent external thermal insulation vessels of the at least one external modular thermal insulation vessel elements (22), wherein coupling the two adjacent external thermal insulation vessels comprises an external sleeve positioned around an external diameter of a bottom external thermal insulation vessel of said at least one external modular thermal insulation vessel element (22), wherein the external sleeve is adapted to be raised in position to be welded or coupled to the bottom external thermal insulation vessel and to a next external modular thermal insulation vessel element (22) of the bottom external thermal insulation vessel, to close a cryostat section with weld spots (34); coupling two adjacent internal modular column elements of the at least one internal column elements (23…23n), wherein the coupling comprises the at least one internal modular column element(s) (23…23n) wrapped in a multi-layer insulation, except for a final section thereof dedicated to be coupled to a next internal modular column element of the at least one internal modular column element (23…23n), wherein the final section is adapted to be covered with the multi-layer insulation in place, after the performing the welding; each of the at least one external modular thermal insulation vessel element(22…22n) and the at least one internal modular column element (23…23n) comprises one or more bellows, arranged there along for compensating for thermal expansion along a height of the each of the at least one external modular thermal insulation vessel element (22…22n) and the at least one internal modular column element (23…23n) by contraction or expansion of the one or more bellows along a total height of the cryogenic distillation column.

9. The method according to claim 8, wherein said each of the at least one external modular thermal insulation vessel elements (22…22n) and the at least one internal column elements (23…23n) are first accommodated in final positions thereof and connected together with respective the next external modular thermal insulation vessel element and next internal modular column element by welding.

10. 29 The method according to claim 8, wherein the at least one or more central modular element(s) (5…5n) 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, either by means of rock bolts (31) or via connections to the walls of the shaft or to the rocks surroundings the wall of the shaft, wherein the connections including tenon joints fixed into mortises recessed into the walls of the shaft or rocks.

11. The method according to claim 8, wherein the at least one or more central modular element(s) (5...5n) is coupled with structural supports (28) which are connected to a platform (29) secured to an external support frame having a tall tower.

12. The method according to claim 8, further comprising a refrigerant fluid including argon, krypton, or xenon to extend a range of process operating temperatures.