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US 3,971,842 AGranted
Continuous displacement chromatographic separation
AssigneeAtlantic Richfield Company
InventorJohn R. Ewbank
Life of this patent
Estimating the term…
Abstract
In a plant for uranium enrichment using a cascade of ion exchange beds, each bed operates more efficiently because an annular chamber is rotated about a stationary annular ion exchange bed at a speed corresponding to the speed of migration of a region so that, with respect to such rotating chamber, each of the regions of a system remains substantially stationary. An aqueous solution of ferric chloride is pumped to the ferric region and flows forwardly to the forwardly moving rear boundary of the uranium region.
Claims7
In a method in which an ion exchange bed is employed for modifying the isotope distribution in aqueous solutions of uranium compounds by preferential sorption rates in an ion exchange bed having a significant length relative to a cross sectional dimension, there being a plurality of regions along the length of said ion exchange bed, one of said regions being a uranium isotope separation region, the improvement which consists of:
- maintaining the ion exchange bed as an annulus;
- surrounding the annulus-shaped ion exchange bed with a chamber having a plurality of modifying zones in which aqueous solutions are withdrawn, injected, or pressurized, each modifying zone permitting flow of solutions between the core of the bed and the liquid transfer zone adjacent the sidewalls of the bed without substantial distortion of the desired cross sectional patterns of the liquid flow along the length of the bed;
- withdrawing from a zone adjacent the front boundary of said uranium isotope separation region, a solution containing increased concentrations of ions of the 235 uranium isotope, such increased concentration being attributable to chromatographic displacement phenomena and such solution withdrawal being from side walls of the annular ion exchange bed;
- withdrawing from a zone adjacent a rear boundary of the uranium isotope separation region a solution containing a controlled decreased concentration of ions of the 235 uranium isotope, such decreased concentration being attributable to chromatographic displacement phenomena, such solution withdrawal being to side walls of the ion exchange bed;
- feeding to an intermediate portion of the uranium isotope separation region a stream of a solution containing mixture of ions of uranium isotopes at a rate totaling the rates of withdrawal from said boundaries, the total liquid flow through the uranium isotope separation region being several times said rate of feeding the mixture to be separated, the large ratio of total liquid flow to feed flow in the separation region being attributable to chromatographic displacement phenomena, such solution feeding being to side walls of the ion exchange bed;
- supplying to a region in advance of the uranium isotope separation region a solution of trivalent titanium compound for the maintenance of an appropriate chemical reaction at the constantly advancing front boundary of the uranium isotope separation region;
- supplying to the region rearward of the uranium isotope separation region a solution of ferric chloride, a portion of which solution flows forwardly to provide a chemical reaction at the rear boundary of the constantly advancing uranium isotope separation region, the length of the separation region remaining substantially constant because the migration speeds of the front and rear boundaries are substantially identical;
- supplying regeneration solution to a regeneration region of the length of the ion exchange bed, whereby each portion of the length of the ion exchange bed may be repetitively used;
- said solutions being supplied to maintain the speed of migration of the boundaries of the uranium isotope separation region at a controlled speed;
- and
- controlling the relative speed of movement between the length of the annular ion exchange bed and its surrounding chamber to be exactly equal and opposite to the migration speed of the boundaries, whereby the relative positions of the chamber and the boundaries is maintained stationary, and whereby the injection of solutions and withdrawal of solutions is constantly accurate notwithstanding such relative migration of boundaries along the length of the annular ion exchange bed and such relative movement between the annular ion exchange bed and its surrounding annular chamber.
8 more elements
In a method in which an ion exchange bed is employed for separating a mixture by preferential sorption rates in an ion exchange bed having a significant length relative to a cross sectional dimension, there being a plurality of regions along the length of said ion exchange bed, one of said regions being a separation region, the improvement which consists of:
- surrounding the ion exchange bed with a chamber having a plurality of modifying zones in which solutions are withdrawn, injected, or pressurized, each modifying zone permitting flow of solutions between the core of the bed and the liquid transfer zone adjacent the sidewalls of the bed without substantial distortion of the desired cross sectional patterns of the liquid flow along the length of the bed;
- withdrawing from a zone adjacent the front boundary of said separation region, a solution containing increased concentrations of ions of a selected component of said mixture, such increased concentration being attributable to chromatographic displacement phenomena and such solution withdrawal being from side walls of the ion exchange bed, there being no liquid flow to or from end walls of the ion exchange bed;
- withdrawing from a zone adjacent a rear boundary of the separation region a solution containing a controlled decreased concentration of ions of said selected component, such decreased concentration being attributable to chromatographic displacement phenomena, such solution withdrawal being to sidewalls of the ion exchange bed, there being no liquid flow to or from end walls of the ion exchange bed;
- feeding to an intermediate portion of the separation region a stream of a solution containing the mixture of ions to be separated at a rate totaling the rates of withdrawal from said boundaries, the total liquid flow through the separation region being several times said rate of feeding the mixture to be separated, the large ratio of total liquid flow to feed flow in the separation region being attributable to chromatographic displacement phenomena, such solution feeding being to side walls of the ion exchange bed, there being no liquid flow to or from end walls of the ion exchange bed;
- supplying to a region in advance of the separation region a solution for the maintenance of an appropriate chemical reaction at the constantly advancing front boundary of the separation region;
- supplying to a region rearward of the separation region a solution, a portion of which solution flows forwardly to provide a chemical reaction at the rear boundary of the constantly advancing separation region, the length of the separation region remaining substantially constant because the migration speeds of the front and rear boundaries are substantially identical;
- supplying regenerating solutions to a regenerating region of the length of the ion exchange bed, whereby each portion of the length of the ion exchange bed may be repetitively used;
- said solutions being supplied to maintain the speed of migration of the boundaries of the separation region at a controlled speed;
- and
- controlling the relative speed of movement between the length of the ion exchange bed and its surrounding chamber to be exactly equal to the migration speed of the boundaries, whereby the relative positions of the chamber and the boundaries is maintained stationary, and whereby the injection of solutions and withdrawal of solutions is constantly accurate notwithstanding such relative migration of boundaries along the length of the ion exchange bed and such relative movement between the ion exchange bed and its surrounding chamber.
7 more elements
Dependencies are inferred from the claim text.