Principle of Operation
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The Annular packing of the HP-RFC columns results in a uniform packed bed. In the packed bed the resistance of the resin is the only parameter to determine ΔP over the length (height) of the bed. The bed length (height) is identical in A-B-C-D-E. Hence the resistance by the resin is identical in A-B-C-D-E, thus the ΔP is identical. Absolute P (top to bottom) is influenced by the height of the the column. However the water column exists on outer and inner space (communicating vessels) and therefore ΔP is still only determined by the resistance of the resin.
The dead-space outside the outer frit and inside the inner frit are similar the vertical liquid velocity in the dead-spaces “Vo” and “Vi” are identical Vo=Vi .
The sloped line is a dramatized representation of the product-front.
It indicates the saturation of the column will start from the top down.
The "head-start" that the product in "lane-A" has over "lane-E" is lost again on the inside of the column since Vo=Vi and the vertical speed is identical.
Hence the height (= volume !) of the column does not influence the performance of the radial column.
Why would the liquid not take a diagonal through the column.? The diagonal is a longer distance through the bed = more resistance. Since liquid will always take the path of least resistance. All flow will automatically align horizontal.(A=B=C=D=E)
(ΔP1 = ΔP2 = ΔP3)
(Vo = Vi) (RV0 = RVI) |
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Suitability of radial columns for compressible media is explained in fig. 2 and 3. The forces on the media are partially radial and partially tangential causing less deformation and therefore resulting in less resistance = less operating pressure = higher flow. Even Metacrylate and polystyrene are compressed. Apart from the obvious suitability of agaroses sepharoses and celluloses, polymeric resins are extremely well suited for radial columns.
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Fig 2: Radial Forces |
Fig 3: Axial Forces |
Radial:
Normal (radial) forces partially absorbed tangentially (sideways)
- Reduced directional compression
- Reduced deformation (soft gel)
- Reduced flow resistance
Axial:
Compression forces are in-line to the direction of the flow
- Increased directional compression
- Increased deformation (soft gel)
- increased flow resistance