Bead packing

Gels made in this way have virtually no usable porosity and are called Jordi solid bead packings. They can be used in the production of low surface area reverse phase packings for fast protein analysis and in the manufacture of hydrodynamic volume columns as well as solid supports for solid-phase syntheses reactions. An example of a hydrodynamic volume column separation is shown in Fig. 13.2 and its calibration plot is shown in Fig. 13.3. The major advantage of this type of column is its ability to resolve very high molecular weight polymer samples successfully. 

S. L. Codd, S.A. Altobelli 2003, (A PGSE study of propane gas flow through model porous bead packs), J. Magn. Re-son. 163, 16. 

In order to understand the nature and mechanisms of foam flow in the reservoir, some investigators have examined the generation of foam in glass bead packs (12). Porous micromodels have also been used to represent actual porous rock in which the flow behavior of bubble-films or lamellae have been observed (13,14). Furthermore, since foaming agents often exhibit pseudo-plastic behavior in a flow situation, the flow of non-Newtonian fluid in porous media has been examined from a mathematical standpoint. However, representation of such flow in mathematical models has been reported to be still inadequate (15). Theoretical approaches, with the goal of computing the mobility of foam in a porous medium modelled by a bead or sand pack, have been attempted as well (16,17). 

The determination of sulphur in the tube with bead packing is carried out in a manner analogous to that employed in the argento-metric determination of halogen (see p. 73). 

Several groups used sol-gel transition to immobilize the beads packed in a capillary. For example, Dulay et al. [102] packed a slurry of ODS beads in tetraethylorthosilicate solution and heated it to 100 °C to achieve the sol-gel transition and create the monolithic structure shown in Fig. 17. This technology is extremely sensitive and even a small deviation from the optimal conditions leads to cracks in the monoliths and a rapid deterioration in the column performance. However, even the best efficiency of 80,000 plates/m achieved with these column was relatively low. Henry et al. modified the original procedure and increased the efficiencies to well over 100,000 plates/m [103,104]. 

Six commercial narrow UWD polystyrene standards ( Applied Research Laboratories Limited, England ) and five broad MWD 2-polybuta-diene fractions were used to calibrate an ARL 950 GPG instrument with silica bead packed columns. The ARL polystyrene standards were also used to calibrate a number of homeMnade SEC column units packed with silica beads or styrene-divinylbenzena copolymer beads, Hie average molecular weights of these samples are listed in Table I. Tetrahydrofuran or toluene was used as eluents for these columns. 

Fig. 8. Displacement propagators recorded for flow of water through a packed bed of l-mm-diarnctcr glass beads packed within a 10-inin-diameter column. The average flow velocity was 0.77mms corresponding to Pe and Re of 350 and 0.77, respectively. Propagators are shown for observation times, A = 0.3s (----), Is (-----), and 2s ( ).

Fig. 15. 2-D slice sections through 3-D MR images of water distribution within an initially water-saturated packing of 500-pin glass spheres. Voxel resolution is 94 pm x 94 pm x 94 pm. Data are shown before drying commenced and at three time intervals during the drying process. Only the water within the inter-particle space of the bead packing was imaged (white pixels). No signal was obtained from the solid and gas phases present.

A similar result is accomplished by using as one phase a solid powder or fine "beads" packed in a vertical column or spread in a thin layer on a plate of glass. The methods are usually referred to as chromatography, a term proposed by Tswett to describe separation of materials by color. In 1903 Tswett passed solutions of plant leaf pigments (chlorophylls and carotenes) in nonpolar solvents such as hexane through columns of alumina and of various other adsorbents and observed separation of colored bands which moved down the column as more solvent was passed through. Individual... 

Glass-bead-packed one-dimensional column experiments were performed with vertically oriented 2.5 cm I.D., 15.0 cm long, 74.0 ml. total volume glass columns. The glass bead diameter ranged from 0.23 to 0.36 mm, and... 

Q. He, C. Pang, Y.-C. Tai, T.D. Lee, Ion liquid chromatography on-a- chip with beads-packed parylene column. Proceedings of the 17th IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2004). Maastricht, The Netherlands, Jan 25-29 (2004). 

Fig. 7 (a) Beads packing device working in a flow system, taking advantage of a leaky wall (reproduced from [27]) (with permission), (b) a scanning electron microscopy image of a flow through reactor composed of pillar made walls used to pack microspheres (reproduced from [28]) (with permission)... 

The theory of effective viscosity has been developed by Betherton [172], Hirasaki and Lawson [173], Falls et al. [171] and Kovscek and Radke [153]. It was shown that the effective viscosity is a sum of three terms the first accounts for the contribution of the slugs of liquid between bubbles, the second is the resistance against surface deformation in the advancement of bubbles through the capillaries (pores) and the third is the gradient of surface tension caused by the withdrawal of the surfactant (from the bubble front to the bubble back). The experimental data of Falls et al. [171], Hirasaki and Lawson [173], Ettinger and Radke [166] for bead packs and Berea core agree with the calculations from Hirasaki and Lawson s models [173],... 

Fig. 10.19. Steady pressure gradient of flowing foam in glass bead packs as a function of sail concentration.

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