Slurry packing principles

The up-fill slurry packing method is used for packing conventional diameter columns. It is unsuitable for packing small diameter columns. It is easily adapted to the simultaneous packing of several columns and generally used with low viscosity slurry liquids. The principle of the packing method is based on the upward displacement of a stable slurry into the column blank from a reservoir whose contents are continuously diluted by incoming pressurized solvent [646,659]. Dilute slurries (1-10% w/v) and... 

Fig. 4 Graded size distribution to maximize the packing fraction of ideal spherical particles, and thereby minimize the amount of water needed to fluidize the slurry. In this illustration, there are four different sizes of particles present. A similar principle will maximize the packing fraction of real, irregularly shaped particles.

Particles below 20 pm in diameter cannot be packed in dry form as they tend to become lumpy, thus precluding the preparation of high-performance columns. The material must be suspended in a liquid to give a slurry. A high-pressure pump then conveys the slurry into the column at great speed. There are almost as many methods for wet packing as there are column manufacturers. Proponents are convinced that their own ways and means are the best, making it difficult for the uninitiated to choose between them. Slurry production itself is based on a few essential principles ... 

Closure After completing this chapter, the reader should be able to derive differential equations describing diffusion and reaction, discuss the meaning of the effectiveness factor and its relationship to the Thiele modulus, and identify the regions of mass transfer control and reaction rate control. The reader should be able to apply the Weisz-Prater and Mears criteria to identify gradients and diffusion limitations. These principles should be able to be applied to catalyst particles as well as biomaierial tissue engineering. The reader should be able to apply the overall effectiveness factor to a packed bed reactor to calculate the conversion at the exit of the reactor. The reader should be able to describe the reaction and transport steps in slurry reactors, trickle bed reactors, fluidized-besd reactors, and CVD boat reactors and to make calculations for each reactor. 

The principle of the DAC packing is to transfer the slurry into the column and then pack using a hydraulic piston. To be able to perform a good DAC packing, the column volume should be sufficient to receive all the slurry or an extension tube should be attached to the column body (Figure 4.27). 

If neither solvent density nor viscosity are important in column packing, then what is The missing factor is the interaction of the particles with each other, which is mediated by the slurry solvent. This is the factor that had been recognized by Kirkland (4) when he developed the packing technique using a stabilized aqueous suspension of silica particles. The technique as implemented by Kirkland, however, works only for unmodified silica, and cannot be used for bonded phases without modification of the procedure. But the underlying principle is correct. 

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