Dead-head piping systems

Regardless of the needs dictated by these factors, the piping system itself will fall into a few general variations as shown in Fig. 4. Dead-head style piping systems are unusual and can only be used with a very well-suspended slurry. This type of system can minimize the loss of volatile components, such as ammonia from a slurry like Rodel Klebosol, since there is no circulation through a daytank or any other head space that would permit ammonia evaporation. It can also be attractive to minimize slurry turnovers to a shear- or gelling-sensitive slurry. Cabot SS-25 is well-suspended, but if... 

The total dead time ttotal is the time a non-retained substance needs from the point of sample introduction to the point of detection. It depends on the hold up within the column itself as well as the hold up of the system or plant, which is, for instance, influenced by pipe length and diameter, pump head volume (if the sample is introduced via a pump) and the detector volume. Therefore, the dead time of the plant without the column tpiant has to be determined as well to get the correct dead time of the column to by subtraction of tpiant from ttotai. Tracer molecules are used to determine the dead time. These molecules should not be adsorbed by the solid phase but should have the same size as the components to be separated so as to penetrate the pore system in a comparable way. 

The total dead time ttotai is the time a nonretained substance needs from the point of sample introduction to the point of detection. It depends on the holdup within the column itself as well as on further holdup in the system or plant, which is, for instance, influenced by pipe lengths and diameters, pump head volumes... 

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