a) The first one involves the alternating motion of some intrinsic elements of the column.
It may be worth mentioning the pulsing plates column (Figure 11.1-a), in which the
pulsation is generated by means of an upwards-downwards motion of plates (Baird
and Rao, 1988; Skala and Veljkovic, 1988) and the columns with a piston pulsator
(Figure 11.1-b), where a plug is coupled to the bottom of the column (Harrison and
Mackley, 1992).
b) In the second type, pulsation is generated by the hydraulic transmission of a
perturbation to the liquid contained in the column. The systems using positive
displacement pumps (plug or membrane) to introduce the feed into the column (Mak
et al., 1992) and the pneumatic pulsation systems (Figure 11.1-c) are characteristic of
this type. In the latter, the pulsation is generated by means of a pressurised gas, which
propels the liquid contained in a parallel branch to the column (Murthy et al., 1987).
The self-propelled pulsators, shown in Figure 11.1-d, are based on a different
Figure 11.1 Types of pulsing devices,
a. Pulsing plates column, b. Piston
pulsator. c. Pneumatic pulsator. d.
Self-propelled pulsator.
Pulsing bioreactors 329