Fig. 7.49. Schematic diagram of 20 m3 bubble column fermenter fitted with internal cooling coil (Carrington et al., 1992). (pH and DO indicate positions of pH and oxygen electrodes.)
and mixing in the middle compartment were found to be comparable with those obtained with conventional internal loop air-lift vessels, although some tangential liquid flow was observed in this compartment.
Some designs of continuous culture fermenter achieve the necessary mechanical power input with a pump to circulate the liquid medium from the fermenter through a gas entrainer and back to the fermenter (Fig. 7.51; Hamer, 1979; Meyrath and Bayer. 1979). Two basic construction principles have been used for the gas entrainer nozzles. The injector and the ejector (Fig. 7.52 ; Reuss, 1992). In an injector a jet of medium is surrounded by a jet of compressed air. The gas from the outlet enters the larger tube with a nozzle velocity of 5 to 100 m s"1 and expands in the tube to
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