GB703344A - Improvements in or relating to the aeration of liquids, particularly in microbiological processes - Google Patents

Abstract

<PICT:0703344/IV(b)/1> A totally enclosed apparatus for aerating liquids, more especially culture media, by continuous circulation of gas through the same comprises a sealed aeration vessel 1 within which is arranged a rotary impellor comprising radial vanes 13 shrouded by annular end plates 11, 12 which rotate with small radial clearance within a stator comprising a plurality of fixed radial vanes 7 supported by annular end plates 5 and 6. The impellor is driven by an electric motor having an armature 15 within a sealed cylinder 8 on the cover plate 2 of the aeration vessel, the stator windings 16 being mounted externally of the cylinder. The motor shaft 9 extends through a central tube 3 and in operation air above the level of liquid in the vessel is drawn through an aperture 4 in this tube and through an aperture 14 which communicates with a hollow lower end portion of the shaft 9, into the eye of the impellor, and is discharged peripherally with liquid drawn into the eye through the orifice formed by the annular plates 6 and 12. The stator element prevents swirling of the liquid whilst the small clearance between the impellor and stator facilitates the production of small air bubbles. The stator vanes may be inclined oppositely to the direction of rotation of the impellor. In a modification, Fig. 3 (not shown) liquid circulating from a separate liquid reservoir is aerated, in an apparatus similar to that of Fig. 1, with gas circulating from a separate gas reservoir. Alternatively, a single reservoir may be employed from which both liquid and gas is circulated. The apparatus has application to the production of antibiotic substances by deep culture methods and the fermentive methods of preparing substances such as citric acid.