Performance characteristics of mechanical foam‐breakers fitted to a stirred‐tank reactor

Abstract

In a stirred-tank reactor (STR), a comparison of the performance of mechanical foambreakers: a six-blade turbine (F-B), a six-blade vaned disk (V-D), a two-blade paddle (T-P), a conical rotor (C-R), a fluid-impact dispersion apparatus (FIDA) and a rotating disk mechanical foam-breaker (MFRD) was carried out using defined foaming media. The foam-breaking ranges (relative to the gas superficial velocity, U g ) of the T-P, C-R and FIDA were inferior to that of the F-B, V-D and MFRD. The power consumption, P kc , for foam-breaking in the MFRD was the lowest among the F-B, V-D and MFRD. Operation of the F-B and V-D in the STR caused a considerable amount of liquid droplets from the collapsed foam to be entrained with the exhaust air.

Performance Characteristics of a Stirred-Tank Reactor with a Mechanical Foam-Breaker Utilizing Shear Force

“…-3 -7.58 × 10 -3 m·s -1 , N i = 6.67-30.0 s -1 and 0.01 vol% anionic soft detergent solution (Takesono et al, 2002). The foaming characteristic term of this detergent solution was almost identical to that of Triton X-100 solution used in the present work (Takesono et al, 1993a(Takesono et al, , 1993b.…”

“…In most of the proposed mechanical foam-breakers, the resultant secondary foams are returned to the area of primary foam generation and are thus accumulated in the reactor over its long lifetime. Examples include mechanical foam-breakers with rotating installations such as turbines, vaned disks, and paddles (Ng and Gutierrez, 1977;Deshpande and Barigou, 1999;Takesono et al, 2001Takesono et al, , 2002. In such devices, persistent secondary foams recirculate into the foam-breaker, but cannot be broken twice by the foam-breaker.…”

Improvement of foam breaking and oxygen-transfer performance in a stirred-tank fermenter

“…Therefore, the improved foam-breaking performance with increasing D F is attributable to the increased suction force caused by increased D F . Because the rotational speed of the agitation impeller was increased, thereby increasing the foaming capacity, the foam tended to break up less [14,20]. On the other hand, the foam-breaking performance of the foam-breaking impeller was enhanced by the increased suction force created by the increased rotational speed.…”

“…Numerous mechanical foam-control devices have been proposed [2,3]. Mechanical foam-control devices with rotating installations are the most common among these: impellers [13,14], conical dishes [2], centrifugal basket [10], and inverted hollow spinning cones [11,12]. Various kinds of impellers have been reported as foam-breaking impellers: a six-blade turbine [13,14], a six-blade vaned disk [14], a two-blade paddle [13,14], a two-blade paddle with three slits [13], and a two-blade paddle with 168 needles [13].…”

“…Previous studies have used a stirred-tank reactor containing various foaming liquids to examine the foambreaking performance of mechanical foam-control devices with rotating installations that had been mounted on a separate shaft that was driven independently of the agitator for agitation: a six-blade turbine, a six-blade vaned disk, and a two-blade paddle [14]. Such mechanical foam-control devices-foam-breaking impellers-draw foam into their lower end by virtue of the low pressure resulting from the shaft rotation.…”