Power consumption, gas holdup and oxygen mass transfer in agitated gas-liquid columns have been studied for an airwater system. Measurements have been carried out in a reciprocating plate reactor using five different types of perforated plates and in a stirred tank reactor with one, two and three Rushton turbines, a helical ribbon impeller with and without surface baffles. Each mixing vessel had an identical geometry with a working volume of 17 L. For reciprocating plate stacks, the gas holdup is a complex function of the perforation diameter, the frequency of agitation and the gas superficial velocity. For radial-type mixing devices, the gas holdup increases more rapidly with the speed of rotation for the helical ribbon. The power imparted to the fluid by the mixing device is independent of the gas superficial velocity for the plate stacks and the helical ribbon impeller for a given frequency or speed of agitation whereas it decreases for Rushton turbines. The correlation of the power consumption obtained for all mixing devices plotted against the reciprocating frequency or speed of rotation to the third power shows a linear fit. KLa values were correlated very well with the power input per unit volume and superficial gas velocity for all mixing devices. At lower power input per unit volume, KLa is a function of only the gas superficial velocity. At higher input power per unit volume, KLa increases rapidly with an increase in the intensity of agitation. Reciprocating plates with larger diameter perforations led to higher KLa values whereas the lowest KLu were obtained with the helical ribbon impeller. Correlations for one and three Rushton impeller assemblies were almost identical whereas measured KLa were much higher for the two-impeller assembly due to the presence of a highly mixed zone in the vicinity of the dissolved oxygen probe.La puissance consommCe, la rCtention de gaz et le transfert d'oxygkne dans une colonne agitCe aCrCe ont CtC CtudiCs pour un systkme air-eau. Les mesures ont Ct C rCalisCes dans un rCacteur B plateaux B mouvement alternatif munis de cinq diffkrents systkmes de plateaux perforCs. Pour le rCacteur agitC aCrC, ce sont des combinaisons de une, deux ou trois turbines Rushton ou d'un ruban hClicofda1 avec ou sans chicanes de surfaces qui ont Ct C CvaluCes. Les deux rCacteurs ont une gComCtrie identique et un volume utile de 17 L. Pour les systkmes de plateaux, la retention de gaz est une fonction complexe du diamktre des perforations, de la frCquence d'agitation et de la vitesse superficielle du gaz. Pour les systbmes d'agitation de type radial, la rktention de gaz augmente plus rapidement avec la vitesse de rotation pour le ruban hClico'idal. La puissance fournie au fluide par le systkme d'agitation est indCpendante de la vitesses superficielle de gaz pour les plateaux perforks et le ruban hClicoida1 pour une friquence ou une vitesse d'agitation donnee, tandis qu'elle diminue pour les turbines Rushton. La corrklation de la puissance consommCe obtenue pour tous les systkmes d'agitation en...

An experimental program has been initiated to use a reciprocating plate column for aerobic fermentations. This paper reports the results of the initial phase consisting of the hydrodynamic studies and the evaluation of the power consumption as a function of the level of agitation and gas superficial velocity. The variation of the gas holdup is pwented and compared to a correlation. It is shown that a simple correlation can predict adequately the gas hol&p when water is used. The power consumption, necessary for scale-up and design considerations, was evaluated using the pressure variation at the base of the column, the pressure difference across the column and the force exerted on the central shaft to reciprocate the plate stack. Results for the power consumed by the fluid mixture obtained with the three methods are presented and analyzed. The three methods give approximately the same value of the power consumption.On a entrepris un programme experimental dans lequel on utilise une colonne i plateaux reciproques pour des fermentations airobiques. On prtsente dans cet article les resultats de la phase initiale comprenant les Ctudes hydrodynamiques et I'Cvaluation de la consommation de puissance en fonction du degrC d'agitation et de la vitesse superficielle du gaz. La variation de la retention de gaz est prCsentCe et comparCe 51 une correlation. On montre qu'une simple correlation peut prCdire correctement la retention de gaz lorsque de I'eau est utilisee. La consommation de puissance, donnee nicessaire pour des considkrations de mise B I'echelle et de conception, a Cte Cvaluee selon trois critkres: la variation de pression B la base de la colonne, la difference de pression dans la colonne et la force exercee sur I'axe central pour faire osciller la pile de plateaux. On analyse les rCsultats de puissance consommee par le melange fluide pour les trois mkthodes. Les trois methodes donnent sensiblement la mCme valeur pour la consommation de puissance.

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Axial mixing in a reciprocating plate column with different amplitudes has been investigated for single‐phase and two‐phase (air‐water) systems. Experiments were performed in water in a semi‐batch scheme (no water flow) in a 1.26 m high and 101.6 mm internal diameter column. It was found that the axial dispersion coefficient is a strong function of reciprocation speed and amplitude. The presence of gas considerably affects the axial dispersion coefficient but its contribution appears to saturate at low gas flow rates and then, over a large range of gas flow rates, the axial dispersion coefficient was almost constant. Models are proposed based on experimental data to account for the effects of gas superficial velocity, amplitude and reciprocating frequency. The models predictions are compared with experimental data, obtained over a wide range of operating conditions, and the agreement between them was found to be good. A new class of nonlinear models, for which it is not necessary to have a constant dependency on each operating variable, was also used to correlate the axial dispersion coefficient. This new model allows to carry out sensitivity analysis on each operating variable.