Hydrodynamics and power consumption of a reciprocating plate gas–liquid column

Abstract

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.

Power consumption and mass transfer in agitated gas‐liquid columns: A comparative study

“…The power input ( P J was calculated using two different methods (Lounbs and Thibault, 1993). The first one uses the instantaneous pressure drop (AP) at the bottom of the column:…”

“…For water, the average power consumption is proportional to as suggested by the following equation (Lounbs and Thibault, 1993). In this equation, the pressure drop was calculated from the energy conservation law of a liquid passing through an orifice.…”

“…Achievement of high mass transfer at low mixing power input and relatively low shear rates in aerobic fermentation processes can be obtained with the reciprocating plate reactor (RPR) due to its particular geometry (Lounbs et al, 1995;Lounbs and Thibault, 1996;Audet et al, 1997). It provides desired flow characteristics that produce very efficient mixing with the results that microorganisms, nutrients and air bubbles are properly distributed (Brauer,199 1).…”

Pressure drops in gas—liquid flow in a 15 cm reciprocating platecolumn

“…under single phase batch conditions, APal, was seen to decrease slightly with reciprocation intensity # According to Equation (2), there should be no time-average effect of reciprocation in the absence of any net fluid flow, but a slight deviation from sinusoidal wave-form could have accounted for the observed effect. In the presence of gas flow at lJ[/ = 3.5 c d s , Lounes and Thibault (1993) reported that APlll increased slightly with Afin the presence of glycerol or 64% aqueous glycerol, but decreased in the presence of water. The decrease in "POI, with Afin the presence of water is consistent with the present data in Figure 7 at the highest gas rate, U,= 1.88 c d s .…”

“…The data for the intermediate gas rate (UCl = 1.2 c d s ) show little effect of agitation, due perhaps to a balance of the two effects discussed above. Lounes and Thibault (1993) reported some data on APLII in their 10 cm diameter column (see Table 1) under conditions of U, = 0. In the absence of gas rate, i.e.…”