Mitsuo Kamiwano

Characterization of non-newtonian behavior during mixing of bacterial cellulose in a bioreactor

The mixing properties of bacterial cellulose (BC) in an aerated and agitated vessel are described. To characterize the mixing of BC culture broth, which can affect the productivity of BC, non-Newtonian behavior during mixing of a 1% BC suspension was studied using an image processor capable of detecting decoloration of a pH indicator and was compared with that of a 2% carboxy methyl cellulose (CMC) solution. CMC solution was mixed homogeneously within the measured range of agitation speed, but the BC suspension was not mixed homogeneously at agitation speeds lower than 15 rps because mixing was delayed in some areas of the vessel. A possible reason for the inhomogeneity of the BC suspension at low agitation speeds is the non-Newtonian behavior which increases viscosity at low shear rates.

The measurement of bubble diameter distributions and liquid side mass transfer coefficients in a gas-liquid agitated vessel using a real-time,high-speed image processing system

In this study, we report the measurement results of various spatial distributions, such as Sauter diameter, gas holdup ratio, and interface area per unit liquid volume, in a vessel using a real-time, high-speed image processing system developed by ourselves. We attempted to separate liquid side mass transfer coefficients, k L , from overall volumetric mass transfer coefficients, k L a, based on the results mentioned above. And we examined the relations between power consumption per unit volume, P v , and both k L and k L a in order to establish correlation equations of k L and k L a with P v , gas holdup ratio, gas superficial velocity, v s , and surface tension.

A technique for prediction of the mixing time of high-viscosity liquid-mixing systems with negligible diffusivity of solute

Abstract A technique for predicting the mixing time of a high-viscosity liquid-mixing system with negligible diffusivity of solute is discussed on the basis of a cycle-time distribution in connection with the model equation proposed by Ottino et al. The study was carried out by using two types of mixers. The mixing time predicted using an arbitrarily chosen criterion of mixture is compared with that determined experimentally, using the same criterion. The predicted values are found to be in good agreement with those determined experimentally.