Determination of Effective Shear Rate in a Pilot-plant External Loop Airlift Reactor

• Main Authors: W.A. Al-Masry, M. Chetty
• Format: Article
• Language: English
• Published: Elsevier 1998-01-01
• Series: Journal of King Saud University: Engineering Sciences
• Online Access: http://www.sciencedirect.com/science/article/pii/S1018363918306883

Shear rate is an important design parameter in bio-reactors for its role in estimating cell-damage rate in shear-sensitive environment as well as in correlating hydrodynamics and mass transfer coefficients in non-Newtonian systems. One of the serious shortcomings in the analysis of non-Newtonian behaviour in airlift loop reactors is the lack of a reliable method for determining effective shear rate and viscosity appropriate to the airlift geometry.This work has been carried out in a pilot-plant external loop airlift reactor of 6.5 m in height and 0.225 m diameter of both riser and downcomer. Biological media were simulated using non-Newtonian solutions of xanthan gum and carboxymethyl cellulose. The resulting shear rates are compared to the available literature, and show an increase in shear rate with increasing superficial gas velocity. Also, it has been found that non-Newtonian solutions with similar rheological properties and different chemical structure have different shear rate trends at a given superficial gas velocity.