Hydrodynamic of liquid circulation in closed airlift reactor photobioreactor: Optimization of draft tube geometry

Reactors or bioreactors used in industries or for the growth and reproduction of microorganisms face several challenges. The poor mass transfer and heat transfer with the generation of dead zones are the most important of these challenges. The current research is a serious attempt to improve the mixing efficiency in these reactors to provide suitable conditions for reactions. Numerical modelling of liquid hydrodynamics was developed for optimization of the geometry of inner draft-tube in an airlift bioreactor operating for chemical or biochemical applications. The performance of the mixing was based on the velocity of liquid phase in riser region. Effect of height, radius, and position of draft tube on the recirculation of liquid in rizer region was investigated in current study. The study showed that reducing the diameter of the inner tube has a positive effect on the mixing efficiency, provided that it is not less than the diameter of the diffuser. While increasing the diameter reduces the mixing efficiency, even if the height of the pipe or its location in relation to the base of the reactor increases. The study concluded that the internal engineering parts of the reactor have an effect on the dynamic movement of the fluid.