New method to design large-scale high-recirculation airlift reactors

Abstract

High-recirculation airlift reactors (HRARs) are efficient for treating waste water. They use air to push a mixture around a reactor and to provide oxygen (O2) for biological microorganisms. Design methods have been limited in functionality and accuracy and have needed significant expert input and interpretation. This paper describes the creation of new structured methods that are faster and more efficient. Models and calculations are described. Improvements are made by analysing and improving the steady-state models of fluid dynamics within an HRAR. The models also deliver information about reactor design, in particular which parameters to modify to reach a steady-state result. Two-phase flow of water and air is modelled for an airlift bioreactor and applied to HRARs. Tests show that varying superficial gas velocity or simultaneously varying down comer and riser diameters can create a steady-state solution. The research investigated an HRAR and the associated Imperial Chemical Industries design program, created a new design program to replace it and then improved it using simple models of steady-state fluid dynamics. Mathematical models are used to forecast steady-state situations in the HRAR for specific gas or liquid flow rates and for various constructions. Experimental relationships forecast mass transfers between gas and liquid phases, and they predict flow.