Simulation of a bubble column reactor using CFD approach. Application: ferrous biooxidation

Extended abstract Understanding the complexity of the fluid dynamics in bubble column and airlift reactors is important due to their application in the chemical and bioprocess industries. So the objective of this research was to develop a fundamental understanding of the hydrodynamics and interactions with the chemistries involved in the bubble column reactor to maximize overall efficiency for the ferrous biooxidation according to the following reaction:. 23 22 1 2 22 2 A ferrooxidans F e H O F e HO + ++ + + → + (1) In the present attempt bacterial oxidation of Fe +2 to Fe +3 in a bubble column reactor was simulated using a commercially available computational fluid dynamics package (FLUENT). Gas-liquid interactions were modeled using an Eulerian model implemented in the software [1]. The finite volume method is adopted to solve three dimensional governing equations. The solver specifications for the discretization of the domain involve the first-order upwind for momentum and phase coupled SIMPLE [2] for velocity–pressure coupling, respectively. For the volume fraction and concentration of species in the liquid phase, first-order discretization scheme was used. The initial ferric concentration was set to zero. At the walls, no-slip boundary condition was applied (Dirichlet boundary condition). For inlet flow, constant fluid velocity with given phase concentrations, and for the outlet flow, the pressure were specified as boundary conditions. The superficial gas velocity was adjusted between 0.01 and 0.5 m s-1 , and results showed that at velocities higher than 0.1 m/s the biological rate was decreased. The reason is that in very high velocities bacteria will damage and therefore the bacterial activity will be decreased. Gas holdup is an important factor that affects on interfacial surface area and also activity of microorganisms and therefore the reaction rate. For the ferrous biological oxidation, air volume fraction in the bioreactor is one of the variables that needs to be