Two-fluid model simulations of an internal airlift loop reactor

Two and three dimensional simulations of an airlift reactor in a steady state at low gas flow rates are presented. The simulations are based on a two-fluid model with a k -ε model for the turbulence and as little as possible ad hoc closure terms. The results are compared with a one-dimensional mechanical energy balance and are found to be in good agreement. The 2D results show sensitivity to the gas inlet geometry: whether or not gas is partially sparged into the liquid directly next to a wall affects the liquid velocity distribution and thereby the gas disengagement at the top of the airlift. The 3-dimensional calculations make a more realistic geometry possible. The friction in the system is found to be about a factor of two larger in the 3D case at the same gas inlet conditions. For a given gas flow rate, the mean gas fraction in the riser is the same for the 2D and 3D simulations, the liquid circulation rate is about 30% higher in the 2D case than in the 3D one.