Mathematical modeling of the residence time distribution in loop reactors

The axial dispersion model was applied to the riser and down-comer, respectively, of an airlift loop reactor and a mathematical model was developed to describe its residence time distribution (RTD). A numerical solution was first obtained for the case where there is no gas–liquid separator. A tracer impulse was considered to flow in an infinite tube comprising alternating riser, gas–liquid separator and down-comer. The tracer concentration at a point in the reactor is the sum of all the tracer concentrations at the corresponding points in the infinite tube. Based on this model, an analytical solution was obtained for the mathematical model. The comparison between the analytical solution and experimental data shows that the model can be used to simulate the RTD in airlift loop reactors. By using the analytical solution in a loop reactor with partial recirculation, the solution with a recycle factor is obtained. A comparison with data in the literature shows that the solution with the recycle factor can be used for the RTD in a loop reactor with partial recirculation.