Aeration in Chemical and Biological Reactors

In industrial process engineering, aeration is a unit operation that involves the homogeneous dispersion of the gas-phase into the liquid-phase and the maximization of mass transfer (absorption or desorption. Absorption of gas into liquid to produce a chemical reaction is often a critical duty). Sometimes, the gas merely provides energy -via buoyancy- for mixing the liquid. The aeration in reactors plays an essential role for many processes in the water-treatment, chemical, pharmaceutical and biotechnology industries.

Using CFD Simulations, we are able to analyze critical process parameters such as:

Fine bubble aeration is the best way to enhance the contact surface between the gas and the liquid phase resulting on higher mass transfer rate.

Figure 1: Aerated tank reactor with fine bubble diffusers

Figure 2: Local SOTR analysis for an entire aerated reactor

For many applications fine bubble diffusers cannot be installed or perform with a poor efficiency, for this cases coarse bubble aerators are installed. Furthermore, coarse bubble aeration system are a good solution to add turbulence and mixing into the system.

Figure 3: Coarse bubble aerator in a single test tank

In oxidation ditches a natural conflict occurs between circulation flow induced by horizonal flow generators and vertical flow induced by the buoyancy forces of the air load. These reactors can be simulated, analyzed and optimized with the help of CFD simulations.

Figure 4: Volume fraction o fair in oxidation ditch (Racetrack)

Figure 5 shows typical vortex structures that are induced by a too high air flow rate.

Figure 5: Aeration induced vortex structures in oxidation ditch

The design of aerated tank reactors is by no means a trivial task, THINK Fluid Dynamix has the tools, the people and the experience to help our clients to achieve their goals.