Fine bubbles
Optimum mass transfer by new gas-inducing mixer

Jongia’s, the leading mixer manufacturer in the Netherlands, latest development is the gas inducing mixer with good capacities e.g. for hydrogenation and similar processes.

Gas-liquid reactions often require a high transfer rate. Process examples of some common gas-liquid reactions are: hydrogenation, oxidation, chlorination, fermentation, waste water treatment, and carbonic acid synthesis. Especially when the reaction is fast, the transfer of the reactant from the gas to the liquid phase easily becomes the limiting step. Parameters influencing the mass transfer, and thus influencing the limitation, are: dispersion fineness of the gas, gas flow and power input.
Conventional systems are using a gas sparger (ring) below the mixer impeller to disperse the gas and require an external gas compressor. Other gas-inducing systems had only limited success due to the poor scale-up results, the limited gas flow induced (resulting in a small transfer capacity) or mechanical instability due to the interaction with the liquid surface.

The Jongia gas-inducing mixer combines:
- a high induced gas flow rate;
- a fine dispersion of the gas, so a large interfacial area;
- good, accurately predicted mass transfer, also on large scale;
- stable mechanical operation at moderate (sub-critical) stirrer speed;
- recirculation of the unused gas.
The gas-inducing mixer consists basically of a mixer impeller combined with a gas inducer, mounted together on a hollow shaft, equipped with holes above the liquid surface, through which gas is sucked into the liquid. The driving force is the under pressure behind the gas inducer. The high local power in the liquid due to the impeller liquid flow guarantees the break-up of the gas into fine bubbles.
For long, slender reactors the system can be equipped with additional impellers for top-to-bottom mixing, promotion of heat transfer and/or solids suspension. The gas-inducing mixer has been applied in a number of commercial units (10-40m3) and in all cases a substantial improvement was achieved in terms of better mass transfer, shorter batch times, less use of catalyst, better selectivity and a better flexibility in operation.