Whether oxidation using oxygen gas or implementation with carbon dioxide or ammoniac: the application-specific requirements for gas-solid reactions are complex and call for correspondingly sophisticated technical capabilities. As demonstrated by a Druvatherm® Reactor type VT 50, Lödige Process Technology offers a broad product portfolio of tailor-made solutions.
Lödige’s product offerings range from “simple” solids mixers to drying systems and pressure vessels for reactions under overpressure. In practice, Lödige has already realized operating pressures of up to 40 bar in the reactor. Reactor sizes range from the small laboratory mixer with a 5-litre drum capacity to production machines with a volume of more than 50,000 litres.
This equipment can be used both for batch operation and continuous production lines. In these reactors the solid particles move in a fluidized bed that is mechanically generated in the drum. It is created through the input of energy via a horizontally arranged mixer shaft fitted with mixing elements. Thermal energy is supplied or dissipated through a heat transfer medium such as water, steam, thermal oil or molten salt. Temperature ranges of up to 700°C can be realised with electric heating. The choice of respective material qualities and mixing elements and sealing technology is always individually matched to the process.
Chemical reactions in the Lödige Reactor
Reactions in multi-phase systems (solid-liquid-gaseous) can be carried out with extremely good results with the described mixing technology. Homogeneous heat and concentration distributions prevail in the mechanically generated fluidised bed. This is important, because temperature gradients, i.e. inhomogeneous temperature profiles, speed-determining partial reactions (material transport, diffusion) can have a limiting influence.
Two possible process variants exist, e.g. for the realisation of a gas-solid reaction. Either the reaction gas can be passed through the mechanically generated fluidised bed, or the reactor is filled with the respective stoichiometric amount and the reaction takes place in the closed system under pressure and at a constant temperature. The latter method, of course, has a correspondingly positive effect on reaction kinetics.
The DRUVATHERM® Reactors thus offer variable liquid and gas proportioning with the corresponding reaction control. Parameters such as overpressure, temperature control with a double shell and cooler or final drying under vacuum can be precisely controlled. The corresponding reactors are thus particularly suited to carrying out so-called one-pot reactions. A continuous gas flow through the solid fluid bed of a continuously operated reactor is also conceivable.