The Davy oxidation system, based on COMPRESS™ PTA technology, comprises a simple liquid-phase oxidation step followed by crystallisation and drying to yield a solid product.
The process feedstock consists of reactant dissolved in a solvent. Catalysts are also present in the mixture, and will usually include bromide, cobalt and manganese ions.
This feed enters the oxidation vessel at moderate temperature and pressure. As air blows through the reactor, a proprietary agitation system ensures the reactants are well mixed and causes oxidation to proceed.
Solvent, along with water produced by the oxidation reaction, vaporise as they absorb the heat of reaction.
The majority of these vapours are condensed and recycled back to the oxidation reactor. However, to ensure the water content in the reaction vessel remains constant, a portion of these off gasses are sent to distillation, which separates the solvent and water. The recovered solvent recycles back to the reactor while the water is used elsewhere.
The oxidation product is largely insoluble, and consequently the reactor contains significant amounts of solid product crystals which form a slurry with the solvent.
The slurry proceeds through a series of vessels which flash cool the mixture and induce further product crystallisation.
The resulting flash vapours go to the solvent recovery distillation column, while the remaining process slurry proceeds to rotary pressure filtration which recovers the product crystals.
A final drying stage removes residual liquor from the solid product.