Process for the final purification of fluorine-containing waste gases

摘要

The invention relates to a process for the final purification by absorption of fluorine-containing waste gases and for producing usable alkali metal fluorides in crystalline form by a separate crystallisation which is included in the absorbent circulation. The process is a use variant of the fundamental principle described in WP 127 548 and is particularly suitable for those fluorine-containing waste gases which, in addition to fluorine compounds, also contain constituents which influence the solubility behaviour of the fluorides and/or for those fluorine-containing waste gases whose inlet temperature into the absorption is above 100 DEG C. The process operates without the production of waste water and purifies the fluorine-containing waste gas to a final content of 1 mg of fluorine per m<3> of clean gas. The removal according to the invention of only a part of the fluoride solution from the absorbent circulation leads to a minimal crystalliser volume at a minimum residence time of 20 minutes. Furthermore, for certain industrial sectors, there is the possibility of the work-up of the fluorine-containing waste acid to give a usable alkali metal fluoride.