Process for Recovering the Salts of Anthraquinonedisulphonic Acid from a Washing Liquid Stream

摘要

The invention concerns a process for recovering the salts of anthraquinone disulfonic acid (ADA) from a sub-stream of washing liquid. In the so-called Stretford process, an alkaline solution of salts of anthraquinone disulphonic acid (ADA) is used as a washing liquid, for washing hydrogen sulfide from gases or gas mixtures which contain it. The alkaline component is normally sodium carbonate. In a modern variant of the Stretford process, sodium metavanadate is added to accelerate certain partial reactions. In an initial, relatively very fast reaction step, sodium hydrogen sulfide is formed by reaction between the hydrogen sulfide and the sodium carbonate, from which elementary sulfur is then liberated by reduction of the oxidation state of the vanadium from +5 to +4, along with the formation of caustic soda. The anthraquinone disulphonic acid salt now acts, along with the effect of the caustic soda, to restore the vanadium to its original oxidation state. The anthraquinone disulphonic acid salt which is reduced in this way - in general the sodium salt is used - is then re-oxidized by addition of oxygen, normally in the form of air. The purpose which forms the basis of the invention is, therefore, to provide a process of the type stated at the beginning, which makes it possible to recover the valuable salts of anthraquinone disulphonic acid in a simple and economical way. Further, the process steps which have to be carried out should, as far as possible, be integrated into the overall process. It turned out that the retention of the salts of anthraquinone disulfonic acid is based on (due to) the macroporous structure of the adsorber resins. (ERA citation 10:045961)