Process for the recovery of ammonia and sulphur dioxide from a contaminated ammonium salt of sulphuric acid

In a process for the recovery of ammonia and sulphur dioxide from a by-product mixture containing ammonium salt of sulphuric acid and organic impurities by reacting said by-product mixture in a finely divided state at an elevated temperature with gases obtained from the combustion of a fuel with oxygen and separating ammonia and sulphur dioxide from the resulting reaction mixture, the improvement wherein

• said by product mixture is obtained as a by-product in the preparation of .epsilon.-caprolactam or cyclohexanone oxime, and
• said by-product mixture is reacted at a temperature of from 700.degree. to 950.degree. C. with gases obtained from the combustion of said fuel with an amount of oxygen 85% to 99.5% of the theoretical additional amount of oxygen that would be required to convert the nitrogen, sulphur, hydrogen and carbon in said fuel and by-product mixture into N.sub.2, SO.sub.2, H.sub.2 O and CO.sub.2, respectively.