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Recycling of Waste Sulphuric Acid

Process description

Acids burdened with organic impurities are reusable if the impurities evaporate with water or are destroyed by oxidation. Waste acids with high levels of non-volatile organic impurities can only be processed by thermal cracking. The processing costs of a thermal cracking system are determined by the process gas volume flow as well as its sulphur dioxide concentration.

Messer solution

When oxygen is used as the oxidising medium, the nitrogen burden of the air is reduced and replaced by process gas containing sulphur dioxide, which can lead to a considerable increase in sulphuric acid production.


  • Increase in performance (Debottlenecking) of existing plants  
  • Reduced heat losses   
  • Flue gas conditioning
  • Increase in turnover and yield
  • Lower energy costs
  • Improved product quality


Table: Comparison of waste sulphuric acid process with and without oxygen input:

  without O2 with O2
quantity of spent sulphuric acid [%] 100 152
spec. energy consumption [kcal/KG SA] 2421 1724
air flow rate total [m3/h] 3500 3500
O2 flow rate total [m3/h] 0 327
spec. O2 consumption [m3/t SA] 0 252
O2 concentration equivalent [% Vol] 21 27,8


The use of oxygen allows a significant increase in production and reduces the specific energy consumption per kg of sulphuric acid.