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WSA Process

The WSA process (wet gas sulphuric acid) combines compliance with emission regulations and profitable handling of sulfurous exhaust gases. Actually, the wet catalytic sulfuric acid process is one of the most important gas cleaning processes. As it ensures  ecological safety and economical benefit in the form of saleable sulphuric acid. 

The WSA process is common in the petrochemical industry, especially for:

  • Treatment of H2S from the amine regenerator (MDEA scrubber)
  • Regeneration of spent sulfuric acid from alkylation
  • Purification of exhaust gases from the Claus plant
  • Cleaning of flue gases from the combustion of highly sulfurous fuels, e.g. petroleum coke

LiquiSonic® sonic velocity measurement


In the first step of the wet catalytic process, the sulfur component H2S from the exhaust gases is catalytically converted to SO2. In a subsequent step at 400°C, the conversion to SO3 takes place, which then reacts with the atmospheric moisture to produce sulfuric acid. By using the heat of the reaction and the exhaust gases, this process can be operated without additional ther-mal energy even at low exhaust gas concentrations (S-components < 0.2 Vol%).

LiquiSonic® ensures an accurate concentration measurement of sulfuric acid, even at high acid concentrations. Each process step can be both monitored continuously with the inline LiquiSonic® analyzer and be optimally set. Sonic velocity changes significantly with minor changes in sulfuric acid concentration, allowing the LiquiSonic measurement to reach an accuracy of +/- 0.05 wt%.


The LiquiSonic® immersion sensor is easily installed into pipelines after the condenser in sulfuric acid pro-duction as well as at the blending station. By using the LiquiSonic® controller 30, up to four  sensors can be connected, allowing the simultaneous monitoring of several measuring points. 

Typical measuring range:
concentration range from H2SO4: 80 to 100 wt%
temperature range: 20 to 90 °C

Customer value

The robust sensor construction and the optional special materials, like Hastelloy C2000, promote long process life. 

LiquiSonic® enables a reduction of labor cost through the elimination of manual process steps: 

  • time saving: 1 h per day

In comparison to conductivity and density measure-ment, LiquiSonic® generates a clear signal in the 80 to 100 wt% concentration range and provides reliable process information.