Large Volume Inorganic Chemicals - Ammonia ... - ammk-rks.net

Chapter 44.4.9 Combined wet/dry catalysis processesDescriptionCombined wet/dry contact processes are double contact/double absorption processes, used inparticular for processing gases containing H 2 S. If the H 2 S content is low, H 2 S gases are burnedtogether with elemental sulphur. After reducing the temperature to about 400 °C, the wetcombustion gases are directly fed into the contact tower. SO 3 formed by the catalytic conversionimmediately reacts with the moisture of the gases and forms sulphuric acid. The sulphuric acidis absorbed in an intermediate absorber installed after the second or third catalyst bed.Remaining SO 2 is converted in the following catalyst bed(s) according to a dry contact process.The combined wet/dry process uses the same catalyst materials as in a conventional doublecontact plant.Achieved environmental benefits• enables the conversion of wet SO 2 gases• SO 2 conversion rates up to 99.8 %• SO 3 emissions of 30 mg/Nm 3 .Cross-media effectsNone believed likely.Operational dataNo specific information provided.ApplicabilityApplicable to wet SO 2 gases, e.g. with a low H 2 S content.EconomicsNo specific information provided.Driving force for implementationRecovery of sulphur from waste gases..References to literature and example plants[57, Austrian UBA, 2001], Lenzing AGLarge Volume Inorganic Chemicals – Ammonia, Acids and Fertilisers 187