Single Contact Process for sulfur production:Four stages involved: Sulfur Burning: Sulfur is fed in the burner where it reacts with dry air to produce sulfur dioxide (SO2). The air is dried using concentrated sulfuric acid.S(s)+ O2(g)==>SO2(g) H= -297 kj/mol Oxidation: The sulfur dioxide is oxidised to sulfur trioxide by oxygen using vanadium(V)oxide as a catalyst.2SO2(g)+ O2(g)2SO3(g) H= -197 kj/mol Absorption: Concentrated sulfuric acid is used to dissolve sulfur trioxide where it forms oleum (H2S2O7) in an absorption tower. SO3(g)+ H2SO4(l)==>H2S2O7(l) Cooling: Oleum is then mixed with water to obtain sulfuric acid.H2S2O7(l)+ H2O(l)==> 2H2SO4(l)Overall Reaction:SO3(g)+ H2O(l)==> H2SO4(l)

Key points: Single SO3 absorption tower Can be operated at low SO2 concentration(6-10% by volume) Does not meet emission regulation of SO2 Maximum conversion 97.5-98 % Simple and easy to start up and operate therefore preferred for new plants