Describe the manufacture of H2SO4 by contact process?
The steps involved in the manufacture of sulphuric acid by contact process are as shown:
(1) Sulphur (or iron pyrites) are burnt in air to form sulphur dioxide.
(2) Catalytic oxidation of sulphur dioxide to sulphur trioxide.
The reaction is reversible and exothermic.
(3) Sulphur trioxide is dissolved in 98% sulphuric acid to form oleum (fuming sulphuric acid).
(4) Oleum is diluted with water to form sulphuric acid of desired concentration.
Manufacture of H2SO4 by contact process involves three steps:
1. Burning of sulphur in air to generate SO2.
2. Conversion of SO2 to SO3 by oxidation with air in the presence of V2O5 as catalyst.
3. Absorption of SO3 in H2SO4 to obtain oleum H2S2O7. A flow diagram for the manufacture of H2SO4 is given below: