GB687160A - Manufacture of sulphuric acid - Google Patents

Abstract

Sulphuric acid is produced by contacting a gas comprising sulphur trioxide with an aqueous fluid under such conditions that the resulting sulphuric acid reaches a temperature of at least 150 DEG C, the acid then being cooled by contact with air and the air after effecting cooling being contacted <PICT:0687160/III/1> with water or dilute sulphuric acid to effect heat and material exchange. The resulting heated dilute acid may be employed as the aqueous fluid which is contacted with the sulphur trioxide. In the Figure, sulphur trioxide enters an adsorber 2 at 1 and is washed with boiling sulphuric acid, the heat-concentrated acid then passing through pipe 3 to an air cooler 4. Air enters at 5 and after cooling the acid and entraining acid vapours, passes through pipe 6 to a heat and material-exchanger 10 irrigated partly by the acid pumped from the cooler 4 via line 9 and partly by dilute acid added to the system at 11. The cooled gases, freed from sulphur trioxide and acid vapours, are evacuated at 13 and may be recycled to the cooler 4 to avoid the introduction of water vapour to the cooler. Product acid is withdrawn at 8. The aqueous fluid used to absorb the sulphur trioxide may be diluted acid resulting from drying and heating gases with concentrated sulphuric acid, the absorbed water being partly reacted with the sulphuric trioxide and partly evaporated by the heat of the reaction, thereby reconcentrating the acid. Alternatively, the dilute acid supply may be that from a refrigeration device where water evaporated under low pressure is absorbed in concentrated sulphuric acid.