Sulphuric Acid Production

The Contact Process

Raw materials used

• Oxygen from air or water
• Sulphur dioxide from roasting iron pyrites or Sulphur in air

 

Conditions needed

• 450^oC temperature
• Vanadium (v) oxide – 1 atmosphere pressure.

 

The Contact Process

• Sulphuric acid is produced at Zimphos near Harare.
  

 

Stage 1

iron sulphide/iron pyrites/sulphur is roasted to form sulphur dioxide

Sulphur + Oxygen⇔ Sulphur Dioxide

(g)

Stage 2

sulphur dioxide is mixed with excess air and passed to a convertor where it is converted to sulphuric acid by contact process. This reaction is reversible. To speed up, a catalyst vanadium (V) oxide is used to speed up reaction. Also pressure of one atmosphere is used. This will yield up to 95%

Sulphur dioxide + Oxygen ⇔ Sulphur Trioxide + water

450ºC , 1 Atmosphere

(g) + heat

 

Stage 3:

• Production of oleum
  

• Sulphur trioxide is cooled and absorbed into concentrated sulphuric acid to produce oleum.
• Oleum is a mist of sulphuric acid which is difficult to condense

Sulphur Trioxide + sulphuric acid ⇔ oleum

(g)

Stage 4:

Oleum is diluted with water or dilute acid to give concentrated sulphuric acid

(aq)

 

Uses of sulphuric acid

• Making of fertilizers such as superphosphate and ammonium sulphate
• Cleaning surfaces of iron and steel surface before galvanization or electroplating
• To manufacture plastics and fibres
• As electrolyte in car batteries
• In refining of petroleum
• In production of dyes, drugs, explosives, paint, pesticides and making detergents etc. – Drying agent or flocculant for paper making

 

Production of ammonium nitrate

• Ammonium nitrate is made by direct neutralization of nitric acid by ammonia. Ammonia is bubbled through nitric acid, an acid base reaction takes place and ammonium nitrate is produced in solution.
• (aq)

• The solution is evaporated to produce a saturated solution. The saturated solution is dried in a prill tower to give solid prills (granules).
• The ammonium nitrate crystallizes out of the solution.