Question

Describe the Ostwald's process for the manufacture of nitric acid with labelled diagram.

Answer 1

Diagram for Ostwald process:



Major steps in Ostwald process:

1. A mixture of ammonia and dust free, filtered air in the ratio 1:10 is admitted into a catalytic chamber from the top. The mixture is passed through a platinum gauze catalyst at a temperature of 800^oC. Ammonia is then oxidised to nitric oxide. The reaction is exothermic and maintains the temperature of the chamber.

$4{\mathrm{NH}}_3+5{\mathrm{O}}_2\underset{800°\mathrm{C}}{\overset{\mathrm{Pt}}{\to }}4\mathrm{NO}+6{\mathrm{H}}_2\mathrm{O}+\mathrm{Heat}$

2. The hot gases from the base of the chamber are then cooled by passage through a heat exchanger, where the gases are cooled to the vicinity of 50^oC. Here, the nitric oxide reacts with atmospheric oxygen to form nitrogen dioxide.

$2\mathrm{NO}+{\mathrm{O}}_2\to 2{\mathrm{NO}}_2$

3. The nitrogen dioxide is then passed with excess air through an absorption tower, where water trickles in from the top. Nitrogen dioxide in the gas flow reacts with water in the presence of atmospheric oxygen to form nitric acid, which is collected at the bottom of the tower.

$4{\mathrm{NO}}_2+{\mathrm{O}}_2+2{\mathrm{H}}_2\mathrm{O}\to 4{\mathrm{HNO}}_3$