Nitric Acid
(Ostwald’s Process)
Introduction
On industrial process three methods
are employed for the manufacture of nitric acid. Ostwald’s Process uses Ammonia
as raw material.
Ostwald’s Process
When a mixture of ammonia and air is
passed through a catalytic chamber containing electrically heated Platinum
Gauze, (NO) nitric oxide is formed. This nitric oxide combines with more oxygen
to form nitrogen dioxide (NO2). This gas is then absorbed by water to form
nitric acid. The plant used in Ostwald’s Process consists of following parts.
1. Catalytic Chamber
A mixture of pure and dry ammonia is
passed through catalytic chamber containing heated (800 º C) platinum, which
serves as catalyst. Here ammonia is completely oxidized to nitric oxide.
2. Oxidation Tower
The nitric oxide is passed into
oxidation tower where the temperature of gases falls to 200ºC – 250ºC. At this
temperature nitric is oxidized to nitrogen dioxide.
2NO + O2 —-> 2NO2
3. Absorption Tower
Now the gases containing NO2 and
oxygen are than sent to a series of absorption tower, which is filled with
broken quartz and water is showered from top of the tower. Then NO2 reacts with
H2O in the presence of oxygen to form HNO3.
4NO2 + 2H2O + O2 —-> $HNO3
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