Birkeland–Eyde process
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The Birkeland–Eyde process was developed by Norwegian industrialist and scientist Kristian Birkeland along with his business partner Sam Eyde in 1903, based on a method used by Henry Cavendish in 1784.[1] This process was used to fix atmospheric nitrogen which was in turn used to produce nitric acid, used for production of synthetic fertilizer. A factory based on the process was built in Rjukan and Notodden in Norway, combined with the building of large hydroelectric power facilities.[2] The process is inefficient in terms of energy usage, and is today replaced by the Ostwald process, that produces nitrous acid from ammonia instead of air (usually from the Haber process).[3]
The process
An electrical arc was formed between two coaxial electrodes, and through the use of a strong magnetic field, was spread out into a thin disc. The plasma temperature in the disc was in excess of 3000°C. Air was blown through this arc, causing some of the nitrogen to react with oxygen forming nitric oxide. By carefully controlling the energy of the arc and the velocity of the air stream, yields of up to 4% nitric oxide were obtained. The process is extremely energy intensive. Birkeland used a nearby hydroelectric power station for the electricity as this process demanded about 15 MWh/Ton of nitric acid. The same reaction is carried out by lightning, providing a natural source for converting atmospheric oxygen to soluble nitrates.[4]
- N
2 + O
2 → 2 NO
The hot nitric oxide is cooled and combines with atmospheric oxygen to produce nitrogen dioxide.
- 2 NO + O
2 → 2 NO
2
This nitrogen dioxide is then dissolved in water to give rise to nitric acid, which is then purified by fractional distillation.[5]
- 3 NO
2 + H
2O → 2 HNO
3 + NO
References
- ^ Aaron John Ihde (1984). The development of modern chemistry. Courier Dover Publications. p. 678. ISBN 0486642356.
- ^ G. J. Leigh (2004). The world's greatest fix: a history of nitrogen and agriculture. Oxford University Press US. pp. 134–139. ISBN 0195165829.
- ^ Trevor Illtyd Williams; Thomas Kingston Derry (1982). A short history of twentieth-century technology c. 1900-c. 1950. Oxford University Press. pp. 134–135. ISBN 0198581599.
- ^ Karl Fisher; William E. Newton (2002). G. J. Leigh (ed.). Nitrogen fixation at the millennium. Elsevier. pp. 2–3. ISBN 0444509658.
- ^ Douglas Erwin (2002). Industrial Chemical Process Design. McGraw-Hill. p. 613. ISBN 0071376216.