Birkeland–Eyde process

It was developed by Norwegian industrialist and scientist Kristian Birkeland along with his business partner Sam Eyde in 1903,[2] based on a method used by Henry Cavendish in 1784.

[3][4] A factory based on the process was built in Rjukan and Notodden in Norway, combined with the building of large hydroelectric power facilities.

[7] An electrical arc was formed between two coaxial water-cooled copper tube electrodes powered by a high voltage alternating current of 5 kV at 50 Hz.

A strong static magnetic field generated by a nearby electromagnet spreads the arc into a thin disc by the Lorentz force.

By carefully controlling the energy of the arc and the velocity of the air stream, yields of up to approximately 4–5% nitric oxide were obtained at 3000 °C and less at lower temperatures.

Birkeland used a nearby hydroelectric power station for the electricity as this process demanded about 15 MWh per ton of nitric acid, yielding approximately 60 g per kWh.

The same reaction is carried out by lightning, providing a natural source for converting atmospheric nitrogen to soluble nitrates.

[13] This nitrogen dioxide is then dissolved in water to give rise to nitric acid, which is then purified and concentrated by fractional distillation.

Reactor used in Rjukan from 1916 to 1940 having a capacity of 3000 kW (outside Norwegian Museum of Science and Technology )
Diagram of the production of a plasma disc using water-cooled electrodes and an electromagnet
One type of reactor used at Rjukan from 1912 to 1940 now located in a park in Rjukan
Reactor Building II behind the Såheim Hydroelectric Power Station in which 35 Birkeland-Eyde reactors were installed requiring 3000 kW each