Claude Process

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Ammonia synthesis is the basis for agricultural fertilizer production and nowadays the Haber-Bosch process is ubiquitous. An estimated 1.8% of the world consumption of fossil energy goes into the production of ammonia and 90% of ammonia production is based on natural gas. The alternative Claude Process based on electrolytically generated hydrogen is proven technology - operated in the 1930's - and if powered by renewable electricity at a sufficiently attractive price, provides two major benefits:

  1. Displaces the natural gas consumption - and CO2 emissions of Haber-Bosch
  2. Provides an interruptible electricity demand
The Claude Process. This process is [sic] worked at numerous factories
in France and Belgium. The cost of the hydrogen used in the
HABER-BOSCH process accounts for about 75 per cent of the cost
of the ammonia produced: in the CLAUDE process the hydrogen is
made by the electrolysis of water. Some of this hydrogen is burned
in air, leaving nitrogen to be used in the ammonia synthesis and
synthetic water suitable for the electrolytic cells. The rest of the
plant, which works at 750 atmospheres, will be understood from the
diagram. To withstand the enormous pressures the converters are
made of special steel, and the catalyst is mounted on a gun breech-
block device to allow easy withdrawal for replacement. Many
variations of the process are possible; in some the nitrogen is
obtained from producer-gas, in others from liquid air.[1]

Flow diagram

There are several operational and efficiency improvements that spring to mind. Instead of the rather wasteful burning of hydrogen in air to produce nitrogen, the air could be pre-processed e.g. using membrane separation or pressure-swing adsorption to enrich the nitrogen content. The remaining oxygen could then be removed by catalytic reaction with a reduced amount of hydrogen. So if the oxygen content were reduced from 21% to 5%, this would represent ~ 75% saving. Depending on how intermittent the renewable electricity is, gas holders might be provided for both nitrogen and hydrogen. And most of the efficiency improvements developed for the Haber-Bosch process such as better catalysts would apply equally to the Claude process


  1. A Textbook of Theoretical and Inorganic Chemistry, F.A Philbrick, E.J.Holmyard, 1932