The technical novelty of Luigi Casale’s[aut]Casale, Luigi synthetic ammonia process, which operated at 850 atmospheres pressure, arose from several significant innovations, most especially the design of the converter (reaction tube), the ability to control overheating within the catalyst bed, and a device called an ejectorEjector (Casale) which improved the recirculation of unreacted gases. As with the Haber–Bosch processCatalystsHaber Bosch process, the Casale process was based on a closed loop, or train. The converter was made of ordinary steel, which posed problems of failure in the other early ammonia processes. Success was made possible by the design of the internals: an arrangement of concentric tubes which ensured that the severe reaction conditions, brought on by pressure, heat, and a catalyst, did not place undue stress on the shell of the converter. The ammonia was a pure, anhydrous liquid, a feature made possible by the extremely high operating pressure. The ejector, introduced in the mid-1920s, reduced the number of moving parts.