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    Nitrogen+Syngas 323 May-Jun 2013

    30 June 2013

    Problem No. 18: HP stripper passivation air

    The high pressure CO2 stripper, invented by Petrus J.C. Kaasenbrood of Stamicarbon in 1967, revolutionised urea process technology, reducing the energy consumption figures of urea plants by roughly a factor two. Further, Stamicarbon and Sandvik developed the austenitic stainless steel 25-22-2 to handle the relatively tough corrosion conditions in a HP stripper. The HP NH3 stripper, introduced by Saipem, operates at higher temperatures than a HP CO2 stripper and materials of construction like titanium and zirconium, sometimes in combination with 25-22-2 were therefore applied.

    Back in 1955, Joseph P.M. van Waes of Stamicarbon made the discovery that austenitic stainless steels could be protected against carbamate corrosion by adding oxygen in the urea process. The oxygen forms a chromium oxide layer protecting the stainless steel and reducing corrosion rates to acceptable levels. This discussion explores the experiences with different amounts of oxygen in the HP stripper in various urea processes.

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