Keywords: Centrifugal casting; iron-chromium-nickel alloys; high temperature; creep resistance, creeps rupture strength; micro-alloying; steam reformer; synthesis gas; ammonia.
Manufacture of most ammonia based fertiliser involves steam reforming of natural gas. This process uses catalyst tubes that are made of centrifugally cast high-alloy materials. One of the most important material properties for steam reformer tubes is the creep rupture strength as it determines the tube lifetime. This paper will describe the development of such materials for high-temperature service in steam reformers. The latest alloy development with significantly improved creep rupture strength can be utilised by ammonia plant operators to fully optimise their operation. This advanced material with optimal balanced chemical composition can either be incorporated in revamps on existing units to increase capacity. Additional benefits include improved heat transfer, lower fuel consumption and reduced skin temperature leading to longer tube life. Examples have been selected for specific case of steam reformer tubes used for synthesis gas generation in ammonia plant and the advantages of using newer material in terms of overall life cycle cost is demonstrated.
Shankar Venkataraman and Dietlinde Jakobi, Schmidt + Clemens GmbH + Co. KG, P O Box 1140, D 51779 Lindlar, Germany.
17 pages, 3 figures, 7 tables, 11 references.