51313-02287-High-Temperature Corrosion Resistance of Spun-Cast Materials for Steam-Cracking Furnaces

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Product Number: 51313-02287-SG

ISBN: 02287 2013 CP

Author: Dietlinde Dr. Jakobi

Publication Date: 2013

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Steam-cracking furnace radiant coils operate under severe alternating conditions with reducing and oxidizing atmospheres and at temperatures even beyond 1100 °C. Besides sufficient creep strength the coil materials should provide excellent resistance against high temperature corrosion and catalytic coke formation at the inner tube surface.

In this work a comparative test method will be presented in which samples from radiant coils are subjected to a cyclic corrosion test in a laboratory testing unit. The tests examine samples at conditions which are close to the situation inside a steam cracking furnace and consist of a sequence of alternating cracking in a mixture of steam and hydrocarbons and subsequent decoking with a steam-air mixture. Sample temperature is raised during the cracking cycle up to 1100 °C to produce a highly aggressive atmosphere corresponding to the most severe phase in the pyrolysis heater.

The first aim of this study was to investigate and understand the process of materials deterioration from the initial steps of oxidation during the heating-up to the first corrosive attack and finally to the state in which the high temperature resistance of the material is starting to fail. Secondly the tests were applied to different state-of-the-art spun cast alloys to work out differences between alloys with a chromia- or spinel-based oxide protection and alloys which are protected by alumina. The testing procedure was optimized to obtain distinct results in affordable time and under conditions still representative for the real cracker operation.

Test results will be presented. The key differences between the two alloy concepts in stability of the inner tube wall against corrosion and the behavior in coke formation will be introduced and discussed.