Failure mechanisms and material degradation processes at high temperatures in ammonia synthesis

Abstract

Ammonia has been manufactured on an industrial scale for almost 100 years. Nevertheless, this process still presents a challenge to the materials involved and to the material engineers who are responsible for the selection of materials. This is due to the temperatures and the media handled. Failure mechanisms that have been known in ammonia plants since the industrial production of ammonia started are hydrogen attack, creep and embrittlement. Since the new generation of plants characterised by optimised heat recovery have been in service, metal dusting has emerged as a relatively common problem in ammonia plants following the secondary reformer. In the present study, the wide range of failure mechanisms and material degradation processes observed in ammonia plants is illustrated by a number of examples, some of which relate to the historical development of the process.