ESTIMATING METAL DUSTING ATTACK ON STAINLESS STEEL ALLOYS IN SYNGAS ENVIRONMENTS

摘要

Metal dusting is a major limiting factor in the development of more efficient processes for producing syngas. This type of deterioration causes a form of pitting or crevice attack in high temperature processes. This paper proposes that the rate-limiting step in metal dusting is the diffusion of carbon into the alloy. The activity of carbon in equilibrium with syngas increases as the temperature decreases, and that increased activity provides the driving force for diffusion. The temperature at which the carbon activity is unity, designated carbon precipitation temperature (CPT) in this paper, is a good predictor of metal dusting potential of a syngas. The higher this temperature is, the more aggressive the syngas will be. A severity function based on Ficks Law of Diffusion is proposed to evaluate the tendency of syngas to cause metal dusting at temperatures below this CPT. This severity function predicts the behavior of metals in metal dusting service that simulates observed behavior.