《A New Nickel-Base Alloy for Resisting Metal Dusting Attack》.pdf

A New Nickel-Base Alloy for Resisting Metal Dusting Attack B. A. Baker, V. W. Hartmann Special Metals Corporation, Huntington, WV 25705, USA Dr. S. A. McCoy Special Metals Wiggin, Ltd. Holmer Road, Hereford HR4 9SL, UK INTRODUCTION Metal dusting is a carburisation phenomenon that can cause rapid and often unpredicted failure in chemical and petrochemical plants. Processing high temperature gases such as in the synthesis of hydrocarbon feedstocks, methanol and ammonia, as well as in direct iron ore reduction often involves creation of gas streams having high carbon activity with high ratios of carbon monoxide-to-carbon dioxide and low ratios of steam-to-hydrogen. When such gas mixtures are present in the process stream within the critical temperature range of roughly 400-750°C, metal dusting can be a severe corrosion problem. Chemical reactors, furnaces, steam generators and down-stream reformer components can all suffer from this rapid form of material wastage, resulting in costly downtime. In the case of syngas generation, processing conditions and the use of advanced nickel oxide-based catalyst systems have heightened the tendency of synthetic gas streams to promote metal dusting. The technique of injecting sulphur containing species into the gas stream is no longer viable given the likelihood that the catalyst will be poisoned. Higher reforming gas pressures and temperatures in conjunction with lower steam-to-carbon ratios, all combine to make metal dusting conditions more aggressive, and are becoming more common in