A fundamental study on high temperature corrosion of boiler tubes in smelting off-gas environments

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The overall objective of the proposed project is to mount a study to develop a better fundamental understanding of the corrosion of alloy 625 and other candidate materials at high temperatures (200-400 C) and specifically under operating conditions prevailing in the KIVCET boiler off-gas at Teck-Cominco Trail, BC, operation. In addition, suitable alloy(s) for the boiler tube overlay or methods relating to corrosion protection which would increase the service life of the boiler tubes will be recommended. It is intended to further the knowledge gap by applying innovative research. Specific objectives of the proposed research are: (1) to carry out a thorough failure analysis of boiler tubes at Tech-Cominco's KIVCET smelter to define root cause of failure and assist in understanding the complex corrosion mechanism, (2) to study the effects salts and the composition of the off-gas on the corrosion performance of Alloy 625 and others potential alloys, (3) to provide a better fundamental understanding of corrosion mechanism of Alloy 625 and other alloy under the boiler conditions, using both thermochemical modeling and experimental approaches and (4) to recommend the best suitable alloy systems for application at as boiler overlay at Teck-Cominco KIVCET smelter. The study will involve a detailed literature review, failure analysis on representative samples of corroded / failed tubing, thorough physical and chemical characterization of representative deposit samples and thermochemical analysis of the system will be undertaken to determine the stability and equilibria in both the gas phase and phase stability in the deposits, using commercial software FactSage and HSC. Also, an extensive experimental testing program on Alloy 625 and selected candidate alloys will be performed. The testwork will be divided into two types, high temperature corrosion testing using a tube furnace, and electrochemical testing using an autoclave, and high temperature furnace. A post doctoral fellow and a Ph.D. student will work on this research project. The anticipated benefits of the work to Canada and to Teck-Cominco are significant and will have a direct impact on the ability of Canadian companies, to compete effectively in the global market.